Wrapping machine

摘要

A film changing unit(7) is located on one, preferably both sides of a feeding table(2). Each film changer has a stored(8) and an active(9) film roll. Both the active(3) and stored(22) film strip pass through a film sealing unit(10) with a cutting and welding unit(36,37). On changeover between active and stored films a compressed transverse cut seam is made between the working and the stored films The film sealing unit(10) comprises three separate components(15,16,17) forming two parallel slits(18,19) and the stored film strip passes through one slit and is partly wrapped around the center component(16). The active film(3) passes vertically through the other slit(19,18). Each cutting and welding unit(36,37) comprises a heating element and an opposing tool separated by the film slits. Clamping strips are located on the opposing tool or on the heating element and a cutting edge is formed on either component. One of the latter components moves relative to the other. When each heating element has a cutting edge these are static and in the center component of the film sealing unit. The cutting edges face the film slits and the opposing tools are in the other two components and have rubber cutting profiles which move towards the center component. A spring plate with openings for film strip clamping is allocated to each heating element and the film strips are clamped between the opposing tool and the plate. The opposing tool comprises a rubber rail and the heating element is impulse heated. A clamp(31), comprising a strip(32) and a spring(33), holds the projecting leader(34) of the stored film(22) against the underside of the central component. A swiveling guide roll moving between two positions ensures that the active film strip always passes along the outer edge(23) of the film slit. Continuous monitoring of a roll thickness is effected by a light sensor which emits a signal to initiate the film clamping stage and/or the heating stage. An Independent claim is included for a process for film roll changeover in which: (i) the stored film strip is guided through a first slit between a first and a central component of the sealing unit(10); (ii) passed around the central component and through a second slit, through which the active strip(3) also passes; (iii) the projecting leader of the stored storage film is clamped(31); (iv) the stored film and adjacent active film strip are parted by the cutting and welding unit which simultaneously welds the rear end of the active film to the stored film and stored film leader to the remaining length of active film strip; (v) the empty active film roll is exchanged for a new, full one.