GB2065929A - Liquid flow control valve - Google Patents

Abstract

A liquid flow control valve wherein the position of a closure member 33 in a fluid flow passage determines the extent of fluid flow therealong. The closure member bounds, and is slidably moveable within, a fluid filled cavity 39 which, in dependence on the position of a force transmitting member 43 may be coupled to a vent V via passages 91, 87, permitting movement of the closure member in an opening sense or to the inlet port 21 via passages 81, 87, permitting movement in a closing sense. The extent of the movement is controlled by a spring 61 which extends between the force transmitting member and the closure member, and is determined by the magnitude of a preselectable force applied to the force transmitting member. The preselectable force may be applied by a solenoid 71, by a hydraulic plunger or by a manual lever. <IMAGE>

Description

SPECIFICATION Liquid flow control valves This invention relates to liquid flow control valves.

According to the invention there is provided a liquid flow control valve comprising a body member having a liquid flow passage accommodating, between inlet and outlet ports, a movable closure member whose position in the passage determines the extent of the flow therealong and which has a surface portion, remote from the passage, bounding a liquid filled cavity therein, and the body member also accommodating a force transmitting spool which is coupled to the closure member by resilient biasing means and adapted to receive, in a sense appropriate for opposing the action of the biasing means, a preselectable force for causing the closure member to assume a corresponding position appropriate for permitting a desired flow, wherein the body member and the spool are adapted to couple the cavity to a vent when the preselectable force exceeds the force applied thereto by the biasing means, thereby allowing the closure member to move in an opening sense, against the action of the biasing means, in response to pressure in the inlet port, and so increasing the force applied to the spool by the biasing means, and wherein the body member and the spool are adapted to couple the cavity to the inlet port when the preselectable force is less than the force applied thereto by the biasing means, thereby allowing the closure member to move, in a closing sense, and so reducing the force applied to the spool by the biasing means, the preselectable force having a magnitude appropriate for balancing the force applied to the spool by the biasing means when the closure member assumes the said corresponding position.

A particular embodiment of the invention is now described, by way of example only, by reference to the accompanying drawing which shows a longitudinal sectional view through a liquid flow control valve.

Referring to the drawing, the liquid flow control valve comprises a body member 1 including adjoining upper and lower portions 3 and 5 respectively. The lower portion 5 has a cylindrical bore 7 accommodating a closely fitting sleeve 9 whose inner surface 11 defines, in part, the side walls of a cavity 39. The portion 5 also has an inlet port 21, coaxial with the bore 7, and an orthogonal outlet port 25 which communicate with one another via a cylindrical opening 27 in the sleeve to form a liquid flow passage. The upper portion 3 of the body member has a cylindrical bore 1 5 disposed coaxially with, but of smaller diameter than, the bore 7. The bore 1 5 also defines part of the cavity and, at the end thereof adjoining the lower portion 5, has an annular spigot 1 7 disposed to bear against the sleeve and retain it securely in position.To prevent leakage of liquid from the cavity liquid tight seals 97 are provided between adjoining faces of the body parts 3 and 5 and the sleeve 9.

The extent of flow through the liquid flow passage is determined by the position of a generally cylindrical closure member 31 which is accommodated within the sleeve and slidingly engages the inner walls 11 thereof in liquid tight manner.

The member 31 has a tail portion 33 of reduced diameter which is disposed to extend through a complementary aperture in a seating 23 which terminates the sleeve 9. The tail portion has a channel 33 whose sides 33a, 33b are inclined to one another and meet at an apex, X. In this example the depth of the channel is chosen so that when the closure member assumes as fully seated position the tail portion isolates the inlet and outlet parts and so prevents flow therebetween. Displacement of the closure member, however, from the seated position permits flow via a channel formed by those portions of the inclined sides 33a, 33b which then extend beyond the seating.The relationship between the extent of liquid flow and the displacement of the closure member is determined, in this example, by the inclination of the channel sides, but it will be appreciated that a different relationship between flow and displacement could be achieved by using an alternatively shaped channel.

The closure member 31, at the end thereof remote from the tail portion 33, includes a hollow cylindrical collar 37, whose inner surface 37' bounds the cavity which is thereby separated from the liquid flow passage, despite movement of the closure member necessary for achieving liquid flow.

The upper portion 3 of the body member 1 has a further cylindrical bore 41 which extends therethrough coaxially from the cavity 39. The bore 41 accommodates a generally cylindrical force transmitting spool 43 which is provided with land portions 45,47,49, 51 which are dimensioned to slidingly fit within the bore 41 in fluid tight manner, so that the spaces between each pair of adjacent lands are isolated from one another. The spool is coupled to the closure member by a helical spring 61 which is'disposed within the cavity 39 and extends between anchorage plates 53 and 63 which are respectively mounted to the end of the spool and the inner surface 37' of the closure member.The anchorage plate 53 has a diameter significantly greater than that of the major portion of bore 1 5 and is accommodated within an enlarged portion 15' thereof, this arrangement tending to inhibit excessive movement of the spool.

In this example of the invention the cavity 39 is coupled to the bore 41 via a conduit 87 which extends entirely within the upper portion 3 of the body member and may, optionally include a flow restrictor 95. Similarly the inlet port 21 and a vent, indicated at V, are respectively coupled to the bore via different conduits 81 and 91 which extend through the upper and lower portions of the body member and form openings in the bore, respectively below (i.e. relatively close to the cavity 39) and above the opening formed by the conduit 87. By moving the spool axially within the bore, therefore, the land portion 47 may be disposed to isolate either or both conduits 81 and 91 from the cavity 39 and, as will be described in detail below, this technique can be used to influence the position of the closure member 33 to effect opening or closure of the liquid flow passage.

In this example of the invention, the position of the closure member 33 is determined by the magnitude of the force applied through the armature 73 of a proportional solenoid 71 which is disposed to bear upon the end 44 of the spool, the magnitude of the applied force being controlled by the current passed to the solenoid.

When, in use of the valve, a current is applied to the solenoid 71 the resulting force on the spool opposes the action of the spring 61. When the applied force exceeds the force of the spring, the spool is displaced causing the land portion 47 to assume a position wherein the cavity 39 is coupled to the vent V, the conduits 87 and 91 being linked by the region of the bore 41 which intervenes the adjacent land portions 45 and 47 of the spool. By coupling the cavity to the vent in this way the closure member 33 is permitted, in response to pressure in the inlet port, to move in an opening sense, thereby expelling liquid from 'the cavity and compressing the spring. Such compression increases the force exerted by the spring upon the spool thereby tending to urge the spool back towards the solenoid.When the force of the spring balances the force applied by the solenoid the spool assumes an equilibrium position wherein the land portion 47 isolates the cavity from both the vent and the inlet port thereby inhibiting further movement of the closure member. A desired position of the closure member may be obtained, therefore, by applying an appropriate preselected force to the spool and this can be achieved by suitably selecting the current applied to the solenoid. Thus by increasing the applied preselected force yet further the cavity is again coupled to the vent thereby causing the closure member to open further and so increasing the flow in the liquid flow passage.In contrast, if the preselected force applied to the spool is reduced the excessive force of the spring then urges the spool towards the solenoid thereby coupling the cavity 39 to the inlet port 21 via the conduits 81 and 87 which, by virtue of the movement of the spool become linked by the region of the bore which intervenes the land portions 47 and 49. In this manner, a pressure in the inlet port is communicated to the cavity thereby causing the closure member 33 to move in a closing sense so reducing the compression of the spring 66. This reduced compression influences the spool which, as before, then moves to an equilibrium position, to inhibit further movement of the closure member when the force of the spring balances the preselected force applied by the solenoid.

In this example the pressure exerted by the liquid on the spool itself is hydraulically balanced by an additional conduit 87' which links conduit 87 to the bore region, remote from the cavity, lying beyond the land portion 45. The pressure of liquid on the armature 73 is similarly hydraulically balanced by passages not shown in the drawings.

It will be appreciated that the invention has been described by reference to a particular embodiment, but it will be understood that the invention also encompasses other embodiments.

In particular, although the force applied to the spool is generated, in the above-described example, by a proportional solenoid and is transmitted to the spool by an associated armature, the force could be generated in other ways, for example a manual lever or a secondary hydraulic plunger could be used.

Moreover the single helical spring 61 could be replaced by a pair of helical springs, one mounted to the closure member and the other to the spool, which communicate via spaced pressure plates disposed within the cavity.

Claims (8)

1. A liquid flow control valve comprising a body member having a liquid flow passage accommodating, between inlet and outlet ports, a movable closure member whose position in the passage determines the extent of the flow therealong and which has a surface portion, remote from the passage, bounding a liquid filled cavity therein, and the body member also accommodating a force transmitting spool which is coupled to the closure member by resilient biasing means and adapted to receive, in a sense appropriate for opposing the action of the biasing means, a preselectable force for causing the closure member to assume a corresponding position appropriate for permitting a desired flow, wherein the body member and the spool are adapted to couple the cavity to a vent when the preselectable force exceeds the force applied thereto by the biasing means, thereby allowing the closure member to move in an opening sense, against the action of the biasing means, in response to pressure in the inlet port, and so increasing the force applied to the spool by the biasing means, and wherein the body member and the spool are adapted to couple the cavity to the inlet port when the preselectable force is less than the force applied thereto by the biasing means, thereby allowing the closure member to move, in a closing sense, and so reducing the force applied to the spool by the biasing means, the preselectable force having a magnitude appropriate for balancing the force applied to the spool by the biasing means when the closure member assumes the said corresponding position.

2. A valve according to Claim 1 wherein the spool has a land portion which is dimensioned to fit slidingly, in liquid tight manner, in a spool bore in the body member, and wherein the cavity is coupled to the vent and the inlet port via respective first and second conduits which include a common part, communicating between the bore and the cavity, and respective first and second remaining parts which communicate between the bore and the vent and the bore and the inlet port, the spool being adapted to move within the bore, in response to a force applied thereto, so that the land portion isolates the common portion from the first and second remaining portions when the preselectable force is respectively less than or greater than the force applied to the spool by the biasing means.

3. A valve according to Claim 2 wherein the common portion includes a flow restrictor.

4. A valve according to Claims 1 to 3 wherein the closure member is shaped so as to influence the flow through the flow passage in a predetermined manner in dependence on its position therein.

5. A valve according to Claim 4 wherein the closure member has a channel having inclined sides which meet at an apex, the channel being disposed to provide a flow passage between the inlet and outlet ports.

6. A valve according to Claims 1 to 5 including a solenoid having a movable armature adapted to engage the plunger member to apply said preselectable force.

7. A valve according to Claim 6 wherein the solenoid armature is balanced.

8. A valve substantially as hereinbefore described by reference to and as illustrated in the accompanying drawing.