CA2721166A1 - Improvement to a disc brake pad - Google Patents

Abstract

The present invention is an improved disc brake pad wherein its two components, namely a steel backing plate and a friction pad or puck, are fabricated separately. The steel backing plate is stamped with a pattern of discrete protrusions rising from one face.
The pads are cut from friction material extruded into any shape of rod or into a thick sheet then cured hard and finished ready for use. The friction pads have a pattern of discrete recesses matching the plate's protuberances. An adhesive is used to bond the two components into a completed brake pad. In this way a wide range of vehicle brake pads can be assembled from prepared pads and plates.

Description

SPECIFICATIONS
FIELD OF THE INVENTION

The present invention is in the field of disc (or disk) brakes for vehicles whereby a rotating disc (rotor) attached to a wheel, rotates through a very narrow gap between opposing disc brake pads held in a powerful hydraulic caliper. During braking, the brake pads move through the small gap to squeeze the rotor with enormous force, slowing the vehicle. Each disc brake pad comprises a steel backing plate (plate) with a brake friction pad on one side. During braking, enormous shearing forces are generated between the pad and plate which is resisted by the adhesive and various mechanical means. The friction pad wears away with each application of the brakes.

BACKGROUND OF THE INVENTION
The present invention is for an improved disc brake pad.

In the present invention the backing plate and the friction pad are mass produced separately with interlocking, mating features, and then adhesively assembled to create a disc brake pad.

The thick, stiff, steel backing plates are continuously stamped in the required shape from coiled steel stock. During or after this stamping, discrete protuberances are formed on one face of the plate for engagement-mating with the friction pad to provide resistance to shear forces under braking.

Friction pads are punched-formed-molded-slit-cut from friction material and discrete recesses formed in one face for engagement-mating with the plate. They are then cured hard. The plate and pad are then mated with an adhesive therebetween.

Using the present method of manufacture enable the use of many smaller friction pads on a plate which offers advantages such as lower cost and better cooling which, in turn, extends the life of the disc brake pad, which, in turn, lowers vehicular operating cost.

SUMMARY OF THE INVENTION

A method of making brake pads comprising the steps of making plates and pads with complimentary engagement features and then bonding them together with adhesive.

In the plate of the present invention, a discrete pattern of discrete protuberances is provided one face of said plate. Protuberances may include such shapes as pins, hooks, burrs, bristles, knurls, ridges, rings and the like. Preferably the discrete protrusions form a discrete pattern. Preferable the discrete pattern of discrete protuberances is repeated at different locations on the plate.

Friction mixture is formed into pads such as disc-like pads. Discrete recesses are also formed in the same discrete patten as the discrete protuberances on the plate.
The pads are then cured (made hard) ready to be mated and adhesively bonded to the plate.
Pads may be of any shape or size but preferably thick, disc-like pucks.

Preferably the protrusions on the plate are short so as to maximize the life of the pad before wear exposes their tips for unwanted contact with the rotor.

The protrusions may also be added to the plate as weldments, by, for example, stud welding techniques or by attaching an appropriately shaped material such as spheres, beads, wire, meshes, metal wools, or bristles, to the plate. Separately formed sheet metal having the necessary protuberances may also be attached to the plate by, for example, spot welding.

In one embodiment, pads may be cut from a large, pre-made plate of brake friction material using a laser, mill, or waterjet to cut the final contours.

2 In another embodiment, if the lining is made into plate for cookie-cutting the pads therefrom, the plate can be formed in layers of different friction compositions such as gradients of hardness. For example the thermal conductivity may be increased by having a more metallic composition near the plate and less near the rotor face. In this way the thinning pad can offer driver safety through better management of the different stages of pad wear.

The present invention also contemplates the use of pads made from different lining compounds such as those of different hardnesses or having canceling NHV
characteristics to be used at the leading and trailing edges of the brake pad (relative to rotor contact.

In all cases, the pad and plate have complimentary mating features. The features should be fully contained within the perimeter of the pad so that the adhesive forms a surrounding seal that will prevent the ingress of water which could disadvantageously lead to interfacial rusting and then, almost certainly, to delamination.

The engagement of pads-to-plate may be such that an assembly force may preferentially be required. The recess walls may, for example, be lightly engaged by the plate's protuberances. The recess can be made slightly deeper than necessary to accommodate the sheared of puck material in the resulting pocket at the top of each post.

The adhesive applied to the pad and/or plate may be of a heat curing formula whereby the adhesive may be pre-applied as liquid and then dried. After assembly heating cures the adhesive. The adhesive necessarily forms a thin layer between pad and plate and thus can serve a secondary valuable function - that of a noise, harshness, vibration (NHV) dampening medium. The adhesive layer may be increased in thickness to improve its NHV dampening by incorporating particles such as glass beads to prevent too-intimate face-to-face contact between the plate and pad.

3 Further, the features on the plate and pad could be reversed such that the plate has recesses and the pad has protuberances. For example, the plate may have circular depressions and the pad raised plateaus that engage the depressions.

In yet another embodiment, a combination of recesses and protuberances may be formed on each component.

In this way the myriad range of vehicular plate designs can all be fitted from a range of `stock' pads in contrast to the slow, messy, and expensive current batch manufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1, 2 and 3 shows the Prior Art; a backing plate with a bonded on, one-piece lining and showing other features sometimes present;

Figures 4, 5, and 6 shows the same plate design but with separate plate and pads mechanically engaged and adhesively bonded; the pattern of protrusions and recesses are shown to have a radial symmetry such that assembly is not dependent on a pad's radial orientation or position;

Figure 7 shows detail of the plate and two pads where a pattern of recesses on a first face of the lining line up to mate with a like pattern of post-style protrusions on the first face of the plate;

Figure 8 shows variations of protrusions which may be the preferred hooks on the upper portion of the plate and ridges or burrs, pins, dimples, ridges, or knurl, and the matching engagement recesses;

Figure 9 shows the second face of the plate and the punch marks left from the extrusion of pin-like protrusions on the opposite first face where the lining will be attached;

4 Figure 10 shows another variation on the upper portion of the plate where a grid of wire mesh is welded to the first face of the plate and a matching grid of recesses on the lining allow their engagement; on the lower portion is shown knurls (pyramid shaped) raised features formed in the preferred circular pattern for easy assembly of the matching pads (not shown) thereon;

Figure 11 shows other multiple pad shapes;

Figure 12 shows a one-piece pad based on the present invention and where multiple groups of engagements are provided;

Figure 13 shows another embodiment where a single, larger recess in the lining encloses multiple protrusions, such as the preferred raised hook or burr shown, and how this arrangement is repeated in different locations on the lining and plate;

Figure 14 shows the same embodiment in a side view;

Figure 15 shows an extruded rod of compacted friction material and multiples of individual pad sliced therefrom;

Figure 16 shows multiple pads that are cookie-cut from a sheet of compacted friction material.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, Figures 1-3 depict a Prior Art disc brake pad 100.
Fig I is the front view of the second face 2b of friction lining 2 which is the face that contacts the disc brake rotor. Fig 2 is a side view of the same embodiment showing the first and second faces, 2a and 2b respectively of lining 2 and, first and second faces Ia and lb respectively of the brake pad backing plate 1. Fig 3 is a back view of brake pad 100 where is shown the second face lb of the plate 1 that contacts the caliper piston and/or anvil.

In the Prior Art the first face 2a of the one-piece lining 2 is bonded during molding to the first face la of the backing plate 1. Features such as holes 3 in the face la of plate 1 are filled with lining material 2c during the molding process and serves to help anchor the lining to the plate. This particular Prior Art brake pad has an auxiliary feature in the form of a locator pin 5 protruding from the second face lb of plate 1, although this is not present on all designs of disc brake pads, its inclusion here is for reference and show how pin 5 has been formed by punch-extrusion from the second face lb of plate 1.
The pin-shaped punch has left a cavity 4 in the surface of the second face that has a shape and volume very similar to the shape and volume of pin 5. Having no purpose on the first face Cavity 4 is covered over by lining 2. Its function may be to locate certain pieces such as anti-rattle clips when the brake pad is installed in a caliper.

Other features known to exist on Prior Art plates 1 include raised hooks, weldments, ridges and the like. However these are all designed for embedment in the flowable friction material during the molding operation previously described.

Prior Art brake pads linings 2 may also include features such as grooves 41 and chamfers 31 to manage harshness, noise, and vibration (HNV) and for thermal and dust control.

In summary the Prior Art disc brake pad comprises a steel backing plate which may have certain raised or recessed features such as hooks, pins and holes 3 on its first face l a, and, a lining 2 which is pressure- and temperature molded from flowable friction material onto the first face la of plate 1 and into or about any such features which become embedded or filled 2c by it.

In the disc brake pad of the present invention, the plate 1 and pad 2 are produced separately and the first face la of plate 1 and first face 2a of pad 2 are provided with a complimentary pattern of features that can interdigitate, interlock, engage, mate or plug together. An adhesive 60 (shown only in Fig 5) is provided on either or both first faces I a, 2a, including in and on their respective interlocking features (not shown).
The plate and pad are then brought together and the adhesive is cured to permanently secure the pad to the plate resulting in a novel brake pad.

Figs 4, 5 and 6 show this inventive brake pad 10 in the same view configurations as the Prior Art described above but with multiple pads 2, in this case circular ones. Recesses 20 are on first face 2a of pad 2, protuberances 21 are on first face l a of plate 1, and cavities 20 are on second face lb of plate 1. Punch-pin cavities 20 do not have any operative function but are remnants of the punch that created (one form of) protuberances 21.

In Figs 4-6 all the protuberances are pin-or post-like structures shown punch-extruded from second face lb resulting in cavities 20 in second face lb. The four pads 2 are shown to be cylindrical, such a shape being the simplest and cheapest to manufacture in that they can be sliced like bread from a continuously extruded rod of friction material 46. These pads 2 can be made in a variety of diameters to enable a best-fit to a wide range of plate 1 shapes and sizes. The first face of the uncured lining is pressed onto an appropriate form, such as a pattern of tapered pins, so as to create the shallow recesses 22.
After curing hard the pads are then ready for further processing such as grinding to finished size or application of adhesive.

In Figs 4-6 dashed line 30 represents the pad outline of the Prior Art lining.
The pads 2 are nested together so as to be within the required area indicated by line 30.
As can be appreciated the shape and number of pad 2 can be whatever is required in terms of cost and total area contacting the disc brake rotor (not shown).

Fig 7 shows a pre-assembly view of the two first faces of plate and pad 1 a, 2a with their respective protuberances 21 and recesses 22. The recesses are such that the plate and pad fully engage allowing the face surfaces to contact each other where minimum adhesive thickness is specified.

Fig 8 shows a preferred embodiment where a pattern of hook-like burrs 5 are raised directly from first face la of plate 1 and only in areas covered by the pad.
On the same plate is shown another form of mating where the plate 1 has a recessed ring 25 and a centered recess 26. They mate with raised groove shape 24 and plug shape 23 respectively on pad 2.

Fig 9 shows how the plate 1 may have the recesses 25a and 26a to mate with raised features on the pad (not shown).

Fig 10 shows how a weldments such as the a wire mesh 43 shown on plate 1 may be mated with a complimentary pattern of recesses 42 on pad 2. Also show in Fig 10 are knurl protrusions 45 which are pyramid-shaped features often used to provide grip on surfaces (matching pad not shown);

Fig 11 shows different shapes of pads 2 that maximize coverage within line 30 that represents the Prior Art pad area.

Fig 12 shows another embodiment where a single pad 2 has four separate areas of mating structures. Pad 2 is shown as being one piece but may be two or any number.
Fig 13 shows another embodiment where recesses 50 in pad 2 are large enough to enclose a multitude of burrs 5. The burrs are shown to have been formed in a pattern as would result from a plurality of parallel toothed blades used to raise the burrs. The recess would be filled with adhesive on assembly. Fig 14 shows the same embodiment in side view. With this embodiment multiple pads could each have one or more large recess(es) each recess encompassing a multitude of plate protrusion burrs 5.

Fig 15 shows a rod-shaped circular extrude 46 from which multiple pads 2 are sliced while Fig 16 shows a molded plate or extrude 47 for cookie-cutting multiple pads 2.

Fig 16 also shows the laminated form of pad where the final wearing layer 48 adjacent the plate (not shown) contains a tell-tale material that, as the pad wears down, is eventually ablated or also worn away. Dispersed as an air-born powder some will deposit onto nearby wheel, body and suspension parts. The tell-tale material in layer 48 may include those that fluoresce under ultra violet light, for example. This fluorescent deposit can be readily detected visually using ultraviolet light to provide a safety to alert to the vehicle owner to schedule a brake pad replacement. Beside fluorescent materials, the tell-tale material may also emit an odour, a sparkle, a colour, or a sound, or any combination thereof.

Some examples of minerals that fluoresce in colour under ultraviolet light include the red or orange fluorescence of calcite, the green fluorescence of willemite, the yellow fluorescence of esperite, and the orange fluorescence of wollastonite.

The present invention also includes an automatic, drive-by ultraviolet light and fluorescent detector for gas- and service stations.

The present invention should become mandated in the interest of everyones safety.
It will be appreciated that any combination of the embodiments herein described can be used as may be required for safe, low-cost brake pad manufacture.

Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a disc brake pad comprising a backing plate with friction pad secured thereto, the improvement comprising:

providing said backing plate with discrete protrusions arranged in a discrete pattern;
providing said friction pad with at least one discrete recess to engage at least one said discrete protuberances; and mating said at least one said recess with at least one said discrete protuberances so as to reinforce the securing of said friction pad to said backing plate.

2. The improvement of Claim 1 where said discrete protrusions arranged in said discrete pattern are provided at multiple discrete locations on said backing plate, and where each said discrete location receives a said friction pad.

3. The improvement of Claim 2 where one said discrete recess in said friction pad is provided for each said discrete protrusions on said backing plate.

4. A disc brake pad comprising a backing plate with a discrete pattern of discrete protrusions arranged in multiple locations, and a friction pad for each said location each having discrete recesses to engage said protrusions.