Patent GB-850291-A (GB)
Title: Improvements in or relating to apparatus for magnetically recording sound and for reproducing magnetically recorded sound
IPC: G11B25/04
Filed: 1957-01-24
Abstract: 850,291. Magnetic recording and reproducing apparatus. TOKYO DENKI KAGAKU KOGYO KABUSHIKI KAISHA. Jan. 24, 1957 [Jan. 25, 1956; Jan. 28, 1956; Feb. 14, 1956; Feb. 25, 1956 (2): March 2, 1956 (2)], No. 2671/57. Class 40 (2). A magnetic sound recording and reading apparatus has a plurality of heads mounted on a turn-table for scanning transversely a magnetic coating on a rectangular sheet, e.g. of writing paper, spread against a plate, the turntable being mounted for rotation on a table which during scanning traverses the apparatus linearly and an arcuate guide being provided for the scanning heads whereby only one head is in scanning contact with the coating at any given time and as one head leaves the film the next head moves into contact. The sheet 4, Figs. 2, 5, 7, having a magnetic coating 5 on one surface and visual information on the other as in Specification 833,266 is placed as in Specfications 794,788 and 796,251 over locating pins 12 in a frame 11 of the recording apparatus, where it is secured by hinged plates 45, 16 before the pressure plate 6 is lowered into position... The plate 16, which is spring-hinged, is locked in the holding position by a pivoted latch 23. Plate 15 may be similarly locked and the latches may be interconnected for simultaneous release. Openings 14 in the plate 6 engage the pins 12 above similar openings in the plates 15 16. Beneath the frame is a disc supporting equispaced recording or reproducing heads a, b, c, the transverse position of the disc being indicated on a scale 41, Figs. 8 and 9, by a pointer 39 carried by an endless band 36, which is connected to the mounting of the disc so that as a screw-shaft 33 is rotated the pointer travels along the scale. A motor 30 rotates the disc 1 through reduction gearing 31 and a friction wheel 32, while the disc support 27 is guided linearly by rollers 28 engaged with rods 29. By operating a key 35 the mounting member 34 can be disengaged from the shaft 33 and the turn-table 1 moved manually to prepare the apparatus for operation. Pointer 39 may be replaced by an electric lamp 44 as in Fig. 11. Switches which control a lamp to indicate the beginning and ending of recording may be arranged as in Fig. 12, where the carriage 56 of disc 1 has a projecting arm 57 to operate switches 47, 48 and 49. The shaft 33 is driven by a motor 63 through mechanism 58 and the switches are adjustably mounted on a guide rod 46 so that the range of scanning can be controlled. In Fig. 11, the rotatable heads are supported by a table 105 carried by the shaft 33, the table being halted at the right-hand side when an abutment 60 presses switch 49. As the table reaches the left-hand side, an abutment 47<SP>11</SP> operates switch 47<SP>1</SP> to give a warning signal and on further movement, abutment 4811 operates switch 48<SP>1</SP> to stop the drive. In normal rotation of the shaft 33, the drive from motor 63 is established through bevel gears 69, 70. Rapid forward and return drive is made by engaging a pulley 73 with the shaft 33, the pulley 73 being driven by a belt 72 from the motor 63. A clutch 51<SP>1</SP> keys the pulley 73 to shaft 33 when an electromagnet 74 is energised and at the same time gears 69, 70 disengage. Adjustment.-To return the heads a, b, c to the starting position, a motor 75, Figs. 11 and 13, is used to drive a friction roller 82 carried by a sleeve 81, whose position on the shaft 76 is controlled by a governor 78, 79. When the motor is idle, the roller 82 is above the friction surface 83. On starting the motor, the governor pulls the roller downwards and the roller rotates the turn-table until it enters a groove 84 and on stopping the motor, the roller rises once more above the surface 83. To adjust the sheet M to allow for elongation or shrinkage due to himidity and temperature changes, the panel 11 has guide grooves 85 into which slides a frame 87 receiving a frame 26, Fig. 17, containing the sheet M and the plate 6. Fixed to the frame 87 are racks 88 meshing with pinions 90 on a shaft 89 having an adjustment knob 91 at one end by means of which the sheet may be shifted to bring exact coincidence between the tracks of the heads a, b, c and the record tracks 7. Similar mechanism may be used to adjust the sheet M in its plane at right angles to the first adjustment. In Fig. 11, the whole panel 11 is adjusted by knob 91. Control of scanning heads.-To prevent heads b, c operating while head a is acting, the heads are mounted in metal housings 101, Fig. 21, at the free ends of leaf springs 100 carried by the table 1 around the circumference of which is a arcuate guide 103 having cam end portions. Guide 103 is fixed to the table 105, Fig. 11, so that as the turn-table 1 rotates projections 102 on the idle heads b, c engage the guide 103 and hold the heads b, c away from the coating 5. As head a leaves the film, head b is released by the cam surface of guide 103. To keep all the heads inoperative during return of the carriage, an arcuate member 106 is placed in the gap between the ends of the guide 103. This member 106 is attached to the armature of an electromagnet 107 and engages projections 102 of head a, so that when the magnet 107 is energised the head a is pulled away from the coating 5. A similar arrangement may be used with a demagnetising head. Demagnetising heads a<SP>1</SP>, b<SP>1</SP>, c<SP>1</SP> may be arranged in front of the scanning heads a, b, c. The recording heads are mounted to allow some play in a vertical direction, Fig. 22, by housing the head 128, 130 in a box 129 which is supported by balls 133, 133<SP>1</SP> in posts 131 and by an adjustable spring 138. The table 105 may be shifted by means of a screw 147, Fig. 11, and a control panel 150 may connect with sound amplifiers. The casing 93 may contain a microphone 151 and a loudspeaker 153 together with pilot lamps 152. Specifications 654,584 and 758,026 are referred to.