EP0699161B1

EP0699161B1 - Tamper-evident lid for plastic containers

Info

Publication number: EP0699161B1
Application number: EP94916193A
Authority: EP
Inventors: Vanda Casartelli
Original assignee: RIGLIETTI Antonio
Current assignee: Febus SRL
Priority date: 1993-05-10
Filing date: 1994-05-04
Publication date: 1996-12-27
Anticipated expiration: 2014-05-04
Also published as: WO1994026609A1; AU6795494A; DK0699161T3; EP0699161A1; ITVI930074A0; ES2098945T3; ITVI930074A1; DE69401275T2; DE69401275D1; IT1270773B

Abstract

A tamper-evident seal for plastic containers of the type which includes a tray and a lid (2) with a flat wall (4). The tray and the lid have respective complementarily shaped edges (7; 11) with outer peripheral portions (8; 12) that are substantially vertical or slightly inclined. Protrusions (14) are arranged along the outer peripheral portion (12) of one of the edges and are suitable to elastically and unidirectionally couple by pressing within slots (15) which are arranged along the outer peripheral portion (8) of the other edge. The protrusions (14) are substantially radial with respect to the outer peripheral portion (12) of the edge on which they are formed and are shaped like teeth which are slightly inclined outward. The openings (15) are substantially parallel to the outer peripheral portion (8).

Description

The present invention relates to a tamper-evident seal for plastic containers according to the pre-characterizing portion of Claim 1.
Tamper-evident seals of the type described above are known which are particularly suitable for containers that have a generally rectangular or polygonal plan shape. These known seals include one or more pairs of engagement parts, for example shaped like pins with arrow-shaped tips that engage in complementarily shaped elastic cavities, arranged along the edges of the tray and of the container respectively at the corners of the container. These engagement parts are adapted to cooperate unidirectionally when closing the container, so that in order to release the lid it is necessary to break them, i.e. separate them from the corresponding portion of the tray or lid by levering between them or by acting on adapted grip wings.
The possible shapes of the containers are limited by the arrangement of these conventional seals at the corners. While containers that have for example a circular shape must be provided with a series of radial wings on which the seals are formed, with evident higher manufacturing costs and greater bulk of the finished product.
Furthermore, in this type of seal the engagement action is applied locally and is not uniformly distributed along the entire extension of the edge.
Another drawback of conventional tamper-evident seals is the fact that in order to obtain strong engagement parts and because of their relative complexity, the lid and the tray must be produced by injection-molding, and it is not conceivable to use a process for molding thermoplastic material.
Furthermore, in some known types of seal one of the engagement parts, after opening, can remain loosely attached to the corresponding edge, and may accidentally fall inside the container.
Also, in many cases it is not possible to positively check whether the seal has been broken, and consequently the user is not truly assured of the integrity of the package.
From FR-A-2 437 987 a plastic container with a seal having all the features defined in the preamble of claim 1 is known, wherein a series of openings are formed on a strip which has a weakened line in the area of connection with the edge of the lid. The rupture of the strip along the weakened line is often uncertain as the resistant sectional area is difficult to control.
From EP-A-0 121 172 a similar frangible seal for plastic containers is known in which one of the engageable members is attached to the edge of the lid along one or more weakened lines, the fracture of which is unreliable and not fully apparent.
The aim of the present invention is to eliminate the drawbacks described above by providing a tamper-evident seal that can be broken in a reliable and evident way and can be applied on containers of any shape without altering the outer profile of the tray or of the lid.
An object is to provide a tamper-evident seal that can be produced indifferently with a process for the molding of thermolastic sheets or for the injection-molding of melted plastic material, so as to achieve savings in production.
Another object is to provide a tamper-evident seal that extends along the entire circumference of the lid and must be removed completely to allow to open the container.
This aim, these objects and others which will become apparent hereinafter are achieved by a tamper-evident seal for plastic containers according to claim 1.
With an arrangement of this kind, the seal can be applied to containers having any shape, for example a circular one, without altering the outer profile of the tray or of the lid since it is not necessary to have a corner or a protrusion of the edges in order to place the engagement parts, thereby achieving the main aim of the invention.
Furthermore, the engagement means is distributed along the entire circumference of the closing edges, with greater assurance of a hermetic seal.
Finally, any tampering with the seal is clearly evident on the outside by virtue of the peripheral position of the engagement means, thereby achieving one of the objects of the invention.
According to the invention the first engagement means can be constituted by a series of protrusions which are substantially radial with respect to the outer peripheral portion of the edge on which they are formed.
Preferably, the protrusions consist of a plurality of teeth which are slightly inclined outward and are approximately shaped like a trapezium, with the longer parallel side directed inward, and are formed monolithically with the corresponding outer peripheral portion in angularly equidistant positions along its extension.
The second engagement means is constituted by a series of openings which can be substantially parallel to the outer peripheral portion of the edge on which they are formed.
According to the invention the openings are formed by a strip of material which is joined to the corresponding edge by a series of transverse wings that are at least equal in height to the maximum thickness of the protrusions, in angularly equidistant positions that match those of the protrusions.
According to the invention the wings taper upward at the region where they are connected to the outer peripheral portion of the corresponding edge, and the connection region has a smaller tear-resistant cross-section than the region for connection to the strip.
Advantageously the strip can have a substantially radial grip tab with a transverse cross-section that is at least equal to the maximum cross-section of the wings, and has a transverse notch in a position which is adjacent to a lateral corner of the grip tab so as to form a region for the prefracture and initial breaking of the strip and for the subsequent separation of the wings from the peripheral portion of the edge to which it is connected.
By virtue of the embodiment of the seal according to claim 1, both the tray and the lid can be obtained indifferently with an injection-molding process or with a process for the forming of plastic sheets, ensuring the same mechanical strength as conventional seals at distinctly lower costs, thus achieving one specified object of the invention-
Further characteristics and advantages will become apparent from the following detailed description of an exemplifying but non-limitative embodiment of a seal according to the invention, illustrated with the aid of the accompanying drawings, wherein:

Figure 1 is a front and partially sectional view of a tray and of a lid with a tamper-evident seal according to the invention, prior to closure;
Figure 2 is a front enlarged-scale view of a detail of Figure 1, with the container closed;
Figure 3 is a sectional view of the detail of Figure 2, taken along the plane III-III;
Figure 4 is a sectional view of a detail of Figure 3, taken along the plane IV-IV.

With reference to the above figures, a container for food or other commercial products is generally designated by the reference numeral 1. The container includes a lid 2 with a substantially flat central wall 4 and a tray 3 with a side wall 5 and a bottom wall 6. Both the lid and the tray can be made of plastic, such as polyethylene, polypropylene, PVC or other equivalent materials, using injection-molding processes or by forming sheets of preheated material.
The lid 2 has a folded edge 7 with an external peripheral portion 8 which is approximately vertical or, better still, is slightly inclined by approximately 10° to facilitate extraction, and is joined to an internal peripheral portion 9 by an annular region 10 which is approximately flat and horizontal.
The tray 3 has a folded edge 11 with an outer peripheral portion 12 which is also inclined by approximately 10° and is joined to the side wall 5 by means of an annular region 13 which is approximately flat and slightly inclined with respect to the horizontal.
The edges 7 and 11 are substantially complementarily shaped in order to sealingly couple mainly along their respective internal and external peripheral regions even after the first opening action.
Conveniently, according to the invention, a respective engagement means is distributed along the outer peripheral portions 8 and 12 of the edges 7 and 11 and is suitable to be elastically and unidirectionally coupled by pressing in order to hermetically close and seal the container.
In particular, along the outer peripheral portion 12 of the tray there is a series of protrusions or teeth 14 that extend radially and are inclined outward at approximately 40° with respect to the peripheral portion 12. The protrusions can be shaped approximately like a trapezium in which the longer parallel side is joined to the peripheral portion 12, with a predetermined height S and a width L.
Along the peripheral portion 8 of the edge of the tray there is a series of openings or slots 15 in angularly equidistant positions which match those of the protrusions 14.
The openings 15 result from the coupling between a strip 16 that runs uninterruptedly along the circumference and transverse wings 17 which join the strip 16 to the peripheral portion 8.
The wings 17 have an approximately pyramid-like shape which tapers upward and have upper and lower connecting regions 18 and 19. The resulting openings 15 are elongate in a substantially parallel direction to the peripheral portion 8 and have a maximum width in the upper connecting region 18 of the wings to the peripheral portion 8 and a minimum width W in the lower region 19 of the wings to the strip 16. The resisting cross-section of the connecting regions 18 is relatively smaller than that of the regions 19. The minimum width W of the openings 15 between the bases of the wings 17 is greater than the width L of the protrusions 14.
After filling the tray, the packager moves the lid closer and compresses it toward the tray so as to align the protrusions 14 with the openings 15, causing the engagement of the protrusions in the openings. The lid cannot lift due to the negative-allowance fit of the upper edge 16' of the strip 16 against the base of the teeth 14.
Conveniently, a tab 20 for grip on the part of a user is joined to the strip 16. As shown more clearly in Figure 4, the strip has, at one of the corners of the tab 20, a wedge-shaped notch or prefracture 21 that forms a stress raiser of the strip.
A consumer can see that the container is sealed by the presence of the strip 16. When the consumer wishes to open the container, he/she can grip the tab 20 and pull it outward and upward, breaking the strip at the notch 21. As the pulling action continues, the consumer separates the strip from the outer peripheral portion 8 at the connecting regions 8 that have the smallest resisting cross-section. In this manner the lid is released and can be lifted.
In subsequent use, as already mentioned, tightness is in any case ensured by the contact of the facing surfaces of the inner and outer peripheral portions of the complementary edges.
The seal according to the invention achieves the intended aim and all the objects, and in particular it is noted that it can be applied to containers having any shape, even without corners. Furthermore, it can be obtained by means of processes for the forming of thermoplastic sheets or indifferently by injection.
Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims

Tamper-evident seal for plastic containers of the type comprising a tray (3) with side (5) and bottom (6) surfaces, and a lid (2) with a substantially flat wall (4), said tray (3) and said lid (2) having respective complementarily shaped edges (7; 11) with outer peripheral portions (8; 12) which are substantially vertical or slightly inclined, which seal comprises first engagement means (14) consisting of a series of substantially radial protrusions (14) formed along one (11) of said edges, and second engagement means (15) consisting of a series of openings (15) formed along the other one (7) of said edges, said protrusions (14) being in register with said openings (15) along the respective edges (7; 11) on which they are formed and being formed at regularly spaced position lengthwise the entire extension of said edges (7; 11), said first and second engagement means (14; 15) being complementarily shaped and arranged for elastical and unidirectional mutual coupling by snap fitting to provide a sealing action between the lid (2) and the tray, said openings (15) being defined by the coupling between a continuous strip (16) of plastic material and a series of regularly spaced wings (17) attaching said strip (16) to the corresponding edge (7) in a spaced apart position, the height (H) of said wings (17) from the edge (7) being at least equal to the height (S) of said protrusions (14), characterized in that said wings (17) are upwardly tapered towards the region of connection (18) with the corresponding edge (7) to define in this region a smaller tear-resistant cross section of the wings (17) than at the region of connection (19) of the wings (17) with said strip (16).
Seal as claimed in claim 1, wherein said protrusions (14) consist of a plurality of teeth which are formed monolithically with the corresponding outer peripheral portion (12).
Seal as claimed in claim 2, wherein said teeth are slightly outwardly inclined with respect to the outer peripheral portion (12) on which they are formed and have a predetermined width (L) and a transverse cross-section which is shaped approximately like a trapezium with the longer base joined to the said outer peripheral portion (12), said longer base having a length corresponding to the height (S) of the protrusion (14).
Seal as claimed in claim 3, wherein said openings (15) are elongate in a substantially parallel direction to the outer peripheral portion (8) of the corresponding edge (11) and have a length (W) which is equal or greater than the width (L) of said teeth.
Seal as claimed in claim 1, wherein said strip (16) has a grip tab (20) having a transverse cross-section that is at least equal to the cross-section of said wings (17) in the region of connection (19) with said strip (16).
Seal as claimed in claim 5, wherein said strip has a transverse notch (21) in a position which is adjacent to a side edge of said grip tab (20) so as to form a weakened zone enabling the subsequent separation of said wings (17) from the peripheral portion of the edge to which they are connected.
Seal as claimed in claim 1, wherein said edges (7; 11) have a substantially U-shaped cross-section, said protrusions (14), said wings (17) and said strip (16) being formed monolithically respectively with the edges of said lid (2) and of said tray (3) by injection-molding or by forming plastic sheets.
Seal as claimed in claim 1, wherein said protrusions (14) and said opening (15) are formed respectively along the edge of the lid (2) and of the tray (3).
Seal as claimed in claim 1, wherein said protrusions (14) and said opening (15) are formed respectively along the edge of the tray (3) and of the lid (2).