Patent GB-707090-A (GB)
Title: Improvements in cutting machines
IPC: B26D5/20
Filed: 1951-09-11
Abstract: 707,090. Photo-electric control of paper-cutting machinery. LAWSON CO., Inc., E. P. Sept. 11, 1951 [Dec. 9, 1950], No. 21391/51. Class 40 (3). [Also in Group VIII] A machine for cutting paper comprises a horizontal table 100, Fig. 1, a reciprocating knife, a reciprocating work clamp, a work-feeding bar or back gauge 31 movable on the table by driving mechanism towards and away from cutting position, and a series of stop units which control the energization of a photo-sensitive electrical circuit and thereby the speed and operation of the driving mechanism. The mechanism for driving the back gauge consists of a hydraulic motor 104 which drives through belts and pulleys a feed screw 204 engaging the gauge. The hydraulic circuit of the motor includes a pump 83, reservoir 81, and two solenoid-actuated valves 97, 98 as described in Specification 707,088, [Group VIII]; the valves can be set automatically so as to provide fast forward drive, slow forward drive, and reverse drive of the gauge. The control of the solenoids actuating the valves is a photosensitive device housed in a carriage 63, Figs. 17 and 18, which is movable along a bar 64 disposed transversely of the machine above the cutting position. The carriage 63 is connected by cables 60 passing over pulleys to the back gauge so that it moves synchronously therewith, and its movement may be read on a scale 460. The photosensitive device consists of a light source 359, co-operating through a slit 365 and lens 362 with a photo-electric cell 360; a second, but less sensitive photo-electric cell 665 is disposed adjacent the cell 360 for operating a light signal for indicating whether or not the back gauge has stopped in correct position. As the carriage 63 moves along the bar 64 in synchronism with the gauge, the energization of the cell 360 by the light beam is controlled by a series of stop units carried by a cross-bar 376 so as to provide the desired sequence of operations. The controlling electric circuit comprises, as shown in Fig. 9, relays CR1, CR2, CR3, CR4, CR5, solenoids A1, A2, B1 for actuating the valves 97, 98, relays PR1, PR2 which are energized when the photoelectric cells 360, 665 are energized, and various switches for controlling the desired operation. For automatic operation of the gauge in the forward direction, actuation of switches 590, 545 permits the light beam to energize the cell 360 and results only in energization of the solenoid A2, whereby the valves 97, 98 are set so that the motor 104 drives the gauge at slow speed. At the same time, the energization of the relay CR2 causes its contacts CR2b to initiate the operation of a timer 580 which is effective, after a short interval, to complete a circuit which energizes the solenoid B1; the valves 97, 98 are then set for the drive of the gauge at fast speed. When the carriage 63 has moved to the extent that a stop unit cuts off the light beam, the circuit is effective to de-energize the solenoid B 1 whereby the gauge again moves at slow speed until the light beam clears the stop unit so that the solenoid A2 is de-energized and the gauge halted. If the gauge has stopped in correct position, only the cell 360 would be energized and the circuit would be effective to energize a light signal 600; over-travel or under-travel of the carriage would, however, result in the cell 665 being energized to break the signal circuit. With the gauge in correct position, the operator initiates operation of the cutting knife which, during its return, actuates a switch 410 to cause the gauge to repeat its cycle under the control of the next stop unit. When the gauge reaches its forward position after a complete series of cuts, a switch 530 may be automatically actuated to set the valves for the return of the gauge at high speed. When setting up the machine, the switch 590 may be actuated to move the gauge forward at high speed so long as the switch 545 is operated. The electric circuit also includes a stop switch 527, forward and reverse limit switches 532, 549, on adjustably-mounted switch 547 for stopping the reverse movement of the gauge at any point, and switch 523 for opening the circuit when the operator clamps the screw 204 and gauge in fixed position. The bar 376, which carries the stop unit, is of hexagonal form and supported on bearers 680. 680a, Fig. 17, between spring-pressed centres 93, 95, one of which is movable by a handle 971 to permit release of the bar. The bar is locked in position by a spring-pressed latch 681 which engages one of a series of slots 691 in the end of the bar, and, when in this position, acts through an arm 699 to close a normally open safety switch 525 in the electric circuit; when the carriage 63 is moved to the right in Fig. 17, it strikes an arm 669a to disengage the latch. The stop units may, as shown in Fig. 17, consist of opaque areas 499 on a transparent strip carried by brackets 503, 504 from the bar, or, as shown in Fig. 23, a number of angle elements 365 secured in spaced relation in grooves 367 in the various faces of the bar so that their depending lugs control the photo-sensitive device. Stop units of the latter kind may be uniformly spaced along the bar for cutting labels from a printed sheet. When, however, a series of printed labels on the sheet to be cut is followed by a narrow unprinted strip which must be trimmed out, it is necessary to provide a special stop unit to deal with this strip; the spacing of this unit from the previous unit and its width are such as to operate the back gauge as before, except that the timer 580 will not be effective and the gauge will travel only at slow speed. These trimout units may be adjustably mounted on the bar 376 and in the form of hinged parts whereby the effective width and spacing of the units may be varied. If desired, a combination unit may be built up from an ordinary unit and a trimout unit. To permit setting up the stop units on the bar 376 to provide the desired cycle, the carrige 63 is provided with a lens 461, Fig. 17, and indicator 462 co-operating with the scale 460; a blocking member on the carriage is moved upwardly at the desired positions of the stop units so that the latter can then be correctly located.