Abstract:
Spiral wound tubes may be formed utilizing the method and apparatuses described herein. The method includes providing a mandrel and a web material having a first overlap region and a second overlap region. A binding agent is applied to at least one of the overlap regions. The mandrel is wrapped with the web material such that the second overlap region covers the first overlap region of the previously wound web and the binding agent is disposed between the previously wound first overlap region and the currently wound second overlap region. The spiral wound tubes of the invention demonstrate improved axial crush resistance.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a continuation-in-part of U.S. patent application Ser. No. 10/610,044 filed Jun. 30, 2003. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to spiral wound tubes. More particularly, this invention relates to single ply, spiral wound tubes, and to methods and apparatuses for winding the tubes.  
       BACKGROUND OF THE INVENTION  
       [0003]     Spiral wound tubes are well known. Web materials such as aluminum foil, tissue paper, hard grades of paper and the like are provided to consumers wound on spiral wrapped paper tubes.  
         [0004]     Typical spiral wound tubes are comprised of at least two plies of paper web. The outer ply completely overlaps the inner ply and a layer of binding agent is disposed between the outer and inner plies. These tubes comprise fully overlapped plies and therefore the outer circumferential surface of the tubes is generally smooth.  
         [0005]     A tube comprising a single ply of web material requires less web material and less bonding agent to form the tube. Less equipment is necessary since only a single roll of web material is provided at a time. Less time is spent changing rolls of web material for the same reason.  
       SUMMARY OF THE INVENTION  
       [0006]     Spiral wound tubes comprising a single ply of paper web material may be formed by the method and apparatus herein described. In one embodiment, the method comprises steps of providing a mandrel and a single ply of web material. The web material comprises an outer surface, having a first region, and an inner surface, opposed to the outer surface and having a second region. A binding agent is applied to at least one of the first region and the second region. The web material is wound about the mandrel. The first region of the previously wound web is covered by the second region of the currently wound web. The binding agent is disposed between the first region of the previously wound web and the second region of the currently wound web and binds the successive wraps of the web one to the next.  
         [0007]     In one embodiment the apparatus comprises a mandrel, a binding agent applicator, and a binding agent reservoir coupled to the applicator. In another embodiment, the apparatus further comprises a binding agent pump and a binding agent conduit coupling the output of the pump and the applicator. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1   a  is a schematic side view of the apparatus according to one embodiment of the invention.  
         [0009]      FIG. 1   b  is a schematic side view of the opposite side of the embodiment of the invention illustrated in  FIG. 1   a.    
         [0010]      FIG. 2  is a lateral cross sectional view of a spiral wound tube made according to the method of the invention.  
         [0011]      FIG. 3  is a schematic side view of a second embodiment of the apparatus of the invention. 
     
    
       [0012]     All test methods and patents cited in the Detailed Description of the Invention, are hereby incorporated herein by reference.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     As illustrated in  FIG. 1   a  and  FIG. 1   b,  web material  10  is provided to a winding apparatus  100  at an angle A. The web material  10  is provided from a parent roll and the length of the web material  10  is substantially greater than the width or thickness of the material. The thickness of the web material across its width may be uniform or may vary due to the method used to manufacture the web material  10 . The web material  10  has a first surface  12  that forms the outer surface  22  of the wound tube  20 . The first surface  12  has a first overlap region  14  adjacent to a first lateral edge  15  of the web material  10 . The web material  10  has a second surface  16  that forms the inner surface  26  of the wound tube  20 . The second surface  16  has a second overlap region  18  adjacent to a second lateral edge  19  of the web material  10 .  
         [0014]     According to  FIG. 1   a  the web material  10  is routed proximally to an applicator  200 . A binding agent  30  is applied to the web material  10  from the applicator  200 . In the embodiment illustrated in  FIG. 1   a,  the binding agent  30  is applied to the first overlap region  14  of the web material  10 . In another embodiment, the binding agent  30  may be applied to the second overlap region  18  of the web material  10 . In yet another embodiment, illustrated in  FIG. 3  the binding agent  30  may be applied to both to the first overlap region  14  by a first applicator  200  and to the second overlap region  18  by a second applicator  300 . In this embodiment, a single-component binding agent may be applied to both the second overlap region  18  and the first overlap region  14 . Alternatively, a first component of a two part binding agent system may be applied to the first overlap region  14  by a first applicator  200  and a second component of a two component binding agent system may be applied to the first overlap region by a second applicator  300 . The binding agent may comprise a single-component adhesive, a multi-component adhesive, a single-component cohesive, or a multi-component cohesive. An exemplary binding agent is Resyn™ 32-1357, available from National Starch and Chemical, Bridgewater, N.J.  
         [0015]     The applicator  200  may comprise a slot extruder. The slot extruder comprises a pair of opposed plates separated a predetermined distance by a shim or set of shims. A gap is cut in the shim or shim set such that a slot as wide as the gap and as long as the thickness of the shim(s) is present between the opposed plates. The binding agent  30  is disposed onto the web material  10  from the slot. The web material  10  may be routed to contact the slot extruder such that the deposited film of binding agent is maintained at a desired film thickness and such that a generally uniform thickness binding agent layer is deposited on the web  10 .  
         [0016]     In another embodiment the slot extruder comprises a slot machined into one plate and does not comprise any shims. IN either embodiment the size of the slot must be adequate to enable the application of sufficient adhesive to the core material while maintaining the application of a thin film of adhesive.  
         [0017]     As shown in  FIG. 3 , a binding agent conduit  210  may connect the slot extruder to the output of a binding-agent pump  220 . The input of the binding-agent pump  220  is disposed to receive binding agent from a binding-agent reservoir  240 . In another embodiment, the slot extruder may be incorporated into a lower portion of a binding agent reservoir. The binding agent then proceeds from the slot extruder under the influence of gravity.  
         [0018]     The applicator  200 , applies a thin film of binding agent to the web material  10 . The width of the film may correspond to the width of the overlap region to which the binding agent is applied. In another embodiment, the width of the film of binding agent  30  may be less than the width of the overlap region to allow for some spreading of the film of binding agent  30  after application and prior to the final set of the binding agent  30 . In another embodiment, the width of the film may be wider than the width of the overlap region. The additional binding agent  30  is disposed along the seam on the outer surface of the tube  20 . The presence of the additional binding agent  30  may reduce the possibility that the tube  20  will delaminate at the seam if the tube  20  is cut into discrete lengths. The width of the film of the binding agent  30  may have a width that is about 0.03 to about 0.125 inches (about 0.76 to about 3.17 mm) wider than the overlap region. If the width of the film is excessively wider than the width of the overlap region, winding machine hygiene problems may be created.  
         [0019]     As illustrated in  FIG. 1   a  and  FIG. 1   b,  the web material  10  is routed from the binding agent applicator  200  to the mandrel  110 . The web material  10  is wound about the mandrel  110 . The first overlap region of a previous winding may be covered by the second overlap region of the next successive winding. Previous winding and successive winding refer respectively to sequential 360° wraps of the mandrel  110  by the web material  10 . A new wrap may begin after 360° of wrap as the web material  10  begins to overlap the previous wrap or winding. Web width, web tension and wrap angle may each have an impact upon the extent of the web overlap.  
         [0020]     The concept of a spiral wrapped core may be based on the equations of a helix. The helix equation yields one geometry that will produce the ideal spiral given a specific web width and mandrel diameter. This geometry ignores the thickness of the web  10  and assumes that the edges of the web  10  perfectly abut. Each element of the web  10  width travels the same distance around the mandrel. This results in equal stress across the web  10  width. Theoretically single-ply cores maintain the same geometry while adding to the web  10  width. The additional width is “overlapped” creating the lap seal that produces the single-ply core. Since the web  10  overlaps itself, the leading edge must travel additional distance in one revolution, equal to twice the thickness of the web  10 . Given that the web  10  is basically inelastic, the edge of the web  10  normally traveling the shorter distance, tries to compensate by traveling a distance equal to the other edge. This may produce a “bubble” where the two edges meet. The bubble may be compressed under the winding belt, and may be seen throughout the length of the finished core (log) as wrinkle. To compensate for this phenomenon, additional tension (drag) may be added to the web  10  prior to winding. This tension may stretch the web  10 , flattening it out prior to being wound. The tension (measured prior to the winding mandrel) applied to the web  10  may be in the range of from about 5 to about 15.5 pounds per inch of web  10  width (about 8 N/cm to about 27 N/cm). A two ply core winding process may apply a web tension in the range of between about 2.5 to about 6 pounds per inch of web  10  width (about 4 N/cm to about 27 N/cm of web  10  width).  
         [0021]     As the speed of the core winder changes via the winding belt speed changes, the tension of the core web  10  may change. This may result in a small change in the amount of overlap in the core. As the speed increases, the tension may increase and the overlap may decrease. As the speed decreases, the web  10  tension may decrease and the overlap may increase to the limit of the helical equation. The typical overlap is about 0.375 inches (about 9.5 mm), and can be increased or decreased depending on the helix equation of web  10  width and wrap angle. During a speed change and at different speeds the tension of the web  10  may impact the amount of overlap. A small change in overlap of only 0.01 inches (0.254 mm) will result in a change in core length of 0.25 inches (6.35 mm) for every the 25 overlaps in the wound core. To produce a consistent core length the web  10  tension must be substantially constant. A controlled web  10  tension may yield a consistent core strength and core length with the single-ply core process with variable speeds and web  10  splicing.  
         [0022]     Several different methods may be employed to produce and control the tension. In one embodiment a tension measuring device (i.e. load cell) with a feedback loop may control a servo-motor driven roll, roll pair or nip, a simple pneumatic brake, or an electromagnetic particle brake. In another embodiment the tension may be provided by routing the web  10  around a set of static friction bars.  
         [0023]     The mandrel  110  may be stationary, or the mandrel  110  may be capable of rotating about the winding axis of the tube by supporting the mandrel  110  with rolling element bearings or bushing material. A rotating mandrel  110  may be freely turning or may be driven. The driven mandrel  110  may be driven directly by a motor integral to the mandrel or by being directly coupled to a motor. The mandrel may be indirectly driven through the use of belts, chains, or gears, as are known in the art. The driven mandrel  110  may be driven by a variable speed drive system. The speed of the mandrel  110  may be varied according to the speed of the web material  10  being wound about the mandrel  110 . The surface of the driven mandrel may be a low friction or high friction surface. A high friction surface may comprise a knurled surface or a surface coated with a high friction material, or the mandrel may be comprised of a high friction material. A low friction surface may be used to reduce the build up of heat caused by the slipping of the web material  10  past the surface of the mandrel. A low friction surface may be achieved by the use of a low friction material in the fabrication of the mandrel  110  or by the coating of the mandrel  110  with a low friction material.  
         [0024]     The winding of the web material  10  about the mandrel  110  may be accomplished by any means known in the art. In one embodiment, the web material  10  may be wound by imparting an appropriate torque to the web material  10  via the hand, or hands, of a human being. In an alternative embodiment, the torque may be imparted to the web material  10  by the use of a belt, or plurality of belts, as these methods are known in the art. The high friction mandrel described above, may be used in driving the motion of the web material  10  during the winding of the tube  20 .  
         [0025]     The web material  10  is wound about the mandrel  110  to produce a tube  20  having consistent dimensions. Wax may be applied to at least a portion of the inner surface of the web material  10  to reduce the friction between the web material and the mandrel during high speed winding operations. An exemplary wax is Cerelube™, available from Stevenson-Cooper, Inc., Philadelphia, Pa. The wax may be applied by contacting a block of wax with the moving web. An exemplary wax is In another embodiment, silicone may be applied to a portion of the inner surface of the web or to the mandrel. An exemplary silicone is Masil™ SF 500, available from PPG Industries, Pittsburg, Pa.  
         [0026]      FIG. 2  illustrates the lateral cross section of a portion of a tube  20  made according to the present invention.  FIG. 2  shows a previous winding a overlapped by a subsequent winding b. The binding agent  30  is disposed between the first overlap region  14  of previous winding a and the second overlap region  18  of subsequent winding b.  
         [0027]     The wound core, or tube  20  may be cut to a desired length by using a mechanical core cutter (not shown) or a servo core cutter (not shown). Alternatively, the wound core  20  may be wound until the supply of web material  10  is depleted. Either the mechanical core cutter or the servo core cutter may traverse a path parallel to the mandrel while bringing a cutting blade into contact with the tube  20 . The mechanical cutter comprises a knife type blade and the blade rotates freely about a center axis. The servo cutter comprises a drive motor to actively rotate the cutting blade against the tube  20 . Both mechanical and servo cutter are known in the art.  
         [0028]     An optional aspect of the method and apparatus of the invention comprises the treatment of the web material prior to winding the web material  10  about the mandrel  110  to increase the flexibility of the web material  10 . The web material  10  may be moistened by a mist of water or by applying steam to the web material. Either the water mist or the steam may be applied to the web material  10  through the use of a spray nozzle adapted to handle the water or steam. The flexibility of the web material  10  may also be increased by the application of a softening agent to the web material  10 .  
         [0029]     Applicants have found that the axial crush strength of the single ply tubes of the present invention is greater than the axial crush strength of two ply tubes of similar diameter. Tubes comprising a single ply of 46 lb/1000 ft 2  (22.5 kg/100 m 2 ) paperboard demonstrate more than a 20% increase in axial crush strength when compared to tubes comprising two plies of 26 lb/1000 ft 2  (12.7 kg/100 m 2 ) paperboard. The tubes were tested using Composite Can and Tube Institute (CCTI) Axial End Crush test CT-107. An axial crush strength factor may be calculated by dividing the CT-107 test results by the basis weight of the tube paperboard in lbs/1001 ft 2 . For the single ply tubes of the invention, the axial crush strength factor has an average value of 0.46. The axial crush strength factor for the tubes comprising two plies of 26 lb/1000 ft 2  paperboard averaged 0.33.  
         [0030]     The method of the invention is described by the following non-limiting examples.  
       EXAMPLE 1  
       [0031]     A single ply of 46 pound/1000 ft 2  (22.5 kg/100 m 2 ) kraft paper, 3⅞ inches (9.842 cm) wide and approximately 17,500 feet (5334 m) long is delivered on a roll approximately 60 inches (1.524 m) in diameter. The roll is unwound and fed toward the core winding mandrel. A code is printed on the underside of the paper. The paper turns an encoder wheel and the speed of the paper is determined and transmitted to a Programmable Logic Controller (PLC). Wax is applied to the underside of the paper and National Starch and Chemical Resyn™ 32-1357 adhesive is applied to the first overlap region of the paper. The paper is captured between the inside surface of a driven belt and the outside surface of the mandrel and is wound about the mandrel. The paper is wound at an angle A such that the second overlap region of the paper overlaps the first overlap region of the previous wrap by about 0.375 inches (9.52 mm). The adhesive is therefore disposed between the first overlap region and the second overlap region of the paper.  
         [0032]     The adhesive is applied utilizing an ITW Dynatec Ribbon-coater Nozzle, Model No. 106945 A2 V2, having a slot size of 0.375×0.015 inches (9.52×0.38 mm). This nozzle is mounted on an ITW Dynatec Mod Plus glue gun, Model No. BF0441BD2S. The adhesive is provided to the glue gun from a hot melt tank, ITW Dynatec Model No. S0 5 , via glue hose ITW Dynatec Model No. 06X12, 20-24, HD/A, DC. The hot melt tank, the glue hose and the glue gun are each heated to a temperature of between 105° F. and 110° F. (40.5-43.3 C) Each of the above described components are available from ITW Dynatec of Hendersonville, Tenn., USA.  
         [0033]     The tubes were produced on a Paper Converting Machine Company core winder, Model No. CM-12, available from the Paper Converting Machine Company of Green Bay, Wis., USA. The tubes were cut to a length of LENGTH utilizing a Paper Converting Machines core cutter model number ECM-14.  
       EXAMPLE 2  
       [0034]     A single ply of 46 pound/1000 ft 2  (22.5 kg/100 m 2 ) kraft paper, 3⅞ inches (9.842 cm) wide and approximately 17,500 feet (5334 m) long is delivered on a roll approximately 60 inches (1.524 m) in diameter. The roll is unwound and fed toward the core winding mandrel. A code is printed on the underside of the paper. The paper turns an encoder wheel and the speed of the paper is determined and transmitted to a Programmable Logic Controller (PLC). Tension is applied to the web prior to the winding mandrel using a static s-wrap. Wax is applied to the underside of the paper and National Starch and Chemical Resyn™ 32-1357 adhesive is applied to the first overlap region of the paper. The paper is captured between the inside surface of a driven belt and the outside surface of the mandrel and is wound about the mandrel. The paper is wound at an angle A such that the second overlap region of the paper overlaps the first overlap region of the previous wrap by about 0.375 inches (9.52 mm). The adhesive is therefore disposed between the first overlap region and the second overlap region of the paper.  
         [0035]     The adhesive is applied utilizing an ITW Dynatec Ribbon-coater Nozzle, Model No. 106945 A2 V2, having a slot size of 0.375×0.015 inches (9.52×0.38 mm). This nozzle is mounted on an ITW Dynatec Mod Plus glue gun, Model No. BF0441BD2S. The adhesive is provided to the glue gun from a hot melt tank, ITW Dynatec Model No. S05, via glue hose ITW Dynatec Model No. 06X12, 20-24, HD/A, DC. The hot melt tank, the glue hose and the glue gun are each heated to a temperature of between 105° F. and 110° F. (40.5-43.3 C) Each of the above described components are available from ITW Dynatec of Hendersonville, Tenn., USA.  
         [0036]     The tubes were produced on a Paper Converting Machine Company core winder, Model No. CM-12, available from the Paper Converting Machine Company of Green Bay, Wis., USA. The tubes were cut to a length of LENGTH utilizing a Paper Converting Machines core cutter model number ECM-14.  
         [0037]     While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.