Patent GB-505152-A (GB)
Title: Improvements in or relating to electric motors
IPC: H02K7/12
Filed: 1938-08-16
Abstract: 505,152. Electric motors ; clutches combined with brakes. UTAH RADIO PRODUCTS CO. Aug. 16, 1938, No. 24155. Convention date, Oct. 15, 1937. [Class 35] [Also in Group XXIV] The rotor 10 of an electric motor is moved axially by the magnetic attraction between the rotor and the stator, upon energization of the motor, so as to bring a clutch member 46, fast on the rotor shaft 43, into driving engagement with a driven clutch member 47 loose on the shaft 43, while, on de-energization of the motor, the rotor is urged in the opposite direction by a spring so as to disengage the clutch, the member 47 being carried along by the friction between itself and the shaft into frictional engagement with a fixed surface so as to brake the member 47. A reversible induction motor of the shaded-pole type for operating the tuning mechanism of a radio receiver is shown. The laminated stator core 15 has four polepieces, each unshaded pole 16 being fitted with a main winding MW1 or MW2, while each pole 17 is fitted with a copper shading ring 18 and with two auxiliary windings AWl and AW2, or AW3 and AW4 which produce opposite polarities and which are alternatively energiz. able under the control of a switch 19, Fig. 9, so as to produce rotation of the rotor in opposite directions. The laminations are held together by the windings and by the rings 18, which are themselves secured in place by wedges 30 of insulating material, assisted by steel bridges 31 press-fitted between adjacent polepieces. Each wedge 30 has secured thereto a metal eyelet to which the winding connections are soldered. End plates 34 and 35 and a plate 37 for mounting the motor on the receiver chassis are secured to the stator core by bolts 36. The shaft 43 is mounted in self-aligning porous bushes 42 carried by the plates 34 and 35 and brackets 44 secured thereto, these brackets containing oil-impregnated absorbent material. The clutch members 46 and 47, which are of the claw type; are arranged within a U-shaped bracket 49 secured to the plate 34, the interior face of this bracket constituting the fixed surface with which the member 47 engages on de-energization of the motor. The member 47 is fast on a pinion 48 which is connected to a driven shaft 57 through gears 51, 54 and 55, the integral gears 51 and 54 being journalled on a spindle 52 secured between the plate 34 and a projecting part 53 of the bracket 49 while the shaft 57 is journalled in a bushing 58 secured to the plate 37. The spring acting on the rotor shaft consists of a spring finger 66 engaging the end of the shaft. This finger carries a contact 70 co-operating with a contact 69 on an adjacent spring finger 65, the two fingers being secured to the plate 35. The two contacts are normally separated, but, when the rotor moves axially in response to energization of the motor, the contacts close to complete a muting circuit. A switch 71 incorporated in the motor circuit as shown in. Fig. 9 is normally closed, but opens in response to abnormal heating of the motor. This switch comprises a bimetallic blade 72 controlling a pair of contacts, the blade being mounted on a " Bakelite " (Registered Trade Mark) plate 77 extending across an aperture in the plate 35, so that the blade, while being exposed to heat radiated from the motor, is thermally isolated from outside sources of heat.