GB2105809A - Cam operated valve - Google Patents

Abstract

A hand operable vehicle air brake valve has a housing 1 for a self-lapping valve assembly above the plunger 4 of which a guide block 20 is located to carry a hard metal roller 9 which acts between a handle operated valve cam 6 and the plunger 4 itself to remove lateral forces on the plunger and permit easy selection of the cam-orientation in relation to the valve housing. <IMAGE>

Description

SPECIFICATION Cam operated valve assemblies This invention relates to cam operated valve assemblies and relates especially but not exclusively to hand operable valves for vehicle braking systems.

Hand operated valve assemblies have been known for many years whereas in a valve plunger is spring urged against a cam which in turn is rotatable by a handle for positioning the plunger in a range of operating positions. In such valve assembies it has been found that in some cases undue wear has tended to occur either on the cam itself or on the part at the head of the plunger which engages the cam.

Also, in the absence of special counter-measures lateral forces are transmissible from the cam to the plunger which can introduce a probability of leakage around the plunger.

The present invention provides a cam-operated valve assembly including a valve plunger resiliently urged towards a cam member which is moveable for positioning the plunger within the assembly and wherein a rotatable roller element is positioned between the plunger and the cam said roller element being retained by a guide track constraining its movement to being in line with the plunger.

The guide track may be provided in a cage block which can be positioned in the housing in one of a number of positions corresponding to a choice of angular positions for the cam about the axis of the plunger.

In order that the invention may be more clearly understood and readily carried into effect the same will be further described by way of example with reference to the accompanying drawings in which: Figure 1 illustrates in part sectional view a hand operable pneumatic valve assembly for use in controlling a secondary brake circuit of a fluid pressure braking system and, Figure 2 illustrates to enlarged scale a plan at (a) and two sectional views at (b) and (c) of a cage block included in the valve assembly of Figure 1.

Referring to Figure 1, the hand valve assembly shown has a main body 1 mounted by screws 2 to a recess plate 3 for fitting into an aperture in the facia panel at the driving position of a road vehicle. The valve can thus be readily mounted vertically together with pipe connections to a sloping facia panel. The main body 1 contains a self-lapping valve arrangement which is of known form carried by an axially moveable plunger the upper end 4 of which is indicated. The plunger is spring urged upwardly along its axis represented by vertical broken line 5 towards a nylon cam 6 which is rotatable by a handle assembly 8 about a horizontal axis 7. A hard metal roller 9 the axis of which is parallel to the axis 7 is located between the head 4 of the valve plunger and the cam 6 such that the cam acts on the plunger through the intermediary of the roller.

The roller is retained in accordance with the present embodiment of the invention buy a cage which is assembled into a desired position in the housing, the cage 20 providing a guide track permitting vertical movement of the roller and rotational movement about its own axis but preventing horizontal movement in axial or transverse directions.

Referring to Figure 2 the housing of the valve assembly is designed with a substantially square chamber denoted in Figure 2(a) by a broken outline 21 into which the cage 20 comfortably fits and is retained in position by the top cover 11 which is held in position by four set screws not shown in Figure 1 but the positions of which are denoted at 22 in Figure 2. The guide track for the roller is constituted by the internal walls 23 of the block between which the roller is a good sliding fit. Likewise the length of the roller is chosen to provide positive location between the ends at annular shoulders 24.

By virtue of the shape of the guide block which enables it to be located in a square chamber it will be appreciated that it can be positioned in either of four orientations. In other words the cam of Figure 1 can be assembled to operate alternatively in two positions in the plane or of the two positions in the plane at right angles to the plane of the drawing of Figure 1.

By providing a roller such as 9 retained by a guide block in accordance with the invention the probability of wear between the cam 6 and the head 4 of the valve plunger is appreciably reduced and also lateral forces which may otherwise lead to wear of seals, in the bore of the housing 1 in which the plunger operates, are almost completely removed.

1. A cam operated valve assembly including a housing and valve plunger therein resiliently urged towards a cam-member which is moveable for positioning the plunger within the housing and wherein a rotatable roller element is positioned between the plunger and the cam said roller element being retained by a guide track constraining its movement to being in line with the plunger.

2. A cam-operated valve assembly as claimed in claim 1 wherein said guide track is provided in a guide block located within the housing.

3. A cam-operated valve assembly as claimed in claim 2, said guide block being shaped to permit a choice of a plurality of positions thereof in the housing when assembling the valve to give a desired orientation of the cam about the axis of the plunger.

4. A cam-operated valve assembly as claimed in claim 2 or 3 wherein the guide block is of generally square outer dimension to permit location in a square recess in the housing in one of four positions.

5. A cam-operated valve assembly substantially as described herein with reference to Figure 1 and Figure 2 of the accompanying drawings.

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

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Cam operated valve assemblies This invention relates to cam operated valve assemblies and relates especially but not exclusively to hand operable valves for vehicle braking systems. Hand operated valve assemblies have been known for many years whereas in a valve plunger is spring urged against a cam which in turn is rotatable by a handle for positioning the plunger in a range of operating positions. In such valve assembies it has been found that in some cases undue wear has tended to occur either on the cam itself or on the part at the head of the plunger which engages the cam. Also, in the absence of special counter-measures lateral forces are transmissible from the cam to the plunger which can introduce a probability of leakage around the plunger. The present invention provides a cam-operated valve assembly including a valve plunger resiliently urged towards a cam member which is moveable for positioning the plunger within the assembly and wherein a rotatable roller element is positioned between the plunger and the cam said roller element being retained by a guide track constraining its movement to being in line with the plunger. The guide track may be provided in a cage block which can be positioned in the housing in one of a number of positions corresponding to a choice of angular positions for the cam about the axis of the plunger. In order that the invention may be more clearly understood and readily carried into effect the same will be further described by way of example with reference to the accompanying drawings in which: Figure 1 illustrates in part sectional view a hand operable pneumatic valve assembly for use in controlling a secondary brake circuit of a fluid pressure braking system and, Figure 2 illustrates to enlarged scale a plan at (a) and two sectional views at (b) and (c) of a cage block included in the valve assembly of Figure 1. Referring to Figure 1, the hand valve assembly shown has a main body 1 mounted by screws 2 to a recess plate 3 for fitting into an aperture in the facia panel at the driving position of a road vehicle. The valve can thus be readily mounted vertically together with pipe connections to a sloping facia panel. The main body 1 contains a self-lapping valve arrangement which is of known form carried by an axially moveable plunger the upper end 4 of which is indicated. The plunger is spring urged upwardly along its axis represented by vertical broken line 5 towards a nylon cam 6 which is rotatable by a handle assembly 8 about a horizontal axis 7. A hard metal roller 9 the axis of which is parallel to the axis 7 is located between the head 4 of the valve plunger and the cam 6 such that the cam acts on the plunger through the intermediary of the roller. The roller is retained in accordance with the present embodiment of the invention buy a cage which is assembled into a desired position in the housing, the cage 20 providing a guide track permitting vertical movement of the roller and rotational movement about its own axis but preventing horizontal movement in axial or transverse directions. Referring to Figure 2 the housing of the valve assembly is designed with a substantially square chamber denoted in Figure 2(a) by a broken outline 21 into which the cage 20 comfortably fits and is retained in position by the top cover 11 which is held in position by four set screws not shown in Figure 1 but the positions of which are denoted at 22 in Figure 2. The guide track for the roller is constituted by the internal walls 23 of the block between which the roller is a good sliding fit. Likewise the length of the roller is chosen to provide positive location between the ends at annular shoulders 24. By virtue of the shape of the guide block which enables it to be located in a square chamber it will be appreciated that it can be positioned in either of four orientations. In other words the cam of Figure 1 can be assembled to operate alternatively in two positions in the plane or of the two positions in the plane at right angles to the plane of the drawing of Figure 1. By providing a roller such as 9 retained by a guide block in accordance with the invention the probability of wear between the cam 6 and the head 4 of the valve plunger is appreciably reduced and also lateral forces which may otherwise lead to wear of seals, in the bore of the housing 1 in which the plunger operates, are almost completely removed. CLAIMS

1. A cam operated valve assembly including a housing and valve plunger therein resiliently urged towards a cam-member which is moveable for positioning the plunger within the housing and wherein a rotatable roller element is positioned between the plunger and the cam said roller element being retained by a guide track constraining its movement to being in line with the plunger.

2. A cam-operated valve assembly as claimed in claim 1 wherein said guide track is provided in a guide block located within the housing.

3. A cam-operated valve assembly as claimed in claim 2, said guide block being shaped to permit a choice of a plurality of positions thereof in the housing when assembling the valve to give a desired orientation of the cam about the axis of the plunger.

4. A cam-operated valve assembly as claimed in claim 2 or 3 wherein the guide block is of generally square outer dimension to permit location in a square recess in the housing in one of four positions.

5. A cam-operated valve assembly substantially as described herein with reference to Figure 1 and Figure 2 of the accompanying drawings.