Note: Descriptions are shown in the official language in which they were submitted.
CA 02571965 2006-12-20
TITLE: PLASTIC WATER TIGHT CONTAINER
FIELD OF THE INVENTION
The invention relates generally to injection molded plastic food containers.
BACKGROUND OF THE INVENTION
Inexpensive plastic containers have been manufactured for several decades.
These
containers generally include a lid section mated to a bowl section. Both the
lid and bowl portions
are generally thin walled products manufactured by using injection molding or
thermoforming
processes. These inexpensive bowls are an important part of the food service
industry because
they permit food products to be served to the public in a relatively secure
container.
Unfortunately, water tight containers are not simple to construct. The most
effective way to
ensure a secure water tight seal between the lid and the bowl portion of the
container is to
provide some sort of rubber sealing gasket at the intersection of lid and
bowl. This greatly
increases the cost of manufacturing the container. Alternatively, it is
possible to design water
proof plastic containers provided the plastic walls of the container are
relatively thick and the lid
and bowl are very closely mated to each other. This design approach, while
effective, also results
in an expensive container. An improved container having a water tight seal
which does not
require thick walled products or sealing gaskets is therefore desirable.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided an
improved plastic
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CA 02571965 2006-12-20
container wherein the lid and bowl portions of the container fit together to
form a water tight seal
without the need for sealing gaskets. The plastic lid portion of the container
includes a lid lip
having a generally sinusoidal shape including a U shaped portion and a first
inverted U shaped
portion, the first inverted U shaped portion having a first wall, a first
upper portion and an
interior, a retaining bead projecting from the first wall into the interior of
the first inverted U
shaped portion, the U shaped portion having a second wall opposite the first
wall of the first
inverted U shaped portion. The bowl includes a bowl lip having a second
inverted U shaped
portion. The second inverted U shaped portion has third and fourth walls, a
second upper portion
and a lip edge. The third wall extends from a terminal end to the second upper
portion, the
fourth wall being contiguous with the bowl and the lip edge being positioned
between the fourth
wall and the top portion. The second inverted U shaped portion is dimensioned
and configured
to fit snugly within the interior of first inverted U shaped portion such that
when the second
inverted U-shaped portion is fully inserted into the first inverted U-shaped
portion, a first seal is
formed by the terminal end of the third wall bearing against a portion of the
first wall
immediately above the bead, a second seal is formed by a portion of the fourth
wall bearing
against a portion of the second wall and a third seal is formed by the lip
edge bearing against the
upper portion of the first inverted U-shaped portion.
With the foregoing in view, and other advantages as will become apparent to
those skilled
in the art to which this invention relates as this specification proceeds, the
invention is herein
described by reference to the accompanying drawings forming a part hereof,
which includes a
description of the preferred typical embodiment of the principles of the
present invention.
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DESCRIPTION OF THE DRAWINGS
FIGURE 1. is a side view of the lid portion of a container made in accordance
with the present
invention.
FIGURE 2. is a side view of the bowl portion of a container made in accordance
with the present
invention.
FIGURE 3. is a cross sectional view of the lip portion of the bowl shown in
figure 2.
FIGURE 4 is a cross sectional view of the lip portion of the lid shown in
figure 1.
FIGURE 5 is a cross sectional view of the lip portions of the lid and bowl
portions of the present
invention being joined together.
FIGURE 6 is a cross sectional view of the lip portions shown in figure 5
showing force vectors.
In the drawings like characters of reference indicate corresponding parts in
the different
figures.
DETAILED DESCRIPTION OF THE INVENTION
Referring firstly to figures 1 and 2, the present invention is a plastic bowl
having lid 12
and bowl 14. Lid 12 is made of a thin walled lid which is injection molded
from a plastic such as
polypropylene or the like. Lid 12 has bottom portion 26 and domed portion 28.
Cleats 30 are
fornled on dome 28 and lip portion 16 is formed on bottom portion 26. Lip 16
extends all the
way around the lid. Likewise, bowl portion 14 has bottom dome 20 with bottom
22 and top
portion 24. Lip portion 18 extends all the way around top portion 24 of bowl
portion 14.
Referring now to figures 3 and 4, lip portion 16 is sinusoidal in shape having
U-shaped
portion 32 and first inverted U-shaped portion 34. Inverted U-shaped portion
34 has a first outer
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wall 36, interior 35 and top portion 37. Interior 39 is formed between first
outer wall 36 and
second wall 40 of U-shaped member 32. Bead 38 is formed on first wall 36 and
projects into
interior 35. Wa1136 is preferably sufficiently thin to permit it to deform
slightly.
Lip portion 18 has second inverted U-shaped member 42. Second inverted U-
shaped
member 42 has third wall 44, top portion 46, terminal end 48 and fourth wall
50. Fourth wall 50
is contiguous with the rest of the bowl portion. Lip edge 15 is formed between
top portion 46
and fourth wall 50 and is oriented towards bowl 14. Edge 15 is preferably
relatively sharp,
preferably just over about 90 or so.
Lip portion 18 is dimensioned to fit snugly within interior 35 of first
inverted U-shaped
portion 34. Preferably, first inverted U-shaped portion 34 has an internal
diameter measured
between first wall 36 and second wall 40, while second inverted U-shaped
portion has an exterior
diameter measured by the exterior of third wal144 and fourth wall 50.
Preferably the internal
diameter of first inverted U-shaped portion 34 is less than the external
diameter of second
inverted U-shaped portion 42. When the second inverted U-shaped portion 42 is
fully inserted
into interior 35 of first inverted U-shaped portion 34, terminal end 48 and
portion 51 of first wall
36 bear against each other tightly to form seal A, portion 52 of wall 50 bears
against portion 54
of second wall 40 with sufficient force to form seal B and edge 15 bears
against top 37 of the
first inverted U-shaped portion to form seal C. Preferably, wall 44 is
dimensioned such that
when fully inserted into the first inverted U-shaped portion, terminal end 48
is positioned
immediately above bead 38, thereby preventing the second inverted U-shaped
portion from
slipping out of the first inverted U-shaped portion. Fist inverted U-shaped
portion 34 and second
inverted U-shaped portion 42 are dimensioned such that seal formed between
walls 40 and 50 is
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positioned below the seal formed by walls 36 and 44.
As shown in figure 6, the outside diameter of portion 42 is sufficiently
greater than the
inside diameter of portion 34 such that lateral forces represented by vectors
E and F are formed.
Seals A and B are formed by the lateral forces represented by vectors E and F.
Seals A and B are
formed as substantially point like seals having relatively small surface
areas, ensuring that the
seals are tight and water tight. The relative sizes of portions 34 and 42 are
such that transverse
forces represented by vectors D and G are formed between portion 48 and edge
15. These forces
are balanced and in opposite directions ensuring that portion 42 remains
within portion 34. Edge
15, being relatively sharp, forms a tight seal C as it presses against the
intersection of portions 37
and 40.
Seals A, B and C are point seals that are continuous all along lips 16 and 18,
thereby
ensuring a continuous seal between lid and bowl. Seals A, B and C are arranged
to form a
triangular arrangement illustrated by triangle H. Preferably, seals A, B and C
are arranged such
that triangle H is approximately an equilateral triangle to ensure that the
three seals remain tight
and secure. By having the three seals in an equilateral triangular
arrangement, the lid remains
very tightly sealed to the bowl and will resist being dislodged, even if the
container drops.
A specific embodiment of the present invention has been disclosed; however,
several
variations of the disclosed embodiment could be envisioned as within the scope
of this invention.
It is to be understood that the present invention is not limited to the
embodiments described
above, but encompasses any and all embodiments within the scope of the
following claims.
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