US3527343A - Packages for flat films - Google Patents

Description

Sept. 8, 1970 P. w. RUTTER 3,527,343

PACKAGES FOR FLAT FILMS Filed Dec. 31, 1968 2 Sheets-Sheet l Sept. 8, 1970 P. w. RUTTER 3,527,343'

PACKAGES FOR FLAT FILMS Filed Dec. 31, 1968 2 Sheets-Sheet 2 Mr wmim RuHu' Gus Wan. 4164M A'HO 'M; M

United States Patent 3,527,343 PACKAGES FOR FLAT FILMS Peter William Rutter, Ilford, England, assignor to Ilford Limited, llford, England, a British company Filed Dec. 31, 1968, Ser. No. 788,144 Claims priority, applicatio;14/G6reat Britain, Jan. 3, 1968, 3 8

Int. Cl. B65!) 61/00; B65d 85/30 U.S. Cl. 206-62 12 Claims ABSTRACT OF THE DISCLOSURE The application describes a method of packing a stack of sheet material which comprises applying to both the top and bottom faces of the stack an element which comprises a flat base sheet of rigid material of length and width slightly smaller than the sheet of material and which has upstanding walls on two adjacent sides of the said base sheet, said walls being of less height than the stack, binding the resultant pack with binding material so as to urge the upstanding walls of the two elements into close contact with the sides of the stack.

This invention relates to a method of packaging a stack of sheet material. a

By stack of sheet material is meant a pile of rectangular sheets of material in register.

It is difficult to pack stacks of sheet material so that during transportation of the stack there is no relative movement of the sheets. Such relative movement can often cause scratching or marking of the surfaces of the sheet material if any particulate material such as dust is entrapped between any of the sheets of the stack. Such surface scratching or marking gives rise to particular trouble when the sheet material is a light-sensitive film as any marking of the light-sensitive emulsion, which is on the surface of the sheet, alters its sensitometric properties in such a way that, depending on the conditions, either a sensitised or desensitised spot is produced, resulting in either a black or a white spot on development of the film. As it is almost impossible to exclude dust completely from the atmosphere when packing films it is thus very important to lessen the effect of entrapped dust particles by preventing the relative movement of the sheets of film in a stack. A relative movement of as little as one hundredth of an inch can cause each entrapped dust particle to produce a very noticeable black or white spot on the developed film.

According to the present invention therefore there is provided a method of packing a stack of sheet material which comprises applying to both the top and bottom faces of the stack an element which comprises a flat base sheet of rigid material of length and width slightly smaller than the sheet of material and upstanding walls on two adja cent sides of the base sheet, said walls being of less height than the stack, and binding the resultant pack with bind ing material so as to urge the upstanding walls of the two elements into close contact with the sides of the stack.

It is preferred that the two elements used in the method of the present invention are of similar dimensions but one may be smaller than the other.

Various methods of the pack may be employed for example a single band of strapping material may be used which is placed around the four upstanding walls, and then drawn tight so that it is under tension or there may be two tension bands crossing over two other tension bands at right angles, each band extending over two other tension bands at right angles, each band extending over both of the base sheets.

The binding material may be composed, for example,

Patented Sept. 8, 1970 of metal or of a plastic material such as polypropylene, nylon or rayon/ fibre glass. Tension may be applied to the strapping material and the material joined to form a band by apparatus in general use in packaging materials. It is preferred that the strapping material is of plastics material as it is easy to join such material by metal clips or the like. In the case of some plastic material they can be joined by heat welding.

It is also possible instead of narrow bands to use a wide band or bands of thin plastic film which when heated contract in width or length or in both directions and thus apply compression in all three planes to the pack. This technique is termed shrink wrapping and materials of use in such a technique are polyethylene, polypropylene or polyvinyl chloride.

As the band or hands of binding material are under tension they act to urge the upstanding sides towards each other and thus press tightly against the stack of sheet material from all four sides, disabling individual sheets from moving relatively to each other.

The stack of sheet material can not buckle due to the presence of the base sheets of rigid material on each side of the pack. By rigid material is meant material which cannot easily bend, for example wood, thick cardboard or some plastic materials such as polystyrene or copolymers of acrylonitrile-butadiene-styrene known as ABS material.

Instead of using bands of heat shrinkable material the whole pack, i.e. the stack of sheet material with the two elements in position, may be enveloped in a sleeve of heatshrinkable material. When heat is applied the sleeve shrinks and tightly binds round the pack on all sides urging the upstanding sides of the elements towards each other and thus pressing tightly against the stack of sheet material from all four sides, in the same way as the bands of strapping material.

In some cases it is preferred, and in the case of lightsensitive materials, essential, that the stack of sheet material is placed initially in a light-tight folder such as a polyethylene bag.

The accompanying drawings will serve to illustrate two embodiments of the present invention.

FIG. 1 shows the front and back elements used for packing a stack of sheet material.

FIG. 2 is a perspective view of a stack of sheet material showing the front and back elements held in position by bands of strapping material.

FIG. 3 is a perspective view of a stack of sheet material showing front and back elements in position, the stack being in a sleeve of polyethylene.

FIG. 4 is the same stack of sheet material after the sleeve of polyethylene has been heat-sealed on to the stack.

FIG. 1 is a perspective view of front and back elements as used in the present invention. In the figure element 2 comprises three parts, a base sheet 4, one upstanding wall 5 and a hidden upstanding wall 5A which is shown in outline. Similarly element 3 comprises a base sheet 3A and two side walls 6 and 7.

In FIG. 2 a stack of sheet material 1 is partially enclosed by the two elements 2 and 3, of element 2 the base sheet 4 and one upstanding wall 5 are shown; of element 3 the two upstanding walls 6 and 7 are shown. Holding the pack together are four bands of polypropylene 8-11 under tension.

In FIGS. 3 and 4 the numbers denote the same parts as in FIGS. 1 and 2, but in the case of these figures there are no hands of polypropylene; the pack in FIG. 3 being totally enveloped in a sleeve of polyethylene 14 which has two open ends 15 and 16.

After heating the polyethylene shrinks onto the pack as shown in FIG. 4. The open end of the sleeve 16 having shrunk to the area indicated by 16a on the upstanding wall 5.

I claim as my invention:

1. A method of packing a stack of sheet material to prevent relative movement between the sheets which comprises applying to both the top and bottom faces of the stack an element which comprises a flat base sheet of rigid material of length and width slightly smaller than the sheet of material and which has upstanding walls on two adjacent sides of the said base sheet, said walls being of less height than the stack, binding the resultant pack with binding material so as to urge the upstanding walls of the two elements into close contact with the sides of the stack and thus disable the stack of sheet material from being flexed during transportation.

2. A method according to claim 1 wherein the binding material comprises bands of polypropylene.

3. A method according to claim 2 wherein the bands of polypropylene are joined by heat welding.

4. A method according to claim 1 wherein the binding material is a sleeve of heat-shrinkable material.

5. A method according to claim 1 wherein the stack of sheet material is enclosed in a light-tight folder.

6. A method according to claim 5 wherein the stack of sheet material is a stack of light-sensitive material.

7. A pack of sheet material free from relative movement between the sheets which comprises a stack of sheet material which has on both the top and bottom faces of the stack an element which comprises a fiat base sheet of rigid material of length and width slightly smaller than a sheet of material and which has upstanding walls on two adjacent sides of the base sheet, said Walls being of less height than the stack, the four said upstanding side walls partially covering the four sides of the stack of sheet material, the two said elements being held in position on the stack by binding material such that flexion of said stack is prevented during transportation.

8. A pack according to claim 7 wherein the binding material comprises bands of polypropylene.

9. A pack according to claim 8 wherein the bands of polypropylene are joined by heat welding.

10. A pack according to claim 7 wherein the binding material is a sleeve of heat-shrunk material.

11. A pack according to claim 7 wherein the stack of sheet material is enclosed in a light-tight folder.

12. A pack according to claim 11 wherein the stack of sheet material is a stack of light-sensitive material.

References Cited UNITED STATES PATENTS 1,254,991 1/ 1918 Darst 229-6 1,654,225 12/ 1927 Tanner.

2,517,801 8/ 1950 Roush.

2,579,518 12/1951 Schaefer 22932 2,675,123 4/1954 Baird 206-65 3,043,487 7/1962 Fowle 206-62 3,185,298 5/1965 Verspecht 206-62 3,368,323 2/1968 Wood.

3,425,544 2/ 1969 Ayer et al. 206-4533 WILLIAM T. DIXSON, JR., Primary Examiner US. Cl. X.R.

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