Patent GB-683904-A (GB)
Title: Improvements in or relating to drive and control arrangements for magnetic record transducing apparatus
IPC: G11B5/56
Filed: 1950-03-06
Abstract: 683,904. Magnetic recording and reproducing apparatus. BRUSH DEVELOPMENT CO. March 6, 1950 [April 23, 1949], No. 5594/50 Class 40 (ii). In a magnetic record transducing apparatus in which an elongated record is driven forward and backwards on reels having means and limit means as in Specification 653,649, setting means are provided which are selectably movable to different positions to effect forward or rewinding operations, and which are interconnected with the limit means whereby an opposite record reeling opera- .tion is carried out in a predetermined sequence. The operation of the mechanism is diagrammatically illustrated in Fig. 1. The drive of the reels 31 and 32 is effected by means of a bar 2-11 under the control of a bar 2-21 pivoted at 2-22. A bar 2-36, also connected to the bar 2-21, operates a tilting delay-action mercury switch 2-34 in circuit with the motor 60. Fig. 1 shows the bar 2-11 in the neutral position. A bar 2-70, biased towards its operative position by a spring 2-74. as shown in Fig. 1, holds the erazing head 19, on a tilting plate 89, out of contact with the magnetic record 20 by means of the tongue 2-27. When the bar 2-70 is moved to the operative (right-hand) position, the erazing head is similarly held in the inoperative position by a tongue 2-73 unless the plate 89 is tilted by finger pressure on a rod 93 while the bar 2-70 is moved. When the bar 2-70 is returned to the inoperative position, the erazing head 19 is always brought to the inoperative position, even if previously in the operative position, owing to the sloping surface 2-77 of the tongue 2-72. Movement of the bar 2-70 to the operative position also moves backing member 76 and pressure wheel 81 against the transducer 18 and driving capstan 67, respectively. The tilting of the plate 89 also serves to operate the change-over switch 21 for connecting the transducer 18 to the output side of the amplifier when recording (and at the same time erazing), and to the input side when reproducing (i.e. when not erazing). When the control rod 3-10, surmounted by the control knob 3-11, is moved from the neutral position shown to position 3-10-17 for slow-forward reeling, as when recording or reproducing, the bar 2-70 is moved to the right, to function as described and a tongue 3-34 thereon moves out of the way of a forward projection 3-28 of a locking frame 3-25, so that the said projection 3-28 may pass through the aperture 3-31 of the bar 2-21 which is then moved to the right, about the pivotal point 2-22, whereby forward reeling commences. At the same time, a bar 3-45 is moved endwise to rotate a cam-disc 2-61 which cocks the trip levers 2-42, 2-53 to the positions shown. An upward tongue 3-29, shown dotted at 3-29-A, on the frame 3-25 is pressed against the bar 2-41 by the tension of spring 2-74 and thereby holds the bar 2-21 in the right-hand position after the control rod 3-10 has been returned to the neutral position. The bar 2-70 is also held in the right-hand position by the engagement of the tongue 3-34 of the bar 2-70 with the projection 3-28 of the frame 3-25. When reel 31 is nearly empty a limit member 51, as described in the above Specification, engages the end 2-48 of a trip member which is moved counterclockwise so that its end 2-44 is moved along a sloping surface 2-50 on the lever 2-42 which is rotated a small amount clockwise about point 2-43 under the influence of spring 2-47. The endwise movement of the bar 2-41 causes the tongue 3-29 to slip from its end, so that the bars 2-11 and 2-70 are moved to the extreme left-hand positions under the influence of spring 2-74. Owing to the withdrawal of the backing members 76, 81, a fast rewinding operation is thereby automatically initiated, and continues until the limit member 55 trips the lever 2-53, and a bar 2-51 under the influence of a spring 2-57 pushes the tongue 3-29 on the frame 3-25 so that the projection 3-28 is moved out of the aperture 3-31 of the bar 2-21, and the tongue 3-34 on bar 2-70 takes up the position relative to the frame as indicated by the dotted position 3-34-A. The bar 2-21 thus takes up the neutral position indicated in Fig. 1, under the influence of a centreing spring 2-31, whereby rotation of the reels ceases. The trip levers 2-42, 2-51 may be cocked prior to a fast-forward or a fast rewinding operation, when it is required to effect automatic stopping by moving the control rod forwardly so that the bar 3-45 rotates the cam-disc 2-61. The control rod 3-10 is then withdrawn and moved to either the fast-forward position 3-10-18 or the fast rewind position 3-10-19 in which position the rod is locked by levers 2-37 or 3-38, respectively, until released after a tripping operation by bar 3-47 or bar 3-48, respectively. Specifications 642,136 and 664,994 also are referred to.