CA1112190A - Drum brake having parking mechanism - Google Patents

Drum brake having parking mechanism

Info

Publication number
CA1112190A
CA1112190A CA321,443A CA321443A CA1112190A CA 1112190 A CA1112190 A CA 1112190A CA 321443 A CA321443 A CA 321443A CA 1112190 A CA1112190 A CA 1112190A
Authority
CA
Canada
Prior art keywords
pair
brake
levers
assembly
drum
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA321,443A
Other languages
French (fr)
Inventor
Donald D. Johannesen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Bendix Corp
Original Assignee
Bendix Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bendix Corp filed Critical Bendix Corp
Application granted granted Critical
Publication of CA1112190A publication Critical patent/CA1112190A/en
Expired legal-status Critical Current

Links

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16DCOUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D65/00Parts or details
    • F16D65/14Actuating mechanisms for brakes; Means for initiating operation at a predetermined position
    • F16D65/16Actuating mechanisms for brakes; Means for initiating operation at a predetermined position arranged in or on the brake
    • F16D65/22Actuating mechanisms for brakes; Means for initiating operation at a predetermined position arranged in or on the brake adapted for pressing members apart, e.g. for drum brakes
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16DCOUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D65/00Parts or details
    • F16D65/38Slack adjusters
    • F16D65/40Slack adjusters mechanical
    • F16D65/52Slack adjusters mechanical self-acting in one direction for adjusting excessive play
    • F16D65/56Slack adjusters mechanical self-acting in one direction for adjusting excessive play with screw-thread and nut
    • F16D65/561Slack adjusters mechanical self-acting in one direction for adjusting excessive play with screw-thread and nut for mounting within the confines of a drum brake
    • F16D65/565Slack adjusters mechanical self-acting in one direction for adjusting excessive play with screw-thread and nut for mounting within the confines of a drum brake arranged diametrically opposite to service brake actuator, and subjected to service brake force
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16DCOUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D2125/00Components of actuators
    • F16D2125/18Mechanical mechanisms
    • F16D2125/58Mechanical mechanisms transmitting linear movement
    • F16D2125/60Cables or chains, e.g. Bowden cables

Abstract

DRUM BRAKE HAVING PARKING MECHANISM
ABSTRACT OF THE DISCLOSURE
A drum brake assembly includes a pair of brake shoes which are movable to a braking position by a hydraulic actuator. In order to maintain the pair of brake shoes adjacent the drum an adjuster is disposed between the pair of brake shoes opposite the hydraulic actuator. The adjuster carries a parking mechanism to manually move the pair of brake shoes to the braking position independently of the hydraulic actuator. The parking mechanism comprises a pair of levers which are pivotally connected to pro-jections on the adjuster and the levers oppose one of the pair of brake shoes such that pivoting of the pair of levers moves the adjuster and the other brake shoe away from the one brake shoe. A spacer and a washer are dis-posed between the one brake shoe and abutment surfaces on each pair of levers and the adjuster movably supports the spacer and the washer.

Description

O

The present invention relates to a drum brake assembly, and more particularly, to a brake assembly including an extendible assembly and a parking assembly cooperating therewith.
In a drum brake assembly, such as illustrated in Canadian Patent No. 1,072,459, issued February 26, 1980, a parking strut and a lever generally cooperate to manually urge a pair of brake shoes to a braking position. The strut extends between the pair of brake shoes near a hydraulic actuator and the lever is pivotally mounted on one of the brake shoes such that the lever is pivoted to push the strut and other brake shoe away from the one brake shoe which pivotally supports the lever.
When large diameter axle shafts are required, the amount of space available within a drum brake assembly is -~
reduced so that a parking brake strut, which extends between a pair of brake shoes near the hydraulic actuator, inter-feres with the axle shaft between the pair of brake shoes.
~- Consequently, it is desirable to eliminate the parking brake strut, but retain the parking brake feature.
The present invention resides in a drum brake assembly having a brake drum rotatable about an axis and a pair of brake shoes which are movable radially by a hydraulic actuator from a non-braking position to a braking position in engagement with the drum during a service .
brake application. An extendibIe assembly is provided which has a longitudinal axis and is engageable with the - pair of brake shoes to substantially define the non-braking position. A pair of levers is secured to the ; 30 extendible assembly, and the pair of levers is pivotal in opposite directions relative to the extendible assembly to move the pair of brake shoes from the non-braking position . ~ --1--'' ~12~0 to the braking position during a parking brake application.
The extendible assembly includes a pair of projections extending radially therefrom in opposite directions from the extendible assembly to define mountings which are radially offset from each other relative to the drum axis and axially offset from each other in a direction parallel to the drum axis. The mountings pivotally secure the pair of levers to the extendible assembly such that the pair of levers are pivotally secured on opposite sides of the extendible assembly at axially spaced locations.
In a specific embodiment of the invention, the extendible assembly is movable with one of the pair of brake shoes as the one brake shoe is moved relative to the other brake shoe in response to pivoting of the pair of levers, and the extendible assembly movingly carries a -spacer engageable with the pair of levers and the other brake shoe.
It is a primary object of the present invention to incorporate a parking mechanism with an adjustment means for a drum brake assembly so that a conventional parking brake strut extending between a pair of brake shoes can be eliminated.
BRIEF DESCRIPTION OF T~E DRAWINGS
Figure 1 is a side view of a drum brake assembly --constructed in accordance with the present invention;
: Figure 2 is a cross-sectional view taken along - line 2-2 of Figure l; and ' Figure 3 is a cross-sectional view taken along line 3-3 of Figure 2.
DETAILED DESCRIPTION
The drum brake assembly 10 illustrated in Figure 1 is similar to the drum brake assembly of Canadian Patent 1 .
'I ' ,, .

```` `` ~L1~2i9~) No. 1,075,176, issued April 8, 1980 of which I am a co-inventor. A backing plate 12 is secured by any suitable means to an-axle housing (not shown) and an opening 14 is ~`; dimensioned to permit a large diameter axle shaft to extend axially therethrough.
A plurality of lugs at 16 extend radially from the backing plate 12 to slidably support a pair of brake shoes 18 and 20 and a hydraulic actuator 22 is engageable with one end of the brake shoes 18 and 20. The hydraulic ` 10 actuator 22 operates to move the pair of brake shoes 18 and 20 to a braking position engaging the drum 24. In order to maintain the pair of brake shoes adjacent the drum 24, regardless the friction lining dimension of each brake shoe, an adjustment means 26 is engageable with the other end of each brake shoe to take up the wear of the friction lining of each brake shoe. The adjustment means 26 comprises an extendible member 28 which includes a nut - 30, a sleeve 32 and a threaded stem 34. A star wheel 36 is engageable with a pawl 38 so that the pawl imparts rotation to the star wheel and threaded stem when the clearance between the pair of brake shoes and the drum is greater than a predetermined value.
Turning to Figure 2, it is seen that the brake shoes 18 and 20 include bifurcated webs for fixedly securing - a plate 40 which is attached to the brake shoe 20 and a ; plate 42 which is attached to the brake shoe 18. The nut 30 and the sleeve 32 i~clude slots 44 and 46 which receive the plate 40 and 42, respectively. Consequently, the ,~ extendible member 28 is carried between the pair of brake shoes opposite the hydraulic actuator 22.
In accordance with the invention the nut 30 forms projections 48 and 50, see Figure 3, which extend radially !~

219~

therefrom to define pins 52 and 54, respectively. The projections and pins extend from opposite sides of the nut and are offset from each other, so that the lever 58 is pivotally mounted on the top side of the extrudible member 28 and the lever 56 is pivotally moun,ed on the bottom side of the extrudible member 28, as shown in Figure 1.
In Figure 3 it is seen that the projection 50 extends upward from the nut 30 and the projection 48 extends down-ward from the nut 30. Moreover, the projection 50 and pin 54 are offset to the right of the center of the nut 30, while the projection 48 and pin 52 are offset to the left of the center of nut 30. The pair of levers 56 and 58 are pivotally anchored on the respective pins 52 and 54 and the pair of levers 56 and 58 extend from their pivotal connection with the nut 30 to engage a conduit 60 and a cable 62 extending from the conduit 60, respectively. Because the cable 62 is substantially concentric with the conduit 60, the lever 56 and the lever 58 are bent to provide for the engagement between the pair of levers and the conduit and cable to coincide with the axis of the conduit. The :~ pair of levers cooperate with the extendible member and the pair of brake shoes to substantially define a parking mechanism.
; A spacer 70 is slidably carried by the nut 30 between the projections 48 and 50 and the engagement with ~ - the plate 40 of the brake shoe 20. Adjoining the spacer is - a washer 72 which is free to slide with the spacer on the - nut 30 and rotate relative to the nut 30. The spacer is 1 engageable with the brake shoe plate 40 and the washer 72 ;¦ 30 is engageable with an abutment surface 74 on the lever 56 , and an abutment surface 76 on the lever 58. The abutment ,.
~ surface 74 on lover 56 is disposed above the pivotal -` ~$1~
connection at pin 52 while the abutment surface 76 on lever 58 i~ disposed below the pivotal connection at pin 54.

~ ' :
.

.

. .

i ~4a-MODE OF OPERATION
When a vehicle operator steps on a brake pedal, pressurized fluid is comnunicated to the hydraulic actuator 22 to radially expand the pair of brake shoes 18 and 20 into engagement with the rotating drum 24, thereby ~ -retarding the rotation of the latter. The operation of the drum brake assem-bly 10 during service braking is the same as the operation of a conventional drum brake.
When the vehicle is parked, the vehicle operator steps on the parking brake pedal (not shown) which retracts the cable 62 within the con-10 duit 60 as the cable 62 is connected by any suitable means to the parking brake pedal. In addition, the conduit 60 moves relative to the cable 62 to telescope the cable into the conduit 60. Therefore, the lever 56 is pivoted counterclockwise, viewing Figure 2, about pin 52 and the lever 58 is pivoted clockwise about pin 54. The pivoting of the pair of levers causes the abut-ment surfaces 74 and 76 to rotate relative to the pins, thereby imparting movement to the washer 72 and spacer 70 towards the brake shoe plate 40.
With the spacer 70 in engagement with the plate 40, the piwting of the abutment surfaces toward the washer 72 imparts a force to the nut 30 urging the nut 30 to move away from the plate 40. Consequently, further pivoting 20 of the levers and abutment surfaces causes the nut 30, stem 34 and sleeve 32,' to move away from the plate 40, thereby radially expanding the brake shoe 18 into engagement with the drum 24. When the brake shoe 18 is in engagement with the drum 24, the pivoting levers and abutment surfaces continue to slide the spacer and washer on the nut 30 away from the brake shoe 18, thereby urging the brake shoe 20 to radially expand into engagement with the ; drum 24. When both brake shoes are in engagement with the drum 24 the drum . .
is prevented fro~ rotating so that the vehicle is rendered stationary.
Viewing Figure 1, it is seen that the pair of levers 56 and ~8 extend axially inwardly relative to the backing plate 12 between two con-30 secutive lugs 16 so that the levers take up a small radial width and are '`

spaced from the central space defined by the inner periphery of the pair of brake shoes. Therefore, the opening 14 can be dimensioned large enough to accept large diameter axle shafts.
With the pair of levers 56 and 58 rotating in opposite directions, the w3sher 72 is urged to rotate in a counterclockwise direction, viewing Figure 3, by both levers. As a result, the abutment surfaces 74 and 76 slide over the rotating washer, thereby preventing scoring of the washer at one location.
Although the parking mechanism described hereinabove is illustrated with a pair of brake shoes which include bifurcated webs, it is intended that such a parking mechanism is readily adaptable for use with any type of drum brake assembly. In addition, many variations of the present invention are possible by one skilled in the art and these variations are included within the scope of the appended claims.

Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLOWS:
1. In a drum brake assembly having a brake drum rotatable about an axis and a pair of brake shoes which are movable radially by a hydraulic actuator from a non-braking position to a braking position in engagement with the drum during a service brake application, an extendible assembly having a longitudinal axis and engageable with the pair of brake shoes to substantially define the non-braking position, and a pair of levers secured to the extendible assembly, the pair of levers being pivotal in opposite directions relative to the extendible assembly to move the pair of brake shoes from the non-braking position to the braking position during a parking brake application, the extendible assembly including a pair of projections extending radially there-from in opposite directions from the extendible assembly to define mountings which are radially offset from each other relative to the drum axis and axially offset from each other, in a direction parallel to the drum axis the mountings pivotally securing the pair of levers to the extendible assembly such that the pair of levers are pivotally secured on opposite sides of the extendible assembly at axially spaced locations.
2. The drum brake assembly of claim 1 in which the extendible assembly is movable with one of the pair of brake shoes as the one brake shoe is moved relative to the other brake shoe in response to pivoting of the pair of levers and the extendible assembly movably carries a spacer engageable with the pair of levers and the other brake shoe.
3. In a drum brake assembly having a brake drum rotatable about an axis and a pair of brake shoes which are movable radially by a hydraulic actuator from a non-braking position to a braking position in engagement with the drum during a service brake application, an extendible assembly having a longitudinal axis and engageable with the pair of brake shoes to substantially define a non-braking position and a parking assembly cooperating with the extendible assembly to move the pair of brake shoes radially from the non-braking position to a braking position in engagement with the drum during a parking brake application, characterized by the parking assembly including a pair of levers pivotally secured to the extendible assembly, the pair of levers defining abutment surfaces, which oppose one of the pair of brake shoes, and pivoting in opposite directions relative to the extendible assembly during a parking brake application, the extendible assembly including a first projection pivotally mounting one of the pair of levers and a second projection pivotally mounting the other lever, and the one lever pivotally engages the first projection at a location which is radially offset from the pivotal engagement between the second projection and the other lever relative to the drum axis from the pivotal engagement between the second projection and the other lever in a direction parallel to the drum axis, said projections defining mountings securing the pair of levers to the extendible assembly such that the pair of levers are pivotally secured on opposite sides of the extendible assembly.
CA321,443A 1978-03-27 1979-02-14 Drum brake having parking mechanism Expired CA1112190A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US89075278A 1978-03-27 1978-03-27
US890,752 1986-07-25

Publications (1)

Publication Number Publication Date
CA1112190A true CA1112190A (en) 1981-11-10

Family

ID=25397104

Family Applications (1)

Application Number Title Priority Date Filing Date
CA321,443A Expired CA1112190A (en) 1978-03-27 1979-02-14 Drum brake having parking mechanism

Country Status (7)

Country Link
JP (1) JPS54134261A (en)
AU (1) AU521187B2 (en)
CA (1) CA1112190A (en)
DE (1) DE2909713A1 (en)
FR (1) FR2421305A1 (en)
GB (1) GB2017235B (en)
IT (1) IT1112402B (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4344512A (en) * 1980-02-20 1982-08-17 The Bendix Corporation Duo servo drum brake and parking mechanism therefor
US5085296A (en) * 1990-08-23 1992-02-04 Allied-Signal Inc. Mechanically actuated brake with automatic adjustment

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2347366A (en) * 1941-01-03 1944-04-25 Automotive Prod Co Ltd Internal shoe drum brake
DE939072C (en) * 1949-09-24 1956-02-16 Teves Kg Alfred Shoe brake, especially for motor vehicles
FR64442E (en) * 1953-06-30 1955-11-10 Brake for motor vehicles
FR1145621A (en) * 1956-03-12 1957-10-28 Brake control and brake comprising this control
US3027981A (en) * 1959-07-15 1962-04-03 Gen Motors Corp Brake actuator
FR1318157A (en) * 1962-03-22 1963-02-15 Girling Ltd Device for mechanically actuating the shoes of a drum brake

Also Published As

Publication number Publication date
AU4488079A (en) 1979-10-04
AU521187B2 (en) 1982-03-18
GB2017235B (en) 1982-05-06
IT1112402B (en) 1986-01-13
IT7921228A0 (en) 1979-03-23
JPS54134261A (en) 1979-10-18
FR2421305B1 (en) 1982-11-19
DE2909713A1 (en) 1979-10-11
FR2421305A1 (en) 1979-10-26
GB2017235A (en) 1979-10-03

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