Patent: GB189901758 (A) - 1900-01-13

Improvements in Portable Hand Dynamos parts of which Improvements are applicable to Small Power Dynamos and Motors for other purposes.

 1758. Evershed & Vignoles and Evershed, S. Jan. 25. Dynamos and motors.-Relates mainly to portable hand dynamos, adapted for testing purposes, but the improvements are also applicable in part to small-power dynamos and motors generally, to exploders for firing electric fuses, and to small motors for use in some forms of electric supply meters. The machines are preferably of the type provided with permanent field magnets, but shunt or series-wound magnets may also be employed. Armatures ; commutators.-The armature A may be of drum or ring type, preferably the former, and, in order to obtain a high electromotive force, it is wound with as many diametrical coils as a convenient number of holes in the periphery of the core will allow, and each of these coils is connected to one of a series of two-part commutators C, placed alongside one another on the armature shaft. The commutators consist of a number of deep and narrow washers, each divided into two parts by radial slots, and mounted on a sleeve of insulating-material with insulating distance-pieces between them. Each commutator is provided with a pair of disc brushes, all of which are connected in series as shown in Fig. 9. Brushes.-Each brush consists of a pair of thin metal discs with concentric corrugations. These are mounted side by side on a metal spindle supported in a standard, and receive the commutator segments between them. For a multisectional commutator, single-disc brushes set obliquely may be employed, e.g., in a motor-meter. Dynamos, driving.-The armature spindle is driven by a handle H, either directly or through speed gearing G, the moving parts being provided with ball or other bearings. The handle is pivoted to a sleeve on the driving-shaft, so that it can be folded over into a recess in the side of the containing box. It is held in its operative position by a knob detent, which engages with an eye formed by a pair of spring arms. Terminals, arrangement of.-A double terminal piece L, fitting into a recess in the side of the box, is provided with a cord conductor l, passing round a spring drum K in the cover of the box, and connected through a peripheral ring and the base plate of the drum to the hinges of the box, and through these to the brushes. When the terminal piece is drawn out, the spring drum is prevented from returning it by a pawl M.


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