Abstract: A disc brake includes a positioning device (40) which is pressure responsive to control the amount of retraction for a piston (22) within the disc brake. The positioning device includes a plug (44) movably and sealingly carried within the piston (22) and a pair of legs (48, 50). The plug (44) cooperates with the pair of legs (48, 50) to move the latter to a position in spaced relation to a caliper housing (12) when the pressure level within a pressure chamber (28) is above a predetermined value. A spring (52) cooperates with the plug (44) and the pair of legs (48, 50) to engage the latter with the caliper housing (12) when the fluid pressure within the pressure chamber (28) is below the predetermined value.

Abstract: Resilient rings are fitted between the caliper and the mounting bolts to provide free caliper movement and permanent corrosion protection. One resilient ring has internal lands contracting the mounting bolt and positioned within the caliper. The lands act as a rubber spring with memory which retracts the caliper, reducing brake drag. Reduced rubber contact area with the mounting bolt reduces adhesion of the rubber to the bolt. The resilient ring may alternatively have external lands which grip or slip on the caliper housing instead of the mounting bolt. A seal may be provided as an extension of the one resilient ring to protect the mounting bolt surface.

Abstract: An internal shoe drum brake having a pair of brake shoes mounted on a back plate with double ended expanders located one between each pair of adjacent ends of the shoes. The expander has a strut assembly slidable within itself so that when the expander is operated the strut assembly transmits braking loads from one shoe to the other so that the brake operates in a duo servo mode. With the expanders arranged to operate vertically the weight of the shoes and acts against the strut assembly. In order to support the upper brake shoe and prevent the shoes moving off-center a variable length support acts between the upper shoe and the wheel cylinder. The support has a spring therein so that the support can resiliently collapse when the sheos move during duo servo braking.

Abstract: A disc brake includes a caliper assembly (12) cooperating with a pair of friction elements ((14, 16) to brake a rotor (10). A pin assembly (30) supports the caliper assembly (12) and includes a bolt (34) defining an axial spacing for a sleeve (36) which engages the caliper assembly (12) via a resilient bushing (32). The sleeve is permitted to move axially through a clearance (62) with each brake application and a spring (38) biases the sleeve and caliper to always retract through the clearance upon termination of braking.

Abstract: An automatic locking and adjustment assembly for securing a cable (28, 34) to a lever 16 includes a housing (36, 38). A cage (42) cooperates with the housing (36, 38) to carry gripping means (40) engageable with the cable (28, 34) and the housing (36, 38). The cage (42) cooperates with the gripping means (40) to provide for movement therebetween when the gripping means (40) is engageable with the housing (36, 38).

Abstract: A servomotor which actuates the throw-out device of a clutch, particularly in an automotive vehicle, has a piston which is reciprocable in a housing and is adapted to be coupled to a reciprocable motion transmitting rod for the throw-out device by a compensating device having cylindrical rollers which establish a motion transmitting connection between the piston and the rod as soon as the piston leaves its starting position in response to evacuation of air from the housing at one side of the piston. The rollers are automatically disengaged from the rod when the piston returns to its starting position so that the rod can be moved by the clutch in a first direction to compensate for wear upon the parts of the clutch or in a second direction to compensate for expansion of one or more friction discs in the clutch.

Abstract: A brake cylinder comprises a brake actuator device having a fluid operable piston and a coaxial adjoining hand brake operable device for axial actuation of a coaxial tubular push rod, there being a slack adjuster for selectively adjusting the retraction of the push rod. An actuating rod is connected to the piston and the actuating rod is selectively connected and disconnected from the internal periphery of the push rod by locking rollers selectively cooperating with a wedge shaped annulus disposed between the actuator rod and the inner periphery of the push rod. Slack adjustment is permitted by axial travel of the push rod beyond free travel limits as permitted by a friction sleeve connection between the outer periphery of the push rod and the brake cylinder housing. In a modification, the locking device is provided for a fluid spread brake cylinder that is adapted by levers to be connected to a conventional freight brake rigging to be used, for example, for hand brake applications.

Abstract: The invention consists of a slack-adjuster for a brake which comprises a pair of interengaged screw threaded members which are urged towards an extended relative position by an axial bias applied to one member. The screw thread has a high helix angle to permit adjustment to take place on release of the brake and reverse rotation is prevented by frictional engagement of the leading member with a brake applying plunger part and by the use of a saw-tooth screw thread.

Abstract: A disc brake 10 has a caliper 34 including apparatus 52 for retracting the piston 68 of the fluid motor portion 44 of the caliper to a non-braking position when the brake is not applied. Consequently, runout, wobble, or axial movement of the brake disc 12 may space the friction elements 62, 64 of the brake from the friction faces 18, 20 of the brake disc so that the friction elements do not drag on the disc when the brake is not applied.

Abstract: A disc brake having a piston retraction assembly includes a caliper (12) receiving a piston (14) for biasing a friction pad (16) into engagement with a rotor (18). A recess (30) on the caliper receives the retraction assembly 32 and a boot assembly 34 cooperates with the retraction assembly (32) to limit movement of the latter with the piston (14). A resilient member (40) engages the boot assembly (34) to bias the piston (14) via friction ring (36) to return to its rest position.

Abstract: In a disc brake assembly, one braking pad is associated operatively with a piston, which moves in a cylinder, and another braking pad is associated with a caliper, which is movable together with the cylinder. A first biasing means retracts the braking pads from opposite faces of a disc upon release of hydraulic pressure from a piston. A second biasing means retracts the caliper upon release of such pressure. A drag part, which grips a shaft frictionally, is able to move axially along the shaft, if the force being transmitted by the caliper upon application of such pressure exceeds the force required to energize the second biasing means, so as to compensate for wear of the second braking pad. A limiting means, which cooperates with the drag part so as to limit retraction of the caliper to a fixed distance.

Abstract: A piston anti-knock back assembly in a disc brake assembly having a brake actuator comprising a piston slidably mounted within a cylinder bore and operable to urge a fricton surface into contact with a rotary disc surface upon supply of hydraulic fluid under pressure to said cylinder bore, comprises an expanded resilient split ring in frictional contact with a main portion of the cylinder bore and loosely axially located in an annular piston groove adjacent a conical head of said piston.

Abstract: The mechanism provides a disc brake assembly with zero drag when released. It controls the retractive movements of the caliper housing and the actuating piston, relying on predetermined dimensional and mechanical properties for functional repeatability. It uses friction rings and spring washers.

Abstract: A disc brake assembly provides a caliper (22) cooperating with a pair of friction pads (16, 18) to brake a rotor (20). A piston assembly (28) is carried by the caliper 22 and is constructed from a pair of pistons (42, 42) and a resilient member 44. The pistons (40, 42) form an auxiliary pressure chamber (52) which cooperates with the resilient member (44) to control movement between the pair of pistons (40, 42).

Abstract: An automatic adjusting device in a disc brake for adjusting a clearance between a brake disc and a friction pad. A fixed pin is axially disposed within a hydraulic cylinder, and a regulating plate frictionally fitted over, the fixed pin is connected to the piston through a return spring having a given deformation allowance. The fixed pin, the regulating plate and the return spring cooperate to automatically move the piston backward at all times in a given amount and accurately. The amount of backward movement of the piston is sufficiently obtained by selection of a predetermined deformation allowance of the return spring, thus automatically and sufficiently obtaining a clearance between the brake disc and the friction pad.

Abstract: A disc brake pad retractor includes a resistance member carried on a rod positioned between a pair of brake pads. The resistance member will be moved laterally as the pads wear. A spring loaded housing is associated with the resistance member and will serve to urge a brake pad away from the rotor when the disc brake is disengaged.

Abstract: A disc brake includes a pair of friction elements which cooperate with a caliper (26) to engage a rotor (10). A torque plate (12) movably supports the caliper via at least one pin (24). The pin is received with an aperture (40) on the caliper and a resilient member (44) within the aperture accommodates the clearance between the pin and caliper. The resilient member defines at least one rib (54 or 56) substantially disposed outside the aperture. The rib is deformable axially to generate a restoring force biasing the caliper and at least one of the pair of friction elements to return to a rest position.

Abstract: A device for taking up wear in a disc brake assembly which is particularly suitable for aircraft comprises first and second spaced jaw members carrying a piston and cylinder actuating assembly operable by fluid pressure to displace friction linings and disc brakes towards one of the jaw members to compress the friction linings against the disc brakes and effect braking. The piston is in two telescoping parts and friction rings disposed therebetween normally retain the relative position of the two piston parts against the effect of a spring which operates on one of the piston parts to return the piston to a rest position. The displacement of this one piston part from the rest position is limited by an abutment and, in the event of this limited displacement being insufficient to effect braking, due to wear in the friction linings, the other piston part is displaced further by the fluid pressure against the effect of the friction rings to effect braking.

Abstract: A fully lined disk brake has a brake housing rotatably mounted on a wheel and segmented arcuate shaped brake shoes supported in the brake housing by a fixed mounting on the wheel assembly which extends over the radially outward open end of the housing to support the brake shoes and is movable from over the open end of the housing to permit access thereto for replacing the brake shoes without dismantling the brake actuating mechanism. The invention provides brake shoes having a device for association with the mounting to support the brake shoes and brake shoe actuating mechanism which automatically adjusts the brakes for optimum operation.

Abstract: An improvement on a caliper guiding mechanism for a disc brake in which an auxiliary slide pin is arranged to be slidable in metallic contact, instead of conventional elastic contact, in the same manner as a main slide pin to an extent corresponding to a distance of a gap normally existing between a disc and each of friction pads. The invented arrangement is such that there is no difference between these slide pins in resistance to caliper sliding movement to prevent uneven wear and dragging of the friction pads. Despite of the sliding arrangement, the auxiliary slide pin is capable of absorbing a certain degree of machining error or a change in the parallel relative positions of the sliding pins caused by a torque during brake application.

Abstract: In a disc brake of the spreading type an automatic adjuster is located within the housing of the brake. The adjuster comprises an extensible strut which acts between radial lugs on pressure plates to maintain the pressure plates in relative angular positions in which the braking clearances are maintained within the predetermined limits. In the construction described the strut is coupled at each end to a respective plate through a lever which is urged into a neutral position by a spring. The load in the spring is chosen to permit the lever to move angularly about a pivotal connection with its respective plate and prevent the effective length of the strut from being increased further as a result of loads which are transmitted through the strut as a consequence of structural deflection of the housing. The adjuster is therefore said to be "load-insensitive" for both directions of disc rotation.

Abstract: The guiding device for brake pad supports of a spot-type disc brake includes a pair of guide pins supported in the caliper housing movable in an axial direction, and a spring clamped between the guide pins and the brake housing with the spring being loaded by the axial movement of the guide pins, when the brake is applied. The spring acts to return the guide pins to their previous position, when the brake is released, in order to achieve a positive retraction of the brake pad guided by the pins.

Abstract: The invention provides a simple robust non-return device. The essential features of the device are a housing having in it a stepped bore, and a rod. The bore conveniently has an asymmetric step. The rod fits into the narrower part of the bore. As the housing and rod are relatively pivoted in one direction the rod becomes jammed in the narrower part of the bore and so cannot move. If the housing and the rod are relatively pivoted in the opposite direction the rod is able to slide freely in the bore. Therefore the rod can only move relative to the housing in one direction.

Abstract: A combination brake and brake wear take-up device is disclosed. The device comprises a disc brake assembly and a link assembly connected to actuator discs. A link assembly pull rod is connected to a fluid power piston slidably disposed in a cylinder. One or more conical washer members are carried around the piston and permit the piston to slide in the cylinder in one direction over a relatively extended distance, but permit the piston to slide in the opposite direction over only a limited distance. A snap ring disposed in the cylinder interior and a shoulder formed in the cylinder interior define the axial extent of that limited piston return motion.

Abstract: A drum brake of the inner shoe type has a self-adjusting device which comprises a push rod, one end of which cooperates with a first brake shoe, while the other end cooperates with a second brake shoe with the intermediary of an adjusting wedge, the position of which determines the effective length of the push rod. In the released state of the brake, the brake shoes abut the push rod-and-wedge assembly, whereby an air gap is defined between the brake lining and the drum. A clamping spring urges the push rod and the second brake shoe against the one and the other wedge flank. The wedge angle of the adjusting wedge is so selected that normally no shifting of the wedge occurs. The push rod has an abutting and displacing arrangement which--as soon as the brake shoe travel exceeds, during brake actuation, a basic structurally determined desired air gap--shifts the push rod against the force of the clamping spring and thus loosens the wedge.

Abstract: An improved brake for winches. The brake has a main brake and an emergency brake. Both brakes are solenoid operated and brake when the power is turned off or fails. Means are provided for slightly delaying the operation of the emergency brake compared to the main brake so that the braking force is applied in stages in an emergency. The brakes are mechanically linked together so that either of the main or emergency solenoids operate both brakes if one of the solenoids fails.

Abstract: An improved seal is disclosed for hydraulically sealing a piston-cylinder assembly used in activation of a floating caliper disc brake. The improved seal comprises an annular groove circumscribing the cylinder wall within which a ring type elastomeric seal is seated so as to sealingly engage the piston. The floor of the annular groove has a flat portion and sloped portion. By varying the ratio of the flat portion to the sloped portion a desired axial force resisting retraction of the piston into the cylinder may be pre-determined thereby preventing excessive brake shoe drag upon the rotor.

Abstract: The invention relates to internal shoe drum brakes having an automatic adjuster to maintain a substantially constant clearance between the brake shoes and the drum, when the brakes are released. A strut having a variable overall effective length acts between the shoes for automatic adjustment of the clearance and has one end portion connected to one brake shoe through a lost motion device. The lost motion device comprises a main lost motion connection for providing a minimum clearance and a secondary lost motion connection which provides a greater clearance for de-adjusting the brake, and a first spring acts to ensure that for normal service conditions the lost motion device acts through the main connection and the bias of this spring is overcome by manual operative device before the secondary connection becomes operable.

Abstract: A caliper housing is slidably mounted on support pins with rubber-like bushings. Each bushing is compressed in a housing groove when the disc brake is actuated to move the housing in the brake apply direction. The bushing has a toroidal main body and a series of circumferentially spaced axially extending protrusions. The main body grips the cylindrical surface of a pin in slip-stick relation. Upon brake actuation the protrusions are compressed. Upon brake release they return to their original configuration, moving the housing on the pins in the release direction to provide zero brake drag of the brake shoes on the disc. The bushing main body slips relative to the pins only when sliding movement of the caliper housing during brake actuation is sufficient to require adjustment of the brake release position of the caliper housing relative to the support pins.

Abstract: An actuator mechanism for a brake having a plurality of friction disc compressed between a pressure plate and a backing plate. The actuator mechanism has a piston located in a bore of a housing. A pin fixed to the housing extends through and locates the piston in the bore. A first tube made of an insulator material is located in the bore between the piston and the pressure plate. A second tube concentric to the first tube has an inwardly projecting flange adjacent to the piston and an outwardly projecting flange. A keeper attached to the first tube cages a spring between the outward projecting flange and the first tube. A third tube which engages the inwardly projecting flange is connected to the pin through a button fastener thereby establishing an air gap between the first tube and the pressure plate. The piston, in response to an operational input, initially moves in the bore by overcoming the spring and brings the first tube into engagement with the pressure plate to eliminate the air gap.

Abstract: A brake assembly comprises(a) a carrier having a bore, and a piston slidable axially in the bore to transmit force of fluid pressure acting on the piston to a brake pad,(b) shaft structure defining an axis and extending axially to transmit auxiliary thrust to the piston,(c) a rotary actuator member rotatable about the axis,(d) coupling device responsive to rotation of the member in one direction to effect axial advancement of the shaft structure toward the piston and responsive to rotation of the member in the opposite direction to allow axial retraction of the shaft structure,(e) first wear compensation mechanism subject to adjustment to axially shift the shaft structure in response to fluid pressure produced axial displacement of the piston beyond a predetermined amount, and(f) second wear compensation mechanism subject to adjustment to axially shift the shaft structure in response to rotation of the member beyond a predetermined amount,(g) the first and second compensation mechanisms being operatively inte

Abstract: A brake retractor assembly in which the automatic adjustment apparatus includes a slitted drag tube and a ball carried by an adjusting pin engageable with the tube. The ball is slightly larger than the inside diameter of the tube so that as the brake wears the ball is pulled through the tube causing progressive expansion of the tube and thereby providing the necessary adjustment for wear. Increased resistance to movement of the ball is created on the ends of the drag tube by a "V" notch with a disappearing taper, a flange, or a high friction inner surface of the tube.

Abstract: An automatic clearance adjusting mechanism is provided for brake in which a piston fitted in an actuator for urging a friction pad onto a rotor member. The piston is retained at a predetermined position in the actuator by a frictional force, and is allowed to axially move a predetermined distance from the retained position against an elastic force. The mechanism includes friction giving ring such as an elastic seal ring for restoring the piston to its original position, by taking advantage of the pressure within the actuator, when the same has been forcibly displaced from the predetermined position due to the elasticity deflection of brake component parts in the event of an unusual pressure rising within the wheel cylinder beyond a predetermined limit.

Abstract: A drum brake includes a pair of brake shoes and a hydraulic actuator which is engageable with the brake shoes to expand the latter during braking. The hydraulic actuator carries a pair of elastomeric sealing rings which are deformable during braking as a pair of pistons slidably disposed with the hydraulic actuator are movable upon a braking application. When braking is terminated, the elastomeric sealing rings return to their original stored configuration thereby retracting the pair of pistons within the hydraulic actuator. In order to retract the pair of brake shoes with the pistons through a predetermined distance, a first spring engages the pair of brake shoes substantially opposite the hydraulic actuator and biases the brake shoes toward each other while a second spring biases the brake shoes away from each other. The second spring is carried by a strut on a parking brake actuator and the strut extends from one of the brake shoes to a lever which is pivotally mounted on the other brake shoe.

Abstract: An automatic adjustment apparatus for a friction brake containing at least two braking elements between which there is arranged a brake lining and which are pressed against one another in a braking position. At least one of the brake elements is adjustably arranged. There is provided a cylindrical portion having a shoulder, and disc-shaped adjustment elements are arranged upon the cylindrical portion to both sides of the shoulder. The disc-shaped adjustment elements are displaceable by means of the adjustable braking element which is movable relative to the shoulder upon wear of the brake lining. Upon such wear of the brake lining amounting to the thickness of an adjustment element or a predetermined fraction of such thickness, the adjustment element arranged directly at the shoulder upon the larger diameter part of the cylindrical portion is displaceable onto its smaller diameter part.

Abstract: A cam actuated brake adjuster reduces automatically the clearance between the brake lining and the brake drum which exists when the brakes are released, if this clearance exceeds a predetermined value. A one-way drive mechanism which adjusts the angular position of a camshaft with the aid of a worm gear is actuated by an adjusting rod assembly, which yields to a given adjusting force corresponding to a given brake force, to prevent an excessive adjustment which might result from a drum distortion caused by the application of a great braking force.

Abstract: An internal shoe drum brake is provided with an automatic shoe adjusting device comprising a strut extending between the shoes; said strut being coupled to one shoe through a lost motion coupling and to the other shoe through a one-way coupling device comprising a cam rocker lever pivoted on one shoe. The end of the rocker lever opposed to the cam surface is connected through a tension spring to the other shoe.

Abstract: A sealing member in a disk brake, in which a piston fitted in a cylinder is to urge a friction pad onto a rotating disk, includes a sealing ring disposed in a circumferential groove provided in the cylinder or on the piston. A spring member is disposed between the forward surface of the sealing ring and the forward wall of the groove for constantly biasing the sealing ring backwardly in order to return the piston substantially to the same position when the brake is released, regardless of the magnitude of the braking pressure applied, while preserving the function of automatic compensation for the wearing of the friction pad.

Abstract: A seal for use on a disc brake piston/caliper assembly which seals the piston and also functions as a piston-return spring. The seal has a seal-retaining portion, a sealing lip portion, and a radially extending flex portion therebetween for retracting the piston by an amount equal to the flex portion retraction, thus automatically adjusting the piston position to compensate for normal pad wear. The seal can also include a locking flange and a separate pressure sealing lip to allow the seal to function without the previously required separate lathe cut sealing ring.

Abstract: In an hydraulically operated disc brake a stop is incorporated for determining the retracted position of the piston, the stop being movable towards the disc to compensate for wear of the friction pads and also acting as an anti knock-back device. The stop comprises a plate having an aperture through which a pin projects, the pin being fixed to the cylinder or to a second piston in the cylinder. An abutment member provides an abutment for the plate, and a first spring acts between the abutment member and the plate so as to urge the plate into a locked tilting position inclined with respect to the pin. A second spring acts on the abutment member to urge it in a direction away from the pad assembly.

Abstract: A piston-cylinder unit for use in a disc brake assembly includes a cylinder and a hydraulically actuated piston received in the cylinder for axial movement therein. The unit has a flexible seal member with its opposite ends attached in sealing engagement to respective axially opposed portions of the piston and cylinder for elastic expansion and contraction in the axial direction. The flexible seal member and the opposing portions of the piston and cylinder form a chamber for receiving fluid pressure for actuation of the piston.

Abstract: A disk brake assembly including a stamped sheet metal integral body having at least one substantially flat side wall with top and end portions projecting from the top and end edges, respectively, of the side wall. An actuator opening is formed in the side wall, and a flange projects from the periphery of the opening to define an integral sleeve. A disk brake actuator module is received in the opening and sleeve, the module including a cylindrical housing having a closed end and an open end with an actuator mounted therein and axially extendable and retractable with respect to the housing in response to fluid pressure changes in the housing. The module housing is received in the sleeve with a friction fit and is formed with a retaining flange that engages the side wall of the integral body to prevent axial movement of the housing in one direction relative to the side wall.

Abstract: A disc brake assembly including a self-contained actuator for urging a brake shoe into frictional engagement with a friction disc; the actuator including an actuated piston movably supported within a cylinder for moving the brake shoe into engagement with the friction disc, an actuating piston movably supported within the cylinder which is separated from the actuated piston by a fluid-filled chamber which defines a fluid link therebetween and a rotatable, threaded shaft member connected to the actuating piston for transmitting rotational motion to axial motion whereby rotation movement of the shaft member causes axial movement of the actuating piston which in turn causes axial movement of the actuated piston through the fluid link. In order to compensate for separation between the actuated and actuating pistons as a result of brake wear, the cylinder includes a fluid reservoir for supplying additional fluid to the fluid-filled chamber upon separation of these two members.

Abstract: An automatic brake adjust and reset device particularly adapted for use in a multiple disc aircraft disc brake and having one or more spring loaded axially movable tubular members engaged by a movable cutting member connected to and actuated by a brake applying pressure plate. A pair of spaced apart fixed stops operatively connected to the tubular member serve to limit axial movement thereof to a brake released position under the influence of the spring load thereon and to a brake applying position under the influence of the brake applying pressure plate connected to the cutting member. The tubular member is fixed at the brake applying position whereupon continued movement of the pressure plate and cutting member attached thereto results in cutting or slitting of the tubular member by the cutting member to the extent necessary to compensate for axial wear of the multiple brake discs.

Abstract: A brake retractor assembly in which the automatic adjustment mechanism includes a tube and a cutter engageable with the tube upon relative movement thereof. The tube is mounted on the retractor for limited axial movement in a manner such that after a predetermined movement of the cutter and tube together, there is relative movement thereof and the tube is cut by the cutter an amount equal to the wear of the brake parts providing the necessary adjustment to compensate for the wear.

Abstract: A brake assembly having a friction disc mounted on a rotatable wheel, a friction element selectively movable into frictional engagement with the friction disc to apply a braking force, an actuator for moving the friction element into engagement with the friction disc, and biasing springs for retracting the friction element from such engagement. The actuator includes an open-ended hollow piston member and a cylinder housing slidably supporting the piston member. A shaft-like member is removably connected to the housing and extends into the cavity and the open end of the piston member to a distal end. The piston has a recess extending thereinto from the open rear end to define a first shoulder. A gripping member engages the shaft-like member for moving along the shaft-like member only in the direction toward the distal end of the shaft-like member. The piston also has a groove extending inwardly from the recess and axially spaced from the first shoulder.

Abstract: A friction pad of a disc brake is indirectly actuated through a yoke to move between brake application and brake release positions with respect to a braking disc. Supports on the yoke each have elastomeric bushings arranged to slidingly receive a collar on a rod fixed to the stationary hydraulic cylinder so as to guide the yoke in its movements. The elastomeric bushings are so configured that the elastomeric bearings slide over the collars with less frictional resistance during brake application movement than during brake release movement.

Abstract: A gas spring for maintaining motor vehicle trunk lids or hatchbacks open, comprises a gas spring piston having a circumferential groove for retaining therewithin a snap ring, and a cooperative annular recessed groove in the internal wall of the cylinder housing located at a position of maximum movement of the piston rod from the cylinder so that in such position the piston is locked in place.

Abstract: A disc brake comprising: a caliper housing having axially aligned first and second cylinder bores; a first piston slidable within the first bore and bearing against one of the friction pads; a second piston slidable within the second bore and having an internally threaded tubular piston rod projecting into the first bore; a threaded clearance-takeup member screwed into the piston rod and having a head abutting against the bottom of the first piston; springs acting against one side of the second piston in the direction to apply the brakes; a hydraulic fluid connection for applying pressure fluid to the other side of the second piston so as to release the brake and compress the spring; and a torsion spring having one end connected through a housing to the second piston, and its other end connected to a tubular sleeve that is nonrotatably connected to the clearance-takeup member.