GB2472461A

GB2472461A - Park brake valve

Info

Publication number: GB2472461A
Application number: GB0913937A
Authority: GB
Inventors: Matthew Fry; Colin Ross
Original assignee: Knorr Bremse Systeme fuer Nutzfahrzeuge GmbH; Knorr Bremse Systems for Commercial Vehicles Ltd
Current assignee: Knorr Bremse Systeme fuer Nutzfahrzeuge GmbH; Knorr Bremse Systems for Commercial Vehicles Ltd
Priority date: 2009-08-07
Filing date: 2009-08-07
Publication date: 2011-02-09
Anticipated expiration: 2029-08-07
Also published as: EP2462012A1; WO2011015831A1; EP2462012B1; GB2472461B; HUE033680T2; GB0913937D0

Abstract

A park brake valve arrangement for a trailer of a commercial vehicle having a main air supply line 1 which supplies a manually operable shunt valve 12 connected to a first and second two-way valves 13, 14. The first two-way valve is connected to a park valve 15 and an exhaust 3. The second two-way valve also receives an input from a trailer based reservoir, which input is also connected with an output of the shunt valve 12 and the inlet of the first two-way valve 13. The outlet of the second two-way valve is connected to an electrically biased two way valve 16 adapted to control the park valve 15 which park valve 15 is connected to the spring brakes 2 of the trailer and the exhaust 3. When the arrangement is in the Drive position (fig 2), the main line is pressurized and there is an electrical connection from the tractor to the EBS, the shunt valve 12 is connected to both two-way valves 13, 14. The outlet of the first two way valve 13 is connected to the park valve 15, which supplies pressure to the spring brakes 2. The spring brakes are biased into the on position so that the spring brakes are held in the off position when pressurised.

Description

Trailer Park Brake Valve Arrangement The invention relates to a park brake valve arrangement for a trailer of a commercial vehicle tractor/trailer.

Modem braking systems for tractor/trailer units are invariably fluid-operated, the fluid typically being air, for economic and practical reasons. A pressunsed air supply is generated by an engine-driven compressor on the tractor which supplies air to the trailer through a supply line, so that when the service brake is applied by the driver, the brakes on the tractor and the trailer are applied by the supply of compressed air to the individual wheel brakes. It is also known to have a spring-applied brake system in which the braking force is generated by a spring in a spring actuator, which is biased in a direction to apply the brake. In normal operation, the brake is held in the off position by the application of compressed air acting counter to the braking force of the spring. In an emergency, if the compressed air supply is lost, the spring actuator automatically applies the brake on the trailer to bring the trailer to a standstill. An alternative arrangement is also known in which in an emergency, if the compressed air supply is lost, pressure from the reservoir is applied to the individual wheel brakes to bring the trailer to a standstill.

It is also known for such trailers to have a parking brake in which the braking force is supplied by a spring actuator, the brake being normally held off by an air supply. The control valve for the parking brake is operable manually to vent the valve to atmosphere and hence apply the parking brake. In use, when parking a trailer, the driver has to de-couple the supply line connection between the tractor and trailer and also an electrical connection through which electrical components on the trailer are connected to the tractor electrical supply. The correct procedure at this stage is that the driver should manually operate the parking brake valve to ensure that the parking brake is applied. The driver can then uncouple the pivotal connection between the tractor and trailer to enable the tractor to be driven away leaving the trailer in the parked condition.

It will be apparent from the earlier description that when the supply line is decoupled from the trailer, the trailer brakes are automatically applied by the compressed air contained in the reservoir on the trailer or the release of pressure from the spring brakes. As in this condition, which equates to the emergency braking mode, there is an open connection between the reservoir and the brakes, the brakes are held on and the trailer held stationary, that is braked, by these means.

The unintended consequence of this is that drivers often rely on the braking achieved in this way when parking a trailer and, either through laziness, inadvertence or a reluctance to get dirty, because the valves are often situated in an exposed, low down, position on the trailer, they do not operate the manual valve to apply the park brake. This can have dangerous consequences which have led to fatalities.

The brakes are held on in this "emergency mode", and the trailer held stationary, by the compressed air in the system but, inevitably, there is a slight leakage of air in the system, with the result that the air gradually leaks out until the brakes are no longer held on, so that where the emergency valve applies the service brakes the trailer can roll away. A further dangerous situation can arise when a driver re-couples a tractor to a trailer which has been parked in this way. As soon as the driver couples the supply line to the trailer, the valve arrangement on the trailer is reset to cancel the emergency braking mode, with the result that the trailer is no longer braked and can either roll away backwards, breaking the supply line, or can roll forwards with the risk of crushing the driver between the trailer and the tractor cab. Furthermore, if the driver has left the tractor, without putting on the tractor parking brake, as soon as the supply line is connected the emergency brake is released and the whole tractor/trailer can roll away.

GB2417764 discloses a trailer park valve in which the parking brake is moved to a locked condition when the pneumatic and the electrical connection are removed. To release the valve from the locked position to the drive position, the driver has to manually reconnect both the electrical and pneumatic connections. Whilst this valve represents a significant safety enhancement over the prior art systems, the valve construction is different to the standard park and shunt valve arrangements in use.

The present invention therefore seeks to provide an alternative valve arrangement According to the invention there is provided a park valve arrangement for a trailer for a commercial vehicle having a main air supply line, electrical connection and a reservoir, which trailer is provided with spring applied brakes adapted to be held in an off position by pneumatic pressure, wherein the valve arrangement controls the application of pressure to the spring brakes such that when the main air supply is absent or disconnected the spring brakes are applied, wherein if the electrical connection is present, the spring brakes are applied but park control released, wherein if the electrical connection is disconnected, the spring brakes are applied but park control set such that the valve is operable with the main supply and electrical connection disconnected to enable the spring brakes to be released.

Preferably, when the main supply is exhausted and an electrical connection present, air pressure is supplied from the reservoir to the inlet of the first two way valve and the inlet of the second two way valve, such that the electrically biased two valve provides a control signal to the park valve enabling this to remain in the Drive position.

Preferably, when the electrical connection is disconnected, the electrically biased two way valve moves to a second position, opening its outlet and supplying a control signal to the park valve causing it to move to a second position in which the pressure to the spring brakes is exhausted via the exhaust, thereby the spring brakes being applied and the park control being set.

In the known systems if the control (or "yellow") line from the truck to the trailer is cut or open, the truck brake system will detect this condition and the truck brake system will attempt to apply the trailer brakes via the service (or "red") line. In the known systems, if there is also a loss of pressure in the service line, which may indicate a break away of the trailer, the park brake is automatically set. The park brake then remains set and continues to brake until it is manually reset, which can cause problems if the pressure is returned to the service line. The present invention advantageously provides that if the control line is cut or open, then the electrical connection ensures that the brakes are applied but if the service line pressure is released then the trailer brakes will still work, thereby ensuring compliance with Regulation ECEI3.

An exemplary embodiment of the invention will now be described in greater detail with reference to the drawings in which: Fig. I shows schematically the brake valve circuit diagram; Fig. 2 shows the valve arrangement in the drive position; Fig. 3 shows the valve arrangement with the automatic brake applied; Fig. 4 shows the valve arrangement with the trailer disconnected from the tractor; Fig. 5 shows the valve arrangement set for manoeuvring a parked disconnected trailer.

Figure 1 shows schematically a valve arrangement 10 in which air is supplied from a main supply line 1 to a manually operable shunt valve 12. The outlet of the shunt valve 12 is passed to an inlet of a two way valve 13 via a non-return valve 18, which two way valve 13 is pressure biased with a non-return, and to the control port of a pressured biased two valve 14. A first outlet of the valve 13 is connected to an inlet of a park valve 15 and a second outlet of the valve 13 is connected to an exhaust 3. The two way valve 14 also receives an input from a trailer based reservoir, which input is also in pneumatic connection with an outlet of the shunt valve 12 and the inlet of the valve 13. The outlet of the two way valve 14 is connected to an inlet of an electrically biased. two way valve 16, the outlet of which provides the pneumatic control signal to the park valve 15. A first outlet of the park valve is connected to the spring brakes of the trailer and a second outlet of the park valve 15 is connected to the exhaust 3.

Figure 2 shows the valve arrangement in the Drive position, in which the main supply line I is pressurised and the ISO 7638 electrical connection from the tractor to the trailer EBS is connected. In this condition, the shunt valve 12 is in fluid connection with the inlet of two way valve 13 and supplies a control signal to the control input of the two way valve 14. The outlet of the two valve way 13 is in fluid connection with the inlet of the park valve 15, which supplies pressure to the spring brakes 2. As the spring brakes are biased into the on position, this pressure holds the spring brakes off. The main supply line is also in fluid communication with the reservoir and accordingly can charge this as necessary.

The control signal supplied to the valve 14 ensures that the outlet of the valve 14 is closed and accordingly the valve 16 is unpressurised and there is no control signal to the park valve 15.

Figure 3 shows the valve arrangement when the automatic brake is applied. In this condition, the main supply line is exhausted but the electrical connection from the ISO 7638 connector is still present. This condition could, for example, indicate an incipient break away. In this condition, the spring brakes are applied but the park control remains released. The output of shunt valve 12 is depressurised and hence the control signal to the two way valve 14 is changed, causing this to change position. In this condition, air pressure is supplied from the reservoir to the inlet of the two way valve 13 and the inlet of the two way valve 14. The fluid connection between the two way valve 14 and the electrically biased two way valve 16 is pressurised but the outlet of the two way valve 16 is closed so that the control signal to the park valve 15 remains the same as in the Drive position. As the pressure on the inlet of the two way valve 13 is reduced, the pressure bias of this valve causes it to move to a second position removing the air supply to the park valve 15, which is accordingly depressurised via two way valve 16 to the exhaust 3. There is accordingly no pressure on the outlet of the park valve 15 and hence no pressure to withhold the spring brakes, which are then applied. In this condition the park valve 15 is not directly connected to the exhaust and so the park control remains released.

Figure 4 shows the valve arrangement when the pneumatic connection trailer has been completely disconnected from the tractor. This could occur, for example, when the trailer is parked or if it has broken away from the tractor. In this condition, the main supply line is exhausted and the 1S07638 is disconnected so that the trailer has no electrical supply.

This results in the spring brakes being applied and the park control being set. In the absence of the main supply line, the output of shunt valve 12 is depressurized and the control signal to the two way valve 14 is changed from the Drive position, causing this valve to change position. The inlet of the two way valve 14 is still pressurized from the reservoir and the outlet supplies a pressure to the valve 16. However, as the electrically biased two way valve 16 now no longer receives an electrical control signal, it moves to a second position, opening its outlet and supplying a control signal to the park valve 15 causing it to move to a second position in which the pressure to the spring brakes is exhausted via the exhaust 3 and the connection to the two valve 13 is closed, although the outlet of this valve also remains depressurized. When the pneumatic connection is restored, the spring brakes remain applied until they are manually reset.

Figure 5 shows the valve in the condition for manoeuvring as it is sometimes necessary to move a parked disconnected trailer when a tractor is not present, for example in a loading depot. In this condition the main supply line is exhausted and the 1S07638 is disconnected so that the trailer has no electrical supply. The shunt valve 12 is manually actuated to the position shown in Figure 5, in which it receives a supply pressure from the reservoir and can supply a control pressure to the two way valve 14. Supplying this control pressure causes the valve 14 to close its outlet and remove the pressure in the conduit to the valve 16, which in turn removes the control signal from the park valve 15. This allows the valve to be moved to the position it has in the Drive position and a pressure is then supplied via the two way valve 13 to the valve 15 and to the spring brakes. This supply of pressure to the spring brakes biases them to the off position so that it becomes possible to move the trailer.

The valve arrangement of the invention has the advantage over known alternatives in that it can be offered as an add-on to other products and so need not be included in markets where this type of valve is not desired or required.

Claims

Claims 1. A park valve arrangement for a trailer for a commercial vehicle having a main supply line, electrical connection and a reservoir, which trailer is provided with spring applied brakes adapted to be held in an off position by pneumatic pressure, wherein the valve arrangement controls the application of pressure to the spring brakes such that when the main supply is absent or disconnected the spring brakes are applied, wherein if the electrical connection is present, the spring brakes are applied but park control can be released, wherein if the electrical connection is disconnected, the spring brakes are applied but park control set such that the valve is operable with the main supply and electrical connection disconnected to enable the spring brakes to be released.
2. A park valve arrangement according to Claim 1, wherein the arrangement comprises a shunt valve adapted to receive air from the main supply line, which shunt valve is connected to a two way valve, which two way valve is connected to a park valve, which park valve is adapted to provide park control.
3. A park valve arrangement according to Claim 2, wherein the shunt valve is further connected to a second two way valve in parallel to the first two way valve, which second two way valve is connected with an electrically biased two way valve, the output of which is connected to the park valve.
4. A park valve arrangement according to any one of Claims 1 to 3, wherein the shunt valve can be connected to the reservoir.
5, A park valve arrangement according to any one of Claims ito 4, wherein, when the main supply is exhausted and an electrical connection present, air pressure is supplied from the reservoir to the inlet of the first two way valve and the inlet of the second two way valve, such that the electrically biased two valve provides a control signal to the park valve enabling this to remain in the Drive position.
6. A park valve arrangement according to any one of Claims ito 5, wherein when the electrical connection is disconnected, the electrically biased two way valve moves to a second position, opening its outlet and supplying a control signal to the park valve causing it to move to a second position in which the pressure to the spring brakes is exhausted via the exhaust, thereby the spring brakes being applied and the park control being set
7. A park valve arrangement according to Claim 4, wherein the shunt valve supplies a pressure from the reservoir to the second two way valve, which valve removes the control signal from the park valve, thereby enabling the park valve to be moved to a Drive position.
8. A park valve arrangement according to Claim 5, wherein in the Drive position a pressure is supplied to the spring brakes to bias them to the off position.
9. A park valve arrangement substantially as described herein, with reference to, and as illustrated in, the accompanying drawings.