Patent GB-199803-A (GB)
Title: Improvements in or relating to electrically driven gramophone tables
IPC: G11B17/00
Filed: 1922-03-28
Abstract: 199,803. Youldon, C. A. March 28, 1922. Driving; speed-regulating; starting and stopping; turntables. -A portable platform device which may be substituted for the usual record table of a gramophone of the disc type consists of a table having near its periphery the rotor poles of an electric motor which drives it about an axial member carried by the device and forming a bearing for a flanged sleeve carried by the table. The form shown comprises a table 1 driven by a thin flat electric motor, the rotor 9 of which is attached to the table and has a flanged sleeve 4 bearing on an axial member 5 carried by the stator 10. The member 5 passes freely over the spindle of the ordinary motor of the gramophone when the usual rotary table has been removed and serves to centre the device on the gramophone box. The rotor and stator of the motor comprises series of electromagnets arranged radially and having solid cores 9, 10 of thin section and substantially of L-shape. The table extends beyond the rotor periphery and acts as a flywheel. The rotor is provided with twice as many electromagnets as the stator, and the windings of alternate rotor electromagnets are connected to brushes 12 and 12<1> respectively. These brushes are carried by the rotor and alternately engage with contact studs connected to conductors 21, 22, Fig. 3. The stator windings and each set of alternate windings on the rotor are divided into two sections which can be connected in series or parallel through switches A, B, C, D so that the motor is adaptable for use with different voltages. Further subdivision of the windings may be made and a variable resistance may be provided whereby the motor may be used on other voltages. The speed of the motor may be controlled by means of a beltdriven governor carried by the base plate and comprising a disc 79 moved axially by governor weights 83 into engagement with a rubber pad 81. The position of the plate 80 carrying the pad 81 may be adjusted vertically. Instead of controlling the speed of the motor by means of a friction brake the control may be effected by the disc 79 breaking the circuit of the motor when it rises to a certain height, the circuit being again completed when the disc begins to fall. A switch 60, Fig. 3, is provided which is actuated by the tone-arm to break the circuit when the record is finished. The switch 60 comprises two contacts 66, 67, Fig. 6, the contact 66 being carried by a switch arm 65, 64 pivoted to the end of a cranked arm 61, the other end of which is frictionally held by a boss 68 carrying the second contact 67. the two contacts are held together by a spring 69. When the tone-arm reaches the end of its travel it engages with the switch arm 64 and opens the switch 60. When the apparatus is not in use the arm 61 is rotated to move the contact 66 of the contact 67 so that it lies on the insulating member 68. The Provisional Specification states that the governor may act through a lever working on the underside of the stator casing and that the supply terminals and switch may be housed in a recess below the centre of the table; also that the magnet poles may be laminated.