Patent GB-756461-A (GB)
Title: Improvements in or relating to bias cutting machines
Inventor: POWER DOUGLAS MERTON
IPC: B29D30/46
Filed: 1953-11-17
Abstract: 756,461. Photo-electric control systems. DUNLOP RUBBER CO., Ltd. Nov. 9, 1954 [Nov. 17, 1953], No. 31807/53. Class 40 (3). [Also in Groups VIII and XIX] A bias cutting machine comprises an endless belt conveyer carrying the material to be cut and three photo-electric detectors spaced along the conveyer and responsive to the arrival of the material to slow, stop and reverse the feed respectively, the arrangement being such that if the leading edge is between the second and third detectors for a sufficiently long period a strip is cut and the feed commences. As shown, the conveyer comprises a number of parallel conveyer belts 11 driven by the output shaft 21 of a differential gearbox fed by fastrunning motor 22 and slow-running motor 23, provided with solenoid-actuated brakes 35, 36 respectively so that either motor may be stopped when the conveyer will run at a speed appropriate to the other. Situated over a longitudinal space between two parallel belts of the conveyer are three photo-electric cells each behind one of lenses 55, 58, 59 called the first, second and third cells while below are three light sources 54, 52, 53 each illuminating one of the cells. Both the cells and light sources are slidable on rails 40, 41 and are positioned by screws 43, 45 driven by motor 48. The first cell is situated upstream from the other two and the second is about <SP>1</SP>/ 16  in. upstream of the third. A power-driven rotatable knife is provided which is traversible by mean sof an electric motor 61 along guide rails 62 mounted upon the conveyer. The angular position of these rails with respect to the conveyer is adjustable by means of a handwheel-adjusted worm wheel co-operating with a worm wheel segment. The width of the strip to be cut is measured by a scale 71 attached to links 72, 73 and to a carriage 70 sliding on a rod 69 attached to guide rail 62. The scale is guided by rollers 75 carried on the photo-cell housing and a point marked on this indicates the width of strip cut on the scale. In operation the required bias angle is set by hand-wheel 63 and the photo-cells adjusted to give correct strip width by means of motor 48. The knife is then operated under manual control to cut the leading edge of the fabric. Motor 22 is now started and the leading edge of the fabric is fed forward until the light reaching the first photo-cell is cut off. Motor 22 is de-energized and solenoid-operated brake 38 energized. The slow-speed motor 23 is energized and continues to drive the conveyer through the differential gear but at a reduced speed. When the light reaching the second cell is interrupted the correction motor is deenergized and braked so that the conveyer stops. If the conveyer so far over-runs as to interrupt the third beam the slow motor is reversed until the leading edge of the fabric is between the second and third cells. A timedelay device operates the cutter provided the fabric is in this position for a long enough period. At the end of its cutting stroke a mechanism associated with the knife starts the main motor and the conveyer again moves forward. If narrow widths of fabric are to be cut motor 22 may be operated at low speed. The distance between the first and the second and third detectors may be reduced by driving the first detector towards the other by a geared electric motor.