Patent GB-355399-A (GB)
Title: Improvements in or relating to disc talking machines
IPC: G11B19/265
Filed: 1930-06-05
Abstract: 355,399. Gramophones. PARKES, S., 119, Richmond Road, Crewe, Lancashire. June 5, 1930, No. 17392. [Class 40 (ii).] Driving.-In disc talking machines wherein the stylus is caused to track the record at a constant linear speed by driving the record or turntable, or a plate associated therewith, by a friction disc which is moved towards or away from the record centre in synchronism with the stylus, the friction disc is positively traversed and is constrained to move in a curved path similar to that traversed by the stylus carried by a swing- ing tone-arm, and provision is made whereby the friction disc is traversed in synchronism with the movement of the stylus under the control of an electric make- and-break device. The machine is also adapted for constant speed tracking. In one arrangement, Fig. 2, the friction disc 15 is slidable along and driven by a shaft 14 mounted in guides in a frame 12, 12a and pressed upwardly by links 18 and springs 19 so that the disc bears against the underside of the turntable 5 which is loose on its spindle 7. The frame 12, 12a is mounted in brackets 13 to turn about the spindle 7 and carries a traversing screw 20 engaged by a half nut 22 pivoted and slidable along a guide rod 24 and mounted between brackets 25 embracing the friction disc so that lateral movement of the nut by the screw is transmitted to the disc. The spindle 7 is driven by a spring or electric motor 8 and drives the shaft 14 through a splined pinion 26 and the screw 20 through a clutch 32 and pinion 27. The disc 15 is constrained to traverse in a curved path by a rod 49 pivotally anchored to the fixed tone arm mounting 46 and embracing the disc, and the rod may be extended and bent upwardly through a slot in the casing top to carry an indicator finger for showing the position of the friction disc and a knob by means of which the rod and the shaft 14 may be depressed against the springs 19 to lower the disc 15 out of contact with the turntable. On such depression a pin on the bracket 25 disengages the nut 22 from the screw 20, permitting the disc to be adjusted below the stylus of the sound-box 4 on the tone-arm 1. A rod 27 fixed to the vertical part of the tone-arm is bent up through a slot in the casing and carries an indicator finger adjacent to that carried by the rod 49, whereby the relative positions of the stylus and disc 15 are indicated. To maintain the traverse of the disc in synchronism with that of the stylus, the bracket 25 carries a pin 40 extending into an insulated forked member provided with contacts 36a, 36b and mounted on the rod fixed to the tonearm, and if the disc travels too fast the pin moves against a contact to complete a circuit through an electromagnet which acts through a lever 43 to release the clutch 32 and arrest the drive of the screw 20. As shown in Fig. 1, a further pinion 57 and clutch 58 are provided which reverse the drive of the screw when the electromagnet is excited due to loss of synchronism. A clutch 56 operable by a hand-lever 55 is provided for direct drive of the turntable from the spindle 7. In a modification, the motor drives the turntable spindle through a governor-controlled sleeve whereby the screwed spindle for traversing the friction disc is driven at a speed varying in accordance with the speed of the turntable so that less work is thrown on the means for synchronizing the movement of the disc with that of the stylus. The indicating fingers in this case are on arms 65, 66, Fig. 10, mounted on sleeves 69, 70 geared respectively with members 3, 47 moving with the tone-arm and with the disc. The fingers are visible through a glazed cover 67a on a casing 67 mounted on the machine, and the arms carry the contacts 40, 36a of the synchronizing circuit. In another modification, Fig. 12, the friction disc mounting 12, 12a is arranged above the turntable and is pivoted and slidable on a curved rod 81 pivoted on the machine and engages over the turntable spindle 7 when in operative position but can be turned up about the rod 81. The disc shaft 14 and the traversing screw 20 are driven from a motor 86 through a flexible shaft 85. A forked member embracing the disc is connected to a rod 49 and constrains the disc to travel on a curved path. Loss of synchronism between the travels of the disc and stylus is corrected by a pin on the rod 49 completing circuits through contacts on an arm 37 geared to move in synchronism with the tone-arm whereby the clutches 32, 58 control the drive of the screw 20.