INSULATION DEVICE FOR A BRAKE ACTUATOR LINKAGE

Description

[0001] The invention relates to an isolation device for a brake actuation linkage.

[0002] Such a brake actuation linkage, particularly in agricultural tractors, serves to transmit the operating force exerted by the driver via a foot pedal to a control element of a brake valve for the hydraulic actuation of the associated wheel brake devices. Operational vibrations caused by a hydraulic system connected to the brake valve can be transmitted back to the foot pedal via the brake actuation linkage in a manner that is perceptible or unpleasant to the driver. In this context, the rubber dampers typically used for vibration isolation can influence the operating force exerted by the driver via the foot pedal, consequently leading to an undefined or ineffective braking response.

[0003] Document US 2023 / 031027 A1 is known from the state of the art.

[0004] In view of this, it is an object of the present invention to provide an improved isolation device of the type mentioned above with regard to the actuation behavior of the foot pedal, which at the same time ensures that an undesirable transmission of vibrations from the brake valve to the foot pedal is reduced.

[0005] This problem is solved by an isolation device for a brake actuation linkage having the features of claim 1.

[0006] Accordingly, the isolation device for a brake actuation linkage comprises, in addition to a cylindrical isolation or damping bushing, which includes an inner cylinder sleeve, an outer cylinder sleeve coaxially surrounding the inner cylinder sleeve forming an annular gap, and an elastic element filling the annular gap and firmly connected to the two cylinder sleeves, a linkage section on the brake pedal side and a linkage section on the brake valve side, wherein the two linkage sections engage the isolation bushing along its cylinder axis on opposite sides in such a way that the elastic element is reversibly sheared under the influence of an increasing actuation pressure exerted on the linkage sections, with the two cylinder sleeves being displaced parallel to each other until a mechanical end stop limiting the parallel displacement is reached.

[0007] When installed, the isolation device is connected with the brake pedal-side linkage section to a foot pedal intended for brake actuation, or with the brake valve-side linkage section to an actuating element of a brake valve for the hydraulic control of associated wheel brake devices.

[0008] The shear strength of the elastic element is preferably selected such that, when an actuation pressure typical for achieving increased braking deceleration is applied, further parallel displacement is blocked by the mechanical end stop, thus overriding the function of the elastic element. This results in a defined actuation behavior of the foot pedal, which is therefore efficient in terms of braking effect and desirable, for example, when performing an emergency braking maneuver. The actuation pressure required for this is typically on the order of 500 Newtons.

[0009] In the case of braking operations, as are typical for normal driving, the actuation pressure is below such a critical value, so that the mechanical end stop is not reached and the damping properties of the elastic element remain unaffected.

[0010] Advantageous further developments of the isolation device according to the invention are set out in the dependent claims.

[0011] To ensure that the actuating force acting via the brake linkage is directed along the cylinder axis into the insulating bushing, the linkage section on the brake valve side preferably comprises a plunger which is positively engaged with the inner cylinder sleeve, wherein the inner cylinder sleeve has a projection extending beyond the elastic element, against which an actuating element rotating on the plunger is supported under the action of the actuating pressure exerted on the linkage sections.

[0012] The plunger is in particular an integral part of the linkage section on the brake valve side, wherein a ball stud is formed at an end facing away from the plunger for articulated mounting in a ball receptacle or socket, which is connected to the actuating element of the brake valve.

[0013] The actuating element can be, in particular, a threaded nut screwed onto an external thread of the plunger. The diameter of the external thread corresponds to the inner diameter of the inner cylinder sleeve, thus creating the desired positive fit between the two parts. Alternatively, the actuating element is an integral part of the plunger and is formed on it as a circumferential collar. In this case, the plunger is unthreaded and runs flat along an inner wall of the inner cylinder sleeve.

[0014] Furthermore, it is conceivable that the plunger is mounted within the inner cylinder sleeve so as to be longitudinally displaceable along the cylinder axis. This allows, when the brake actuation linkage is installed, the insulating bushing or the elastic element it encompasses to a certain extent to be pre-tensioned by turning the threaded nut, in order to adjust the damping characteristics. For this purpose, the external thread is a fine thread, enabling precise adjustment.

[0015] Furthermore, the linkage section on the brake pedal side can include a bell-shaped housing for the positive-locking reception of the insulating bushing. Within this bell-shaped housing, a radially circumferential shoulder is formed, which, when the elastic element is relaxed, holds an inner end face of the inner cylinder sleeve at a distance from an inner housing head end. This results in a particularly compact design for the insulating device, with the insulating bushing being additionally protected from external influences within the bell-shaped housing. The distance to the inner housing head end ensures the necessary clearance for the inward deflection of the inner cylinder sleeve under the influence of the actuating pressure.

[0016] It is also possible that the mechanical end stop is formed by the inner housing head end, with the inner end face of the inner cylinder sleeve coming into contact with it. In this case, the actuating pressure is transmitted between the two linkage sections by bridging the elastic element via the rigid inner cylinder sleeve in between.

[0017] In order not to impede an inward deflection of the inner cylinder sleeve relative to the outer cylinder sleeve in the area of ​​the elastic element, the width of the radially circumferential shoulder is preferably dimensioned such that it does not exceed the wall thickness of the outer cylinder sleeve supported on it, thus preventing it from projecting into the annular gap and therefore into the movement area of ​​the elastic element.

[0018] Particularly in the case of a plunger positively engaged with the inner cylinder sleeve, if a plunger end protrudes beyond the inner end face of the inner cylinder sleeve, a blind hole with an inner diameter matching or larger than that of the inner housing head end can be provided at the inner housing head end. This allows the plunger end to immerse in the space created by the blind hole without the possibility of collision with the adjacent housing head end.

[0019] Furthermore, it is possible that a mounting bracket extending along the cylinder axis is formed on the bell-shaped housing. This bracket receives a free or first end of a connecting rod from the brake pedal-side linkage section. A second end, facing away from the free or first end, also has a mounting eye for articulated attachment to a corresponding mounting point on the foot pedal. An additional external thread is formed along the free or first end of the connecting rod, which screws into an internal thread running along the cylinder axis in the mounting bracket. By rotating the mounting bracket and securing it with a further threaded nut, the length of the brake actuation linkage can be precisely adjusted.

[0020] The isolation device according to the invention for a brake actuation linkage is explained in more detail below with reference to the accompanying drawings. Components that are identical or comparable in function are marked with the same reference numerals. The drawings show: Fig. 1 shows an exemplary embodiment of the isolation device according to the invention as part of a brake actuation linkage, Fig. 2 shows the in Fig. 1 Figure 3 shows the brake actuation linkage in its installed state in the footwell of a driver's cab of an agricultural tractor; Figure 3 shows a detailed sectional view of the isolation device in its unactuated state; and Figure 4 shows the in Fig. 3 Reproduced isolation device in fully activated state.

[0021] Fig. 1 Figure 1 shows an exemplary embodiment of the isolation device 10 according to the invention as a component of a brake actuation linkage 12, wherein the isolation device 10 is arranged accordingly Fig. 2 in an installed state in the footwell 14 of a driver's cab 16 of an agricultural tractor 18 not shown in detail and is connected with a brake pedal-side linkage section 20 to a foot pedal 22 provided for brake actuation or with a brake valve-side linkage section 24 to an actuating element 26 of a brake valve 28 for hydraulic control of associated wheel brake devices 30 of the agricultural tractor 18.

[0022] In Fig. 3 Figure 4 shows a detailed cross-sectional view of the isolation device 10. Accordingly, the isolation device 10 comprises a cylindrical isolation or damping sleeve 32, which includes an inner cylindrical sleeve 34, an outer cylindrical sleeve 38 coaxially surrounding the inner cylindrical sleeve 34 to form an annular gap 36, and an elastic element 40 filling the annular gap 36 and firmly connected to the two cylindrical sleeves 34, 38. The elastic element 40, consisting of a vibration-damping rubber compound, is permanently bonded to the inner and outer cylindrical walls 42 and 44 of the inner and outer cylindrical sleeves 34 and 38, respectively, which are made of galvanized and passivated steel, by vulcanization.

[0023] Here, the two linkage sections 20, 24 engage the insulating bushing 32 along its cylinder axis 46 on opposite sides 48, 50 such that the elastic element 40, starting from a Fig. 3 The unactuated state is depicted under the influence of an increasing actuating pressure F_brake exerted on the linkage sections 20, 24, causing the two cylinder sleeves 34, 38 to shear against each other in parallel displacement until a mechanical end stop 52 limiting the parallel displacement is reached. The latter corresponds to a Fig. 4 The fully actuated state of the elastic element 40 is shown. The shear is reversible due to the elastic properties of the insulating bushing 32, i.e., the elastic element 40 returns to the unactuated state by itself as the actuating pressure F_brake decreases.

[0024] The shear strength of the elastic element 40 is selected such that, when an actuation pressure F_brake, typical for achieving increased braking deceleration, occurs, further parallel displacement is blocked by the mechanical end stop 52, thus overriding the function of the elastic element 40. This results in a defined actuation behavior of the foot pedal 22, which is therefore low-loss in terms of the achievable braking effect and is desirable, for example, when performing an emergency braking maneuver. The actuation pressure F_brake required for this is typically on the order of 500 Newtons.

[0025] In the case of braking operations, such as those typical for normal driving of the agricultural tractor 18, the actuation pressure F_brake is below such a critical value, so that the mechanical end stop 52 is not reached and the damping properties of the elastic element 40 remain unaffected.

[0026] To ensure that the actuating force F_brake, acting via the brake linkage 12, is transmitted along the cylinder axis 46 into the insulating bushing 32, the linkage section 24 on the brake valve side includes a plunger 54 which is positively engaged with the inner cylinder sleeve 34. The inner cylinder sleeve 34 has a projection 56 extending beyond the elastic element 40, against which an actuating element 58, rotating on the plunger 54, is supported under the influence of the actuating pressure F_brake exerted on the linkage sections 20, 24. The plunger 54 is an integral part of the linkage section 24 on the brake valve side, with a ball stud 62 for pivotal attachment in a Fig. 2 visible ball receptacle or socket 64, which is connected to the actuating element 26 of the brake valve 28.

[0027] For example, the actuating element 58 is a threaded nut 68 screwed onto an external thread 66 of the plunger 54. The diameter of the external thread 66 corresponds to the inner diameter of the inner cylinder sleeve 34, so that the desired positive fit between the two parts is achieved.

[0028] The plunger 54 is mounted within the inner cylinder sleeve 34 so as to be longitudinally displaceable along the cylinder axis 46. This allows, when the brake actuation linkage 12 is installed, the insulating bushing 32, or the elastic element 40 encompassed by it, to be pre-tensioned to a certain extent by turning the threaded nut 68, in order to adjust the damping behavior. The external thread 66 is a fine thread, enabling precise adjustment.

[0029] Furthermore, the linkage section 20 on the brake pedal side includes a bell-shaped housing 70 for the positive-locking reception of the insulating bushing 32. Within the bell-shaped housing 70, a radially circumferential shoulder 72 is formed, which holds an inner end face 74 of the inner cylinder sleeve 34 at a distance d from an inner housing head end 76 when the elastic element 40 is relaxed. The distance d to the inner housing head end 76 ensures the necessary clearance for an inward deflection of the inner cylinder sleeve 34 under the influence of the actuating pressure F_brake.

[0030] In this case, the mechanical end stop 52 is formed by the inner housing head end 76, whereby the inner end face 74 of the inner cylinder sleeve 34 comes into contact with it. The actuating pressure F_brake is transmitted between the two linkage sections 20, 24 by bridging the elastic element 40 via the intervening rigid inner cylinder sleeve 34.

[0031] In order not to impede an inward deflection of the inner cylinder sleeve 34 relative to the outer cylinder sleeve 38 in the area of ​​the elastic element 40, the width of the radially circumferential shoulder 72 is dimensioned such that it does not exceed the wall thickness of the outer cylinder sleeve 38 supported on it, thus preventing it from projecting into the annular gap 36 and thus into the movement area of ​​the elastic element 40.

[0032] For the in Fig. 3 In the case shown in Figure 4, where a plunger end 78 projects beyond the inner end face 74 of the inner cylinder sleeve 34, a blind hole 80, aligned with the contour of the inner cylinder sleeve 34 and with an inner diameter equal to or larger than that of the inner cylinder sleeve, is located at the inner housing head end 76. In this case, the plunger end 78 is able to move into the space created by the blind hole 80 without any possibility of collision with the adjacent housing head end 76.

[0033] Additionally, a mounting stud 82 extending along the cylinder axis 46 is formed on the bell-shaped housing 70. A free or first end 84 of a connecting rod 86 of the linkage section 20 on the brake pedal side is received in the mounting stud 82; a second end 88, facing away from the first end 84, further has a mounting eye 90 for articulated attachment to a corresponding mounting point 92 on the foot pedal 22 (see also Fig. 2 )

[0034] Along the first end 84 of the connecting rod 86, a further external thread 94 is formed, which is screwed into an internal thread 96 running along the cylinder axis 46 in the mounting sleeve 82. By rotating the mounting sleeve 82 and counter-tightening it with a further threaded nut 98, a targeted length adjustment of the brake actuation linkage 12 is possible.

Claims

1. Insulating device for a brake actuating linkage, with a cylindrical insulating or damping bushing (32) which comprises an inner cylinder sleeve (34), an outer cylinder sleeve (38) coaxially surrounding the inner cylinder sleeve (34) so as to form an annular gap (36), and an elastic element (40) which fills the annular gap (36) and is fixedly connected to the two cylinder sleeves (34, 38), with a brake-pedal-side linkage section (20) and a brake-valve-side linkage section (24), the two linkage sections (20, 24) engaging the insulating bushing (32) along their cylinder axis (46) on opposite sides (48, 50) in such a way that the elastic element (40) is sheared reversibly under the action of an increasing actuating pressure (F_brake) applied to the linkage sections (20, 24) by parallel displacement of the two cylinder sleeves (34, 38) in relation to each other until a mechanical end stop (52) limiting the parallel displacement is reached.

2. Insulating device according to Claim 1, characterized in that the brake-valve-side linkage section (24) comprises a plunger (54) which is received in a form-fitting manner by the inner cylinder sleeve (34), wherein the inner cylinder sleeve (34) has a protrusion (56) which projects beyond the elastic element (40) and on which an actuating element (58) surrounding the plunger (54) is supported under the action of the actuating pressure (F_brake) applied to the linkage sections (20, 24).

3. Insulating device according to Claim 2, characterized in that the plunger (54) is an integral component of the brake-valve-side linkage section (24).

4. Insulating device according to Claim 2 or 3, characterized in that the actuating element (58) is a threaded nut (68) screwed onto an external thread (66) of the plunger (54).

5. Insulating device according to at least one of Claims 2 to 4, characterized in that the plunger (54) is mounted longitudinally displaceably along the cylinder axis (46) within the inner cylinder sleeve (34).

6. Insulating device according to at least one of the preceding claims, characterized in that the brake-pedal-side linkage section (20) comprises a bell-shaped housing (70) for the form-fitting receiving of the insulating bushing (32), wherein a radially surrounding shoulder (72) is formed within the bell-shaped housing (70), said shoulder keeping an inner end face (74) of the inner cylinder sleeve (34) at a distance (d) from an inner housing head end (76) when the elastic element (40) is relaxed.

7. Insulating device according to Claim 6, characterized in that the mechanical end stop (52) is formed by the inner housing head end (76), by the inner end face (74) of the inner cylinder sleeve (34) coming to rest flat against said housing head end.

8. Insulating device according to Claim 6 or 7, characterized in that the width of the radially surrounding shoulder (72) is preferably dimensioned such that it does not exceed the wall thickness of the outer cylinder sleeve (38) supported thereon.

9. Insulating device according to at least one of Claims 6 to 8, characterized in that at the inner housing head end (76) there is a blind hole (80) which is aligned with the profile of the inner cylinder sleeve (34) and has an inner diameter which corresponds thereto or is larger.

10. Insulating device according to at least one of Claims 6 to 9, characterized in that a fastening stub (82) running along the cylinder axis (46) is formed on the bell-shaped housing (70), in which fastening stub a free end (84) of a connecting rod (86) of the brake-pedal-side linkage section (20) is received, wherein a further external thread (94) is formed along the free end (84) of the connecting rod (86) and is screwed into an internal thread (96) running along the cylinder axis (46) in the fastening stub (82).