Envelopes – wrappers – and paperboard boxes – Paper or paperboard cup
Reexamination Certificate
2000-10-02
2001-07-24
Elkins, Gary E. (Department: 3727)
Envelopes, wrappers, and paperboard boxes
Paper or paperboard cup
C229S004500, C229S005500
Reexamination Certificate
active
06264100
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to cups formed of paperboard and, in particular to methods and apparatus for making a cup bottom that is to be attached to a sidewall of the cup.
In the manufacture of paper cups, i.e. cups made of paperboard material which could optionally be coated with a foamed substance, it is conventional to form a cup bottom and then wrap a cup sidewall around the bottom and attach the sidewall to the bottom by an adhesive.
A longitudinal sectional view through a conventional paper cup
10
is depicted in FIG.
1
. As can be seen therein, the cup includes a bottom
12
and a sidewall
14
attached thereto. The bottom
12
comprises a disk-shaped base
16
and a cylindrical lip or skirt
18
projecting from an outer periphery of the base
16
. The sidewall
14
is wrapped around the circumference of the lip
18
, and an end
20
of the sidewall is folded over the free edge of the lip
18
. The lip
18
thus becomes sandwiched between portions of the cup sidewall and is bonded thereto by an adhesive.
Prior to being wrapped with the sidewall, the cup bottom is formed by passing a paper web across a cutter which cuts out a circular blank. Then a draw pushes the blank through an opening having a smaller diameter than the blank. Hence, an outer periphery of the blank is bent over to form the lip, the lip being squashed as it travels through a gap between the draw and a surface of the opening. A conventional apparatus for the manufacture of the cup bottoms is disclosed in Budziszewski U.S. Pat. No. 5,624,367, the disclosure of which is incorporated by reference herein.
It will be appreciated that the lip-forming outer periphery of the blank has a first circumference before the bending, and a smaller circumference after the bending. That means that there is extra paper material after bending, and that extra paper material produces pleats
21
,
22
which project from the surface of the lip (see FIG.
2
). The pleats extend axially (i.e., in a vertical direction when the cup sits upright). Some of the pleats
21
project by a small distance from the lip surface (i.e. they have a very a short height) and do not present problems, because they will become flattened when the lip is compressed in the gap, as shown in FIG.
2
. Other pleats
22
, however, are tall enough to become folded over when the lip is compressed in the gap. Such folded-over pleats can produce leakage paths between the lip and the cup sidewall which permit liquid to leak from the cup.
The apparatus disclosed in U.S. Pat. No. 5,624,367 attempted to deal with that problem by producing radial score lines in the outer periphery of the blank prior to the bending. The score lines constitute pre-weakened regions of the blank. It was anticipated that the pleats would be formed in a controlled manner along the score lines, and that the problem of folded-over pleats would be eliminated. That proposal has not met with complete success, because folded-over pleats are still formed in the cup bottom.
It is, therefore, an object of the present invention to produce cup bottoms having only pleats which are not tall enough to become folded-over when the bottom lip is compressed.
SUMMARY OF THE INVENTION
The present invention relates to a method of forming a bottom for a paper cup. The method comprises the steps of:
A. applying a clamping force to an outer peripheral portion of a circular paperboard blank;
B. pushing a center portion of the blank into a circular opening of smaller diameter than the blank while maintaining the clamping force to prevent movement of the outer peripheral portion, whereby the blank becomes stretched; and
C. progressively releasing the clamping force following the stretching of step B, to permit the outer peripheral portion to enter the opening and become bent at a substantially right angle relative to the center portion.
The invention also pertains to a method of making a paper cup, wherein a bottom is formed as described above, and wherein a paperboard cup-sidewall blank is wrapped around an end edge of the lip and secured thereto.
The invention also pertains to a cup bottom comprising a one-piece paperboard element including a circular center portion and a bent-over generally cylindrical lip portion projecting from an outer periphery of the center portion at a substantially right angle. The lip portion includes pleats extending parallel to a longitudinal axis of the lip portion. All of the pleats are in the form of micropleats that are flattened in a non-folded over state.
The invention further pertains to a cup which comprises a bottom as described above, and further including a cup sidewall which is wrapped around an end edge of the lip portion and secured to the lip portion.
REFERENCES:
patent: 3118351 (1964-01-01), Jagenberg
patent: 4191322 (1980-03-01), Kinney
patent: 4349400 (1982-09-01), Gilden
patent: 4599123 (1986-07-01), Christensson
patent: 4619636 (1986-10-01), Bogren
patent: 4721500 (1988-01-01), Van Handel et al.
patent: 4865506 (1989-09-01), Kaminski
patent: 5449337 (1995-09-01), Konzal
patent: 5531235 (1996-07-01), Hassenboehler, Jr.
patent: 5624367 (1997-04-01), Budziszewski
patent: 6135936 (2000-10-01), Brown et al.
patent: 4-282235 (1992-10-01), None
Brown David C.
Curcio Anthony N.
Grishchenko Grigory
Burns Doane , Swecker, Mathis LLP
Elkins Gary E.
Fort James Corporation
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