Patent GB-806829-A (GB)
Title: Improvements relating to recording and reproducing apparatus
IPC: G11B5/52
Filed: 1957-06-06
Abstract: 806,829. Magnetic recording and reproducing apparatus. SOUNDSCRIBER CORPORATION. June 6, 1957 [Jan. 31, 1957], No. 18005/57. Class 40 (2). Recording-reproducing apparatus wherein a plurality of transducer heads 93 (Fig. 18), spaced round the periphery of a rotating drum 19 ((see also Fig. 12), move along a succession of transverse tracks on a magnetic tape T (Fig. 2) longitudinally fed past the drum in timed relation to its rotation, has adjusting means to vary momentarily the relative speed of the tape feed and the drum during reproduction, so as to align the heads accurately with the tracks. The adjusting means may be (a) coarse, comprising a roller 78 (Figs. 3 and 9) spring-pressed into an opening in an annular wall 75 on a pulley 74 secured to the shaft 17 of the tape capstan 16, the roller 78 being movable, by manipulation of a knob 89, over the teeth of a gear 76 driven from a shaft 44, Fig. 12 (coupled to the shaft 28 of the drum 19) by a train 65, 66, 67, 71, 82 (Figs. 2 and 3); and (b) fine, comprising a movable mounting 80 for the idler gear 82, which is adjustable about the shaft 17 by an eccentric pin 83 (Fig. 3) engaging its bifurcated end 86, the pin 83 being set by a hand knob (not shown). General operation.-The tape T passes from reel 11 to reel 12 over fixed guide spindles 15, 23 between which it is constrained to an arcuate section by passage between fixed guide-rings 130, 131 (Fig. 12) and retractable semicircular guides 120, 121 carried by a curved shield 118 hinged on a member 22a (see also Fig. 2) itself hinged to the chassis plate 10; two quartercylindrical pressure shoes, one of which is shown at 123 in Fig. 12, are resiliently mounted within the shield 118 to press the tape on to the rotating heads 93, their adjacent edges being so shaped that the part of the longitudinal gap between them forward of the heads is out of line with that beyond the heads; the shoes are recessed at 126 in register with the heads. Fixed hooks 127, 128 (Figs. 2 and 9) locate the tape when the shoes are retracted. As the shaft from an electric motor 55 (Fig. 2) to the worm 48 (Fig. 12) is inclined, its front mounting includes a thrust ball seated in a cap 53 (Fig. 9); the shaft 44 driven thereby is coupled to the shaft 28 by a flexible coupling 43 which prevents flutter of the drum 19, assisted by a flywheel 32 (Fig. 2) shielded from the tape T by a projection 33. A pressure roller 18 (Fig. 12) coacting with the capstan 16 is mounted on a lever 157 spring- loaded at 161 clockwise about its pivot 145, and is retracted by a cam 159 acting on a roller 158; the shield 118 is urged towards the drum 19 by a spring 140 (Figs. 2 and 12) assisted by the spring 150 of its operating lever 144, also pivoted at 145 and retracted by a cam 153 acting on a roller 152; the cams 153, 159 are fixed to a common shaft 147 controlled by a knob 165, and they have end recesses 155, 156 and 163, 164 respectively defining the retracted and operative positions of the shield 118 and pressure roller 18. The top half of the drum 19 is magnetically screened by the movable shield 118, and its lower half by a fixed horizontal screen 115 (Fig. 12) and vertical screens against the chassis plate 10 and at 116 (Fig. 9) having forward and rearward shelves at their tops which terminate adjacent the edges of the shield 118; rotation of the drum 19 urges the tape T against the shelf at the top of part 116, and the corresponding ends of guides 120, 121 enter openings therein to hold the tape in place. An annular projection 97 on the cast brass drum 19 (Figs. 12 and 18) continues the line of the polepieces 96 of the transducer heads 93 mounted in a diagonal groove 92 in the casting; the heads are connected in series between terminal studs 98 which support an insulating disc (not shown) carrying slip-rings coacting with brushes 106, 107 (Fig. 12) to connect the heads to a record-playback amplifier mounted on plates 59, 60 (Fig. 2).