Document QMmgzdLvaZ9519pXDb9zjv0Jk

United States Patent Office 3,647,744 Patented Mar. 7, 1972 12 Test for the Characterization of Brake Linings. The au 3,647,744 FRICTION MATERIAL ADDITIVES FOR IMPROVED PERFORMANCE thors are Anderson, Gratch and Hayes The outstanding characteristic of this machine is that it employs a con Janies L. Rich, Allen Park, and Marvin H. Welnfranb, stant rubbing velocity and with this constant rubbing ve Oak Park, Mlch^ assignors to Ford Motor Company, 6 locity absorbs energy at a fixed rate by varying the pres Dearborn, Mich. sure between the brake lining under test and the member Filed Jan. 22,1970, Ser. No. 5,060 Int. Cl. C08k 1/18 U.S. CL 260--30 2 Claims upon which the brake lining rubs. The graph depicted in FIG. 1 has time and temperature, as the abscissae and lining pressure for constant energy dissipation as the ordmate. Obviously, the smaller the ABSTRACT OF THE DISCLOSURE value of the pressures recorded on the ordmate scale, the more satisfactory the lining under test, other factors being This invention teaches that conventional automotive equal. Attention is invited to the fact that the four 888 brake linings which are basically compounded from as curves of FIG 1 represent unaltered lining, lining plus bestos and a synthetic thermosetting resm can be greatly 15 6% sodium fluoride, lining plus 6% potassium fluoride improved by the addition of a small amount of any of and lining plus 6% lithium fluoride. These four curves the alkali metal fluorides and especially by the addition show, at best, only minor effects of these additives to of sodium fluoride. brake lining, insofar as friction qualities and fade is concerned. However, attention is invited to the tabulation 20 in the upper right-hand comer of FIG 1 demonstrating BACKGROUND OF INVENTION a dramatic reduction in the wear suffered by the altered The function of automotive brake linings is to convert the kinetic energy inherent in a moving vehicle to heat and to absorb this heat and transfer it, eventually, to the ambient It is usually desirable that the coeflicient of fric tion between the brake lining and the metal drum be as high as possible, be independent of inevitable variations in operating conditions such as temperature and moisture, and that the necessary energy conversion be accomplished with a minimum of wear of the lining and the drum. The conventional brake lining employed in the auto motive industry is based upon asbestos and a thermo-setting resm modified by sundry additives to enhance specific properties. Typical brake lining compositions are described in detad in United States Letters Patent 3,227,249, dated Jan 4, 1966. This patent is interesting in that it 35 30 , 35 brake linings and especially the lining containing sodium fluoride FIG. 2 has been presented to demonstrate the favorable effect the addition of 7% sodium fluoride exerts upon the fade characteristics of a brake lining The table included in this figure also emphasizes the enhanced wear char acteristics of sodium fluoride altered brake lining. This figure contains data upon a conventional brake lining, an experimental lining and the same experimental lining plus seven percent sodium fluoride This last lining con sisted of fifty-seven percent absestos, ten percent ground cashew particles, fifteen percent novolac resm, ten percent barium sulfate, one percent carbon black and seven per cent sodium fluoride. The superior cold stopping ability of the sodium fluoride altered lining is apparent from this describes as a particular additive to brake lining composi tions, the compound cryolite Cryolite is defined as a double fluoride of sodium and aluminum and having the 40 figure. It is to be understood that this invention is applicable to other friction applications such as clutch facing. formula NasAlFe. This invention is predicated upon our discovery that the fluorides of the alkali metals are superior to cryolite as a brake lining additive and less costly to use. Particu larly attractive results have been obtained with sodium fluoride, although lithium and potassium fluoride are beneficial. THE INVENTION 45 We claim as our invention: 1. An automotive friction material comprising as its essential ingredients; asbestos, a synthetic thermo-setting resin, and an alkali metal fluoride selected from the group consisting of lithium fluoride, sodium fluoride and po tassium fluoride, in an amount to substantially increase the resistance of the brake lining material to wear 2. The automotive friction material recited in claim 1 in which the alkali metal fluoride is sodium fluoride and To illustrate this invention a standard production brake 50 the amount of sodium fluoride additions, does not sub lining composition was modified by the addition of vary stantially exceed twenty percent. ing amounts of lithium fluoride, sodium fluoride and potassium fluoride. Lithium fluoride was added in the References Cited amounts of 6%, 12% and 18% The preferred additive, sodium fluoride, was added in the amounts of 6%, 12% gg and 20%. Potassium fluoride was added in the same amounts as the sodium fluoride. The results obtained with the brake linings, so com 1,932,912 2,554,128 3,227,249 UNITED STATES PATENTS 10/1933 Rosner106--36 5/1951 Spokes 260--38 1/1966 Kuzmick et al 188--251 pounded, as compared to each other and to' the unaltered MORRIS LIEBMAN, Primary Examiner lining composition, is best understood from a study of gg FIG 1 FIG 1 represents results obtained from a brake S. M. PERSON, Assistant Examiner lining testing machine described in a Society of Automo tive Engineers publication 670,079 published Jan. 9-13, 1967 and entitled A New Laboratory Friction and Wear U.S. Cl. XR. 106--36; 260--DIG. 39 S-FORD-300 SCF-FORD-0796