GB547668A - Improvements in or relating to permanent magnet motors - Google Patents

Abstract

547,668. Direct current motors. HITCHCOCK, S. I. Jan. 31, 1941, Nos. 1306 and 15231. [Class 35] The motor has moving and stationary magnet systems, one of which comprises one or more permanent magnets having a number of polepieces, while the other comprises one or more electrically energized magnets having a number of pole-pieces, succeeding poles of each system in the path of rotation being of like polarity, and a cam-operated contact-breaker in the circuit of the energized magnets periodically energizes them, the relative position of the cam and contact breaker being adjustable to control the speed and direction of rotation. In the form described, the cylindrical permanent magnet 6, Fig. 1, is assembled on a non-magnetic rotatable shaft 5 with two laminated pole-pieces 7 having each four polar projections 11 opposite stator poles 12 carrying field coils 14 joined in series. The shaft 5 carries a cam 15, Fig. 4, actuating a rocking arm 16 pressed against it by a spring 25. Each end of the arm carries two contacts 19 facing four fixed spring-loaded contacts 20. The whole interrupter mechanism may be moved relatively to the rotor by handle 33 engaging a toothed rack 34, so that the speed of the motor may be regulated or reversed. The field coils are connected through the contacts to a source of direct-current so as to give either an attraction or a repulsion drive to the pole-pieces or a combination of the two. In the first two cases the second pair of contacts 20 is not required and may be used for additional windings utilizing or quenching the induced back voltage or additional contacts may be used for this purpose. The permanent magnet 6 is preferably subjected to an axial magnetic field during annealing so as to effect axial orientation of the molecules. The cylinder may be replaced by a number of bar or horse-shoe magnets clamped between the pole-pieces, with or without moulded cylindrical housing, Figs. 6 and 7 (not shown). A number of magnets and pole-pieces may be assembled alternately on the same shaft. The casing 1 may be of magnetic material forming the yoke for the stator poles 12, or it may be of moulded synthetic resin, when the poles 12 must be joined by independent yokes.