U.S. patent number 3,568,872 [Application Number 04/771,238] was granted by the patent office on 1971-03-09 for insulated plastic container.
This patent grant is currently assigned to Monsanto Company. Invention is credited to James C. Logomasini.
United States Patent |
3,568,872 |
Logomasini |
March 9, 1971 |
INSULATED PLASTIC CONTAINER
Abstract
A double walled container wherein at least one of the enclosed
sides of the opposing walls has a portion of its surface provided
with a foam covering associated with said wall.
Inventors: |
Logomasini; James C.
(Wilbraham, MA) |
Assignee: |
Monsanto Company (St. Louis,
MO)
|
Family
ID: |
25091163 |
Appl.
No.: |
04/771,238 |
Filed: |
October 28, 1968 |
Current U.S.
Class: |
220/1.5;
215/12.2; 220/902; 220/62.11 |
Current CPC
Class: |
B65D
1/265 (20130101); Y10S 220/902 (20130101) |
Current International
Class: |
B65D
1/26 (20060101); B65D 1/22 (20060101); B65d
025/18 () |
Field of
Search: |
;220/9 (L2S)/ ;220/9
(F)/ ;229/1.5 (B)/ ;215/13 ;161/160,161 ;156/77,78,79 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Leclair; Joseph R.
Assistant Examiner: Garrett; James R.
Claims
I claim:
1. A container having an improved combination of insulating and
structural characteristics comprising two substantially similarly
shaped thin walled thermoplastic receptacles, each having a bottom
wall and a sidewall extending generally upwardly from the margin of
said bottom wall, said receptacles being telescopically associated
such that the inner surface of the sidewall of the outer receptacle
opposes the outer surface of the sidewall of the inner receptacle
and wherein at least a portion of one of said opposing surfaces is
provided with a foamed layer, such layer having been formed from
the plastic material of the sidewall upon which the said one
opposing surface is disposed, the face of said foamed layer which
is remote from said one opposing surface being heat sealed to the
other of said opposing surfaces.
Description
The present invention relates to a double walled container and more
specifically to a double walled container having a foam surface on
at least one of the inner opposing walls.
Thin wall plastic disposable containers have been used for some
time to hold hot and cold liquids. It is well-known, however, that
when such containers are used to hold hot liquids, they cannot be
held without some discomfort due to the heat transfer through the
container sidewalls.
More recently, thin wall containers have been developed which have
at least partially resolved the heat transfer problem.
Unfortunately, however, these solutions have not been sufficient in
terms of either reduction of heat transfer and/or the cost of
producing such containers to warrant commercial acceptance over the
noninsulated thin wall plastic containers now generally in use.
Some of the solutions to this problem have involved thickened foam
container walls, plastic containers having variously shaped
gripping fins around thin outer walls, solid plastic containers
which either have a foam outer strip or have been partially foamed
and double thin walled plastic containers which have been somewhat
intricately designed to maintain an air space between the walls.
The present invention is an improvement in insulating containers
obtained by an unusual and unique combination of insulating factors
resulting in a highly insulated thin walled container which is both
simple and economical to produce.
The primary object of the present invention is to provide a plastic
container which may be held by a user without discomfort when
filled with hot liquid.
Another object of the present invention is to provide a strong but
lightweight container which will not substantially deflect in a
user's hand.
A further object of the present invention is to provide a highly
heat insulated container which can be easily and economically
constructed.
These and other objects are accomplished by a container of double
thin wall construction wherein a portion of one of the inner
opposing walls is provided with a foam surface.
Other objects and advantages of the present invention will become
apparent from the following description when taken in conjunction
with the accompanying drawings wherein:
FIG. 1 is a partial, sectional side view of a container constructed
in accordance with the principles of the present invention.
FIG. 2 is a partial, sectional side view of an alternated container
constructed in accordance with the principles of the present
invention wherein the bottom of the container is also provided with
a foam interlayer.
FIG. 3 illustrates a stepwise process by which the container of
FIG. 2 may be made.
Referring to the drawings and more specifically FIG. 1, there is
shown a sectional side view of a container 10 which comprise two
interfitting or telescopically associated thin wall plastic
receptacles 12 and 14 having a foam portion 16 provided on the
outer side 18 of the sidewall 20 of the receptacle 14. The
receptacles 12 and 14 are held in place by the double curl 22 at
the mutual top of both receptacles. In this embodiment the foam
portion 16 may be attached or provided on either the outer side 18
of the sidewall 20 or the inner side of the sidewall 24 by any
suitable means, i.e., adhesives, etc., or is preferably an integral
part of one of the receptacle sidewalls.
In FIG. 2, there is shown a container 22 comprising interfitting or
telescopically associated receptacles 26 and 28. In this embodiment
the foam portion 30 extends around and down covering the bottom
side 32 of the inner receptacle 28. Although the foam portion 30
may be bonded as a separate piece to one of the receptacle
sidewalls, it is preferably provided by a rather unique technique
which is referred to herein as the "partial foaming process" which
is described more in detail in U.S. Pat. No. 3,262,625. More
specifically, a thin wall receptacle 40 shown in step a FIG. 3 is
partially immersed in a solvent 42 contained in a tank 44 as shown
in step b of FIG. 3 and held for a sufficient period of time to
permit solvent to be absorbed to a predetermined depth within the
wall of the receptacle 40 from its immersed outer surface 46. The
receptacle 40 is then removed from the solvent 42 and heated by any
means, i.e., lamps 48 shown in step c of FIG. 3 resulting in the
formation of a foamed outer covering on the outer surface 46 of the
receptacle 40 extending partially within the wall of the original
receptacle. The partially foamed receptacle 40 from step c is then
fitted into a second but unfoamed receptacle similar to that shown
in step a resulting in a double wall internally insulated container
such as shown in step d of FIG. 3 producing a relatively thin
double wall container which is extremely strong and of a highly
heat insulating character. The word "similar" as used herein means
that the two receptacles are shaped such that both receptacles can
be fitted together without substantial difficulty and yet not be
overly loose. Consequently, it is obvious that one receptacle could
be configured somewhat differently to include for example, a
container gripping section, stacking means and the like which might
not be included in the other receptacle.
As previously indicated, the structure of the container which has
been described provides unusual heat insulating characteristics due
to the combined effect of the double wall and inner foam. In
addition, the inner foam portion serves to maintain a distance
between the opposing walls which is important for high heat
insulating characteristics while at the same time providing an
improved structural stability with a minimum of material usage. In
the case of lightweight disposable cups, particularly of the
vending variety, the combination of thin wall, lightweight
construction with high heat insulating character is especially of
importance for containing hot liquids such as coffee. Also, due to
its composite structure the container may be easily structured to
incorporate such additional effects as finger grips, stacking rings
and the like. In general, any substantially thermoplastic resin
material capable of being shaped in the form of a thin wall
receptacle may be utilized to produce a double walled container
having an internal foam section associated with at least one of the
walls of the container. If the partial forming process is used to
produce the foam the plastic of the receptacle which is treated has
to be capable of absorbing or being admixed with an expanding
agent.
In general, the present invention is concerned with thin wall
containers which might be used in vending machines or as
over-the-counter disposable cups particularly for hot coffee,
chocolate or other heated beverages. For these purposes the wall of
each of the two telescopically associated receptacles will
generally be in the order of 3 to 20 mils preferably 5 to 15 mils
while the foam thickness between the wall would generally be in the
order of 3 to 30 mils preferably 3 to 20 mils. In addition, it is
apparent the wall thickness of one receptacle might be different
from its associated receptacle. In any event, the composite nature
of the walls wherein the foam is associated with at least one wall
of the container imparts unusual strength to the overall
structure.
In its broadest sense the containers of the present invention can
be manufactured by various means. For example, the receptacles may
be formed by any of the known plastic systems, i.e., thermoforming
using a plug assist, vacuum forming and the like. The foaming is
generally applied or produced on the plastic after the plastic
shaping step although it is possible to do it prior to the shaping
step by molding the foam and solid plastic together. The foam
portion may be applied to the wall of the receptacle by any means
such as adhering a foam strip to the wall of the container, coating
the wall with a foamable coating which is subsequently foamed or by
preferably utilizing what is referred to as the "partial foaming
process."
As indicated above, the preferred technique for providing a foam
covering on the wall of the receptacle is by the partial foaming
technique which in its broad sense involves the expansion of an
expanding agent within the wall of at least one of the receptacles
used to form the the container. The expanding agent may be
incorporated into the receptacle wall either before the formation
of the receptacle, i.e; during the extrusion process or preferably
after the formation of the receptacle such as described in U.S.
Pat. No. 3,262,626. More specifically, the expanding agent is
incorporated into the wall of at least one of the receptacles by
exposing the wall surface of the receptacle to a medium absorbable
by the plastic of the receptacle or a volatile solvent by
immersion, brush, spray or the like for a predetermined length of
time to permit the medium or solvent to be absorbed partially into
the receptacle wall and subsequently heating the receptacle to
produce a foam covering on that portion of wall which was exposed
and heated. The thickness of the foam will generally depend on the
length of time the plastic is exposed to the solvent. The heating
step necessary to produce the foam covering may be carried out
prior to interfitting the receptacles to form the double wall
container or even after the receptacles are interfitted. The latter
procedure might be advantageous if subsequent heat operations are
employed, for example, to form a rim or other operation which might
be used to mate the upper portion of both receptacles. It is, of
course, apparent that both receptacles may be solvent treated to
produce a double foaming effect, if desired. Although a rim is
generally formed on the container which helps to secure both
receptacles together, the frictional effect of the foam between the
walls of the container is such that it may be possible to eliminate
a separate receptacle mating operation, i.e., heat seal,
particularly if the fit is tight.
While the preferred embodiments of the invention have been shown
and described herein, it is obvious that many structural details
may be changed without departing from the spirit and scope of the
appended claims .
* * * * *