Metal working – Method of mechanical manufacture – Assembling or joining
Patent
1995-11-01
1998-09-22
Hughes, S. Thomas
Metal working
Method of mechanical manufacture
Assembling or joining
294695, 156212, 1563073, 156475, 1565831, B23P 1100, C09J 506
Patent
active
058096272
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to the manufacture of bonded articles and in particular to the manufacture of friction elements of the so-called bonded type in which a friction lining is bonded to a platform of a carrier or body solely by a cured thermosetting resin adhesive substance.
BACKGROUND
The invention is particularly, but not exclusively, applicable to friction elements comprising brake shoes of the cylindrically curved drum type. It is, however, also applicable to friction elements comprising brake shoes of the generally flat disc type and to friction elements of similar types used within a clutch arrangement. Accordingly, in this specification, the term "shoe" is used principally to describe a carrier or body structure having a cylindrically curved platform on which such a cylindrically curved lining is carried, but within its general sense is also intended to include a structure having a substantially flat platform or backplate on which a corresponding flat friction lining is carried for engagement by a flat surface of a disc or the like, notwithstanding the use of a carrier or body of either form with a friction lining analogously in relation to a clutch arrangement.
Friction elements in which the friction lining is adhesively bonded to the body are employed for example in the form of brake shoes for light vehicles and similar uses and are distinguished from friction elements in which the lining is secured to the platform by mechanical location with interlocking parts, such as rivets, clips, plugs and the like.
This specification is concerned only with such shoes of the bonded type but the invention disclosed herein is best understood and placed in perspective as a result of some consideration of their manufacture in relation to mechanically located linings as well.
Mechanically located linings, which may in addition be adhesively bonded, require a greater number of manufacturing steps but may be preferred when the size/cost of the shoe body and platform requires its re-use with a new lining and/or the braking shear forces are of such magnitude as to require more security than adhesive bonding alone has been considered able to provide.
Where operating conditions and cost factors permit the use of adhesively bonded linings, such shoes enable manufacture to be effected more cheaply, at least in respect of securing the brake lining to the shoe platform, but reduced costs have not always been realized, particularly as production of the brake friction lining itself is generally performed similarly for both types.
It is known to form friction linings from a variety of friction modifying materials held in, and bound by, a matrix of, inter alia, thermosetting liquid resin, such as a phenolic resin, nitryl rubber copolymer matrix, reinforced with various fibers and cured to define an essentially rigid structure.
It is also known to produce for use with a shoe body having a cylindrically curved platform an arcuate friction lining segment including such liquid resin material, in a plastic state and roll-formed to generally align the reinforcement fibers and to define the thickness and density of the material and curvature of the lining prior to curing the resin matrix at elevated temperature. In a roll formed friction lining element in which the reinforcement fibers tend to be substantially parallel to the major faces and which in a green form has a density less than the theoretical maximum due to interstitial voids, subjecting the element to elevated temperature to cure the resin matrix causes the element to swell or expand due to evolution of gases and vapors from volatile constituents (including water), and to some extent by oxidation of some constituents, and reduce in density as the resin matrix cures to a solid, notwithstanding that before cure is complete, some gasses and vapors force their escape from the surface and disrupt the structure.
There is a preferential expansion ion the direction in which the fibers are aligned and with a tendency to expand in a direction of minimum dimensio
REFERENCES:
patent: 2452284 (1948-10-01), Beare
patent: 2690820 (1954-10-01), Raes
patent: 4173681 (1979-11-01), Durrieu et al.
patent: 4193956 (1980-03-01), Kalnins
patent: 4452346 (1984-06-01), Stukenborg
patent: 4701378 (1987-10-01), Bagga et al.
patent: 5595266 (1997-01-01), Cecere
Patent Abstracts of Japan JP55138055 Oct. 1980 vol. 5 No. 12 "Sintered Alloy having lubrication function preparation of the same, and friction mate-material using the same".
G B Tools & Components Exports Limited
Hughes S. Thomas
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