GB1586054A

GB1586054A - Drum brake and mounting means therefor

Info

Publication number: GB1586054A
Application number: GB12077/78A
Authority: GB
Original assignee: Bendix Corp
Current assignee: Bendix Corp
Priority date: 1977-04-04
Filing date: 1978-03-28
Publication date: 1981-03-18
Also published as: AU519918B2; ES468428A1; IT1093971B; MX144866A; FR2386733B1; FR2386733A1; BR7801946A; IT7821712A0; AU3438478A; DE2812043A1; CA1075176A; JPS53123774A

Description

(54) DRUM BRAKE AND MOUNTING MEANS THEREFOR (71) We, THE BENDIX CORPORATION, a corporation duly organised and existing under the laws of the State of Delaware, United States of America, of Bendix Center, Executive Offices, Southfield, Michigan 48075, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a drum brake for an automotive vehicle.

Drum brakes generally provide a pair of brake shoes slidably mounted relative to a backing plate and engageable with a drum to retard the rotation of the drum. Such drum brakes also dispose a hydraulic actuator and an adjustment mechanism between the pair of brake shoes at opposite locations. The pair of brake shoes are urged radially outwardly by the hydraulic actuator and the adjustment mechanism maintains a running clearance between the pair of brake shoes and the drum.

As the drum brake is disposed within the drum on a vehicle axle assembly and an axle shaft extends through a central opening on the backing plate, it is desirable to provide a simple drum brake construction which is narrow in the radial dimension.

To this end, the invention proposes a drum brake comprising a backing plate including a plurality of radially outwardly extending lugs, and at least a pair of brake shoes slidably received on said lugs and prevented from axial movement relative to said backing plate, characterized in that said backing plate further includes at least a pair of radially outwardly extending flanges defining recesses receiving respective portions of said brake shoes, resilient means being provided between each said portions and a corresponding of said lugs adjacent said portion to biase the latter into engagement with the corresponding recess when the brake is released.

According to another aspect of the invention the brake shoes include inner and outer webs, said lugs, said flanges and said resilient means extending between said inner and outer webs, the cooperation between said lugs and said inner and outer webs preventing axial movement of said brake shoes relative to said backing plate.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a front view of a drum brake made in accordance with the present invention; Figure 2 is a cross section taken along a line 2-2 of Figure 1; Figure 3 is a cross section taken along a line 3-3 of Figure 1; Figure 4 is a cross section taken along a line 44 of Figure 1; and Figure 5 is a cutaway of the circumscribed portion of Figure 1 showing the resilient mounting of the brake shoe on the backing plate.

A drum brake illustrated in Figure 1 is generally referred to by numeral 10. The drum brake includes a backing plate 12 which is provided with a plurality of radially outwardly extending lugs 14. The backing plate 12 is secured to a non-rotating portion of a wheel assembly such as a flange on the axle housing (not shown).

A pair of brake shoes, 16 and 18, are supported by the backing plate 12 in a manner to be described hereinafter and are movable radially for engagement with a rotating drum (not shown) to effectuate braking. The brake shoe 16 is provided with a friction lining 20, an axial outer web 22 and an axial inner web 24 such that the outer web 22 and the inner web 24 slidingly engage the lugs 14 when the brake shoe 16 is supported by the backing plate 12. The axial width of the lugs 14 is substantially equal to the spacing between the inner web 24 and the outer web 22. Consequently, the sliding engagement between the lugs 14 and the webs 22, 24 provides for radial movement of the brake shoe 16 but prevents any axial movement therebetween.

The brake shoe 18 is also provided with a friction lining 26, an axial outer web 28 and an axial inner web 30. Moreover, the spacing between the respective inner and outer webs 30 and 28, is such that the lugs 14 slidingly engage the webs 28 and 30 to permit radial movement of brake shoe 18 yet prevent axial movement of the brake 18 relative to the lugs 14.

The backing plate 12 further includes pair of radially outwardly extending flanges 32 and 34 which are provided with contoured recesses 36 and 38, respectively. The contoured recesses 36 and 38 receive corresponding pins 40 and 42 which are secured to the inner and outer webs of the brake shoes 18 and 16, respectively. The pins 40 and 42 are inserted in matching openings on the webs and secured thereto by any suitable means, such as welding.

In order to resiliently retain the pins in engagement with the contoured recesses, two of the lugs 14 on the backing plate 12 adjacent the flanges 32 and 34 are provided with projections 44 and 46. The projections 44 and 46 mount corresponding springs 48 and 50 which resiliently engage the respective pins 40 and 42 to bias the same into engagement with the contoured recesses 36 and 38, respectively. Moreover, the ends of the springs 48 and 50 engaging the pins 40 and 42 are V-shaped to maintain their engagement with the corresponding pins. The contour of the recesses 36 and 38 is such that the pins 40 and 42 within these recesses can move radially out of engagement with the recesses to contract the corresponding springs 48 and 50 during a braking application. Consequently, the pins move in opposition to the springs to engage the friction linings with the drum during braking and the springs urge the brake shoes away from the drum such that the pins engage the contoured recesses when braking is not occuring.

It is an important feature of the present invention that the backing plate projections 44 and 46, the springs 48 and 50, the pins 40 and 42, and the flanges 32 and 34 are disposed between the inner and outer webs and substantially within the radial width of these webs. With this structural arrangement, the drum brake 10 takes up little radial width, thereby enabling large axle shafts to extend through the drum brake assembly.

The brake shoes 16 and 18 cooperate with each other to support a floating double cylinder or hydraulic actuator 60 and automatic adjustment means 62 opposite the double actuator 60. The double actuator 60 and the adjustment means 62 are supported by the inner webs 24 and 30 and the outer webs 22 and 28 of brake shoes 16 and 18.

Turning to Figure 2, the double actuator 60 includes a housing 64 with two parallel bores 66 and 68 and slidably sealingly receiving two pistons 70 and 72 respectively. The housing 64 defines a common pressure chamber 74 communicating with a master cylinder (not shown). The chamber 74 communicates with bores 66 and 68 so that pressuriied fluid within chamber 74 urges piston 70 and piston 72 toward the left, viewing Figure 1. As shown in Figure 1, the housing 64 and the piston 70 include grooves or indentations 76 and 78 for receiving extensions 80 and 82 on the outer webs of brake shoes 16 and 18, respectively.

The housing 64 includes a second groove for receiving an extension (not shown) on the inner web 24 and the piston 72 includes a second groove for receiving an extension (not shown) on the inner web 30.

As the four grooves or indentations each receive an extension of either brake shoe 16 and 18, the double hydraulic actuator 60 is prevented from rotating relative to the shoes while being carried between the latter. A sealing boot 84 protects the bores 66 and 68 from contamination.

As shown in Figure 4, the adjustment means 62 include an extensible member 86 which is carried between two plates 88 and 90 secured respectively to the brake shoe 16 and the brake shoe 18. In the described embodiment, the plate 88 is press fitted into a slot 92 on outer web 22 and a slot 94 on inner web 24 in order to secure the plate 88 to the shoe 16 and the plate 90 is secured to the shoe 18 in a similar manner via slots on the latter. However, it will be understood that the plates 88 and 90 can be secured to the shoes 16 and 18 by any other suitable means.

The extensible member 86 comprises a rotating portion 93 having a start wheel 96 engaged by a pawl 98 and two stationary portions engaging plates 88 and 90 via Vshaped recesses 100 and 102. The V-shaped recesses 100 and 102 permit slight rotation of the extensible member 86 in a radial plane relative to the brake shoes. The pawl 98 includes a groove 104 about which it is pivotally mounted on an insert 120 on plate 88.

Furthermore, a spring 106 engages the pawl 98 and an insert 122 on plate 90 to maintain the pawl 98 in engagement with the star wheel 96.

A pivoting leg 108 connects pawl 98 with a rocker arm 112 pivotally mounted on brake shoe 16, and a pivoting leg 110 is mounted between rocker arm 112 and a plug 114 carried by the backing plate 12. The spring 106 maintains the plates 88 and 90 in engagement with the V-shaped recesses 100 and 102 and imparts rotation to the portion 93 via the star wheel 96 when the pawl 98 rotates through an increment of the radial displacements of brake shoes 16 and 18 during a brake application, in a manner well known in the art.

While the invention has been described in conjunction with a specific embodiment, it is evident that many alternatives, modifications and variations are apparent to one skilled in the art. Consequently, these alternatives, modifications and variations are intended to fall within the scope of the appended claims.

WHAT WE CLAIM IS: 1. A drum brake comprising a backing plate including a plurality of radially outwardly

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. movement of brake shoe 18 yet prevent axial movement of the brake 18 relative to the lugs 14. The backing plate 12 further includes pair of radially outwardly extending flanges 32 and 34 which are provided with contoured recesses 36 and 38, respectively. The contoured recesses 36 and 38 receive corresponding pins 40 and 42 which are secured to the inner and outer webs of the brake shoes 18 and 16, respectively. The pins 40 and 42 are inserted in matching openings on the webs and secured thereto by any suitable means, such as welding. In order to resiliently retain the pins in engagement with the contoured recesses, two of the lugs 14 on the backing plate 12 adjacent the flanges 32 and 34 are provided with projections 44 and 46. The projections 44 and 46 mount corresponding springs 48 and 50 which resiliently engage the respective pins 40 and 42 to bias the same into engagement with the contoured recesses 36 and 38, respectively. Moreover, the ends of the springs 48 and 50 engaging the pins 40 and 42 are V-shaped to maintain their engagement with the corresponding pins. The contour of the recesses 36 and 38 is such that the pins 40 and 42 within these recesses can move radially out of engagement with the recesses to contract the corresponding springs 48 and 50 during a braking application. Consequently, the pins move in opposition to the springs to engage the friction linings with the drum during braking and the springs urge the brake shoes away from the drum such that the pins engage the contoured recesses when braking is not occuring. It is an important feature of the present invention that the backing plate projections 44 and 46, the springs 48 and 50, the pins 40 and 42, and the flanges 32 and 34 are disposed between the inner and outer webs and substantially within the radial width of these webs. With this structural arrangement, the drum brake 10 takes up little radial width, thereby enabling large axle shafts to extend through the drum brake assembly. The brake shoes 16 and 18 cooperate with each other to support a floating double cylinder or hydraulic actuator 60 and automatic adjustment means 62 opposite the double actuator 60. The double actuator 60 and the adjustment means 62 are supported by the inner webs 24 and 30 and the outer webs 22 and 28 of brake shoes 16 and 18. Turning to Figure 2, the double actuator 60 includes a housing 64 with two parallel bores 66 and 68 and slidably sealingly receiving two pistons 70 and 72 respectively. The housing 64 defines a common pressure chamber 74 communicating with a master cylinder (not shown). The chamber 74 communicates with bores 66 and 68 so that pressuriied fluid within chamber 74 urges piston 70 and piston 72 toward the left, viewing Figure 1. As shown in Figure 1, the housing 64 and the piston 70 include grooves or indentations 76 and 78 for receiving extensions 80 and 82 on the outer webs of brake shoes 16 and 18, respectively. The housing 64 includes a second groove for receiving an extension (not shown) on the inner web 24 and the piston 72 includes a second groove for receiving an extension (not shown) on the inner web 30. As the four grooves or indentations each receive an extension of either brake shoe 16 and 18, the double hydraulic actuator 60 is prevented from rotating relative to the shoes while being carried between the latter. A sealing boot 84 protects the bores 66 and 68 from contamination. As shown in Figure 4, the adjustment means 62 include an extensible member 86 which is carried between two plates 88 and 90 secured respectively to the brake shoe 16 and the brake shoe 18. In the described embodiment, the plate 88 is press fitted into a slot 92 on outer web 22 and a slot 94 on inner web 24 in order to secure the plate 88 to the shoe 16 and the plate 90 is secured to the shoe 18 in a similar manner via slots on the latter. However, it will be understood that the plates 88 and 90 can be secured to the shoes 16 and 18 by any other suitable means. The extensible member 86 comprises a rotating portion 93 having a start wheel 96 engaged by a pawl 98 and two stationary portions engaging plates 88 and 90 via Vshaped recesses 100 and 102. The V-shaped recesses 100 and 102 permit slight rotation of the extensible member 86 in a radial plane relative to the brake shoes. The pawl 98 includes a groove 104 about which it is pivotally mounted on an insert 120 on plate 88. Furthermore, a spring 106 engages the pawl 98 and an insert 122 on plate 90 to maintain the pawl 98 in engagement with the star wheel 96. A pivoting leg 108 connects pawl 98 with a rocker arm 112 pivotally mounted on brake shoe 16, and a pivoting leg 110 is mounted between rocker arm 112 and a plug 114 carried by the backing plate 12. The spring 106 maintains the plates 88 and 90 in engagement with the V-shaped recesses 100 and 102 and imparts rotation to the portion 93 via the star wheel 96 when the pawl 98 rotates through an increment of the radial displacements of brake shoes 16 and 18 during a brake application, in a manner well known in the art. While the invention has been described in conjunction with a specific embodiment, it is evident that many alternatives, modifications and variations are apparent to one skilled in the art. Consequently, these alternatives, modifications and variations are intended to fall within the scope of the appended claims. WHAT WE CLAIM IS:

1. A drum brake comprising a backing plate including a plurality of radially outwardly

extending lugs, and at least a pair of brake shoes slidably received on said lugs and prevented from axial movement relative to said backing plate, wherein said backing plate further includes at least a pair of radially outwardly extending flanges defining recesses receiving respective portions of said brake shoes, resilient means being provided between each said positions and a corresponding of said lugs adjacent said portion to biase the latter into engagement with the corresponding recess when the brake is released.

2. A drum brake according to Claim 1, wherein said brake shoes include inner and outer webs, said lugs, said flanges and said resilient means extending between said inner and outer webs, the cooperation between said lugs and said inner and outer webs preventing axial movement of said brake shoes relative to said backing plate.

3. A drum brake according to Claim 2, wherein said brake shoe portion comprises a pin extending between the inner and outer webs and said resilient means extends from said adjacent lug to the pin to urge the latter into the corresponding recess.

4. A drum brake according to either Claim 2 or 3, wherein a hydraulic actuator is supported by said brake shoes, said actuator including grooves receiving extensions formed by the axially inner and outer webs of each brake shoe.

5. A drum brake according to Claim 4, wherein said hydraulic actuator comprises a housing in which at least two pistons axially spaced from each other are slidably received, said pistons and housing including said grooves for receiving the extensions.

6. A drum brake according to either Claims 4 or 5, wherein automatic adjustment means are disposed axially between the inner and outer webs and opposite said hydraulic actuator the latter cooperating with ends of the brake shoes near said backing plate flanges.

7. A drum brake according to Claim 6, wherein said adjustment means comprise a pair of plates, each said plates being received in slots provided in the inner and outer webs of the respective brake shoes, an extensible member extending between said plates and operatively engaging the latter to prevent rotation relative thereto, and a retention spring engaging one of the plates and urging said brake shoes together.

8. A drum brake according to Claim 7, wherein a pawl is pivotally mounted on the other of the plates and the retention spring engages the pawl to urge the latter into engagement with the extensible member.

9. A drum brake according to Claim 8, wherein said pawl includes a V-shaped groove for receiving the other of the plates in order to pivotally mount said pawl on the other of said plates.

10. A drum brake substantially as described and as illustrated with reference to the accompaying drawings.