Claims
- 1. An apparatus for longitudinally compressing a web under the influence of driving forces provided at a nip line defined by spaced-apart pairs of matched rotating disks and under the influence of retarding forces provided by sets of retarding fingers inserted in the spaces between the disks, wherein the retarding fingers of at least one set are associated with a yieldable support enabling movement of the fingers to positions respectively further apart and closer together dependently with increase and decrease in force applied to the fingers by the web, the fingers being constructed and arranged so that over the range of said positions of said fingers, in the downstream region close to the nip line, web-contacting surfaces of the sets of fingers diverge in the direction of travel of the web whereby, regardless of the position of said fingers, the longitudinally copressed web is always subjected to tightest constraint of its thickness at a point longitudinally close to the nip line, and downstream therefrom, while still confined, said corresponding sections of web are released from tightest constraint, said diverging surfaces promoting uniform movement of the corresponding oncoming sections of compressed web while enabling relatively steady retarding forces to be transmitted laterally through the web to retard the adjacent sections of the web that are in line with said disks, whereby the longitudinal compressive treatment of both the sections of the web in line with said fingers and the sections in line with said disks can be substantially regular.
- 2. The apparatus of claim 1 wherein at least one of the opposed surfaces of said sets of fingers is convexly curved in the region close to the nip line to provide divergence of those surfaces from the surfaces of the other set of fingers.
- 3. The apparatus of claim 2 wherein the opposed surfaces of both sets of the fingers are convexly curved in the region close to the nip line to contribute to the divergence of the surfaces of each set of fingers from the surfaces of the other set.
- 4. The apparatus of claims 2 or 3 wherein the radius of curvature of the surface of each of said convexly curved fingers is of the order of the radius of the disks alongside which each lies.
- 5. The apparatus claim 1 wherein fingers of at least one of said sets are structually supported from a point downstream of said nip, the said fingers protruding upstream therefrom, with their tips disposed entirely within the respective spaces, below the path of travel of the web.
- 6. The apparatus of claim 5 wherein both fingers of both said sets are mounted in the manner defined in claim 5.
- 7. The apparatus of claim 1 wherein, beginning at a region spaced downstream substantially from said nip line at which region the space between said fingers has widened relative to the tightest constraint so that the major portion of face-wide pressure upon the treated web has been relieved, there is defined an elongated dwell cavity in which the surfaces engaged with said web become substantially parallel.
- 8. An apparatus for processing a web of material comprising
- two side-by-side rolls rotating respectively in opposite directions about two spaced apart axes, each roll having larger diameter segments and smaller diameter segments along its length, said larger and smaller diameter segments of said two rolls being matched to form a series of relatively shallow driving nips along a nip line alternating with relatively deep non-driving spaces, said larger diameter segments imposing face-to-face compressive forces and longitudinal driving forces on the corresponding regions of said web which pass through said nips,
- regions of said web which pass through said non-driving spaces being driven indirectly by said larger diameter roll segments acting via forces transmitted through the substance of the web from said directly driven web regions to said non-directly driven web regions, and
- closely disposed retarding means in the form of pairs of generally divergent fingers slidably engaging the web, located to apply longitudinal retarding forces on both faces of the non-directly driven regions of said web immediately as they emerge from the nip line, said retarding forces having the opposite direction to said driving forces, and producing immediate, continual shortening of the emerging web, the shortened web thereupon subject to a zone of less constraint,
- said non-driving spaces adjacent said web permitting reorientation of said non-directly driven web regions during said shortening with less face-to-face compression than the face-to-face compression applied to the driven web regions,
- said driven web regions being retarded indirectly by said closely disposed, divergent fingers acting via forces transmitted through the substance of the web from said non-directly driven web regions, to cause said driven web regions to undergo their immediate regular longitudinal shortening,
- at least one finger of each pair of said fingers being adjustable further apart and closer together relative to the other finger of the pair, the fingers being constructed and arranged so that in the downstream region close to the nip line, regardless of the adjusted position of said fingers, said fingers diverge in the downstream direction, whereby the web is always subjected to tightest contraint in the direction of its thickness at a point longitudinally close to the nip line.
- 9. The apparatus of claim 8 wherein each said larger diameter segment has a peripheral driving surface that is narrower in width measured in the axial direction of the roll than the width of the space between said peripheral driving surface and the peripheral driving surface of the next adjacent larger diameter segment.
- 10. The apparatus of claim 9 wherein said peripheral driving surface has a width that is about one half of or less than the width of said space.
- 11. The apparatus of claim 8 or 9 wherein the width of said spaces is about 0.10 inch.
- 12. The machine of claim 11 wherein the width of said peripheral driving surfaces is about 0.05 inch or less.
- 13. The apparatus of claim 8 wherein a said larger diameter segment has a peripheral driving surface which bears an enhanced friction treatment.
- 14. The apparatus of claim 8 wherein a said larger diameter segment includes
- a cylindrical peripheral driving surface that is narrower in the axial direction than the full axial width of said larger diameter segment, and
- a pair of tapered shoulders on opposite sides of said driving surface.
- 15. The apparatus of claim 14 wherein said shoulders are smooth and said driving surface bears an enhanced friction treatment.
- 16. The apparatus of claim 13 or 15 wherein said enhanced friction treatment comprises lines of knurling that lie at substantial angles to the direction of travel of said driving surface.
- 17. The apparatus of claim 13 or 15 wherein said enhanced friction treatment comprises plasma coating of fine abrasive particles.
- 18. The apparatus of claim 8 further comprising means for maintaining said rolls with a constant distance between said axes.
- 19. The apparatus of claim 8 wherein said retarding means comprises stationary, cantilevered finger-form retarders each having a surface exposed for contact with a face of one said non-directly driven web regions, said surface having an extent along the length of said rolls less than the space between corresponding adjacent larger diameter segments.
- 20. The apparatus of claim 19 wherein each said finger-form retarder rests within one of said non-driving spaces of one said roll and includes a second surface opposite said web contacting surface, said second surface being spaced away from the peripheral surface of said smaller diameter segment.
- 21. The apparatus of claim 19 wherein on each side of said web there are finger-form retarders which are integral, upstream extensions of a respective continuous element which extends across the width of the web, said finger-form retarders of each said element being interdigitated in the non-driving spaces respectively of the corresponding roll, said contact surfaces of said two elements being separated by a space, during operation, to permit passage of said non-directly driven portions of said web.
- 22. The apparatus of claim 21 wherein during operation said retarders are held at substantially fixed distances from the plane on which said axes lie.
- 23. The apparatus of claim 21 wherein said retarders are relatively rigid in the direction perpendicular to the faces of the web.
- 24. The apparatus of claim 19 wherein said finger-form retarders are supported by means permitting slight resilient yielding in the longitudinal direction of the position of the fingers during initial feeding of the web into the machine during start-up.
- 25. The apparatus of claim 19 wherein both sets of said finger-form retarders are supported from the outfeed side of the machine.
- 26. The apparatus of claim 8 including means defining a slidable pathway for passage of web after it has been shortened and reoriented, said pathway being thereafter sufficiently shallow to apply a degree of face-to-face compressive force to said reoriented and compacted non-directly driven web regions as they pass via said pathway.
- 27. The apparatus of claim 8 or 21 including means defining a slidable pathway for passage of web after it has been shortened and reoriented, said pathway being sufficiently deep so as to minimize face-to-face compressive forces applied to said non-directly driven web regions as they pass via said pathway.
- 28. The apparatus of claim 8 further comprising
- a dwell cavity for receiving said web, said cavity being located on the outfeed side of said nip beyond the place where said longitudinal shortening occurs, said cavity comprising a pair of cavity faces.
- 29. The apparatus of claim 28 wherein a uniform or increasing distance between said faces is maintained along the length of said dwell cavity away from said nip.
- 30. The apparatus of claim 29 further comprising means for providing a temperature differential along said dwell cavity faces, with higher temperatures nearer said nip.
- 31. The apparatus of claim 28 further comprising means for applying face-to-face pressure along the length of said dwell cavity, said pressure being even or decreasing with distance from said nip.
- 32. The apparatus of claim 28 wherein one said face is a continuation of a slidable retarding surface, and the other said face comprises a plate attached to a member supporting a slidable retarding surface on the opposite side of the web.
Parent Case Info
This application is a continuation-in-part of application Ser. No. 933,087, filed Nov. 20, 1986, now abandoned.
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Continuation in Parts (1)
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Number |
Date |
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Parent |
933087 |
Nov 1986 |
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