GB2229795A

GB2229795A - Manually operable control valve mechanism

Info

Publication number: GB2229795A
Application number: GB9002125A
Authority: GB
Inventors: P Jennison
Original assignee: Bendix Ltd
Current assignee: Honeywell UK Ltd
Priority date: 1989-01-31
Filing date: 1990-01-31
Publication date: 1990-10-03
Anticipated expiration: 2010-01-31
Also published as: GB8902048D0; GB9002125D0; GB2229795B

Abstract

A hand operable vehicle fluid pressure brake control valve includes a valve assembly providing a secondary and parking brake operation, the assembly being operable by a control lever 5 movable about a transverse axis through a gate or slot 2 in the housing, the lever having a handle 7 which has to be rotated against a spring bias about a longitudinal axis to permit respective dogs 10 thereof to pass between mutually facing inward detents 8, said dogs normally preventing such passage and avoiding spurious parking brake release. <IMAGE>

Description

Manually Operable Control Valve Mechanism This invention relates to a manually operable control valve mechanism especially but not exclsively for a control valve 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 handle moveable from a first brake. releasing position through d 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 releasable locking element which is moveable longitudinally of the handle and lockingly engageable in the housing in the parked position.Despite the provision of this locking element a shortcoming of such a control valve assembly may exist to the extent that vibration or inadvertent interference with 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 properly to control the vehicle. A further shortcoming is that there is a possibility that the locking element may find a rest position wherein although it is not fully lockingly engaged it gives the impression of being so engaged whilst in factthe position-.s unstable and thus the brake may be spuriously releasable.

The object of the invention is to provide a manually operable control valve mechanism wherein the above shortcomings are removed or apparently reduced.

According to the present invention there is provided a manually operable control valve mechanism including in a housing a valve assembly operable by a control member moveable through a range of positions along a gate or slot of the housing and including stop means dividing said gate or slot into two parts said control member carrying engaging means normally in a position to be engageable with said stop means to prevent movement thereof from one said part to the other said part and said engaging means being moveable by rotation of said member to permit movement thereof from one said part to the other part.

Preferably the locking means is spring biassed towards a rest position in which it presents to sad opening a width greater than the constructed width thereof.

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 of which Fig. 1 illustrates a fragmentary iew of a control valve in accordance with one example of the invention, Fig. 2 illustrates a sectional view of the control handle and lever of the valve of Fig. 1, Fig. 3 illustrates on a larger scale a spring to be referred to in connection with Fig. 2 and Fig. 4 illustrates how the spring is located.

Referring to Fig. 1 a manually operable brake control valve has a housing the upper end of which is denoted by reference 1.

This comprises a top cover provided with a gate slot 2 and within the housing there is an operating cam 3 rotatable about an axis 4 and a lever 5 having an axis 6 normal to axis 4 and projecting through the gate slot to carry a control handle 7.

The gate slot 2 is provided on each side thereof with an inwardly projecting detents 8 directly opposite each other dividing the slot into two parts which tereby construct the width of the gate slot to allow free passage therethrough only of the diameter of lever 5. The handle 7 is of moulded plastics and has moulded into it at its lower end a robust metal insert 9 with downwardly extending dogs 10 which in the position shown in Fig.

1 restrict the movement of the lever to the part of the gate slot to one side of the detents 8. However the handle 7 is generally T-shaped and is manually rotatable on the lever 5 through an angle of 900 from the position shown. This thereby allows the dogs 10 and lever 5 to pass between detents 8 to the other part of the slot. Return rotation of the handle 7 on lever 5 then permits the movement of the lever to be constrained only to the latter part of the gate slot, Normally, the lever 5 is biassed, by a spring in the valve mechanism, in the direction of the Arrow 11 and the rotatable handle 7 is provided with a captive internal helical spring 12 so designed that the handle 7 takes up a stable rotational position as shown on the lever 5.The helical spring 12 is shown on its own in Fig. 3 and it will be seen therefrom that spring 12 has a transverse mid part p3 formed as a straight section receivable in an axial diametral slot 14 at the outer end of lever 5. The ends 15 and 1.6 of the spring extend tangentially and are constrained in a generally D-shaped recess 17 within the handle moulding. The handle 7 is further retained axially in position on the lever 5 by a circlip 18 and retaining washer 19 concealed by a snap-in cover piece 20 as shown in Fig. 2.

In normal operation the handle 7 rests in the brakes off position A (Fig. 1) under the influence of the mentioned internal spring. In order to apply secondary braking the driver moves the handle in a direction towards the detents 8. Upon engaging detents 8 the full secondary brake pressure is achieved. In order to park the vehicle however the driver has to manually rotate the handle through 900 in either direction whereby the dogs 10 can now pass between detents 8 and allow the handle to be moved into the other part of the slot and adopt 'park' position B. The mentioned internal spring and the helical spring 12 then together serve to ensure that the lever 5 is securely locked by virtue of the dogs 10 firmly resting against detents 8. Two initial movements are necessary in order to release the parking brake. It is necessary firstly to move the lever 5 slightly beyond position B and secondly to rotate the handle through 900 to permit the dogs 10 to again align with and then pass between detents 8 and aliow lever 5 to be returned to the former part of the slot and to release position A. This release operation is unlikely to be able to occur in any accidental manner other than with the full attention and control of the vehicle driver performing the above two initial movements and the probability of the handle resting in an unstable position which is not fully locked is considered to be exceedingly small.

Claims

CLAIMS.

1. A manually operable control valve mechanism including in a housing a valve assembly operable by a control member movable through a range of positions along a gate or slot of the housing and including stop means dividing said gate or slot into two parts said control member carrying engaging means normally in a position to be engageable with said stop means to prevent movement thereof from one said part to the other said part and said engaging means being movable by rotation of said member to permit movement thereof from one said part to the other part.

2. A manually operable control valve mechanism as claimed in claim 1 said member comprising a lever assembly movable in said gate or slot about a first axis transverse to its longitudinal axis said gate or slot having at least one inwardly extending detent which lies in the path of a part of said member in said gate or slot and said member being rotatable about its longitudinal axis to permit said part of said member to pass said detent.

3. A manually operable control valve as claimed in claim 2 said slot having two mutually facing inwardly extending detents engageable with respectivet parts of said member.

4. A manually operable control valve as claimed in said control member being resiliently biassed into said position wherein said engaging means are engageable with said stop means.

5. A manually operable control valve as claimed in claim 1, wherein said control member is rotatable, movable in either direction about said longitudinal axis.

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