Park brake actuator

Abstract

A park brake actuator, comprising: a housing; a piston comprising a piston rod and a piston head, the piston being provided in the housing; a spring, wherein the spring is arranged between the piston head and one side of the housing; an opening in the housing in which the piston rod is movably inserted; a fluid chamber being provided between the piston head and a side of the housing, wherein fluid is insertable into a fluid space, wherein the piston comprises at least one first guiding element which is adapted to guide the piston rod in the opening, and; at least one first seal between the piston rod and the opening.

Claims

1.-15. (canceled)

16. A park brake actuator, comprising: a housing; a piston comprising a piston rod and a piston head, the piston being provided in the housing; a spring, wherein the spring is arranged between the piston head and one side of the housing; an opening in the housing in which the piston rod is movably inserted; a fluid chamber being provided between the piston head and a side of the housing, wherein fluid is insertable into a fluid space, wherein the piston comprises at least one first guiding element which is adapted to guide the piston rod in the opening, and; at least one first seal between the piston rod and the opening.

17. The park brake actuator according to claim 16, wherein the at least one first seal is integrally formed with the first guiding element.

18. The park brake actuator according to claim 16, further comprising a membrane being adapted to delimit the fluid chamber from the spring.

19. The park brake actuator according to claim 16, further comprising a second seal between the piston head and at least one of the housing and a second guiding element provided at the piston head, being adapted to guide the movement of the piston head in the housing.

20. The park brake actuator according to claim 19, wherein the second seal and the second guiding element are integrally formed.

21. The park brake actuator according to claim 16, wherein at least one of the first guiding element and the second guiding element are a bushing.

22. The park brake actuator according to claim 21, wherein the bushing is comprised of polytetrafluoroethylene.

23. The park brake actuator according to claim 16, wherein the piston is not connected to a second actuator.

24. The park brake actuator according to claim 23, further comprising at least one connecting element being adapted to connect the piston rod with a lever, the lever being adapted to actuate a caliper.

25. The park brake actuator according to claim 24, wherein the connecting element comprises a push rod.

26. The park brake actuator according to claim 25, wherein the push rod is provided within a bore of the piston rod.

27. The park brake actuator according to claim 26, wherein the bore comprises a tapered portion, wherein the push rod is arranged in the bore and adapted to be connected to the ball joint on the lever of the caliper.

28. The park brake actuator according to claim 27, wherein a maximum displacement angle of the push rod within the bore is between 5 and 20.

29. The park brake actuator according to claim 27, wherein a maximum displacement angle of the push rod within the bore is between 10 and 15.

30. The park brake actuator according to claim 27, wherein the ball joint is provided within the bore of the piston rod.

31. The park brake actuator according to claim 30, wherein the push rod is slideably fixed within the bore by at least one alignment element.

32. The park brake actuator according to claim 31, wherein the alignment element is at least one of a rubber part and an alignment spring adapted for an angular alignment of the push rod.

33. The park brake actuator according to claim 32, further comprising a vulcanized rubber and at least one of a pin connection and a magnetic connection, being adapted to connect the push rod to the lever of the caliper.

34. The park brake actuator according to claim 24, further comprising at least one of a roller bearing and a needle bearing, which is adapted to connect the piston rod to the lever of the caliper.

35. The park brake actuator according to claim 24, wherein the piston rod is adapted to be connected to the lever of the caliper by a rack provided at the piston rod and a pinion provided at the lever.

Description

DETAILED DESCRIPTION OF THE DRAWINGS

[0039] In the following, advantageous embodiments of the present application are provided by the attached figures.

[0040] FIG. 1 shows different possibilities for an arrangement of brakes at an axle of a utility vehicle.

[0041] FIG. 2 shows an inner design of a park brake actuator according to a first embodiment of the present invention.

[0042] FIG. 3 shows an arrangement of a membrane within a park brake actuator according to a second embodiment of the present invention.

[0043] FIG. 4ashows an arrangement of a push rod, connecting a park brake actuator according to a first embodiment of the present invention to further elements of the brake caliper.

[0044] FIG. 4bshows the arrangement of a push rod in a connection between a park brake actuator and a lever of a park brake caliper.

[0045] FIG. 5 shows three possibilities in order to fix a push rod connecting a park brake actuator according to a first embodiment of the present invention to further elements of the brake caliper in a bore of the piston rod.

[0046] FIG. 6 shows three possibilities of connecting a push rod to a lever of a caliper.

[0047] FIG. 7 shows a direct connection between a push rod and a lever via a bearing.

[0048] FIG. 8 shows a direct connection between a push rod and a lever via a rack and pinion.

[0049] FIG. 9 shows a connection between a park brake actuator according to a first embodiment of the present invention and a lever of a caliper, wherein a piston rod with a tapered bore is used.

[0050] In FIG. 1 a), the arrangement of a combined brake actuator PS at a wheel is shown, such combined actuator PS is used for each wheel. Such combined brake actuator PS is used in the state of the art.

[0051] In FIG. 1 b), a service brake actuator S and a park brake actuator P are arranged with radial separation, hence being shorter and consuming less space in the axial direction. The structure of the brake in FIG. 1 b) is according to the present application, where a separate park brake actuator (P) is used.

[0052] FIG. 2 shows a park brake actuator P according to a first embodiment of the present invention. A piston 1 comprises a piston rod la and a piston head 1b. A spring 2 is provided between the piston head 1b and a housing 3, in particular in an upper part of the housing 3. Between the piston head 1b and the lower part of the housing 3, there is a fluid space 3b, into which air, in particular pressurized air, can be inserted and released. Furthermore, there is a bore 3a in the housing, where the piston rod 1a is inserted. Within the opening 3a, a first seal 4a and a first guiding element 5a are provided. The first seal seals a fluid space 3b against the environment. The guiding element 5a guides the piston rod 1a in the opening 3a. Furthermore, there is also a second seal 4b provided between the piston head 1b and the housing 3, and furthermore there is a second guiding element 5b, also provided between the piston head 1b and the housing 3. The guiding elements 5a and 5b ensure the axial movement of the piston 1 within the housing 3. The spring 2 actuates, i.e. pushes, the piston 1 to actuate the brake mechanics. The actuation is done by releasing air pressure from the fluid space 3b. Then, the spring force pushes the piston 1, and the piston 1 is sliding with the help of the guiding elements 4b and 5b and separated seals 4a and 4b in a purely linear motion. The park brake actuator P can be directly mounted to a park brake caliper that is intended to only function as a park brake caliper. In the present figure, the guiding elements 4b and 5b are adapted to cope with high-radial forces (e.g. deflections) resulting from a connection element to a park brake caliper C (not shown here).

[0053] FIG. 3 shows a second embodiment of the present invention: This second embodiment is very similar to the first embodiment, however, a membrane 6 is provided in the lower part of the housing 3. Again, there is a piston rod la and a piston head 1b, wherein the membrane is provided below the piston head 1b and is connected to the housing 3. Hence, the fluid space 3b is defined between the lower part of the housing and the membrane 6. In this case, only a first seal 4a and a first guiding element 5a in the opening 3a of the housing 3 are needed. Optionally further guiding elements 4b and 5b can be used at the opening 3a of the housing 3 to avoid a tilting of the piston 1. Also, an air passage 11 is shown in FIG. 3, for inserting compressed air into the fluid space 3b, and to release it.

[0054] FIG. 4 a) shows a park brake actuator P according to the first embodiment of the present invention, all the parts are about the same as in FIG. 1. However, a bore 1c is provided within the piston 1 (in particular in the piston rod la), pointing away from the piston head 1b (i.e. outside of the housing 3). In the bore 1c, a push rod 7a is inserted for connecting to a lever L of a brake caliper C (not shown here). It can be seen that the push rod 7a can deflect during linear movement of the piston 1, and can also move to different directions to a certain extent.

[0055] FIG. 4 b) shows a connection of the park brake actuator P to a lever L of a brake caliper C (not shown here) via the push rod 7a.

[0056] FIG. 5 shows three different connection mechanisms between a bore 1c of a piston rod la and a push rod 7a.

[0057] In FIG. 5 a), there is a ball joint connection 7b on top of the push rod 7a, wherein there are two pairs of alignment elements 7c arranged within the bore 1c. They restrict the deflection of the push rod 7a.

[0058] In FIG. 5 b), there is only one pair of alignment elements 7c, however broader ones (compared to FIG. 5 a)) with a tapered front section. These alignment elements 7c also allow certain deflections of the push rod 7a.

[0059] FIG. 5 c) shows a further possibility of alignment elements 7c, however fixing the ball joint 7b in the bore 1c more tightly and rigidly, hence allowing less deflections of the push rod 7a compared to FIGS. 5a) and 5b).

[0060] FIG. 6 a) to 6 c) show three possibilities to connect the push rod 7a to a lever L of a park brake caliper C (not shown here) directly.

[0061] In FIG. 6 a), there is a connection via of vulcanized rubber 7d, which connects the lever L and the push rod 7a.

[0062] In FIG. 6 b), there is a pin connection 7e, wherein a pin is joining the lever L and the push rod 7a.

[0063] In FIG. 6 c), there is a magnetic connection 7f between the push rod 7a and the lever L, also allowing a movement of the push rod 7a and the lever L.

[0064] In FIG. 7, a direct connection between the piston la and a lever L of a park brake caliper C (not shown here) is provided via a bearing 8. The bearing 8 is preferably provided as a roller bearing or needle bearing, both allowing a rotational movement of the lever, while still only allowing a mainly linear movement of the piston 1a.

[0065] FIG. 8 shows another possibility of a connection of the piston rod la of the park brake actuator P to a park brake caliper C (not shown here). In this case, a rack 9 is provided on the piston la, and a pinion 10 is provided at the lever L (not shown in this presentation). Also in this case, a linear movement of the piston 1 can be converted in an angular movement of a lever L.

[0066] In FIG. 9, a further connection between the piston rod la of the park brake actuator and a lever L of a brake caliper C (not shown here) is shown. In this case, only the connection between the piston la and the lever L is shown, without the remaining parts of the park brake actuator. Herein, the bore 1c of the piston rod la is a tapered bore. The tapered bore 1c of the piston rod 1a guides the push rod 7a, which is connected to the lever L with a ball joint 7b. There is a self-alignment of the push rod 7a by the angled side of the bore 1c during assembly. Herein the displacement angle is the angle between the center line of the piston la and the push rod 7a.

[0067] The present invention is not limited to the above described embodiments.

[0068] The push rod 7a can have different shapes. Also, the transmission of the forces to the caliper C can be performed via different connection mechanisms 7.

LIST OF REFERENCE SIGNS

[0069] P Park brake actuator [0070] S Service brake actuator [0071] PS Combined actuator [0072] W Wheel [0073] C Caliper [0074] L Lever [0075] 1 Piston [0076] 1a Piston rod [0077] 1b Piston head [0078] 1c Bore [0079] 2 Spring [0080] 3 Housing [0081] 3a Housing opening [0082] 3b Fluid space [0083] 4a First seal [0084] 4b Second seal [0085] 5a First guiding element [0086] 5b Second guiding element [0087] 6 Membrane [0088] 7 Connecting element [0089] 7a Push rod [0090] 7b Ball joint [0091] 7c Alignment element [0092] 7d Vulcanized rubber [0093] 7e Pin connection 7f Magnetic connection [0094] 8 Bearing [0095] 9 Rack [0096] 10 Pinion [0097] 11 Air passage