GB1572744A

GB1572744A - Fluid-pressure-operated brakes for vehicles

Info

Publication number: GB1572744A
Application number: GB896577A
Authority: GB
Original assignee: Girling Ltd
Current assignee: Girling Ltd
Priority date: 1978-03-01
Filing date: 1978-03-01
Publication date: 1980-08-06

Description

(54) IMPROVEMENTS IN FLUID-PRESSURE-OPERATED BRAKES FOR VEHICLES (71) We, GIRLING LIMITED, a British Company of Kings Road, Tyseley, Birmingham 11, 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; This invention relates to fluid-pressureoperated drum brakes for vehicles of the kind in which friction members are adapted to be applied by fluid-pressure-operable means to the internal face of a rotatable drum.

In known brakes of the kind set forth which may be operated hydraulically the friction members usually comprise a pair of arcuate shoes which are mounted on a back plate and which are adapted to be urged into engagement with the drum by an actuator for separating adjacent shoe ends, or by a pair of actuators, each acting on an actuated end of one of the shoes, and the drag on the shoes when the brake is applied is taken by abutment means on the back plate with which non-actuated shoe ends engage.

According to our invention in fluid-pressure-operated drum brake of the kind set forth for vehicles the friction members comprise at least two friction pad assemblies which are symmetrically arranged with respect to the drum and which are slidably guided for movement towards and away from the drum in a substantially radial direction between drag-taking abutments in a relatively stationary drag-taking member.

Preferably the pad assemblies are adapted to be applied to the drum by means of pistons working in radially disposed cylinders in the drag-taking member.

Preferably the drag-taking member comprises a spider having at least three angularly spaced radial arms, conveniently four, with a cylinder located in each arm, and a friction pad assembly is guided between circumferentially spaced drag-taking extensions of each arm projecting outwardly beyond the outer end of the cylinder in that arm.

By applying individual friction pad assemblies directly to the drum in substantially radial directions has the advantage of providing a substantially fade free brake which is comparable to a disc brake but with the ability to operate in a drum where large swept areas can be obtained to give longer lining and drum life.

The pad assemblies are retained in position by removable keepers which are releasable from the inboard side of the dragtaking member so that the pad assemblies can be withdrawn axially in an inboard direction for replacement, leaving the drum in situ.

The drag-taking member may comprise a single casting or forging, or it may be of pressed metal construction with individual cylinders and integral extensions comprising housings located in gaps in the pressing. In either construction the drag-taking member may be carried by or integral with a stub axle for a vehicle.

Some embodiments of our invention are illustrated in the accompanying drawings in which: - Figure 1 is a plan of a drum brake suitable for a driven wheel including a section through an hydraulic cylinder; Figure 2 is a section on the line 2-2 of Figure 1; Figure 3 is a plan similar to Figure 1 but with the drag-taking member combined with a stub-axle for a non-driven wheel; Figure 4 is a section on the line 4-4 of Figure 3; Figure 5 is a plan similar to Figure 1 with the drag-taking member of fabricated pressed metal construction; Figure 6 is a section on the line 6-6 of Figure 5; Figure 7 is an elevation of one of the arms showing an modification; Figure 8 is an end view of the same showing retaining means for a friction pad assembly in the arm; and Figure 9 is a - perspective view of the same.

In the drum brake illustrated in Figure 1 a drag-taking member 1 comprising a casting or forging in the form of a spider is mounted within a dirt shield 2 on a stationary part. The drag-taking member 1 has four equiangularly spaced radial arms 3. Each arm is enlarged at its outer end to provide a cylinder 4, suitably hydraulic in which works a piston 5. Symmetrically arranged pairs of circumferentially spaced parallel extensions 6 project forwardly beyond the outer end of each arm 3, and a friction pad assembly 7 for engagement with a rotatable drum, not shown, is guided for movement towards and away from the drum between the inner faces of the extensions which define drag-taking abutments.

Each friction pad assembly 7 is of arcuate outline and comprises a pad or lining 8 of friction material carried by a rigid backing plate 9. The ends of the backing plated 9 are notched so that the bases of the notches slidably engage with the drag-taking abutments, and lugs on opposite sides of the notches straddle the extensions 6 and substantially U-shaped clips or strips 10 of resilient material which act as anti-rattle devices.

Each piston 5 is coupled to the base of the cylinder 4 in which it works by means of an adjustable return stop 11 of known type which serves to maintain braking clearances at a substantially constant value to compensate for wear of the friction linings 8.

When the brake is applied the four cylinders are pressurised to advance the four pistons 5 simultaneously to apply the pad assemblies 7 to the drum and, depending on the direction of drum rotation, the drag on the pad assemblies 7 is taken by the dragtaking abutment of that pair of extensions 6 with which any point on the surface of the drum last comes into alignment for that direction of drum rotation.

In the brake illustrated in Figures 3 and 4 the drag-taking member 1 is integral with a stub axle 12, and the assembly is adapted to be connected to suspension means through upper and lower suspension eyes 13 and 14.

The construction and operation of the brake is otherwise the same as that of Figures 1 and 2 and corresponding reference numerals have been applied to corresponding parts.

In the brake illustrated in Figures 5 and 6 the drag-taking member 1 comprises a metal pressing 15 of generally circular dished outline, and each cylinder 4 and extensions 6 comprise separate housings 16 which are received in gaps 17 in the edge of the pressing 15 with the housing 16 being rigidly secured by bolts 18 to the pressing 15 on opposite sides of the gaps 17.

The construction and operation of the brake of Figures 5 and 6 is otherwise the same as that of Figures 1 and 2 and corresponding reference numerals have been applied to corresponding parts.

In the construction described above the dirst shield 2 can be apertured and the arms 3 can be modified as shown in Figures 7 to 9 of the drawings so that circumferentially extending lugs 19 at opposite ends of the backing plates 9 are received in gaps 20 between open-sided recesses 21 in the extensions 6 and detachable keepers or plates 22 located on the inboard side of the arm 3 and releasably connected by removable screws 23. Therefore, by removing the keeper or plate 22, the pad assemblies 7 can be removed from the brake with the drum in situ by withdrawing them axially in an inboard direction through the apertures in the dirt shield.

WHAT WE CLAIM IS: 1. A fluid-pressure-operated frum brake of the kind set forth in which the friction members comprise at least two friction pad assemblies which are symmetrically arranged with respect to the drum and which are slidably guided for movement towards and away from the drum in a substantially radial direction between drag-taking abutments in a relatively stationary drag-taking member.

2. A fluid-pressure-operated drum brake as claimed in Claim 1, in which the pad assemblies being adapted to be applied to the drum by means of pistons working in radially disposed cylinders in the drag-taking member.

3. A fluid-pressure-operated drum brake as claimed in Claim 2, in which the drag-taking member comprises a spider having at least three angularly spaced radial arms, with a cylinder located in each arm, the friction pad assembly being guided between circumferentially spaced drag-taking extensions of each arm projecting outwardly beyond the outer end of the cylinder in that arm.

4. A fluid-pressure-operated drum brake as claimed in Claim 3, in which the drag-taking member has four arms.

5. A fluid-pressure-operated drum brake as claimed in any preceding claim, in which the pad assemblies are retained in position by removable keepers which are releasable from the inboard side of the drag taking member so that the pad assemblies can be withdrawn axially for replacement, without disturbing the drum.

6. A fluid-pressure-operated drum brake as claimed in Claim 5, in which the keepers are attached to the drag-taking

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. arms showing an modification; Figure 8 is an end view of the same showing retaining means for a friction pad assembly in the arm; and Figure 9 is a - perspective view of the same. In the drum brake illustrated in Figure 1 a drag-taking member 1 comprising a casting or forging in the form of a spider is mounted within a dirt shield 2 on a stationary part. The drag-taking member 1 has four equiangularly spaced radial arms 3. Each arm is enlarged at its outer end to provide a cylinder 4, suitably hydraulic in which works a piston 5. Symmetrically arranged pairs of circumferentially spaced parallel extensions 6 project forwardly beyond the outer end of each arm 3, and a friction pad assembly 7 for engagement with a rotatable drum, not shown, is guided for movement towards and away from the drum between the inner faces of the extensions which define drag-taking abutments. Each friction pad assembly 7 is of arcuate outline and comprises a pad or lining 8 of friction material carried by a rigid backing plate 9. The ends of the backing plated 9 are notched so that the bases of the notches slidably engage with the drag-taking abutments, and lugs on opposite sides of the notches straddle the extensions 6 and substantially U-shaped clips or strips 10 of resilient material which act as anti-rattle devices. Each piston 5 is coupled to the base of the cylinder 4 in which it works by means of an adjustable return stop 11 of known type which serves to maintain braking clearances at a substantially constant value to compensate for wear of the friction linings 8. When the brake is applied the four cylinders are pressurised to advance the four pistons 5 simultaneously to apply the pad assemblies 7 to the drum and, depending on the direction of drum rotation, the drag on the pad assemblies 7 is taken by the dragtaking abutment of that pair of extensions 6 with which any point on the surface of the drum last comes into alignment for that direction of drum rotation. In the brake illustrated in Figures 3 and 4 the drag-taking member 1 is integral with a stub axle 12, and the assembly is adapted to be connected to suspension means through upper and lower suspension eyes 13 and 14. The construction and operation of the brake is otherwise the same as that of Figures

1 and 2 and corresponding reference numerals have been applied to corresponding parts.

In the brake illustrated in Figures 5 and 6 the drag-taking member 1 comprises a metal pressing 15 of generally circular dished outline, and each cylinder 4 and extensions 6 comprise separate housings 16 which are received in gaps 17 in the edge of the pressing

15 with the housing 16 being rigidly secured by bolts 18 to the pressing 15 on opposite sides of the gaps 17.

member by means of at least one screw.

7. A fluid-pressure-operated drum brake as claimed in any preceding claim, in which the drag-taking member comprises a single casting or forging.

8. A fluid-pressure-operated drum brake as claimed in any of Claims 1 to 6, in which the drag-taking member is of pressed metal construction, with individual cylinders and integral extensions comprising housings located in gaps in the pressing.

9. A fluid-pressure-operated drum brake as claimed in Claim 7 or Claim 8, in which the drag-taking member is combined with a stub axle for a vehicle.

10. A fluid-pressure-operated drum brake as claimed in any preceding claim, in which the fluid pressure is hydraulic.

11. A fluid-pressure-operated drum brake substantially as herein described with reference to, and as illustrated in the accompanying drawings.