JPH025565B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to containers, such as paper or plastic cups, used to contain food products. To protect the food inside the container from contamination and spillage, it is common to seal the top of the cup with a lid or foil membrane. Common foods such as milk, juice, jelly, and peanuts are packaged in cups, ie, heat-sealed foil lids that are peeled off the top of the container.

Foil lids are often sealed to the top rim of the container using heat. The seal between the foil and the container must be leak-tight and must also be fairly strong to prevent the mouth from loosening open due to movement of the contents when the container is transported.

There have been many approaches to designing a proper seal between the foil and the top of the container. If the top surface of the container rim is flat, the integrity of the seal is strengthened to a considerable extent. Heat sheathing between the foil-style lid and the round rim at the top of the container requires significant axial loading of the foil. Since some containers, such as plastic cups, can fail under axial loads, it is important that not only a leak-tight seal be provided, but that the containers will not fail under the axial loads required during the sealing operation.

It is known in the prior art to produce containers such as plastic cups with flat rims on the top. An example of such a plastic cup with a flat rim is the December 1967
No. 3,357,053 to WBLyon et al., dated 12 May. In particular, FIG. 13 shows a cut rim which has a rolled shape, but whose upper surface is completely flat.
The flat top surface of the rim shown in U.S. Pat. No. 3,357,053 is produced by applying air pressure applied by a special air passage connected directly to the cut prim machine.

The prior art also includes some examples in which containers are initially molded with mating male and female molds, such as for injection molding and steam box molding. Using this molding method, the shape of the container rim can be made into almost any desired shape.

In the case of rolling the container rim, the flat top surface is created by post-pressing, which requires additional processing and handling of the container.

FIELD OF THE INVENTION This invention relates generally to containers. More particularly, the present invention relates to a method and apparatus for manufacturing compacted rims for containers such as cups. The top surface of the cut prim is substantially flat, facilitating sealing of the foil-type lid to the rim. The mold for making the rim of the cup includes a rim-forming cavity contoured such that the rim initially takes on an arcuate shape and rapidly transforms into a flat-topped rim.

The containers or cups of the present invention are constructed with rims similar to rims previously developed for paper cups. The material associated with the container of the present invention is a plastic material such as polyethylene foam. In the manufacture of containers or cups made by the method of the invention, the foam sheet material is extruded into a tubular shape in either uniaxial or biaxial orientation. The foam sheet material is then printed on one side, cut into long strips, and then cut into square blanks. This material is then formed into a cylindrical shape on a winding mandrel, bonded to the bottom member, and heat shrunk to the final shape.
The final shape is wholly or partially a truncated cone. This semi-formed container is then sent to a rim forming machine where the rim is rolled outward and downward to create a smooth, crack-free bead. The shape of the bead is generally circular and the upper edge of the cup is contained or wrapped within the bead.

When forming beads on a paper tip, a circular cavity is used to form the beads. There are no major problems associated with bead formation as the paper has a tendency to assume the shape it last received.

Plastic materials, such as foam sheet materials, can also be formed into the desired circular cut rims by applying some form of heat prior to or during processing to soften the plastic material.

Figure 1 of the drawings is a cross-sectional view of a standard rim forming tool. Plastic cups were introduced into molding tools,
A rim is then molded to the upper edge of the cup. The entire device is designated by the numeral 10 and the cup into which the rim is formed is designated by 12. During the actual rim forming operation, the cup 12 is loaded or positioned within the cup support 14. The internal cavity of cup support 14 is the same as the external shape of cup 12. Cup support 14 supports the entire exterior sidewall of cup 12 except for the top 16 of the sidewall. The top sidewall portion 16 remains protruding from the cup support 14 so that it can be formed into a rim.

The cup is preferably held rigid while the rim is being formed, and is therefore further stabilized by the plunger 18, which is loaded with a spring (not shown). Plunger 18 is disc-shaped and has an outer surface 20 that generally corresponds to the inner surface of cup 12. Once cup 12 is positioned within cup support 14, non-rotating support shaft 24 and connecting plunger rod 22 are lowered to move plunger 18 into contact with the interior surface of cup 12. The rod 22 connected to the non-rotating plunger 18 is connected to the support shaft 24.
It operates in a telescopic relationship. Plunger 18 can and does apply clamping pressure to the inner cup wall at position 20, thus
Holds the cup in a fixed and non-rotating position. It can be seen that the cup 12 is thus supported on the cup support 14 and is particularly supported near the top of the cup 12 where the plunger 18 cooperates with the cup support 14 to support the side walls of the cup 12. .

The aforementioned support shaft 24 is part of the overall cup rim forming assembly that is movable towards and away from the cup support 14. A pair of cut prim molding molds consisting of an inner mold 26 and an outer mold 28 are mounted so as to rotate around the support shaft 24. As shown in FIG. 1, a bearing 30 is provided on the non-rotating support shaft 24, and the inner mold 26 and
A means is provided for rotating an outer mold 28 attached to a housing (not shown) that supports an inner mold 26. Although not shown in its entirety, the outer mold 28 is divided into six or eight circular pieces that cooperate to form a portion of the continuous bead cavity 32. Each divided outer mold 28
is a pivot 34 fixed to the aforementioned housing.
It is pivoted on. Each divided outer mold 28 has a push rod 3
6 or its equivalent. Thus, when the push rod 36 is moved downwardly, the outer mold 28 rotates about the pivot 34. push rod 3
6 is moved upwardly, the outer mold 28 assumes its normal position under the influence of springs or similar biasing means (not shown, but within the knowledge of those skilled in the art).

Above, the individual parts of the Katsuprim forming apparatus have been shown in the drawings and explained in detail. During the cup rim forming process, the cup 12 is held immobile by the clamping effect of the cup support 14 and the plunger 18. The entire support shaft 24, including the inner mold 26 and the outer mold 28, is lowered toward the side wall portion 16 of the cup 12.
The inner mold 26 and the outer mold 28 are rotating around the support shaft 24. Due to the rotation of the molds 26 and 28, the side wall portion 16 is rolled up into a curl that hangs down to the outside.
In this way, a bead is formed on the cup 12. Once the bead is formed, the push rod 36 rotates the outer mold 28 into position from below the bead just formed in the cup 12. Once all the outer mold segments have been rotated into position, the entire support shaft 24 can be moved away from the cup 12;
The upper edge or bead of the cup 12 is thus unconstrained. Plunger 18 is then withdrawn from cup 12. An ejector device 38 is located in the bottom structure of the cup support 14 to facilitate removal of the completed cup from the cup support 14.

The finished cup is then ready to be filled with product and sealed with a foil lid.

FIG. 2 shows an enlarged fragmentary view of the bead cavity 32 formed by the inner mold 26 and the outer mold 28.
The top side wall 16 of the plastic cup also has an upper edge 40.
is shown entering bead cavity 32.

Typically, the internal shape of bead cavity 32 is generally circular. This is because it is preferred that the beads of the container have a similar shape.

In the following discussion, the present invention will be described with reference to cross-sectional views of bead cavities, although, of course, the actual bead cavities are generally toroidal shaped along the upper edge of the cup.

The internal shape of the bead cavity 32 of the present invention is as follows:
The bead of the container to be molded is formed so that the upper surface thereof is flat. The top mold section 42 of bead cavity 32 is flat, as is the outer mold section 44. The outer mold side portion 44 extends beyond the joint 46 formed by the contact portion of the inner mold 26 and outer mold 28. The remainder of bead cavity 32 is defined by radius 48 and radius 50.

In order to obtain a flat rim that coincides with the top horizontal plane of the container, it is necessary to provide the mold section 42 at the top of the bead cavity 32 with a negative angle, shown as angle K in FIG. It has been determined that the negative angle K must be greater than 3°. This magnitude of negative slope allows the foam plastic cup material to elastically recover to a position where the top surface of the bead is substantially horizontal with the top plane of the cup.

In a bead forming operation, the support shaft and its associated inner and outer molds 26 and 28 are moved down toward the top upright sidewall 16 of the cup 12, which is immobilized by the cup support 14 and plunger 18. The molds 26 and 28 are engaged for rotational movement about the support shaft 24 before actually contacting the upper edge 40 of the cup. The rotating bead cavity 32 is moved down until the upper edge 40 of the cup meets a sharply curved portion of the bead cavity 32 with a radius 52.

FIG. 3 shows that the upper edge 40 of the cup is pressed directly outward into an arcuate shape, and then the upper edge 40 of the cup is moved downwardly so that radii 48 and 50
The figure shows contact with the curved surface of the outer mold 28 near the portion . At this point, the upper edge of the cup 4
0 is pressed against the surface of the outer mold 28 and the remainder of the top sidewall 16 is free from the bead cavity because it does not follow a properly defined curved surface, unlike that present in standard circular bead forming equipment. Start filling the space within 32. When the top sidewall 16 contacts a large portion of the inner surface of the bead cavity 32, the support material from the back creates a large resistance force on the top sidewall 16, causing the upper edge 40 of the cup to move further into a tight spiral. , thus completing the bead.

FIG. 4 shows the completed cup bead within the bead cavity 32. The shape shown in FIG. 4 represents the final shape of the cup bead, except for the negative slope angle indicated by angle K. Once the cup bead is released from the restraint by the bead cavity 32, the top of the bead assumes a horizontal position.

It has been found that the present invention is suitable for processing containers made from foam sheet materials whose composition is polystyrene. Typical densities for foam sheet materials range from 10 to 18 pounds per cubic foot. The overall thickness of foam sheet material is 0.015 ~
It is in the range of 0.040 inch.

The actual profile of bead cavity 32 is a combination of radii. For example, it has been found that the length of radius 52 must be less than the length of radii 48 and 50. Radius 52 is 0.030 inch, and radii 48 and 50 are 0.050 and 0.080 inch, respectively. Additionally, radius 54 is 0.010 inch.

The upper surface of the resulting bead has a flat profile that substantially corresponds to the flat surface of the top mold section 42. The flat top surface of the bead of the cup allows the heat-sealable lid to be more securely attached to the bead than was possible with conventional bead shapes that were circular in cross-section.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a standard cut rim forming apparatus. FIG. 2 is an enlarged split sectional view of the rim molding cavity showing the cut rim entering the rim molding cavity. FIG. 3 is an enlarged cross-sectional view similar to FIG. 2 showing a partially formed cut rim. Figure 4 shows the completed Katsupurim.
FIG. 3 is an enlarged sectional view similar to FIG. 2; 12...Cup, 14...Cup support, 16...Top side wall portion, 26...Inner mold, 28...Outer mold, 32
...Bead cavity, 42...Top mold part, 4
4...Outer mold part, 48, 50, 52, 54...
Radius, K...Inclination angle.

Claims (1)

[Claims] 1. A method for forming a rim with a flat top on a thin-walled container, including the following steps: (a) A bead forming mold cavity 32, including a top mold portion 42 and an outer mold. The portion 44 has a generally flat configuration in cross section, and the top mold portion 42 slopes downwardly at a predetermined angle and has an outwardly arcuate shape formed by an arc of radius 52. introducing a top sidewall section 16 of a thin-walled container into the bead cavity 32 using a bead cavity 32 having a shaped section and moving the top sidewall section 16 until its upper edge 40 meets said arcuate section; (b) moving the top sidewall portion 16 further along a generally flat top mold portion 42 within the bead cavity 32 that slopes downwardly at a predetermined angle, thereby lowering the top edge 40 downward; The side wall portion 16 is bent into a curved shape and the upper edge 40
(c) contacting the top sidewall portion 16 with one end thereof in an arcuate shape formed by an arc of radius 48 and radius 50; The bead cavity 32 is moved further into the radius 50.
The top side wall portion 16 fills the space inside the cavity 32 while rolling the upper edge portion 40 inward along the upwardly curved arcuate portion formed by the arc of the curve, thereby converting a portion of the curved shape into a straight line shape. and (d) removing the container from the bead mold cavity 32. 2. A method for forming a rim with a flat top on a thin-walled container according to claim 1, characterized in that the linear portion is generally flat and located on the top surface of the bead. 3 In an apparatus for forming a rim with a flat top surface on a thin-walled container, a bead forming mold having an overall toroidal shape along the upper edge of the container is formed by attaching a plurality of outer mold segments to an inner mold part. a mold cavity and an inlet for inserting the top edge of the container into the bead mold cavity, the bead mold cavity, when viewed in cross-section, for guiding the top edge of the container. The first straight part for retraction,
a first arcuate portion following the first linear portion; a top portion or second linear portion that slopes downward at a predetermined angle following the first arcuate portion; a second arcuate portion following the second linear portion; Apparatus for forming a flat-topped rim on a thin-walled container, characterized in that it is defined by an outer part or third straight part following two arcuate parts and a third arcuate part following the third straight part. 4. Claim 3, characterized in that each of the arcuate portions is formed by a circular arc.
Apparatus described in section. 5. The device of claim 4, wherein the arc of the first arcuate portion is larger than the arc of the second arcuate portion. 6. Device according to claim 4, characterized in that the third arcuate portion is formed by two different circular arcs. 7. Apparatus according to claim 6, characterized in that the smaller of the circular arcs is adjacent to the third straight section. 8. Device according to claim 6, characterized in that the arc of the first arcuate portion is smaller than any of the different arcs. 9. The device according to claim 6, wherein the third straight line portion is common to both the inner mold and the outer mold. 10. The device of claim 10, wherein the slope of the second straight section is at least 3 degrees.