Patent GB-668098-A (GB)
Title: Improvements in or relating to magazine gramophones
IPC: G11B17/16
Filed: 1949-07-23
Abstract: 668,098. Magazine gramophones. DAWSON, T. C. W. July 23, 1949. No. 19455/49. Class 40 (ii). All of the operations of record changing are performed by a cam wheel 1 driven from the turntable spindle 6 through a one-revolution clutch formed by the omission of several peripheral teeth of wheel 1 to leave a gap 9. An arm 18 rigidly coupled to the vertical rotation axis 16 of the tone arm 13 carries a camfollower pin 19 which engages in a cam groove 20a-20f in wheel 1 to determine the lateral movements of the tone arm. A pin 23 passing through the axis 16 engages in an arcuate depression 21 in the wheel 1, arranged so that in the central position shown the tone arm is lowered to the playing position but when wheel 1 moves so that pin 23 engages the end portions of depression 21, the tone arm is raised clear of the record. Starting from the position shown, a 10 inch record is about to be played, and wheel 1 is stationary. As-the tone arm 13 moves inward, pin 19 traverses part 20f of the cam groove which is arcuate about axis 16. At the end of the record, the lead-off groove swings the tone arm in and causes pin 19 to engage part 20a to rotate wheel 1 enough to engage its peripheral teeth to initiate a single revolution in a clockwise direction. During the first part 20b which is concentric, there is no lateral movement, but the tone arm is raised by pin 23 passing out of depression 21. Groove part 20c then moves the tone arm outwards until a point A is reached. Then, if a stop 45 is in position for engaging arm 18, pin 19 will enter groove 20e which positions the tone arm for a 10 inch record, but if stop 45 is withdrawn, pin 19 follows groove 20d to position the tone arm for a 12 inch record. The last parts of grooves 20d, 20e are concentric and during this movement, pin 23 has entered depression 21 and is passing towards the middle to lower the tone arm to playing position, and the wheel 1 then stops. Stop 45 is carried by a lever 44 and is moved into the operative position for 10 inch records by a leaf spring 47 on wheel 1 passing under the tail 43a. When, however, a 12 inch record falls on to the turntable its edge turns lever 44 to the inoperative position appropriate to 12 inch records. The records are stacked on a spindle 30, Fig. 2, provided with release mechanism as described in Specification 668,097 operated by raising a rod 32 through a lever 33. For depressing the right hand end of lever 33 at the correct instant, cam wheel 1 has pivotally mounted in it a cam block 39, Fig. 6, and over the end of lever 33, an abutment 40 is mounted to support block 39 and cause it to depress lever 33 as wheel 1 rotates. To repeat a record, abutment .40 is withdrawn by means of knob 66 and levers 60, 62, allowing cam block 39 to tilt instead of operating the record changing lever 33. The tone arm is, however, positioned as before by wheel 1, which also carries a cam 60a for restoring the repeat knob to the inoperative position shown. An extension 69 of lever 60 moves under selector lever 44 and prevents it being reset by spring 47 thus allowing a repeat of a 12 inch record. To switch the motor off automatically after playing a predetermined number of records, a ratchet wheel 71 is turned through the appropriate number of tooth spaces. As each record is played, a pin 72 on wheel 1 returns ratchet 71- through one tooth space until, after the set number, a pin 73 on the ratchet operates the motor switch 75. The repeat lever 60 is arranged to step the ratchet wheel each time it is operated, so as to include the repeat playings in the set number. To reject a record, a knob 53 is moved in an arcuate slot 54 to cause a pad on the end of a lever (not shown) to wipe the edge of cam wheel 1 to move it to engage its gears and initiate a record changing operation.