WO2012118724A1

WO2012118724A1 - Clamshell formed of fiber and methods for making clamshell

Info

Publication number: WO2012118724A1
Application number: PCT/US2012/026689
Authority: WO
Inventors: Calvin S. Krupa
Original assignee: Krupa Calvin S
Priority date: 2011-02-28
Filing date: 2012-02-27
Publication date: 2012-09-07

Abstract

A clamshell (10) formed of biodegradable material includes a container (20) having a first edge (23) with a notch (28), forming two lugs (31) in each of two ends (23a) of the first edge (23). A lid (56) is integrally formed with the container (20) and pivotable towards the container (20) to engage a tab (68) on a second edge (57) of the lid (56) with the notch (28). Two ears (70) of the tab (68) are movable across the lugs (31) to retain the clamshell (10) in a closed state. Ribs (32, 72) formed on the lugs (31) and the tab (68) give the lugs (31) and the tab (68) structural strength to prevent corners (31c, 70a) of the lugs (31) and the ears (70) from pivoting from an overlapping condition. The clamshell (10) can be formed by shaping a wet pulp formation (525) using two mold halves (127, 139).

Description

CLAMSHELL FORMED OF FIBER AND METHODS FOR MAKING CLAMSHELL

BACKGROUND

A clamshell, such as for receiving food, is shown formed of fiber. Methods for making such a clamshell are also disclosed.

Clamshells are conventionally made of plastic material by injection molding or thermoforming and include a container and a lid integrally formed with the container. To retain the clamshell in a closed state, one of the container and the lid includes a male member with an enlarged head for releasable engagement with a female socket in the other of the container and the lid. In another approach, a lip extends downward from a female member and spaced from a body of one of the container and the lid, and a male member slips between the lip and the body. However, use of plastic is not eco-friendly. Clamshells made of fiber have been proposed for eco-protection. Since clamshells made of fiber can not be formed by injection molding or thermoforming as is plastic material, conventionally, a tab is provided on the lid and inserted into a die cut slot in a side of the container for keeping the clamshell in the closed state. However, formation of the slot requires a separate step in manufacture.

In a further approach to retain the clamshell in the closed state while allowing easy formation, a tab with two ears are formed on an edge of the lid, and a notch is defined in a corresponding edge of the container to form two lugs in an opening of the notch. The tab is engaged with the notch, with the ears moved across the lugs into an overlapping condition to retain the clamshell in the closed state. However, the ears and the lugs at the end portions of the tab and the notch are apt to pivot away from the overlapping condition, failing to retain the clamshell in the closed state and leading to the risk of falling of the food received in the clamshell. Thus, a need exists for a clamshell that can be easily made of biodegradable material and that can be reliably retained in the closed state and for methods for making such a clamshell.

BRIEF SUMMARY

This need and other problems in the field of easy manufacture and reliable use of clamshells formed of biodegradable material are solved by providing, in a form, a clamshell including a container having a bottom wall and a first annular portion extending from the bottom wall. The bottom wall and the first annular portion define a first compartment adapted for receiving food. The first annular portion includes a first edge and a first connecting edge spaced from the first edge in a width direction of the container. Each of the first edge and the first connecting edge is spaced from the bottom wall in a depth direction of the container perpendicular to the width direction of the container. A notch is formed in an intermediate portion of the first edge and defines a lug on each of two ends of the first edge. A bottom face of each lug is located intermediate a top face of the lug and the bottom wall in the depth direction of the container. Each lug has a first corner. The first corners of the lugs face each other and define the notch. A first rib is formed in each lug and is in the form of a protrusion on one of the top and bottom faces of one of the lugs and forms a recess in the other of the top and bottom faces of the lug. A lid includes a second connecting edge integrally formed with the first connecting edge of the container as a single monolithic piece. The lid is pivotable relative to the container along the first and second connecting edges. The lid further includes a second edge spaced from the second connecting edge in a width direction of the lid. The second edge includes inner and outer faces spaced in a depth direction of the lid perpendicular to the width direction of the lid. A tab is formed on an intermediate portion of the second edge and includes two ends each having an ear with a second corner. The tab further includes inner and outer faces extending between the ends of the tab and coplanar to inner and outer faces of the second edge. A second rib is formed in the tab and located intermediate the ears. The second rib is in a form of a protrusion on one of the inner and outer faces of the tab and forms a recess in the other of the inner and outer faces of the tab.

The lid is pivotable towards the container to engage the tab with the notch. The ears of the tab are movable across the lugs to retain the clamshell in a closed state in which the lugs and the ears are in an overlapping condition. The first and second ribs give the lugs and the tab structural strength to prevent the first corners of the lugs and the second corners of the ears from pivoting from the overlapping condition. Thus, the clamshell can be reliably retained in the closed state to prevent falling of the food received in the first container.

In the form shown, the first annular portion of the container includes a first peripheral wall that is annular. The bottom wall is connected to a bottom edge of the first peripheral wall. The bottom wall and the first peripheral wall define the first compartment. A ledge is annular and extends outward from a top edge of the first peripheral wall spaced from the bottom edge of the first peripheral wall in the depth direction of the container. A second peripheral wall is annular and extends from the ledge and away from the bottom wall in the depth direction of the container. A first lip is annular and integrally extends outward from a top edge of the second peripheral wall in a transverse plane perpendicular to the depth direction of the container. The first lip includes the first edge and the first connecting edge. A length of the first edge in the length direction of the container is substantially the same as a length of the first connecting edge in the length direction of the container. The first lip further includes two lateral edges spaced in the length direction of the container and extending between the first edge and the first connecting edge. The first lip includes top and bottom faces coplanar to the top and bottom faces of each lug. The bottom face of the first lip is located intermediate the top face of the first lip and the ledge in the depth direction of the container. Each first rib includes a rectilinear main section extending along the first edge and aligned with the notch. Each first rib further includes a tip extending in a joint area between the first edge and one of the lateral edges of the first lip. A wavy portion is formed between each first rib and the second peripheral wall and has an extent equal to a length of each first rib in the length direction of the container. The wavy portions of the container give the lugs structural strength to prevent the lugs from pivoting relative to the container, maintaining the clamshell in the closed state.

In the form shown, the lid includes an end wall and an annular second portion extending from the end wall. The annular second portion includes a third peripheral wall that is annular. The end wall of the lid is connected to an annular outer edge of the third peripheral wall. A second compartment defined by the third peripheral wall and the end wall is in communication with the first compartment when the clamshell is in the closed state, providing a larger space for receiving the food. A first section is annular and extends outward from an annular inner edge of the third peripheral wall. A second section is annular and extends from the first section in the depth direction of the lid. A ridge is annular and extends outward from the second section and surrounded by an outer peripheral wall that is annular. A second lip is annular and extends outward from the outer peripheral wall and includes the second edge and the second connecting edge. A wavy portion is formed between the second rib and the outer peripheral wall of the lid. The wavy portion of the lid extends coextensively with the second rib in a length direction of the lid perpendicular to the width and depth directions of the lid. The wavy portion of the lid gives the tab structural strength to prevent the tab from pivoting relative to the lid, maintaining the clamshell in the closed state.

In a method, the clamshell is formed by shaping a wet pulp formation using two mold halves.

Illustrative embodiments will become clearer in light of the following detailed description described in connection with the drawings.

DESCRIPTION OF THE DRAWINGS

The illustrative embodiments may best be described by reference to the accompanying drawings where: Figure 1 shows a perspective view of a clamshell in an open state.

Figure 2 shows a cross sectional view of the clamshell of Figure 1 according to section line 2-2 of Figure 1.

Figure 3 shows a cross sectional view of the clamshell of Figure 1 according to section line 3-3 of Figure 1.

Figure 4 shows a cross sectional view of the clamshell of Figure 1 according to section line 4-4 of Figure 1.

Figure 5 shows a cross sectional view of the clamshell of Figure 1 according to section line 5-5 of Figure 1.

Figure 6 shows a top view of the clamshell of Figure 1 in a closed state.

Figure 7 shows a cross sectional view of the clamshell of Figure 6 according to section line 7-7 of Figure 6.

Figure 8 shows a side view of the clamshell of Figure 6.

Figure 9 shows a cross sectional view of two clamshells of Figure 1 in a stack, with each clamshell cross-sectioned according to section line 9-9 of Figure 1.

Figure 10 shows a flow diagram illustrating an example of a method for preparing and using the clamshell.

Figure 11 shows a cross sectional view of a mold for making a wet pulp formation from pulp.

Figure 12 shows a cross sectional view of a heating and pressing mold for drying the wet pulp formation.

All figures are drawn for ease of explanation of the basic teachings only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the illustrative embodiments will be explained or will be within the skill of the art after the following teachings have been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following teachings have been read and understood.

Where used in the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the terms "first", "second", "third", "lower", "upper", "top", "bottom", "inner", "outer", "end", "portion", "section", "spacing", "outward", "upward", "length", "depth", "width", "transverse", and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the illustrative embodiments.

DETAILED DESCRIPTION

A clamshell formed of biodegradable material, such as for food, is shown in the drawings and generally designated 10. According to the form shown, clamshell 10 includes a container 20 having a bottom wall 48 and a first annular portion 20A extending from bottom wall 48, with bottom wall 48 and first annular portion 20A defining a first compartment 50 adapted for receiving food. Specifically, first annular portion 20A includes a first peripheral wall 40 that is annular and that includes top and bottom edges 40a and 40b spaced in a depth direction of container 20. Bottom wall 48 is connected to bottom edge 40b of first peripheral wall 40. First peripheral wall 40 and bottom wall 48 together define first compartment 50. First peripheral wall 40 has decreasing areas towards bottom wall 48 in the depth direction of container 20. Bottom wall 48 includes a top face 48a facing first compartment 50 and a bottom face 48b opposite to and spaced from top face 48a in the depth direction of container 20. A recess 49 (Figure 7) is formed in a center of bottom face 48b of bottom wall 48 and forms a bulge on top face 48a of bottom wall 48. A ledge 38 is annular and extends outward from top edge 40a of first peripheral wall 40. Ledge 38 has a peripheral edge 38a spaced from first peripheral wall 40. A second peripheral wall 42 is annular and extends upward from peripheral edge 38a of ledge 38 and away from bottom wall 48 in the depth direction of container 20. Second peripheral wall 42 has a top edge 42a, with ledge 38 located intermediate top edge 42a and bottom wall 48. Second peripheral wall 42 and ledge 38 together define an engaging groove 36 in communication with first compartment 50.

In the form shown, a first lip 22 is annular and integrally extends outward from top edge 42a of second peripheral wall 42 in a transverse plane perpendicular to the depth direction of container 20. First lip 22 is parallel to and is spaced from ledge 38, bottom wall 48, and recess 49 in the depth direction of container 20. Specifically, ledge 38 is located intermediate bottom wall 48 and first lip 22. First lip 22 includes top and bottom faces 22a and 22b spaced in the depth direction of container 20. Bottom face 22b of first lip 22 is located intermediate top face 22a of first lip 22 and ledge 38 in the depth direction of container 20. First lip 22 further includes a first edge 23 and a first connecting edge 24, with first edge 23 and first connecting edge 24 spaced from first edge 23 in a width direction of container 20 perpendicular to the depth direction of container 20. Each of first edge 23 and first connecting edge 24 has a top face that is a portion of top face 22a of first lip 22. Each of first edge 23 and first connecting edge 24 has a bottom face that is a portion of bottom face 22b of first lip 22. First edge 23 includes two ends 23a spaced in a length direction of container 20 perpendicular to the depth and width directions of container 20 and an intermediate portion 23b between ends 23a. A length of first edge 23 in the length direction of container 20 is substantially the same as a length of first connecting edge 24 in the length direction of container 20. First lip 22 further includes two lateral edges 26 parallel to each other and spaced in the length direction of container 20 and extending between first edge 23 and first connecting edge 24.

In the form shown, a notch 28 is formed in intermediate portion 23b of first edge 23 of first lip 22 and defines a lug 31 on each end 23a of first edge 23 of first lip 22. Notch 28 has substantially trapezoidal cross sections in the transverse plane and has decreasing widths and then increasing widths away from second peripheral wall 42 in the width direction of container 20. Each lug 31 includes top and bottom faces 31a and 31b coplanar to top and bottom faces 22a and 22b of first lip 22. Namely, bottom face 31b of each lug 31 is located intermediate top face 31a of lug 31 and bottom wall 48 in the depth direction of container 20. Each lug 31 has a corner 31c. Corners 31 c of lugs 31 face each other and define notch 28. A first rib 32 is formed in each lug 31 and has substantially U-shaped cross sections. Each first rib 32 has a top 39 parallel to and spaced from first lip 22, ledge 38, bottom wall 48, and recess 49. Top 39 is flat in the form shown. Furthermore, each first rib 32 is substantially in the shape of a comma as viewed from the top. A rectilinear main section 32a of each first rib 32 extends along first edge 23 and is aligned with notch 28. A tip 35 of each first rib 32 extends in a joint area between first edge 23 and one of lateral edges 26. Each first rib 32 has a peripheral wall 37 extending between top 39 and top face 31a of lug 31. Peripheral wall 37 of each first rib 32 has decreasing cross sectional areas away from first lip 22. In the form shown, each first rib 32 is in the form of a protrusion on top face 31a of lug 31 and forms a recess in bottom face 31b of lug 31. However, each first rib 32 can be in the form of a protrusion on bottom face 31b of lug 31 and forms a recess in top face 31a of lug 31, with top 39 of first rib 32 located intermediate first lip 22 and bottom wall 48.

In the form shown, a wavy portion 34 is formed between each first rib 32 and second peripheral wall 42. Wavy portion 34 includes first and second arcuate grooves 34a, with an arcuate protrusion 34b defined between first and second arcuate grooves 34a. Each of first and second arcuate grooves 34a is arc-shaped in cross section parallel to second peripheral wall 42. Wavy portion 34 has an extent equal to a length of first rib 32 in the length direction of container 20. Each of first and second arcuate grooves 34a has a bottom 34d at a level below top face 22a of first lip 22 and below top edge 42a of second peripheral wall 42 but above ledge 38 in the depth direction of container 20. Namely, bottom 34d of each of first and second arcuate grooves 34a has a spacing to top 39 of first rib 32 in the depth direction of container 20 and is located intermediate first lip 22 and ledge 38 in the depth direction of container 20. Arcuate protrusion 34b has a top 34c located at the same extent as first lip 22 and located intermediate bottom 34d of each of first and second arcuate grooves 34a and top 39 of first rib 32 in the depth direction of container 20. Each of first and second arcuate grooves 34a includes a side coextensive with and contiguous to peripheral wall 37. Each wavy portion 34 has a uniform thickness in the depth direction of container 20 equal to a thickness between top and bottom faces 22a and 22b of first lip 22 in the depth direction of container 20.

In the form shown, a plurality of dents 52 is formed in an annular joint section 53 between ledge 38 and first peripheral wall 40. The annular joint section 53 includes an inner face facing first compartment 50 and an outer face opposite to the inner face of annular joint section 53. Each dent 52 is a recess in the inner face of annular joint section 53 and forms a protrusion on the outer face of the annular joint section 53.

In the form shown, clamshell 10 further includes a lid 56 integrally formed with container 20 as a single continuous monolithic piece. Lid 56 includes an end wall 88 and a second annular portion 56A extending from end wall 88. Specifically, second annular portion 56A of lid 56 includes a third peripheral wall 82 that is annular and that includes an annular outer edge 82a and an annular inner edge 82b spaced from annular outer edge 82a in a depth direction of lid 56. End wall 88 is connected to annular outer edge 82a of third peripheral wall 82. A second compartment 90 is defined by third peripheral wall 82 and end wall 88. A first section 84 is annular and extends outward from annular inner edge 82b of third peripheral wall 82. A second section 86 is annular and extends from first section 84 in the depth direction of lid 56. In the form shown, a ridge 76 is annular and extends outward from second section 86 and is generally parallel to but spaced from end wall 88, with first section 84 located intermediate ridge 76 and end wall 88 in the depth direction of lid 56. An outer peripheral wall 75 is annular and surrounds ridge 76. Ridge 76, second section 86, and outer peripheral wall 75 define a generally trapezoidal shape and define an annular groove 78 in an outer face of lid 56 that faces away from second compartment 90. Annular groove 78 surrounds second compartment 90 of lid 56. A second lip 58 is annular and integrally extends outward from outer peripheral wall 75. Second lip 58 includes a second connecting edge 54 integrally formed with first connecting edge 24 of first lip 22 as a single continuous monolithic piece. Lid 56 is pivotable relative to container 20 along first and second connecting edges 24 and 54. A plurality of perforations 55 is formed in a joint section between second connecting edge 54 of second lip 58 and first connecting edge 24 of first lip 22 and defines a line allowing easy pivotal movement of lid 56 relative to container 20 about the line. Second lip 58 further includes a second edge 57 opposite to and spaced from second connecting edge 54 in a width direction of lid 56 perpendicular to the depth direction of lid 56. Second edge 57 of second lip 58 further includes inner and outer faces 57a and 57b spaced in the depth direction of lid 56, with outer face 57b located intermediate inner face 57a and end wall 88 in the depth direction of lid 56.

In the form shown, a tab 68 is formed on an intermediate portion of second edge

57. Tab 68 has substantially trapezoidal cross sections and includes two ears 70 on two ends thereof, with each ear 70 having a corner 70a. Tab 68 has increasing widths away from second lip 58. Tab 68 includes inner and outer faces 68a and 68b coplanar to inner and outer faces 57a and 57b of second edge 57 of second lip 58 and extending between the two ends of tab 68. A second rib 72 is formed in tab 68 and located intermediate ears 70. Second rib 72 is substantially trapezoidal in cross section and has a bottom 79 parallel to and spaced from end wall 88 and tab 68. Bottom 79 is flat in the form shown. Inner face 68a of tab 68 is located intermediate bottom 79 of second rib 72 and outer face 68b of tab 68 in the depth direction of lid 56. Furthermore, second rib 72 has a peripheral wall 77 extending between bottom 79 and inner face 68a of tab 68. Peripheral wall 77 of second rib 72 has decreasing cross sectional areas away from tab 68. In the form shown, second rib 72 is in the form of a protrusion on inner face 68a of tab 68 and forms a recess in outer face 68b of tab 68. However, second rib 72 can be in the form of a protrusion on outer face 68b of tab 68 and can form a recess in inner face 68a of tab 68, with bottom 79 of second rib 72 located intermediate second lip 58 and end wall 88 in the depth direction of lid 56.

In the form shown, a wavy portion 74 is formed between second rib 72 and outer peripheral wall 75. Wavy portion 74 includes a plurality of grooves 74a, with an arcuate protrusion 74b formed between two adjacent grooves 74a. Each groove 74a is arcuate in the form shown, and each of grooves 74a and arcuate protrusions 74b is arc-shaped in cross section. Wavy portion 74 extends coextensively with second rib 72 in a length direction of lid 56 perpendicular to the depth and width directions of lid 56. Each groove 74a includes a bottom 74c located intermediate end wall 88 and tab 68 in the depth direction of lid 56. Each arcuate protrusion 74b has a top 74d at the same extent as tab 68 and located intermediate bottom 79 of second rib 72 and bottom 74c of each groove 74a in the depth direction of lid 56. Each groove 74a includes first and second sides coextensive with outer peripheral wall 75 and peripheral wall 77, respectively. Wavy portion 74 has a uniform thickness in the depth direction of lid 56 equal to a thickness between inner and outer faces 57a and 57b of second edge 57 in the depth direction of lid 56.

In the form shown, a plurality of dents 92 is formed in an annular joint portion

94 between second section 86 and ridge 76. Annular joint portion 94 includes an inner face facing second compartment 90 and an outer face opposite to the inner face of annular joint portion 94. Each dent 92 is a recess in the inner face of annular joint portion 94 and forms a protrusion on the outer face of the annular joint portion 94.

Clamshell 10 including container 20 and lid 56 can be formed by molding formation of or by die cutting a single sheet of fiber, such as sugarcane, wheat straw or other biodegradable fiber, providing an eco-friendly product. It can be appreciated that tab 68 and notch 28 can be formed as a part of clamshell 10 by the die cutting, such that no extra manufacturing step is required. Dents 52 and 92 can be formed in differing locations of container 20 and lid 56 of simultaneously formed clamshells 10, such that dents 52 and 92 respectively of stacked clamshells 10 may be offset from each other.

Figure 10 shows a flow diagram illustrating an example of a method for making and using clamshell 10. Specifically, wheat straw 500 is taken from a farm to a pulping factory in large bales. The straw bales are torn apart by a straw shedder 505 of the pulping factory and then ground into small pieces having a length of approximately 1 inch (2.54 cm). The ground straw is transferred to a soaking tank 510 filled with water. A bio-enzyme is added into soaking tank 510 to break down the straw and to release fibers of the straw for the purposes of creating pulp 515. About 1700 pounds (about 772 kg) of usable pulp are obtained from about one ton (about 915 kg) of straw. Pulp 515 is transferred to a pulp molding machine 520 that contains a mold 115 having a closed side 119 and an open side 117, with an opening cavity 121 defined in open side 117 having a shape corresponding to that of clamshell 10. A vaccum fitting 125 is mounted in a hole 123 in closed side 119 and connected to a vacuum pump or the like. Pulp 515 suspended in water 1 13 is deposited in opening cavity 121 of mold 115. The vacuum pump is activated to remove water 113 from mold 115, creating a wet pulp formation 525 having a moisture content in the order of 50%. It is appreciated that no adhesives are added while preparing wet pulp formation 525. Wet pulp formation 525 without adhesive is removed from pulp molding machine 520 and deposited into a heating and pressing mold 530. Heating and pressing mold 530 includes first and second mold halves 127 and 139 which define a cavity 151 having a shape corresponding to that of clamshell 10. In the form shown, first mold half 127 includes an inner surface 131 and an outer surface 129 opposite to inner surface 131. Second mold half 139 includes an inner surface 143 and an outer surface 141 opposite to inner surface 143. The heating and pressing mold halves are engaged with each other, with cavity 151 defined between inner surfaces 131 and 143. A pressure in the order of 1000 psi (about 70 kg/cm²) is applied to heating and pressing mold 530. Furthermore, heating and pressing mold 530 is heated to 350 degrees Fahrenheit (about 177 degrees Celsius) for approximately 45 seconds to dry wet pulp formation 525 to a moisture content in the order of 15%, obtaining a cured product (i.e., clamshell 10). In the example shown, heating and pressing mold 530 is heated by passing steam 155 through first and second mold halves 127 and 139. However, other approaches for heating heating and pressing 530 for the purpose of drying wet pulp formation 525 can be used. First and second mold halves 127 and 139 are polished to a shine to give a very smooth surface to the cured product. The cured product is removed from heating and pressing mold 530 (see 535) after separating first mold half 127 from second mold half 139. The trimmed product does not include a release coat. Food can be placed into the trimmed product (see 540) and baked to a temperature of up to 425 degrees Fahrenheit (about 218 degrees Celsius) (see 545). Baked food is then removed from the trimmed product, and the trimmed product can be composted (see 550). It can be appreciated that clamshell 10 made from the method can be used to receive food without baking. Pulp 515 can be prepared from material other than wheat straw. Furthermore, pulp 515 can be prepared by procedures other than those disclosed. Further, the cured product does not have to be trimmed if a smooth outer surface of the cured product is not necessary. When not in use, a plurality of clamshells 10 is stacked to save space for storage. With reference to Figure 9, first peripheral wall 40 and bottom wall 48 of container 20 of an upper clamshell 10 are received in first compartment 50 of a lower clamshell 10. Third peripheral wall 82 and end wall 88 of lid 56 of upper clamshell 10 are received in second compartment 90 of lower clamshell 10. The protrusions of dents 52 of upper clamshell 10 abut ledge 38 of lower clamshell 10. The protrusions of dents 92 of upper clamshell 10 abut ridge 76 of lower clamshell 10. An annular outer face of first peripheral wall 40 of upper clamshell 10 is spaced from an annular inner face of first peripheral wall 40 of lower shell 10. An annular outer face of first section 84 of upper clamshell 10 is spaced from an annular inner face of first section 84 of lower clamshell 10. Furthermore, lugs 31 of upper clamshell 10 are spaced from lugs 31 of lower clamshell 10, and tab 68 of upper clamshell 10 is spaced from tab 68 of lower clamshell 10. Further, ridge 76 of lower clamshell 10 is partially received in annular groove 78 of upper clamshell 10 and spaced from ridge 76 of upper clamshell 10. The contact area between upper and lower clamshells 10 is significantly reduced. Thus, the friction between upper and lower clamshells 10 is reduced to allow easy, manual separation of upper clamshell 10 from lower clamshell 10. However, clamshells 10 can be stably stacked without the risk of inadvertent disengagement.

In use, food is placed into first compartment 50 of container 20, and lid 56 is pivoted towards container 20 to engage tab 68 with notch 28 to close container 20. Second compartment 90 of lid 56 is in communication with first compartment 50, providing a larger space for receiving the food. Ridge 76, second section 86, and outer peripheral wall 75 of lid 56 are received in engaging groove 36 of container 20. Ears 70 of tab 68 are moved across lugs 31 to retain clamshell 10 in the closed state, with lugs 31 and ears 70 in an overlapping condition. Furthermore, first and second ribs 32 and 72 give lugs 31 and tab 68 structural strength to prevent corners 31c and 70a of lugs 31 and ears 70 from pivoting from the overlapping condition, and wavy portions 34 and 74 give lugs 31 and tab 68 structural strength to prevent lugs 31 and tab 68 from pivoting relative to container 20 and lid 56 to maintain clamshell 10 in the closed state without the need of an elastic band or the like. Wavy portions 34 and 74 giving lugs 31 and tab 68 structural strength allow repeated use of clamshell 10 if desired.

The food can be retrieved after separating ears 70 of tab 68 from lugs 31. However, the food can be baked in clamshell 10 and then removed from clamshell 10, and clamshell 10 can be composted, as mentioned above.

Now that the basic teachings have been explained, many extensions and variations will be obvious to one having ordinary skill in the art. For example, container 20 does not have to include first lip 22, and first annular portion 20A of container 20 can merely include first peripheral wall 40, with first edge 23 and first connecting edge 24 being two opposite edges of top edge 40a of first peripheral wall 40. In another form, first annular portion 20A of container 20 does not have to include second peripheral wall 42 and first lip 22, with first edge 23 and first connecting edge 24 being two opposite edges of peripheral edge 38a of ledge 38. Further, lid 56 can be in the form of a flat piece including second edge 57 and second connecting edge 54 and does not include second annular portion 56A. In another form, lid 56 does not have to include second lip 58, and second annular portion 56A of lid 56 can merely include third peripheral wall 82, with second edge 57 and second connecting edge 54 being two opposite edges of annular inner edge 82b of third peripheral wall 82. Further, clamshell 10 does not have to include perforations 55 while still allowing pivotal movement of lid 56 relative to container 20.

Thus since the illustrative embodiments disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope is to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Claims

1. A clamshell for food comprising, in combination:

a container including a bottom wall and a first annular portion extending from the bottom wall, with the first annular portion and the bottom wall defining a first compartment, with the first compartment adapted for receiving food, with the first annular portion including a first edge and a first connecting edge spaced from the first edge in a width direction of the container, with each of the first edge and the first connecting edge spaced from the bottom wall in a depth direction of the container perpendicular to the width direction of the container, with the first edge having two ends and an intermediate portion between the two ends, with a notch formed in the intermediate portion of the first edge and defining a lug on each of the two ends of the first edge, with each of the lugs including top and bottom faces spaced in the depth direction of the container, with the bottom face of each of the lugs located intermediate the top face of the lug and the bottom wall in the depth direction of the container, with each of the two lugs having a first corner, with the first corners of the two lugs facing each other and defining the notch, with a first rib formed in each of the lugs, with each of the first ribs being in a form of a protrusion on one of the top and bottom faces of one of the lugs and forming a recess in the other of the top and bottom faces of the lug; and

a lid including a second connecting edge integrally formed with the first connecting edge of the first annular portion of the container as a single monolithic piece of biodegradable material, with the lid being pivotable relative to the container along the first and second connecting edges, with the lid further including a second edge spaced from the second connecting edge in a width direction of the lid, with the second edge including inner and outer faces spaced in a depth direction of the lid perpendicular to the width direction of the lid, with a tab formed on an intermediate portion of the second edge, with the tab including two ends each having an ear with a second corner, with the tab further including inner and outer faces coplanar to the inner and outer faces of the second edge of the lid and extending between the two ends of the tab, with a second rib formed in the tab and located intermediate the ears, with the second rib being in a form of a protrusion on one of the inner and outer faces of the tab and forming a recess in the other of the inner and outer faces of the tab,

wherein the lid is pivotable towards the container to engage the tab with the notch, with the ears of the tab movable across the lugs to retain the clamshell in a closed state in which the lugs and the ears are in an overlapping condition, with the first and second ribs giving the lugs and the tab structural strength to prevent the first corners of the lugs and the second corners of the ears from pivoting from the overlapping condition.

2. The clamshell as claimed in claim 1, with the first annular portion of the container including a first peripheral wall, with the first peripheral wall being annular and having top and bottom edges spaced in the depth direction of the container, with the bottom wall of the container connected to the bottom edge of the first peripheral wall, with the first peripheral wall and the bottom wall of the container defining the first compartment, with a ledge being annular and extending outward from the top edge of the first peripheral wall, with a second peripheral wall being annular and extending from the ledge and away from the bottom wall in the depth direction of the container and having a top edge, with a first lip being annular and integrally extending outward from the top edge of the second peripheral wall in a transverse plane perpendicular to the depth direction of the container, with the first lip including the first edge and the first connecting edge, with the ledge located intermediate the first lip and the bottom wall in the depth direction of the container, with the first lip including top and bottom faces spaced in the depth direction of the container and coplanar to the top and bottom faces of each of the lugs, with the bottom face of the first lip located intermediate the top face of the first lip and the ledge in the depth direction of the container.

3. The clamshell as claimed in claim 2, with the protrusion of each of the first ribs located on the top face of one of the lugs, with the recess of each of the first ribs formed in the bottom face of one of the lugs, with each of the first ribs having a top spaced from the top face of one of the lugs in the depth direction of the container and a peripheral wall extending between the top of the first rib and the top face of the lug, with the peripheral wall of each of the first ribs having decreasing cross sectional areas away from the first lip in the depth direction of the container.

4. The clamshell as claimed in claim 3, with a wavy portion formed between each of the first ribs and the second peripheral wall, with each of the wavy portions including first and second arcuate grooves, with an arcuate protrusion defined between the first and second arcuate grooves, with each of the wavy portions having an extent equal to a length of each of the first ribs in a length direction of the container perpendicular to the width and depth directions of the container, with the wavy portions giving the lugs structural strength to prevent the lugs from pivoting relative to the container to maintain the clamshell in the closed state.

5. The clamshell as claimed in claim 4, with each of the first and second arcuate grooves being arc-shaped and having a bottom located intermediate the first lip and the ledge in the depth direction of the container, with the arcuate protrusion having a top located at a same extent as the first lip and located intermediate the bottom of each of the first and second arcuate grooves and the top of one of the first ribs in the depth direction of the container.

6. The clamshell as claimed in claim 5, with each of the first and second arcuate grooves including a side coextensive with and contiguous to the peripheral wall of one of the first ribs, with the first lip having a thickness between the top and bottom faces thereof, each of the wavy portions of the container having a uniform thickness in the depth direction of the container equal to the thickness of the first lip.

7. The clamshell as claimed in claim 6, with the bottom wall of the container including a top face facing the first compartment and a bottom face opposite to and spaced from the top face of the bottom wall in the depth direction of the container, with a recess formed in a center of the bottom face of the bottom wall of the container and forming a bulge on the top face of the bottom wall of the container.

8. The clamshell as claimed in claim 6, with each of the first edge and the first connecting edge of the first lip of the container having a length in the length direction of the container, with the length of the first edge of the first lip being substantially the same as the length of the first connecting edge of the first lip, with the notch having substantially trapezoidal cross sections in the transverse plane and having decreasing widths and then increasing widths away from the second peripheral wall in the width direction of the container.

9. The clamshell as claimed in claim 8, with the first lip further including two lateral edges spaced in the length direction of the container and extending between the first edge and the first connecting edge, with each of the first ribs being substantially in a shape of a comma, with each of the first ribs including a rectilinear main section and a tip, with the rectilinear main section of each of the first ribs extending along the first edge and aligned with the notch of the container, with the tip of each of the first ribs extending in a joint area between the first edge and one of the two lateral edges.

10. The clamshell as claimed in claim 9, with the container further comprising a plurality of dents formed in an annular joint section between the ledge and the first peripheral wall, with the annular joint section including an inner face facing the first compartment of the container and an outer face opposite to the inner face of the annular joint section, with each of the plurality of dents being a recess in the inner face of the annular joint section and forming a protrusion on the outer face of the annular joint section.

1 1. The clamshell as claimed in claim 2, with the lid including an end wall and an annular second portion extending from the end wall, with the second annular portion including the second edge and the second connecting edge, with the outer face of the second edge located intermediate the inner face of the second edge and the end wall of the lid in the depth direction of the lid.

12. The clamshell as claimed in claim 11, with the annular second portion of the lid including a third peripheral wall, with the third peripheral wall being annular and having an annular inner edge and an annular outer edge spaced from the annular inner edge in the depth direction of the lid, with the end wall of the lid connected to the annular outer edge of the third peripheral wall, with a second compartment defined by the third peripheral wall and the end wall, with a first section being annular and extending outward from the annular inner edge of the third peripheral wall, with a second section being annular and extending from the first section in the depth direction of the lid, with a ridge being annular and extending outward from the second section, with the first section located intermediate the ridge and the end wall in the depth direction of the lid, with an outer peripheral wall being annular and surrounding the ridge, with a second lip being annular and extending outward from the outer peripheral wall, with the second lip including the second edge and the second connecting edge,

wherein the lid is pivotable towards the container to engage the tab with the notch, and wherein the second compartment of the lid is in communication with the first compartment when the clamshell is in the closed state, with the first and second compartments adapted for receiving the food.

13. The clamshell as claimed in claim 12, with the lid further including a wavy portion formed between the second rib and the outer peripheral wall of the lid, with the wavy portion including a plurality of grooves, with an arcuate protrusion formed between two adjacent grooves of the wavy portion, with the wavy portion extending coextensively with the second rib in a length direction of the lid perpendicular to the depth and width directions of the lid, with the wavy portion giving the tab structural strength to prevent the tab from pivoting relative to the lid to maintain the clamshell in the closed state.

14. The clamshell as claimed in claim 13, with the protrusion of the second rib located on the inner face of the tab, with the recess of the second rib formed in the outer face of the tab, with the second rib including a bottom, with the inner face of the tab located intermediate the bottom of the second rib and the outer face of the tab in the depth direction of the lid, with the second rib having a peripheral wall extending between the bottom of the second rib and the inner face of the tab, with each of the plurality of grooves of the wavy portion of the lid including a bottom located intermediate the end wall and the tab in the depth direction of the lid, with each of the arcuate protrusions of the wavy portion of the lid having a top at a same extent as the tab, with the top of each of the arcuate protrusions of the wavy portion of the lid located intermediate the bottom of the second rib and the bottom of each of the plurality of grooves of the wavy portion in the depth direction of the lid.

15. The clamshell as claimed in claim 14, with the peripheral wall of the second rib having decreasing cross sectional areas away from the tab, with each of the plurality of grooves of the wavy portion of the lid being arcuate and including first and second sides coextensive with the outer peripheral wall of the lid and the peripheral wall of the second rib, respectively, with the second edge having a thickness between the inner and outer faces thereof, with the wavy portion of the lid having a uniform thickness in the depth direction of the lid equal to the thickness of the second edge.

16. The clamshell as claimed in claim 15, with the lid having an outer face facing away from the second compartment, with the ridge, the second section, and the outer peripheral wall of the lid defining a trapezoidal shape and defining an annular groove in the outer face of the lid, with the annular groove surrounding the second compartment.

17. The clamshell as claimed in claim 13, with the lid further including a plurality of dents formed in an annular joint portion between the second section and the ridge of the lid, with the annular joint portion including an inner face facing the second compartment of the lid and an outer face opposite to the inner face of the annular joint portion, with each of the plurality of dents being a recess in the inner face of the annular joint portion and forming a protrusion on the outer face of the annular joint portion.

18. The clamshell as claimed in claim 13, with a plurality of perforations formed in a joint section between the first and second connecting edges, with the plurality of perforations defining a line, with the lid being pivotable relative to the container along the line.

19. The clamshell as claimed in claim 12, with the second peripheral wall and the ledge of the container together defining an engaging groove in communication with the first compartment, with the ridge, the second section, and the outer peripheral wall of the lid received in the engaging groove of the container when the clamshell is in the closed state.

20. The clamshell as claimed in claim 11, with the container and the lid integrally formed of a single sheet of biodegradable fiber.

21. A method for making a clamshell for food, comprising:

preparing a welt pulp formation; and

shaping the wet pulp formation into a clamshell by using first and second mold halves, with the clamshell including:

a lid including a second connecting edge integrally formed with the first connecting edge of the first annular portion of the container as a single monolithic piece, with the lid being pivotable relative to the container along the first and second connecting edges, with the lid further including a second edge spaced from the second connecting edge in a width direction of the lid, with the second edge including inner and outer faces spaced in a depth direction of the lid perpendicular to the width direction of the lid, with a tab formed on an intermediate portion of the second edge, with the tab including two ends each having an ear with a second corner, with the tab further including inner and outer faces coplanar to the inner and outer faces of the second edge of the lid and extending between the two ends of the tab, with a second rib formed in the tab and located intermediate the ears, with the second rib being in a form of a protrusion on one of the inner and outer faces of the tab and forming a recess in the other of the inner and outer faces of the tab.

22. The method as claimed in claim 21, with preparing the wet pulp formation including:

depositing pulp in an opening cavity of a mold; and applying a vacuum to the mold to remove water from the pulp, creating the wet pulp formation having a moisture content in an order of 50%; and

removing the wet pulp formation from the mold.

23. The method as claimed in claim 21, with shaping the wet pulp formation including:

depositing the wet pulp formation into a heating and pressing mold, with the heating and pressing mold including the first and second mold halves, with the first and second mold halves defining a cavity having a shape corresponding to a shape of the clamshell; and

pressurizing and heating the first and second mold halves of the heating and pressing mold to dry the wet pulp formation to a moisture content in an order of 15%, obtaining a cured product of the clamshell.