GB2116660A

GB2116660A - Anti-theft spring brake system

Info

Publication number: GB2116660A
Application number: GB08305482A
Authority: GB
Inventors: Ian Edward Davis; George Anstey Webb
Original assignee: Bendix Ltd
Current assignee: Honeywell UK Ltd
Priority date: 1982-03-12
Filing date: 1983-02-28
Publication date: 1983-09-28
Also published as: GB8305482D0

Abstract

In an air-pressure operable vehicle spring brake control circuit, control pressure for releasing spring brake actuators is supplied from a pressure control valve 3 via a security valve 7 which can be set by the driver after parking of the vehicle to divert any output pressure from the control valve 3 to atmosphere via an audible alarm device 9. The value 7 may be key- operated. <IMAGE>

Description

SPECIFICATION Parked vehicle security This invention relates to parked vehicle security and relates particularly to means for use in a fluid pressure operable braking system for preventing unauthorised release of the brakes of a parked vehicle.

Heavy commercial road vehicles are fitted with compressed air operable spring brakes on one or more wheel axles for the purposes of parking and possibly secondary braking.

A spring brake is a brake actuator which contains a heavy spring the force of which is applied to an actuator rod in response to a reduction of controlling fluid pressure to actuate wedge brake or cam brakes.

Whilst externally accessible mechanical means may be provided to permit manual release of a spring brake without the use of compressed air, normal release of a spring brake is achieved by operating a secondary or park control valve to apply air under pressure from a reservoir to a piston or diaphragm which counteracts the force of a spring.

In order to increase the security of a parked vehicle it has been proposed to include means for locking the secondary or park control valve to prevent it being moved to a release position. However, such means involves modification of the secondary or park control valve and also does not offer the possibility of generating warning signals in the event of unauthorised attempts to effect parking brake release.

The present invention provides in a fluid pressure operable vehicle braking system having a fluid pressure control valve operable to apply a fluid pressure signal to a pressure line for controlling a parking brake less than a predetermined valve of said pressure signal being operable to effect application of the parking brake and characterised by a suitable security device connected in said line and operable when set to divert fluid pressure from said line.

In order that the present 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 part of a secondary/park braking system for a heavy commercial road vehicle, Fig. 2 illustrates a security device for use in the system of Fig. 1 and, Fig. 3 illustrates an example of a secure key arrangement for a security device such as that of Fig.

2.

Referring to Fig. 1, the complete braking system for a heavy commercial road vehicle consists of a service brake system which may be provided with one or more independent circuits and a secondary park braking system. Since the present invention has no bearing on the service brake system this is not shown. In Fig. 1, there are shown two reservoirs denoted by references 1 and 2 to provide sources of fluid pressure for the secondary/park control valve 3 and for a relay valve 4 to supply a trailer. The hand control valve 3 has a first output 5 for connection to a multi relay valve which is not shown for controlling trailer brakes. A second output 6 of the hand control valve 3 is connected via a security valve 7 to an input to a spring brake secondary/park relay valve 8 the output of which is derived from the reservoir 1 and applied to spring brakes which are not shown.The security device 7 has an output connection to an air-operated audible alarm device 9 such as a simple air horn or an air operated switch to activate an electric alarm.

Referring to Fig. 2 this shows in sectional schematic manner the construction of the security device 7, the secure setting of which is shown in Fig. 2a and the normal operating position of which is shown in Fig. 2b. The device 7 is provided with three main ports, 21,22 and 23 and a small vent port 24.

Sealingly rotatable within the body there is provided a central core 25 which is provided with two air flow paths 26 and 27. In the secure setting for the device, the larger diameter paths 26 (Fig. 2a) provides a connection between ports 22 and 23 and the smaller path 27 provides a connection between the port 21 and the vent 24. Alternatively, in the normal running condition, the path 26 provides a full flow path between the port 22 and the port 21 and the path 27 provides for venting of the port 23. The device is connected in Fig. 1 as shown with the ports 21,22 and 23 connected to the relay valve 8, the output 6 of valve 3 and the warning device 9 respectively.

In normal running, operation of the hand valve 3 enables fluid pressure to be applied from the reservoir 1 via the port 22, path 26 (Fig. 2b) and port 21 to the relay valve 8 to control the secondary braking and/or parking by the spring brake. Under these conditions the supply to the warning device 9 is simply vented by port 24. With the device 7 set to the secure position of Fig. 2a however by the driver of the vehicle, after having placed the valve 3 in the park condition in which the spring brakes are vented, subsequent unauthorised operation of the hand valve 3 results in direct application of reservoir pressure to the audible warning device 9. If the valve 3 is left in the operated state position, the warning device 9 will operate continuously until the reservoir 1 is fully depleted whereupon it will not be possible to release the spring brakes until the system is recharged.

The security device 7 may be provided if desired with a suitable key which the driver can insert and set the device to the position of Fig. 2b for normal running, the key only being removeable by the driver after setting the device to the condition shown in Fig. 2a.

Various secure plug-in devices for achieving this will be readily apparent to the persons skilled in the art of security devices but one such arrangement is illustrated in Fig. 3.

In Fig. 3 a detachable turn key has a generally The drawing(s) originally filed were informal and the print here reproduced is taken from a later filed formal copy.

cylindrical body 31 and a through-pin 32 for ease of turning.

The body of the security valve 7 (Fig. 1) is provided with a protective cylindrical shell 33 into which a spigot 34 projects, the spigot being the means for turning the central core of the valve between the 'secure' and normal running positions.

The key body 31 is dimensioned to fit snugly but axially slidingly between the spigot 34 and the shell 33 and inner and outer surfaces of body 31 and spigot 34 are provided with respective flat surfaces 36 and 37 whereby body 31 is able to turn spigot 4 about its axis to set the valve.

In the interest of increased security the spigot 34 is provided with a small projection 38 which in the line-up position of flats 36 and 37 is also lined up with a corresponding groove 39 provided on the inner cylindrical surface of key body 31. Unless, therefore, the key 31 is so designed having regard to the angular position of the projection 38 the key 31 will not fit the valve.

Additionally, the key body 31 is also provided with a small projection 40 which if it matches the valve will similarly line up with a groove 41 in the inner cylindrical surface of shell 33. When, and only when, the key is fully inserted, can it be turned since only in the fully inserted position is the projection 40 able to move around another groove 42 in the inner surface of shell 33. The groove 42 also serves to.determine the extent of angular movement of the spigot 37 by the key 31 to set the valve and it will be noted that only in the initial position where 40 is lined up with 41 can the driver of the vehicle remove the key from the valve. This position is the secure position as illustrated in Fig. 2b.

By varying the position of the projections 38 and 40 and the corresponding respective grooves 39 and 41 many unique combinations can be produced in the interest of security to prevent unauthorised release of spring brakes.

Claims

1. A fluid pressure operable vehicle braking system having a fluid pressure control valve operable to apply a fluid pressure signal to a pressure line for controlling a parking brake, less than a predetermined valve of said pressure signal being operable to effect application of the parking brake, and characterised by a suitable security device connected in said line and operable when set to divertfluid pressure from said line.

2. Afluid pressure operable vehicle braking system as claimed in Claim 1 characterised by said security device being operable when set to divert fluid pressure from said line to atmosphere.

3. Afluid pressure operable vehicle braking system as claimed in claim 1 or claim 2 characterised by said security device being operable when set to divert fluid pressure from said line to a warning device.

4. Afluid pressure operable vehicle braking system as claimed in Claim 3 characterised by said warning device comprising an air-operated audible warning device.

5. A fluid pressure operable vehicle braking system substantially as described with reference to Fig. 1 of the accompanying drawings or Figs. 1,2 and 3 of the accompanying drawings.