EP0747758A1

EP0747758A1 - Container for lithographic sheets

Info

Publication number: EP0747758A1
Application number: EP95112799A
Authority: EP
Inventors: Donald J. Martin
Original assignee: Rock City Box Co Inc
Current assignee: Rock City Box Co Inc
Priority date: 1995-06-06
Filing date: 1995-08-15
Publication date: 1996-12-11

Abstract

A container for shipping and storing lithographic plates is made of corrugated sheet material, with side walls and end walls that are V-grooved and folded as tubular box walls with honeycomb filler bodies. The container can also be made of coated corrugated board, or can have a plastic moisture barrier laminated to the corrugated board. The container is placed directly into an automated plate setter, in which the container is tilted on one side and the plates are automatically withdrawn for use. At the end of preparation, the lid is replaced on the container and the container and unused lithographic plates are stored. The V-grooved box wall construction provides strength to support the weight of the lithographic plates. The container walls meet at stepped or zig-zag corners to prevent stray light from leaking in through the corners and fogging or exposing the lithographic plates.

Description

Background of the Invention

This invention relates to boxes for shipping and storing sheets of photosensitive material, and is more particularly concerned with boxes for shipping and storing photosensitive lithographic plates. The invention is more specifically directed to light-tight containers made of corrugated board, in which unexposed lithographic plates can be stored, and from which the plates can be fed automatically to a lithographic plate setter in a hands-off lithographic printing operation.
Lithographic plates of this type are employed in a computer-to-plate system, which includes a computer-to-plate imagesetter. Equipment of this type comprises a filmless system, preparing press-ready plates for the printing industry, and can print from digital files directly to lithographic plates. The finished plates are completed on the press floor, giving the press crew complete control of just-in-time preparation of the plates to reduce make-ready time and for shorter run lengths. Systems of this type are employed by publishers who rely on electronic processes to create their finished product.
The lithographic plates themselves are flat plates of aluminum, typically about 24 inches by 35 inches, and packed 50 -- 100 to a box. A fully loaded box of plates weighs about 35 -- 70 pounds (i.e., 16 - 32 Kg). The boxes are stored and shipped flat, but the box is tilted in use for automated withdrawal of the plates for exposure in the plate setter.
The boxes or containers are flat and rectangular. The plate setter machine automatically opens the box and withdraws the sheets as needed, one at a time. When finished, the machine automatically replaces the lid, and the partly filled box or container is removed and stored. The box has to be light-tight, and the walls of the box have to be strong enough to support the weight of the plates, e.g., about 35 -- 70 lbs. The boxes are shipped and stored flat, i.e., horizontal, but in use the box is pitched at about 70 degrees so the weight of the unused lithographic plates bears on one of the side walls. The box or container has to be made light-tight, so that stray light does not leak into the container and expose or fog the plates.
A number of corrugated containers and containers of other materials have been proposed for storing and shipping photographic or other light-sensitive sheets.
Mikulin U.S. Pat. No. 4,984,688 describes a packaging system for photographic film sheets. This system involves a container with inner tray elements. The inner tray elements are made of plastic, while the container proper is formed of corrugated board.
Laido U.S. Pat. No. 4,802,619 describes a box and lid system for storing heavy, flat items, and these can be photographic plates or X-ray film plates. The container has side and end walls that are folded at score lines to create a hollow wall of rectangular section. An end flap created in the side walls folds over and fits into the hollow space of the end walls.
Rulon U.S. Pat. No. 2,354,706 shows another box for packaging sheets of photographic film.
In each of these containers, the corrugated or fiber material is folded at score lines to form the container walls. This means that the material itself has to be of limited thickness. As a result, the boxes have a limited inherent strength, and cannot support great amounts of weight. Also in these patents, little attention has been paid to the problem of light leakage into the container at the corners where the side walls join the end walls. As a result of this, the plates must be wrapped and sealed in a light barrier material. However, the automatic plate setter cannot feed from a sealed barrier box or container, and so a container has been needed that is suitable for storage and handling of these lithographic sheets, and which could be used with an automatic plate setter. None of the containers described in the above-mentioned U.S. patents are suited to this application.
Further, lithographic plates are rather sensitive to moisture, and the container for them should prohibit moisture in the storage area from entering the container and contaminating the plates. However, none of the prior containers has addressed this problem.

Objects and Summary of the Invention

Accordingly, it is an object of this invention to provide a strong, light-tight container which avoids the drawbacks of the prior art, and which is both suitable for storing photosensitive lithographic plates and suitable for use in an automatic feed plate setter.
It is another object of the invention to provide a durable container of simple design and which can support the full weight of lithographic plates during shipment and storage, and which can be tilted on one side without crushing.
It is a further object to provide a container that can be made of a durable, high strength corrugated sheet material, in which a V-grooving technique defines the side and end walls.
It is yet another object to provide a container that will not allow moisture to enter into contact with the lithographic sheets or plates.
According to an object of this invention, a shipping or storage container is constructed for use with lithographic plates or similar photosensitive sheets. The container is formed of a heavyduty corrugated board or other sheet material of a predetermined thickness and in which a filler is sandwiched between an inner liner and an outer liner. A generally rectangular base panel is defined on the sheet material to form the floor or base of the container. A first end panel is formed unitary with the base panel at one end edge of the base panel. Similarly, there are a second end panel formed unitary with the base panel at an opposite end edge thereof, a first side panel unitary with said base panel at one side edge of the base panel, and a second side panel unitary with the base panel at an opposite side edge thereof. Four respective first V-grooves are cut in the sheet material through the inner liner and filler at the end edges and side edges of the base panel. Each of the end panels and each of the side panels has a series of three parallel V-grooves, i.e., second, third, and fourth V-grooves, cut through the inner liner and the filler and extending parallel to the associated first V-grooves. The end panels and the side panels also each have a free edge parallel to the V-grooves. Accordingly, the first and second V-grooves define between them an outer wall panel, the second and third V-grooves define an upper wall panel, the third and fourth V-grooves define an interior wall panel, and said fourth V-groove and the associated free edge define a base wall panel. Each of the V-grooves forms a ninety-degree bend such that the end panels and side panels form respective tubular box walls. In these box walls, the associated base wall panel extends the said interior wall panel to the outer wall panel parallel to the upper panel and lies adjacent the base wall. The tubular box walls meet at stepped corners so that the adjoining side and end walls define a zig-zag junction, and obstruct light leakage through the corners of the container. The tubular walls define a rectangular space within them, and a fill material, such as a corrugated honeycomb, is placed within each of the rectangular spaces. Preferably, the fill material comprises a honeycomb material having flutes oriented perpendicular to the plane of the base panel.
In a preferred mode, the outer wall panels of the first and second end panels have ends aligned with the side edges of the base panel, and the associated upper, interior, and base wall panels have square ends aligned with one another and offset a predetermined amount from the ends of the respective outer wall panels. Favorably, the predetermined amount of offset is substantially equal to the width of the upper wall panel of the adjoining side panel. When the end and side panels are folded on the V-grooves to form the tubular side and end walls, this construction forms the zig-zag or stepped corner joint, and avoids any straight line path for light leakage, Thus, this construction provides an advantage over a standard, mitered corner. The container will also comprise opaque tape affixed over the corners.
The container is provided with a cover formed of an upper rectangular flat sheet member dimensioned to reach to the outer wall panels of the box walls, and a lower rectangular sheet member attached thereto and dimensioned to reach between the interior wall panels of the box walls. This cover also avoids any straight line path for light leakage when the cover is taped or clamped in place.
The V-grooved corrugated container of this invention is of simple, economical construction and is sturdy and robust enough to stack horizontally for shipping, with sufficient wall strength to support the lithographic plates while tilted on one side within the plate setter. The light-tight container also maintains the lithographic plates free from exposure to stray light, without need for special foils and liners that can reduce the post-use recyclability of the container.
The above and many other objects, features and advantages of this invention will become apparent from the ensuing description of a preferred embodiment, which should be read in conjunction with the accompanying Drawing.

Brief Description of the Drawing

Fig. 1: is an assembly view of a container, pad, and lid according to one embodiment of the present invention.
Fig. 2: is a plan view of a corrugated blank from which the container of this embodiment is constructed.
Fig. 3: is an enlargement of one side wall panel of the corrugated blank of this embodiment, taken at 3-3 of Fig. 2,
Fig. 4: is a cross sectional view showing the box wall construction of this embodiment, taken at 4-4 of Fig. 1.
Fig. 5: shows details of a corner of the container of this embodiment.

Detailed Description of a Preferred Embodiment

With reference to the Drawing, and initially to Fig. 1, a container 10 for storing and shipping lithographic plates is constructed of a die-cut, V-grooved and folded sheet or blank of a corrugated paper material, or of another suitable sheet material. Here, the container 10 has a base or floor 12, with box-construction end walls 14 and box construction side walls 16. A rectangular pad 18 of corrugated material fits into the rectangular opening defined between the end walls 14 and between the side walls 16 and provides a cushion for the underside of the lithographic sheets or plates.
A lid 20 is made of two parts, i.e., an upper panel 22 and a lower panel 24 that is centrally secured, by an adhesive, to the lower side of the panel 22. The upper panel 22 has the same dimensions as the outer dimensions of the container 10, and the lower panel 24 is dimensioned to span the opening defined by the end walls 14 and the side walls 16.
The end walls 14 and side walls 16 meet to form stepped corners 26, i.e., non-mitered corners, that avoid any straight line path for stray light leakage through the corners of the container. The corners 26 are formed with at least one step, and could have several to create a zig-zag path for stray light.
Fig. 2 shows a die-cut blank 30 of corrugated material that is used to create the container 10. The blank 30 is V-grooved as shown to create a rectangular base panel 32 that is defined between a pair of side V-grooves 34 and a pair of end V-grooves 36. The blank 30 has opposed end wall portions 38 unitarily formed with the base panel 32 at first and second ends of the base panel and separated from it by the respective V-grooves 36. There are also opposed side wall portions 40 formed unitarily with the base panel 32 at first and second lateral sides thereof, and separated from it by the respective V-grooves 34. An enlargement of the blank 30, featuring one of the side wall portions 40, is shown in cross-section in Fig. 3.
On each of the side wall portions of the blank there is a series of parallel V- grooves 42, 44, and 46 between the associated V-groove 34 and a free edge 48, and parallel to them. The V- grooves 34 and 42 define between them an outer side wall panel 50, the V- grooves 42 and 44 define between them a top wall panel 52, the V- grooves 44 and 46 define between them an interior wall panel 54, and the V-groove 46 and associated free edge 48 define between them a base wall panel 56. As also shown in Fig. 3 a filler body 58 of a honeycomb corrugated material, and of rectangular cross section, is employed to fill the rectangular void defined by the four wall panels 50, 52, 54, and 56.
The blank itself is made of a corrugated sheet material 60, comprising an upper liner 62, a lower liner 64 and a corrugated filler 66. The V- grooves 34, 42, 44, and 46 are cut through the upper liner 62 and the filler 66 at a forty-five degree angle, leaving the lower liner 64 intact. The side wall portion 40 is folded at ninety-degrees at each of the V-grooves, forming a box wall around the honeycomb filler 58, as shown in cross section in Fig. 4.
Returning to Fig. 2, the end wall portions 38 are also provided with parallel V-grooves 142, 144, and 146 between the V-groove 36 and the associated free edge 148, to define an outer wall portion 150, a top wall portion 152, an interior wall portion 154, and a base wall portion 156. Here, the elements that have been described in respect to the side wall portions 40 are identified th similar reference numbers, but raised by 100. There is a honeycomb filler body also enclosed within the end walls 14, similar to that of the side walls 16.
As shown in Fig. 2, the outer wall portions 150 of the end wall portions 38 have square ends 158 that are aligned with the V-grooves 34. The remaining wall panels 152, 154, and 156 have aligned square ends 159 that are offset inwards from the ends 158 a predetermined amount, i.e., by the width of the box wall. This construction forms the stepped corner joint to be described shortly.
To form the box construction of the side walls 16, an adhesive is applied to the V- grooves 34, 42, 44, and 46 and to the upper liner 62 on the wall portions 50, 52, 54, and 56. Adhesive is also applied to the margin of the base panel 32 where the base wall panel 56 is to contact it. Then, the filler body 58 is placed on the wall portion 50, the wall portion is bent at 90 degrees at each of the V-grooves, and the wall panels are wrapped around the filler body 58. This results in the tubular box wall construction shown in cross section in Fig. 4. The base panel portion lies horizontal on the margin of the base panel 32, i.e., parallel to the upper wall panel 52, with the interior wall panel facing the inside of the container, and the outer wall panel facing outwards. Preferably, the filler body has its flutes oriented vertically, that is, perpendicular to the plane of the base panel 32.
The end walls 14 are similarly formed, and so the description thereof can be omitted here.
As mentioned above, the offsets in the end walls 14 results in a non-mitered, stepped corner construction that helps block stray light from entering the container. The ends of the side walls 16 meet the stepped-out or offset ends of the outer wall panels 150 of the end wall panels, and the ends of the end walls 14 abut the upper liner on the outer wall panels 50 of the side walls 16. This creates a zig-zag path 66 with sharp turns that any stray light would have to take to reach the interior of the container through the corner 26. In addition, an opaque tape 68 is applied over the corners, as shown in Fig. 5, and then additional opaque tape 70 is applied along the walls 14, 16 over the corners 26. In the latter positions, a short slit is cut at the corners, and the tape 70 is folded under the container 10 at the dash line shown in Fig, 5.
The lid 20 also provides a stepped path for blocking any light leakage when the container is closed.
The container 10 is intended to hold about fifty to one-hundred aluminum lithographic plates. For shipment or storage, these are supported on the pad 18 that rests on the base 12. A container fully loaded with one hundred plates typically weighs thirty-five to seventy pounds. Within the plate setter, the container is tilted onto one side edge, and so the side wall 16 has to be robust enough to support the thirty-five to seventy pounds of lithographic plates.
The V-grooved, box-wall construction of this embodiment permits the container to be constructed out of sheet material of one-quarter inch (¼") corrugated or of even greater thickness. The sheet material can be single wall, double wall, or triple wall material, if desired.
For shipping and storing, the containers can be bundled twenty-five deep on a pallet or skid, and then banded or shrink-wrapped in place on the skid.
Because the light-tight, rugged container can be constructed without foils or other nonrecyclable materials, post-use disposal does not present a problem for the user.
Most preferably, the container is constructed not to allow moisture into the area of the container where the plates are stored. This can be accomplished by using a specially coated corrugated board, a moisture barrier laminated to corrugated board, or a plastic corrugated board. Also, the container can employ an interior pre-formed plastic tray inside the corrugated lid, and a plastic tray liner below the lithographic sheets.
While this invention has been described in detail with reference to a preferred embodiment, it should be recognized that the invention is not limited to that embodiment. Rather, many modifications and variations would present themselves to persons skilled in the art without departure from the scope and spirit of the invention, as defined in the appended claims.

Claims

A shipping or storage container for photosensitive sheets, the container being formed of a sheet material of a predetermined thickness and in which a filler is sandwiched between an inner liner and an outer liner; comprising a generally rectangular base panel, a first end panel unitary with the base panel at one end edge of the base panel, a second end panel unitary with the base panel at an opposite end edge thereof, a first side panel unitary with said base panel at one side edge of the base panel, and a second side panel unitary with the base panel at an opposite side edge thereof, with respective first V-grooves cut in said sheet material through the inner liner and filler at each of said end edges and said side edges of the base panel, and with each of said end panels and said side panels having a respective plurality of parallel V-grooves cut therein through said inner liner and said filler extending parallel to the associated first V-grooves, and each having a free edge parallel to said V-grooves, such that the V-grooves and said free edge define therebetween a plurality of parallel, successive wall panels; each said V-groove forming a ninety-degree bend such that said end panels and side panels form respective tubular box walls; and wherein said tubular box walls meet at stepped corners such that the adjoining side and end walls define a zig-zag junction to obstruct light leakage through the corners of the container.
The container of claim 1, wherein the wall panels of each of said tubular walls define a rectangular space therewithin; and comprising a body of a fill material within each of the rectangular spaces.
The container of claim 2, wherein the body comprises a honeycomb material having flutes oriented perpendicular to the plane of the base panel.
The container of claim 1, wherein each said plurality of parallel V-grooves includes a second, a third, and a fourth V-groove, such that the first and second V-grooves define therebetween an outer wall panel, the second and third V-grooves define therebetween an upper wall panel, the third and fourth V-grooves define therebetween an interior wall panel, and the fourth V-groove and the associated free edge define therebetween a base wall panel, in which the associated base wall panel extends from the interior wall panel to said outer wall panel parallel to said upper wall panel and lies adjacent said base panel.
The container of claim 4, wherein the outer wall panels of said first and second end panels have ends aligned with the side edges of the base panel, and the associated upper, interior, and base wall panels have square ends aligned with one another and offset a predetermined amount from the ends of the respective outer wall panels.
The container of claim 5, wherein the predetermined amount of offset is substantially equal to the width of the upper wall panel of the adjoining side panel.
The container of claim 4, further comprising a cover formed of an upper rectangular flat sheet member dimensioned to reach to the outer wall panels of the box walls, and a lower rectangular sheet member attached thereto and dimensioned to reach between the interior wall panels of said box walls.
The container of claim 1, further comprising an opaque tape affixed over said corners.