Patent GB-1290553-A (GB)
IPC: F16D65/12
Filed: 1969-09-25
Abstract: 1290553 Disc brakes; member constructions; friction clutches ABEX CORP 25 Sept 1969 [1 Oct 1968] 47339/69 Headings F2C and F2E A friction member, e.g. 20, Fig. 2, in a brake or clutch consists of carbon-to-carbon bonded carbonized cloth or fabric and carbonized resin, and needs no backing plate or member to hold it in shape. As shown, the member is made by laying-up flat sheets of woven cellulosic material each impregnated with a carbonizable resin and the assembly is pressed and sintered at a temperature so highthat the resin is not merely cured but, like the fabric, is completely carbonized. Alternatively, the fabric may be carbonized before the resin is applied. Driving slots 23 may be milled or otherwise provided in the periphery. Radial expansion slots (not shown) may also be provided. Apparatus for making a member by winding a tape is shown in Fig. 4. Tape 40 (e.g. ¢ or ¥ inch wide) e.g. of rayon, is drawn from a reel 41 through a controlled-atmosphere furnace 42 to carbonize the cloth and produce a controllable shrinkage. It is next drawn through a tank 43 containing a solvent and resin. Solvent is evaporated from the resin by heating at 44 and the material is then wound on a mandrel 45. Next, the coiled membel is cooled, the mandrel 45 is withdrawn, and the member is sintered in a controlled atmosphere furnace 46 to carbonize the resin. For mandrel 45 may be substituted a cardboard tube which carbonizes and falls apart during sintering. The finished product is shown in Fig. 5. Driving slots 53 are part-formed initially by a pointed or rounded punch 47, Fig. 4, and subsequently machined out. In an alternative procedure, rayon is wound on a mandrel, resin-impregnated, cured at 450‹ F., pre-carbonized at 700‹ F., carbonized at 1300‹ F., re-impregnated with uncured resin, and re-carbonized at 1300‹ F. A wound-up ring as in Fig. 5, but without the notches, may be severed radially to provide partly-rounded trapezoidal pads 60, Fig. 6. An arcuate segment having concentric outer and inner surfaces may be cut from the outer periphery of the ring of Fig. 5 (without the notches), the segment then being bonded adhesively or otherwise directly to an arcuate brake shoe without the interposition of a backing plate to form part of an internal drum brake (Fig. 7, not shown). A member with a small central hole (Fig. 8, not shown), may be re-formed before sintering to provide a trapezoidal member 90, Fig. 9, in which the hole is not retained. A composite member (Fig, 10, not shown), may be made by proceeding as in Fig. 4 but at a certain stage discontinuing winding the resinimpregnated tape and joining-on a tape incorporating, besides resin, "friction-tailoring" agents, e.g. powders, of SiC, alumina or iron, so that the finished product has a radially inner portion in which driving slots may be machined later, and a radially outer portion incorporating the agents; in such outer portion, alternatively, the agents may be introduced between the tape layers during winding. The radial locations of the two parts of the composite member may be reversed. In other alternatives, a metal or ceramic filler may be added as a strengthening agent at areas of driving-tooth engagement only, or an additional resin-curing step provided at this location.