GB2193297A - Solenoid valve - Google Patents

Abstract

A solenoid valve has a valve body (12,13) which defines a chamber (16) with coaxial ports (19 and 20), one port at each end of the chamber. A valve spindle (28) is mounted coaxially of ports (19 and 20) and has a pair of valve members (30) each adapted to seat against and close one of the ports (19 and 20). Valve members (30) are arranged such that in a first position of the spindle (28), port (19) will be closed while port (20) remains open; and in a second position, port (20) will be closed while port (19) remains open. Spring means (42) is provided to urge the spindle (28) towards the first position while a solenoid (44) is provided to selectively urge the spindle (28) towards the second position. The chamber (16) is divided into two compartments (37 and 38) by means of a diaphragm (31) which is mounted between the spindle (28) intermediate of valve members (30) and the valve body (12,13) and separate passages (47 and 48) are provided to each of the compartments (37 and 38). <IMAGE>

Description

SPECIFICATION Solenoid valves This invention relates to solenoid valves.

With solenoid valves which are used to selectively connect means to a source of fluid of relatively high pressure or to a source of fluid of relatively low pressure, for example in a servo mechanism, a large solenoid load is required to overcome the load applied to the valve member by the pressure differential.

According to one aspect of the present invention, a solenoid valve comprises; a valve body which defines a chamber; a first port provided at one end of the chamber and a second port provided coaxially of the first port at the other end of the chamber; a valve spindle mounted coaxially of the two ports and having a first and second valve member; said first valve member being adapted to seat against and close said first port while the second valve member is spaced from the second port, in a first position of the valve spindle; and said second valve member being adapted to seat against and close said second port while the first valve member is spaced from said first port, in a second position of the valve spindle; spring means to urge the valve spindle into said first position; and a solenoid arranged to urge the valve spindle against the spring load into said second position; a diaphragm being provided between a portion of the spindle intermediate of the valve members and the wall of the chamber, to divide the chamber into two compartments, separate passages being provided to each of the compartments.

With the solenoid valve described above the compartments of the valve are connected to sources of fluid at different pressures via the passageways, the pressure exerted on the closed valve member is balanced by the pressure exerted on the diaphragm and consequently on energisation of the solenoid, the solenoid need only overcome the force of the spring means to open the first port and close the second port.

According to a further aspect of the present invention, a solenoid valve assembly comprises a pair of solenoid valves as described above, said solenoid valves being interconnected, the first and second ports of each valve opening into an intermediate chamber, a first valve selectively controlling connection of the intermediate chamber to a source of fluid at relatively high pressure or a source of fluid at relatively low pressure and a second valve selectively controlling connection of the intermediate chamber, via a path of relatively high restriction or a path of relatively low restriction.

An embodiment of the invention is now described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a sectional side elevation of a solenoid valve formed in accordance with the present invention; and Figure 2 shows a section along the line ll-ll in Figure 1.

The solenoid valve illustrated in Figures 1 and 2 comprises a valve block 11 formed from two body portions 12 and 13 and a top and bottom plate 14 and 15, which are bolted together by means of a series of bolts (not shown).

The two body portions 12 and 13 each have a pair of stepped bores which when the body portions 12 and 13 are assembled together define; a pair of cylindrical chambers 16 and 17, each chamber having a cylindrical groove 18 formed at the interface of the two body portions 11 and 12 and a pair of axial ports 19 and 20 and 21 and 22 respectively, one at each end of the chamber.

Rectangular recesses 23 and 24 are provided in the remote faces of body portions 12 and 13 and these are closed by the top and bottom plates 14 and 15, to form galleries 25 and 26. Gallery 25 interconnects port 19 with port 21 and gallery 26 interconnects port 20 with port 22. The galleries 25 and 26 are interconnected by means of a bore 27 which is formed through the body portions 12 and 13.

A valve spindle 28 is mounted coaxially of chamber 16. This valve spindle 28 has a pair of valve members 30 which are located on the spindle 28 such that; in one position, one of the valve members 30 will seat against and close port 19 while the other valve member 30 is spaced away from port 20; and in another position the other valve member 30 will seat against and close port 20 while the first valve member 30 is spaced away from port 19.

An elastomeric diaphragm 31 is located at its inner periphery 32 in a circumferential groove 33 in an enlarged diameter portion 34 of spindle 28, intermediate of the valve members 30. The outer periphery 35 of diaphragm 31 is clamped in a crimped ring 36, which is retained in cylindrical groove 18. A formation 39 on the outer periphery of the diaphragm 31 provides a fluid tight seal with the groove 18, so that the diaphragm 31 divides chamber 16 into a pair of fluid tight compartments 37 and 38. The crimped ring 36 also defines a seat for a helical compression spring 42 which acts against the upper valve member 30, to urge it into engagement with port 19. The crimped ring 36 also serves to locate the body portions 13 and 14 relative to one another.The valve spindle 28 with valve members 30, diaphragm 31, crimped ring 36 and spring 42 may be preassembled and the ring 36 located in the larger diameter ends of the stepped bores which define the groove 18, before the body portions 13 and 14 are clamped together.

Similarily, a valve spindle 29 which is of identical structure to valve spindle 28, is mounted coaxially of chamber 17 to divide that chamber into two fluid tight compartments 40 and 41.

Valve spindle 28 is connected to the plunger 43 of a solenoid 44 by means of which it may be moved downwardly against spring 42, to open port 19 and close port 20; and valve spindle 29 is connected to the plunger 45 of solenoid 46 by means of which it may be moved downwardly against spring 42 to open port 21 and close port 22.

A pair of threaded connections 47 and 48 are provided to compartments 37 and 38 respectively, and a similar threaded connection 49 is provided to compartment 40. A threaded connection 50 with restriction 51 is provided to compartment 41. Compartment 40 is also connected to gallery 25 by means of a restricted bore 52 which bypasses port 21. This bore 52 has a non-return ball valve 53 which seats towards the gallery 25.

The solenoid valve described above may be used to control an air servo mechanism, in which a flexible diaphragm defines two chambers, one of said chambers being open to atmosphere and the other selectively connected to a source of air under pressure or to atmosphere, so that the pressure differential across the diaphragm may be varied to cause movement of an actuating plunger.

In such an application, connection 47 may be connected to a source of air at a pressure of the order of 3 bars and connection 48 may be connected to atmosphere. Connections 49 and 50 are interconnected externally of the valve block 11 and are connected to the variable pressure chamber of the servo mechanism.

With both solenoids 44 and 46 de-energised as illustrated in Figure 1, the chamber of the servo mechanism is connected to atmosphere via connection 50, restriction 51, compartment 41, port 22, gallery 26, port 20, compartment 38 and connection 48.

The pressure of air in compartment 37 acting against the valve member 30 is balanced by the pressure of air acting on diaphragm 31 and consequently upon energisation of the solenoid 44, a relatively low solenoid load is required to move the spindle 28 against spring 42, so as to open port 19 and close port 20. In this condition, a restricted flow of air will be able to pass from the source of pressurised air to the servo chamber via connection 47, compartment 37, port 19, gallery 25, bore 27, gallery 26, port 22, compartment 41, restriction 51 and connection 50 and also from gallery 25 via restricted bore 52 past the non-return valve 53, compartment 40 and connection 49. Because of the restrictions 51 and 52, the rate of flow of air to the servo chamber will be relatively slow.

If the solenoid 46 is now energised, port 21 is opened and port 22 closed, so that air may pass through the relatively unrestricted path defined by the connection 47, compartment 37, port 19, gallery 25, port 21, compartment 40 and connection 49. The rate at which the air flows to the servo chamber will consequently be increased.

De-energisation of solenoid 44 will then close port 19 and open port 20 and connect the servo chamber to atmosphere via connection 49, compartment 40, port 21, gallery 25, bore 27, gallery 26, port 20, compartment 38 and connection 48, so that air will be allowed to flow out of the servo chamber at a relatively fast rate.

Finally, de-energisation of solenoid 46 will close port 21 and open port 22, so that air will be allowed to flow out of the servo chamber at a relatively slow rate, via connection 50, restriction 51, compartment 41, port 22, gallery 26, port 20, compartment 38 and connection 48. Flow of air out of the servo chamber via connection 49, chamber 40 and restricted bore 52 will be prevented by nonreturn valve 53, so that the slow rate of flow of air out of the servo chamber, will be slower than the slow rate of flow of air into the servo chamber.

The valve described above thus permits the flow of fluid to or from a fluid operated means, at relatively fast or relatively slow rates, the relatively slow rate of flow from said means permitted by the valve, being greater than the relatively slow rate of flow to the means permitted by the valve. The sequence in which the valve permits the fluid to flow depends upon the sequence in which solenoids 44 and 46 are energised and de-energised which may be controlled as required.

Various modifications may be made without departing from the invention. For example, while in the above embodiment the valve assembly includes a pair of solenoid valves, the solenoid valves may be used independently, for example to control connection to sources of fluid at different pressures, without providing different rates of flow. Also the restricted passage 52 bypassing port 21 may be omitted to give equal slow rates of flow to or from the intermediate compartment defined by galleries 25 and 26 and bore 27.

Claims (8)

1. A solenoid valve comprising a valve body which defines a chamber; a first port provided at one end of the chamber and a second port provided coaxially of the first port at the other end of the chamber; a valve spindle mounted coaxially of the two ports and having a first and second valve member; said first valve member being adapted to seat against and close said first port while the second valve member is spaced from the second port, in a first position of the valve spindle; and said second valve member being adapted to seat against and close said second port while the first valve member is spaced from said first port, in a second position of the valve spindle; spring means to urge the valve spindle into said first position; and a solenoid arranged to urge the valve spindle against the spring load into said second position; a diaphragm being provided between a portion of the spindle intermediate of the valve members and the wall of the chamber, to divide the chamber into two compartments, separate passages being provided to each of the compartments.

2. A solenoid valve according to Claim 1 in which a formation is provided on the inner periphery of the diaphragm and this formation locates in a corresponding formation in the valve spindle, for retention thereof.

3. A solenoid valve according to Claim 1 or 2 in which the outer periphery of the diaphragm is clamped in a crimped ring, said ring being located in a cylindrical groove in the wall of the chamber.

4. A solenoid valve according to Claim 3 in which the outer periphery of the diaphragm is provided with a sealing formation which engages a surface of the cylindrical groove or the wall of the chamber.

5. A solenoid valve according to Claim 3 or 4 in which the crimped ring also provides a seat for a helical compression spring which acts against the first valve member to urge the valve spindle into said first position.

6. A solenoid valve assembly comprising a pair of solenoid valves as claimed in any one of Claims 1 to 5, said solenoid valves being interconnected, the first and second ports of each valve opening into an intermediate chamber, a first valve selectively controlling connection of the intermediate chamber to a source of fluid at relatively high pressure or to a source of fluid at relatively low pressure and a second valve selectively controlling connectinon of the intermediate chamber to means, via a path of relatively high restriction or a path of relatively low restriction.

7. A solenoid valve assembly as claimed in Claim 6 in which the passage to one of the components of the second valve, has a restriction to flow of fluid.

8. A solenoid valve assembly substantially as described herein with reference to, and as shown in, Figures 1 and 2 of the accompanying drawings.

8. A solenoid valve assembly as claimed in Claim 7 in which a restricted passageway is provided between the other compartment of the second valve and the intermediate chamber, to bypass the port to that chamber, a non-return valve being provided in the restricted passageway to prevent flow of fluid from the compartment of the valve to the intermediate chamber.