# US 4,397,381 A · Magnetic brakes and clutches > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,397,381 A - Document ID: US4397381A - Status: Granted - Kind: A - Application number: 06/325,144 - Filed: 1981-11-27 - Granted: 1983-08-09 - Earliest claimed: 1981-11-27 - Inventors: Charles B. Fisher; Sidney T. Fisher - Web page: https://patentgrep.com/patent/US4397381A ## CPC - F16D 28/00: Electrically-actuated clutches (arrangements for synchronisation F16D23/02; clutches actuated directly by means of an electromagnet F16D27/00; automatic clutches F16D43/00 - F16D45/00; external control F16D48/00) - F16D 49/00: Brakes with a braking member co-operating with the periphery of a drum, wheel-rim, or the like (similar clutches F16D13/10) - F16D 51/00: Brakes with outwardly-movable braking members co-operating with the inner surface of a drum or the like (similar clutches F16D13/14) - F16D 2121/20: using electromagnets - F16D: COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES ## Abstract Drum-type brakes and band-type clutches which are activated by expansion or compression, or both, of one or more concentric magnetic members, with conducting windings carrying electric currents. Circular annular mating members carrying one or more conducting windings expand or contract in diameter, due to magnetic forces caused by currents in the winding or windings, and operate as a brake or a clutch. ## Claims ### Claim 1 A frictional rotational torque transfer device, comprising external and internal circular cylindrical annular mating members, at least one of said members being magnetic and carrying at least one toroidal insulated conducting winding, and at least one of said members carrying a friction lining, which is actuated by changes in mechanical dimensions, caused by circumferential magnetic fields induced in one or both of said mating members of said device, by electric currents in said windings, which change the rotational friction between at least one of said members and at least one of said frictional linings. ### Claim 2 (depends on 1) Said device according to claim 1, which comprises: said external circular annular magnetic mating member, attached to a first external mechanism, carrying an even number of alternate insulated conducting windings of opposed directions of windings, the total number of turns wound in one of said directions being substantially equal to the total number of turns wound in said opposed direction, and a first substantially non-magnetic friction lining, internally attached to said external magnetic mating member, and said internal circular annular magnetic mating member, attached to a second external mechanism, concentric with said external magnetic mating member, carrying at least one insulated conducting winding, all said winding or windings being in series, and generating circumferential magnetic flux in the same direction when carrying direct current, and a second substantially non-magnetic friction lining, externally attached to said internal magnetic mating member, said first and said second friction linings being separated by an air gap when a substantial current flows in said windings, and being strongly pressed against each other when substantially no current flows in said windings. ### Claim 3 (depends on 2) A frictional rotational torque transfer device according to claim 2, in which said conducting insulated windings are present on only one of said mating members. ### Claim 4 (depends on 2) A frictional rotation torque transfer device according to claim 2, in which at least one of said friction linings is omitted. ### Claim 5 (depends on 1) Said device according to claim 1 which comprises: said external circular annular magnetic mating member, attached to a first external mechanism, carrying at least one insulated conducting winding, all turns of said winding or windings having the same direction of winding, and a first substantially non-magnetic friction lining, internally attached to said external magnetic mating member, and said internal circular annular magnetic mating member, attached to a second external mechanism, concentric with said external magnetic mating member, carrying an even number of alternate insulated conducting windings of opposed directions of windings, the total number of turns wound in one of said directions being substantially equal to the total number of turns wound in said opposed direction, and a second substantially non-magnetic friction lining, externally attached to said internal magnetic mating member, said first and said second friction linings being separated by an air gap, when substantially no current flows in said windings, and being strongly pressed against each other, when a substantial current flows in said windings. ### Claim 6 (depends on 5) A frictional rotational torque transfer device according to claim 5, in which said conducting insulated windings are present on only one of said mating members. ### Claim 7 (depends on 5) A frictional rotational torque transfer device according to claim 5, in which at least one of said friction linings is omitted.