WO1997005414A1

WO1997005414A1 - Fluid flow control valve

Info

Publication number: WO1997005414A1
Application number: PCT/GB1996/001757
Authority: WO
Inventors: Graham William Osborne
Original assignee: Graham William Osborne
Priority date: 1995-07-25
Filing date: 1996-07-22
Publication date: 1997-02-13
Also published as: GB9515191D0

Abstract

A fluid flow control valve has first and second valve seats (12 and 13) spaced apart within a passageway (11) and a valve member (15) is mounted within the passageway, for sliding movement between the two seats. A spring (20) biases the valve member (15) into engagement with the first seat (12) so that a one-way valve is formed therebetween. The valve member (15) is movable into engagement with the second seat (13) to close the passageway (11) in the event there is excessive fluid flow.

Description

FLUID FLOW CONTROL VALVE

This invention relates to a fluid flow control valve, and in particular to such a valve having a combined shut-off and flow limiting function.

There have been proposals for fluid flow control valves which are configured to limit the flow rate of a fluid along a duct within which the valve is fitted. For example, in US Patent No. 5,105,850, there is described a poppet valve having a valve member spring- loaded to an open position but which moves to a closed position against a seat should the flow over the valve member exceed some pre-determined value. Another proposal is to be found in US Patent No. 4,301,833, wherein a valve member is pivoted for movement between open and closed positions within a duct through a valve body, the valve member being spring-urged to the open position. The valve member has an aerofoil section whereby flow over the valve member generates lift on the member and in turn that causes the valve member to pivot to a closed position. In many fluid flow installations, it is necessary to provide at some point in a pipeline a non-return valve. Such a valve may be in the form of a valve member engageable with a valve seat and biased to the closed position, the valve being installed such that the normal direction of fluid flow will lift the valve member off the seat, against the spring bias. Under no flow conditions, the valve member returns to its seat and blocks return flow.

The present invention aims at providing a compound fluid flow control valve, able to perform the combined functions of a non-return valve and a flow limiting control valve, in a simple and economic manner.

According to the present invention, there is provided a fluid flow control valve having a fluid flow passageway, a first and second valve seats spaced apart along the length of the passageway, and a valve member mounted within the passageway between the first and second valve seats for movement therebetween, the valve member having first and second faces for co-operating with the first and second valve seats respectively, and spring means biasing the valve member into engagement with the first valve seat.

It will be appreciated that in the valve of the present invention, the valve member is disposed between and may alternately engage the first or second valve seats, to effect a seal therewith. The valve member is urged into engagement with the first valve seat whereby the valve member in conjunction with that first seat operates as a non-return valve. Normal fluid flow will lift the valve member off that seat, towards the second seat. Increasing fluid flow will further move the valve member against the spring bias until eventually the flow rate is sufficient to engage the valve member with the second valve seat, so closing the valve consequent upon the excessive fluid flow.

In a preferred embodiment of valve of this invention, the valve member is mounted for linear sliding movement within the fluid flow passageway, and the valve seats and said faces of the valve member are substantially annular. Conveniently, therefore, the valve member is in the form of a poppet valve having a valve stem projecting from one side of a valve head, the valve stem being slidably mounted within a valve guide co-axially disposed with respect to the passageway.

In order to allow the valve to operate, the force exerted by the spring means should depend upon the movement of the valve member away from the first valve seat. Conveniently, a compression spring is arranged to act between the valve member and a fixed part of the valve. It may be advantageous to have the spring force which engages the valve member with the first valve seat relatively small as compared to the force exerted by the spring when the valve member engages the second valve seat. In this case, the compression spring may have a variable spring rate dependent upon the compression thereof, for example by arranging for turns of the spring to move into engagement with each other as compression of the spring increases. Alternatively, a second spring means may be provided to bias the valve member away from the second valve seat, that second spring means being inactive when the valve member is in engagement with the first valve seat.

The operating characteristics of the valve may be controlled by providing different flow areas for the first and second valve seats. However, it is preferred for those flow areas for the two seats to be substantially the same.

By way of example only, one specific embodiment of fluid flow control valve of the present invention will now be described with reference to the accompanying drawings, in which:-

Figure 1 shows the embodiment of the valve in its first, non-return position; Figure 2 shows the valve of Figure 1 in an intermediate position; and

Figure 3 shows the valve in a flow limiting position.

The embodiment of fluid flow control valve shown in the drawings comprises a valve body 10 defining a circular fluid flow passage 11. Provided within that passage 11 are first and second annular valve seats 12 and 13, spaced apart axially within the passage 11. A valve guide 14 is disposed axially within the passage 11 and a valve member 15 having a valve stem 16 is slidably carried within the valve guide 14. The valve member 15 has a head 17 disposed between the first and second valve seats 12 and 13, the head 17 having first and second part-conical faces 18 and 19, respectively engageable with the first and second valve seats 12 and 13. A compression spring 20 acts between the free end of the valve stem 16 and a fixed part (not shown) of the valve body.

Figure 1 shows the valve in its normal, rest position with the spring 20 maintaining face 18 of the head 17 in engagement with the first valve seat 12. Normal fluid flow, in the direction of arrow A, will lift the valve head 17 off the first valve seat 12, so that fluid flow through the valve may take place, as shown in Figure 2. Flow in the direction opposed to arrow A will be blocked by the engagement of the head 17 with the first valve seat 12.

Fluid flow past the valve head 17 will drive the valve member against the force provided by the spring 20, which force increases as the compression of the spring increases. Thus, the greater the flow, the further the valve member is moved towards the second valve seat 13. Eventually, should the flow rate increase to a sufficient extent, the flow head 17 will engage the second valve seat 13, so shutting off the fluid flow. Dependent upon the fluid pressure attempting to create that flow, either the valve member will remain in the position of Figure 3 until the pressure decreases, or the valve member may move away from the second valve seat to a limited extent, balancing the spring force with the force on the valve member created by the fluid flow. in the latter case, the valve will perform a flow rate limiting function, without actually shutting off the fluid flow altogether. The fluid flow control valve described above may be used in a variety of installations, but a particular application is in the case of a supply line for a pressurised delivery forecourt fuel dispensing system. Fuel, such as petrol or diesel oil, is often pumped under pressure from a storage tank to a metering and delivery device (conventionally referred to as a fuel pump). To ensure the pipe always remains full, even if the pump delivering fuel from the storage tank into the pipe is shut down, it is the usual practice to install a one-way valve at the outlet from the pump. In order to prevent significant leakage from the pressurised pipe in the event that the pipe becomes fractured, or a fuel pump is broken away from its base, the valve of the present invention may be installed at the outlet from the storage tank pump, the valve then serving the combined purpose of preventing flow back into the storage tank and also of shutting off fuel delivery if the flow rate through the pressurised pipe exceeds some pre-determined value.

Claims

1. A fluid-flow control valve having a fluid flow passageway, a first and second valve seats spaced apart along the length of the passageway, and a valve member mounted within the passageway between the first and second valve seats for movement therebetween, the valve member having first and second faces for co-operating with the first and second valve seats respectively, and spring means biasing the valve member into engagement with the first valve seat.

2. A fluid-flow control valve as claimed in claim 1 , wherein the valve member is mounted for linear sliding movement within the passageway.

3. A fluid-flow control valve as claimed in claim 1 or claim 2, wherein the valve seats and said faces of the valve member are substantially annular.

4. A fluid-flow control valve as claimed in claim 1 or claim 3, wherein the valve member is in the form of a poppet valve having a valve stem projecting from one side of a valve head, the valve stem being slidably mounted within a valve guide co-axially disposed with respect to the passageway.

5. A fluid-flow control valve as claimed in any of the preceding claims, wherein the spring means comprises a compression spring acting between the valve member and a fixed part of the valve.

6. A fluid-flow control valve as claimed in claim 5, wherein the compression spring has a variable spring rate dependent upon the compression thereof.

7. A fluid-flow control valve as claimed in any of the preceding claims, wherein there is provided second spring means arranged to bias the valve member away from the second valve seat.

8. A fluid-flow control valve as claimed in claim 7, wherein the second spring means acts on the valve member only after the first face of the valve member has moved away from the first valve seat.

9. A fluid-flow control valve as claimed in any of the preceding claims, wherein the effective diameters of the first and second valve seats are substantially the same as each other.