Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-05-19
2001-09-04
Sells, James (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S228000, C156S307100, C156S358000, C156S583100
Reexamination Certificate
active
06284074
ABSTRACT:
This invention relates to the manufacture of bonded articles and in particular to the manufacture of friction elements in which one major face of a friction lining is bonded to a platform of a carrier by a cured thermosetting resin adhesive system.
Friction elements in which the friction lining is adhesively bonded to a platform of shoe a body are employed inter alia as brake shoes for dynamic (service) brakes and static (parking) brakes for light vehicles such as automobiles and vans and static brakes for heavier commercial vehicles, and are distinguished from friction elements in which the lining is secured to the platform principally by mechanically location with interlocking parts, such as rivets, clips, plugs and the like.
The invention is particularly applicable to friction elements comprising brake shoes of the cylindrically curved drum type wherein the carrier comprises a shoe body having a structure comprising a cylindrically curved platform, on which a correspondingly curved friction lining is carried, and a transverse supporting web.
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, although in this specification the term shoe body is used principally to describe a carrier structure having a cylindrically curved platform, 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.
The principal differences between flat and arcuate friction elements in terms of production are that the former are more readily produced by a moulding process in which the friction material (consisting essentially of fibrous and/or filamentary reinforcement and friction modifying materials in a matrix of a thermosetting resin copolymer as a binder) is dry, that is, the uncured thermosetting copolymer is in powder or particulate form, enabling it to be readily disposed into, and uniformly compacted in, a mould cavity to which a mould closing force is applied unidirectionally. It will be appreciated that it is less easy to compact a powder into an arcuate form of lining element because of the varying angles at which a unidirectional force is applied.
It has therefore been more usual in the art to provide friction lining material with a liquid form of thermosetting resin as a binder to achieve a plastic consistency that can be pre-compacted to an acceptable extent by rolling. Although such a rolled plastic consistency is suitable for producing preforms or lining element which are arcuate prior to curing and setting-up of the thermosetting binder, there is no technical reason why such plastic form of friction lining element should not take a flat form and be bonded to a flat carrier platform.
This specification is concerned with a bonded friction elements in which the lining comprises a preformed plastic lining element of fibrous reinforcement and friction modifying materials in a matrix of uncured liquid based thermosetting resin binder, that is, a green lining element, in which the thermosetting resin binder is cured to form the lining contemporaneously with curing of the thermosetting adhesive system to effect bonding to the carrier platform.
Such combined curing and bonding per se is described in patent specification GB 2278800 in a form which can take advantage of existing bonding equipment, curing facilities and procedures typically available to a manufacturer of brake shoes, and the disclosure thereof, including that in relation to other prior manufacturing methods, is incorporated herein by reference. However, when a manufacturer does not have such existing equipment to employ and/or when it is desirable to improve upon the article throughput rate for individual apparatus, that is, operation cycle time and/or simultaneous manufacture of parts, the combined curing and bonding method known therefrom may not be optimal.
Although the aforementioned specification is concerned with such friction lining in which the adhesive bonding is the sole means of resisting motion between the lining and carrier platform, it is known to combine adhesive bonding with some degree of mechanical interlocking achieved by co-operating projections and recesses of the lining and carrier as additional resistance to shear forces.
Thus, preserving the generality of the foregoing as to the form of carrier, it is an object of the present invention to provide a method of manufacturing more quickly and with less tooling than hitherto a friction element that includes a carrier having a thermoset friction lining, bonded to the carrier by thermosetting adhesive bonding with contemporaneous setting thereof. It is also an object of the present invention to provide an arrangement for manufacturing a bonded friction element more quickly and simply than hitherto.
According to a first aspect of the present invention, a method of manufacturing a bonded friction element comprises (1) producing a plastic friction lining element, including fibrous reinforcement and friction modifying materials in a matrix of an uncured thermosetting resin binder disposed between opposite major faces defining its thickness, (2) disposing one of the two major faces of the lining element adjacent a platform of a carrier with a thermosetting resin adhesive system between, and in contact with, the element and the platform, and (3) curing the resins of both adhesive system and lining element by cross-linking at elevated temperature to a degree of cure whereby the element forms a lining bonded to the platform, the method being characterised by (4) preparing the surface of the carrier platform to receive said thermosetting adhesive system, (5) preheating the carrier to a platform temperature in excess of that required to initiate crosslinking of said adhesive system,(6) sandwiching the lining element and adhesive system between the pre-heated platform and a bed of a stabilising press preheated to a temperature in excess of that required to cross-link the lining element binder and adhesive system, said bed being shaped to conform substantially to the platform and further recessed to receive within said recess the lining element with the opposite major face bearing against the floor thereof, (7) applying to the sandwiched element and adhesive system by way of the platform and bed a consolidating pressure increasing over a predetermined consolidating interval from substantially zero to a predetermined level, permitting plastic flow of the adhesive system and element into conformity with the platform and recess but without significant extrusion before onset of cross-linking of the thermosetting resins, and thereafter maintaining the separation between platform and bed achieved at the end of the consolidating interval for a setting-up interval to permit cross-linking adjacent the heated surfaces to define a stably bonded intermediate product including a partially cured, dimensionally stabilised lining element having substantially the final dimensions and density of the lining, (8) removing the bonded intermediate product from the stabilising press and (9) baking the intermediate product unconstrained at a predetermined baking temperature and for a baking interval to effect further curing of the thermosetting resin of the dimensionally defined lining element to a predetermined level of hardness and strength.
According to a second aspect of the present invention an arrangement for producing a bonded friction element, of the type having one major face of a thermoset friction lining secured to a platform of a carrier by a thermosetting adhesive system, comprises a) formulating means, operable to produce a green paste friction lining element, comprising fibrous reinforcement and friction modifying materials in a matrix of uncured thermosetting resin binder between said one major face of the element and an opposite major face defining its thickness, of les
Braund Robert W
Morrison William C
Tennant Angus WJ
Baker, Jr. Thomas S.
G B Tools & Components Exports Limited
Sells James
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