Patent GB-553378-A (GB)
Title: Improvements in phonographs
IPC: G11B25/00
Filed: 1941-11-21
Abstract: 553,378. Phonographs. DICTAPHONE CORPORATION. Nov. 21, 1941, No. 15008. Convention date, Nov. 23, 1940. [Class 40 (ii)] [Also in Groups XXIV, XXXVII and XXXIX] Relates to sound recording and reproducing apparatus in which the recording base is in the form of an endless belt stretched between two cylinders and consists mainly in operatively interconnecting the means for adjusting the distance between the cylinders with the control means for driving the cylinders. External arrangements. The machine parts including an electronic amplifier are enclosed in a casing 12, Fig. 8, having a slot 45a all round a part 45 of the right hand side 13 for the insertion and removal of a record belt. The front has a sloping upper part with a recess for a handle 114 which controls the insertion and ejection of the record belt, and a vertical lower part at which are disposed the handle 181 of the stylus head carriage, the knob 319 for conditioning the machine for recording or reproducing, and a signal lamp 450. The transducer combination 393 is connected by a cable 394 to a socket on'the left side of the casing where there is also a main switch. At the back, a cable connects to a wall-plug. Film recorddriving mechanism. A wide endless band 38, Fig. 6, extends over an upper driving cylinder 39 and a lower idle cylinder 40, and on its way from cylinder 40 to cylinder 39 passes over an anvil 100 opposite an electric stylus head 211. The shaft 41 of the cylinder 39 is driven through a clutch 54, 59, Fig. 9, by a grooved pulley 48 connected by a doublereeved belt 49 to a pulley 37, Fig. 3, driven through a reducing gear box 16 by an electric motor 15. The belt is kept taut by an idler pulley 50 on a spring-urged arm 51. The clutch member 59 is moved in and out of clutching engagement by means of a stem 57 keyed to the shaft 41 and to a sleeve 62 thereon by a cross-pin 63, said sleeve being movable by a bracket 64 rocked to one side or the other about a pivot 69 by the up stroke of a rod 75 or of a rod 76. The bracket is held in its set positions by a spring catch. The motor shaft 32, Fig. 3, carries a cooling fan 33 and is connected to the gear box 16 by a sleeve coupling. 35. The motor and the gear box are fastened together by bolts 17 and are resiliently mounted by brackets 18, 25 on studs 21, 27 fitted with springs 22, 28..;The shaft 77, Figs. 6 and 42, of the lower cylinder 40 is mounted in slots in vertical slides 79, 83 supported by pins 89 projecting from forks 87 on a shaft 86. The weight of the parts hanging from the forks 87 serves to keep the record belt 39 tight. The shaft 77 is adjustably clamped in the slots of the slides, 79, 83 by screws 80 in a vertical plane forming a slight angle with the vertical plane through the shaft 41 of the upper driving cylinder. This gives a small horizontal component to the grip of the driving cylinder on the record belt causing the belt to seat firmly against an inner flange 90 on the driving cylinder during operation Film inserting and removing. To permit the withdrawal of a record belt 38, Fig. 6, from its driving and tightening cylinders, 39, 40, Figs. 6 and 42, the grip is loosened by the lifting of the lower cylinder 40 by an arm 108 acting underneath one of the slides 79 carrying the cylinder. The arm 108, which is pivoted at 109, is connected by a link 111 to one end of a double armed lever 119, the other end of which bears on a cam 150 on a shaft 113 provided with a handle 114. When the handle is turned up, the cam 150 rocks the lever 119, thereby lifting the arm 108 and the cylinder 40. The record belt 38 is embraced by a double U-shaped frame 121, Figs. 6 and 7, comprising two sets of longitudinal bars 123, 125 and cross-bars 122, 124. This frame slides along grooves in a fixed support 43, 45, 46 between the two cylinders 39, 40. Pins 131 on the frame 121 are engaged by the forked ends of arms 137a pivoted on a spindle 140. One of these forks is also engaged by a pin 142, Fig. 2, on a double-armed lever 141 pivoted at 143 and forked at its other end 145 for engagement by a pin 149 on a lever 148 on the shaft 113 of the handle 114, Fig. 42. When the handle 114 is turned up, its first action is to lift the cylinder 40 to slacken the record belt 38 as explained above. After this, the pin 149 enters the fork 145 and rocks the lever 141 and the arms 137a to the dotted line position, thereby sliding the frame 121 outwards and exposing the edge of the record belt out of the side of the casing of the apparatus. In this position, springs 34 on the frame spring inwards, as shown by dotted lines in Fig. 7, and remove pins 135 from the mouth of the gaps between the bars 123, 125. The record belt can now be gripped by hand and pulled out, and a fresh one inserted. The handle 114 may then be turned down again when the operations are reversed. The record belt is first drawn in by the frame 121, the fingers 135 closing in to confine the belt in the frame. Then the cylinder 40 is allowed to drop and tension the belt. Stylus head carriage. This carriage 151, Figs. 1 and 6, is slidably mounted on a shaft 153 and guided by a parallel rod 156, and is provided with a slidable bar 171 formed with a segmental nut 170 urged by a spring to engage a feed screw 162, which is driven through worm gears 164, 168 by a pinion on the shaft 41 of the cylinder 39. The half nut 70 may be disengaged by the lifting of a hand lever 181 about a pivot on the carriage, a lug 183 on the lever engaging the bent end 184 of the nut bar 171. The carriage may then be traversed by hand. Automatic back-spacing means are also provided-see below. Magnet-controlled devices for clutching, declutching, and back spacing. These devices comprise three electromagnets 261, 300, 306, Figs. 2 and 4, controlling three cam mechanisms. Each of these devices comprises a bell-crank lever 270 adapted to be rocked up and down by each operation of the corresponding electromagnet. Thus when the magnet 261 is energized and attracts its armature 258, a bell-crank lever 262 carrying the armature strikes the hookshaped end of a link 260, thereby rocking a lever 266 counter clockwise on the pivot 267 of the bell-crank 270. This causes one of two toothed segments 283 to engage a toothed pinion 292 on a shaft 293 connected by a flexible belt coupling 294 to the shaft of the pulley 37 continuously driven by the motor 15, Fig. 3, when the motor is running. The toothed segments 283 are on a plate 282, which rotates about a pivot 281 on the bell-crank 270 and is shaped like a cam, so that the driving of the segment causes the bellcrank to move counter clockwise until the gap between the segments is reached when the bellcrank 270 moves back to its normal position and remains there until the magnet is again energized. If the magnet were maintained energized, successive rockings up and down of the bell-crank 270 would take place automatically ; this is used in back-spacing. The step by step movements of the segments is controlled by pins 289, 284 thereon co-operating respectively with a cam-shaped lever 287 pivoted at 288 on the bell-crank 270 and with the hooked lower end 286 of the lever 266. The bell-crank 270 of the cam mechanism controlled by the magnet 261 serves to lift and lower the rod 75, Fig. 9, by the raising of which the clutch, Fig. 9, is engaged. The corresponding bell-crank of the cam mechanism 301 controlled by the magnet 300 serves to lift and lower the rod 76 for disengaging the clutch. And the corresponding bell-crank of the cam mechanism 308 controlled by the magnet 306 serves to lift and lower a rod 310 to tilt a plate 311, Figs. 2 and 6, about a sprindle 312 to act on a power-operated backspacing mechanism. The plate 311 comes to rest against a rubber cushion 309. Back-spacing mechanism, power operated. This mechanism comprises a pawl 190, Fig. 20, pivoted at 191 on a lever 176 mounted on a pivot 178 on the carriage 151. When the projecting end 187 of the lever 176 is deflected by the tilting of the plate 311 described above, the lever 176 first engages a pin 199 on the feed-nut bar 171 thereby withdrawing the nut 170 from the feed screw 162. Then the pawl tip 197 is brought into engagement with the feed-screw 162, and by toggle action due to the pivots 191, 178 causes the carriage to be moved back the space of one thread of the feed screw. If the control magnet 306 described above is maintained energized, successive back-spacing steps occur automatically. If the carriage reaches its leftward limit while the magnet is still energized, each operation of the pawl causes the carriage to compress a rubber bumper ; but between each operation the bumper expands and annuls the last back-feed step of the pawl. Stylus-head mounting. The stylus-head 211, Fig. 11 is designed to act as a recorder or reproducer and is mounted on the carriage 151 by a mechanism which provides for the various adjustments of the device including means for positioning the stylus 210 on and off the record belt 38 and for giving the stylus-head heavier spring pressure during recording and lateral freedom during reproduction. The stylus-head 211 is attached to a plate 215 pivoted on a longitudinal spindle 217 on a cradle 218, Fig. 14, itself pivoted on a transverse spindle 220 on a trunnion 221 attached by a bracket 224 to the carriage 151. The pivot 217 allows movement of stylus to and from record belt 38. The pivot 220 allows lateral freedom to the stylus-head during reproduction ; but during recording, the cradle 218 is locked by a cam 233 when this is turned by an outward displacement of a rod 238 pivotally connected to the end of an arm 239 on the cam 233. During recording also, an additional spring pressure is applied to the stylus-head by a double-armed lever 243 pivoted at 246 and bearing under the projection 227 of the plate 215. When the rod 238 is moved inward to turn the cam 233 to release the cradle to give lateral freedom