US 3203611 A
Description (OCR text may contain errors)
Aug. 31, 1965 T. F. ANDERSON ETAL 3,203,611
INSULATED NESTABLE CONTAINER AND METHOD OF MAKING THE SAME Filed July 10, 1962 3 Sheets-Sheet l INVENTORS THOMAS F. Auouzgou I DMQD C. TQ lMbLE DONALD 21.5mm; Eowm B. HOFFMAN ATTORNEYS Aug. 31, 1965 T. F. ANDERSON ETAL 3,203,611
INSULATED NESTABLE CONTAINER AND METHOD OF MAKING THE SAME Filed July 10, 1962 3 Sheets-Sheet 2 Fig. 8
72 5a so INVENTORS THOMAS F Ammww 5 m m 5m m NF 0 E m .B C DM D AME D DONALDHSTOQEY BY 5 Aug. 31, 1965 T. F. ANDERSON ETAL INSULATED NESTABLE CONTAINER AND METHOD OF MAKING THE SAME 3 Sheets-Sheet 3 Filed July 10, 1962 INVENTORS I00 THoMA5 FT ANQEQWN DAVID C- TQIMEBLE, m B. HOFFMAN ATTORNEYS DONALD HSTOREY i Euw BY ted States Patent 3,245,611 INSULATED NESTABLE KCGNTAINER AND METHOD OF MAKING THE SAW Thomas F. Andersen, Wilmington, David (I. Trimble,
Yorklyn, and Donald H. Storey and Edwin B. Hotfman,
Wilmington, DeL, assignors to Haveg Industries, lino,
a wholly-owned subsidiary of Hercules Powder Company, New Castle, Del, a corporation of Delaware Filed July 10, 1962, Ser. No. 208,866 4 Claims. (Cl. 229-) This invention relates to plastic containers and more particularly to thin-walled plastic containers such as drinking cups and the like and an improved method for making the same.
There are currently available a great variety of plastic containers for a great variety of ditferent uses. A large portion of these containers are made by a simple injection molding procedure wherein the plastic material is simply fed between cooperating male and female molds and after either curing or hardening the molded container is removed from the molds. Contamers made in this Way can be used to good advantage where reusage is contemplated and high cost is not a significant factor. In those applications where the containers are to be used only once and then thrown away cost is an important factor, as for example, containers utilized in vending machines and in the carry out restaurant business. It has been found advantageous mainly from a cost point of view, to form such containers from a plastic sheet or film by drawing the sheet or film into suitable molds. This latter procedure is more economical, primarily for the reason that it is possible to form .a container utilizing a minimum amount of plastic material. Assuming that mass production techniques can be utilized, a major fac tor in determining the economy of production is the amount of plastic material which is required to form the container. Where injection molding procedures are utilized, the wall thickness of the container cannot be held to the same minimum requirements as is the case where a drawing procedure is employed. That is, it has not been found to be commercially feasible to form the Wall of a container by injecting a plastic material between cooperating male and female dies without providing a relative.y thick minimum wall thickness. When utilizing a drawing procedure the Wall thickness can be considerably less than when an injection molding procedure is employed, due to the fact that .it is not necessary to form the wall between the cooperating die surfaces.
For the reasons indicated above, drawn plastic containers have received widespread acceptance in vending machine operation as well as carry out type operations. T he containers used in vending machines present probably the most severe requirements, particularly where the machines are dispensing hot beverages. In this application, a thin walled container is not only desirable from the standpoint of cost, but from the standpoint of being able to store a maximum number of containers Within a given space.
It will be appreciated that an important consideration in determining stacking tolerances is the thickness of the walls of the container. Another factor in this regard is the angle of taper of the frusto-conical side wall of the container. This angle of taper in a liquid container is limited to the inherent physical requirements of the container. That is, the taper cannot be too great or else the bottom surface will be too small to stably support the container with liquid therein. Thus, within the requirements necessary for the taper of the wall, the stacking height can be minimized by providing a minimum wall thickness. However, where very hot drinks are involved, a very thin wall provides the disadvantage of too ice great a heat transfer, thus rendering the container uncomfortable to handle.
There have been several attempts to alleviate this problem. For example, the container Walls have been provided with various configurations which provide a minimum heat transfer to the user. An example of a cup of this type is disclosed in James R. Caine application Serial No. 711,739, filed January 28, 1958, now Patent No. 3,045,887.
Of course, the heat transfer problem can be overcome by sufliciently increasing the Wall thickness but this does not constitute the complete solution, because of the fact that increased wall thickness results in an increased stacking height and therefore a considerably lesser number of cups can be stored in the vending machine. For example, there are currently available on the market several containers which are formed entirely of a foamed plastic such as foamed polystyrene. In general, these containers are formed in cooperating male and female dies by procedures similar to compression molding and have a substantial thickness throughout. Indeed, the increased stacking height provided by such cups is such that they have not been adopted for vending machine use. Moreover, the softness of the foam material presents ditlic-ulties in mechanical handling.
Qther proposals have been made to provide a container which would be satisfactory under the demanding conditions indicated above, for example, various containers formed primarily of paper are currently available. While these containers may provide slightly better heat transfer properties than thin walled plastic containers and are of such wall thickness as to present a favorable stacking height, nevertheless they present the disadvantage that many consumers object to the paper taste, particularly when drinking hot coffee or other hot drinks. There have been many efforts to overcome this disadvantage, but to date they have not been entirely satisfactory. For example, it has been proposed to provide a plastic coating over such paper containers and to laminate certain plastics on the paper. This type of approach has not been entirely acceptable, and of course, adds to the costs involved.
An object of the present invention is the provision of a thin-walled plastic container which will meet the demanding requirements for hot beverage vending machines by providing a Wall sturcture having a minimum thickness so as to thereby minimize the stacking height, which wall construction will provide adequate heat transfer properties to enable the user to handle the container filled with a hot beverage with very little or no discomfort.
Another object of the present invention is the provision of a container of the type described provided with a gripping portion including a foamed plastic capable of expanding to increase the insulation porperties of the container in response to increases in the temperature of the material contained therein.
Another object of the present invention is the provision of a container of the type described having improved structure embodied therein for enabling a series of such containers to be nested in stacked relation in a minimum height so that they may be freely removed from such stack without adjacent containers sticking together.
Another object of the present invention is the provision of a novel method of producing the containers of the type described which includes the steps of depositing a pre formed blank of foamed plastic in a die and drawing a plastic sheet or film into the die so as to adhere to the pre-formed blank and conform to the configuration of the die.
Still another object of the present invention is the provision of a novel procedure for forming a pro-formed blank of foamed plastic in a tubular shape.
These and other objects of the present invention will become more apparent during the course of the foilowing detailed description and appended claims.
The invention may best be understood with reference to the accompanying drawings wherein an illustrative embodiment is shown.
In the drawings:
FIGURE 1 is a perspective view of a container em bodying the principles of the present invention;
FIGURE 2 is an enlargerd top plan View of the container;
FIGURE 3 is a vertical sectional View showing two containers in stacked relation;
FIGURE 4 is an enlarged fragmentary cross-sectional view taken along the line 4-4 of FIGURE 3;
FIGURE 5 is a view similar to FIGURE 4 illustrating a modified form of the container;
FIGURE 6 is an elevational view of a modified form of container embodying the principles of the present invention;
FIGURE 7 is an enlarged fragmentary cross-sectional View taken along the line 7-7 of FIGURE 6;
FIGURE 8 is a top plan view of the foamed plastic sheet material illustrating the manner in which the blank pieces are severed therefrom;
FIGURE 9 is an enlarged fragmentary cross-sectional view taken along the line 9-9 of FIGURE 8;
FIGURE 10 is a perspective view illustrating the foamed plastic blank in its opened condition preparatory to insertion within the die cavity;
FIGURE 11 is a view similar to FIGURE 10 illustrating a modified form of the blank;
FIGURE 12 is an enlarged fragmentary view illustrating another embodiment of a foamed sheet material which may be utilized in making the container of the present invention;
FIGURE 13 is a view similar to FIGURE 12 showing still another modified form of the sheet material;
FIGURE 14 is a vertical sectional view of the die cavity of a mold utilized in carrying out the method of the present invention, showing the blank inserted therein;
FIGURE 15 is a view similar to FIGURE 14 illustrating the manner in which the plastic sheet is mounted over the die cavity;
FIGURE 16 is a view similar to FIGURE 15 illustrating the manner in which the plastic sheet is mechanically moved into the die cavity;
FIGURE 17 is a View similar to FIGURE 16 illustrating the manner in which the plastic sheet is drawn into conformity with the blank and the walls of the die cavity; and
FIGURE 18 is a fragmentary view similar to FIGURE 17 illustrating the manner in which the formed container is severed from the sheet while in the die cavity.
Referring now more particularly to the drawings, there is shown in FIGURES 1-4 a container, generally indicated at 10, which embodies the principles of the present invention. The container 10 is made up of a body which includes a bottom 12 and an upwardly and outwardly tapering frusto-conical peripheral wall 14 extending upwardly from the peripheral edge of the bottom and terminating in a radially outwardly extending peripheral rim 16 defining an open top. The peripheral wall 14 is preferably made up of a laminated construction including an inner wall portion 18 which is preferably formed integral with and of the same material as the bottom 12. Secured to the exterior surface of the inner wall portion 18 is an outer wall portion 29 which is of foamed plastic construction. As shown, the outer wall portion 20 has a multiplicity of openings extending therethrough, as indicated at 22.
As best shown in FIGURES 1-3, formed at the bottom 12. is a stacking means, generally indicated at 24, providing vertically spaced upwardly and downwardly facing stacking surface means, the upwardly facing surfaces serving to engageably receive the downwardly facing surfaces of a similar container so as to support the similar container in nested relation therein, as shown in FIGURE 3, wherein the peripheral wall 14 of the nested container is freely fitted within the peripheral wall of the container receiving the same so as to permit substantially free separation of the nested containers. As shown, the bottom 12 is formed to provide the stacking means 24 with a horizontal relatively narrow peripheral rim portion 2a which provides the means for supporting the container on a horizontal supporting surface. Preferably, the rim portion 26 is provided with a radially extending groove 28 therein which provides a vent for the passage of air into and out of the space beneath the bottom when it is resting on a horizontal surface.
While the stacking means 24 described above and shown in the drawings constitutes a preferred embodiment, it will be understood that other stacking means may be employed. For example, a stacking means of the type shown and described in the above-mentioned Caine application could be embodied in the peripheral wall 14 of the container 16 adjacent the bottom 12 in lieu of the stacking means. In this case, the lower edge of the blank would extend to the upper edge of the stacking means.
Extending inwardly and upwardly at a relatively shallow angle from the inner periphery of the rim portion 26 is an annular wall section 36. The upwardly facing surfaces of the stacking means 24 are provided by a pair of horizontally extending spaced, wall sections 32 of segmental arcuate configuration. The arcuate edges of the wall sections 32 are interconnected with the inner edges of the annular wall section 30 by upwardly and inwardly tapering arcuate wall sections 34. The straight edge of each wall section 32 has a wall section 36 which extends downwardly and outwardly therefrom, the end of each wall section 36 being interconnected with the adjacent end of the arcuate wall section 34 by a triangular shaped vertical wall section 38. Finally, the lower edges of the wall sections 36 and 38 are interconnected by a shallow inverted V-shaped wall section 46, the latter providing the downwardly facing stacking surfaces of the stacking means 24.
Referring now more particularly to FIGURE 4, it can be seen that the peripheral rim 16 includes an inner annular rim portion 42 extending generally radially outwardly from the peripheral wall and an outer annular rim portion 44 extending upwardly from the outer edge of the inner rim portion. A modified construction of the annular rim 16 is shown in FIGURE 5 and indicated at 16' wherein there is provided a turned under rim portion 46 so as to provide a rounded mouth-engaging edge to the container.
Referring now more particularly to FIGURES 6 and 7, there is shown therein a modified form of the container, generally indicated at It), embodying the principles of the present invention. The container ill is identical to the container 10 previously described except that the peripheral wall, indicated at 14, includes a foamed plastic outer peripheral wall portion 20' which is pro vided with a series of spaced longitudinally extending grooves embossed therein, as indicated at 48.
The present invention also includes a preferred method of forming the containers described above. In general, the method comprises the step of positioning a preformed frusto-conical blank 5d of foamed plastic sheet material, which forms the outer peripheral wall portion 26 or 29' of the completed container, within a die cavity and then drawing a heated sheet 52 of solid plastic into engagement with the blank so as to conform the sheet and blank to the configuration of the die cavity. In FIGURES 8- 12 there is illustrated one method of forming the preformed blank of foamed plastic material and in FIG- URES l4l8 a preferred method of drawing the plastic sheet into a die cavity is shown. While this latter method is illustrated as being preferred, it will be understood that the container described above may be constructed by other methods.
Referring now more particularly to FIGURES 813, in constructing the preformed frusto-conical blank 50 of foamed plastic material, it is preferable to utilize foamed material in sheet form. The foamed plastic sheet material is first positioned into two superposed plies, as indicated at 54 and 55 in FIGURE 9. With the two plies in superposed position, two pieces 58 and 69 in the form of a segment of a circular band are severed from the plies 54 and 56. One embodiment of a cutting tool for severing the pieces 53 and 6t from the plies 54 and se is illustrated in FIGURES 8 and 9 and generally indicated at 62. The cutting tool 62 includes a suitable frame 64, having a peripheral cutting blade 66 corresponding to the shape of the pieces 58 and 6t extending downwardly therefrom. The two arcuate portions of the blade 66 are provided with relatively sharp cutting edges as indicated at 68, while the two straight portions are provided with relatively blunt or dull cutting edges, as indicated at 79 and shown somewhat exaggerated in FIG- URE 9.
In addition, the cutting tool 62 may be provided with a plurality of pin 72 arranged to cooperate with an apertured plate 73 to pierce the pieces 58 and 6% during the peripheral severing operation so as to provide the openings 22 previously described.
The provision of the relatively blunt or dull cutting edges 70 is of significance in that it has been found that by providing such cutting edges securement of the straight edges of pieces 53 and 60 is obtained during the movement of the cutting tool 62 into cutting engagement with the plies 54 and 56 of the foamed sheet material against the plate 73. The relatively sharp cutting edges 68 along the arcuate portions of the cutting blade 66 sever these portions of the pieces 53 and 6%) from the plies with a scissors or shearing action by cooperation with the plate 73 without any tendency for the edges of the pieces to adhere together. Thus, by severing the pieces from the plies, as indicated above, the straight edges of the pieces are secured together as a result of the fusion occurring when the material is pinched between the blunt edges 70 and the plate 73, so that the two pieces can then be opened to form the frusto-conical blank 59, as indicated in FIGURE 10. In this regard it will be noted that the fusion of the straight edges can occur without the necessity of adding heat to the cutting edges 70 although under some circumstances it may be preferable to heat the blunt cutting edge 70 to obtain a more secure bond or fusion between the adjacent edges of the plies. The blank 50 shown in FIGURE 11 is formed in the same manner as the blank shown in FIGURE 10, except that rather than utilizing the pins 68, the grooves 43 are embossed in the pieces 58' and 60 during the cutting action by suitable embossing elements (not shown) embodied in the cutting tool 62, in lieu of the pins '72..
In one embodiment of the present invention not illustrated, the pin holes are formed simultaneously with the formation of the fused side edges at one station by one tool and then the blank is severed from the plies at a second station by a second tool operable to cut by a shearing action the arcuate edges of the blank.
It will be understood that the pin holes 22 may be formed in the sheet material prior to the cutting action of the arcuate edges, as may the embossing of the grooves 43. Moreover, various designs, insignia, lettering and the like may be embossed in the sheet material prior to, during or after the cutting of the pieces. FIGURES 12 and 13 illustrate two variations of a watfie type embossrnent which may be formed in the sheet material prior to the cutting of the pieces 58 and 60 therefrom. In FIGURE 12 the embossment is in a checkerboard formation wherein every other square of the checkerboard is embossed in an opposite direction from the adjacent square, as indicated at 74 and 76. The embossment as shown in FIGURE 13 is in the form of a series of intertitting, dome-like embossments of generally rounded triangular configuration, as indicated at 78. It will be understood that sheet material embossed as indicated in FIGURE 12 or 13 as well as other types of embossing designs may be utilized to form the plies from which the pieces 58 and 6d are cut to form the preformed frusto-conical blank Sll of foamed plastic material.
Rererring now more particularly to FIGURES 1418 there is shown therein a mold, generally indicated at El which is constructed generally in accordance with the construction of the mold disclosed in Caine application Serial No. 711,739, the disclosure of which is hereby incorporated by reference into this application. The mold 8t) includes a die cavity $2 which conforms in shape to the exterior shaee or" the container ltl. Formed on the mold in surrounding relation to the upper open end of the die cavity 32 is a ring 84 arranged to receive on it upper surface the sheet of plastic 52 which is to be drawn into the die cavity. Cooperating with the mold is a plunger assembly, generally indicated at 86, which includes a centrally apertured disk-like member 88 arranged to engage the upper surface of the plastic sheet when the latter is in supporting relation to the ring 84 so as to maintain the sheet in pressure-tight engagement with the ring. The plunger assembly also includes a separately reciprocable plunger 9t) having a central quenching air inlet passage 92 extending therethrough and a plurality of branch air inlet passages 93 extending radially therefrom adjacent the upper end portion of the plunger. Formed on the upper end of the plunger is an annular flange or shear plate 94 which is provided with a plurality of annularly spaced restricted air outlet passages 96. The lower surface of the shear plate 94 is arranged to engage with a blunt cutting edge 98 formed in the mold in surrounding relation to the portion of the die cavity which forms the rim of the container. As shown, the mold itself is provided with passages nae for communicating a fluid under a negative pressure or vacuum to the portion of the die cavity adjacent the edge 9% and to the portion of the die cavity defining the bot tom of the container to be formed.
As shown in FIGURE 14, the container of the present invention is made by first inserting the preformed blank 5a) of foamed plastic material into the die cavity 82 of the mold St Next, the sheet of plastic material 52, heated as by direct passage from an extruder, is positioned above the ring 8- 1 and the aperture disk member 88 of the plunger assembly is engaged on the upper surface of the sheet so as to provide an air-tight seal between the sheet material 52 and the ring 84, as shown in FIGURE 15. Next, the plunger E is moved vertically relative to the mold so that the plunger enters into the die cavity 82 carrying with it the central portion of the sheet held to the ring. Insofar as the precise action of the plunger on the sheet of plastic is concerned during its downward movement into the die cavity, reference can be had to the detailed description contained in the Caine application. Suffice it to say at this time that the passages Mill in the mold are sealed ofi or otherwise back-pressure controlled so that the air within the die cavity 32 will be compressed during the movement of the plunger therein, thus maintaining the sheet material out of contact with the blank 59 disposed within the die cavity adjacent the walls thereof.
When the plunger reaches approximately of an inch from the full extent of its movement within the die cavity, as shown in FIGURE 16, passages ltlll in the mold are communicated with a vacuum source, so as to draw the sheet of plastic 52 moved into the die cavity by the plunger into contact with walls of the die cavity to engage the pre-forrned blank 56 disposed therein and conform the latter as well as the plastic sheet itself to the configuration of the die cavity, as shown in FIGURE 17.
The above operation is performed generally in accordance with the disclosure of the previously mentioned Caine application. In the normal operation of the structure of the Caine application, passage 92 is operable to permit atmospheric air to enter the space defined between the interior of the sheet conformed with the die cavity and the exterior surface of the plunger during the movements of the sheet into conformity with the wall of the die cavity. For present purposes, it is necessary to maintain the temperature of the blank 53 below a predetermined temperature within the time period during which expansion will occur. Consequently, in forming the container of the present invention, there is provided an air quenching system which serves to maintain the temperature of the blank within the tolerable limits during the formation of the container.
Insofar as the present operation is concerned it has been found that there is no necessity to permit the entrance of atmospheric air through the passage 92 during the vacuum drawing step since any air which is trapped between the sheet and the plunger will become heated and thus readily expand during the drawing step. Immediately following the start of the vacuum drawing operation the plunger will descend to its fully extended position, as shown in FIGURE 18, to first effect a seal between the sheet 52 contacted by the shear plate 94 and then finally to effect a shearing against the shear ring $8. During this procedure air under pressure is delivered through the passage 92 and branch passages 94 (from a suitable source not shown) at a pressure sufficient to cause the heated air between the sheet and the plunger to pass outwardly through the restricted outlet passages 96. The inlet pressure and the size of the orifices in the outlet passages are such that sufiicient evacuation or displacement of the heated air within the space between the sheet and the plunger takes place that the eated air is replaced by the incoming cooler air under pressure thus effecting an immediate reduction or control of the decrease in the temperature of the sheeet and blank conforming to the walls of the die cavity.
The method as described above is preferably carried out with the use of polystyrene, both as the sheet material 52 which is drawn into the die cavity, and as the foamed sheet material utilized to form the pre-formed frusto-conical blank 5%. it is preferable to use the same material for both sheets for the reason that an extremely intimate bond between the two materials is obtained in the process, and any rejects or imperfect containers which are formed during the operation could not be economically salvaged for reuse as basic plastic material or re-circulation to the extruder unless the same material is utilized both as to the plain sheet material and the foamed sheet material. Stated differently, if the two sheet materials are of a different plastic, it would be economically feasible to separate the two after imperfect formation, so as to reclaim separately the two plastics utilized therein.
The present invention is by no means limited to the use of polystyrene. For example, the following are illustrative examples, of various plastic materials which may be utilized, it being understood that while it is preferable to utilize the same plastic material both for the solid sheet material and the foamed sheet material, that different plastic materials may be utilized if desired.
Thus there also can be used as the plastic vinyl type plastics such as poly alpha methyl styrene, polyvinyl toluene, polyvinyl chloride, polyethylene, vinylidene chloride polymer coated on polyethylene, polypropylene, irradiated polyethylene, eg. irradiated to an extent of 2 to 25 megarep, polyurethanes, eg the reaction product of toluene diisocyanate and an ester such as trimethylol propane modified polyethylene adipate having hydroXy end groups or the reaction product of toluene diisocyanate with polypropylene glycol molecular weight 2025, the reaction product of toluene diisocyanatc with tris poly- Cit 3 propylene glycol 2025 phosphite, vinyl chloride vinyl acetate copolymer, polyesters such as polyethylene terephthalate, polyamides of the nylon type, e.g. polymeric hexamethylene adipamide, styrene-acrylonitrile copolymer.
The foamed plastic sheet can be made by foaming any of the plastics set forth above or can be a different foamed material such as foamed natural rubber, foamed synthetic rubber, e.g. foamed butadiene-styrene copolymer.
The presently preferred foamed sheet materials are foamed polystyrene and foamed polyurethanes.
The plastic materials should be selected so that they will not melt or unduly soften at the temperature of hot water. Preferably the plastic chosen should not soften at 100 C.
It will be understood that a container made in accordance with the method described above would have generar utility not only as drinking glasses for liquids, both hot and cold, but as storage containers or packaging containers for any liquid or semi-solid material. The container described above is particularly suited for use in hot drink dispensing or vending machines. The requirements of a container which will successfully function in a vending machine are quite severe and any container which will meet these requirements will perform quite satisfactorily in other one shot uses, as, for example, in carryout restaurants and the like, or for home use. With respect to the requirements of a container for a hot drink vending machine it should be noted first that there is a limited space within the vending machine to store a supply of containers. For this reason the containers must be of the nestable type. Moreover, the containers must be stacked in nested relation so that the lowermost container of the stack will be freely removable from the stack. That is, any tendency for the stacked containers to stick into nested relation would tend to cause the vending machine to malfunction and prevent the container dispensing mechanism from properly depositing a container into proper position to receive the liquid dispensed. The stacking means provided by the present invention amply meets these requirements. First, it will be noted that the wall sections 32 providing the upper stacking surfaces of the container are spaced apart a distance less than the width of the wall section 4-0, which provides the downwardly facing stacking surfaces, an amount greater than twice the wall thickness of the bottom. With the configuration illustrated, these stacking surfaces will be in alignment in only two positions of relative rotation between any two containers. Of course, when the two surfaces are out of alignment there will be full transverse engagement of the surfaces positively preventing wedged engagement of the two containers. Even when the containers are aligned as shown in FIGURE 3, the relative spacing of the surfaces is such that there is positive contact preventing the containers from becoming wedged together. Moreover, it will be noted that the upwardly facing surfaces tend to move together by virtue of the angular disposition of the wall section 36 in response to increase in load on the surfaces. Thus, even in a relatively high stack of containers there is positive prevention even of the lowermost containers from becoming wedged together.
The provision of the stacking means in the bottom of the container is regarded to be advantageous from the point of view that it enables the container to have a com.- pletely uniform peripheral wall 14. The upwardly projecting wall sections 32, 34, 36 and 38 provide a false bottom effect in the container. However, since the bottom is irregular a certain amount of turbulence is imparted to any liquids poured into the container which aids in mixing the contents.
The particular stacking construction also has advantages when utilized in the preferred method of construction. The inverted V-shaped wall section, after formation, will yield inwardly so as to permit the container to be easily removed from the die cavity. It will be understood that the portions of the die cavity which form the upwardly and inwardly converging wall sections present some diihculty of container removal after formation, but with the above-mentioned action this removal is simplifled. Furthermore, with the peripheral rim section there is provided adequate supporting surface for the container while at the same time, the radial groove 28 prevents hot gases from being trapped by the annular surface which may have the effect of condensing vapor on the surface which supports the container when hot liquids are held in the container. Thus, the radial groove 28 as well as the upwardly projecting wall sections afford adequate air circulation under the bottom of the container when it is resting on a horizontal surface.
it will be understood that the vertical distance between the upwardly facing stacking surface of the wall sections 32 and the downwardly facing stacking surfaces of the wall section 40 is of a minimum distance sufficient to provide a minimum stand ofi distance between the inner wall portion 20 of the lowermost container of the stack and the outer wall portion of the container nested therein, preventing these wall portions from wedgingly engaging each other. The vertical distance between the upper and lower stacking surfaces provided by the container determines the number of containers which can be stacked within a given storage space within the vending machine. As indicated above, this space is limited and it is highly desirable that a maximum number of containers can be stored in this space. The minimum vertical dimension between the upper and lower stacking surfaces or stacking height provided by the container is limited by two considerations: first, the wall thickness of the container; and second, the angle of taper of the peripheral wall. For practical purposes the angle of inclination of the peripheral wall must be greater than in order to permit nesting and less than 90 to enable the container to hold material. The intermediate angle utilized is dictated to a large extent by the general size and proportion of the container desired. For any given size of container, the angle of taper of the peripheral wall cannot be too great in relation to the height of the container, or else the bottom surface will be too small to stably support the container when filled with material. However, from the point of view of minimizing the stacking height, the angle of taper of the peripheral wall should be as great as possible. It has been found that an an le of taper on the order of between 410 presents a practical range and, of course, the minimum stacking height for any given wall thickness within this range increases as the angle of taper decreases. Conversely, for any given stacking height the maximum wall thickness which can be utilized increases as the angle of taper of the peripheral wall increases.
A preferred embodiment of a 6 ounce container constructed in accordance with the principles of the present invention has an angle of taper of 7% a stacking height of A inch, and a peripheral wall thickness including the foam that varies from a minimum of .020 inch to a maximum of .028 inch in accordance with the variations in wall thickness as disclosed in the aforementioned Caine application.
= 'n the practical limits of a container which is satisfactorily proportioned and sized for vending machine use, the wall thickness will have a determining factor on the minimum stacking height that can be provided. In some instances it is permissible to utilize a thin-walled container, but where such containers must hold hot liquids, such as coffee and the like, the thickness of the wall does not normally oifer sut'ficient insulation to permit the user to hold the container with the hot liquid therein without some unpleasant sensation. It has been proposed to modify the configuration of the wall without increasing the thickness thereof, so as to provide optimum heat transfer characteristics to the wall. An example of a container constructcd with this principle in view is shown in the abovementioned co-pending Caine application. While containers of this type have received some acceptance, they are still somewhat difiicult to handle with hot coffee and other hot drinks. The mere provision of additional material in the wall does not provide an adequate solution because of the increased costs involved. Moreover, the amount of solid plastic necessary to provide better insulating qualities would not only be prohibitive from a cost standpoint, but would be of such extent that the stacking height would be increased substantially.
The present container achieves the necessary improved insulating qualifications with the addition of a minimum amount of material adding a minimum thickness to the peripheral wall of the container so as to achieve the desired result without too much increased cost or increased stacking height.
0f primary significance is the fact that the material is capable of expansion in response to exposure to temperatures of the type encountered when the container is used for hot drinks such as coffee or the like. Conversely, it would be undesirable if expansion occurred at ambient temperatures or excessive temperatures which might be encountered in ambient conditions. The time of exposure to the excessive temperature has a bearing on the expansion. Essentially the expansion is caused by the material itself reaching a predetermined elevated temperature, the greater the temperature the greater the expansion. Thus, an instantaneous exposure to a highly elevated temperature would not result in the material itself reaching such a temperature; whereas continued exposure would result in the temperature of the material reaching a point closely approximating that of the source.
From the above it can be seen that it is preferable that the material have a maximum expansion characteristic so long as there is not appreciable expansion under ambient conditions. A material which is capable of expansion of approm'mately 200% at 212 F. and approximately 20% at P. will achieve the desired result. A preferred material is capable of expansion of approximately 350% at 212 F. and approximately 40% at 170 F. The figures indicated above are those obtained by subjecting the material by itself to an oven temperature for a period of time (approximately four minutes) sufficient to raise the temperature of the material to that indicated. It has been found that the amount of expansion increases as the temperature is increased within the range indicated. It will be understood that the percentage of expansion in the foam material when embodied in the container having a liquid at a temperature of 170 F. and 212 F. will be less, the above figures merely representing a maximum. The longer that the liquid is retained in the container the more nearly the expansion will approach the maximum figures indicated.
The characteristic of the foam material to expand in response to exposure to elevated temperatures to the ex tent indicated above can be achieved in several different ways. First, where the foamed material has a closed cellular structure it is entirely possible that the gases within the closed cells will expand when exposed to elevated temperatures, thus expanding the material. This characteristic may also be built into the product by stopping the foaming action during the formation of the material, so that there will be residual blowing agent remaining therein capable of being reactivated when the material is again exposed to elevated temperatures. Another way of achieving this characteristic in the material is to mechanically compress the material as by running the same through calendering rolls or the like. The exact manner in which the characteristic is built into the material utilized, whether by one or more of the procedures indicated above or otherwise, is of no great importance so long as the material utilized has the characteristics indicated. With such characteristics it will be noted that the wall thickness added by the provision of the foamed material will be at a minimum, thus maintaining a minimum stacking height with the container.
When a hot liquid is poured into the container, as during the normal use of a hot drink Vending machine, the heat of the liquid will be conducted to the foamed materia1, causing the same to expand. This expansion increases the insulating characteristics of the container and such increase in the insulating properties becomes greater as the need for such properties increases. That is, the hotter the liquid within the container, the greater the expansion and hence the greater the insulation provided. The extent of expansion is such that, once the container has been exposed to temperature conditions at least of the type encountered when the container is used with hot drinks, the wall thickness will have increased to a dimension greater than that provided by the stacking height of the container necessary to permit the containers to freely nest within one another. In other words, once the containers have been exposed to the elevated temperature such as is present when hot drinks are in the containers, the containers could not be freely nested together to an extent such that they could be depended upon to operate in a vending machine container dispensing mechanism. In this way a minimum amount of plastic material which will afford the greatest possible insulating properties is utilized and the construction is such that the wall thickness when the container is in stacked relation where the insulating properties are not needed is less, thus permitting a desired minimum stacking height and yet when the insulating properties are needed, they are available on demand to an extent greater than that afforded by the material in its initial thickness. This property of the present construction makes it possible to achieve a desired minimum stacking height while maintaining manufacturing tolerances in wall thickness which simply could not be utilized in the absence of such expansion without an undesirable sacrifice in the insulation properties of the containers.
From the above it follows that during the drawing of the heated plastic sheet 52 into the die cavity into contact with the frusto-conical foamed blank, provision must be made to maintain the temperature exposure conditions of the blank except on the solid plastic contacting surface thereof below approximately 170 F. for the period of time within which expansion will take place. The air quenching system previously provided is normally capable of obtaining this end although it may be desirable in some instances to provide the mold with a cooling liquid adjacent the surfaces which form the peripheral wall of the container.
It can be seen that the container of the present method cannot be practically formed by first laminating the solid plastic with the foamed plastic and drawing the laminate into the die cavity, since the heat required in the drawing action would destroy the expansion characteristics. Even if the drawing operation could be done cold, there would be considerable destruction of the cellular construction of the foamed material in the drawing procedure. It would be possible to initially form the unitary shell of the container and then to subsequently apply a band of foamed material to the exterior peripheral wall of the shell. Such a method of forming the present container is disclosed in the commonly assigned United States application Serial No. 208,867 filed July 10, 1962 concurrently herewith in the name of Walter O. Weber.
It will also be understood that in conjunction with the expansion of the foamed material for insulating purposes, the stiffness of the container is also increased by the expansion. Another advantage of the present construction is that the orientation of the foamed material is different from the orientation of the solid plastic material. It is Well-known that a drawing operation has a tendency to orient the plastic so that it will tend to fail by fracture longitudinally down the peripheral wall. The container made in accordance with the present method effects an excellent bond between the solid plastic and the foamed i2 plastic but, of course, does not disturb the normal orientation of the foamed material. In this way the foamed material would tend to resist any cracking in the direction of orientation of the solid material.
With respect to the bonding of the solid plastic material with the pre-formed frusto-conical foamed plastic blank, an excellent bond is achieved in the normal steps of the procedure. However, care must be taken to permit he surfaces of the two materials to intimately contact each other and therefore, where the foamed material is of a closed cellular construction, it is possible to trap pockets of air between the two plastic materials unless provision is made to insure that such air is allowed to pass from between the two materials as they are moved together. it is for this reason that in the preferred container it), the pin holes 22 are formed in the blank. It will also be noted that where longitudinally extending embossed grooves 48 are formed in the blank, as shown in FIGURES 7, 8 and 11, these grooves will provide passages to allow any air between the two materials to escape. Likewise, the embossed foamed material as shown in FlGURES 12 and 13, would permit the air to pass from between the two materials.
The foamed material is easily embossed prior to formation resulting in an image formation in the solid plastic during formation so that designs, letters and other indicia may be provided without the necessity of utilizing inks or other coloring. In addition, however, where the foamed material is of a closed cellular construction, the exterior surface thereof will readily receive any type of printing.
it thus will be seen that the objects of this invention have been fully and effectively accomplished. It will be realized, however, that the foregoing specific embodiment has been shown and described only for the purpose of illustrating the principles of this invention and is subject to extensive change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.
What is claimed is:
it. A thin Walled nestable container comprising a container body including a bottom and an upwardly and outwardly tapering peripheral wall extending upwardly therefrom so as to enable said container body to be nested within a similar container with the peripheral wall of said container body inside the peripheral wall of the similar body, said bottom having a pair of upwardly projecting portions spaced inwardly from said peripheral wall and defined by a plurality of thin walled sections disposed in concavo-convex relation, the thin walled sections defining each upwardly projecting portion including an upwardly and inwardly extending arcuate walled section, an upwardly and inwardly extending straight walled section disposed between the ends of said arcuate walled section, and an arcuately segmental walled section extending horizontally between the upper edges of said arcuate and straight walled sections, said pair of upwardly projecting portions providing a pair of upwardly facing horizontally extending stacking surfaces spaced horizontally apart, said bottom including a pair of downwardly facing horizontally extending stacking surfaces spaced horizontally apart a distance which is greater than the distance between said upwardly facing stacking surfaces an amount greater than twice the wall thickness of said bottom.
2. A container as defined in claim 1 wherein said bottom includes a shallow inverted V-shaped wall section extending between said straight wall sections.
3. A container as defined in claim 2 wherein said bottom includes a relatively narrow horizontal rim portion adjacent said peripheral wall having a radially extending groove formed therein.
4. A container as defined in claim 1 including a layer of foamed plastic material adhered to the exterior surface of said peripheral wall and disposed at least in the area thereof which would normally be gripped to hold the container body, said layer of foamed plastic material being expansible to increase the stiffness and insulating properties of said peripheral wall in response to exposure to the temperature conditions encountered when hot drinks are contained therein to an extent such that said container body after expansion will not nest freely with a similar container body.
References Cited by the Examiner UNITED STATES PATENTS 2,737,332 3/56 Amberg 2291.5
Politis 1819 Politis 1819 Witzke 229-1.5
Shappell 2291.5 Edwards.
Edwards 229-1.5 X
GEORGE O. RALSTON, Primary Examiner.