Abstract:
A temperature dependent actuating device for a valve having a closure member which must be moved from a first to a second position to close the valve, the actuating device comprising a body, an actuating member supported by the body and moveable from a first non-actuating position to a second actuating position, a biasing device urging the actuating member toward the second position, and a temperature dependent device for releasably retaining the actuating member in the first position provided the temperature is below a predetermined level. The body is adapted to be mounted such that the actuating member is positioned to engage the valve closure member such that if the temperature in the vicinity of the valve rises above the predetermined temperature, the actuating member is released and moves to its second position, moving the valve closure member to its second position and closing the valve.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is claims benefit of PCT application Serial No. PCT/GB00/03916, filed 12 Oct. 2000, which is hereby incorporated herein by reference. 
     The present invention relates to a temperature dependent actuating device. Particularly, but not exclusively, the invention relates to a device for actuating the closure mechanism of a valve, and in particular a discharge valve as fitted to hazardous fluid containers such as a fuel tankers. 
    
    
     BACKGROUND OF THE INVENTION 
     There are many different situations in which safety concerns require that mechanisms must be provided for quickly shutting off a valve or the like in potentially dangerous circumstances. For instance, in relation to fuel tankers (including both road and rail tankers) it has long been a requirement to provide a mechanism for shutting off the valve from a remote position in the event of a leakage or similar accident. Conventionally this is done by fitting a boden cable to the operating lever of the valve, the cable extending around the periphery of the tanker so that the valve can be closed simply by pulling on the cable from any position around the tanker. 
     More recent safety regulations specify not only that it must be possible to manually close a fluid discharge valve from a remote position, but also that the valve must close automatically in the event of a fire. Clearly re-designing and replacing all existing discharge valves with valves designed to close in the event of a fire would be a massive and expensive operation. It is therefore an object of the present invention to obviate the need to re-design or replace conventional discharge valves. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention there is provided a temperature dependent actuating device for a valve having a closure member which must be moved from a first to a second position to close the valve, the actuating device comprising a body, an actuating member supported by the body and moveable relative to the body from a first non-actuating position to a second actuating position, biasing means which urges the actuating member towards the second position, and temperature dependent means for releasably retaining the actuating member in said first position against the biasing action of the biasing means provided the temperature is below a predetermined level, wherein said body is adapted to be mounted adjacent the valve with said actuating member positioned to engage the valve closure member, such that if the temperature in the immediate vicinity of the valve rises above said predetermined temperature said actuating member is released from said first position and is biased to its second position thereby moving the valve closure member from its first to its second position and closing the valve. 
     The present invention thus provides an actuating device which may be retro-fitted to existing valve assemblies and which responds to temperatures in the immediate vicinity of the valve assembly to shut the valve in the event of the temperature rising to a dangerous level. The “predetermined temperature” may not be determined precisely, what is important is that the actuating member will be activated in the event of a dangerous situation such as a fire. 
     The body of the actuating device may have fixing means, such as flanges etc, designed to mate with flanges or the like of conventional valve assemblies. Alternatively, a separate bracket or clamp arrangement may be provided to mount the actuating device to the valve assembly. 
     Movement of the actuating member may either push or pull the operating mechanism into the closed position. 
     Suitably, when in said first position the actuating member is clear of the closure member but strikes the closure member when released into its second position thereby pushing the closure member into the closed position. 
     Alternatively, the actuating member is connected to the closure member via a linkage, the linkage being arranged to translate movement of the actuating member to movement of the valve closure member from its first position to its second position, thereby closing the valve. 
     Preferably, said biasing means comprises a coil spring which is under compression when said actuating member is held in said first position. 
     Suitably, the first position of the actuating member is a retracted position (relative to the body) and the second position is an extended position (relative to the body) and 
     The temperature dependent release means preferably comprises a fusible material, such as a relatively low melting point metal or metal alloy (e.g. a solder). In preferred embodiments the fusible material is used to weld the actuating member in said first position relative to the body so that when the temperature rises above the predetermined temperature the weld melts and the actuating member is released. 
     According to a second aspect of the present invention there is provided a temperature dependent actuating device comprising a body, an actuating member supported by the body and moveable relative to the body from a first retracted position to a second actuating position in which it extends from the body, biasing means which urges the actuating member towards the second position, and means comprising a body of fusible material for releasably retaining the actuating member in said first position against the action of the biasing member, wherein said body of fusible material is selected to melt at a temperature above a predetermined temperature thereby releasing said actuating member. 
     Preferably when in said retracted position the actuating member is received entirely within the body. This need not necessarily be the case and a portion (or even all) of the actuating member may extend from the body when in said first position in which case the actuating member will extend further from said body when in said second position. 
     According to a third aspect of the present invention there is provided a valve assembly comprising a closure member which must be moved from a first to a second position to close a valve, and a actuating member positioned to engage the valve closure member, the actuating member being supported by a body and being moveable relative to the body from a first non-actuating position to a second actuating position, temperature dependent means being provided for releasably retaining the actuating member in said first position against the biasing action of a biasing means which urges the actuating member towards the second position, the arrangement being such that a rise in temperature in the immediate vicinity of the valve assembly above a predetermined temperature causes said retaining means to release the actuating member so that the actuating member is biased to its second position thereby moving the valve closure member from its first to its second position and closing said valve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Specific embodiments of the present invention will now be described, byway of example only, with reference to the accompanying drawings, in which: 
     FIG. 1 illustrates an actuating device according to the present invention fitted to a conventional fuel tanker discharge valve assembly (the actuating device is shown in axial section); 
     FIG. 2 is an enlarged view of the actuating device of FIG. 1, again shown in axial section; 
     FIGS. 3 a ,  3   b  and  3   c  are different views of a mounting bracket used to mount the actuating device to the valve assembly as illustrated in FIG. 1, FIG. 3 b  being a view looking in the direction of arrow B on FIG. 3 a  and FIG. 3 c  is a view looking in the direction of arrow C on FIG. 3 a ; and 
     FIG. 4 illustrates a second actuating device according to the present invention, fitted to a conventional ball valve. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, this illustrates a conventional fuel tanker discharge valve assembly retrofitted with an actuating device  1  according to the present invention. The discharge valve assembly comprises a primary discharge valve  2  and a secondary valve  3 . The primary valve  1  includes a first mounting flange  4  provided to mount the valve assembly to a tanker (not shown). A second flange  5  provides a mounting for the secondary valve  3 . A discharge hose  6  is then mounted to the body of the secondary valve  3 . The primary and secondary valves  2  and  3  are operated via lever arms  7  and  8  respectively. Lever arm  7  is sprung with an over-centre mechanism such that levering the arm past a centre point in either direction causes the valve to either snap shut or snap open respectively (the closed position is shown with a dotted line). As mentioned above, the discharge valve assembly is entirely conventional and thus further details of its construction and operation will not be described. 
     The actuating device  1  is mounted to the valve assembly mounting flange  4  using a bracket  9  (illustrated in detail in FIGS. 3 a  to  3   c ). The bracket  9  is part cut away in FIG. 1 to reveal details of the actuating device  1 . The mounting bracket is described in more detail further below. 
     Referring to FIGS. 1 and 2, the actuating device  1  comprises a plunger  10  housed within a two part tubular casing  11  and  12 . The casing part  11  is open at one end and turned in at the other end to form an internal annular shoulder  13 . This part is preferably made from a hard metal such as stainless steel. The casing part  12  is narrower in diameter than the part  11  and comprises a copper tube which abuts against the outside surface of the shoulder  13 . 
     The plunger  10  extends through the copper tube  12  into the casing part  11  and has a radially extending annular flange  14  at its end adjacent the open end of the casing part  11 . A brass bush  15  is secured to the opposite end of the plunger  10  via a set screw  16 . The bush  15  is welded into the end of the copper tube  12  using a relatively low melting point metal alloy or solder  17 . A helical spring  18  is located around the plunger  10  in the relatively wide part  11  of the casing and acts between the shoulder  13  and the flange  14  of the plunger  10  tending to bias the plunger  10  out of the casing. This motion is resisted by the copper tube  12  (which is welded to the bush  15 ) bearing against the outside surface of the annular shoulder  13 . 
     Referring now to FIGS. 3 a - 3   c , the mounting bracket X comprises a flange  19  provided with two apertures  20  which enables the bracket  9  to be bolted to the conventional valve assembly mounting flange  4 . A hook portion  21  extends from the mounting flange  19  and provides a cradle to receive the steel part  11  of the casing. The hook portion  21  is provided with an aperture  22  and boss  23  to receive a bolt (not shown) to clamp the actuating device  1  in position as shown in FIG.  1 . 
     From FIG. 1 it will be seen that in normal circumstances the plunger  10  will be clear of the handle in  7  and so will not impede normal operation of the valve assembly (and in addition will not impede operation of a conventional boden cable (not shown) to provide remote closure of the valve). However, in the event of a fire in the immediate vicinity of the valve  2  the low melting point metal  17  will melt releasing the plunger  10  to be driven forward by the spring  18 . The copper tube  12  and brass bush  15  ensure good heat conduction to the weld  17 . 
     As the plunger  10  is driven forward it strikes the handle  7  of the primary valve  2  moving it into the closed position (only a small amount of travel in the plunger  10  is required since it operates on the valve lever relatively close to its pivot point and furthermore since the over-centre mechanism means that the lever  7  only has to be driven marginally past the centre position for it to snap shut). The extent of travel of the plunger  10  is limited to the distance between the brass bush  15  and the annular shoulder  13  which prevents the plunger  10  from being ejected from the casing which might itself present a hazard. 
     Once the actuating device has been activated, it is not necessary to replace the entire device. Rather, the original bush  15  can simply be removed and a new tube  12  with a bush pre-welded therein positioned on the end of the casing part  11  so that the plunger  10  can be depressed back into the casing and screwed to the new bush. 
     The present invention therefore provides a relatively simply (and thus reliable) mechanical mechanism which operates to shut the valve  2  in response to a rise in temperature in the locality of the valve. 
     A second actuating device according to the invention is illustrated in FIG.  4 . The actuating device  30  is attached to a ball valve  31  of the type fitted to liquid petroleum gas (LPG) tanks, and is arranged to automatically move the ball valve  31  to a closed configuration when the temperature in the vicinity of the ball valve  31  rises above a predetermined level. 
     The actuating device  30  operates in the same manner as the first actuating device described in relation to FIGS. 1 to  3 . A cylindrical copper tube  32  contains a plunger (not visible in FIG. 4) which is biased by a helical spring towards an outer end of the tube  32 . The plunger is welded to the tube  32  using a relatively low melting point metal alloy or solder. The weld restrains the plunger from moving in accordance with the bias of the coiled spring. A chain  33  is fixed to an inner end of the plunger, and is guided via an opening  34  out of an inner end of the tube  32 . 
     The actuating device  30  is fitted to the ball valve  31  by a bracket  37  which is provided at one end with a cylindrical opening  38  to receive the tube  32 , and is provided at an opposite end with a flat plate which is bolted to a flange  39  of the ball valve  31 . 
     The valve is provided with a lever arm  35  for moving the ball valve  31  between open and closed configurations. The lever arm  35  actuates the ball valve  31  via a shaft (not visible in FIG.  4 ). The ball valve  31  is in the closed position in FIG. 4, with the open position represented by a section of the lever arm  35 ). 
     A plate  36  having a generally semicircular shape is fitted to the shaft which actuates the ball valve  31 . The connection to the shaft is rigid such that the plate  36  and shaft are constrained to rotate together. An inner end of the chain  33  is fixed to an outer surface of the plate  36  by passing a pin of the chain through an eyehole provided in the plate  36 . 
     The chain  33  is sufficiently long that, prior to actuation of the device  30 , the lever arm  35  may be moved unimpeded between open and closed positions. 
     When the temperature of the actuating device rises to a predetermined level, the weld melts and the plunger is driven towards the outer end of the tube  32  by the coiled spring. The plunger draws the chain  33  into the tube  32 , thereby rotating the plate  36  and moving the ball valve  31  to the closed configuration. The plunger is restrained from leaving the tube  32  by the chain  33 . 
     The actuating device shown in FIG. 4 has been actuated, and the chain  33  is therefore drawn into the tube  32 . As mentioned above, prior to actuation the length of chain  33  extending from the tube  32  is sufficient to allow the lever arm  35  to be moved unimpeded between open and closed positions. 
     The actuating devices may be fitted as simple retro-fit to conventional valve assemblies and alternative brackets may be provided to enable the devices to be readily fitted to valves different from that illustrated thereby avoiding the requirement to redesign the actuating devices themselves. 
     It will be appreciated that many modifications could be made to the detail of the illustrated actuating devices. For instance, the fusible material used to hold the plunger in position against the action of a spring need not form a weld between the plunger and the body (or vice versa) but could be in the form of a projection from the plunger which engages the body preventing the plunger from moving until the projection melts. Alternatively, the fusible material may be provided as a key which locates in an aperture or the like in both of the casing and the plunger locking the two together until the material melts. Other possible variations will be apparent to the skilled person. It will also be appreciated that any suitable fusible material may be used, the only requirement being that the material melts above a predetermined acceptable “safe” temperature. 
     The casing need not necessarily be a two-part casing as illustrated but could, for instance, comprise a single body. 
     In the illustrated examples the plunger is driven from the casing by a spring under compression. It will be appreciated that modifications in which, for instance, a spring in extension acts on the plunger can readily be devised. However, use of a spring in compression allows the size of the actuating device to be minimised. In other possible arrangements the spring may act to withdraw the plunger which may be attached to the valve assembly lever in such a way as to pull the lever into a closed position rather than to push it. 
     Although the actuating member according to the present invention has been designed for a particular application, it will be appreciated that the device may have application in other situations to automatically operate a mechanical lever, or switch etc, in the event of a fire or unacceptable rise in temperature. 
     Other possible modifications will be readily apparent to the appropriately skilled person.