Cam and follower arrangement

摘要

A cam and follower arrangement in which the cam consists of a track carried by a rotatable member. The track has one or more abrupt directional transitions (17) and the follower (17) is biassed to engage one wall or the other (21) of the track (21) appropriate to the direction of rotation of the member by means including a direct-current electric motor operated in a stalled condition. The arrangement may be employed in a monochromator for spectrophotometric apparatus to drive a filter-holder to position one of a number of optical filters arranged in the incoming beam of light.