GB532797A - Improvements in or relating to automatic paper feeding machines - Google Patents

Abstract

532,797. Photo-electric control of paper-feeding mechanism. THOMPSON, J. J. Feb. 8, 1939, No. 4172. Convention date, Nov. 15, 1938. [Class 40 (iii)] [Also in Group XXXV] Registration. An automatic paper feeding mechanism, associated for example with a paper cutting device, comprises a feed roll and a differential gear having all of its driving elements adapted to be operatively coupled to the feed roll drive to adjust the speed thereof and a control system comprising a photo-electric cell, a gas filled discharge tube to the control grid of which the cell is directly connected, and a relay energized upon activation of the cell to cause a temporary change in the speed of the feed roll, an oscillatable or reciprocable element permitting the speed adjusting operation of the differential gear only when interception of a light beam by indicia on the paper is out of register. As shown in Fig. 2 a motor 33 drives a rotary cutter 27, paper feed rolls 26, feed-speed adjusting means 35 and a pin 53. The paper has indicia 25 co-operating with photo-electric means 18 to lift periodically a latch 51 permitting a spring 49 to move a clutch conducter 39 splined on a shaft 37 to complete the drive of the adjusting means 35. The pin 53 operates against the spring 49 to prevent any adjustment if the paper is in correct register when the cutter operates, by moving the clutch member 39 into engagement with a fixed conductor 43. A differential gear couples the main feed roll drive with the adjusting means and the feeding speed is preferably somewhat excessive so that the adjustment acts in a retarding sense. Fig. 4 shows an arrangement having a reciprocating cutter and intermittent paper feed in which the feed-speed adjustment is affected by a constantly reciprocated pawl 72 held normally out of engagement with a ratchet 70 by a spring controlled lever 76 engaging a pawl face until detained by a latch 85 whereupon the pawl effects an adjusting stroke. The latch is actuated by an electromagnet 11 from the photoelectric device only when the indicia are out of register cam actuated switches 64, 66 rendering the photo-cell circuit operative only for a brief period in each cycle of the mechanism. The paper is checked each time the reciprocating cutter 91 is operated by a cam 107 which uncouples a clutch 99 and causes it to engage a member 106 to lock the main drive of the feed rolls 26. In a modification having a rotary cutter a cam-actuated shutter periodically obturates the light beam. Three arrangements of the photo-cell circuits are described. In Fig. 1 a gas filled rectifier 8 in an A.C. supply energizes the electromagnet 11, when the photo-cell 1 is not illuminated, i.e. on the passage of a black spot on the paper. A modification of this A.C. arrangement whereby the electromagnet is energized when a white area is passing the cell has the battery 4 reversed and a negative grid bias is applied by a battery connected between the cathode 7 and resistance 5, Fig. 3, shows a D.C. circuit arrangement for use with the switches 64, 66 above described. The switch 66 periodically interrupts the anode circuit of the valve and the switch 64 prevents the activation of the cell 1 by a white area from causing a discharge in the valve. Specification 429,218, [Group XVI], is referred to.