Patent GB-732087-A (GB)
Title: Improvements in or relating to apparatus for automatically cutting-off pre-determined lengths of strip material
IPC: D06H7/02
Filed: 1953-07-24
Abstract: 732,087. Photo-electric control of strip feed. CHAMBERS, L., and C.B.B.C. ELECTRONIC DEVICES, Ltd. July 24, 1953, No. 20642/53. Class 40 (3). [Also in Group XVI] In apparatus for cutting-off predetermined lengths from strip material having a repetitive pattern, means are provided for intermittently feeding the material, and photoelectric means are provided securing the strip and operating an electromagnetic brake when a predetermined part of the pattern moves into the field of view of the photo - electric means, the strip then being cut after its movement has been arrested. General operation (Figs. 1, 5, 7). The invention is described with reference to cutting labels from a continuous textile strip 2 and to folding over the ends of these labels. Initially the strip 2 lies on a feed table 1 and the end of the strip is bent over a tilting platform 3 where it is gripped by tweezers 11 attached to feed mechanism 10. At the commencement of the cycle the feed mechanism moves to the right the tweezers drawing the folded end of the strip with it. When the selected point in the pattern comes into the field of view of the photo-electric scanning device comprising light source 14 and photo-cell 17, electromagnetic brake 12 is applied stopping the forward movement of the web. The tweezers now slip off the end of the web and blade 8 descends and severs it, the trailing end of the cut label lying over pressing blade 18. Table 3 now tilts, pressing the leading edge of the next label against a heater 26 and pressing blade 18 begins to rise towards folding blade 19 (this condition is shown in Fig. 5). The folding blade moves rearwardly, folding the leading edge of the web while the pressing blade rises to a point above the folding blade. The folding blade now moves forwardly and folds the trailing edge of the cut label under the pressing blade (see Fig. 7). The pressing blade is then withdrawn, pressing the trailing edge of the label supported on the folding blade. A pair of stacking blades 20 then rise and lower the cut and folded label past ledges 23 into the bottom of a stack 21. A gravity pressure plate 24 holds the labels,in position in ledges 23. Construction of apparatus (Figs. 9, 10). The drive to the machine is derived from shaft 31 and is transmitted to a main operating shaft 32 running longitudinally of the machine and carrying cams 34a, 35, 36, 37, 38 and eccentric 34. A roll of labels is fed over a skid 40 between transversely adjustable guide 39, be. tween further guides 42, under the brake bar 12 and over the tilting platform 3. Movable cutter 8 is actuated by face cam 34a, carried on shaft 32, the end of a pivoted bell-crank lever 102 riding on the cam with which it is maintained in contact by a spring 104. The other end of the lever is formed into a fork which engages a pin on the end of the cutter 8. This cutter is held in contact with a fixed blade by a spring. The tilting platform 3 and folding blade 18 are both actuated by cam 35. A cam follower is carried by a bar (Fig. 10), not shown, to the end of which is fixed a lever 108 pivoted at 109. The other end of this lever carries the folding blade 19. Movement of lever 108 by cam 35 causes a backward and forward movement of folding blade 19. Also mounted on the cam follower actuating lever 108 is a block 110 carrying a rod 111 and spring 113 slidable in a bore in the block and having a check nut. Anti-clockwise movement of lever 108 pulls rod 111 downwardly to tilt platform 3. When the end of the platform touches heater 26, rod 111 slides into block 110. Tension spring 115 normally urges lever 108 in an anti-clockwise direction. The pressing blade is actuated by cams 36 and 37. A support lever 116 is pivoted at 117 and carries a cam follower 118. Pivoted at 120 to the forward end of this lever is a support 119 for pressing blade 18. The lower end of this support is operated by cam 37, and a tension spring 121 is provided for the support. The arrangement of the two cams is such that as lever 116 pivots about arms 117 cam 37 rises more rapidly, thereby maintaining the movement of pressing blade 18 vertical. When the highest part of cam 36 is reached, cam 37 still rises hence support 119 tilts in a clockwise direction removing the pressing blade 18 from the completed fold. The feed mechanism consists of a bar 43 fastened to a guide block 44 sliding on guides 45 at one end, the other end of the bar being supported by rollers 46. The rear end of rod 43 forms one jaw of the tweezers. The other is pivoted to a connecting rod 54 parallel to rod 43. The forward end of rod 54 is pivoted at 55 to a link 56 the other end of which is pivoted to bar 43 and carries two lateral stops 58, 59. A reciprocating drive is connected to the feed mechanism by a link 60. Initially bar 54 moves rearwardly, opening the jaws of the tweezers. When abutment 59 contacts bar 43 the whole assembly moves forward until when the stroke is reversed, the tweezers close on the end of the web further movement drawing the label out. A crank mechanism (Figs. 13 and 14, not shown), the throw of which may be adjustable is provided for oscillating the tweezers by means of a connection to link 60. Brake 12 is actuated by solenoid 69 through a rod 70 against the action of a spring 71. The stacking blades 20 (Fig. 9), are operated by a cam follower 139 carried by a support 140 to which the blades are attached. A solenoid may also be used to open the tweezer jaws to prevent them pulling threads. Circuit (Fig. 15). The mark on the pattern is detected by a photo-multiplier tube 17, the output of which is used to increase the common cathode current of a double triode valve 95. The signal developed across the anode resistor of one half of the triode is used to unblock a mixer valve 88, the triode grid of which is fed with the output of a Wien bridge oscillator 85 providing a 3000 c.p.s. signal. This signal passes the mixer as long as the mixer is held unblocked by the output of the photo tube. The oscillations pass to an amplifier 98 and thyratron 99 which fires operating the brake solenoid 69. The solenoid remains operated until its anode circuit is broken by camactuated switch 100. This switch also prevents the brake operating if the pattern is repetitive and a single label is to contain more than one repetition.