US 3709399 A
A food container having an injection moulded polypropylene body with an open end around which extends a circumferential flange to which a metal lid having a frusto-conical annular wall is attachable. The walls of the container are tapered in thickness near the open end to accommodate the outwardly flaring frusto-conical wall so that the wall can provide suitable support for the container wall during a seaming operation where the lid is seamed to the flange by means of a conventional tin can seaming machine.
Description (OCR text may contain errors)
United States Patent Nughes 1 Jan. 9, 1973  FOOD STORAGE CONTAINERS FOREIGN PATENTS OR APPLICATIONS  Inventor: Giovanni Nuglies','MiI5nIIial 563,775 '9/1958 Canada ..220 42  Filed: W July 21, 197 1 V I I Primary Examiner-Joseph R. Leclair Assistant Examiner-James R. Garrett  Appl Attorney--Richatd C. Sughrue et al. 30] raragsapmrcaaanFriorrtymia"  ABSTRACT Aug. 11,1970 Italy ..69772A/70 A food container having an injection moulded  U.S.i2l..'.'.' I....'.III...'. ....IIQ....I....Lii0/67 P yp py y t all P end around which  Int. Cl. ..B65d 7/42 extends a circumferential flange to which a metal lid  Fi ld f S h 220/67 42 B, 42 C; 150/,5 having a frusto-conical annular wall is attachable. The
' walls of the container are tapered in thickness near  Referen es Ci d the open end to accommodate the outwardly flaring frusto-conical wall so that the wall can provide suita- UNITED STATES PATENTS ble support for the container wall during a seaming 2 382 378 3 Bloedom 220/67) operation where the lid is seamed to the flange by 2:8l6z589 12/1957 Tupperum I I l I "150/5 means ofa conventional tin can seaming machine. 3,073,478 Ill 963 Henchert ..220/67 3,341,059 9/1967 Schild et al.... ..220/67 6 Claims 6 Drawing Fgms 3,524,568 8/1970 Nughes ..220/67 3,543,963 12/1970 Hcisler et al. ..220/67 10 11. L. Rf I \\\\q F I 12 r 16A 10A 16B A PATENTEUJMI 9 197a SHEET 1 [IF 4 Eiql I PRIOR ART INVENTOR 5/0 VA N/Y/ Noah/6 51 4M 72 /4012? M 1 BY 2 I a a #L ATTORNEYS seam and the lid seam meet.
The present invention relates to food storage containers having a substantially rigid polypropylene body of low yieldability. v
The body of such containers is conveniently injection moulded and has a circular cylindrical shape similar'to that conventional tin can" although a variety of other suitable shapes may be employed. As described in my earlier U.S. Pat. No. 3,5 24,568 the body of the container is formed with an outwardly directed circumferential flange at the open end and a metal lid can be seamed to the flange of the body by means of a conventional double hook seam. In this way it is possible to use the novel polypropylene can body in conjunction with conventional metal lids and to join the body and the lid tin plate, the angle between the shoulder forming wall together by means of a conventional seam on a conventional' seaming machine operating on the so-called seam spinning principle. For this purpose the metal lids are formed with a peripheral flange parallel to the general plane of the lid axially displaced from this plane by a smallamount and joined to the main disc of the lid by anaxially extending wall.
Storage containers of this type are particularly suited for the manufacturing of food produce in view of various problems such as sterilization, longitudinal seaming, transference of metallic taste and susceptibility to acid and hydrogen sulphide attack, encountered with the use of metal cans which are explained in greaterdetail in U.S. Pat. No. 3,524,568. Many of these problems are overcome, or at least minimized by the use of the polypropylene containerbody; for example, a polypropylene body can be injected moulded and thus does not have a longitudinal side seam as do conventional metal cans. There is thus no risk of the side seam weakening and no weak The importance of the detailed configuration of the outwardly directed circumferentialflange for satisfactory seaming to a metal lid is also discussed in U.S. Pat. No. 3,524,568. It has previously been considered essential for the circumferential flange to be formed with a progressively tapering cross section reducing from the region where theflange meets the'body of the cam to a minimum at the periphery of the flange in order-to ensure a satisfactory seam with the metal lid.
It has now been found however, that, irrespective of any tapering of the flange, the seaming operation is stronglyinfluenced by the relative configuration of the can and the lid in the region of thewall of the lid. In
points where the side I particular, it has been found that the support which the v wall of the lid is able to offer the body of the container, in the region of the opening, during the seaming process greatly affects the efficacy of the seaming process. It has also been found that, once the problems connected with this phenomena are overcome, the thickness of the flange can be constant without deleteriously affecting the efficacy of the seaming process.
Considering, for example, a cylindrical container (of the type of the common tin can), it is known that the small axially extending wall portion of the lid which forms the above mentioned wall is never truly cylindrical, but has a slightly conical shape due to the conditions under which the lid is formed. This conical shape varies from case to case; for example, in lids made of and the longitudinal axis of the lid (the cone angle) is typically between about 5 and about 6"30', while in lids of aluminum the cone angle varies in the range from about 330 to about 430. It will be seen that the angles under consideration are very small and, until now, they have never been given particular importance in regard to the seaming process, particularly because the variation of the diameter of the shoulder wall from the narrowest part to the widest part due to such a small cone angle appeared to be insignificant.
It has now been found, however, that polypropylene containers as described in the patent mentioned above are very sensitive to this small deviation from a true cylindrical shape. In particular it has been found that as alid is pressed into the opening of a polypropylene container the taper of the lid wall causes a radially outward pressure on the container walls which has a maximum value at the end of the wall where the outwardly turned flange is situated. As a result of this pressure, and as a result of the difference between the taper of the lid wall and the-shapeof the container wall there is a lack of radial support from the inside of the container wall during the seaming operation, and this deleteriously affects the efficacy of the seaming operation. To avoid this defeet the diameter of the lid wall could be increased slightly so that the lid would enlarge the container wall when pressed into the opening of the container body. However, it is possible, in-this case, for the circumferential flange to .warp and therefore to miss the hook formed by the flange during the seaming operation thereby forming an incomplete seal between the body and the lid.
According to the present invention a container for food comprises a polypropylene body of low yieldability having an open end with a circumferential flange and a metal lid seamed to the. circumferential flange, in which the lid has a frusto conical annular wall and the container wall is tapered in thickness toward the said open end, the length of the tapered portion being at least equal to the depth of the said frusto-conical wall.
This tapered portion of the container wall extends to the arcuate transition region between the container wall and the circumferential flange, beginning from which the thickness of the flange may be constant or, if desired, may still taper towards the outer edge of the flange in the known way. Preferably the container wall is bevelled internally, the bevelled. portion being at an angle to the axis of the can which is at least equal to the angle of the wall of the lid. Typically, the angle of bevel is in the range from about 3 to about 10, depending on the angle of taper of the wall of the lid;
In one embodiment of this invention, the angle of bevel of the inside of the container wall is slightly greater than the angle of taper of the wall of the lid so that the pressure between the lid wall and the container wall is greatest at the region of contact between the lid and the wall remote from the flange. The lid wall thus deforms the container wall as the lid is pressed into the opening, and this deformation is such asto ensure intimate contact between the flange of the lid and the circumferential flange of the container.
Various embodiments of the present invention will now bemore particularly described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a partial axial section of part of a wall of a known type of polypropylene container showing a lid in position but before seaming;
FIG. 2 is a partial axial section of a part of a wall of a known type of polypropylene container in the same position as FIG. 1 but showing a lid of larger diameter in position;
FIG. 3 is a partial axial section of part of a wall of one embodiment of the invention;
FIG. 4 is a partial axial section of part of a wall of a second embodiment of the invention;
FIG. 5 is a partial axial section-of part of the wall of a third embodiment showing a lid immediately before it is pressed into the opening; and
FIG. 6 is a partial axial section of the embodiment of FIG. 5 showing a lid after it has been pressed into position but before a circumferential seam has been formed.
Referring now to FIGS. 1 and 2 these illustrate the disadvantages discussed above, of a lack of radial support for a container wall 16 by a wall 12 of a lid 10- pressed onto a container 14. As will be seen in FIG. 1, due to the slight taper of the wall 12 (shown exagerated in FIG. 1) there is a gap 18 between the wall 16 and the wall 12 extending the length of the wall 12 with the exception of the end where it meets the flange. The presence of this gap means that the wall 12 cannot provide the required support to hold the wall 16 rigidly during the seaming operation and this results in frequent failures and difficulties in the seaming operation. The proposed attempt to provide suitable radial support by increasing the diameter of the lid 10, however, frequently leads to buckling of the circumferential flange 20 as shown in FIG. 2. This in turn results in the flange 10B of the lid 10 failing to make a satisfactory seal with the buckled portion of the flange.
In the embodiment illustrated in FIG. 3 the wall 16 of the container body 14 is progressively reduced in thickness from the inside, from a level 22 lower-than that of the central disc 10A of the lid 10 when the lid 10 is in position. This reduction in thickness is effectively in the form of a bevel the angle of which is substantially the same as the angle of the wall 12 so that the wall fits snugly into the frusto-conical opening formed by the bevel 16A. Thus, during the seaming operation, the bevelled portion 16A of the wall 16 is supported radially by the wall 12.
The embodiment illustrated in FIG. 4 is similar to that of FIG. 3, except that the frustoconical opening formed-by the bevel 16A has a step 168 at the level of the central disc 10A of the lid l0. This arrangement has the advantage that when the lid 10 is removed by a conventional can opener which cuts or shears the lid at the line 24 the sharp edge thus produced will not project dangerously from the inside surface of the container.
in the embodiment illustrated in FIG. 5, the angle X of the bevel 16A is slightly greater than the angle X of the wall 12 of the lid (as seen in cross section). For example, the angle X could be 10 if the angle X were 6. The diameter D of the upper end of the wall 12 adjacent the lid flange 10C is equal to the diameter of the corresponding part of the opening 16A of the container body 14. Consequently, when the lid 10 is pressed onto the container body 14 the bevelled region 16A of the container wall 16 is deformed by the wall 12 of the lid 10 as shown in FIG. 6. In this case the greatest pressure between the wall 12 and the container wall 16 occurs at the level of the central disc 10A of the lid. As a consequence, there is a progressive deformation of the wall 16 of the container body 14 in the direction indicated by the arrow M in FIG. 6. In this case the container wall in the bevelled region 16A is firmly radially supported by the wall 12 due to the fact that there is a pressure between the wall 12 and the wall 16. Moreover, the expansion indicated by the arrow M causes the flange 20 to be pressed against the corresponding part of the flange 10C of the lid so that the flange 20 is in positive engagement with this flange, and the hooked part 108 of the flange 10C readily engages the flange 20 during seaming.
It will be appreciated that the above described invention can be applied not only to containers with circular cross section, which are the most common type of container, but also to containers of any other shape which allow the manufacture of a double hook seam, for example elliptical or rectangular with rounded angles (of the type frequently used for corned beef) and other cross sectional shapes may be used. In such cases the frusto-conical opening will not be that of a circular cone but of some other base shape. The references in this specification to the cone angle of such shapes will be understood to refer to the angle of inclination of the planes of the figure with respect to the axis of the con tainer. Moreover, it should be borne in mind that nominally cylindrical containers made by injection moulding are, in practice, slightly conical to make it possible to remove them from the mould; therefore, the reference line 30 in FIGS. 3, 4 and 5 should be considered as parallel to the wall of the container (in longitudinal section) rather than parallel to the axis of the container.
Furthermore, it will be appreciated that the thickness of the container wall depends on the size of the container. For example in FIGS. 3-6, with cylindrical containers with a diameter of 8-12 cm, the thickness of the part 16 may typically be about 1.5 to about 2mm and.
decreases to about 0.4 mm at the flange 20. The maximum value of the deformation of the container wall 16 illustrated in FIG. 6 is practically very small considering that the height H ofthe shoulder 12 of the lid 10 (FIG. 5) amounts generally to 2.5-6 mm and that the difference between the angles X and X is not more than about 7.
What I claim is: l. A container for food, said container comprising a polypropylene body of low yieldability having a side wall defining an open end,
a circumferential flange on said body at said open end,
an outwardly flaring frusto-conical annular wall on said lid,
said side wall having a circumferential portion tapered in thickness towards said open end adjacent said open end, said tapered portion of said container wall is formed by an internal bevel on the'inner surface of the container wall, the length of said tapered portion axially of the container being at least equal to the depth of said frustoconical wall on said lid.
2. The container of claim 1 wherein the angle of said bevel, with respect to the longitudinal axis of said container being at least equal to the cone angle of said wall jacent to and co-operating with said wall on said lid.
6. The container of claim 1 wherein the angle of said tapered portion of said container wall is greater than thecone angle of said frusto-conical annular wall on said lid, said lid deforming said tapered portion of said container wall, when in position in said opening, by an amount increasing progressively away from said open end for the depth of said lid wall.
UNITED STATES PATENT OFFICE CERTIFICATE GE CORRECTION Patent No. 3, 709; 399 Dated January 9, 1973 In Giovanni Nughes It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
In The Heading:
The Assignees Name was omitted. Should read:
-Assignee: Star Stabilimento Alimentare S. p.A. Milan, Italy-- Signed and sealed this 13th day of November 1973.
EDWARD M.FLETCfiER,JR. RENE D. TEGTMEYER Attesting Officer Acting Commissioner of Patents FORM PO-1050 (10-69) USCOMM-DC 60376-1 69 w u,s. GOVERNMENT PRINTlNG OFFICE: I969 o-qss-aaa,