Patent GB-690196-A (GB)
Title: Improvements in or relating to portable magnetic recording and/or reproducing devices
IPC: G11B5/00
Filed: 1950-11-29
Abstract: 690,196. Magnetic recording and reproducing apparatus. McNABB, L. A. Nov. 29, 1950 [Dec. 7, 1949], No. 29214/50. Class 40 (ii). A pocket size portable magnetic recording and reproducing apparatus has a self-contained power supply in the form of dry batteries for driving the magnetic medium past the transducer and operating the recording and reproducing means. The apparatus is housed in a container 30 having a control panel 41, an indicator 47 for showing the amount of wire medium passed from one reel to the other, low-tension battery compartment 38 and high-tension battery compartment 37, both rendered accessible by flap 39, and a compartment 29 for a detachable cassette 35, Fig. 6, containing the reels 62, 63 and level winding device 150, said cassette being rendered accessible by flap 40. The reels are driven by a motor 49 which is pivotally supported at points 51, defining a line passing through its centre of gravity, by bearings 61 in a fixed yoke 50. A countershaft 55, carrying friction pulleys 58, 59, is mounted in a frame 96 pivoted at its centre of gravity at points 56 in bearings 60 in the yoke 50. The motor 49 is mounted on an arm 84 and the frame 96 on an arm 85, both arms being movable by resilient members 82, 83, respectively on a control bar 75a operated by knob 43. During forward winding, i.e., for recording or listening, the control bar 75a is moved by the cam 78 to the left, as viewed in Figs. 3 and 5, so that wheel 59 is pressed against the pulley 64 on the motor shaft 65, and pulley 58 is pressed against rim 67, Fig. 7, of take-up reel 63, and wire is thereby drawn from reel 62 past transducer 135 on to reel 63. During rewinding, the control bar 75a is moved to the right so that pulley 59 is pressed against the plain part 66 of reel 62 by the pulley 64 on the motor shaft 65, so that wire is drawn at high speed from reel 63 to reel 62. The cassette 35 containing the reels 62, 63 also incorporates the level winding device 150 which is made to traverse to and fro on a shaft 137 during movement of wire from one reel to the other by means of an endless helical track in the shaft 137, which is rotated by means of a train of pinions 113, 139, 140, 141 driven by reel 62. The magnetic transducer 135 has a V-shaped groove in the polepieces to guide the wire across the non-magnetic gap and is slidably mounted on fixed rods 143, 144 in the container 30. The transducer 135 is provided with an extension 162 which snugly engages a slot in the level winding device 150 so that the transducer. traverses therewith. A braking device is provided which immediately locks the reels 62, 63 when the bar 75a is moved to its "off" position, i.e. the intermediate position. This comprises a rod 68, Fig. 5, whose rotary position in the cassette is controlled by a lever 72 in the container 30 which engages a tongue at the end of the rod 68 and carries a roller 73 which is pressed against bar 75a by a spring 200. In the "off" position the roller rests in notch 279 in the bar 75a, and brake shoes 69 are pressed against the rims of the reels 62, 63 by springs 253 acting on rod 70. When the bar 75a is moved left to the "record" or "listen" position or right to the "rewind" position the lever 72 is rotated clockwise and the brake shoes 69 are lifted from the rims of the spools by the rod 70 and member 252 which has a large clearance hole about the rod 70. A further train of pinions 141, 188, 190, between the shaft 137 and worm shaft 185 rotates an indicator disc 169, Fig. 21, which indicates the amount of wire which has been removed. from one reel to the other. The disc 169 is supported on a boss 174 carrying a notched disc 183, which, after performing one complete revolution, corresponding to almost the entire amount of wire on one reel, receives in its notch 206 the tongue 205 of a spring-loaded lever 204 carrying a pin 212 serving to unlatch a spring leaf member 211 which normally couples the control bar 75a to a spring-loaded cam follower bar 75b. The bar 75a thus moves to its "off" position owing to the pressure of roller 73. A resetting knob 208 enables the bar 75a and cam follower 75b to be relatched and the tongue 205 to be withdrawn. A spring-loaded member 201 serves to cover the notch 206 and prevent the tongue 205 re-engaging until the disc 183 has performed another complete revolution. The knob 43 also serves to complete the switching of current to the valves 219, 220, 221, Fig. 4 (not shown) of the amplifier. Movement of the bar 75a from its intermediate or "off" position serves to close the contacts 301 of the switch controlling the motor 49.