GB2137739A - Hand control lever for brake valve - Google Patents

Abstract

A hand operable secondary and parking brake control valve for air brake systems has a control handle (2) (which is movable over a range of positions between a fully released position and a park position through a full secondary brake position) and an over-centre mechanism (13, 14, 17) Fig. 3 which once the handle has been moved beyond the full secondary position towards the park position tends to drive the handle to the park position and on the other hand otherwise tends to drive the handle away from the full secondary position. A catch (24, 26) is included the operation of which is necessary to allow the handle to pass through the secondary position in either direction. A different type of over-centre mechanism is disclosed in Fig. 4. <IMAGE>

Description

SPECIFICATION Hand control valve mechanism This invention relates to hand control valve mechanisms and relates especially to mechanisms of control valves for vehicle compressed air braking systems.

In compressed air braking systems for heavy vehicles it is customary to provide a foot operable valve for operation of service brakes and to provide a hand control valve device for operating secondary and/or parking brakes. Such a hand control valve device may typically comprise two valves operable by a single handle one valve being for providing graduable secondary control air pressure and the other valve providing an air pressure signal for controlling spring brakes. The arrangement may be such as to provide handle movement from a first release position through a control range to a full secondary position and beyond that to a special parking position at which the output pressure from both valves falls to zero.

In the parking position of the valve mechanism secondary control air is thus removed and demonstrable parking is achieved by spring brakes.

A shortcoming of such hand control device may exist in that vibration or inadvertent manual operation of the handle of the device may cause the brakes to be applied violently during service or alternatively may result in inadvertent release of the brakes when the driver is not in a position to have proper control of the vehicle. The object of the invention is therefore to provide such a valve mechanism wherein the chances of such inadvertent operation are appreciably reduced.

According to the present invention there is provided a hand control valve mechanism comprising a valve operating handle moveable through a range of positions including a second position between a first and third position said handle having first means which when approaching the second position acts in a sense to urge the handle away from the second position towards the first position or the third position as the case may be and further means operation of which is necessary to permit movement of the handle away from the third position towards the second position.

In one embodiment of the invention said first means comprises a first member which when approaching the second position of the handle makes resilient engagement with a second shaped member the resilience acting in a sense to urge the handle away from the second position towards the first position or the third position as the case may be.

In a further embodiment said first means comprises a spring assembly one end of which is pivotted to the handle at a front off-set from the axis of movement of the handle and the other end of which is pivotted to the housing of the valve mechanism at a point such that with the handle between the second and third position the line of action lies to one side of said axis and with the handle between the second and first position the line of action lies to the other side of said axis.

In a preferred embodiment of the invention operation of the further means is also necessary to permit movement of the handle through the second position to the third position.

In order that the invention may be more clearly understood and readily carried into effect, the same will be further described with reference to the drawings of which: Fig. 1 illustrates a part sectional side view of a compressed air control valve, Fig. 2 illustrates a part sectional side view at right angles to the section of Fig. 1, Fig. 3 illustrates on a larger scale the geometry of the first and second members of the valve arrangement of Fig. 1 and Fig. 2 in accordance with one embodiment of the invention and, Fig. 4 illustrates an alternative embodiment of the invention.

Referring to Fig. 1 the valve arrangement shown therein is a secondary and/or parking valve for use in a heavy vehicle compressed air braking system and comprises a main body denoted by reference 1 intended to be mounted vertically as shown and a control handle 2 pivotally mounted to the body about an axis 3 of a spindle generally at right angles to the drawing as seen in greater detail in Fig. 2. The handle 2 engages with 3 by means of locating pins 4 and 5 which are readily removeable for dismantling and servicing. The handle 2 is thus located at each end of the spindle 3 and located on 3 within the housing of the valve cam members 6 and 7 for operating through guide rollers 8 and 9 respective self-lapping valves denoted generally by the references 10 and 11 for controlling complimentary upright and inverse output pressures.

The details of valves 10 and 11 have little bearing on the present invention in that they are of generally known form and they will therefore not be described in detail. However, the cams 6 and 7 are so shaped to be moveable in complimentary fashion having regard to their normal control functions but to permit the valves 10 and 11 to move to a venting condition upon movement of the handle beyond its normal surface range to a parking position.

Mounted and located centrally upon the spindle 3 between the cams 6 and 7 a member 12 carries a member 13 which is itself engageable via a roller element with a resilient cam member 14 aided by a rubber spring 1 7 at one end and fixed at the other end to the body of the mechanism.

This member is further referred to below with reference to Fig. 3.

The handle 2 is provided with a main fixed horizontai grip 1 5 and a parallel radially outwardly slideable compressible grip 1 6 which is urged radially inwards with springs 18 and 19 and guided by side portions 22 and 23 slideable in channel sections 20 and 21 formed in the respective sides the ends of which are located on spindle 3. The side portions 22 and 23 have elongated apertures 28 to permit movement of the side portions relative to the spindle 5 and shaped extensions 24 and 25 engageable or abutable with fixed pins 26 and 27 respectively.

Referring to Fig. 3 this illustrates on an enlarged scale the aforementioned roller and resilient cam member together with the extension 24 and fixed pin 26 with which 24 is locatable or abutable.

Considering, therefore, the operation of the valve mechanism and assuming the handle to be moved by an operator in a clockwise direction from the fully released position for the brakes through a secondary brake control range towards a position where the roller 1 3 begins to engage the rising ramp portion 'A' of the resilient cam member 14 a progressively increasing opposing force is experienced by the operator up to a position denoted by the line 'X' where the handle is in a position which becomes full secondary braking.In this position the extension 24 is in the position of the dotted outline and engages with pin 26 and extension 25 engages pin 27 (Fig. 2). In order to move the handle from this position (wherein the roller and cam plate are also shown dotted) to a parking position wherein the roller and cam plate are shown as solid lines, it is necessary for the driver to grip the member 16 and to cause outward radial movement thereof and enable the extensions 24 and 25 to move over respective pins 26 and 27.As the roller moves off the steeper part 'B' of 14 and leftward from the position shown dotted towards the parked position on part 'C' the resilient cam member 14 is such as to exert an assisting force the direction of which now tends to drive the handle towards a parked position at which the slot 29 of the extension 24 is able to drop over pin 26 and thereby lock the handle. In order to release the handle from the parked position not only does this locking require to be released but also the opposing force exerted by 14 has to be overcome.It will be seen that as a result of the geometry of the cam plate 14 if the handle is released by the driver in a position midway between the second and third positions since the force acting thereon is such as to tend to drive the handle towards the parked position, parking in such a dangerous condition or inadvertent release of the brake (say by the slamming of a cab door) when a driver is in no position to control the vehicle is substantially prevented.

Whilst in the aforegoing resilient cam member 14 is shown to be fixed at one end and resiliently biassed by a rubber spring 1 7 at the other it will be appreciated that various alternative forms of resilient arrangement as between cam plate and roller may be readily conceived.

Referring to Fig. 4, in the alternative embodiment of the invention shown therein the roller 1 3 and resilient cam member 14 of Fig. 2, are dispensed with and the combined effect of these elements is achieved by a spring assembly in the form of a resiliently compressible plunger device denoted by reference 40. This plunger device consists of an internal member 41 the outer end of which is pivotted to a stud 42 of the handle and between which and the lower end of 40 there is a captive compression spring. The lower end is pivotted to a stud 43 carried on a bracket 44 carried in the main body of the valve.

The handle 2 and the mechanism for operating the shaped extension 24 in relation to pin 26 remain substantially as before.

In operation it will be seen that the spring plunger device 40 has two generally possible directions 45 and 47 of action in relation to the unstable direction 46 through the centre of spindle of the handle 2.

Assuming the handle to be moved by an operator in a clockwise direction from a fully released position for the brakes through a secondary brake control range towards a position where the handle begins to meet the action of the plunger in direction 47, a progressively increasing opposing force is experienced by the operator up to a position where the face 48 engages the right hand side of pin 26. This is the full secondary brake position. The operator can then actuate the mechanism of member 24 to enable this to pass across the pin 26 and the line of action of plunger mechanism 40 passes through the position 46 to position 45. The action is then such that even if the catch is not effected by member 24 the action of plunger 40 is such as to drive the handle into the fully parked position.The brake is only releaseable then by operation of the mechanism to lift member 24 and also by the necessary movement of the handle to take the line of action of plunger mechanism 40 back through 46 towards 47.

Whilst the mechanism described in the foregoing with reference to Fig. 4 has means 40 arranged externally of the handle, in the interests of neatness and cleanliness for maintenance purposes the means 40 may be arranged within the handle assembly. For example the means 40 may be arranged to cooperate with a small lever keyed to the spindle 3 at a mid point between the valve operating cam members such as 6 and 7 shown in Fig. 1.

By virtue of the invention whereby not only is the means urging the handle away from the second position towards the first or third position but also further means which is required to be operated to permit movement of the handle away from the third position an extremely safe hand control valve mechanism is provided which is not susceptible to being released from a parked condition by engine vibration or other disturbances such as the violent closing of a vehicle cab door.

Claims (8)

1. A hand control valve mechanism comprising a valve operating handle moveable through a range of positions including a second position between first and third positions said handle having first means which when approaching the second position acts in a sense to urge the handle away from the second position towards the first position or the third position as the case may be and further means operation of which is necessary to permit movement of the handle away from the third position towards the second position.

2. A hand control valve mechanism as claimed in claim 1 said first means comprising a first member which when approaching the second position of the handle makes resilient engagement with a second shaped member the shape and the resilience acting in a sense to urge the handle away from the second position towards the firstor third position as the case may be.

3. A hand control valve mechanism as claimed in claim 2, the resilience being provided by the shaped member.

4. A hand control valve mechanism as claimed in claim 3, the shaped member comprising a cam member biassed by a spring.

5. A hand control valve mechanism as claimed in claims 2, 3 or 4, the first member comprising a roller for rolling engagement of the shaped member.

6. A hand control valve mechanism as claimed in claim 1, said first means comprising a spring assembly one end of which is pivotted to the handle at a point off-set from the axis of movement of the handle and the other end of which is pivotted to the housing of the valve mechanism at a point such that with the handle between the second and third position the line of action lies to one side of said axis and with the handle between the second and first position the line of action lies to the other side of said axis.

7. A hand control valve mechanism as claimed in claim 6 said spring assembly being a compression spring assembly.

8. A hand control valve mechanism substantially as described herein with reference to Figs. 1, 2 and 3 or Fig. 4 of the accompanying drawings.