WEB TENSION CONTROL SYSTEM FOR USE WITH A WEB UNWIND STAND

摘要

1,272,817. Feeding webs. F.M.C. CORP. 10 Sept., 1969 [17 Sept., 1968], No. 44756/69. Heading B8R. A web unwind stand comprises a frame in which are rotatably mounted a pair of turret arms 62, (61) Fig. 2 (not shown) for supporting a first roll 66 in a position for unwinding a web therefrom in a counter-clockwise sense, as shown, or in a clockwise sense (Fig. 4, not shown) and for supporting a second roll 64 in a standby position, and a plurality of splicing rollers 49, 51, 57 mounted between pivoted brackets 41, (43) for movement between splicing a web unwinding in a counterclockwise sense to a position for splicing a web unwinding in a clockwise sense. As shown, when the running roll 66 approaches exhaustion an operator gives a pull-start to the standby roll 64 so that the leading end of the new web 67, prepared with an adhesive strip 68, drops vertically between the splicing rollers 57, 49 and contacts the expiring web. Pneumatic cylinders 53, (55) are then actuated so that nip pressure is applied to the splice in two places, between rollers 57 and 49, and between rollers 57 and 51. If the running roll has to be unwound in a clockwise sense a lock 45 is disengaged and the brackets 41, (43) are pivoted into a second position where the lock 45 can engage within a hold 47, and the arms 62, (61) are suitably positioned (Fig. 4, not shown) so that the same procedure as described above can be followed when it is desired to make a splice. The unwind stand may form part of an installation (Fig. 1, not shown) including a printing station, a drying oven, and a rewind stand, and it is provided with a control system to maintain the in-feed web tension constant. This tension control system includes first and second pneumatic brakes (75), (76) Fig. 2, (not shown) interconnected with the core shaft of the running roll to apply braking torque thereto under the control of signals derived from a tension sensing dancer roller (22) Figs. 1, 5 and 6 (not shown), the arrangement being such that brakes (75), (76) are both energized at the start of a full roll, but only brake (75) being effective later in the unwinding process. Electric brakes may replace the pneumatic brakes (75), (76) and a load cell type of sensing roller may be used instead of the dancer roller (22).