Brakes – Wheel – Transversely movable
Reexamination Certificate
1999-01-29
2001-03-27
Schwartz, Christopher P. (Department: 3613)
Brakes
Wheel
Transversely movable
C188S327000, C188S328000
Reexamination Certificate
active
06206148
ABSTRACT:
This invention relates to a drum brake having a duo mode of operation. In a service mode, a hydraulic actuator moves brake pads into engagement with a drum to effect a first brake application and in a parking brake mode, a mechanical operated lever pivots on an extendible shaft of an adjustable strut to move brake pads into engagement with the drum and effect a second brake application.
BACKGROUND OF THE INVENTION
Duo-mode drum brakes of a type disclosed in U.S. Pat. Nos. 4,249,646 and 4,364,456 are frequently used in combination on vehicles having front wheel disc brakes. For parking brake functions, the disc brake is mechanically actuated by applying a force through a lever arm which is carried on a web of a brake shoe. The lever arm has a first end which is pivotally attached to the web and a second end which is linked to a cable located adjacent a pivot block. The cable typically being attached to the second end in a manner as disclosed in U.S. Pat. No. 5,706,914. The mechanical actuation of this type drum brake is capable of providing sufficient braking force for parking and is adequate for most applications, however, the cost associated with manufacturing has resulted in customers requesting an alternate for implementing the function of a parking brake. In-addition when this type brake is used on vehicles identified as sport-utility models it is desirous to have all components as far away from the ground as possible to avoid the engagement with sand, rocks, stumps, and non-level ground.
In an effort to develop a robust brake for the rear of a front wheel drive vehicle it has been proposed to use disc brakes on all of the wheels and provide for a parking brake function through a drum brakedisc brake, as disclosed in U.S. Pat. Nos. 5,180,037 and 5,529,149 and commonly referred to as drum-in-hat. The drum brake being actuated through a scissors arrangement in responds to mechanical input. This arrangement performs in an adequate manner but the cost and weight has resulted in some manufacturers looking for a low cost and light-weight brake.
SUMMARY OF THE INVENTION
On review of the use and performance required for braking a front wheel driven vehicle or a rear wheel drive on an all wheel drive vehicle, it was determined that a drum brake could meet the operational requirements and the parking brake function could be achieved through the duo-use of the drum brake. In the present invention, a drum brake assembly having first and second brake shoes is retained on a backing plate by first and second pins. Each of the first and second brake shoes has a first end aligned on an anchor block and a second end connected to a hydraulic actuator assembly. An adjustable strut mechanism located between the first and second brake shoes has a extendable shaft with a first end that engages the first end of the first brake shoe and a second end that engages the first end of the second brake shoe. A first resilient member urges the first and second brake shoes toward the hydraulic actuator assembly and second resilient member urges the first and second brake shoes toward the anchor block. The length of the extendable shaft is periodically adjusted by the operation of a ratchet pawl to establish a predetermined running clearance between the first and second friction pads and drum. The hydraulic actuator assembly responds to a first input to respectively move first and second friction pads associated with the first and second brake shoes into engagement with a drum and effect a first brake application during the service mode of operation. A mechanical actuator has a lever, which extends through the backing plate adjacent the hydraulic actuator, is pivotally connect to an arm that extends from the extendable shaft. The lever has a variable surface which is connected to the web of the second brake shoe. A second input applied to lever is axially applied to the first and second brake shoes through the extendable shaft to correspondingly move the first and second friction pads associated with the first and second brake shoes into engagement with a drum to effect a second brake application during the parking brake mode of operation.
An advantage of the present invention resides in a mechanical actuator which is positioned on an extendable shaft associated with an adjustable strut to provide an input to effect a parking brake function of a vehicle.
A further advantage of this invention is to provide a drum brake with a duo-mode of actuation whereby a service brake is converted to a parking brake by substituting a manual input through a lever carried on a adjustable strut which maintains a desired running clearance.
REFERENCES:
patent: 3941218 (1976-03-01), Torii
patent: 5002159 (1991-03-01), Brix et al.
patent: 5029676 (1991-07-01), Yamamoto
patent: 5058713 (1991-10-01), Evans
patent: 5092428 (1992-03-01), Kobayashi et al.
patent: 5180037 (1993-01-01), Evans
patent: 816706 (1998-07-01), None
patent: 8303492 (1996-11-01), None
patent: 10299801 (1998-11-01), None
Capek Joseph Carl
Hostetler Norman Lee
Comstock Warron
McCormick Jr. Leo H
Nguyen Xuan Lan
Robert Bosch Corporation
Schwartz Christopher P.
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