Patent GB-670246-A (GB)
Title: Sound recording and reproducing apparatus
IPC: H02N13/00
Filed: 1948-08-03
Abstract: 670,246. Electromagnetic recording apparatus. DICTAPHONE CORPORATION. Aug. 3, 1948. [Aug. 7, 1947] No. 20499/48. Class 40 (ii). [Also in Group XXIV] A sound recording and reproducing apparatus utilising a thin, foldable, record sheet, comprises an endless path record supporting structure, and coupling elements, at least one of which is non-clamping, for coupling the record sheet to the structure to permit smooth disposition in spite of small dimensional changes in the record sheet, and means for maintaining the record sheet in a smoothly spread condition during recording and reproducing. General. Figure 1 shows the general view of a dictating machine utilising records consisting of rectangular sheets of paper or plastic material having a magnetic coating such as that described in Specification 670,300. The record sheets are placed on shelf 18 and pressure of plunger 14 starts an automatic drive which winds the record sheet on drum 24. A carriage 26 carries the electromagnetic recording and reproducing head, and a control lever 32, which has a central "neutral" . position and is raised for "reproducing" and lowered for "recording". In the "neutral" position of lever 32, carriage 26 may be moved horizontally along rods 30, and movement of this carriage to the extreme left position operates an automatic record ejecting arrangement, in which drum 24 revolves in the reverse direction to eject the sheet record through slot 20. A correction and "progress of recording" indicator mechanism 34, with its associated pad 38, "correction" lever 44 and "length of letter" lever 46 may be provided. The arrangement includes a hand microphone with associated hook switch and press button control, or a desk microphone and foot operated switch mechanism. Knob 47 provides a phasing control to ensure correspondence between the reproducer head and the record track. A signal light 12 operates in correspondence with a main power control switch 10. Driving mechanism and electric control. The driving mechanism comprises a motor 50 (Fig. 2) driving a pulley 60 which is coupled by a reversible clutch mechanism to pulley 78 fixed to drum 24. Pulley 78 is also coupled through gearing to feed screw 25 which provides the transverse drive for carriage 26 bearing the transducer head, for recording purposes. Carriage 26 is coupled to feedscrew 25 by a feed-nut, the engagement of which is under the control of lever 32. Fig. 6 (not shown) shows the reversible clutch mechanism coupling pulleys 60 and 78. When forward solenoid 90 is energized, lever 96 is rotated so that friction wheel 104 establishes contact between the hub of pulley 60 and the edge of pulley 78. When reverse solenoid 106 is energized, lever 112 is rotated so that two friction wheels 116, 118 establish contact between pulleys 60 and 78 to drive 78 in the reverse direction. If neither solenoid is energized, both clutch levers are held disengaged by spring 121, so that pulley 78 is not driven. Figure 26 shows the electrical circuit used to control the driving means in response to switch operations as described later. The operation of power switch 10 energizes amplifier 51 and signal lamp 12. For the "record loading" operation, carriage 26 is at the extreme left position so that switch 280 is operated by cam 276, and microphone hook switch 49 is also operated. When loading plunger 14 is pressed, switch 442 disconnects the clutch reverse solenoid 106 and connects forward solenoid 90, and switch 380 energizes the motor 50 and solenoid 90. After two revolutions of drum 24 for winding on the record, switches 442 and 380 release. For recording, 'carriage 26 is moved slightly to the right to release switch 280, and the microphone is held to release switch 49 which operates the motor, and recording proceeds under the control of microphone press button switch 452 which is in series with forward solenoid 90, 10 control the drive to drum 24. At the end of the recording, the microphone is replaced to operate switch 49, and carriage 26 is moved to the extreme left position to operate switch 280 and 380 which energizes the reverse drive solenoid 106 to eject the record. After two revolutions of drum 24, switch 380 releases to de-energize motor 50 and reverse solenoid 106. If, during recording, carriage 26 reaches the extreme right position, limit switch 446 operates, which breaks the circuit to forward solenoid 90 stopping the drive to drum 24. Record ejection. On completion of a record, le.ver 32 is set to "neutral", and carriage 26 moved manually to the extreme left position. Movement of lever 32 which is keyed to shaft 30 (Figs. 2 and 8), controls a sliding plate 184, Fig. 9 (not shown) on carriage 26 having cams which engage levers associated with feedout 120 and transducer head 122 so that these elements are withdrawn from feedscrew 25 and the record sheet respectively, when lever 32 is in the "neutral position". When carriage 26 reaches the extreme left position, (i) cam follower 272 on carriage 26 engages spiral cam 270 (Fig. 2) to rotate shaft 260 so that fingers 264 (Fig. 8) descend to cover the transducer slot 255 (to prevent the record sheet from being ejected through this slot) and cam 276, Fig. 18 (not shown), on shaft 260 operates switch 280 ; (ii) cam 282, Fig. 18 (not shown), on carriage 26 lifts plate 288, so that later, plate 296 may be rotated in response to pressure of plunger 14 ; (iii) cam 300 (Figs. 8, 21) on carriage 26 depresses lever 308 so that later spring biassed lever 318 may move into recess 326 in drum 24 to lock drum 24 in the index position : (iv) the upper surface of cam 331 (Fig. 21) on carriage 26 rotates lever 340 about 342 until the end of lever 340 drops off cam 331 causing pawl 348, Fig. 20 (not shown), to rotate a ratchet 354 and its associated cams 368, 370 (Fig. 21), for 60 degrees. Cam 368 forces down lever 318 to release drum 24 and cam 370 operates switch 380 to energize the reverse drive, and also rotates lever 414 to move one end 412 out of recess 415 (Fig. 19) to allow rotation of plate 398 and the other end 418 engages lever '425 to prevent operation of plunger 14. Drum 24 now rotates and a pin 394 on pulley 78 engages plate 398 so that pawl 406 rotates ratchet 354 and cams 368, 370 60 degrees for each revolution of drum 24. After two revolutions, which follow the initial 60 degrees rotation, cams 368, 370 are displaced 180 degrees so that switch 380 releases and lever 318 enters recess 326 (Fig. 88 to lock drum 24, and spring biassed lever 414 rotates so that 412 engages the recess 415 to hold plate 398 in the lower position. During the rotation, the record sheet has been ejected through slot 20. Record loading. A record sheet is placed through slot 20 (Figs. 1 and 8) to engage the first of three rectangular teeth 22 on drum 24 and loading plunger 14 is then pressed. This causes plate 296, Fig. 18 (not shown) to rotate and depress end 423 of lever 424 so that a projection 438 operates switch 442. End 425 of lever 424 (Fig. 21 ) rotates lever 340 to cause pawl 348, Fig. 20 (not shown) to advance ratchet 354 and cams 368, 370 by 60 degrees. As before, this causes lever 318 to disengage from drum 24, and 412 to move out of recess 415 (Fig. 19) to allow movement of plate 398. End 418 of lever 414 moves under end 425 of lever 424 to hold switch 442 operated. End 423 of lever 424 engages plate 296 (Fig. 18 not shown) to prevent further operation of plunger 14 after the loading cycle has been initiated. Cam 370 closes switch 380 to energize the drive for drum 24 and after two revolutions when cams 368, 370 have rotated 180 degrees, 318 moves up to lock drum 24, 412 latches plate 398, 418 withdraws to -release lever 414 and .thus releases switch 442, and switch 380 releases to stop rotation of drum 24. Record sheet 2 (Fig. 8) has been wound on drum 24 during the two revolutions. Recording. To set the machine for recording, carriage 26 is moved slightly to the right and lever 32 is raised to the "recording" , position thereby connecting carriage 26 to the feedscrew drive 25 and positioning the transducer head 122 near the record sheet. The movement of carriage 26 away from the extreme left position (i) withdraws cam 282, Fig. 18 (not shown) from plate latch 288 so that further operation of plunger 14 is prevented ; (ii) withdraws cam 300 (Figs. 8, 21) from the end of lever 308 causing lever 318 to be depressed to release drum 24; (iii) withdraws cam follower 272 (Figs. 2 and 8) from spiral cam 270 to allow shaft 260 to rotate and move fingers 264 away from slot 255 and cam 276, Fig. 18 (not shown) to release switch 280. Lifting the microphone releases hook switch 49 which energizes motor 50, and recording proceeds with the drum drive and feed mechanism under the control. of microphone button switch 452. Limit switch 446 (Fig. 2) is operated by a screw 448 on carriage 26 when the carriage reaches the extreme right position and the operation of this switch may be associated with an audible alarm. Reproducing. Reproducing, or listening back during the recording can be effected by placing lever 32 in the "neutral" position and sliding back carriage 26 to the required point and then placing lever 32 in the "reproduce" position. The microphone is then used as a loudspeaker, appropriate changes in amplifier 51 being effected by means of a switch lever 198 (Fig. 2) which is moved by the rotation of shaft 30 when lever 32 is operated, reference being made to Specification 502,423. Details. Figs. 9, 10, 11 (not shown) give details of the carriage assembly including feednut 120 and the mounting of the transducer head 122 on pivots 144. Figure 14 shows a section of the transducer head in which flat pole pieces 208, 210 consisting of magnetic material and shaped like hockey sticks are located in coils 204, 206. U-shaped pieces 212 of magnetic material complete the magnetic circuit, and an arcuated sheet of non-magnetic material 214 is provided to secure