US1932912A - Manufacture of brake lining - Google Patents

Description

Patented Oct. 31, 1933 UNITED STATES PATENT OFFICE MANUFACTURE or BRAKE more corporation of Illinois No Drawing. Application December 7, 1928 Serial No. 324,572

14 Claims. (Cl. 188-251) This invention relates to friction materials such as brake linings, clutch facings, etc., and has for its object to provide a material which will not injure the brake drum, which has a coefllcient of friction which is as constant as possible, and which is not injured by heat. I have found that these and other advantages can be attained by introducing into the friction material certain salts or other non-metallic substances having desirable effects set forth below.

Preferably these substances are relatively inert at ordinary braking temperatures, except for their mechanical effect as a part of the friction mass, but at relatively high temperatures such as might cause scoring,-i. e. ordinarily between 1,000 F. and 1,700 F.,--they soften or melt or are otherwise activated to minimize the frictional efiect of the lining, probably by lubricating the surface which engages the brake drum. Many substances of high melting point have this desirable characteristic, among them being sodium chloride, sodium cyanide or ferrocyanide, barium carbonate alone or mixed with sodium cyanide, bichromate of potassium, and others. These materials lower the coeificient of friction, thereby minimizing the tendency to grab, and at the same time make the coefficient of friction more uniform under varying temperatures, pressures, and other conditions. Moreover, the coefficient drops somewhat as the salt softens or melts, thus softening the final retarding effect.

Itwill be seen that among these are a. number of salts, including the sodium cyanide and ferrocyanide, the barium carbonate, and the bichromates, which have a case-hardening effect on steels. This, according to a highly important phase of my invention, permits the use in the brake of a relatively low-carbon drum, which is easily worked and therefore inexpensive, without scoring and without flaking off particles of steel to become imbedded in the brake lining. The carbon-containing salts, preferably sodium cyanide, while relatively inert during ordinary braking, are activated by excessive surface temperatures of the steel, and also of the lining, to react on the steel drum to introduce carbon into its surface to case-harden it. The tendency of the drum surface to soften at these high temperatures facilitates the case-hardening effect.

Similarly the chromium-containing salts harden the drum gradually in use by introducing chromium into the surface of the steel when activated by these high temperatures.

Some of these materials, notably the sodium cyanide, also have the advantage that the cyanide,

for example, forms fumes at high temperatures which act on the copper of the brass wire used in the asbestos yarn from which the usual lining is woven, and on the copper of the brass lining rivets, to form a'soft compound which wears away without scoring the drum, merely forming a brown powder whlchsifts out of therdrum as fast as it is formed.

A woven lining of my new type may be formed by impregnating the yarn forming the transverse threads of the lining, and which ordinarily consist of an asbestos-copper or asbestos-brass yarn,

with a suitable friction agent mixed with powdered sodium cyanide. Such an agent may consist of a mixture including an oxidizing oil such as 7 0 China-wood oil or a mixture of China-wood oil and castor oil. diluted if desired with kerosene and/or gasoline, or in some cases a vulcanizable rubber composition is used. The yarn forming the warp, or longitudinal threads, is impregl6 nated with this or a similar agent just before it reaches the loom where it is woven, and may be dusted with pulverized sodium cyanide or other salt while still wet and before weaving on the loom. The fabric after weaving is cured in the usual manner by heating and rolling.

If preferred, the lining may first be woven, then impregnated with a solution of the salt, then dried, and finally impregnated with the usual waterproof bituminous friction dope. Where asbestos is formed into a paper made from a pulp, and thereafter made into the lining, the salt may be mixed into the pulp.

A molded lining may be made by impregnating asbestos fiber with phenolic or other synthetic 9 condensation material such-as furfural containing the sodium cyanide or other salt. This material may also be used with a woven lining in place of the materials described above. The impregnated fiber is molded under heat and pressure.

Asbestos fiber or sheets may also be impregnated with a sodium cyanide or other salt solution and thereafter treated with synthetic resin or rubber for water proofing purpose previous to curing or molding under heat or pressure and heat. In still other methods of manufacturing lining, it may be desirable to mix the salt directly into the usual friction dope withwhich the fabric is impregnated.

In addition to the drum-hardening effect, and the minimizing of scoring and grabbing, I find that these salts, notably sodium chloride and sodium cyanide, give desirable and hitherto difflcul y-obtainable friction characteristics to the 0 lining regarded purely as a friction material. Thus tests show that the coefficient of friction is much more nearly constant than usual, but drops away slightly at high pressure, probably due to liquidation of the salt, thus giving an additional safeguard against grabbing. The average wear in severe use and especially at high temperatures is more than doubled, probably due to a glaze of the salt forming on the surface of the lining.

It is not my intention to limit the invention to the exact materials, or to the exact methods described above, or otherwise than by the terms of the appended claims. Part of the subjectmatter of this case is continued from my prior application No. 319,459, filed November 14, 1928.

I claim:

1. A friction material for a brake lining comprising a substantial amount of barium carbonate.

2. A friction material for a brake lining comprising a substantial amount of barium carbonate and sodium cyanide.

3. A friction material for use in rubbing engagement with steel, and which comprises a carbon-containing salt activated by relatively high temperatures to carburize the surface of the steel.

4. A friction material, for a brake lining or the like, containing a cyanide.

5. A friction material, for a brake lining or the like, containing an alkaline cyanide.

6. A friction material, for a brake lining or the like, containing sodium cyanide.

7. Brake lining friction material comprising a woven body with its threads carrying a cyanide.

8. A brake lining comprising asbestos and a metal, together with impregnating material containing a cyanide.

9. A brake lining material impregnated with a drying oil containing a cyanide.

10. A brake comprising a steel drum, in combination with friction material engaging the drum and containing a cyanide.

11. That method of making a brake lining which comprises mixing an asbestos material with a cyanide.

12. That method of making a brake lining which comprises forming a yarn, impregnating the yarn with a friction agent and a cyanide, and thereafter weaving the yarn into a brake lining fabric.

13. That method of making a brake lining which comprises impregnating an asbestos material with a cyanide and waterproofing agent.

14. That method of making a brake lining which comprises impregnating an asbestos material with a cyanide and synthetic resin and thereafter molding it under heat or pressure and heat.

ADOLPH ROSNER.