GB2119065A

GB2119065A - Mixing and diverting valves

Info

Publication number: GB2119065A
Application number: GB08311640A
Authority: GB
Inventors: John Alfred Lipscombe
Original assignee: Walton Engineering Co Ltd
Current assignee: Walton Engineering Co Ltd
Priority date: 1982-04-28
Filing date: 1983-04-28
Publication date: 1983-11-09
Also published as: GB2119065B; GB8311640D0

Abstract

A valve comprises a valve body 10 incorporating two flow passages 14, 15 opening to a chamber 12 via ports 16, 17 in a flat valve face 13, a valve member 11 which is rotatable to control the ports, and a third flow passage 20 opening to the chamber 12. The valve member is shaped in relation to the ports 16, 17 to cause the sum of their uncovered areas to be substantially equal to the effective area of the third flow passage 20. Means may be provided to compensate for the effect of the pressure difference across the valve member on the axial force between the valve member 11 and the valve face 13, and in preferred arrangements such means is self-regulating. <IMAGE>

Description

SPECIFICATION Improvements in or relating to mixing and diverting valves This invention relates to valves and more particularly to valves intended to bring together two fluid streams to be mixed and to valves for diverting a proportion of a fluid flowing through the valve.

According to the invention there is provided a valve comprising a valve body having a chamber internally thereof bounded in part by a flat valve face, a valve member mounted in the chamber for rotational adjustment in face-to-face sealing contact with said valve face, said valve body having two passages therein which open to said valve face in respective ports extending circumferentially about the axis of rotation of the valve member in nonoverlapping relationship with each other, said body having a third passage in permanently open communication with the chamber, the two ports and said third passage having substantially equal effective areas, and said valve member being so shaped that the sum of the areas of the two ports left uncovered by the valve member is substantially constant for all rotational positions of the valve member.

Preferably said chamber is cylindrical and the third passage extends radially with respect to the chamber.

In one construction the valve member is springloaded into engagement with said valve face, for example for use where said two passages are inlet passages. Where the said two passages are outlet passages the valve member may be spring-loaded in a direction axially away from said valve face in order to compensate for the resultant fluid pressure difference on the valve member.

In preferred arrangements, self-regulating means is provided for compensating for the effects of the pressure drop across the valve member so as to retain an effective seal between the valve member and the valve face while keeping low the frictional forces between them, and hence the power needed to operate the valve.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a sectional elevation of a valve according to the invention on the line B-B of Figure 2, Figure 2 is a sectional underneath plan view on the line A-A of Figure 1, Figures 3 and 4 are fragmentary views respectively showing two alternative constructions in which the valve member is spring-loaded to compensate in part for the fluid pressures thereon, and Figures 5, 6 and 7 respectively show three further modified constructions in which the axial loads on the valve member are compensated in part in a self-regulating manner.

Referring to Figures 1 and 2 of the drawings, the valve comprises a valve body 10 and a valve member 11 mounted in a cylindrical chamber 12 within the body. The chamber has an axially facing flat valve face 13 at one end, and two curved passages 14, 15 open at one end to arcuate ports 16, 17 in the face 13 and lead to respective flanged joint faces 18, 19 of the body. Athird passage 20 extends from a flanged joint face 21 and opens to the chamber through an aperture 22 in the circumferential wall of the chamber. The areas of the ports 16, 17 and the effective area of the third passage 20 are equal.

The ports 16,17 are controlled by the valve member 11, which is in the general form of a semi-circular disc with a boss 25. A shaft 26 extends through the boss and is secured thereto by a diametrically-extending drive pin 27. The shaft is mounted in a bearing 28 between the ports 16, 17 and in a bearing bush 29 in a plate 30 which closes off one end of the chamber 12. The shaft 26 extends through the plate 30 and has its other end arranged for rotational movement by a servo motor (not shown) responsive to a condition, e.g. a temperature, of the fluid flowing through the valve. Axial movement of the shaft is limited in each direction by distance pieces 31,32 which are mounted on the shaft and of which piece 31 abuts the bush 29 and a shoulder 33 on the shaft and the distance piece 32 abuts the boss 25 of the valve member.

As will be seen from Figure 1, the ports 16, 17 do not overlap. The disc portion of the valve member is shown blanking off the whole area of port 16. As the valve member is rotated, port 17 becomes progressively blanked off and to the same extent port 16 is progressively opened, so that the sum of the open areas of the ports is substantially constant for all positions of the valve member and is equal to the effective area of the third passage 20. Thus, there is substantially no variation in the output flow through the third passage 20.

In order to equalise the fluid pressure acting axially upon the disc portion of the valve member a vent passage 34 is provided in the disc portion and extends between the space within the chamber and a recess 35 formed at the opposite axial side of the boss portion.

Modification to the flow characteristics can be obtained by shaping an end edge of the disc portion of the valve member, for example as shown at 36.

In the construction shown in Figures 1 and 2, which is a mixing valve, it is necessary for there to be an axial clearance between the valve face and the disc portion to enable the valve member to be rotated freely, and in consequence there will be a small leakage flow even when the port 16 or 17 is nominally closed.

Referring now to Figure 3, in order to reduce or prevent leakage and to control the pressure between -the underside of the disc portion and the valve face the valve member is left free for limited axial movement relative to the shaft by disposing the drive pin 27 in an axial slot 38 in the shaft and a spring 39 is arranged to load the valve member into engagement with the valve face. The distance piece 32 is omitted and an annular extension 25a of the boss portion forms an annular recess to receive a compression spring disposed between distance piece 31 and the bottom of the recess.The spring is designed to produce a predetermined sealing pressure between the disc portion and the valve face having regard to the difference in the fluid pressure acting on the upper and lower faces of the valve member, two fluids to be mixed being fed along the passages 14, 15 to the chamber. In addition, the lower face of the valve member has secured to it a plate 40 made from a low friction material.

In the arrangement shown in Figure 4for a diverting valve or by-pass valve, the direction of flow is from the chamber through the passages 14, 15. In this case a compression spring 42 is provided acting in the opposite direction to that in Figure 3 and is accommodated in an annular recess at the lower end of the valve member and acting between the valve body and the valve member to produce on the valve member a force in opposition to the force arising from the fluid pressure difference thereon.

The plate 40 engaging the valve face may be replaced by a film of low friction material bonded to the lower face of the valve member.

Figures 5 to 7 of the drawings show three alternative modified constructions in which partial compensation is provided for the axial loading on the valve member and is self-regulating.

Referring now to Figure 5, the end plate 30 is of modified form and provides a cylinder 45 in which a piston 46 secured to the boss 25 and equipped with an anti-friction sealing ring 47 is slidably mounted.

The cylinder opens at one side of the piston to the chamber 12 and at the other side of the piston is in permanently open communication with passage 14 adjacent the valve member by way of drillings 48 in the end plate and drillings 49 in the valve body 10.

Sealing rings 50 prevent leakage along shaft 26 from the cylinder at said other side of the piston. A degree of axial freedom in the coupling (not shown) between the shaft 26 and the drive motor is provided to allow the shaft and valve member to position itself under the axial forces.

This construction causes a force produced by the pressure drop across the disc portion of the valve member to be compensated by the pressure drop applied to the piston 46. By suitably selecting the area of the piston 46 the axial load between the disc portion of the valve member and the valve face can be reduced or increased according to the direction of flow through the valve to give a controlled force, thus reducing the friction forces between the members and reducing the power required to operate the valve. The force should be sufficiently large to ensure a complete seal when one or other of the ports 16, 17 is closed.

Figure 6 shows an arrangement similar to Figure 5 but having a flexing diaphragm 52 in place of the piston 46. The diaphragm is made of metal and is welded to the boss 25 and its outer edge is therefore slidably engaged between an O-ring 53 disposed in an annular groove in a ring 54 secured to the end plate and a flat sealing ring 55 disposed in a rebate in the end plate. As in the arrangement of Figure 5 drilling 48,49 are provided, and serve to cause the pressure in the passage 14 to be applied to the side of the diaphragm remote from the valve member.

The arrangement of Figure 7 is similar to Figure 6 except that its diaphragm 57, which may be made from metal or other suitable material, does not rotate with the boss 25 and consequently has its outer edge clamped between sealing rings 58, 59 respectively disposed in rebates in the end plate and a clamping ring 60. The diaphragm is welded or otherwise sealingly secured to a non-rotating collar 61 freely encircling the shaft 26 and abutting the boss 25 of the valve member through an anti-friction washer 62. This construction is designed for arrangements in which the valve is used as a mixing valve so that the compensating force is required always to press the valve member towards the valve face.

The arrangements shown in Figures 6 and 7 operate in the same way as that of Figure 5.

Claims

1. A valve comprising a valve body having a chamber internally thereof bounded in part by a flat valve face, a valve member mounted in the chamber for rotational adjustment in face-to-face sealing contact with said valve face, said valve body having two passages therein which open to said valve face in respective ports extending circumferentially about the axis of rotation of the valve member is nonoverlapping relationship with each other, said body having a third passage in permanently open communication with the chamber, the two ports and said third passage having substantially equal effective areas, and said valve member being so shaped that the sum of the areas of the two ports left uncovered by the valve member is substantially constant for all rotational positions of the valve member.

2. A valve as claimed in claim 1, wherein said member is cylindrical and the third passage extends radially with respect to the chamber.

3. A valve as claimed in claim 1 or claim 2, wherein the valve member is spring-loaded into engagement with said valve face.

4. Avalve as claimed in claim 1 or claim 2, wherein self-regulating means is provided for controlling the axial pressure between the valve member and the valve face in dependence on the pressure difference across the valve member

5. A valve as claimed in claim 4, wherein said self-regulating means comprises a piston having the valve member connected to it to move axially therewith, and means whereby pressures dependent on pressures acting against opposite axial faces of the valve member are respectively applied to opposite axial sides of the piston in such a manner that the pressure difference across the piston acts on the valve member in opposition to the difference of said pressures acting on the valve member itself.

6. A valve as claimed in claim 4, wherein said self-regulating means comprises a diaphragm whereof the outer periphery is secured to the valve body, said diaphragm having the valve member connected to it to move therewith, and means whereby pressures dependent on pressures acting against opposite axial faces of the valve member are respectively applied to opposite axial faces of the diaphragm in such a manner that the pressure difference across the diaphragm acts on the valve member in opposition to the difference of said pressures acting on the valve member itself.

7. A valve substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2, or any one of Figures 3 to 7 of the accompanying drawings.