GB2039644A - Vehicle friction brake - Google Patents

Abstract

The Specification describes a vehicle friction brake having a brake shoe (4) bearing a friction lining (9) and mounted on a support plate (2) for movement across the plate towards and away from a brake drum rotation of which is to be braked. The shoe (4) is biased by a spring (12) towards the support plate (2) and as shown the friction lining (9) overlaps the edge of the shoe (4) to engage a pad, lining or coating of friction material (11) mounted on the plate (2) or alternatively the plate (2) itself. In an alternative arrangement the friction material (11) engages either the shoe (4) itself or the shoe (4) and lining (9) and the lining (9) does not overlap the shoe (4). The friction between the plate (2) and shoe (4) prevents noise-producing vibration during braking. <IMAGE>

Description

SPECIFICATION Vehicle friction brake This invention relates to a vehicle friction brake having a brake shoe bearing a friction lining and mounted on a support plate for movement across the plate towards and away from a brake drum or other member rotation of which is to be braked, the shoes being spring biased towards the support plate.

During operation, such friction brakes (which usually have two brake shoes) tend to produce noises, particularly screeching. These noises, which can occur under various operation conditions, are usually produced by vibration of the brake shoes during braking, the vibration being transmitted to the drum and radiated thence in the form of sound.

The purpose of spring-biasing the shoes to engage the support plate is to reduce the vibration, but even so the vibration can still be annoying during certain operating conditions.

An aim of the invention is to improve a friction brake so as to reduce or substantially avoid vibration which causes undesirable noise.

According to the invention,this aim is achieved in a friction brake of the construction set out in the opening paragraph of the Specification by constructing the friction lining to extend beyond an edge of the brake shoe adjacent the support plate so that an edge of the lining engages the support plate or a part carried by the plate.

As a result of this feature, the tendency of the brake shoe to vibrate when actuated is effectively reduced because of the high friction between the lining edge and the brake support plate which it abuts.

In order to obtain still higher friction between the brake shoe lining and the support plate it is preferred that the region of the support plate (or part carried by the plate) which is engaged by the edge of the brake lining carries a lining, coating or pad of a material having a high coefficient of friction with the material of the brake lining.

A preferred embodiment a friction brake according to the invention will now be described by way of example and with reference to the accompanying drawing in which: Figure 1 is a plan view of a shoe and drum brake according to the invention, and Figure 2 is a larger-scale cross-section along line I-I in Figure 1, the view being inverted and omitting the brake drum.

The drum and shoe brake shown in the drawing is in most respects of conventional design and will therefore be described only briefly. It comprises a brake drum 1 fast with a vehicle wheel or drive shaft (not shown) which is to be braked. Behind the drum 1 there is a stationary brake support plate 2 on which two brake shoes 4, 5 are mounted for pivoting about a pin 3. Shoes 4 and 5 are arranged to be pivoted by a hydraulic brake cylinder 6 which is likewise mounted on plate 2. When pressure medium is supplied to the cylinder 6 two cylinder pistons (not h b ^ b ^ ^ A C: h shoes to move across the plate 2 towards the drum 1, the shoes pivoting about the pin 3 to cause friction linings 9 and 10 carried by the shoes to engage the drum 1 and effect braking.Two tension springs 7,8 connect the shoes 4 and 5 and bias the shoes towards the illustrated position in which the shoes are spaced from the drum 1 and the brake is off. The shoes 4 and 5 are T-shaped in cross-section as shown in Figure 2, and the linings 9 and 10 are so dimensioned and disposed on the shoes 4,5 that they project beyond edges of the shoes on the side facing the adjacent plate 2. Plate 2, at the places where it abuts linings 9 and 10, carries a material 11 (which could be a lining coating or pad) having a high coefficient of friction with the material of the linings 9,10. In order to maintain a permanently constant bearing pressure between the friction part 11 and the linings 9 and 10 the shoes 4, 5 are loaded by springs 12, 13 respectively.As shown in Figure 2, springs 12,13 are held by a retaining pin 14which projects through them and through bores in plate 2 and in shoe 4. The pin 14 has a head 15 at one end which is held in plate 2 and a projection 16 at its other end, the projection 16 being releasably engaged with a washer bearing against spring 12. Of course, springs 12 and 13 have a given prestress, so that linings 9, 10 exert a constant pressure on parts 11 of plate 2. As a result of the high coefficient of friction between linings 9, 10 and parts 11,vibration of shoes 4 and 5 is largely eliminated or suppressed when the brake is actuated.

In an alternative embodiment which is not illustrated the linings 9 and 10 could engage the plate 2 directly and the friction material 11 could be omitted.

In another embodiment, the linings 9 and 10 could terminate adjacent that edge of the brake shoes facing the plate 2 instead of projecting beyond that edge of the shoes. In this case, the friction material 11 would engage the shoes 4,5 and/ortheir linings 9, 10 to reduce brake shoe vibration.

1. A vehicle friction brake having a brake shoe bearing a friction lining and mounted on a support plate for movement across the plate towards and away from a brake drum or other member rotation of which is to be braked, the shoe being spring biased towards the support plate and the friction lining extending beyond an edge of the brake shoe adjacent the support plate so that an edge of the lining engages the support plate or a part carried by the plate.

2. A brake according to claim 1, in which the region of the support plate (or part carried by the plate) which is engaged by the edge of the brake lining carries a lining, coating or pad of a material having a high coefficient of friction with the material of the brake lining.

3. A vehicle friction brake having a brake shoe bearing a friction lining and mounted on a support plate for movement across the plate towards and away from a brake drum or other member rotation of which is to be braked, the shoe being spring biased +S~r,lc thP ciinnnrt nl to which hnnrn A linings.

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

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Vehicle friction brake This invention relates to a vehicle friction brake having a brake shoe bearing a friction lining and mounted on a support plate for movement across the plate towards and away from a brake drum or other member rotation of which is to be braked, the shoes being spring biased towards the support plate. During operation, such friction brakes (which usually have two brake shoes) tend to produce noises, particularly screeching. These noises, which can occur under various operation conditions, are usually produced by vibration of the brake shoes during braking, the vibration being transmitted to the drum and radiated thence in the form of sound. The purpose of spring-biasing the shoes to engage the support plate is to reduce the vibration, but even so the vibration can still be annoying during certain operating conditions. An aim of the invention is to improve a friction brake so as to reduce or substantially avoid vibration which causes undesirable noise. According to the invention,this aim is achieved in a friction brake of the construction set out in the opening paragraph of the Specification by constructing the friction lining to extend beyond an edge of the brake shoe adjacent the support plate so that an edge of the lining engages the support plate or a part carried by the plate. As a result of this feature, the tendency of the brake shoe to vibrate when actuated is effectively reduced because of the high friction between the lining edge and the brake support plate which it abuts. In order to obtain still higher friction between the brake shoe lining and the support plate it is preferred that the region of the support plate (or part carried by the plate) which is engaged by the edge of the brake lining carries a lining, coating or pad of a material having a high coefficient of friction with the material of the brake lining. A preferred embodiment a friction brake according to the invention will now be described by way of example and with reference to the accompanying drawing in which: Figure 1 is a plan view of a shoe and drum brake according to the invention, and Figure 2 is a larger-scale cross-section along line I-I in Figure 1, the view being inverted and omitting the brake drum. The drum and shoe brake shown in the drawing is in most respects of conventional design and will therefore be described only briefly. It comprises a brake drum 1 fast with a vehicle wheel or drive shaft (not shown) which is to be braked. Behind the drum 1 there is a stationary brake support plate 2 on which two brake shoes 4, 5 are mounted for pivoting about a pin 3. Shoes 4 and 5 are arranged to be pivoted by a hydraulic brake cylinder 6 which is likewise mounted on plate 2. When pressure medium is supplied to the cylinder 6 two cylinder pistons (not h b ^ b ^ ^ A C: h shoes to move across the plate 2 towards the drum 1, the shoes pivoting about the pin 3 to cause friction linings 9 and 10 carried by the shoes to engage the drum 1 and effect braking.Two tension springs 7,8 connect the shoes 4 and 5 and bias the shoes towards the illustrated position in which the shoes are spaced from the drum 1 and the brake is off. The shoes 4 and 5 are T-shaped in cross-section as shown in Figure 2, and the linings 9 and 10 are so dimensioned and disposed on the shoes 4,5 that they project beyond edges of the shoes on the side facing the adjacent plate 2. Plate 2, at the places where it abuts linings 9 and 10, carries a material 11 (which could be a lining coating or pad) having a high coefficient of friction with the material of the linings 9,10. In order to maintain a permanently constant bearing pressure between the friction part 11 and the linings 9 and 10 the shoes 4, 5 are loaded by springs 12, 13 respectively.As shown in Figure 2, springs 12,13 are held by a retaining pin 14which projects through them and through bores in plate 2 and in shoe 4. The pin 14 has a head 15 at one end which is held in plate 2 and a projection 16 at its other end, the projection 16 being releasably engaged with a washer bearing against spring 12. Of course, springs 12 and 13 have a given prestress, so that linings 9, 10 exert a constant pressure on parts 11 of plate 2. As a result of the high coefficient of friction between linings 9, 10 and parts 11,vibration of shoes 4 and 5 is largely eliminated or suppressed when the brake is actuated. In an alternative embodiment which is not illustrated the linings 9 and 10 could engage the plate 2 directly and the friction material 11 could be omitted. In another embodiment, the linings 9 and 10 could terminate adjacent that edge of the brake shoes facing the plate 2 instead of projecting beyond that edge of the shoes. In this case, the friction material 11 would engage the shoes 4,5 and/ortheir linings 9, 10 to reduce brake shoe vibration. CLAIMS

1. A vehicle friction brake having a brake shoe bearing a friction lining and mounted on a support plate for movement across the plate towards and away from a brake drum or other member rotation of which is to be braked, the shoe being spring biased towards the support plate and the friction lining extending beyond an edge of the brake shoe adjacent the support plate so that an edge of the lining engages the support plate or a part carried by the plate.

2. A brake according to claim 1, in which the region of the support plate (or part carried by the plate) which is engaged by the edge of the brake lining carries a lining, coating or pad of a material having a high coefficient of friction with the material of the brake lining.

3. A vehicle friction brake having a brake shoe bearing a friction lining and mounted on a support plate for movement across the plate towards and away from a brake drum or other member rotation of which is to be braked, the shoe being spring biased +S~r,lc thP ciinnnrt nl to which hnnrn A linings.

coating or pad of high friction material against which an edge of the shoe and/or its friction material bears.

4. A vehicle friction brake substantially as described herein with reference to the accompanying drawing.