|Title of Invention||
FRICTION BRAKE SUBASSEMBLY AND A METHOD OF FABRICATING A FRICTION BRAKE SUBASSEMBLY
|Abstract||A friction brake subassembly is provided with a metallic backing plate element and with a friction material brake lining element integrally adhered to the backing plate element, the brake lining element friction material composition comprising friction material particles and an epoxy resin binder preferably in the approximate range of from 10% to 4 0% of the friction material composition total weight. Methods are disclosed for integrally bonding the brake lining element to the backing plate element. PRICE: THIRTY RUPEES|
This invention relates generally to/friction brake subassembly
/particularly concerns a novel friction brake composition and
methods for making friction brake subassemblies such as brake shoes
and brake pads using the novel friction brake composition.
BACKGROUND OF THE INVENTION
Heretofore it has been a common industrial practice in
the United States to manufacture friction brakes subassemblies such
as the friction brake shoes and friction brake pads typically
utilized in automotive vehicle brake systems to first form a
friction material particulate mixture having an included phenolic
resin binder into a cured brake lining shape of specific configuration and afterwards join the cured brake lining shape to
a cooperating brake member backing plate by mechanical fasteners such as rivets or by a suitable adhesive such as a cured phenolic
resin, a cured elastomeric rubber, or a like adhesive. The
friction material particulate mixture cured brake lining shape is typically constituted of inorganic compound particles, organic
compound particles, metallic particles, reinforcing fibers, and sometimes carbon particles, in addition to the phenolic resin binder.
Another form of conventional friction brake member, sometimes referred to as an integrally molded brake shoe or integrally molded brake pad, is manufactured using a method wherein the required adhesive material is applied to the brake subassembly backing plate element in its uncured condition and the friction material brake lining with phenolic resin binder is placed in contact with the applied uncured adhesive. The adhesive material is subsequently cured simultaneously with the necessary curing of the brake lining friction material particulate composition mixture.
I have discovered that both the need for multi-step resin curing processes and the need for separate particle binder resin and adhesive resin systems can be avoided in the manufacture of friction brake subassemblies to economic advantage byj utilizing a friction material composition wherein the included uniformly dispersed resin binder system functions satisfactorily both as a composition particle binder and as an adhesive joining the brake lining cured composition to its brake backing plate element.
Other advantages of my invention will become apparent during a careful consideration of the detailed information which follows.
SUMMARY OF THE INVENTION
The friction brake subassembly of this invention is basically comprised of a metallic backing plate element, generally in the form of a rigid, metallic (low-carbon steel) member of suitable configuration and size, and a cured brake lining friction material integrally joined to the backing plate element. The brake lining cured friction material typically is comprised of particles such as organic material particles, inorganic compound particles, and metallic particles, and of reinforcement fibers, uniformly dispersed and embedded in a cured epoxy resin binder comprising approximately from 10% to 40% by weight of the total friction material composition. In some instances the brake friction material composition also may include a carbonaceous particles constituent.
From a method or manufacturing process standpoint, the preferred friction material composition, following mixing and forming into a brake lining pre-form shape while remaining in an plastic condition, is placed in compression-forming apparatus in direct contact with a cooperating backing plate element. Next, the partially cured brake lining pre-form and backing plate element are pressed together and heated in the incorporating apparatus at elevated pressures and temperatures for sufficient time to form a friction brake subassembly having the partially-cured friction material integrally adhered to the backing plate element and fully
cured. The completed friction brake subassembly with adhering friction material is then removed from the mold cavity and subjected to optional subassembly finishing operations.
Accordingly, the present invention provides a friction brake subassembly comprising: a metallic backing plate element having a lining surface; and characterized by a substantially homogenous friction material brake lining element having a top braking surface and a bottom surface comprised of a cured epoxy resin matrix and friction materials embedded in the cured epoxy resin matrix, said substantially homogenous friction material brake lining element bottom surface being directly adhered to said lining surface of said metallic backing plate element by said brake lining element cured epoxy resin matrix such that said substantially homogenous friction material brake lining element extends from said backing plate element lining surface to said top braking surface.
Accordingly, the present invention also provides a method of fabricating a friction
_a brake subassembly comprising, the steps of: shaping a plastic mixture of friction material
^ particles and epoxy resin binder into a brake lining plastic pre-form shape; placing said
.plastic pre-form shape in direct contact with said metallic backing plate element; and
said plastic pre-form shape to elevated pressures and temperatures for .»
extended time period sufficient to cause said plastic pre-form shape to become a
relatively rigid brake lining element integrally adhered to said metallic backing plate
Additional information regarding the invention is provided with reference to the accompanying drawings, detailed description, and claims which follow.
Figure 1 is a perspective view of a preferred embodiment of a friction brake subassembly manufactured in accordance with the present invention and having a representative drum brake shoe configuration;
Figure 2 is a sectional view taken at the plane defined by intersecting lines 2-2 of Figure 1;
Figure 3 is a plan view taken of one form of compression forming apparatus utilized in the practice of the present invention with the subassembly of Figure 1 positioned therein; and
Figure 4 is a sectional view taken along line 4-4 of Figure 3.
i Figure 1 illustrates a friction brake shoe subassembly 10 incorporating the
£ essential features of this invention and having
a representative configuration of an automobile drum brake shoe subassembly as distinguished from an automobile disc brake pad subassembly to which the invention has equal application. As shown in Figure 1, subassembly 10 is comprised of a metallic backing plate element 12 with integral reinforcing rib, usually fabricated of a low-carbon steel, and a cured friction material brake lining 14 integrally adhered to the exterior cylindrical surface 16 of backing plate element 12. It should be noted that subassembly 10 does not utilize mechanical fasteners such as rivets or the like to join the cured friction material to back plate element 12 and similarly does not utilize an intermediate layer of adhesive composition to join those components together. See Figure 2 which illustrates, in section, the direct or integral bonding of brake lining element 14 to element 12.
The friction material of brake lining 14 is processed to a fully-cured condition in place and typically is comprised of a mixture of inorganic particles, organic particles, metallic particles, and fiber particles combined with a uniformly dispersed epoxy resin which functions to both bind the particulate materials together and adhere the cured composition of element 14 to the subassembly 10 backing plate element 12. For the purpose of the present invention I find that the epoxy resin constituent should comprise on a weight basis approximately from 10% to 40% of the composition total weight. Such range essentially equates to a volumetric range basis of approximately 13% to 53%.
In formulating friction material composition 'for brake
lining element 14 I normally select inorganic particles selected
from the group comprised of alumina particles, magnesia particles,
silica particles, aluminum silicate particles, and various mineral
particles including calcium carbonate particles, barium compound
particles (barite particles), and rottenstone (siliceous limestone)
particles. In the composition category of organic particles
generally I select a material or materials from the group which
consists of rubber tire peel particles and cashew nut shell
Generally, the friction composition metallic particles constituent is most often selected from the group comprised of iron oxide powder and iron particles. On occasion it may be desifable to utilize particles of one or more different non-ferrous metals.
The fiber constituent or constituents preferred in the
I practice of the present invention are generally selected from the
group comprised of glass fibers, steel wool fibers, ceramic fibers,
and polyacrylonitrile fibers. If, as suggested above, it is
desirable to include a carbon constituent to develop an inherent
lubricating quality in the composition, such may be obtained by
incorporating one or more of the different carbon particulates
which comprise the group consisting of natural graphite particles, I
synthetic graphite particles, coke particles, carbon black
particles, and even coal particles.
Most importantly, the required epoxy resin constituent is
preferably an epoxy resin system which because of its liquid epoxy
resin constituent develops a plastic quality in the composition
upon complete mixing of the composition particulate constituents with the composition binder. In at least one actual embodiment of the present invention I have found it advantageous to utilize an epoxy resin binder comprised of both epoxy cresol novolac resin particles and bisphenol F/epichlorohydrin epoxy resin liquid. Such resins were combined in relative proportions which imparted to the friction brake material composition mixture, following combination of the epoxy resin with the other friction brake material constituents, a degree of composition plasticity which permitted the resulting material to be subsequently rolled or extruded to shape prior to final curing. (It should be noted that from a procedural standpoint the composition particulate epoxy resin constituent was thoroughly mixed with the other composition particulate ingredients prior to addition of the liquid epoxy resin constituent) .
The following Table I provides specific composition or formulation information for two different friction btake materials which have been used in the practice of the present invention (all proportions are given on a percentage weight basis):
CONSTITUENT SYSTEM 139 SYSTEM 140
Organic Particles 15.72 19.10
Inorganic Particles 4 6.61 44.75
Metallic Particles 2.76 2.65
Fiber Particles 9.46 9.08
Epoxy Resin 25.45 24.42
TOTAL 100.00 100.00
Figure 3 illustrates a compression-type forming apparatus 20 which may be utilized advantageously in the practice of the present invention to join two pre-cured friction material extruded or rolled brake lining pre-forms 14 to a pair of backing plate elements 12. Apparatus 20 is basically comprised of an "endless" loop or band component 22, preferably fabricated of a flexible, strip-like steel material, and of a cooperating expander component 24. Expansion component 24, in turn, is essentially comprised of a spaced-apart pair of rigid adaptor elements 26 and 28 joined by a conventional compression spring element 30. Apparatus 10 basically functions to compress each partially cured friction material pre-form 14 placed in apparatus 2 0 between band component 22 and its respective brake backing plate element 12 when elements 2 6 and 28 are engaged with backing plate elements 12 and compression spring 30 is released from its compressed apparatus installation condition. As will be later indicated, compression
spring element 30 is sized to develop a pressure in the approximate range of 20 pounds per square inch to 50 pounds per square inch throughout each of the friction material pre-forms 14 placed in apparatus 20 to complete the curing of the included epoxy resin binder.
Although not illustrated in the drawings, it Is necessary to place a strata of separation material such as polytetrafluoro-ethylene ("Teflon") tape between that portion of the interior surface of band element 22 that would otherwise contact ' any partially-cured friction material composition and the cooperating friction material. Alternatively, a thin high-temperature material such as aluminum foil may be utilized if subsequent processing of the completed subassembly 10 involves the grinding or other removal of friction material surface material.
Each assembly of apparatus 20 and an included .pair of partially completed brake shoe subassemblies 10 is subsequently heated to elevated temperatures (e.g., temperatures in the approximate range of from 300° F. to 500° F.) for an extended period of time generally in the approximate range of from 2 hours to 10 hours to complete the curing of the epoxy resin binder constituent dispersed throughout the friction material of pre-forms 14. Drum brake shoe subassemblies heretofore fabricated in accordance with the present invention utilizing process parameters within the ranges specified have developed material-to-backing plate bond shear strengths in the range of 1900 pounds per square inch to 24 00 pounds per square inch depending on the pressure
applied to the friction material composition by apparatus 20 during
the prolonged cure cycle. Such values are typical of those
obtained when bonding either fully-cured or partially-cured
friction composition brake linings or brake lining preforms onto
backing plates using a rubber-modified phenolic brake lining
In addition to eliminating the need for a bonding adhesive, the use of an epoxy resin system as a matrix binder has an additional benefit. The curing reaction of an epoxy resin is a ring-opening polymerization and, as such, produces no volatiles. Therefore, the friction material can be applied directly to the backing plate element immediately after it is mixed and without the need for a time1- and energy-consuming drying operation before curing. This is in direct comparison to the cure of a phenolic resin binder which is a condensation reaction and, as such, releases volatiles which must be carefully removed during a drying cycle to prevent the formation of blisters and delaminations in the resulting cured brake lining.
Other materials, component shapes, and component sizes than those detailed in the drawings and descriptions of this application may be utilized in the practice of my invention without departing from the scope of the claims which follow.
I claim as my invention:
1. A friction brake subassembly comprising: a metallic backing plate element having a lining surface; and characterized by a substantially homogenous friction material brake lining element having a top braking surface and a bottom surface comprised of a cured^epoxy- re.sin matrix and friction materials embedded^-Jhe cured epoxy resin matrix, said substantially homogenous friction material brake lining element bottom surface being directly adhered to said lining surface of said metallic backing plate element by said brake lining element cured epoxy resin matrix such that said substantially homogenous friction material brake lining element extends from said backing plate element lining surface to said top braking surface.
2. The friction brake subassembly as claimed in claim 1 wherein said cured epoxy resin matrix comprises approximately 10% to 40% of the weight of said friction material lining element. . ',. .... - ; • •'■'■ •
3. The friction brake subassembly as claimed in claim 1 wherein said cured epoxy resin matrix is the polymerization product of a particulate epoxy cresol novolac resin and a liquid bisphenol F/epichlorohydrin epoxy resin.
4. A method of fabricating a friction brake subassembly as claimed in any one of the claims 1 to 3 comprising, the steps of:
shaping a plastic mixture of friction material particles and epoxy resin binder into a brake lining plastic pre-form shape;
placing said plastic pre-form shape in direct contact with said metallic backing plate element; and
subjecting said plastic pre-form shape to elevated pressures and temperatures for an extended time period sufficient to cause said plastic pre-form shape to .become a relatively rigid brake lining element integrally adhered to said metallic backing plate element.
5. The method as claimed in claim 4 wherein, said epoxy resin binder comprises 10% to 40% by weight of the mixture shaped into said brake lining plastic pre-form shape.
5. The method as claimed in claim 5 wherein said epoxy resin binder is
comprised of an epoxy cresol noyolac resin and a bisphenol F/epichlorohydrin
spoxy resin. '
■.'*••••• ' •. .*.
7. The method as claimed in claim 4 wherein said brake lining plastic pre¬form shape is subjected to temperatures in the range of 300° F. to 500° F.
8. The method as claimed in claim 4 wherein said brake lining plastic pre¬form shape is subjected to internal pressures in the range of 20 pounds per square inch to 50 pounds per square inch.
9. A friction brake subassembly, substantially as herein described and illustrated with reference to the accompanying drawings.
10. A method of fabricating a friction brake subassembly as herein described and illustrated with reference to the accompanying drawings.
|Indian Patent Application Number||1039/MAS/1996|
|PG Journal Number||08/2007|
|Date of Filing||12-Jun-1996|
|Name of Patentee||M/S. MOOG AUTOMOTIVE PRODUCTS INC|
|Applicant Address||6565 WELLS AVENUE, St. LOUIS MISSOUR 63133,|
|PCT International Classification Number||F16D65/02|
|PCT International Application Number||N/A|
|PCT International Filing date|