GB2171495A

GB2171495A - Valves

Info

Publication number: GB2171495A
Application number: GB08504879A
Authority: GB
Inventors: Alan R Turner
Original assignee: Bendix Ltd
Current assignee: Honeywell UK Ltd
Priority date: 1985-02-26
Filing date: 1985-02-26
Publication date: 1986-08-28
Also published as: GB2171495B; DE3688429T2; GB8504879D0; EP0257145A1; DE3688429D1; EP0257145B1

Abstract

In a compressed air vehicle brake valve a control member such as a hand lever (9) is lockable in a predetermined position by a locking element (10) which is normally spring biassed into the locking position but a further spring (23) is located on the lever between the locking element (10) and a release member (14) this spring being compressible by the action of the release member to apply a reverse bias to the locking element which will cause it to release when frictional or other retaining means is overcome. <IMAGE>

Description

SPECIFICATION Manually operable control valves This invention relates to manually operable control valves and relates especially but not exclusively to control valves for vehicle compressed air braking systems.

In compressed air braking systems for heavy vehicles, it is customary, in addition to a foot operable control valve for operation of service brakes also to provide a manually operable control valve device for operating secondary and/or parking brakes. Such a control valve device may be a single valve, or alternatively, may comprise one valve for controlling spring brakes and one valve for providing graduable secondary control. The valve assembly may include a control member moveable from a first brakes released position through a control range to a full secondary brake position and beyond that to a special parking brake position. For security purposes it is normal to provide a spring-biassed manually releaseable locking element which is engageable in the housing in the parked position.

Despite the provision of the mentioned locking element a shortcoming of such a control valve assembly may exist to the extent that vibration or inadvertent knocking of the control member may cause undesired release of the locking element and result in unsafe release of the parking brake when a driver is not in a position to properly control the vehicle.

The object of the invention is to provide a manually operable control valve mechanism wherein the possibility of such an inadvertent operation is even further reduced.

According to the present invention there is provided a manually operable control valve mechanism having a valve assembly in a housing operable by a control member, said control member being provided with a locking element lockingly engageable with the housing in a pre-determined position of the control member and a release member normally spring biassing the locking element into such engagement actuation of said release member to overcome said bias being effective to apply a reverse spring bias permitting the locking element to disengage only when the control member is moved to relieve friction or other retention means.

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 drawing which illustrates an embodiment of the invention.

Referring to the drawing the manually operable control valve mechanism shown therein is intended to be used in controlling secondary and/or parking brakes of a heavy vehicle fitted with a multi-circuit compressed air braking system. The mechanism has a housing 1 provided with an input port 2 for connecting to a compressed air supply reservoir, an output port 3 for connecting to a control line for secondary or parking brake actuators of the vehicle and a vent port 4. A self-lapping valve assembly (not shown) is operable by a cylindrical plunger 5 axially guided in the housing and actuable via a roller 6 by a cam 7 pivotted at 8 transversly with the plunger axis.

The roller 6 is guided for movement in line with said axis by means such as is described for example in the Specification of copending British Application No. 8214144. The mentioned self-lapping valve is operable to connect the output port 3 alternativeiy to the input port 2 or to the vent port 4 to produce graduable air pressure at port 3 dependent upon the position of the plunger 5 as set by the cam 7.

The cam 7 which is biassed clockwise by a return spring which is not shown is rotatable about axis 8 by a control member in the form of a lever 9 which engages with the cam and is guided in a gate assembly 12 on the top of the housing. The lever 9 is provided with a locking element 10 which is slideably along the lever 9, the lower end 11 thereof being moveable into and out of engagement with the gate assembly 12. In the position shown the locking element 10 is shown as engaged with the gate assembly in a predetermined position which will normally be the parking position of the gate lever. The locking element 10 is urged into such locking engagement by means of a captive spring 13 retained in a release member 14 in the form of a moulded plastics assembly which is also slideable on the lever 9.The spring 13 is located between a lower washer 16 which rests against a shoulder 15 within the member 14 and an washer 17 which rests against a tubular collar and stop element 18 retained on the lever 9 by a screwed-on control knob 19. The collar 18 has a flange at 20 to act as a stop for the member 14 when moved upwards. The member 14 has a further lower shoulder indicated by reference 21 between which and a upper shoulder 22 of the locking member 11 there is a lighter spring 23 which in the position shown is designed to be uncompressed.

In operation of the valve assembly, the position shown is intended to be the parked position wherein if the valve is controlling spring brakes, the output at port 3 will be vented. In order to move the lever out of this parked position it is necessary for the vehicle driver first to pull upwards the release member 14 against the stop 20. By so doing the downward bias on the locking element 11 is removed and replaced by an upward bias introduced by some compression of the spring 23 which now acts on the upper flange 22 of element 11. However, by virtue of the return spring action tending to move lever 9 away from the position shown, there is sufficient friction acting against the gate assembly and the element 11 to prevent 11 moving out of locking engagement therewith until the lever 9 is moved against the rotational spring biassed.

By such movement the frictional forces are removed and the spring 23 is effective to lift the element 11 out of the locking engagement. By releasing the member 14 th spring 13 again becomes effective to urge the element 11 in a locking direction such that it will engage with the gate assembly when the lever 9 is placed in the predetermined position.

As an alternative to placing reliance on friction between the lower end of element 11 and the gate assembly these may be designed to provide a positive latching function. One possibility for this is shown enlarged at inset A, wherein the lower end of 11 is shamfered at 31 and providec with an annular groove 32 whereby it locks into engagement with the gate assembly under the action of spring 13 and is only releaseable following slight clockwise rotation of the lever 9 and upward movement of the release member.

Claims

1. A manually operable control valve mechanism having a valve assembly in a housing operable by a control member, said control member being provided with a locking element lockingly engageable with the housing in a predetermined position of the control member and a release member normally forward biassing the locking element into such engagement and actuation of said release member to overcome said bias being effective to apply a reverse spring bias the locking element in a sense to effect disengagement when the control member is moved to release frictional or other retention means.

2. A manually operable control valve mechanism as claimed in claim 1, said control element comprising a lever on which the locking element is slideable into and out of engagement with the housing the release member being slideable along said lever and relative to the locking element a substantially normally unloaded spring being retained between the locking element and the release member.

3. A manually operable control valve mechanism as claimed in claim 1 or 2, said release member normally biassing the release member by virtue of a spring captive between the release member and means slideable on the lever and cooperable with the locking element.

4. A manually operable control valve mechanism as claimed in claim 3, said means being engageable with a stop inside the release member.

5. A manually operable control valve mechanism as claimed in claim 1, 2, 3 or 4, having catch means between the locking element and the housing whereby the lever is required to be moved through a predetermined angle in relation to the housing to permit release.

6. A manually operable control valve mechanism substantially as described herein with reference to the accompanying drawing.