| 摘要 |
1,148,232. Tape dispensers. MINNESOTA MINING & MFG. CO. 22 April, 1966 [23 April, 1965 (2)], No. 17806/66. Heading A4G. A tape dispenser has pushes 14, Fig. 1, dispensing measured tape lengths according to indications on an adjustable range of lengths indicator 190, pushes 16 giving lengths determined by dials 22 and a random length push 18. The pushes, indicator and dials set a resistance matrix in device 30, Fig. 3, whereby a pre-charge is placed via a linear current generator 294 on condenser 280 (Fig. 6A, not shown) in a control circuit 32 and, via transistorised circuitry, pulses a flip-flop 38 into an unstable condition and, via a load circuit containing a rectifier transistor which becomes conductive (490, Fig. 6B, not shown) allows an A.C. source 144 to energize solenoid 92 which depresses lever 56 about pivot 64 so that pressure roll 70 presses the tape 50 on to drive roll 80, cutter 72 is raised and a micro-switch 106 operated allowing A.C. source 118 to drive motor 112 which rotates drive roll 80, and also a light chopper 122 in a housing 126 containing a light source, an encapsulated photosensitive transistor and amplifier 130 whereby fixed amplitude but variable duration pulses are sent to pulse shaper 36 producing fixed duration pulses as a measure of the length of tape dispensed. The push determined number of pulses are fed into the control 32 and build up the pre-charge on condenser 280 to a predetermined level at which a unijunction transistor (324, Fig. 6A) conducts, a charge resets the flip-flops 38 and makes transistor (490) non-conductive whereby solenoid 92 is de-energized, lever 56 rises to stop the motor 112 and tape feed at 70, 80 and lowers cutter 72 on to the tape. |
