A typical production-packaging apparatus for wrapping a stack of objects with a film has at least one film supply for the film, a film-feed head for feeding the film, and a device for pulling the film down over the stack of objects. The invention further relates to a method of wrapping a stack of objects with a film. Within the scope of the invention, “film” means in particular a plastic film, preferably an elastic thermoplastic film. It is within the scope of the invention that the stack of objects to be wrapped is a stack of products. The stack may also be a single object or whiteware, for example refrigerators or the like. The stack of objects to be wrapped is advantageously accommodated on a pallet.
In practice, it is not uncommon for stacks of objects or pallets carrying these stacks of objects having different orientations to be consecutively supplied to a wrapping station of an apparatus for wrapping the stack of objects. Thus, a stack of objects that in top view are not square or a pallet that in top view is not square having the length/width dimensions L/W is initially supplied and wrapped, and subsequently another stack of objects that has the dimensions W/L and that is rotated by 90° about a vertical axis with respect to the first stack of objects must be supplied and wrapped. Additional measures are necessary here in order to obtain a film or film sheet that in such a case is also optimally adapted to the dimensions of the stack of objects or of the pallet.
In practice it is known, among other things, to lift the stack of objects using the elevator of a shrink-wrapping device and to rotate the stack of objects by 90° for the covering operation. However, this often results the stack of objects falling over, together with product losses and facility down times. It is also known to provide in the conveyor a rotatable table underneath the film-feed head so that the stack of objects may be appropriately rotated. However, constrictions result in the transition regions between the rotatable table and the conveyor edge due to the fact that the pallets associated with the stacks of objects often become stuck at the transitions, and the stacks of objects then frequently fall over. It is also known in practice to design the entire film-feed head to be rotatable by 90° so that the film can always be fed in the desired direction. This approach is relatively complicated, and the process is also too slow, in particular because of the large mass that has to be moved.
It is further known in practice for the film initially to be completely provided in the feed head and welded, and then transferred to a roller and rolled up by the roller. This roller is then rotated by 90° with respect to the direction of transport, and the film is transferred from the roller to the pull-down device. These measures known in practice are also relatively complicated. The multiple transfers of the film result in a relatively high susceptibility to malfunctions.