US3901431A

US3901431A - Cylindrical leak-resistant, thermoplastic coated, paperboard container

Info

Publication number: US3901431A
Application number: US498571A
Authority: US
Inventors: Richard Warren Carlson
Original assignee: International Paper Co
Current assignee: International Paper Co
Priority date: 1974-08-19
Filing date: 1974-08-19
Publication date: 1975-08-26
Anticipated expiration: 1992-08-26
Also published as: CA999273A

Abstract

A generally cylindrical, thermoplastic coated, paperboard container having a leak-resistant, flat-bottomed structure, formed from a side seamed, thermoplastic coated paperboard blank having a plurality of alternating tapered fingers and angular fingers on one of its edges, the tapered fingers and angular fingers being separated by triangular gusset panels foldably connected to the fingers by score lines in the blank, the angular fingers being adapted to abut on the bottom, exterior surface of the container with a flat profile and the tapered fingers being adapted to overlap on the bottom, interior surface of the container to seal the bottom of the container.

Description

United States Patent 1 1 Carlson Aug. 26, 1975 [75] Inventor: Richard Warren Carlson, Warwick,

[73] Assignee: International Paper Company, New

York, NY.

22 Filed: Aug. 19, 1974 21 Appl. NO.2 498,571

2.09l,29l 8/l937 Ringler 229/41 C UX 3,768,720 10/1973 Bundy 229/4l C X 3,773,246 1 [/1973 Tyrseck 229/41 C X Primary E.\'aminerDavis T. Moorhead Attorney, Agent, orFirm-Ronald A. Schapira [57] f ABSTRACT A generally cylindrical, thermoplastic coated, paperboard container having a leak-resistant, flat-bottomed structure, formed from a side seamed, thermoplastic coated paperboard blank having a plurality of alternating tapered fingers and angular fingers on one of its edges, the tapered fingers and angular fingers being separated by triangular gusset panels foldably connected to the fingers by score lines in the blank, the angular fingers being adapted to abut on the bottom, exterior surface of the container with a flat profile and the tapered fingers being adapted to overlap on the bottom, interior surface of the container to seal the bottom of the container.

16 Claims, 7 Drawing Figures CYLINDRICAL LEAK-RESISTANT, THERMOPLASTIC COATED, PAPERBOARD CONTAINER BACKGROUND OF THE INVENTION This invention relates to generally cylindrical, coated, paperboard containers for a liquid, paste, or frozen material. This invention is particularly concerned with a bottom construction for such containers having a substantially flat profile, whereby the container will stand stably on flat surfaces without rocking or tipping over. This invention is also particularly concerned with providing such a bottom construction which will be leak-resistant, so that the contents of the container will not leak out of the container or seep into the paperboard base stock, thereby weakening the paperboard and destroying the integrity of the container. This invention is further particularly concerned with providing such a container for relatively heavy loads, on the order of about 25 to 50 pounds.

Generally cylindrical, coated paperboard containers having bottom constructions formed from abutting or overlapping fingers are well known in the art. The bottom constructions in such containers have not, however, been entirely satisfactory for providing a leakresistant, flat-bottomed container for relatively heavy loads of liquids, pastes and frozen materials. One reason for this has been that such bottom constructions have tended to be weak and prone to leak. This situation has required that additional sealant members and sealant materials be used to supplement the overlapping or abutting fingers in the bottom of the containers. See, for example, US. Pat. Nos. 1,866,496, 1,867,914, 2,160,488, and 2,097,893. Another reason has been that such bottom constructions have had to be recessed in order to assure that the container is stable when placed on a flat surface, the overlapping fingers tending to make the bottom constructions uneven and hence unstable. This has made such containers undesirable for use with relatively heavy loads. See, for example, US. Pat. Nos. 1,362,090, 1,867,914, 1,904,365, 1,443,280 and 2,097,893. Still another reason has been that the bottom constructions have been quite prone to fail due to wicking of a fluid product into exposed portions of the paperboard base stock. Bottom constructions formed from a plurality of over-lapping paperboard fingers have heretofore invariably contained relatively large areas of exposed paperboard at the edges of the fingers. These exposed areas of paperboard have generally been left unprotected by the surface coatings applied to the paperboard. Due to the problem of wicking, the likelihood of failure of prior, cylindrical containers has been quite high, particularly when such containers have been utilized for storing liquids, pastes or frozen materials over a relatively long period of time.

SUMMARY OF THE INVENTION In accordance with this invention, in a thermoplastic coated, paperboard container provided with a generally cylindrical side wall, an improved bottom construction is provided which comprises a plurality of abutting, angular fingers on the bottom, exterior surface of the container; and a plurality of overlapping, tapered fingers on the bottom, interior surface of the container; each of said angular fingers and said tapered fingers being separated by and foldably connected to a triangular gusset panel; and said fingers being foldably connected to the cylindrical side wall of the container. In accordance with a second aspect of this invention, a thermoplastic coated, paperboard blank, which can be formed into the generally cylindrical, flat-bottomed container of this application, includes a substantially rectangular panel; a plurality of angular fingers; and a plurality of tapered fingers; each of said angular fingers and said tapered fingers being separated by and foldably connected to a triangular gusset panel; and each of said fingers being foldably connected to one edge of said rectangular panel.

By this invention, a bottom construction for a generally cylindrical, flat-bottomed, leak-resistant container is provided which can be expeditiously formed by conventional mass production techniques and which is adapted for storing relatively large quantities of liquids, pastes and frozen materials over a relatively long period of time.

DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of a blank which can be formed into the cylindrical, leak-resistant, thermoplastic coated, paperboard container of this invention.

FIG. 2 is a fragmentary, side elevational view of a cylinder, formed by side-seaming the blank of FIG. 1.

FIG. 3 is a fragmentary, side elevational view of the cylinder of FIG; 2, the lower portions being urged inwardly of the cylinder to form the bottom construction of this invention.

FIG. 4 is a side elevational view showing the forming and sealing of the bottom of the cylinder of FIG. 3 to form the container of this invention.

FIG. 5 is a fragmentary, perspective view of the bottom exterior of the container formed from the blank of FIG. 1.

FIG. 6 is a sectional view, taken along line 66 in FIG. 5, showing the bottom interior of the container formed from the blank of FIG. 1.

FIG. 7 is a fragmentary, sectional view, taken along line 7-7 inFIG 6, of the bottom construction of the container of FIGS. 5 and 6.

DETAILED DESCRIPTION OF THE INVENTION This application relates to a generally cylindrical, leak-resistant, thermoplastic coated, paperboard container formed from a blank, generally 10, shown in FIG. 1. The blank 10 includes a substantially rectangular panel 1 La plurality of angular fingers 12, and a plurality of tapered'fingers 13. Each of the angular fingers 12 and the tapered fingers 13 is separated by and foldably connected "to a triangular gusset panel 14. Each of the angular fingers l2 and tapered fingers 13 is also foldably connected to a first edge 11a of the rectangular panel 1 l.

The paperboard blank 10 can be formed from any conventional, thermoplastic-coated, paperboard base stock. For example, the blank 10 can be formed from a paperboard base stock coated on one or both surfaces with a polyolefin, such as polyethylene or polypropylene; saran, i.e., polyvinylidine chloride; an ethyleneacrylic acid copolymer; or a Surlyn ionic copolymer. The blank 10 is preferably coated on both surfaces with a polyolefin, particularly low density polyethylene.

In the blank 10, the thickness of the thermoplastic coating is not critical, and any thickness greater than about 0.0005 inches, sufficient to enable a plastic to plastic bond to be formed between the thermoplastic coatings on the surfaces of the blank 10, can be suitably utilized. Preferably, the thickness of the thermoplastic coatings on the surfaces of the blank is from about 0.0010 inches to about 0.0020 inches, particularly a thickness between about 0.0010 inches and 0.0015 inches.

Also in the blank 10, any paperboard base stock conventionally utilized in coated, paperboard containers can be utilized. Preferably, the paperboard base stock has a basis weight of from about 150 pounds to about 400 pounds per 3,000 sq. ft. and a thickness of about 0.010 inches to about 0.030 inches. It is especially preferred that a paperboard base stock of about 325 to about 340 pounds per 3,000 sq. ft. and of about 0.024 to about 0.028 inches thickness be utilized, particularly a paperboard base stock having a basis weight of about 333 pounds per 3,000 sq. ft. and a thickness of about 0.026 inches.

In the blank 10, the angular fingers 12 and the tapered fingers 13 are foldably connected to the triangular gusset panels 14 and to the rectangular panel 11 along a plurality of score lines, generally 15, in the blank 10. The score lines 15 define the first rectangular panel edge 11a, as well as the foldably connected, abutting edges of the angular fingers 12, the tapered fingers 13 and the triangular gusset panels 14. The size and configuration of the individual score lines 15 in the blank 10 are not critical, and any conventional dimensions and configurations for score lines in blanks for paperboard containers can be utilized. Preferably, the score lines 15 are formed to a depth of about 0.006 to about 0.0085 inches in the blank 10.

In the blank 10, the exact size and configuration of the substantially rectangular panel 11, the angular fingers 12, the tapered fingers 13 and the triangular gusset panels 14 are also not critical. However, as shown in the drawings and as will be discussed hereinafter, the elements of the blank 10 preferably have a size and configuration adapted to cooperatively provide a container having: a generally cylindrical side wall formed from the generally rectangular panel 11; a bottom, exterior surface having a fiat profile, formed by abutting, angular fingers 12; and a bottom, interior surface which is sealed and reinforced by overlapping, tapered fingers 13 and by triangular gusset panels 14, which are foldably attached to and horizontally aligned between the angular fingers l2 and the tapered fingers 13.

Preferably, the first rectangular panel edge 11a and the opposite edge of the rectangular panel 11, i.e. the second rectangular panel edge llb describe concentric curves, rather than parallel straight lines, and the radius of curvature of the first edge 11a is somewhat smaller than the radius of curavature of the second edge 11b. This results in the side wall of the preferred container of this invention being tapered inwardly from its top to its bottom, rather than being vertical. The tapered side wall of the resulting container constitutes a means for nesting a plurality of such containers.

In the blank 10, each of the angular fingers l2 preferably defines a pentagon. As seen in FIG. 1, a first side or edge 12a of the pentagon abuts the first rectangular panel edge 11a and each of the second and third sides or

edges

12b and 120 of the pentagon, adjacent the first pentagon edge 12a, abuts a first side or edge 14a of a triangular gusset panel 14. It is particularly preferred that the remaining two sides or edges 12d and l2e of each pentagonal, angular finger 12 be of equal length and that the two remaining edges 12d and l2e include an angle such that the sum of the angles included by the two remaining edges 12d and 122 in all the angular fingers totals 360 In this way, all the pentagonal angular fingers 12 will abut on the exterior surface of the bottom construction formed in accordance with this invention. The number of angular fingers of pentagonal configuration is not critical, and any number greater than three can be suitably utiilized. However it is preferred that between five and eight angular fingers, especially six angular fingers, be utilized. It is also preferred that all of the angles included between the two remaining edges 12d and 12:: of the pentagonal, tapered fingers 12 be the same, e.g., 60 when six angular fingers 12 are utilized. so that all the angular fingers will abut at the center of the resulting container.

In the blank 10, each of the tapered fingers 13 preferably defines a figure of at least four edges, such as a square, a pentagon, a hexagon, a truncated ellipse, etc., a hexagon being particularly preferred. As seen in FIG. 1, a first side or edge 13a of the hexagon abuts the first rectangular panel edge 11a, and each of the second and third sides or

edges

13b and 13c of the hexagon, adjacent the first tapered finger edge 13a, abuts a second side or edge 14b of a triangular gusset panel 14. It is particularly preferred that the remaining edge or

edges

13d, 13e, 13f, etc. of the tapered fingers l3 define a sufficiently large area so that a portion of the tapered fingers 13 will overlap on the interior surface of the container bottom construction, formed in accordance with this invention. In this regard, the extent to which the tapered fingers overlap in the formed container is not critical. However, as shown in FIG. 1, it is preferred that the area of the tapered fingers 13 be such that only a minor portion of each tapered finger is in overlapping relationship with other tapered fingers. As also shown in FIG. 1, it is particularly preferred that one of the tapered fingers 13' be longer than the other tapered fingers, as measured from its first edge 130, so that the one, longer tapered finger will overlie the center of the bottom construction in the formed container, besides being overlapped or overlapping other, tapered fingers 13.

As shown in FIG. 1, in the blank 10, the triangular gusset panels 14 preferably have the same size and configuration to assure that the inside and outside of the bottom construction of the formed container is as flat as possible. It is also preferred that the angle included between the first and second triangular gusset panel edges 14a and 14b be the same, i.e., equal to 360 divided by the number of triangular gusset panels 14. For example, when twelve gusset panels are utilized, the angle between the first and second gusset panel edges 14a and 14b in each triangular gusset panel 14 should be 30.

The blank 10 further includes a substantially rectangular edge portion 16 foldably connected along the score line 15 to the first rectangular panel edge 1 1a and to a second triangular gusset panel edge 14b. The edge portion 16 is located adjacent a first edge 10a of the blank 10. A surface of the rectangular edge portion 16 is adapted to be bonded, e.g., heat-sealed or adhesively secured, to a surface of the tapered finger 13 adjacent an opposite edge 10b of the blank 10.

As a first step in forming'the generally cylindrical, leak-resistant paperboard container of this invention, the blank 10 is side seamed along the entire length of the first blank edge a. In side seaming the blank 10,

a surface of the edge portion 16 is bonded to a surface of the tapered finger 13 adjacent the opposite blank edge 10b, and a surface of the rectangular panel 11 adjacent the first blank edge 10a is bonded to a surface of the rectangular panel 11 adjacent the oppositeblank edge 10b. A cylinder 17, shown in FIG. 2, is formed by this step. The surfaces of the blank 10 can be bonded together to form the cylinderl7 by any conventional method, as for example, by heatsealing or adhesive bonding. Preferably, the surfaces of the blank 10 are bonded together by forming a conventional, heatsealed, side seam bond between the thermoplastic coatings on the surfaces of the paperboard base stock. As shown in FIG. 2, the cylinder 17 is preferably formed faces of the angular fingers 12. At the same time, the

upper surfaces of the angular fingers 12 are heatsealingly pressed against the lower, overlying surfaces of the triangular gusset panels 14.

The container, generally 23, formed by the use ofthe pressing means 18 and the irons l9 and 20 is shown in FIGS. 5, 6 and 7.

from the blank 10 by bonding a surface of the rectanguopposite blank edge l0band bonding a surface of the rectangular panel 1 1, adjacent the first blank edge 10a, to an underlying surface of the rectangular panel 11, adjacent the opposite blank edge 10b.

Schematically shown in FIG. 3 is the second step in forming the container of this invention. The angular fingers 12, the tapered fingers 13 and the triangular gusset panels 14 are urged upward and radially inward of the cylinder 17 by a means 18, pressing simultaneously upon these fingers and gusset panels. As urged inwardly and upwardly by the pressing means 18, the angular and

tapered fingers

12 and 13 fold about the score line between these fingers and the first rectangular panel edge 1 la. In this step, the angular and tapered fingers and the triangular gusset panels also fold about the score lines separating them. As folded, the tapered fingers l3 overlie the angular fingers l2, and the triangular gusset panels 14 lie between the angular fingers 12 and the tapered fingers 13, the

fingers

12 and 13 and gusset panels 14 preferably being positioned substantially about the plane defined by the first rectangular panel edge 11a. A preferred means 18 for urging the fingers and

gusset panels

12, 13 and 14 radially inward and upward, whereby the tapered fingers 13 properly overlie the triangular gusset panels 14 and the angular fingers 12 about the plane of the first rectangular panel edge 11a, is a means pressing only the tapered fingers l3 simultaneously inward and upward.

The last step in forming the container of this invention is schematically shown in FIG. 4. After the angular fingers l2, tapered fingers l3 and triangular gusset panels 14 have been urged radially inward of the cylinder 17, the

fingers

12 and 13 and gusset panels 14 are bonded together. It is preferred that the fingers and gusset panels be bonded together by forming intimate, plastic to plastic bonds between the thermoplastic coatings on their surfaces. Such plastic to plastic bonds are preferably formed by heat-sealing the fingers and

gusset panels

12, 13 and 14 together, preferably by urging heated irons l9 and against the fingers l2 and 13 and the gusset panels 14. One of the irons 19 heatsealingly presses downwardly, through the cylinder 17, against the upper surface of the fingers and gusset panels. At the same time, the other iron 20 heat-sealingly presses upwardly against the lower surfaces of the fingers and gusset panels. For this purpose, the irons l9 and 20 preferably have substantially flat, heated faces 21 and 22, with an area conforming to the bottom area of the cylinder 17. By this step, all of the lower surfaces As seen in FIG. 5, the container 23 includes a generally cylindrical side wall 24 and a bottom construction, generally 25. The bottom 25 comprises a plurality of abutting, angular fingers 12 on the exterior surface of the container 23, foldably connected to the cylindrical side wall 24. As also seen in FIG. 5, the edges 12d and 12e of adjacent, pentagonal angular fingers 12 abut and intersect at about the center 26 of the bottom 25.

As seen in FIG. 6, the bottom 25 of the container 23 also includes a plurality of overlapping, tapered fingers 13 on the interior surface of the container 23, foldably connected to the cylindrical side wall 24 and overlying the angular fingers 12. As also seen from FIG. 6, minor portions of each of the tapered fingers l3 overlap. Preferably, one of the tapered fingers 13' is longer than the others and overlies the center 26 of the container bottom 25. The other tapered fingers l3 overlie or underlie portions of the one, longest tapered finger 13'. It is particularly preferred that the one, longest tapered finger l3 overlie the center 26 of the bottom 25 and that the other tapered fingers 13 merely surround the center As seen in FIG. 7, the bottom 25 further includes a plurality of horizontally aligned, triangular gusset panels 14, disposed between the'overlapping, tapered fin- 'gers 13 and the abutting, angular fingers 12. As also preferred that the one tapered finger 13' be pressed radially inward and upward by the means 18 either before the

other fingers

12 and 13 or more rapidly than the other fingers. Preferably, the longest tapered finger 13' is also provided with a dab of hot melt adhesive on a portion of its surface overlying the center 26 of the bottom construction 25. By providing the hot melt adhesive, an additional means is provided for expeditiously assuring that leaking and/or wicking does not occur at the center of the bottom 25 of the container 23. For this purpose, any conventional hot melt adhesive can be utilized.

Because the bottom construction 25 of this application is formed from a unitary blank 10, having no cuts between the

fingers

12 and 13 and the

panels

11 and 14, this bottom construction provides superior leakresistance with reduced potential for failing due to leaking ot wicking, even during prolonged exposure to liquid, paste or frozen materials. Furthermore, because, the plastic to plastic bonds of the bottom contruction 25 are formed from both bottom and top, preferably by heat-sealing, the thermoplastic coating tends to flow and to fill-in spaces between the

fingers

12 and 13 and the gusset panels 14 through which leaks might occur and also to cover any exposed paperboard edge through which wicking might occur.

The container 23 formed in accordance with this invention from the blank can be filled with a wide variety of liqui, paste and frozen materials. The open end of the container can be closed with a conventional, plastic or metal lid.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

1 claim:

1. In a thermoplastic coated, paperboard container, provided with a generally cylindrical side wall, an improved bottom construction, comprising: a plurality of abutting, angular fingers on the bottom, exterior surface of the container; a plurality of overlapping, tapered fingers on the bottom, interior surface of the container; each of said angular fingers and said tapered fingers being separated by a triangular gusset panel, foldably connected to and horizontally aligned between said angular fingers and tapered fingers; and said angular fingers and tapered fingers being foldably connected to said side wall.

2. The container of claim 1 wherein each of said angular fingers defines a pentagon.

3. The container of claim 2 wherein two, adjacent sides of each of said pentagonal, angular fingers are of equal length and include an angle such that the sum of the angles included by said two, adjacent sides in each pentagonal, angular finger totals 360.

4. The container of claim 3 wherein said angle included between said two, equal adjacent sides in each of said pentagonal, angular fingers is equal.

5. The container of claim 4 wherein said container includes six pentagonal, angular fingers and said included angle in each finger is 6. The container of claim 2 wherein each of said tapered fingers defines a hexagon.

7. The container of claim 1 wherein one of said tapered fingers is longer than the others.

8. The container of claim 7 wherein said one, longer tapered finger is the only tapered finger overlying the center of said bottom construction.

9. The container of claim 7 wherein said one longer tapered finger overlies a portion of all the other tapered fingers.

10. The container of claim 1 wherein each of said triangular gusset panels includes at least one angle that is the same.

11. A blank for a generally cylindrical, paperboard container comprising:

a substantially rectangular panel, and

a plurality of alternating tapered fingers and angular fingers, foldably connected to an edge of said rectangular panel;

each of said angular fingers and said tapered fingers being separated by and foldably connected to a triangular gusset panel.

12. The blank of claim 1 1 wherein each of said angular fingers defines a pentagon.

13. The blank of claim 12 wherein two adjacent sides of each of said pentagonal angular fingers are of equal length and include an angle such that the sum of the angles included by said two, adjacent sides in each pentagonal, angular finger totals 360.

14. The blank of claim 13 wherein said angle included between said two, equal adjacent sides in each of said pentagonal, angular fingers is equal.

15. The blank of claim 12 wherein each of said tapered fingers defines a hexagon.

16. The blank of claim 10 wherein one of said tapered fingers is longer than the others.

Claims

3. The container of claim 2 wherein two, adjacent sides of each of said pentagonal, angular fingers are of equal length and include an angle such that the sum of the angles included by said two, adjacent sides in each pentagonal, angular finger totals 360*.

5. The container of claim 4 wherein said container includes six pentagonal, angular fingers and said included angle in each finger is 60*.

6. The container of claim 2 wherein each of said tapered fingers defines a hexagon.

11. A blank for a generally cylindrical, paperboard container comprising: a substantially rectangular panel, and a plurality of alternating tapered fingers and angular fingers, foldably connected to an edge of said rectangular panel; each of said angular fingers and said tapered fingers being separated by and foldably connected to a triangular gusset panel.

12. The blank of claim 11 wherein each of said angular fingers defines a pentagon.

13. The blank of claim 12 wherein two adjacent sides of each of said pentagonal angular fingers are of equal length and include an angle such that the sum of the angles included by said two, adjacent sides in each pentagonal, angular finger totals 360*.