The present invention relates to a machine for dry-cleaning articles such as clothes, household linen, towels, curtains and the like.

In particular, the present invention relates to the drying circuit of such a machine which is also designed to simultaneously perform an action, also known as abatement, removing from the articles the solvent used for dry-cleaning.

Examples of such machines are known from documents EP 1584731, or JP 2006 181219, EP 1637641, GB 2060713, US 4494317, JP 08038791.

There are prior art dry-cleaning machines comprising a drying and abatement circuit which, also integrating the drum in which the articles are treated, comprise a fan for circulation of the air, a condenser for condensing the solvent contained in the air and a heating element for heating the air before reintroducing it into the drum in which, thanks to its high temperature, it can remove the dry-cleaning solvent from the articles by vaporisation.

The condenser usually consists of the evaporator of a refrigeration circuit whilst the condenser of the same circuit forms the above-mentioned air heating element.

In order that the air circulating in the drying circuit reaches a temperature value sufficient to guarantee an effective drying action and abatement of the solvent from the articles, additional heating elements are used, positioned in series relative to the refrigeration system condenser.

Such additional heating elements are usually of the type with an electric heating element or steam powered.

The presence of the heating elements is not without disadvantages. Irrespective of the specific type selected, it involves considerable energy absorption with consequent increases in the costs per dry-cleaning cycle.

The aim of the present invention is to overcome the above-mentioned disadvantage with a machine for dry-cleaning articles such as clothes, household linen, towels, curtains and the like, which allows the effective and economical execution of dry-cleaning and drying cycles for said articles, the machine being simple and economical to make and easy and practical to use.

The technical features of the present invention, in accordance with the above aims, are clear from the content of the claims herein, in particular claim 1, and from any of the claims directly or indirectly dependent on claim 1.

The present invention also relates to a method for dry-cleaning articles.

The method according to the present invention is described in claim 10 and any of the claims directly or indirectly dependent on claim 10.

The advantages of the present invention are more apparent in the detailed description which follows, with reference to the accompanying drawings which illustrate preferred, non-limiting embodiments of the invention, in which:

• Figure 1 is a schematic view of a preferred embodiment of the machine for dry-cleaning articles in accordance with the present invention;
• Figure 2 is a schematic view of an alternative embodiment of the machine of Figure 1.

With reference to Figure 1, the numeral 1 denotes as a whole the machine for dry-cleaning articles in accordance with the present invention.

The machine 1 comprises a drum 2 or container in which the articles to be dry-cleaned are inserted.

The drum 2 rotates, driven by motor elements of the substantially known type not described or illustrated, about an axis of rotation A.

The machine 1 comprises a closed circuit 3 for the circulation of air for drying the articles contained in the drum 2 which are not illustrated. As Figure 1 clearly shows, the drum 2 is positioned in the closed circuit 3.

At the drum 2 outfeed, according to the direction of the air flow indicated by the arrows FA illustrated in Figure 1, the closed circuit 3 comprises a filtering zone 4 designed to catch any materials carried by the air flow, such as hairs and threads detached from the articles during drying.

Downstream of the filtering zone 4, on the circuit 3 there is a fan 5 for moving the air. Downstream of the fan 5, again according to the direction of the arrows FA, the circuit 3 comprises an ascending duct 6 which conveys the air to a condensation battery 7 and to a heating element 8.

The condensation battery 7 is designed to condense the solvent in vapour form transported by the flow of drying air, whilst the heating element 8 is designed to raise the temperature of the air circulating along the circuit 3.

At the condensation battery 7 there is a zone 9 for collection of the solvent condensed, which is fed to a collection tank 12 through a recovery duct 10 and a respective filter 11.

Using inlet and drainage means of the known type and not illustrated, the solvent is sent to and drained from the drum 2 respectively from and to the collection tank 12.

Downstream of the heating element 8 the circuit 3 comprises a descending duct 13 which introduces the heated air into the drum 2, thus closing the circuit 3.

As illustrated in Figure 1, the machine 1 comprises a refrigeration system 14 along which a respective refrigerant flows.

The refrigeration system 14 comprises, positioned one after another, a refrigerant compressor 15, a first condenser 16, a refrigerant receiver 17, a filter 18 for catching any impurities, a refrigerant expansion valve 19 and a first evaporator 20 for the refrigerant.

The above-mentioned elements of which the refrigeration system 14 consists are in fluid connection with one another by means of a plurality of pipes having numerous on - off and check valves. Both the pipes and the valves are described in detail below.

In Figure 1 the above-mentioned pipes are labelled from T1 to T13, whilst the on - off valves are labelled V1 to V7. The check valves are labelled 21.

As is explained in more detail below, the first evaporator 20 and the first condenser 16 of the refrigeration system 14 are integrated in the closed circuit 3 to perform a heat exchange with the air circulating in it, and they respectively form the heating element 8 and the condensation battery 7. The first condenser 16 and the first evaporator 20 are therefore two heat exchangers which, in the circuit 3, form respective means for the treatment of the air circulating in the circuit 3.

The refrigeration system 14 also comprises an auxiliary heat exchanger 22 which is positioned outside the circuit 3, so that it does not perform any heat exchange with the air circulating in the circuit 3.

The auxiliary heat exchanger 22 comprises a respective fan, not illustrated, designed to increase the efficiency of the heat exchange by establishing a forced air flow.

The machine 1 comprises a computerised control and operating unit for controlling the opening and closing of the on - off valves according to the different machine 1 operating steps.

Along the air circulation circuit 3, downstream of the fan 5, there is a first element 23 for detecting the air temperature, hereinafter indicated simply as the sensor 23.

In practice, after inserting the articles to be dry-cleaned in the drum 2, a dry-cleaning solvent is introduced into the drum 2.

There follows a step in which the drum 2 is made to rotate about its axis A so as to distribute the solvent effectively on the articles to be dry-cleaned.

Once the dry-cleaning operations are considered complete, the articles must be dried to remove the liquid solvent used for dry-cleaning from them.

To dry the solvent from the articles, the articles are struck by a flow of hot air.

Therefore, said air must be treated, both to heat it and to remove from it the solvent which, in the form of vapour, is removed from the articles.

The air treatment, that is to say, basically its heating and the removal from it, by condensation, of the vaporised solvent, involves special operating steps by the refrigeration system 14 described above.

In particular, a first step of heating the air from an ambient temperature to to a predetermined temperature t₁, is carried out by activating the passage of the refrigerant through the first condenser 16 forming the circuit 3 heating element 8, but without allowing the refrigerant to circulate through the first evaporator 20 forming the circuit 3 condensation battery 7. In this way, the air circulating in the circuit 3 is heated after the heat exchange which takes place at the heating element 8 and, therefore, its temperature is raised.

A second step with simultaneous heating of the air and condensing of the vapour contained in it takes place starting from the temperature t₁ until the air reaches a temperature t₂ higher than t₁.

In this second step the refrigerant passes through both the first condenser 16 to heat the air, and through the first evaporator 20 to condense the solvent contained in the air in vapour form.

The first step of only heating the air is therefore a transient step in which the air is heated from the temperature to to the temperature t₁.

During said first transient step of machine 1 starting, the refrigerant coming out of the compressor 15 flows along the pipe T1 as far as the point P1 of intersection with the pipes T2 and T3. From the point P1, with the valve V4 open and the valve V5 closed, the refrigerant flows to the first condenser 16, in the direction indicated by the arrow F1.

As it passes through the first condenser 16, the refrigerant is condensed, transferring heat to the air circulating in the closed circuit 3, therefore said air is heated.

As it comes out of the first condenser 16, the refrigerant flows along the pipe T4 according to the direction indicated by the arrow F2 until it reaches the point P2 of intersection of the pipe T4 with the pipes T5 and T6.

With the valve V2 open and the valve V3 closed, the refrigerant flows along the pipe T5 according to the direction indicated by the arrow F3 and reaches the receiver 17, passing through the point of intersection P3 towards which there also converges a pipe T6' from the auxiliary heat exchanger 22.

A check valve 21 is advantageously positioned on the pipe T5 close to the point of intersection P3.

The refrigerant receiver 17 is of the known type and therefore its functions in the refrigeration system 14 are not described in detail.

The refrigerant coming out of the receiver 17 flows along the pipe T7 according to the direction indicated by the arrow F4 and reaches the expansion valve 19. Positioned along the pipe T7 there is a filter 18 for filtering the refrigerant coming out of the receiver 17, catching any impurities present in it.

The refrigerant which expands in the expansion valve 19, with the on - off valve V1 closed and the valve V6 open, passes through the point P5 of intersection between the pipes T8 and T9 and, flowing along the latter according to the direction indicated by the arrow F5, reaches the auxiliary heat exchanger 22. At the latter, the refrigerant performs a heat exchange with the outside air, absorbing heat from it and evaporating.

Therefore, during the present transient step of machine 1 starting the auxiliary heat exchanger 22 forms a second evaporator, alternative to the first evaporator 20. In said transient step, the refrigerant does not flow through the first evaporator 20.

During the transient step, the refrigerant comes out of the auxiliary heat exchanger 22 through the pipe T10 along which it flows according to the direction indicated by the arrow F6 to the point P4 of intersection with the pipes T3, T6 and T11.

With the valves V3 and V5 closed and the valve V7 open, the refrigerant reaches the point P6 of intersection between the pipes T11, T12 and T13, flowing along the pipe T11 according to the direction indicated by the arrow F7. Therefore, passing through the point P6, the refrigerant flows along the pipe T12 according to the direction indicated by the arrow F8 until it goes back into the compressor 15.

At the same time as the refrigeration system 14 transient step takes place, the air circulating in the closed circuit 3 is heated by heat exchange with the heating element 8 consisting of the refrigeration system 14 first condenser 16.

The transient cycle described above is repeated until the sensor 23 located downstream of the fan 5 detects air temperature values lower than a predetermined value t₂, for example between 30°C and 40°C. Reaching the temperature value t₂ confirms the end of the transient step and the start of a refrigeration system 14 regular operation step.

In particular, when the predetermined temperature t₂ is reached, the computerised control and operating unit referred to but not illustrated issues the command to close the valve V6 and simultaneously open the valve V1. In this way, the refrigerant which expanded in the expansion valve 19 flows along the pipe T8 according to the direction indicated by the arrow F9, reaching the first evaporator 20 integrated in the drying circuit 3.

In practice, whilst in the previous transient step the refrigerant was diverted at the point P5 towards the auxiliary heat exchanger 22, now, in the regular operation step, the refrigerant is directed towards the first evaporator 20.

At the first evaporator 20, the refrigerant evaporates, absorbing heat from the moist hot air circulating in the closed circuit 3 and so causing the vaporised solvent present in said hot air to condense.

Most of the thermal power removed from the air at the first evaporator 20 is the latent heat of vaporisation.

The refrigerant evaporated in the first evaporator 20 then flows along the pipe T13, according to the direction indicated by the arrow F10, towards the point P6 of intersection and from there, because the on - off valve V7 is closed, again into the compressor 15 through the pipe T12.

Machine 1 operation involves transient safety steps during which the refrigeration system 14 cycle is subject to transient modifications compared with its regular operation just described, so as to bring within predetermined safety ranges several parameters such as the air temperature in the circuit 3 or the pressure of the refrigerant in the refrigeration system 14.

In a first transient safety step, starting with normal regular operation, if the refrigerant coming out of the compressor 15 reaches a pressure value greater than a predetermined calibration value p₁ of a first pressure switch 24, the computerised control and operating unit closes the valve V4 and, at the same time, opens the valve V5.

In this way, the refrigerant coming out of the compressor 15, having reached the point P1 of intersection, is diverted along the pipe T3 along which it flows according to the direction indicated by the arrow F11 and, having reached the point P4 of intersection, because the valves V3 and V7 are closed, it flows directly towards the auxiliary heat exchanger 22, through the pipe T10. This time, it flows along the pipe T10 according to the direction indicated by the arrow F12, that is to say, in the opposite direction to that during the transient starting step described above.

The simple flowing of the refrigerant along the exchange circuit in the auxiliary heat exchanger 22, usually of the coil type, generates, due to the pressure losses linked to the circuit, an inevitable reduction in the pressure of the refrigerant, irrespective of the heat exchange which takes place along the circuit and of the consequent condensation.

If the refrigerant reaches an even greater pressure value p2, of calibration of a second pressure switch 25, the computerised unit switches on the respective fan, not illustrated, belonging to the auxiliary heat exchanger 22, so as to make the release of heat to the outside even more efficient.

Therefore, during the present first transient safety step, the auxiliary heat exchanger 22 forms a second condenser for the refrigerant, alternative to the first condenser 16.

As it comes out of the auxiliary heat exchanger 22, the refrigerant flows along the pipe T6' according to the direction indicated by the arrow F13 and is reintroduced into the receiver 17. From the receiver 17, the refrigerant again flows through the pipe T7 and from there towards the expansion valve 19.

The first transient safety step is concluded as soon as the pressure switch 24 and/or the pressure switch 25 detect refrigerant pressure values less than their respective calibration values p₁ and p₂.

A second transient safety step is implemented, starting with normal regular operation, if a second temperature detection element 26 detects a temperature greater than a predetermined safety value t_s for the refrigerant entering the first condenser 16. For example, the value of t_s is advantageously approximately 95°C.

In the second transient safety step, if it is detected that the refrigerant has reached the temperature value t_s, the computerised control and operating unit, not illustrated, by closing on - off valve V2 and simultaneously opening valve V3, diverts the flow coming out of the first condenser 16 along the pipe T6 along which it flows according to the direction indicated by the arrow F13. Having reached the point P4 of intersection, since both of the valves V5 and V7 are closed, the refrigerant flows directly towards the auxiliary heat exchanger 22, through the pipe T 10, along which it flows according to the direction indicated by the arrow F12.

At the auxiliary heat exchanger 22, if necessary even by switching on the respective fan, not illustrated, the refrigerant transfers heat to the outside before returning to the receiver 17 and, from there, to the expansion valve 19.

In this way, the temperature of the refrigerant has been lowered by making it perform an additional heat exchange with the outside, not included in the normal regular operation cycle of the refrigeration system 14.

Therefore, as in the first transient safety step described above, in this second transient safety step the auxiliary heat exchanger 22 forms a second condenser for the refrigerant, additional to the first condenser 16.

As soon as the temperature of the refrigerant detected by the second detection element 26 returns to values lower than the predetermined valve t_s, the second transient safety step is ended and the computerised control and operating unit returns the valves V2 and V3 to their respective configurations adopted during regular operation of the refrigeration system 14, that is to say: valve V2 open and valve V3 closed.

The refrigeration system 14 comprises two additional pressure switches: a third safety pressure switch 27, positioned along the pipe T1, and a fourth pressure switch 28 for minimum pressure, positioned along the pipe T11, upstream of the compressor 15.

The third safety pressure switch 27 is designed, through the computerised control and operating unit with which it is connected, to stop machine 1 operation if the pressure of the refrigerant exceeds a predetermined safety pressure value.

The fourth pressure switch 28 is designed, through the computerised control and operating unit with which it is connected, to stop machine 1 operation if the pressure of the refrigerant is lower than a predetermined pressure value below which the refrigeration system 14 could be damaged.

The above-mentioned on - off valves V1, V2, V3, V4, V5; V6, V7, together with the check valves 21, form valve means for the refrigeration system 14.

Said valve means, together with the computerised control and operating unit referred to but not illustrated, form control means for regulating the flow of refrigerant in the refrigeration system 14.

Figure 1 does not illustrate means for introducing the solvent into and/or extracting it from the drum 2, since these are of the substantially known type and are not useful to an understanding of the present invention.

By way of example only, it was proven that using HFC 134a gas (commercially also known as Freon R134a) as the refrigerant, partly because of its low impact on the ozone, the machine operating temperatures, considering to to be ambient temperature, are as follows:

• t₁ between 30 and 40 °C,
• t_s between 90 and 100 °C.

Tests have shown optimum machine operation with the air temperature t₁ set at around 36 °C and the maximum temperature t_s of the refrigerant set at around 95 °C.

The value of temperature t₂ is closely linked to the type of articles being dry-cleaned and to the temperatures they can tolerate without deteriorating. An average drying air temperature t₂ able to allow effective drying of articles is, for example, around 70 °C.

Again by way of example, assuming that HFC 134a gas is used as the refrigerant, possible values for the calibration pressures p₁ and p₂ of the pressure switches 24 and 25 are, respectively, around 24 Bar and 24.5 Bar.

Therefore, advantageously, the present invention allows the treatment of the air for drying dry-cleaned articles without the need for thermal power in addition to that supplied by the refrigeration system normally coupled to the machine.

With the machine disclosed, the thermal power generated with the refrigeration cycle is sufficient to dry the articles. Tests have shown that, with the refrigerant indicated above, the air temperature on average reaches the value of 70 °C in very short periods of time and absolutely compatible with the duration of the dry-cleaning cycles currently used.

According to the alternative embodiment illustrated in Figure 2, the machine 1 comprises a circuit 100 for cooling the solvent fed to the drum 2, the circuit 100 extending from the pipe T7, downstream of the filter 18 according to the direction indicated by the arrow F4.

The circuit 100 comprises an on - off valve V8, a cooler 101 and, inserted between them, an expansion valve 102. The cooler 101 comprises a coil heat exchanger 103 outside which there flows the above-mentioned solvent to be sent into the drum 2. Figure 2 does not illustrate the respective solvent feed and extraction ducts to and from the cooler 101, since they are considered to be of the substantially known type. In practice, by means of the on - off valve V8, the refrigerant coming out of the filter 18 is diverted to the cooling circuit 100 and expands at the expansion valve 102.

The refrigerant which expanded in the valve 102 flows along the circuit 100, reaching the cooler 101, where it evaporates, absorbing heat from the solvent circulating outside the coil heat exchanger 103, thus causing the solvent to cool. The circuit 100 joins the pipe T12 again and the refrigerant then flows towards the compressor 15.

Use of the solvent cooling circuit 100 disclosed by the alternative embodiment illustrated in Figure 2 advantageously allows the temperature of the solvent to be kept within required values, thus guaranteeing, when necessary, the availability of low temperature solvent, for example for dry-cleaning delicate articles.

The invention described above may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all details of the invention may be substituted by technically equivalent elements.