Note: Descriptions are shown in the official language in which they were submitted.
CA 02558048 2006-08-29
TITLE
TAMPER EVIDENT THERMOFORMED CONTAINERS
BACKGROUND OF THE INVENTION
The present invention relates in general to plastic containers and, more
particularly, to improving the tamper evidence of plastic containers having a
resealable
lid or cover.
1o Resealable plastic containers are well known in the art. See, for example,
U.S-. Pat. No. 5,339,973, to Edwards et al, and U.S. Pat. No. 5,413,239, to
Rider, Jr.
These containers are most typically used for packaging perishable items (e.g.,
foods)
and other items being packaged on a small scale and/or close to the point of
sale (e.g.,
a grocery store). Containers may be two-piece with a bottom tray and a top
tray or lid,
15 or may be one-piece with a hinge connecting the tray and lid. Transparent
plastics
such as PET or PLA are commonly used, and the contaiilers are typically made
by
thermoforming in a mold.
Because of the possibility of tampering with the contents of plastic trays of
this type, they are typically not used for packaging food or similar items by
large scale
2o manufacturers because the items pass through many hands in the distribution
chain
and the potential for tampering is greater. Thus, it would be desirable to
improve the
tamper evidence of resealable plastic containers.
Consumer appeal of resealable plastic containers comes both from the high
level of freshness maintained, the convenience of resealability, and the
ability to
25 visually. inspect the contents without opening. Any attempts to increase
tamper
evidence of the container should not compromise these other desirable
properties.
Moreover, it is desirable to provide a container that can be used by the
packager
without requiring special equipment.
3o SUMMARY OF THE INVENTION
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A preferred embodiment of the invention employs a single-piece
thermoformed tray consisting of a bottom portion and a top portion joined by a
hinge,
incorporating one or more sets (pairs) of male and female locking mechanisms
joining
s the top and bottom portions at one or more mating tabs at the opposite side
of the tray
from the hinge. A perforation line is disposed in the top and/or bottom
portions (e.g.,
in a mating tab) between a locking mechanism and the main body of the tray to
allow
one-time tamper evidence when access is gained to the interior of the tray.
The shape, size, type, and number of locking mechanisms vary to
o accommodate different usages of the container. Locking features can be
created in the
container during initial formation'or incorporated at a later stage. Locking
mechanisms are located to the outside of the perforation lines. One preferred
locking
mechanism uses male/female mating parts that interlock and prevent removal
once
inserted. Alternatively, a machine closing operation can be used such as heat
staking.
1 s The length, shape, pattern, gate size, orientation, and number of gates of
each perforation line vary to accommodate different tray dimensions, volumes,
degree
of tamper evidence, and ease of separation. A perforation line is provided
between
each lock and the container seal. The number of paired perforations/locking
mechanisms may vary according to tray dimensions, volumes, or degree of tamper
2o evidence desired.
In one aspect of the invention, a container is provided comprising a tray
body having a top lid portion and a bottom portion. The top lid portion and
bottom
portion form a re-closable seal around their periphery. A top tab extends from
the top
lid portion. A bottom tab extends from the bottom portion. A locking mechanism
is
2s formed in the top and bottom tabs for substantially permanent engagement. A
perforation line in at least one of the top and bottom tabs isolates the
locking
mechanism, whereby the perforation line must be broken when gaining access
inside
the tray body.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an isometric view of an open container according to a first
preferred embodiment prior to locking.
s Figure 2 is an isometric view of the container of Figure 1 after closing and
locking.
Figure 3 is an isometric view of the container of Figure 2 after being re-
opened, showing the lock separated along the perforation line.
Figure 4 is a top view of the open container of Figure 1.
to Figure 5 is a cross-sectional view of the lock of Figure 2 with the lock
parts
engaged.
Figure 6 is a cross-sectional view of the lock of Figure 3 after re-opening
and showing the male lock part separated from the lid.
Figures 7A through 7E are plan views showing examples of perforation
1s lines that can be used in the present invention.
Figure 8 is a cross section showing another preferred embodiment of
obtaining a lock using heat staking.
Figure 9 is an isometric view of an open container according to another
preferred embodiment prior to locking.
2o Figure 10 is an isometric view of the container of Figure 9 after closing
and
locking.
Figure 11 is a top view of the open container of Figure 9.
Figure 12 is a top view of an open container according to yet another
embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
A general description of performance of the tray is as follows. In order to
seal and protect the tray contents, the container is closed to engage the
peripheral
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re-closable seal between the top and bottom portions. Likewise, the male
(e.g., top)
and female (e.g., bottom) locks are snapped together. Lock engagement is
permanent,
such that the male part cannot be removed from the female part without either
destroying them or altering them so that they cannot re-lock. Once the locks
are
s closed, any force applied to open the container will partially or completely
break one
or more perforation lines, thus providing clear tamper evidence.
The perforations must be broken to access the contents of the container.
The perforation lines can be separated by simply pulling the cover away from
the base
or by bending and then ripping along the perforation lines, for example. In
order to
1o ease the task of separating the locks and/or breaking the perforation
lines, one or more
flaps may be provided. The flaps may also assist in opening the re-closable
seal of the
tray during subsequent use.
A perforation line comprises a series of aligned cuts (i.e., gates) or
indentations into or through the surface of a tab or flap that goes between
two edges of
15 the tab or flap so that a locking mechanism is completely isolated. The
perforation
line can also comprise a continuous indentation or other weakening of the tab
or flap,
or may comprise a series of cuts completely through the tab with the
intervening areas
being partially cut or indented. When using a series of discontinuous cuts or
indentations, the number of gates may be between 5 and 11 per inch. The linear
length
20 of each gate may be between about 0.10 and 0.25 inches. In one preferred
embodiment, a perforation line comprises 7 gates, each gate being 0.167 inches
long.
The shape of a perforation line may be other than straight in order to better
show
evidence of tampering.
Instead of being joined by a hinge; the top cover and base could
2s alternatively comprise two separate pieces. Locking mechanisms and
corresponding
perforation lines would be placed around the periphery of the tray at a
sufficiently
close spacing to prevent entry into the tray without breaking a perforation
line (e.g.,
locking mechanisms at four corners of the tray).
Turning now to the drawings, Figures 1-4 show a transparent container 10
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formed of PET or PLA and having a bottom tray portion 11 and an upper lid
portion
12 joined by a hinge portion 13. Bottom tray portion 11 has reinforcing ribs
14, and
lid portion 12 has reinforcing ribs 1 S. An inner circumferential flange 16
extends
downward from lid portion 12 to sealingly mate with an outer circumferential
flange
17 formed along the lip of bottom tray portion 11. A guard rib 18 is provided
around
the periphery of outer flange 17 to receive an outer edge 20 of lid portion 12
to help
defeat attempts at prying apart portions 1 l and 12 at areas away from hinge
13 and the
lock mechanism to be described next. Guard rib 18 may be continuous or may
include
separate sections spaced around the periphery as shown in Figures 1-4.
1o A top tab 21 extends from lid portion 12 and includes an isolated section
22
separated from lid portion 12 by a perforation line 23. Isolated section 22
has a male
lock part 24 extending in the direction of bottom tray portion 11. , A bottom
tab 25
extends from bottom tray portion 11 and has a female lock part 26 for
lockingly
receiving male lock part 24. Male lock part 24 may have a generally figure-8
shaped
~5 profile with crosscuts and/or lateral indentations which allow male lock
part to
compress during insertion into female lock part 26 and subsequently expand
after
insertion. Female lock part 26 may include a narrowed upper neck that acts to
compress male lock part 24 during insertion and then block any removal of male
lock
part 24. Other configurations for interlocking parts will be readily apparent
to those
2o skilled in the art. Moreover, the invention also encompasses locating a
male lock part
on the bottom tab and a female lock part on.the top tab.
Top tab 21 includes a grasping section 27 to facilitate opening of container
10. Section 27 may preferably be scored with a legend such as "LIFT" or other
instruction to the user so that it will be apparent that the container can be
opened by
25 pulling apart bottom tab 25 and grasping section 27. As these are
separated, isolated
section 22 tears away from top tab 21 along perforation line 23. Isolated
section 22
remains locked with bottom tab 25. After tearing, top tab 21 exhibits a
roughened
edge 28 which is distinguishable after re-closing container 10, thereby making
evident
any tampering. A decorative rib 29 may be provided on grasping section 27 to
provide
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a fill-in between different sections of guard rib 18 and/or to facilitate
grasping by a
user.
Figure 5 illustrates a cross section through top and bottom tabs 21 and 25
when container 10 has been closed and locked. Female lock part 26 has narrowed
s upper neck 30 to retain an expanded portion 31 of male lock part 24. The
main
compartment of the container is sealed as a result of the sloped and
interference
mating of flanges 16 and 17. Figure 6 illustrates a similar cross section
after the
locked container has been opened. Perforation line 23 has been separated so
that
isolated section 22 remains locked in place but does not interfere with
subsequent re-
~o closing of the container at flanges 16 and 17.
Many useful configurations of the locking parts and the perforation line can
be used in the present invention. Some such configurations are shown in
Figures 7A
to 7E. These Figures show a locking mechanism at one corner of a rectangular
tray.
Other tray shapes and other locations of the locking mechanism away from the
hinge
~s are possible and are within the scope of the invention.
Figure 7A shows locking parts 35 having a generally elliptical profile. A
perforation line 36 includes gates in two parallel lines with the individual
gates being
staggered or offset between the lines. Figure 7B shows locking parts 37 having
a
generally circular profile and a perforation line 3 8 having gates in two
parallel lines
2o with the individual gates being side-by-side., A single, straight
perforation line 40 is
shown in Figure 7C along with cut-outs 41 and 42 on either side of isolated
section 43.
Cut-outs 41 and 42 may provide for easier grasping of the lid portion and/or
the top
tab when the container is closed. They also provide a lead-in for perforation
line 40.~
As shown in Figure 7C, perforation line 40 preferably includes gates that
intersect the
2s edges of isolated section 43 to make tearing easier.
As shown in Figures 7D and 7E, non-straight perforation lines such as a
cornered perforation line 45 or a curved perforation line 46 may be used. A
non-
straight line can make the torn. condition of the tab more noticeable to a
user after the
container is re-closed, thereby making tampering done prior to purchase more
evident.
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Figure 8 shows an alternative locking mechanism employing a heat staking
machine having a heater tip 50. After inserting male lock part 24 into female
lock part
26, tip 50 is pressed against the bottom well of the lock parts and generates
sufficient
heat to cause melting between the lock parts at 51. Alternatively, male and
female
s lock parts can be eliminated (e.g., the top and bottom tabs may be flat) and
the lock
created by heat staking the flat tabs together at the isolated section. In
another
alternative embodiment, male and female lock parts can be used without
compression
or expansion so that they can be freely joined and separated until they are
heat staked.
Either of these two alternative embodiments would allow a manufacturer or
filler of
1o the container to close and re-open the container before activating the
locking
mechanism.
Figure 9 is an isometric view of an alternative embodiment of a container 60
wherein an outside-fit lid 61 seals to a bottom tray 62. A flange 63 extends
upward
along the periphery of lid 61 and sealingly receives a flange 64 extending
upward from
is bottom tray 62. This embodiment is referred to as outside-fit because the
peripheral
seal extends outward from the container, as opposed to the inside-fit
embodiment of
Figures 1-4 wherein the sealing flanges extend inward into the container.
Figure 10 is an isometric view of container 60 in a closed and locked
condition. Figure 11 is a top view of open container 60 prior to locking.
Substantially
2o identical locks are provided at adjacent corners of the rectangular
container on the side
of the container opposite a hinge 65. One of the locks includes a top tab 66
extending
from lid 61 including an isolated section 67 separated from lid 61 by a
perforation line
68. Isolated section 67 has a male lock part 70 extending in the direction
(when
closed) of bottom tray 62. A bottom tab 71 extends from bottom tray 62 and has
a
2s female lock part 72 for lockingly receiving male lock part 70. In the
present
embodiment, lock parts 70 and 72 have an interfering circular profile. Female
lock
part 72 may include a narrowed upper neck that acts to compress male lock part
70
during insertion and then block any removal of male lock part 70.
Top. tab 66 includes cut-outs 73 and 74 providing lead-ins to perforation line
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68. Cat-out 73 is located between isolated section 67 and a grasping section
75 to
facilitate opening of container 60. A grasping section 76 on bottom tab 71
coincides
with cut-out 73 so that grasping sections 75 and 76 can be grasped with
different
hands and easily separated in a manner that tears perforation line 68 to open
container
s 60. Another grasping section 77 may be provided in top tab 66 by making a
cut-out 78
in bottom tab 71 so that it is possible with smaller containers to break
perforation lines
at both corners of the container simultaneously.
Figure 12 shows another alternative embodiment wherein locks are
completely removed from a container in order to open it. Thus, one lock
comprises an
1o isolated section 80 on the top tab which locks with an isolated section 81
on the
bottom tab. Another lock comprises an isolated section 82 on the top tab which
locks
with an isolated section 83 on the bottom tab. The locked isolated sections
are torn off
along the perforation lines and discarded to open the container. The slightly
rough
edges of the perforation lines remain in order to provide tamper evidence.
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