GB2177183A - Vent/relief valve - Google Patents

Abstract

A diaphragm pump has a combined vent and pressure relief valve 13 between the pumping chamber (11) and its one-way outlet valve 6, the valve including a flap valve member 30 covered by a diaphragm 16, biased towards a secting face 28,33 by a spring (20) loaded plunger 19 and which opens in response to a pressure differential between the inlet passage 17 and an outlet passage 18, and an axially movable back-up member 21 having two distinct axial positions one (Fig. 2) of which defines a highly stressed "pressure relief valve" configuration for the diaphragm-biasing spring 20 and the other (to the right of the Fig. 2 position) of which positions defines a relatively unstressed "vent valve" configuration for the spring. <IMAGE>

Description

SPECIFICATION Vent/relief valve The present invention relates to a combined vent/relief valve.

It is an object of the present invention to provide a single valve which may serve both to vent air from a system, for example when priming a pump in which the valve is incorporated, and which may also serve as a pressure relief valve.

Accordingly the present invention provides a vent/pressure relief valve having: a valve body, an inlet passage to said valve body; an outlet passage from said valve body; a valve seating face including ports to said inlet and outlet passages; a diaphragm covering said seating face; a flap valve member between said diaphragm and said seating face and having a movable portion adapted to open and close the port to said inlet passage; means resiliently biasing said diaphragm towards said seating surface, for communicating said inlet passage with said outlet passage in response to an excess of inlet pressure over outlet pressure of a predetermined threshold value; and back-up means movable between first and second positions to pre-stress the resilient biasing effect on said diaphragm more highly in said first position than in said second position, whereby in said second position of the backup means the valve serves as a vent valve and in said first position of the back-up means the valve serves as a pressure relief valve.

In order that the present invention may more readily be understood the following description is given, merely by way of example, with reference to the accompanying drawings in which: FIGURE 1 is a sectional view of a diaphragm pumping head incorporating the valve in accordance with the present invention; FIGURE 2 is an enlarged sectional view, taken on the line ll-ll of Figure 1 but showing only the combined vent/pressure relief valve of the pump; and FIGURE 3 is an exploded view of the com ponents of the valve of Figure 2.

Referring now to the drawings, Figure 1 shows the pump head 1 as comprising a plun ger 2 driven by a reciprocating drive shaft 3 from a suitable drive mechanism to convert rotary motion to reciprocating motion. One such drive mechanism is disclosed and claimed in British Patent No.2,045,379.

The pump further includes a one-way inlet valve 4 in an inlet passage 5 to the pump, and a one-way outlet valve 6 in a delivery passage 7 from the pump. Furthermore, inlet and outlet unions 8 and 9, respectively, allow the pump to be connected to fluid-conveying lines such as the line 10 connected to the outlet union 9.

Between the pumping chamber 11, of which one wall is defined by a diaphragm 12, and the outlet one-way valve 6 is a combined venting and pressure relief valve 13 which will be described in more detail with reference to Figure 2.

Figure 2 shows the valve 13 as comprising a first body portion 14 and a second body portion 15 having a female portion internally threaded for engagement with an externally threaded male portion of the first housing portion 14, the first housing portion having a flat operating face 28 (Figure 3) receiving a diaphragm 16 which becomes clamped between the first and second body portions 14 and 15, respectively, in the assembled condition of the pump. The female threaded part of the second body portion 15 covers the operating face 28.

An inlet passage 17 to the pump communicates with the bore along the pump delivery line 7 and opens at a central inlet port of the operating face 28 of the first body portion 14 of the valve. A kidney-shaped surrounding port to the passage 18, also communicating with the operating face of the first valve body portion 14, is additionally communicated to a return line 29 (Figure 3) to remove any overspill liquid and vented air from the kidneyshaped outlet port to passage 18 of the valve.

The diaphragm 16 is urged against the face 28 of the first valve body portion 14 by means of a plunger 19 which is itself biased towards the diaphragm by means of a helical compression spring 20 strained between the end wall of the plunger 19 and an opposing end face of an actuating member 21.

The actuating member 21 is mounted for rotation within the second valve body portion 1 5 and is coupled for conjoint rotation and axial translation with a rotatable outer control member 22 for axial movement between a first position in which the actuating member 21 is in the Figure 2 configuration and close to the adjacent end of the skirt of the plunger 19, and a second position in which the actuating member 21 is backed-off from the plun ger skirt and holds the spring 20 either un strained or only very lightly strained in com pression.

Figure 1 also shows that the diaphragm 16 is immediately adjacent a flap valve plate, ref erenced 29 in Figure 3, having a central disc portion 30 and an outer peripheral portion 31 to which it is joined, leaving a kidney-shaped slot 32 centred on the centre of the disc 29 and substantially in register with the annular passage 18.

Figure 3 shows the individual components of the valve 13 in more detail, and illustrates the fact that the actuating member 21 has a pair of diametrically opposed fins 23 which are able to enter slots 24 diametrically op posed with respect to a bore 25 in the end face of the second valve body member 15, but only in one position of rotation of the actuating member 21. When the actuating member is rotated so that its fins 23 are not aligned with the slots 24, by rotation of the control member 22 which is linked for rotation with the actuating member 21 by virtue of a square end 26 of the actuating member being received in a square hole 27 of the control member, the actuating member 21 is held in a forward position in which it holds the spring 20 in its more highly strained configuration.

Figure 3 also shows the flat operating face of the second body portion 15, with the inlet and outlet ports to passages 17 and 18, respectively, opening into that face and able to be isolated from one another when the diaphragm 16 is firmly pressed onto the face 28 by virtue of the plunger 19.

The valve of Figures 2 and 3 operates as a vent valve (having a low opening pressure) when the fins 23 are received in the slots 24 and functions as a pressure relief valve (with a much higher opening pressure) when the control member 22 has been pushed inwardly (i.e.

leftwardly in Figure 2) and rotated to bring the fins 23 out of line with the slots 24. Means (not shown) may be provided for defining a distinct second position of rotation of the actuating member 21 to hold the actuating member such that it cannot vibrate in rotation back to the position where the fins 23 become aligned with the slots 24 and this prevents the valve from re-adopting, accidentally, its venting configuration.

Figure 3 shows more clearly than Figure 2 the configuration of the slot 32 in the flap valve plate 29.

The functioning of the plate 29, which is formed of a material inert to the liquid medium being pumped, for example it may be made of neoprene (poly(2 chloro-1,3 butadiene)) or of polytetrafluoroethylene, is to allow the central passage 17 to remain closed until some selected threshold pressure, for example a pressure in excess of 15 bar, has been attained whereupon the central disc portion 30 of the plate 29 will lift clear of its seating 33 on the first body member 14 and will allow the pumped liquid in the central passage 17 to vent to the surrounding annular passage 18. In this case the annular passage 18 is connected to a return line 34 to allow the vented liquid to return to a suitable location, for example the inlet side of the pump 1. The selected pressure can be altered merely by rotating the control member 22 as explained above.

This lifting of the central disc portion 30 of the plate 29 is of course resisted by the force exerted by the spring 20, acting through the agency of the plunger 19 and the diaphragm 16, such that when the pressure in the central passage 17 drops below the selected venting pressure the central disc portion 30 of the plate 29 again seats on its surface 33 to close off the passage 17 and thereby to stop the venting action.

As indicated above, the plate 29 is inert to the liquid being pumped and the diaphragm 16 serves to define a barrier to contain the pumped liquid which may be highly corrosive and which should not come into contact with the plunger 19 and the spring 20.

Any other suitable form of flap valve member may be incorporated in place of a circular disc having a circular kidney-shaped slot 32 therein. Likewise, the flap valve member may be made of any suitable material which will have the desired properties of being inert to the pumped liquid and nevertheless a sufficient degree of stiffness to function as a flap valve but sufficient resilience to avoid pre-loading the valve to an extent which diminishes the effect of the spring 20 and of the effect of rotating the control member 22 to vary the strain in the spring 20.

The valve illustrated in Figures 2 and 3 is particularly advantageous in that the first body portion 14 may be a part of the main pump body and the second body portion 15 with its diaphragm, plunger, actuating member and control member are all replaceable.

Another advantage is the fact that although in Figure 3 the first body member 14 has a return line 34 which merely accommodates vented air and/or excess pumped liquid released during the pressure relieving action of the valve, this form of valve body member may be replaced by an alternative first body member in which the return line 34 has been replaced by a more substantial delivery line,and the existing delivery line 7 is dispensed with,in order to allow the valve to serve as a pressure loading valve in that liquid is only pumped once the biasing pressure of the spring 20 has been overcome by the pressure differential between the inlet passage 17 and the outlet passage 18 of the valve 13.Thus a standard design of second valve body member 15,with all its movable components,can be used with either the "pressure loading valve" first body member or the "vent/pressure relief valve" body member.

A further advantage of the valve in accordance with the present invention is that the corrosive pumped liquid comes into contact only with the walls of the inlet and outlet passages 17 and 18 of the valve, the flat face 28, and the diaphragm 16, all of which will be inert to the particular chemical being pumped.

The diaphragm thus defines with the first body member 14 a sealed enclosure which ensures that there is no risk of the pumped liquid contaminating the exterior of the second valve body member 15 and/or the control member 22. This allows the operator to actuate the valve between its vent mode and its pressure relief mode by manually rotating the control member 22 rather than having to use special tools in order to avoid risk of contact with corrosive chemicals.

The resilient diaphragm 16 may be of polytetrafluoroethylene, or of rubber which may, if desired, be reinforced, for example fabric-reinforced.

Claims (10)

1. A vent/pressure relief valve having: a valve body, an inlet passage to said valve body; an outlet passage from said valve body; a valve seating face including ports to said inlet and outlet passages; a diaphragm covering said seating face; a flap valve member between said diaphragm and said seating face and having a movable portion adapted to open and close the port to said inlet passage; means resiliently biasing said diaphragm towards said seating surface, for communicating said inlet passage with said outlet passage in response to an excess of inlet pressure over outlet pressure of a predetermined threshold value; and back-up means movable between first and second positions to pre-stress the resilient biasing effect on said diaphragm more highly in said first position than in said second position, whereby in said second position of the back-up means the valve serves as a vent valve and in said first position of the back-up means the valve serves as a pressure relief valve.

2. A valve according to claim 1, wherein said flap valve member is a disc having a kidney-shaped arcuate slot centred on the centre of the disc, thereby defining an inner flap valve tongue resiliently connected to an outer annular seating portion of the disc; and wherein said port to the inlet passage of the valve is in the centre of said seating face of the valve body and is surrounded by said port to the outlet passage.

3. A valve according to claim 1 or 2, wherein the flap valve member is made of PTFE or neoprene (poly(2 chloro-1,3 butadiene)).

4. A valve according to any one of claims 1 to 3, wherein said biasing means comprises a helical compression spring positioned between said diaphragm and movable back-up means, and which can be moved axially to select in one position said first predetermined biasing force, or in the other position said second predetermined biasing force or zero biasing force.

5. A valve according to any one of claims 1 to 4, wherein said back-up means comprise a rotatable member having two axially spaced positions and interengaging formations on the rotatable member and said body member of the valve, whereby the second axial position, corresponding to a lower operating pressure of the valve is attainable only in one position of rotation of the rotary member, and in all other positions of rotation of the rotary member the rotatable member is held in said second axial position corresponding to a higher operating pressure.

6. A valve according to claim 5, and including an axially movable and rotatable control fixed to said rotatable member and able to allow manual displacement of said rotatable member axially and rotatably between its positions corresponding to the two operating pressures of the valve.

7. A valve according to claim 5 or 6, wherein said diaphragm is urged towards said seating face by means of a hollow plunger having a flat end face in contact with the diaphragm, the plunger being furthermore received for axial sliding movement in a bore of the valve body and having a skirt which slidingly engages said bore and surrounds the or a helical compression spring biasing said plunger and diaphragm.

8. A valve according to any one of the preceding claims, wherein said valve body comprises a first body portion with said inlet and outlet passages and said seating face; and a second body portion adapted to be fastened to said first body portion so as to cover said seating face, the diaphragm and the flap valve member; and an alternative said first body portion, the first mentioned said first body portion having a continuous passage for liquid flow through the valve and its inlet passage as a branch from said continuous passage, and said alternative first body portion having an inlet communicating with said inlet passage of the valve and an outlet communicating with said outlet passage of the valve, whereby use of the said first mentioned first valve body portion enables the valve to function as a vent valve and/or a pressure relief valve, and the use of said alternative first valve body portion allows the valve to function as a pressure loading valve.

9. A valve according to claim 8, wherein the or each said first valve body portion has an externally threaded male part with said seating face extending across the end of it, and the second valve body portion includes an internally threaded female portion to be screwed onto said male portion and furthermore includes the means resiliently biasing the diaphragm towards said seating face.

10. A valve substantially as hereinbefore described with reference to, and as illustrated in, Figures 2 and 3 of the accompanying drawings.