EP0035612B1

EP0035612B1 - Method and apparatus to stretch wrap an object in plastics film

Info

Publication number: EP0035612B1
Application number: EP80300641A
Authority: EP
Inventors: Ladislav Stephan Karpisek
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-03-04
Filing date: 1980-03-04
Publication date: 1984-11-07
Also published as: ATE10178T1; EP0035612A1

Abstract

A method and an apparatus to stretch wrap an article in a tubular plastic film, the method comprising the steps of locating a length of elastically stetchable tubular plastic film 5 on a holder 2 and thereafter expanding the holder to stretch the tube to a size enabling the tube and the holder to be passed over the article to be wrapped which may be located on pallet 3 mounted on stand 4 and at the same time stripping the tube off the holder so the tube can contract and elastically embrace the object. The tube preferably has an end closed and is folded concertina fashion on the holder. The frame 2 is in sections which telescope or pivot to effect outward expansion.

Description

This invention relates to a method and apparatus to stretch wrap an object in plastics film. film.
The packaging of one or more objects by surrounding or enclosing the same with a plastics film which has elastic properties is highly advantageous, so that improved techniques for applying the film are of considerable importance.
U.S. Specifications Nos. 3,902,303 and 4,050,219 disclose previous proposals for stretch wrapping objects in elastic plastics film.
In both of the above U.S. Specifications four upstanding fingers or horns are used to support a tube of plastics film material as a puckered band, the tube and thus the band being too small to pass over a load to be wrapped. The fingers or horns are separated to stretch the puckered band so it can pass over the load to be wrapped. The load is then passed through the band, or vice versa, and the tube is stripped from the horns and, when relieved of the stretching forces, contracts to embrace the load.
Whilst theoretically this approach appears practical in reality where the plastics material is drawn off over the corners of the fingers or horns there is a concentration of stresses and this results in a predisposition for the plastics material to tear or to undergo severe local stretching. This causes holes and destroys or lessens the protective effect of the plastics cover placed over the load.
The invention as claimed overcomes this problem in that while the wrapper in the form of a concertina-folded band is stripped from the holder said wrapper is supported along all of its perimeter by a continuous pressure rail forming part of the holder, which holder comprises a four-way telescopically expandable frame.
Ways of carrying out the invention are described in detail below with reference to drawings which illustrate specific embodiments, and in which:-

Figure 1 schematically illustrates a wrapper in the form of a plastics bag and a holder therefor,
Figure 2 schematically illustrates the plastics bag of Figure 1 being mounted as a concertina-folded band on the holder,
Figure 3 schematically illustrates the bag fully mounted on the holder,
Figure 4 schematically illustrates the expansion of the holder to enlarge the internal cross-section of the bag,
Figure 5 schematically illustrates an expanded bag about to be passed over a loaded pallet on a stand,
Figure 6 schematically illustrates the expanded bag passing over the loaded pallet,
Figure 7 schematically illustrates the bag partly stripped from the holder and contracted onto part of the pallet load,
Figure 8 schematically illustrates the loaded pallet encased in the contracted bag, and
Figure 9 illustrates in more detail the expandable holder, diagrammatically shown in Figures 1-8.

The method will be described with reference to Figures 1 to 8 and using a wrapper in the form of a bag. The expandable holder may have many forms and these are described later.

Figure 1 shows a bag having a basic substantially square cross-section and as would be . used to wrap object(s) on a 46" x 46" (1170 mm x 1170 mm) pallet. The basic size of the bag side could be in the order of 40" (1016 mm) and thus the bag is initially 40" x 40". The finished size will be in the order of 46" x 46" embracing objects stacked to the perimeter of the pallet loading area. The holder 2 would have a minimum contracted side size of say 38" (965 mm) expandable to said 48" (1219 mm).
Figure 2 shows the bag in the process being mounted on the expandable holder.
Figure 3 shows the bag fully mounted on the holder:
Figure 4 shows the bag being expanded, say to 48" x 48".
Figure 5 shows the expanded bag-holder combination about to be lowered over a plurality of cartons stacked to the perimeter of a 46" x 46" pallet 3 mounted on a stand 4.
Figure 6 shows the bag in the process of being stripped from the holder as it is lowered, the stripping being due to the engagement of the bag end on the upper cartons.
Figure 7 shows the bag stripping further advanced, and 5 indicates the contraction of the bag due to the memory of the plastic from the size on the holder the size of the objects which is greater than the basic internal cross-section of the bag.
Figure 8 shows the bag fully elastically embracing the load and the pallet and the open end 6 of the bag contracted and curled under the pallet to lock the bag at its lower end. The holder 2 at this stage is around the stand 4 and in its expanded form can be readily removed by moving it straight upwardly over the wrapped load.

The bag is preferably of flexible elastically stretchable plastic film having a memory.
The bag may be replaced by a tube without ends. The procedure would be as above except that portion of the bag-adjacent the upper end would not be expanded and only a major part of the tube length would be on the holder and expanded. The non expanded upper end of the tube would not like the bag end to assist in stripping the tube from the holder. If desired, for example on high loads, a short bag could be placed on the load and a sleeve would be used to complete the wrapping. In this case the whole of the tube would be on the holder and expanded. The tube could be placed on the load either before or after the bag.
Turning now to the holding frame 2, various constructions are possible but Figure 9 shows a preferred construction comprising an expandable frame 7 of two similar right-angle parts. Each part has an upper rail 8 and a lower rail 9 separated by vertical bars 10. There are two similar corner assemblies 11 each comprising an upper bend 12 and a lower bend 13 separated by vertical bars 14. The bends 12-13 are telescopically coupled to the rails 8-9 at 15. The upper rails 8-8 and the upper bends 12-12 constitute a continuous pressure rail P which varies in size as the frame varies in size. Bevel gear assemblies 16 with treaded jack screws 17 are mounted on each corner assembly and the screws 17 engage nuts on the rails 9. By means of handles the gear 1'6 and screws 17 are rotated and the telescopic joints 15 provide a four-way expansion of the frame 2 to enlarge its size. The bag or tube is supported on the bars 10-14. This form of frame is preferred for use with a bag, i.e. a tube with a closed end.
It will be understood that for manual operation handles indicated H in Figure 9 would be used as required.
It is also within the scope of the invention to substitute mechanical devices such as piston-and-cylinder combinations for the jacking screw arrangements described above.

Claims

1. A method of stretch wrapping one or more objects by means of a wrapper (1) of elastically stretchable plastics film comprising a tube (28) the perimeter of which is smaller, in the unstressed condition, than the perimeter of the object or objects (29) to be wrapped but which can be stretched to have a greater perimeter than said object or objects (29), the method comprising storing at least a major part of the wrapper (1) as a concertinaed band (26) on an expandable holder (2) (7), expanding the holder (2) (7) to give the wrapper (1) thereon said greater perimeter, relatively moving the expanded holder (2) (7) and the object or objects (29) to be wrapped so that the wrapper (1) is progressively stripped from the holder (2) (7) as the object or objects (29) pass relatively through the holder (2) (7), allowing the wrapper (1) to contract onto the object or objects (29) to provide an elastically embracing enclosure therefore and removing the wrapper (1) from the holder (2) (7), characterised in that while the wrapper (1) is stripped from the holder (2), said wrapper is supported along all of its perimeter by a continuous pressure rail (P) forming part of the holder (2), which holder comprises a four-way telescopically expandable frame (7).

2. A method as claimed in claim 1, wherein the wrapper (1) additionally comprises a closed end (27) of the tube (28) so that the wrapper (1) is in the form of a bag.

3. A method as claimed in claim 1 or claim 2, wherein the length of the tube (28) is in excess of the height of the object or objects (29) to be wrapped.

4. Apparatus to carry out the method of any one of claims 1-3, wherein the holder (2) comprises a four-sided, four-way telescopically expandable frame (7) including a continuous pressure rail (P) formed by two similar right-angle subframes (8) (9) (10) oppositely disposed and by two corner assemblies (1) between adjacent ends of the two sub-frames, and extensible means (16) (17) coupling the corner assemblies (11) to the sub-frames (8) (9) (10) telescopically to move the corner assemblies (11) and sub-frames (8) (9) (10) apart to increase the perimeter of the frame (7) and therefore the perimeter of the pressure rail (P).