GB2153467A

GB2153467A - Vehicle braking from two positions

Info

Publication number: GB2153467A
Application number: GB08501945A
Authority: GB
Inventors: Barry Aggett
Original assignee: Bendix Ltd
Current assignee: Honeywell UK Ltd
Priority date: 1984-01-28
Filing date: 1985-01-25
Publication date: 1985-08-21
Also published as: GB8501945D0; GB8402294D0; GB2153467B

Abstract

A fluid pressure operable vehicle braking system includes a service brake circuit and a parking spring brake circuit operable by service and parking valves (1) and (5) respectively at a normal driving position as is a changeover device (17) operation of which closes a valve (13) in the spring brake circuit to prevent release thereof from the normal driving position and which changeover device at the same time enables both a valve (11) which actuates the service brake and a valve (15) via which an alternative release pressure can be applied to the spring brakes both the latter valves then being controllable from a remote position for off-road operation. <IMAGE>

Description

SPECIFICATION Remotely operable control systems for vehicles This invention relates to a remotely operable control system for a vehicle and relates especially to a system whereby a vehicle may be moved under the control of an operator positioned at an elevated working location or other such position out of reach of a normal driving position for the vehicle.

According to the present invention there is provided a remotely operable control system for a vehicle having a fluid pressure operable service brake control pressure line the pressure in which is controllable by a service brake valve for operation at a first drivers position and a parking brake control pressure line the pressure in which is controllable by a parking brake control valve for operation at the first or normal driving location and including a manually operable changeover device at the first location operable to over-ride a brake releasing pressure signal from the parking brake control valve and enable further parking brake control means located at a remote position.

In order that the invention may be more clearly understood and readily carried into effect the same will be described by way of example with reference to the single figure of the accompanying drawing which illustrates in diagrammatical form part of a remotely operable vehicle braking and transmission control system.

Referring to the drawing, this illustrates the interconnection of essential components of an airover-hydraulic braking control system for a vehicle modified by the provision of manually operable and other means to enable the braking and transmission control to be effected from a position located remotely from the normal on-road driving position for the vehicle. The system illustrated is intended for a vehicle which is provided with an elevated or other remote working position from which for off-road use a driver may wish to be able to release the brakes and to move the vehicle albeit slowly.

In the drawing, connecting lines which are shown double are fluid control lines which are either hydraulic or pneumatic and the single connecting lines are electrical connecting lines.

The basic air-over-hydraulic braking system for the vehicle consists of a dual-circuit service brake having a dual foot operable control valve 1 supplied from independent air pressure reservoirs 2 and 3, a further reservoir 4 supplying compressed air to a parking and/or secondary control valve denoted by reference 5. The dual service braking system has air-over-hydraulic master cylinders 6 and 7 outputs of which are derivable on hydraulic lines 8 and 9 for application to hydraulic slave cylinders of the vehicle brakes. The master cylinder 6 is fed from one circuit of the foot valve 1 via a double check valve 10, a second or alternative input connection to which from the reservoir 3 is via a normally de-energised solenoid valve 11. This valve is thereby ineffective for normal driving.Parking of the vehicle is effected by spring brake actuators such as the actuator 27, supplied via a further double check valve 12 and a normally open and deenergised solenoid valve 13 from the manually operable parking brake control valve 5. The release of the parking brake is therefore effected by moving the valve 5 to a position where it supplies air under pressure from reservoir 4 to the actuator. A second input to actuator 27 via the double check valve 12 is derived from an output of an on/off relay valve 14 supplied from reservoir 4 through a normally de-energised and closed solenoid valve 15.The controlling input of relay valve 14 is derived via a pressure responsive governor device 26 from reservoir 3 whereby the relay valve 14 inhibits the supply to the actuator 27 of any compressed air via solenoid valve 15 in the event of the pressure in reservoir 3 falling below a predetermined level.

In addition to the service control valve 1 and the parking brake control valve 5 together with the associated fluid pressure circuits described above and operable from the normal driving location of the vehicle, there is provided at said normal driving location a change over switch denoted by reference 17 and shown in the drawing as set to an "on-road" driving condition. The output from the switch 17 when set to the alternative position is supplied on the one hand over normally closed contacts 18 of a relay 19 to an energising coil of solenoid valve 11 and on the other hand to the energising coil of the solenoid valve 13.Furthermore, at the remote driving location there is provided a foot operable switch 20 and a manually operable switch 21 the output of which when closed, conditional on the foot switch 20 being closed, is applied on the one hand to relay 19 and on the other hand to output connection 22 for energising a slow speed transmission means of the vehicle. With the switches 17 and 20 closed, the solenoid valve 15 is also energised.

In operation of the apparatus, assuming that the changeover switch 17 is in the position shown, the driver located at the normal on-road driving position is able to drive the vehicle in a normal manner operating the service brake 1 to control the pressure in the service brake pressure control lines 23 and 25 and operating the parking brake control valve 5 to control the pressure in the parking brake control line 24, it being understood that reduction of the pressure in the line 24 below a given level results in application of brake force by the parking spring brake actuator 27.Following stopping of the vehicle in a desired position, the driver may leave the normal on-road driving position after first placing the changeover switch 17 into the position opposite to that shown thereby electrically energising the solenoid valve 13 to disconnect and vent the spring brake control line 24 so that it is now independent of the setting of the parking brake valve 5.

Operation of 17 also energises the solenoid valve 11 to by-pass the foot valve 1 and apply pressure from the reservoir 3 directly via double check valve 10 to the master cylinder 6. The vehicle is thus parked by virtue of operation of the spring brake 27 on the one hand and the air over hydraulic circuit controlled by master cylinder 6 on the other.

At the remote location, the driver is abie to place his foot on the switch 20 to thereby energise the solenoid valve 15 and apply fluid pressure from the reservoir 4 via relay valve 14 and double check valve 12 to release the spring brake 27, assuming that there is sufficient pressure in the reservoir 3 to maintain the relay valve 14 open by virtue of operation of the govenor 16. In order to move the vehicle the operator has then to close the manually operable switch 21 to on the one hand energise relay 19 to break the contact 18 and thereby interrupt the supply of air to master cylinder 6 to release the service brake and on the other hand to energise the transmission of circuit 22 whereby slow drive to the vehicle wheels can be engaged. Clearly, "forward" and "reverse" and other controls can be incorporated as required.

In the event that the fluid pressure in the reservoir 3 is below the set level for governor 26, it will be impossible for any release air pressure to reach the spring brake 27 from reservoir 4 via relay valve 14. This prevents the parking brake being released in the event that there is insufficient pressure in reservoir 3 to hold the vehicle on the associated service circuit controlled by master cylinder 6.

Claims

1. A remotely operable control apparatus for a vehicle having a fluid pressure operable service brake control pressure line the pressure in which is controllable by a service brake control valve operable at a first driver's position and a parking brake control pressure line thb pressure in which is controllable by a parking brake control valve also operable at a first driver's position and characterised by a manually operable change-over device operable at said first position and which can over-ride a brake releasing pressure signal from the parking brake control valve and enable a further parking brake control means located at a remote position.

2. A remotely operable control apparatus as claimed in claim 1, said further control means including means for energising a further fluid pressure control valve operable to apply an alternative parking brake-releasing pressure signal.

3. A remotely operable control apparatus as claimed in claim 2 including means whereby said alternative parking brake releasing pressure signal is conditional upon a predetermined stored service brake pressure being present.

4. A remotely operable control apparatus as claimed in claim 1, 2 or 3 said changeover device operating also to actuate means for applying brake pressure to the service pressure line independently of the service brake valve, which pressure is then releaseable only by the remotely positioned means.

5. A remotely operable control apparatus substantially as described herein with reference to the accompanying drawing.