GB2453562A

GB2453562A - Air braking system having a failsafe operating pressure and reset valve

Info

Publication number: GB2453562A
Application number: GB0719817A
Authority: GB
Inventors: Brian Ross
Original assignee: AVALCO Ltd
Current assignee: AVALCO Ltd
Priority date: 2007-10-11
Filing date: 2007-10-11
Publication date: 2009-04-15
Anticipated expiration: 2027-10-11
Also published as: GB2453562B; GB0719817D0

Abstract

An air braking system 1 for use with a vehicle which system has service braking and handbrake operations and includes a compressor activated when the engine is started which feeds pressurised air to the system; an operating valve 6 set to a failsafe operating pressure for the system and a reset valve 11 that is in direct communication with the operating valve 6 so that when the reset valve 11 is opened to reset the system 1 pressurised air is fed directly via the reset valve to one side of the operating valve at a pressure sufficient to reset the operating valve to an operational condition. The operating valve 6 may be a spring activated spool valve. Preferably air pressure of 4 bar is needed to operate the valve 6. The braking system may also comprise a door open alarm. The reset valve 11 may be a push button.

Description

Braking System This invention relates to a braking system for a vehicle, and in particular, to an air braking system for a lorry.

In order to provide a heavy vehicle, such as a lorry, with an easily controllable, braking system compressed air is used to activate the operation of the components of the braking system. These are generally referred to as air brakes, and with this type of system a compressor is included in the circuit, which is driven from the engine of the vehicle.

Air brakes fulfil three important functions in the operation of the vehicle. Specifically they can act as a service brake, parking brake and emergency brake for a vehicle. The service brake is operated by the action of the driver of the vehicle on the brake pedal during normal driving of the vehicle. The parking brake is activated when the vehicle is parked. The emergency brake activates when there is a brake failure in the vehicle and uses components of the service braking system and the parking brake system to bring the vehicle to a stop.

Conventional air braking systems have been in use for a large number of years. There have been a few problems with these systems and these have to come to fore in recent times. One of the major problems is that of a rollaway which is where the lorry literally rolls away because the park brake has not been applied, for example on an incline. This is not much of a problem when the driver is in the cab as he can simply apply the necessary brake and arrest the vehicle. However where the driver is not in the cab it is a major problem as the vehicle can rollaway and not be stopped safely. This later situation happens all to often because the driver has failed to apply the handbrake before leaving the cab.

The present invention is concerned with providing a braking system in which the above mentioned problem is at least alleviated if not overcome.

In accordance with the present invention there is provided an air braking system for use with a vehicle which system has service braking and handbrake operations and includes a

I

compressor activated when the engine is started which feeds pressurised air to the system; an operating valve set to a failsafe operating pressure for the system and a reset valve that is in direct communication with the operating valve so that when the reset valve is opened to reset the system pressurised air is feed directly via the reset valve to one side of the operating valve at a pressure sufficient to reset the operating valve to an operational condition.

In a preferred arrangement of the present invention the operating valve preferably comprises a spring activated spool valve that the pressurised air acts against to move the valve to an operating position. Preferably, a pressure of around 4 bar is needed to move the valve to an operating position.

The braking system may alternatively or in addition include a door open alarm that incorporates a logic valve arrangement.

The system also includes a door open alarm system.

The reset valve may be operated by a simple push button.

The invention will now be illustrated, by way of description of an example as shown in the attached drawing, in which: Figure 1 shows a schematic representation of a braking system made in accordance with the present invention.

Now referring to Figure 1 of the drawings there is shown a representation of a braking system 1 incorporating a system in accordance with the present invention. The braking system as shown includes a parking braking system, and an emergency braking feature.

There are also certain alarm features in the system as well.

This type of system is intended for use on the trailer section of an articulated lorry although as will be well appreciated by those skilled in the art it can be used on other vehicles including fixed bed lorries.

The system I is connected to an air compressor (not shown) and reservoir tank (not shown) from which a mains line 2 feeds high-pressure air into the system.

The mains line 2 is connected to a main spool valve 6. The main spool valve 6 includes a spring 3 which acts to maintain and restore the valve 6 to a closed flow position in which the system is deactivated and the braking system is not active and the hand brake is in the failsafe applied position. The spring 3 is sized and gauged so that a pressure of approximately 4.5 bar is required across the valve 6 to move the spool from the closed to the open flow position. When the valve 6 is in the open flow position the handbrake can be released as the valve 7 becomes active.

Further the system is designed so that on start up of the vehicle until the system has been properly activated and primed the valve 6 will remain in the flow closed position so the handbrake part of the system remains applied with the parking brake system being held in the applied position.

A line 4 feeds the outlet side of the handbrake spool valve 7 connecting in the remaining parts of the system.

A first branch line 8 connects the line 2 to one side of an alarm spool valve 9 that has a failsafe in the closed position.

A second branch line 10 connects the line 2 to one side of a reset valve 11 that is normally in the closed position and operated by button 12. This part of the system is the reset for the system. When the system pressure falls below 4 bar upon start up of the vehicle the system needs to be reset and primed for operation.

A third branch line 21 is located between the valve 6 and the handbrake spool valve 7 and connects the main line 2 to the Visiwink and logic valve 22.

The line 4 connects to one side of a door open alarm valve 13. The door open alarm valve 13 is set so that when the door of a cab is closed the valve 13 is in the closed position and when the door is open the valve 13 is in an open position connecting to an alarm system. Further when the door is opened the valve 13 also moves to the open position connecting pressurised air to the alarm system. The output side of the valve 13 is connected by line 14 to one input of a logic valve arrangement 15. The output from the logic valve 15 is connected by line 16 to a spool valve 9.

A second logic valve 17 is provided in this part of the system. The valve 17 is connected on the input side to the line 4 via a branch line 18, and to line 19 that feeds to an air horn alarm device. On the output side the valve 17 via line 20 connects to the second input of the logic valve arrangement 15.

In the particular arrangement shown the valve 15 is an "or" type logic valve having two inputs and with this type of valve the valve will be open if a signal is received from either of the inputs. The valve 17 is an "and" type logic valve having two inputs and this type of valve will only be open if a signal is received by both of the inputs to the valve.

The output side of the reset valve 11 is connected to one of the inputs of a second logic valve 22. The second input of the logic valve 22 is connected to a line 23 that feeds to the Visiwink in the cab of the vehicle. The output of the logic valve 22 is connected via line 24 to pilot of the valve 6.

The branch line 21 of the line 2 is connected to the line 23.

The system shown in the drawing is shown with the handbrake in the activated position and therefore applied with the valve 7 in the closed position. Further the door alarm valve 13 is shown in the position with the door opened so the valve is in the open position.

When the vehicle is about to be started, having been left for an amount of time the system is depressurised and the valves 6, 7, 9 & 11 are in the closed positions. Further provided the driver's door is closed the valve 13 will also be in the closed position. This is the standard start up position and configuration for the system at start up.

Consequently when the vehicle is started the compressor charges the system with compressed air to the operating pressure of around 8 to 10 bar, filling the reservoir tank with pressurised air. However the air braking system remains in an off position.

Specifically the service braking system is not activated and the handbrake part of the system remains in the applied position. The valve 6 remains closed.

In order to move the system to a brake activate position where the service braking system is active the system has to be manually activated by the driver to reset and prime the system.

The system is reset and primed by depressing the button 12, positively moving the valve 11 from the closed to the open position. Pressurised air is transmitted via the valve 22 to the valve 6 building a pressure to act against the valve bias (4 bar is envisaged for the system of the example) and when this is achieved moving the spool of valve to a flow open position and the system recharged with pressurised air.

Further the valve 7 now has a feed of pressurised air and can be moved from the closed to the open position allowing removal of the handbrake. In turn the line 4 and the systems described above which feed from this line are charged.

Whilst the system pressure is maintained above the pressure rating of the spring 3 of the valve 6 (above 4 to 4.5 bar) the valve 6 remains open and the system remains operational.

If the driver attempts to start the system with his door open, or alternatively opens his door with the system running, and the park brake his not applied valve 13 will be out, or moved to, the open position allowing pressurised air into the line 14 and to the logic valve arrangement 15. The valve 15 will allow air to be communicated to the valve 9 via the line 16 moving the valve 9 to an open position and so sound the air horn alarm.

In addition the logic valve 15 will receive a signal that is transmitted to the valve 17 so that the line 19 is opened to the flow of pressurised air also. Therefore, simply closing the door, and so closing the valve 13 cannot turn off the air horn, as the flow through the line 19 will be maintained. In order to turn the air horn off the service brake has to be applied.

If there is a pressure failure of the system during operation there will be a loss of pressure in the system. When the pressure on valve 6 falls below 4 bar the spring moves the spool of the valve 6 to the closed position and the pressure loss will be detected via the line 21 and conmiunjcated to the Visiwink. In addition the closing of the valve activates the handbrake system and the brakes are applied.

However with the conventional air braking systems in lorries the braking system also includes a failsafe system that will activate the brakes when the pressure falls below a certain level, normally in the region of 5 or 5.5 bar. Therefore this system will not unduly activate the brakes but acts to reinforce the emergency application of the braking system in the normal characteristic operation of the braking system.

The advantage of the present system relates to the simplification of the system around the reset and recharging of the system. Conventional systems include an additional valve arrangement so that when the braking system is to be reset the reset button is depressed moving a first valve to an open position and this opens the feed to enable the equivalent valve 6 to be moved to the open and set position. In effect the reset is isolated from the equivalent valve 6. In addition in the conventional systems the air horn is isolated in the event of pressure failure in the system by valves either side of the feed to the air horn and this has also been simplified in the current system.

Claims

Claims 1 An air braking system for use with a vehicle which system has service braking and handbrake operations and includes a compressor activated when the engine is started which feeds pressurised air to the system; an operating valve set to a failsafe operating pressure for the system and a reset valve that is in direct communication with the operating valve so that when the reset valve is opened to reset the system pressurised air is feed directly via the reset valve to one side of the operating valve at a pressure sufficient to reset the operating valve to an operational condition.
2 An air braking system as claimed in claim 1 wherein the operating valve comprises a spring activated spool valve in which pressurised air acts against the spring to move the valve to an operating position.
3 An air braking system as claimed in claim 2 wherein a pressure of around 4 bar is needed to move the valve to an operating position.
4 An air braking system as claimed in any preceding claim wherein the braking system includes a door open alarm that incorporates a logic valve arrangement.

An air braking system as claimed in claim I wherein the reset valve may be operated by a simple push button.