Patent GB-490551-A (GB)
Title: Improvements in magazine gramophones
IPC: G11B17/02
Filed: 1936-11-16
Abstract: 490,551. Magazine gramophones. CLARKE, H. M. G. Nov. 16, 1936, No. 31260. [Class 40 (ii)] Relates to gramophones in which the turntable rotates about a substantially horizontal axis for example as described in Specification 485,562. According to the invention, the tone arm 104, Fig. 1, carrying the pick-up or pick-ups is counterbalanced, and the balance is temporarily upset by a member 111, which causes the pick-ups to be lowered from an uppermost outward position to the level of the starting groove of the record, when the member 111 is arrested by the edge of the record. The member 111, which is pivoted on a spindle 110, has a rubber or felt pad 113 for bearing against the edge of the record, and an adjustable screw 129 for bearing on a bracket 128 on the tone arm 104 to depress the pick-ups to the level of the starting grooves. The pick-ups 100, 101 are carried by resilient arms 102, 103 on the tone arm 104, which is mounted on a spindle 106 and is counterbalanced by an adjustable main weight 107 and by a nut 108 for final adjustment. The spindles 106, 110 are carried by a frame 78 pivoted on a vertical pivot 79 to enable one or the other of the pick-ups 100, 101 to be brought into operation with one side of the record or the other. The various parts of the machine are mounted on a frame work comprising side panels a<2>, a<3>, a front panel a, and a hinged rear panel b, which carries the magazine m. The machine is closed by a hinged lid c, which has a catch d to hold the panel b closed. When the magazine is loaded, a switch 81, Fig. 2, is closed by the records ; and when the lid c is closed, it closes a switch 83, 84. The turntable spindle 12 carries a fly-wheel pulley 13 driven by a belt 15 from a pulley 16 on an electric motor 18. The mechanism is controlled by another electric motor 50 connected by gearing 52, 51, 54 to a toothed wheel 55 on a shaft 56, which carries a pinion 120 and three cams 61, 62, 63. The pinion 120 has only a partial crown of teeth 121 in mesh with a pinion 122 on a crank-shaft 123, which has two sets of cranks, one 124 connected to a rod 115 passing through a slot in the tone arm 104, and the other 125 connected to a rod 118 passing through a slot in a finger 117 on the spindle 110 of the member 111. The rods 115, 118 are provided with nuts 116, 119 to adjust their points of co-operation with the tone arm 104 and finger 117 respectively. The toothed wheel 55 carries four pins 70, 71, 72, 73 adapted to turn a star wheel 74 a quarter turn at a time. This star wheel is on a shaft 75 which carries two oppositely directed cams 76, 77 co-operating with'opposite ends of the frame 78. The toothed wheel 55 also carries on its other side a pin 57 for operating an L-shaped cam 58 for record changing as described in Specification 485,562. The turntable motor 18 is a capacitor type of motor comprising a main winding 67, Fig. 2, and an auxiliary winding 68. The electric connections are as indicated in Fig. 2. The sequence of operations is controlled by means of a switch 211, 212 opened and shut by the tone-arm in a known manner as follows : a lever 200 hangs loosely on the pivot 202 of two arms 201, 203, and is frictionally coupled to these arms under the pressure of a spring 204. A shoulder 200<1> on the lever 200 normally holds a lever 205 down against the action of a spring 207 ; and a pawl 210 on the lever 205 then holds the switch 211, 212 open. During the playing of a record, the bracket 128 on the tone-arm bears on the arm 203 and turns it gradually with the arm 201 and lever 200 about the axis of the pivot 202 ; but an arm 20 on the turntable spindle 12 periodically knocks a rubber plate 213 at the end of the lever 200 and pushes this lever back. When, however, the needle enters the knock-off groove at the end of a record, the rapid motion of the lever 200 releases the lever 205, and the switch 211, 213 closes. When the tone-arm is lifted back, it turns the arms 203, 201 and lever 200 in the opposite direction, and an inclined face 200<2> on the lever 200 wedges the lever 205 down into engagement again with the shoulder 200<1>. The lever 200 is moreover connected by a cable 221 to one end of a lever 218 fitting at its other end into a slot 217 in a press-button 214 controlled by a spring 215. If the playing or the completion of playing of a side of the record is not desired, the button 214 is pressed in, whereby the lever 200 is rocked and the switch 211, 212 closes as if the tone-arm had reached the end of the record. The successive operations of the machine will be described starting when the magazine is loaded, the lid closed, and the machine ready to operate with the parts in the position diagrammatically indicated by Fig. 5, where the several devices on the shaft 56 are shown at different levels for clearness of illustration. The operation is started by closing a main switch 82. The circuit of the motor 50 being in this starting position closed by switch 60 operated by cam 61, the motor starts and drives toothed wheel 55 for half a revolution when a flat 61b on cam 61 comes opposite switch 60 and allows said switch to open. During this half revolution of toothed wheel 55, cam 58 is first operated to discharge a record from the turntable, if one is present thereon, and to feed a fresh record from the magazine to the turntable, then teeth 121 engage pinion 122 and crank-shaft 123 turns half a revolution bringing crank 125 down and crank 124 up to allow tone arm to come down to level of starting groove of record, star wheel 74 is turned a quarter turn by pin 70 and causes cams 76, 77 to rock plate 78 to put needle of pick-up 100 in starting groove on one side of record, switch 64 is closed by cam 62 to start motor to play this first side of record, and member 111 is lifted off the edge of the record as the crank-shaft 123 completes its half revolution. At end of first side of record, tone-arm causes switch 211, 212 to close, again starting motor 50 to drive toothed wheel 55 for a quarter of a revolution, when a second flat 61a on cam 61 again allows switch 60 to open, which switch had maintained circuit of motor 50 closed after the re-opening of switch 211, 212. During this quarter turn of toothed wheel 55, star wheel 74 is turned a quarter turn by pin 71 causing cams 76, 77 to return plate 78 to central position to remove needle from record, then the tone arm is lifted beyond the record and lowered back to the level of the starting groove by a full rotation of crank-shaft 123 by teeth 121, next star wheel 74 is turned another quarter turn by pin 72 causing the cams 76, 77 to rock plate 78 to bring needle of pick-up 101 in starting groove in second side of record, and switch 65 is closed by cam 63 to start motor in reverse direction to play the second side of the record. At the end of second side of record, tone-arm again causes switch 211, 212 to close, again starting motor 50 to drive toothed wheel 55 another quarter turn, during which star wheel 74 is rotated a final quarter turn, causing cams 76, 77 to return plate 78 to central position to remove needle from record. All parts resume the position shown in Fig. 5, and the sequence of operations is repeated, i.e. the played record is discharged, and a fresh one fed into position and played on both sides. If, however, the record last played is the last one and the magazine is empty and the switch 81 therefore open, then the operation of the machine ceases when the position, Fig. 5, is reached, because an extra lobe 69 on the cam 63 then opens contact 66 in shunt with switch 81 and the electric supply is cut off.