Note: Descriptions are shown in the official language in which they were submitted.
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~ of the Invention
Sheetlike expanded polystyrene has long been a popular
material for use ln the manufacture of the body portions of
nestable drinking cups because of its good thermal insulating
properties. U.S. Patent 2,917,217 (Sisson) shows such a drink-
ing cup in which the body portion is fabricated from a laminate
of sheetlike expanded polystyrene and paperboard and U.S. Patent
3,468,467 (Amberg) shows such a drinking cup in which the body
portion is fabricated from a single layer of sheetlike expanded
polystyrene. Such cups have good thermal insulating properties,
in relationship to conventional cups fabricated from paperboard,
and, as a result such cups enjoy widespread use for the serv-lng
of hot beverages such as coffee.
One of the major advantages of insulated cups, such as
those described above, over other popular types of insulated cups,
such as those formed by the fusing of expanded beads of polysty-
rene in a closed steam-heated mold, is that cups whose bodies are
fabricated from blanks of sheetlike material may be made on con-
ventional paper Cllp manufacturing machines with very little modi-
fication thereto. One of the modifications which has proven to
be quite desirable, however, is the incorporation of a heating
station immediately upstream of the rim-forming station to soften
the thermoplastic material in the portion of the cup body blank
from which the cup rim is to be formed. Coventionally, the heat-
ing of the rim portion of such blank is done conductively, by
means of a heated conical metal tamper which is oscillatable into
and out of direct contact with the edge of the cup body blank at
a station on the cup-making machine immediately upstream of the
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rim-rolling station. However, in order Eor such a cup-manufac-
turing machlne to malntain commercially acceptable rates of cup-
product~on, e.g. customarily of the order of 100 - 120 cups per
minute, the contact time between the heated tamper and the edge
of the cup body blank must be ~uite limited, e.g. oE the order
of 0.3. sec. Thus, to obtain even marginally satisEactory heating
with such an arrangement, the surEace temperature of the heated
tamper must be maintained very near to the softening temperature
of polystyrene foam used in the cup body blank, or perhaps even
above such softening temperature. Such a relationship between
tamper temperature and foam softening point occasionally leads
to overheating of the surface of the foam, causing an undesirable
fuzz to form thereon or causing the cup body to stick to the
tamper and to be extracted therewith.
Gene'r'al D'escription of the Invention
In accordance with the present invention, however, the
aforesaid and other rim-rolling problems encountered in the
fabrication of the bodies of disposable CUp5 and containers from
sheetlike polystyrene foam or from laminates thereof with paper
may be corrected by the substitution of a convective heating
station on the cup-forming machine for the conductive, oscill-
atable heated tamper station previously utilized. In such an
arrangement, a stream of indirectly heated air or other gas at a
suitable temperature is directed against the edge of the cup body
for a brief period of time from a diffuser spaced apart therefrom
immediately before such cup body is advanced to the rim-rolling
station. Because there is no need for physical contact between
a physical tool and the polystyrene foam of the cup body in
such an arrangement, the temperature to which the cup body is
exposed can easily be much higher than the softening point of
the resin from which the foam is produced, thereby permitting
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the foam to be heated to a much greater depth in the brlef time
period during which it can be exposed to heat. As a result of
such heat penetration9 a tighter and more uniform rim will be
Eormed when such cup body is contacted by a rimming tool.
In the practice of the method of the present invention,
it has been found desirable to use indirectly heated air at a
temperature oE the order of 800-900F to heat the edge of a
cup body formed from a laminate of polystyrene foam and paper in
which the polystyrene foam is of the order of 0.013 inch (13 mil)
in thickness and of the order of 11 pounds per cubic foot in
average density, and it has been found desirable to use indirectly
heated air at a temperature of the order of 400-500F to heat
the edge of a cup body formed from a monolithic layer of poly-
styrene foam of a thickness of the order of 0.038 inch (38 mil)
and of an average density of the order 13 pounds per cubic foot.
The optimum temperature for any style of such cups has been found
to vary from t~me to time depending, apparently, on variations
in the brittleness of the polystyrene foam therein. In the heat-
ing of such air, it has been found desirable to avoid the use of
fuel burners or other direct heating means, because the products
of combustion which will then be contained in the air stream can
lead to undesirable chemical reactions with the polystyrene foam.
For a further understanding of the present invention
and the objects thereof, attention is directed to the drawing,
to the following description thereof, to the detailed description
of the invention and to the appended claims.
Description of the Drawing
Fig. 1 is a fragmentary front elevational view of a
heating device for use in the practice of the method of the
present invention;
Fig. 2 is a fragmentary side elevational view, partly
in section, of the heating device of Fig. l;
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Fig. 3 is a plan schematic view illustrating the
applicatlon of the heating device of Figs. 1 and 2 in relation-
ship to other elements of a cup-making machine;
Fig. 4 is an enlarged view of the unrimmed cup body
illustrated in Fig. 3; and
Fig. 5 is a fragmentary sectional view, at an enlarged
scale, of the material used in the cup body of Figs. 3 and 4.
Detailed Description of the Invention
In the fabrication of nestable cup bodies from crescent-
shaped blan~s of a suitable sheetlike material, as is known in
the art, the cup bodies are first formed on mandrels and are then
transferred, in sequence, into the holding pockets of an inter-
mittently driven, or indexing, turret for further processing,
including the rolling of a reversely turned rim in the outer
larger end of such cup bodies. In the arrangement shown in the
drawing, one of such cup holders is indicated generally at 11
and a cup body 12 is so held in such holder that an outer mar-
ginal or edge portion extends outwardly beyond the confines of
such holder.
Located adjacent the path of travel of the cup holders
at a position immediately before each of the cup holders is
advanced to present the exposed edge portion of the cup body to
a rimming tool is a convective rim heating device indicated
generally at 13. This arrangement is shown in Fig. 3 where a
longitudinally oscillatable rim-rolling tool of conventional
character is shown schematically by reference numeral 14 at the
next station to which the cup holder 11 will be indexed. By
locating the heating station immediately upstream of the rimming
station, as shown and described, appreciable cooling of the
heated edge of the cup body will be avolded. Heating device 13
is so positioned, with respect to cup holder 11, t~ be spaced
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~w.ly trolll tlle idg~ of clJp body L2 container thereill. ileating
device 13 is shown as comprising a heated alr diEfuser 15 which
is adapted to direct a stream of heated air against the inner
foam polystyrene surface of cup body 12 in a concentrated annular
stream. Diffuser 15 is located at the end of a biEurcated air
f]ow plenum 16, each leg of which is provided with an indirect
air heating device 17 such as a Kamweld hot air gun. Each such
air heating device contains an electrical heating element (not
shown), which receives power from a conductor 18, and an air
inlet fitting 19 through which air at a regulated pressure, e.g.
8-9 p.s.i.g., is introduced by way of a regulator 21 of conven-
tional character, air being del-ivered to regulator 21 from a
- plant supply at a higher pressure, e.g. 40 p.s.i.g. or higher,
by means of conduit 22. To be able to heat the air to a tem-
perature of the order of 800-900F, which is required to
i satisfactorily heat the edge of a foam/paper laminated cup body
in the available cycle time of about 0.3 sec. if a production
rate of 100 - 120 cups per minute is to be met, approximately
14-16 amps of heat input is required, and each of the separate
heating elements should therefore, be sized at 7-8 amps. This
heat input can be obtained by using a 2200 watt Kamweld KHAG-2
hot air gun. Percentage of voltage to each such heating device
should preferably be regulated so that it is discontinued, or
substantially reduced, during periods when cup production is
discontinued for short time periods to avoid overheating of the
cup body edge which remains in front of diffuser 15 during such
shutdowns. A two level, selenium controlled rectifier temperature
controller (not shown) has been found to be well suited for this.
Figs. 3-5 illustrate the practice of the present in-
vention with respect to a cup body formed from a laminate of an
inner thin sheet of polystyrene foam 22 and an outer thin sheet
j of paper 23, it being understood that a very thin layer of a suit-
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able adhesive, not shown~ ls ordinarily employed ln producing
such a laminate. In producing cups with such laminated bodies,
the temperature oP the air Prom difPuser 15 should be about 800-
900F,and this temperature can be achieved with a total power
lnput of from both heaters oE about 14-16 amps. When using the
arrangement shown to produce all foam cups, the heating element
of one of the heating devices 17 is preferably electrically dis-
connected and the power input to the heating element of the other
heating device 17 should be reduced to about 5-6 amps as by the
use of a suitable temperature controller, as described above.
Finished cups made by the method of the present inven-
tion have been found to have, in relationship to similar cups
made by a method using a heated tamper to heat the cup body edge
in preparation for rimming, reduced rim thickness and outside
diameter, and an inner foam surface which is free of fuzz. On
the same basis of comparison, the practice of such method has
also resulted in less machine downtime for cleaning plastic
buildup on machine parts and has eliminated the incidence of un-
rimmed cup bodies being removed from the cup holder turret.
The best mode known to us to carry out this invention
has been described above in terms sufficiently full, clear,
concise and exact as to enable any person skilled in the art to
make and use the same. It is to be understood, however, that it
is within our contemplation that certain modifications of the
above-described mode of practicing the invention can be made by
a skilled artisan without departing from the scope of the in-
vention and it is, therefore, desired to limit the invention
only in accordance with the appended claims.
