CA2323264C

CA2323264C - Brake backing plate with integrally formed spring hole plug

Info

Publication number: CA2323264C
Application number: CA 2323264
Authority: CA
Inventors: Ray Arbesman
Original assignee: Individual
Current assignee: Nucap Industries Inc
Priority date: 2000-10-13
Filing date: 2000-10-13
Publication date: 2010-01-12
Anticipated expiration: 2020-10-13
Also published as: CA2323264A1

Abstract

The invention provides a disc brake backing plate with an integrally formed spring hole plug. A blind hole is defined within the plate, terminating at a closed boss (plug) on the friction material- receiving surface of the plate. The blind hole is adapted to receive and secure an end of a conventional shoe retaining spring for mounting the finished brake pad within a disc brake caliper. The integral boss prevents friction material from entering the hole at the friction molding stage, relieving the manufacturer of the need to add separate blocking hardware. A method of manufacturing the plate with an integrally formed spring hold plug is also provided.

Description

BRAKE BACKING PLATE WITH INTEGRALLY FORMED SPRING HOLE PLUG
TECHNICAL FIELD
This invention relates to brakes, and in particular to fastening means for attaching a brake plate to a vehicle brake assembly.

BACKGROUND OF INVENTION

A conventional automobile brake pad (or shoe) combines two main parts, namely a plate (backing plate) and a friction pad. The plate is mounted in a brake assembly and may be formed by making a plate with a variety of bosses, holes, or other features for receiving and retaining the friction pad. Various methods of attaching a friction pad to a backing plate are well known.

In a current method of mounting the friction pad on the backing plate, a pressurised molding process is used to mold the friction pad directly onto the plate. As pressure is applied to the mold assembly, a pre-form is heated and begins to flow, filling the mold and covering the contact surface of the plate. In this process, the pre-form material is caused to flow into and around the various features of the plate to improve the bond between the plate and the friction pad. Where the backing plate contains holes, the material will tend to flow into the holes, either entirely or partially filling the holes with friction material.

Hardware springs (shoe retaining springs) are employed within the brake caliper assembly of many modern disk brakes (see Fig. 6 showing the typical spring design known in the prior art).
The springs are used to lodge the finished brake pad inside the brake caliper within the inboard cylinder bore (Fig. 7). The spring is designed to be inserted into a hole on the non-friction side of the brake pad and to snap securely onto an outer edge of the plate (Fig.
5). In mounting the finished pad in the caliper, a portion of the spring extends for engagement with a hollow portion of a brake piston within the piston bore. The spring permits the pad to float inside the caliper for engagement with the rotor when braking force is applied. The spring also reduces noise and rattle in the brake.

In the prior art, it is known to attach springs permanently to the plate by means of rivets (US
5,494,140; US 5,860,495) or other fasteners (US 5,704,452). Alternatively, springs may be looped over stabilizing pins run through holes in the plate (CA 1 304 701) or biased against machined slots and flanges in the plate (CA 1 079 207).

In one known method of attachment, a hole for receiving the spring is machined in the backing plate. Typically, the hole is machined in a taper to allow an end of the spring to be inserted securely within the hole. The taper provides sufficient friction to prevent the end of the spring from dislodging.

There is, however, a risk of the spring hole being filled with friction material. In order to prevent friction material from entering the hole at the friction molding stage, the hole is covered by a small piece of blocking hardware used as a plug, typically a conventional washer (flashing plate).

There are two drawbacks to the use of separate blocking hardware in the brake manufacturing process. First, human insertion of the blocking hardware adds time and cost to the process.
Second, there is the potential for error. If the blocking hardware is accidentally omitted, friction material will enter the clip hole at the molding stage, and the brake pad may be rendered useless, or may require repair efforts to redrill the spring hole, wasting time and resources.

2 SUMMARY OF THE INVENTION

It is an object of the present invention to provide a brake backing plate with an integrally formed spring hole plug. The integrally formed spring hole plug reduces time and cost by requiring fewer manufacturing steps and avoids potential human error in the manufacturing process.

Further features of the invention will be described or will become apparent in the course of the following detailed description.

According to an aspect of the present invention, a friction material plate is provided for connection to a brake assembly fastener. The plate comprises a contact surface and a second surface. Friction material is attached to the plate at the contact surface.
The second surface opposes the contact surface. The plate defines a blind hole opening on the second surface.
The blind hole comprises a closed end, which is impermeable to the friction material. The closed end is preferably proximate to the contact surface. The blind hole receives a gripper for attaching the brake assembly fastener to the friction material plate.

In a preferred embodiment of the plate, the closed end of the blind hole comprises a boss on the contact surface. The boss is preferably integrally formed from the plate.

In the preferred embodiment of the plate, the gripper within the blind hole comprises a burr, which may be integrally formed from the plate. The burr is preferably recessed within the blind hole between the second surface and the contact surface.

The blind hole preferably receives the brake assembly fastener. The burr preferably receives and secures a portion of the brake assembly fastener.

3 According to another aspect of the present invention, a method of manufacturing a friction material plate for connection to a brake assembly fastener is provided. The plate includes a contact surface and a second surface. The method comprises two steps:

a) forming a first hole through the friction material plate between the second surface and the contact surface; and b) applying force to the second surface proximate to the periphery of the first hole to form a second concentric hole beginning at the second surface and terminating before the contact surface, so that material is removed from the second surface and extends from the first hole at the contact surface to form a closed end which is impermeable to the friction material and proximate to the contact surface.
In an embodiment of the method, step (b) further comprises creating a boss at the contact surface.

In a further embodiment of the method, the method further comprises applying force to the second surface to push material from a wall of the second hole into a protrusion on the wall of the second hole. The protrusion is preferably recessed between the second surface and the contact surface and comprises a gripper for receiving the brake assembly fastener.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more clearly understood, preferred embodiments thereof wili now be described in detail by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of the contact surface of the plate.
Figure 2 is a bottom plan view of the second surface of the plate.
Figure 3 is a cross-sectional view of Figure 2 along line A-A.

4 Figure 4 is a detail view of area B of Figure 3.

Figure 5 is a perspective view of the plate with a spring secured in a hole on the plate.
Figure 6 is a perspective view of the spring.

Figure 7 is a perspective view of a disc brake caliper assembly showing a brake pad being secured within the caliper.

DETAILED DESCRIPTION

Figures 1-2 show views of a brake backing plate 1. The plate 1, which is intended to receive a friction material (not shown) for use as a friction brake pad (or shoe), has two surfaces: a contact surface 4 for attaching the friction material to the plate, and a second surface 5 opposing the contact surface 4.

The plate 1 defines a blind hole 3, commencing on the second surface 5, and terminating in a closed end 2 at the contact surface 4. In a preferred embodiment, the closed end comprises a raised boss 2 (best shown in detailed cross-section in Figure 4). The boss 2 is preferably integrally formed from the plate 1.

Within the blind hole 3, as is best seen in cross-sectional views Figures 3-4, the hole 3 receives a gripper 6, which is defined within a recess 7, the recess 7 beginning at the open end of the hole 3 at the second surface 5.

The blind hole 3 is adapted to receive an end of a fastener, preferably a shoe retaining spring 8.
The preferred fastener 8 (Figures 5-6) comprises a roughly sigma-shaped (F) body with a plate hole engaging member 9 at one end, and a pair of plate edge gripping members 10 at the opposite end. A piston engaging member 11 juts out from the body. The spring 8 design permits the insertion of the plate hole engaging member 9 into the blind hole 3 on the second

5 surface of the plate. The plate edge gripping members 10 can be snapped securely onto an outer edge of the plate 1(Figure 5). The edge of the plate may be notched (and/or chamfered) to receive the members 10 securely. The piston engaging member 11 may be engaged within a hollow portion of the brake piston within the caliper 12 (Figure 7) when the pad is put into place.
Figure 5 illustrates the conventional placement of the spring 8 on the plate 1.

In the preferred embodiment of the present invention, the plate hole engaging member 9 is inserted behind the gripper 6 in the blind hole 3. Preferably, the gripper 6 comprises a burr 6 adapted to lodge the plate hole engaging member 9 securely in the hole 3. The burr 6 is preferably integrally formed from the plate 1.

To manufacture the pad, according to the preferred embodiment, a backing plate 1 is first machined with a variety of bosses, holes and other features for receiving and retaining the friction pad. A hole 3 is also created to receive the spring fastener 8.
According to standard machining practices, a relatively small, cylindrical hole is first bored entirely through the plate 1.
A larger gauge punch is then used to remove material from the outer walls of the hole 3, pushing the material out through the bottom of the hole 3 (at the contact surface 4) to pool in a raised round boss 2 on the contact surface 4, substantially sealably covering the end of the hole 3 with the removed material. Due to the flow of the removed material, in some cases, a pin-sized hole may remain in the boss 2. However, such holes are considered insignificant to the impermeability of the boss 2 to the friction material when molded on the contact surface 4. The closed end 2 is considered "impermeable" as that term is used in this invention. A blind hole 3 is thus defined within the backing plate 1, and an integrally formed boss 2 is formed at the contact surface 4 to prevent the ingress of friction material at the friction molding stage.

6 The preferred dimensions of the hole 3 and the boss 2 will vary depending on the dimensions of the fastener 8. To accommodate a shoe retaining spring 8, the finished hole 8 may be approximately 8 mm in diameter. The depth of the blind hole is preferably equal to the thickness of the plate to allow sufficient depth for the plate hole engaging member 9 to seat securely. The resulting boss 2, according to the process described above, may be approximately 1 cm in diameter with a height of approximately 1 mm above the contact surface 4 of the plate. The preferred dimensions of the boss approximate the dimensions of the prior art washer (flashing plate) used to block the ingress of friction material into the hole.

To manufacture the gripper 6, a punch is preferably used to push material from the wall of the blind hole 3 into a burr-shaped protrusion on the inner wall of the blind hole 3, recessed 7 between the contact surface 4 and the second surface 5 (sample placement shown in Figures 3-4).

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention and the appended claims and their equivalents.

7

Claims

1. A friction material plate for connection to a brake assembly fastener, comprising:

a) a contact surface for attaching the friction material to the plate; and b) a second surface opposing the contact surface, the plate defining a blind hole, a closed end of the blind hole impermeable to the friction material and proximate to the contact surface; and c) a gripper received within the blind hole for attaching the brake assembly fastener to the friction material plate.

2. The plate according to claim 1, further comprising a boss on the contact surface proximate to the closed end of the blind hole.

3. The plate according to claim 2, wherein the boss substantially covers the closed end of the blind hole.

4. The plate according to claim 2, wherein the boss is integrally formed from the plate.

5. The plate according to claim 1, wherein the gripper comprises a burr.

6. The plate according to claim 5, wherein the burr is integrally formed from the plate.

7. The plate according to claim 5, wherein the burr is recessed within the blind hole between the second surface and the contact surface.

8. The plate according to claim 1, wherein the blind hole receives the brake assembly fastener.

9. The plate according to claim 5, wherein the burr receives and secures a portion of the brake assembly fastener.

10. A method of manufacturing a friction material plate for connection to a brake assembly fastener, the plate including a contact surface and a second surface, the method comprising:

a) forming a first hole through the friction material plate between the second surface and the contact surface; and b) applying force to the second surface proximate to the periphery of the first hole to form a second concentric hole beginning at the second surface and terminating before the contact surface, so that material is removed from the second surface and extends from the first hole at the contact surface to form a closed end which is impermeable to the friction material and proximate to the contact surface.

11. The method according to claim 10, wherein step (b) further comprises creating a boss at the contact surface.

12. The method according to claim 10, wherein the method further comprises:

c) applying force to the second surface to push material from a wall of the second hole into a protrusion on the wall of the second hole recessed between the second surface and the contact surface, the protrusion comprising a gripper for receiving the brake assembly fastener.