EP0293527B1

EP0293527B1 - Tubular package and end cap forming component of same

Info

Publication number: EP0293527B1
Application number: EP19870305007
Authority: EP
Inventors: Lazlo Vajtay; Stephen M. Vajtay
Original assignee: Slm Manufacturing Corp
Current assignee: Slm Manufacturing Corp
Priority date: 1987-06-05
Filing date: 1987-06-05
Publication date: 1991-12-18
Also published as: DE3775393D1; EP0293527A1

Description

This invention relates to the forming of tubular containers or packages by axially inserting end caps as locking closures within the ends thereof, and more particularly to a container or package in which the end caps are formed of a similar, but heavier gauge, sheet material to that forming the container or package tube.
US-A-3,986,659 and US-A-3,913,774 disclose a tubular package in which a tube having flexible sidewalls, and normally formed of a thermo-plastic material approximately 0.005 to 0.02 inches (0.13 to 0.51 mm) in thickness, is held to a preformed or desired shape, as for instance a polygon, by rigid end caps. In the past, the rigid end caps have been coupled to the ends of the tube, i.e., to the flexible sides thereof, by use of adhesives, tape, staples and other fasteners. In the above-mentioned patents, a flexible thermoplastic material such as polyvinyl chloride (PVC), oriented poly-styrene (OPS), or other flexible semi-rigid sheet material forms the basic stock material for the sides of the container or package. The sheets may be pre-extruded, extruded or calendered to a thickness of approximately 0.005 to 0.02 inches (0.13 to 0.15 mm) and adhesively joined along a longitudinal seam to form a tube. Additionally, the sheets or tubes may be creased along a predetermined number of edges to form a container with a polygonal cross-section, such as rectangle. The resultant, creased tubular stock member may be then cut into desired lengths, depending upon the size of the container to be fabricated, and perforations punched near the ends for permitting mechanical interlocking between end caps borne thereby and the ends of the container or package tube.
The end caps employed in the structures of the above-mentioned patents are formed of a plastic material as by moulding to create rigid end members, providing strength and rigidity to the entire container. The dimensions and shape of the end caps conform to the dimensions and shapes of the flexible sides of the tube. The end caps include a base portion substantially forming an end cover for the container tube and sidewalls. The end caps also have engaging means for interlocking with the perforations within the two flexible sides, i.e., projections extending outwardly of the sidewalls to achieve a positive mechanical lock for holding the end caps to the container or package.
As such, the package or container of the patents referred to above is uniquely assembleable by either hand or machine, since the end cap locks to the tube by mere insertion without the need for adhesives, tapes, staples or other fasteners and without any secondary operation. Further, during the assembly process, the perforations and the projecting, engaging means are virtually self-aligning, completing the package or container when the end cap engaging means interlocks with the perforations.
While the known tubular packages or containers are sufficiently rigid, and permit the ready completion of the package by manual or machine projection of an end cap within the open end of the tube proper, with the end caps being automatically locked to the ends of the tube to achieve a relatively rigid container or package, the requirement to mould the end cap and the mass of material needed for the same, adds considerably to the overall costs of the container or package thus formed.
It is, therefore, a primary object of the present invention to provide an improved, low cost end cap for a tubular container which is formed from identical or similar plastic sheet material as the tube proper of the container or package.
It is a further object of the present invention to provide a low cost end cap for a tubular container or package which automatically locks upon being axially insertable into the end of the container or package tube, and which may be severed from a prefolded flexible semirigid strip of thermo-plastic material such that end caps of differing lengths may be formed from such basic stock material by simple severing the same transversely to required end cap length.
In one aspect, the invention provides a tubular package comprising: an open ended, flexible plastic sheet material tube of rectangular cross-section including laterally opposed sidewalls and longitudinally opposed end walls; and an end cap carried by said tube at an open end thereof closing off said open end; which package is characterised in that: said end cap comprises a folded, flexible, semi-rigid plastic sheet of a heavier gauge than that of said tube and including a rectangular central portion; said end cap central portion is of rectangular configuraiton corresponding to said tube, having a length generally equal to the longitudinal distance between said end walls of said tube and a width equal to the lateral distance between said tube sidewalls; said end cap central portion has at opposite sides, double folded flat sheet portions integral with said central portion and forming inner sidewalls at right angles to the central portion and outer sidewalls folded back towards the central portion; said inner and outer sidewalls have ends thereof extending generally parallel to each other and are joined by a crease defining a double layer slot generally equal to the thickness of said plastic sheet material tube sidewall, said end cap central portion being positioned internally of said tube with said tube sidewalls slidably inserted within said slot; said end walls of said flexible plastic tube adjacent said one open end carrying said end cap include aligned, coplanar perforations, respectively; and said end cap central portion includes integral tabs sized to the perforations, projecting outwardly of the ends of the end cap and received by respective coplanar perforations of said tube, such that the end cap automatically locks to the end of the flexible plastic material tube, the fitted engagement between the tube sidewalls and the double layer slot defining end cap sidewalls maintains the tabs within the perforations of the flexible tube end walls and the tab and perforation couplings maintain the tube sidewalls between said opposed folded end cap sidewalls to create a relatively stable end cap closed package at low cost.
In another aspect, the invention provides an end cap for a tubular package for closing off an end of a flexible plastic sheet material tube of rectangular cross-section, said tube including laterally spaced sidewalls and longitudinally spaced end walls characterised in that: said end cap is constituted by a folded, flexible, semi-rigid plastic sheet of heavier gauge plastic sheet material than that of said tube and including a rectangular central portion of a length corresponding to the distance between said tube end walls; said central portion is of a width approximately equal to the laterial distance between sidewalls of said tube; said end cap further includes double folded integral opposite sides forming double layer flat sidewalls perpendicular to the plane of the central portion with said end cap folded sidewalls joined by a crease remote from said central portion and forming a narrow slot between said folded end cap sidewalls, with said slot having a size of the order of the thickness of the plastic tube sheet material, said crease functioning to seat a respective sidewalls of said tube when the sidewalls are slidably inserted within said double layer sidewalls of said end cap with said end cap central portion closing off the end of said tube; said tube includes perforations within the respective end walls of said tube adjacent an axial open end thereof, said perforations being coplanar and aligned with each other; and said end cap sheet central portion includes integral tabs projecting outwardly of said sheet central portion away from each other, being sized to the perforations for being received thereby to mechanically lock the end cap to the tube such tha the end cap automatically locks to the end of the tube and maintain a fitted engagement between the tube sidewalls and the double layer sidewalls of the end cap and the fitted engagement of said tube sidewalls within the slot defined by said end cap sidewalls to maintain said tabs within said perforations the engagement between the tabs and the perforations and to create a relatively stable end cap closed package at low cost.
In order that the invention may be more readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawing, in which:

Figure 1 is an exploded, perspective view of a package or container forming a preferred embodiment of the present invention;
Figure 2 is a perspective view of a portion of the package or container of Figure 1 with an end cap coupled to the package tube; and
Figure 3 is a perspective view of a portion of alternative form of an end cap forming a further embodiment of the invention.

Referring to Figure 1, a container or package indicated generally at 10 comprises three components, namely a central tubular section or central tube indicated generally at 12 and a pair of end caps 14 at the top and bottom of the tube 12, the end caps being of identical form, but inverted one relative to the other. Unlike the patents referred to above, both tube 12 and end caps 14 are formed of thin plastic sheet material such as polyvinyl chloride (PVC). Further, the thin, flexible, plastic sheet material forming the container or package tube 12 may be thinner than that forming the end caps 14.
Tube 12 is rectangular, having laterally opposed sidewalls 16, 18 and longitudinally opposed end walls 20, 22. The tube 12 may be cut from preformed rectangular tubular stock material by taking a flexible plastic sheet and bending it at right-angles to form four corners as at 21 and overlapping the edge portions thereof to form a seam as at 23. The overlapped edges of the sheet forming the tube stock material may be joined or bonded by heat sealing, by adhesive application or the like to form seam 23.
Unlike the patents referred to above, in the present invention there are no moulded rigid end caps or plugs nor are end caps 14 significantly heavier than the tubes 12 to which they are joined. It should be noted that longitudinally opposed, aligned, coplanar perforations 28, 30 are provided within the longitudinally opposed end walls 20, 22 of tube 12 adjacent the open ends thereof. In this respect, tube 12 has its tope open at 24, and its bottom open at 26.
The description to this point is essentially identical to the description given to tube 12 in U.S. Patent 3,986,659. While the tube 12 is shown as being square in transverse cross-section in Patent 3,986,659, the tube 12 in the illustrated embodiment of the present invention is essentially oblong with the sidewalls 16 and 18 being substantially longer than the width of end walls 20, 22.
The end caps 14 are identical and a detailed description of the lower end cap 14 will suffice for both end caps. Each end cap 14 is formed with a rectangular base or central portion 34 which has the same length and width corresponding as the length and width of the interior of tube 22 so that base 34 closely fits to the interior of the tube with the base or central portion 34 filling the tube top and bottom openings 24, 26 when end caps 14 are applied thereto to close off the open ends of tube 22. The end caps 14 are formed of flexible, semi-rigid thermo-plastic sheet material of a guage which is preferably somewhat heavier than the gauge of the sheet material forming tube 12. Such sheet material for tube 12 and caps 14 may be similarly transparent or translucent, although the sheet material may be opaque if desired.
In similar fashion to the formation of tube 12, there may be initially formed from a plastic sheet, a generally U-shaped or channel form stock material strip of folded plastic sheet material from which end caps of various lengths are severed. In this respect, it is necessary to bend the sheet longitudinally along both sides of the end cap center portion 34, first at right angles to form a vertical inner sidewall, as at 36, and then at or in slight excess of 180°, forming reverse fold at crease 37 to create a vertical or near vertical, outer sidewall 38 ending at outer edges at 42, 44, respectively. Figure 3 depicts an alternative form of end cap 14' with the bend or fold at crease 37 being in excess of 180°. In this embodiment, like elements bear like numerical designations. The plastic sheet material or equivalent plastic sheet material has a memory and resists bending. Bending is achieved by localized heating of the end cap plastic sheet material along parallel lines to soften the material at the desired fold or bend lines, then bending or folding the material and subsequently cooling after bending or folding so that the initial memory is eliminated at the localized lines, and a new memory created at the fold or crease lines. Thus, after folding, and cooling, the end caps resist deformation. Further, by forming a fold at a slight excess to 180° at crease 37, as in Figure 3, the outer edges 42, 44 of the outer sidewall 38 contact the inner sidewalls 36 to close off the slots 40 formed thereby adjacent the outer edges 42, 44 of the end cap sidewalls 38. Slots 40 are at least narrower than the thickness of the tube sidewalls 16, 18. Thus, double layers of the sheet material form vertical slots 40 therebetween. Slots 40 function to slidably, and in one case, frictionally receive the laterally spaced sidewalls 16, 18 of tube 12 when the end caps 14 are assembled to the tube 12. Crease 37 of the end cap is adapted to seat the edge of a respective tube sidewall 16, 18 within slot 40.
Further, in all embodiments, in cutting of the folded end cap stock material transversely to a desired length equal internally to the length between tube end walls 20, 22, integral, longitudinally projecting tabs 50 are preferably cut out at the center of each end cap 14, the tabs 50 being in line with each other and of a width equal to that of the opposed perforations 28, 30 within respective tube end walls 20 and 22. The perforations 28, 30 receive the tabs 50, when the end caps 14 are snapped into engagement with the open ends of tube 12 and with the bases or central portion 34 of the end caps 14 filling the open ends 24, 26 of container or package tube 12.
It should be noted that the spacing for perforations 28 and 30 from the bottom or top ends of tube 12 is equal to the distance between the creases 37 of the rectangular end caps and the tabs 50 integral with the end cap base portion 34 such that the lower edges of tube sidewalls 16 and 18 are securely seated into the crease 37 defined by the folded sidewalls 36, 38 of each end cap, to opposite sides thereof, when tabs 50 snap into respective perforations 28, 30. The way in which the assembly is completed and by which a very rigid, stable coupling is achieved between the end cap 14 and the container or package tube 12 may be seen by reference to Figure 2.
It should be kept in mind that, while the preferred embodiment utilizes the tabs 50 penetrating the perforations 28, 30 within tube end walls 20, 22, respectively, for mechanically locking the end caps 14 to the ends of tube 22, other means may be provided for locking the end caps to the tube. Adhesives, tape, staples and other fasteners or fastening materials may be employed to fix the end caps to the containers in a more or less permanent form after the tube sidewalls 16, 18 are forced into slots 40 to opposite sides of the end cap. Figure 2 shows staples 52 locking end cap 14 to the bottom end of tube 12.
In similar manner to the referred to patents, the package may be manually completed by projecting base portion 34 of the end caps into the respective open ends 24, 26 of tube 12, while simultaneously causing the tube sidewalls 16, 18 to move into the narrow slots 40 of the rectangular end caps. Tabs 50 and the flexible tube walls flex to permit end cap penetration. Upon tabs 50 reaching the level of the opposed perforations 28, 30 of end walls 20, 22 of the tube, the tabs, which may flex during the penetration of the end cap base into the interior of the tube 12 are released, realigning with base 34 and pass into the perforations 28, 30 to project at right angles to the plane of the end walls 20, 22, thereby mechanically locking the end caps to respective ends of tube 12 of the package 10. This locking is achieved with the ends of sidewalls 38, 35 of the folded portion of the sheet material abutting the interior surfaces of tube end walls 20, 22 to increase the rigidity of the overall package 10. Assembly may be completed either manually or by automated machinery with similar effects and the assembly in each case is achieved in an expeditious and low cost manner.
It should be appreciated that it is the result of the end cap and plastic tube snap coupling involving tabs 50 and slots 30 of the end cap center portion and tube, respectively, along with the frictional engagement between the cap sidewalls 16 that create a relatively rigid, stable package with the cap and tube integrity maintained as a result thereof.
Further, with sidewalls 36, 38 of the end cap extending parallel to each other and the reverse 180° bend at crease 37, the semi-rigid plastic material sidewalls strongly resist flexing apart from crease 37 outwards, to maintain the two sidewalls 16 captured therebetween. This action and the presence of the mechanical interlock at tabs 50 and slots 30 at each end of the end cap, in itself creates a relatively rigid stable end cap to tube coupled package or container.

Claims

A tubular package (10) comprising: an open ended, flexible plastic sheet material tube (12) of rectangular cross-section including laterally opposed sidewalls (16, 18) and longitudinally opposed end walls (20, 22); and an end cap (14) carried by said tube (12) at an open end (24 or 26) thereof closing off said open end; which package is characterised in that: said end cap (14) comprises a folded, flexible, semi-rigid plastic sheet of a heavier gauge than that of said tube (12) and including a rectangular central portion (34); said end cap central portion (34) is of rectangular configuration corresponding to said tube (12), having a length generally equal to the longitudinal distance between said end walls (20, 22) of said tube (12) and a width equal to the lateral distance between said tube sidewalls (16, 18); said end cap central portion (34) has at opposite sides, double folded flat sheet portions (36, 38) integral with said central portion (34) and forming inner sidewalls (36) at right angles to the central portion (34) and outer sidewalls (38) folded back towards the central portion (34); said inner and outer sidewalls (36, 38) have ends thereof extending generally parallel to each other and are joined by a crease (37) defining a double layer slot (40) generally equal to the thickness of said plastic sheet material tube sidewall (16, 18), said end cap central portion (34) being positioned internally of said tube (12) with said tube sidewalls (16, 18) slidably inserted within said slot (40); said end walls (20, 21) of said flexible plastic tube (12) adjacent said one open end (24 or 26) carrying said end cap (14) include aligned, coplanar perforations (28, 30), respectively; and said end cap central portion (34) includes integral tabs (50) sized to the perforations (28, 30), projecting outwardly of the ends of the end cap (14) and received by respective coplanar perforations of said tube (12), such that the end cap (14) automatically locks to the end of the flexible plastic material tube (12), the fitted engagement between the tube sidewalls (22, 23) and the double layer slot (40) defining end cap sidewalls (36, 38) maintains the tabs (50) within the perforations (28, 30) of the flexible tube end walls (22, 23) and the tab (50) and perforation (28, 30) couplings maintain the tube sidewalls (16, 18) between said opposed folded end cap sidewalls (36, 38).
A tubular package according to claim 1, wherein said outer sidewalls (38) are folded back towards the central portion (34) in excess of 180° to said inner sidewall (36), such that the end of the outer sidewall (38) tends to contact said inner sidewall (36), whereby said double layer slot (40) narrows toward its open end opposite said crease (37) to less than the thickness of the plastic sheet material tube sidewall (16, 18), such that the end cap double layer slot sidewalls (36, 38) tend to frictionally grip the tube sidewalls (16, 18) over the portion of the tube sidewalls (16, 18) within said slot (40).
An end cap (14) for a tubular package (10) for closing off an end (24, 26) of a flexible plastic sheet material tube (12) of rectangular cross-section, said tube (12) including laterally spaced sidewalls (16, 18) and longitudinally spaced end walls (22, 23), characterised in that: said end cap (14) is constituted by a folded, flexible, semi-rigid plastic sheet of heavier gauge plastic sheet material than that of said tube (12) and including a rectangular central portion (34) of a length corresponding to the distance between said tube end walls (22, 23); said central portion (34) is of a width approximately equal to the laterial distance between sidewalls (16, 18) of said tube (12); said end cap (14) further includes double folded integral opposite sides forming double layer flat sidewalls (36, 38) perpendicular to the plane of the central portion (34) with said end cap folded sidewalls (36, 38) joined by a crease (37) remote from said central portion (34) and forming a narrow slot (40) between said folded end cap sidewalls (36, 38), with said slot (40) having a size of the order of the thickness of the plastic tube sheet material, said crease (37) functioning to seat a respective sidewalls (16, 18) of said tube when the sidewalls (16, 18) are slidably inserted within said double layer sidewalls (36, 38) of said end cap (14) with said end cap central portion (34) closing off the end of said tube (12); said tube (12) includes perforations (28, 30) within the respective end walls (22, 23) of said tube (12) adjacent an axial open end (24, 26) thereof, said perforations (28, 30) being coplanar and aligned with each other; and said end cap sheet central portion (34) includes integral tabs (50) projecting outwardly of said sheet central portion (34) away from each other, being sized to the perforations (28, 30) for being received thereby to mechanically lock the end cap (14) to the tube (12) such that the end cap automatically locks to the end of the tube (12) and maintain a fitted engagement between the tube sidewalls (16, 18) and the double layer sidewalls (36, 38) of the end cap (14) and the fitted engagement of said tube sidewalls (16, 18) within the slot (40) defined by said end cap sidewalls (36, 38) to maintain said tabs (50) within said perforations the engagement between the tabs (50) and the perforations (28, 30).
An end cap according to claim 3, wherein said narrow slot (40) between said folded end cap sidewalls (36, 38) narrows to a gap less than the thickness of the plastic tube sheet material at the open end of said slot (40) remote from said crease (37), such that the sidewall (16, 18) of the tube (12) is frictionally gripped by the double layer sidewalls (36, 38) of said end cap (14) over the portion of the tube sidewall (16, 18) inserted within the slot (40) defined by said double layer end cap sidewalls (36, 38).