Patent GB-551022-A (GB)
Title: Improvements in and relating to automatic record changers for phonographs
IPC: G11B17/16
Filed: 1941-09-19
Abstract: 551,022. Magazine gramophones. BRITISH THOMSON-HOUSTON CO., Ltd. Sept. 19, 1941, No. 12141. Convention date, Sept. 19, 1940. [Class 40 (ii)] Relates to magazine phonographs of the kind in which a stack of record discs is supported above the turntable and one record at a time is dropped on the turntable by the oscillation of plattens supporting the edges of the records, and in which a hinged finger detects the diameter of the record to be played or the absence of a record from the magazine in order automatically to position the needle on the record according to its diameter or to stop the machine when the magazine is empty, for example as described in Specification 477,325. According to the invention, the detecting finger 19, Figs. 1 and 3, is integral with a cam disc 35 and is coupled for example by friction and a spring 37 to a vertical shaft 12 carrying the records supporting plattens 14, 15 so as to be moved against the edge of the bottom record just before that record is dropped, the cam disc 35 serves to position a tone-arm stop-lever 40, and this lever.is adapted to be held in position by a catch 43. The operation of the apparatus shown in Figs. 1 and 3 is as follows. After the last record of a stack has been played and the tone-arm lifted and moved out, the inward return of the tone-arm is stopped by the engagement of a finger 50 with the outer notch 48 of the stoplever 40, and the tone-arm then rests on a vertical rod 51 and by its weight opens a switch 54, 54<SP>1</SP> in the motor circuit. This is the position shown. To start operation after a fresh supply of records has been stacked over the supporting pillars, a handle 18 is turned to the right. A wedge 56<SP>1</SP> on an arm 56 on the spindle 55 of the handle 18 wedges the rod 51 up, the switch 54, 54<SP>1</SP> closes and starts the motor 5 which drives the turntable 1 through a friction pinion 6. The spindle 2 of the turntable transmits motion through a worm gear 23, 22 to the ratchet wheel 83 of a clutch 21. This clutch is normally open ; but, when the handle 18 is turned, the arm 56 thereon moves the sliding rod 57 against a lever 24 of the clutch. The lever 24 moves a rocker 72 counterclockwise about a pivot 73 causing a tooth 77 attached to the rocker 72 and projecting through a notch in a disc 75 to engage the ratchet wheel 83. At the same time, a tooth 71 on the rocker 72 leaves a notch 70 in a fixed drum 60, so that motion is transmitted from the ratchet wheel 83 to the disc 75, which is fast with cams 26, 27 on a shaft 20. This shaft makes one revolution to perform the record-changing and associated operations and is stopped by the re-engagement of the tooth 71 with the notch 70. The handle 18 must be released before this rotation is completed to enable the rod 57 to be pulled back by a spring 571 to free the lever 24 to enable the rocker 72 to be turned back by a spring 80. The spring 57<SP>1</SP> in pulling back the rod 57 also returns the handle 18 to its mid position. During the rotation of the cam shaft 20, the cam 26 first lifts a rod 28 which lifts the pick-up arm, so that the switch 54, 541 remains closed by its spring action even after the handle 18 returns to its middle position. After the pick-up arm has been lifted, the cam 27 rocks a follower 29 fast with a shaft 30, which transmits motion by a crank 31 and a link 32 to a lever 34. This lever is connected by links and cranks 85, 86 to the vertical spindles 12 to which the record supporting plattens 14, 15 are attached. The lever 34 is also connected by a pin 87 to a lever 88 provided with a rod 90, which is moved outwards by the first stroke of the cam follower 29. The rod 90 bears against an arm 99 and holds the tone-arm in its outward position. The first or counter-clockwise stroke of the cam-follower 29 then causes the platten 15 to release the bottom record while the platten 14 moves in below the next record to support the stack. During the return stroke, the platten 14 is withdrawn and allows the stack to drop on to the platten 15 in readiness for the next operation. At the beginning of the first stroke the finger 19 is dragged by a shaft 12 into contact with the edge of the bottom record just before that record is released. The cam-disc 35, which has three operative parts 36, 39, 38 of different diameters, turns with the finger 19 and is therefore stopped in one position for a 12-inch record, in a second position for a 10-inch record, or in a third position when the magazine is empty and the finger 19 moves further in. After the finger 19 has completed its stroke, an arm 92 on the shaft 12 engages an arm 93, which turns a spindle 94 thereby withdrawing the catch 43 from the stop-lever 40. This lever is then turned by a spring until a spring finger 45 on the lever bears against the cam disc 35. During the return stroke of the cam follower 29, the rod 90 moves inward and allows a spring 49 to turn the tone-arm inward, the spring 49 acting on a lever 97 which has a part 98 bearing against the arm 99. The inward movement of the tone-arm is stopped by the engagement of the catch 50 on the lever 97 with the notch 47 or 46 of the stop-lever 40 according to whether the record just delivered is a 12-inch or 10-inch one. After this, during the completion of the rotation of the shaft 20, the cam 26 allows the rod 28 and the tone-arm to fall to bring the needle in engagement with the record. When the playing of the record is completed, an arm 25 moving with the tonearm bears on the cam lever 24 and causes a fresh rotation of the cam shaft 20 to produce a fresh record-changing operation. This time, however, the tone-arm is in the inward position when raised by the rod 28 and cam 26 and is moved out by the arm 90, after which the operation proceeds as in the first instance. When the last record has been played, the operations again proceed in the same way, but the inward return of the tone-arm is limited by the engagement of the catch 50 with the outer notch 48 of the stop-lever 40 and, when lowered by the cam 26, comes to rest on the rod 51, whereby the switch 54, 54<SP>1</SP> is opened and the motor stopped. In addition, at any time during the play of a record, a record-changing operation can be initiated by a movement of the handle 18 to the right, or the machine may be stopped by a movement of the handle 18 to the left. This movement to the left brings an arm 124 on the handle 18 against the stop-lever 40 and moves the stop-lever to the position where the notch 48 is in the path of the catch 50 irrespective of the position of the cam-disc 35. In a modification, Fig. 5, the automatic operation of the clutch at the end of the playing of a record is brought about by the quick inward movement imparted to the tone-arm. The arm 25 is not rigid with the tone-arm bracket 99 and can be periodically pushed back by the clutch lever 24 when this is rocked by the engagement of a pin 107 on the ratchet wheel 83 with the bent end 106<SP>1</SP> of a lever 106 on the spindle 108 of the lever 24. A quick inward movement of the arm 25, however, takes the bent end 106<SP>1</SP> of the lever 106 out of the path of the pin 107 and operates the clutch engaging member 77. In another modification, Fig. 7, the tone-arm when returned to its outward position is held to the lever 97, 98 by a hook 111 and is only released from the hook when the tone-arm is lowered by the rod 28. After this, a light spring 112 moves the tone-arm gently inwards to engage the needle with the first groove of the record. In still another modification, Fig. 8, the rod 90, instead of acting directly on the tone-arm, acts on a lever 132, the other arm 133 of which carries a finger 134. When the rod 90 moves outwards, it turns the lever 132, 133 until the finger 134 reaches and deflects a hair spring 140 and abuts a shoulder 139 on a flange 136 on the tone-arm supporting sleeve 130, 99. The finger 134 then enters a slot 138 in the flange 136, and the interlocked parts are then moved together to position the needle over the edge of the record ; and when the tone-arm is lowered, the finger 134 leaves the slot 138, and the hair-spring gives the tone-arm a light inward push to lead the needle into the first groove of the record.