GB2076182A

GB2076182A - Fluid Control Valve

Info

Publication number: GB2076182A
Application number: GB8113356A
Authority: GB
Original assignee: Chubb Fire Security Ltd
Current assignee: Chubb Fire Ltd
Priority date: 1980-04-30
Filing date: 1981-04-30
Publication date: 1981-11-25
Also published as: GB2076182B

Abstract

A pair of identical fluid control valves 13 and 14 control the supply of a pressurised working fluid from a source 18 to the two sides 8A, 8B of a double-acting hydraulic actuator 8. Each valve has a chamber 33 with three ports 13A/14A, 13B/14B and 13C/14C opening to it. The ports 13A/14A and 13B/14B at the opposite ends of each chamber can be closed by respective balls 36,32 biased by springs 37,34 against their seats 38,35. The ports 13A/14A are connected to the source 18 of pressurised working fluid which fluid can unseat the balls 36 and flow to the chambers 33; the ports 13B/14B are connected to an unpressurised drain 19; and the ports 13C/14C communicate the pressure in the chambers 33 to the respective sides of the actuator 8. Respective pistons 30 are provided to control the balls 32 in response to signal fluid pressures in lines 26A and 26B, and when a signal pressure of sufficient strength is applied to one of the pistons 30 it unseats the associated ball 32 to connect the corresponding chamber 33 to the drain 19. At the same time the ball 32 urges a rigid spacer 41 against the associated ball 36 to restrict communication of the corresponding chamber 33 with the source 18. There is thus a drop in pressure within that chamber 33 and hence a pressure difference exists across the actuator under which it moves to perform its corresponding function. <IMAGE>

Description

SPECIFICATION Fluid Control Valve The present invention relates to fluid control valves.

Particularly, though not exclusively, the invention is concerned with a form of pilot operated control valve which can be used in an hydraulic control system as described in our copending United Kingdom patent application No.

8113355 [Agent's reference 14216/80 filed concurrently herewith]. In such a system there are a pair of double-acting hydraulic actuators for controlling eg the orientation of a fire-fighting monitor nozzle, and the supply of a pressurised working fluid to each side of each actuator is controlled by a respective one of four similar pilot operated control valves.More particularly, each valve is biased into a position in which it can communicate a source of the working fluid with the respective side of the respective actuator, and each valve is operable independently, against its bias, in response to the transmission thereto of a selected hydraulic signal pressure or range of hydraulic signal pressures, to restrict the communication of the source of working fluid with the respective side of the respective actuator and to communicate that side of that actuator with a relatively unpressurised reservoir, drain or the like region whereby a pressure differential is set up across the actuator under which it performs its corresponding function.In accordance with the invention described in our said copending application the signal pressure or range of signal pressures to which each control valve is adapted to respond is or are of a greater value than the working pressure at which the working fluid is supplied to the valves.

In one aspect the invention seeks to provide valves of compact construction and reliable operation suitable for use as the pilot-operated control valves in an hydraulic control system of the foregoing nature. Valves in accordance with the present invention may be of more general utility, however, and in particular the invention is not necessarily restricted to pilot-operated control valves in which there is the same ratio of pilot/working pressures as indicated above, neither indeed is it essential that valves in accordance with the invention be pilot-operated.

According to the invention a fluid control valve comprises: means defining a chamber; first, second and third ports opening to said chamber; first and second valve seats respectively surrounding said first and second ports; first and second valve elements disposed in said chamber for co-operation respectively with said first and second seats to control fluid flow through said first and second ports; first and second spring means for biasing respectively said first and second valve elements against said first and second seats; means for unseating said first valve element against the bias of said first spring means in response to a control action; and means for establishing an operative connection between said first and second valve elements when second valve element moves away from said second seat against the bias of said second spring means by a certain distance, whereby when such connection is established the operation of said unseating means is effective both to move said first valve element away from said first seat and to move said second valve element back towards said second seat.

When such a valve is used in a control system as described above said first port is connected to the aforesaid drain or other relatively unpressurised region, said second port is connected to the source of pressurised working fluid and said third port is connected to the respective side of an actuator. Normally the first valve element is seated under the bias of its spring means so as to isolate the third port and actuator from the relatively unpressurised region.

The second valve element can, however, be unseated by the working fluid against the bias of its spring means in the manner of a non-return valve, the working fluid thus being supplied through the chamber and third port to the actuator. Upon operation of the unseating means the first valve element is unseated to communicate the actuator with the relatively unpressurised region while the second valve element, through the aforesaid connection with the first valve element, is moved towards its seat to restrict the communication of the source of working fluid with the actuator.

In a preferred embodiment of a valve in accordance with the invention said first and second ports are located at opposite ends of said chamber with the third port at an intermediate location; said first spring means act effectively between said first valve element and a fixed abutment while said second spring means act effectively between said second valve element and said first valve element; and said means for establishing an operative connection comprise a rigid element which is seated at one end against the first valve element and which is engaged at its other end by the second valve element when the latter moves away from its seat by the aforesaid distance.

In the case where the valve is a pilot-operated control valve the said unseating means may comprise a slidable piston arranged at one end to receive hydraulic pressure signals and arranged at the other end for abutment with the first valve element. In other cases, valves in accordance with the invention may be adapted for manual or other operation by the inclusion of suitable control means associated with the unseating means.

Preferably, both said first and second valve elements are balls.

The invention will now be more particularly described, by way of example, with reference to the accompanying schematic sectional view of a pair of valves according to the invention set up to control the movement of a double-acting hydraulic actuator.

Referring to the drawing, there is a double acting hydraulic actuator 8 which is used eg for controlling the movement about one axis of the pivoted nozzle (not shown) of a fire-fighting monitor or the like device. Pressurised working fluid for the actuator 8 is provided from a source 18 and the supply of this fluid from the source 18 to the two ports 8A and 8B of the actuator opening to either side of its piston 8C is controlled by respective pilot valves 13 and 14 provided within an associated valve block 10.

Each valve 13 and 14 has a compound valve member comprising a piston 30 slidably sealed in a bore 31; a first ball 32 in a chamber 33 and urged by a spring 34 against a seat 35, to control communication through a respective valve port 13B, 14B between the chamber 33 and bore 31; and a second ball 36 urged by a spring 37 against a seat 38, to control communication through a respective valve port 1 3A, 1 4A between the chamber 33 and a bore 40. The spring 37 acts between the ball 36 and the ball 32 via a spacer 41, and is lighter than the main valve biasing spring 34. Opening from each chamber 33 between the seats 35 and 38 are respective valve ports 1 3C and 1 4C which connect through respective bores 42 to the ports 8A, 88 of the actuator 8.A bore 43 leads to the bore 40 between the two seats 38, and is connected to the source 18 of working fluid. A respective bore 44 leads from the bore 31 of each valve between the seat 35 and piston 30, this constituting the exhaust connection of the respective valve and leading to a drain 19. Finally, respective signal pressure lines 26A and 26B lead from a remote signal pressure generating unit (not shown) to the bores 31 of the valves on the side of the respective piston 30 opposite to the seat 35.

The drawing illustrates the valves in the condition which pertains when there is no pressurised working fluid connected to the bore 43 and no signal pressures applied to the lines 26A and 26B, ie both balls 32, 36 of each valve are on their respective seats 35, 38. In normal operation, however, when the pressurised working fluid supply is connected to bore 43, and thence to bore 40, each ball 36 can be displaced from its seat 38 against the biasing action of its spring 37 to seat instead against the spacer 41, thereby opening the chambers 33 to the bore 40 through the respective port 1 3A, 1 4A. In the absence of a signal pressure in lines 26A, 268 the balls 32 remain on their seats 35 under the action of the spring 34, so the full working fluid pressure supplied to the chambers 33 from the bore 40 is transmitted via respective ports 1 3C, 1 4C and bores 42 to opposite sides of the actuator 8, to hydraulically lock its piston 8C.

When a signal pressure of adequate strength is now applied to, say, the line 26A the piston 30 of valve 13 is moved to the right (in the sense of the drawing) and by way of its integral piston rod 45 unseats the ball 32 against the biasing action of its spring 34. More particularly the entire assembly of piston 30/ball 32/spacer 41/ball 36 behaves in effect as a single valve member moved to the right (in the sense of the drawing) under the action of the signal pressure in line 26A.The effect of this movement is to open the chamber 33 of valve 13 through port 138 to Its bore 21 and thence bore 44 and drain 19 by virtue of the unseating of ball 32, and at the same time to restrict the communication through port 1 3A of the bore 40 with its chamber 33 by virtue of the movement of spacer 41 and ball 36 back towards the seat 38. As will be appreciated, the size of the opening between the bore 40 and chamber 33 progressively decreases as the size of the opening between the chamber 33 and bore 31 progressively increases, the displaced position of the compound valve member 30/32/41/36 at any time being determined by the strength of the applied signal pressure opposing the spring 34.

As will be further appreciated, in any such position there will be a corresponding reduction in the water pressure within the chamber 33 of valve 1 3 and hence in the presssure applied to port 8A of the associated actuator. Throughout, however, the valve 14 is unaffected and the full working fluid pressure remains applied from its chamber 33 to port 88 of the actuator.The actuator piston 8C therefore moves to the left (in the sense of the drawing) under the differential pressure at ports 8A and 88, working fluid draining from theiactuator through port 8A and passing through the bore 42, port 13C, chamber 33, port 13B and bore 31 (of valve 13), to the respective bore 44 and drain 19, while the volume is made up on the other side of the piston 8C by working fluid supplied through valve 14.

When the signal pressure is released from line 26A the ball 32 of valve 13 is allowed to re-seat under the action of its spring 34, so that the actuator piston 8C is relocked in its new set position.

The balls 36 have a non-return function in addition to their function of controlling the working fluid pressure in the respective chamber 33 when a signal pressure is applied to the respective valve. That is to say in the event that an unbalanced, external load is applied to the actuator piston 8C tending to displace it from a position in which it has been set, and thereby to displace working fluid from one side of the actuator back through the respective valve chamber 33 to the bore 40, the corresponding ball 36 will close against its seat 38 to prevent such displacement. In fact, by virtue of the biasing action of its spring 37 each ball 36 will tend to close against its seat 38 whenever the pressure within the corresponding chamber 33 is in balance with the supply pressure in the bore 40.

In a preferred embodiment the valves 13, 14 and actuator 8 form part of an hydraulic control system as described in our aforesaid copending patent application No. 8113355. In such a case the working fluid supplied from source 18 is water at a pressure of, say, 80-100 psig (5-7 bar) while the signal pressure fluid in lines 26A and 26B is an hydraulic oil. Furthermore the strength of the main valve springs 34 is so related to the cross-sectional areas of the pistons 30 exposed to the signal pressure fluid that a signal pressure in the region of 400 psig (27 bar) is required in the lines 26A, 26B to initiate displacement of the respective baIl 32, while the signal pressure required for maximum displacement of the balls 32 is in the region of 450 psig (31 bar).

Claims

1. A fluid control valve comprising: means defining a chamber; first, second and third ports opening to said chamber; first and second valve seats respectively surrounding said first and second ports; first and second valve elements disposed in said chamber for co-operation respectively with said first and second seats to control fluid flow through said first and second ports; first and second spring means for biasing respectively said first and second valve elements against said first and second seats; means for unseating said first valve element against the bias of said first spring means in response to a control action; and means for establishing an operative connection between said first and second valve elements when said second valve element moves away from said second seat against the bias of said second spring means by a certain distance, whereby when such connection is established the operation of said unseating means is effective both to move said first valve element away from said first seat and to move said second valve element back towards said second seat.

2. A valve according to claim 1 wherein: said first and second ports are located at opposite ends of said chamber with the third port at an intermediate location; said first spring means act effectively between said first valve element and a fixed abutment while said second spring means act effectively between said second valve element and said first valve element; and said means for establishing an operative connection comprise a rigid element which is seated at one end against the first valve element and which is engaged at its other end by the second valve element when the latter moves away from its seat by the aforesaid distance.

3. A valve according to claim 1 or claim 2 wherein said unseating means comprise a slidable piston arranged at one end to receive hydraulic pressure signals and arranged at the other end for abutment with the first valve element.

4. A valve according to any preceding claim wherein both said first and second valve elements are balls.

5. A fluid control valve substantially as hereinbefore described with reference to the accompanying drawing.

6. A fluid control system including a fluid control valve according to any preceding claim, said second port being connected to a source of pressurised working fluid, said first port being connected to a relatively unpressurised region, and said third port being connected to an actuator adapted to perform a function under the action of said working fluid.