GB2204662A

GB2204662A - Wafer check valves

Info

Publication number: GB2204662A
Application number: GB08711441A
Authority: GB
Inventors: Michael Dennis Stone
Original assignee: Goodwin R International Ltd
Current assignee: Goodwin R International Ltd
Priority date: 1987-05-14
Filing date: 1987-05-14
Publication date: 1988-11-16
Anticipated expiration: 2007-05-14
Also published as: GB2204662B; GB8711441D0

Abstract

A wafer check valve having an annular body with a passage therethrough divided into two parts by a cross member, two generally semicircular pivoted flaps to close respective parts of the passage, each flap having two hinges, the hinges of one flap being lower hinges 36, 37 and the hinges of the other flap being upper hinges 34, 35, and the weight of each flap being taken by a reduced friction bearing 46, 47 offering less friction than that between the hinges of the flaps and a corresponding supporting surface. <IMAGE>

Description

WAFER CHECK VALVES This invention relates to wafer check valves.

Wafer check valves are well known and generally comprise an annular housing with a passage through it closable by two semicircular flaps which are pivoted on a diammetral hinge pin. A diammetral cross member divides the passage into two parts corresponding to the two flaps, each of these two parts surrounding a valve seat. The flaps are spring urged to a valve closing position in which the semicircular parts defined by the diammetral cross piece are closed, and they can move against the spring to an open position in which they lie generally parallel to the housing axis. Frequently there is a stop pin provided parallel to and behind the hinge pin to prevent either flap rotating more than 900 from the valve closing position.

Wafer check valves are used as non return valves which open in response to pressure of a given level on the upstream side, that is pressure applied to the semicircular openings. If the flow rate drops the spring controlling the flaps tends to shut the flaps. When the flow ceases altogether an automatic closing occurs without in general any slamming or hammering of the flaps.

Normally each flap member has two hinges mounted on the pivot pin. Conventionally the hinges of one flap rest upon the hinges of the other, the lower hinge of the lower set of hinges simply resting on the housing or an insert in which the hinge pin is located. As a result of this arrangement there is a disparity between the forces necessary to close one of the flaps and the forces necessary to close the other, because the lower hinges have an increased loading and thus an increased friction force resists their pivoting movement. This is an undesirable effect because the times of closing the two flaps and their response to pressure difference should ideally be the same, and in any event for the sake of speed and sensitivity in response reduction in friction would be desirable.

British patent 1518576 discloses constructions designed to overcome the difficulty of difference in frictional resistance by the provision between the upper and lower hinges of a collar upon which the upper hinge rests. This collar is either attached to the hinge pin, so that the weight of the flap with the upper hinges is carried directly by the hinge pin, or is mounted on a sleeve which passes through the lower hinge pin so as to transfer weight directly to the housing.

With the present invention we propose to provide a valve in which the weight of each flap is taken by a reduced friction bearing. A reduced friction bearing is one offering less friction than that between the hinges of the flaps and a supporting surface. For instance a ball bearing or race of ball bearings is one example of reduced friction bearing, and bearings of small radius also offer reduced frictional effect on the flaps.

Each bearing may take the weight of only one flap. Preferably the lower hinges are not used to transfer weight from the upper ones. The weight of the flap with the upper hinges is preferably taken by the hinge pin itself. This can be achieved, in a preferred construction, by the hinge having an internal step resting upon an external step on the hinge pin.

The hinge pin can be designed to rotate with the upper hinges and to be supported by one reduced friction bearing. In some forms, such bearing can be surrounded by a small diameter sleeve having or embodying another low friction bearing and taking the weight of the flap with the lower hinges.

In other preferred embodiments the weight of the lower hinge is taken by a cup which has a reduced friction bearing where it contacts the housing, and the pin which takes the weight of the flap with the upper hinges extends into the cup with a bearing therebetween. These bearings can be for instance rounded projections or ball bearings.

The cup therefore takes the weight of both flaps, but the frictional resistance of turning each flap is minimized by the respective ball bearings.

In preferred forms of the present invention therefore there is provided a wafer check valve having two openings, respective flaps for closing the openings and a hinge pin on which the flaps are mounted, a cup in which the lower end of the hinge pin extends, a bearing for the cup, a bearing between the cup and the lower end of the hinge pin, the weight of one flap being borne by the cup and the weight of the other flap being borne by the hinge pin. The cup may be replaced by a small diameter sleeve, with the bearing at the lower end of the hinge pin being within but not supported by the bush.

The invention also seeks to reduce friction in flap valves in another way. In flap valves another source of friction is between the hinges and the hinge pin. This arises because the weight of the flaps is offset from the pivot axis, so that the upper hinge pulls on the pin and the lower hinge pushes against it. One consequence is that frictional resistance arises when a flap is turned.

Another consequence is that there are local twisting forces in the pin, and these can become exaggerated if the flaps should move suddenly and slam open or closed.

In another aspect we propose to provide a wafer check valve in which there are sleeves surrounding the hinge pin and extending within a pair of the hinges. Thus there will generally be two sleeves, one within the upper two hinges and one within the lower two. The sleeves will generally extend only within part of the length of each hinge, they are preferably arranged to be a close fit in one hinge, for instance the lower of each pair, and a sliding fit in the other one, resulting in no side loads on the pin when the flaps are in the closed position.

At least when the valve is closed, these sleeves go far to eliminating hinge friction. The reason is that the effects of the two flaps cancel each other out. In other words, while the upper pair of hinges each tends to be pulled away from the pin by the flap weight, these forces are applied to the pivot sleeve where they cancel out. There is no side load. The sleeve will not twist provided it is rigid enough, and due to being a sliding fit on the pin only little friction results.

As the flaps open, the pulling effects tend to become in the same direction, so that friction develops as the sleeve is pulled against the pin. However, this is less important than friction at near closing positions which is what needs to be minimised. Similar considerations arise regarding the forces arising at the lower pair of hinges. Also, the pivot sleeves help to prevent hinge pin twisting.

In order that the invention may be more clearly understood the following description is given by way of example only with reference to the accompanying drawings in which: Figures 1 and 2 are front and rear views of a wafer check valve of known type; Figure 3 is a partial longitudinal cross section through a wafer check valve according to the invention.

As shown in Figures 1 and 2 a wafer check valve comprises an annular housing 20 with a transverse member 21 dividing the opening therethrough into two semicircular ports such as 22. Closing these ports are flaps 23 and 24 mounted by respective pairs of hinges 23a, 23b and 24a, 24b on hinge pin 27 received in inserts 28 and 29. Surrounding the hinge pin is a spring 19 tending to urge both the flaps 23 and 24 to the closed position against seats surrounding the ports 22. It can be seen from Figure 2 that the upper hinges rest upon the lower ones and the lowermost hinge 23b rests upon the insert 29.This means that the total frictional resistance to the movement of both the flaps 23 and 24 includes the frictional resistance between the pairs of hinges, which is proportional to the weight of the flap 24, and the frictional resistance between the lowermost hinge of the insert 29 which is proportional to the weight of both flaps 23 and 24. In addition there will be a frictional resistance due to the fact that the flap 24 is trying to tip to the right as shown in Figure 2 and the flap 23 to the left. Thus the respective hinges react on the hinge pin proportionally to the weight of the flaps, and the distance of the centre of gravity thereof from the hinge pin. Further, there is a twisting effect in the hinge pin.

Turning now to Figure 3 there is shown an annular housing 30 in which there are received inserts 31 and 32 with recesses to receive means associated with the hinge pin and also to receive a stop pin shown at 40 which prevents over-opening of either flap. These inserts are retained by dowells 60 located in end plates 41, 42 extending circumferentially to either side of the recesses for the pins.

There are shown a pair of upper hinges 34 and 35 and a pair of lower hinges 36 and 37 surrounding the hinge pin which is at 33. The lowermost hinge rests on a cup 38 in the recess 39. The pin 33 rests within the cup 38.

Near its upper end the pin has a shoulder 39 and the uppermost hinge 34 has an internal shoulder resting thereon, so that the weight of the flap associated therewith is taken by the shaft. The weight of the flap associated with the lowermost hinge is taken by the cup 38.

Between the cup 38 and the housing is a ball bearing support 46 and between the pin 35 and the cup 38 is a second such support 47 so that both flaps are supported by reduced friction bearings. The upper end of the pin 33 is received in another cup 48 located within the upper insert 31. Though not shown, a ball bearing arrangement could be provided if desired at each end, so that the resulting valve is invertable as to which way up it should be located.

Sleeves 51 and 52 extend between adjacent pairs of hinges. As shown the sleeves are a close fit in the lower of each hinge of a pair and a sliding fit in the upper, and they are a sliding fit around the hinge pin 33.

A result of this is that, when the flaps are in the closed position extending generally in the same plane, the reactions on the sleeves due to the weights of the flaps cancel each other out, and do not create a frictional effect with the pin. Although the two forces on each sleeve due to the weights transmitted by two hinges are offset from each other, the sleeve will be designed not to twist, and thus not to preferentially contact the pin at any point. This effect of cancelling the forces and reducing friction diminishes as the flaps open however, and when the flaps are fully open the weight of both flanges pulls on the pin at the upper pair of hinges and pushes on it at the lower.

In use the pin 33 rotates with the flap having the upper hinges 34, 36 while the cup 38 rotates with the other flap.

As a result of the invention, in both aspects, the force necessary to rotate each flap is much reduced, and the forces necessary for rotating the two flaps are substantially the same, with beneficial effect upon the operation of the valve. The two aspects of the invention described above can be employed separately or together.

Claims

1. A wafer check valve having an annular body with a passage therethrough divided into two parts by a cross member, two generally semicircular pivoted flaps to close respective parts of the passage, each flap being hinged to a hinge pin, and the weight of each flap being taken by a reduced friction bearing in which there is less friction than that between hinges of the flaps and a corresponding supporting surface.

2. A wafer check valve according to claim 1 wherein the reduced friction bearing is a ball bearing or race of ball bearings.

3. A wafer check valve according to claim 1 wherein the reduced friction bearing has a small radius to give reduced friction.

4. A wafer check valve according to any preceding claim wherein each bearing takes the weight of only one flap.

5. A wafer check valve according to claim 4 wherein the weight of the flap with upper hinges, that is hinged which are above the hinges of the other flap, is taken by the hinge pin.

6. A wafer check valve according to claim 5 wherein the hinge pin has an external step on which the adjacent one of the upper hinges rests.

7. A wafer check valve according to claim 6 wherein said adjacent upper hinge has an internal step matching the external step on the pin.

8. A wafer check valve according to claim 5, 6 or 7 wherein the hinge pin is adapted to rotate with the upper hinges and is supported by a said reduced friction bearing.

9. A wafer check valve according to claim 8 wherein the said reduced friction bearing is surrounded by a small diameter sleeve which takes the weight of the flap with the lower hinges.

10. A wafer check valve according to claim 5, 6, 7 or 8 including a cup taking the weight of the flap with the lower hinges, the cup having a reduced friction bearing at its lower end and wherein the hinge pin extends into the cup and has a reduced friction bearing engagement therein.

11. A wafer check valve according to claim 10 wherein the reduced friction bearings are rounded projections or balls.

12. A wafer check valve having an annular body with a passage therethrough divided into two parts by a cross member, two generally semicircular pivoted flaps to close respective parts of the opening, a hinge pin on which the flaps are hinged, a cup in which the lower end of the hinge pin extends, a first bearing for the cup, and a second bearing between the cup and the lower end of the hinge pin, the weight of one flap being borne by the cup and first bearing, and the weight of the other flap being borne by the hinge pin and second bearing, the bearings being reduced friction bearings in which there is less friction than that between hinges of the flaps and a corresponding supporting surface.

13. A wafer check valve according to any preceding claim including at least one sleeve surrounding the hinge pin and extending within a hinge of each flap.

14. A wafer check valve according to claim 13 wherein the or each sleeve extends only within part of the length of each hinge within which it is extends.

15. A wafer check valve according to claim 13 or 14 wherein the or each sleeve is a close fit in one hinge and a sliding fit in the other.

16. A wafer check valve having an annular body with a passage therethrough divided into two parts by a cross member, two generally semicircular pivoted flaps to close the respective parts, each flap being hinged received to a hinge pin, and at least one sleeve surrounding the hinge pin and extending within a hinge of each flap.

17. A wafer check valve according to claim 16 wherein the or each sleeve extends only within part of the length of each hinge within which it extends.

18. A wafer check valve according to claim 16 or 17 wherein the or each sleeve is a close fit in one hinge and a sliding fit in the other.

19. A wafer check valve constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.