BRAKE ACTUATOR

Abstract: A brake lever (10) is splined to an actuator shaft (14). A first face cam (32) is splined to the actuator shaft (14) and a second face cam (34) is splined to a housing (70). Each face cam has plural opposed circumferentially spaced cam grooves. Rollers (28) are positioned in the grooves. As the shaft is turned, rollers ride up the grooves in the opposite cams forcing the cams apart. The first cam (32) is supported against axial movement in the housing by roller thrust bearings (36). The second cam (34) slides along its splines (26) pushing a piston (40) against the force of a return spring (66) to actuate the brake.

Description: BACKGROUND OF THE INVENTION Brake actuators have special problems. The problems are compounded in disc brake actuators in which substantial and uniform axial braking force must be applied with relatively small axial movements. The actuators must be capable of quickly applying and quickly removing braking force all with small axial movements. At the same time, contact between the parts must be maintained so that very little movement is required before braking force is applied. The present invention proposed solutions to the existing problems. SUMMARY OF THE INVENTION The present invention solves the problem of disc brake actuation uniquely by relatively turning opposed face cams with interposed rollers and supporting one face cam in a housing by thrust rollers while allowing the other face cam to slide on splines within the housing. The later axially movable face cam presses on a piston against the force of a return spring to apply brake pressures. In a preferred embodiment, roller cam actuator apparatus moves a piston axially upon rotation of a lever at one end of the shaft. The shaft is mounted for rotation in a disc brake caliper assembly. The lever is splined to the shaft and the shaft is supported in a housing which is connected to a caliper by roller bearings. Preferably, the cam apparatus has roller means with inward facing splines for connecting to splines on the shaft and stator means with outward facing splines for connecting to splines on the caliper-housing. The stator and rotor have opposed axial faces spaced apart at a predetermined distance. The opposed faces have complimentary cam grooves therein. Rollers are mounted between the faces and positioned in the grooves. As the rotor is turned by the shaft, the cam gooves turn the rollers and move the rollers with respect to the opposing faces of the stator and rotor. The rollers moving in the cam grooves causes the faces to separate and urge the stator and rotor axially apart. A thrust bearing on the opposite face of the rotor permits rotation of the rotor with respect to the housing. Preferably the stator slides along the splines which prevent relative rotation of the stator and housing. As the statter slides it pushes a piston which actuates a brake. A stop washer on an end of the shaft opposite from the lever has a washer like stop. In a preferred embodiment, a compression return spring bears against the stop as an inward extension of the piston tending to axially slide the piston and the stator in the direction of the rotor. A brake lever is moved by any conventional means, for example, mechanical means or pneumatic means such as by a brake air cylinder. Turning of the lever turns one actuator element connected to the lever and expands the actuator in an axial direction so that the actuator pushes against the piston. In a conventional manner the piston pushes against a brake pad which in turn pushes against the disc face. An opposite reaction causes the caliper in which opposing pads are mounted to move axially, squeezing the disc between two opposing pads to apply the brakes. Each of the axial movements is small. To keep the movement small, it is necessary that the brake be automatically adjusted during its use. Because the movements are small, the adjustment is difficult. The present invention uniquely provides the adjustment by mounting a clutch on the end of the actuator shaft mounting a sleeve on the end of the actuator shaft and turning the sleeve with a clutch until axial pressure of the actuator against the piston prevents turning of the sleeve. The sleeve has external splines which engage internal teeth on an inward projection on the turnable piston portion. As soon as the actuator applies brake applying force on the piston, the piston portions can no longer relatively turn, and the sleeve slips in the shaft. The rotation portion of the piston has a relatively large gear with radially extending teeth on its outer perimeter. The gear engages a relatively small pinion on the manual brake adjuster. The manual brake adjuster includes a ratchet which prevents rotation of the pinion, and thus, prevents rotation of the gear in a direction which would tend to shorten the piston. Because of the relatively large size of the gear and the relatively small size of the pinion, a small angular rotation of the gear effects a relatively large angular rotation of the pinion which is sufficient to move the ratchet to the new locking position. A spring on the end of the shaft tends to push the adjustable portion of the piston in the direction of the actuator. That spring has several functions, one of which is to tend to encourage the engagement of the piston with the actuator to prevent slop. Another function of the spring is the movement of the rotatable piston portion in an actual direction away from the brake applying direction so that the rotatable piston portion may freely turn on threads interconnecting it to the slideable piston portion until brake applying force is applied by the actuator. A preferred internal automatic brake adjuster for disc brakes has a shaft with first and second ends. A lever is connected to the first end of the shaft for rotating the shaft. Friction clutch means mounted on the second end of the shaft and annular spline means mounted on the second end of the shaft adjacent the friction clutch means rotate with the shaft until another force overrides the clutch and causes the spline means to slip on the shaft. A brake applying piston has first and second concentric portions which are connected by helical adjusting threads which permit relative turning of the elements in adjustment when the piston is not leaded. When brake applying force is applied to the piston, the helical threads lock the piston portions against turning. The turnable piston portion has an inward projection with teeth which engage the spine means which is mounted on the second end of the shaft. As the spline means turns with the shaft, the inward projection turns the turnable piston portion with respect to the non-turnable piston portion. The relative turning of the piston portions effects adjustment. The adjustment is prevented when actuator applies brake applying force to the piston, whereupon the spline means and friction clutch slip as the brake applying shaft is further turned. In a preferred embodiment of the invention, the inward projection on the turnable piston portion is positioned adjacent the actuator. In one preferred form of the invention, ratchet means is connected to the turnable portion of the piston means to prevent rotation of the turnable portion in a direction which would tend to shorten the piston means. In a preferred form of the invention, the spline means is a collar mounted on a second end of the shaft with radially extending splines on the collar. The inward projection on the turnable piston portion is a flat circular plate which faces the actuator and which has inward projecting teeth to engage the spline means on the sleeve. In a preferred embodiment, a washer is mounted on the second end of the shaft and a compression screen extends between a washer and the inward projecting plate to urge the plate and the piston in the direction of the actuator. In one preferred embodiment, the friction clutch is a Belville spring positioned between the washer and the sleeve for encouraging the sleeve to rotate with the shaft, washer, and Belville spring. In one preferred embodiment, the turnable piston portion has a large gear machined in its outer surface to engage a small pinion and a manual adjuster. The pinion is permitted to rotate in only one direction by a ratchet, which prevents rotation of the pinion and gear in a piston shortening rotation. These and other and further objects and features of the invention are apparent in the disclosure which includes the specification with the above and ongoing description and the claims and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an elevational view partionally in cross section of a disc brake apparatus showing the actuator and adjusting device. Figure 2 is a cross-sectional detail of a manual adjuster showing a pinion and ratchet which permit adjustment of the brake only in the piston lengthening sense of rotation. Figures 3 and 4 are details of the brake actuator shown in Figure 1, Figure 3 being taken along line 3-3 in Figure 4 and Figure 4 being taken along line 4-4 in Figure 3. DETAILED DESCRIPTION OF THE DRAWINGS Referring to Figure 1, a disc brake apparatus is generally referred to by the numeral 1. Disc 2 is braked by opposing pads 4 which are mounted in a caliper generally indicated by the numeral 6. The caliper assembly 6 is mounted on a spider 8. The brake is actuated by rotating lever 10 which is spline 12 to shaft 14. Shaft 14 is splined 18 to the first element 20 of an actuator generally indicated by the numeral 22. A second element 24 of the actuator is splined 26 to the brake housing so that the second element can not rotate as the shaft 14 is rotated. Rollers 28 are mounted in a cage 30 between the first actuator element 20 and the second actuator element 24. As lever 10 and shaft 14 rotate the first actuator 20, rollers 28 ride up cam surfaces 32 and 34, which causes the actuator elements 20 and 24 to move axially apart. Actuator element 20 is supported by roller bearings 36 which prevent axial movement. Actuator element 24 pushes a pressure member 38 against piston 40, which tightens the caliper and squeezes brake pads 4 on opposite faces of rotor 2. Over long use, the brake pads 4 wear. The length of piston 40 is adjustable to compensate for that wear. Piston 40 has two parts, an inner element 42 and an outer element 44 which are interconnected by adjusting threads 46. Turning the outer member 44 on inner member 42 in one direction causes the piston to elongate. Helical threads 46 have slope which locks the piston elements 42 and 44 against rotation when brake applying force is applied to the piston 40. Shaft 14, which has splines 12 on its first end, has a second end 48 which has a reduced diameter. A splined sleeve 50 with radially directed axially extending splines 52 is mounted for rotation on the reduced shaft second end 48. The extreme second end 54 of the shaft 14 is threaded to receive a nut 56 which holds a washer 58 on the shaft. A Belville spring 60 acts as a friction clutch to encourage the collar 50 to rotate with the shaft. Outer piston member 44 has welded thereto at its end facing the actuator 22 a inward projecting plate 62 with inward extending teeth 64 which engage the splines 52 on collar 50. As the friction clutch 60 turns the collar 50 with shaft 14, the inner projection 62 turns the outer piston member 44 on the inner piston member 42, tending to elongate the piston 40. Compression spring 66 extends between the washer 58 and the inward projection 62, tending to move the piston 40 in the direction of actuator 22 and tending to unload the threads 46 so that the piston members 44 and 42 may relatively turn. When actuator element 26 presses against inward projection 62 and piston member 44, the piston applying force locks threads 46, prevention further rotation of the piston members. Belville spring friction clutch 60 then permits adjusting collar 50 to remain in position while shaft 14 turns within the adjusting collar. As shown in Figure 1, the two elements 72 and 74 of the housing 70 are held together with bolts 76. Lubrication fitting 78 supplies lubricating channels 80 which in turn supply roller bearings 82 which support shaft 14 in housing 70 and which supply thrust roller bearings 36 and sleeve 50. As shown in Figure 2, manual adjustment mechanism 84 contains a ratchet 86 which prevents relative rotation of piston member 44 on piston member 42 in a direction which would tend to shorten the piston. As shown in 51, the piston member 44 is formed with a large outward extending gear 88, which engages a relatively small pinion 90. Pinion 90 is splined to adjusting shaft 93 which is fixed to the ratchet 86. As gear 88 turns pinion 90 in a direction which tends to elongate the piston, ratchet 86 turns to permit movement of the pinion and gear. Ratchet 86 prevents turning in the opposite sense of direction, and thus, prevents turning of pinion 90 and gear 88 in a direction which would tend to shorten the piston. Spring 94 permits shaft 92 to move axially to release the ratchet as it is being turned. Shaft 92 may also be turned manually by inserting a wrench in socket 96. Figures 3 and 4 are details of the actuator 22. Rollers 28 move up cam surfaces 32 and 34 as actuator element 20 is rotated with the actuator shaft by the splines 18. That movement of the rollers 28 on the cam surfaces 32 and 34 causes the element 24 to slide axially. Spline 26 prevent rotation of element 24. While the invention has been described with reference to specific embodiments, modifications and variations of the invention may be constructed without departing from the scope of the invention as defined in the following claims.

Claims: 1. Roller cam actuator apparatus for axially actuating a piston upon rotation of a lever at an end of a shaft in a disc brake caliper comprising a shaft mounted for rotation in a disc brake caliper assembly, a lever means, means for connecting the lever means to the shaft for rotating the shaft in the disc brake caliper assembly upon movement of the lever means, radially directed spline means connected to the shaft, rotor means having inward facing spline means for connecting to the spline means in the shaft and stator means aligned in the caliper parallel to the rotor means and means connecting the stator means to the caliper to prevent relative rotation of the stator means and caliper means, the stator means and rotor means having opposed axial faces spaced apart at a predetermined distance, the opposed faces having complementary cam grooves therein and roller means mounted between the faces and positioned in the complementary cam grooves whereby as the rotor is turned by the shaft, the cam grooves turn the roller means and move the roller means with respect to the faces, wherein the roller means moving in the cam grooves causes the faces to separate and urge the stator and rotor axially apart, and further comprising thrust bearing means connected between one of these stator and rotor and the caliper means for preventing relative axial movement of one of the rotor and stator means and the caliper means and further comprising sliding means connected between the other of the rotor and stator means and the caliper means for permitting relative sliding of the other means with respect to the caliper means and means on the said other means for urging a piston in a brake applying direction. 2. The apparatus of claim 1 wherein the thrust means is mounted in the caliper to support the rotor against axial movement and to permit the rotor to rotate with the shaft. 3. The apparatus of claim 1 wherein the sliding means is connected to the stator to permit the stator to slide axially with respect to the caliper and wherein the stator pushes against the piston to operate the brake. 4. The apparatus of claim 3 further comprising, a stop means mounted on the shaft at a portion thereof remote from the lever connecting means and return spring means connected to the stop and extending in a direction toward the lever connecting means and plate means adjacent the return spring means for pushing on the stator means and moving the stator means in a return direction toward the rotor upon release of the brake. 5. The apparatus of claim 1 wherein the shaft means further comprises bearing means on the shaft means adjacent the spline means and wherein the roller means further comprises annular mounting means having a central opening for mounting on the bearing means and having plural roller retaining means for holding rollers in radial alignment and plural rollers mounted in the plural retaining means and contacting the cam grooves in the opposite faces of the rotor and stator. 6. The apparatus of claim 5 wherein the caliper has a large central cavity and wherein the shaft has a relatively large portion near the lever mounting means and further comprising, roller bearing means surrounding the relatively large portion of the shaft and supporting the shaft for rotation in the caliper means and wherein the spline means is mounted on the shaft means axially adjacent the relatively large portion with the roller bearing and wherein the shaft is reduced in the next axial inward position adjacent the spline means and wherein the roller mounting means is mounted on the reduced portion of the shaft.

Inventors: WEBER, JAMES LEO
Applicants: ROCKWELL INTERNATIONAL CORPORATION
Application year: 1986
Main classification: F16D65
IPC codes: F16D65