GB2202613A - Relief valves - Google Patents

Abstract

A relief valve 1 includes a body 2, having an inlet 3, an outlet 4 and an orifice 5, forming a communication between the inlet and outlet, a valve closure member 6 movable within the body 2 between a closed position in which it shuts off communication through the orifice 5 and open positions in which communication through the orifice 5 is possible, biasing means 12 for urging the valve closure member 6 into said closed position, and retaining means 20, the valve closure member 6 being adapted to open in response to temperature and/or pressure within a system with which said relief valve is used exceeding a predetermined value, said retaining means 20 being operative to hold the valve closure member 6 in an open position and become operative automatically when said valve closure member 6 moves to said open position, which is preferably adjustable. <IMAGE>

Description

RELIEF VALVES This invention is concerned with relief valves and particularly such valves which open in response to excessive temperature or pressure conditions. Such temperature and pressure relief valves (TPR valves) have wide application and are commonly used in domestic water heating systems. It will be convenient to hereinafter describe the invention with particular reference to water heating systems.

Valves of the foregoing kind open in response to abnormal conditions such as an excessive pressure within the associated system, or excessive temperature of the water contained in that system. Each of those excessive conditions can result from a malfunction which persists if not corrected by appropriate remedial action, and such persistence could produce a potentially dangerous situation. The existence of a malfunction of the foregoing kind may remain undetected for a considerable period of time because conventional TPR valves return to a closed position when the system pressure or temperature falls below the critical level. Occasional opening of such a valve may not be readily detectable in which event a potentially dangerous malfunction may remain unattended for some time.

It is an object of the present invention to provide a valve of the foregoing kind which overcomes or at least minimises the aforementioned problem.

According to the invention there is provided a relief valve comprising a body having an inlet, an outlet and an orifice forming a communication between the inlet and outlet, a valve closure member movable within the body between a closed position in which it shuts off communication through the orifice and an open position in which communiction through the orifice is possible, biasing means for urging the valve closure member into said closed position, and retaining means, the valve closure member being adapted to open in response to temperature and/or pressure within a system with which said relief valve is used exceeding a predetermined value, said retaining means being operative to hold the valve closure member in an open position and becomes operative automatically when said valve closure member moves to said open position.

An embodiment of the invention is described in detail in the following passages of the specification which refer to the accompanying drawings. The drawings, however, are merely illustrative of how the invention might be put into effect, so that the specific form and arrangement of the various features as shown is not to be understood as limiting on the invention.

In the drawings: Figure 1 shows a cross-sectional side view of a valve according to the invention, and Figure 2 shows an enlarged cross-sectional side view of part of that valve in an open condition. As shown in the drawings a valve 1 includes a hollow body 2 having an inlet 3 and an outlet 4 which communicate through an orifice 5 provided within the body 2.

Communication through the orifice 5 is controlled by a closure member 6 which is movable away from and into a position at which it closes the orifice 5 and thereby prevents communication between the inlet and the outlet. Such a closed condition is the normal condition of the valve.

In the arrangement shown, the closure member 6 is located on the outlet side of the orifice 5 and includes a cylindrical piston-like section 7 which is slidably located within a bore 8 of the valve body 2. That bore 8 is axially aligned with the orifice 5 and extends through a top side 9 of the valve body. Any appropriate sealing means may be provided between the piston section and the bore, and in the embodiment shown in the drawing a resilient O-ring seat 27 is used.

A valve seat 10 is formed around the orifice on the outlet side so as to be engageable by the closure member 6.

In order to improve the closing effect, a resilient annular element 11 is attached to the piston section 7 so as to engage against the valve seat 10 in the closed condition of the valve.

The closure member 6 is urged into the closed position by a spring 12 acting between the piston section 7 and an oppositely facing surface. That surface in the embodiment shown is formed by a support member 13 which is located within the aforementioned bore 8 and is held against movement relative to the valve body 2. It is further preferred that the axial position of the support member 13 is adjustable. In the adjustable arrangement shown, adjustment enables variation of the closing force of the spring 12 and therefore the pressure at which the valve 1 will open.

A thermostat 14 of known form and operation is located on the inlet side of the orifice 5. The thermostat 14 includes a tubular body 15 which is attached to the valve body 2 against relative movement, and a movable push rod 16 which is arranged to engage against an end surface 17 of the closure member. The end surface 17 is exposed at the orifice 5. The thermostat 14 responds to increasing temperature so that the push rod 16 moves against the closure member 6 and pushes it against the action of the associated spring 12 so as to cause the valve to open. Excessive pressure on the inlet side of the orifice 5 will also cause the valve 1 to open and that can occur independent of any action of the thermostat 14.

The valve 1 also includes hold-open means which becomes operative when the valve closure member 6 moves a certain distance away from the closed position. In the particular form shown, that hold-open means includes a stem 18 which has one end attached to the piston section 7 and extends axially from that section to slidably locate in an axial opening 19 formed through the support member 13. The arrangement is such that the stem moves with the piston section 7 during opening and closing movement of the closure member 6 and that movement is relative to the support member 13.

A snap ring 20 or similar radially expandable device is located around a portion of the stem so as to be held against axial movement relative thereto. The relevant stem portion 18 is located within the aforementioned opening 19 when the valve is closed, and the snap ring is confined against radial outward expansion by engagement with a surface 21 of that opening. That engagement is sliding engagement to permit the necessary movement of the closure member 6 relative to the support member 13.

When the closure member 6 moves away from the closed position, the snap ring 20 slides towards an upper side 22 of the support member 13 and eventually achieves a position at which it is freed from the restraining influence of the aforementioned surface 21. The ring 20 then expands radially outwards and as a consequence overlies the upwardly facing surface 22 of the support member 13. Return movement of the closure member 6 to the closed position is then prevented by engagement of the snap ring 20 with the aforementioned upwardly facing surface 22. That condition is clearly shown in Figure 2 of the drawings.

Access to the snap ring can be gained through the top end 9 of the valve so as to permit its return to the unexpanded condition at which the valve is able to close. A removable cap 23 is provided for closing the open end of the valve body bore 8. The cap is provided with an operating lever 24.

Axial adjustment of the support member 13 relative to the valve body 2 will of course vary the axial distance between the valve seat 10 and the aforementioned upwardly facing surface 22 of the support member 13. Such adjustment therefore has the potential to vary the degree of axial movement of the closure member 6 which is necessary to cause actuation of the snap ring 20 as discussed above. It is preferred, however, that the valve is arranged to be opened at a predetermined temperature as a consequence of operation of the thermostat. It is further preferred that only a relatively small degree of axial movement of the closure member away from the closed position is sufficient to cause actuation of the snap ring. Such an arrangement ensures that the valve does not fluctuate between open and closed positions and thereby maximises the chance of a malfunction being detected.

In order to achieve the foregoing preferred aspects, the valve may be provided with a second adjustment facility which enables the axial position of the snap ring to be varied to suit different circumstances. According to the arrangement shown, the effective length of the closure member stem 18 is variable for that purpose. One end potion of the stem 18 is cooperatively engaged within a screw-threaded bore 25 of the piston section and the snap ring 20 is mounted on the opposite end portion of the stem. Such an arrangement enables the position of the snap ring 20 to be adjusted relative to the sealing surface of the valve closure member to suit the particular position of the support member 13. This adjustment facility will also serve as a sensitivity adjustment so that the valve can be used in differing operating conditions.

It will be appreciated that the hold-open facility can take a variety of forms. With regard to the particular example shown, the snap ring 20 could be mounted on the support member 13 or the valve body 2 rather than the closure member stem 18, and in that event would actuate by radial inward movement to engage a groove in the closure member stem 18.

It is to be also understood that relative terms such as Ztopw and 'upward" as used in this specification have no limiting effect. Such terms are used for convenience of description only and are not intended to suggest that the valve must have a particular disposition when in use.

Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the ambit of the invention as defined in the appended claims. In particular, it will be possible to mount the retaining means on the body of the valve and for that retaining means to be operative to engage with the valve closure member when the valve closure member moves to said open position.

Claims (15)

CLAIMS:

1. A relief valve comprising a body having an inlet, an outlet and an orifice forming a communication between the inlet and outlet, a valve closure member movable within the body between a closed position in which it shuts off communication through the orifice and open positions in which communiction through the orifice is possible, biasing means for urging the valve closure member into said closed position, and retaining means, the valve closure member being adapted to open in response to temperature and/or pressure within a system with which said relief valve is used exceeding a predetermined value, said retaining means being operative to hold the valve closure member in an open position and becomes operative automatically when said valve closure member moves to said open position.

2. A relief valve according to claim 1 wherein the retaining means is connected to the valve closure member and movable relative to the valve closure member into an operative position to engage a part of the body when the valve closure member moves to said open position thereby holding said valve closure member in said open position.

3. A relief valve according to claim 1 wherein said retaining means is spring biased to said operative position.

4. A relief valve according to any preceding claim wherein the valve closure member is comprised of a cylindrical piston slidable in a bore in the body to open the valve.

5. A relief valve according to claim 4 wherein a valve seat is formed around said orifice, the valve seat being of circular form, the bore being axially aligned with the valve seat and extending through a side wall of the body.

6. A relief valve according to either claim 4 or 5 wherein a resilient seal is located between the wall of the bore and the piston.

7. A relief valve according to one of claims 4 to 6 wherein a resilient annular element is secured to the piston for engagement with the valve seat to shut off the valve.

8. A relief valve according to one of claims 4 to 7 wherein a spring acts between the piston and an oppositely facing support member, the spring urging the piston into said closed position, the axial position of the support member being adjustable relative to the body.

9. A relief valve according to claim 8 wherein the retaining means comprises a spring clip located on the piston and adapted to engage with the support member to hold the piston in an open condition.

10. A relief valve according to claim 9 wherein the piston has an axial rod fixed thereto which extends through a bore in the support member, the spring clip located on the rod and being restrained against outward movement by the wall of the bore through the support member when the piston is in a closed condition, the spring clip being adapted to snap to an unrestrained and operative condition when the piston moves away from the valve seat thereby acting on the support member to hold the piston off the valve seat.

11. A relief valve according to claim 10 wherein the length of the axial rod is adjustable.

12. A relief valve according to claim 5, or any claim which depends therefrom, the opening through the wall of the body providing access to the retaining means.

13. A relief valve according to claim 12 wherein the opening through the wall of the body is closed off by a removable closure cap.

14. A relief valve according to claim 1 wherein said retaining means is connected to said body and movable relative to the body into an operative position to engage the valve closure member when the valve closure member moves to said open position thereby holding said valve closure member in said open position.

15. A relief valve substantially as hereinbefore described with reference to the drawings.