Methods of reducing the stacking height of containers, lids, and bases

Abstract

A method for forming a reduced-height stack of containers wherein the containers stacked contain at least one undercut and at least one undercut receiving structure. The first container having an undercut at a first position and an undercut receiving structure at a second position. The second container having an undercut at a third position and an undercut receiving structure at a fourth position. The containers may be arranged so that the at least one undercut of the first container at the first position aligns with and fits into the at least one undercut receiving structure at the fourth position of the second container below the first container in the stack.

Description

FIELD OF THE INVENTION

The present invention generally relates to the packaging industry. More particularly, the present invention relates to reducing the stacking height of a stack of containers, lids, or bases.

BACKGROUND OF THE INVENTION

The packaging industry has produced a number of containers, lids, and bases to be used in applications such as egg cartons, carry-out containers, fruit trays, and other container types. These containers, lids, and bases are typically transported from a manufacturer to an entity that utilizes a container, lid, or base. The containers often have locking mechanisms between its bases and lids. A container that is not securely closed could open inadvertently and spill the contents of the container. Typically this locking mechanism is controls the design of the stack height. These containers, lids, and bases are often transported by being stacked inside boxes. The size of these transportation boxes is often referred to as the cube of the outer packaging.

Referring now to prior art FIG. 1, a portion of a stack 30 that includes a plurality of containers 10 is shown. The distance indicated by arrow A is the stack height between two containers. The term “stack height” as used in this application means the distance between identical features of adjacent containers in a stack. It can be observed in prior art FIG. 1 that the stack height A is governed by a lead-in surface 18 of the locking mechanism of the top container of the stack 30 resting on an undercut rim 16 of the locking mechanism of the bottom container of the stack 30.

Similarly, in prior art FIG. 2 a portion of a stack 40 that includes a plurality of containers 20 is shown. The distance indicated by an arrow B is the stack height between two containers. The stack height B of prior art FIG. 2 is driven by an undercut rim 26 of the locking mechanism of the first container resting on a lead-in surface 28 of the locking mechanism of the second container in the stack 40.

A greater stack height results in a larger cube for the transportation boxes. A typical stack may include several hundred or even several thousand containers, lids, bases, and combinations thereof. Having an inefficient stacking of containers, lids, and bases is costly because of the higher transportation costs involved. Additionally, potential storage costs may be incurred by the entities that use such items because of the inefficient stacking. Further, a large stack also requires additional store shelf-space, which increases the cost associated with marketing the containers. Such costs are ultimately passed onto the end user of the containers, lids, and bases.

A need therefore exists for a method to stack containers that results in a reduced stack height for an equal number of containers.

SUMMARY OF THE INVENTION

A method for forming a reduced-height stack of a plurality of containers provides a first and second container. The first container has at least a first undercut and at least one undercut receiving structure. The at least a first undercut is located at a first position. The at least a first undercut receiving structure is located at a second position. The second container has at least a second undercut and at least one undercut receiving structure. The at least a second undercut is located at a third position. The at least one undercut receiving structure is at a fourth position. The third position is a different location from the first position. The fourth position is a different location from the second position. The first and second containers are generally equal in size. The method arranges the first and second container to form a stack of a plurality of containers. The at least a first undercut of the first container aligns with and fits within the at least one undercut receiving structure of the second container at the fourth position to reduce the stack height.

According to another method of the present invention, a method of forming a reduced-height stack of containers provides a mold base that comprises at least a first mold cavity that has a first design and a second mold cavity that has a second design. The first design is different from the second design. This method makes a first container in the first mold cavity that has at least one undercut located at a first position and at least one undercut receiving structure located at a second position. The method also makes a second container in the second mold cavity that has at least one undercut located at a third position and at least one undercut receiving structure located at a fourth position. The third position is a different location than the first position. The fourth position is a different location than the third position. This method removes the first and second containers from the respective first and second mold cavities. The method arranges the first and second containers to form a two-container stack. The at least a first undercut of the first container at the first position aligns with and fits within the at least one undercut receiving structure of the second container at the fourth position to reduce the height of the two-container stack.

According to a further method of the present invention, a method of forming a reduced-height stack of containers provides a mold base that comprises at least a first mold cavity and a second mold cavity. The design of the first mold cavity is substantially identical to the design of the second mold cavity. The second mold cavity is rotated in the mold base relative to the first mold cavity. This method makes a first container in the first mold cavity that has at least one undercut located at a first position and at least one undercut receiving structure located at a second position. The method also makes a second container in the second mold cavity that has at least one undercut located at a third position and at least one undercut receiving structure located at a fourth position. The third position is a different location than the first position. This method removes the first and second containers from the respective first and second mold cavities. The method arranges the first and second containers to form a two-container stack. The at least one undercut of the first container at the first position aligns with and fits within the undercut receiving structure at the fourth position of the second container to reduce the height of the two-container stack. The containers align without further rotation of the containers after they are removed from the mold cavities.

According to yet another method of the present invention, a method of forming two reduced-height stacks of containers provides a mold base that comprises at least a first mold cavity, a second mold cavity, a third mold cavity, and a fourth mold cavity. The mold cavities are arranged in two rows and two columns. The first and second mold cavities comprise a first column of mold cavities. The third and fourth mold cavities comprise a second column of mold cavities. The design of the first mold cavity is different than the design of the second mold cavity. The design of the third mold cavity is different than the design of the fourth mold cavity. This method makes a first container in the first mold cavity that has at least one undercut located at a first position and at least one undercut receiving structure located at a second position. The method also makes a second container in the second mold cavity that has at least one undercut located at a third position and at least one undercut receiving structure located at a fourth position. The third position is a different location than the first position. A third container is made in the third mold cavity that has at least at least one undercut located at a fifth position and at least one undercut receiving structure located at a sixth position. A fourth container is made in the fourth mold cavity that has at least at least one undercut located at a seventh position and at least one undercut receiving structure located at an eighth position. The fifth position is a different location than the seventh position. This method removes the first, second, third, and fourth containers from the respective first, second, third, and fourth mold cavities. The method arranges the first and second containers to form a two-container stack. The at least one undercut of the first container at the first position aligns with and fits within the undercut receiving structure at the fourth position of the second container to reduce the height of the two-container stack. The method arranges the third and fourth containers to form a two-container stack. The at least one undercut of the third container at the fifth position aligns with and fits within the undercut receiving structure at the eighth position of the fourth container to reduce the height of the two-container stack.

According to yet a further method, a method of forming two reduced-height stacks of containers provides a mold base that comprises at least a first mold cavity, a second mold cavity, a third mold cavity, and a fourth mold cavity. The mold cavities are arranged in two rows and two columns. The first and second mold cavities comprise a first column of mold cavities. The third and fourth mold cavities comprise a second column of mold cavities. The design of the first mold cavity is substantially identical to the design of the second mold cavity. The second mold cavity is rotated within the mold base relative to the first mold cavity. The design of the third mold cavity is substantially identical to the design of the fourth mold cavity. The fourth mold cavity is rotated within the mold base relative to the third mold cavity. This method makes a first container in the first mold cavity that has at least one undercut located at a first position and at least one undercut receiving structure located at a second position. The method also makes a second container in the second mold cavity that has at least one undercut located at a third position and at least one undercut receiving structure located at a fourth position. The third position is a different location than the first position. A third container is made in the third mold cavity that has at least at least one undercut located at a fifth position and at least one undercut receiving structure located at a sixth position. A fourth container is made in the fourth mold cavity that has at least at least one undercut located at a seventh position and at least one undercut receiving structure located at an eighth position. The fifth position is a different location than the seventh position. This method removes the first, second, third, and fourth containers from the respective first, second, third, and fourth mold cavities. The method arranges the first and second containers to form a two-container stack. The at least one undercut of the first container at the first position aligns with and fits within the undercut receiving structure at the fourth position of the second container to reduce the height of the two-container stack. The first and second containers align without further rotation of the first and second containers after they are removed from the mold cavities. The method arranges the third and fourth containers to form a two-container stack. The at least one undercut of the third container at the fifth position aligns with and fits within the undercut receiving structure at the eighth position of the fourth container to reduce the height of the two-container stack. The third and fourth containers align without further rotation of the third and fourth containers after they are removed from the mold cavities.

According to still another method of the present invention, a method of forming a reduced-height stack of containers provides a mold base that comprises at least a first mold cavity and a second mold cavity. The design of the first mold cavity is substantially identical to the design of the second mold cavity. This method makes a first container in the first mold cavity that has at least one undercut located at a first position and at least one undercut receiving structure located at a second position. The method also makes a second container in the second mold cavity that has at least one undercut located at a third position and at least one undercut receiving structure located at a fourth position. The third position is a different location than the first position. This method removes the first and second containers from the respective first and second mold cavities. At least one of the containers rotates after it is removed from the mold cavity. The method arranges the first and second containers to form a two-container stack. The at least one undercut of the first container at the first position aligns with and fits within the undercut receiving structure at the fourth position of the second container to reduce the height of the two-container stack.

According to one embodiment, a stack of containers comprises a first container and a second container. The first container comprises a locking mechanism. The first container locking mechanism includes at least one undercut at a first position and at least one undercut receiving structure at a second position. The second container comprises a locking mechanism. The second container locking mechanism includes at least one undercut at a third position and at least one undercut receiving structure at a fourth position. The first and second containers stack such that the at least one undercut at the first position is aligned with the at least one undercut receiving structure at the fourth position. The at least one undercut at the first position contacts the undercut receiving structure at the fourth position to reduce the height of the stack.

According to another embodiment, a stack of containers comprises a first container, a second container, a third container, a fourth container, and a fifth container. The first container comprises a locking mechanism. The first container locking mechanism includes at least one undercut at a first position and at least one undercut receiving structure at a second position. The second container comprises a locking mechanism. The second container locking mechanism includes at least one undercut at the first position and at least one undercut receiving structure at the second position. The third container comprises a locking mechanism. The third container locking mechanism includes at least one undercut at a third position and at least one undercut receiving structure at a fourth position. The fourth container comprises a locking mechanism. The fourth container locking mechanism includes at least one undercut at the first position and at least one undercut receiving structure at the second position. The fifth container comprises a locking mechanism. The fifth container locking mechanism includes at least one undercut at the first position and at least one undercut receiving structure at the second position. The second container aligns so that the at least one undercut at the first position of the second container aligns with the at least one undercut at the first position of the first container. The third container aligns so that the at least one undercut at the third position of the third container aligns with and fits within the at least one undercut receiving structure at the second position of the second container. The fourth container aligns such that the at least one undercut at the first position of the fourth container aligns with and fits within the at least one undercut receiving structure at the fourth position of the third container. The fifth container aligns so that the at least one undercut at the first position of the fifth container aligns with the at least one undercut at the first position of the fourth container. The stack height between the second, third, and fourth containers is minimized, and the total stack height is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.

FIG. 1 is a sectional view of a prior art stack of containers;

FIG. 2 is a sectional view of another prior art stack of containers;

FIG. 3 is a sectional view of a locking mechanism for a container according to one embodiment of the present invention;

FIG. 4 is a sectional view of a locking mechanism for a container according to another embodiment of the present invention;

FIG. 5 a is a schematic view of a stack of two containers according to one embodiment of the present invention;

FIG. 5 b is a sectional view of a stack of two containers according to another embodiment of the present invention;

FIG. 6 is a functional diagram of a mold base to be used to manufacture containers according to one embodiment of the present invention;

FIG. 7 is a functional diagram of a mold base to be used to manufacture containers according to another embodiment of the present invention;

FIG. 8 is a functional diagram of a mold base according to a further embodiment of the present invention;

FIG. 9 is a functional diagram of a mold base according to yet another embodiment of the present invention;

FIG. 10 is a sectional view of a stack of five containers according to yet another embodiment of the present invention; and

FIG. 11 is a functional diagram of a mold base according to yet a further embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed but, on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

Turning now to the drawings, FIG. 3 shows a locking mechanism 12 of a container 1 in the closed position. As used in this application the word “container” is defined herein as including, trays, lids, bases, bowls, combinations of lids and bases, combinations of lids and bowls, bases with hinged lids, bowls with hinged lids, and combinations thereof. The locking mechanism 12 comprises a rim flange 14 and a corresponding undercut 16. The locking mechanism 12 functions by having the undercut 16 go over the rim flange 14 so as to close the container 1. The undercut 16 of FIG. 3 includes a lead-in surface 18.

Referring to FIG. 4, a locking mechanism 22 of a container 2 is shown in the closed position according to another embodiment. The locking mechanism 22 comprises a rim flange 24 and an undercut 26. The locking mechanism 22 functions by having the rim flange 24 inserted into the undercut 26 so as to close the container 2. The undercut 26 has a lead-in surface 28.

FIG. 5 a shows a schematic view of a two container stack 50 that includes a first container 52 and a second container 54. The first and second containers 52, 54 comprise respective locking mechanisms 22, 32 that further comprise an undercut receiving structure 56 and an undercut 58. The undercut receiving structure 56 is designed to allow the undercuts 58 of the locking mechanisms 22, 32 of the containers 52, 54 in the stack 50 to be in closer proximity to each other, thus reducing stack height C (FIG. 5b) of the stack 50. The undercut receiving structures 56, as well as the undercuts 58, of the locking mechanisms 22, 32 of the containers 52, 54 are offset relative to each other in stack 50. This offset allows the undercut receiving structure 56 of the locking mechanism 32 of the container 54 to align with the undercut 58 the locking mechanism 22 of the container 52 in the stack 50.

Turning to FIG. 5b, a partial section view of the container stack 50 is shown. The stack height C of the stack 50 is reduced because the undercut 58 of the locking mechanism 32 of the container 54 aligns with the undercut receiving structure 56 of the locking mechanism 22 of the container 52. The depth of undercut receiving structure 56 of the locking mechanism desirably corresponds with the height of the undercut 58 of the locking mechanism. For example, a deeper undercut receiving structure 56, up to the depth of the undercut 58, reduces the stack height C by a greater amount, while a shallower undercut receiving structure 56 reduces the stack height C by a lesser amount. The shape of the undercut receiving structure 56 may vary from that depicted in FIG. 5b, so long as the shape of the undercut receiving structure 56 is capable of stacking on the undercut 58 of the container below it in the stack and of receiving the undercut 58 of the container above it in the stack. Methods of obtaining the offset of the undercut receiving structure 56 of the locking mechanism 32 of the container 54 relative to the undercut 58 of the locking mechanism 22 of the container 52 are shown in FIGS. 6 and 7.

FIG. 6 shows a mold base 60 comprising mold cavities 62a-d for producing containers. The containers produced by the mold cavities 62a-d are shown to be an approximately square shape. Other shapes are contemplated, such as rectangular, or polygonal. The mold base 60 is a two by two mold base because it has two columns and two rows of mold cavities, and may mold four containers at once. Each of the mold cavities 62a-d is shown with four undercut receiving structures 64 and four undercuts 66. According to one process, once the containers have been molded, they are removed from the mold base 60 and trimmed to the proper shape. The trimmed containers are then stacked. It is contemplated that the container stack order may be from bottom to top as follows: the container from the mold cavity 62a, the mold cavity 62b, the mold cavity 62d, and the mold cavity 62c. Stacking the containers in this order reduces the stack height, because the undercuts 66 of the locking mechanisms of the containers are aligned with the undercut receiving structures 68 of the locking mechanisms of the container directly preceding it in the stack. It is contemplated that the containers produced by mold cavities 62a-d of several cycles of mold base 60 may be stacked in the order described above so that a stack with more than four containers is produced.

Other stack orders are also contemplated in the present invention. An alternate container stack order may be from bottom to top as follows: the container from the mold cavity 62a, the mold cavity 62d, the mold cavity 62c, and the mold cavity 62b. This order reduces the stack height, but the reduction in stack height is not as significant as the prior stacking order. The stack height is not reduced as much in this stacking order because undercut to undercut contact occurs in the stack of containers.

It is further contemplated that larger mold bases, such as a four by two cavity mold base, or an eight by four cavity mold base may be used in the current invention. It is also contemplated that a stack of containers would be formed from each column of the mold base 60. According to one process, the order of the first stack of containers may be from bottom to top as follows: the container from the mold cavity 62a, the mold cavity 62c. The order of the second stack may be from bottom to top as follows: the container from the mold cavity 62b the mold cavity 62d. It is contemplated that the containers of several cycles of mold base 60 may be stacked in this order to produce two stacks with more than two containers per stack. It is further contemplated that a non-matrix mold may be used.

The embodiment depicted in FIG. 7 is similar to that depicted in FIG. 6 except that the mold base 70 produces containers that have a generally circular shape in mold cavities 72a-d. Other shapes are contemplated, such as oval or oblong. The mold base 70 depicted in FIG. 7 is a two by two mold base because it has two columns and two rows of mold cavities and may mold four containers at once. Each of the mold cavities 72a-d is shown with three undercut receiving structures 74 and three undercuts 76. According to one process, once the containers have been molded, they are removed from the mold base 70 and trimmed to the proper shape. The trimmed containers produced by the mold cavities 72a-d are then stacked. It is contemplated that the stack order may be from bottom to top as follows: the container from the mold cavity 72a, the mold cavity 72c, the mold cavity 72b, and the mold cavity 72d. Stacking the containers in this order reduces the stack height, because the undercuts 76 of the locking mechanisms of the containers are aligned with the undercut receiving structures 78 of the locking mechanism of the container directly preceding it in the stack. It is contemplated that the containers of several cycles of mold base 70 would be stacked in the order described above so that a stack with more than four containers was produced.

Other stack orders are also contemplated in the present invention. Using the mold 70, an alternate stack order may be from bottom to top as follows: the container from the mold cavity 72a, the mold cavity 72b, the mold cavity 72c, and the mold cavity 72d. This order reduces the stack height, but the reduction in stack height is not reduced as much as the prior stacking order using containers formed from mold 70, as undercut to undercut contact is taking place.

It is further contemplated that larger mold bases, such as a four by two cavity mold base, or an eight by four cavity mold base may be used in the current invention, or any other matrix mold base may be used. It is also contemplated that a stack of containers may be formed from each column of the mold base 70. According to one process, the order of the first stack may be from bottom to top as follows: the container from the mold cavity 72a, the mold cavity 72c. The order of the second stack may be from bottom to top as follows: the container from the mold cavity 72b, the mold cavity 72d. It is contemplated that the containers of several cycles of the mold base 70 may be stacked in this order to produce two stacks with more than two containers per stack. It is also contemplated that non-matrix mold base may be used.

Turning now to FIG. 8, a mold base 80 is shown that is capable of producing three containers per cycle in mold cavities 82a-c. Mold base 80 is a 1 by 3 mold base because it has one column of mold cavities and three rows of mold cavities. The mold cavities 82a-c are identical except that the first cavity 82a is at a first angle D relative to the mold base 80, the second cavity 82b is at a second angle E relative to the mold base 80, and the third cavity 82c is at a third angle F relative to the mold base 80. The first angle D is from about 80° to about 100°, the second angle E is from about 50° to about 70°, and the third angle F is from about 20° to about 40°.

Each of the mold cavities 82a-c is shown with three undercut receiving structures 84 and three undercuts 86. According to one process, once the containers are molded they are removed from the mold base 80 and trimmed to the proper shape. The trimmed containers are then stacked. It is contemplated that the stack order may be from bottom to top as follows: the container from the mold cavity 82a, the mold cavity 82c, and finally the mold cavity 82c. Stacking the containers in this order reduces the stack height, because the undercuts 86 of the locking mechanisms of the containers are in alignment with the undercut receiving structure 88 of the locking mechanism of the container directly preceding it in the stack.

It is contemplated that the containers of several cycles of mold base 80 would be stacked in the order described above so that a stack with more than three containers is produced.

It is further contemplated that larger mold bases, such as a two by three cavity mold base, or an eight by four cavity mold base may be used in the current invention. It is also contemplated that a stack of containers would be formed from each column of a multi-column mold base. It is also contemplated that a non-matrix mold base may be used.

It is additionally contemplated that the mold cavities as shown in FIG. 8 may have a different shape from the generally round shape depicted. For example, the mold cavities may be generally polygonal. If generally polygonal mold cavities are employed, the angle of rotation of the mold cavities within the mold base would vary from that described in connection to FIG. 8. For example, if a generally rectangular mold cavity is employed the angle of rotation between each mold cavities is approximately one hundred and eighty degrees (180°).

It is additionally contemplated that the methods of using mold bases 70, 80 may be combined such that a mold base with mold cavities of varying geometry are combined with the rotation of the mold cavities relative to the mold base to produce a stack of containers with undercuts aligning with the undercut receiving structures of the preceding container in the stack.

Referring to FIG. 9, a mold base 90 is shown comprising mold cavities 92a-f. The mold base 90 of FIG. 9 is a two by three mold base because it has two columns of mold cavities and three rows of mold cavities and is capable of molding six containers at once. Each of the mold cavities 92a-f of the mold base 90 is of an approximately polygonal shape. Each of the mold cavities 92a-f is shown with four undercut receiving structures 94 and four undercuts 96. According to one process, there are two mold cavity designs in mold base 90 of FIG. 9. The mold cavities 92a, 92c, and 92e are the first mold cavity design, and mold cavities 92b, 92d, and 92f are the second mold cavity design. Once the containers have been molded they are removed from the mold base 90 and trimmed to the proper shape. The trimmed containers are then stacked. It is contemplated that the stack order may be from bottom to top as follows: the container from the mold cavity 92a, the mold cavity 92b, the mold cavity 92c, the mold cavity 92d, the mold cavity 92e, and the mold cavity 92f. Stacking the containers in this order will reduce the stack height, because the undercuts 96 of the locking mechanisms of the containers are in alignment with the undercut receiving structures 94 of the locking mechanisms of the container directly preceding it in the stack. It is contemplated that the containers produced by mold cavities 92a-f of several cycles of mold base 90 would be stacked in the order described above so that a stack with more than six containers is produced.

It is further contemplated that larger mold bases, such as a four by two cavity mold base, or an eight by four cavity mold base may be used in the current invention. It is also contemplated that a stack of containers would be formed from each column of mold base 90. According to one process, the order of the first stack may be from bottom to top as follows: the container from the mold cavity 92a, the mold cavity 92b, and the mold cavity 92c. The order of the second stack may be from bottom to top as follows: the container from the mold cavity 92d, the mold cavity 92e, and the mold cavity 92f. It is further contemplated that the containers of several cycles of mold base 90 may be stacked in this order to produce two stacks with more than three containers per stack.

FIG. 10 shows a partial stack 100 of containers produced by a column of the mold base 90 of FIG. 9. The stack 100 comprises containers 102-110, the containers are from three cycles of mold base 90. The first container 102 is from the third cycle of the mold base 90, the second, third, and fourth containers 104,106,108 are from the second cycle of the mold base 90, and the fifth container 110 is from the first cycle of the mold base 90. The container 102 at the top of the stack, and the container that is second from the bottom of the stack 108 were produced in the third mold cavity 92c of the mold base 90 of FIG. 9. The second container from the top 104 of the stack 100 and the bottom container 110 of the stack 100 were produced in the first mold cavity 92a of the mold base 90 of FIG. 9. The middle container 106 of the stack 100 were produced in the second mold cavity 92b of FIG. 9.

The middle container 106 of the stack 100 is the only container that is made by a mold cavity with the second mold cavity design in this stack 100. Therefore, the undercuts of the locking mechanism of the container 104 are in alignment with the undercut receiving structures of the locking mechanism of the container 106, and the undercuts of the locking mechanism of the container 106 are in alignment with the undercut receiving structures of the locking mechanism of the container 108. However, the undercuts of the locking mechanism of the container 102 are in alignment with the undercuts of the locking mechanism of the container 104, and the undercuts of the locking mechanism of the container 108 are in alignment with the undercuts of the locking mechanism of the container 110. The overall height of stack 100 therefore is not truly optimized, as undercut to undercut alignment is occurring among the locking mechanisms of the containers. However, this undercut to undercut alignment of the locking mechanisms is unavoidable when an odd number of rows of mold cavities are present in a mold base, and the shape of the containers prevents the rotation of the containers when forming the stack 100.

This process reduces the stack height of the stack 100, since locations are present where the undercuts of the locking mechanism of one container are in alignment with the undercut receiving structures of the locking mechanism of the preceding container. For example, a stack height H between the second container 104 from the top of the stack 100 and the middle container 106 of the stack 100, and between the middle container 106 of the stack 100 and the second container from the bottom 108 of the stack 100 is the reduced stack height. A stack height G between the top container 102 and the second container 104 from the top of the stack 100 and between the second container from the bottom 108 and the bottom container 110 is the full stack height.

Referring to FIG. 11, a mold base 200 is shown comprising mold cavities 210a,b. The mold base 200 of FIG. 11 is a one by two mold base because it has one columns of mold cavities and two rows of mold cavities and is capable of molding two containers at once. Each of the mold cavities 210a,b of the mold base 200 is of an approximately polygonal shape. Each of the mold cavities 210a,b is shown with four undercut receiving structures 212 and four undercuts 214. As shown in FIG. 11, each of the undercut receiving structures 212 and each of the undercuts 214 are located generally within each of the corners of the containers formed by the cavities 210a,b and are at a generally diagonal orientation. According to one process, there are two mold cavity designs in mold base 200 of FIG. 11. The mold cavity 210a is a first mold cavity design, and mold cavity 210b is a second mold cavity design. Once the containers have been molded they are removed from the mold base 200 and trimmed to the proper shape. The trimmed containers are then stacked. It is contemplated that the stack order may be from bottom to top as follows: the container from the mold cavity 210a, the mold cavity 210b. Stacking the containers in this order will reduce the stack height, because the undercuts 214 of the locking mechanisms of the containers are in alignment with the undercut receiving structures 212 of the locking mechanisms of the container directly preceding it in the stack. It is contemplated that the containers produced by mold cavities 210a,b of several cycles of mold base 200 would be stacked in the order described above so that a stack with more than two containers is produced.

It is further contemplated that undercuts and undercut receiving structures located generally within a corner of a container at a generally diagonal orientation may vary from that depicted in FIG. 11. For example, it is contemplated that a mold base may contain a first mold cavity that contains two undercut receiving structures in a first corner and a second corner along a first lateral edge, and two undercuts in a third corner and a fourth corner along a second lateral edge, generally opposite the first lateral edge. The mold base contains a second mold cavity that contains two undercut receiving structures in a fifth corner and a sixth corner along a third lateral edge, and two undercuts in a seventh corner and an eighth corner along a forth lateral edge, generally opposite the third lateral edge. A first container made in the first mold cavity would be stacked with a second container made in the second mold cavity such that the under cut receiving structures of the second container align with the undercuts of the first container.

It is further contemplated that various methods of reducing the stacking height of containers may be combined. For example, it is contemplated that a mold base may have three mold cavities, wherein the first mold cavity and the second mold cavity have generally identical designs that are at a different orientation relative to each other, and the third mold cavity has a different design.

It is still further contemplated that a mold base may have three mold cavities, wherein the first mold cavity and the second mold cavities have a different design, and the third mold cavity has a design that is generally identical to the design of the first mold cavity, but the third mold cavity is rotated within the mold base relative to the first mold cavity.

The amount of stack height reduction achieved will vary based on the geometry of the container that is being stacked. According to one embodiment, the stack height was reduced by about sixty percent (60%). In an embodiment of the present invention where only partial stack height reduction may be achieved based on the number of mold cavities and the mold base cavity geometry the stack may only be reduced by about twenty percent (20%).

The reduction in stack height reduces the cube size of the transportation packaging for a stack of containers. A reduced cube size for the transportation packaging reduces the transportation costs for transporting a stack of containers, as smaller containers are generally more cost effective to ship than larger containers. A reduction in the cube size for the transportation packaging also lowers the cost of storing the containers before the are used, because the smaller transportation packaging occupies less storage space.

The containers of the present invention are typically formed from polymeric materials, but may be formed from materials such as paper or metal. The polymeric containers are typically formed from orientated polystyrene (OPS), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyolefins (e.g., polypropylene), and combinations thereof. It is contemplated that other materials may be used to form the polymeric containers. The containers may be made from a mineral-filled polymeric material such as, for example, talc or calcium carbonate-filled polyolefin. An example of paper that may be used in forming the containers is paperboard or molded fiber. Paperboard and molded fiber typically have a sufficient coefficient of friction to maintain the first and second containers in a lockable position.

The materials used in forming the containers may assist in releasably locking the containers. For example, the material(s) forming the containers may have a fairly tacky laminate on one side that corresponds with a fairly tacky laminate on the opposing side, resulting in a desirable releasably lockable container. It is contemplated that additives may be added to the containers.

The containers of the present invention are typically made from a thermoforming process. However, it is also contemplated that the containers may be made using other processes known in the art such as, but not limited to, an injection molding process, a rotomolding process, a rotational molding on a planar surface process, a stamping process, or a molded fiber process.

The containers of the present invention are typically disposable, but it is contemplated that they may be reused at a future time.

As discussed above, the containers may be used with food items. A method of using such containers includes placing the food and locking the container to form a container with food therein. The container is then placed in a heating apparatus and heated. Typical heating apparatuses include microwaves and conventional ovens. The containers may contain solid food products. The containers may be used for storage in the refrigerator and/or the freezer.

The thickness of the container generally ranges from about 0.002 to about 0.25 inch, but is typically from about 0.005 to about 0.04 inch. The containers may be opaque or a variety of colors or color combinations. The containers may be transparent if it is desired for the customer to ascertain the nature of the accommodated product and the condition thereof without having to open the container.

While particular embodiments and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations may be apparent from the foregoing descriptions without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method for forming a reduced-height stack of a plurality of containers comprising: providing a first container having at least a first undercut and at least one undercut receiving structure, the at least a first undercut being located at a first position, the at least one undercut receiving structure being located at a second position; providing a second container having at least a second undercut and at least one undercut receiving structure, the at least a second undercut being located at a third position, the at least one undercut receiving structure being located at a fourth position, the third position being a different location from the first position, the fourth position being a different location from the second position, the first and second containers being of generally equal sizes; and arranging the first and second containers to form a stack of a plurality of containers, wherein the at least a first undercut of the first container at the first position aligns with and fits within the at least one undercut receiving structure of the second container at the fourth position so as to reduce the stack height.

2. The method of claim 1 wherein the first and second containers are made using a forming process.

3. The method of claim 1 wherein the first and second containers are thermoformed.

4. The method of claim 1 wherein the first and second containers are injection molded.

5. The method of claim 1 wherein the first and second containers are polymeric containers.

6. The method of claim 1 wherein the first and second containers are made of molded fiber.

7. The method of claim 1 further comprising: providing a plurality of first containers; providing a plurality of second containers; and arranging a plurality of two-container stacks, the respective undercuts of the plurality of first containers at the first position being aligned with and fitted within with respective undercut receiving structures of the plurality of second containers at the fourth position so as to reduce the stack height.

8. A method for forming a reduced-height stack of containers comprising: providing a mold base comprising at least a first mold cavity having a first design and a second mold cavity having a second design, the first and second designs being different; making a first container in the first mold cavity, the first container having at least one undercut located at a first position and at least one undercut receiving structure located at a second position; making a second container in the second mold cavity, the second container having at least one undercut located at a third position and at least one undercut receiving structure located at a fourth position, the third position being a different location from the first position, and the second position being a different location from the fourth position; removing the first and second containers from the respective first and second mold cavities; and arranging the first and second containers to form a two-container stack, wherein the at least a first undercut of the first container at the first position aligns with and fits within the at least one undercut receiving structure of the second container at the fourth position so as to reduce the height of the two-container stack.

9. The method of claim 8, wherein the mold base further comprises a third mold cavity having a generally identical design as the first mold cavity, the third mold cavity being rotated within the mold base relative to the first mold cavity; making a third container in the third mold cavity, the third container having at least one undercut located at a fifth position and at least one undercut receiving structure located at a sixth position; removing the third container from the third mold cavity; and arranging the third container with the first and second containers to form a three-container stack, wherein the at least a first undercut of the third container at the fifth position aligns with and fits within the at least one undercut receiving structure of the first container at the second position so as to reduce the height of the three-container stack.

10. The method of claim 8, wherein the mold base further comprises a third mold cavity and a fourth mold cavity, the mold cavities being arranged in two rows and two columns, the first and second mold cavities comprising a first column of mold cavities, the third and fourth mold cavities comprising a second column of mold cavities, the design of the third mold cavity being different from the design of the fourth mold cavity, the method further comprising: making a third container in the third mold cavity, the third container having at least one undercut being located at a fifth position and at least one undercut receiving structure being located at a sixth position; making a fourth container in the fourth mold cavity, the fourth container having at least one undercut being located at a seventh position and at least one undercut receiving structure being located at an eighth position, the fifth position being a different location from the seventh position; removing the third and fourth containers from the respective third and fourth mold cavities; arranging the third and fourth containers to form a two-container stack, the at least one undercut of the third container at the fifth position being aligned with and fitted within the at least one undercut receiving structure of the fourth container at the eighth position so as to reduce the height of the two-container stack.

11. A method for forming a reduced-height stack of containers comprising: providing a mold base comprising at least a first mold cavity and a second mold cavity, the design of the first mold cavity being substantially identical to the design of the second mold cavity, the second mold cavity being rotated in the mold base relative to the first mold cavity; making a first container in the first mold cavity, the first container having at least one undercut being located at a first position and at least one undercut receiving structure being located at a second position; making a second container in the second mold cavity, the second container having at least one undercut being located at a third position and at least one undercut receiving structure being located at a fourth position, the first position being a different location from the third position relative to the mold base; removing the first and second containers from the respective first and second mold cavities; and arranging the first and second containers to form a two-container stack, the at least one undercut at the first position of the first container being aligned with and fitted within the undercut receiving structure at the fourth position of the second container so as to reduce the height of the two-container stack, without further rotating the containers after removing the containers from the mold cavities.

12. The method of claim 11, wherein the mold base further comprises a third mold cavity having a design different than the first mold cavity; making a third container in the third mold cavity, the third container having at least one undercut located at a fifth position and at least one undercut receiving structure located at a sixth position; removing the third container from the third mold cavity; and arranging the third container with the first and second containers to form a three-container stack, wherein the at least a first undercut of the third container at the fifth position aligns with and fits within the at least one undercut receiving structure of the first container at the second position so as to reduce the height of the three-container stack.

13. The method of claim 11, wherein the mold base further comprises a third mold cavity and a fourth mold cavity, the mold cavities being arranged in two rows and two columns, the first and second mold cavities comprising a first column of mold cavities, the third and fourth mold cavities comprising a second column of mold cavities, the design of the third mold cavity being substantially identical to the design of the fourth mold cavity, the method further comprising: making a third container in the third mold cavity, the third container having at least one undercut being located at a fifth position and at least one undercut receiving structure being located at a sixth position; making a fourth container in the fourth mold cavity, the fourth container having at least one undercut being located at a seventh position and at least one undercut receiving structure being located at an eighth position, the fifth position being a different location from the seventh position; removing the third and fourth containers from the respective third and fourth mold cavities; arranging the third and fourth containers to form a second two-container stack, the undercut of the third container located at the fifth position being aligned with and fitted within the undercut receiving structure of the fourth container located at the eighth position so as to reduce the height of the second two-container stack, without further rotating the containers after removing them from the third and fourth mold cavities.

14. A stack of containers comprising: a first container comprising a locking mechanism including at least one undercut at a first position and at least one undercut receiving structure at a second position; and a second container comprising a locking mechanism including at least one undercut at a third position and at least one undercut receiving structure at a fourth position, the first and second containers are stacked such that the at least one undercut at the first position is aligned with the at least one undercut receiving structure at the fourth position, and the at least one undercut at the first position contacts the undercut receiving structure at the fourth position thereby reducing the stack height.

15. The stack of containers of claim 14 further comprising a third container, the third container comprising a locking mechanism including at least one undercut at a third position and a least one undercut receiving structure at a fourth position, wherein the third container is stacked such that the at least one undercut at the third position is aligned with the at least one undercut receiving structure of the first container at the second position, and the at least one undercut at the third position contacts the undercut receiving structure at the second position thereby reducing the stack height.

16. A stack of containers comprising: a first container wherein the first container comprises a locking mechanism including at least one undercut at a first position and at least one undercut receiving structure at a second position; and a second container wherein the second container comprises a locking mechanism including at least one undercut at the first position and at least one undercut receiving structure at the second position; a third container wherein the third container comprises a locking mechanism including at least one undercut at a third position and at least one undercut receiving structure at a fourth position; a fourth container wherein the fourth container comprises a locking mechanism including at least one undercut at the first position and at least one undercut receiving structure at the second position; and a fifth container wherein the fifth container comprises a locking mechanism including at least one undercut at the first position and at least one undercut receiving structure at the second position, wherein the second container is aligned such that the at least one undercut at the first position is aligned with the at least one undercut at the first position of the first container, the third container is aligned such that the at least one undercut at the third positioned is aligned with and fitted within the at least one undercut receiving structure at the second position of the second container, the fourth container is aligned such that the at least one undercut at the first position of the fourth container is aligned with and fitted within the at least one undercut receiving structure at the fourth position of the third container, and the fifth container is aligned such that the at least one undercut at the first position of the fifth container is aligned with the at least one undercut at the first position of the fourth container, such the stack height between the second, third, and fourth containers is minimized and the overall stack height is reduced.