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Патент USA US3040958

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June 26, 1962
Filed Jan. 27, 1959
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United States Patent O?ice
Patented June 26, 1962
body of this tray may be non~absorbent or only slightly
absorbent, and instead of becoming absorbed the liquid
Roger Wells, Stamford, Conn, assignor to Diamond
National tlorporation, a corporation of Delaware
is mechanically trapped in the cup-shaped depressions
due to their particular size, shape and arrangement.
Filed Jan. 27, 1959, Ser. No. 789,433
2 tClaims. (til. mans)
This invention relates to molded pulp articles, and
methods of molding such articles. More particularly the
invention relates to molded pulp containers especially
suitable for packaging foods, and to methods of making
such containers.
Containers made of molded pulp are customarily used
in most retail food markets today for packaging fresh
meat, poultry, ?sh or other commodities from which
some natural juices are likely to exude. These containers
are usually in the form of a shallow, generally rectangu
lar tray, and a transparent covering sheet of cellophane
or polyethylene may be Wrapped around the tray and
heat-sealed to the bottom surface thereof. Such con
tainers present an attractive display While providing ade 20
quate protection during the sale and temporary storage
of foodstuffs, particularly for naturally juicy fresh poultry
and the like, from which some blood may exude.
It is desirable to absorb any exuded blood or other
The present invention relates to an improved construc
tion for food containers designed to overcome the above
mentioned problems associated with the presence of ex
cess ?uid drained from packaged foods. This is accom
plished, in accordance With the invention, ‘by providing
molded pulp trays and other containers, which may be
molded from a non-absorbent grade of pulp, with an
integrally molded layer of absorbent pulp on the upper
surface of its bottom wall. This absorbent layer may be
provided with a multiplicity of uniformly distributed
cup-shaped depressions adapted to trap any excess liquid
which then becomes absorbed into the sides of said de
pressions. Thus, the invention is embodied in containers
which are of two ply construction in their bottom por
tion and single ply elsewhere, such as their side walls.
Another important aspect of the invention relates to new
methods of manufacturing molded pulp articles which
are two ply in speci?c areas.
It is therefore an object of this invention to provide
new and improved molded pulp articles and methods of
juices to prevent such ?uids from being free to run around 25 molding such articles.
A speci?c object of the invention is to provide new and
the inside of the sealed package during normal handling
improved molded pulp containers for packaging foods
by the customers or prospective purchasers. For this
and methods of molding such containers.
purpose the entire body of the molded pulp tray has
Another object of the invention is to provide new and
sometimes been made of an unsized grade of pulp to
improved food containers, particularly suitable for pack
render it inherently absorbent. However, ‘when the
aging fresh poultry or other naturally wet or juicy food,
amount of ?uid present is excessive, this type of tray may 7
which containers are provided with means for trapping
become soggy and weakened, resulting in an unattractive
any excess freely‘ ?owable ?uids drained from the pack
appearance and possible leakage from the package. It
aged r'ood.
has been proposed that certain wet strength resins could
Still another object of the invention is to provide new
be incorporated into the molded pulp to prevent weakness
and improved food containers having integral means for
caused ‘by sogginess, but the resulting tray may still show
absorbing excess ?uids without dehydrating food pack
blood stains on the outer surfaces of its ‘bottom and side
aged therein.
walls. Furthermore, a signi?cant disadvantage of this
Yet another object of the invention .is to provide
type of tray is that it exhibits a tendency to dehydrate
pulp trays, dishes and other types of containers
the meat or poultry contained in the package.
with an integral highly absorbent portion limited to the
Another instance in which great quantities of con
upper surface of the inside bottom wall thereof, and
tainers are used and similar problems are encountered
to provide new methods of molding such containers.
is in the packaging of freshly killed ‘chickens at the whole
Other objects and the nature and advantages of the
sale terminal level. The ‘freshly killed and dressed
instant invention will be apparent from the following de
chickens are taken directly from the tubs of crushed ice,
tailed description, taken in conjunction with the accom
they are cut into sections, and while they are still wet
panying drawings, wherein:
they are packed into containers for shipment to retail
FIG. 1 is a top plan view of a molded pulp tray em
markets. It would be desirable if the ‘Wholesale packers
bodying the invention;
at the terminals could package the chickens directly into 50 FIG. 2 is an enlarged vertical section taken along
individual containers suitable for retail sale, but one of
the line 2—2 of FIG. 1;
the major reasons this procedure has seldom been prac
FIG. 3 is a sectional view corresponding to FIG. 2
ticed is the fact that so much free water and exuded juice
but showing a modi?cation of the invention;
drains off the chicken by the time it reaches the retail
FIG. 4 is a vertical section of a portion of the bot
store that the package becomes W612 and unsightly. Ef
tom wall of a molded pulp tray representing another
forts have been made to absorb such ?uids by inserting
embodiment of the invention; and
loose blotting sh sets into the bottom of the containers, '
but this has not always provided adequate protection.
Furthermore, these blotters constitute an extra expense,
and they involve added handling, inventory and labor
One suitable container structure designed to trap any
freely flowable ?uids without dehydrating the packaged
food, is described and claimed in copending application
Serial No. 750,495, ?led July 23, 1958, for “Food Con
tainer,” naming as inventors Richard F. Reiiers and the
present inventor. The structure covered by said co
FIG. 5 is a sectional view of a suction mold shown
at one stage of a molding method embodying the inven
in order to illustrate the principles of the invention
as applied to a typical Widely used article of commerce,
the molded pulp trays embodying the invention shown
in the drawings appear relatively shallow and generally
rectangular in overall con?guration, and it should be
understood that this con?guration may be varied as de
ing the upper surface of its bottom wall provided with
a multiplicity of uniformly distributed cup-shaped de
sired. The illustrated trays are particularly suitable for
packaging fresh meat, poultry or ?sh for sale. in retail
food markets.
The tray shown in FIGS. 1 and 2 comprises a gen»
erally ?at horizontal bottom wall 10‘ from the edges of
pressions possessing certain critical dimensions.
which project integral upstanding inclined sidewalls 12
pending application comprises a molded pulp tray hav
terminating in a peripheral lip 14. The upper surface
of the bottom well ill‘ on the inside of the tray is pro
vided with a multiplicity of cup-shaped depressions l6
uniformly distributed over the entire area of this surface.
irregular deposition pattern around the cylindrical side
walls of the cup-shaped depressions, and a regular pat
tern on the upper surface of the bottom wall of the tray
between these depressions. Pulp deposited in the irreg
ular pattern exhibits greater absorbency than the pulp
In accordance with the present invention, the entire
deposited in the regular pattern. Consequently, the side
bottom wall lit} of the tray is composed of two integrally
walls of the depressions are inherently more absorptive
united layers of molded pulp, constituted by an upper
layer 18 and a lower layer Ztl, resulting in a composite
than the upper surface of the bottom of the tray between
two-ply construction. The upper layer 18 is intended
the depressions. Due to this construction, most of the
to be highly absorbent, and for this purpose it may be 10 free liquid is trapped and absorbed Within the depressions
molded from unsized sulphite pulp stock. On the other
rather than elsewhere on the bottom of the tray, and the
tendency to dehydrate the packaged food resting on the
hand, the lower layer 2i?‘ as well as the integral side- .
walls 12 and the peripheral lip 14 are preferably non
surface ‘between the depressions is minimized.
The embodiment of the invention illustrated in FIG. 4
absorbent or only slightly absorbent in character, and
they may be molded from highly sized groundwork stock.
The sidewalls 12 and the lip 14 are preferably of single
represents a modi?cation of the tray shown in FIGS.
ply homogeneous construction, and none of the highly
absorbent pulpstock employed to form the upper layer
to assist in preventing any tendency to dehydrate food
packaged in the tray. This tray is provided with a bot
tom wall 40, of which only a portion is shown in FIG. 4,
18 of the bottom wall 10 should be allowed to extend
1 and 2, wherein an extra protective coating is employed
(The cup-shaped depressions to may be limited in
depth to extend only partially through the upper layer
18, or they may extend completely through the layer
18, and they may also extend partially through the thick
and the sidewalls and rim of this tray which do not ap
pear in this view are identical in structure and in function
ness of the lower layer 20 of the bottom wall it}.
pulp, a highly absorbent pulp layer 44 is superimposed
upon and integrally united with the lower layer 42, and
depressions 16 when properly constructed in size, shape
and arrangement serve to provide traps for mechanically
holding any freely ?owable fluid, and these depressions
also impart a distinctive attractive appearance to the
trays. Any ?uid trapped within the depressions 16 even
tually becomes absorbed into the cylindrical side walls
thereof. However, primarily the absorbency of the en
tire upper layer 1% is relied upon to control the excess
?uid, and the provision of the depressions 16 to serve
as ?uid traps is optional.
FIG. 3 shows an embodiment of the invention where
in'such depressions have been omitted. In this embodi~
ment, the tray is provided with a bottom wall Tall, inte
gral upstanding sidewalls 32, and a peripheral lip 34,
which are related to each other in the same manner as
the corresponding parts described for the tray shown
in FIGS. 1 and 2.
The bottom wall 30 is composed of
to the corresponding sections of the trays depicted in
FIGS. 1, 2 and 3. The bottom wall 4t) includes a lower
layer 42 of non-absorbent or slightly absorbent molded
the entire area of the bottom wall 4@ is provided with a
multiplicity of cup-shaped depressions 46 which corre
spond to the depressions 7.6 of the tray disclosed in FIGS.
1 and 2. However, the tray shown in FIG. 4 is equipped
with a thin liquid impervious protective coating 43 cover
ing the entire upper surface of the highly absorbent layer
44. The protective coating 48 may be formed by spray
ing a suitable sizing composition onto the layer 44, or
' by bonding ‘a sheet of wax paper thereto, or in any other
suitable fashion. Of course, the protective coating 43,
whether formed by spraying or by a bonded sheet or
otherwise, must not extend down into the depressions 46.
It is intended that any free ?uid trapped within the de
pressions as should become absorbed into the portions
of the layer 44 ‘constituting the cylindrical side walls of
these depressions. Whatever food is packaged in the
two integrally united layers of molded pulp, namely, an
tray rests upon the protective coating 48, and due to the
'irnperforate upper layer 36 of highly absorbent pulp
liquid impervious nature of this coating the normal tend
and a similarly imperforate lower layer 38 of non-ab 45 ency of the absorbent layer 44 to cause dehydration of
sorbent or slightly absorbent pulp.
the packaged food is prevented.
In the aforesaid copending application Serial No. 750,
It is evident that the tray illustrated in FIG. 4 offers
495, details are given of the required size, shape and ar
the greatest protection against possible dehydration of
rangement, as well as the critical dimensions, for the de
food packaged therein, but that some measure of pro
pressions to serve effectively as fluid traps. It is dis 50 tection is provided in all of the disclosed containers em
closed therein that due to the surface tension of the
bodying the invention, due to the con?nement of the
?uid, drops will enter the depressions without running
out when the container is inverted, if the diameter of
the depressions is in the critical size range of about
5%32" to 732”. The preferred depth of the depressions is
in the range of about 0.06" to 0.125” but is not limited
thereto. In spacing they may be centered about 5/16”
apart in alternately staggered parallel rows and columns,
highly absorbent pulp layer to the upper inside surface
of the bottom of the tray while the upstanding sidewalls
of the tray are made non-absorbent or only very slightly
55 absorbent.
Moreover, due to the previously described
deposition pattern of the pulp ?bers, the surfaces pos
sessing the greatest powers of absorption are located
down inside of the cup-shaped depressions, and this fact
also contributes to the prevention of dehydration of the
and in aggregate areas the depressions may occupy from
about one-?fth to one-third of the total surface area of 60 packaged food.
the bottom wall inside the container.
The preferred method molding containers embodying
In order to achieve maximum effectiveness as ?uid
the invention involves the successive deposition of two
traps, the cup-shaped depressions should have smooth
cylindrical sidewalls and sharply defined upper edges.
different layers of pulp from two different grades of pulp
stock onto a specially constructed suction mold.
They may be formed with such characteristics simulta 65 FIG. 5 there is shown a portion of such a mold with
neously with the formation of the main body of the
the two different layers of pulp deposited thereon at an
molded pulp tray, by providing the usual drainage screen
intermediate stage of the molding operation. This mold is
on the surface of the mold with a plurality of uniformly
provided with a tubular body 59 adapted to be con
spaced and distributed solid projecting nubbins made of
nected to a suitable source of suction.
metal, rubber or a plastic.
Covering the
It has been observed that 70 open end of the tubular body 50 is a perforated forming
the ‘pulp ?bers which deposit in the vicinity of these
plate 52 contoured to produce a generally rectangular
shallow tray. A foraminous wire straining screen 54 is
whereasrthe pulp ?bers deposited on the perforate other
secured over the forming face of the plate 52 by means
portions of the mold appear felted in a regular sym
of a peripheral retaining ring 56. The straining screen
metrical pattern. This results in the production of an 75 54 may be of the ordinary well known type for produc
nubbins assume an irregular or heterogeneous pattern,
tion of imperforate articles similar to the tray shown in
FIG. 3, and for the production of trays having the cup
shaped depressions 16 or 46, this screen could be pro
vided with the previously described spaced solid project;
ing nubbins.
The perforated forming plate 52 is provided with a plu
rality of spaced transverse perforations 58, and it is im
portant to notice that the perforations 58 are present only
on a rotary drum type molding machine adapted to ad
vance the mold through a vat divided vertically into two
sections containing the two different slurries, in a manner
well known to those skilled in the art. Of course, more
than two layers may be deposited in this fashion if de
Following these suction molding operations, the usual
drying and ?nishing steps are performed to complete the
fabrication of the molded pulp articles.
in areas of the forming face where the molding of a
Although the invention has been illustrated and de
two-ply structure is desired. When the mold is submerged 10
scribed with particular reference to the production of food
?rst in a thin slurry of sulphite stock and then is dipped
containers, and especially to containers having an inte
into a thick slurry of groundwood stock, a two-ply struc
gral absorbent inside bottom portion adapted to trap free
ture is formed directly over the area of the forming plate
?uids, the principles of the invention may be applied ad
52 where the perforations 58 are located, and elsewhere
over this forming plate a single ply structure is deposited. 15 vantageously in other types of molded pulp articles. For
example, pocketed molded pulp containers for packaging
The thin sulphite stock has such a high drainage rate that
industrial or electronic parts may be provided with pock
the slurry passes through the ?rst ?bers deposited above
ets of two-ply construction including a cushioning lin
the perforations and gradually builds up a relatively thick
ing of one grade of pulp, while the main body of the
layer 60 of absorbent molded pulp, but no ?bers are de
posited elsewhere on the mold from this dilute slurry. 20 container may be made more rigid and strong by a differ
ent grade of pulp in a single ply.
When the partially coated mold, having the layer 60 coat
It will be obvious to those skilled in the art that various
ed thereon only above the perforations 58 is then sub
changes may be made without departing from the spirit
merged in the thick slurry of groundwood pulp stock, the
of the invention, and therefore the invention is not limited
?bers deposited from the slurry accumulate on top of the
layer 60 until a natural barrier against further drainage 25 to what is shown in the drawings and described in the
speci?cation, but only as indicated in the appended claims.
is formed, and then deposition occurs over the remainder
What is claimed is:
of the forming face of the plate 52 resulting in the for
l. A food container of pulp material adapted for the
mation of a layer 60. The length of immersing and the
packaging of meat and poultry comprising a tray having
degree of suction applied to the mold in the two‘ different
slurries can be so controlled that the wall thickness in 30 a bottom wall and upstanding side Walls, said bottom wall
having three plies of material extending therethrough, the
the single ply portions is substantially the same as that
lower ply being relatively non-absorbent, the intermediate
in the two-ply portions of the tray. Thus, even though
ply being relatively absorbent and the upper ply being
two successive deposits form the bottom of the tray, no
an impermeable ?lm, depressions extending downwardly
extra thickness need be created thereby, and the ?nished
article may have the same dimensions and proportions as 35 from the upper surface of said bottom wall through the
upper ply and at least partially through the intermediate
a conventional tray.
ply, said depressions being of such shape and size as to
be capable of mechanically trapping any juices therein due
the surface tension of said juices, whereby any juices
in water, and this percentage should not be greater than
about 1%. The relatively thick slurry of groundwood 40 resulting from any food products stored therein will pass
into said depressions from whence they will be absorbed
stock is preferably kept at about 1% by weight of pulp
by said intermediate ply.
?bers in water, which is approximately the consistency
The thin sulphite pulp stock contemplated should pref
erably contain about 1A % by weight of unsized pulp ?bers
2. A food container in accordance with claim 1, where
in the depressions are in the shape of cylindrical cups, each
groundwood stock, up to about 3%, may be employed 45 said cup having a sharply de?ned vertical side wall and
upper lip.
if desired. A small quantity of a suitable sizing compo
sition may be incorporated into the groundwood slurry.
References Cited in the ?le of this patent
The consistency of both the sulphite stock and the ground
wood stock may be varied slightly to regulate the thick
ness of the deposited layers of pulp ?bers. Sulphite stock 50 1,848,056
Chaplin ______________ __ Mar. 1, 1932
possesses a higher drainage rate than that of groundwood
1,974,898 '
Rutledge _____________ __ Sept. 25, 1934
stock at the same percentage of pulp ?bers, and advantage
Farnham _____________ __ May 25, 1937
is taken of this dilference to produce molded pulp articles
Chaplin ______________ __ July 11, 1950
in accordance with the present invention.
Chaplin ______________ __ Feb. 24, 1953
Molds having perforations limited to areas where the
Reifers _______________ _.. Mar. 14, 1961
usually employed for molding simple pulp articles such
as trays.
However, somewhat thicker slurries of the
molding of a two-ply structure is desired, such as the mold
illustrated in FIG. 5, may be dipped successively into
two separate vats of slurry, or this mold may be placed
France _______________ _- Feb. 10, 1956
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