Abstract:
A pressure pad suitable for use in the heat sealing of a substantial universe of bottom-panel folding designs for closing the bottom of a carton or container. This new pressure pad includes a pattern of sculpting of that surface thereof which is presented to the infolded panels of the bottom of a laminated paperboard carton thereby providing a pressure pad that is substantially universal with respect to its ability to repeatedly effect the desired heat sealing of a plurality of geometrically differing combinations of bottom panels defining the bottom of a paperboard carton.

Description:
FIELD OF INVENTION 
     This invention relates to methods and apparatus for the forming of folded, generally tubular, cartons from cut blanks and particularly to methods and apparatus for forming the closed bottoms of such cartons employing heat and pressure. 
     BACKGROUND OF INVENTION 
     In the manufacture or cartons for milk, juices and other liquids in common sizes of quarts, 2-liter and half-gallons, it is common practice to cut blanks of the carton from a sheet of multi-layered, laminated, paperboard which includes a thermoplastic polymeric material, such as polyethylene on its exterior surfaces. These blanks include cut edges which are free of the thermoplastic. The blanks commonly are scored along fold lines to define multiple panels, and subsequently erected into a four-sided tubular geometry. This formed tube is thereafter fitted onto a mandrel having a flat outboard end. While on this mandrel, the bottom-forming panels of the blank are infolded toward the longitudinal centerline of the tube to define a closed bottom of the tube. The infolded bottom panels are captured between the flat end of the mandrel and a pressure pad disposed externally of the tube. Application of heat to the panels and pressure via the pressure pad, effects heat sealing of the bottom-defining panels to one another to complete the bottom. 
     It will be noted from FIG. 1 herein that each of the outer perimetral edges of a blank is a cut edge. Each such edge is free of thermoplastic material and therefore is susceptible to absorption and wicking of liquid into the interior structure of the paperboard with consequential weakening of the carton wall or bottom. 
     A typical carton bottom includes at least first and second bottom panels disposed opposite one another across the bottom of the carton and which are designed to be infolded toward the longitudinal centerline of the tubular carton. This infolding defines two multiple-layered generally triangular segments of the bottom, the apices of the triangular segments being disposed adjacent one another at or near the longitudinal centerline of the carton. Others of the bottom panels are of generally rectangular geometry and are infolded toward the centerline of the carton to position their outboard side edges transverse of the carton bottom and lying generally at or adjacent one of the transverse centerlines of the plane of the carton bottom. Each of these other bottom panels commonly comprises a single ply or layer of the paperboard, but as the panels are folded inwardly to define the bottom of the carton, multiple layers of paperboard are developed in certain, but not all, areas of the bottom of the carton. Moreover, (a) the number of layers may vary between one and five layers, for example, (b) the location of the those areas which include more than one layer of paperboard frequently are not contiguous over the bottom of the carton, and (c) the actual area of the bottom which is defined by a given number of layers varies in size (e.g., two or more areas of four layers thickness may be at different locations over the area of the bottom. These and other factors militate against the desired uniform application of that sealing pressure and heat distribution over the area of the bottom of the carton which will result in full effective sealing of the bottom panels. In the prior art, it has been the practice to provide a patterned pressure pad which includes a pattern of raised areas on that surface of the pad which engages the infolded bottom panels. For each folding configuration of the bottom panels of a paperboard carton, heretofore, there has been provided a specifically patterned pad. These prior art pressure pads are basically designed to develop inordinately large pressure in selected regions of the carton bottom in an attempt to over compensate the pressure aspect of the heat sealing operation, the theory being that higher pressure in a given area will ensure a good seal in such area. The result of these prior art pressure pads is deleterious compression of the thickness of the paperboard in these high pressure areas. In use of the carton, these “thin walled” areas of the paperboard tend to develop leaks in the carton, especially the carton bottom. 
     Each fold in a bottom panel presents a possibility of leakage of liquid into or from the carton. Heat sealing of the bottom panel along the folds thereof is complicated by the relative bulkiness of the panels at these folds. Caution must be exercised in squeezing of the folds in that excessive squeezing of a fold between the pressure pad and the mandrel can create weakened areas in the folds which can be the source of leakage of liquid into or from the carton in the course of its life from formation through consumer use. 
     Still further, the presence of portions of the cut edges of the blank within the bottom of the carton are particularly susceptible to liquid absorption and wicking. In an effort to reduce the overall exposed area of one or more of the cut side edges of the bottom panels and to permit these side edges to more effectively be sealed within the bottom of the carton, these cut side edges may be skived, then folded back upon themselves and bonded together in an effort to eliminate exposure of a cut edge of the blank to liquid and elimination or reduction of wicking of liquid at the cut edge of the blank. The skived and back-folded side edges of a panel present a still further thickness value (ie, a thickness of more or less than one layer of the paperboard) to be dealt with in the formation of the bottom of the carton. In addition to the consideration of the thickness of the skived and back-folded panel edges, consideration must be given to the width of the back-fold to ensure full sealing of this side edge against the wicking of absorbed liquid along the length dimension of the side edge if liquid happens to bypass other sealing locations associated with the side edge. 
     All of these militating factors associated with the heat sealing of the bottom panels of a carton bottom are made more problematic by the industry practice of designing different geometric configurations of the bottom panels of the carton. As will be recognized, each different combination of geometric configurations of the bottom panels brings about different heat sealing requirements for each given combination of bottom panels. In one known instance, as many as twenty different bottom panel combinations exist for forming the bottom of a paperboard tubular carton for different liquid contents of the carton. As a consequence, each pressure pad must be especially designed for use with a specific combination of paperboard and folding pattern for a given carton. Thus, when it is desired to change from one bottom folding design to another design, it has been necessary that the carton-forming apparatus be taken off-line and the pressure pads thereof changed. Commonly, carton-forming apparatus includes a plurality of mandrels mounted on a carousel so that many pressure pads must be changed each time there is a switch between bottom folding designs. In addition to the time and expense of this pad changeout procedure, it is required that the manufacturer maintain an inventory of each type of pressure pad, at substantial cost to the manufacturer. 
     For many years, the industry has sought a pressure pad which is universal with respect to the number of different carton bottom geometrical configurations which can be successfully sealed with the pad. This search has been partially confounded by the further need for locating, i.e., alignment of, the infolded bottom panels of the intended carton bottom with respect to the pressure pad. Misalignment of the pad relative to the infolded panels of the carton bottom can result in each seal being misaligned with respect to the infolded panels. Such misalignment can result in complete or partial failure of seal formation and/or in deleterious thinning out of the paperboard at various locations over the area of the bottom of the carton, such as in the folds, and resultant premature failure of the bottom of the carton in use. In the prior art, as each pressure pad was designed to accommodate a variety of carton bottom designs, the need for proper alignment increased, thereby discouraging the use of such pads. 
     Further, alignment (ie., spacing apart) of the exposed sculpted surface of the pressure pad relative to the flat surface of a mandrel disposed internally of the tubular carton and in opposition to the pressure pad, is also required to ensure proper separation distance between the mandrel surface and the exposed surface of the pressure pad. Otherwise, there may be more or less of the required pressure applied to the panels of the carton bottom which are captured between the mandrel and pressure pad, with the result being possible rupture of the folds of the panels, incomplete sealing of the panels to one another, and/or the application of excessive pressure in some regions of the bottom, and insufficient pressure in other regions of the bottom. In this respect it is to be noted that known carton-making machines which employ a mandrel fitted inside the tubular carton for forming the closed bottom of the carton, include a pressurized piston-cylinder device mounted in alignment with the mandrel. This cylinder has the pressure pad mounted on the end of the piston for movement of the piston toward and away from the mandrel. Adjustment of the position of the cylinder and its piston and pad mounted thereon relative to the mandrel is provided for so as to permit adjustment of the position of the pressure pad relative to the mandrel. 
     In one common design for the bottom of a paperboard carton for liquids, a portion of the  5 th panel, integrally bonded to a side edge of one of the bottom panels, extends into the bottom of the carton. This design creates unusual sealing problems so that alignment of the pad and mandrel in this area of the carton bottom has been used for aligning the pad and mandrel. Heretofore, it has been the practice to attempt a first trial alignment of the pad and carton bottom, perform a few trial sealing operations, and then visually observe whether the “stake” seals associated with the 5 th  panel are properly aligned with the 5 th  panel. If misalignment was observed, the entire alignment process was repeated until proper alignment was achieved. 
     SUMMARY OF INVENTION 
     In accordance with one aspect of the present invention, the inventors have discovered a pressure pad which is suitable for use in the heat sealing of a substantial universe of bottom-panel folding designs. This new pressure pad includes a pattern of sculpting of that surface thereof which is presented to the infolded panels of the bottom of a laminated paperboard carton which provides a pressure pad that is substantially universal with respect to its ability to repeatedly effect the desired heat sealing of a plurality of geometrically differing combinations of bottom panels defining the bottom of a paperboard carton. 
     To this end, the present inventors provide a pressure pad having that surface thereof which is presented to the infolded plurality of panels which make up the bottom of a carton, sculpted substantially in quadrants of the overall area of the bottom of the carton. The quadrants are defined by first and second diagonals mutually intersecting at the center of the pad and projecting therefrom through respective opposite corners of the pad to virtually divide that surface of the pressure pad which engages the infolded panels that define the bottom of the carton into substantially quadrantal regions, each of said quadrantal regions having one of their apices disposed at the center of the pad and each of their other apices disposed at a corner of the pad. In a preferred embodiment, an opposite two of the virtual quadrantal regions are of a size less than the virtual quadrantal regions defined by the two diagonals of the pad, and an opposite further two of the virtual quadrantal regions are of a size greater than the virtual quadrantal regions defined by the two diagonals of the pad. By this means, the oblique side edges of a first quadrantal region overlap into side margins of adjacent third and fourth quadrantal regions, and the oblique side edges of a second quadrantal region overlap into others of the side margins of the adjacent third and fourth quadrantal regions. 
     At least one of the quadrantal regions includes a first sculpted projection having a flat outboard surface disposed substantially parallel to the central cross-sectional plane of the pad and extending to a first height from that surface of the pad facing the mandrel and defining a platform for establishing the separation distance between the pad and the mandrel. 
     Further, each of the quadrantal regions includes a sculpted surface including at least one further projection extending from the sculpted surface of the pad and defining a flat outboard surface which faces the mandrel and which is oriented in a plane that is essentially parallel to the cross-sectional plane of the pressure pad, and which extends to a height from that surface of the pad facing the mandrel, such height being less than the first height and being a function of the wall thickness of the paperboard from which the carton is formed. In selected areas of the present pressure pad, reliefs may be defined as desired to receive therein portions of the bottom panels of the carton. 
     In a specific embodiment, each projection or relief is adapted to accommodate the application of that pressure required for heat sealing differing thicknesses of the paperboard, such as the common triangular portions of infolded bottom panels, (gussets) which include multiple layers of the paperboard. Still further areas of the surface of the pressure pad are sculpted to accommodate the sealing of a stretch of skived side edge of one or more of the bottom panels. 
     In one aspect of the present invention, the inventors have found that displacement of the outer extremes of at least some of the sculpted areas of the pad, in spaced apart relationship from the folds formed by the infolding of the gussets of the panels, reduces the likelihood that the bottom sealing operation will adversely affect the fold itself and tend to create a possible source of future leakage. 
     In accordance with another aspect of the present invention, alignment of the pressure pad with the bottom of the carton is achieved by alignment of centrally disposed triangular areas of the pad, with portions of the sides edges of facing apices of the two opposing infolded gussets which comprise the multi-layered triangular folds of the bottom. This feature substantially reduces the time and effort required to achieve proper alignment of the pad with the bottom, and assures that all the out-lying pressured areas generated by the pad will be located properly relative to their desired locations and that each of the heat seals generated through the use of the pressure pad will be consistently disposed in the desired location relative to the bottom of the carton. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a plan view of a typical prior art blank from which a carton of the type referenced herein may be formed; 
     FIGS. 2 a-   2   d  are perspective views of a “J”-bottom end of a carton and depict the process of infolding of the bottom panels of the blank to close and form the bottom of the carton; 
     FIGS. 3 a-   3   d  are perspective views of the bottom end of a further carton and depict a further process of infolding of the bottom panels of the blank to close and form the bottom of the carton; 
     FIG. 4 is a partial sectional view taken generally along the line  4 — 4  of FIG. 2 d  and depicting the back folding of a portion of one cut edge of a bottom panel; 
     FIG. 5 is a partial sectional view similar to FIG.  4  and taken generally along the line  5 — 5  of FIG. 3 d , and depicting a one cut edge of a bottom panel underlying a further cut edge of a further panel; 
     FIG. 6 is a plan view depicting sculpted surface of a pressure pad embodying various of the features of the present invention; 
     FIG. 7 is a plan view as in FIG. 6, and including coolant conduits depicted in phantom within the interior of the pad of FIG. 6; 
     FIG. 8 is a plan view as in FIG. 6, and partially depicting a carton bottom overlaid over the depicted pad; 
     FIG. 9 is a plan view of the exterior surface of one embodiment of a carton bottom formed employing a pressure pad of the present invention; 
     FIG. 10 is a plan view of the interior surface of the carton bottom depicted in FIG. 9; 
     FIG. 11 is a schematic representation of a bottom-forming portion of carton-forming device; and, 
     FIG. 12 is a graphic representation of the relationship of the height of a projection relative to the thickness of paperboard disposed between the projection and the mandrel. 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     With reference to FIG. 1, a typical blank for a prior art carton of the gable-top variety is identified generally by the numeral  10 . The prior art blank  10  includes first through fourth rectangular side wall panels  12 ,  14 ,  16 , and  18  and heat-sealable side glue panel (5 th  panel)  20  which are consecutively articulated to one another along parallel fold lines  22 ,  24 ,  26  and  28  respectively. The first side wall panel  12  is further defined by a raw edge of paperboard material  30  which extends parallel to the fold line  22 . A first bottom fold line  32  and a first top fold line  34  extends between the raw edge  30  and the fold line  22  to further define the first side panel  12 . 
     A first bottom panel  36  is articulated to the first side panel  12  of the blank  10  along the first bottom fold line  32 . The first bottom panel  36  is further defined by a side raw edge  38  which extends generally colinearly from the raw edge  30 . The first bottom panel  36  is further defined by a fold line  40  which extends colinearly from the fold line  32  and by a bottom raw edge  42  which extends between the side raw edge  38  and the fold line  40 . The bottom raw edge  42  typically will be disposed at an interior location on the gable carton formed from the prior art blank  10 . In the depicted embodiment, the bottom raw edge  42  includes a rectangular tab  41  disposed centrally of the length of the raw edge  42  and defined by first and second cuts  43  and  45  and a fold line  47 . Further, the opposite ends of the raw edge  42  are provided with cutaway portions  49  and  51  which aid in the insertion of this raw edge during the infolding of the bottom panels to define the bottom of the carton. 
     The second side panel  14  is further defined by a second bottom fold line  44  and a second top fold line  46 . A second bottom panel  48  is articulated to the second side panel  14  along the second bottom fold line  44 . The second bottom panel  48  is further defined by converging fold lines  50  and  52 . A triangular web panel  54  is articulated to the second bottom panel  48  along the fold line  50  and is articulated to the first bottom panel  36  along the fold line  40 . The triangular web panel  54  is further defined by a raw edge  56  extending between the fold lines  40  and  50 . Similarly, a triangular web panel  58  is articulated to the second bottom panel  48  along fold line  52 . The triangular web panel  58  is further defined by fold line  60  which extends colinearly from the fold line  24  and by raw edge  62  which extends between the fold lines  52  and  60 . 
     The third side panel  16  of the blank  10  is further defined by a third bottom fold line  64  and a third top fold line  66 . A third bottom panel  68  is articulated to the third side panel  16  along the third bottom fold line  64 . The third bottom panel  68  is articulated to the bottom web panel  58  along fold line  60  and is further defined by a side raw edge  70  extending colinearly from the fold line  60  and generally orthogonal to the raw edge  62  of bottom web panel  58 , a transverse raw edge  72  which extends orthogonally from the side raw edge  70  a major distance across the third bottom panel  68 ; and, diagonal raw edge  74  which extends between the bottom raw edge  72  and the fold line  76 . As will be explained further below, the third bottom panel  68  defines an external wall on the carton erected from the blank  10  and the raw edges  70 - 74  of the third bottom panel  68  are substantially exposed on exterior regions of the carton. 
     The fourth side panel  18  of the blank  10  is further defined by a fourth bottom fold line  78  and a fourth top fold line  80  which extend orthogonally between the fold lines  26  and  28 . A fourth bottom panel  82  is articulated to the fourth side panel  18  along the fold line  78 . The fourth bottom panel  82  is further defined by converging fold lines  84  and  86 . A triangular bottom web panel  88  is articulated to the third bottom panel  68  along fold line  76  and is further articulated to the fourth bottom panel  82  along fold line  84 . The web panel  88  is further defined by a raw edge  90  which extends orthogonally to the fold line  76  to the intersection of fold lines  84  and  86 . The triangular bottom web panel  92  is further defined by a raw cut edge  96  which extends orthogonally from the fold line  94  to the intersection of fold lines  84  and  86 . 
     The heat sealable side panel  20  of the blank  10  is further defined by top and bottom fold lines  98  and  100  and by a raw side edge  102 . A bottom heat sealable panel  104  is articulated to the web panel  20  along fold line  100  and to the heat sealable side panel  20  along fold line  100 . The bottom heat sealable side panel  104  is further defined by a diagonal raw edge  106  and a side raw edge  108  which extends colinearly from the side edge  102 . 
     In the blank depicted in FIG. 1, the edge  42  of the bottom panel  36  is provided with a tab  41  disposed centrally between the opposite ends of the edge  42 . This tab is formed by cuts  43  and  45  which extend perpendicularly from the edge  42 , and inwardly of, the panel  36 . A fold line  47  is provided for facilitating the folding of the tab  41  back upon the panel  36 . This aspect of the blank is at times referred to in the art as a “J-fold”. 
     The blank  10  depicted in FIG. 1 is also provided with a plurality of top panels indicated generally by the numerals  110 - 116 . These top panels are foldable to define the well-known gable top closure of the carton. These panels are not pertinent to the present invention. 
     The prior art blank  20  is commonly cut and scored by the paperboard manufacturer. The paperboard manufacturer also typically will fold the heat sealable panels  20  and  94  (and pertinent portions of the top panels) relative to the remainder of the prior art blank  10  about the colinear fold lines  28 , and  94 , respectively. The entire blank  10  will further be folded substantially in half about the colinear fold lines  24  and  60 . The heat sealable panels  20  and  104  will be adhered to sides for the first side panel  12  and the first bottom panel  36 . It will be appreciated that in the condition described above, the folded blank will be substantially flat with the first side panel  12  being in substantially face-to-face relationship with the fourth side panel  18  and with second side panel  14  being in substantially face-to-face relationship with the third side panel  16 . The folded blank  10  then typically will be shipped from the paperboard manufacturer to the dairy or producer of some other liquid to be stored in the carton formed from the blank  10 . 
     The dairy or other such producer of liquid to be stored in the carton formed from the blank  10  will have equipment for forming and sealing the ends of the carton. The equipment will be operative to form the collapsed blank  10  into a generally tubular open ended structure. The bottom end of the tubular structure is closed by rotating the second and fourth bottom panels  48  and  82  inwardly about the second and fourth bottom fold lines  44  and  78  respectively. The first and third bottom panels  36  and  68  will then be rotated inwardly about the first and third bottom fold lines  32  and  64  respectively. This latter folding is carried out such that the first bottom panel  36  leads the third bottom panel  68 . Thus, the bottom raw edge  42  of the first bottom panel  36  will be disposed interiorly relative to the third bottom panel  68 . However, the side raw edge  38  of the first side bottom panel  36  will be substantially exposed along a bottom edge of the carton formed from the blank  10  as shown in FIGS. 3A-3D. Similarly, the raw edges  70 - 74  of the third bottom panel  68  will be exposed in a position extending substantially centrally across the bottom of the carton formed from the blank  10 . The folded bottom panels  36 ,  48 ,  68  and  82  are adhered in overlapping relationship to one another by an appropriate heat sealing operation. This step of the carton forming process is carried out by placing the tubular carton with its folded bottom onto a mandrel having an outboard flat surface (See FIG. 11) as is well known in the art. The sealing of the bottom of the carton is achieved by appropriate application of heat to the bottom panels, followed by pressure from the pressure pad working against the mandrel. 
     The paper board material from which the prior art blank  10  is formed is a laminate which includes a major layer of a fibrous material having a natural tendency to absorb liquids. The opposed faces of the blank  10  typically will be coated with a thermo plastic to render these faces heat sealable, among other reasons. However, raw edge regions of the cut blank  10  are capable of absorbing liquid, and function as wicks which enable the liquids to travel from one location in the paperboard material to another location. Absorption of liquids and wicking from edge regions of the heat sealable panels disposed interiorly of the carton, including bottom heat sealable side panel  104 , can be prevented by grinding away all or a major portion of the paperboard material along the raw edge but leaving the coating. The remaining coating can then be folded over the raw edge of the remaining paperboard material to effectively seal this interiorly disposed edge and prevent absorption and wicking i.e., developing a skived edge  102 , 108 . This action narrows the heat sealable panels  20 , 104 . 
     FIG. 4 depicts a cross-sectional view of one embodiment of the bottom of a carton wherein the panel of the blank includes a tab  41  which is folded back upon the panel  36 . In this embodiment, the tab is partially overlaid by the edge  72  of the panel  68  as depicted in FIGS. 2 a-   2   d . In the embodiment of FIGS. 3 a-   3   d  and  5 , there is depicted a similar cross-section of the bottom of a carton wherein panel  68 ′ is overlaid panel  36 ′, without a back folding panel such as panel  41  of FIGS. 2 a - 2   d , and exposing the raw edge  42 ′, which is in underlying relationship to panel  68 ′, as depicted in FIGS. 3 a - 3   c . FIG. 5 a cross sectional view of FIG. 3 d , and depicts a view of the bottom of a carton in which the edge  42 ′ of panel  36 ′ is exposed in an underlying relationship to the panel  68 ′. Other versions of the infolding of the bottom panels of the carton will be recognized by one skilled in the art. 
     Referring to FIGS. 6-8 and  11 , in one embodiment, the pressure pad  120  of the present invention comprises a rigid solid square/rectangular block of metal, such as a stainless steel alloy having first, second, third and fourth side edges  121 ,  123 ,  125  and  127 , (see FIGS. 6-8) respectively, first and second transverse centerlines  129  and  135 , respectively, (FIGS. 6 and 7) a cross-sectional plane  192 , and a longitudinal centerline  133  extending through the thickness dimension of the pad. The pad is essentially non-compressible and does not flex under the pressure applied thereto in the course of forming the bottom of a carton. 
     The depicted pad  120  includes a first surface  122  which is intended to be mounted on a mounting block  121  which is adjustable secured, as by a bolt  123 , on the outboard end  124  of the reciprocating piston rod  126  of a piston-cylinder device indicated generally by the numeral  128  as is well known in the industry. In the preferred embodiment, the pad  120  is releasably secured to the mounting block as by means of bolts  130 ,  132 . As is also well known in the art, the piston-cylinder device is mounted so as to be adjustable with respect to its position relative to a mandrel  134  onto which a tubular carton  136  is fitted in position for heat sealing of the infolded bottom panels of the carton bottom. These infolded bottom panels are indicated generally by the numeral  138  in FIG.  11  and are depicted as being captured between the flat outboard surface  140  of the mandrel  134  and an exposed surface  142  of the pressure pad  120 . Typically, in the course of forming and closing the bottom of a carton, the carton is placed on the mandrel, the bottom panels are infolded and heated to the fusion temperature of the thermoplastic outer layer of the paperboard laminate. The mandrel is then rotated to align the heated infolded bottom panels between the outboard end of the mandrel and the pressure pad. Thereupon, the piston-cylinder device is activated and the pressure pad is urged against the heated infolded bottom panels with a preselected pneumatic pressure, such as about 100 psi. The force of the applied pneumatic pressure is evenly distributed over the entire surface  142  of the pad. The movement of the pressure pad toward the mandrel is limited to a preselected separation distance between the pressure pad and the mandrel. Thus, if the surface  142  of the pressure pad were uniformly flat and aligned substantially parallel to the outboard flat surface of the mandrel, the entire area of the infolded bottom panels which are captured between the pad and the mandrel will experience only about 5000 lbs of force. 
     With reference to FIGS. 6-8, and recalling that FIG. 8 depicts a carton bottom overlaid over the exposed surface of a pressure pad as depicted in FIGS. 6 and 7, the outboard surface  142  (FIG. 11) of the pressure pad of the present invention which faces the mandrel is sculpted to selectively adjust the pressure experienced by different areas of the bottom of the carton, as a function of the number of layers of paperboard that are present in a given area, when the pressure pad is urged into engagement with the infolded panels of the carton bottom. In accordance with one aspect of the present pressure pad, the outboard surface of the pressure pad is virtually (as opposed to “literally”) divided into first, second, third and fourth quadrantal regions,  150 ,  152 ,  154 , and  156 , respectively, as by diagonals  157 ,  159 . The apices  158 ,  160 ,  162 , and  164  of the quadrantal regions converge on the center  166  of the surface  142  of the pad. The side edges  168 ,  170  of the first quadrantal region extend from the center of the pad, diagonally to intersect the corners  172 ,  174  of the pad. In like manner, the side edges  176 ,  178  of the second quadrantal region extend from the center of the pad, diagonally to intersect the corners  180 ,  182  of the pad. The side edges  184 ,  186  of the third quadrantal region are common with the side edges  170  and  178 , respectively, of the first and second quadrantal regions  150  and  152 . Further, the side edges  188 , 190  of the fourth quadrantal region extend from the center of the pad, diagonally to intersect the corners  172  and  180  of the pad. The side edges  188 ,  190  of the fourth quadrantal region are common with the side edges  168  and  176 , respectively, of the first and second quadrantal regions  150  and  152 . 
     Within each of the quadrantal regions, there is provided at least one sculpted projection extending from the pad in a direction generally perpendicularly from the outboard surface  142  of the pad and having a flat outboard surface  196  facing the mandrel. Preferably, the flat outboard surface of each such sculpted projection is oriented substantially parallel to the cross-sectional plane  192  of the pad (see FIG. 11) and faces the mandrel when the pad and mandrel are aligned as depicted in FIG.  11 . 
     In the embodiment of the pressure pad of the present invention depicted in FIGS. 6-8, the first quadrantal region includes a first projection  194  extending from the pad in a direction generally perpendicularly from the outboard surface  142  thereof to a first height. This projection includes a flat outboard surface  196  which defines a platform for establishing a separation distance between the pad and the mandrel. This separation distance, in the depicted embodiment, establishes the stopping point of the movement of the pad toward the mandrel in a heat sealing operation, and as a point of reference from which the height of all other sculpted areas of the pad surface are established. By this means, the present invention provides for the magnification within selected areas or regions of the pressure pad of the overall pressure with which the pad is urged toward the mandrel. For example, the 5000 lbs overall force employed can be increased in selected areas or regions of the pressure pad through the sculpted projections of the present invention as a function of the number of layers of paperboard present in a given area of the carton bottom. Each projection presents a flat surface having an area which is less than the total area of the exposed surface  142  of the pad. 
     As depicted, a first projection  194  is of a generally triangular cross-section. The apex  200  of this cross-section is disposed at the center  166  of the pad and its side edges  202  and  204  are aligned substantially parallel to the side edges  168  and  170 , respectively, of the first quadrantal region  150 , but spaced apart therefrom. The spacing between the side edge  202  and the side edge  170  (see FIG. 8 also) accommodates therein a portion of the apical region of one side edge fold  208  of a first one  210  of first and second triangular gussets  210  and  212  formed by the infolding of the bottom panels  48  and  82 . Similarly, the spacing between the side edge  204  of the projection  194  and the side edge  168  accommodates therein a portion of the apical region of a side edge fold  209  of the second gusset  212 . As depicted, each of the side edge folds  208  and  209  of the gussets  210  and  212 , respectively, are substantially coincidental with respective legs  211  and  213  of the diagonals  170  and  168  respectively. 
     Between the area of the flat surface  196  of the first projection  194  and the mandrel, in the depicted embodiment, there is disposed only a single thickness of paperboard when tab  41  is back folded. However, due to the proximity of projection  194  to the side edge folds  208  and  209  of the gussets  210  and  212 , the height of the flat surface  196  is selected to be sufficient to result in no material compression of the single layer of paperboard. By this means, the side edge folds of each gusset are undamaged by excessive crushing there of by the applied sealing pressure. 
     The major remaining area of the first quadrantal region  150  comprises a second sculpted projection  216  having a flat surface  218  which projects to a height which is less than the height of the first projection  194  by an amount which is substantially equal to one-half the wall thickness of the paperboard times the number of layers of paperboard disposed between the area of the second projection and the mandrel. By this means, the pressure to which that area of the paperboard which is disposed between the flat surface  218  and the mandrel is subjected to only that pressure which compresses each layer (thickness) of the paperboard to its wall thickness. E.g., when the pressure pad is urged to its closest proximity to the mandrel during a heat sealing operation, the separation distance between the flat surface  218  of the second projection and the mandrel is substantially equal to the wall thickness of the depicted single layer of paperboard disposed within the area of the flat surface  218 . Thus, in the area where no heat sealing of the paperboard is desired, there is minimal, if any, compression of the wall thickness of the paperboard. 
     As depicted in FIGS. 3 a-   3   d , when tab  41  is not employed, between the area of the flat surface  196  of the first projection  194  and the mandrel, there is disposed a double thickness of paperboard. However, due to the proximity of projection  194  to the side folds  208  and  209  of the triangular gussets  210  and  212 , the height of the flat surface  196  is sufficient to result in that degree of displacement of the double layers of paperboard which will effect bonding of the overlying layers of paperboard in this crucial central area of the carton bottom where multiple-layered portions of the carton bottom exist in close, even contiguous, relationship to one another. 
     Within the second quadrantal region  152  there is provided a sculpted projection  220  of generally truncated triangular cross section extending from the pressure pad. The truncated end  222  of this cross-section is disposed adjacent the center  166  of the pad and the oblique portions  224  and  226  of its side edges  228  and  230  are aligned substantially parallel to the side edges  176  and  178 , respectively, of the fourth and third quadrantal regions  156  and  154 , respectively, but spaced apart therefrom. The spacing between the oblique side portions  226  and  224 , and the sides edges  178  and  176  (see FIG. 8) accommodates therein a portion of the apical region of a first side edge fold  215  of the first one  210  of the first and second triangular gussets  210  and  212  and a portion of the apical region of a first side edge fold  217  of the second gusset  212 , respectively. 
     The major remaining area of the second quadrantal region  152  comprises a third sculpted projection  240  having a flat surface  242  which projects to a height which is less than the height of the first projection  194  by an amount which is substantially equal to one-half the wall thickness of the paperboard times the number of layers of paperboard disposed between the area of the third projection  240  and the mandrel. By this means, the pressure to which that area of the paperboard which is disposed between the flat surface  242  and the mandrel is subjected to only that pressure which compresses each layer (thickness) of the paperboard to its original wall thickness. E.g., when the pressure pad is urged to its closest proximity to the mandrel during a heat sealing operation, the separation distance between the flat surface  242  of the second projection and the mandrel is substantially equal to the wall thickness of the single layer of paperboard disposed within the area of the flat surface  242 . Thus, in the area where no heat sealing of the paperboard is desired, there is minimal, if any, compression of the wall thickness of the paperboard, thereby retaining the strength and structural integrity of the paperboard. 
     Within the third quadrantal region  154  there are provided fifth and sixth sculpted projections  244  and  246 , respectively, each of which extends from the pressure pad to a height which is less than the first height by a distance approximately equal to the thickness of the paperboard from which the carton is formed. The fifth projection  244  is of a substantially right triangular cross-section having its side opposite  248  disposed along the side edge  178  of the second quadrantal region and spaced apart therefrom by a distance sufficient to receive therein the first folded side edge  215  of the first gusset  210  (see FIG.  8 ). By this means, the side opposite  248  of the fifth projection  244  is spaced inwardly of the first side edge fold  215  of the first gusset  210  so that the fifth projection applies sealing pressure to the gusset up to, but not directly to, first side edge fold  215 . Thus, in a sealing operation, the first side edge fold  215  of the first gusset  210  is not unduly compressed to the extent that this fold is damaged and becomes a possible source of leakage of liquid into or from the carton or into the interior of the paperboard with resultant weakening of the integrity of the paperboard in the area of this fold. 
     The first adjacent side  250  of the fifth projection is coincident with a portion of third side edge  125  of the pad and the second adjacent side  252  of the fifth projection  244  is disposed substantially parallel to, but spaced apart from, the second transverse centerline  135  of the pad. 
     The sixth projection  246  is also of a substantially right triangular cross-section having its side opposite  256  disposed along the side edge  170  of the second quadrantal region  150  and spaced apart therefrom by a distance sufficient to receive therebetween the second folded side edge  208  of the first gusset  210  (see FIG.  8 ). By this means, the side opposite  256  of the sixth projection  246  is spaced inwardly of the second folded side edge  208  of the first gusset  210  so that the sixth projection applies sealing pressure to the gusset up to, but not directly to, second folded side edge  208 . Thus, in a sealing operation, the second side edge fold  208  of the first gusset  210  is not unduly compressed to the extent that this fold is damaged and becomes a possible source of leakage of liquid into or from the carton or into the interior of the paperboard with resultant weakening of the integrity of the paperboard in the area of this fold. A first adjacent side  258  of the sixth projection  246  is coincident with a portion of the side edge  125  of the pad. The second adjacent side  260  of the sixth projection includes a first leg  262  which extends obliquely from the side edge  125  of the pad inwardly of the pad a distance sufficient to cause this leg  262  to overlie a tapered portion  264  (see FIG. 1) of the end edge  42  of the panel  36  when the bottom panels are infolded and captured between the pad and the mandrel. A second leg  266  is disposed substantially parallel to the second transverse centerline  135  of the pad and extends from the inward end of the first leg  262  to the intersection thereof with the side opposite  256  of the sixth projection. 
     Between the adjacent side  250  of the fifth projection and the adjacent side  260  of the sixth projection there is defined a seventh projection  270  which is disposed within the third quadrantal region and which is at a height which is less than the first height by a distance substantially equal to about twice the thickness of the paperboard from which the carton is formed. 
     Substantially within the third quadrantal region there is provided a eighth projection  272  of multiple sides which extends to a height which is less than the first height by a distance equal to approximately one-fourth the thickness of the paperboard from which the carton is formed. This eighth projection is disposed within the apical area  162  of the third quadrantal region and is generally of a rectangular cross-section having one of its corners truncated to define an oblique side  274  thereof. This truncated corner portion of the eighth projection extends out of the third quadrantal region and into the second quadrantal region such that the oblique side  274  thereof is aligned parallel to and generally along the side edge  178  of the second quadrantal region and is coincident with the oblique portion  226  of the third projection  220  disposed within the second quadrantal region. This eighth projection is thereby disposed in position to overlie one end of the tab  41  which is folded back upon the bottom panel  36  when the bottom panels are infolded to define the bottom of the carton, plus overlie a portion of the apical end of the first folded side edge  215  (see FIG. 8) of the first gusset  210  to provide enhanced pressure toward sealing of this side edge of the gusset to itself and to that portion of the tab which underlies the apical end of the side edge of the gusset. 
     Within the fourth quadrantal region of the depicted pressure pad there are provided ninth and tenth sculpted projections  280  and  282 , respectively, each of which extends from the pressure pad to a height which is less than the first height by a distance approximately equal to the thickness of the paperboard from which the carton is formed. The ninth projection  280  is of a substantially right triangular cross-section having its side opposite  283  disposed along the side edge  168  of the second quadrantal region and spaced apart therefrom by a distance sufficient to receive therein the first folded side edge  209  of the second gusset  212  (see FIG.  8 ). By this means, the side opposite  283  of the ninth projection is spaced inwardly of the first side edge fold  209  of the second gusset  212  so that the ninth projection applies sealing pressure to the gusset up to, but not directly to, first side edge fold  209 . Thus, in a sealing operation, the first side edge fold  209  of the second gusset  212  is not unduly compressed to the extent that this fold is damaged and becomes a possible source of leakage of liquid into or from the carton or into the interior of the paperboard with resultant weakening of the integrity of the paperboard in the area of this fold. 
     The first adjacent side  284  of the ninth projection is coincident with a portion of third side edge  127  of the pad. The second adjacent side  286  of the ninth projection includes a first leg  288  which extends obliquely from the side edge  127  of the pad inwardly of the pad a distance sufficient to cause this leg  288  to overlie a tapered portion  51  (see FIG. 1) of the side edge  42  of the panel  36  when the bottom panels are infolded and captured between the pad the mandrel. A second leg  290  is disposed substantially parallel to the second transverse centerline  135  of the pad and extends from the inward end of the first leg  288  to just short of the projected intersection of the second leg  290  and the side opposite  282  of the ninth projection. 
     The tenth projection  282  is also of a substantially right triangular cross-section having its side opposite  292  disposed along the side edge  176  of the second quadrantal region  152  and spaced apart therefrom by a distance sufficient to receive therebetween the second folded side edge  217  of the second gusset  212  (see FIG.  8 ). By this means, the side opposite  292  of the tenth projection is spaced inwardly of the second folded side edge  217  of the second gusset  212  so that the tenth projection applies sealing pressure to the gusset up to, but not directly to, the second folded side edge  217 . Thus, in a sealing operation, the second folded side edge  217  of the second gusset  212  is not unduly compressed to the extent that this fold is damaged and becomes a possible source of leakage of liquid into or from the carton or into the interior of the paperboard with resultant weakening of the integrity of the paperboard in the area of this fold. 
     A first adjacent side  294  of the tenth projection is disposed parallel to, but spaced apart from, a portion of the fourth side edge  127  of the pad and is of a length whereby this first adjacent side  294  is disposed intermediate the first transverse centerline  129  and the fourth side edge  127  of the pad. A second adjacent side  296  of the tenth projection is disposed parallel to, but spaced apart from, the second transverse centerline  135  of the pad such that the first and second adjacent sides  294 , 296  of the tenth projection, the adjacent side  286  of the ninth projection, a portion of the fourth side  127  of the pad, and a portion of the second side  123  of the pad define therebetween an eleventh projection  298  of generally “L” shaped geometry and which is disposed within the fourth quadrantal region. One leg  300  of this eleventh projection is disposed parallel to the fourth side edge  127  of the pad, and extends from approximately the second transverse centerline line  135  of the pad fully to that corner  180  of the pad which is common to the second and fourth quadrantal regions. The other leg  302  of this eleventh projection is disposed substantially parallel to the second transverse centerline  135  of the pad. This eleventh projection is of a height which is less than the first height by a distance substantially equal to about twice the thickness of the paperboard from which the carton is formed. 
     Further within the fourth quadrantal region of the pad of the present invention there is provided a plurality of elongated stakes  304 , which are aligned with one another and which are disposed transversely of the first adjacent side  294  of the tenth projection. Substantially one-half the length of each stake is disposed on each of the opposite sides of the first adjacent side  294  of the tenth projection so that one-half of each stake is located within the area of the tenth projection  282  and the other half thereof is located within the leg  300  of the eleventh projection  298 . That half of each stake which is disposed within the area of the tenth projection extends to a height which is less than the first height by a distance approximately equal to about one-half the thickness of the paperboard from which the carton is formed. That half of each stake which is located within the area of the eleventh projection extends to a height which is less than the first height by a distance approximately equal to about one thickness of the paperboard. In this respect, it is to be noted that the cut side edge  108  of that portion  104  of the 5 th  panel which extends into the bottom of the carton, underlies at least the first adjacent side  294  of the tenth projection. Thus, the stakes  304  are located so that they apply sealing pressure transversely of the cut side edge  108  of the 5 th  panel and ensure sealing of this cut side edge against wicking along the cut side edge of the 5 th  panel of any liquid which may be absorbed through this cut side edge. The height of that half of the stakes which are located within the area of the tenth projection is such as will accommodate the single-layer thickness of the side edge  108 . Further, in the event the cut side edge  108  is skived and folded back upon itself, the fold of the side edge  108  falls fully within the area of the leg  300  of the eleventh projection. This skived and folded back side edge presents a paperboard thickness greater than a single thickness of the paperboard, hence the height of those halves of the stakes which are located within the area of the eleventh projection accommodate such increased paperboard thickness(es) to perform a proper seal, but without undue crushing and damage to the side edge  108  of the 5 th  panel. 
     Optionally, but preferably, one or more further stakes, such as stakes  310 - 332 , may be located at strategic locations on the pad to enhance the assurance of non-wicking of any liquid which may be absorbed into the paperboard through a cut edge thereof. 
     Substantially within the fourth quadrantal region there is provided a twelfth projection  340  of multiple sides which extends to a height which is less than the first height by a distance equal to approximately one-fourth the thickness of the paperboard from which the carton is formed. This twelfth projection is disposed within the apical area  164  of the third quadrantal region and is generally of a rectangular cross-section having one of its corners  342  truncated to define an oblique side  344  thereof. This portion of the twelfth projection extends out of the third quadrantal region and into the second quadrantal region such that the oblique side  344  thereof is aligned parallel to and generally along the side edge  176  of the second quadrantal region and is coincident with the oblique portion  224  of the third projection  220  disposed within the second quadrantal region. This twelfth projection is thereby disposed in position to overlie one end of the tab  47  which is folded back upon the panel  36  when the bottom panels are infolded to define the bottom of the carton, plus overlie a portion of the apical end of the first folded side edge  217  of the second gusset  212  to provide enhanced pressure toward sealing of this side edge of the gusset to itself and to that portion of the tab which underlies the apical end of the side edge of the gusset. 
     As noted, the blank  10  depicted in FIG. 1 is representative of the blanks currently employed in the industry. With particular reference to FIG. 8, it is to be noted that the pressure pad of the present invention includes sculpted areas which are located on the exposed surface of the pad in position to overlie a wide variety of combinations of the geometrical designs of the bottom panels depicted in FIG.  1 . For example, as depicted in FIGS. 2A-2D and  3 A- 3 D, the bottom panels may or may not included a folded-back tab (at times referred to in the art as a “J-flap”) which are presently in common use in the industry. Most all known cartons of the type referenced herein include first and second gussets defined in the infolded bottom panels of the carton. Importantly in the present invention is the fact that the fifth, sixth, ninth and tenth projections provide spacing between their respective side opposites and the respective folded side edges of the two gussets. This separation has been found to reduce the compression of these folded side edges to thereby decrease the incidence of destruction or damage to the folded side edges of the gussets. In one particular embodiment, this separation distance is about 0.030 inch. In accomplishing this aspect of the present invention, it is important that the combined areas of the fifth and sixth projections be less than the overall area of the first gusset which underlies these projections, and in like manner, that the combined areas of the ninth and tenth projections be less than the overall area of the second gusset. Still further, it has been found useful in the present pressure pad to provide a relief  350 ,  352 , and  354  (FIG. 7) in the approximate central area of each of the fifth, sixth and ninth projections, respectively. Each of these reliefs are at a height which is less than the first height by a distance approximately equal to about three thickness of the paperboard thereby providing ample “free” space into which the uncompressed paperboard may move as the outer peripheries of the fifth, sixth and ninth projections compress their respective underlying areas of the gussets. 
     As also noted, alignment of the present pressure pad with the mandrel, hence the infolded bottom panels overlying the exposed face of the mandrel, to ensure that each of the sculpted projections of the pressure pad register with their desired underlying bottom panel and/or side edge of the bottom panels, is readily accomplished by positioning the first and third generally triangular projections in register with the side edges of the gussets in the apical regions of the gussets, as opposed to the prior art technique of attempting alignment of the plurality of elongated stakes with the side edge of that portion of the 5 th  panel which extends into the bottom of the carton. A further advantage is gained with the present invention by employing the first projection as the “ground-level” from which all other heights of the various projections are set. Use of the first projection in this manner has been found to permit the ready calculation of the heights of all other projections as a function of the number of thickness of paperboard which is to underlie each such other projection. This factor permits the application of substantially uniform pressure per square inch to all areas of the infolded bottom panels which define the bottom of the carton as opposed to the prior art concept of applying greater pressure per square inch over only those areas where there is believed to be a need for “extra” sealing pressure. It is therefore possible when employing the pressure pad of the present invention to choose a given overall pressure per square inch to be applied to the pad and to distribute this same pressure per square inch uniformly over all areas of the sculpted and non-sculpted areas of the exposed surface of the pad. Under these circumstances, in the depicted embodiment of the present pressure pad, no layer of the paperboard is compressed to greater than about one-half its thickness, with the exception of the areas of the gussets which underlay the fifth, sixth and ninth projections. In these areas which need relatively greater compression to ensure good physical contact between the layers of each gusset, there is made available the greater compression of the thicknesses of the layers of paperboard, but notably without deleterious effect upon the sensitive side edge folds of these gussets. 
     In FIG. 12, there is depicted graphically the relationship of various of the sculpted projections for one embodiment of the present pressure pad. This graph assumes a paperboard thickness of about 0.025 inch and that the height of the first projection is taken as 0.000 inch. 
     Whereas the present invention has been described in detail, it is to be recognized that variations are possible with respect to certain aspects of the invention and it is intended that the invention be limited only as set forth in the claims appended hereto.