GB2279416A

GB2279416A - Three port valve in a vehicle parking brake system

Info

Publication number: GB2279416A
Application number: GB9312887A
Authority: GB
Inventors: David Bramley; Peter Wayman
Original assignee: BRAMLEY DAVID ENG Ltd
Current assignee: BRAMLEY DAVID ENG Ltd
Priority date: 1993-06-22
Filing date: 1993-06-22
Publication date: 1995-01-04
Anticipated expiration: 2013-06-22
Also published as: GB9312887D0; GB2279416B

Abstract

A valve (50), in a vehicle parking brake system including a manually openable valve (16) comprises a housing (55) having first, second and third ports (61, 62, 63) and an opening; a body portion (65) rotatably mounted inside the housing (55), the body portion (65) including first and second channels (71, 72) passing therethrough; a non-return valve means (75, 76) disposed in the second channel (72) which permits fluid to flow therethrough in only one direction; a lock disposed in the opening which can be activated to rotate the body portion such that one of either the first or second channels extends from the first to the second port (61, 62), while the other of the first or second channels (71, 72) is in communication with the third port (63). For brake release compressed air flows to the brake via conduits (24, 26) and first channel (71). Brake application occurs when body portion (65) is rotated anti-clockwise (fig. 2) to vent conduits (24, 26). <IMAGE>

Description

THREE PORT VALVE The present invention relates to a three port valve and to a parking brake system for a vehicle, which includes the three port valve.

Lorries are usually equipped with two independent braking systems: an hydraulic foot brake system for braking the lorry when it is in motion; and a pneumatic, parking brake system, activated by a handbrake, which once the lorry has stopped, maintains the lorry in a stationary state.

A known parking brake system for a lorry is shown in schematic form in Figure 4.

The system comprises a compressor (not shown) which supplies compressed air via conduit 10 to a reservoir 12. The reservoir 12 is connected via a conduit 14 to a handbrake unit 16. The handbrake unit 16 includes a control member 18 actuatable by an operator into ON and OFF positions; an outlet 20; and a vent 22. The outlet 20 of the handbrake unit 16 is connected via conduit 24 to an inlet of a parking brake (not shown). The compressor and the handbrake unit together comprise a handbrake means.

The parking brake is a conventional pneumatic brake (and hence is not shown) in which a braking cylinder having a piston mounted therein is positioned at the inlet of the parking brake. The piston is coupled to braking blocks which can be brought into braking contact with the lorry wheels. The piston is biased by the applied pressure of a spring into a position at which the braking blocks are in braking contact with the lorry wheels. On application of air pressure to the inlet beyond a given superatmospheric level, the biasing action of the spring can be overcome and the piston moved such that the braking blocks do not contact the lorry wheels.

In operation, when the control member 18 is in an OFF position, the handbrake unit 16 provides an open communication path 15 between the conduits 14, 24. This permits the compressed air from the compressor to flow directly to the inlet of the parking brake and, thereby, build-up the air pressure at the inlet of the park brake to a level at which the biasing of its spring is overcome and the brake blocks are released from engagement with the lorry wheels. On placing the control member 18 into an ON position, the handbrake unit 16 is operable to obstruct the communication path 15 and so isolate the conduits 14, 24 from one another, and then to vent the compressed air in conduit 24 to atmosphere through vent 22. This brings the air pressure in the conduit 24, and hence at the inlet of the parking brake, down to atmospheric pressure and, thus, causes the parking brake to effect braking, as previously explained.

It is an object of the present invention to modify the parking brake system shown in Figure 4 so as to provide a system of greater security.

The present invention is defined in the appended claims.

Exemplary embodiments of the invention are hereinafter described with reference to the accompanying drawings, in which: Figure 1 shows a valve of the present invention in its drive state; Figure 2 shows a valve in Figure 1 in its locked state; and Figure 3 shows a parking brake system in accordance with the present invention incorporating the valve of Figures 1 and 2.

Referring to Figure 1, the valve 50 of the present invention comprises a housing 55 having first, second, and third ports 61, 62, 63, respectively, and an opening (not shown). A body portion 65 having first and second intersecting channels 71, 72 passing therethrough is rotatably mounted in the housing 55.

A key operated lock (not shown) is disposed in the opening and coupled to the body portion 65 such that on activation of the lock using a key, the body portion 65 is rotated within the housing 55 so that one of either the first or second channels 71, 72 provides a communication path between the first and second ports 61, 62, while the other channel is in communication with the third port 63.

In Figure 1, the first channel 71 provides a communication path between the first and second ports 61, 62 and the valve 50 can be said to be in its unlocked or drive state. Whereas in Figure 2, the second channel 72 provides a communication path between the first and second ports 61, 62 and the valve can be said to be in its locked state.

The second channel 72 is provided with a valve means comprising a spring 75 and a steel ball 76, which is biased to one end of the second channel 72.

Thus, it will be appreciated from Figures 1 and 2 that the end of the second channel 72 to which the steel ball 76 is biased can either be adjacent the second port 62 or the third port 63. Accordingly, in the housing 55, sealing means in the form of O-ring seals 77 have been provided at the second and third ports 72, 73. In this manner, when the ball 76 contact either of the O-ring seals 77, air is permitted to flow through the second channel 72 in only one direction.

The valve 50 has particular, but not exclusive, application to a parking brake system for a lorry. Such a system, in accordance with the present invention, is shown in Figure 3. This system is identical to the one described in the preamble of the application and shown in Figure 4 and (accordingly, similar parts have been given the same reference numeral), except that the valve 50, having an air horn 80 connected to its third port 63, is connected between the outlet of the handbrake unit 16 and the inlet of the parking brake. This connection is effected by means of conduits 24, 26, which connect the outlet of the handbrake unit 16 with the first port 61 of the valve 50, and the inlet of the parking brake with the second port of the valve 50, respectively.

When the valve 50 is its unlocked or drive state, as depicted in Figure 1, the operation of the system is identical to that described in relation to Figure 4, as the valve 50 merely presents an open communication path between the conduits 24, 26, as indicated by the arrows A. In this state, the third port 73 is always sealed by the ball 76 which is biased into contact with the O-ring seal 77.

However, when the valve 50 is in its locked state, as depicted in Figure 2, the behaviour of the system is somewhat different, as the ball 76 blocks the passage of air from the first to second ports 61, 62, but permits the passage of air from the first to third ports 61, 63 and from the second to third ports 62, 63. Thus, when the control member 18 is in an OFF position, the compressed air from the compressor is vented to atmosphere as indicated by arrows B and the air in the conduit 26 and the parking brake is vented to atmosphere as indicated by the arrows C, thereby locking the parking brakes on.

It will be understood, that if an attempt is made to drive the vehicle away with the valve 50 in the locked state, the air horn 80 is sounded continually by the compressed air from the compressor exiting the valve 50 via the third port 63, and the parking brakes remain locked on as no compressed air can pass the ball 76.

Furthermore, as an added measure of security, the system of the present invention can be provided with a further means which is responsive to the orientation of the body portion and operable to disable the ignition system of the vehicle when the valve 50 is in its locked state. This can be achieved using, for example, microswitches mounted on the body portion.

Claims

1. A parking brake system for a vehicle comprising: a handbrake means, which includes a source of compressed air; an outlet to which the compressed air is supplied; and a control member actuatable by an operator, the handbrake means being operable, when the control member is in an ON position, to isolate the source of compressed air from the outlet and vent the outlet to atmosphere and, when the control member is in an OFF position, to provide a flow path between the source of compressed air and the outlet; a parking brake having an inlet to which can be supplied compressed air from the outlet of the handbrake means, the parking brake being operable to effect braking when the air pressure at its inlet is below a given superatmospheric level; the system further comprising a lockable valve connected via first and second ports between the outlet of the handbrake means and the inlet of the parking brake, the valve including a third, ventilation port, wherein, in an unlocked state, the valve provides a flow path between its first and second ports, and in a locked state, the valve provides a ventilation path between the first and third ports and/or the second and third ports.

2. A valve comprising: a housing having first, second and third ports; a body portion rotatably mounted inside the housing the body portion including first and second channels passing therethrough; a valve means disposed in the second channel which permits fluid to flow therethrough in only one direction; a lock which can be activated to rotate the body portion such that one of either the first or second channels extends from the first to the second port, while the other of the first or second channels is in communication with the third port.

3. A valve as in claim 2, wherein the valve means comprises a spring and a ball.

4. A valve as in claim 3, wherein sealing means, co-operable with the ball, are located adjacent the second and third ports.

5. A parking brake system for a vehicle comprising: a handbrake means, which includes a source of compressed air; an outlet to which the compressed air is supplied; and a control member actuatable by an operator, the handbrake means being operable, when the control member is in an ON position, to isolate the source of compressed air from the outlet and vent the outlet to atmosphere and when the control member is in an OFF position, to provide a flow path between the source of compressed air and the outlet; a parking brake having an inlet to which can be supplied compressed air from the outlet of the handbrake means, the parking brake being operable to effect braking when the air pressure at its inlet is below a given super-atmospheric level; the system further comprising a valve as defined in any of claims 2 to 4, wherein the outlet of the handbrake means is connected to the first port of the valve and the inlet of the parking brake is connected to the second port of the valve.

6. A parking brake system as in claim 1 or 5, wherein an air-operated horn is connected to the third port.

7. A valve constructed, arranged and adapted to operate substantially as hereindescribed with reference to the Figures 1 to 3 of the accompanying drawings.

8. A parking brake system constructed, arranged and adapted to operate substantially as hereindescribed with reference to Figures 1 to 3 of the accompanying drawings.

9. A parking brake system for a vehicle comprising: a handbrake means, which includes a source of compressed air; an outlet to which the compressed air is supplied; and a control member actuatable by an operator, the handbrake means being operable, when the control member is in an ON position, to isolate the source of compressed air from the outlet and vent the outlet to atmosphere and, when the control member is in an OFF position, to provide a flow path between the source of compressed air and the outlet; a parking brake having an inlet to which can be supplied compressed air from the outlet of the handbrake means, the parking brake being operable to effect braking when the air pressure at its inlet is below a given superatmospheric level; the system further comprising a lockable valve which is operable in a locked state to disable the parking brake.