EP0106884B1 - Rigid paperboard container and method and apparatus for producing the same - Google Patents

Rigid paperboard container and method and apparatus for producing the same Download PDF

Info

Publication number
EP0106884B1
EP0106884B1 EP83901558A EP83901558A EP0106884B1 EP 0106884 B1 EP0106884 B1 EP 0106884B1 EP 83901558 A EP83901558 A EP 83901558A EP 83901558 A EP83901558 A EP 83901558A EP 0106884 B1 EP0106884 B1 EP 0106884B1
Authority
EP
European Patent Office
Prior art keywords
rim
blank
paperboard
container
thickness
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP83901558A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0106884A4 (en
EP0106884A1 (en
Inventor
Patrick H. Wnek
John L. Petit
Gerald J. Van Handel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fort James Corp
Original Assignee
James River Dixie Northern Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by James River Dixie Northern Inc filed Critical James River Dixie Northern Inc
Publication of EP0106884A1 publication Critical patent/EP0106884A1/en
Publication of EP0106884A4 publication Critical patent/EP0106884A4/en
Application granted granted Critical
Publication of EP0106884B1 publication Critical patent/EP0106884B1/en
Expired legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D1/00—Containers having bodies formed in one piece, e.g. by casting metallic material, by moulding plastics, by blowing vitreous material, by throwing ceramic material, by moulding pulped fibrous material, by deep-drawing operations performed on sheet material
    • B65D1/34—Trays or like shallow containers
    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47G—HOUSEHOLD OR TABLE EQUIPMENT
    • A47G19/00—Table service
    • A47G19/02—Plates, dishes or the like
    • A47G19/03—Plates, dishes or the like for using only once, e.g. made of paper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
    • B27N5/00—Manufacture of non-flat articles
    • B27N5/02—Hollow articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B31—MAKING ARTICLES OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER; WORKING PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
    • B31B—MAKING CONTAINERS OF PAPER, CARDBOARD OR MATERIAL WORKED IN A MANNER ANALOGOUS TO PAPER
    • B31B50/00—Making rigid or semi-rigid containers, e.g. boxes or cartons
    • B31B50/59—Shaping sheet material under pressure
    • B31B50/592—Shaping sheet material under pressure using punches or dies

Definitions

  • This invention pertains generally to the field of processes and apparatus for forming pressed paperboard products such as paper trays and plates and to the products formed by such processes.
  • Formed fiberboard containers such as paper plates and trays, are commonly produced either by molding fibers from a pulp slurry into the desired form of the container or by pressing a paperboard blank between forming dies into the desired shape.
  • the molded pulp articles after drying, are fairly strong and rigid but generally have rouch surface characteristics and are not usually coated so that they are susceptible to penetration by water, oil and other liquids.
  • Pressed paperboard containers on the other hand, can be decorated and coated with a liquid-proof coating before being stamped by the forming dies into the desired shape. Large numbers of paper plates and similar products are produced by each of these methods every year at relatively low unit cost. These products come in many different shapes, rectangular or polygonal as well as round, and in multicompartment configurations.
  • Pressed paperboard containers tend to have somewhat less strength and rigidity than do comparable containers made by the pulp molding processes.
  • Much of the strength and resistance to bending of a plate-like container made by either process lies in the side wall and rim areas which surround the center or bottom portion of the container.
  • the side wall and overturned rim of the plate are unitary, cohesive structures which have good resistance to bending as long as they are not damaged or split.
  • the flat blank when a container is mude by pressing a paperboard blank, the flat blank must be distorted and changed in area in order to form the blank into the desired three dimensional shape.
  • Score lines are sometimes placed around the periphery of blanks being formed into deep pressed products to allow the paperboard to fold or yield at the score lines to accommodate the reduction in area that takes place during pressing.
  • the provision of score lines, flutes, or corrugations in the blank may result in a formed product with natural fault lines about which the product will bend more readily, under less force, than if the product were unflawed.
  • Shallow containers, such as paper plates may also be formed from paperboard blanks which are not scored or fluted, but the pressing operation will cause wrinkles or folds to form in the paperboard material at the rim and side walls of the container at more or less random positions; these folds, again, act as natural lines of weakness within the container about which bending can occur.
  • a sheet or web of paperboard is cut to form the blank-a circular shape for a plate-and the blank is then pressed firmly between upper and lower dies which have die surfaces conforming to the desired shape of the finished container.
  • the paperboard web stock is usually coated with a liquid-proof material on one surface and may also have decorative designs printed under the coating.
  • the surfaces of the upper and lower dies have typically been machined such that, when they begin to compress the shaped paperboard blank between them, the die surfaces will be generally spaced uniformly-apart over the entire surface are of the formed paperboard.
  • the lower die is spring mounted to limit the maximum force applied to the paperboard between the dies; and this force is distributed over the entire area of the paperboard if the spacing between the dies is uniform.
  • the machining of the dies is such that random high and low spots are commonly formed on the die surfaces, resulting in random, localized areas of the paperboard which are highly pressed while other areas are unpressed.
  • the dies are also generally heated to aid in the forming and pressing operation. Paperboard plates produced in this manner have good decoration quality -and liquid resistance because of the surface coating, and are suited to high production volume with resulting relatively low unit cost. However, as noted above, the plates suffer from a lower than desired level of rigidity and are subject to greater bending during normal household use than is perhaps most desirable.
  • Distortion of the shape of the soft and flowable fiberboard is prevented by driving the forming dies to a stop at which the surfaces of the dies are uniformly spaced apart a distance approximately equal to or slightly less than the desired thickness of the formed container.
  • the shaped fiberboard material dries under the heat and pressure applied by the dies and the fibers within the material build up internal bonds upon drying which help to maintain the strength and rigidity of the deformed portions of the paperboard material.
  • the apparent limitations of such a process are the complex dies required to allow release of the water vapours from the pressed fibreboard, handling problems with high moisture fibreboard and slower production times required because of the time necessary to allow removal of the water vapour from the paperboard during the pressing operation, thereby all contributing to increased production costs.
  • US ⁇ A ⁇ 2 832 522 discloses a container in accordance with the prior art portion of claim 1.
  • the container of the present invention is characterised as specified in claim 1. Particular embodiments of the invention are indicated in dependant claims 2 to 5. With this construction an extremely rigid container is formed in that densified regions are provided in the rim in which three layers of paperboard have been reformed into an integrated fibrous structure. There is no suggestion of such compacted reformed layers in US-A-2 832 522. In GB-A-981 667 there is simply disclosed compression at the rim area and the provision of existing corrugations to assist deformation of the side wall area.
  • the paperboard container of the present invention is formed from fibrous substrate stock in such a way that the raised areas of the container are substantially free of the type of fault lines which are found in paperboard containers pressed in a conventional manner.
  • the container has a bottom wall, an upturned side wall extending from the bottom wall, and a rim extending from the side wall.
  • the bottom wall of the formed container is substantially equal in thickness and density to the blank, whereas the rim is preferably somewhat denser generally than the blank and is substantially denser in those areas where folds are formed in the rim during initial shaping.
  • Those portions of the paperboard which are folded up during forming are substantially the same thickness as the rest of the container, although containing more fibrous material, and the entire surface of the rim area is essentially smooth.
  • the upturned side wall, or a portion thereof, may also be densified, particularly in the areas of the folds formed therein.
  • the container may be formed in the various geometric shapes used for pressed paperboard products.
  • the rim preferably has a downturned edge portion, compressed and densified, which is found to particularly enhance the rigidity of the container structure.
  • the paperboard stock may be coated in a conventional manner to provide decoration and liquid-proofing. Because of the lack of voids and other fault lines, the container of the invention will have a rigidity at least 40% and often 100% greater than conventional containers pressed from the same paperboard stock.
  • US ⁇ A ⁇ 2 832 522 discloses a method in accordance with the prior art portion of claim 6.
  • This prior method will not provide the improved rigidified construction of the present invention in that there is no reforming of the fibrous structure of the container and there is not obtained the reformed rigidified structure of the rim of the container as made by the method of the present invention as characterised in claim 6.
  • the method of the present invention requires the reforming of the rim portion of the container using heat, pressure and a required moisture content so as to provide radially extending areas of densified material. There is no suggestion or requirement for such radially extending reformed dense areas in US-A-2 832 522.
  • the blank material is selected to have a moisture content before forming in the range of preferably 9.5% to 10.5% by weight.
  • the blank is then pressed between a pair of mating dies having die surfaces generally conforming to the shape of the formed plate, but with the adjacent surfaces of the dies at the rim area being closer together than at the bottom wall area as the die surfaces approach.
  • the surfaces of the two dies engage the paperboard blank between them and distort the blank into the general shape of the formed product.
  • the more closely spaced die surfaces at the rim engage the paperboard in the area of the rim between them before the paperboard in the bottom wall portion of the blank is firmly engaged; as a result, extremely high compression forces are applied in the rim area and, in particular, at any downwardly extending portions of the rim. Compression force may also be applied to the upturned side wall to press out wrinkles and voids created therein during initial shaping of the container.
  • the moisture in the paperboard helps to weaken the fibre bonds within the paperboard, thereby allowing the fibres to disengage from one another and flow under the intense compression force applied to the rim area, particularly at the folds.
  • the flowing of the fibres within the fibreboard under pressure causes the wrinkles and other fault lines within the rim to be substantially eliminated so that, after the dies are removed from the paperboard and the bonds between fibres are reformed, the rim area of the formed container is a substantially integral structure.
  • the dies are maintained at a temperature between 121°C and 160°C (250°F and 320°F). These temperatures are found to yield the best conditions of fibre flow and distortion under the intense pressures applied by the dies without overheating the blank and causing surface blisters or scorching of the paperboard. As moisture is driven out of the heated paperboard, bonds between fibres are reformed in their compressed positions.
  • the dies are mounted in a conventional manner, such that the motion of the die surfaces toward one another is stopped only by the compression of the paperboard material between them.
  • the force applied to the dies is limited by the spring mounting of the lower die, typically at a force of at least 26688N (6000 lbs) and preferably 35590 N - (8000 lbs) or more for containers in the common 22.86 to 25.4 cm (9 to 10 inch) diameter range. Most of the force between the dies is applied to the rim area of the formed plate, yielding typically pressures in the rim area of at least 1379 Kpa (200 Ibs per in 2 ) and even greater localised pressures at the areas where the paperboard is initially folded.
  • a further aspect of the invention provides apparatus in the prior art portion of claim 14 disclosed by GB-A-981 667 characterised with the additional features as specified in claim 15 to provide the utilityto make the container of claim 1.
  • a paperboard container in the form of a plate is shown in perspective at 10 in Fig. 1.
  • This container structure will be described to illustrate the invention, although it will be readily apparent that the invention can be incorporated in many other container geometries being in accordance with the claims.
  • the form of the plate 10 is typical of commercially produced plates now distributed in the mass market: it has a substantially flat, circular bottom wall portion 11, an upturned side wall portion 12 which serves to contain food and particularly juices on the plate, and an overturned rim portion 13 extending from the side wall.
  • the plate portions 11, 12, and 13 are formed integrally with one another. The distinctions between the portions may be best illustrated with respect to the cross-sectional view of Fig. 2.
  • the flat bottom wall 11 of the plate extends to about the position in the plate denoted at 15, at which the side wall 12 begins rising upwardly; the upturned side wall 12 terminates at about the position marked 16 in Fig. 2, at which the paperboard begins to curve over and down about a smaller radius to form the overturned rim 13 which terminates at a peripheral rim edge 17.
  • the rim 13 serves a number of purposes in the paper plate product. It provides a more aesthetically pleasing appearance than would a plate which simply has an upturned side wall terminating in an edge, and it provides a generally lateral area which can be gripped by a user when carrying the plate. From the standpoint of the structural integrity of the plate, the most important function of the rim 13 isto make the plate rigid and resistant to bending when held by a user. As is apparent from an examination of the cross-sectional view of Fig. 2, the vaulted shape of the overturned rim 13 provides a structure which is naturally resistant to bending about any radial axis extending from the center of the plate.
  • the plate will resist bending in the hand of a user until the plate is loaded so heavily that the paperboard in the rim 13 is under tensile stress sufficient to cause the paperboard to yield and buckle.
  • the maximum tensile stress in the plate under normal loading will lie across a generally radial cross-section through the rim area.
  • the paperboard plate 10 of the invention is also formed from a unitary flat blank of paperboard stock, either scored or unscored, and thus must also undergo folding in the side wall 12 and rim 13.
  • the resulting fold lines are shown for illustrative purposes at 20 in Fig. 1.
  • the plate 10 is produced in such a way that the paperboard in the vicinity of the rim portions of the folds 20 is tightly compressed and essentially bonded together so that the folds 20 in the rim do not present natural hinge lines or lines of weakness and, in fact, have a tensile strength substantially similar to that of the integral paperboard.
  • the paperboard material in the rim 13 is densified at the folds, and any voids or disruptions formed in the rim areas of the folds 20 during the pressing operation are compressed out and new bonds are formed between the tightly compacted fibers in these areas.
  • the entire rim is preferably densified and slightly reduced in thickness compared with the bottom of the plate. As shown in the cross-sectional view of Fig. 2, in which the dimensions are exaggerated for purposes of illustration, the thickness of the plate 10 at the flat bottom wall 11 and the upturned side wall 12 is essentially the same as that of the nominal thickness of the unpressed blank from which the plate is made.
  • the entire downwardly extending portion of the rim-the portion of the rim from the top 21 to the edge 17- is thus preferably compressed to a thickness somewhat less than the thickness of the bottom wall.
  • the material of the rim is commensurately denser than the paperboard material in the remainder of the plate, and the areas of the folds 20 are substantially denser than the bottom wall.
  • the paperboard of the blank preferably has a nominal caliper in the range of 0.025 to 0.1 cm (0.010 inch to 0.040 inch) with a basis weight in the range of approximately 0.163 to 0.65 Kg/m (100 pounds to 400 pounds per 3,000 square feed).
  • the density of the paperboard in the bottom wall and side wall portions is preferably approximately 660 Kg/m 3 (10.3 pounds per 0.001 inch caliper per ream (3,000 square feet).
  • Containers formed in accordance with the invention have much greater rigidity than comparable containers formed of similar paperboard blank material in accordance with the prior art processes.
  • a test procedure has been used which measures the force that the plate exerts in resistance to a standard amount of deflection.
  • the test fixture utilized a Marks II Plate Rigidity Tester, has a wedge shaped support platform on which the plate rests.
  • a pair of plate guide posts are mounted to the support platform at positions approximately equal to the radius of the plate from the apex of the wedge shaped platform.
  • the paper plate is laid on the support platform with its edges abutting the two guide posts so that the platform extends out to the center of the plate.
  • a straight leveling bar mounted for up and down movement parallel to the support platform, is then moved downwardly until it contacts the top of the rim on either side of the plate so that the plate is lightly held between the platform and the horizontal leveling bar.
  • the probe of a movable force gauge such as a Hunter Force Gauge, is then moved into position to just contact the top of the rim under the leveling bar at the unsupported side of the plate. The probe is lowered to deflect the rim downwardly one-half inch, and the force exerted by the deflected plate on the test probe is measured.
  • Fig. 3 shows a cross-section of the upper die 25 and lower die 26 which are utilized to press a flat, circular paperboard blank 27 into the shape of the plate 10.
  • the construction of the dies 25 and 26, and the equipment on which they are mounted is substantially conventional; for example, .as utilized on presses manufactured by the Peerless Manufacturing Company.
  • the dies are segmented in the manner shown.
  • the lower die 26 has a circular base portion 29 and a central circular platform 30 which is mounted to be movable with respect to the base 29.
  • the platform 30 is cam operated in a conventional manner and urged toward a normal position such that its flat top forming surface 31 is initially above the forming surfaces 32 of the base 29.
  • the platform 30 is mounted for sliding movement to the base 29, with the entire base 29 itself being mounted in a conventional manner on springs (not shown). Because the blank is very tightly pressed at the peripheral rim area, moisture in the paperboard which is driven therefrom during pressing in the heated dies cannot readily escape. To allow the release of this moisture, at least one circular groove 33 is provided in the surface 32 of the base, which vents to the atmosphere through a passageway 34.
  • the top die 25 is segmented into an outer ring portion 35, a base portion 36, and a central platform 37 having a flat forming surface 38.
  • the base portion has curved, symmetrical forming surfaces 39 and the outer ring 35 has curved forming surfaces 40.
  • the central platform 37 and the outer ring 35 are slidingly mounted to the base 39 and biased by springs (not shown) to their normal position shown in Fig. 3 in a commercially conventional manner.
  • the die 25 is mounted to reciprocate toward and away from the lower die 26. In the pressing operation, the blank 27 is first laid upon the flat forming surface 31, generally underlying the bottom wall portion 11 of the plate to be formed, and the forming surface 38 makes first contact with the top of the blank 27 to hold the blank in place as the forming operation begins.
  • the die 25 moves sufficiently far down so that the platform segments 30 and 37 and the ring segment 35 are fully compressed such that the adjacent portions of forming surfaces 38 and 39 are coplaner and the adjacent portions of surfaces 39 and 40 are coplaner, and similarly, that the forming surface-31 is coplaner with the adjacent portion of the forming surfaces 32.
  • the upper die 25 continues to move downwardly and thus drives the entire lower die 26 downwardly against the force of the springs (not shown) which support the die 26.
  • the dies exert a force on each other, through the formed blank 27 which separates them, which is equal to the force applied by the compressed springs supporting the die 26.
  • the amount of force applied to the formed blank 27, and distributed over its area can be adjusted by changing the length of the stroke of the upper die 25.
  • the dies 25 and 26 are heated with electrical resistance heaters (not shown), and the temperature of the dies is controlled to a selected level by monitoring the temperature of the dies with thermistors (not shown) mounted in the dies as close as possible to the forming surfaces.
  • the dies 25 and 26 were machined such that the forming surfaces 38, 39 and 40 of the die 25 were nominally substantially parallel to the forming surfaces 31 and 32 of the lower die 26 at a selected spacing approximately equal to the thickness of the blank being pressed. From a consideration of the geometry of the die surfaces, it can be seen that the upturned sidewall and any downturn on the rim would receive the greatest compressive forces initially if the selected spacing at which the die surfaces are parallel is less than the blank thickness; whereas the top of the rim and the bottom wall would receive substantially all the compressive force if the selected parallel spacing is greater than or equal to the blank thickness.
  • the force between the dies will be distributed over the entire area of the paperboard between the dies, including the bottom wall which comprises more than half the area of the pressed plate, except where irregularities in the machining of the die surfaces cause high or low spots.
  • plates pressed utilizing uniform die forming surface clearances had relatively low rigidity, primarily due to the severe disruption of the fibers at the wrinkles in the rim of the plate.
  • the forming surfaces 38, 39 and 40 of the upper die 25 are not entirely parallel to the forming surfaces 31 and 32 of the lower die 26 at any spacing.
  • the preferred spacing of the die surfaces is shown in the view of Fig. 4, which illustrates a cross-section of the two dies closely adjacent to one another-substantially in the position that they would be in with a paperboard blank between them during the pressing operation.
  • the relative spacing between the die surfaces will depend upon the thickness of the paperboard blank being formed.
  • the topography of the die surfaces can be specified, in general, by assuming that at the circumferential position 41 in the die surfaces at which the side wall of the plate ends and the rim begins, the die surfaces are spaced apart a thickness substantially equal to the nominal thickness of the paperboard blank.
  • the die surfaces are preferably formed such that the spacing between the surfaces decreases gradually and continuously from such reference position toward the rim edge of the paperboard plate formed between the dies.
  • the location in the die surfaces which corresponds to the rim edge is denoted at 42 in Fig. 4, and the location in the die surfaces corresponding to the top of the rim in the formed plate is denoted at 43 in Fig. 4.
  • the spacing between the upper die surface and the lower die surface decline continuously from the nominal paperboard thickness at the location 41 to at least 0.0051 cms (0.002 inch) less than the nominal thickness at the location 43 and to at least 0.0076 cms (0.003 inch) less than the nominal thickness at the rim edge location 42.
  • the spacings between the upper and lower dies at other points not on the rim are preferably at least as great as the nominal thickness of the paperboard blank.
  • the spacing between the die surfaces at the bottom wall is substantially greater than the thickness of the paperboard blank so that the bottom wall area receives little pressure.
  • satisfactory die surface spacings are: position 42, 0.33 mm (0.013 inch); position 43, 0.36 mm (0.014 inch); position 41, 0.41 mm (0.016 inch); position 44, 0.48 mm (0.019 inch); and at positions 46, 47, and 48, at least 0.51 mm (0.02 inch).
  • the actual die clearances can be measured by laying strips of solder radially across the surface of the bottom die, pressing the dies together, and measuring the height'ofthe solder at various positions on the die surface after pressing.
  • the pressure applied to the paperboard in the rim would be approximately 3620 KPa (525 pounds per square inch). Because of the inevitable slight misalignments between the upper and lower dies, high and low spots in the dies, and variations in the paperboard thickness, the pressure applied to the paperboard at some points on the rim will be less than this maximum amount but almost certainly at least 1379 KPa (200 pounds per square inch), twice the pressure that would be placed upon the rim if the compressive force were distributed uniformly over the area of the pressed plate, as has nominally been the case in prior paperboard pressing operations.
  • the compressive forces should be even greater at the folds in the paperboard, since these areas are raised above the rest of the paperboard and contain more fibrous material. There folded areas will comprise a small percentage of the area of the rim, e.g., 4 to 5 percent, so that the compressive force concentrated in these areas may attain many millions of Pa (thousands of pounds per square inch). This tremendous pressure serves to greatly densify the fibrous material at the folds in the rim.
  • the ideal die surface configurations given above would preferably be maintained around the entire circumference of the dies, so that all the die surfaces were perfectly symmetrical.
  • the most critical tolerances are those within the rim area from the position 41 to the position 42. It is highly preferred that the die clearances in the rim be uniform along any circumferential line around the rim so that all folded areas in the rim receive the intense compressive forces.
  • a satisfactory radial gradient of die surface spacing is for nominal paperboard thickness "N" at position 41, N-0.05 mm (0.002 inch) at position 43, and N-0.076 mm (0.003) inch at position 42. Satisfactory results have been obtained with dies that have been measured to conform to this gradient within plus or minus 0.05 mm (0.002 inch), with best results obtained with dies maintained within 0.025 mm (0.001 inch), provided that the spacing between the dies at the positions 45 ⁇ 47 is at least as great as the nominal paperboard thickness N and preferably 0.075 to 0.203 mm (0.003 to 0:008 inch) greater than the nominal thickness N.
  • the paperboard which is formed into the blanks 27 is conventionally produced by a wet laid papermaking process and is typically available in the form of a continuous web on a roll.
  • the paperboard stock is preferred to have a basis weight in the range of 0.163 to 0.65 Kg/m 2 (100 to 400 pounds per ream (3,000 square feet)) and a thickness or caliper in the range of about 0.25 to 1 cm (0.010 inch to 0.040 inch. Lower basis weight and caliper paperboard is preferred for ease of forming and economic reasons.
  • Paperboard stock utilized for forming paper plates is typically formed from bleached pulp furnish, and is usually double clay coated on one side. Such paperboard stock commonly has a moisture (water) content varying from 4.0% to 8.0% by weight.
  • the effect of the compressive forces at the rim is greatest when proper moisture conditions are maintained within the paperboard: at least 8% and less than 12% water by weight, and preferably 9.5% to 10.5%.
  • Paperboard in this range has sufficient moisture to deform under pressure, but not such excessive moisture that water vapor interferes with the forming operation or that the paperboard is too weak to withstand the high compressive forces applied.
  • the paperboard is treated by spraying or rolling on a moistening solution, primarily water, although other com- p onents such as lubricants may be added.
  • the moisture content may be monitored with a hand held capacitive-type moisture meter to verify that the desired moisture conditions are being maintained. It is preferred that the plate stock not be formed for at least 6 hours after the moistening operation to allow the moisture within the paperboard to reach equilibrium.
  • the paperboard stock is typically coated on one side with a liquid-proof layer or layers.
  • the plate stock is often initially printed before being coated.
  • a first layer of polyvinyl acetate emulsion may be applied over the printed paperboard with a second layer of nitrocellulose lacquer applied over the first layer.
  • the plate stock is moistened on the uncoated side after all of the printing and coating steps have been completed.
  • the web of paperboard stock is fed continuously from a roll through a cutting die (not shown) to form the circular blanks 27, which are then fed into position between the upper and lower dies 25 and 26.
  • the dies are heated, as described above, to aid in the forming process. It has been found that best results are obtained if the upper die 25 and lower die 26-particularly the surfaces thereof-are maintained at a temperature in the range of 121°C to 160°C (250°F. to 320°F). and most preferably 149°C (300°F.) plus or minus 5.6°C (10°F). These die temperatures have been found to facilitate the plastic deformation of paperboard in the rim areas if the paperboard has the preferred moisture levels.
  • the amount of heat applied to the blank is apparently sufficient to liberate the moisture within the blank under the rim and thereby facilitate the deformation of the fibers without overheating the blank and causing blisters from liberation of steam or scorching the blank material. It is apparent that the amount of heat applied to the paperboard will vary with the amount of time that the dies dwell in a position pressing the paperboard together.
  • the preferred die temperatures are based on the usual dwell times encountered for normal production speeds of 40 to 60 pressings a minute, and commensurately higher or lower temperatures in the dies would generally be required for higher or lower production speeds, respectively.
  • a paper container produced in accordance with the present invention may best be compared with prior paperboard containers formed of similar materials by examining the photomicrographs of Figs. 5-10.
  • Figs. 5-7 show various cross-sections through a paperboard plate made in accordance with the prior commercial practice in which the die surfaces are uniformly spaced; whereas Figs. 8-10 are cross-sections through a paper plate made in accordance with the present invention.
  • Both paper plates were formed of 0.28 Kg/m 2 (170 pound per ream (3,000 square feet)), 0.41 mm (0.016 inch) caliper, low density bleached plate stock, clay coated on one side, printed on one surface with standard inks, coated with a first layer of polyvinyl acetate emulsion and overcoated with a nitrocellulose lacquer.
  • the density of the paperboard stock averages about 660 Kg/m 3 (about 10.3 pounds per 0.001 inch of thickness per ream), and the Taber Stiffness of the paperboard ranges, with the grain, from about 110 to 300, and across the grain, from about 55 to 165.
  • Fig. 5 (140X) is through the center portion of the prior plate structure. It may be observed that there are numerous voids within the fiber structure, indicating that the board is not substantially compacted, although the fiber distribution is relatively uniform. The thickness of the cross-section is about 0.41 mm (0.016 inch).
  • Fig. 6 (80X) is a cross-sectional view through the rim area of the prior plate, generally cut along a circumferential line at about the top of the rim. The particular view of Fig. 6 is through one of the areas in the rim which has a fold or wrinkle in it. As is graphically apparent from an examination of Fig.
  • the paperboard at the wrinkle has been badly disrupted, leaving large voids between the fibers, with adjacent fibers ripped apart, so that a fault line or very weak area exists within the paperboard at the fold.
  • the surface of the paperboard at the wrinkle is discontinuous, with a large gap existing between adjacent portions.
  • the thickness of the cross-section at the fold is about 0.66 mm (0.026 inch) and is greater than the original thickness for some distance away from the fold.
  • Fig. 7 (80X) is a cut through the rim, generally along a circumferential line at a position very close to the edge of the rim. This cut shows the termination of the one of the wrinkles running through the rim in the prior plate. Again, in the area of the wrinkle there are wide voids and a rough discontinuous surface structure.
  • the thickness is about 0.51 mm (0.020 inch) maximum, at the fold.
  • Fig. 8 is a cross-section through the approximate center of a plate made in accordance with the present invention.
  • a comparison of Fig. 8 with Fig. 5 shows that the structure of the paperboard at the center of the pressed plates is substantially similar in both cases; both have relatively even surfaces and substantial voids distributed throughout the matrix of fibers within the board which is characteristic of the unpressed, low density paperboard stock material from which the pressed plates are made. The average thickness is about 0.41 mm (0.016 inch).
  • Fig. 9 is a photomicrograph taken along a cut through the top of the rim portion of a plate made in accordance with the invention, with the cut lying along a circumferential line through one of the folded or wrinkled areas of the pressed plate.
  • Fig. 9 The contrast between Fig. 9 and Fig. 6 is significant.
  • the paperboard in the area through which the section of Fig. 9 was taken is highly compacted, leaving very little empty space between the fibers; the structure of this folded region is in marked contrast to the folded regions of Fig. 6 in which there are gapping voids between fiberboard which account for the badly weakened condition of the rim in this area.
  • the paperboard in the rim shown in Fig. 9 has been compacted and its density increased so that the paperboard is clearly denser than at the center region shown in Fig. 8.
  • the maximum thickness of this cross-section, occurring at the two folds shown is about 0.43 mm (0.017 inch), substantially the same as the bottom wall.
  • the thickness of the rim is about the same as or somewhat thinner than the bottom wall. Since the folded-over areas contain substantially more solid fibrous material than the rest of the paperboard; perhaps 40 to 100% more, the density of the'folded areas is substantially greater than the remainder of the paperboard.
  • the surfaces of the paperboard of Fig. 9 are essentially smooth and continuous, in contrast again to the discontinuity of surfaces shown in the view of Fig. 6, and the folds within the paperboard of Fig. 9 have been turned back upon themselves and the folded-over surfaces have been squeezed tightly together.
  • the bottom surface, in particular, of the slice shown in Fig. 9 is smooth and continuous, rather than being disrupted at the wrinkle lines as shown in Fig. 6.
  • the coating which covers the top surface of the plate is clearly visible in the view of Fig. 9, and this coating well illustrates where the folds began to occur in the rim of the plate as the plate was being formed.
  • the extreme high pressure applied to the rim of the plate has caused virtually all traces of the fold to disappear at the bottom portion of the paperboard where the fibers of the paper have been essentially bonded together, leaving only the vestigial traces of the fold remaining in the top of the paperboard where the coating on the surface prevents the intermingling of fibers.
  • the heat and pressure applied during the forming process may be sufficient to cause some melting and surface adhesion between the abutting coated surfaces which lie along the fold lines, although the nitrocellulose outer coating is resistant to heat and pressure.
  • FIG. 10 A cross-section through a plate of the invention taken just inside of the rim edge is shown in Fig. 10 (110X).
  • the fibers within the plate are substantially compacted, and virtually all evidence of the folds that existed in the rim area during the forming operation had disappeared, except for small areas where the overcoated tops of the folded regions have been laid back upon themselves.
  • the bottom of the paperboard surface is again smooth and unbroken, in sharp contrast to the section through the prior art plate shown in Fig. 7.
  • the fibers are tightly and closely compressed together, leaving very few voids or air spaces, and the overall structure is densified so that even though the rim of the plate becomes progressively thinner as the edge is approached, as illustrated in Fig.
  • the basis weight of the paperboard in this region is substantially uniform because of the compaction of the fibers.
  • the thickness of the paperboard shown in Fig. 10 is about 0.389 mm (0.0153 inch), about 4 to 5% thinner than the bottom wall.

Landscapes

  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Mechanical Engineering (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Food Science & Technology (AREA)
  • Forests & Forestry (AREA)
  • Making Paper Articles (AREA)
  • Paper (AREA)
  • Auxiliary Devices For And Details Of Packaging Control (AREA)
  • Supplying Of Containers To The Packaging Station (AREA)
  • Containers Having Bodies Formed In One Piece (AREA)
EP83901558A 1982-04-13 1983-04-11 Rigid paperboard container and method and apparatus for producing the same Expired EP0106884B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US36788082A 1982-04-13 1982-04-13
US367880 1982-04-13

Publications (3)

Publication Number Publication Date
EP0106884A1 EP0106884A1 (en) 1984-05-02
EP0106884A4 EP0106884A4 (en) 1985-10-24
EP0106884B1 true EP0106884B1 (en) 1989-01-18

Family

ID=23449009

Family Applications (1)

Application Number Title Priority Date Filing Date
EP83901558A Expired EP0106884B1 (en) 1982-04-13 1983-04-11 Rigid paperboard container and method and apparatus for producing the same

Country Status (8)

Country Link
EP (1) EP0106884B1 (it)
AU (1) AU561748B2 (it)
CA (1) CA1225342A (it)
DE (1) DE3378949D1 (it)
FI (1) FI834526A0 (it)
IT (1) IT1161135B (it)
NO (1) NO834593L (it)
WO (1) WO1983003530A1 (it)

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU572632B2 (en) * 1984-03-20 1988-05-12 James River Corporation Of Virginia Rigid paperboard container
US5088640A (en) * 1991-09-06 1992-02-18 James River Corporation Of Virginia Rigid four radii rim paper plate
JPH08504705A (ja) * 1992-05-08 1996-05-21 ビジー ボード プロパティーズ プロプライエタリー リミテッド 成形容器
USD481592S1 (en) 2001-05-01 2003-11-04 Pactiv Corporation Plate having condiment wells
US7172072B2 (en) 2001-05-01 2007-02-06 Pactiv Corporation Compartment plates having themes and method for manufacturing and packaging the same
USD481260S1 (en) 2001-05-01 2003-10-28 Pactiv Corporation Plate having condiment wells
USD489941S1 (en) 2001-05-01 2004-05-18 Pactiv Corporation Plate having condiment wells
US7104030B2 (en) 2001-05-01 2006-09-12 Pactiv Corporation Compartment plates having themes and method for manufacturing and packaging the same
USD480922S1 (en) 2001-05-01 2003-10-21 Pactiv Corporation Plate having condiment wells
USD483998S1 (en) 2001-05-01 2003-12-23 Pactiv Corporation Plate having condiment wells
US7013618B2 (en) 2001-05-01 2006-03-21 Pactiv Corporation Compartment plates having themes and method for manufacturing and packaging the same
USD485731S1 (en) 2003-02-19 2004-01-27 Pactiv Corporation Plate having two compartments

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US232684A (en) * 1880-09-28 Trunk
USRE22487E (en) * 1944-05-30 Molded article and method of
US2071734A (en) * 1933-10-28 1937-02-23 Westinghouse Air Brake Co Mold for piston packing
US2760231A (en) * 1952-01-17 1956-08-28 Continental Can Co Die assembly for molding hollow structures
US2832522A (en) * 1953-11-20 1958-04-29 Keyes Fibre Co Container cover and method of making
FR1251528A (fr) * 1960-02-18 1961-01-20 Bellofram Patents Inc Perfectionnements apportés aux membranes d'étanchéité pour rotules
US3099377A (en) * 1960-08-17 1963-07-30 American Can Co Dish or the like
GB981667A (en) * 1963-08-23 1965-01-27 Bowater Res & Dev Company Ltd Trays made of fibrous sheet material
US3401863A (en) * 1966-12-12 1968-09-17 American Can Co Compartmented tray
US3632276A (en) * 1969-04-28 1972-01-04 Werz Furnier Sperrholz Mold for producing molded elements with parts of different thicknesses from fibrous mixtures
US4149841A (en) * 1978-03-27 1979-04-17 Peerless Machine & Tool Corporation Apparatus of making a compartment tray
US4313899A (en) * 1980-02-07 1982-02-02 Champion International Corporation Process for forming laminated paperboard containers
US4381847A (en) * 1981-03-30 1983-05-03 Packaging Corporation Of America Carry-out tray

Also Published As

Publication number Publication date
WO1983003530A1 (en) 1983-10-27
NO834593L (no) 1983-12-13
AU561748B2 (en) 1987-05-14
IT1161135B (it) 1987-03-11
DE3378949D1 (en) 1989-02-23
IT8320556A0 (it) 1983-04-13
EP0106884A4 (en) 1985-10-24
CA1225342A (en) 1987-08-11
EP0106884A1 (en) 1984-05-02
FI834526A (fi) 1983-12-09
AU1550883A (en) 1983-11-04
FI834526A0 (fi) 1983-12-09

Similar Documents

Publication Publication Date Title
US4609140A (en) Rigid paperboard container and method and apparatus for producing same
US4721500A (en) Method of forming a rigid paper-board container
US4721499A (en) Method of producing a rigid paperboard container
EP0162540B1 (en) Rigid paperboard container and method for producing same
US4832676A (en) Method and apparatus for forming paperboard containers
EP0106884B1 (en) Rigid paperboard container and method and apparatus for producing the same
US3305434A (en) Method and apparatus for forming rigid paper products from wet paperboard stock
US9833088B2 (en) Pressed paperboard servingware with improved rigidity and rim stiffness
JP6293613B2 (ja) アーチ形の底板と急唆な周縁の切り替え部とを有する圧板紙食器
US5326020A (en) Rigid paperboard container
US5938112A (en) Rigid paperboard container
CA1069364A (en) Method and apparatus of making a compartment tray
US8474689B2 (en) Method for in-die lamination of plural layers of material and paper-containing product made thereby
US5029749A (en) Paper container and method of making the same
US6783720B2 (en) Punch stripper ring knock-out for pressware die sets
CA2193386A1 (en) Method for forming corrugated paper container and container made therefrom
US20030214076A1 (en) Rotating inertial pin blank stops for pressware die sets
EP0082209B1 (en) An apparatus and method for forming a paperboard receptacle
US4558813A (en) Container and sidewall blank having sinusoidal edge pattern
JP4121832B2 (ja) 成形容器の製造方法と製造装置及び成形容器
US1189822A (en) Process for the manufacture of paper receptacles or drinking vessels or cups.
JPS59500701A (ja) 硬質板紙容器及び同容器を製造する方法及び装置
CN110181860B (zh) 酒瓶包装盒的加工模具
CA2146695C (en) Decorative debossed rigid paperboard container and method of forming the same
EP4413203A1 (en) Press molding method of a cup shaped fiber product, a fiber press mould and a cup shaped fiber product

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): BE CH DE FR GB LI NL SE

17P Request for examination filed

Effective date: 19840416

17Q First examination report despatched

Effective date: 19870227

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): BE CH DE FR GB LI NL SE

REF Corresponds to:

Ref document number: 3378949

Country of ref document: DE

Date of ref document: 19890223

ET Fr: translation filed
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19920430

Year of fee payment: 10

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19931101

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
EAL Se: european patent in force in sweden

Ref document number: 83901558.3

REG Reference to a national code

Ref country code: GB

Ref legal event code: IF02

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 20020328

Year of fee payment: 20

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20020403

Year of fee payment: 20

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: BE

Payment date: 20020416

Year of fee payment: 20

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CH

Payment date: 20020423

Year of fee payment: 20

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20020429

Year of fee payment: 20

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20020531

Year of fee payment: 20

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION

Effective date: 20030410

Ref country code: GB

Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION

Effective date: 20030410

Ref country code: CH

Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION

Effective date: 20030410

BE20 Be: patent expired

Owner name: *JAMES RIVER-DIXIE/NORTHERN INC.

Effective date: 20030411

REG Reference to a national code

Ref country code: GB

Ref legal event code: PE20

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

EUG Se: european patent has lapsed