Patent GB-321427-A (GB)
Title: Improvements in and relating to electric motors
IPC: H02K5/128
Filed: 1928-08-02
Abstract: 321,427. Gold, R., and Schmauss, J. Aug. 2, 1928. Insulation; armatures and field magnets, cooling; casings.-The stator of an electric motor which can work under water or other liquids or in deleterious atmospheres is enclosed in a fluid tight casing including a thin partition arranged between the stator and rotor, and the stator enclosure is filled with any combination of solid, fluid and gaseous media in order to prevent deformation of the partition. The stator enclosure alternatively may be filled with a solid substance such as an artificial resin which is fluid at ordinary temperatures, can be introduced into the stator chamber at atmospheric or other pressure, becomes solid at the ordinary or higher temperature and remains solid at the maximum temperature of operation of the motor. The tube 13, Fig. 1, is preferably of steel of a thickness of only a small fraction of a millimeter and is held tightly against flanges 11, 12 on the stator. Filling bodies in powder or granular form may be employed in the stator chamber, and these may be of high-resistance metal so as to conduct away the generated heat without forming the seat of eddy currents. The spaces between the particles may be occupied by liquid, gas or another solid. If the stator is entirely filled with solid material having a low coefficient of expansion the deformation of the thin tube will be small and it will be supported against outside hydrostatic pressure. To compensate for differences of pressure when the enclosure contains liquid or gas, a sensitive diaphragm box 16 may be connected to the stator chamber so as to be surrounded by the liquid in which the motor is immersed. Alternatively, the stator chamber may be connected with gas-filled expansion vessels having rigid walls. The expansion chambers may be arranged inside or outside the motor casing or they may be constituted by an enlargement of the casing. The stator casing may be connected to an open pipe emerging above the surface of the surrounding liquid and one or more enlargements may be provided in the pipe to reduce the fluctuations in the level of the filling substance as the pressure in the stator chamber varies. If a gaseous filling substance is employed, the pressure may be below that of the external liquid at ordinary temperatures. Compressed gas or liquid may be supplied to the stator chamber, if necessary under the control of pressure-responsive devices, and the gas or liquid conducts away the generated heat. The motor casing may be entirely closed and the medium from the stator chamber may be used to cool the rotor and prevent the entry of the external liquid into the casing. To improve the cooling, the rotor is formed at the centre with a space 17 maintained by sleeves 18 on the conductors 19, and one half of the core is formed with longitudinal channels 21 near the shaft. The external liquid enters through holes 22 in the end casing 8, passes through the channels 21, space 17 and the air gap and is expelled at the openings 23 and partly redrawn into circulation at the end 8. The cap 24 prevents the entry of impurities into the bearing 4. The thin tube 13 may be secured to the flanges 11, 12 by means of rings 25, 26, Fig. 3, of 'wedge section. The ring 25 is divided and is formed with threaded slots in which engage screws 27 bearing abutments 29. On tightening the screws 27, the ring 25 causes the tube 13 to be pressed against the flange 11. In another form, Fig. 5, the tube 13 is pressed against the grooved flange 11 by a rolled or wrought iron ring 31. In a further modification, Fig 6, each end of the tube is flanged at 33 and is held against the flange 11 by a pressure ring 34.