HK40005867A - Closure vent for tamper evident container - Google Patents

Description

Closed vent for tamper evident container

Cross Reference to Related Applications

Not applicable.

Statement regarding federally sponsored research or development

Not applicable.

Sequence listing, table or computer program on optical disc

Not applicable.

Technical Field

The present invention generally relates to vented plastic food containers. The present invention more particularly relates to venting mechanisms for single use tamper evident plastic food containers.

Technical Field

In the food preparation and catering industry it is known to use plastic containers for packaging prepared food. Typical food containers of the prior art are constructed of a clear or solid colored base and a clear cover. In order to maintain the quality of the food contents and prevent tampering with the contents of the sealed container, it is desirable that the food container, once initially sealed, not be initially opened without a visible indication that the container has been opened. To accomplish this feature, container manufacturers have designed containers with complete tamper-evident features. Typically, these containers include a lid hingedly attached to a base. The lid is sealed to the base by superimposing the edge of the lid over the edge of the base. This type of plastic container is sold as a one-piece container and is commonly referred to as a "clamshell" container or package.

Some manufacturers of tamper-evident clamshell containers have incorporated the tamper-evident feature as part of the structure forming or including the hinge. In these containers, the container is designed to require breaking near the hinge in order to unseal (first open) the container. This configuration makes the hinge a disposable hinge. One example of a container having a tamper evident hinge structure is shown in U.S. patent No.9,580,219(Cimmerer et al).

One disadvantage of prior art tamper-evident containers is the fact that they are not suitable for holding warm food or cut-out products that produce internal vapor or gas (collectively referred to herein as "vapor" pressure). Indeed, if the container is not properly vented, the rise in pressure within the sealed container can overcome the force of the container rim engaging and cause the container to pop open, thereby destroying its tamper-evident properties. On the other hand, one cannot simply apply the common venting techniques used on standard containers to tamper evident containers. In this regard, it is known in the food packaging industry to provide holes or slits in the top surface of plastic containers in order to vent the containers. However, the addition of such a vent port to a tamper-evident container provides an access port into the container that defeats the purpose of the tamper-evident structure of the container. The apertures and slots in the top surface of the container also allow for leakage or spillage of the food contents if the container is inverted. They also allow bacteria to enter the container.

It is also known in the food packaging industry to provide a venting structure at the engaging edge of the container to allow venting through the edge of the container. One example of a container having such a structure is disclosed in U.S. patent No.8,875,927(Pohlman et al). The ventilator of the Pohlman's vessel is built into the edge-engaging surfaces of the lid and base edges and, when the vessel is under pressure, utilizes internal vapor pressure to cause at least one edge to move slightly relative to the other edge to create a vent passage through the edge. However, known through-the-rim venting solutions do not work with prior art tamper-evident containers because the lid rim and base rim of such containers are designed to securely and non-removably engage when the container is sealed. Thus, once the container is sealed, the edges once engaged do not allow for secondary vent movement relative to each other. This is because these rigid rim engagement designs prevent opening of the container by any technique other than deployment by an opening mechanism built into the container. Thus, providing venting through the rim around the periphery of the container may locally weaken the frictional engagement of the lid and base rim and thereby circumvent the need to use the provided opening mechanism. Furthermore, providing a vent passage in the accessible rim may provide a possible lever or insertion point where an elongated tool or object may be inserted through the rim of the container.

Accordingly, there is a need in the art for a tamper evident plastic food container that allows for the elimination of excess vapor pressure but allows the container to retain its tamper evident function.

Disclosure of Invention

The present invention satisfies the need in the art and provides an aesthetically appealing food container that is easy to use while allowing excess vapor pressure to be removed from a tamper evident container that employs a container opening mechanism in a container hinge forming structure. In this regard, the plastic food container of the present invention includes a lid adapted to be in a sealed condition with a base. The lid has a peripheral edge structure that complementarily engages the edge structure of the base to achieve a substantially leak-proof seal by mating the lid and base edge structures at a particular region (referred to herein as a sealing region).

In particular, preferred embodiments of the food product container of the present invention are capable of adopting a stowed condition and an initial sealed condition. The container includes a base and a lid. The base has a base edge circumferentially surrounding the base and the lid has a lid edge circumferentially surrounding the lid. The hinge-forming structure extends from a first hinge joint on the edge of the lid to a second hinge joint on the edge of the base. In the initial sealed state, the first hinge joint overlies all or part of the second hinge joint. The container region where the first hinge joint overlaps the second hinge joint defines an overlapping portion of the first and second hinge joints. For brevity, this overlapping portion of the first hinge joint and the second hinge joint is referred to herein as an "overlapping" portion.

In the initial sealed state, the base rim and the lid rim are frictionally engaged with each other such that they form one or more proximal seal regions. One or more vent channels are formed in either the lid edge or the base edge and are located within the overlap portion. The one or more channels form a complete discontinuity in the one or more proximal seal regions when the container is in the sealed state. To ensure tamper-evident, the plastic food container should not have any vents outside the overlap region. Furthermore, in a preferred embodiment, when the container is in an initial sealed state, the base rim and the lid rim are frictionally engaged with each other such that they form a first distal sealing area in the engagement rim structure. One or more channels each form a partial discontinuity in such first distal seal region. When the embodiment container is configured in the above-described fashion, the lid of the container remains engaged with the base, but when the pressure within the sealed container reaches a certain level, the lid allows gases and vapors within the initially sealed container to vent through the one or more vent channels without manually repositioning the lid on the base.

In the preferred embodiment container, the lid rim has a lid retention bead. The lid retention bead has a peripherally projecting bottom section, a peripherally projecting lid rim flange, and an outer vertically oriented portion disposed between the peripherally projecting horizontal section and the peripherally projecting lid rim flange. The edge of the base body is provided with a base body retaining convex strip. The base retention bead has a peripheral raised platform section, a peripheral raised top section, and an inner vertical wall disposed between the peripheral raised platform section and the peripheral raised top section. In the initial sealed state, the base rim and the lid rim are frictionally engaged with each other such that the peripherally projecting bottom section of the lid rim and the peripherally projecting platform section of the base rim are in contact with each other and form a first proximal sealing area. Further, in the initial sealed state, the outer vertically oriented portion of the lid rim and the inner vertical wall of the base rim contact each other and form a second proximal sealing area. One or more channels established within the overlap portion form a complete discontinuity in the first and second proximal seal regions when the container is in the sealed state. In a further preferred embodiment of the container, when in the initial sealed state, the base rim and the lid rim are frictionally engaged with each other such that the peripherally projecting lid rim flange of the lid rim and the peripherally projecting top section of the base rim are in contact with each other and form a first distal sealing area. One or more channels established within the overlap portion each form a partial discontinuity in the first distal seal region.

As just described, one or more vent channels are formed in either or both of the lid skirt and base skirt structures to form discrete areas in the sealing region. These discrete regions serve as channels in which pressurized steam can escape from the container and through the joined edges of the sealed container. The channel is constrained in the overlapping portion of the container, more particularly in the region close to the joining edge of the hinge forming structure, and it is within the end points of both the first hinge joint and the second hinge joint. Preferably, these vent channels are located at a distance within those end points such that they are not directly accessible by a finger or tool. When the vent passages are so restrictively positioned, they are protected from access and manipulation by the hinge forming mechanism of the container. Thus, the pressurized steam exits through the rim of the container and into the empty hinge space defined by the hinge-forming structure of the container. The initially sealed container thus retains its tamper evidence entirely, but also allows venting.

Drawings

Figure 1 shows a perspective view of a preferred embodiment of the container of the invention in a sealed state.

Figure 2 shows a perspective view of a preferred embodiment of the container of the invention in a loaded state.

Figure 3 shows a detailed perspective view of the base rim of the preferred embodiment container of the present invention with vent channels formed therein.

Fig. 4 shows a detailed cross-sectional view of the joint rim structure outside the area where the hinge forming structure is connected to the container of the preferred embodiment container for the sealed state.

Fig. 5 shows the same view of the structure shown in fig. 4, shown instead as a sealing area.

Fig. 6 shows a detailed cross-sectional view of the joint edge structure of the hinge forming structure of the preferred embodiment near the sealing state.

Fig. 7 shows the same view of the structure shown in fig. 6, shown instead as a sealing area.

Detailed Description

Fig. 1 and 2 show a preferred embodiment container 1 of the invention in an initial sealed state and in a loaded state. As can be seen in the figures, the inventive plastic food container is capable of adopting an initial sealed state and a loaded state. In actual use, the outer surface of the bottom surface 26 of the base 3 will generally rest on a surface that is considered horizontal to the user (e.g., a table top). Thus, with respect to the orientation shown in fig. 1-7, the directional terms "vertical" and "horizontal" and the like are used to describe the container 1 and its components and are used for purposes of clarity and illustration only. For example, fig. 1 and 6-7 illustrate the container and the hinge area of the container 1 when the container 1 is in an initial sealed state. In the orientation shown in fig. 6, the lid flange 9 is "vertically" higher than the base flange 10. The directional terms "internal" and "inwardly" and the like are used herein to refer to a direction along a directional component toward the geometric center of the container relative to the container as described when the lid 2 of the container 1 is sealed or closed on the base 3. Similarly, the directional terms "radially," "outwardly," "peripheral," and the like, are used herein to refer to a direction along a directional component away from the geometric center of the container, relative to the container as depicted, when the lid 2 of the container 1 is sealed or closed to the base 3. Additionally, the terms "upwardly", "downwardly", and the like, are used to describe the spatial relationship between the structures when the lid 2 of the container 1 is sealed or closed on the base 3.

The container includes a hinge-forming structure 40 that includes an opening mechanism 45 with which the end user will open the container from an initial sealed state. In the case of the preferred embodiment container shown, the opening mechanism 45 is representatively shown as depicted in U.S. patent No.9,580,219(Cimmerer et al). This is merely exemplary as the invention described herein is also effective for containers using other opening mechanisms located in the hinge forming structure. When the opening mechanism 45 for initially sealing the container is used, then the container is in a state to be opened. When the lid is detached from the base body from this state to be opened, the container is in an opened state.

As shown in these figures, the container 1 comprises a lid 2 and a base 3. The lid 2 includes a lid portion 33 that extends outwardly to form the inner wall 18 of the multi-segmented rim 4 of the preferred embodiment. The edge 4 preferably comprises a bead formed by an inner vertical wall 18, an outer vertical wall 19 and a peripheral convex bottom section 20 arranged between the inner wall 18 and the outer wall 19. The lid 2 and the base 3 are made of conventional plastic materials. Preferably, the cover 2 is transparent. The lid portion 33 may be flat or domed and may include lid ribs 34 according to the prior art to enhance such factors as restricting access to the lid rim flange 9 and stacking of sealed containers. The base body 3 has a base body edge 5 which circumferentially surrounds the base body 3 so as to form a container cavity 7. The lid 2 has a lid rim 4 that circumferentially surrounds the lid 2.

The structure of the lid skirt 4 of the preferred embodiment will now be discussed in more detail. As best shown in fig. 4 and 5, the lid skirt 4 includes a peripheral raised bottom section 20 that extends between the inner wall 18 and the outer wall 19 forming a lid skirt channel 23. The cross-sectional profile of the section 20 is substantially horizontal. However, the profile may be shaped to include structures such as ribs, bends or curves to tailor the strength, rigidity or flexibility of the rim to enhance the closing, sealing and opening functions of the rim as desired. The figures show the cross-sectional profile of a preferred embodiment of such a peripheral projection. As shown in fig. 4 and 5, the outer wall 19 extends upwardly between the peripheral flange section 20 and the peripherally disposed and projecting flange 9. The outer wall 19 may be beveled to better frictionally engage the inner wall 12 of the base rim 5 as described further below.

The base 3 includes a horizontal or bottom surface 26 adjacent to the bottommost portion of the sidewall 27. Side walls 27 extend between the base bottom surface 26 and the multi-segmented edge 5 of the preferred embodiment. Preferably, the side wall 27 includes a chamfered corner 30 for reinforcement. The rim 5 comprises a raised inner wall 12. Fig. 4 and 5 best illustrate the structure of the base body 3 and its edge structure 5 of the preferred embodiment. The base body edge 5 comprises a peripheral raised platform section 6. The platform section 6 is bent upwards to form the inner wall 12. The inner wall 12 extends upwardly from the peripheral raised platform section 6 to form a peripheral raised top section 14. Preferably, the inner wall 12 is inwardly inclined to provide maximum frictional engagement against the outer wall 19. As seen in fig. 4, in the preferred embodiment, the peripheral convex top section 14 is horizontal and spans between the inner wall 12 and the outer wall 13. Preferably, the rim 5 comprises a peripheral flange 10 extending outwardly from the base 3 from the bottom of the outer wall 13.

As shown, in the preferred embodiment, the wall 12 includes three portions: an upper portion 12 a; a middle portion 12 b; and a lower portion 12 c. Preferably, the upper portion 12a forms a chamfer between the top section 14 and the middle wall portion 12 b. The lower portion 12c is bent or chamfered upwardly from the platform 6 to the middle portion 12 b. The middle portion 12b is disposed between the upper portion 12a and the lower portion 12 c. As seen in the figures and described below, the engagement of the edges 4, 5 forms one or more proximal seal regions and one or more distal seal regions.

By virtue of the inclination of the inner wall 12 of the rim 5 and the outer wall 19 of the rim 4, when the container 1 is in a sealed condition, the peripheral protruding section 20 of the lid rim 4 is pressed down on the platform section 6 of the lid rim 5 and is in tight contact with the platform section 6 of the lid rim 5 to form a first proximal sealing area a. In a preferred embodiment, the first proximal seal area a is horizontally oriented. Likewise, when the container 1 is in the sealed condition, the wall 12 of the base rim 5 (preferably at the central portion 12B) tightly contacts the wall 19 of the lid rim 4 to form a second proximal sealing area B. In a preferred embodiment, the second sealing area B is vertically oriented. By virtue of the configuration and shape of the components of the edges 4, 5, the edges 4, 5 are securely engaged when the lid 2 is sealed to the base 3. Thus, in the normal sealing state, the mating edge surfaces provide a leak-proof seal. In addition, when container 1 is in a sealed state, lid rim flange (outer peripheral convex section) 9 contacts outer peripheral convex top section 14 of base rim 5 to form a first distal sealing area C. In a preferred embodiment, the first distal sealing region C is horizontally oriented. By so manipulating the container 1, the flange 9 is accessible, but its short length and the close tolerances of the configuration of the edges 4, 5 make it difficult to grasp.

As shown in fig. 6 and 7, the container 1 also includes a hinge forming structure 40. The hinge-forming structure 40 extends from the base edge 5 to a distal point 49 and then back to the lid edge 4 and defines a received hinge space 46. The hinge-forming structure 40 is connected to the lid rim flange 9 by a transition section 41. The hinge-forming structure 40 is connected to the base body edge flange 10 by a transition section 42. Along its connection to the lid rim 4, the hinge-forming structure 40 defines a first hinge joint 43 on the lid rim 4. This is best shown in fig. 1 and 2. Similarly, along its connection with the base edge 5, the hinge-forming structure 40 similarly defines a second hinge joint 44 on the base edge 5. This can best be seen in fig. 2 and 3. As shown in fig. 1, first hinge joint 43 has a length L1 extending along lid edge 4 between endpoints 47a and 47 b. The second hinge joint 44 has a length L2 extending between the end points 48a and 48b, as best seen in fig. 3. In most containers, the first hinge joint 43 has the same length as the hinge joint 44. In other words, L1 would be equal to L2, and endpoints 47a and 48a would be vertically aligned, as would endpoints 47b and 48 b. In this case, the first hinge joint 43 and the second hinge joint 44 will also be aligned completely vertically and will overlap completely vertically. However, the hinge forming structure 40 may be manufactured such that the first and second hinge joints 43, 43 are staggered, have different lengths, or both, in which case the first and second hinge joints will only partially vertically overlap. In either case, in the initial sealed state, the first hinge joint 43 on the lid skirt 4 and the second hinge joint 44 on the lid skirt 5 will have a superposed position relative to each other such that they define a vertical overlap of the first and second hinge joints. In the preferred embodiment shown, since L1 and L2 have the same endpoints, the overlap on the joined container edges 4, 5 will be within the area bounded by endpoints 47a and 47b and endpoints 48a and 48 b. Thus, in fig. 3, the overlap corresponds to distance L2, and in fig. 1, which shows the container in an initial sealed state, the overlap corresponds to distance L1.

As seen in fig. 2 and 3, one or more vent channels 50 are formed in the base edge 5 within the second hinge joint 44. This is merely representative and one or more vent channels 50 may be formed in the lid rim 4 within the first hinge joint 43. In the preferred embodiment shown, the vent passages 50 are grooves provided transversely in the base edge 5. One or more vent channels 50 are positioned on either or both of edges 4 or 5 such that they are located within the boundaries (endpoints) of both hinge joints 43 and 44 and such that they are located within the vertically overlapping portions (L1 in fig. 1). Thus, when the container is in the sealed condition, the hinge-forming structure 40 is positioned adjacent to, but outwardly from, the one or more vent passages 50. More preferably, one or more vent channels will be located in the overlapping portion of the edges 4, 5, sufficiently inward from the end points 47a, 47b, 48a, 48b to be out of reach of the operator's fingers or any practically available tamper tool. This is best seen in fig. 3. By so positioning, the vent passage or passages 50 are not directly accessible for tampering, as the hinge-forming structure 40 will block any such fingers or tools from accessing the vent passage or passages 50. To reduce the chance of tampering, the edges 4, 5 of the container 1 of the preferred embodiment should not include vent channels outside the area defined as the vertical overlap on the joined edges 4 and 5.

As seen in fig. 3 and 5, when the container is in a sealed condition, the one or more channels form a complete discontinuity in the horizontal first proximal seal area a and a complete discontinuity in the vertical second proximal seal area B. In a preferred embodiment, the vent channel forms a partial discontinuity in the first distal seal area C. The complete discontinuity in the one or more proximal seal areas a and B forms a path from the interior of the container to the one or more distal seal areas, the first distal seal area C, through which pressurized steam can flow. Those steam-backed pressures are sufficient to lift the flange 9 from the top section 14 of the base body edge 5. Once the flange 9 is lifted from the top section 14, the container steam can leave the container 1 and be vented into the hinge space 46. As seen in fig. 6 and 7, the vent passage 50 changes the shape of the section 14 so as to form a partial discontinuity of the sealing area C at the location of the vent 50.

As shown in fig. 6 and 7, the container can be made with a second distal sealing area D, preferably formed between the transition section 41 of the hinge forming structure 40 and the outer wall 13 extending towards the flange 10. As in the case of the first distal sealing area C, the pressure behind the container vapour is sufficient to separate the transition section 41 from the top section 14 of the base body edge 5, also separating the section 41 from contact with the wall 13. Once section 41 is separated from wall 13, the container vapor can exit container 1 and vent into hinge space 46. Thus, for the container of the present invention, the lid of the container is adapted to remain engaged with the base, but when the pressure in the sealed container reaches a certain level, the vapor within the sealed container is allowed to vent through the one or more vent channels 50 without having to manipulate the lid on the base. The inclusion of one or more vent channels 50 in the overlapping portion of the container at the hinge joint region of the rim means that the proximal surfaces of the rims 4, 5 can be securely engaged around the periphery of the container to seal the container and render it tamper-evident. Thus, at those proximal surfaces, no secondary vent movement of the engaged edges occurs. Instead, the only secondary vent movement occurs at the distal region of the engagement edge, past the location of the vent channel, and only in the overlapping portion of the engagement edge. Thus, this secondary movement is minimal compared to the secondary venting movement of prior art containers. Once the pressurized steam is removed, the flange 9 and the section 41 assume their original sealed and leak-proof condition, without manual intervention.

The above-described venting feature means that a genuine tamper-evident container can be provided with a venting mechanism that does not compromise the tamper-evident properties of the container. Thus, the container of the present invention eliminates the need for a typical lid vent, which reduces the likelihood of tampering with the package contents after capping. In addition, the venting feature utilizes a sealed area between the vent groove and the atmosphere, allowing the package to remain leak-proof when the contents are not under pressure. When the package contents develop pressure, as in the case of cut fruit, the pressure is released as it forces open the sealed area between the vent groove and the atmosphere. In addition, the venting feature allows pressure relief if the consumer squeezes the edges of the package with excessive force, otherwise the lid may "pop" off the base. The placement of the venting feature below the hinge reduces the visibility and detectability of the feature. It is not important which rim, lid or base is provided with one or more vent channels 50 in the practice of the invention. In addition, in another embodiment, the outer wall 19 and the section 20 of the lid rim 4 may be provided with a venting channel 50.

Containers constructed in accordance with the present invention can be manufactured in a variety of shapes and sizes and are preferably formed of a resin or plastic material including, but not limited to, polyethylene, polypropylene, polyvinyl chloride, or polyethylene terephthalate ("PET"). The container may be thermoformed, blow molded or injection molded. The container lid and base may be transparent or translucent and in either case may be tinted. Further, the container may be of any shape, including circular or polygonal.

Having described the invention in detail above, those skilled in the art will appreciate that modifications may be made to the invention without departing from the spirit thereof. Therefore, it is not intended that the scope of the invention be limited to the specific embodiments illustrated and described.

Claims (10)

1. A plastic food container capable of assuming a loaded condition and an initially sealed condition with the container rim engaged, the container comprising:

a base and a cover;

the base having a base rim circumferentially surrounding the base and the lid having a lid rim circumferentially surrounding the lid;

a hinge forming structure extending from a first hinge joint of the lid edge to a second hinge joint of the base edge;

in an initial sealed state, the first hinge joint overlies all or part of the second hinge joint, the region of the first hinge joint overlying the second hinge joint defining an overlapping portion of the first and second hinge joints at a joining edge;

in an initial sealed state, the base rim and lid rim frictionally engage each other such that they form one or more proximal seal regions;

one or more vent channels are formed in either the lid edge or the base edge and are located within the overlap portion; and

the one or more channels form a complete discontinuity in one or more proximal seal regions when the container is in the closed state.

2. The plastic food container of claim 1 wherein the container does not have any vents outside of the overlap region.

3. The plastic food container of claim 1 wherein, when the container is in an initial sealed state, the base rim and lid rim frictionally engage each other such that they form a first distal seal area and the one or more channels each form a partial discontinuity in the first distal seal area.

4. The plastic food container of claim 3 wherein, when the container is in an initial sealed state, the base rim and lid rim are frictionally engaged with one another such that they form a second distal seal area distal from the first seal area.

5. The container of claim 1, wherein the lid of the container is adapted to remain engaged with the base, but when the pressure in the sealed container reaches a certain level, the lid allows gases and vapors within the initially sealed container to vent through the one or more vent channels without manually repositioning the lid on the base.

6. A plastic food container capable of assuming a loaded condition and an initially sealed condition with the container rim engaged, the container comprising:

a base and a cover;

the base having a base rim circumferentially surrounding the base and the lid having a lid rim circumferentially surrounding the lid;

a hinge forming structure extending from a first hinge joint of the lid edge to a second hinge joint of the base edge;

in an initial sealed state, the first hinge joint overlies all or part of the second hinge joint, the region of the first hinge joint overlying the second hinge joint defining an overlapping portion of the first and second hinge joints at a joining edge;

the lid rim having a lid retention bead with a peripherally projecting bottom section, a peripherally projecting lid rim flange, and an outer vertically oriented section disposed between the peripherally projecting horizontal section and the peripherally projecting lid rim flange;

the base edge having a base retention bead with a peripheral raised platform section, a peripheral raised top section, and an interior vertical wall disposed between the peripheral raised platform section and the peripheral raised top section;

in an initial sealed state, the base rim and lid rim are frictionally engaged with each other such that,

said peripherally projecting bottom section of said lid rim and said peripherally projecting deck section of said base rim are in contact with each other and form a first proximal seal area; and is

The outer vertically oriented section of the lid edge and the inner vertical wall of the base edge contact each other and form a second proximal seal area;

one or more vent channels are formed at either the lid edge or the base edge and are located within the overlap portion; and is

The one or more channels form a complete discontinuity in the first proximal seal region and the second proximal seal region when the container is in a sealed state.

7. The plastic food container of claim 6 wherein the container does not have any vent holes outside the overlapping region.

8. The plastic food container of claim 6 wherein, in an initial sealed state, said base rim and lid rim frictionally engage one another such that said peripherally projecting lid rim flange of said lid rim and said peripherally projecting top section of said base rim contact one another and form a first distal seal area, and said one or more channels each form a partial discontinuity in said first distal seal area.

9. The plastic food container of claim 8 wherein, when the container is in an initial sealed state, the base rim and lid rim are frictionally engaged with one another such that they form a second distal seal area distal from the first seal area.

10. The container of claim 6, wherein the lid of the container is adapted to remain engaged with the base, but when the pressure in the sealed container reaches a certain level, the lid allows gases and vapors within the initially sealed container to vent through the one or more vent channels without manually repositioning the lid on the base.