GB2125938A

GB2125938A - Thermoelectric valves

Info

Publication number: GB2125938A
Application number: GB08302297A
Authority: GB
Inventors: Paolo Fornasari
Original assignee: Eltek SpA
Current assignee: Eltek SpA
Priority date: 1982-01-27
Filing date: 1983-01-27
Publication date: 1984-03-14
Also published as: FR2520470B1; GB8302297D0; ES8401214A1; DE3302315A1; FR2520470A1; ES519218A0

Abstract

A thermo-electrically controlled valve having one or more ways, particularly for washing machines and/or heat engines, comprising a hollow body (1) provided with at least one inflow connection (2) and one or more outflow connections (3) for fluids; said hollow body containing a valve (5, 6) which is closed by the reaction of calibrated elastic means (7) and controlled for its opening by the pressure generated by the volume increase of a wax mass (9), heated by a thermistor (11) with a positive temperature coefficient (PCT) which may be supplied electrically. <IMAGE>

Description

SPECIFICATION Thermoelectric valves The present invention relates to thermoelectric valves.

In the present specification the term "thermoelectric valve" is intended to mean a valve for fluid which is electrically actuated, and in which the actuation requires the production of heat, via an electrical heating means. The valve has applications in washing machines and in heat engines such as refrigerators.

In washing machines, it is known to control the flow of water by a valve driven by an electromagnet which, if excited, opens one or more capillaries producing a pressure imbalance capable of opening the valve. This known type of electrically operated valve has the following drawbacks; 1) the capillaries may become blocked by calcinareous deposits or other extraneous bodies; 2) the mobile core of the valve may become jammed in the open or closed position with a consequent risk of flooding; 3) the electro-magnet windings may fail, either by going open-circuit or by short-circuiting, which may lead to overheating and fusion of plastic or resinous parts; 4) the operation of the valve may be noisy, and this noise may increase as the valve becomes warm;; 5) a "water hammering" may occur when the valve closes, such an effect is difficult to control and carries the risk of breaking the feeding tubular branch; 6) groups of valves with a plurality of outputs may be impractically large, and 7) it may be difficult, when the pressure of the water supply is low, for the valve to operate correctly, and admit the necessary quantity of water into the tank of the machine.

A further common application of fluid control valves, is to be found in refrigerating machines.

In refrigerating machines having a single refrigeration cell, as in the majority of cases, a single heat engine is employed. This heat engine may comprise a compressor, an external radiator, a condensor within the cell, a set of tubular ducts, filters and an adjustable thermostat.

-The present requirements of the domestic refrigerator include having a cool space at a temperature above 00C for the cold storage of vegetables, wines and other foodstuffs and a further cold space, generally at or below 00C for the storage of "frozen foods". These requirements present the problem of how to provide two regions, the temperatures of which are independently controllable, without adding a second heat engine.

At present, there is the tendency for domestic refrigerators to adopt the "cellular cell" design in which two cool spaces are defined and the cooler of these two cold spaces acts as a heat sink for the warmer of the spaces.

This solution, although well accepted, presents the drawback that although the temperature of the cooler of the two spaces may be controlled, it is not possible to equally well control the warmer or "cellular" space.

A previous solution, has been to mount two separate independent heat engines. However, this solution is obviously expensive.

A known alternative solution is the provision of an electro-magnetically actuated valve which may divert the refrigerant fluid to cool one space or the other according to the control of a thermostat.

Although the electro-magnetically actuated valve is somewhat expensive, this solution offers a remarkable saving with respect to the use of two independent heat engines and offers, in addition, the possibility of adjusting the temperatures of the two spaces within fine limits.

According to the present invention there is provided a thermoelectric valve, comprising a hollow body and a valve means capable of opening and closing a passage for fluid in said body, said valve means comprising: a closed chamber containing a mass, the volume of said mass, varying in relation to the quantity of heat contained in said mass, an elastic means, a movable member actuated by a change in the volume of said mass, and a heating means, the arrangement being such that when heat is supplied to the mass by the heating means the movable member is actuated against the reaction of the elastic means to open or close the passage in said body.

Another object of the present invention is to obviate all the particulate drawbacks of some known electro-valves.

Another object of the present invention is to provide a valve which operates reliably with the time, having a simple structure and a cost economically advantageous, suitable to be used on washing machines.

Another object of the present invention is to provide a valve with thermoelectric control suitable to intercept fluids at very high pressures and therefore suitably employed on refrigerant machines.

According to the above said objects, the subject matter of the present invention is a valve with thermoelectric control, particularly for washing machines and/or refrigerators, characterised in that it comprises an envelope containing a valve body which is pushed in the closing position by the pressure of calibrated resilient means and controlled for its opening by the pressure generated within a chamber, and transmitted-to the valve, by the volume increase of a wax mass, heated by a thermistor.

The thermistor, or other electrical heating means, preferably has a positive temperature coefficient (PTC) in order to prevent thermal runaway.

The invention will be further described with reference to the accompanying figures in which:~ Figure 1 is a longitudinal cross section of a valve according to the present invention; Figure 2 illustrates a variant of some details of the valve of Figure 1; Figure 3 is a partial view of the valve according to a further embodiment; Figures 4 to 10 are longitudinal cross section of further embodiments of the present invention.

With reference to Figure 1, the horizontal plane passing through axis x-x distinguishes one half valve shown in the open position, illustrated above the axis, from one half of same valve shown in the closed position, illustrated below the axis.

Structurally, the valve comprises the envelope 1, provided with a connection nipple 2, which acts as an inlet for water in the direction indicated by arrows -y-. A connector 3, connects the valve to the washing machine and a filter 4 is provided for the incoming fluid. The valve body 5, provided is with an elastic gasket 6, and mounted with its stem 5a longitudinally sliding with respect to the support 1 d. A spring 7, keeps the valve in the closing position, as represented in the lower half of Figure 1. The end of stem 5a rests on a gasket 8 which is mounted slidably and sealingly within the tubular support 1 dwhich opens in the chamber 9 defined by the cap 10 and the envelope 1.The chamber 9 is filled with a suitable wax, or other mixture of suitable materials, having a characteristic expansion coefficient at a predetermined thermal value, at which said wax mass undergoes a considerable volume increase whereby, within said chamber 7, a rapid and considerable increase of pressure occurs which acts against the gasket 8 and causes it to move to position 8ddriving the stem 5a longitudinally, in the direction opposed to that indicated by arrows -y- and, therefore opening the valve 5, 6 against the reaction of the spring 7, as indicated in the upper part of Figure 1.

Within the wax mass enclosed within the chamber 9, one or more thermistors 11 are embedded and connected to electrical terminals 1 a which sealingly pass through the cap 10 which is firmly connected to the valve body 1.

The terminals 1 a are connected via a control means to the electrical supply circuit of the machine.

In operation the terminals 1 a are supplied with electricity, the thermistor or thermistors 1 1 warms up and stabilizes itself at its characteristic temperature.

Since the characteristic temperature is higher than the temperature at which the wax melts, the wax melts in a short time. This change of state is accompanied by an expansion which increases the pressure within chamber 9 whereby a thrust is generated which acts towards the gasket 8 and pushes the stem 5a; the reaction of the spring 7 is overcome and the valve 5, 6 is opened. When the electrical supply to the terminals 1 a ceases, the thermistor(s) 11 and the wax cool and the volume of the wax reduces and therefore the reaction of spring 7 returns the valve 5, 6 to a position abutting its seat 1 a blocking the path of the controlled fluid.

In the embodiment, represented in Figure 2, the chamber 9, containing the wax, is defined by a metallic sheath 12. The sheath 12 is first mounted in a recess 16 of body 1 formed of a plastic material which is thereafter thermically deformed and closed as indicated by 17. The thermistor 11 and the electrical terminals 1 1 a are protected by a thin layer of an insulating resin 13. The terminals 1 a pass through the gasket 18 which is electrically insulating with respect to the sheath 12 and protrude beyond the sheath bottom. The stem 5a of the valve, rests against the resilient gasket 14 and is further provided with a peripheral groove which receives an annular resilient gasket 15 in order to assure a competent seal between the controlled fluid and the wax contained in chamber 9.

Figure 3 illustrates another embodiment according to which the thermistor or the thermistors 11 are located outside of a chamber 9 which is defined by a sheath 1 2a. The cage 19 protects the one or more thermistors and has holes 1 9a, in order to increase the air circulation around the thermistors and thus expedite cooling of the thermistors when the supply of electricity via wires 1 a ceases.

Figures 4 and 5 illustrate a variant of the valve provided for its particular use on refrigerant machines.

The valve of Figure 4 comprises a metallic body 1 on whose end a control means 22 is mounted and retained by means of the nut engaging the threaded stem 23. In Figure 4, the control means 22 is represented in a cross section and therein one or two thermistors 1 1 of a suitable power are housed and electrically fed through electric terminals 1 a in contact with the housing 27 made of suitable electrically insulating and heat-resistant material. The housing 27 is directly in contact with the hollow extension 1 e filled with wax 9.

The chamber 9 containing the wax has only one opening, occupied by a gasket 8 sealingly and slidably mounted, within the support of the push rod 5a of the valve 5 which, in the represented position, abuts against the valve seat (1 a), to close the pathway between the inlet connector 4 and the outlet connector 3. Between the end of the rod 5a, which drives the valve 5, and the valve S there is provided a gap 25. The spring 7 tends to keep the valve 5 abutting against the seat 1 a.

In operation, electrical supply at terminals 1 a causes the heating of the thermistor or thermistors 11 and the consequent melting of wax 9, which by the increase of its volume presses upon gasket 8 and drives one end of the rod Sa, the other end of which, after having crossed the gap 25, causes the axial displacement of valve 5 away from seat 1 a. With the valve open, the fluid passes through the inlet connector 4 to the output connector 3 until the electrical supply at the terminals 1 a ceases with the consequent cooling of the wax in the chamber 9 which, by shrinking, allows the spring 7 to return the valve 5 to its position abutting against the seal 1 a.

In the embodiment represented by Figure 5, the operation is substantially similar to that of the embodiment of Figure 4, except that the body 1 of valve is provided with an inflow connector 4 and two downflow connectors 3, 3b or vice versa.

Alternatively, the inflow connectors may be two and the downflow two or only one.

In this embodiment, the gap existing between the end of rod 5a and the seat formed in the valve 5, contains a spring 24 having a set clearly greater than that of the spring 7. This feature eliminates "water hammering" during the valve operation and allows the absorption of the subsequent thrust exerted on rod 26, even with the valve closed. Also according to this embodiment the valve 5, which in the position represented abuts against seat 1 c and leaves open the passage to the outlet 3, in operation the temperature of the wax 9 is kept at such a level as to generate, on rod 5a a relatively, moderate thrust and such as to not totally compress the spring 7, thus admitting fluid to both outlet connectors.

In the de-energization phase of the one or more thermistors, the spring 24, relaxes before the spring 7, reacts the first which causes the axial displacement valve 5 until it comes to abut upon the seat 1 c, The axial clearance in the gap 25 of rod 5a with respect to the valve 5 is chosen in order to compensate for thermal drift, that is, if the valve is used in a relatively warm ambient, the wax 9 increases its volume and applies a given thrust on the rod 5a but without causing the opening of the valve until the end of the rod has recovered the compensating clearance available in the gap 25.

In an embodiment of the present invention, the spring 24 may be present (Figure 5) or not (Figure 4); if it is present its set may be more or less than the set of spring 7, according to the required valve operation.

The spring 7, as shown in Figures 4 and 5 is intended to close the valve when the thrust on stem 5a ceases and may have a shape and structure other than those represented and may be differently mounted in its operating seat.

In the embodiment represented in Figure 6, the thermistor 1 1 is located outside of the chamber 30 containing the wax 9 or other suitable material.

The heat supplied by the thermistor 1 1 is transmitted to the wax 9 through the walls of the chamber 30. As illustrated in the detail indicated by A, the wall of the chamber 30 may be advantageously provided with a pressure screw 31, by which it is possible to vary the inner volume of the chamber containing the wax 9. The 1 h part of body 1, is formed of an electrically insulating material and crossed by electric supply lines 1 a of thermistor 1 1. Part 1 h preferably carries the threaded seat for a screw 28 which acts on a cup spring 29 mounted in contact with the thermistor 1 1 in order to assure the perfect contact of same with the metallic skirt of chamber 30.A rigid diaphragm 34 crossed by the same piston 35 which against the reaction of spring 37 and under the thrust of wax 9, presses or not on the second resilient diaphragm 32 which intercepts or not the passage 4h on the connector 4.

In the embodiment illustrated on Figure 7, which is substantially similar to that illustrated in Figure 6, the thermistor 1 1 has a cup shape and embraces the external surface of the chamber 30 which contains the wax 9.

In the embodiment illustrated in Figure 8, the thermistor 11 has a cup shape and the screw 28 and the cup spring 29 act advantageously the chamber 30, instead of the thermistor, in order to compensate eventual axial movements, which may be generated by thermal variations between the elastic membrane 36 and the rigid diaphragm 39. The small piston 35 passing across the second rigid diaphragm 34 controls a valve moving against the reaction of the spring 37.

In the embodiment illustrated in Figure 9, the thermistor 11 is embedded in the wax 9 enclosed in the chamber.defined by cap 30, substantially as described for the embodiment of Figure 1. The volumetric variations of the wax 9 are transmitted to the elastic membrane 36 and thereby to a second corrugated elastic membrane 32 which acts on the small piston 35. The valve may have two or three paths indicated by 3, 4, 4c.

In the embodiment illustrated in Figure 10, the small piston 35 is omitted whereby the second elastic membr#ane 32 is so shaped as to be capable of directly abutting against the seat 4h of connector 4, substantially as has been described for the embodiment of Figure 6.

In the various embodiments of the present invention, illustrated in Figures 6 to 10, one object has been to hermetically separate the chamber enclosing the wax 9, from the valve body, with the object of preventing any infiltrations of the controlled fluid, into the wax 9. If the controlled fluid is a warm and in this case, corrosive gas, as for example, the one known as "FREON 12", used in the refrigerating circuits, infiltrations of the gas in the chamber which contains the wax 9 and/or the thermistor 11, would damage said members causing problems in valve operation and eventual failure.

From what has been described, it can be seen that clear advantages result from the use of the valves as disclosed, more particularly, ~reliable valve operation for an extended time: - a notable cost savings with respect to the use of present electrovalves and associated relays and/or other high cost elements; ~an advantageous use of the valve mainly on washing machines and refrigerating machines; - a wide field of use of the valve for control of fluids under pressure.

Various modifications may be made within the scope of the present invention. A talic powder or an oxide with a high thermal conductivity may be added to the wax or other suitable material, in any of the embodiments described herein. Any heating means with a positive temperature coefficient may be employed instead of a thermistor or thermistors. Any change of state other than melting of a solid into a liquid may be employed where this change of state is accompanied by a change in volume. During any such change of state, the temperature of the body need not rise as the change of state may be accomplished at a fixed temperature with a change in the quantity of heat contained by the material.

Claims

1. A thermoelectric valve comprising a hollow body and a valve means capable of opening and closing a passage for fluid in said body, said valve means comprising: a closed chamber containing a mass, the means of said mass varying in relation to the quantity of heat contained in said mass, an elastic means, a movable member actuated by a change in the volume of said mass, and a heating means, the arrangement being such that when heat is supplied to the mass by the heating means the movable member is actuated against the reaction of the elastic means to open or close the passage in said body.

2. A thermoelectric valve particularly for washing machine and/or frigorific machines, comprising a hollow body wherein a valve in the closing or in the opening position, controls a passage way for the water or any other fluid and co-operates with an elastic member, characterized in that the movable member of the valve is controlled for closing or opening of the controlled way, by the pressure generated within a closed chamber containing a determined volume of wax or other suitable thermal expanding and one or more thermistors (PTC) electrically connected to a programming or timer device of the machine; said thermistors, if electrically fed, raise the temperature of the wax mass which, melting, it increases its volume and generates a high pressure within said chamber - pressure which, through elastic sealing gaskets or membranes generates a thrust transmitted to the valve obturator member which assumes the opening or the closing position and so remains, against the reaction of elastic means, until the thermistor or thermistors are electrically fed.

3. A thermoelectrically controlled valve, according to Claim 2, characterized in that it comprises, in a hollow body, a valve provided with a cylindrical stem mounted longitudinally slidable in a corresponding seat wherein there is also mounted at least one sealing gasket and which, communicates with a tight chamber filled with a mass which is thermo-expanded by the heat generated by one or more thermistors drowned in the wax, and is crossed by electric terminals which extend on the outside of said chamber.

4. A valve according to Claim 2, characterized in that the thermistors are mounted outside said chamber enclosing the wax.

5. A valve according to Claim 2, wherein the elastic means co-operating with the valve, are formed by a leaf spring or helical spring.

6. A valve according to Claim 2, wherein the chamber containing the wax is formed by a metallic sheath suitable to rapidly disperse the heat generated by the thermistor or thermistors.

7. A valve according to any of the preceding Claims 2 to 6, characterized in that its opening is operated by means which are independent from the pressure of the water or of the controlled fluid, in order to allow the inflow of the fluid in the machine even at low pressure of the feeding net.

8. A valve according to Claim 2 and to a variant characterized in that the stem which controls it in the axial movement, is engaged with respect to the valve by the insertion of one of its ends, with a longitudinal clearance of a pre-established amplitude in order to compensate eventual pressures coming from the wax chamber, pressures deriving from the expansion of the wax due to the temperature of the ambient wherein the valve operates.

9. A valve according to Claims 2 and 8, characterized in that in the longitudinal space predisposed between the insertion seat formed in the valve and the stem end a spring is contained which reacts at compression in order to avoid hammerings.

10. A valve with a thermoelectric control, according to Claim 2, characterized in that the hollow part of the valve body through which passes the controlled fluid, is hermetically separated from the chamber enclosing the thermo-expansible mass with the associated thermistor on the outside or the inside of the chamber.

1 1. A valve according to Claims 2 to 10, characterized in that the division of the distinct chambers made within the valve body, is obtained by means of elastically deformable membranes and diaphragms.

12. A thermoelectric valve according to Claims 2 and 1 1, characterized in that the diaphragm which divides the chamber enclosing the thermoexpanding mass and if that is the case the thermistor (PTC) from the remaining of the valve, is formed by an elastically deformable lamina cooperating with an elastomeric, thermo-resistant and electrically insulating membrane.

13. A valve according to Claims 2 and 12, characterized in that the elastically deformable lamina which forms the separating diaphragm of the chambers is so shaped as to intercept the seat connected to the fluid downflow connector and acts as a shutter of the valve.

14. A thermoelectric valve according to Claim 2 wherein the elastically deformable diaphragm cooperates with a valve with a stem controlling one or more downflow seats, against the reaction of calibrated elastic means.

15. A thermoelectric valve according to any of Claims 2 to 14, characterized in that the chamber enclosing the thermo-expanding mass is provided with means suitable to vary its inner volume in order to vary the intervention distinctive features of the valve.

1 6. A valve according to Claim 8. characterized in that the means suitable to vary its intervention distinctive features are formed by one or more pressure screws which can be manoeuvred from the outside and protruding inside of the tight sheath containing the thermo-expanding mass and, if that is the case, the thermistor.

17. A thermoelectric valve according to any of the preceding claims, wherein the thermoexpanding mass is formed by a waxy element mixed with metallic powders and/or high thermal conductivity oxides.