GB2075640A - Quick release valve - Google Patents

Abstract

A quick release valve is provided having an input port 5 which communicates with a dish shaped volume wherein a flexible valve disc member 8 is housed moveable between a position in which it closes off the inlet port or a position in which it closes off a concentric vent port 7. Access to output ports 10, 11 is around another part of the disc which overhangs the vent port. A small aperture 12 is provided in the disc annulus, to provide a path for release of pressure from the output port even with the vent port closed off. Hysteresis of the valve is thus reduced. <IMAGE>

Description

SPECIFICATION Quick release valves This invention relates to quick release valves and relates especially to quick release valves for fluid pressure-operable vehicle braking systems.

Quick release valves have been proposed for installation in compressed air braking systems for road vehicles, such valves being positioned close to fluid pressure-operable brake actuators for the purposes of hastening the exhaust of air from the actuators when the applied actuator pressure is released. This avoids the necessity for exhausted air to travel through relatively long lines to the exhaust passage of the brake control valve or relay valve which may be located at some distance from the brake actuators.

One form of quick release valve which is commercially available is described in the technical Pamphlet No. 10/008, issued by Bendix Westinghouse Limited, and this consists of an housing including a rubber diaphragm member positioned between, on one side, a compressed air input port and, on the other side, a port connected to exhaust and one or more ports for connection to respective brake actuators. When air is applied to the fluid pressure supply port, the diaphragm valve member is urged away from a seat covering the inlet port and is urged against an exhaust valve seat to thereby permit flow of air only from the inlet to the actuators. On subsequent reduction of the control pressure, the diaphragm is deflected in the opposite direction by the dominating actuator pressure thereby enabling the actuator pressure to be quickly exhausted via the now uncovered exhaust port.

It is found that in such quick release valves, there is a tendency for the movement into the position in which the actuator pressure is released through to the exhaust port, is subject to hysteresis and one object of the present invention is to reduce this hysteresis.

According to the present invention, there is provided a quick release valve which comprises a flexible valve member moveable between an inlet valve seat and an exhaust valve seat and via which when the flexible valve member is in closing engagement with the vent valve seat a fluid pressure path is open between an inlet port and one or more outlet ports and a leakage aperture in the valve member lies between the inlet port and the outlet port or ports.

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 single Figure of the accompanying drawing which illustrates a sectional view of a quick release valve including the invention.

Referring to the drawing, the valve shown therein is formed of a main body having an upper part 1 and a lower part 2, joined together with an intermediate seal 3 by means of suitable screws such as 4. The upper part is provided with an inlet port 5 and the inlet port communicates with the interior of the valve arrangement via an inlet valve seat 6 between which an exhaust valve seat 7 there is a circular rubber disc 8. In the position shown, the rubber disc 8 is shown in engagement with the exhaust valve seat thereby closing-off a path therethrough to an exhaust port 9 formed in the lower part of the assembly. The lower part also includes outlet ports 10 and 11 for connection to respective brake actuators.In accordance with the invention, the valve disc 8 is provided with a small leak aperture denoted by reference 12, the diameter of which is chosen in accordance with the volume of utilisation means connected to ports 10 and 11. Typically one-sixteenth of an inch.

In operation of the quick release valve as employed in a vehicle fluid pressure braking system the inlet port 5 is connected to the line by which fluid pressure is to be supplied to utilisation means, typically brake actuators and output ports 10 and 11 are connected to respective such actuators. Exhaust port 9 would ordinarily be connected via a suitable non-return device not shown for preventing the ingress of contaminating grit etcetera.

When fluid pressure is applied at the port 5, the rubber disc 8 is deflected into the position shown thereby providing a communication between the inlet port 5 to ports 10 and 11 to operate the actuators. Under these conditions of a brake application the pressure differential across the centre part of the disc 8 is such as to maintain the disc 8 firmly seated against the exhaust valve seat 7 so that there is no leakage to the exhaust port 9. However, it is to be noted also that because of this, especially in the absence of the aperture 1 2 when a reduction of the fluid pressure is made at the inlet port 5 to produce a reduction of brake effort the pressure has to be reduced sufficiently to overcome the pressure differential before any air is vented from the actuators.This gives rise to the above mentioned hysteresis and it can be more particularly significant for slower brake force reductions.

Considering now the effect of the aperture 12, upon a reduction of pressure at the port 5 to reduce the brake actuator pressure, there is an immediate commencement of pressure reduction via the aperture 1 2 so that in the case of very slow pressure reductions the actuator air may be vented entirely through the aperture 1 2 and closely follow the pressure at port 5. In the case of more rapid brake reductions the pressure at 5 may fall sufficiently to overcome the differential across the valve disc 8 so that 8 lifts off its lower seal and seals the upper seat and the actuators are then quickly released from the actuators via the vent port 9.

By virtue of the small leakage aperture 12, the movement of the actuators into a release condition may be caused to commence slightly sooner than would otherwise be the case for all rates of brake pressure reduction and an inherent hysteresis effect therefore tends to be reduced thereby.

The size of the leakage aperture 1 2 may be varied in accordance with the number of actuators which are supplied via a quick release valve according to the invention. Alternatively, it may be desirable to standardise upon a particular size of such aperture and to include one such aperture for each actuator which is supplied via the valve. By this means, an assembler being instructed as to a number of actuators will readily select and insert a valve disc having a corresponding number of such small apertures.

Claims (4)

1. A quick release valve which comprises a flexible valve member moveable between an inlet valve seat and an exhaust valve seat and via which when the flexible valve member is in closing engagement with the vent valve seat a fluid pressure path is open between an inlet port and one or more outlet ports and a leakage aperture in the valve member lies between the inlet port and the outlet port or ports.

2. A quick release valve as claimed in claim 1 wherein the aperture is predetermined in size in accordance with the volume of utilisation means to be connected to the or each outlet ports.

3. A quick release valve as claimed in claims 1 or 2 wherein the aperture is one of a plurality of standard size apertures the number of which is determined in accordance with the number of utilisation means to be connected to the or each outlet port.

4. A quick release valve substantially as described herein with reference to the accompanying drawing.