(72) Inventor ROBIN JAMES THOMAS CLABBURN (54) TEMPERATURE-ACTUATABLE VALVE CONTROL MEANS(71) We, RAYCHEM LIMITED, a BritishCompany, of Moor House, London Wall,London EC2Y 5HP. do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to temperatureactuatable valve-actuating devices, especally safety devices, and to valves equipped with such devices.
It has been proposed to form temperature actuatable devices from so-called "memory metals", i.e. metallic materials from which a heat-recoverable article can be made, that is an article which can be deformed from an original heat-stable configuration to a different heat-unstable configuration in which it will remain until raised above a temperature known as the transition temperature when it will return or attempt to return towards its original configuration, without the further application of outside force. The use of such memory metals in devices to open and close valves has also been described.
The present invention is based on our surprising observation that a safety device for a fluid valve, especially a conventional gas valve, can be made from a memory metal as a simple one-piece member without the need for co-operating bias means or co-operating temperature control means.
The present invention provides a valveactuating device which comprises a length of memory metal (as hereinbefore defined) material formed into a heat-recoverable member comprising a central coiled portion and first and second terminal portions, the arrangement of said terminal portions with respect to said coiled portion being such that when the latter is positioned with its central longitudinal axis vertical, said first terminal portion projects upwardly from said coiled portion and said second terminal portion projects downwardly from said coiled portion, the device being capable, on recovery, of winding or unwinding to cause relative movement of said terminal portions around the central longitudinal axis of the coil.
The present invention also provides a valve equipped with said device, the valve comprising a coiled member, the device being positioned so that the central coiled portion surrounds at least a part of the valve housing and the first, upper and second, lower terminal portions are in contact with the control member and a part of the valve housing and/or the pipeline to which it is connected, respectively (or vice versa) so that, on recovery of the device, the first, upper portion moves around the central axis of the coil to actuate the control member whilst the second, lower portion remains stationary (or vice versa).
The device may, for example, be formed from a wire, bar or strip of a suitable member metal and, obviously, given the basic configuration the exact design of the device may readily be varied according to the application. For example, the upper and lower terminal portions may be straight or may be bent or otherwise formed to -facilitate co-operation with the control member, e.g. a handle, or the valve housing. Similarly the central portion may comprise a single turn or two or more turns. Equally, whilst it is preferred that the device be formed as a single piece, in some applications it may be advantageous to provide auxiliary means to facilitate its operation. For example the upper and lower terminal portions may be provided with means for attaching them to the control member or the valve housing (or in some cases the pipeline itself).
Another preferred design feature is that the upper and lower portions should bedisposed away from the central longitudinalaxis of the coiled portion, so as to enhancethe degree of torque obtained on recovery.
One preferred application for the deviceis as a safety closeure for a conventionalgas valve, i.e. one which will close the valve in the event of a fire. In such anapplication, it is not important that thedevice should be reusable (although it can in any case be redeformed if desired) on cooling and therefore it is not necessary to provide the valve or the device with any bias means to achieve this end. However, it may in some cases be advantageous to provide bias means so that the device may act as a valve control means, rather than as a valve closure or valve opening means. Equally, whilst, in general, it is preferred that the member should not itself be a spring member, in some cases it may be advantageous for it to exhibit a certain amount of resilience so that it can be firmly snapped into position on the valve.
Amongst suitable memory metals for use in the present invention there may be mentioned various alloys of titanium and nickel which are described, for example in U.S. Patents Nos. 3,174,851; 3,351;463; 3,753,700; 3,759,552, British Patents Nos.
1,327,441 and 1,327,442 and-NASA Publication SP 110, "55-Nitinol-The Alloy with a Memory, etc." (U.S. Government Printing Office, Washington, D.D. 1972). The property of heat-recoverability has not, however, been solely confined to )such titanium-nickel alloys. Thus, for example, various beta-brass alloys have been demonstrated to exhibit this property in, e.g. N. Nakanishi et al, Scripta Metallurgica 5, 433-440 (Pergamon Press 1972) and such materials may be doped to lower their transition temperatures to cryogenic regimes by known techniques. Similarly, 304 stainless steels have been shown to enjoy such characteristics, E. Enami et al, id at pp. 663-68.
In general these metals have a transition temperature within the range of from -1960C to +1350C, especially from -1960C to -700C (this being the lowest temperature they are liable to encounter during everyday use), and thus may be brought into their martensitic state by immersion in liquid nitrogen. However, more recently, it has been possible to "precondition" memory metals so as transiently to raise their transition temperature. This enables the articles made from such alloys to be kept at room temperature prior to use, when they can be recovered by heating. Such preconditioning methods, which eliminate the need for liquid nitrogen during storage and transportation, aredescribed, for example, in German Applications OS 2 603 878 and OS 2603 911.
The preferred transition temperature forthe memory metal used-in the device willdepend upon the particular application. In general, where the device is used forsafety purposes in the event of fire it will be necessary for the transition temperature to lie sufficiently above ambient temperatture that the device will not be actuatedduring normal operation of the valve butsufficiently low that it will function at the onset of danger. For these reasons, transition temperatures in the range of from 35 to 1350C are advantageously employed.
(Recovery in fact takes place over a narrow temperature range of, for example, 30"C and, because the transition temperature rises with increasing applied stress, the recovery temperature may also be raised if the force necessary to actuate the valve is high.)The device is preferably rigid but the size and thickness of the metal wire, bar or strip can be varied according to the size and stiffness of the valve. Of course, the cross-section of the member may be of any convenient shape and the relative lengths of the upper and lower terminal portions may be varied according to the application.
One form of device according to the present invention will now be described, by way of example only, with reference to the drawings accompanying the provisional specification, in which:Figure 1 illustrates the device; andFigure 2 shows the device in position about a valve.
Referring to Figure 1, there is shown one form of device according to the present invention comprising a coiled central portoion 1, an upwardly projecting portion 2 and a downwardly projecting portion 3. As can be seen, the device has been formed from a length of metal rod of circular cross-section, the metal preferably being a beta-brass alloy, of the type described, having a transition temperature of from 35"C to 135"C. The upwardly projecting portion 2 is bent at its upper end to form an arm 4. The device has been deformed below the transition temperature by unwinding the coiled central portion 1 so that its diameter in the deformed state is greater than its undeformed diameter.
During this deformation upper portion 2 has been moved in an anticlockwise direction (viewed from above) with respect to lower portoion 3.
Figure 2 shows the device of Figure 1 in position about a valve 5 connected to a pipeline 6. As shown, the valve has a handle 7 which is in the open position. The terminal part 4 of the upper portion 2 of the device abuts the handle 7 and the lower portion 3 contacts the housing 8 of the valve.
At ambient temperature this arrangement will maintain. However, as soon as the temperature rises to the transition temperature of the memory alloy the device will attempt to return to its original undeformed configuration. That is to say, the upper portion 2 will attempt to move in a clockwise direction relative to lower portion 3 so as to wind up the coiled central portion 1. Because the lower portion 3 abuts the housing 8 of the valve 5 it cannot move and consequently movement of the upper portion 2 forces the handle 7 in the direction shown by the arrow so as to shut the valve. It will be appreciated that a device similar to that shown could be made so that it would unwind upon recovery and force the handle 7 into a closed (or open) position.Equally it will be appreciated that the upper and lower portions need not lie in an exact north-south position relative to the plane of the coiled central portion.
An important feature of the device as shown which is advantageously possessed by all devices of the present invention, is that the handle 7 can be closed and opened, for example manually, even when the device is in position. That is to say, operation of the valve is not dependent upon the balance of two mutually biassed forces. The heat-recoverable device acts purely as a safety mechanism which will close the valve in extreme circumstances.
It otherwise has no function in the operation of the valve.
In some cases it may be advantageous for the device to exhibit a degree of resilience so that it can be firmly placed in position with respect to the valve. However, it should be stressed that the present invention does not generally seek to utilise the change in strength of a spring device.
That is to say, the object of the present invention is to provide simple actuating devices which operate purely by virtue of heat recovery of the device from a deformed configuration towards a heat stable configuration.
WHAT WE CLAIM IS:1. A valve-actuating device which comprises a length of memory metal (as hereinbefore defined) material formed into a heat-recoverable member comprising a central coiled portion and first and second terminal portions, the arrangement of said terminal portions with respect to said coiled portion being such that when the latter is positioned with its central longitudinal axis vertical, said first terminal portion projects upwardly from said coiled portion and said second terminal portion projects downwardly from said coiled portion, the device being capable, on recovery, of winding or unwinding to cause relative movement of said terminal portions around the central longitudinal axis of the coil.
2. A valve-actuating device as claimed in claim 1, wherein the upper terminal portion is bent towards its end so as to form an arm.
3. A valve-actuating device as claimed in claims 1 or 2, which is formed from a bar, wire or strip of the memory metal.
4. A valve-actuating device as claimed in any one of claims 1 to 3, wherein the memory metal is a P-brass alloy.
5. A valve-actuating device as claimed in any one of claims 1 to 4, wherein the memory metal has a recovery temperature in the range of from 35 to 1359C.
6. A valve-actuating device as claimed in claim 1, substantially as described herein with reference to, and as illustrated in, the drawings accompanying the provisional specification.
7. A valve equipped with a device as claimed in any one of claims 1 to 6, the valve comprising a control member, the device being positioned so that the central coiled portion surrounds at least a part of the valve housing and the first, upper and second, lower terminal portions are in contact with the control member and a part of the valve housing and/or the pipeline to which it is connected, respectively (or vice versa) so that, on recovery of the device, the first, upper portion moves around the central axis of the coil to actuate the control member whilst the second, lower portion remains stationary (or vice versa).
8. A valve as claimed in claim 7, which is a domestic gas valve.
9. A valve as claimed in claims 7 or 8, wherein the arrangement is such that the valve may be controlled manually without interfering with the memory metal device.
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