GB2178599A

GB2178599A - Solenoid valve

Info

Publication number: GB2178599A
Application number: GB08615807A
Authority: GB
Inventors: John Thomas Marsden; Colin Griffiths
Original assignee: Parmeko Ltd
Current assignee: Parmeko Ltd
Priority date: 1985-06-27
Filing date: 1986-06-27
Publication date: 1987-02-11
Anticipated expiration: 2006-06-27
Also published as: GB2178599B; GB8615807D0; GB8516277D0

Abstract

A guide for the armature of a solenoid valve is provided by a winding former (18) moulded from plastics material. The armature (22) is axially movable between a first position closing a fluid port (36). A magnetic circuit for the solenoid is formed by a pole piece (23) coaxial with the armature and carrying the first port (24), a field can (44) coaxial with the armature and annular field members (46). The field can (44) is contained in valve body (12) also moulded from plastics material. The winding (14), field can (44), pole piece (23) and field members (46) are accurately positioned and assembled prior to injection moulding of the former and valve body. This enables the bore in which the armature slides to be precisely dimensioned and to facilitate final assembly. <IMAGE>

Description

SPECIFICATION Solenoid valve The present invention relates to solenoid valves for controlling the flow of fluids.

The term "fluid" as used herein means a liquid or gas.

In a known type of Solenoid valve an electro-magnet has a magnetic path which includes an armature movable between extreme positions to control the flow of fluid through the valve and around the armature, the armature being spaced from adjacent members of the magnetic path by an air gap which is partially filled by a guide tube for the armature.

The guide tube is precision machined from, for example, stainless steel to provide a low friction guide for the armature and has to be precisely machined in order to enable the air gap to be kept as small as possible for efficient operation of the valve. As will be appreciated, this provides an expensive and time consuming assembly.

The present invention seeks to provide an improved form of solenoid valve.

Accordingly, the present invention provides a solenoid valve for controlling the flow of fluid between ports comprising a valve body and an electro-magnet in said body, said electro-magnet having a magnetic circuit including an armature spaced from adjacent members of said magnetic circuit by an air gap and movable between first and second positions for controlling the flow of fluid between said ports, and guide means for guiding said amature between said first and second positions characterised in that said guide means is moulded from plastics material whereby to enable said air gap to be maintained at a minimum.

Preferably, said magnetic circuit includes at least one annular field member co-axial with said armature and moulded in said guide means, said field member being spaced from said armature by said air gap.

The use of a moulded guide means enables the field member to be secured in position with a minimum sized air gap between the armature and the field member.

The present invention is further described hereinafter, by way of example, with reference to the accompanying drawing, which illustrates a preferred embodiment of solenoid valve according to the present invention.

The drawing shows a solenoid valve 10 having a valve body in the form of a housing 12 containing an electro-magnet 14. The housing 12 conveniently is in two parts, an upper part 12a and a lower, base part 12b, moulded from plastic material.

The electro-magnet 14 has a winding 16 which is wound on a plastics material former 18 having a central bore 20 in the lower portion of which (as seen in the drawing) an armature 22 is axially movable. The upper portion of the central bore 20 contains an insert 23 secured to the former 18, conveniently being a press fit, and having a co-axial bore 24 which opens into a transverse bore 26 in the uppermost portion of the housing 12 for connection to external fluid lines. The end of the bore 24 adjacent the armature 22 forms a valve seat 28 which is controlled by a closure member 30 in the adjacent end of the armature 22. The opposite end of the armature has a further closure member 32 which cooperates with a valve seat 34 of a port 36 in a further insert 38 in the housing part 12b, the port 36 also being connectable to external fluid lines.The insert 38 also has a further port 40 which opens towards the adjacent end of the armature 22.

Communication of the port 40 with the port 36 is controlled by the closure member 32 while communication of the port 40 with the bore 24 is controlled by the closure member 30, fluid able to flow between these latter two ports through axial slots formed in the radially outer surface of the armature 22. The closure members 30 and 32 are conveniantly seals formed of rubber or plastics material.

Power is supplied to the winding 16 via terminals 42 (only one of which is shown in the drawing) to energise the electro-magnet and cause the armature 22 to move towards the insert 23 and close the valve seat 28, interupting the flow of fluid between the port 40 and the bore 24 and enabling fluid flow between the ports 36 and 40. When the electro-magnet is de-energised, a coil spring 43 returns the electro-magnet to its rest position in which the port 36 is closed and the bore 24 is open to the port 40.

A magnetic circuit for the electro-magnet is provided by a field can 44, which is conveniently moulded in the housing part 12a, and one or more annular field washers 46 whose radially outer surfaces are connected to the inner surface of the lower end of the field can 44(as seen in the drawing). The washers are coaxial with the armature 22, surrounding the lower end of the armature. The lower portion of the armature 22 adjacent the field washers 46 is of an enlarged diameter in order to reduce the air gap between the two to as small a value as possible, to maximise the effect of the magnetic circuit. The field washers 46 are conveniently moulded into the former 18.

The former 18 also serves as a guide for the armature 22 and the moulding of this from plastics material enables the bore in which the armature 22 slides to be precisely dimensioned and the field washers 46 to be accurately positioned relative to the armature to ensure that the air gap between the two is at a minimum. This avoids the necessity of having a precision machined metal tube as a slide for the armature and allows the various components, i.e. the field washers 46, the field can 44, the winding 14 and the insert 23 to be accurately positioned and assembly relative to one another prior to injection moulding of the former 18 and housing part 12a. This facilitates final assembly of the solenoid valve since the aforementioned parts are all accurately retained in position by the injection moulded parts.

The assembly is then completed by attaching the housing part 1 2b containing the insert 38 to the housing part 1 2a.

CLAlS 5. A solenoid valve for controlling the flow of fluid between ports comprising a valve body and an electro-magnet in said body, said electro-magnet having a magnetic circuit including an armature spaced from adjacent members of said magnetic circuit by an air gap and movable between first and second positions for controlling the flow of fluid between said ports, and guide means for guiding said armature between said first and second positions, said guide means being moulded from plastics material whereby to enable said air gap to maintain at a minimum.

2. A solenoid valve as claimed in claim 1 wherein said magnetic circuit includes at least one annular field member co-axial with said armature and moulded in said guide means, said field member being spaced from said aramature by said air gap and being retained in spaced relationship thereto by said guide means.

3. A solenoid valve as claimed in claim 2 wherein said guide means serves as a former for a winding of the electro-magnet.

4. A solenoid valve as claimed in claim 3 wherein a fluid passage terminating in one of said ports is formed in an insert means serving as a pole piece of said solenoid.

5. A solenoid valve as claimed in claim 4 wherein said magnetic circuit further comprises field can means co-axial with said armature and ocnnected to said field member; said valve body is moulded from plastics material and wherein said field member, said field can means, said winding and said insert are assembled prior to moulding of said guide means and said valve body whereby moulding of said guide means and said valve body retains said field can means, said field member, said winding and said insert in precise relationship to one another.

6. A solenoid valve as claimed in any of claims 1 to 5 wherein said armature has valve closure members at respective axial ends thereof, a first closure member cooperating with a votive seat of a first said port and a second cooperating with a valve seat of a second port, said solenoid further comprising a third port communicable with said first port when said armature is in said first position and communicable with said second port when said armature is in said second position.

7. A solenoid valve as claimed in claim 6 wherein said third port is adjacent said second port and is communicable with said first port via said air gap surrounding said armature.

8. A solenoid valve substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

can 44, the winding 14 and the insert 23 to be accurately positioned and assembly relative to one another prior to injection moulding of the former 18 and housing part 12a. This facilitates final assembly of the solenoid valve since the aforementioned parts are all accurately retained in position by the injection moulded parts.

The assembly is then completed by attaching the housing part 1 2b containing the insert 38 to the housing part 1 2a.

CLAlS

5. A solenoid valve for controlling the flow of fluid between ports comprising a valve body and an electro-magnet in said body, said electro-magnet having a magnetic circuit including an armature spaced from adjacent members of said magnetic circuit by an air gap and movable between first and second positions for controlling the flow of fluid between said ports, and guide means for guiding said armature between said first and second positions, said guide means being moulded from plastics material whereby to enable said air gap to maintain at a minimum.
2. A solenoid valve as claimed in claim 1 wherein said magnetic circuit includes at least one annular field member co-axial with said armature and moulded in said guide means, said field member being spaced from said aramature by said air gap and being retained in spaced relationship thereto by said guide means.
3. A solenoid valve as claimed in claim 2 wherein said guide means serves as a former for a winding of the electro-magnet.
4. A solenoid valve as claimed in claim 3 wherein a fluid passage terminating in one of said ports is formed in an insert means serving as a pole piece of said solenoid.
5. A solenoid valve as claimed in claim 4 wherein said magnetic circuit further comprises field can means co-axial with said armature and ocnnected to said field member; said valve body is moulded from plastics material and wherein said field member, said field can means, said winding and said insert are assembled prior to moulding of said guide means and said valve body whereby moulding of said guide means and said valve body retains said field can means, said field member, said winding and said insert in precise relationship to one another.
6. A solenoid valve as claimed in any of claims 1 to 5 wherein said armature has valve closure members at respective axial ends thereof, a first closure member cooperating with a votive seat of a first said port and a second cooperating with a valve seat of a second port, said solenoid further comprising a third port communicable with said first port when said armature is in said first position and communicable with said second port when said armature is in said second position.
7. A solenoid valve as claimed in claim 6 wherein said third port is adjacent said second port and is communicable with said first port via said air gap surrounding said armature.
8. A solenoid valve substantially as hereinbefore described with reference to the accompanying drawing.