Heating system

Abstract

 The present invention relates to a system for heating fluid, this comprising both liquids and gases. Such systems are generally known and are applied for instance in automatic milking systems in order to generate a steam surge for the purpose of thereby cleaning equipment, such as the milking cups of such an automatic milking system. A system according to the invention comprises for this purpose a heating chamber with a heating element; a feed which is connected to the heating chamber and via which the heating chamber can be selectively filled; and a discharge which is likewise connected to the heating chamber and via which fluid can be discharged from the heating chamber, wherein at least the discharge is connected at or at least close to the bottom of the heating chamber. Accumulation of residues can thus be effectively prevented in that they can be discharged each time heated fluid is removed from the heating chamber.

Description

[0001] The present invention relates to a system and a method for heating fluid, this comprising both liquids and gases. Such systems and methods are generally known and are applied for instance in automatic milking systems in order to generate a steam surge for the purpose of thereby cleaning equipment, such as the milking cups of such an automatic milking system. The use of fluid heated with the system is also referred to below as an external application in order to make clear that disinfection of milking cups is only one possible embodiment.

[0002] Known systems comprise a heating chamber with a heating element, a feed which is connected to the heating chamber and via which the heating chamber can be selectively filled (with fluid for heating); and a discharge which is likewise connected to the heating chamber and via which fluid can be discharged from the heating chamber. It is known that heated steam or gases and warmer heated liquid (gases and liquids are both fluids) accumulate in the upper part of a heating chamber. Because of this known systems have the discharge on an upper side thereof for the purpose of making available a quantity of steam or hot water for disinfecting milking cups or for other applications where a quantity of steam or heated liquid has to be provided.

[0003] The known systems further usually have complex and costly cleaning components in respect of the feed in order to minimize the quantities of residue in the heating chamber. However, despite these known prior art measures so many residues still remain in the heating chamber that operation thereof has to be regularly interrupted in order to clean the interior of the heating chamber. The residues accumulate at the bottom of the heating chamber, and cleaning often includes flushing out the interior of the heating chamber in an attempt to discharge the residues such as limescale, sand, grit and other more or less solid substances.

[0004] It is thus known from WO-01/63182 that an outlet, as addition to a discharge to a usable external application for the purpose of employing fluid heated in the chamber, is provided at the bottom of a heating chamber in order to be able to regularly interrupt the operation of the system known therefrom for the purpose of flushing the heating chamber. The discharge for providing heated fluid to a usable external application is after all connected at the top of the heating chamber, optionally via an upright pipe to an upper area in the heating chamber for the purpose of extracting heated fluid with certainty from the heating chamber when this is required for the usable external application. Fluid which has not yet been heated or is insufficiently heated can be present at the bottom of the heating chamber, so heated fluid is extracted (optionally via an upright pipe) from the chamber on the top side thereof.

[0005] The outlet is separate from and/or additional to a discharge to an active use of heated fluid in an external application, this increasing cost because of the large number of components. Flushing must further take place with substantially cold water, for which purpose the normal operation of providing heated fluid has to be interrupted and the supply and the outlet are both opened. The supply remains open so as to enable emptying of the heating chamber, this costing fluid for heating, and without this opening the emptying cannot be achieved because of underpressure in the heating chamber. It will thus be apparent that complete emptying is not achieved in this known system. This known system is further intended and designed for domestic use, where the temperatures to be reached of fluid for heating seldom come close to or exceed 60°C.

[0006] The necessity of regular interruption of the operation of the heating chamber detracts from the effectiveness and the efficiency of the system, in particular (though not exclusively) in applications where a quantity of heated fluid has to be generated at intervals, such as a steam surge for cleaning an udder of a cow with steam, while if the regularity of cleaning is decreased in order to increase effectiveness and efficiency there is the danger of residues causing permanent damage to the system. Professionals have heretofore found it to be an insoluble dilemma to develop a workable solution to these conflicting considerations, thereby creating the current situation where both manufacturers and users have resigned themselves to accepting that the lifespan of the known systems is very limited, even in the case the heating chamber is cleaned with great regularity.

[0007] The invention has for its object to obviate or at least reduce the above stated and/or other problems of the prior art, for which purpose a system according to the present invention is distinguished from the known systems at least in that at least the discharge is connected to the interior of the heating chamber at or at least close to the bottom of the heating chamber.

[0008] It is remarkable, and this testifies to a high degree of inventiveness, that a measure which in itself is so simply formulated can provide the solution to the stated (and possibly also other than stated) challenges, contradictions and problems of and with the known systems. It is nevertheless the case that according to the invention residues are discharged each time (a surge of) steam or heated liquid is discharged from the heating chamber via the discharge, whereby continuous operation has become possible. After all, the desired steam or heated liquid is made available with a small quantity of solid or similar substances for the intended purpose, such as the disinfection of milking cups, without these substances thus forming residues in the heating chamber. The substances are suctioned away together with each charge of heated liquid or gas or vapour, and gravitational force also assists here in discharging the substances from the heating chamber. This is particularly (though not exclusively) the case when the system is utilized in a type of cyclic operation to heat a quantity of fluid at a time in the chamber, which is completely closed for this purpose. Only when a desired temperature has been reached, so as to for instance generate steam, is the discharge (and preferably only the discharge) opened to make the heated fluid available for the external application and to simultaneously discharge residues in favourable manner each time a quantity of heated fluid is released. Cleaning of the heating chamber therefore takes place substantially continuously here, which provides great advantages compared to the above cited prior art.

[0009] In a preferred and therefore non-limitative embodiment the system according to the invention has the feature that the discharge comprises a discharge valve with which connection of the discharge to the heating chamber can be selectively opened and closed. As soon as the discharge valve is opened in order to provide heated liquid and/or steam to an external application (such as disinfection of milking cups), a pressure drop occurs provided the heating chamber is completely closed and pressure is increased therein by heating of the liquid therein, whereby in association with a temperature reached in the heating chamber a liquid therein rapidly changes to vapour or steam. There occurs as it were a controlled explosion under the influence of the pressure prevailing in the heating chamber, whereby liquid and vapour or steam are driven out of the heating chamber. It is noted that in the known systems the supply is also opened when steam and/or vapour and liquid is or are discharged from the heating chamber, at least before the heating chamber is wholly emptied. It is for instance the intention here to utilize the pressure of the water or the other liquid to thereby enhance the expulsion of vapour or steam and heated liquid from the heating chamber. The temperature of vapour or steam and heated liquid emitted from the heating chamber following opening of the supply is however hereby also decreased, and this may also involve a considerable reduction in the effectiveness of the external application, such as the disinfection of milking cups, to which the steam or vapour and heated liquid has to be provided.

[0010] In an alternative or additional preferred and therefore non-limitative embodiment the system according to the invention has the feature that the feed comprises a feed valve with which connection of the feed to the heating chamber can be selectively opened and closed. The feed side can thus be closed and the heating chamber can be brought to pressure by increasing the temperature of the liquid therein, provided the discharge valve - if present - is closed here.

[0011] In an embodiment with a discharge valve and a feed valve the system according to the present invention can further have the feature of a single connection to the heating chamber for the discharge and the feed. A considerable simplification of the configuration of the heating chamber can thus be achieved by being able to dispense with at least one connection.

[0012] In such an embodiment with a single connection the system according to the invention can further have the feature that the feed valve and the discharge valve form a unit. A three-way valve is also possible. This can achieve a simplification simply because a single three-way valve is easier to control than two two-way valves. It is noted in this respect that a three-way valve is then exposed to considerable temperature differences, which makes heavy demands of such a three-way valve. In order to enable a reduction in these temperature differences the feed could comprise a preheating, whereby the speed of the system can also be increased.

[0013] In an alternative or additional preferred and therefore non-limitative embodiment the system according to the invention has the feature that the heating chamber is a pressure chamber such as a boiler, and the feed comprises an inlet combination. This is a highly suitable embodiment of the system according to the invention, which can thus be formed wholly from very common components and elements.

[0014] In an alternative or additional preferred and therefore non-limitative embodiment the system according to the invention has the feature of a control. The control can be utilized to bring about a properly adjusted operation of the various components and elements of the system.

[0015] In such an embodiment with a control the system according to the invention can further have the feature that the control is adapted to act on at least the feed valve so that it remains closed when the discharge valve is open. It is thus possible to prevent supply of fresh fluid for heating from lowering the increased temperature of already heated fluid as is the case in the prior art, wherein it has been assumed that pressure in/of the feed is even necessary to expel heated fluid from the heating chamber.

[0016] In an embodiment with a control the system according to the invention can additionally or alternatively have the feature that the control is adapted to act on at least the discharge valve so that it opens intermittently for a predetermined period of time. This period of time is of course selected in accordance with options for the capacity of the heating, the volume of the heating chamber, the heat capacity of the fluid for heating, the intervals within which new emission of heated fluid for the external application (such as the disinfection of milking cups) is required and so on.

[0017] In an alternative or additional preferred and therefore non-limitative embodiment the system according to the invention has the feature of a pressure relief device in respect of pressure in the heating chamber. In the case of a malfunction or unexpected functioning the pressure relief device will prevent damage to the heating chamber and/or other components and elements.

[0018] In such an embodiment with a pressure relief device the system according to the invention can further have the feature that the pressure relief device comprises a hose-like element designed to tear in the case of a predetermined pressure over a predetermined period. A hose tears or bursts open more easily than a fixed conduit or a boiler as embodiment of a heating chamber, and practical and unexpected use is thus made of this property in order to implement the pressure relief device for the purpose of protecting the heating chamber and/or fixed conduits.

[0019] In an alternative or additional preferred and therefore non-limitative embodiment the system according to the invention has the feature that the discharge valve is arranged at least substantially immediately at the heating chamber. There is therefore no (or only a small quantity of the) fluid in a conduit or hose between the heating chamber and the discharge valve that is exposed to the action thereon by or with the heating. The emission of heated fluid to the external application is not therefore preceded by a substantially unheated quantity.

[0020] In such an embodiment with a discharge valve in the discharge immediately at the heating chamber and a hose-like element as pressure relief device, the system according to the invention can further have the feature that the feed comprises the hose-like element. A favourable embodiment is thus realized in respect of placing of the discharge valve in the immediate active vicinity of the heating chamber.

[0021] In an alternative or additional preferred and therefore non-limitative embodiment the system according to the invention has the feature that the heating element is arranged against or round an outer wall of the heating chamber, and the outer wall of the heating chamber at least partially comprises material conducting heat to the interior of the heating chamber. An embodiment can thus be realized without measuring instruments or heating elements in the interior of the heating chamber, this facilitating maintenance and improving resistance to malfunction.

[0022] The present invention also relates to a method as according to the appended method claim with which a chamber is at least substantially wholly evacuated before the chamber is refilled with fluid, so that all residues are discharged during normal operation of the heating chamber, this operation usually being a cyclic process.

[0023] The present invention will be further elucidated hereinbelow on the basis of several possible embodiments thereof as shown in the accompanying drawings and described below with reference to the figures. The same or similar components, parts and elements can be designated with the same reference numerals in different embodiments despite the fact that these embodiments differ. The specific features of the relevant embodiments are by no means intended, and should not be interpreted, as limitations to the scope of protection of the present invention, which is limited only by the definitions of the appended claims, and more particularly only the single independent claim. In the drawing:

Figure 1 is a schematic view of an embodiment of a heating system according to present invention;

Figure 2 is a schematic view of another embodiment of a heating system according to the present invention; and

Figure 3 is a schematic view in cross-section of a possible embodiment of a constriction for the purpose of lengthening the time of a steam surge or other emission under the pressure of a quantity of heated fluid from the heating chamber in an embodiment as according to Fig. 1 or 2.

[0024] Figure 1 shows a system 1 for heating fluid. System 1 comprises a heating chamber in the form of a boiler 3, which forms a pressure chamber, with a heating element 4. Boiler 3 has a cylindrical outer surface around which the heating element 4 is arranged as a sleeve. The wall of boiler 3 on which heating element 4 is arranged comprises heat-conducting material for the purpose of transferring heat from heating element 4, which is arranged outside boiler 3, to the fluid in the interior of boiler 3.

[0025] Connected to boiler 3 is a feed 5 via which the boiler 3 can be filled. In the shown embodiment feed 5 connected to boiler 3 on the upper side thereof, but could also be connected on the underside of boiler 3 or at some height along or on a side wall of boiler 3. Heating element 4 will in practice often extend no higher than a maximum of three-quarters of the height of boiler 3 as seen from the underside of boiler 3 in order to prevent the temperature in the upper part of the interior of boiler 3 being or becoming 100°C higher than in the bottom of boiler 3.

[0026] Feed 5 comprises a connection to the mains 6 via a feed valve 7, an inlet combination 8 with a sewer connection 13, and a hose 9 forming a pressure relief device. Hose 9 breaks or bursts, because it is so designed, if the pressure in boiler 3 exceeds a value of for instance 40 or 50 bar for a predetermined period of for instance several minutes. Damage to boiler 3 and other components and elements of the system can thus be effectively prevented at the cost of only hose 9, which can form the pressure relief device in elegant and simple manner. It is noted by way of alternative that a hose, because of the relatively limited lifespan thereof, can be replaced by a fixed conduit such as a copper pipe. This must then have a minimal length in order to limit heat transfer from the heating chamber to the inlet combination and thus prevent possible damage to the inlet combination caused by heat. Inlet combinations such as inlet combination 8 are per se known, though not in the combination of features, elements, components and functionalities as according to the present invention.

[0027] Heating element 4 can be electrically connected in selective manner via a switch 10 to an electricity power source 11.

[0028] System 1 further comprises a discharge 14 connected to boiler 3 and having a discharge valve 15 close to or immediately at the boiler 3 and a conduit 16 to an external application, which is not further defined, for heated fluid from boiler 3, such as a cleaning system for milking cups of milking systems which utilizes a steam surge to clean the cups. Discharge valve 15 lies on or close to boiler 3 in order to limit to a minimum the quantity of liquid in a hose or conduit between boiler 3 and discharge valve 15 which is not heated directly and in boiler 3.

[0029] Switch 10, feed valve 7 and discharge valve 15 are operated with a control 12. The heating 4 normally remains continuously connected to power supply 11, but for maintenance or the like can be uncoupled or disconnected from power supply 11 by appropriate operation of switch 10 by control 12.

[0030] Heated fluid from boiler 3 can be discharged via discharge 14 to the external application, wherein the discharge 14 to the external usable application is connected at or at least close to the bottom 17 of boiler 3.

[0031] Feed valve 7 and discharge valve 15 are controlled by control 12 so that they are both closed during heating of fluid in boiler 3. It is however noted that feed valve 7 is not or need not be closed during heating. During heating the pressure increases against a non-return valve inherently present in inlet combination 8. For this reason water cannot flow through the feed valve to or from boiler 3. At this stage of the heating the feed valve thus fulfils only a kind of back-up function.

[0032] When fluid has been heated in boiler 3, for instance following a preset period of time or when a temperature measured or to be measured with a thermostat (not shown) has been reached, discharge valve 15 is opened and inlet combination 8 and feed valve 7 remain closed under the influence of control 12. Due to the resulting pressure drop in boiler 3 and the prevailing temperature therein increased by heating 4, a further additional part of heated liquid in boiler 3 evaporates. Owing to this pressure drop suction occurs in discharge 14, while the pressure built up in the fluids seeks a way out of the interior of boiler 3 and all fluids in boiler 3 are emitted in a short period of time from boiler 3. When boiler 3 has thus been at least substantially wholly emptied, with all potential residues also being removed here, discharge valve 15 is reclosed. Only then according to the present invention are feed valve 7 and the inlet combination opened to admit a fresh quantity of fluid for heating into boiler 3 via inlet combination 8 by opening feed valve 7 through the action of control 12.

[0033] Valves 7, 15 are preferably switched as simultaneously as possible from open to closed, and vice versa, each in its own sequence, but then for instance with a single control signal from control 12, so substantially at exactly the same time. In another possible embodiment with separate control signals a short interval could occur, which is not desirable because some pressure could then possibly be built up again, and this could make filling of boiler 3 more difficult.

[0034] As soon as a desired and/or suitable and/or measured quantity of fluid has been admitted into boiler 3, control 12 closes feed valve 7 again while inlet combination 8, or at least the non-return valve inherently present therein, does in fact already close the feed of boiler 3 so that in a practical embodiment the feed valve does not actually have to be closed. Both valves 7, 15 and inlet combination 8 are then closed (or at least the inlet combination closes the feed quickly following admission of fluid for heating into heating chamber 3 when the pressure therein rises due to the fluid being heated in chamber 3) and, provided the electrical connection of heating 4 to the electricity power supply has in the meantime been closed, heating 4 is reconnected to power supply 11 by control 12. This process is repeated in order to provide a dose of heated fluid at regular intervals to the "external application", such as for instance a part (not shown) of an installation for disinfecting milking cups. The control can for this purpose open discharge valve 15 intermittently following a predetermined period of time which is related to, or even depends on, the quantity of fluid in the boiler, the heating capacity of heating 4, quantities of heated fluid required by the external application, and so forth.

[0035] In a particularly favourable, simple, elegant and robust and reliable embodiment the control 12 comprises "only" two thermostats, for instance KLIXON thermostats, and only the control signal for the valves is supplied externally.

[0036] The embodiment of a system 2 shown in Fig. 2 differs from that of Fig. 1 in several respects. A heating element 18 is thus arranged in the interior of boiler 3 for heating for instance water 23, wherein steam 24 accumulates at the top of boiler 3. A single connection 19 is further applied for both the feed and the discharge, wherein a three-way valve 20 operated by control 21 selects whether the feed or the discharge, or neither of the two, can or may be connected to (the interior of) boiler 3 via connection 19. Three-way valve 20 is a variant in which the feed valve and the discharge valve form a unit. The operation of the system shown in Fig. 2 is substantially the same as in the foregoing description relating to Fig. 1.

[0037] Fig. 3 shows a constriction 25 which can be arranged in the conduit 16 in each of the embodiments of Fig. 1 or 2. The purpose hereof is to regulate the speed of the emission of heated fluid from the heating chamber of Fig. 1 or 2, in order to control the time duration thereof. Constriction 25 comprises a connection 26 for conduit 16 (which is not shown in Fig. 3), a cone 27 which is arranged in a throughfeed 29 and which is oriented with the tip 30 thereof in a direction counter to the flow direction (arrow A) of heated fluid, a passage 28 through cone 27 from the tip 30 thereof, and a connection for a continuation (not shown in Fig. 3) of conduit 16 or other conduit to the external usable application of the heated fluid from the direction of arrow A. The constriction, formed particularly by passage 28, makes it possible to lengthen the time duration of generation of heated fluid, such as hot water and steam, compared to an embodiment without such a constriction. It is particularly desirable that the steam surge - in the case water is heated in chamber 3 for the purpose of disinfecting for instance a milking cup of a milking robot - has at least or approximately a time duration of about 5 to 6 seconds in order to provide sufficient thermal contact. Such a time duration will be longer or shorter for other usable applications, and the skilled person must be deemed capable of making corresponding modifications him/herself in the design of the constriction (or nozzle) in the light of the wishes or requirements associated with such other usable applications.

[0038] The constriction is preferably placed downstream of outlet valve 15, 20 in the direction of emission (arrow A). Such a constriction 25 or nozzle reduces to the desired extent the quantity of heated fluid or steam to be allowed through per unit of time and changes nothing in the construction of the heating chamber and related elements and components as shown in the embodiments of Fig. 1 and/or 2.

[0039] Since the tip 30 of constriction 25 is oriented counter to the flow direction of arrow A, dirt and particles are given practically no opportunity to accumulate in passage 28. Owing to the sloping sides of cone 27 a vortex will occur and possible contaminants will collect there again and again or become so small that they are nevertheless discharged via passage 28. It is noted that passage 28 further acts as a venturi in the sense that the pressure drop over passage 28 contributes toward evaporation of particularly water particles or droplets which could be left in the steam. Customized steam times (time durations) and speeds can be provided by varying the diameter of passage 28 in combination with different sizes of heating chambers 3.

[0040] After examination of the foregoing description many additional and alternative embodiments will occur to the skilled person which all fall within the letter and/or spirit of the scope of protection of the present invention as defined in the appended claims, in particular the single independent claim 1. It is thus possible within the context of the present invention to manufacture an embodiment with an internal heating element and separate feeds and discharges. The inlet combination can be other than conventional and/or the control can be manual. Valves 7, 15 and 20 can be embodied in a random alternative manner to that described above and shown in the drawing. All combinations of features of the shown and other variants and embodiments fall within the scope of protection.

Claims

1. A system (1) for heating fluid for the purpose of an external application of heated fluid, comprising:

- a heating chamber (3) with a heating element (4; 18);

- a feed (5; 19) which is connected to the heating chamber (3) and via which the heating chamber (3) can be selectively filled; and

- a discharge (14; 19) which is likewise connected to the heating chamber (3) and via which fluid can be discharged from the heating chamber (3), wherein at least the discharge (14; 19) is connected to the interior of the heating chamber (3) at or at least close to the bottom of the heating chamber (3),
characterized in that
the discharge (14; 19) can at least be connected to a conduit (16) to an external application of fluid heated in the heating chamber (3).

2. The system as claimed in claim 1, wherein the discharge (14; 19) comprises a discharge valve (15; 20) with which connection of the discharge (14; 19) to the heating chamber (3) can be selectively opened and closed.

3. The system as claimed in claim 1 or 2, wherein the feed (5; 19) comprises a feed valve (7; 20) with which connection of the feed to the heating chamber (3) can be selectively opened and closed.

4. The system as claimed in claims 2 and 3, with a single connection (19) to the heating chamber (3) for the discharge and the feed.

5. The system as claimed in claim 4, wherein the feed valve (20) and the discharge valve (20) form a unit (20).

6. The system as claimed in at least one of the foregoing claims, wherein the heating chamber is a pressure chamber (3) such as a boiler, and the feed comprises an inlet combination (8).

7. The system as claimed in at least one of the foregoing claims, further comprising a control (12; 21).

8. The system as claimed in at least claim 7, wherein the control (12; 21) is adapted to act on at least the feed valve (7; 20) so that it remains closed when the discharge valve (15; 20) is open.

9. The system as claimed in claim 7 or 8, wherein the control is adapted to act on at least the discharge valve (15; 20) so that it opens intermittently for a predetermined period of time.

10. The system as claimed in at least one of the foregoing claims, further comprising a pressure relief device (9) in respect of pressure in the heating chamber (3).

11. The system as claimed in claim 10, wherein the pressure relief device comprises a hose-like element (9) designed to tear in the case of a predetermined pressure over a predetermined period so as to prevent damage to the heating chamber (3).

12. The system as claimed in at least one of the foregoing claims, wherein the discharge valve (15; 20) is arranged at least substantially immediately at the heating chamber (3).

13. The system as claimed in claims 11 and 12, wherein the feed (5; 19) comprises the hose-like element (9).

14. The system as claimed in at least one of the foregoing claims, wherein the heating element (4) is arranged against or round an outer wall of the heating chamber (3), and the outer wall of the heating chamber (3) at least partially comprises material from the group comprising at least brass and/or stainless steel conducting heat to the interior of the heating chamber (3).

15. The system as claimed in at least one of the foregoing claims, further comprising a constriction (25), at least in association with the conduit 16, for regulating a speed and/or time duration of the emission of fluid heated in the heating chamber (3).

16. A method for heating fluid in a heating chamber (3) with a heating element (4; 18), a feed (5; 19) which is connected to the heating chamber (3) and via which the heating chamber (3) can be selectively filled, and a discharge (14; 19) which is likewise connected to the heating chamber (3) and via which fluid can be discharged from the heating chamber (3), and comprising the steps of: filling the heating chamber (3) via the feed (5; 19), heating the fluid with the feed (5; 19) and discharge (14; 19) closed, and opening the discharge (14; 19) following a predetermined period of time or when a desired temperature has been reached, and waiting with refilling of the heating chamber (3) until at least the greater part of the fluid heated in the heating chamber (3) has left the heating chamber (3) via the discharge (14; 19).

17. The method as claimed in claim 15, wherein at least the discharge (14; 19) is connected to the interior of the heating chamber (3) at or at least close to the bottom of the heating chamber (3).

Drawing