This invention relates to a method and apparatus for securing a bundle with strapping material, and more particularly to securing a package or bundle with a strap having a heat sensitive adhesive thereon which may be reactivated by application of heat.
Machines and methods are known for forming a tensioned loop of strapping material about a bundle. Such machines often include means for forming a strap loop around the object, means for pulling the strap loop trailing portion to tension the strap loop about the object, means for securing the overlapping strap portions together, and means for severing the strap trailing portion from the loop.
In the past, strapping used may have been made of thermoplastic material. A heating element was inserted between two overlapping portions of the strap to heat and somewhat melt the thermoplastic material, the heating element had to be removed from the position between the two strap portions and the two strap portions had to be immediately pressed together under pressure to adhere them to each other.
In other prior apparatus and methods an adhesive was injected into the space between the two overlapping portions of the strap prior to their being pressed together. In some applications a moisture sensitive adhesive may be part of the strap and application of moisture, such as water, in the space between the overlapping strap portions activated the adhesive previously applied to the overlapping strap sections, after which they are then pressed together for joining.
In other prior strapping apparatus and methods, metal strapping or wire has been used, with overlapping sections secured together either by fusion welding to each other or by being clamped or tied together to secure the overlapping portions.
Although metal strap and wire works well to secure a bundle, such is not always well adapted for safety and recycling. Explaining further, when metal or wire strapping is released, since it is under tension, the cut ends may fly from the packaged articles creating a safety hazard. Further, if the bundled materials are of a fibrous nature which is to be recycled, such as by being broken down or re-pulped, a metal, wire, or thermoplastic strap may produce problems should it be passed into the deconstructing or repulping process.
Various pulpable strap material has been devised recently. One such strapping tape material comprises multiple elongate elements secured together by a heat sensitive adhesive which may be reactivated by application of heat. These multiple elongate elements, or strands, may be twisted paper or yarn elements forming long string-like elements which are adhered together in adjacent, side-by-side orientation to form a substantially flat tape or strap. The adhesives and strand material used in the manufacture of such a strap may be specifically formulated to be easily repulped. The adhesive may be applied cold or heated and may be a heat sensitive adhesive which may be reactivated by the application of heat.
Other strapping has been made that is a flat strap made of multiple folds of a wider thin sheet of paper-like material. These folds may be held together by an adhesive and thus laminated one over the other to form a flat strap.
An object of this invention is to provide a method for binding a bundle by providing an elongate strap having a heat sensitive adhesive thereon which may be reactivated by the application of heat, extending the strap about a bundle, drawing the strap taut about the bundle with portions of the strap overlapping, pressing the overlapping portions of the strap together, and simultaneously applying heat to at least one external surface of the overlapping portions of the strap to reactivate the adhesive to bond the strap portions together.
Another object of the invention is to provide apparatus for binding a bundle with an elongate strap having heat sensitive adhesive thereon which may be reactivated by application of heat. The apparatus includes mechanism for feeding the strap to form a loop about the bundle with a leading end portion, overlapping first and second strap portions, and a trailing portion of the strap. A pair of opposed press elements are disposed on opposite sides of the overlapping strap portions with at least one of the press elements being heated. Clamping mechanism is operable to shift at least one of the press elements toward the overlapping strap portions to apply heat and pressure externally thereto to reactivate the adhesive in the strap material to secure the overlapping strap portions together.
Further, the apparatus is such that operating mechanism for gripping, clamping, and severing remainder portions of the tape are shiftable between first positions for operating upon the tape to bind it about a bundle, and second positions laterally therefrom to release the tape to surround the bundle and allow the bundle to be removed from the apparatus.