The invention relates to a parking brake for a vehicle, in particular a parking brake valve for controlling a parking brake actuator of a trailer. The invention further relates to a braking system comprising the parking brake valve, a vehicle, in particular a trailer comprising the parking brake valve or the braking system, as well as a vehicle combination comprising the trailer. Moreover, the invention relates to a method for controlling a parking brake.

A parking brake is known in the state of the art. A parking brake for vehicles comprises at least one parking brake actuator, which is preferable a spring-loaded actuator. In particular, on the rear axle of a vehicle spring-loaded actuators are integrated in the service brakes to form so-called tristop brake cylinders. Furthermore, a parking brake comprises an air supply, which provides a pneumatic pressure for the parking brake actuator. Spring-loaded actuators, forming the parking brake actuator, are generally configured to close without pneumatic pressure by a force of a spring and to open against the force of the spring when a pneumatic pressure is applied by compressed air exceeding a certain pressure threshold.

Consequently, for opening the spring-loaded actuators, a source for compressed air must supply compressed air to the actuators and for closing the actuators compressed air must be discharged to decrease the pneumatic pressure of the actuators. Thus, the pneumatic pressure in the spring-loaded actuator must be controlled, which is done by a parking brake valve.

According to the state of the art, the described parking brake is used on heavy tractors, or trucks, and trailers. When a tractor is coupled to a trailer, a parking brake of the trailer is released as soon as a pneumatic pressure supply line of the trailer is pressurized by compressed air supplied by the tractor. If the trailer is parked on a slope, the trailer may move, which may lead to safety issues, in particular for the driver. The reason for this is that a pneumatic pressure, which is provided to the trailer via the pneumatic pressure supply line when connecting a trailer interface to a tractor, is provided through a parking brake valve to the parking brake actuators. Consequently, the spring-loaded actuator opens and the parking brake is released.

Therefore, it is known in the state of the art to provide a safety mechanism on the parking brake valve. The safety mechanism comprises a button on the parking brake valve, which has, after connecting the pressure supply line from the tractor to the trailer, to be pushed or pulled manually to open the parking brake valve which blocks a connection in the supply line. By pushing or pulling the button the parking brake is released. However, despite this security button, safety issues are not completely eliminated. In the case, for example, that a draw bar of a trailer is not correctly connected to a hitch of the tractor, remaining unnoticed by the driver, the trailer might move without being under control by the driver when the pneumatic supply line is connected and the button is pushed or pulled.

It is therefore desirable to address at least one of the above problems. In particular, the object of the invention is to find a device and a method to increase safety when the parking brake of a vehicle is released. A further object of the present invention is to propose an alternative to the state of the art.

In accordance with the invention, the object is solved in a first aspect by a parking brake valve for a vehicle according to claim 1 .

In accordance with the invention, a parking brake valve for a vehicle, in particular a trailer, is proposed, which comprises a supply port for connecting to a pneumatic pressure supply line of a tractor. Furthermore, the parking brake valve comprises a delivery port for controlling a parking brake actuator, in particular with a spring-loaded actuator. Furthermore, the parking brake valve comprises an exhaust port, which may in particular be an outlet connected with environmental pressure.

Furthermore, the parking brake valve comprises a main valve, which has a first position and a second position. In the first position, an internal line of the parking brake valve is connected to the delivery port for providing a pneumatic pressure at the internal line to the delivery port. In the second position of the main valve, the exhaust port is connected to the delivery port for discharging a pneumatic pressure at the delivery port to the exhaust port. In particular, in the second position of the main valve, the parking brake is applied and the first position of the main valve serves to release the parking brake actuators.

Furthermore, according to the invention, the parking brake valve further comprises an internal valve. The internal valve comprises a first position and a second position. In the first position of the internal valve, the supply port is connected to the internal line for providing the pneumatic pressure at the pneumatic pressure supply line of a tractor to the internal line when a pneumatic pressure supply line is connected to a supply of compressed air of a tractor. Furthermore, in the second position of the internal valve, the connection between the internal line and the supply port is blocked. Moreover, the internal valve comprises a pilot port for connecting to a pneumatic pressure control line of a tractor. In particular, the pneumatic pressure control line of a tractor is a line which provides no pneumatic pressure until a driver applies a foot brake pedal on the tractor. When a force is applied to the foot brake pedal, this force results in an increased pressure on the pneumatic pressure control line. However, the internal valve is arranged to switch from the second position to the first position when a pneumatic pressure above a switching pressure threshold value is provided on the pilot port.

Consequently, for releasing the parking brake of a trailer, two sub-valves of the parking brake valve need to be in defined positions. When the two sub-valves, namely the main valve and the internal valve, are in the defined positions, they allow the pneumatic pressure provided at the supply line being forwarded to the brake actuators. However, although a driver brings the main valve into a position to connect the internal line to the delivery port, the internal valve stays in a blocking position, namely the second position, until the driver pushes the foot brake pedal. In fact, pushing the foot brake pedal leads to switching the internal valve from the second position to the first position. Thus, the supply port of the parking brake valve is connected to the delivery port via the main valve, the internal line and the internal valve. Consequently, it is ensured that the driver is in the driver cabin when the parking brake is released and thus, even when the trailer is parked on a slope and the draw bar of the trailer is not connected or incorrectly connected to the hitch, a trailer moving away out of control of a driver cannot hurt the driver. Furthermore, the parking brake valve combines the function of two sub-valves in one housing, wherein only one button is provided to control the main valve and wherein further, the internal valve is switched automatically.

According to a first development of the invention, the internal valve comprises an internal pilot port, which is connectable to the delivery port via an internal pilot line. Moreover, the internal valve is arranged to hold the first position, when a pneumatic pressure above an internal switching pressure threshold value is provided on the internal pilot line.

By connecting the internal pilot port to the internal pilot line, the first position of the internal valve is held after the pneumatic pressure above a switching pressure threshold value provided on the pilot port is reduced below the switching pressure threshold value. The pneumatic pressure on the internal pilot line is received from the delivery port and thus, the first position will be held in case a sufficient pressure, namely a pressure above the internal switching pressure, is provided on the delivery port via the main valve and the internal valve from a tractor.

Consequently, it is ensured that, when the driver stops operating the foot brake pedal, the internal valve stays in the first position and the parking brake still remains released independently of the foot brake pedal position and thus independently of the pneumatic pressure at the pneumatic pressure control line of a tractor. This function can be called self-holding function.

However, this development enables extended safety for the driver. Namely, if the driver couples the trailer to the tractor, gets back into the cabin and depresses the foot pedal, the internal valve is transferred to the first position. If the driver then realizes that the main valve is not yet in the first position and gets out again to change this position, without the present development the brakes would be released immediately after the main valve has been transferred to the first position. This is prevented because the selfholding function is only activated when pressure is also provided by the main valve at the delivery port.

According to a further development, the internal valve is further arranged to connect the delivery port to the internal pilot line in the first position for providing the pneumatic pressure at the delivery port to the internal pilot port only. In the second position, the internal valve is arranged to block the connection between the delivery port and the internal pilot line.

Consequently, when the parking brake valve provides a release mode in which pneumatic pressure is provided to the delivery port by a reservoir, the internal valve will not be held in or transferred to the first position. After changing from a release mode to a park mode, the internal valve will not be transferred from its defined rest position, namely the second position.

According to a further development, the internal valve is arranged to connect the internal pilot line to the exhaust port or a further exhaust port in the second position of the internal valve. Thus, in the second position the self-holding function is safely deactivated because the internal pilot port is vented.

According to a further development, the internal valve is a 5/2-valve. The internal valve comprises a first input, which is connected to the exhaust port. Furthermore, a second input is connected to the supply port and a third input is connected to the internal pilot line. Moreover, a first output is connected to the internal line and a second output is connected to the delivery port. In the first position the second input is connected to the first output, the third input is connected to the second output and a first connection between the second input and the first output is connected to a second connection between the third input and the second output via a check valve. The check valve is directed to block a flow from the first connection to the second connection and to allow a flow from the second connection to the first connection.

Furthermore, in the second position, the first input is connected to the first output and the third input is connected to a third connection between the first input and the first output via a further check valve. The further check valve is directed to allow a flow from the third input to the third connection and to block a flow from the third connection to the third input. The terms input and output have been chosen here to better distinguish the ports of the internal valve. However, the terms do not limit the function of the ports to one fluid flow direction. Rather, individual or all ports can also allow bidirectional fluid flow. This development describes a space-saving realization of the internal valve, which provides comprehensive functions.

According to a further development of the invention, the pilot port of the internal valve is connected to the pneumatic pressure control line. Furthermore, the internal valve comprises an internal pilot port wherein the internal valve is arranged to hold the first position when a pneumatic pressure above an internal switching pressure threshold value is provided on the internal pilot port, wherein the internal pilot port is connected to the internal line.

Consequently, by connecting the internal pilot port to the internal line the first position of the internal valve is held after the pneumatic pressure above a switching pressure threshold value provided on the pilot port is reduced below the switching pressure threshold value. This occurs because after providing the pneumatic pressure above a switching pressure threshold value on the pilot port for switching the internal valve from the second position to the first position, the internal line is connected to the supply port and thus the pneumatic pressure of the pneumatic pressure supply line of a tractor is provided to the internal line. By connecting the internal pilot port to the internal line, a pneumatic pressure is provided on the internal pilot port of the internal valve and serves to hold the internal valve in the first position. However, this development is an alternative to the above-mentioned development which on the one hand realizes the self-hold function. On the other hand, this development can be realized with a simplified implementation of the internal valve, in particular with a 3/2-valve. However, this development accepts that if the driver realizes that the main valve is not yet in the first position, gets out again to change this position after coupling the trailer and depressing the foot pedal the brakes would be released immediately after the main valve has been transferred to the first position. This occurs because the self-holding function remains activated when pressure is provided by internal line.

According to a further development, the internal valve comprises a reset means, in particular a reset spring. The reset means in the parking brake valve is arranged at the internal valve to put the internal valve in the second position, when a pneumatic pressure on the pilot port or the internal pilot port is below the switching pressure threshold value or below the internal switching pressure threshold value, respectively. Consequently, the connection between the supply port and the internal line is blocked when the pneu- matic pressure on the pneumatic pressure supply line drops below the switching pressure threshold value or the internal switching pressure threshold value. In this case, when the internal valve switches to the second position, the internal line is preferably connected to a further exhaust port or the exhaust port by the internal valve. Consequently, without applying a force to the foot brake pedal independently of increasing the pneumatic pressure on the supply port, the internal valve will still be closed and the parking brake is applied. According to a special development, the internal valve comprises a reset means to put the internal valve in the second position, when a force on the pilot button is received to switch the main valve to the second position.

According to a further development, the parking brake valve comprises a reservoir port for providing a pneumatic pressure to the main valve. The main valve comprises a third position in which the reservoir port is connected to the delivery port.

Consequently, independent from the position of the internal valve, the main valve, when providing and connecting a pneumatic pressure reservoir to the braking valve, can provide a pressure to release the parking brake without the need of a tractor. If a pneumatic pressure is provided on the reservoir port, by switching the main valve to the third position, a pneumatic pressure is provided to the delivery port for releasing the parking brake by piloting the parking brake actuator.

A trailer can thus be maneuvered without the help of an external pneumatic pressure source provided by a tractor.

According to a further development, the parking brake valve comprises a pressure actor, in particular a pneumatic cylinder with a piston, wherein the pressure actor, in particular the cylinder, is connected to the supply port. The pneumatic cylinder is arranged to push, in particular by the piston, the main valve from the third position to the first position when a pneumatic pressure above a supply pressure threshold value is provided by the supply port of the parking brake valve. Consequently, when the main valve is in the third position in a release mode for maneuvering the trailer without a tractor and the trailer will be coupled to the tractor, by connecting the supply port to the pneumatic pressure supply line the main valve automatically is pushed to the first position and thus if the driver applies the foot brake pedal to switch the internal valve, the parking brake stays released and is ready for a drive mode. According to a further development, the main valve comprises a pilot button for switching from any of the first position, the second position and the third position of the main valve to any of the first position, the second position and the third position of the main valve. With the pilot button, which is preferably arranged with reset means for fixing the position of the main valve, the main valve can be manually switched between the three positions. Consequently, the pilot button serves for switching the parking brake valve into a parking mode, into a drive mode or into a release mode. In particular, in the release mode the position of the main valve corresponds to the third position, in the parking mode to the second position and in the drive mode to the first position.

Preferably, besides manual switching by the pilot button, the above-mentioned pressure actor is arranged to push the main valve from the third position to the first position. No further reset means or actors beside the pressure actor and the pilot button are provided or needed in order to control the main valve.

According to a further development, the parking brake valve comprises a check valve connected between the supply port and the reservoir port. The check valve has an installation direction to block a fluid flow from the reservoir port to the supply port and to allow a fluid flow from the supply port to the reservoir port.

Consequently, the parking brake valve serves to load a reservoir which is connected to the reservoir port to a pneumatic pressure from the pneumatic pressure supply line, namely by a pressure which is provided by a tractor. After releasing a connection between the supply port and a pneumatic pressure supply line, the provided pneumatic pressure in the reservoir will be held in the reservoir, preferably to supply the parking brake actuator when the main valve is transferred to the third position.

Consequently, no further valve or port is needed to charge the reservoir.

According to a further development, the switching pressure threshold value is arranged by designing the parking brake valve in the range of 1 .5 to 3.5 bar, in particular in the range of 2 to 3 bar, in particular the switching pressure threshold value corresponding to 2.5 bar. Alternatively or additionally, when the parking brake valve comprises the internal pilot port, the internal switching pressure threshold value is below the switching pressure threshold value, wherein the internal switching pressure threshold value is in the range between 1 and 2 bar, in particular the switching pressure threshold value corresponding to 1 .5 bar. Finally, the supply pressure threshold value may in particular be in the range of 0.5 to 1 .5 bar, in particular the supply pressure threshold value corresponding to 1 bar.

In a second aspect of the invention, a braking system is proposed. The braking system comprises at least one parking brake valve according to the first aspect of the invention. Moreover, the braking system comprises at least one parking brake actuator connected, in particular via a braking module, to the delivery port of the parking brake valve, a pneumatic pressure control line, in particular with a foot pedal for providing a control pressure, connected to a pilot port of an internal valve of the parking brake valve and a pneumatic pressure control line connected to the supply port of the parking brake actuator, wherein the pneumatic pressure control line may in particular be connected to a pneumatic source.

According to a third aspect of the invention, a vehicle is proposed. The vehicle in particular may be a trailer or more in particular a semi-trailer, a central-axle trailer or a drawbar trailer. The vehicle comprises a parking brake valve according to the first aspect or a braking system according to the second aspect.

According to a fourth aspect of the invention, a vehicle combination is proposed. The vehicle combination comprises a vehicle according to the third aspect of the invention and a tractor.

Furthermore, according to a fifth aspect of the invention, a method for controlling a parking brake, in particular with a parking brake valve according to the first aspect of the invention is proposed.

The method comprises the following steps for piloting the parking brake from a brake mode to a drive mode: Receiving a pneumatic pressure at least above a supply pressure threshold value on a supply port of the parking brake valve. Furthermore, receiving a force on a pilot button of a main valve to switch the main valve from a second position, in which an exhaust port is connected to a delivery port of the parking brake valve, to a first position. In the first position, an internal line of the parking brake valve is connected to the delivery port for providing a pneumatic pressure of the internal line to the delivery port. Moreover, a pneumatic pressure above a switching pressure threshold value is received from a pneumatic pressure control line of a tractor on a pilot port of an internal valve of the parking brake valve to switch the internal valve from a second position, blocking a connection between the internal line and a supply port, to a first position, in which the supply port is connected to the internal line for providing the pneumatic pressure at the supply port to the internal line.

According to a development of the method, the method comprises the following steps for piloting the parking brake to a release mode: A force on the pilot button of a main valve is received to switch the main valve from the second position to a third position. In the second position, the exhaust port is connected to the delivery port. In the third position, the delivery port is connected to a reservoir port of the parking brake valve.

According to a further development, the method comprises the following steps for piloting the parking brake to a brake mode: In a step, a force on the pilot button of the main valve is received to switch the main valve to the second position. Alternatively, in particular when the supply line is decoupled, a pneumatic pressure on the supply port is received which is below the internal switching threshold value on the internal pilot port, in particular no pneumatic pressure on the supply port is receive.

According to a further embodiment of the method, the method comprises the following steps for piloting the parking brake from a release mode to a drive mode:

In a step, a pneumatic pressure from the supply port is received which is above a supply pressure threshold value in order to transfer the main valve from the third position to the first position with a pressure actor. Furthermore, a pneumatic pressure from the control line above a switching pressure threshold value on the pilot port of the internal valve to switch the internal valve from the second position to the first position is received. Additionally, a pneumatic pressure from the internal line above the internal switching pressure on the internal pilot port holds the internal valve in the first position.

Further advantages, features and details of the invention result from the following description of the preferred embodiments as well as from the drawings, which show in Fig. 1 a vehicle combination according to a first embodiment of the invention,

Fig. 2 a parking brake valve according to a first embodiment in a brake mode,

Fig. 3 the parking brake valve of Fig. 2 in a drive mode,

Fig. 4 the parking brake valve of Figs. 2 and 3 in a release mode,

Fig. 5 a parking brake valve according to a second embodiment in a brake mode,

Fig. 6 the parking brake valve of Fig. 5 in a drive mode,

Fig. 7 the parking brake valve of Figs. 5 and 6 in a release mode,

Fig. 8 the steps of a method for controlling a parking brake according to an embodiment,

Fig. 9 the steps of the method for piloting a parking brake valve to a release mode,

Fig. 10 the steps of the method for piloting the parking brake valve to a brake mode,

Fig. 11 the steps of the method for piloting the parking brake valve from a release mode to a drive mode and

Figs. 12 to 24 a schematic hardware configuration of a parking brake valve according to an embodiment of the invention.

Fig. 1 shows a vehicle combination 100 comprising a vehicle 200, namely a trailer 202, which is towed by a tractor 300. The trailer 202 comprises a parking brake 230. The tractor 300 comprises a tractor pneumatic pressure interface 310, which is connected to a pressure source 320. The pressure source 320 provides a pneumatic pressure and is, for example, a pressure tank, which is sourced by a compressor, which is not shown in the figure. Furthermore, a foot pedal 330 is provided in the tractor 300, which can be applied by a driver. Fig. 1 is a schematic representation wherein the pressure source 320 and the foot pedal 330 are connected to the tractor pneumatic pressure interface 310 directly. However, according to further embodiments, the pressure source 320 as well as the foot pedal 330 are indirectly connected to the pneumatic pressure interface 310 via a tractor braking system, which is not shown in detail in Fig. 1 .

The pressure source 320 provides a pneumatic pressure supply on a red output coupler 340. Furthermore, on a yellow output coupler 350, a pneumatic pressure control is provided. The pneumatic pressure on the pneumatic pressure control depends on the position of the foot pedal 330. The red output coupler 340 is connected to a trailer pneumatic pressure supply input 204 via a pneumatic pressure supply connection line 205 to provide a pneumatic pressure on a pneumatic pressure supply line 206 of the trailer 202. Furthermore, the yellow output coupler 350 is connected to a pneumatic pressure control input 208 via a pneumatic pressure control connection line 209 to provide pneumatic pressure control on a pneumatic pressure control line 210. Consequently, an interface 212 of the trailer 202 forwards the pneumatic pressure to a supply port 10 of a parking brake valve 12 via the pneumatic pressure supply line 206. A reservoir port 14 of the parking brake valve 12 is connected to a pneumatic reservoir 224 of the trailer 202, wherein via the parking brake valve 12 the pneumatic pressure from the pneumatic pressure supply line 206 is forwarded to the pneumatic reservoir 224. The pneumatic reservoir 224 is further connected to a braking module 226, which can provide pneumatic pressure to brake actuators 228 of the trailer 202. The pneumatic pressure forwarded to the brake actuators 228 in a drive mode of the vehicle combination 100 depends on the position of the foot pedal 330 wherein the position is forwarded by the pneumatic pressure control line 210, which is connected via the pneumatic pressure interface 212 of the trailer 202 to the braking module 226.

Furthermore, the pneumatic pressure control line 210 to a pilot port 16 of the parking brake valve 12 is connected via the interface 212 of the trailer 202. A delivery port 18 of the parking brake valve 12 is further connected to the braking module 226 to provide a pneumatic pressure for piloting the brake actuators 228 in a park position or to release from the park position. Furthermore, the parking brake valve 12 comprises a pilot button 34, for manually switching the mode of the parking brake valve 12.

Fig. 2 shows a connection diagram of the parking valve 12 in a brake mode 20. The parking brake valve 12 comprises the supply port 10 and the reservoir port 14 as well as the pilot port 16 and the delivery port 18. Furthermore, an exhaust port 24 is shown. Moreover, main elements of the parking brake valve 12 are a main valve 26 and an internal valve 28. The main valve 26 and the internal valve 28 are connected by an internal line 30. The main valve 26 is shown in the second position 32 in which the exhaust port 24 is connected to the delivery port 18. Pneumatic pressure at the delivery port 18 can be drained by the exhaust port 24 through the main valve 26 in the second position. However, the main valve can be switched manually by a pilot button 34 in two further positions, which are explained in the further figures. Moreover, the internal valve 28 is held in a second position 36 by a reset means 37, namely a spring 38, in which a connection between the internal line 30 and the supply port 10 is blocked. However, if the pneumatic pressure on the supply port 10 is higher than a pressure on the reservoir port 14, fluid flows from the supply port 10 through a check valve 40 to the reservoir port 14 in order to fill the pneumatic reservoir 224.

In the brake mode 20, which is shown in Fig. 2, braking actuators 228 are vented via the braking module 226 and the delivery port 18, which is connected to the exhaust port 24. The braking actuators 228, for example spring-loaded brakes, are in a braking position and the trailer 202 is held in position by the actuators 228 even when parked on a slope.

Fig. 3 shows a drive mode 46 of the parking brake valve 12. In this position a driver has switched the main valve 26 to the first position 48 by the button 34. The internal line 30 is connected to the delivery port 18. Furthermore, the internal valve 28 is switched to the first position 50 by a pressure received via the pilot port 16 against the force of the spring 38. In this position, a pneumatic pressure received at the supply port 10 is forwarded to the internal line 30 by the internal valve 28, which connects the internal line 30 to the supply port 10. Furthermore, the internal line is connected to an internal pilot port 54 of the internal valve 28 to hold the internal valve 28 in the first position 50 even if the pressure on the pilot port 16 falls below a threshold. Furthermore, the pneumatic pressure on the internal line 30 is forwarded through the main valve 26 to the delivery port 18. Consequently, the pneumatic pressure on the supply port 10 is forwarded to the delivery port 18, which releases the brake actuators 228 via the braking module 226.

Fig. 4 shows a release mode 60 of the parking brake valve 12 wherein the internal valve 28 is in the second position 36. The release mode 60 can be applied after a brake mode 20 or if the pressure on the supply port 10 drops below a threshold value. Consequently, the spring 38 resets the internal valve 28 in the second position, namely a reset position.

Although there is no pneumatic pressure above a threshold on the supply port 10, if a pneumatic pressure is available in a reservoir 224, which is connected to the reservoir port 14, it is possible to release the brake actuator 228 by the parking brake valve 12. This is possible by the main valve 26, which can be brought into a third position 62 by a driver by the button 34. In this position, the reservoir port 14 is connected to the delivery port 18 and a pneumatic pressure in the reservoir is forwarded to the brake actuators 228 via the braking module 226. The release mode 60 is used for maneuvering a trailer 202 without the need of a tractor 300.

However, when in the release mode 60, a pneumatic pressure is supplied to the supply port 10, a pressure actor 64, which is connected by its cylinder 65 to the supply port 10, drives a piston 66, which pushes the main valve 26 from the third position 62 to the first position to bring at least the main valve 26 automatically in the drive mode 46. The internal valve 28 stays in the second position 36, in which a connection between the supply port 10 and the internal line 30 is blocked. In fact, the internal line 30 is connected via the internal valve 28 to the exhaust port 24. Consequently, the brakes on the trailer 202 will be vented and the trailer 202 is braked until via the pilot port 16 a pressure above a threshold for switching the internal valve 28 from the second position 36 to the first position 50 is applied.

Fig. 5 shows a connection diagram of the parking valve 12 in a brake mode 20 according to a further embodiment. The parking brake valve 12 comprises the supply port 10 and the reservoir port 14 as well as the pilot port 16 and the delivery port 18. Furthermore, an exhaust port 24 is shown. Moreover, main elements of the parking brake valve 12 are a main valve 26 and an internal valve 29. The internal valve 29 differs from the internal valve 28 in Figs. 2 to 4, wherein the differences will be discussed later. However, in the same manner as in Figs. 2 to 4, the main valve 26 and the internal valve 29 are connected by an internal line 31 . The main valve 26 is shown in the second position 32 in which the exhaust port 24 is connected to the delivery port 18. Pneumatic pressure at the delivery port 18 can be drained by the exhaust port 24 through the main valve 26 in the second position. However, the main valve 26 can be manually switched by a pilot button 34 in two further positions, which are explained with regard to Figs. 6 and 7. Moreover, the internal valve 29 is held in a second position 36 by a reset means 37, namely a spring 38, in which a connection between the internal line 31 and the supply port 10 is blocked. However, if the pneumatic pressure on the supply port 10 is higher than a pressure on the reservoir port 14, fluid flows from the supply port 10 through a check valve 40 to the reservoir port 14 in order to fill the pneumatic reservoir 224.

In the brake mode 20, which is shown in Fig. 5, braking actuators 228 are vented via the braking module 226 and the delivery port 18, which is connected to the exhaust port 24. The braking actuators 228, for example spring-loaded brakes, are in a braking position and the trailer 202 is held in position by the actuators 228even when parked on a slope.

Fig. 6 shows a drive mode 46 of the parking brake valve 12 shown in Fig. 5. In this position, by the button 34, a driver has switched the main valve 26 to the first position 48. The internal line 31 is connected to the delivery port 18. Furthermore, the internal valve 29 is switched to the first position 50 by a pneumatic pressure received via the pilot port 16 against the force of the spring 38. In this position, a pneumatic pressure received at the supply port 10 is forwarded to the internal line 31 by the internal valve 29, which connects the internal line 31 to the supply port 10. Furthermore, the pneumatic pressure on the internal line 31 is forwarded through the main valve 26 to the delivery port 18. Consequently, the pneumatic pressure on the supply port 10 is forwarded to the delivery port 18, which releases the brake actuators 228 via the braking module 226.

Moreover, according to the embodiment in Figs. 2 to 4, the internal valve 28 comprises an internal pilot port 54. In contrast to the embodiment of Figs. 2 to 4, in the first position 50 of the internal valve 29 the internal pilot port 54 of the internal valve 29 is connected to the delivery port 18 via an internal pilot line 49 to hold the internal valve 29 in the first position 50 even if the pressure on the pilot port 16 falls below a threshold. This function can be referred to as a self-holding function.

The self-holding function is realized by the internal valve 29 of the embodiment disclosed in Figs. 5 to 7. The internal valve 29 according to this embodiment connects the delivery port 18 to the internal pilot line 49 in its first position 50 for providing the pneumatic pressure at the delivery port 18 to the internal pilot port 54. However, in the second position 36, which is shown in Fig. 5, the connection between the delivery port 18 and the internal pilot line 49 is blocked.

In particular, the internal valve 29 here in particular may be realised as a 5/2-way valve. The valve comprises a first input 51 , which is connected to the exhaust port 24. A second input 52 is connected to the supply port 10. A third input 53 is connected to the internal pilot line. Moreover, a first output 55 is connected to the internal line 31 and a second output 56 is connected to the delivery port 18. To realize the mentioned function, in the first position 50, the second input 52 is connected to the first output 55 by a first connection 57. Furthermore, the third input 53 is connected to the second output 56 by a second connection 58. The first connection 57 between the second input 52 and the first output 55 is connected to the second connection 58 between the third input 53 and the second output 56 via a check valve 59, wherein the check valve 59 is directed to block a flow from the first connection 57 to the second connection 58 and to allow a flow from the second connection 58 to the first connection 57.

In the second position 36 of the internal valve 29 as shown in Fig. 5, by the valve, the first input 51 is connected to the first output 55 by a third connection 61 . The third input 53 is connected to the third connection 61 between the first input 51 and the first output 55 via a check valve 63, wherein the check valve 63 is directed to allow a flow from the third input 53 to the third connection 61 and to block a flow from the third connection 61 to the third input 53.

Fig. 7 shows a release mode 60 of the parking brake valve 12 wherein the internal valve 29 is in the second position 36. The release mode 60 can be applied after a brake mode 20 or if the pressure on the supply port 10 drops below a threshold value. Consequently, the spring 38 resets the internal valve 29 in the second position, namely a reset position. Although there is no pneumatic pressure above a threshold on the supply port 10, if a pneumatic pressure is available in a reservoir 224, which is connected to the reservoir port 14, it is possible by the parking brake valve 12 to release the brake actuator 228. This is possible by the main valve 26, which can be brought into a third position 62 by a driver by the button 34. In this position, the reservoir port 14 is connected to the delivery port 18 and a pneumatic pressure in the reservoir is forwarded to the brake actuators 228 via the braking module 226. The release mode 60 is used for maneuvering a trailer 202 without the need of a tractor 300.

However, when in the release mode 60 a pneumatic pressure is supplied to the supply port 10, a pressure actor 64, which is connected by its cylinder 65 to the supply port 10, drives a piston 66, which pushes the main valve 26 from the third position 62 to the first position to bring at least the main valve 26 into the drive mode 46 automatically. The internal valve 29 stays in the second position 36, in which a connection between the supply port 10 and the internal line 31 is blocked. In fact, the internal line 31 is connected to the exhaust port 24 via the internal valve 29. Consequently, the brakes on the trailer 202 will be vented and the trailer 202 is braked until via the pilot port 16 a pressure above a threshold for switching the internal valve 29 from the second position 36 to the first position 50 is applied.

Fig. 8 shows the steps of a method 68 for controlling a parking brake with a parking brake valve 12 into a drive mode 46. In the first step 70, a pneumatic pressure with a release pressure value 72 is received on the supply port 10. In the next step 74, a force on a pilot button 34 of the main valve 26 is received to switch the main valve 26 from the second position to the first position. In step 76, a pneumatic pressure above a switching pressure threshold value 78 is received from a pilot port 16 of the parking brake valve 12 to switch the internal valve 28, 29 from a second position 36 blocking the connection between the internal line 30, 31 and the supply port 10 to a first position 50 connecting the supply port 10 to the internal line 30, 31 for providing the pneumatic pressure to the internal line 30, 31 . In step 84, pneumatic pressure on the internal pilot port 54 above the internal switching pressure threshold value 92 is received to hold the internal valve in position 50. Fig. 9 shows the steps of the method for piloting the parking brake to a release mode 60. In step 80, a force on the pilot button 34 is received to switch the main valve 26 to a third position 62 in step 82.

Fig. 10 shows the step of a method according to an embodiment for piloting the parking brake to a brake mode 20. In step 86, a force on the pilot button 34 is received to switch the main valve 26 to the second position 32 in step 88. In the case of a parking valve 12 with an internal valve 29 as described with respect to Figs. 5 to 7, at the same time the internal switching pressure threshold pressure gets exhausted and the internal valve 29 gets reset to the second position 36. Alternatively, in step 90, a pneumatic pressure on the supply port 10 is received which is below an internal switching pressure threshold value 92 to switch the internal valve 28, 29 to the second position 36.

Fig. 11 shows the step of the method for piloting the parking brake from a release mode 60 to a drive mode 46. In step 96, a pneumatic pressure from the supply port 10 is received which is above a supply pressure threshold value 91 and in step 97, the main valve is transferred from the third position 62 to the first position 48 by a pressure actor 64. In step 94, a pneumatic pressure above a switching pressure threshold value 78 is received on the pilot port 16 to switch the internal valve 28, 29 from the second position 36 to the first position 50 in step 95.

Figs. 12 to 24 shows a schematic hardware configuration of a parking brake valve 12 according to an embodiment of the invention.

The parking brake valve 12 with a park safe function as shown in Figs. 12 to 24 comprises five ports and three key modes. The ports of the parking brake valve 12 comprise a supply port 10, a reservoir port 14, a pilot port 16, a delivery port 18 and an exhaust port 24. The key modes of the parking brake valve 12 comprise a brake mode 20, a drive mode 46, and a release mode 60. The modes are already explained above with respect to Figs. 5 to 7. Same reference numbers in Figs. 12 to 24 correspond to same features.

The parking brake valve 12 as shown in Fig. 12 comprises a main valve 26 with a main spool operated manually by a button 34 to attain primary functions as parking brake apply in the brake mode 20 and parking brake release in the release mode 60 and the driving mode 46. The bottommost air chamber 122 in the device serves as an automatic pop-out function of the main spool 120 as shown in Figs. 13a and 13b, which automatically changes the mode from release mode 60 to drive mode 46 as soon as the supply port 10 is pressurized. The pop-out function has been described in detail with respect to Figs. 4 and 7. The bottommost air chamber 122 is equivalent to an air chamber of pressure actuator 64 shown in Figs. 4 and 7 defined by a pneumatic cylinder 65 and a piston 66.

A park safe function is fulfilled by an inbuilt park safe module, namely the internal valve 29. The internal valve 29 comprises a pilot-operated spool 124 which attains the primary function of park safe activation in its second position 36 and deactivation in its first position 50 based on a pneumatic pressure control signal triggered from the foot pedal valve received via the pilot port 16. Activation and deactivation of the park safe function is also linked to the button 34 position, which enables and retains the park safe in deactivated condition, namely the first position 50, only when button 34 is in driving position, namely the main valve 26 is its first position 48.

When the tractor 300 is coupled to the trailer 202, trailer pneumatic pressure supply line 206 is pressurized and compressed air flows into the parking brake valve 12 through the supply port 10 and enters the air chamber 126 as shown in Fig. 12. Concurrently the compressed air also flows into the automatic pop-out chamber 122 as shown in

Figs. 13a and 13b. This flow line in the parking brake valve 12 ensures the button 34 and main valve 26 are switched to driving position, namely the first position 48 as shown in Fig. 13b, if the button was in release position, namely the main valve 26 was in the third position 62, as shown in Fig. 13a.

In the absence of a control signal from the foot pedal valve, namely if no pneumatic pressure is received via the pilot port 16, the supply port 10 will not be connected to the delivery port 18 ensuring the parking brake or emergency brake is not released. In this position, the park safe module spool 124 of the internal valve 29 is rested in its second position 36 due to the spring force of a spring 38 as shown in Fig. 14. Once the driver steps into the tractor 300 and presses a foot brake pedal, the pilot port 16 gets energized and pushes a control piston 128 upwards leading to deactivation of the park safe function as shown in Fig. 15. Now the internal valve 29 is in its first position 50 and allows supply air pressure to flow from chamber 126 via the second input 52 of the inter- nal valve 29 into a further chamber 130 via the first output 55 of the internal valve 29 shown in Fig. 15.

Fig. 16 shows the flow path from chamber 130 through a flow path created by the internal line 31 and main valve 26, namely by a distribution plate 132, main spool 120, sealing element and main housing 136, to the delivery port 18 for releasing the emergency brake.

Inbuilt construction of the park safe module, namely the self-holding feature, ensures that the park safe function is retained in the deactivated condition irrespective of removal of control pressure, namely pressure on the pilot port 16. While the control line pressure is energized, the park safe is in its deactivated position as described above. Supply pressure flows to chamber 130 via chamber 126 as in Figs. 12 and 15. From chamber 130, the air flows to the chamber 138 through the flow path in the distribution plate 132 shown in Fig. 17. From chamber 138, the air flows into the chamber 140 called a selfholding chamber through the small flow passage in the form of a hole 141 in the park safe housing as shown in Fig. 18. In this way the supply pressure (greater than the threshold value) is active beneath the park safe module spool 124 and retains it in the deactivated position even in the absence of control signal.

Through another flow path, supply pressure is isolated from the self-holding chamber by a check valve 59, which is shown in Fig. 19. This check valve 59 ensures one-way flow. When the self-holding pressure falls below the specified pressure (due to a drop in supply pressure), the spring 38 pushes the spool 124 down and the air inside the selfholding chamber 140 is evacuated through the check valve 59. This evacuated air connects to the chamber 130 and finally connects to the atmospheric pressure through the exhaust port 24. This leads to activation of the park safe function.

When the tractor and trailer are coupled, along with the chamber 126, the supply pressure also flows into the chamber 142 as shown in Fig. 20. From the chamber 142 through channels provided in the distribution plate, the air flows through a check valve 40 to the reservoir port 14 as shown in Fig. 21 . This ensures the reservoir tanks fill.

To activate the release function in release mode 60, the button 34 has to be pushed to bring the main valve 26 into the third position 62 as shown in Fig. 22. The compressed air in the reservoir tanks flows through the reservoir port 14 to the delivery port 18 through the distribution plate 132, main spool 120 and through the sealing elements. The delivery of compressed air from the delivery port 18 serves as an input pressure to release the emergency or parking brake.

Fig. 23 shows activation of the park mode, namely the brake mode 20. To activate the parking mode, the button 34 is pulled to its parking position, namely the main valve 26 is pulled to the second position 32. The compressed air in the delivery port 18 flows to the chamber 144 through the housing, sealing elements, gaskets, and flow channels in the distribution plate. Fig. 24 shows the air flow path from chamber 144 which connects the exhaust port 24 by the flow channels provided in the distribution plate 132 and the housing. Evacuation of the delivery pressure releases the emergency or parking brake.

Reference signs (part of the description) supply port parking brake valve reservoir port pilot port delivery port brake mode exhaust port main valve internal valve internal valve internal line internal line second position of the main valve button second position of the internal valve reset means spring check valve drive mode first position of the main valve internal pilot line first position of the internal valve first input second input third input internal pilot port first output second output first connection second connection check valve release mode third connection third position of the main valve check valve pressure actor pneumatic cylinder piston steps of a method first step release pressure value step step switching pressure threshold value step step step step step step supply pressure threshold value internal switching pressure threshold value step step step step vehicle combination spool chamber spool chamber control piston chamber distribution plate main housing chamber chamber hole chamber chamber vehicle trailer trailer pneumatic supply input pneumatic pressure supply connection line trailer pneumatic pressure supply line trailer pneumatic control input pneumatic pressure control connection line trailer pneumatic pressure control line interface pneumatic reservoir braking module brake actuators parking brake tractor tractor pneumatic pressure interface pneumatic source foot pedal red output coupler yellow output coupler