Patent GB-130788-A (GB)
Title: An Improved Mechanical Movement adapted for use in Brake Mechanism for Talking Machines.
Inventor: CONDON EDWARD THOMAS
IPC: G11B17/02
Filed: 1918-08-14
Abstract: 130,788. Condon, E. T. Aug. 14, 1918. Periodic.-Mechanism for arresting a talking- machine when the tone-arm ceases to advance at the conclusion of a record comprises a cam and wedge driven by the motor, a trip member operated by the cam to place it in the path of the wedge, and means dependent on the advance of the tone-arm for withdrawing the trip member before it is engaged by the wedge. The engagement of the wedge and trip member causes the application of a brake and, in electrically-driven machines, the opening of a switch in the motor circuit. Fig. 2 is a plan, Fig. 3 a sectional elevation, and Fig. 6 a detail of one form of the apparatus. The tone-arm 6 is rigidly connected to a disk 14 having a spherical periphery bearing in the upper end of a vertical rotatable sleeve 9. A pin 15 presses diametrically through the disk 14 and has a lateral play in slots 16 in the sleeve 9, its ends moving in a circumferential recess in the fixed socket 7. The lower end of the sleeve is guided by a cross-pin 10 and a ring 23 and carries a toothed sector 21 engaging a pinion 24 which is mounted on a pin projecting downwardly from the top-plate 2. An arm 28 having a frictional connexion to this pinion carries at its outer end a vertical pin 30, the upper end of which cooperates with a lever 43 controlling the motor switch 54 and the turntable brake 51. The lower end of the pin co-operates with a cam 33 and wedge 39 formed on the upper face of a horizontal pulley 31 driven by belt reducing-gear from the turntable spindle. At each rotation of the cam, the surface 33 engages the V-shaped lower end 38 of the pin 30, and swings the arm 28 to the position shown in Fig. 2. While the tone-arm is making its normal progress across the record, the consequent rotation of the pinion 24 returns the arm and brings the pin 38 into a position to pass between the wedge 39 and the circular portion of the cam. When, however, at the conclusion of a record, the tone arm comes to rest, the pin 38 is engaged by the inner face of the cam 39, and is thus given a further movement, and its upper end operates the lever 43, opening the motor switch 54 and applying a circular pad 51 to the inner face of the turntable rim 4. A spring 52 tends to hold the lever 42 in either of its two positions. The return movement of the tone arm to its starting position causes a pin 42 to release the brake, and a screwed pin 40 engages a spring extension 41 of the arm 28 and holds the pin 30 in contact with the cam-plate. In the modification shown in Fig. 7, the external cam 75 and a wedge 76 are rotated by belt and spur gearing from the turntable spindle 3 and co-operate with a pin 83 on an arm 80 having a frictional connexion to a pinion 77 mounted on a fixed spindle. The tonearm 6 has a pin-and-slot connexion, with slight play, to a plate 67 which rocks about a pivot 63 and rotates the pinion 77 by means of a segmental rack 69. The action is similar to that described above, the cessation of the tone-arm movement causing the wedge 76 to engage the pin 83, giving an abnormal movement to the arm 80, thereby actuating the brake-lever 84 and bringing the block 86 into contact with the turntable rim. The whole mechanism is mounted on a base-plate 60, so that it may be applied to an existing machine.