Patent GB-1345796-A (GB)
Title: Apparatus for spreading a web of cloth
IPC: B65H23/02
Filed: 1971-04-19
Abstract: 1345796 Laying fabrics CUTTER MACHINE CO Inc 19 April 1971 [4 May 1970] 26253/71 Heading D1S [Also in Divisions G1 and G3] A cloth spreading or laying machine particularly for aligning patterned cloth having longitudinal stripes or linear divisions of colour or shade thereon has, in addition to photo-electric edge sensing and aligning control, a photo-electric sensing and control means to sense any deviation of the or a selected stripe from its normal course and to move a web of said cloth and a cloth supply roll whereby to restore the stripe to its correct normal course. The machine, Fig. 4, includes a frame 16 moveable on a spreading table 18 and carrying a cloth feed carriage 19 supporting a motor driven cloth roller 20. A web 21 of striped cloth is fed via a guide bracket member 58 to a spreader unit 27 where the web 21 is spread upon the table 18 in layers 28. The guide arrangement includes a friction roller 60 rotatable in side bars 59 which are pivotal in a pair of carrier arms 64. The arms are fixed to a carrier 65 which is reciprocable transversely of the frame to shift the web by means of a reversible motor (72), Fig. 2 (not shown) mounted on the frame and controlled by a circuit 75 (Fig. 11) in dependence upon stripe deviation sensed by a sensing head 52 adjustably fixed to the frame 16. The cloth carriage 19 is also arranged to shift the cloth supply roll transversely and simultaneously with the shifting of the guide arrangement 58, a photoelectric edge sensing head 77 being fixed to the carrier 65 and guide arrangement 58 and connected through a control circuit (83), Fig. 12 (not shown) to a reversible cloth carriage motor 78 which is arranged to transversely move the carriage 19 relative to the spreader frame 27. Stripe sensor (Figs. 5, 6). The sensor head 52 includes a light emitting cavity 85 with a light source 87 (white light or ultra violet) between a pair of light receiving cavities 89, 90 housing photo resistive cells 91, 92 respectively and disposed at equal angles to the cavity. Each cavity 89, 90 has a triangular cross-section as shown, to permit the quantity of light received by one to decrease as the light received by the other increases due to movement of the stripe 55 relative to its correct course.  Shipe alignment control circuit (Fig. 11). The guide motor 72 field 104 is energized via a bridge rectifier 103. The motor armature is energized via a rectifier bridge 107 with SCRs 108, 109 and via a relay switch 106 controlled by a relay coil 110 in the motor starting circuit including push switch 112 and holding relay switch 112. Control signals for the SCRs are from a balance circuit 120.  The circuit 120 is balanced and produces a zero error signal when the stripe 55 is on its correct course. Any deviation therefrom in one direction decreases the resistance of one photo cell 91 or 92 and increases that of the other so that an error signal is produced causing either UJ transistor 125 or 126 to fire and turn ON either SCR 108 or 109 respectively Thereby the web guide motor 72 is rotated in a direction such as to reduce the error to zero, and at a speed proportional to the error magnitude, the speed gradually reduces as the error approaches zero, and is determined by the firing angle of the SCR operating, which in turn is dependent on the degree of unbalance of the circuit 120. In the balance condition the potential at point 135 equals that at a wiper 143 so that the conductive states of transistors 138, 142 are the same. As the potential of 135 changes due to stripe deviation either 138 or 142 conducts to turn ON a respective transistor 130 or 129 charge a respective capacitor 132 or 131 which subsequently causes firing of a respective UJ transistor 126 or 125 to produce a firing signal for the appropriate SCR 108, 109. If desired, an allowable deviation magnitude can be pre-set by adjustment of a "dead zone" pot 148. A similar circuit, Fig. 12 (not shown) is used for edge alignment control whereby the carriage is movable transversely, an edge sensing head 77 being linked to the web guide member 58 for simultaneous transverse movement therewith.  Light intensity control (Fig. 11). By manual operation of a change-over switch 181 182 either a white light lamp 86 or an ultra violet lamp 87 is selected. A signal proportional to the intensity of reflected light is derived from the photo cells 91, 92 at a point C whereby to control amplifying transistors 172, 173, 176, 177 to change the voltage of the white light source 86 and maintain a substantially constant intensity of reflected light received by the cells thereby compensating for light reflected from other light sources. If the ultra violet source 87 is used, the intensity control circuit operates via UJ189 and SCR rectifier bridge 190 controlling current through a transformer 191 to control the light intensity of the U.V. lamp 87.