Patent GB-712536-A (GB)
Title: Improvements in or relating to magnetic transducing apparatus
Inventor: PAYNE EDWIN MALCOLM
IPC: G11B15/18
Filed: 1951-10-24
Abstract: 712,536. Magnetic reproducing apparatus. ELECTRIC & MUSICAL INDUSTRIES, Ltd. Oct. 20, 1952 [Oct. 24, 1951], No. 24799/51. Class 40 (2). In a magnetic reproducing apparatus of the kind employing a removable magazine 2 containing spools carrying a magnetic tape or similar medium 36, a magnetic head is movable from an inoperative position outside the magazine, through an aperture 32 therein, into contact with the said medium. The apparatus, which is intended particularly for the use of the blind as a talking-book machine, is described with reference to a medium in the form of a wide magnetic tape containing a multiplicity of parallel tracks recorded in alternate directions, means being provided to give audible warning at the end of each track, so that the operator may switch off the machine or reset the transducer to reproduce the next parallel track. In operation, the magazine 2, with the shutter 31 withdrawn on to location pins 35 on plate 1 of the apparatus. The bottom of the magazine 2, comes into contact with a pin 22, Fig. 2, on a spring-loaded hinged arm 18 which is thereby moved out of the path of a limb of a lever 12 which is movable by a control knob 5 and designed to move the transducer head unit 3 towards, and away from, the record tape 36. As the magazine is lowered into position, a sloping post 61 engages a hole in a sliding plate 51 having angular slots 53a, 54 which engage pins 55, 56 on spring leaf members 57, 58 which are thereby withdrawn from contact with flanges 49 on spools 37, 38 to permit the spools to rotate freely. When the magazine 2 is seated in position, prongs 47 on driving shafts 43, 44 engage holes 42a in the flanges 49. The clockwise rotation of knob 5 moves lever 12 about pin 13 by means of a pin and slot connection 11, 14 to the postion shown dotted in Fig. 1, whereby one arm 27 of the lever 12 closes a master switch 27a, while the end 16 engages a pin 17 on the transducer head unit 3, and moves it towards' the magazine 2. The transducer 134 is thus pressed against the tape 36, and a pressure roller 88 on an arm 86 presses the tape 36 against a capstan 74 so that it is driven past the transducer 134. At the same time a pin 83, Fig. 6, on the transducer head unit 3 moves a bar 81 so that a pin 79 thereon moves a plate 75 in the magazine 2 and, by means of pins 77 and sector plates 65, 66, draws tape guides 63, 64 thereon in a direction away from resilient felt-padded arms 71, 72 towards guide members 73. The arms 71, 72 then serve to hold the tape 36 against posts 90 mounted on plate 1 and having mutually insulated electrical contact portions for detecting the presence of a conductive coating 89 at each end of the tape 36. The transducer 134 is initially set, under the control of a knob 7 and leadscrew 138, Figs. 9 and 10, to its lowest position. At each half turn of the leadscrew the transducer is raised by an amount corresponding to one track of the tape 36, and a cam 146 moves a slide bar 113 in an opposite direction. The movement of the slide bar 113 moves a lever 115, Fig. 7, and operates a change-over switch 127 and to make the appropriate connections to a reversible-split-phase induction motor 176 which is coupled to a flywheel 92, Fig. 8, through one or other of jockey pulleys 94, 95, according to the direction of rotation. The shaft 93, Fig. 7, carrying the flywheel 92 has an enlarged end 74 which forms the driving capstan shown in Fig. 4. Movement of the lever 115 also serves to move a spring-loaded lever 117 past a dead centre and transfer a moveable jockey pulley 98 permanently coupled by pulley 97 to shaft 93, from one to the other of discs 99, 100 having friction slip couplings 101 to shafts 43, 44, the particular shaft being driven depending on which of the shafts 43, 44 corresponds at the moment to the take-up spool. The spring- loading 119 of the lever 117 is only tensed when the transducer head unit 3 is moved to the engaged position, and this tensing is effected when a pin 122 on the unit 3 engages one end of a lever 120, Fig. 7, which is pivoted on a stub shaft 121 and coupled to one end of lever 117. When the tape 36 has been nearly fully wound from one reel to the other one of the conductive coatings 89 short-circuits the contacts on one of the posts 90 and de-energises a relay 183 whereupon the motor 176 stops and the grid of valve 166 is connected to an audio oscillator 189 whereby an audible note is produced at the loud-speaker 167. The operator then either switches the apparatus off or rotates the knob 7 through 180 degrees until the audible note ceases, whereupon the motor is set to run in the opposite direction and the relay 153 re-energised. The shaft 138a of the leadscrew 138 carries earthed contact surfaces 149 having gaps 150 whereby the relay 183 is de-energised resulting in the continued emission of the audible note and the motor switched off until the knob 7 has been exactly set 180 degrees from the previous setting. Accurate adjustment of the position of the transducer 134 transversely of the tape 36 is effected by means of adjusting knob.8, Fig. 9.