WASHING APPARATUS WITH DYNAMIC PUMP PRESSURE

Abstract

 There is provided a method of homogenizing at least one property of a fluid in a tank (102) of a washing apparatus (100) for washing protective equipment, the fluid being a fluid for washing of the protective equipment, the method comprising the steps of: pumping fluid at an operating pressure from the tank (102) to a washing chamber (101) of the washing apparatus (100) configured to receive the protective equipment so as to wash the equipment; and pumping fluid at a circulation pressure from the tank (102) through a circulation loop (105) back to the tank (102), wherein the circulation pressure is lower than the operating pressure.

Description

TECHNICAL FIELD

[0001] The present invention relates to a washing apparatus, and more particularly to a washing apparatus for cleaning protective equipment, such as personal protective equipment, and methods of operating the same.

BACKGROUND

[0002] Protective equipment, such as clothing, gear, and/or garments, are used in many industries including firefighting, health care, quarrying, mining, and chemical industries. The protective equipment is used to protect workers from hazardous substances, including dust particles, soot particles and combustion gases. Some of these substances include hazardous toxins and/or carcinogens, such as polycyclic aromatic hydrocarbons (PAH) particles which pose a real threat to human health. Furthermore, as the protective equipment is used in harsh environments, it may be heavily soiled and, coarse particles such as stone or rock material may be stuck to it.

[0003] When the work assignment is completed, it is therefore important that the protective equipment is cleaned, washed, and decontaminated in order not to expose the wearer or user to the substances when handling the protective equipment.

[0004] However, cleaning the equipment by hand may be both time consuming and hard work and also poses a health risk due to unprotected exposure to the toxins and/or carcinogens.

[0005] A washing apparatus may therefore be used to clean or wash the protective equipment. However, known washing apparatuses may have difficulty in cleaning the protective equipment. For example, the particles removed from the protective equipment during the washing process may cause the washing apparatus to cease to function, or at least wash with reduced efficiency. Furthermore, a long time is commonly required to start up the washing apparatus once a user has loaded the protective equipment therein and pressed the button to start a wash cycle. Moreover, the temperature of the fluid used for washing the protective equipment in the washing apparatus, may have a fluctuating temperature throughout the wash cycle.

[0006] Therefore, there is a need for improved washing apparatuses that can overcome at least some of the above-described challenges.

SUMMARY

[0007] The invention is defined by the appended independent claims. Additional features and advantages of the concepts disclosed herein are set forth in the description which follows, and in part will be clear from the description, or may be learned by practice of the described technologies. The features and advantages of the concepts may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the described technologies will become more fully apparent from the following description and appended claims, or may be learned by the practice of the disclosed concepts as set forth herein.

[0008] In a first aspect, there is provided a method of homogenizing at least one property of a fluid in a tank of a washing apparatus for washing protective equipment, the fluid being a fluid for washing of the protective equipment, the method comprising the steps of: pumping fluid at an operating pressure from the tank to a washing chamber of the washing apparatus configured to receive the protective equipment so as to wash the equipment; and pumping fluid at a circulation pressure from the tank through a circulation loop back to the tank, wherein the circulation pressure is lower than the operating pressure.

[0009] The method according to the first aspect allows fluid in the tank to be circulated such that one or more properties of the fluid in the tank is homogenised or made more uniform. This ensures that a wash cycle can be performed with a substantially constant fluid temperature, and in turn protects temperature-sensitive equipment from being damaged during the wash cycle. It also ensures that the quality of wash is adequate, and that the protective equipment is properly cleaned. Furthermore, the homogenised fluid in the tank allows properties of the fluid to be accurately measured, and accurately adjusted.

[0010] Preferably, the step of pumping fluid at the circulation pressure is performed during a time period when equipment is not washed by the washing apparatus, and/or outside of a washing cycle of the washing apparatus.

[0011] The method thus advantageously utilizes an otherwise idle time period between wash cycles to circulate fluid in the tank to ensure homogenization. Hence, a start-up time of a wash cycle may be reduced.

[0012] Preferably, the circulation pressure is less than 0.5 of the operating pressure, optionally less than 0.2 of the operating pressure, optionally less than 0.1 of the operating pressure. Additionally or alternatively the circulation pressure is less than 2, optionally less than 1.5, optionally less than 1.2, optionally less than 1.1, optionally less than 1, optionally less than 0.9, optionally less than 0.7, optionally less than 0.5, of a pressure required to pump the fluid from the tank to an inlet of the washing chamber. The reduced circulation pressure advantageously reduces the energy usage.

[0013] Preferably, the washing apparatus comprises one or more rotational wash arm for ejecting the fluid into the washing chamber, wherein the operating pressure is sufficient to cause the one or more rotational wash arms to rotate by the fluid being ejected therefrom, and wherein the circulation pressure is substantially insufficient to cause at least one of the one or more rotational wash arms to rotate.

[0014] Preferably, the circulation loop is at least partially formed by a bypass circuit dividing a flow between the tank and the washing chamber. Furthermore, the circulation pressure may be sufficient to pump fluid through the circulation loop but substantially insufficient to pump fluid into the washing chamber. Preferably, during the step of pumping fluid at the operating pressure, the fluid is discharged to a drain after having entered the washing chamber.

[0015] Thus, the fluid may be recirculated without entering the washing chamber, and contamination of the circulated fluid may thus be reduced. The bypass circuit, optionally in combination with a discharge drain from the washing chamber, is particularly advantageous for rinsing fluid because rinsing fluid must be clean.

[0016] Preferably, the circulation loop is at least partially formed by a return circuit connecting an outlet of the washing chamber to the tank. Thus, fluid entering the washing chamber may be recirculated and hence water consumption and energy usage may be reduced.

[0017] Preferably, a pressure at the inlet to the washing chamber caused by the circulation pressure is less than 20%, optionally less than 10%, optionally less than 5%, optionally less than 2%, than a pressure at the inlet to the washing chamber caused by the operating pressure. Hence, the pumping power required may be reduced as the circulated fluid is not ejected or sprayed into the washing chamber at an unnecessarily high speed.

[0018] Preferably, the method further comprises a step of heating the fluid in the tank. Preferably, the step of heating the fluid in the tank may be performed outside of the step of operating the pump at operating pressure (i.e. outside of a wash cycle), such as during the circulation step and/or between circulation steps. The fluid may thus be maintained at the operating temperature. Hence a time required to start the wash cycle (i.e. the time between the wash cycle is initiated by a user and the pumping of fluid into the washing chamber is started) may be reduced.

[0019] Preferably, the step of pumping fluid at the circulation pressure is performed in dependence on a measured or estimated amount of heat supplied to the fluid in the tank being greater than a threshold amount. The measured or estimated amount of heat supplied may be an amount of heat supplied after the step of pumping fluid at the operating pressure and/or an amount of heat supplied after a previous step of pumping fluid at the circulation pressure. Hence, circulation is performed when it is likely that the fluid is non-uniform (i.e. when sufficient heat has been supplied, the fluid is likely to have formed a temperature gradient in the tank). Thus, the energy required to perform circulation may be reduced as circulation is only performed when necessary.

[0020] Preferably, the calculation pressure is determined in dependence on a volume or height of fluid in the tank. Because the pumping pressure required to pump fluid through the circulation loop is dependent on the height of fluid (or fluid level) in the tank, a lower circulation pressure may be used when there is a large volume of fluid in the tank, allowing the circulation pumping power to be reduced.

[0021] In a second aspect, there is provided a washing apparatus for washing protective equipment, the washing apparatus comprising: a washing chamber for receiving the protective equipment, a tank for holding fluid, a pump unit for pumping the fluid from the tank into the washing chamber so as to wash the protective equipment, and a bypass circuit dividing a fluid connection between the tank and the washing chamber and forming a circulation loop back to the tank.

[0022] Preferably, the washing chamber comprises an outlet connected to a drain for discharging the fluid after the fluid has been pumped into the washing chamber.

[0023] Preferably, the bypass circuit is arranged such that a lower pump pressure is required to pump the fluid through the circulation loop than into the washing chamber.

[0024] Preferably, the pump unit is arranged upstream of the bypass circuit.

[0025] In a third aspect, there is provided a method of operating a washing apparatus for washing protective equipment, the method comprising: pumping fluid at an operating pressure from a tank of the washing apparatus to a washing chamber of the washing apparatus so as to wash the protective equipment, and pumping fluid, during a first predetermined time period, at an elevated pressure, higher than the operating pressure, from the tank to the washing chamber.

[0026] The method according to the third aspect is particularly suitable for washing apparatuses intended to wash equipment that is soiled and/or at least partially covered in particles such as dust, stone, and/or rock material. The particles may get stuck in the mechanics of the apparatus, hindering movable parts from rotating and/or moving as intended. The method according to the third aspect has been found to advantageously cause particles to come loose and allow the washing apparatus to function properly again. Thus the operational reliability of the washing apparatus is improved.

[0027] The elevated pressure may additionally, or alternatively, be used to alter or vary the washing pattern. Hence, the elevated pressure improves the efficiency of the washing of the protective equipment. For example, a higher spraying velocity may be used.

[0028] Preferably, the washing apparatus comprises at least one rotational wash arm for ejecting the fluid into the washing chamber, the ejecting of fluid causing the rotational washing arm to rotate. The method, and in particular the elevated pressure, has been found to be particularly advantageous in dislodging particles hindering rotational wash arms from rotating.

[0029] Preferably, the step of pumping fluid at the operating pressure is performed during a second predetermined time period. Preferably, the first predetermined time period is less than the second predetermined time period. For example, the first predetermined time period may be between 5 and 60 seconds, optionally between 10 and 45 seconds, optionally between 20 and 40 seconds, optionally about 30 seconds. For example, the second predetermined time period may be between 1 and 10 minutes, optionally between 1 and 5 minutes, optionally between 1 and 3 minutes, optionally about 2 minutes.

[0030] It is preferred to only operate the pump at the elevated pressure for relatively short intervals, to reduce the energy consumption of the pump unit.

[0031] Furthermore, periodic, and relatively short boosts have been found particularly suitable for making stuck particles come loose. Furthermore, by only operating at the elevated pressure for short intervals, components of the washing apparatus may be designed and/or dimensioned substantially only in dependence on the operating pressure. Thus, smaller components, such as smaller pump units, may be used in the washing apparatus.

[0032] Preferably, the elevated pressure is between 5% and 40%, optionally between 10% and 30%, optionally between 15% and 25%, optionally about 20%, higher than the operating pressure. This ensures that the boost is efficient in removing stuck particles, while not risking damage to the components of the washing apparatus.

[0033] Preferably, the method further comprises a subsequent step of pumping fluid at the operating pressure from the tank to the washing chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to best describe the manner in which the above-described embodiments are implemented, as well as define other advantages and features of the disclosure, a more particular description is provided below and is illustrated in the appended drawings. Understanding that these drawings depict only exemplary embodiments of the invention and are not therefore to be considered to be limiting in scope, the examples will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

Fig. 1

shows a washing apparatus according to embodiments;

Fig. 2

shows a washing apparatus according to embodiments;

Fig. 3

shows a washing apparatus according to embodiments;

Fig. 4

shows a method of operating a washing apparatus according to embodiments;

Fig. 5

shows pumping pressure as a function of time during operation of a washing apparatus according to embodiments;

Fig. 6

shows a washing apparatus according to embodiments;

Fig. 7

shows a method of operating a washing apparatus according to embodiments; and

Fig. 8

shows pumping pressure as a function of time during operation of a washing apparatus according to embodiments.

[0035] Further, in the figures like reference characters designate like or corresponding elements or parts throughout the several figures. The first digit in the reference character denotes the first figure in which the corresponding element or part appears.

DETAILED DESCRIPTION

[0036] Various embodiments of the disclosed methods and arrangements are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components, configurations, and steps may be used without parting from the spirit and scope of the claimed invention.

[0037] Hereinafter, certain embodiments will be described more fully with reference to the accompanying drawings. It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the inventive concept. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice disclosed herein. It is to be understood that elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed or omitted, certain features may be utilized independently, and embodiments or features of embodiments may be combined, all as would be apparent to the skilled person in the art.

[0038] The embodiments herein are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept, and that the claims be construed as encompassing all modifications, equivalents and alternatives of the present inventive concept which are apparent to those skilled in the art to which the inventive concept pertains. If nothing else is stated, different embodiments may be combined with each other.

[0039] The present disclosure relates to cleaning, washing, and/or decontamination of protective equipment, such as personal protective equipment. The protective equipment includes protective equipment used in, for example, firefighting, health care, mining, quarrying, and/or chemical industries.

[0040] The term "protective equipment" as used herein refers to any equipment used in industry to protect a worker from environments where hazardous substances, such as hazardous gases, hazardous liquids, and/or hazardous particles, are present.

[0041] For example, protective equipment includes self-contained breathing apparatuses (SCBA), helmets, face masks, boots, goggles, visors, breathing masks, respirators, breathing tubes, and/or gloves.

[0042] The protective equipment may be at least partially covered by hazardous substances, including dust particles, soot particles and rest products from combustion processes. Some of these substances include hazardous toxins and/or carcinogens, such as polycyclic aromatic hydrocarbons (PAH) particles. The protective equipment may additionally, or alternatively, be heavily soiled. It is therefore particularly important that the protective equipment is properly cleaned.

[0043] Furthermore, particles, such as dust, stone or rock material may be brought into the washing process when cleaning the dirty protective equipment. These particles may impair the functioning and/or operational reliability of a washing apparatus configured to clean the protective equipment. In particular, large, course, rough, and/or sharp-edged particles may impair the functioning and/or operational reliability of the washing apparatus. However, also fine particles such as dust or ash, may cause problems by forming clay, mud, or the like.

[0044] A washing apparatus for cleaning protective equipment thus has fundamentally different requirements compared to traditional washing machines (i.e. for everyday clothes) and/or dishwashers (i.e. for kitchen utensils, ceramics, and glasses).

[0045] Fig. 1 shows a block diagram of a washing apparatus 100 according to embodiments. The washing apparatus 100 comprises a washing chamber 101, at least one tank 102, at least one pump unit 103, and at least one control unit 104.

[0046] The washing or cleaning of the protective equipment is performed in the washing chamber 101. The washing chamber 101 is accordingly configured to receive the protective equipment to be washed. For example, the washing chamber 101 may comprise one or more baskets or the like for holding the protective equipment.

[0047] The washing chamber 101 comprises at least one inlet for receiving a fluid or medium used in the wash cycle. The fluid or medium will henceforth be referred to as a fluid. It will be appreciated that the fluid may comprise particles, particulates, granules, or the like, in particular in the form of suspended particles, suspended particulates, suspended granules or the like.

[0048] The at least one inlet may comprise one or more rotatable wash arms 601 provided with nozzles for ejecting the fluid. The ejection of fluid may, during operation of the washing apparatus 100, cause the rotatable wash arms 601 to rotate. Preferably, the washing chamber 101 comprises two rotatable wash arms 601, located on different or opposite sides of the washing chamber 101 (e.g. at a bottom side and a top side) so as to allow fluid to be ejected from different sides.

[0049] The washing chamber 101 may additionally, or alternatively, comprise one or more fixed nozzles for ejecting the fluid into the washing chamber 101.

[0050] The washing chamber 101 further comprises an outlet for discharging fluid from the washing chamber 101. The outlet may be connected back to the tank 102 for circulation of fluid, i.e. the washing apparatus 100 may comprise a circulation loop 105. Additionally, or alternatively, the outlet may be connected to a drain 106 for disposing of the fluid.

[0051] The tank 102 is configured to store or hold fluid used in a wash cycle. The tank 102 may be any suitable container for storing or holding the fluid.

[0052] The tank 102 may be provided with one or more heaters configured to heat the fluid in the tank 102. Alternatively, or additionally, one or more heaters may be provided along the path of the fluid in the washing apparatus 100. For example, one or more heaters may be provided along a pipe connecting the tank 102 to the washing chamber 101, and/or one or more heaters may be provided in the circulation loop 105.

[0053] The tank 102 may further be provided with one or more sensors for measuring the temperature of the fluid in the tank 102.

[0054] The pump unit 103 is configured to pump the fluid from the tank 102 to the washing chamber 101. The pump unit 103 may comprise one or more pumps. The one or more pumps may be any suitable pumps for pumping the fluid at a pressure and flow rate suitable for washing the protective equipment in the washing chamber 101.

[0055] The control unit 104 is configured to control the pump unit 103. In particular, the control unit 104 is configured to control one or more pump parameters of the pump unit 103. For example, the control unit 104 may be configured to control the pumping pressure, pumping flow rate, pump speed, or a combination thereof. Preferably, the control unit 104 is configured to dynamically control the pump parameters. In other words, the pump unit 103 may be dynamically controlled.

[0056] The control unit 104 may further be configured to control other components or processes of the washing apparatus 100, such as the heaters for heating the fluid. The control unit 104 may further be configured to receive and/or process sensor readings (e.g. output signals from sensors) from one or more sensor in the washing apparatus 100, such as the one or more temperature sensors in the tank 102.

[0057] The fluid used in the washing apparatus 100 may comprise water, laundry detergent, washing chemicals, granules, dry cleaning agents, RO-water, disinfectant, soap, washing-up liquid, dish soap, dishwasher detergent, degreaser, ultrapure water, or a combination thereof.

[0058] The fluid may be a washing fluid and/or a rinsing fluid. The rinsing fluid may comprise substantially only water or ultrapure water. In particular the rinsing fluid may not be reused after having entered the washing chamber 101 and/or rinsed the equipment. Rather, the rinsing fluid may be discharged from the washing chamber 101 into a drain 106.

[0059] The path of the fluid during the wash cycle is indicated by the arrows in Fig. 1. It will be appreciated that only some of the shown fluid paths may be present in a washing apparatus 100 according to embodiments, as will be described in more detail later.

[0060] During a wash cycle, the fluid is pumped, by the pump unit 103, from the tank 102 into the washing chamber 101. The fluid may then be returned to the tank 102 through a circulation loop 105 such that the fluid can be reused. Alternatively, or additionally, the fluid may be discharged to a drain 106.

[0061] The washing apparatus 100 may further comprise a bypass circuit 107 dividing the flow between the tank 102 and the washing chamber 101. When present in the washing apparatus 100, the bypass circuit 107 is arranged to allow at least a portion of the fluid pumped by the pump unit 103 to return to the tank 102 through a circulation loop 105. The circulation loop 105 formed by the bypass circuit 107 may, or may not, be part of the same circulation loop 105 that connects the washing chamber 101 to the tank 102.

[0062] In embodiments, one or more of the fluid lines may be provided with valves. For example, a fluid line between the pump unit 103 and the washing chamber 101 may be provided with a valve. If a bypass circuit 107 is present, a valve may be provided on the fluid line between the pump unit 103 and the washing chamber 101 downstream of the fork of the bypass circuit 107. Additionally or alternatively, a fluid line between the washing chamber 101 and the drain 106 may be provided with a valve. Thus, when at least one of the valves are closed, fluid pumped by the pump unit 103 may be forced to circulate back to the tank 102 through the circulation loop 105 and/or the bypass circuit 107. In embodiments, at least one of the valves may be controlled (e.g. electronically) by the control unit 104.

[0063] The wash cycle may be separated into substantially two stages: a washing stage and a rinsing stage. For example, a first portion of the wash cycle may comprise the washing stage, and a second portion of the wash cycle may comprise the rinsing stage. Both the washing stage and the rinsing stage may be performed by the same washing apparatus 100. Alternatively, the washing stage may be performed by a first washing apparatus 100, and the rinsing stage may be performed by a second washing apparatus 100.

[0064] Fig. 2 shows a block diagram, including a flow circuit, of a washing apparatus 100, or a part of a washing apparatus 100, used in a washing stage of a wash cycle. The circuit shown in Fig. 2 may also be referred to as a washing fluid circuit.

[0065] The washing apparatus 100 comprises a wash tank 102a for holding a washing fluid. The wash tank 102a is substantially similar to the tank 102 of Fig. 1. The washing apparatus 100 further comprises a pump unit 103, a control unit 104, and a washing chamber 101 as previously described.

[0066] As indicated by the arrows in Fig. 2, the washing fluid is pumped, by the pump unit 103, from the wash tank 102a to the washing chamber 101. The washing fluid is then circulated back to the tank 102 through the circulation loop 105.

[0067] Although not shown in Fig. 2, the washing chamber 101 and/or the wash tank 102a may be connected to a drain 106 to allow the washing fluid to be discharged once it is deemed unsuitable for re-use.

[0068] Although not shown in Fig. 2, the washing fluid circuit may further comprise a bypass circuit 107 dividing a flow from the pump unit 103 to the washing chamber 101 to allow circulation therethrough.

[0069] Fig. 3 shows a block diagram, including a flow circuit, of a washing apparatus 100 used in a rinsing stage of a wash cycle. The circuit shown in Fig. 3 may also be referred to as a rinsing fluid circuit. The rinsing fluid circuit may be separate from the washing fluid circuit. Alternatively, the rinsing fluid circuit may share components, such as the pump unit 103, control unit 104, and/or washing chamber 101, with the washing fluid circuit.

[0070] The washing apparatus 100 comprises a rinse tank 102b for holding a rinsing fluid. The rinse tank 102b is substantially similar to the tank 102 of Fig. 1. The washing apparatus 100 further comprises a pump unit 103, a control unit 104, and a washing chamber 101 as previously described.

[0071] As indicated by the arrows in Fig. 3, the rinsing fluid is pumped, by the pump unit 103, from the rinse tank 102b to the washing chamber 101. From the washing chamber 101, the rinsing fluid may be discharged to a drain 106. In other words, the rinsing fluid entering the washing chamber 101 and/or being used to rinse the protective equipment therein, is preferably not re-used.

[0072] The washing apparatus 100 further comprises a bypass circuit 107. The bypass circuit 107 is arranged, in a first end, to divide a fluid connection between the rinse tank 102b and the washing chamber 101. The bypass circuit 107 is arranged in a second end, to form a circulation loop 105 back to the rinse tank 102b. That is, the bypass circuit 107 forms a secondary connection back to the rinse tank 102b allowing at least some of the rinsing fluid to pass through the bypass circuit 107 back to the rinse tank 102b without entering the washing chamber 101.

[0073] Preferably, the bypass circuit 107 comprises a fork (e.g. a three-way fork) in the fluid connection between the rinse tank 102b and the washing chamber 101.

[0074] Preferably, the bypass circuit 107 is arranged downstream of the pump unit 103. When the pump unit 103 is used, at least a portion of the rinsing fluid will flow through the bypass circuit 107 back to the rinse tank 102b without entering the washing chamber 101. The rinsing fluid, circulated through the bypass circuit 107, is thus not contaminated by any dirt, soot, or the like that may be present in the washing chamber 101.

[0075] Preferably, the bypass circuit 107 has a small cross-sectional area to ensure only a small portion of the flow is divided to the bypass circuit 107. Preferably, the cross-sectional area of the bypass circuit is less than the cross-sectional area of the fluid connection between the rinse tank 102b and the washing chamber 101, preferably less than 0.7 of the cross-sectional area of the fluid connection between the rinse tank 102b and the washing chamber 101, preferably less than 0.5 of the cross-sectional area of the fluid connection between the rinse tank 102b and the washing chamber 101, preferably less than 0.3 of the cross-sectional area of the fluid connection between the rinse tank 102b and the washing chamber 101.

[0076] Thus, the pump unit 103 may compensate for the loss of fluid to the washing chamber 101 by a small increase in the pumping pressure.

[0077] Preferably, the bypass circuit 107 is arranged such that rinsing fluid will flow through the bypass circuit 107 even when the pumping pressure is insufficient to pump the rinsing fluid into the washing chamber 101. In other words, a lower pumping pressure is required to pump the rinsing fluid through the bypass circuit 107 than to pump the rinsing fluid into the washing chamber 101.

[0078] Although the bypass circuit 107 has been described in relation to the rinsing fluid circuit of Fig. 3, it will be appreciated that a bypass circuit may also be provided in the washing fluid circuit of Fig. 2. A bypass circuit may thus be arranged to allow at least a portion of the fluid pumped by the pump unit 103 to return to the wash tank 102a.

[0079] Fig. 4 shows a method of operating a washing apparatus 100 according to embodiments.

[0080] In step 401, the pump unit 103 is operated so as to pump fluid at an operating pressure from the tank 102 to the washing chamber 101. The operating pressure is sufficient to eject fluid into the washing chamber 101 at a sufficiently high velocity to satisfactorily wash or clean the protective equipment therein. In other words, the operating pressure is the default, nominal, or normal pressure used in a wash cycle for cleaning or washing protective equipment. Step 401 thus corresponds to normal operation of the washing apparatus 100 during which protective equipment is intended to be located in the washing chamber 101 and thereby being washed. Step 401 may thus also be referred to as a wash cycle.

[0081] In step 403, the pump unit 103 is operated so as to pump fluid at a circulation pressure from the tank 102 through the circulation loop 105 back to the tank 102. The circulation pressure is lower than the operating pressure. Step 403 may also be referred to as a circulation step or a circulation process. Preferably, step 403 is performed between two wash cycles. That is, during a time period when the washing apparatus 100 is not used, and/or intended to be used, to clean protective equipment.

[0082] The method may further comprise another subsequent step 405 during which step 401 is repeated. In other words, step 401 may be performed before and/or after step 403.

[0083] Step 403 may be repeated one or more times. Step 403 may be performed a plurality of time between a first wash cycle 401 and a second wash cycle 405. For example, step 403 may be repeated periodically between a first wash cycle 401 and a second wash cycle 405. Alternatively, or additionally, step 403 may be performed in response to one or more criteria being fulfilled, such that step 403 is repeated every time the one or more criteria are fulfilled.

[0084] The inventors have realised that a step of pumping fluid at the circulation pressure through the circulation loop 105 (i.e. step 403), will homogenise one or more properties of the fluid in the tank 102.

[0085] In conventional washing apparatuses, the washing apparatus will be idle between wash cycles. During this idle time period between wash cycles, the fluid in the tank will start forming layers with varying properties, e.g. gradients of one or more properties may be formed. The one or more properties may include temperature, pH-value, concentration of chemicals, or the like. For example, a temperature gradient will form in the tank because of the difference in density of the fluid with temperature. Similarly, a concentration (e.g. a concentration of chemicals or the like) gradient will form because of the difference in density of the fluid with concentration.

[0086] The gradients in the fluid in the tank may also be referred to as the fluid in the tank being non-homogeneous, heterogeneous, and/or non-uniform. The inventors have realised that the presence of non-homogenous fluid in the tank has several drawbacks.

[0087] First, the non-homogenous fluid makes it difficult to accurately measure properties of the fluid in the tank. For example, a measured temperature by a sensor near the top of the tank will be different from a measured temperature by a sensor near the bottom of the tank. Thus, when a user initiates another wash cycle, it is difficult to know, for example, how much the fluid should be heated before the wash cycle starts (i.e. to reach an operating temperature) and/or how much chemicals, detergent, or the like, that should be added to the fluid to reach a desired concentration. For example, if the fluid is heated such that the mean temperature of the fluid reaches the operating temperature, because of the non-uniformity of fluid temperature in the tank, some of the fluid will be hotter than the operating temperature, while some of the fluid will be colder than the operating temperature.

[0088] Second, when the wash cycle is started and fluid is pumped from the tank with non-homogenous fluid into the washing chamber to wash the protective equipment, a first volume of fluid pumped through the system and ejected into the washing chamber may have a different temperature than a second volume of fluid. Thus, the temperature of the fluid ejected into the washing chamber may vary throughout the wash cycle. This is undesirable because wash cycle has been configured to give optimal wash results at the operating temperature. Any deviation in the fluid temperature will thus affect the quality of the wash, leading to the protective equipment being insufficiently cleaned. For example, if some of the fluid is at a temperature colder than the operating temperature, the fluid may not be able to remove grease or the like from the protective equipment. Furthermore, if some of the fluid ejected into the washing chamber is hotter than the operating temperature, the high temperature may cause damage to temperature-sensitive protective equipment. For example, temperature sensitive equipment includes equipment with an antifog coating and/or other coating (e.g. visors with antifog or other coating), equipment with integrated electronics, equipment comprising parts at least partially made from thermoplastic elastomers, and the like.

[0089] The inventors have realised that the above-described drawbacks may be mitigated by circulating the fluid between wash cycles using a pump unit 103 configured to pump the fluid at a circulation pressure. Hence, the washing apparatus 100 according to embodiments (e.g. as shown in Figs. 1 to 3) utilises an otherwise idle time period between wash cycles to circulate fluid in the tank 102 such that one or more properties of the fluid in the tank 102 is homogenised or made more uniform.

[0090] This ensures that the fluid temperature remains substantially constant throughout a subsequent wash cycle. It also ensures that the quality of wash is adequate, and that the protective equipment is properly cleaned. It allows properties of the fluid (e.g. temperature and concentration) to be accurately measured, and accurately adjusted at the start of a wash cycle. Furthermore, it protects temperature-sensitive equipment from being damaged during the wash cycle.

[0091] To ensure good circulation of the fluid in the tank 102, it is preferable that the pump unit 103 is connected to a lower portion of the tank 102 such that fluid located near the bottom of the tank 102 is pumped into the washing chamber 101. Furthermore, the circulation loop 105 is preferably connected to an upper portion of the tank 102, thus circulated fluid is discharged near the top of the tank 102.

[0092] This is particularly preferable if the fluid has a lower density at higher temperature, which is true for most fluids. As the fluid will typically be colder after it has been circulated through the circulation loop 105 (due to e.g. heat being conducted to pipes and other components of the washing apparatus 100), it is preferable if the circulated fluid is discharged near the top of the tank 102, facilitating circulation by convection.

[0093] Between wash cycles, the washing apparatus 100 may further be configured to heat the fluid in the tank 102, by one or more heaters, to substantially maintain the operating temperature. For example, heating may take place during step 403, between steps 401 and 403, between steps 403 and 405, and/or between subsequent steps 403.

[0094] By maintaining the fluid temperature at, or close to, the operating temperature, less heat needs to be supplied to start the wash cycle. Hence a time required to start the wash cycle (i.e. the time between the wash cycle is initiated by a user and the pumping of fluid into the washing chamber 101 is started) may be reduced.

[0095] Because circulation occurs in the tank 102 (i.e. pumping through the circulation loop 105 at circulation pressure), and the fluid in the tank 102 thereby has substantially homogeneous temperature, it can be determined using simple estimations and optionally measurement from e.g. one temperature sensor, when heating is necessary to maintain the operating temperature. In conventional washing apparatuses, on the other hand, it would be difficult to determine if heating of the fluid in the tank should be performed during an idle time period (i.e. in between wash cycles when no circulation occurs). Due to the non-uniform temperature of the fluid in the tank, it would, in conventional washing apparatuses, be impossible to determine, based on a temperature measurement from e.g. one sensor, if heating would be required to maintain the operating temperature. If heating of the fluid in the tank was performed during an idle time period of a conventional washing apparatus, there would be a risk that at least a portion of the fluid was heated too much, necessitating a cooling period before a wash cycle could be initiated.

[0096] The heating, in the washing apparatus 100 according to embodiments, can also advantageously compensate for any heat losses due to the fluid circulating through the circulation loop 105.

[0097] Fig. 5 shows the pumping pressure as a function of time during operation of a washing apparatus 100 according to embodiments. The operating pressure is denoted Po and the circulation pressure is denoted Pc.

[0098] Fig. 5a shows a washing apparatus 100 configured to pump at the circulation pressure during substantially the whole time between two wash cycles. That is, the washing apparatus 100 is configured to perform a first wash cycle (corresponding to step 401) by pumping fluid at the operating pressure. The washing apparatus 100 is then configured to perform circulation by pumping fluid at the circulation pressure (corresponding to step 403), until a second wash cycle is initiated by a user which causes the washing apparatus 100 to again pump fluid at the operating pressure (corresponding to step 405).

[0099] The operating pressure may be split into two components. The first component is the (total) pressure required for the fluid to reach the inlet to the washing chamber 101. That is, the pressure required to overcome any pressure losses, e.g. any hydrostatic pressure losses and/or friction losses experienced by the fluid between the tank 102 and the inlet to the washing chamber 101. The second component is the (total) pressure of the fluid at the inlet to the washing chamber 101 and may be referred to as the ejecting pressure or spraying pressure. That is, the pressure at which the fluid is ejected or sprayed into the washing chamber 101 The ejecting pressure or spraying nozzle may also be referred to as the dynamic pressure at the inlet to the washing chamber 101.

[0100] The circulation pressure is lower than the operating pressure, but sufficient to allow the fluid to flow through the circulation loop 105. The circulation pressure may be less than 0.5 of the operating pressure, optionally less than 0.2 of the operating pressure, optionally less than 0.1, of the operating pressure.

[0101] The circulation pressure may alternatively, additionally, be less than twice, optionally less than 1.5, optionally less than 1.2, optionally less than 1.1, optionally less than 1, optionally less than 0.9, optionally less than 0.7, optionally less than 0.5 of the pressure required to pump the fluid from the tank 102 to the inlet of the washing chamber 101 (i.e. the first component of the operating pressure).

[0102] Optionally the circulation pressure may be substantially equal to the pressure required to pump the fluid from the tank 102 to the inlet of the washing chamber 101 (i.e. the first component of the operating pressure), i.e. the pressure required to overcome any pressure losses, e.g. any hydrostatic pressure losses and/or friction losses experienced by the fluid between the tank 102 and the inlet to the washing chamber 101.

[0103] Additionally, or alternatively, the circulation pressure may be determined in dependence on a volume or height (e.g. the fluid level in the tank) of fluid in the tank 102. For example, the circulation pressure may be relatively higher when there is a relatively smaller volume of fluid in the tank than when there is a relatively larger volume of fluid in the tank. Thus, the circulation pressure may compensate for an increase in hydrostatic pressure losses experienced when there is a relatively small amount of fluid in the tank. In other words, the circulation pressure may compensate for a change in hydrostatic pressure losses due to a varied fluid level in the tank.

[0104] The circulation pressure may, if wash arms are present in the washing apparatus, alternatively, or additionally, be substantially insufficient to cause the rotational washing arms at the washing chamber 101 inlet to rotate. That is, if the fluid reaches the inlet of the washing chamber 101 when pumped at the circulation pressure, the circulation pressure is insufficient to allow the fluid to be ejected or sprayed into the washing chamber 101 through the rotational wash arms 601 with such pressure and/or velocity to cause the wash arms 601 to rotate.

[0105] If a bypass circuit 107 is present in the washing apparatus, the circulation pressure may alternatively, or additionally, be sufficient to pump the fluid through the circulation loop 105 formed by the bypass circuit 107, but substantially insufficient to pump the fluid into the washing chamber 101. Preferably, the circulation pressure is less than 1, optionally less than 0.9, optionally less than 0.7, optionally less than 0.5 of the pressure required to pump the fluid from the tank 102 to the inlet of the washing chamber 101 (i.e. the pressure required to overcome any pressure losses between the tank 102 and the inlet of the washing chamber 101 including e.g. hydrostatic pressure losses and/or frictional pressure losses). Additionally, the circulation pressure may be substantially equal to or larger than a pressure required to overcome any pressure losses (e.g. hydrostatic pressure losses, and/or frictional pressure losses) experienced through the circulation loop 105 formed by the bypass circuit 107 to allow the fluid to flow through the bypass circuit 107.

[0106] Fig. 5b shows a washing apparatus 100 configured to pump at the circulation pressure during a part of a time period between two wash cycles.

[0107] The washing apparatus 100 is configured to perform a first wash cycle (corresponding to step 401) by pumping fluid at the operating pressure.

[0108] After the first wash cycle, the washing apparatus 100 is configured to not pump fluid (i.e. be idle or substantially idle) until a circulation criterion has been fulfilled. When the circulation criterion has been fulfilled, the washing apparatus 100 is configured to perform circulation by pumping fluid at the circulation pressure (corresponding to step 403). The washing apparatus 100 may be configured to perform circulation until a non-circulation criterion is fulfilled. Circulation (i.e. step 403) may be performed one or more times before a user initiates a second wash cycle causing the washing apparatus 100 to again pump fluid at the operating pressure (corresponding to step 405). For example, circulation may be performed every time the circulation criterion is fulfilled.

[0109] The circulation criterion may be a predetermined time from an end of a wash cycle and/or from an end of a previous circulation. The washing apparatus 100 may, for example, be configured to perform circulation according to a predetermined time schedule, such as performing circulation every 10 minutes, every 5 minutes, every 3 minutes, every 2 minutes, every minute, every 30 seconds, or the like.

[0110] Alternatively, or additionally, the pump unit may be configured to start the circulation step based on an estimated and/or measured amount of heat supplied to the fluid in the tank. For example, the circulation may start when the amount of heat supplied to the fluid in the tank exceeds a threshold amount. The amount of heat supplied may be an amount of heat supplied since the end of a previous wash cycle and/or an amount of heat supplied since the end of a previous circulation step 403.

[0111] Alternatively, or additionally, the circulation criterion may be based on a measured and/or estimated temperature of the fluid in the tank 102. For example, the pump unit may be configured to start the circulation step when a measured and/or estimated temperature of the fluid in the tank exceeds a threshold amount. The estimated temperature may be determined in dependence on an estimated and/or measured amount of heat supplied and/or an estimated and/or measured volume of fluid in the tank.

[0112] Alternatively, or additionally, the circulation criterion may be based on a deviation between a measured temperature of the fluid in the tank 102 and an estimated temperature of the fluid in the tank 102. In particular, the circulation criterion may be a deviation between a measured temperature of the fluid in the tank 102 and an estimated temperature of the fluid in the tank 102 exceeding a threshold.

[0113] The measured temperature may be measured by one or more temperature sensors arranged to measure a temperature of the fluid in the tank 102.

[0114] The estimated temperature may be determined in dependence on a measured or estimated heat supplied to the fluid in the tank 102 using one or more heaters, and a fluid amount or volume in the tank 102.

[0115] For example, the amount of supplied heat may be measured by any type of power or energy meter. As another example, the amount of heat supplied may be determined in dependence on a (measured or estimated) voltage supplied to the heater, an electrical resistance of the heater, or the like.

[0116] The estimated amount of heat supplied and/or the estimated temperature may further take into account estimated heat losses, such as conductive and/or convectional heat losses, to the surrounding environment. Examples of such heat losses include heating of surrounding air, heating of the tank 102 structure, heating of nearby components of the washing apparatus 100, or the like.

[0117] If no heat is supplied to the fluid in the tank 102, the estimated temperature may be based on estimated heat losses.

[0118] The inventors have realised that, when (i) a sufficient amount of heat has been supplied, (ii) the temperature is sufficiently high, and/or (iii) the measured temperature deviates from the estimated temperature by a threshold amount, the fluid in the tank 102 is likely to be non-homogenous, i.e. a temperature gradient is likely to exist. Thus, either of the parameters (i)-(iii) exceed a threshold, the circulation step may be performed to ensure that the fluid in the tank 102 is circulated.

[0119] The non-circulation criterion, i.e. the criterion for ending the circulation step, may be based on a predetermined time from a start of the circulation step. For example, the washing apparatus 100 may be configured to perform the circulation step for a predetermined time, such as 5 seconds, 10 seconds, 20 seconds, 30 seconds, 45 seconds, 1 minute, 2 minutes, 3 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 1 hour, or the like.

[0120] The non-circulation criterion may alternatively, or additionally, be based on the deviation between the measured temperature of the fluid in the tank 102 and the estimated temperature of the fluid in the tank 102 being below the threshold. This indicates that the circulation has been performed sufficiently long for the fluid in the tank 102 to have a substantially uniform temperature.

[0121] Fig. 6 shows an exemplary washing apparatus 100 comprising both a washing fluid circuit (as previously described in relation to Fig. 2) and a rinsing fluid circuit (as previously described in relation to Fig. 3).

[0122] The washing apparatus 100 comprises a washing chamber 101 comprising at least two inlets. Each inlet may be provided with a rotational wash arm 601. One wash arm 601 is arranged near the top of the washing chamber 101 and one wash arm 601 is arranged near the bottom of the washing chamber 101. Alternatively, the inlets may comprise fixed nozzles.

[0123] A control unit 104 (not shown) is configured to control a pump unit 103a of the washing fluid circuit and a pump unit 103b of the rinsing fluid circuit. In embodiments, one pump unit 103 may be used to pump fluid in both the washing fluid circuit and the rinsing fluid circuit.

[0124] The washing fluid circuit comprises a wash tank 102a for holding washing fluid and a pump unit 103a for pumping the washing fluid. The washing apparatus 100 comprises fluid connections (e.g. pipes) from the wash tank 102a to both inlets of the washing chamber 101 (i.e. to both the rotational wash arms 601), as indicated by the solid arrows in Fig. 6, to allow the washing fluid to flow to both inlets (i.e. to both rotational wash arms 601). Furthermore, an outlet 602 of the washing chamber 101 is connected to the wash tank 102a thus forming a circulation loop 105.

[0125] During the washing stage of a wash cycle, the pump unit 103a pumps the washing fluid at the operating pressure to both rotational wash arms 601 where the fluid is ejected into the washing chamber 101 at high speed so as to wash the protective equipment located therein. The pressure of the washing fluid is sufficient to cause the rotational wash arms 601 to rotate, thus ensuring that fluid is ejected from multiple directions.

[0126] Between wash cycles, the pump unit 103a is configured to pump the washing fluid at a first circulation pressure so as to circulate the washing fluid in the wash tank 102a, as previously described. The first circulation pressure is preferably sufficient to allow the washing fluid to enter the washing chamber 101. The washing fluid thereafter flows through the outlet of the washing chamber 101 back into the wash tank 102a.

[0127] Preferably, the circulation pressure allows washing fluid to reach only the lower wash arm 601. Note that the upper wash arm 601 is located at a higher vertical position than the lower wash arm 601, and at a further higher vertical position than the wash tank 102a.

[0128] Preferably, the first circulation pressure thus substantially corresponds to the pressure required to pump the washing fluid into the washing chamber 101 through the lower rotational wash arm 601. In other words, the first circulation pressure is substantially the pressure required to reach the lower inlet of the washing chamber 101. It is preferable for the first circulation pressure to not be significantly higher than the pressure required to pump the washing fluid into the washing chamber 101 through the rotational wash arm 601, since a higher pressure would involve higher power and/or energy consumption of the pump unit 103. The circulation pressure may therefore preferably be less than twice, optionally less than 1.5, optionally less than 1.2, optionally less than 1.1, optionally substantially 1, of the pressure required to pump the fluid from the tank 102 to the inlet of the washing chamber 101.

[0129] Preferably, the first circulation pressure is substantially insufficient to cause the rotational wash arms 601 to rotate. For example, the pressure at the inlet to the washing chamber 101 during the circulation step may be less than 20%, optionally less than 10%, optionally less than 5%, optionally less than 2%, than the ejecting or spraying pressure of the operating pressure during the washing stage of a wash cycle.

[0130] If the washing fluid circuit additionally comprises a bypass circuit (not shown in Fig. 6), the first circulation pressure may be insufficient to pump fluid into the washing chamber 101 and/or reaching the washing chamber 101 inlet. Thus, the first circulation pressure may be less than 1, optionally less than 0.9, optionally less than 0.7, optionally less than 0.5 of the pressure required to pump the fluid from the tank 102a to the inlet of the washing chamber 101 (i.e. the first component of the operating pressure, or in other words, the pressure required to overcome any pressure losses between the tank 102a and the inlet of the washing chamber 101 including e.g. hydrostatic pressure losses and/or frictional pressure losses). The first circulation pressure may also be sufficiently large to pump the washing fluid through the bypass circuit.

[0131] Note that the bypass circuit may be located at a vertically lower height than the inlets to the washing chamber 101, similarly to the bypass circuit 107 of the rinsing fluid circuit, requiring less pressure to pump the washing fluid through the bypass circuit than into the washing chamber 101. The first circulation pressure may therefore be substantially equal to or larger than a pressure required to overcome any pressure losses (e.g. hydrostatic pressure losses, and/or frictional pressure losses) experienced through the circulation loop 105 formed by the bypass circuit. In other words, the first circulation pressure may preferably be sufficient to pump the washing fluid through the circulation loop 105 formed by the bypass circuit, but substantially insufficient to pump the washing fluid into the washing chamber 101.

[0132] The rinsing fluid circuit, on the other hand, comprises a rinse tank 102b for holding rinsing fluid and a pump unit 103b for pumping the rinsing fluid. The washing apparatus 100 comprises fluid connections (e.g. pipes) from the rinse tank 102b to both of the rotational wash arms 601, as indicated by the dotted arrows in Fig. 6, to allow the rinsing fluid to flow to both rotational wash arms 601. Furthermore, a bypass circuit 107 divides the fluid connection to the two inlets of the washing chamber 101, and provides a fluid connection back to the rinse tank 102b so as to form a circulation loop 105.

[0133] During the rinsing stage of a wash cycle, the pump unit 103b pumps the rinsing fluid at the operating pressure to both rotational wash arms 601 where the rinsing fluid is ejected into the washing chamber 101 at high speed so as to rinse the protective equipment located therein. The pressure of the rinsing fluid is sufficient to cause the rotational wash arms 601 to rotate, thus ensuring that rinsing fluid is ejected from multiple directions.

[0134] Between wash cycles, the pump unit 103b is configured to pump the rinsing fluid at a second circulation pressure so as to circulate the rinsing fluid in the rinse tank 102b, as previously described. The second circulation pressure is preferably lower than the first circulation pressure.

[0135] The second circulation pressure is preferably insufficient to pump fluid into the washing chamber 101 and/or reaching the washing chamber 101 inlet, because rinsing fluid entering the washing chamber 101 may become contaminated by dirt, soot or the like in the washing chamber 101, and may therefore be discharged to a drain 106 rather than to be re-circulated and re-used. Thus, if the second circulation pressure is sufficiently large to allow the rinsing fluid to enter the washing chamber 101, rinsing fluid may be wasted leading to a large water consumption. Thus, the second circulation pressure is preferably less than 1, optionally less than 0.9, optionally less than 0.7, optionally less than 0.5 of the pressure required to pump the fluid from the tank 102 to the inlet of the washing chamber 101 (i.e. the first component of the operating pressure, or in other words, the pressure required to overcome any pressure losses between the tank 102 and the inlet of the washing chamber 101 including e.g. hydrostatic pressure losses and/or frictional pressure losses).

[0136] The second circulation pressure is also sufficiently large to pump the rinsing fluid through the bypass circuit 107. Note that the bypass circuit 107 is located at a vertically lower height than the inlets to the washing chamber 101. Thus less pressure is required to pump the rinsing fluid through the bypass circuit 107 than into the washing chamber 101. The second circulation pressure may therefore be substantially equal to or larger than a pressure required to overcome any pressure losses (e.g. hydrostatic pressure losses, and/or frictional pressure losses) experienced through the circulation loop 105 formed by the bypass circuit 107.

[0137] In other words, the second circulation pressure is preferably sufficient to pump the rinsing fluid through the circulation loop 105 formed by the bypass circuit 107, but substantially insufficient to pump the rinsing fluid into the washing chamber 101.

[0138] Fig. 7 shows a method of operating a washing apparatus 100 according to embodiments. The method of Fig. 7 is a method of operating a washing apparatus 100 during a wash cycle.

[0139] The washing apparatus 100 may be similar or identical to the washing apparatus 100 that have been previously described. Alternatively, the washing apparatus 100 may be any other washing apparatus 100 suitable for washing protective equipment.

[0140] The method of Fig. 7 may be used in combination with, or independently of, the previously described method(s) of operating a washing apparatus 100.

[0141] In step 701, the pump unit 103 is operated so as to pump fluid at an operating pressure from the tank 102 to the washing chamber 101. The operating pressure is sufficient to eject fluid into the washing chamber 101 so as to wash and/or clean the protective equipment therein. In other words, the operating pressure is the default, nominal, or normal pressure used in during a wash cycle for cleaning or washing protective equipment. Step 701 thus corresponds to normal operation of the washing apparatus 100 during which protective equipment is intended to be located in the washing chamber 101 and thereby being washed.

[0142] In step 703, the pump unit 103 is operated so as to pump fluid at an elevated pressure from the tank 102 to the washing chamber 101. The elevated pressure is higher than the operating pressure. Pumping at the elevated pressure may also be seen as a boost or turbo. Step 703 may thus also be referred to as a boosting step or a turbo step.

[0143] Step 703 preferably occurs during the wash cycle of the washing apparatus 100. That is, protective equipment is intended to be located in the washing chamber 101 and thereby being washed during step 703 in addition to step 701.

[0144] The method may further comprise another subsequent step 705 during which step 701 is repeated.

[0145] The method of Fig. 7 may be repeated one or more times during and/or between one or more wash cycles.

[0146] The method of Fig. 7, and in particular step 703, improves the operational reliability of a washing apparatus 100 when washing protective equipment, and in particular protective equipment that is soiled and/or at least partially covered in particles such as dust, stone, and/or rock material. In particular, large, course, rough, and/or sharp-edged particles may impair the functioning and/or operational reliability of a washing apparatus 100. However, also fine particles such as dust, may cause problems by forming clay, mud, or the like.

[0147] These particles are brought into the washing apparatus 100 by the protective equipment and are removed from the protective equipment during the washing cycle. The particles are thus carried by the fluid pumped into the washing chamber 101, which may circulate through the different parts of the washing apparatus 100. The particles may thus get stuck in the mechanics of the apparatus, for example hindering movable parts (e.g. pumps, rotatable wash arms) from rotating/moving as intended or making the rotation/movement incomplete.

[0148] The boost of step 703 using an elevated pressure has been found to advantageously cause the particles to come loose and allow the washing apparatus 100 to function properly again. Thus the operational reliability of the washing apparatus 100 is improved.

[0149] The above-described problems with particles impairing the functioning of a washing apparatus are particularly prone to happen in washing apparatuses using rotational wash arms 601. The particles may enter bearing means of the rotational wash arms 601, impairing the rotation of the wash arms 601. Hence, as the wash arms 601 are hindered from rotating, fluid ejected by the wash arms 601 is only ejected in specific directions causing the protective equipment to be inadequately cleaned and/or washed.

[0150] Fig. 8 shows pumping pressure as a function of time during an exemplary wash cycle according to embodiments.

[0151] After the wash cycle has been initiated, the pump unit 103 operates at the operating pressure, denoted Po in Fig. 8. That is, fluid is pumped to the washing chamber 101 at the operating pressure. This corresponds to step 701.

[0152] Thereafter, the pump unit 103 is configured to operate at an elevated pressure, denoted P_E in Fig. 8, which is higher than the operating pressure. The elevated pressure may be maintained for a first predetermined time period, denoted t₁ in Fig. 8. This corresponds to the boost of step 703.

[0153] The elevated pressure may be between 5% and 40%, optionally between 10% and 30%, optionally between 15% and 25%, optionally about 20%, higher than the operating pressure. This ensures that the boosts are efficient in removing stuck particles, while not risking any sort of damage to the components of the washing apparatus 100.

[0154] After the first predetermined time period, i.e. when the boost is completed, the pump unit 103 is configured to return to the operating pressure.

[0155] During the wash cycle, the pump unit 103 may be configured to perform a plurality of boosts. In particular, the boosts may be performed at periodic intervals. For example, a time between two subsequent boosts may be a second predetermined time, denoted t₂ in Fig. 8. The periodically increased pressure during the wash cycle facilitates the removal of particles stuck in rotating and/or moving parts of the washing apparatus 100, such as the rotational wash arms 601, thereby promoting the functionality of the wash arms 601 and/or the washing apparatus 100.

[0156] Preferably, the first predetermined time period is shorter than the second predetermined time period. For example, the first predetermined time period may be between 5 and 60 seconds, optionally between 10 and 45 seconds, optionally between 20 and 40 seconds, optionally about 30 seconds. The second predetermined time period may be between 1 and 10 minutes, optionally between 1 and 5 minutes, optionally between 1 and 3 minutes, optionally about 2 minutes.

[0157] It is preferred to only operate the pump unit 103 at the elevated pressure for relatively short intervals, to reduce the energy consumption of the pump unit 103. Furthermore, periodic and relatively short boosts have been found particularly suitable for making stuck particles come loose.

[0158] By only operating at the elevated pressure for short intervals, components of the washing apparatus 100 may be designed and/or dimensioned substantially only in dependence on the operating pressure. Thus, smaller components, such as smaller pump units 103, may be used in the washing apparatus 100, without encountering problems that might occur if the same components were operated at the elevated pressure continuously. In other words, the periodic and short intervals of elevated pressure allow the components in the washing apparatus 100 to be utilised to their full potential. The short intervals of elevated pressure also reduce the risk of damage to the components.

[0159] The elevated pressure may additionally, or alternatively, be used to alter or vary the washing pattern. In other words, by ejecting fluid into the washing chamber 101 at an elevated pressure, the velocity of the fluid being ejected or sprayed into the washing chamber 101 can be changed (e.g. increased). Furthermore, because of the elevated pressure, the rotational speed of the rotational wash arms 601 may increase. This allows the fluid to hit the protective equipment in new and/or different locations and/or directions compared to when the fluid is pumped at the operating pressure. Hence, the elevated pressure improves the efficiency of the washing of the protective equipment. Similarly, if the washing apparatus 100 is operated at the elevated pressure between, or outside of, wash cycles, the increased rotational speed and/or the varied wash pattern, may be used to clean the washing chamber 101, for example during a self-cleaning program.

[0160] It will be appreciated that although reference have been made to protective equipment, the washing apparatus according to embodiments may also be used to wash other types of goods.

[0161] Throughout this specification, the word "may" is used in a permissive sense (i.e. meaning having the potential to), rather than in the mandatory sense (i.e. meaning must).

[0162] Throughout this specification, the words "comprise", "include", and variations of the words, such as "comprising" and "comprises", "including", "includes", do not exclude other elements or steps.

[0163] As used throughout this specification, the singular forms "a", "an", and "the", include plural referents unless explicitly indicated otherwise. Thus, for example, reference to "an" element includes a combination of two or more elements, notwithstanding use of other terms and phrases for one or more elements, such as "one or more" or "at least one".

[0164] The term "or" is, unless indicated otherwise, non-exclusive, i.e. encompassing both "and" and "or". For example, the feature "A or B" includes feature "A", feature "B" and feature "A and B".

[0165] Unless otherwise indicated, statements that one value or action is "based on", "in response to" and/or "in dependence on" another condition or value or action, encompass both instances in which the condition or value or action is the sole factor and instances where the condition or value or action is one factor among a plurality of factors.

[0166] Unless otherwise indicated, statements that "each" instance of some collection have some property should not be read to exclude cases where some otherwise identical or similar members of a larger collection do not have the property, i.e. each does not necessarily mean each and every.

[0167] Embodiments include the following numbered clauses:

1. A method of homogenizing at least one property of a fluid in a tank of a washing apparatus for washing protective equipment, the fluid being a fluid for washing of the protective equipment, the method comprising the steps of:

pumping fluid at an operating pressure from the tank to a washing chamber of the washing apparatus configured to receive the protective equipment so as to wash the equipment; and

pumping fluid at a circulation pressure from the tank through a circulation loop back to the tank, wherein the circulation pressure is lower than the operating pressure.

2. The method of clause 1, wherein the step of pumping fluid at the circulation pressure is performed during a time period when equipment is not washed by the washing apparatus, and/or outside of a washing cycle of the washing apparatus.

3. The method according to clause 1 or 2, wherein the circulation pressure is less than 0.5 of the operating pressure, optionally less than 0.2 of the operating pressure, optionally less than 0.1 of the operating pressure.

4. The method according to any preceding clause, wherein the circulation pressure is less than 2, optionally less than 1.5, optionally less than 1.2, optionally less than 1.1, optionally less than 1, optionally less than 0.9, optionally less than 0.7, optionally less than 0.5, of a pressure required to pump the fluid from the tank to an inlet of the washing chamber.

5. The method according to any preceding clause, wherein the washing apparatus comprises one or more rotational wash arm for ejecting the fluid into the washing chamber, wherein the operating pressure is sufficient to cause the one or more rotational wash arms to rotate by the fluid being ejected therefrom, and wherein the circulation pressure is substantially insufficient to cause at least one of the one or more rotational wash arms to rotate.

6. The method according to any preceding clause, wherein the circulation loop is at least partially formed by a bypass circuit dividing a flow between the tank and the washing chamber.

7. The method according to any preceding clause, wherein the circulation pressure is sufficient to pump fluid through the circulation loop but substantially insufficient to pump fluid into the washing chamber.

8. The method according to any preceding clause, wherein during the step of pumping fluid at the operating pressure, the fluid is discharged to a drain after having entered the washing chamber.

9. The method according to any preceding clause, wherein the circulation loop is at least partially formed by a return circuit connecting an outlet of the washing chamber to the tank.

10. The method according to any preceding clause, wherein a pressure at the inlet to the washing chamber caused by the circulation pressure is less than 20%, optionally less than 10%, optionally less than 5%, optionally less than 2%, than a pressure at the inlet to the washing chamber caused by the operating pressure.

11. The method according to any preceding clause, wherein the method further comprises a step of heating the fluid in the tank.

12. The method according to any preceding clause, wherein the step of pumping fluid at the circulation pressure is performed in dependence on a measured or estimated amount of heat supplied to the fluid in the tank being greater than a threshold amount,

13. The method according to any preceding clause, wherein the measured or estimated amount of heat supplied is an amount of heat supplied after the step of pumping fluid at the operating pressure and/or an amount of heat supplied after a previous step of pumping fluid at the circulation pressure.

14. The method according to any preceding clause, wherein the circulation pressure is determined in dependence on a volume or height of fluid in the tank.

15. A washing apparatus for washing protective equipment, the washing apparatus comprising:

a washing chamber for receiving the protective equipment,

a tank for holding fluid,

a pump unit for pumping the fluid from the tank into the washing chamber so as to wash the protective equipment, and

a bypass circuit dividing a fluid connection between the tank and the washing chamber and forming a circulation loop back to the tank.

16. The washing apparatus according to clause 15, wherein the washing chamber comprises an outlet connected to a drain for discharging the fluid after the fluid has been pumped into the washing chamber.

17. The washing apparatus according to clause 15 or 16, wherein the bypass circuit is arranged such that a lower pump pressure is required to pump the fluid through the circulation loop than into the washing chamber.

18. The washing apparatus according to any of clauses 15 to 17, wherein the pump unit is arranged upstream of the bypass circuit.

19. A method of operating a washing apparatus for washing protective equipment, the method comprising:

pumping fluid at an operating pressure from a tank of the washing apparatus to a washing chamber of the washing apparatus so as to wash the protective equipment, and

pumping fluid, during a first predetermined time period, at an elevated pressure, higher than the operating pressure, from the tank to the washing chamber.

20. The method according to clause 19, wherein the washing apparatus comprises at least one rotational wash arm for ejecting the fluid into the washing chamber, the ejecting of fluid causing the rotational washing arm to rotate.

21. The method according to clause 19 or 20, wherein the step of pumping fluid at the operating pressure is performed during a second predetermined time period.

22. The method according to clause 21, wherein the first predetermined time period is less than the second predetermined time period.

23. The method according to any of clauses 19 to 22, wherein the first predetermined time period is between 5 and 60 seconds, optionally between 10 and 45 seconds, optionally between 20 and 40 seconds, optionally about 30 seconds.

24. The method according to any of clauses 21 to 23, wherein the second predetermined time period is between 1 and 10 minutes, optionally between 1 and 5 minutes, optionally between 1 and 3 minutes, optionally about 2 minutes.

25. The method according to any of clauses 19 to 24, wherein the elevated pressure is between 5% and 40%, optionally between 10% and 30%, optionally between 15% and 25%, optionally about 20%, higher than the operating pressure.

26. The method according to any of clauses 19 to 25, wherein the method further comprises a subsequent step of pumping fluid at the operating pressure from the tank to the washing chamber.

Claims

1. A method of homogenizing at least one property of a fluid in a tank of a washing apparatus for washing protective equipment, the fluid being a fluid for washing of the protective equipment, the method comprising the steps of:

pumping fluid at an operating pressure from the tank to a washing chamber of the washing apparatus configured to receive the protective equipment so as to wash the equipment; and

pumping fluid at a circulation pressure from the tank through a circulation loop back to the tank, wherein the circulation pressure is lower than the operating pressure.

2. The method of claim 1, wherein the step of pumping fluid at the circulation pressure is performed during a time period when equipment is not washed by the washing apparatus, and/or outside of a washing cycle of the washing apparatus.

3. The method according to claim 1 or 2, wherein the circulation pressure is sufficient to pump fluid through the circulation loop, but insufficient to wash equipment in the washing chamber, wherein optionally the circulation pressure is substantially insufficient to pump fluid into the washing chamber.

4. The method according to any preceding claim, wherein the washing apparatus comprises one or more rotational wash arm for ejecting the fluid into the washing chamber, wherein the operating pressure is sufficient to cause the one or more rotational wash arms to rotate by the fluid being ejected therefrom, and wherein the circulation pressure is substantially insufficient to cause at least one of the one or more rotational wash arms to rotate.

5. The method according to any preceding claim, wherein the circulation loop is at least partially formed by:

a bypass circuit dividing a flow between the tank and the washing chamber, and/or

a return circuit connecting an outlet of the washing chamber to the tank.

6. The method according to any preceding claim, wherein during the step of pumping fluid at the operating pressure, the fluid is discharged to a drain after having entered the washing chamber.

7. The method according to any preceding claim, wherein the method further comprises a step of heating the fluid in the tank.

8. The method according to any preceding claim, wherein the step of pumping fluid at the circulation pressure is performed in dependence on a measured or estimated amount of heat supplied to the fluid in the tank being greater than a threshold amount, wherein optionally the measured or estimated amount of heat supplied is an amount of heat supplied after the step of pumping fluid at the operating pressure and/or an amount of heat supplied after a previous step of pumping fluid at the circulation pressure.

9. The method according to any preceding claim, wherein the circulation pressure is determined in dependence on a volume or height of fluid in the tank.

10. A washing apparatus for washing protective equipment, the washing apparatus comprising:

a washing chamber for receiving the protective equipment,

a tank for holding fluid,

a pump unit for pumping the fluid from the tank into the washing chamber so as to wash the protective equipment, and

a bypass circuit dividing a fluid connection between the tank and the washing chamber and forming a circulation loop back to the tank.

11. A method of operating a washing apparatus for washing protective equipment, the method comprising:

pumping fluid at an operating pressure from a tank of the washing apparatus to a washing chamber of the washing apparatus so as to wash the protective equipment, and

pumping fluid, during a first predetermined time period, at an elevated pressure, higher than the operating pressure, from the tank to the washing chamber.

12. The method according to claim 19, wherein the washing apparatus comprises at least one rotational wash arm for ejecting the fluid into the washing chamber, the ejecting of fluid causing the rotational washing arm to rotate.

13. The method according to claim 19 or 20, wherein the step of pumping fluid at the operating pressure is performed during a second predetermined time period, wherein optionally the first predetermined time period is less than the second predetermined time period.

14. The method according to any of claims 19 to 22, wherein:

the first predetermined time period is between 5 and 60 seconds, optionally between 10 and 45 seconds, optionally between 20 and 40 seconds, optionally about 30 seconds; and/or

the second predetermined time period is between 1 and 10 minutes, optionally between 1 and 5 minutes, optionally between 1 and 3 minutes, optionally about 2 minutes.

15. The method according to any of claims 19 to 25, wherein the method further comprises a subsequent step of pumping fluid at the operating pressure from the tank to the washing chamber.

Drawing