EGG CARTON CELL STRUCTURE
United States Patent 3687350
An egg carton structure comprising a carton cover member joined to a cellular bottom member with a locking flap attached thereto whereby such a carton, when in a closed position, is maintained in a releasably locked position by cooperation of locking elements located on the locking flap and the front wall of the carton cover member. The cellular bottom member is characterized by having individual egg-retaining cells specifically designed to minimize or eliminate egg breakage when compressive forces are applied against the closed carton.
US Patent References:
Molded pulp egg carton
Reifers - January 1962 - 3016176
Molded pulp produce package
Reifers - March 1967 - 3310218
Nestable egg trays
Rudd - November 1966 - 3282458
Fruit-packing trays
Martelli - January 1963 - 3074582
Molded pulp egg carton
Reifers - September 1965 - 3207409
Molded pulp egg carton
Reifers - January 1962 - 3016176
Molded pulp produce package
Reifers - March 1967 - 3310218
Nestable egg trays
Rudd - November 1966 - 3282458
Fruit-packing trays
Martelli - January 1963 - 3074582
Molded pulp egg carton
Reifers - September 1965 - 3207409
Application Number:
05/042368
Publication Date:
08/29/1972
Filing Date:
06/01/1970
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
264/321
International Classes:
B65D85/32; B65D85/30; B65D85/32
Field of Search:
229/2.5,29M
US Patent References:
| 3166467 | Method for producing molded pulp articles | January 1965 | Reifers |
Primary Examiner:
Norton, Donald F.
Claims:
What is claimed is
1. A thermoplastic foam egg carton structure comprising a cover member hinged to a bottom cellular member, said cellular member having a plurality of egg-receiving cells formed therein, each of said cells having at least one vertical wall section adapted to allow for cell expansion upon the application of compressive forces exerted on individual eggs positioned in said cells, said egg-receiving cells being further characterized by having a substantially flat base integrally joined to said wall, said cell wall extending upwardly and outwardly from said base, said cell wall comprising a plurality of relatively flat surfaces vertically spaced apart by concave surfaces, each of said relatively flat surfaces and said concave surfaces extending from the bottom of said cell wall to substantially the top of said cell wall.
1. A thermoplastic foam egg carton structure comprising a cover member hinged to a bottom cellular member, said cellular member having a plurality of egg-receiving cells formed therein, each of said cells having at least one vertical wall section adapted to allow for cell expansion upon the application of compressive forces exerted on individual eggs positioned in said cells, said egg-receiving cells being further characterized by having a substantially flat base integrally joined to said wall, said cell wall extending upwardly and outwardly from said base, said cell wall comprising a plurality of relatively flat surfaces vertically spaced apart by concave surfaces, each of said relatively flat surfaces and said concave surfaces extending from the bottom of said cell wall to substantially the top of said cell wall.
Description:
BACKGROUND OF THE INVENTION
I. FIELD OF THE INVENTION
This invention relates to the structure of disposable egg-cartons which may be fabricated from materials such as molded pulp, paste board, and plastic, including expanded or formed plastics such as polystyrene foam for example. The carton is particularly characterized by having a bottom cellular section, a locking flap hinged to one longitudinal edge of the bottom section and an inverted dish-like cover section hinged along the opposite edge of the bottom section. The bottom portion of the cells in the carton cellular section are provided with individual cell feet to impart carton stability when the carton is positioned on a flat surface. The carton's cellular bottom section includes transversely extending walls intermediate pairs of egg cells to impart lateral strength to the carton and to prevent twisting thereof when loaded with eggs.
The carton latching flap is adapted to coact with the cover for retention of the carton in a releaseably locked position.
II. Description of the Prior Art
Egg cartons of this general type have been common in the art for many years. An early type is shown by the patent to Cox U.S. Pat. No. 2,517,465 in which a carton latching flap is positioned exteriorly of the carton's top section front wall, tabs being located at opposite ends of the latching flap for insertion into slits located in the cover front wall to lock the carton in a closed position. Cartons of the same general nature but having an inner latching element are shown by Schilling U.S. Pat. No. 2,600,130 in which the latching flap is extended to provide upper cells intended to afford greater protection to the packaged eggs. Schilling provides a friction type latch in which a protrusion in front of the flap engages a matching recess in the cover.
Cox U.S. Pat. No. 2,771,233 discloses an egg carton structure having a bottom cellular section, substantially similar to prior art cellular sections, wherein adjacent eggs in each of the two longitudinally extending rows of cells are separated by concave cell wall portions 19 positioned below the uppermost level of the bottom cellular section. Such an arrangement offers no positive separation between adjacent eggs to effectively guard against egg breakage problems as opposed to applicants'unique egg cell construction.
SUMMARY OF THE INVENTION
The egg carton construction of the present invention comprises a bottom cellular section having hinged along one longitudinal edge thereof an inverted dish-like cover section, and a latching flap hinged to the opposite longitudinal edge of the bottom cellular section. The bottom cellular section comprises a plurality of contoured walls defining egg-receiving cavities arranged in two rows of six each. The walls between the rows of cavities extend upwardly to form projecting tips and at least one partition wall is located between adjacent cavities in a row which are substantially the same height as the projecting tips and which walls extend completely across the rows of cavities in the carton structure. The base portions of the egg receiving cavities are further characterized by having carton stabilizing cell-feet which may be generally positioned to extend outboard of the carton proper. In certain instances, to facilitate carton denesting on automatic denesting equipment, one or more of the cell feet may be located in an inboard position with respect to the carton proper.
The carton structure of the present invention includes a carton locking system which, in addition to providing positive but manually releasable engagement of the carton sections in the closed position of the carton, imparts rigidity to the carton front wall cover and latching flap and also provides proper guidance of the carton sections upon closing to insure proper seating and positive engagement of the carton latching elements.
BRIEF DESCRIPTION OF THE DRAWINGS
Specific embodiments of the egg carton structure of the invention are illustrated in the drawings wherein:
FIGS. 1, 2 and 3 respectively are perspective views of one form of the carton in varying stages of closure;
FIGS. 4 and 5 are sections along the lines 4--4 and 5--5 of FIGS. 2 and 3 respectively illustrating how the carton latching elements engage upon closure.
FIG. 6 is a fragmentary view of a series of carton cover members in nested arrangement;
FIG. 7 is a cross sectional view taken on line 7--7 of FIG. 1 illustrating the cell and cell-foot configuration of the carton;
FIG. 8 is a planar view of the undersurface of the carton bottom cellular section illustrated in FIGS. 1 through 3.
FIG. 9 is a top-planar view of a specific form of egg-retaining cell;
FIG. 10 is a cross-sectional view taken on line 10--10 of FIG. 9 illustrated;
FIG. 11 is a cross-sectional view taken on line 11--11 of FIG. 9;
FIG. 12 is a rear-elevational view of the egg-retaining cell illustrated in FIG. 9 and taken on line 12--12 of FIG. 9;
FIG. 13 is a front-elevational view of a fragmentary section of a carton-bottom cellular portion;
FIG. 14 is a top-planar view of another specific form of egg-retaining cell;
FIG. 15 is a cross-sectional view taken on line 15--15 FIG. 14;
FIG. 16 is a cross-sectional view of a series of carbon-bottom cellular members in nested arrangement.
BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS
As illustrated in the drawings, the carton structure of the present invention comprises a cellular bottom tray portion 11, a cover 12, and a latching flap 13. The tray portion is formed to provide a plurality of cells 14 for reception of eggs. The cover 12 is formed integrally with the tray 11 and connected thereto by a portion of reduced thickness constituting a hinge 16.
Latching flap 13 is formed integrally with the tray 11 and is connected thereto by a line of reduced thickness constituting a resilient hinge 17.
As formed in a mold, the three portions of the carton are in their greatest extended position such that the flange 18 of the cover lies in the same plane as flange 15 of the tray and the latching flap 13 lies extended out to the other side of the carton as formed. This imparts to the hinges 16 and 17 a bias toward extended position even when the carton assumes the completely closed position as illustrated in FIG. 3.
With particular reference to the cover 12, this is constituted by upper surface 19 which, in the embodiment shown is essentially planar except for a recess 20, essentially as shown. Molded integrally with the top surface 19 are side walls 21, back wall 22 and front wall 23. Formed in the front wall are recesses constituted by depressed surfaces 24 and webs 25 of a structure such as to impart to the front wall a high degree of strength and rigidity capable of supporting burdens of cartons stacked one above the other and of maintaining alignment of the front surface for efficient action of the latching mechanism characteristic of this invention. The latch elements of the cover are constituted by detents 26 formed of recessed surfaces and webs similar to those of the guiding elements, but terminating in a free edge 27.
Formed in the latching flap 13 are recesses constituted by recessed surfaces 28 and webs 29 complimentary to the recesses in the cover front wall 23. It will be noted that the cover recesses and the flap recesses are wedge shaped and complimentary in form. This structure assures that these guidance elements shall become engaged after cover section 12 is rotated into closed position, and that as the flanges 15 and 18 approach contact, the complimentary recesses fit snugly together and assure positive latch engagement.
The latching element of latching flap 13 is constituted by a recess similar, but shorter in extent, than those which impart strength and guidance. A recessed surface 30 is connected to the main body of the flap by webs 31. The essentially web shaped recess terminates short of the upper edge of the flap to provide a latching bar 32 above the recess. Upon rotation of the cover to closed position, the detent 26 enters into the recess bounded by webs 31 and detent edge 27 engages the latching bar 32. This manner of closure is more fully illustrated in FIGS. 2, 3, 4 and 5 showing how the rigid face of the cover front wall presses latching flap 13 rearward against its resilient hinge 17 until the latch elements are engaged as illustrated, in FIGS. 3 and 5.
To provide stability of the carton when set on a flat surface, it is preferred that the bottom outward portion of cells 14 be provided with feet 36', details of which appear in FIGS. 7 and 8. As more clearly illustrated in FIG. 8, which is a planar view of the bottom cellular section 11, cell feet 36 extend outboard of the carton with the exception of the cell feet 36' which, in a specific embodiment of the cartons of the present invention as illustrated in FIG. 8, extend inwardly of the carton bottom member 11. This inward extention of cell feet 36' in certain specific embodiments of the carton structure of the present invention, has been found desirable to facilitate carton denesting when such cartons are denested on particular types of automatic denesting equipment. It should be noted, however, that cell feet 36', as contemplated within the scope of the present invention, may all extend in a uniform direction. for example all of the cell feet 36' may extend outwardly, i.e. generally in a transverse direction with respect to the longitudinal extent of cellular bottom section 11.
According to the present invention, the cellular bottom section 11 of the cartons of the present invention is formed with transverse walls 37 which extend across the egg carton, to link the walls of two egg receiving cavities together. Thus, transverse walls 37 are formed to separate all pairs of transversely aligned egg cells 14 from one another. Small upstanding tips 42 comprising the inner longitudinal walls of the cells 14, in addition to providing positive egg separation, permit insertion of fingers to remove individual eggs without breakage. Transverse wall 37, has sloping sides 38 and 39. At the lowermost point of the sloping sides 38, 39 seen from the top, that is where sloping sides 38, 39 intersect with side 40, a ridge 41 (FIG. 8) is formed which interconnects the lower portions of the egg cells 14 to provide additional stiffness to the entire structure and prevent deformation upon twisting stresses which may be applied thereto during normal processing and handling of such cartons. Further, one of the transverse ribs 37 which is located in the central portion of the bottom cellular section 11 is positioned so that when the cover is in closed position, it will abut against the lower edge 20' of central recess 20 located in the planar top section of carton cover member 12. This abuting relationship further serves to reinforce the carton and to resist crushing forces which may be applied to the carton during usage thereof. It will be noted, as illustrated in FIG. 8, a rigidifying effect is imparted to the cellular bottom section of the cartons by virtue of the continuity of the base of flange 15, hereinbefore described, which extends in a non-interrupted fashion completely around the periphery of bottom cellular member 11. It has been shown that such a construction, i.e. flange 15 extending in such an uninterrupted fashion, insures extremely high resistance to applied torsional and flexural forces which may be applied to the carton bottom section of the present invention during normal handling and usage thereof.
As illustrated in FIGS. 1 through 3 and 6, side walls 21 of the carton cover section 12 are provided with an integrally molded rib like projection 21'. Rib member 21' located at the lower edge of side walls 21 of cover section 12, insures that when a plurality of cartons are positioned in nested relationship (see FIG. 6), the carton cover sections do not become so firmly nested together whereby they become wedged, on inside the other, thereby creating difficulties when attempts are made to denest individual cartons from a group of nested cartons. Thus, as shown in FIG. 6, rib member 21' insures that a slight separation to facilitate denesting, is maintained intermediate individual cover members 15 when the cartons are in nested relationship.
Among some of the types of plastic materials which are suitable for fabrication into the carton structures of the present invention are polyolefins such as polyethylene, polypropylene, and polybutene; polystyrene; high impact polystyrene; polyurethane; polyvinylchloride and others. A particular material which has been found to be well suited for fabrication of the present carton structures is foamed polystyrene. The closed cell structure of the foamed polystyrene results in a material which rapidly reaches equilibrium with atmospheric moisture and therefore exerts no drying effect. The foam material itself is extremely light weight permitting ease of handling and transport.
As hereinbefore indicated, a preferred material employed in the formation of the carton structures of the present invention is plastic and in particular, foam thermoplastic materials and especially polystyrene foam. The polystyrene foam may be manufactued utilizing any one of the number of conventional extrusion techniques, for example, extrusion of foamable polystyrene beads, i.e., beads which have a blowing agent already incorporated in them prior to delivery to an extrusion apparatus or, for example, by direct injection extrusion techniques wherein a foaming agent is added to a molten mass of polystyrene contained within an extruder prior to extrusion thereof from a die orifice. See U.S. Pat. No. 3,444,283, Carlson.
After the polystyrene foam sheet material has been produced utilizing conventional extrusion techniques as discussed above, it may be molded to form the carton structures of the present invention. In general, it is desirable to preheat the formed polystyrene sheet before it is molded in order to assure that the sheet will be at a sufficiently elevated temperature to permit rapid forming of the desired structure in the mold.
After preheating the formed polystyrene foam sheet, the cartons of the present invention may be conveniently formed utilizing a molding operation such as matched molding, for example.
The processed employed for forming the cartons may best be understood by a description of a specific embodiment as illustrated in the following example, however, such a description is solely for purposes of illustration and is not to be construed in a limiting sense. For example, the following embodiment sets forth rather specific process and operating conditions employed when preformed polystyrene foam is employed as the starting material for the structure and, of course, such conditions will normally vary when other plastic materials are employed.
EXAMPLE I
A preformed sheet of polystyrene foam material with an average density of about 7 pounds per cubic ft. and approximately 110 mils thick was fed into a radiant preheat oven and heated to a temperature of approximately 225° F. Upon emerging from the preheat oven, the polystyrene sheet was approximately 200 mils thick as a result of the expanding action of the residual blowing agent, in this case pentane, which remains entrapped within the polystyrene cells after it is extruded. The residence time of the polystyrene in the oven was approximately 5 to 2 seconds and the average line speed was about 15 ft. per minute. Immediately upon emergence from the preheat oven, the polystyrene foam sheet passes into a forming mold. The thermoforming mold employed is essentially a temperature controlled female mold maintained at 150° F. and a lower male forming member maintained at a temperature of about 100° F. As the match mold is cycled, the upper and lower mold members are brought together forcing the heated polystyrene foam to assume the configuration of the mold members.
As illustrated in FIGS. 9 through 11 inclusive, a specific embodiment of the egg-retaining cells 51 which may be employed in the cartons of the present invention are characterized by having a relatively flat-bottom surface 52. Cell 51 is further characterized in that, in contrast to the relatively uniform conical cell configuration illustrated in FIGS. 1 through 5 and 7 and 8, it has alternating cell wall segments 53 and 54. Cell wall segment 53 extends upwardly and in an outward direction from the flat cell base 52 and has a flat surface both internally and externally of the cell cavity. Adjacent cell wall segments 53, around the circumference of the egg-receiving cavity, are cell wall segments 54. Cell wall segments 54 are characterized by having a relatively concave inner surface throughout their entire vertical extent. As in the case of flat wall segments 53, concave cell wall segments 54 extend from the relatively flat bottom surface 52 of the cell upwardly and outwardly therefrom. It has been found that, when such a cell configuration is employed in the egg carton structure of the present invention, i.e. a cell characterized by having opposing flat wall portions 53 separated by adjacent, concave cell-wall segments 54, when compressive forces are exerted against the top of an egg positioned in such a cell structure, that the cell, rather than offering a rigid resistance to the thusly compressed egg member, which may result in egg breakage, expands under the compressive forces exerted against the egg to thereby accommodate it. Accordingly, when compressive forces are exerted against a closed carton containing eggs, which carton has the aforedescribed cellular configuration, breakage of the eggs contained in such cartons is substantially reduced.
Another specific embodiment of an egg-retaining cell structure encompassed by the present invention is illustrated in FIGS. 14 and 15. In this embodiment, the configuration of the egg-retaining cell is quite similar to the egg cell configurations as illustrated in FIGS. 1 through 5; 7 and 8. However, as will be noted from FIGS. 14 and 15, the generally frusto-conical configuration of the interior of the egg-receiving cell is non-uniform in that it is interruped by a fluted portion 62. Fluted portion 62, which extends from the cell base 63 to the upper portion of the egg-receiving cell, tapers outwardly as it approaches the top of the egg-receiving cell generally indicated as 64 in FIG. 15. In order to avoid breakage of the individual eggs packaged in cells and to provide for a maximum amount of usable egg cavity space in the cell, the central apex portion 65 of flute 62 extends outwardly from the interior of cell 64. It will be seen that when an egg is position in cell 64, it will be securely held in place by the inner surface 61 of cell member 64 even through interior surface 61 is interruped by fluted member 62. Such arrangement allows for compressive forces to be exerted against the top of a closed carton and the product breakage normally expected is substantially reduced by virtue of the presence of fluted member 62. It will be seen that as the egg is forcibly compressed into cell members 64, fluted member 62 will allow for the outward flexure of cell member 64 as a resultant of the pressures exerted thereon. It has been found that such a specific egg cell configuration greatly reduces the breakage of egg products packaged in such a cellular arrangement when compressive forces, during handling and packaging of filled cartons, are encountered.
It will be noted that in the specific embodiment of the cell structures illustrated, for example in FIGS. 12, 14, and 16 the upper external portion of the egg cell members adjacent hinge member 16, are provided with integrally molded, outwardly projecting nub members 66. As illustrated in FIG. 16, nubs 66 facilitate removal of individual cartons from a nested stack of cartons by preventing the carton bottom cellular sections from prematurely denesting when individual cartons are denested utilizing automatic denesting equipment.
Although the present invention has been described with preferred embodiments, it is to be understood that modifications and variations may be resorted to, without departing from the spirit and scope of this invention, as those skilled in that art will readily understand. Such variations and modifications are considered to be within the purview and scope of the appended claims.
I. FIELD OF THE INVENTION
This invention relates to the structure of disposable egg-cartons which may be fabricated from materials such as molded pulp, paste board, and plastic, including expanded or formed plastics such as polystyrene foam for example. The carton is particularly characterized by having a bottom cellular section, a locking flap hinged to one longitudinal edge of the bottom section and an inverted dish-like cover section hinged along the opposite edge of the bottom section. The bottom portion of the cells in the carton cellular section are provided with individual cell feet to impart carton stability when the carton is positioned on a flat surface. The carton's cellular bottom section includes transversely extending walls intermediate pairs of egg cells to impart lateral strength to the carton and to prevent twisting thereof when loaded with eggs.
The carton latching flap is adapted to coact with the cover for retention of the carton in a releaseably locked position.
II. Description of the Prior Art
Egg cartons of this general type have been common in the art for many years. An early type is shown by the patent to Cox U.S. Pat. No. 2,517,465 in which a carton latching flap is positioned exteriorly of the carton's top section front wall, tabs being located at opposite ends of the latching flap for insertion into slits located in the cover front wall to lock the carton in a closed position. Cartons of the same general nature but having an inner latching element are shown by Schilling U.S. Pat. No. 2,600,130 in which the latching flap is extended to provide upper cells intended to afford greater protection to the packaged eggs. Schilling provides a friction type latch in which a protrusion in front of the flap engages a matching recess in the cover.
Cox U.S. Pat. No. 2,771,233 discloses an egg carton structure having a bottom cellular section, substantially similar to prior art cellular sections, wherein adjacent eggs in each of the two longitudinally extending rows of cells are separated by concave cell wall portions 19 positioned below the uppermost level of the bottom cellular section. Such an arrangement offers no positive separation between adjacent eggs to effectively guard against egg breakage problems as opposed to applicants'unique egg cell construction.
SUMMARY OF THE INVENTION
The egg carton construction of the present invention comprises a bottom cellular section having hinged along one longitudinal edge thereof an inverted dish-like cover section, and a latching flap hinged to the opposite longitudinal edge of the bottom cellular section. The bottom cellular section comprises a plurality of contoured walls defining egg-receiving cavities arranged in two rows of six each. The walls between the rows of cavities extend upwardly to form projecting tips and at least one partition wall is located between adjacent cavities in a row which are substantially the same height as the projecting tips and which walls extend completely across the rows of cavities in the carton structure. The base portions of the egg receiving cavities are further characterized by having carton stabilizing cell-feet which may be generally positioned to extend outboard of the carton proper. In certain instances, to facilitate carton denesting on automatic denesting equipment, one or more of the cell feet may be located in an inboard position with respect to the carton proper.
The carton structure of the present invention includes a carton locking system which, in addition to providing positive but manually releasable engagement of the carton sections in the closed position of the carton, imparts rigidity to the carton front wall cover and latching flap and also provides proper guidance of the carton sections upon closing to insure proper seating and positive engagement of the carton latching elements.
BRIEF DESCRIPTION OF THE DRAWINGS
Specific embodiments of the egg carton structure of the invention are illustrated in the drawings wherein:
FIGS. 1, 2 and 3 respectively are perspective views of one form of the carton in varying stages of closure;
FIGS. 4 and 5 are sections along the lines 4--4 and 5--5 of FIGS. 2 and 3 respectively illustrating how the carton latching elements engage upon closure.
FIG. 6 is a fragmentary view of a series of carton cover members in nested arrangement;
FIG. 7 is a cross sectional view taken on line 7--7 of FIG. 1 illustrating the cell and cell-foot configuration of the carton;
FIG. 8 is a planar view of the undersurface of the carton bottom cellular section illustrated in FIGS. 1 through 3.
FIG. 9 is a top-planar view of a specific form of egg-retaining cell;
FIG. 10 is a cross-sectional view taken on line 10--10 of FIG. 9 illustrated;
FIG. 11 is a cross-sectional view taken on line 11--11 of FIG. 9;
FIG. 12 is a rear-elevational view of the egg-retaining cell illustrated in FIG. 9 and taken on line 12--12 of FIG. 9;
FIG. 13 is a front-elevational view of a fragmentary section of a carton-bottom cellular portion;
FIG. 14 is a top-planar view of another specific form of egg-retaining cell;
FIG. 15 is a cross-sectional view taken on line 15--15 FIG. 14;
FIG. 16 is a cross-sectional view of a series of carbon-bottom cellular members in nested arrangement.
BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS
As illustrated in the drawings, the carton structure of the present invention comprises a cellular bottom tray portion 11, a cover 12, and a latching flap 13. The tray portion is formed to provide a plurality of cells 14 for reception of eggs. The cover 12 is formed integrally with the tray 11 and connected thereto by a portion of reduced thickness constituting a hinge 16.
Latching flap 13 is formed integrally with the tray 11 and is connected thereto by a line of reduced thickness constituting a resilient hinge 17.
As formed in a mold, the three portions of the carton are in their greatest extended position such that the flange 18 of the cover lies in the same plane as flange 15 of the tray and the latching flap 13 lies extended out to the other side of the carton as formed. This imparts to the hinges 16 and 17 a bias toward extended position even when the carton assumes the completely closed position as illustrated in FIG. 3.
With particular reference to the cover 12, this is constituted by upper surface 19 which, in the embodiment shown is essentially planar except for a recess 20, essentially as shown. Molded integrally with the top surface 19 are side walls 21, back wall 22 and front wall 23. Formed in the front wall are recesses constituted by depressed surfaces 24 and webs 25 of a structure such as to impart to the front wall a high degree of strength and rigidity capable of supporting burdens of cartons stacked one above the other and of maintaining alignment of the front surface for efficient action of the latching mechanism characteristic of this invention. The latch elements of the cover are constituted by detents 26 formed of recessed surfaces and webs similar to those of the guiding elements, but terminating in a free edge 27.
Formed in the latching flap 13 are recesses constituted by recessed surfaces 28 and webs 29 complimentary to the recesses in the cover front wall 23. It will be noted that the cover recesses and the flap recesses are wedge shaped and complimentary in form. This structure assures that these guidance elements shall become engaged after cover section 12 is rotated into closed position, and that as the flanges 15 and 18 approach contact, the complimentary recesses fit snugly together and assure positive latch engagement.
The latching element of latching flap 13 is constituted by a recess similar, but shorter in extent, than those which impart strength and guidance. A recessed surface 30 is connected to the main body of the flap by webs 31. The essentially web shaped recess terminates short of the upper edge of the flap to provide a latching bar 32 above the recess. Upon rotation of the cover to closed position, the detent 26 enters into the recess bounded by webs 31 and detent edge 27 engages the latching bar 32. This manner of closure is more fully illustrated in FIGS. 2, 3, 4 and 5 showing how the rigid face of the cover front wall presses latching flap 13 rearward against its resilient hinge 17 until the latch elements are engaged as illustrated, in FIGS. 3 and 5.
To provide stability of the carton when set on a flat surface, it is preferred that the bottom outward portion of cells 14 be provided with feet 36', details of which appear in FIGS. 7 and 8. As more clearly illustrated in FIG. 8, which is a planar view of the bottom cellular section 11, cell feet 36 extend outboard of the carton with the exception of the cell feet 36' which, in a specific embodiment of the cartons of the present invention as illustrated in FIG. 8, extend inwardly of the carton bottom member 11. This inward extention of cell feet 36' in certain specific embodiments of the carton structure of the present invention, has been found desirable to facilitate carton denesting when such cartons are denested on particular types of automatic denesting equipment. It should be noted, however, that cell feet 36', as contemplated within the scope of the present invention, may all extend in a uniform direction. for example all of the cell feet 36' may extend outwardly, i.e. generally in a transverse direction with respect to the longitudinal extent of cellular bottom section 11.
According to the present invention, the cellular bottom section 11 of the cartons of the present invention is formed with transverse walls 37 which extend across the egg carton, to link the walls of two egg receiving cavities together. Thus, transverse walls 37 are formed to separate all pairs of transversely aligned egg cells 14 from one another. Small upstanding tips 42 comprising the inner longitudinal walls of the cells 14, in addition to providing positive egg separation, permit insertion of fingers to remove individual eggs without breakage. Transverse wall 37, has sloping sides 38 and 39. At the lowermost point of the sloping sides 38, 39 seen from the top, that is where sloping sides 38, 39 intersect with side 40, a ridge 41 (FIG. 8) is formed which interconnects the lower portions of the egg cells 14 to provide additional stiffness to the entire structure and prevent deformation upon twisting stresses which may be applied thereto during normal processing and handling of such cartons. Further, one of the transverse ribs 37 which is located in the central portion of the bottom cellular section 11 is positioned so that when the cover is in closed position, it will abut against the lower edge 20' of central recess 20 located in the planar top section of carton cover member 12. This abuting relationship further serves to reinforce the carton and to resist crushing forces which may be applied to the carton during usage thereof. It will be noted, as illustrated in FIG. 8, a rigidifying effect is imparted to the cellular bottom section of the cartons by virtue of the continuity of the base of flange 15, hereinbefore described, which extends in a non-interrupted fashion completely around the periphery of bottom cellular member 11. It has been shown that such a construction, i.e. flange 15 extending in such an uninterrupted fashion, insures extremely high resistance to applied torsional and flexural forces which may be applied to the carton bottom section of the present invention during normal handling and usage thereof.
As illustrated in FIGS. 1 through 3 and 6, side walls 21 of the carton cover section 12 are provided with an integrally molded rib like projection 21'. Rib member 21' located at the lower edge of side walls 21 of cover section 12, insures that when a plurality of cartons are positioned in nested relationship (see FIG. 6), the carton cover sections do not become so firmly nested together whereby they become wedged, on inside the other, thereby creating difficulties when attempts are made to denest individual cartons from a group of nested cartons. Thus, as shown in FIG. 6, rib member 21' insures that a slight separation to facilitate denesting, is maintained intermediate individual cover members 15 when the cartons are in nested relationship.
Among some of the types of plastic materials which are suitable for fabrication into the carton structures of the present invention are polyolefins such as polyethylene, polypropylene, and polybutene; polystyrene; high impact polystyrene; polyurethane; polyvinylchloride and others. A particular material which has been found to be well suited for fabrication of the present carton structures is foamed polystyrene. The closed cell structure of the foamed polystyrene results in a material which rapidly reaches equilibrium with atmospheric moisture and therefore exerts no drying effect. The foam material itself is extremely light weight permitting ease of handling and transport.
As hereinbefore indicated, a preferred material employed in the formation of the carton structures of the present invention is plastic and in particular, foam thermoplastic materials and especially polystyrene foam. The polystyrene foam may be manufactued utilizing any one of the number of conventional extrusion techniques, for example, extrusion of foamable polystyrene beads, i.e., beads which have a blowing agent already incorporated in them prior to delivery to an extrusion apparatus or, for example, by direct injection extrusion techniques wherein a foaming agent is added to a molten mass of polystyrene contained within an extruder prior to extrusion thereof from a die orifice. See U.S. Pat. No. 3,444,283, Carlson.
After the polystyrene foam sheet material has been produced utilizing conventional extrusion techniques as discussed above, it may be molded to form the carton structures of the present invention. In general, it is desirable to preheat the formed polystyrene sheet before it is molded in order to assure that the sheet will be at a sufficiently elevated temperature to permit rapid forming of the desired structure in the mold.
After preheating the formed polystyrene foam sheet, the cartons of the present invention may be conveniently formed utilizing a molding operation such as matched molding, for example.
The processed employed for forming the cartons may best be understood by a description of a specific embodiment as illustrated in the following example, however, such a description is solely for purposes of illustration and is not to be construed in a limiting sense. For example, the following embodiment sets forth rather specific process and operating conditions employed when preformed polystyrene foam is employed as the starting material for the structure and, of course, such conditions will normally vary when other plastic materials are employed.
EXAMPLE I
A preformed sheet of polystyrene foam material with an average density of about 7 pounds per cubic ft. and approximately 110 mils thick was fed into a radiant preheat oven and heated to a temperature of approximately 225° F. Upon emerging from the preheat oven, the polystyrene sheet was approximately 200 mils thick as a result of the expanding action of the residual blowing agent, in this case pentane, which remains entrapped within the polystyrene cells after it is extruded. The residence time of the polystyrene in the oven was approximately 5 to 2 seconds and the average line speed was about 15 ft. per minute. Immediately upon emergence from the preheat oven, the polystyrene foam sheet passes into a forming mold. The thermoforming mold employed is essentially a temperature controlled female mold maintained at 150° F. and a lower male forming member maintained at a temperature of about 100° F. As the match mold is cycled, the upper and lower mold members are brought together forcing the heated polystyrene foam to assume the configuration of the mold members.
As illustrated in FIGS. 9 through 11 inclusive, a specific embodiment of the egg-retaining cells 51 which may be employed in the cartons of the present invention are characterized by having a relatively flat-bottom surface 52. Cell 51 is further characterized in that, in contrast to the relatively uniform conical cell configuration illustrated in FIGS. 1 through 5 and 7 and 8, it has alternating cell wall segments 53 and 54. Cell wall segment 53 extends upwardly and in an outward direction from the flat cell base 52 and has a flat surface both internally and externally of the cell cavity. Adjacent cell wall segments 53, around the circumference of the egg-receiving cavity, are cell wall segments 54. Cell wall segments 54 are characterized by having a relatively concave inner surface throughout their entire vertical extent. As in the case of flat wall segments 53, concave cell wall segments 54 extend from the relatively flat bottom surface 52 of the cell upwardly and outwardly therefrom. It has been found that, when such a cell configuration is employed in the egg carton structure of the present invention, i.e. a cell characterized by having opposing flat wall portions 53 separated by adjacent, concave cell-wall segments 54, when compressive forces are exerted against the top of an egg positioned in such a cell structure, that the cell, rather than offering a rigid resistance to the thusly compressed egg member, which may result in egg breakage, expands under the compressive forces exerted against the egg to thereby accommodate it. Accordingly, when compressive forces are exerted against a closed carton containing eggs, which carton has the aforedescribed cellular configuration, breakage of the eggs contained in such cartons is substantially reduced.
Another specific embodiment of an egg-retaining cell structure encompassed by the present invention is illustrated in FIGS. 14 and 15. In this embodiment, the configuration of the egg-retaining cell is quite similar to the egg cell configurations as illustrated in FIGS. 1 through 5; 7 and 8. However, as will be noted from FIGS. 14 and 15, the generally frusto-conical configuration of the interior of the egg-receiving cell is non-uniform in that it is interruped by a fluted portion 62. Fluted portion 62, which extends from the cell base 63 to the upper portion of the egg-receiving cell, tapers outwardly as it approaches the top of the egg-receiving cell generally indicated as 64 in FIG. 15. In order to avoid breakage of the individual eggs packaged in cells and to provide for a maximum amount of usable egg cavity space in the cell, the central apex portion 65 of flute 62 extends outwardly from the interior of cell 64. It will be seen that when an egg is position in cell 64, it will be securely held in place by the inner surface 61 of cell member 64 even through interior surface 61 is interruped by fluted member 62. Such arrangement allows for compressive forces to be exerted against the top of a closed carton and the product breakage normally expected is substantially reduced by virtue of the presence of fluted member 62. It will be seen that as the egg is forcibly compressed into cell members 64, fluted member 62 will allow for the outward flexure of cell member 64 as a resultant of the pressures exerted thereon. It has been found that such a specific egg cell configuration greatly reduces the breakage of egg products packaged in such a cellular arrangement when compressive forces, during handling and packaging of filled cartons, are encountered.
It will be noted that in the specific embodiment of the cell structures illustrated, for example in FIGS. 12, 14, and 16 the upper external portion of the egg cell members adjacent hinge member 16, are provided with integrally molded, outwardly projecting nub members 66. As illustrated in FIG. 16, nubs 66 facilitate removal of individual cartons from a nested stack of cartons by preventing the carton bottom cellular sections from prematurely denesting when individual cartons are denested utilizing automatic denesting equipment.
Although the present invention has been described with preferred embodiments, it is to be understood that modifications and variations may be resorted to, without departing from the spirit and scope of this invention, as those skilled in that art will readily understand. Such variations and modifications are considered to be within the purview and scope of the appended claims.