GB1595414A

GB1595414A - Valves

Info

Publication number: GB1595414A
Application number: GB285877A
Authority: GB
Original assignee: Northern Engineering Industries PLC
Current assignee: Rolls Royce Power Engineering PLC
Priority date: 1978-01-09
Filing date: 1978-01-09
Publication date: 1981-08-12

Description

(54) VALVES (71) We, NORTHERN ENGINEERING IN DUSTRIES LIMITED, a British company of NEI House, Regent Centre, Newcastle on Tyne NE3 3SB, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to valves.

According to the present invention there is provided a valve comprising a body having a fluid flow path therethrough and around a valve member therein, an annular valve seat between an inlet end of the fluid flow path and an outlet end thereof the valve member being slidably disposed in said body for rectilinear movement in alignment with the general direction of fluid flow through said path and having a circular head having a periphery of greater diameter than the seat and co-operating with the body to define on the inlet side of the valve seat an annular portion of said path of greater diameter than the seat whereby there is created by fluid flow through said path a pressure drop acting to urge the head towards the seat but opposed by a rectilinear bias in alignment with said general direction provided by a spring acting on the valve member, the bias being such that if the outlet pressure becomes less than the inlet pressure by a predetermined amount the bias is overcome and the valve head moves to engage the seat, the valve further comprising a fluid chamber the volume of which is reduced by closing movement of the valve member, the rate of closing movement of the valve member being dependent upon the rate at which fluid flows from the chamber at least through a restricted clearance between the wall of the chamber and the valve member as the volume of the chamber is reduced.

Conveniently the resilient means biassing the valve member into the open position can be a spring disposed in the chamber.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a schematic mainly sectional side view of a vale, and Figures 2 and 3 are similar views illustrating alternative forms of the valve.

The valve shown in Figure 1 has a body 1 having a fluid flow path 2 therethrough from an inlet side 3 to an outlet side 4 of the body.

An annular valve seat 5 in the flow path 2 can be contacted by a seating ring 6 of rubber or similar soft material carried by a head 7 of a valve member. The valve head 7 is a circular disc centrally supported, for sliding movement in the general direction of fluid flow through the path 2, by a shaft 8 of the valve member slidably mounted in the body 1 in a wall portion 1A. The shaft 8 extends through a chamber 11 of significantly greater diameter than the shaft 8. The valve member includes a cup 10 fast with the valve head 7 slidably engages the wall 9 of the chamber 11.

Within the chamber 11 there is a compression spring 12 that acts resiliently to urge the valve head clear of the valve seat 5, the valve fully-open position being determined by engagement of a shoulder 8A on the shaft 8 with the body portion IA.

The valve head 7 co-operates with the body I to define on the inlet side of the valve seat 5 an annular portion 13 of the fluid flow path 2 whereby there is created by fluid flow through the path a pressure drop across the valve head 7 acting to urge the valve member to seat on the valve seat 5. Such fluid flow is indicated by chain dot arrows in the Figure, it being illustrated how the valve can be mounted between flanges 14, 15 in a pipeline through which the fluid is flowing. If the pressure drop becomes sufficiently high to override the action of the spring 12, for example because a fracture occurs in the pipeline on the outlet side of the valve, the valve head 7 will move to seat on the valve seat 5 and close the valve.

Closing movement of the valve member is damped by a damping device constituted by the chamber 11 and a restricted orifice 16 in the valve head 7 that provides a flow path for fluid between the chamber 11 and the path 2 on the inlet side of the annular portion 13 of the path 2. When the valve is open and fluid is flowing, the chamber 11 initially fills with fluid from the inlet side via a bore 18 in the side wall of the cup 10. This bore 18 is located immediately adjacent the wall 9 in the valve fully-open position so that at the commencement of movement of the valve member in the closing direction the bore 18 enters within the wall 9 to be closed thereby.

The volume of the chamber 11 is reduced by the valve member valve closing movement, and the rate at which the valve member moves to close the valve is therefore dependent (after the bore 18 has been closed) upon the rate at which fluid can flow out of the chamber 11, this flow rate being determined partly by the size of the orifice 16. The orifice 16 is, therefore, dimensioned to suit requirements. In a particular form the diameter of the orifice 16 is less then 1 mm. and the pressure generated in the chamber 11 is over 100 p.s.i.

It is to be noted that the cup 10 is not positively sealed against the wall 9 and that some fluid passes from the chamber 11 via a restricted clearance between the valve member and the wall 9 at grooves lOA in the cup 10 to the path 2 downstream of the valve member 7, such flow being very restricted.

The alternative form of Figure 2 is the same as that of Figure 1, except that there is a further orifice 17 through the valve head 7 placing the inlet side of the valve head 7 in direct communication with the outlet side thereof. In this form, therefore, the fluid flow path 2 is a first path that permits full fluid flow when the valve is open, and the orifice 17 provides a second path permitting restricted fluid flow. When the first path is closed by seating of the valve head 7 on the valve seat 5, the second path remains open so that a restricted flow can continue to take place from the inlet side to the outlet side. In this form, therefore, there will always be, in use, a fluid flow through the orifice 17 so that the valve member never completely shuts off the flow path through the valve.However, selection of the dimensions of the orifices 16 and 17, path 2 and valve head 7, and of the strength of the spring 12, enables the operating characteristics of the valve to be chosen to suit particular user requirements. For example, the valve can operate such that a fluid flow of 25 gallons per minute is reduced to approximately 1 gallon per minute upon automatic operation of the valve. The valve in this form can thus be used as a pressure control device, for connection in a fluid flow path, which will function as a protection device in a fluid power supply line to prevent a pump discharging quickly all the stored fluid into the operating area in the event of a sudden rupture of the supply line, and which will function as a flow control valve if excessive flow were to develop without rupture of the supply line.In more detail, if a fracture occurs in an outlet pipe leading from the outlet side 4 of the valve, the fluid pressure in this pipe will fall below the pressure on the inlet side 3 of the valve, and the pressure drop across the valve head 7 will accordingly rise. When this pressure drop reaches a predetermined value the excess inlet pressure will cause the valve head 7 to move to the left in the Figure, overcoming the biassing force of the spring 12 and with the movement damped by the damping device 11/16, so that the valve head 7 seats against the valve seat 5 and automatically partially shuts off the fluid flow.Since some fluid continues to pass through the valve via the orifice 17, when the fracture in the output pipe has been made good, by replacement or in any other convenient manner, the fluid flowing through the orifice 17 re-primes the system until any pressure drop across the valve head 7 is overcome by the force of the spring 12, which then asserts itself to move the valve member into the open position without the need for any mechanical readj ustment.

The third form of Figure 3 is very similar to the second form, except that the orifice 16 is omitted, changes in volume of the chamber 11 being accommodated by the very restricted flow of fluid that can take place via the restricted clearance at the grooves I0A in the cup 10.

WHAT WE CLAIM IS: 1. A valve comprising a body having a fluid flow path therethrough and around a valve member therein, an annular valve seat between an inlet end of the fluid flow path and an outlet end thereof, the valve member being slidably disposed in said body for rectilinear movement in alignment with the general direction of fluid flow through said path and having a circular head having a periphery of greater diameter than the seat and co-operating with the body to define on the inlet side of the valve seat an annular portion of said path of greater diameter than the seat whereby there is created by normal fluid flow through said path a pressure drop acting to urge the head towards the seat but opposed by a rectilinear bias in alignment with said general direction provided by a spring acting on the valve member, the bias being such that if the outlet pressure becomes less than the inlet pressure by a predetermined amount the bias is overcome and the valve head moves to engage the seat, the valve further comprising a fluid chamber the volume of which is reduced by closing movement of the valve member, the rate of closing movement of the valve member being dependent upon the rate at which fluid flows from the chamber at least through a restricted clearance between the wall of the

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Claims

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the path 2. When the valve is open and fluid is flowing, the chamber 11 initially fills with fluid from the inlet side via a bore 18 in the side wall of the cup 10. This bore 18 is located immediately adjacent the wall 9 in the valve fully-open position so that at the commencement of movement of the valve member in the closing direction the bore 18 enters within the wall 9 to be closed thereby.

The volume of the chamber 11 is reduced by the valve member valve closing movement, and the rate at which the valve member moves to close the valve is therefore dependent (after the bore 18 has been closed) upon the rate at which fluid can flow out of the chamber 11, this flow rate being determined partly by the size of the orifice 16. The orifice 16 is, therefore, dimensioned to suit requirements. In a particular form the diameter of the orifice 16 is less then 1 mm. and the pressure generated in the chamber 11 is over 100 p.s.i.

It is to be noted that the cup 10 is not positively sealed against the wall 9 and that some fluid passes from the chamber 11 via a restricted clearance between the valve member and the wall 9 at grooves lOA in the cup 10 to the path 2 downstream of the valve member 7, such flow being very restricted.

The alternative form of Figure 2 is the same as that of Figure 1, except that there is a further orifice 17 through the valve head 7 placing the inlet side of the valve head 7 in direct communication with the outlet side thereof. In this form, therefore, the fluid flow path 2 is a first path that permits full fluid flow when the valve is open, and the orifice 17 provides a second path permitting restricted fluid flow. When the first path is closed by seating of the valve head 7 on the valve seat 5, the second path remains open so that a restricted flow can continue to take place from the inlet side to the outlet side. In this form, therefore, there will always be, in use, a fluid flow through the orifice 17 so that the valve member never completely shuts off the flow path through the valve.However, selection of the dimensions of the orifices 16 and 17, path 2 and valve head 7, and of the strength of the spring 12, enables the operating characteristics of the valve to be chosen to suit particular user requirements. For example, the valve can operate such that a fluid flow of 25 gallons per minute is reduced to approximately 1 gallon per minute upon automatic operation of the valve. The valve in this form can thus be used as a pressure control device, for connection in a fluid flow path, which will function as a protection device in a fluid power supply line to prevent a pump discharging quickly all the stored fluid into the operating area in the event of a sudden rupture of the supply line, and which will function as a flow control valve if excessive flow were to develop without rupture of the supply line.In more detail, if a fracture occurs in an outlet pipe leading from the outlet side 4 of the valve, the fluid pressure in this pipe will fall below the pressure on the inlet side 3 of the valve, and the pressure drop across the valve head 7 will accordingly rise. When this pressure drop reaches a predetermined value the excess inlet pressure will cause the valve head 7 to move to the left in the Figure, overcoming the biassing force of the spring 12 and with the movement damped by the damping device 11/16, so that the valve head 7 seats against the valve seat 5 and automatically partially shuts off the fluid flow.Since some fluid continues to pass through the valve via the orifice 17, when the fracture in the output pipe has been made good, by replacement or in any other convenient manner, the fluid flowing through the orifice 17 re-primes the system until any pressure drop across the valve head 7 is overcome by the force of the spring 12, which then asserts itself to move the valve member into the open position without the need for any mechanical readj ustment.

The third form of Figure 3 is very similar to the second form, except that the orifice 16 is omitted, changes in volume of the chamber

11 being accommodated by the very restricted flow of fluid that can take place via the restricted clearance at the grooves I0A in the cup 10.

WHAT WE CLAIM IS: 1. A valve comprising a body having a fluid flow path therethrough and around a valve member therein, an annular valve seat between an inlet end of the fluid flow path and an outlet end thereof, the valve member being slidably disposed in said body for rectilinear movement in alignment with the general direction of fluid flow through said path and having a circular head having a periphery of greater diameter than the seat and co-operating with the body to define on the inlet side of the valve seat an annular portion of said path of greater diameter than the seat whereby there is created by normal fluid flow through said path a pressure drop acting to urge the head towards the seat but opposed by a rectilinear bias in alignment with said general direction provided by a spring acting on the valve member, the bias being such that if the outlet pressure becomes less than the inlet pressure by a predetermined amount the bias is overcome and the valve head moves to engage the seat, the valve further comprising a fluid chamber the volume of which is reduced by closing movement of the valve member, the rate of closing movement of the valve member being dependent upon the rate at which fluid flows from the chamber at least through a restricted clearance between the wall of the

chamber and the valve member as the volume of the chamber is reduced.
2. A valve according to claim 1, wherein there is a restricted orifice through the head to allow fluid flow from the chamber to said inlet end additionally to flow through said restricted clearance.
3. A valve according to claim 1, or claim 2 wherein a second restricted orifice extending through the head and directly connecting the inlet side of the head to the outlet side of the head permits restricted flow of fluid through the seat when the head is closed on the seat.
4. A valve as claimed in claim 1, 2 or 3, wherein said restricted clearance is defined by an externally grooved portion of the valve member in sliding engagement with said wall.
5. A valve as claimed in any preceding claim wherein in the valve fully-open position said chamber communicates with said fluid flow path through the valve via an opening that is closed by said wall upon initial movement of the valve member in valve-closing direction.
6. A valve as claimed in any preceding claim wherein the valve member is resiliently biassed into said open position by a spring disposed in said chamber.
7. A valve substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.
8. A valve substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.
9. A valve substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.