Permanent magnet coupling torque limiter

Abstract

A torque limited of permanent magnet coupling type is disclosed, in which the value of transmitted torque is varied from a near zero minimum to a maximum. The torque limiter comprises a disk of magnetic material fixed to the output cylinder, and a pair of annular members disposed on both axial sides of the disk with small gaps filled with a powder of magnetic material. The annular members are rotatably supported on the output cylinder. An annular disk-shaped permanent magnet is fixed to one of the annular members at the side surface thereof opposite to the surface facing the disk. Further, an annular disk-shaped plate of magnetic material having an outer diameter greater than that of the permanent magnet is fixed on the outer side surface of the permanent magnet projecting radially from the outer circumferential surface of the permanent magnet. A tube-shaped adjustment member is axially slidable on the outer circumferential surface of a ring of non-magnetic material fitted into the opposing steps formed on the outer circumferential surfaces of the annular members, forming small gaps between the inner circumferential surface of reduced diameter portion thereof and the outer circumferential surfaces of the pair of annular members, and between the inner circumferential surface of increased diameter portion thereof and the outer circumferential surface of the annular disk-shaped plate.