Nestable and Denestable Molded Egg Cartons

This invention relates to cartons and, more particularly, to cartons having a plurality of sections hingedly connected to each other. Such cartons may have a dished bottom section and an inverted dished cover section. More particularly, this invention relates to molded cartons and to molded egg cartons. The example of carton illustrated in the drawing is an open, nestable molded pulp egg carton having a flap hingedly connected to the cellular section and provided with molded buttons for cooperation with openings in a wall of the cover section. More specifically, this invention relates to the denestable structural formation incorporated in molded egg cartons.

Prior to the instant invention, molded egg cartons have been produced from molds so that the rim of the inverted dished cover and the rim of the cellular section and the hinged flap are generally in the same plane. An example of such a prior carton is illustrated in the U.S. Pat. No. to Reifers and Lord, 3,185,370. Such prior cartons are adapted for use in automated egg packing systems.

When cartons of this general character are produced, they are nested in stacks which are packaged for shipment to egg packers, who have the task of denesting each carton so that each carton may be presented to an egg loader and then to a carton closer, and finally, the loaded, closed egg cartons are then packed into egg cases for shipment to the supermarket.

Prior egg cartons in stacks have been separated from each other by denesting ledges located at or around the corners of the cover section and the corners of the cellular sections. Such stacks of egg cartons have been presented to denesting apparatus and have been separated automatically for replacement on conveyors to receive eggs from automated egg loaders. In such prior systems using such prior egg cartons, a certain amount of downtime has been experienced due to the difficulty in separating the end egg carton from the stack because of what has been characterized as "telescoping". This objectionable "telescoping" occurs when the cover section of one carton, or the cellular section of one carton, overrides or partially overrides the denesting ledge of the corresponding portion of the adjacent carton in the stack.

This "telescoping" may occur at the time of nesting of the cartons when the stack is produced, or it may occur in the packaged stack during the course of shipment to the egg packer, as some settling occurs in the stack during shipment by rail or truck, and a single stack of egg cartons in a single package may have one or more incidences of "telescoping".

With the advent of higher and higher speeds of molded egg carton production, and correspondingly, higher speeds of nesting or stacking, the chance for the incidence of "telescoping" to occur is markedly increased. This incidence of "telescoping" occuring at the time of stacking takes place when the molded carton is presented to the stack in somewhat imprecise relationship, or with a departure from absolute parallelism so that a carton then may "telescope" when pressure is applied to the stack in the course of the packaging of the stack. It is known that the height of a stack may decrease during the course of shipment to the egg packer and when this decrease in height occurs coincidently with the presence of a slightly cocked egg carton, then "telescoping" may occur.

When "telescoping" occurs and appears in the stack in the plant of the egg packer, and the egg packer loads a stack with one or more incidences of "telescoping" into his denesting apparatus, a jam will occur during the operation of the automatic equipment resulting in shutdown of the denesting machine, the empty carton take-away conveyor from the denesting machine, the automatic egg loader which serves to load the empty egg cartons, the automatic closer which closes the egg cartons, and the automatic egg case packer which packs the egg cases with closed and loaded egg cartons. Such shutdowns are costly and time consuming.

It is an object of the invention to produce a nestable and denestable egg carton which will be fail-safe or relatively fail-safe with respect to the incidence of "telescoping".

It is another object of the instant invention to provide a strong denesting ledge formation integral with the egg carton.

It is still another object of the instant invention to provide a denesting ledge structure which will not interfere with the operation of the denesting machine.

It is still another object of the invention to provide a denesting ledge formation involving a multi-lobe structure at and adjacent to the outside corners of the egg carton cover and the outside corners of the cellular section.

It is still another object of the instant invention to provide a denesting ledge formation including a relatively thick-walled lobe substantially entirely in the ends of the carton adjacent a lobe in the outside corners of the carton such that on the inner surface of the carton there is a generally vertical, substantially continuous wall surface between the lobes capable of directly transmitting vertical forces or directly supporting vertical loads.

It is still another object of the instant invention to provide a multi-lobe outside corner wherein a lobe in the end wall of a section is of a relatively narrow width as compared to the width of the adjacent lobe extending around an outside corner of the carton.

Other objects and the nature and advantages of the invention will be better understood by reference to the accompanying drawings.

FIG. 1 is a plan view of an outside of an egg carton as it comes from the molding machine showing the denesting ledge formation at the two outside corners of the cover section and the two outside corners of the cellular section;

FIG. 2 is a view in side elevation of a partial stack of nested egg cartons of the type illustrated in FIG. 1;

FIG. 3 is a view in end elevation of a stack of egg cartons illustrated in FIG. 2;

FIG. 4 is a fragmentary view in perspective showing a partial stack of nested egg cartons having denesting ledges and in relation to the outside corner of the cellular section and the adjacent egg carton flaps;

FIG. 5 is fragmentary view in perspective looking somewhat downwardly into the end of an egg cell section and the end of a cover section and illustrating the inner surface adjacent the denesting ledge formations;

FIG. 6 is fragmentary view in perspective looking down from above and slightly to one side showing a stack of nested cartons being formed with the last carton presented to the nest in somewhat cocked fashion;

FIG. 7 is a view similar to FIG. 6 but looking directly down on the ends of the stack of cartons being formed showing the cover section of the last carton presented to the nest in cocked fashion while the hingedly connected cellular section of the last carton is in generally parallel relation to the already stacked cartons; and

FIG. 8 is an enlarged fragmentary vertical section taken through a stack of cartons of the type illustrated in FIG. 1 along line VIII--VIII and looking in the direction of the arrows.

Referring to the drawings, the molded egg carton 10, as illustrated in FIG. 1 in bottom plan view, shows the cover section 11 connected to the cellular section 12 by the hinge line 20. The cellular section 12 is connected to the flap section 13 by the hinge line 21. The flap section 13 is provided with locking buttons 22 for cooperation with the locking holes 23 in the long front side wall of the inverted dished cover 11. The cellular section 12 is provided with egg cells 24.

The generally triangular plane section 25 is located between two cells 24 at each end 12e of the cellular section 12, as illustrated in FIGS. 1 and 5.

The cellular section 12 has two relatively long tapered sides 12s and two relatively short tapered ends 12e so as to form outside rounded corners 30 and inside rounded corners 33. The cover section 11 has two relatively long tapered sides 11s and two relatively short tapered ends 11e so as to form outside corners 32 and inside corners 31.

At the two outside rounded corners 30 and the two outside rounded corners 32, there is provided a multi-lobe denesting formation structure comprising relatively thick-walled and relatively narrow lobes 41 and relatively wide lobes 40. Each lobe 41 is provided with a ledge surface 43 and each lobe 40 is provided with a ledge surface 42. Referring to FIG. 8, the outer surface 46 of the wall of each of the lobes 41 adjacent the ledge surface 43 includes a surface 46a having a reverse taper as compared to the taper of the section ends 11e and 12e and a relatively short surface 46b having substantially no taper located between the surface 46a of reverse taper and the ledge surface 43.

The lobes 40 and 41 project outwardly from the carton and are hollow. Referring to FIG. 8, the wall thickness 41w of the lobe 41 is relatively great as compared with the thickness 10w of the main walls of the carton and as compared to the thickness of the rim which extends about the cover section and the rim which extends about the cellular section. As will be observed in FIG. 5, there is continuity of the vertical surface on the inside of the carton at 44 between the hollow lobe 40 and the hollow lobe 41.

The space extending inwardly from the lobes 41, designated by the reference numeral 45, at each end 11e of the cover section 11 and at each end 12e of the cellular section 12 is reserved for use by the element of a denesting machine so that there will be no interference between the denesting ledges and the operation of the denesting machine.

FIG. 2 illustrates a partial stack of egg cartons in their nesting position as they are received from the egg carton production line.

FIG. 3 illustrates a partial stack of egg cartons in the position that they are loaded in the denesting machine.

FIG. 4 is a fragmentary view in perspective illustrating a partial stack similar to the partial stack illustrated in FIG. 3, but turned at an angle so that the connection between the flap sections and the cellular sections are shown from a different angle. The fragmentary perspective view in FIG. 5 shows the inner surface of the portion of the egg carton 10 and the reverse hollow sides of the narrow lobe 41 and wide lobe 40 with the vertical surface 44 therebetween.

When the molded egg cartons are produced, they appear as illustrated in FIG. 1 with the peripheral rim R of the cover section 11, the peripheral rim R of the cellular section 12 and the outwardly extending flange section 13 generally in the same plane.

Automatic equipment running at very high speed nests the cartons as illustrated in FIG. 2. Due to the nature of the materials, the tolerances of the equipment, and the high operating speeds, the theoretical precise parallelism in the nesting step is not achieved for each and every one of the cartons nested. A small percentage of instances may occur in which nesting takes place with a slight departure from precise parallelism, as illustrated in FIG. 7. With prior constructions, such departure results in a tendency to "telescope" with the rim R of one carton tending to override the denesting ledge of a previously nested carton, as in FIG. 7. However, in accordance with the instant invention, when a next succeeding carton is applied to the nest, the pressure of this application will adjust the previous carton which may be slightly askew so that when the nest is completed, substantial parallelism is effected and the nest is substantially fail-safe and down-time due to telescoping is avoided. This adjustment takes place with pressure of the next succeeding carton application acting to partially rotate the somewhat askew carton to parallelism about the point of contact 41c of the narrow lobe 41, ledge 43 with the rim R of the already nested carton, the point of contact 41c acting as a pivot for this purpose.

Additional factors which provide the pressure to effect parallelism include compacting pressure which is applied to a freshly prepared stack during the carton packing operation and the settling which occurs during shipment of the packaged egg cartons to the egg packer.

Not only do relatively thick-walled and narrow lobes 41 serve to prevent telescoping or overriding of the wide lobes 40, but the lobes 41 also serve to make the wide lobes 40 finally effective when parallelism is achieved, as explained above, so that lobes 40 may carry their share of static load with the utilization of their relatively large bearing area on their ledge surfaces 42, while the lobes 41 carry their share of the static load on their relatively small bearing area on their ledge surfaces 43.

In accordance with the instant invention, the narrow lobes 41 in the ends 11e and 12e function to pivot an irregularly stacked carton to final perfect nesting interval and at the same time make effective the wide lobes 40, located at the corners of the carton, which would have otherwise been rendered ineffective.

Attempts to achieve the elimination of "telescoping" by widening the wide lobe 40 increase the line of connection between the ledge surface 42 and the egg carton. The longer the line of connection, the greater the chance for structural failure along the line. It will be observed that the line of connection between the lobe surface 43 of the thick-walled lobe 41 and the egg carton is very short and the vertical surface 44 between the lobes 40 and 41 provides for the transmission of stresses in a generally vertical direction. Accordingly, the invention accomplishes the substantial elimination of telescoping without increasing the chance of structural failure by widening the wide lobe 40.

It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification.