Drive with continuously adjustable speed variation

Abstract

A belt driving mechanism, providing a speed ratio that is infinitely variable between predetermined limits, of the type in which a belt embraces two pulleys adjustable in effective diameter depending on the separation of two conical discs, is described wherein an actuating element reciprocable between two abutments is mounted coaxially with the driving pulley which has an axially fixed disc and an axially adjustable disc. The actuating element carries a rod with a scale ring screwed onto its outer end, and to urge the axially adjustable disc towards the fixed disc, the actuating element moves the scale ring to take up clearance between itself and a thrust member connected by way of a thrust bearing with the adjustable disc and, on continued movement, to force the thrust member to move the adjustable disc. Each movement of the actuating element covers the full stroke between the abutments so that the movement of the disc is the difference between this stroke and the initial clearance of the scale ring, which clearance can be adjusted by turning the ring on the rod. The thrust member is a coaxial tube containing the actuating element, which may be a piston in an axially fixed cylinder mounted with an intervening journal bearing on a rotary shaft fixed to the axially fixed conical disc. The mechanism relieves the bearings of a motor that drives the shaft of any axial thrust. The speed ratio can be adjusted by the scale ring either when the drive is at a standstill or when it is working.