WO1989004427A1

WO1989004427A1 - Pilot valve cartridge assembly

Info

Publication number: WO1989004427A1
Application number: PCT/US1987/002947
Authority: WO
Inventors: Larry Williamson
Original assignee: Larry Williamson
Priority date: 1987-11-05
Filing date: 1987-11-05
Publication date: 1989-05-18
Also published as: EP0389480A1; EP0389480A4; KR890701941A; JPH02502116A

Abstract

A plunger for the cartridge assembly of a solenoid operated pilot valve comprises an elongated cylindrical magnetically attractable member (32) having a bore (34) extending axially therethrough from end to end with an elastomeric valve seat (54) disposed within said bore (34) and extending therethrough, and said valve seat (54) and cylindrical member (32) having radially extending interfitting portions (50, 62) for limiting relative axial movement of the member (32) and valve seat (52).

Description

PILOT VALVE CARTRIDGE -ASSEMBLY

Field of Invention .

This invention- relates to^" solenoid-operated pilot val es and to an improved cartridge assembly therefore.

Background of Invention^"

The 'cartridge assembly for a solenoid-operated pilot Valve, such as a pneumatic valve, comprises a cylindrical housing closed at one end by a pole piece having a fluid exhaust passageway therethrough for venting the interior- of the housing to atmosphere. A magnetically attractable plunger in the housing is moveable against and away from the pole piece upon impression and release of a magnetic field between the plunger and pole piece. The open end of the cylindrical housing is threadedly connected to the pilot valve body. Elastomeric valve seats in opposite ends of the plunger serve to close an orifice in the valve body and open the exhaust passageway in the pole piece when the .magnetic field is released, and open the orifice and close the exhaust passageway when the magnetic field is . impressed. ' A solenoid coil encircles the cylindrical housing for impressing a magnetic field across the air gap between the plunger and pole piece. A compression spring encircles the plunger and urges it in a direction away from the pole piece to carry the valve seat at the end of the plunger against the orifice in the valve body.

It has heretofore been the practice to provide a compression spring within the plunger bearing at opposite ends against the elastomeric valve seats to- urge them axially outwardly of the plunger to ensure that they bear against the valve orifice in the valve body at one end of plunger travel or adequately block the escape passageway in the pole piece at the other end of plunger travel. The provision of such compression spring and the elastomeric valve seats at opposite ends of the plunger while providing an Operationally satisfactory structure for controlling pilot air flow through the valve, adds substantial expense to the pilot valve cartridge.

Summary of Invention

I have discovered that provision ^' of a pair of elastomeric valve seats, and- the compression spring within the plunger urging such seats axially outwardly may be eliminated- by providing a single valve seat which extends completely through the plunger with means being provided for. preventing unintended relative axial movement between -the plunger _. and valve seat. ^■ Additionally I have found a ^■simple.^'.and^':^'much less expensive way to provide an orifice. ^■in the pole piece which eliminates the rior art necessity of carefully machining the end of the pole piece to provide a satisfactory orifice. As a result of this construction,- ^' substantial cost savings may be effected in the construction of the pilot valve assembly. Testing has indicated that the modified construction is. both reliable arid long lasting.

Brief Description of the Drawings

^•Fig. 1 is . a . longitudinal cross-sectional view through a solenoid pilot valve cartridge - assembly embodying my invention;

Fig. 2 is a cross-sectional view taken substantially on the line 2-2 of Fig. 1; •

Fig. 3 is a fragmentary cross-sectional view showing ■ a modified form of the invention; and

Fig. 4 is an end view looking in the direction of arrow 4 in Fig. 3. Brief Description of the Preferred Embodiments

A solenoid pilot valve assembly embodying my invention includes a cylindrical housing 10 formed of non-magnetic material which is provided with a wrench engaging flange 12 and an externally threaded portion 14 adjacent its open end by which the cartridge assembly may be mounted in the valve body schematically shown in phantom outline at VB by engaging the threaded portion- 14 in complementary female threads of ^• the valve body and tightening the assembly by the use of a wrench engaging the flange 12.

The opposite end of the housing is closed by a

.ferromagnetic ^'. pole- ^' piece 16 having a. .longitudinally extending fluid escape or exhaust passageway 18' opening

. through, opposite ends of the pole piece, i.e. through' he

^• _. pole ^' fa,ce 20 at the inner end of the pole piece and through a counter bore 22 at the outer end of the pole piece. The bore may be threaded at 23 to facilite connecting the passageway 18 to a piping system (riot shown) for piping away air exhausting through the cartridge assembly as hereinafter mentioned. A circular

'.-'■^'. shading coil 24 is disposed . in the ^'end face 20 of the pole piece to promote quiet hold of the plunger thereagainst. Art O-ring seal 26 disposed' in a peripheral groove in the^' pole piece serves to seal the pole piece within the ^■cylindrical housing 10. The housing may be peripherally swaged inwardly, as at 28 to engage within a complimentary groove formed in the periphery of the pole piece to lock the pole piece within the cylindrical housing. The outer end of the pole piece may be externally threaded at 30 to . receive an internally threaded nut retainer (not shown.) for retaining a solenoid coil (not shown) which may be slipped over^' the cylindrical housing to rest against the flange 12 at one end and be held on housing by the nut at the other end. Upon energization of the coil, a magnetic field is impressed across the air gap AG between the face 20 of the pole piece and the opposite end of plunger 32.

The plunger 32 is ferromagnetic and disposed for reciprocation within the cylindrical housing. The plunger is generally cylindrical. It is provided with a longitudinal bore 34 opening through opposite ends. A longitudinally extending slot 36 opens at one end through the pole piece engaging end 38 of the plunger and at -the opposite end through a tapered portion 40. The slot 36 facilitates the escape of air along the length of the plunger through- the cylindrical housing and out through the escape passageway 18 in the pole piece when the solenoid coil .is de-energized. A cross bore 35 opens at

.opposite ends into the slot. 36- and the bore- 34 to permit equalization^■of fluid pressures between the slot and bore.

^■ A transverse groove 42, V-shaped in . cross section,

- communicates at the center with the bore 34 arid with the longitudinal groove 36 to prevent a "jo-block" effect (sticking together) when the plunger end 38 is flush against the end 20 of the pole piece.

• When the solenoid coil is de-energized, the plunger moves from a position abutting the face 20 of the pole piece toward the orifice 44 in the pilot valve body. This movement of. the plunger is caused by a conical compression spring 46 encircling the tapered portion 40 of the plunger and bearing at one end against a should.e 48- within the cylindrical housing and functionally bearing at the opposite end against the plunger. In fact, such spring bears at its smaller end against an inturned lip 50 on the head 52 of a T-shaped valve seat 54 having a shank -portion 56. The head 52 is- hat-shaped and includes a radial flange 58 terminating in an axially extending cylindrical portion 60 at the free end of which the lip 50 is disposed. The cylindrical outer surface of the portion .60 is axially grooved as at 61 in circumaxially spaced relation as shown in Fig. 4. The shank 56 of the valve seat extends through the bore 34 and may either be flush with or extend slightly beyond the end 38. Means are provided for limiting relative axial movement between the valve seat and the plunger 32. Such means is formed by the lip 50 of the valve seat engaging behind a circumferential radial flange 62 formed at the end of the plunger. The plunger bore 34 is. provided with a counter-bore 64 having a shoulder '66 against which bears the head portion 52 of the valve seat for limiting the axial inward movement of the valve seat.

The valve seat is formed of elastomeric material such, as cafboxylated nitrile rubber of approximately 60 durometer. In lieu of carboxylated nitrile rubber, Viton or a Buna-N rubber _.may be used. The elongated shank pprtion 56 is slidingly received within the bore 34 of the plunger. The shank . terminates at one end in the hat-shaped head portion 52 while the opposite en simply extends through the plunger end face 38 as clearly shown in Fig. , 1. Preferably the end 57 of -the shank is flush with . the end 38 of the plunger. Should it be desired to have the shank end project beyond the plunger end 38, the projection .^'should be such in relation to the durometer of the elastomeric .material of which the valve seat is , formed so that upon energization of the solenoid coil to impress a magnetic field across the air gap' AG between the plunger and the pole piece, the valve seat will compress sufficiently to allow mating abutment of the pole piece and plunger ends 20 and 38 while the shank portion 56 closes the end of the exhaust passageway 18.

To prevent a "jo-block" effect between the end 57 of the valve seat shank 56 and the surface 20 of pole piece 16, an annular groove ; 76 is provided in surface 20 concentric with the bore 18 and bridging the peripheral edge of the end face 57 of the elastomeric valve seat to form an orifice 78 to be closed when the plunger moves thereagainst and opened upon reverse movement. This design is much less expensive to fabricate than the prior art technique wherein the end of the pole piece had to be carefully machined to provide an axially projecting orifice surrounded by a carefully machined surface. In the present design the groove 76 is simply machined at the same time as the groove for the shading coil 24, and then the entire surface 20 may be faced with a surface grinder, thus providing an orifice just as effective as the prior art design at considerable cost saving.

The elastomeric nature of the valve seat permits the hat-shaped head to be stretched over the flange 62 of the plunger with the lip 50 engaging behind the flange 62 to^' lock ^'the valve seat in place on the plunger and prevent uncontrolled relative axial movement between the plunger and valve seat. As mentioned, the- compression spring 46 bears against the lip 50- to ensure that it is. retained i position surrounding the flange 62 of the plunger.

The valve sea-t may be provided with a central depression 68 as shown in Fig. 1 or the end 70 of the valve seat may be simply flat as shown in the modification of Fig. 3.

Reviewing briefly the operation of the pilot valve Cartridge assembly,- with a solenoid coil encircling the cylindrical housing and the cartridge assembly threadedly connected- to the pilot valve, upon energization of the solenoid the plunger is shifted to the right as shown in Fig. 1 such that the shank 56 of the valve seat blocks the end of the escape passageway 18 at the orifice 78 in the pole piece to prevent the escape of air through the groove 36. The end 68 (or 70a) of the valve seat is now spaced from, the orifice 44 of the pilot valve permitting air to pass from the orifice to another passageway 74 in the valve body for operating the valve. Upon de-energization of the solenoid coil, the spring 46 immediately urges the plunger to the left such that the end portion 68 (or 70) blocks the orifice 44 to prevent the pressurization of the pilot valve, and the air in the valve is permitted to flow through the groove 36 and out through the escape passageway 18 in the pole piece.

The provision of a valve seat which extends completely through the plunger from one end to the other and in which the plunger in one position will block .the escape passageway in the pole piece or in. the other position will block the pilot valve orifice, has resulted in substantial cost savings in- the manufacture of solenoid pilot valve cartridges and simplifies the overall construction of the cartridge assembly.

The cross bore 35 will serve to equalize fluid pressures between the slot 36 and the bore 34 thereby preventing a tendency to extrude the valve seat axially ^■but of the plunger and interfer with its proper operation, ϊhis cross bore 35 is particularly desirable when the pilot valve is used with higher fluid pressures such as. 200 p.s.i. or above.

The axial grooves 61 facilitate the escape of fluid ■ pressure between the head 52 and the surrounding surface 11 of the housing 10.

Claims

PILOT VALVE CARTRIDGE ASSEMBLYClaims

1. In a cartridge assembly for a solenoid .operated pilot valve having a cylindrical housing closed at one end by a pole piece having a^' fluid passageway opening inwardly of the housing and a magnetically attractable plunger in the housing moveable against arid away from the pole piece upon impression and release of a .magnetic field between the plunger and pole piece, and wherein there is a longitudinally extending ^'bore in . the plunger opening through opposite ends thereof, the invention characterized by. an elastomeric valve . seat extending through ^' said bore from end to end for .closing said flui passageway when the plunger is against the pole piece, said valve seat being exposed at the opposite end . of the plunger to close an orifice with which the cartridge assembly is to .be associated upon movement of the plunger away from the pole piece, and means- for retaining the valve seat ^"in the plunger and limiting relative movement thereof in the plunger.

^■2. The invention defined by Claim 1 wherein said means for retaining the valve seat is disposed adjacent said opposite end of the plunger.

3. The invention defined by Claim 1 wherein said means for retaining the valve seat comprises interfitting portions on the valve seat and plunger.

4. The invention defined by Claim 1 wherein said opposite end of the plunger is provided with a radially extending flange and the valve seat is provided with a radially extending portion trapped behind said flange.

5. The invention defined by Claim 1 wherein said opposite end of the plunger has a circumferential radially outwardly extending flange, arid the corresponding end of the valve seat has a

. circumferential radially outwardly extending flange having a peripheral lip of a smaller diameter than

^■ the diameter of the plunger flange, said valve seat flange . and lip being radially stretchable to be received in gripping engagement over the plunger

^•flange to retain the valve seat On the plunger.

6-^' • The invention defined by Claim 1 wherein said^' valve seat extends beyond opposite ends of said plunger.

7. The invention defined by claim 1 wherein said pole piece has an end face opposing the plunger with an annular groove therein concentric with said fluid passageway and bridging the periphery of the elastomeric. valve seat to provide an orifice to be opened and closed by such seat upon movement of the

^• plunger toward and from the pole piece.

8. A plunger for the cartridge assembly of a solenoid-operated pilot valve comprising an elongated, cylindrical, magnetically attractable, member having a bore extending axially therethrough from end to end; an elastomaric valve seat disposed within said bore and extending therethrough; and said valve seat and cylindrical member having radially extending interfitting portions for limiting relative axial movement of the member and valve seat.

9. The invention defined by Claim 8 wherein said valve seat has a radially extending flange terminating in a peripheral lip stretchable over a radial flange on the plunger to hold the valve seat and plunger against uncontrolled relative movement.

10. The invention defined by Claim 9 wherein said radially extending flange has an axially extending cylindrical portion terminating in said peripheral lip and the exterior surface of said cylindrical portion is provided with axially extending groove means to facilitate fluid flow around said flange.