GB2105012A - Check valve - Google Patents

Abstract

A check valve fitted within a pipe 30 comprises a one-piece housing 10 having a constricted portion 12 forming a seating for a closure member 16 urged towards the closed position by a spring 29. The spring 29 is supported by a spider 23 secured by a latch connection 15, 28 in the housing 10 at the discharge end thereof. <IMAGE>

Description

SPECIFICATION A check valve This invention relates to a check valve namely a means for preventing return flow such as is used in pipes for fluid media so as to ensure that the fluid flows through the pipe in one direction only but is blocked in the opposite direction. Check valves are fitted on, for example, water meters or at other points in a water supply system so as to prevent the return flow of dirty water or industrial water in drinking water pipes.

Known check valves commonly comprise a housing forming a flow duct with a constricted portion and a closure member which is longitudinally movable in the housing and is urged towards the constricted portion by a spring.

In the check valve shown in GB-PS 945,908 the spring is braced against an annular shoulder within the housing. To enable the closure member and the spring to be fitted in the housing, the latter is divided transversely into two parts. The two parts of the housing are interconnected by a screw thread. Since a path for outward flow of the fluid from the interior of the housing is created by the presence of the screw thread, this path requires to be additionally sealed, since otherwise the check valve would not be fluidtight because of leakage and it would permit the passage of fluid in the blocking direction.

The use of a multi-part housing with screwthreaded inter-connection and additional sealing involves considerable expense. A further disadvantage is that since the two parts of the housing are screwed together the bias of the spring acting on the valve member varies in dependence upon the extent to which the screwed connection between the two parts of the housing is tightened. The flow characteristic of the check valve therefore varies in dependence upon the tightness of the screwed connection.

In another known check valve (US-PS 3 346 009), the housing is designed as a double cone, and the spring is braced against one of the cones and the closure member is urged into the other. The housing likewise consists of two halves which are fitted one against the other and which can be interconnected by screw means or by welding. When screw means are used for fitting two housing parts together in the axial direction, the above-mentioned disadvantages result. Welding results in a construction which does not permit manipulations within its housing at a later stage. Furthermore, bracing of the spring against a conicai wall of the housing is unreliable and likely to lead to trouble.

Also known is a check valve (DE-AS 10 44 537) the housing of which consists of two parts screwed together in the axial direction. Clamped between the housing parts is a spider, which has a pin for guiding the closure member. Also, the spider supports the spring for urging the closure member into the closed position. Because of the two-part housing, a construction of this kind likewise leads to the above-mentioned difficulties regarding leakage, i.e. lack of tightness. The flow behaviour is determined, in a decisive manner, by the extent to which the screwed means between the two parts of the housing have been tightened.

Finally, a check valve is known which has a housing which is completely undivided and in which is screwed a spider located directly behind the constricted portion. A sealing ring is arranged between the spider and the housing.

The object of the present invention is to provide a check valve which consists of only a few easily produced components and which has a low resistance to flow in the direction in which a medium passes through it.

The invention accordingly provides a check valve comprising a housing forming a flow duct and having a constricted portion forming a seating for a closure member longitudinally movable in the housing and urged towards the constricted portion by a spring, supported by a spider which extends into the flow duct, the wall of the housing being in one piece and undivided, and the spider being secured by a latch connection at the discharge end of the housing with the rear end-face uncovered.

Since a one-piece housing is used, the side wall of the housing is closed over its entire length, so that no leakage can occur along the side wall. The spider is located at that end of the housing is at the rear in the direction of flow, and it is secured in this position after the valve body and the spring have been fitted.

When the check valve is fitted in a pipe carrying a fluid, the housing is normally secured by the adjacent axial length of pipe.

The zone where the length of pipe joins the check valve is sealed off by an axially compressible disc seal, so that no liquid can flow along the housing on the outside. The connection between the spider and that part of the housing that surrounds it requires no seal.

Assuming that the closure member does not permit the passage of liquid when in the closed condition, no leaks occur at all since the housing has a wall which is continuous in the longitudinal direction and has no screwed connections whatsoever.

In one embodiment of the invention, an annular stepped portion is provided at the discharge end of the housing, and the spider has a peripheral ring the inner face of which is substantially flush with the inner wall of the housing. In this arrangement, the peripheral ring of the spider fills out the stepped portion so that, in the zone of this portion, the inner wall of the peripheral ring forms a continua tion of the wall of the flow duct. Thus, the flow conditions are not appreciably affected by the peripheral ring. Also, the sealing ring does not require to be sealed off against the inner wall of the housing. In order to ensure that the spider is seated firmly and in a specific position on the housing, the peripheral ring may co-operate with the stepped portion by means of a latch connection consisting of a groove and bead.This ensures that the axial position of the spider supporting the spring is precisely fixed, so that the closure force of the closure member against the constricted portion is exactly determined and cannot be subsequently altered.

A check valve in accordance with the invention can be produced in a particularly simple manner from a few parts mainly made of plastics material. In a preferred form of construction, the housing has a substantially constant wall-thickness at all points and is axially symmetrical and has a cross-section which varies in accordance with the Laval flow curve. Since the housing consists of one piece, there are no break-away edges in the flow duct, and thus the check valve can be produced to provide very littie resistance to flow in the direction in which the medium passes.

An embodiment of a check valve in accordance with the invention will now be described in greater detail by reference to the accompanying drawings, in which: Figure 1 is a longitudinal section through the check valve shown fitted in a water pipe, and Figure 2 is an end view in the direction indicated by the arrow II in Fig. 1.

The check valve shown in the drawings as fitted in a pipe 30 comprises an axially symmetrical housing 10 which, at the inlet end, forms an end flange 11 the inner end of which is connected to a cylindrical portion 1 3 by way of a constricted portion 1 2. Located at the discharge end of the housing 10 is a widened zone in the form of an annular stepped portion 14. An annular groove 1 5 is formed in the inner wall of the stepped portion 14.

A closure member 1 6 comprises a disc 1 7 which is displaceable in the axial direction in the flow duct 1 8. Fitted on the rear face of the disc 1 7 is a disc seal 1 8a which projects laterally beyond the disc 17, is supported by a disc-shaped holder 1 9 and is pressed against the rear face of the disc 1 7. The holder 1 9 is secured on a rod 20 which projects rearwardly from the rear face of the disc 1 7 along the axis of the housing 10.

A helical spring 29 coaxially surrounds the rod 20 and acts against the rear face of the closure member 1 6. The helical spring 20 projects into an annular pocket 22 of a spider 23, where it is guided and axially braced. The inner wall 24 of the annular pocket 22 en closes an opening for passage of the rod 20, whereas the outer wall 25 of the pocket 22 is of frusto-conical shape and diminishes in size towards the rear end. In the full open position of the closure member 16, the rear edge of this member closes off the forwardly extend ing opening of the annular pocket 22.

The pocket 22 is a constituent part of the spider 23 which has three radial arms 26 that connect the wall 25 to a peripheral ring 27.

The arms 26 extend radially through the flow duct 1 8. The inner wall of the peripheral ring 27 bears substantially flush against the inner wall of the cylindrical wall 1 3 of the housing 10. The peripheral ring 27 has an outer circular bead 28 which matches the groove 1 5 into which it latches when the peripheral ring 1 3 is pressed into the stepped portion 1 4 of the housing. When the spider 23 is se cured to the housing 10 in this way, its rear face lies approximately flush with the rear end of the housing 1 0.

A sealing ring 32, pressed from the exterior against the rear end of the housing 10, performs the function of sealing off the housing against the adjoining piece of piping. The housing 10 is fitted in the pipe 30, which has at its end a widened portion 31 for receiving the stepped portion 1 4. In this way, the check valve is secured in the pipe 30 so that it cannot be axially displaced. Of importance is the fact that liquid, once having passed into the interior of the housing 10, can only find its way out of the housing through the spider 23, since the wall of the housing 10 extends over the entire length of the check valve and has no passages, interruptions or connecting pieces.

Claims (5)

1. A check valve comprising a housing forming a flow duct and having a constricted portion forming a seating for a closure mem ber longitudinally movable in the housing and urged towards the constricted portion by a spring, supported by a spider which extends into the flow duct, the wall of the housing being in one piece and undivided, and the spider being secured by a latch connection at the discharge end of the housing with the rear end-face uncovered.

2. A check valve according to Claim 1, wherein an annular stepped portion is pro vided at the discharge end of the housing, and the spider has a peripheral ring the inner face of which is substantially flush with the inner wall of the housing.

3. A check valve according to Claim 2, wherein the peripheral ring co-operates with the stepped portion by means of a latch connection consisting of a groove and a bead.

4. A check valve according to any one of Claims 1 to 3, wherein the housing has a substantially constant wall-thickness at all po ints, is axially symmetrical and has a cross section which varies in accordance with the Laval flow curve.

5. A check valve substantially as hereinbefore described with reference to the accompanying drawings.