GB896247A - Improvements in or relating to submersible electric motors - Google Patents

Abstract

896,247. Centrifugal switches; fluid actuation of switches. TAIT MANUFACTURING CO. July 5, 1960, No. 23487/60. Class 38 (5). [Also in Group XXXV] A submersible liquid-filled motor for driving a pump with a shaft within a casing incorporates a switch movable between a starting and a running position by an operating member inside the casing which is normally biased to maintain the switch in a starting position, and is moved by a pressure differential on opposite sides of the operating member produced by a pump driven by the motor shaft. The motor includes a starter 20 carrying main field winding 21 and the starting winding and a rotor 23 secured to shaft 25 whose lower end is supported by bushing 27 in a bracket 30 bolted between end ring 31 and end housing 15. The starting and running circuits of the motor include a starting mercuryswitch 35, a starting capacitor 36, and the starting and main windings 22, 21, respectively. Switch 35 mounted on an arm 40 pivoted at 41 on a mounting 42 carried by bracket 30 is biased by spring 44 to its open position. A spring 52, stronger than spring 44, biases the plunger 51 which slides in the hollow portion 50 of the lower end of shaft 25, against the switch arm 40, so forcing the switch to its closed position. With switch 35 in its closed position, when the motor is first energized, an impeller formed by a disc 55 with radial passages revolves with the motor shaft, developing suction in shaft portion 50, overcoming the force of spring 52, causing spring 44 to push up switch arm 40, and shift switch 35 to the running position. A rubber diaphragm 16 forms a flexible seal between the interior of the motor and the outside atmosphere. In another embodiment described with reference to Figs. 5, 6 (not shown), 7, the centrifugal impeller is secured to the lower end of the motor shaft 61 by screw 96 and lock-washer 97, an extended tubular cylindrical inlet portion 99 forming a guideway for a plunger 100, which is the operating member for a switch 75, Fig. 7. Spring 101, mounted in inlet 99, biases the plunger 100 downwardly to cause its pin 102 to engage the switch button 91 closing switch 75. In this embodiment, the diaphragm is replaced by a bellows which is arranged to operate a cut-off switch when fully expanded.