Abstract
A variable interference anvil and knife combination is provided to selectively sever elastics in a laminate and preferably not sever the nonwoven portions of the laminate. The distance between the anvil and the knife can be programmatically altered to provide for smaller or larger gaps as processing speeds are changed.
Claims
1. In a system having a revolving compression blade and a revolving anvil cooperating to present a nip, a method comprising the step of: spacing a revolving compression blade apart from a revolving anvil during a closest passage between said compression blade and said revolving anvil, said closest passage greater than zero, said closest passage defining a nip gap between the compression blade and the anvil during respective revolutions; changing said nip gap by at least one of the steps of advancing said revolving anvil relative to said compression blade or advancing said compression blade relative to said revolving anvil; receiving in the nip gap a composite web comprising at least two layers; and completely severing at least one layer of said composite web without severing at least another layer of said composite web.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a top view of a pant type diaper during production, with elastic strands laid down over areas with and without adhesive in what will become front and rear portions of the diaper;
[0017] FIG. 2 is a view of a laminate sandwich entering a rotating profiled knife edge/variable interference anvil roll unit;
[0018] FIG. 3 is a side cross sectional view of the laminate before and after entering the rotating profiled knife edge/variable interference anvil roll unit;
[0019] FIG. 4 is a top view of a pant type diaper during production, with elastic strands activated to create a shirring effect to create elasticized zones in what will become front and rear portions of the diaper;
[0020] FIG. 5 is a closeup side view of a rotating profiled knife edge/variable interference anvil roll unit with a larger provided gap between the knife; edge and anvil roll;
[0021] FIG. 6 is a closeup side view of a rotating profiled knife edge/variable interference anvil roll unit with a smaller provided gap between the knife edge and anvil roll;
[0022] FIG. 7 is a perspective view of a knife roll carrying a pair of knife inserts, each knife insert carrying a knife, with the knife inserts aligned in the machine direction;
[0023] FIG. 8 is a perspective view of a knife roll carrying a pair of knife inserts, each knife insert carrying a knife, with the knife inserts offset in the machine direction.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention.
[0025] Referring now to FIG. 1 a top view of a pant type diaper during production is shown. Elastic strands 14 are laid down over areas with adhesive 12 and without adhesive between areas of adhesive 12, in what will become front and rear portions of the diaper. Typically, adhesive 12 is laid down with an intermittent adhesive applicator which is turned on and off as the web 22 migrates downstream, to create the zones of adhesive 12. As is typical, an absorbent core 16, leg cut outs 18, and side seam cuts 20 are provided to achieve the final diaper product after folding (not shown). Strands 14, ribbon, scrim, or a continuous layer of elastic can all be employed interchangeably.
[0026] Referring now to FIG. 2, a side view of web 22 (which can for instance be a laminate comprising nonwoven layers) 22 sandwiching elastic 14 is shown entering into a rotating profiled knife roll unit 40 and variable interference anvil roll unit 50. Knife roll 40 carries knife 42 on knife insert 44. Anvil roll 50 carries a variable interference anvil 52. In the pictured embodiment, the knife roll 40 rotates in a counterclockwise direction, and the anvil roll 50 rotates in a clockwise direction. The force of the knife 42 on the variable interference anvil 52 is enough to sever the elastic 14, but preferably not enough to sever nonwovens 22. As shown in FIGS. 3 and 4, the elastic 14 snaps out of zones without adhesive 12 leaving severed elastic 14, but elastic 14 remains in place in zones with adhesive 12 to provide elasticity in those zones.
[0027] Referring now to FIG. 5, the rotating profiled knife 42 is shown, preferably with a relatively blunt tip or edge 43 to avoid or minimize severing web 22 (which, as indicated, can be a nonwoven). For instance, a radius R.sub.1 of approximately 0.25-10.0 mm can be used at the knife tip or blade edge 43, but more preferably, a radius R1 of approximately 0.25-6.0 mm may be used. Variable interference anvil 52 has a working anvil surface 51 is sloped between a lower trailing end 53 and a higher leading end 55. Between the ends 53, 55, the working anvil surface has a length 57 measured parallel to a tangent of the revolutional path of the anvil 52. The slope of the anvil 52 preferably forms a linear relationship with the nip gap between knife 42 and anvil 52. For instance, for every millimeter along the length 57, a change in approximately 0.0005 of a nip gap () between knife 42 and anvil 52 is provided. That is, when the knife edge 43 is closest to the anvil axis, the knife 42 and anvil 52 may be said to be in a nip position.
[0028] By changing the position of the knife 42 relative to anvil surface 51, the gap 1 can be varied. For instance, as shown in FIG. 5, the knife 42 is positioned relatively near the trailing end 53 of the anvil 52, creating a larger gap 1. By positioning knife 42 relatively near the leading end 55 of the anvil 52, a smaller gap 2 is provided as shown in FIG. 6. At higher rotation speeds of the knife roll 40 and the anvil roll 50, it may be desirable to have a slightly larger gap 1 because less interference is required to deactivate elastic 14. At slower speeds, a smaller gap 2 may be desired. In other words, deactivation of elastics 14 requires less force at higher speeds, so the slightly larger gap 1 is preferred to minimize disruption of the web 22. Phase adjustments (relative rotational positioning) between knife 42 and anvil 52 can be varied to provide the right impact at a given speed.
[0029] Rotational positioning of the knife roll 40 (and thus the knife blade 43) relative to the anvil surface 51 may be done programmatically, such as by controlling servo drive motors that drive the rolls 40,50 respectively for instance by servo drive motors coupled to rolls 40 and 50 (see, e.g., FIG. 2). Adjustments may be made based on thickness 32 of elastics 14 or a thickness 34 of a composite web including the material members to be severed. In this way, accommodations may be made for machine speed or even variations or wear of components. For instance, if the blade 42 is wearing some, the knife 42 can be shifted to a relatively higher point on anvil 52 to return to the desired gap .
[0030] Referring now to FIG. 7, a perspective view of a knife roll 40 carrying a pair of knife inserts 44 is shown. Knife inserts 44 carry knives 42. An operator side and a drive side knife insert 44 are provided, in order to create the severs in elastic 14, for instance near the side seam cuts 20 of FIG. 1, but preferably between adhesive 12 zones on both the front and rear of the diaper product. In the embodiment shown in FIG. 7, the inserts 44 can be aligned in the machine direction. In contrast and as shown in FIG. 8, the knife inserts 44 can be offset in the machine direction by a distance 2 in order to contact the elastics 14 at different times during the manufacturing process, if desired.
[0031] The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.
