| 摘要 |
890,918. Automatic loop control systems. CREED & CO. Ltd. April 24, 1959 [April 26, 1958], No. 14148/59. Class 38 (4). [Also in Group XVI] Apparatus for feeding tape through a writing and/or reading head which includes an electric motor driven tape driving means at the head, a tape feed roller on each side of the head, pressure rollers to press the tape on to each feed roller, a tape supply means, a tape take-up means, an electric motor coupled to each feed roller through a clutch to drive the tape faster than the head tape driving means, a tape loop sensing device on each side of the head, first switching means on each sensing device to switch on and off the respective electric motor coupled to its associated feed roller according to the length of the loop, and means for engaging the feed roller clutches when the head electric motor tape driving means is switched on and disengaging them when it is switched off. Tape 1 read by a head 3 is drawn from a drum 2 by a reed roller 12 co-operating with pressure rollers 13, the roller 12 being driven through an electromagnetic clutch 14 and pinion 15 by an electric motor 16. The motor 16 drives the drum in a clockwise direction through a slipping clutch, not shown, to tension the tape. The tape is fed past the head 3 by a sprocket-wheel 7 driven through gears 8, 9 and 10 by an electric motor 11, the teeth of wheel 7 engaging perforations in the tape. When the electric motor 11 is energized the clutch 14 is energized to couple the roller 12 to the motor 16. When the motor 11 is de-energized the tape feed roller 12 is uncoupled by deenergizing the clutch 14. The sprocket 7 feeds the tape at a slower speed than the rollers 12, thereby causing a loop 5 to increase in size whilst a loop 6 decreases in size, thereby actuating sensing levers 17. Each lever 17 actuates a switch 18 operating in the manner described with reference to Fig. 2 (not shown), to switch on and off the electric motor 16. During continuous tape feeding, the motor 16 is continuously switched on and off in accordance with the size of the loop 5. The clutch 14, Fig. 1, comprises a shaft 29, Fig. 3, carrying a ratchet-wheel 29 driven counterclockwise by the motor 16, Fig. 1, and a pawl 31, Fig. 3, for driving the feed roller. Two electromagnets 32 33 are provided to cause armatures 36, 37 mounted on pivots 38, 39 to be held clear of a lug 41 on the pawl 31 when they are energized, such that the clutch is engaged to drive roller 12, Fig. 1, when the motor 11 is running. Upon de-energization of electromagnets 32, 33, Fig. 3, a spring 40 pulls the armatures 36, 37 together to trip the pawl 31, while a switch 45 short circuits the switch 18, Fig. 1, to ensure that the motor 16 is kept running. When tape is fed intermittently the sensing lever 17 may operate in the manner described with reference to Fig. 4 (not shown) to avoid rapid switching on and off of the motor 16, Fig. 1. The sensing lever 17, Fig. 4 (not shown), actuates a switch 18 which controls the motor 16, Fig. 1, and a switch 43, Fig. 4 (not shown), which controls the energization of the electromagnets 32, 33, Fig. 3. In a modification, the motors 16, Fig. 1, and clutches 14 may be controlled by the control circuit described with reference to Fig. 5 (not shown). |
