Parking brake device

1. A parking brake device, comprising:

a bistable parking brake valve;

a relay valve;

a spring brake; and

electrically actuable valves, wherein the electrically actuable valves selectively connect the parking brake valve to supply pressure or atmospheric pressure;

wherein an outlet of the parking brake valve controls the relay valve, and the relay valve controls the spring brake,

wherein the parking brake valve has a movable piston, which is loaded by a spring and has two coaxial piston faces which delimit a first space and a second space,

wherein supply pressure, atmospheric pressure or a pressure which lies between them and which can be fed to the outlet of the parking brake valve is suppliable to the first space in accordance with the position of the piston, and

wherein the second space can be selectively connected to supply pressure or atmospheric pressure by an electrically actuable valve.

2. The parking brake device of claim 1 , wherein the parking brake valve has a second movable piston which is loaded by a second spring and which forms a first valve seat with a housing wall and a second valve seat with the piston, wherein the valve seats are arranged so that, when a predetermined pressure in the two spaces is exceeded, the first valve seat is closed and the second valve seat is opened and, in this case, supply pressure passes from a first port of the parking brake valve into the first space and hence to the relay valve.

3. The parking brake device of claim 2 , wherein the first port of the parking brake valve is selectively connectable to supply pressure or atmospheric pressure by at least one valve.

4. The parking brake device of claim 1 , wherein a second port, which is connected to the second space, is selectively connectable to supply pressure or atmospheric pressure by means of an electrically controllable valve.

5. The parking brake device of claim 1 , wherein pressure sensors are connected to at least one of the first port of the parking brake valve, the outlet of the parking brake valve, and the outlet of the relay valve.

6. The parking brake device of claim 1 , wherein the parking brake valve has a stepped piston having two coaxial piston faces.

7. The parking brake device of claim 1 , wherein the electrically actuable valves are solenoid valves.

8. The parking brake device of claim 1 , wherein pressure sensors are connected to at least one of the first port of the parking brake valve, the outlet of the parking brake valve, and the outlet of the relay valve, and wherein the parking brake valve has a stepped piston having two coaxial piston faces, and wherein the electrically actuable valves are solenoid valves.

9. A parking brake device, comprising:

a bistable parking brake valve;

a relay valve;

a spring brake; and

electrically actuable valves, wherein the electrically actuable valves selectively connect the parking brake valve to supply pressure or atmospheric pressure;

wherein an outlet of the parking brake valve controls the relay valve, and the relay valve controls the spring brake,

wherein the parking brake valve has a movable piston, which is loaded by a spring and has two coaxial piston faces which delimit a first space and a second space,

wherein supply pressure, atmospheric pressure or a pressure which lies between them and which can be fed to the outlet of the parking brake valve is suppliable to the first space in accordance with the position of the piston,

wherein the second space can be selectively connected to supply pressure or atmospheric pressure by an electrically actuable valve,

wherein the parking brake valve has a second movable piston which is loaded by a second spring and which forms a first valve seat with a housing wall and a second valve seat with the piston, wherein the valve seats are arranged so that, when a predetermined pressure in the two spaces is exceeded, the first valve seat is closed and the second valve seat is opened and supply pressure passes from a first port of the parking brake valve into the first space and hence to the relay valve, and

wherein the valve seats are arranged so that, when a predetermined pressure in both spaces is undershot, the first valve seat opens and the second valve seat closes and the first space and hence a third port are connected to atmospheric pressure via an opening of the parking brake valve.

10. The parking brake device of claim 9 , wherein a second port, which is connected to the second space, is selectively connectable to supply pressure or atmospheric pressure by an electrically controllable valve.

11. The parking brake device of claim 9 , wherein the first port of the parking brake valve is selectively connectable to supply pressure or atmospheric pressure by at least one valve.

12. The parking brake device of claim 9 , wherein pressure sensors are connected to at least one of the first port of the parking brake valve, the outlet of the parking brake valve, and the outlet of the relay valve.

13. The parking brake device of claim 9 , wherein the parking brake valve has a stepped piston having two coaxial piston faces.

14. The parking brake device of claim 9 , wherein the electrically actuable valves are solenoid valves.

15. The parking brake device of claim 9 , wherein pressure sensors are connected to at least one of the first port of the parking brake valve, the outlet of the parking brake valve, and the outlet of the relay valve, and wherein the parking brake valve has a stepped piston having two coaxial piston faces, and wherein the electrically actuable valves are solenoid valves.

16. A parking brake device, comprising:

a bistable parking brake valve;

a relay valve;

a spring brake; and

electrically actuable valves, wherein the electrically actuable valves selectively connect the parking brake valve to supply pressure or atmospheric pressure;

wherein an outlet of the parking brake valve controls the relay valve, and the relay valve controls the spring brake,

wherein the parking brake valve has a movable piston, which is loaded by a spring and has two coaxial piston faces which delimit a first space and a second space,

wherein supply pressure, atmospheric pressure or a pressure which lies between them and which can be fed to the outlet of the parking brake valve is suppliable to the first space in accordance with the position of the piston,

wherein the second space can be selectively connected to supply pressure or atmospheric pressure by an electrically actuable valve, and

wherein the outlet of the parking brake valve is additionally connected to a trailer test valve, the pneumatic control inlet of which is connected by a shuttle valve to the higher of the pressures at a first port and at a second port.

17. The parking brake device of claim 16 , wherein the trailer test valve is a slide valve or a double seat valve.

18. The parking brake device of claim 16 , wherein a pressure medium inlet of the trailer test valve is connected to the outlet of the relay valve.

19. A parking brake device, comprising:

a bistable parking brake valve;

a relay valve;

a spring brake; and

electrically actuable valves, wherein the electrically actuable valves selectively connect the parking brake valve to supply pressure or atmospheric pressure;

wherein an outlet of the parking brake valve controls the relay valve, and the relay valve controls the spring brake,

wherein the parking brake valve has a movable piston, which is loaded by a spring and has two coaxial piston faces which delimit a first space and a second space,

wherein supply pressure, atmospheric pressure or a pressure which lies between them and which can be fed to the outlet of the parking brake valve is suppliable to the first space in accordance with the position of the piston,

wherein the second space can be selectively connected to supply pressure or atmospheric pressure by an electrically actuable valve, and

wherein a shuttle valve, the first inlet of which is connected to the outlet of the parking brake valve and the second inlet of which is connected to a pressure medium line of a service brake, is inserted between the outlet of the parking brake valve and the pneumatic control inlet of the relay valve, wherein the shuttle valve directs the higher of the pressures at the two inlets thereof to the control inlet of the relay valve.

20. A parking brake device, comprising:

a bistable parking brake valve;

a relay valve;

a spring brake; and

electrically actuable valves, wherein the electrically actuable valves selectively connect the parking brake valve to supply pressure or atmospheric pressure;

wherein an outlet of the parking brake valve controls the relay valve, and the relay valve controls the spring brake,

wherein the parking brake valve has a movable piston, which is loaded by a spring and has two coaxial piston faces which delimit a first space and a second space,

wherein supply pressure, atmospheric pressure or a pressure which lies between them and which can be fed to the outlet of the parking brake valve is suppliable to the first space in accordance with the position of the piston,

wherein the second space can be selectively connected to supply pressure or atmospheric pressure by an electrically actuable valve, and

wherein the outlet of the relay valve is connected to one inlet of a shuttle valve, a second inlet of which is connected to a pressure medium from a service brake and the outlet of which is connected to the spring brake.