IL32876A - Temperature responsive elements and thermostatic mixing valves using the same - Google Patents

Description

α»·οοοΐΓ3ηη wianyn » Di onoa?i Din α»3»αοη D»oioVKa D'Vi sw ana atuDiiVDn IMPROVEMENTS IN OR RELATING- TO TEMPERATURE RESPONSIVE ELEMENTS AND TO THERMOSTATIC MIXING- VALVES USING- THE SAME It. THIS INVENTION relates to thermostatic mixing valves .

The invention is especially applicable to thermostatic mixing valves which can be used domestically, for example in controlling the flow of water to a shower, wash basin, bath, kitchen sink or the like.

According to the invention there is provided a thermostatic mixing valve comprising a housing, two fluid inlet ports for admitting fluid to be mixed, an outlet port for discharging fluid from the housing, and thermal control means for adjusting the ratio of quantities of fluid admitted from the inlet ports in response to the temperature of fluid flowing from the inlet ports to the outlet port, said thermal control means including a temperature responsive element comprising a coiled coil, as hereinafter defined, laminated strip mounted in an annular space surrounding a hollow control member and slidingly supported by the hollow control member, and a valve member movable in response to change in axial length of the temperature responsive element to control the proportions of fluid flow through spaced hot and cold mixing ports opening radially through the hollow control member respectively in communication with the two inlet ports, a barrier being provided the hollow control member between the inlet sides of the mixing ports. When using the term "coiled coil" herein we are referring to an element which has been formed first by bending a strip into the form of a helix with spaced convolutions, this helix then being itself formed into a larger helix with the axis of the first helix following the helical form of the larger helix. While normally the laminated strip is of bimetal, it may, for example be fabricated from a non-metallic material such as plastics materials having different coefficients of thermal expansion. The strip may be provided with a protective coating of metal or other material, to prevent or reduce corrosion at the juncture of laminated metals forming the strip. While most Preferably the mixing ports open into the temperature responsive element receiving space at or near one end of the temperature responsive element and the outlet port is provided from said space at a position intermediate the ends of the temperature responsive element. With this arrangement the portion of the space between the outlet port and the other end of the temperature responsive element helps to provide a feed back function helping to prevent excessive fluctuation or hunting of the thermal control means in controlling the proportions of hot and cold fluid being mixed within the mixing valve, while the progressive passage of mixed fluid past successive convolutions of the temperature responsive element provides a particularly quick and accurate response as a function of the rate of change of the control variable.

In one exemplary embodiment later to be described in detail the hollow control member is itself axially displaceable between a valve opening and a valve closing position in respect of one of the inlet ports. As later described in detail the valve member may be secured to one end of the temperature responsive element and the other end of the temperature responsive element may be secured to a temperature control member whereby the temperature of the fluid mixture at the outlet can be controlled by changing the position of the temperature control member. In one exemplary embodiment a manually rotatable member is provided in the housing and is independently controllable both for axial and rotational movement. The rotational movement is utilised to control the position of the temperature control member while the axial movement is utilised to control opening and closing of the main inlet ports.

^ In alternative forms of the invention the control of the temperature setting is provided at the opposite end of the housing to the control for the volume of throughput. This provides simplification of the mixing valve both from the point of view of construction and from the point of view of maintenance during service.

In the preferred embodiment, as later described in detail, the hollow control member is non-axially, but rotatably, movable within the housing, control of the setting of the temperature responsive element being controlled by rotation of the hollow control member. This provides a particularly easily fabricated and maintained structure with the throughput control valve means being cooperable with interior surfaces of the hollow control member.

The invention will be described, by way of example, with reference to Figures 1 to 3 of the accompanying drawings which illustrate in diagrammatic sectional view three embodiments of mixing valve embodying the invention:- In Figure 1 of the drawing there is shown a mixing valve comprising a housing 1 provided with a hot inlet 2, a cold inlet 3 and an outlet port 4. Extending axially within the housing 1 is a hollow control member 5 having a larger diameter portion 6 at one end thereof. Extending radially through the larger diameter cylindrical portion 6 of the hollow control member are hot mixing ports 7 and cold mixing ports 8. A barrier 9 extends across the hollow control member to separate the hot and cold mixing ports 7 and 8. An annular valve member 10 is slidably mounted on the exterior of the larger diameter portion 6 so that upon axial movement relative to the hollow member the hot and cold mixing ports are closed to a greater or lesser extent so as to control the proportion of fluid allowed to pass through the mixing ports in gurfaces of the valve member 10 and the larger diameter portions 6 may be provided with surface coatings of polytetrafluoroethylene or similar low friction material. A coiled coil bimetallic laminated strip 11 is mounted within the annular space between the housing and the hollow member 5. One end 12 of the bimetallic element is connected to the valve member 10 while the other end 13 of the bimetallic element is secured to a temperature control member 14.

The hollow member 5 is supported for sliding movement axially of the housing and is urged to the right, referring to the drawing, by a compression spring 15, the tension of which is controllable by a spring adjustor 16. In the position shown the hot inlet port 2 is closed for the flow of liquid by a valve member 31 engaging an 0-ring valve seat 32.

At the right hand end of the hollow member 5 there is provided a control valve for the cold inlet port 3 which comprises a valve member 18 axially movable into engagement with a valve seat 17 which also is in the form of an 0-ring seal. 0-ring seals can be used for the valve seats 17 and 32 as suitable stops are provided for preventing over-compression of the 0-rings. Suitable keying is provided for holding the hollow member 5 against rotation with the temperature control member 14 being keyed for sliding movement axially of the hollow member 5 so as to be non-rotatable relative to the hollow member 5. A manually rotatable member 20 is provided about the right-hand end of the hollow member 5 and comprises a multi-start quick action thread engageable with a corresponding thread on the temperature control member 14 whereby rotation of the manually rotatable member 20 will cause axial displacement of the temperature control member 14. A temperature setting control knob 21 is provided for rotation at the right hand end of the housing and is drivingly connected to a rotational drive member 23 which at its left hand end com rises a luralit of can establish a balance position with both of the inlet port,? open and with the shoulders 27 and 28 spaced apart. Further opening movement of the valve by rotation of the knob 22 to retract manually rotatable member 20 will cause both inlet ports to be open to a greater extent in a balanced manner.

The ratio of hot and cold fluids fed from the outlet port 4- depends upon the position of the annular valve member 10 and the extent to which it obstructs the hot and cold mixing ports 7 and 8. The position of the annular member 10 is controlled by the bimetallic element 11 which is positioned generally in accordance with the rotational position of the manually rotatable member 20 acting through the quick action multi-start thread on the temperature control member 14. For any particular setting of the temperature control member 14- the right hand end of the bimetallic element 11 will be located in a position such that fluctuations in temperatures of the mixed liquid will cause expansion or contraction of the axial length of the bimetallic element. Thus upon the temperature of the mixture increasing the bimetallic element expands with consequent leftward movement of the annular valve member 10 partially to close the hot inlet mixing port and to open the cold mixing port 8. The elongated nature of the bimetallic element with progressive contact of mixed fluid with the element provides a velocity feed back function whereby particularly quick and accurate response of the bimetallic element is obtained with a control function which has little tendency to hunt or fluctuate widly. By having the outlet ports 4- spaced from the right hand end of the bimetallic element 11 a relatively dead space is provided at the right hand end of the bimetallic element 11 which results in a certain amount of stabilisation of the temperature response signal which again helps to provide a reliable temperature output of mixed fluid.

It will be appreciated that this described thermostatic bimetallic element provides a fast response due to the large surface area of the bimetal and this compares favourable with prior art thermostatic mixing valves which have relied upon vapour pressure bellows type thermal response elements. Thus vapour pressure bellows type elements have a long response time due to the need for evaporation or condensation to take place.

Because of the quick response accurate setting of output temperature can be obtained while the velocity feed back function arising from the graduated sensing of temperature mixed fluid along the length of the element helps to give a quick response with little hunting or fluctuation. Additionally the temperature of the mixed fluid is sensed immediately after mixing in a small cavity xvhich again helps to give the desirable quick response.

Because of the quick response with little hunting the control valve can be arranged to have a large control movement for a given temperature change with consequent increased accuracy. A particularly illustrative embodiment can readily be manufactured out of stainless steel with the provision of cheap and efficient O-ring seals for preventing leakage of fluid. The simple arrangement is such that volume of fluid throughput is controlled by one member, the knob 22, while the output temperature is controlled by another member, knob 21. This leads for particularly simple use of the device due to the balanced floating action of the hollow member 5 which can be properly adjusted when setting up the environment thermostatic valve in a paxtlculaoc simply by adjusting the spring adjustor 16.

A further improvement which can be included in the described embodiment of Figure 1, is the inclusion of means to prevent further rotation of the knob 22 once it has reached a fully open position. Such means may comprise an expansible grip ring provided in a V-section annular groove at the juncture of the members 20 and 23, this ring being expanded into gripping engagement Element 104-.

The hollow member 103 is supported for sliding movement axially of the housing and is urged to the right, referring to the drawing, by a compression spring 117, e tension of which is controllable by a spring adjuster plug 115 which is threaded into the left hand end of the housing 101 whereby screwing the adjuster 115 into, or out of the housing adjusts the position of the manually rotatable member 109 and thus, also, the position of the left hand end of the spring 117. It will be appreciated that alternative means can be used for mounting the spring 117 for adjustability. In the position shown the inlet of hot fluid is closed by a seal 112 of a valve member 113 engaging a valve seat 110 of an inlet port opening axially towards the left hand end of the hollow member 103. The valve member 113 is mounted for rotational movement at the left hand end of the hollow member 103 whereby the seal 112 can rotate in conjunction with the valve seat 110 should the knob 11 be rotated when the inlet port within the valve seat 110 is closed. A ball thrust race 116 is shown provided between the adjuster 115 and the manually rotatable member 109 for absorbing the thrust of the spring 117.

At the right hand end of the hollow member 103 there is provided a control valve for the inlet of cold fluid which comprises an inlet port valve member having a seat 131 engageable with a seal 130 by the hollow member 103. The hollow member 103 is held against rotation by suitable keying co-operating with an axially movable member 119 carried within the housing 101 for axial movement but itself keyed against rotation by engagement with a plug member 121 screwed into the right hand end of the housing 101. Axial movement of the member 119 is controlled by coaction of a coarse pitch thread on that member with a threaded portion of a manually rotatable fluid flow control member 122 carrying a knob The member 132 is shown forming a mixing''change 127 in which fluid admitted through the hot and cold mixing ports 12$ and 126 is mixed before being allowed to leave through a plurality of outlet passages, only one of which is shown at 128. Various O-ring seals are shown in the Figure at appropriate places for preventing leakage of fluid.

The operation of the thermostatic control valve will now be described.

In Figure 2 the control valve is shown in its off-position with both the main inlet ports being closed by their respective main control valves comprising valve members 120 and and with the temperature control mejaker in its extreme cold position 110 and valve seats 130 and il2VT*"ln order to sTfaTt the operation of the valve the knob 123 is rotated so as to cause movement of the member 119 to the right by the action of the coarse pitch thread between members 122 and 119. Initially the spring 11? causes the hollow member 103 to move to the right to allow the admission of the hot fluid to the interior of the hollow member 103 from which it can pass through hot mixing port 125 to the mixing chamber 127, and from thence through the ports 128 to the chamber containing the thermally responsive element 104 and having the outlet port 102. As the spring 118 almost balances the spring 117 any substantial flow through the hot inlet port will cause a decrease in the pressure at the left hand end of the hollow member 103 in comparison with the static pressure acting on the right hand end of the hollow member 103 so that the hollow member 103 can establish a balanced position with both the inlet ports open. Further opening movement of the valve by rotation of the knob 123 to retract the member 119 will cause both inlet ports to be opened to a greater extent in a balanced manner.

The ratio of hot and cold fluid in the mixture fed from the outlet port 102 depends upon the position of the annular valve •3'f the annular member 132 is controlled by the bimetallic element 104 which is positioned generally in accordance with the rotational position of the manually rotatable member 109 acting through a thread, which is preferably of a quick action multi-start type, on the temperature control member 107. For any particular setting of the temperature control member 107 the left hand end of the bimetallic element will be located in position such that fluctuations in temperature of the mixed liquid will cause expansion or contraction of the axial length of the bimetallic element. Thus upon the temperature of the mixture increasing the bimetallic element will expand with consequent leftward movement of the annular valve member 132 partially to close the hot inlet mixing port 125 and to open the cold mixing port 126.

The simple arrangement is such that volume of fluid throughput is controlled by one member, the knob 123, while the output temperature is controlled by another member, knob 114.

With a coarse pitch thread connection between members 119 and 122 a simple lever can be used to replace the knob 123 so that a very quick and ready control of fluid throughput can be given to anyone utilising the valve. This leads to particularly simple use of the device due to the balanced floating action of the hollow member 103 which can be properly adjusted when setting up the thermostatic valve in a particular environment simply by adjusting the spring adjuster 115.

Use of a preliminary mixing chamber 127 allow a pressure drop to be provided between the mixing chamber and the chamber containing the thermally responsive element. As well as providing better mixing this pressure drop allows the use of an open discharg from the outlet port 102 even when high pressure liquid is supplied to both the inlet ports, as should the mixing valve be used at the bottom of a high tower block of flats. If there was no such rovi ion for a res re d there uld be e er Figure 3 discloses an embodiment in which the principle generally the various parts of this embodiment are given the ¾ame reference numerals, where applicable, as the embodiment of Figure 1 with the exception that they are preceded by the number two hundred.

Referring to Figure 3, a hollow control member 205 is screw threadably secured to a rotational drive member 223 so as to be rotatable, but non-axially slidable, with the member 223 within the housing 201. A sleeve 250 is secured by cement 261 to the housing 201 and is keyed to a temperature control member 251 screw threaded, by a quick action thread, to the member 223. With this arrangement rotation of the member 223 will cause the member 2 1 to move axially within the housing 201. A connector 252 is secured to the member 251 and has a portion pivotally received within a plastics sleeve 253 held within the endmost convolution of the smaller helix of the coiled-coil temperature responsive element 211. At the other end 212 of the temperature responsive element a ball 254- and socket connection is provided with the sleeve valve member 210. The ball2 and sleeve 253 m y be made of a plastics material, for example polybetrafluoroethylene and are provided to permit proper accommodation of twisting of the temperature responsive element during temperature changes.

A main valve closing control member 219 is rotatably mounted itfit in the housing 1 and is threaded, by means of a quick- action thread, to a main valve member 229. The member 229 is keyed to a sleeve 26 secured inside the housing 1 so as to be axially movable upon rotation of the main valve member 219. The main valve member 229 carries an 0-ring seal 255 engageable with an interior wall 256 of the hollow control member 205 "to provide a barrier between the hot and cold mixing ports 207 and 208. The member 229 also carries main shut-off seals 259 and 258 respectively engageable with cylindrical surfaces 260 and 257 of the hollow control member to shut-off the flow of fluid to the mixing ports 207 and 208.

Claims (22)

I CLAIM:

1. A thermostatic mixing valve comprising a housing, two fluid inlet ports for admitting fluid to be mixed, an outlet port for discharging fluid from the housing, and thermal control means for adjusting the ratio of quantities of fluid admitted from the inlet ports in response to the temperature of fluid flowing from the inlet ports to the outlet port, said thermal control means including a temperature responsive element comprising a coiled coil, as hereinbefore defined, laminated strip mounted in an annular space surrounding a hollow control member and slidihgly supported by the hollow control member, and a valve member movable in response to changes in axial length of the temperature responsive element to control the proportions of fluid flow through spaced hot and cold mixing ports opening radially through the hollow control member respectively in communication with the two inlet ports, a barrier being provided within the hollow control member between the inlet sides of the mixing ports.

2. A mixing valve according to claim 1, wherein the mixing ports open into the annular space at or near one end of the temperature responsive element and the outlet port is provided from said space at a position intermediate the ends of the temperature responsive element.

3. A mixing valve according to claim 1 or 2, wherein the valve member is slidable on the hollow control member between positions partially closing the outlet sides of the mixing ports for varying the proportions of hot and cold fluid passed therethrough.

4. A mixing valve according to claim 3i wherein the valve member is in the form of a ring surrounding a cylindrical portion of the control member.

5. A mixing valve according to any preceding claim, wherein a main valve closing control member is mounted for movement between valve open and valve closed positions, said valve closing control member in its closed position holding a valve inlet closing member in position closing the inlet to one end of the hollow control member.

6. A mixing valve according to claim 5, wherein the hollow control member is itself axially displaceable between a valve opening and a valve closing position in respect of one of the inlet ports, said valve closing member during movement from its valve open to its valve closed position being operative both to move the hollow member axially to close the one inlet port and to move the valve member into position closing said other inlet port;

7. A mixing valve according to claim 6, wherein the hollow control member is axially displaceable responsive to pressure differences between the inlet ports.

8. A mixing valve according to any one of claims 1 to 4, wherein the hollow control member is located against axial movement in the housing.

9. A mixing valve according to any preceding claim, wherein the valve member is secured to one end of the temperature responsive element and the other end of the temperature responsive element is secured to a temperature control member whereby the temperature of the fluid mixture at the outlet can be controlled by changing the position of the temperature control member axially relative to the housing.

10. A mixing valve according to claim 9 wherein the temperature control member is keyed for axial movement relative to said hollow control member and is axially displaceable by a manually rotatable member carried by the housing, a multi-start quick action thread being provided between said manually rotatable member and said temperature control member.

11. A mixing valve according to claim 10 when appendant to claim 6 or 7, wherein said main valve closing control member is adapted axially to move the manually rotatable member, said manually rotatable member carrying the valve closing member for the other inlet port for co-operation with a valve seat carried by the hollow member, and also being provided with a lost motion connection with the hollow member whereby when the said other valve port is closed, further axial movement of the manually rotatable member will cause axial movement of the hollow member to close the one inlet port, separate rotatable control knobs being provided for controlling the axial and rotational position of the manually rotatable member.

12. O A mixing valve according to any preceding claim, wherein a mixing chamber is provided for mixing fluid from the hot and cold inlets before discharge into the chamber containing the temperature responsive element.

13. O A mixing valve according to claim 12 wherein the mixing chamber is formed within a sleeve forming said valve member and is provided with a reduced section outlet.

14. A mixing valve according to any preceding claim wherein a coil or strand of plastics or elastomeric material is provided within the convolutions of the smaller helix of the coiled coil element.

15. A mixing valve according to claim 8 when appendant to claim 5 or any one of claims 9 to 14 when appendant thereto, wherein the valve inlet closing member comprises a seal slidably engaged within the hollow member to provide said barrier and two valve seals engageable with the interior of the hollow control member in the valve closed position of the valve closing control member to close the inlet through the hollow control member to the hot and cold mixing ports.

16. A mixing valve according to claim 9, or any one of claims 12 to 15 when appendant thereto, wherein the temperature control member is axially but non-rotatably slidable relative to the housing and is connected to the hollow control member by a quick-action screw thread whereby rotation of the hollow control member causes axial adjustment of said other end of the temperature responsive element.

17. A mixing valve according to claim 9) or any preceding claim appendant thereto, wherein a pivotal connection is provided between the temperature control member and a sleeve received within a turn of the small helix of the temperature responsive element near said other end thereof.

18. A mixing valve according to any preceding claim, wherein a ball and socket connection is provided between one end of the temperature responsive element and the valve member.

19. · A mixing valve according to any one of cl ims 1 to » including flow control means for regulating the rate of flow of fluid to he mixed Independently of operation of the thermal control meant*

20. A thermostatic nixing valve constructed and arranged to operate substantially as herein described with reference to and aa illustrated in Figure t of the accompanying drawings.

21. A thermletatlo mixing valve construct* ed and arranged to operate substantially as herein described with re erence to and as illustrated in Figure 2 of the accompanying drawings.

22. A thermostatic mixing valve constructed and arranged to operate substantially as herein described with reference to and as illustrated in Figure 3 of the accompanying drawings* Att icants