Patent GB-235294-A (GB)
Title: Improvements in or relating to sound reproducing machines
IPC: G11B17/00
Filed: 1924-03-10
Abstract: 235,294. Dicker, S. G. S., (Montreal Patents, Ltd.). March 10, 1924. Driving; speed - regulating and indicating; starting and stopping; cases. - A gramophone is driven by an electromotor which is resiliently suspended in such a way that a friction roller on the motorshaft is urged by the weight of the motor into driving engagement with a disc on the turntable spindle. The. friction roller is radially adjustable with respect to the disc, to vary the speed, which may also be controlled by means of a variable resistance in the motor circuit. The motor, which is of the induction type, is suspended from a frame which is attached to a larger plate, adapted to rest upon the usual motorboard; sound-deadening pads of felt are preferably inserted between the motor-board and clampswhich hold the plate. The motor-frame is provided with a bearing (specially designed for holding lubricant) in which the turntable spindle is supported. Means for manually starting the machine and for stopping it automatically or. by hand are mounted upon the upper plate, and consist of a combined brake and switch-actuating device. The switch-member, when in the " closed " position, is held by a trigger which carres an adjustable projection, adapted to be tripped by a finger mounted on the tone-arm so as to stop the machine when the sound-box reaches a predetermined position. Fig. 2 shows the motor-suspending means, comprising bolts 2<b> attached to a frame 50 and passing through lugs 2a which extend laterally from the motor casing on oppositesides and are arranged between the turntable spindle 300 and the centre of gravity of the motor. Pairs of springs 2<d> surround the bolts 2b, and are located respectively between the frame 50 and lugs 2a and between the lugs and nuts 2<c> at the lower ends of the bolts. The armature spindle 2 of the motor is supported in a hub 3<a>, Fig. 19, integral with the motor casing, bushings 3<b> of Babbit metal being provided at opposite ends of a lubricant chamber 3<c> with which a duct 3<d> communicates. Varying speed by adjustment of driving-member. The projecting portion 6 of the motor shaft has a sleeve 7 slidably mounted thereon and connected to it by a key and slot, the sleeve, which is spring-controlled, carrying a friction roller 12, preferably of soft rubber. The roller engages with a disc 40 on the lower end of the turntable spindle 300. Adjustment of the roller along the spindle 2, to enable the speed of the turntable to be controlled, is effected by means of a resilient arm 35 engaging the tip of the sleeve 7, the arm being carried by a spindle 20, Fig. 3, which is supported from the frame 50 and is operated by an arm 31 movable over a graduated plate 34. Means are provided whereby rotation of the spindle 20 is frictionally resisted. Actuation of motor-switch associated with friction brake. The mechanism for starting the machine and stopping it automatically or by hand is constructed as a unit mounted on a plate 70, Fig. 5, which is fixed to the main plate 62. The device includes a switch comprising a fixed contact 74 and a movable spring contact 75<1>, both mounted on an insulating block. The motor circuit is completed when these contacts are pressed together by an insulating cam 81. This is mounted on a pivoted disc having a handle 82 and carrying a brake-pad 86 of leather &c. The cam member is connected to a pivoted trigger arm 90 by a spring 95, which tends to hold the cam in the position shown in Fig. 5, with the switch open and the pad 86 in contact with the turntable. When the cam is moved by the handle 82, to start the machine, the end of the arm 90 snaps past a tooth on the cam member, taking up the same position as before, but holding the cam in the circuit-closing position. The trigger 90 has an extension 92 upon which is stiffly pivoted an arm 105. On this is pivoted a link 107 engaged bv a finger projecting from the tone-arm. 'This mechanism enables the tone-arm to move the trigger and the cam 81, so as to allow the motor switch to open and the brake to be applied, when any predetermined point on the record is reached, the necessary relative adjustment of the parts 105, 92 having been previously made.