Abstract:
Apparatus and method for conditioning an edge of a sheet to be bound so that the edge is conducive to accepting heat activated adhesives used in conventional binding. The sheet is first bent in one direction to form a folding line, with the fold line being a short distance from the edge of the sheet to be conditioned and with that distance being determined primarily by the thickness of the sheet. The bend in the sheet is typically 90 degrees, with the radii of curvature of the opposite sheet surfaces at the fold line being unequal so that a shear force is applied near the sheet end thereby tending to tear or fracture in interior of the sheet near the end. Typically the sheet is then bent in an opposite direction along the folding line so as to produce an opposite shear force that reinforces the creation of tears and fractured in the sheet. These tears and fractures in the sheet greatly enhance the adhesion of binding adhesives to the sheet, particularly sheets having coatings used in photographic applications and the like.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to the field of bookbinding and in particular to apparatus for preparing a stack of sheets to be bound for binding.  
         [0003]     2. Description of Related Art  
         [0004]     Bookbinding apparatus have been developed which permits stacks of sheets to be bound using thermally activated adhesive binder strips. Such binder strips are typically applied using relatively low cost desktop binding machines such as disclosed in U.S. Pat. No. 5,052,873, the contents of which are also incorporated herewith by reference. Referring to the drawings,  FIG. 1  shows a binder strip  20  disposed adjacent the insertion point  30 A of a conventional binding machine  30 . A user first inserts a stack of sheets  32  to be bound in an upper opening of the machine. Controls  30 B are then activated to commence the binding process. The binding machine operates to sense the thickness of the stack  32  and indicates on a machine display  30 C the width of binder strip  20  to be used. Typically, three widths can be used, including wide, medium and narrow. The binder strip includes a flexible substrate  20 A having a length that corresponds to the length of the edge of the stack  32  to be bound and a width somewhat greater than the thickness of the stack. A layer of heat-activated adhesive is formed on one side of the substrate, including a low viscosity, low tack central adhesive band  20 C and a pair of high viscosity, high tack outer adhesive bands  20 B.  
         [0005]     Once the user has selected the binder strip of appropriate width, the user manually inserts the strip  20  into the strip loading port  30 A of the machine. The end of the strip, which is positioned with the adhesive side up, is sensed by the machine and is drawing into the machine using an internal strip handling mechanism. The machine then operates to apply the strip to the edge of the stack to be bound. The strip is essentially folded around the edge of the stack, with heat and pressure being applied so as to activate the adhesives. Once the adhesives have cooled to some extent, the bound book is removed from the binding machine so that additional books can be bound.  FIG. 2  depicts a partial end view of the bound stack  32 . As can be seen, the substrate  20 A is folded around the bound edge of the stack. The high tack, high viscosity outer adhesive bands  20 B function to secure the strip to the front and back sheets of the stack. These sheets function as the front and rear covers and can be made of heavy paper or the like. The central, low viscosity adhesive  20 C functions to secure the individual sheets of the stack by flowing up slightly between the sheets during the binding process.  
         [0006]     Although the above-described binding technique provides a reliable bind in most applications, problems arise when the sheets of the stack have special coatings. Such coatings are applied to the sheets for various purposes to enhance the characteristics of the sheet, such as improving the ability of the sheet to receive special printing inks. In any event, such coatings very frequently prevent the central adhesive  20 C from adhering adequately to the individual sheets of the stack. This results in an unsatisfactory bind where sheets frequently separate from the stack. Various approaches have been used to address this problem. One approach is to use different types of adhesive for the central adhesive  20 C. Another approach is to texturize the stack of sheets prior to binding so that the adhesive is more likely to accept the central adhesive. By way of example, in U.S. Pat. No. 5,961,268 entitled “Method and Device for Adhesive Binding of Printed Products”, a rotating wire brush is applied to the edge of a stack of sheets prior to binding. This approach has not been found satisfactory in addressing the problems relating to coated papers. As a further example, prior art binding systems commonly referred to as perfect binding incorporate milling apparatus that grinds or mills the edge of a stack to be bound. However, stacks of coated sheets processed in this manner cannot be reliably bound using most thermal activated adhesives. Further, such milling results in the production of debris that must be removed and disposed of during the subsequent binding process.  
         [0007]     There is a need for an apparatus and method for conditioning a stack of sheets, prior to binding, that will permit the stack to be reliably bound using conventional thermal adhesive binder strips as previously described. As will be apparent to those skilled in the art upon a reading of the following Detailed Description of the Invention together with the drawings, the present invention meets these and other requirements. Once a stack of coated sheets has been conditioned in accordance with the present invention, a reliable bind can be achieved using conventional relatively low cost desktop binding equipment and binder strips.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a perspective view of a conventional binding machine for use in binding stacks of sheets, including stacks conditioned in accordance with the present invention.  
         [0009]      FIG. 2  is an end elevational view of a stack of sheets bound by conventional thermally activated adhesive binder strips using the binding machine of  FIG. 1 .  
         [0010]      FIG. 3A  illustrates an initial step in the process of conditioning a cut sheet of paper in accordance with one aspect of the present invention where a bending member is positioned adjacent a sheet to be conditioned.  
         [0011]      FIG. 3B  is an expanded view of a portion of  FIG. 3A .  
         [0012]      FIG. 4A  illustrates a further step in the process of conditioning a cut sheet of paper in accordance with one aspect of the present where the bending member has moved to the right thereby folding the edge of the sheet being conditioned.  
         [0013]      FIG. 4B  is an expanded view of a portion of  FIG. 4A .  
         [0014]      FIG. 4C  is a schematic illustration of the angle E 1  between the original straight sheet edge protruding section prior to bending and the position of the sheet protruding section during the final stage of bending in a first direction, with the protruding section tending to move to the original position after the bending force has been removed.  
         [0015]      FIG. 5  illustrates a next step in the conditioning process where the bending member has moved past the folded edge of the sheet and is in positioned to move in a reverse direction.  
         [0016]      FIG. 6A  illustrates a further step in the conditioning process where the bending member has moved in the reverse direction thereby folding the sheet edge in an opposite direction.  
         [0017]      FIG. 6B  is a schematic illustration of the angle E 2  between the original straight sheet edge protruding section prior to bending and the position of the sheet protruding section during the final stage of bending in a second direction opposite the first direction, with the protruding section tending to move to the original position after the bending force has been removed.  
         [0018]      FIG. 7A  illustrates still further step in the conditioning process where the bending member has completed the reverse direction pass of  FIG. 6A .  
         [0019]      FIG. 7B  is an expanded view of a portion of  FIG. 7A  showing details of the conditioned sheet edge.  
         [0020]      FIG. 8A  illustrates a final step in the conditioning process where the bending member is returned to a position which returns conditioned edge to a straight position.  
         [0021]      FIG. 8B  is an expanded view of  FIG. 8A .  
         [0022]      FIGS. 9A and 9B  are respective elevational and plan views conditioned sheet and the bending member, with  FIG. 9B  illustrating a preferred small angle H between the sheet and the bending member.  
         [0023]      FIG. 10A  is a side schematic view of an apparatus for continuously conditioning the edges of a paper web to be subsequently cut into individual sheets in accordance with another embodiment of the present invention.  
         [0024]      FIG. 10B  is a cross-sectional view of a grooved roller of the  FIG. 10A  apparatus showing a groove in the drum for bending one web edge in one direction.  
         [0025]      FIG. 10C  is an enlarged portion of  FIG. 10A .  
         [0026]      FIG. 11  is a perspective view of the  FIG. 10A  apparatus.  
         [0027]      FIG. 12  is a perspective view of one of the four bending blades used in the  FIG. 10A  apparatus.  
         [0028]      FIG. 13  is an elevational partial view of one of the grooved drums of the  FIG. 10A  apparatus showing the manner in which the bending blade of  FIG. 12  functions to bend an edge of the paper web.  
         [0029]      FIGS. 14A-14E  are respective cross-sectional views of the  FIG. 13  arrangement showing various stages in the process of bending the web edge using the bending blade of  FIG. 12 .  
         [0030]      FIGS. 15A and 15B  illustrate the manner in which the conditioning apparatus of  FIGS. 10A and 11  functions to bend each edge of the web is opposite directions.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]     Apparatus and related methods are disclosed for conditioning a sheet of paper, or a web of paper to be cut in sheets, so that such sheets can be readily bound using, for example, the apparatus of  FIGS. 1 and 2 . This includes sheets made of paper, such as coated sheets, which heretofore have been difficult to bind using thermoplastic adhesives. Many details of the manner in which the conditioning apparatus is implemented are not depicted or described because such details are well within the grasp of persons skilled in the art upon a reading the present description of the apparatus and its operation. Also, disclosure of such details may obscure the true nature of the present invention. There may be instances where opposite edges of a sheet are both conditioned, with only one edge being bound in which case one of the conditioned edges will remain exposed. Thus, it is preferable that the conditioning not be readily apparent, with this objective being achievable using the present invention.  
         [0032]     Referring again to the drawings,  FIGS. 3A and 3B  are schematic representations of a conditioning apparatus for conditioning a cut sheet of paper in accordance with one embodiment of the present invention. A cut sheet  36  of paper to be conditioned is first positioned between a pair of clamps  38 A and  38 B, with the clamps then being closed so as to securely grip the sheet. The clamps are movable between an open position (not depicted) for receiving the sheet to be conditioned and a closed position where the sheet is secured between the clamps. A small length  36 A of the sheet to be conditioned is exposed. Segment  36 A of sheet  36  is sometime referred to herein as the protruding section  36 A. Section  36 A is shown in an original position  39  ( FIG. 3B ), with that position being aligned with the remainder of the sheet  36  disposed between the clamps  38 A and  38 B. The length Z ( FIG. 3B ) of the protruding section  36 A is a function primarily of the thickness Y of the sheet  36 . For example, a typical sheet of photograph type paper is typically  0 . 008  inches thick in which case the protruding section  36 A is approximately  0 . 030  to  0 . 050  inches. For thinner sheets, the length Z of  36 A needs to be shorter, with the ratio of section  36 A length Z to sheet  36  thickness Y (Z/Y) typically being in a range of approximately 4 to 6. Preferably, the ratio of the length Z of the protruding section  36 A to the thickness Y of the sheet is no greater than twenty (20).  
         [0033]     A bending member  40  is provided which moves relative to the sheet  36  so as to bend or fold the protruding sheet section  36 A first in one direction and then in the opposite direction, as will be described. This folding typically takes place at a common folding line, with the spacing of the folding line from the end of the sheet defining the width of the protruding section  36 A. In order to achieve this relative movement represented by arrow  41 , it would be possible to keep the sheet  36  in a fixed location and move the bending member  40 , move the sheet while keeping the member  40  fixed or a combination of both. In addition to moving in a direction normal to the sheet  36 , the binding member  40  is also preferably capable of movement parallel the sheet as indicated by arrow  43  ( FIG. 3A ). The member  40  is biased by a spring or the like (not depicted) having a home position proximate the two clamps  38 A and  38 B and spaced a distance X ( FIG. 3B ) from surfaces  48 A/ 48 B the clamps, with distance X being sufficiently large to ensure that the member does not contact the clamps when moving laterally in the direction of arrow  41 . In addition, for reasons that will be explained, the distance X is smaller than the thickness Y of the thinnest sheet  36  anticipated to be conditioned.  
         [0034]     As can best be seen in  FIG. 3B , the bending member  40  includes a bending blade  42  which extends away from the body of member  40  and includes a pair of rounded surfaces  42 A and  42 B to assist in bending or folding the protruding section  36 A. The body member  40  is first driven in a direction indicated by arrow  41 A ( FIG. 3B ) towards the protruding section  36 A. As shown in  FIGS. 4A and 4B , a first leading edge  45 B of the bending blade  42  engages the protruding section  36 A and proceeds to fold the sheet edge as depicted. The rounded surface  42 B of the blade will cause the body member to be displaced slightly downward as indicated by arrow  43 A ( FIG. 4B ) due to the finite thickness Y of the sheet edge. The previously noted biasing structure (not depicted) will continue to apply an upward force on the bending member  40  so that the bending member  40  will continue to apply the small upward force as the member moves, thereby causing the protruding section  36 A to be tightly folded around the sharp corner B of clamp  38 B. As can best be seen in  FIG. 4B , this bending force causes the outer surface  47 A of the section  36 A to move a greater distance than the inner surface  47 B of the edge due to the difference of the radii of curvature of the two surfaces. This difference in movement creates a shearing force along the relatively small length Z of the protruding section  36 A thereby tending to cause the sheet to tear or fracture, primarily in the interior of the sheet intermediate sheet surfaces  47 A and  47 B, as represented by element  44 .  FIG. 4C  is a schematic representation of the maximum angle E 1  of deflection from the original position  39  of the protruding section  36 A, with E 1  being 90 degrees in the example of  FIGS. 4A and 4B  and with E 1  preferably being at least 60 degrees. The radius of curvature of the folding edge B created by clamp  38 B is selected to be relatively small, but not so small as to cut or tear the surfaces  47 A and  47 B of section  36 A.  
         [0035]     Alternatively, the inner gripping surface of clamp  38 B could be considered a first folding surface with the lower surface  48 B of clamp  38 B forming a second folding surface, with the two surfaces meeting at corner B to form a folding member. It can be seen that the clamping action of clamps  38 A and  38 B and the movement of bending blade  42  function to fold the sheet  36  tightly around these first and second folding surfaces of the folding member. Preferably, the angle F 1  ( FIG. 4C ) between the two folding surfaces is 90 degrees, with the intermediate angle F 1  being typically less than 120 degrees.  
         [0036]     As can be seen in  FIG. 5 , the bending member  40  is driven past the protruding section  36 A so that the folded protruding section  36 A is permitted to return in a direction back towards the original position  39 . The absence of section  36 A from between member  40  and clamp  38 B permits the member  40  to moved up to the home position a distance X ( FIG. 3B ) from clamp  38 B by the biasing mechanism. The member  40  is then driven in a reverse direction as shown in  FIG. 6A  and as represented by arrow  41 B so that rounded edge  42 A ( FIG. 3B ) will engage the protruding section  36 A, with the biasing mechanism continuing to apply a small upward force against the protruding section  36 A as the member  40  passes over the edge thereby folding the edge in an opposite direction around corner A ( FIG. 4B ) of clamp  38 A. This action again results in a shear force to be applied to the protruding section  36 A, this time in a direction opposite that of the prior bending action since surface  47 B is now being forced to move a slightly greater distance than that of surface  47 A due to the difference in radii of curvature. This shear force reinforces the tendency of the interior of the protruding section  36 A to tear or fracture, with tear again extending all the way to the end of section  36 A as represented by element  44  of  FIG. 4B .  FIG. 6B  is a schematic representation of the maximum angle E 2  of deflection from the line  39 , with line  39  representing the original position of the extension  36 A shown in  FIG. 3B . Angle E 2  is 90 degrees in the example of  FIG. 6A , with E 2  preferably being at least 60 degrees. Again, the radius of curvature of corner A formed by clamp  38 A is selected to be small, but not so small as to damage the surfaces  47 A and  47 B of the protruding section  36 A.  
         [0037]     Alternatively, the inner gripping surface of clamp  38 A could be considered a third folding surface with the lower surface  48 A of clamp  38 A forming a fourth folding surface, with the two folding surfaces meeting at corner A to form another folding member. It can be seen that the clamping action of clamps  38 A and  38 B and the movement of bending blade  42  function to fold the sheet  36  tightly around these third and fourth folding surfaces of the second folding member, with the surface of the sheet facing the second folding member being the opposite side facing the previously described first and second folding member formed by the inner surface of clamp  38 B and the clamp lower surface  48 B. Thus, the fold is in the opposite direction, as desired. Preferably, the angle F 2  ( FIG. 6B ) between the third and fourth folding surfaces formed by clamp  38 A is 90 degrees, with the intermediate angle F 2  typically being less than 120 degrees.  
         [0038]     Depending upon the nature of the paper sheet being processed and other factors, including but not limited to the Z/Y ratio, the angles E 1  and E 2  and the radius of curvature of corners A and B, usually one or two passes of the member  40  over the protruding section  36 A is sufficient to adequately condition the sheet edge for reliable binding using conventional thermal adhesive binding techniques as described in connection with  FIGS. 1 and 2 . FIG.  7 B shows details of the protruding section  36 A after the second pass, with  44  again representing the tear or fracture in section  36 A which extends all the way to the edge of the section. This fracture or tear is preferably fairly uniformly distributed along the full length of the edge of section  36 A, but even a somewhat non-uniform distribution may be adequate. The tear or fracture  44  in the edge allows the molten binding adhesive to be drawn into the edge by capillary action and other mechanisms, with even the presence of a small amount of adhesive being sufficient to greatly enhance the adhesion properties of the adhesive to the edge of sheet  36 .  
         [0039]     Once a sufficient number of passes by member  40  have occurred, member  40  stops at a predetermined location as shown in  FIGS. 8A and 8B . When stopped, and edge  45 B of bending blade  42  of the member forces the conditioned section  36 A back to approximately the original position  39  ( FIG. 3B ).  
         [0040]     Once the edges of all of the sheets  36  to be bound have been conditioned, the sheets are formed into a stack  32  for binding as shown in  FIGS. 1 and 2  with all of the conditioned edges being positioned in common. As previously noted, the split edges of the sheets tend to absorb the molten adhesive during binding thereby insuring a very reliable bind, even for paper types that would otherwise not accept the adhesive.  
         [0041]     The amount of force required to condition a sheet  36  can be substantially reduced by applying the bending force at an angle with respect to the plane of the sheet. This permits a smaller drive motor to be used thereby reducing the cost of the conditioning machine along with the size of the machine for desktop applications.  FIGS. 9A and 9B  are side and plan schematic views of a typical arrangement for applying the bending force at an acute angle H to the sheet. The clamps  38 A and  38 B are not shown for purposes of clarity. Depending upon the size of angle H, the maximum amount of force required to drive member  40  in either direction  41 A or  41 B is decreased, while the distance that member  40  is required to move is increased accordingly.  
         [0042]     It is also possible to condition the paper during the paper manufacturing process, prior to the paper being cut into individual sheets.  FIGS. 10A, 10B  and  11  are schematic representations of a conditioning apparatus which receives a paper web  56 , also sometimes referred to herein as a continuous sheet  56 , conditions one or both edges of web and cuts the conditioned web into individual sheets  75 . In the present example, the original web  56  has a width somewhat greater than the desired final width of the sheets. The web  56  is drawn in a direction indicated by arrow  54 A around large rollers  60 ,  62  and  64 , with roller  66  being a pinch roller engaging the larger non-grooved roller  64 . Prior to reaching roller  60 , the web  56  is slit to the proper width by a pair of suitably spaced apart slitting blades  71 A and  71 B. Note that if the web width is all ready cut to the appropriate size, this slitting operation is not needed. The slitting produces a pair of end strips  58 A and  58 B which continue to wrap around part of roller  60  after slitting.  
         [0043]     Roller  60  includes a pair of grooves  72 A and  72 B which are aligned with the respective slitter blades  71 A and  71 B, with the grooves extending around the circumference of the roller. The second roller  62  also includes a second pair of grooves which are not visible and which are similar to grooves  72 A and  72 B. The cut web  56  extends around roller  62 , with the direction of rotation of rollers  60  and  62  being opposite as indicated by respective arrows  52 A and  52 B ( FIG. 10A ). Finally, the cut web  56  is pulled over roller  64 , with the web being secured in place by pinch roller  66 . The apparatus for driving the rollers is conventional and not depicted.  
         [0044]     A pair of bending blades  68 A and  68 B are positioned above the respective grooves  72 A and  72 B formed in roller  60 . Blades  68 A and  68 B, in cooperation with an interior wall of the grooves, perform a bending function similar to that previously described in connection with bending blade  42 .  FIG. 12  shows one of the bending blades  68 A associated with groove  72 A. The blade  68 A extends partially into groove  72 A ( FIGS. 10A and 10B ) and functions to fold an outer edge  56 A of the web  56  into groove  72 A, with the blade forcing the outer edge against inner wall  73 A of the groove. As will be explained, the outer surface of the roller  60  and the inner wall form a sharp corner similar to corners A and B formed by respective clamps  38 A and  38 B of  FIG. 4B . Blades  68 A and  68 B form a first bending station associated with roller  60 , with bending blades  70 A and  70 B ( 70 B not shown) associated with roller  62  forming a second bending station which bends the respective web edges  56 A and  56 B in a direction opposite to that of the first station.  
         [0045]     Referring again to  FIG. 12 , a perspective view on one of the bending blades  68 B that is associated with groove  72 B of roller  60  is shown, with the other three blades being of similar construction. The function of the bending blades is engage the web edge that is parallel to the outer surface of the roller and to fold the web edge into the associated groove and force the web edge against an interior wall of the groove as the web is drawn past the blade. As will be subsequently described in detail, blade  68 B includes a bending surface  74  disposed at an angle which functions to rotate the web edge from the horizontal position to almost a vertical position. A second surface  76  then engages the almost folded web edge and forces the web edge against the vertical interior wall of the associated groove.  
         [0046]      FIG. 13  is a cross-section schematic representation of part of roller  60  showing exemplary groove  72 B and the associated bending blade  68 B.  FIGS. 14A-14E  show five cross-sections of bending blade  68 B and the associated web edge as it is being folded when the web is pulled past the blade. Starting with  FIG. 14A , which shows the cross-section  14 A- 14 A of blade  68 B, at this stage the edge of the web  56 B is still in the original horizontal position, with surface  74  of the blade not yet contacting the edge. For purposes of clarity, this view does not show portions of the web edge  56 B which have already been folded by blade  68 B. Note that at this point, the blade  68 B is abutting a stop (not depicted) which causes the blade to be displaced from the interior wall  73 B of the groove a distance that corresponds to distance X of  FIG. 3B , with that distance being again set to be somewhat smaller than the thinnest web sheet to be conditioned. Also, there is again a biasing mechanism that will force the blade  68 B against the web once the web has displaced the blade away from the interior wall a distance greater than X. The mechanism for supporting the blade and for applying the biasing force is not depicted. Also, the end strips  58 B ( FIG. 11 ) cut by slitting blade  71 B is not depicted in  FIG. 14A .  
         [0047]      FIG. 14B  shows the cross-section along line  14 B- 14 B of  FIG. 13  where the associated web edge  56 B first contacts angled surface  74  but has not yet begun to be bent by the surface. As the web  56  progresses past the bending blade as shown in  FIG. 14C , the angled surface  74  commences to deflect the web edge  56 B down into the groove  72 B.  FIG. 14D  shows a cross-section of  14 D- 14 D of  FIG. 13  showing the angled surface  74  as it continues to fold the web edge  56 B around the relatively sharp corner C formed by the upper surface of roller  60  and the inner wall  73 B of groove  72 B. As the folding progresses, the web  56 B has been driven past the angled surface  74  and has engaged the flat surface  76  ( FIG. 12 ) of the bending blade  68 B, with this surface forcing the web flat against the inner wall  73 B of the groove. The previously-noted biasing mechanism (not depicted) forces the blade against the web edge  56 B so that the web is tightly folded around corner C, with this action tending to create a tear or fracture  44  in the edge in the same manner as previously described in connection with  FIG. 4B , for example. Again, the radius of corner C is selected to be small but not so small as to cut or otherwise mar the surface of the web edge  56 B. Eventually, the folded web edge  56 B passes the bending member  68 B completing a single bend in the web. Bending blade  68 A, also of the first bending station, conditions the opposite edge  56 B of the web at the same time edge  56 B is being conditioned.  
         [0048]     The conditioned web  56  is then drawn around roller  62 , with the cut strips  58 A and  58 B being permitted to fall away at this point. The previously bent edges  56 A and  56 B are then flattened as the web begins to pass around roller  62 , with the surface of the web facing roller  62  being the opposite of the web surface facing roller  60 . As previously explained roller  62  has a pair of grooves and associated bending blades  70 A and  70 B which form the second bending station. The blades engage the respective edges  56 A and  56 B of the web and function to bend the edges in the same manner as the blades of the first bending station, but in an opposite direction.  FIGS. 15A and 15B  are respective expanded cross-sections of the groove  72 B formed in roller  60  of the first bending station and a corresponding groove  69 B formed in roller  62  of the second bending station. The bending blades are not depicted. As can be seen, the first bending station of  FIG. 15A  folds the web edge  56 B in a first direction around corner C, with the second bending station of  FIG. 15B  folding the same web edge around corner D formed in roller  62  in the opposite direction.  
         [0049]     As previously explained in connection with  FIG. 4C , the outer surface of roller  60  could be considered to form a first folding surface, with the inner surface  73 B of groove  72 B formed in roller  60  of  FIG. 15A  being a second folding surface, with the two folding surfaces meeting at point C. The two folding surfaces form an angle similar to angle F 1  of  FIG. 4C . Preferably, the corresponding angle F 1  for the  FIG. 15A  apparatus, the angle between the first and second folding surfaces, is 90 degrees, with the typical value being less than 120 degrees. The tension applied to web  56  which holds the web against the surface of drum  60 , the first folding surface, along with the force applied by bending blade  68 B against the inner surface  73 B, the second folding surface, function to fold the web tightly over the first and second folding surfaces as is desired.  
         [0050]     As also previously explained in connection with  FIG. 6B , the outer surface of roller  62  could be considered to form a third folding surface, with the inner surface  78 B of groove  69 B formed in roller  62  of  FIG. 15B  being a fourth folding surface, with the two folding surfaces meeting at point D. The two folding surfaces form an angle similar to angle F 2  of  FIG. 6B . Preferably, the corresponding angle F 1  for the  FIG. 15B  apparatus is 90 degrees, with the value typically being less than 120 degrees. The tension applied to web  56  which holds the web against the surface of drum  62 , the third folding surface, along with the force applied by bending blade  68 B against the inner surface  78 B, the fourth folding surface, function to fold the web tightly over the third and fourth folding surfaces as is desired.  
         [0051]     The two opposite bending operations are usually more than sufficient to effectively condition the edges of the web. If required, further bending stations can be added by adding one or more grooved rollers and associated bending blades. As shown in  FIGS. 10A and 11 , the conditioned web  56  is then drawn between a large non-grooved roller  64  and pinch roller  66  thereby straightening the conditioned edges in a manner similar to that shown in FIG.  8 B. Finally the conditioned web or continuous sheet  56  is cut into individual sheets  75  of the desired final length. The sheets can then be bound along either conditioned edge  56 A or  56 B. Conditioning both edges in this manner is valuable since the conditioning is not visible except upon close inspection. Thus, the conditioned edge not used for binding is not easily visible. On the other hand, if only one edge were conditioned, the end user would have to first determine the appropriate edge for binding and then take that factor into account when assembling the sheets into a stack for binding.  
         [0052]     Note that the apparatus of  FIG. 3A  is implemented to fold the sheet  36  around corner A and B, with A and B being positioned so that there is a common folding line when the sheet is folded in opposite directions. As can be seen in  FIGS. 15A and 15B , the relative lateral positions of grooves  69 B and  72 B can be altered so that folding lines are not in common and thus produce differing values of length Z ( FIG. 3B ). Although this is a less preferred implementation, the two folding lines should both be placed a distance from the edge of the web so that the ratio of the of the distance Z from the edge of the sheet to the thickness Y of the web (Z/Y) is, in both cases, in the approximate range of 4 to 6 and, in any event, less than twenty (20). Note that the apparatus of  FIG. 3A  could also be implemented to produce differing folding lines, with this implementation also being less preferred.  
         [0053]     Thus, various apparatus and related methods have been disclosed which permit a bound stack of sheet to be bound using conventional thermal adhesives for many paper types that could not otherwise be bound using such binding methods. Although such apparatus and methods have been described in some detail, it is to be understood that various changes can be made by those skilled in the art without departing from the spirit and scope of the present invention as set forth in the appended claims.