GB1575176A - Parking brake arrangement with locking means - Google Patents

Description

(54) PARKING BRAKE ARRANGEMENT WITH LOCKING MEANS (71) We, CATERPILLAR TRACTOR CO., a corporation organized and existing under the laws of the State of California, United States of America, of 100 N. E. Adams Street, Peoria, Illinois 61629, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: Conventional parking brakes associated with power trains for vehicles normally comprise a friction member adapted to be actuated by an operator to brake a power shaft employed in the power train. Many such parking brakes are exposed to the environment thus subjecting them to potential wear and clogging.In addition, the parking brakes do not always assure sufficient holding forces to prevent rotation of the power shafts associated therewith when minimal torque loads are imposed thereon.

In accordance with the invention a parking brake arrangement includes a power shaft rotatably mounted relatively to a stationary housing, and a parking brake comprising a locking means including a first toothed member secured to the housing and a second toothed member reciprocally mounted on the power shaft for axial movements between a first position engaging the first toothed member to prevent rotation of the shaft and a second position disengaged from the first toothed member for permitting rotation of the shaft, and actuating means for selectively moving the second toothed member between its first and second positions, the actuating means comprising release means for automatically permitting the second toothed member to rotate relatively to the first toothed member when the torque load imposed on the power shaft exceeds a predetermined magnitude.

A vehicle drive train incorporating a parking brake arrangement constructed in accordance with the invention is illustrated, partly in section, in the accompanying drawing.

The illustrated power drive train includes a transfer gear arrangement 10 comprising an engine-driven power input shaft 11 and a pair of power output shafts 12 and 13.

The input shaft may be connected to the output shafts by suitable intermeshed trans fer gears 14-17, mounted in a stationary case or housing 18. Output shaft 12 has a sleeve 19 suitably secured thereon to form a part thereof and a radial mounting flange 20 is formed integrally on an exposed end of the sleeve.

Mounting flange 20 is suitably connected to a standard drive mechanism (not shown) for driving the front roadwheels of a vehicle whereas a similar mounting flange 21 is secured to output shaft 13 to be drivingly connected to the rear roadwheels of the vehicle. It can thus be seen that the transfer gear arrangement will split the drive torque from the engine which drives input shaft 11 and divide the torque between the front and rear roadwheels of the vehicle. Although a hereinafter described parking brake arrangement 22 is described in association with the illustrated transfer gear arrangement, it should be understood that the parking brake arrangement could be associated with other types of power shafts, e.g., driven wheel axles, or transmission power shafts.In such applications stationary case or housing 18 could be replaced by an axle housing, member, such as the frame of a vehicle.

Parking brake arrangement 22 comprises a locking means 23 including a stationary first annular toothed member 24 having a plurality of circumferentially spaced teeth 25 formed thereon. The member is secured on a cover plate 26 of housing 18 by a plurality of circumferentially disposed bolts 27, along with a pair of annular members 28 and 29 disposed on either side thereof. Output shaft 12 is rotatably mounted on cover 26 by annular roller bearing means 30 whereas annular member 28 is rotatably mounted on sleeve 19 of the output shaft by annular bearing means 31.

Parking brake arrangement 22 futher comprises a second toothed member 32 splined at 33 on sleeve 19 for reciprocal movements thereof. The member has a plurality of circumferentially disposed teeth 34 formed thereon to correspond in number and construction with teeth 25 of first toothed member 24. A coil spring 35 is disposed between a snap ring 36, attached on sleeve 19, and member 32 to bias the member to its illustrated disengaged condition whereby teeth 25 and 34 are maintained out of mesh with respect to each other.

Thus, it can be seen that second toothed member 32 will rotate with output shaft 12 when it is disengaged from first toothed member 24. As will be hereinafter described, member 32 is adapted to be moved rightwardly in the drawing to axially engage member 24 for braking purposes. An annular bearing 37 is mounted between members 29 and 32 to support and position member 32 in place in the parking brake arrangement.

The normally "off" brake may be selectively actuated to an "on" condition of operation by an actuating means generally shown at 38. The actuating means, which may be considered to also include spring 35, comprises a.. bellcrank 39 pivotally mounted by a pin 40 on a stationary bracket 41 secured to member 29. The bellcrank comprises a first arm 42 and a second arm or fork 43 which straddles sleeve 19. The fork is adapted to engage second toothed member 32 to selectively move it rightwardly to its engaged position with first toothed member 24.

Arm 42 is pivotally connected by a pin 44 to a first end of a rod 45 reciprocally mounted in a housing 46. A washer 47 is secured to a second end of rod 45 and a compression coil spring 48 is mounted between the washer and the bottom wall of the housing to normally bias the rod upwardly in the housing, as illustrated in the drawing. The housing is connected to a second rod 49 which is, in turn, connected to a control means schematically illustrated at 50 adapted to be controlled by the operator of the vehicle to selectively move rod 39 upwardly to engage the brake.

For example, control means 50 may in dude a standard pedal-actuated mechanism mounted in the operator's cab of a vehicle whereby depression of the pedal will function to raise rod 49 upwardly in the drawing. Upon such actuation of the pedal and upward movement of-the rod, bellcrank 39 will pivot counterclockwise about pivot pin 40 to thus move toothed member 32 rightwardly into engagement with toothed member 24 for braking purposes. Should the torque load imposed on shaft 12 exceed a predetermined magnitude, teeth 25 and 34 of the respective toothed members will tend to move out of engagement or ratchet to protect components of the power train against damage. The teeth may comprise a standard tapered design to facilitate such ratching therebetween.

WHAT WE CLAIM IS - 1. A parking brake arrangement including a power shaft rotatably mounted relatively to a stationary housing, and a parking brake comprising a locking means including a first toothed member secured to the housing and a second toothed member reciprocally mounted on the power shaft for axial movements between a first position engaging the first toothed member to prevent rotation of the shaft and a second position disengaged from the first toothed member for permitting rotation of the shaft, and actuating means for selectively moving the second toothed member between its first and second positions, the actuating means comprising release means for automatically permitting the second toothed member to rotate relatively to the first toothed member when the torque load imposed on the power shaft exceeds a predetermined magnitude.

2. An arrangement according to claim 1, wherein the actuating means comprises a spring for normally urging the second toothed member to its second position.

3. An arrangement according to claim 2, wherein the spring constitutes a coil spring mounted on the power shaft and engaging the second toothed member.

4. An arrangement according to any one of the preceding claims, wherein the actuating means comprises a bellcrank pivotally mounted on the housing and having an arm thereof normally engaging the second toothed member.

5. An arrangement acocrding to claim 4, wherein the actuating means further com prises a rod having the first end thereof pivotally mounted to a second end of the bellcrank, a washer secured to a second end of the rod and a second housing having the rod reciprocally mounted therein.

6. An arrangement according to claim 5, wherein the release means comprises a compression coil spring disposed in the housing and mounted on the rod between the washer and the second housing for permitting ratcheting of the second toothed member relatively to the second toothed member upon engagement therewith when the torque load imposed on the power shaft exceeds a predetermined magnitude.

7. An arrangement according to claim 5 or claim 6 wherein the actuating means further comprises a second rod having a first end thereof connected to the second housing and a second end thereof connected to an operator-controlled means for selectively reciprocating the second rod.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. comprises a second toothed member 32 splined at 33 on sleeve 19 for reciprocal movements thereof. The member has a plurality of circumferentially disposed teeth 34 formed thereon to correspond in number and construction with teeth 25 of first toothed member 24. A coil spring 35 is disposed between a snap ring 36, attached on sleeve 19, and member 32 to bias the member to its illustrated disengaged condition whereby teeth 25 and 34 are maintained out of mesh with respect to each other. Thus, it can be seen that second toothed member 32 will rotate with output shaft 12 when it is disengaged from first toothed member 24. As will be hereinafter described, member 32 is adapted to be moved rightwardly in the drawing to axially engage member 24 for braking purposes. An annular bearing 37 is mounted between members 29 and 32 to support and position member 32 in place in the parking brake arrangement. The normally "off" brake may be selectively actuated to an "on" condition of operation by an actuating means generally shown at 38. The actuating means, which may be considered to also include spring 35, comprises a.. bellcrank 39 pivotally mounted by a pin 40 on a stationary bracket 41 secured to member 29. The bellcrank comprises a first arm 42 and a second arm or fork 43 which straddles sleeve 19. The fork is adapted to engage second toothed member 32 to selectively move it rightwardly to its engaged position with first toothed member 24. Arm 42 is pivotally connected by a pin 44 to a first end of a rod 45 reciprocally mounted in a housing 46. A washer 47 is secured to a second end of rod 45 and a compression coil spring 48 is mounted between the washer and the bottom wall of the housing to normally bias the rod upwardly in the housing, as illustrated in the drawing. The housing is connected to a second rod 49 which is, in turn, connected to a control means schematically illustrated at 50 adapted to be controlled by the operator of the vehicle to selectively move rod 39 upwardly to engage the brake. For example, control means 50 may in dude a standard pedal-actuated mechanism mounted in the operator's cab of a vehicle whereby depression of the pedal will function to raise rod 49 upwardly in the drawing. Upon such actuation of the pedal and upward movement of-the rod, bellcrank 39 will pivot counterclockwise about pivot pin 40 to thus move toothed member 32 rightwardly into engagement with toothed member 24 for braking purposes. Should the torque load imposed on shaft 12 exceed a predetermined magnitude, teeth 25 and 34 of the respective toothed members will tend to move out of engagement or ratchet to protect components of the power train against damage. The teeth may comprise a standard tapered design to facilitate such ratching therebetween. WHAT WE CLAIM IS -

1. A parking brake arrangement including a power shaft rotatably mounted relatively to a stationary housing, and a parking brake comprising a locking means including a first toothed member secured to the housing and a second toothed member reciprocally mounted on the power shaft for axial movements between a first position engaging the first toothed member to prevent rotation of the shaft and a second position disengaged from the first toothed member for permitting rotation of the shaft, and actuating means for selectively moving the second toothed member between its first and second positions, the actuating means comprising release means for automatically permitting the second toothed member to rotate relatively to the first toothed member when the torque load imposed on the power shaft exceeds a predetermined magnitude.

2. An arrangement according to claim 1, wherein the actuating means comprises a spring for normally urging the second toothed member to its second position.

3. An arrangement according to claim 2, wherein the spring constitutes a coil spring mounted on the power shaft and engaging the second toothed member.

4. An arrangement according to any one of the preceding claims, wherein the actuating means comprises a bellcrank pivotally mounted on the housing and having an arm thereof normally engaging the second toothed member.

5. An arrangement acocrding to claim 4, wherein the actuating means further com prises a rod having the first end thereof pivotally mounted to a second end of the bellcrank, a washer secured to a second end of the rod and a second housing having the rod reciprocally mounted therein.

6. An arrangement according to claim 5, wherein the release means comprises a compression coil spring disposed in the housing and mounted on the rod between the washer and the second housing for permitting ratcheting of the second toothed member relatively to the second toothed member upon engagement therewith when the torque load imposed on the power shaft exceeds a predetermined magnitude.

7. An arrangement according to claim 5 or claim 6 wherein the actuating means further comprises a second rod having a first end thereof connected to the second housing and a second end thereof connected to an operator-controlled means for selectively reciprocating the second rod.

8. An arrangement according to any one

of tE preceding claims, further comprising a pair of annular members disposed one on each side ot the first toothed member and secured to the housing along with the first toothed member by a plurality of circumferentially disposed bolts.

9. An arrangement according to claim 8, further comprising first annular bearing means mounted radially between a first one of the annular members and the power shaft and second annular bearing means mounted radially between a second one of the annular members and the second toothed member.

10. An arrangement according to any one of the preceding claims, wherein the second toothed member is splined on a sleeve of the power shaft for reciprocal movements thereon.

11. An arrangement according to any one of the preceding claims, wherein the power shaft constitutes a first output shaft adapted for connection to front wheels of a vehicle and the arrangement further comprises a power input shaft, a second power output shaft adapted for connection to rear roadwheels of a vehicle and gear means interconnecting the power input shaft and the first and second power output shafts.

12. An arrangement according to claim 1, substantially as described with reference to the accompanying drawings.

13. A vehicle fitted with a parking brake arrangement according to any one of the preceding claims.