U.S. patent number 3,834,606 [Application Number 05/241,574] was granted by the patent office on 1974-09-10 for packaging trays and methods of making them.
This patent grant is currently assigned to Torsten Jeppsson AB. Invention is credited to Sven Ingemar Andersson.
United States Patent |
3,834,606 |
Andersson |
September 10, 1974 |
PACKAGING TRAYS AND METHODS OF MAKING THEM
Abstract
A packaging tray provided with a bottom, side walls, and an
outwardly directed flange surrounding the periphery of the side
walls of the tray, consists of outer and inner layers of a moldable
and stretchable synthetic plastic material, and intermediate layers
of liquid-absorbing material with no or but insignificant
stretchability. At the molding of the tray, the side walls thereof
are formed by stretching of the plastic material and in a softening
operation, an adhesive bond is realized between the outer and inner
layers of the stretched tray side walls which thus present an at
least partially or substantially completely ruptured intermediate
layer.
Inventors: |
Andersson; Sven Ingemar (Ystad,
SW) |
Assignee: |
Torsten Jeppsson AB (Lund,
SW)
|
Family
ID: |
22911249 |
Appl.
No.: |
05/241,574 |
Filed: |
April 6, 1972 |
Current U.S.
Class: |
229/406; 426/129;
220/62.11; 206/204 |
Current CPC
Class: |
B65D
1/34 (20130101); B65D 81/264 (20130101); B65D
81/265 (20130101) |
Current International
Class: |
B65D
81/26 (20060101); B65D 1/34 (20060101); B65d
081/26 () |
Field of
Search: |
;229/2.5,3.1,3.5R,14R
;206/46F ;99/171TC,171LP,174 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Price; William I.
Assistant Examiner: Marcus; Stephen
Attorney, Agent or Firm: Holman & Stern
Claims
What I claim and desire to secure by Letters Patent is:
1. A packaging tray formed of a multi-layered wall material
including an intermediate layer of a substantially non-stretchable
liquid-absorbing material and, on each side of said intermediate
layer, one outer layer of a synthetic plastic material which is
moldable and stretchable when heat softened, said packaging tray
having a bottom, side walls formed by molding and stretching said
multi-layered wall material, and a flange extending outwardly from
side walls around the periphery of the tray, said side walls having
an offset extending around the tray and being substantially plane
parallel with the bottom of the tray, said intermediate layer of
liquid-absorbing material being at least partially ruptured in the
area of said offset of said side walls, and said outer layers of
synthetic plastic material being joined with each other in the area
of said offset of said side walls, said multi-layered wall material
having its tray inside forming outer layer of synthetic plastic
material perforated at least within the bottom area of the tray.
Description
BACKGROUND OF THE INVENTION
This invention relates to a packaging tray which consists of outer
and inner layers of initially flat blanks of a synthetic plastic
material which is moldable when softened and thus stretchable, and
intermediate layers of liquid-absorbing material having no or but
insignificant stretchability, or in other words substantially
non-stretchable said packaging tray having a bottom, side walls
formed by stretching of the plastic material, and an outwardly
directed flange extending around the rim of the tray. The invention
also relates to a method of making the tray.
PRIOR ART
In the manufacture of a prior art tray of this kind, webs of
material representing the outer, inner and intermediate layers are
brought together, while moving in the longitudinal direction, in a
heating zone for softening the webs of plastic material disposed on
opposite sides of the web of absorbing material, the webs are then
molded into the shape of a tray and connected together, and finally
the finished trays are separated from the webs.
When the tray is molded from the webs of material representing flat
blanks for the trays, particularly the plastic material in the side
walls is stretched and the intermediate layer of absorbing material
cannot take part in such stretching. Therefore, the absorbing
material will be retracted in a very irregular manner from the
flange extending around the rim of the tray. The material will
break in the flange and the side walls at indeterminate points
which vary from one tray to the other. The result is a very weak
and often non-existent connection between the outer and inner
layers because the intermediate layer, by taking an indeterminate
position in the flange and the side walls, prevents these layers
from being regularly interconnected by welding. In the prior art
tray it has therefore been suggested to connect the outer and inner
layers together by means of spot welds or continuous welds in the
flange of the tray at the rim thereof. Because of the intermediate
layer portions often prevailing in the flange, there will be formed
a highly varied connection and in too many cases there will be no
connection at all. Moreover, the connection presupposes that
additional measures are taken, such as welding.
SUMMARY OF THE INVENTION
The present invention eliminates the disadvantages outlined in the
foregoing by softening the outer and inner layers of the tray and
realizing an adhesive bond between said layers in the stretched
tray side walls which will thus have an at least partially ruptured
intermediate layer. The side walls have substantially larger
surfaces of contact between the layers than does the flange, for
which reason the probability of an adhesive bond between the outer
and inner layers in the side walls will be greater than in the
flange. Moreover, the softening operation makes the layers tacky,
which considerably facilitates the realization of the bond. The
particular welding operation for establishing said bond is thus
entirely eliminated. A reliable bond between the layers is ensured
by forming the outer and inner layers of the side walls with
interengaging folds which extend in the longitudinal direction of
the side walls, and by the specific method of making the packaging
tray.
The invention will be more fully described hereinbelow with
reference to the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a perspective view and partial section of a packaging
tray;
FIG. 2 is a section on line II--II in FIG. 1; and
FIGS. 3-5 illustrate the method of making the tray.
DETAILED DESCRIPTION OF THE INVENTION
The tray illustrated in the drawings comprises an outer layer 1 and
an inner layer 2 of originally flat blanks made from a plastic
material which is moldable by softening and thus stretchable. The
tray further comprises an intermediate layer 3 of liquid absorbing
material which has no or but insignificant stretchability. In other
words, the intermediate layer is of a substantially non-stretchable
liquid absorbing material. The tray has a bottom 4, side walls 5
formed by stretching of the plastic material in the originally flat
blank, and an outwardly directed flange 6 which extends around the
rim or periphery of the tray. The inner layer 2 at the bottom of
the tray is formed with holes 7. The bottom 4 of the tray has
raised portions 8 which at least partially extend up into the side
walls 5. For the interconnection of the outer and inner layers 1
and 2, there is brought about an adhesive bond 9 between said
layers 1, 2 in the side walls 5 by softening said outer and inner
layers, and the intermediate layer 3 in the side walls 5 has at
least partially ruptured when the plastic material is stretched in
said side walls 5. In order to ensure a strong adhesive bond 9
between the layers 1, 2 in the side walls 5 under any
circumstances, the side walls are formed with interengaging folds
10 which extend in the longitudinal direction of said side
walls.
For the manufacture of the tray, webs of materials (not shown)
representing the outer, inner and intermediate layers 1-3 are
brought together, while moving in the longitudinal direction, in a
heating zone to soften the webs of plastic material. The webs are
then molded into the form of the tray and interconnected, after
which the finished tray is separated from the webs. For practicing
the method according to the invention, use is made of a combined
press tool for the molding of the tray, which tool comprises, as
will be seen from FIGS. 3-5, a punch 11 having an inner punch
portion 12 and an outer punch portion 13, and a die 14. The
brought-together webs, or a flat blank 15 representing said webs,
is introduced between the punch 11 and the die 14 in the initial
position of the punch 11 in which it is raised from the die 14
(FIG. 3). The webs or the blank 15 comprising the three layers 1-3
are compressed and retained or in other words clamped in the area
of the flange 6 by means of the punch portion 13 which is thus
caused to move towards the die 14 before the punch portion 12 is
operated. Then the punch portion 12 is moved towards the blank 15
while the punch portion 13 is held engaged with the blank 15, the
bottom 4 and side walls 5 of the blank 15 being deep-drawn (FIG.
5). The deep drawing is performed in such a way that not all of the
layers 1-3 in the bottom 4 of the tray are subjected to any
appreciable deformation, while the plastic layers 1-3 in the side
walls 5 are considerably deformed. This deformation implies that
the layers 1, 2 are stretched while the intermediate layer 3
ruptures. The facing surfaces of the plastic layers 1, 2 in the
side walls which have been exposed by the rupture of the
intermediate layer 3 and are tacky because of the softening
operation are compressed between the punch portion 12 and the die
14 and are securely bonded. Since all layers 1-3 are compressed
between the punch portion 13 and the die 14 in the area of the
flange 6 to be made, the intermediate layer 3 is retained in this
area nad will rupture only in the region of the side walls 5. The
intermediate layer 3 in the bottom 4 of the tray will thus remain
substantially unaffected. In order always to ensure a reliable bond
between the outer and inner layers 1, 2, folds 10 are formed in
both the outer and the inner layers with the aid of stepped
sections 16, 17 on the punch portion 12 and the die 14,
respectively. The folds 10 formed will engage with each other and
will present surfaces extending in plane-parallel or largely
plane-parallel relationship to the bottom of the tray, and the
entire pressure of the punch 12 can assert itself on the die 14,
whereby a reliable adhesive bond 9 is achieved between the layers
1, 2.
* * * * *