GB2248908A - A resettable thermostatic control valve - Google Patents

Abstract

A resettable thermostatic control valve unit has a control valve (1) including a control member (5) movable from an extended position to a retracted position against the action of an internal spring, and a valve actuator mechanism comprising a bracket (6) carried by the valve, a spring clip (8) carried by the bracket (6) and engageable with the control member (5) to retain the control member (5) in its retracted position and a shape memory alloy member (9) carried by the bracket (6) and engageable with the clip (8). If the member (9) is heated above a predetermined temperature it urges the spring clip (8) away from the position in which it retains the control member (5) in its retracted position, causing it to move to its extended position where it remains upon the temperature falling below the predetermined level. In Figs. 2A-C (not shown) over-heating of the member (9) causes rotation of the control member (5) to release a latch and permit axial movement of the member (5). In Figs. 3A-B (not shown) expansion of an SME spring (24) permits a spring clip (25) to move into the path of the control member (5) and thus prevent its return movement. <IMAGE>

Description

A RESETTABLE THERMOSTATIC CONTROL VALVE This invention relates to a resettable thermostatic control valve.

According to this invention there is provided a resettable thermostatic control valve unit comprising a control valve including a control member movable between an extended position and a retracted position against the action of an internal spring, and a valve actuator mechanism comprising a bracket carried by the valve, a spring clip carried by the bracket and engageable with the control member to retain the control member in its retracted position and a shaped memory alloy material carried by the bracket and engageable with the clip, the shaped memory alloy member being operative in one of its two shapes to urge the spring clip away from the position in which it retains the control member in its retracted position.

According to a second aspect of this invention, there is provided a resettable thermostatic control valve unit comprising a control valve comprising a valve including a control member movable between an extended position and a retracted position against the action of an internal spring and rotatable about its axis, and a valve actuator mechanism comprising a base carried by the valve a latch carried by the base and engageable with an arm carried by the control member to retain the control member in its retracted position when the control member is in a particular angular orientation, and a shaped memory alloy member having one end connected directly or indirectly to the base of the valve actuator mechanism and its other end connected to the spindle, the shaped memory alloy member being operative in one of the shapes it takes up to rotate the control member to the angular orientation in which its arm is engageable with the latch and in its other shape to rotate the control member to an angular orientation in which its arm is not enageable with the latch.

According to a third aspect of this invention, there is provided a resettable thermostatic control valve unit comprising a control valve having a control member movable between an extended position and a retracted position against the action of an internal spring of the valve, and a valve actuator mechanism comprising a support carried by the valve, a spring of shaped memory alloy material extending between the support and the control member, and a latch clip engageable with the control member when in its retracted position to retain the control member in that position, the spring acting when the control member is in its extended position when the temperature rises above a predetermined value to bring the control member to its retracted position against the action of the internal spring of the control valve.

Three exemplary thermostatic reset table control valves will now be described with refrence to the accompanying drawings of which: Figures 1A and 1B are, respectively, a front view and a side view of a first thermostatic resettable control valve in accordance with this invention; Figures 2A, 2B and 2C are, respectively, a front view, a side and a plan view of a second thermostatic resettable control valve in accordance with this invention; and Figure 3A and 3B are respectively a front and a side view of a third resettable thermostatic control valve in accordance with this invention.

Referring to Figures 1A and 1B, a standard pneumatic control valve has an inlet port 2, an outlet port 3 and an exhaust port 4. A control spindle 5 is shown in both Figures 1A and 1B depressed inwardly against the action of an internal spring of the valve. The valve can operate in various configurations and, as an example, the mains air supply is connected to the inlet port 2 and, when the spindle 5 is inwardly depressed as shown, the pneumatic air supply reaches the outlet port 3, where it is connected to a pneumatic system. In the event the spindle 5 is allowed to move outwardly the air supply that flows from the inlet port 2 to the exhaust port 4 and the outlet port 3 is cut off. The air supply at the outlet port 3 is used to control some pneumatically controllable equipment.

Mounted on the valve 1 is a bracket 6 by means of a nut 7 screwed on to a threaded spigot through which the spindle 5 extends.

A spring steel retaining clip 8 is rigidly secured to the end of the bracket 6 above the spindle 5 and in the condition shown in Figures 1A and 1B, engages the end of the spindle 5 holding that spindle 5 in its retracted position within the valve 1. A shape memory alloy (SMA) tongue 9 is secured at its upper end to the top of the bracket 6 and engages, at its free end, the clip 8. The illustrated shape of the SMA tongue 9 is that it takes up at ambient temperature. In the event that the temperature rises above a predetermined level, the SMA tongue 9 changes its shape at that temperature so that its free end exerts a force against the spring clip 8 urging it away from the spindle 5, i.e. to the left as shown in Figure 1A.The force is such as to move the end of the clip 8 to the extent that it releases the spindle 5 which is then urged out of the valve I by the internal spring of the valve 1 so that the air supply is cut off from the outlet port 3 and is exhausted to atmosphere through the port 4.

On a fall in the ambient temperature below the predetermined value, although the SMA tongue 9 regains its original shape, the spring clip 8 cannot revert to its original position because the spindle 5 is now in its extended position so that the pneumatic air supply remains cut off from the outlet port 3. The spindle 5 can be manually depressed to its retracted position whereupon the spring 8 reverts, under its internal resilience, to the position shown in Figure 1A and 1B so that the spindle 5 is held in its retracted position.

Referring now to Figures 2A, 2B and 2C, the valve 1 shown therein is the same as that of the thermostatic resettable control valve the spindle 5 is shown as very much larger and is illustrated as threaded.

The control valve 1 carries a base 10 of an actuator assembly carried above the nut 7; the base 10 carries an upwardly projecting spigot 12 which is formed with an integral latch 13. The latch 13 extends towards but does not touch the spindle 5. The spindle 5 is rotatable and carries a cross pin 14 which, in the condition shown in Figures 2A and 2B, engages the under surface of the latch 13. The spindle 5 is shown in the retracted position in which the inlet port 2 is connected to the outlet port 3 and is urged outwardly by an internal spring of the valve 1. The outward movement of the spindle 5 is restrained by engagement of the pin 14 with the latch 13.A shape metal alloy spring in the form of a generally U-shaped member 15 as seen in the plan view in Figure 2C is secured at one end to the valve spindle 5 and engages at its other end the spigot 11 which projects upwardly from the base 10. The SMA member 15 also extends in the vertical direction as can be seen from Figures 2A and 2B. In the event of a rise of the temperature above a predetermined value, the shape of the SMA member 15 changes rotating the spindle 5 to the extent that the pin 14 no longer engages the underneath surface of the latch 13, permitting the spindle 5 to be urged outwardly by the internal spring of the valve 1. The outward movement of the spindle 5 diverts the pneumatic air supply at the inlet port 2 from the outlet port 3 to the exhaust port 4. In the event that the temperature falls below a predetermined temperature, the U-shaped member 15 reverts to its original shape, bringing the valve spindle back to its original angular orientation. However, the spindle 5 does not move back to its original position because of the force exerted on it by the internal spring of the valve 1; full inward movement of the spindle 5 is prevented because the pin 14 will engage the upper surface of the latch 13.

The spindle 5 can be manually brought back to its original position by rotating it (by means of a screw driver engaging in a slot 16 in the top of the spindle 5) and then depressing it inwardly and then rerotating it back to its original angular position so that the pin 14 engages the lower surface of the latch 13 and is rotated thereby.

The control valve shown in Figures 3A and 3B has a control valve 1 identical to that shown in Figures 1A and 1B. The control valve 1 carries an actuator base 20 to which is secured, above it, a parallel bridge 21 by means of two vertical and threaded posts 22 on either side of the spindle 5 and various nuts. The spindle 5 carries at its free end the transverse plate 23 is shown in its retracted position being pushed downwardly against the internal spring of the valve 1 by a compression spring 24 of shaped memory alloy which extends between the plate 23 and the bridge 21. A spring clip 25 is secured at its upper end to the bridge 21 and its lower free end engages, in the extended position of the spindle 5 shown, the outer peripheral surface of the transverse plate 23.

In the event of the ambient temperature rising above a predetermined value, the SMA spring 24 extends its length substantially exerting a substantial force against the plate 23 pushing the spindle 5 to its retracted position. The latch clip 25 urges its free end towards the centre line of the spindle 5 moving above the top surface of the plate 23. Consequently, when the ambient temperature falls and the SMA spring 24 contracts to its original length, the internal spring of the valve 1 cannot move the spindle 5 outwardly.

When in its retracted position, the valve 1 connects the inlet port 2 to the outlet port 3, whereas when the spindle 5 is in its extended position (that shown), the valve port 1 connects the inlet port 2 to the exhaust port 4.

To bring the valve 1 back to its original condition, i.e.

that shown in which the spindle 5 is in its extended position, the free end of the clip 25 is manually pushed outwardly so that the internal spring of the valve 1 can readily push the spindle 5 to its extended position.

The internal configuration of the valve 1 can obviously be changed.

Claims (5)

1. A resettable thermostatic control valve unit comprising a control valve including a control member movable between an extended position and a retracted position, and a valve actuator mechanism including a shape memory alloy member and serving to move the control member between one of the extended and retracted positions to the other position in response to an increase in temperature, the arrangement being such that upon a fall of temperature, the control member is not moved back to its original position.

2. A resettable thermostatic control valve unit as claimed in claim 1, wherein the control member is movable from the extended position to the retracted position against the action of an internal spring and wherein the valve actuator mechanism comprises a bracket carried by the valve, a spring clip carried by the bracket and engageable with the control member to retain the control member in its retracted position and the shape memory alloy material which is carried by the bracket and is engageable with the clip, the shape memory alloy member being operative in one of its two shapes to urge the spring clip away from the position in which it retains the control member in its retracted position.

3. A resettable thermostatic valve control unit as claimed in claim 1, wherein the control member is movable from its extended position to its retracted positions against the action of an internal spring and is rotatable about its axis and wherein the valve actuator member comprises a base carried by the valve, a latch carried by the base and engageable with an arm carried by the control member to retain the control member in its retracted position when the control member is in a particular angular orientation, and the shape memory alloy member which has one end connected directly or indirectly to the base of the valve actuator mechanism and its other end connected to the spindle, the shape memory alloy member being operative in one of the shapes it takes up to rotate the control member to the angular orientation in which its arm is engageable with the latch and in its other shape to rotate the control member to an angular orientation in which its arm is not enageable with the latch.

4. A resettable thermostatic control valve unit as claimed in claim 1, wherein the control member is movable from its extended position to its retracted positions against the action of an internal spring and wherein the valve actuator member comprises a support carried by the valve, a spring of shape memory alloy material extending between the support and the control member, said spring constituting said shape memory alloy member, and a latch clip engageable with the control member when in its retracted position to retain the control member in that position, the spring acting when the control member is in its extended position when the temperature rises above a predetermined value to bring the control member to its retracted position against the action of the internal spring of the control valve.

5. A resettable thermostatic control valve unit substantially as hereinbefore described with reference to the accompanying drawings.