Patent Application
20130134002
This invention relates in general to vehicle drum and disc brake assemblies and in particular to an improved structure for a vehicle drum-in-hat disc brake assembly and method for producing the same.
Most vehicles are equipped with a brake system for slowing or stopping movement of the vehicle in a controlled manner. A typical brake system for an automobile or light truck includes a disc brake assembly for each of the front wheels and either a drum brake assembly or a disc brake assembly for each of the rear wheels. In some instances, the disc brake assembly can be a “drum-in-hat” type of disc brake assembly. The brake assemblies are actuated by hydraulic or pneumatic pressure generated when an operator of the vehicle depresses a brake pedal. The structures of these drum brake assemblies and disc brake assemblies, as well as the actuators therefor, are well known in the art.
A typical drum-in-hat type of disc brake assembly includes a hydraulically or pneumatically actuated disc service brake and a mechanically actuated drum-in-hat parking and emergency brake. The disc service brake includes a rotor which is secured to the wheel of the vehicle for rotation therewith. The rotor includes a pair of opposed friction plates which are selectively engaged by portions of a caliper assembly. The interior of the rotor defines a cylindrical braking surface.
A caliper assembly is slidably supported by pins secured to a mounting flange. The mounting flange is secured to a non-rotatable component of the vehicle, such as the steering knuckle or the axle flange. The caliper assembly includes a pair of brake shoes which are disposed on opposite sides of the rotor. The brake shoes are operatively connected to one or more hydraulically actuated pistons for movement between a non-braking position, wherein they are spaced apart from the opposed friction plates of the rotor, and a braking position, wherein they are moved into frictional engagement with the opposed friction plates of the rotor. When the operator of the vehicle depresses the brake pedal, the piston urges the brake shoes from the non-braking position to the braking position so as to frictionally engage the friction plates of the rotor and thereby slow or stop the rotation of the associated wheel of the vehicle.
The drum-in-hat parking and emergency brake includes a pair of opposed arcuate brake shoes which are supported on a backing plate for selective movement relative thereto. The backing plate is secured to the mounting flange, or alternatively, can be formed integral therewith. Each of the brake shoes has a friction pad or lining secured thereto. The brake shoes extend within the cylindrical braking surface of the rotor. To effect parking and emergency braking action, the operator of the vehicle manually pulls an actuating lever. The lever is connected to an actuation cable having a park brake cable end which, when pulled, actuates a mechanical actuating mechanism. The actuating mechanism can include a lever pivotally supported on one of the brake shoes. The lever is connected to actuation cable which, when pulled, is operative to move the brake shoes outwardly apart from one another such that the friction pads frictionally engage the cylindrical braking surface of the rotor. Such frictional engagement causes slowing or stopping of the rotational movement of the rotor and, therefore, the wheel of the vehicle in a controlled manner.
A typical drum brake assembly includes a backing plate which is secured to a fixed, non-rotatable component of the vehicle, such as the vehicle axle housing. A pair of opposed arcuate brake shoes are supported on the backing plate for selective movement relative thereto. Each of the brake shoes have a friction pad secured thereto. The brake drum assembly further includes a cylindrical brake drum which is secured to the vehicle wheel for rotation therewith. The interior of the brake drum is hollow, defining an inner cylindrical braking surface. The brake drum is disposed adjacent to the backing plate such that the brake shoes extend within the inner cylindrical braking surface. To effect braking action, the brake shoes are moved outwardly apart from one another such that the friction pads frictionally engage the inner cylindrical braking surface of the brake drum. Such frictional engagement causes slowing or stopping of the rotational movement of the brake drum and, therefore, the wheel of the vehicle in a controlled manner.
One or more actuating mechanisms are provided in the brake drum assembly for selectively moving the brake shoes outwardly apart from one another into frictional engagement with the cylindrical braking surface of the brake drum. Usually, a hydraulically or pneumatically actuated service brake mechanism is provided for selectively actuating the drum brake assembly under normal operating conditions. Such a service brake mechanism can include a hydraulic cylinder having a pair of opposed pistons which abut and move the brake shoes apart from one another into frictional engagement with the cylindrical braking surface of the brake drum.
A mechanically actuated parking and emergency brake mechanism is also usually provided for selectively actuating the drum brake assembly. The parking and service brake mechanism can include an actuating lever pivotally supported on one of the brake shoes. The actuating lever is connected to a cable which, when pulled, moves the brake shoes apart from one another into frictional engagement with the cylindrical braking surface of the brake drum.
This invention relates to an improved structure for a vehicle drum-in-hat disc brake assembly and method for producing the same.
According to one embodiment, the vehicle drum-in-hat disc brake assembly comprises a drum-in-hat adapter adapted to be secured to a fixed component of a vehicle; a backing plate adapted to be secured to the drum-in-hat adapter and to support a pair of brake shoes therein; a parking and emergency brake actuation mechanism adapted to move the brake shoes apart from another between a braking position and non-braking position, the parking and emergency brake actuation mechanism including a brake actuation lever adapted to be pivotally supported on one of the pair of brake shoes; wherein the backing plate includes at least one raised pad and the brake actuation lever includes an abutment surface provided thereon which is disposed adjacent and in sliding support with the raised pad whereby at least a portion of the abutment surface of the brake actuation lever rests against and is supported by at least a portion of the raised pad when the brake actuation lever of the parking and emergency brake actuation mechanism is in both the braking and non-braking positions.
According to another embodiment, the vehicle drum-in-hat disc brake assembly comprises a drum-in-hat adapter adapted to be secured to a fixed component of a vehicle; a backing plate adapted to be secured to the drum-in-hat adapter and to support a pair of brake shoes therein; a parking and emergency brake actuation mechanism adapted to move the brake shoes apart from another between a braking position and non-braking position, the parking and emergency brake actuation mechanism including a brake actuation lever adapted to be pivotally supported on one of the pair of brake shoes; wherein the backing plate includes at least one raised pad defining an outboard facing raised pad side surface and the brake actuation lever includes an inboard facing abutment side surface provided thereon which is disposed adjacent and in sliding support with the outboard facing raised pad side surface whereby at least a portion of the inboard facing abutment side surface of the brake actuation lever rests against and is supported by at least a portion of the outboard facing raised pad side surface of the at least one raised pad when the brake actuation lever of the parking and emergency brake actuation mechanism is in both the braking and non-braking positions.
According to still a further embodiment, the vehicle drum-in-hat disc brake assembly comprises a drum-in-hat adapter adapted to be secured to a fixed component of a vehicle; a backing plate adapted to be secured to the drum-in-hat adapter and to support a pair of brake shoes therein; a parking and emergency brake actuation mechanism adapted to move the brake shoes apart from another between a braking position and non-braking position, the parking and emergency brake actuation mechanism including a brake actuation lever adapted to be pivotally supported on one of the pair of brake shoes; wherein the backing plate is a metal stamping and includes a pair of raised pads, which are formed integrally therewith during the stamping of the backing plate, and the brake actuation lever includes an abutment surface provided thereon which is disposed adjacent and in sliding support with the pair of raised pads whereby at least a portion of the abutment surface of the brake actuation lever rests against and is supported by at least a portion of the pair of raised pads when the brake actuation lever of the parking and emergency brake actuation mechanism is in both the braking and non-braking positions.
Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the invention, when read in light of the accompanying drawings.
Referring now to the drawings, there is illustrated in
As shown in
In the illustrated embodiment, the drum-in-hat adapter 12 is adapted to be secured to a fixed, non-rotatable component of the vehicle, such as an axle flange (not shown) or a steering knuckle (not shown) for enclosing a rotatable axle (not shown). To accomplish this, the adapter 12 includes a relatively large opening 20 and a plurality of smaller holes (not shown) formed therein about the opening 20. In the illustrated embodiment, the adapter 12 has four of the smaller holes. The opening 20 permits an outer end of an axle to extend therethrough to the vehicle wheel (not shown), and suitable fasteners (not shown) are disposed in the smaller holes to secure the adapter 12 to the associated vehicle component.
The adapter 12 further includes a pair of integrally formed outwardly extending ears or lugs 24 and an abutment member 26 which can be formed integral with the adapter 12 or secured thereto by appropriate means. The ears 24 are provided with holes 28 formed therein. A pair of suitable fasteners (not shown) are disposed in the holes 28 of the ears 24 to attach a disc brake caliper assembly (not shown), which is part of hydraulically or pneumatically actuated disc service brake (not shown) of the vehicle drum-in-hat disc brake assembly 10, to the adapter 12.
The drum-in-hat parking and emergency brake portion 16 of the brake assembly 10 includes a pair of brake shoes 30 supported on the backing plate 14. Structurally, the brake shoes 30 are essentially mirror images of one another. Each of the brake shoes 30 includes a web portion 32 which is generally flat and crescent-shaped. A generally arcuate-shaped rim portion 34 is secured to the outer curved surface of the web portion 32, such as by welding. A friction pad 36 is secured to the outer arcuate surface of the rim portion 34 of the brake shoe 30.
In the illustrated embodiment, each of the brake shoes 30 includes a first end 40 and an opposite second end 42. The web portion 32 of the first end 40 of the brake shoe 30 includes a notch 44 formed therein. The notch 44 is adapted to receive an end portion of a part of a pad wear adjustment mechanism 46 in a conventional manner. In the illustrated embodiment, the second end 42 of the brake shoe 30 defines a shoe abutment end. The shoe abutment end is adapted to be received in a recess (not shown) of the abutment 26.
In the illustrated embodiment, each of the brake shoes 30 are adapted to be supported on and secured to the backing plate 14 by a pin 50 of conventional pivot pin and spring-clip assembly, indicated generally at 52. Each pin 50 is adapted to extend through an opening (not shown) provided in the backing plate 14 and through an associated opening (not shown) provided in each of the brake shoes 30. The pins 50 have outer ends which are adapted to be fastened or secured to clips 54 of the spring-clip assemblies 52 to secure the brake shoes 30 to the backing plate 14 in a conventional manner. The illustrated drum-in-hat brake assembly 10 also includes a pair of retraction springs 56 and 58. Alternatively, the structure of the brake shoes 30 may be other than illustrated if so desired.
In the illustrated embodiment the backing plate 14 of the drum-in-hat disc brake assembly 10 is preferably a stamped metal backing plate and includes a relatively large central opening 60 having a plurality of smaller openings 62 formed therein about the opening 60, as best shown in
The central opening 60 permits an outer end of the rotatable axle (not shown) to extend therethrough to a wheel (not shown) of the vehicle. The openings 62 are adapted to allow suitable fasteners, such as threaded mounting studs (not shown), to be used to secure the backing plate 14 to the associated vehicle component. The studs extend and pass freely through the openings 62 of the backing plate 14 and the corresponding openings 22 formed in the drum-in-hat adapter 12 and nuts (not shown) are installed thereon to secure the backing plate 14 and the drum-in-hat adapter 12, and therefore the drum-in-hat disc brake assembly 10, to the associated vehicle component.
In the illustrated embodiment, the backing plate 14 further includes a plurality of raised or embossed “brake actuation lever supporting” pads or supports 70 provided thereon. In the illustrated embodiment, each of the raised pads 70 is generally L-shaped and includes a first “longer” portion or leg 70A and a second “shorter” portion or leg 70B. As can be seen best on the left hand side of
Also, in the illustrated embodiment, the pads 70 on the right left hand and right hand sides of the backing plate 14 are essentially mirror images of one another in order to make the backing plate 14 a non-handed backing plate. However, the pads 70 can be provided only on one side of the backing plate 14, that being the side on which an actuation lever, as will be described below, is provided. Also, in the illustrated embodiment, a pair of adjacent pads 70 on the right side and the left side of the backing plate 14 are connected together by a raised or embossed arcuate “brake shoe supporting” pad or support 72 provided thereon. Each of the pads 72 is located along a circle C which is located near an outer periphery P of the backing plate. The pad 72 defines a supporting surface for the associated brake shoe 30 via the rim portion 34 thereof.
In the illustrated embodiment, the first leg 70A of each of the pads 70 extends in a direction which is generally located along the circle C of the backing plate 14. As will be discussed below, the first leg 70A of the pair of adjacent pads 70 defines a common outboard facing pad support surface for supporting both the associated brake shoe 30 (via the rim portion 34 thereof), and an “internal blade type” actuation lever 80 for actuating the parking and emergency brake mechanism 16 of the vehicle drum-in-hat disc brake assembly 10. Thus, it can be seen in the illustrated embodiment that the first legs 70A of the pair of adjacent pads 70 extend generally along the path as that of the arcuate pads 72. In the illustrated embodiment, the second leg 70B of each of the pads 70 extends in a generally radially inwardly extending direction, generally in the direction of arrow 82, toward a center axis A of the backing plate 14, for a purpose to be discussed below.
Also, in the illustrated embodiment, in order the for the first legs 70A of the pair of adjacent pads 70 to define the common outboard facing pad support surface for supporting both the associated brake shoe 30 (via the rim portion 34 thereof), a height of an outboard surface of the pads 70 is generally the same as a height of an outboard surface of the arcuate portion 72 for the purpose of supporting the rim portion 34 of the associated brake shoe 30. Alternatively, the height of the outboard surface of the pads 70 can be other than illustrated if so desired.
In addition, in the illustrated embodiment the backing plate 14 is shown as having two pads 70 on each of the opposed sides thereof. However, the backing plate 14 may have more (or less) than two of such pads 70 if so desired, although two pads 70 are preferred. Also, the particular shape of the pads 70 may be different than that illustrated and/or can be different from each other and/or the location can be other than illustrated depending upon the particular configuration of the associated components of the brake assembly 10, so long as the pads 70 provide the function or purpose discussed below.
The drum-in-hat disc brake assembly 10 further includes the actuation lever 80, best shown in
As can be seen in
In the illustrated embodiment, the first end 88 of the actuation lever 80 is provided with an opening 88A and the second end 90 is provided with a raised or embossed projection 90A. The opening 88A in the first end 88 of the actuation lever 80 is adapted to receive a suitable fastener, such as a pivot pin 98 (shown in
In the illustrated embodiment, the second end 90 is also provided with a leg or extension 90B (shown in
Turning now to
Next, as shown in
One advantage of the present invention is that the drum-in-hat disc brake assembly 10 fully supports the associated actuation lever 80 relative to the backing plate 14 via the pads 70 when the actuation lever 80 is not actuated and also when the actuation lever 80 is actuated to improve the mechanical efficiency of the actuation lever 80.
In accordance with the provisions of the patent statues, the principle and mode of operation of this invention have been described and illustrated in its preferred embodiments. However, it must be understood that the invention may be practiced otherwise than as specifically explained and illustrated without departing from the scope or spirit of the attached claims.
