Drive means

摘要

Motion imparting means to effect angular movement of a pivoting member (10) mounted for pivoting motion about an upstanding axis (22), wherein said motion imparting means comprises first and second assemblies, said first assembly including drive means (65) comprising a magnetic body (15) that (a) has an outer cylindrical surface and radial end surfaces (b) is polarised axially of the cylindrical surface, and (c) has each radial end engaged by an associated pole plate (14,16) that extends outwardly beyond the body's cylindrical surface with its periphery spaced from that cylindrical surface, said second assembly comprises an engagement plate (53) to be attached to the pivoting member (10) and, in use, be engaged by the pole plates (14,16) and magnetically coupled thereto, and wherein a lever (34) is provided to one end of which the first assembly (65) is to be mounted and that is to be mounted by its opposite end for pivoting motion about an upstanding axis (32) spaced from the pivoting member's pivoting axis (22) and such that said drive means (65) can in use effect a magnetic drive coupling between the first and second assemblies. In one arrangement, one of the pole plates (16) is provided around its periphery with a plurality of mutually spaced protrusions (19) or depressions, and the engagement plate (53) is provided with correspondingly spaced depressions (21) or protrusions, the protrusions (19) of one said plate (16) in use engaging in the depressions (21) of the other said plate (53) to provide a positive inter-engagement between them that resists slippage across magnetically coupled surface portions of the drive means. In another arrangement (Fig 6), each pole plate (14,16) is of generally disc-like form having a peripheral face of cylindrical form, a radial face directed away from the body, and between these two faces a chamfered face (54,56), and the engagement plate (63) has a surface (55) provided with an elongate groove of triangular or frusto-triangular cross-section providing inclined faces which are in use engaged by and magnetically coupled to the two said outwardly-directed chamfered faces (54,56) of the first assembly.