VALVES

Abstract: A valve comprises an inlet chamber (a), a fluid outlet chamber (c) and a bellows chamber (b) defined by a bellows (22) communicating with the inlet chamber (a) via a bleed hole (54). One or both of a restrictor (32) and an end portion (24) of the bellows (22) are flexible and they can abut one another or can come into or out of abutment by relative flexure. The restrictor (32) is disposed between the inlet and outlet chambers (a and c) and has apertures (34, 36) that are closed or opened depending upon whether the seat (32) and bellows end portion (24) are or are not in abutment. When the valve is to be opened, an armature (18) of a solenoid (20) communicates the bellows and outlet chambers (b and c) via a hole (52), the resultant pressure drop in the bellows chamber (b) causing the movable seat (32) and bellows end chamber (24) to come out of abutment to communicate the inlet and outlet chambers (a and c) via the apertures (34, 36). When the valve is to be closed, the armature (18) closes the hole (52) whereby the pressure in the bellows chamber (b) increases by virtue of the bleed hole (54) and the restrictor (32) and bellows end portion (24) come into abutment to close the valve. The restrictor (32) may comprise a movable seat movable away from a fixed seat (30) after the restrictor and bellows end portion (24) have flexed apart so as to increase the extent of communication between the inlet and outlet chambers (a and c).

Description: VALVES This invention relates to valves- Solenoid valves, and in particular solenoid operated diaphragm valves, are generally quick-acting. This characteristic is in many cases undesirable because quick-acting valve closure can generate sharp rises in pressure resulting in the phenomenon known as surge pressure or "water-hammer". Water-hammer is in many cases audible and can cause damage or destruction to fluid systems, in particular to joints and seals. According to the invention there is provided a valve comprising a fluid inlet chamber, a fluid outlet chamber, a restrictor having at least one aperture and disposed between the inlet and outlet chambers, a bellows chamber defined by a bellows and communicating with the inlet chamber via at least one bleed hole, at least one of the restrictor and an end portion of the bellows being flexible and the restrictor and bellows end portion being so mounted that they can abut one another or can come out of or into abutment by virtue of a movement that at least includes flexure of at least one of the restrictor and bellows end portion, the at least one aperture in the restrictor being closed or opened depending upon whether the restrictor and bellows end portion are or are not in abutment, a discharge passage capable of communicating the bellows chamber and the outlet chamber, and actuator means which (i) when the valve is to be opened, opens the discharge passage to put the bellows chamber into communication with the outlet chamber, the resultant drop in pressure in the bellows chamber causing the restrictor and bellows end portion to come out of abutment to establish communication between the inlet and outlet chambers via the at least one aperture in the restrictor, and (ii) when the valve is to be closed, closes the discharge passage to stop the communication between the bellows chamber and the outlet chamber whereby the pressure in the bellows chamber gradually increases, by virtue of the at least one bleed hole, and the restrictor and bellows end portion come into abutment to close the valve. Thus, at least the closing action, and preferably also the opening action of a valve in accordance with the invention is gradual or damped. In one embodiment of the invention described below the restrictor is fixed to or integral with a body of the valve. In another embodiment described below the restrictor comprises a movable seat which, in a closed position of the valve, seats against a fixed seat, and the bellows provides a biassing force tending to bias the movable seat towards the fixed seat, whereby: (a) when the valve is opened, the change in the pressure difference across the movable seat due to the seat coming out of abutment with the bellows end portion enables the movable seat and bellows end portion to move away from the fixed seat in response to pressure changes within the chambers, thereby to increase the extent of communication between the inlet and outlet chambers, and (b) when the valve is to be closed when the movable seat and bellows end portion are spaced from the fixed seat, the increase of the pressure in the bellows chamber by virtue of the bleed hole causes the movable seat first to come into contact with the fixed seat under the influence of hydraulic force resulting from the pressure change and said biassing force, so as partially to close the valve, after which the movable seat and bellows end portion come into abutment so as wholly to close the valve. Such a valve thus has a delayed multi-stage opening and closing action. For the valve to move from the closed to the open position, the bellows chamber pressure must first drop sufficiently to enable the movable seat and bellows end portion to come out of abutment, and a change in the pressure difference across the movable seat must take place via the aperture or apertures in the movable seat for the valve to adopt the open position. Closure involves a generally similar delayed, multi-stage action. Consequently, the chances of such a valve giving rise to problems associated with quick-acting valves, for example "water-hammer", are small, and water hammer should in fact be reduced to an acceptable level by using such valves. In one embodiment of the invention described hereinbelow the actuator means comprises a solenoid, i.e. the valve is a solenoid valve. It is however within the scope of the invention for the actuator means to be driven by some other means than a solenoid or even to be manually operable. In embodiments of the invention described below the end portion of the bellows is flexible and comprises a diaphragm, and the restrictor is substantially rigid. However, as indicated above, it is within the scope of the invention for the restrictor to be flexible instead of or as well as the bellows end portion. The bellows may be of a variety of shapes. However, a generally frusto-conical shape, with the above-mentioned end portion at the narrower end, is preferred, because such a shape is believed to enhance stability and, where the restrictor comprises a movable seat, to provide good separation of the movable and fixed seats. The aperture or apertures in the restrictor is or are preferably such that the total exposed area thereof, i.e. the area thereof via which the inlet and outlet chambers communicate, increases in a progressive manner as the restrictor and bellows end portion flex apart, which is believed to smooth the transition in the kinematic behaviour of the valve as the flexing apart takes place. Valves embodying the invention may comprise means for varying the volume flow resistance of the discharge passage, when open, whereby the valve can adopt different stable positions in which the restrictor and bellows end portions are relatively flexed apart by respective different amounts. Such throttling of the discharge passage provides good control of the extent of opening of the valve. The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawings, in which: Figure 1 is a somewhat schematic sectional side view of a solenoid valve embodying the invention, the valve being shown in a closed position; Figure 2 is a top plan view of a movable seat of the valve, Figure 3 is a sectional side view of the movable seat; Figure 4 is a view corresponding to Figure 1, but showing the valve during the course of movement from its closed position to an open position; OMPI Figure 5 is a view corresponding to Figure 1, but showing the valve in its open position; Figure 6 is a detail view of a modification of the valve in which the movable seat is secured in a different manner to a diaphragm; Figure 7 is a view corresponding to Figure 1, showing other modifications that can be made to the valve; Figures 8 and 9 are detail views of modifications that can be made to a body of the valve; and Figures 10 to 12 show further modifications that can be made to the valves shown in the preceding figures. Figure 1 of the drawings shows a solenoid-operated diaphragm valve operative to control a fluid flowing therethrough in the direction of an arrow 10, the valve being represented in this Figure in its closed position. The valve comprises a body 12 of any suitable material, for example metal or plastics, and a chamber member 14 secured as shown within an opening in the body 12. The chamber member 14 is shaped like an inverted mushroom and includes a guide portion 16 for an armature 18 made from magnetic stainless steel. It also serves to support a solenoid 20. The chamber member 14 may be manufactured from any suitable material, for instance metal or plastics. A bellows 22 is mounted within the valve body 12. The bellows is generally frusto-conically shaped and has its smaller end closed by a flexible, integral diaphragm 24. A flange 26 at the larger end of the bellows 22 is sealingly received between the valve body 12 and the chamber member 14. The frusto-conical shape of the bellows 22 enables good separation between a sealing face 28 of the body 12 that contacts the flange 26 and a fixed valve seat 30 for the valve provided on the body 12. The bellows 22 has an inbuilt spring rate which, in the light of its generally conical shape, results in good stability. This spring rate provides a force biassing the diaphragm 24, and a restrictor 32 secured thereto, towards the fixed valve seat 30. The bellows 22/diaphragm 24 is in this embodiment made of any suitable elastomeric material, for instance a rubber compound, but can be made of other materials such as stainless steel or plastics. The restrictor 32, which in the present embodiment acts as a movable valve seat, is shown in more detail in Figures 2 and 3. The restrictor 32 is a disc-shaped member having a plurality of holes 34, 36 therethrough. The restrictor 32 is moulded from a suitable elastomeric material, for instance a soft rubber compound, to provide a good seal with the fixed valve seat 30. However, to keep the restrictor 32 reasonably rigid or stiff, it has an insert 38 (Figure 3) therein. A rivet 40 serves to secure the restrictor 32 to the diaphragm 24 in the region of the centre of each. The armature 18 is provided with an annular elastomeric (e.g. rubber) seal 42 at its lower end as shown in Figure 1. A shaft 44 extends from the armature 18 through the seal 42 and the rivet 40, to the lower side (as shown in Figure 1) of the restrictor 32 and has a boss 46 mounted to its free end. The boss 46 is secured to the shaft 44 by means of a pin 48. A stainless steel helical compression spring 50 acts between a recess in the lower face of the restrictor 32 and the boss 46 to provide a force resiliently biassing the seal 42 against a sealing face of the rivet 40. The spring rate of the spring 50 is arranged to be as low as possible in order to maintain a sealing force on a discharge hole 52 through which the shaft 44 extends with clearance, and to enable the sealing force to be removed with minimum solenoid power, Figure 1 showing the valve in the condition in which the solenoid 20 is not energised. The interior of the valve body 12 can be considered as being divided, by the above-described components, into an inlet chamber or port a_, a bellows chamber b_ and an outlet chamber or port c. In the closed condition of the valve illustrated in Figure 1, the outlet chamber £ is, of course, isolated from the inlet chamber a. The outlet chamber c is also isolated- from the bellows chamber b in that the discharge hole 52 is closed by the seal 42. One or more small bleed holes 54 are provided in the bellows 22 whereby, in the steady state, the pressure within the bellows chamber b_ will be equal to that in the inlet chamber a. By varying the size and number of the holes or apertures 54, one can vary the rate at which pressure equalisation will occur. The total area of the or each bleed hole 54 is less than the effective area of the discharge hole 52 that can be opened between the bellows chamber b and the outlet chamber c. The operation of the illustrated valve will now be described. During its operation, the valve can be in any one of four states, two of which are static and two of which are transient. The two static states are "VALVE CLOSED" and "VALVE OPEN" and the two transient states are "VALVE CLOSING" and "VALVE OPENING". Each of these states will now be individually described. y » ' (a) VALVE CLOSED Figure 1 shows the valve in its closed position. Under static pressure conditions, i.e. with zero pressure differential across the valve, the pressures in the chambers a, b_ and £ will be approximately equal. The valve is maintained closed by the action of the bellows 22 which, because it has a nominal amount of prε-compression, pushes the diaphragm/movable valve seat restrictor assembly 24/32 towards the fixed valve seat 30. If pumped pressure is applied to the upstream side of the valve, i.e. if there is a pressure differential across the valve, the resultant forces on the assembly of the bellows 22, diaphragm 24 and movable valve seat restrictor 32 apply a net sealing force against the fixed valve seat 30 of a magnitude which is a function of the area of the outlet chamber £ where it meets the valve seat restrictor 32 and the corresponding area on the upper surface of the diaphragm 24 defined by upwardly projecting the area of the outlet chamber c. This sealing force is additional to that provided by the above-mentioned compression of the bellows. When the valve is closed, the higher the circulation pressure then the higher also is the sealing force. (b) VALVE OPENING (UNDER CIRCULATION PRESSURE) The opening action is initiated by energisation of the coil of the solenoid 20, which causes the armature 18 to move into the solenoid 20, i.e. in the upward direction as shown in Figure 1. The spring 50 is compressed thereby to provide a force that opposes the biassing force provided by the bellows 22 and tends to move the movable valve seat restrictor 32 away from the fixed valve seat 30. Movement of the armature 18 also moves the seal 42 away from the sealing face of the rivet 40, which uncovers the discharge hole 52 and thus causes the pressure in the bellows chamber b_ to tend to drop towards the pressure in the outlet chamber £. By virtue of the bleed hole(s) 54, as the pressure in the chamber b_ tends towards that in the chamber £ the pressure in the inlet chamber a will attempt to maintain the pressure in the chamber b. The rate at which these initial pressure changes occur will depend upon the ratio of the effective volume OMPI - flow resistance of the discharge hole 52 to the total volume flow resistance of the bleed hole(s) 54. The immediate effect of these various pressure changes is that the diaphragm 24 flexes or deforms away from the restrictor 32 in a generally conical manner, except of course where it is secured thereto by the rivet 40 adjacent the centre of each. The resultant flexing apart of the diaphragm 24 and restrictor 32 is shown in Figure 4. This flexing or deflection progressively uncovers the holes 34, 36 in the restrictor 32 in a radially inward sense resulting in a progressive and controlled increase in the discharge area available through the restrictor 32. This discharge area produces a tendency for equalisation of the pressure drop between the chambers a and £. Initially, the pressure drop between the chambers a and £ across the restrictor 32 is high. As a consequence, the resultant forces holding the restrictor 32 in place on the fixed valve seat 30 are of a greater magnitude than the opposing forces on the diaphragm 24, which gives rise to the conical flexing or deflection. However, the increase in the discharge area through the restrictor 32 increases the flow therethrough and reduces the pressure drop thereacross. This results in a reduction in the dynamic force holding the restrictor 32 in position. At the same time, the net dynamic force (due to pressure conditions) on the diaphragm 24 is reduced. By this time, however, the diaphragm 24 is nearing its maximum flexing or deformation and thus applies a maximum lifting force to the restrictor 32 via the connection afforded by the rivet 40. This force is supplemented by the biassing force caused by compression of the spring 50 due to the movement of the armature 18. Consequently, the movable valve seat restrictor 32 becomes dislodged from the valve seat and moves upwardly. Immediately after separation the diaphragm 24 looses its conical flexing or deflection whereby the restrictor 32 reverts to contact with the lower face of the diaphragm 24. The whole assembly continues to lift (due to a combination of solenoid pull and the application of pressure imbalance) until a steady open state of the valve is achieved, as shown in Figure 5. A conical surface 56 on the chamber member 14 supports the compressed bellows 22/diaphragm 24 in the open position of the valve. (c) VALVE OPEN In the fully open position, as shown in Figure 5, the bellows 22/diaphragm 24 is held in position by the action of the solenoid 10, which remains energised. The hydraulic forces on the diaphragm 24 are stabilised by the fact that the pressure in the bellows chamber b_ is maintained at a low level. This is so because a flow is maintained through the chamber b_ via the discharge hole 52 and the bleed hole(s) 54, the flow resistance of the discharge hole 52 being less than that of the bleed hole(s) 54 whereby the net force on the diaphragm 24 is upward. A discharge channel 58 (Figure 5) is provided in the chamber member 14 to ensure that the discharge path from the bleed hole(s) 54 to the discharge hole 52 cannot be sealed by the diaphragm 24 pressing against the conical surface 56 of the chamber member 14. (d) VALVE CLOSING (UNDER CIRCULATION PRESSURE) Closure of the valve is initiated by de-energisation of the solenoid 20. As the magnetic pull on the armature 18 decreases the spring 50 pulls the armature towards the diaphragm 24. The seal 42 covers the discharge hole 52. Sealing of the discharge hole 52 causes pressurisation of the bellows chamber b_ via the bleed holε(s) 54. The bellows chamber b_ fills and the assembly of the diaphragm 24 and the movable valve seat restrictor 32 moves towards the fixed valve seat 30. The pressure in the inlet chamber slowly rises and the pressure in the outlet chamber £ falls, though to a lesser extent. At a certain pressure, dictated by the physical parameters of the diaphragm 24 and the movable valve seat restrictor 32, the pressure difference between the chambers a and £ causes the whole assembly to be thrust towards the fixed valve seat 30. Because the diaphragm 24 has a certain amount of inbuilt hydraulic damping, the restrictor 32 tries to separate from the diaphragm 24. That is to say, it moves towards the fixed valve seat 30 at a speed greater than that which the diaphragm 24 can accomplish. Since the restrictor 32 and diaphragm 24 are secured together at their centres, the diaphragm 24 flexes or deflects in a conical manner similar to that experienced during opening. Thus, at this precise moment, the components of the valve, with the OMPI exception of the armature 18, adopt a similar configuration to that shown in Figure 4. The foregoing action is accompanied by opening out of the bottom convolution of the bellows 22 and closing of the top convolution thereof. At this stage, the pressure in the inlet chamber a rises rapidly and the pressure in the outlet pressure £ falls slightly. The bellows chamber b_ then fills via the bleed hole(s) 54 and the conical shape flattens out in an outward radial sense. As the line of contact between the diaphragm 24 and the restrictor 32 moves radially outwardly, the exposed or discharge area of the holes 34, 36 in the restrictor 32 is gradually decreased, whereby the pressure in the chamber a gradually increases and the pressure in the chamber £ falls slightly. When the diaphragm 24 has flattened out so as completely to cover the restrictor 32, the flow through the valve ceases. However, flow continues for a while through the bleed hole(s) 54, causing the top convolution of the bellows 22 to settle. It is believed that this "over-run" phenomenon may be helpful in reducing the chances of the valve mechanism oscillating during closure. Note that, during this process, the amount of deformation of the diaphragm 24 is proportional to the pressure drop across the valve and thus can be said to adjust automatically. The valve described above with reference to the drawings incorporates various advantageous features. The provision of the moving valve seat enables a controlled, two-stage closure to be achieved. The holes in the moving valve seat restrictor can be modified as desired to change the characteristics of the second stage of closure. The flexing or deflection of the diaphragm in a conical manner, in conjunction with the movable valve seat restrictor, enables controlled throttling of the valve near to the point of total closure. Connection of the armature to the bellows/diaphragm enables the valve to operate with a low pressure differential across it. The pressure differential across the valve is in fact used to assist in its operation. As mentioned above, the settling of the convolutions on the bellows is believed in some circumstances to act as a damping mechanism at the instant of closure. Finally, the overall conical shape of the bellows/diaphragm ensures stability and good separation of the mounting point of the bellows and the valve seat, enabling low resistance designs to be provided. OMPI The invention can of course be performed in various other ways than that described above by way of example. For instance, the rivet 40 need not be separate from the diaphragm 24 as it is in the arrangement described above. Instead, as shown in Figure 6, the rivet (40') may be moulded into the diaphragm 24. In this case, as also shown in Figure 6, the armature 18 may be modified to incorporate a conical or "pointed" lower end 60, in which case the seal 42 may be discarded. The valve could also be modified by making the movable valve seat restrictor 32 flexible instead of or as well as the diaphragm 24. That is to say, the diaphragm 24 could be made rigid or replaced with a rigid member. The desired flexing apart will be obtained provided one or both of the two members is flexible. It is not essential that the diaphragm 24 and the movable valve seat restrictor 32 be secured together. For example, the illustrated arrangements could be modified by removing the rivet 40 (and, preferably, decreasing the diameter of the central hole in the diaphragm to be the same as the internal diameter of the rivet). Such a modified arrangement would work in a similar manner to that described above. In particular, the diaphragm 24 would still flex as described, through in most cases to a lesser degree (especially during the closing process) than in the illustrated arrangements. In the modified arrangement, the movement of the diaphragm 24 with respect to the restrictor 32 is translational and flexural rather than solely flexural. In the arrangement described with reference to the drawings, energisation of the solenoid 20 not only opens communication between the chambers £* and £ but provides an opening force on the movable valve seat restrictor 32 that tends to move it away from the fixed seat 30. Such opening force assists the forces resulting from pressure changes to open the valve. The opening force is not however essential in this respect and the illustrated arrangements may therefore be modified such that substantially no such force is provided, the solenoid 20 acting only to establish and stop the communication between the chambers b_ and £. The valve could further be modified in the various ways now to be described with reference to Figure 7, which shows a modified form of valve. Figure 7 largely corresponds to Figure 1 and will only be described in so far as it differs from Figure 1. Items in Figure 7 that correspond to like items in Figure 1 are identified by like references, whereas items in Figure 7 that OMPI correspond to but differ from items shown in Figure 1 are identified by like references with prime superscripts. The rivet 40" in Figure 7 differs from those 40, 40' of Figures 1 and 6 in that, instead of having a flat upper surface that seals with an annular seal 42 on the armature 18, it receives a boss-like seal 42' inside the mouth of the hole 52 therein. Also, the rivet 40" has a lip 62 that receives one end of a helical tension spring 50', the other end of which is received in a groove 64 in the armature 18. Thus, in this arrangement, the tension spring 50' located in the bellows chamber b_ replaces the compression spring 50 located in the outlet chamber £ in the valve of Figure 1, and there is no need for the shaft 44 extending through the hole 52 and the boss 46 thereon. The valve of Figure 7 also differs from that of Figure 1 in that the bellows 22' has a lesser number of convolutions and the convolutions are less angular and more sinuous. In this connection, the bellows employed in valves embodying the invention may be of a great variety of forms. For example, as just explained, the number and/or form of the convolutions may vary; and the bellows may in fact have no convolutions at all, being, for example, a simple cup-shaped member. Further, though it is preferred that, as in the arrangements described, the biassing force provided by the bellows be due to an inbuilt spring rate, i.e. to the bellows being of a resiliently deformable construction, it is within the scope of the invention for the bellows to comprise a floppy (noπ-resiliently deformable) bellows member in combination with one or more biassing springs. In the arrangements described above, the bleed hole(s) 54 are located in the bellows 22, 22' so as directly to communicate the inlet chamber a and bellows chamber b. This, however, is not essential. The bleed hole(s) 54 could be located elsewhere and might for example be constituted by a passage or passages communicating the two chambers, for instance the bore of a pipe extending from the bellows chamber b, possibly externally of the valve body 12, 12' or 12", to the inlet chamber a or to a position on an inlet pipe upstream of the valve body. Although the preceding figures of the drawings show valves in which the inlet and outlet flow directions are at right angles, this relationship is by no means essential. The inlet and outlet directions may bear other relationships. Figures 8 and 9 show respective modified valve bodies 12' and 12" in both of which the flow inlet and outlet directions are aligned and in which, respectively, the actuating mechanism is positioned normally or inclined to such aligned directions. Further modifications of the valves described above will now be described with reference to Figures 10 to 12, in which items corresponding to like items in the preceding figures are identified by like references and items corresponding to but different to items in the preceding figures are identified by like references with prime superscripts. Figure 10 shows a valve which is similar to that of Figure. 1, except that the shaft 44' is tapered whereby the effective area (and therefore the volume flow resistance) of the discharge hole 52 varies as the shaft 44 is moved away from the position shown, and the armature 18 is replaced by a member permitting continuous movement of the shaft. The consequence of this is as follows. For an initial range of movement of the shaft 44' away from the position shown, the effective volume flow resistance of the discharge hole 52 is sufficiently small that, whereas the diaphragm flexes away from the restrictor 42 (as shown in Figure 4) to permit flow between the inlet and outlet chambers a and c via the apertures 34, 36 in the restrictor, the valve does not switch over to the fully open position shown in Figure 5. That is to say, within such range of positions of the shaft 44 the valve stays in a stable partially-open condition as shown in Figure 4. What is more, the extent of stable flexure of the diaphragm 24 within such range of positions of the shaft 44 is proportional to the position of the shaft, whereby the extent of opening of the valve can be proportionally controlled by throttling (controlling the volume flow resistance of) the discharge hole 52 by moving the shaft, which movement could be effected manually or mechanically. Only when the movement of the shaft 44 is such that the effective volume flow resistance of the hole 52 (with respect to that of the bleed hole(s) 54) exceeds a threshold value will the valve open fully as described above with reference to Figure 5. If the area of the shaft 44 were varied in steps (rather than continuously) along its length, then stepwise (rather than continuous) proportional control of the extent of opening of the valve could be obtained in like manner, in which case movement of the shaft might likewise be continuous, the member 18' being, for example, an armature of a multϊ- position solenoid. It may be that, in some cases, opening and closure of the valve by flexing of the diaphragm 24 would be considered sufficient, the above- described full opening provided by movement of the restrictor 32 to the position of Figure 5 not being required. In that case, the arrangement of Figure 10 could be modified by fixing the restrictor 32 to the valve body 12. Alternatively, as shown in Figure 11, the restrictor 32 could be formed integrally with the valve body 12. In both of these cases, flow between the inlet takes place only via the apertures 34, 36 in the (fixed) restrictor 32, such flow being controlled by relative flexing of the restrictor and diaphragm 24. In all the arrangements described above, the discharge hole 52 selectively connecting the bellows chamber b_ and the outlet chamber £ is disposed within the valve, more specifically in the form of a hole extending through the diaphragm 24 and restrictor 32. This, however, is not essential. Figure 12 shows an alternative arrangement. In Figure 12, the diaphragm 24 and restrictor are shown secured together by a rivet 40', for example, which permits relative flexural (or flexural and translational) movement of these two components as described above, but does not provide a discharge passage connecting the bellows chamber £* and the outlet chamber £. Instead, the chambers b and £ are interconnected by a discharge passage schematically represented as a duct or pipe 60 which may, as shown, be located outside of the valve body 12, the pipe 60 extending between the bellows chamber b_ and a position on a pipe downstream of the outlet chamber £ or, as shown, directly to the chamber £. A pilot valve 62 or tap or the like is provided in the pipe 60. The pilot valve 62 may, for example, be a two-position (ON or OFF) valve, in which case opening or stopping of communication between the chambers b_ and £ by operation of the pilot valve causes operation of the valve proper in the same way as the valve of Figures 1 to 5 is operated when the solenoid 20 is energised or de-energised. Alternatively, the position of the pilot valve 62 (i.e. the extent of opening thereof) may be continuously or step-wise variable, in which case the valve can be operated in a proportional fashion in like manner to the valve described above with reference to Figure 10. If such proportional control of the extent of opening of the valve of Figure 12 is considered sufficient, i.e. if full opening of the valve by bodily movement of the restrictor 32 to the position of Figure 5 is not required, the valve of Figure 12 could be modified by fixing the restrictor to the valve body 12 or, as described above with reference to Figure 11, by forming the restrictor integrally with the valve body. OMPI

Claims: CLAIMS 1. A valve comprising a fluid inlet chamber, a fluid outlet chamber, a restrictor having at least one aperture and disposed between the inlet and outlet chambers, a bellows chamber defined by a bellows and communicating with the inlet chamber via at least one bleed hole, at least one of the restrictor and an end portion of the bellows being flexible and the restrictor and bellows end portion being so mounted that they can abut one another or can come out of or into abutment by virtue of a movement that at least includes flexure of at least one of the restrictor and bellows end portion, the at least one aperture in the restrictor being closed or opened depending upon whether the restrictor and bellows end portion are or are not in abutment, a discharge passage capable of communicating the bellows chamber and the outlet chamber, and actuator means which (i) when the valve is to be opened, opens the discharge passage to put the bellows chamber into communication with the outlet chamber, the resultant drop in pressure in the bellows chamber causing the restrictor and bellows end portion to come out of abutment to establish communication between the inlet and outlet chambers via the at least one aperture in the restrictor, and (ii) when the valve is to be closed, closes the discharge passage to stop the communication between the bellows chamber and the outlet chamber whereby the pressure in the bellows chamber gradually increases, by virtue of the at least one bleed hole, and the restrictor and bellows end portion come into abutment to close the valve. 2. A valve according to claim 1, wherein the restrictor comprises a movable seat which, in a closed position of the valve, seats against a fixed OMPI _ seat, and the bellows provides a biassing force tending to bias the movable seat towards the fixed seat, whereby: (a) when the valve is opened, the change in the pressure difference across the movable seat due to the seat coming out of abutment with the bellows end portion enables the movable seat and bellows end portion to move away from the fixed seat in response to pressure changes within the chambers, thereby to increase the extent of communication between the inlet and outlet chambers, and (b) when the valve is to be closed when the movable seat and bellows end portion are spaced from the fixed seat, the increase of the pressure in the bellows chamber by virtue of the bleed hole causes the movable seat first to come into contact with the fixed seat under the influence of hydraulic force resulting from the pressure change and said biassing force, so as partially to close the valve, after which the movable seat and bellows end portion come into abutment so as wholly to close the valve. 3. A valve according to claim 2, wherein the movable seat and bellows end portion are secured together in such a manner as to prevent relative translationai movement, whereby said movement αf the movable seat and bellows end portion as they come into or out of abutment substantially wholly comprises flexure of at least one of the movable seat and bellows end portion. 4. A valve according to claim 2, wherein the movable seat and bellows end portion are so mounted that said movement of the movable seat and bellows end portion as they come into or out of abutment comprises relative translationai movement of the movable seat and bellows end portion as well as flexure of at least one of the movable seat and bellows end portion. 5. A valve according to any one of claims 2, 3 and 4, wherein said biassing force provided by the bellows is due to the bellows being of a resiliently deformable construction. 6. A valve according to any one of claims 1 to 5, wherein the end portion of the bellows is flexible and comprises a diaphragm, and the restrictor is substantially rigid. OMPI __ 7. A valve according to any one of claims 1 to 5, wherein the end portion of the bellows is flexible and comprises a diaphragm, and the restrictor is flexible. 8. A valve according to any one of claims 1 to 5, wherein the end portion of the bellows is substantially rigid, and the restrictor is flexible. 9. A valve according to any one of the preceding claims, wherein the bellows is of a generally frusto-conical shape with said end portion being at the narrower end. 10. A valve according to any one of claims 1 to 9, wherein the discharge passage comprises a hole through the bellows end portion and the restrictor, and the actuator means comprises a member movable with respect to the bellows end portion and restrictor so as to open or close the hole through the bellows end portion and restrictor to put the bellows chamber into communication with the outlet chamber or to stop communication between the bellows chamber and the outlet chamber. 11. A valve according to claim 10, wherein said member is an armature of a solenoid. 12.. A valve according to any one of claims 1 to 9, wherein the discharge passage comprises a duct extending between the bellows chamber and the outlet chamber and the actuator means comprises means for opening and closing the duct. -13. A valve according to any one of the preceding claims, comprising means for varying the volume flow resistance of the discharge passage, when open, whereby the valve can adopt different stable positions in which the restrictor and bellows end portions are relatively flexed apart by respective different amounts. 14. A valve according to any one of the preceding claims, wherein the at least one aperture in the restrictor is such that the exposed area thereof increases in a progressive manner as the restrictor and bellows end portion flex apart. &EAi OMPI 15. A valve according to any one of the preceding claims, wherein the at least one bleed hole comprises a hole in the bellows that directly communicates the bellows chamber and inlet chamber.

Inventors: WILSON ALAN, WILSON, ALAN
Applicants: DREAMLAND ELECTRICAL APPLIANCE, POTTERTON INT LTD, DREAMLAND ELECTRICAL APPLIANCES P.L.C., POTTERTON INTERNATIONAL LIMITED
Application year: 1983
Main classification: F16K31
IPC codes: F16K25, F16K31, F16K47