Photoelectric control device

Claim 1

Apparatus for controlling the diameter of an inflated tubular film 6, comprising a plurality of photoelectric devices 12a-12p disposed on one side of the tubular film 6 in a line extending laterally of the tubular film, a light source 13 arranged on the opposite side of said tubular film 6 to direct a light beam 14 to said line of photoelectric devices 12a-12p, said tubular film 6 positioned to project partially into said light beam 14 in a direction from one end (end at 12a) to the other end (end at 12p) of said line of said plurality of photoelectric devices (12a, 12p), said photoelectric devices (12a-12p being arranged close together in said line so that at least one thereof is assigned to the sector of the said light beam 14 which strikes on the tubular film 6 immediately adjacent a tangent thereof, a plurality of trigger circuits 20a-20p each assigned to one of said photoelectric devices 12a-12p and responsive thereto, said trigger circuits having blocking inputs 34b, a plurality of blocking circuits 23b-23p each connected to two of said trigger circuits which trigger circuits are each assigned to one of two adjacent photoelectric devices in saId line of photoelectric devices 12a-12p and having an input 29b, 29c and an output 30b, 30c, said input 29b, 29c being connected to the output of one trigger circuit 20b, 20c of the said two trigger circuits, which is assigned to that one photoelectric device 12b, 12c of the said two photoelectric devices which is a greater distance than the other 12a, 12b from said one end (end at 12a) of said line of photoelectric devices 12a-12p, said output 30b, 30c being connected to a said blocking input 34b of the other 20a, 20b of said two trigger circuits which is assigned to the other 12a, 12b of said two photoelectric devices, each of said blocking circuits 23b-23p being operable upon the control of said one trigger circuit 20b, 20c of the two trigger circuits assigned thereto when the output signal thereof corresponds to a darkened state of the assigned said one photoelectric device 12b, 12c to affect said other trigger circuit 20a, 20b in a manner corresponding to a darkened state of the photoelectric device 12a, 12b assigned to said other trigger circuit 20a, 20b, and a control circuit 35, 37 having an input connected to the output of each of said trigger circuits 20a-20p, inflating means 5 having pressure control means 1-4, 7-10, 11, 41 to extrude the blown tubular film, and said control circuit 35, 37 connected to said pressure control means to control the pressure within said blown tubular film 6 whereby a predetermined diameter is maintained throughout the blow tubular film.