GB2116593A - Microcreping with surface diversion retarding - Google Patents

Abstract

A method and apparatus for longitudinal compressive treatment of a web (16) which employs a novel sheet-form retarding member (40). The working thereof is comprised of a sat of spaced-apart retarding ridges (46) distributed across the width of the portion of the web to be retarded. The ridges are arranged acutely to the longitudinal feeding direction (S) of the web, with initial portions disposed to apply resistance forces (FR) to corresponding portions of web that arrive at the ridges. The resistance force of each ridge resolves into a retarding force component (FS) that resists forward travel of the corresponding portion of web, and a diverting force component (FD) which at least temporarily diverts the path of travel of this portion of web to a direction acute to its original longitudinal direction of movement. The aggregate effect of the set of retarding ridges is to subject the overall web to a substantial retarding action. <IMAGE>

Description

SPECIFICATION Microcreping with surface diversion retarding Field of the invention This invention relates to the longitudinal compressive treatment of flexible web materials such as knitted and woven textile fabrics, papers, plastics films, and so-called "non-wovens", the latter being of natural or synthetic substance formed into webs e.g. as by air laying or wet laying of fibers.

Background of the invention In the iaboratory from which the present invention comes, we have devoted many years to development of the treatment of webs in which longitudinal compressional forces are applied in the plane of the flexible web material. From this work has come a number of inventions, including the bladed microcreper, U.S. Patents Nos.

3-,260,778 and 3,426,405, and the bladeless microcreper, U.S. Patents Nos. 3,810,280; 3,869,768; and 3,975,806. As implemented by these inventions, the untreated web is driven longitudinally by using a low friction surface to press the web against a rotating drive roll, and then within a short distance of the drive point, retarding forces are applied to the traveling web.

The opposition between the driving and retarding forces, while the material remains confined, produces desirable physical change in the web material, for instance increase in its bulk, thickness and elasticity.

In the case of textile and textile-like materials, the web can be compacted longitudinally within its own plane, without folding of the web upon itself or formation of a crepe, but with crimping in situ of the tiny individual fibers ("microcreping" of the fibers) that make up the threads or yarns of the fabric.

In the case of solid thin sheets such as paper or plastics film, the longitudinal compressive treatment can form barely perceptible undulations or crepes in the web as a whole ("microcreping" of the web), in which the overall appearance of the faces of the web is still one of smoothness, without superficial coarse crepe or folds being present. If, however, coarse crepe is desired, this can be achieved by suitable enlargement of the treatment cavity.

In many cases desirable qualities produced by the longitudinal treatment remain in the web after some or even all of the compression in length of the web is removed by stretching.

In specific examples the treatment can increase the softness or drapability of a web, increase its covering effect and opacity, make the surface texture of the web more appealing, render the web shrinkproof, apply decorative effects to the web, or cause components of the web to be more intimately interengaged in a way that is useful.

Paper webs can be made stretchy and have their burst resistance improved.

In the case of webs of synthetic polymer the effects of the longitudinal compressive treatment have been rendered permanent by heating the web to the heat-set temperature range that has been used in industry for setting other treatments of webs or fibers.

The longitudinal compressive treatment of webs as has been known from our earlier work has been successful in certain commercial applications, but in a number of such cases considerable operator skill has been required in order to deal with changing production conditions. Often the treatment has been limited to slow speeds or to only a limited range of starting materials and end products.

A large number of cases have remained, particularly in the field of thin webs, in which commercialization has not heretofore been possible because of difficulty in setting up the treatment or in accommodating changes during running.

For these reasons there has been a longstanding need for better apparatus and method for the longitudinal compressive treatment of flexible webs.

To explain the limitations of prior approaches, it should be understood that there exists a large number of changeable production conditions that can effect the opposed drive and retarding forces of the longitudinal compressive treatment and contribute to difficulties of initial set up and continued operation.For example any of the following can occur: change in the web-gripping character of the drive roll, for instance due to wear of the drive roll surface or presence of foreign substances or due to change in roll speed; variations in pressure of the web against the drive roll, for instance due to change in the untreated web thickness or in the forces that press the confining surface and web against the drive roll or due to wear or change in the geometry of the confining surfaces; variation in the supply tension applied to the untreated web as it enters the treatment; change in the stiffness or softness of the untreated web as may occur due to change in moisture content or temperature of the original untreated web; change in the depth of the retarding passage through which the web passes; change in other retarder qualities due, e.g., to dimensional or speed change; and change in susceptibility of the web to its being retarded, e.g., due to change in the frictional qualities of the web to be treated, and so forth.

In practice, more than one of the variable conditions often change at the same time, producing a more complicated behaviour.

In the cases where webs undergo their longitudinal compression while confined under a low friction surface, as a variable changes, the point of treatment of the material (i.e., the "0" point in the case of bladeless microcreping, as shown in Fig. 1 of our U.S. Patent No. 3,810,280) tends to shift forward or backward in the treatment region, further affecting the quality of the treatment.

The job of the operator has been to take all conditions into account when establishing the initial running adjustments of the treatment and then, during operation, to observe changes in the conditions as they occur and take steps in attempt to counteract these changes by compensatory adjustments.

In view of the many difficulties that have been mentioned, it is an important object of the present invention to provide new techniques for longitudinal compressive treatment of webs which reduce or eliminate such need for adjustment and enable a uniform, high quality treated web product to be obtained over a wide range of web materials. Other objects of the invention are to achieve increase in production rates, greater energy efficiency, and novel specific treatment processes for web materials.

These objects apply in general to a wide variety of means for the longitudinal treatment.

Furthermore, it is a specific object of the invention to improve the "bladeless" type of microcreping treatment. In "bladeless" microcreping a stationary retarding surface extends beyond the confining surface to lie over the driven roll, forming therewith a retarding passage in which drag forces are applied to the face of the web. In the past this retarding surface has been rough or abrasive-like and is inextensible in the direction of the web travel. The nature of this retarding surface has at times produced picks and unevenness in the web and has not permitted the use of the bladeless type of microcreping treatment on certain materials. One particular example is the so-called "diaper liner" which is an extremely thin nonwoven sheet, typically of spun bonded material, and typically of thickness of the order of 0.075 mm (.003 inch).It is desired to make such web soft and drapable from the relatively harsh and stiff nature that the web has when it comes from the production process.

Use of the bladeless treatment on textile fabrics such as polyester tricot has generally been thought by commercial producers to require, during treatment, a highly heat-softened web and to require speeds limited to 4.5 to 9 meters (5 to 10 yards) per minute. While under the compression forces of the treatment, the surfaces of such a heat-softened web have a glazed-like appearance, and when the web is subsequently stretched and cooled the web surfaces have a sharply defined profile that gives a feeling of harshness to the hand. Subsequent scouring and other treatments have been required to give such webs acceptable texture, hand and softness for commercial use.Sporadic results in the laboratory have suggested however that a very soft fabric, with bloomed fibers and desired level of increased bulk could be obtained directly by longitudinal compressive treatment without need for subsequent scouring or the like, but no reliable means has been available to assure these results under commercial production conditions and with the permanence needed to withstand a standard series of wash tests. Also, defects or picks such as produced by broken fibers, and other surface imperfections, have appeared when webs had been treated in this way.

Summary of the invention The invention relates to a method for longitudinal compressive treatment of a web comprising pressing the web against a driven gripping surface in a drive zone to drive the web forward in a longitudinal direction, and retarding the web in a retarding zone to cause previously compressed material to oppose the progress of the driven untreated material to cause the untreated material to longitudinally compress thereagainst.

According to the invention, the method comprises engaging the face of the web to be retarded by a set of retarding ridges distributed across the width of the web, the ridges disposed acutely to the longitudinal direction and having initial portions disposed to apply resistance forces to the corresponding portions of the web arriving thereat, the resistance force of each ridge having a retaining force component and a diverting force component, the retarding force component being effective to retard the corresponding oncoming portion of web to resist forward travel thereof, and the diverting force component having the effect of at least temporarily diverting the path of travel of the corresponding portion of the web to a direction acute to the longitudinal direction.

In another preferred embodiment, the method comprises engaging the face with ridges that are close together, with the width of the grooves between the ridges exceeding the width of the highest point of the ridges so that retarding forces are spread out across the web.

In one preferred embodiment, the method comprises, in a second retarding region, engaging the face of the web retarded in the first region to a second set of retarding ridges distributed across the width of the web, the ridges in the second retarding region disposed acutely to the longitudinal direction of movement of the web and disposed obtusely as compared to the disposition of the ridges in the first region.

In another aspect, the invention relates to a machine for treatment of a web according to the above method.

According to this aspect of the invention, the retarding means includes a sheet form retarding member having a working surface disposed to engage the face of a web, the working surface being comprised of a set of spaced-apart retarding ridges distributed across the width of the portion of the web to be retarded, the ridges being disposed acutely to the longitudinal direction and having initial portions disposed to apply resistance forces to the corresponding portions of web arriving at the ridges.Again, the resistance force of each ridge has a retarding force component and a diverting force component, the retarding force component being adapted to retard the corresponding oncoming portion of web and the diverting force component having the effect of temporarily diverting the path of travel of the portion of web, the aggregate effect of the set of retarding ridges adapted to subject a contracting web to a substantial retarding action.

In one preferred embodiment of this aspect of the invention, the retarding means comprises a multiplicity of parallel side-by-side ridges set at an angle to the longitudinal direction in the range between about 100 and 600; the ridges are approximately 0.25 mm (.010 inch) high; the ridges are of the order of 0.25 mm (.010 inch) wide and grooves between the ridges are of the order of 0.25 mm (.010 inch) high and of the order of 1.0 mm (.040 inch) wide; and the ridges have planar surfaces disposed for contact with the web, preferably the ridges having horizontal surfaces and the ridges have leading and trailing edges.

In other embodiments, the ridges having leading edges and sloped surfaces in a checkmark form, the surfaces extending from an edge at an angle to the plane extent of the retarding member to the base of the next edge, or the ridges are formed by the intersection of portions sloped in opposite directions.

In some embodiments of the invention, the grooves between the ridges may progressively diverge from one another, with the ridges between the grooves at progressively different angles, preferably in this configuration, the grooves diverge progressively from each other from longitudinal center axis of the retarding member.

In any of these embodiments, the web may be wound about an axis in which the take-up direction corresponds to the longitudinal feed direction, or about an axis in which the take-up direction is at an angle to the longitudinal machine direction.

In a further embodiment, the machine is bladeless, comprising a driven roll and a stationary member on the opposite side of the web that defines both the pressing surface and the retarding surface, the method comprising subjecting the web to retarding while exposing it to the moving surface of the roll which slips forward under it.

In a still further embodiment, the machine has a blade and comprises a driven roll, a stationary member on the opposite side of the web that defines a pressing member, a stationary blade next to the roll surface adapted to divert the web, an extension of the pressing member defining a flexible retarding member having set spacedapart retarding ridges on a face thereof, and the method comprises subjecting the web to a substantial retarding action while diverting the web from the roll surface by means of the blade.

According to still another aspect, the invention comprises a retarding member for use according to the above method.

Brief description of drawings Fig. 1 is a diagrammatic side view of the large components of one embodiment of the improved microcreper according to the invention; Fig. 2 is a somewhat diagrammatic crosssectional view on a magnified scale of the compressive treatment cavity of the machine of Fig. 1; Fig. 3 is a view on an even greater magnified scale of a critical portion of the treatment cavity shown in Fig. 2; Fig. 4 is a diagrammatic plan view of the region depicted in Fig. 3, showing the movement of web material through the treatment cavity; Fig. 4a is a somewhat magnified plan view of the novel retarding element of this embodiment featuring parallel resistant ridges that act upon the face of the material to retard it by a diverting effect;; Fig. 5 is a view similar to Fig. 4a on a less magnified scale, the outline of the path of the fabric past the retarding element also being shown; Fig. 6 is a perspective view on a magnified scale of a portion of the retarding element of Fig.

5; Figs. 7 and 7a are views similar to Fig. 6 of alternate embodiments of the retarding element; Fig. 8 is a diagrammatic plan view of the flow of a web through the machine of the foregoing figures, the illustrated web being a knit fabric; Fig. 9 is a view similar to Fig. 8, illustrating the treatment of a nonwoven web, Fig. 9a is a crosssection similar to Fig. 3 of a machine employing a primary member with a pinked edge, and Fig. 9b is a magnified view of a portion of the web of Fig.

9 on a magnified scale; Fig. 10 is a view similar to Fig. 8 of an alternative takeaway arrangement, in this case the web is a woven fabric being wound up in the bias direction; Fig. 11 is a view similar to Fig. 9 illustrating the treatment of paper to produce a microcreped effect while Fig. 11 a is a view similar to Fig. 3 illustrating the use of a primary member of constant thickness with a straight trailing 'edge; Fig. 12 is a perspective view similar to Figs. 6, 7, and 7a of another retarding element according to the invention, employing relatively wide lands; Fig. 13 is a plan view similar to Fig. 11 showing the effects of the retarding element of Fig. 12; Fig 14 is a perspective view similar to Fig. 12 of another preferred embodiment of the retarder element;; Fig. 1 5 illustrates a fabric treated with the retarding element of Fig. 14 to produce a plisse effect; Fig. 1 6 is a perspective view of still another embodiment of the retarding element, in this case the resistant ridges at the two sides of the material extending in a converging manner toward the centerline; Fig. 1 7 is a view similar to Fig. 5 employing the retarding element of Fig. 1 6 in which the web is compressed both in the longitudinal and in the transverse directions while led straight through the machine; Fig. 18 is a view similar to Fig. 17 in which the retarding element is reversed in position with the effect of causing compression of the web in the longitudinal direction and widthwise stretching;; Fig. 19 is a view of a bladed microcreper arrangement employing the retarder element of the invention; and Fig. 20 is a view similar to Fig. 4a of the flow of the web through the machine of Fig. 19, while Fig. 21 is a cross-sectional view of the retarder element taken on line 21-21 in Fig. 19.

Description of preferred embodiments Referring to Fig. 1, a microcreper, M, is adapted to provide a longitudinal compressive treatment to web 1 6. A driven roll 14 having a gripping surface 12 drives the web in the direction of the arrow S (so-called machine direction). Pressure of web 1 6 against surface 12 is provided by primary member 18 (blue steel sheet typically 0.25 to 0.50 mm (.010 to .020 inch) thickness) which is pressed against the roll by presser member 24. The driving action of roll 14 pulls the web 16 from supply 28, which maintains predetermined tension in the web through the action of the idler 30. A take-up roll 32 draws the treated web from the microcreper.

The speed of take-up of roll 32 is regulated relative to the speed of roll 14 by control 34.

In the region 20 in the vicinity of the trailing edge of the primary member 18, the web passes through a compressive treatment cavity. Referring to Fig. 2 and, in large scale, Fig. 3, this cavity is formed by a number of sheet form elements lying over the roll. Primary member 18 defines a series of steps A, B, C near its end 1 9. These steps progressively increase the space for the web and allow the treatment to occur under the primary member, when desired. The novel retarding member 40, also of sheet form, extends downstream in the machine direction beyond the end 19 of primary member 18. Above and extending the full extent of retarding member 40 is a backing member 42 of sheet form. In the region preceding tip 19 of primary member 18, an upstream portion of the retarding member 40 is captured above the primary member 18 and below backing member 42, and so is held in position.The downstream portion of backing member 42 has a slight downward curvature, approximating the curvature of roll 14, and bends the retarding member 40 into a like configuration.

This maintains the retarding passage depth at a generally uniform value to its end.

Referring to Figs. 3, 4, 4a, 5 and 6, the retarder member 40 has a special web-engaging surface comprised of a series of relatively closely spaced retarding ridges 46 separated by groove passages 48. In most preferred embodiments the ridges are comprised of hard, smooth, polished substance, e.g. hardened spring steel, upon which the web material can readily slide. The leading edges EL of these ridges do the major work.

In the embodiment shown, the ridge and groove configuration is formed by sequential grinding of the face of a blue steel sheet with a narrow diamond grinding wheel. The ridges and grooves extend at angle a relative to the machine direction S, angle a varying in value from about 100 to about 600 (often preferably between 300, preferred for stiff webs, and 450, preferred for soft, flexible webs) depending upon the nature of the material to be treated and the properties desired to be achieved by the treatment. In the embodiment shown in Figs. 3-6, angle a is 450.

Referring to Figs. 4a and 6, the blue steel is of thickness, t, of 0.50 mm (.020 inch). The grooves are formed to a depth, d, sufficient to ensure that the leading edge E, of each ridge 46 is sharp, depth, d, typically being 0.25 mm (.010 inch). In the embodiment shown grooves 48 have widths Wg of 1.0 mm (.040 inch). These grooves are formed on 1.25 mm (.050 inch) centers, giving a ridge width Wr of 0.25 mm (.010 inch). The ridges 46 and grooves 48 extend across the full width of the web 16 and have a density, in this embodiment, sufficient to produce a uniform treatment of a wide variety of web materials.

As shown in Fig. 4, 4a, 5 and 8, the web moves under the primary member 18 in the machine direction S, is diverted to direction R as it passes under the retarding member 40, is drawn off of the machine from under the retarding member in machine direction S, as is shown in solid lines in Figs. 5 and 8, and is wound upon roll 32. In an alternate embodiment, as suggested in dotted lines in Fig. 5, the web may be withdrawn at an angle S' from the machine direction, an angle which may correspond to the direction of the ridges, or may be at less of an angle to the machine direction, depending upon the nature of the treatment desired.

The leading edge EL of each of the ridges 46 faces into the incoming material and its initial part Pi is effective to apply a retarding force to the web. Referring to Fig. 4 and 4a, any web segment, as it reaches a leading edge E" encounters a resistance force FR normal to the direction of extent of the resistance edge E,. This force FR can be resolved into a force component F5 which acts in opposition to the machine direction feed of the material and a diverting force component FD which acts in the direction at right angles thereto.

F D tends to divert the web from the direction S to direction R, at angle a of the ridges and grooves.

This interaction of the web with the resistant edges EL is repeated at every increment of 1.25 mm (.050 inch) across the width of the material, with the aggregate result that the entire web is transformed from movement in the machine direction S to the temporary direction R set at angle a.

The limited degree of permanent offset inflicted upon the web appears to be related to the fact that the main work performed on portion P of the web moving in machine direction S is performed by that section of edge EL which first contacts the web. It also appears, as shown in Fig.

4a, that the resistance force FR has decreasing effect on the web as the web contacts edge EL further from point Pi, due, perhaps, to the combined effect of all the edges EL on the oncoming web.

Since it is generally the leading edges EL of the retarding member that do the major work (and not the second or lazy edge on the other side of the ridge), it can be readily appreciated that other forms of a retarding surface can be employed. For instance, referring to Fig. 7, the retarding edges E, may be machined into a plate in the nature of a "checkmark" cross-section in which the surface of the retarding member slopes at 43 from each edge EL at an angle b to the plane of extent of the retarding member 40'. The slope ends at the step surface h which rises to form the next retarding edge E,, this being repeated across the full surface of the retarding member. In Fig. 7a an escalloped cross-section is shown, with the resistant edges EL formed by the intersection of adjacent concavely curved surfaces 45.

Operation of embodiment of Figs. 1-6 The web 16, as shown in Fig. 2, proceeds from the supply roll 28 at the speed S of the driven roll 14. Initially, to start the action, the web is laid beneath the primary member 18 and retarding member 40 in untreated position and presser member 24 is pressed downwardly to press the primary member 1 8 against the web 1 6. This causes the roll 14 to drive the web forward.

Retarding of the web is initiated to cause a "buildback" of a column of compressively treated web by the action of primary member 1 8 and retarding member 40 on the web or by the operator by hand or by the mechanism pressing the retarding member 40 relatively tightly against web 1 6 on the roll 14. Thus, the condition of Fig. 3 is achieved during start-up. The operator quickly releases the temporary pressure and the retarding member thereafter can perform its retarding function without need of pressure beyond that provided by the back-up member 42. As the fresh web 1 6 in Fig. 3 reaches the progressively more open spaces provided by the steps A, B and C, a point, 0, is reached in which the web slips relatively to roll 14.Each element of web 1 6 is subjected to a forward driving force Ff due to the action of the roll and a backward retarding force Fb. At this point an initial compressive treatment occurs and the treated web slips on the roll 14. In the case of thin webs subject to creping such as tissue paper or nonwovens, an initial, extremely fine microcrepe is formed, which may be only a few thousandths of an inch in height. In the case of textiles, compaction occurs with m icrocreping of component fibers, without creping of the overall fabric. As the driven roll continues to turn, this extremely finely treated web moves to the right, in Fig. 3, until it reaches the end 19 of the primary member 18. At this point the web is free to expand or bloom (as with textiles) or crepe (as with paper) into coarser crepe.In either event the material extends into the grooves 48, and the ridges 46, or at least the leading edges E" bear into the surface of the microcreped material and apply the retarding forces described in Fig. 4a.

The set of diverting forces FD at the leading edges E, of all of the ridges has the aggregate effect of diverting the web to move in the direction of the grooves, R, as a coiumn of compressed material, proceeding at speed slower than that of the roll 1 4. The roll surface slips beneath the treated material. The drive forces of the roll prior to point 0, as well as certain drag effects of the roll slipping beneath the treated web in the region beyond point 0, advance the web through the grooves 48 until the web is released from the retarding member 40. At that point, as shown in Fig. 5 in solid lines, and as well in Fig. 8, the treated web is wound up by roll 32 which pulls the web in direction S, in a path that is offset by distance D as shown in Fig. 8 due to the diverted movement of the web.

Referring to Fig. 8, the treatment of a thin polyester tricot knit fabric of approximately 0.4 mm (.015 inch) thickness, the web goes through a number of stages as shown in the drawing, i.e.

drive, treatment, retarding, setting and windup.

The knit fabric as it is led in has lines K of knit extending in parallel, perpendicular to the machine direction S. As suggested by the lines in the web at the other stations, these lines K never turn. Even in the retarding region, they remain parallel in the crosswise direction. As the web is driven forward, it undergoes a compressive treatment under the steps as illustrated in Fig. 3.

The compressed web readily expands, being soft and pliable, and filis the grooves 48. Because of the smooth surface of grooves and ridges, the web remains uniform,without picks. It is drawn off in the direction S, as previously mentioned, and passes through cooling region 60.

The compressive treatment causes the fibers of the polyester to bloom and makes the fabric much softer to the touch and more drapable while the cooling region sets this treatment.

A similar effect is achieved with respect to nonwovens, as illustrated in Figs. 9, 9a and 9b. In this case the primary member 18' has a uniform thickness to its tip 19', but the trailing edge of the primary member has a pinked configuration as suggested in Fig. 9. Typically the edge is pinked on 1.6 mm (1/16 inch) centers, with 0.8 mm (1/32 inch) from peak to valley. This configuration, which is similarly applicable to the other web materials discussed herein, allows the web to progressively emerge in an action which facilitates progressive engagement with the retarding ridges 46.

At the transition point indicated in the drawings, Figs. 9 and 9b, in addition to microcreping that occurs, the web is subjected to a shear effect due to the moment applied, resulting from the difference in directions of the drive forces and the direction of the resistance forces FR. This shear effect, in the plane of the web, is quite different from the effects encountered in prior art microcreping. Its result, to some extent, is to disturb the fiber-to-fiber bonds in the nonwoven in a desirable way, breaking up those bonds sufficiently to produce a soft texture to the web, while preserving ample bond strength of the web to maintain its integrity. Thus a nonwoven that is harsh and stiff, relatively speaking, when fed to the machine becomes soft and drapable in a way not hitherto possible, at least for certain webs.

This same softening effect can be achieved with other webs formed on paper machines including tissue, wadding, toweling and wrapping grades of paper.

Fig. 10 illustrates the treatment of a woven web. At the feed region 70 the web proceeds in direction S, the warp threads extending to direction S with the fill threads running in the perpendicular direction. The web as above is diverted by the retarding member 40 to direction R, the fill threads remaining perpendicular to direction S while the warp threads are diverted to direction R. In this instance the web is shown being wound on roll 32' aligned with direction R thus taking up a web that has been narrowed to some degree, and has bias effects. These can be useful effects in certain instances, e.g. for prevention of unraveling in later uses and for providing a certain narrowing of the web and ability to stretch widthwise. (The same bias effect can be used to advantage in certain instances with the various other webs mentioned herein).

Referring to Fig.11, the treatment of paper proceeds as with the other embodiments. The paper is driven in direction S, diverted to direction R by the action of the retarding member 40, and taken up, either in direction S or at an angle as described above.

Referring to Fig. 11 a, it is advantageous, especially when providing a microcreped texture that is not very fine, to use a primary member 18n of constant thickness, e.g. 0.25 mm (.010 inch) thickness, ending in a blunt edge 19", as shown.

In this case the retarding member 40, even though pressed down by presser member 24 with great force, can have its ridges and grooves extending upstream from the tip 19" of primary member 18" without these ridges having a deleterious effect on the primary member because of the relative thickness of the primary member.

This feature permits simple assembly in many instances.

(It should be noted that where the primary member 18 of Fig. 3 with the multiple steps A, B and C, i.e. the universal cavity, is employed, the downstream 19 tip of the primary member 18 may be of a thickness of 0.08 to 0.10 mm (.003 or .004 inch). Protection of this thin element can be achieved by having the ridges and grooves of the retarding member begin only at the tip of the primary member and extend downstream, as shown. In the case where the entire surface of the retarding member is formed with ridges and grooves, the grooves can be filled in, e.g as with epoxy, to avoid ridges that can deform the thin primary member, or other precautions can be taken, e.g. by interposition of an additional sheetform member between the retarding member and the primary member to protect the contour of the universal cavity.In such ways the universal cavity can be employed with the surface-diverting retarding action of this invention, to obtain the advantages of extremely fine microcrepe of paper or nonwovens or the treatment of textiles, all as described herein and in the parent application.) In the embodiment of Figs. 12 and 13, relatively wide ridges are employed, i.e. the retarding member 40" has groove width Wg of 1.0 mm (.040 inch), with the grooves 48' spaced on centers, C, of 2.5 mm (.100 inch), resulting in a ridge width Wr of 1.5 mm (.060 inch). It is found, in employing such a retarding member while treating certain grades of paper, such as toweling, that the microcrepe lines formed in the web are continuous; however, they lie at different angles in the regions of the ridges and grooves as shown in Fig. 13.In the regions of the grooves, the microcrepe lines take an angle to the crossmachine direction (perpendicular to direction S), the portion striking the resistant edges E, being retarded more than the portion exposed to the lazy edge Ez. The portion of the microcrepe lines of the relatively stiff toweling grade paper that correspond to the ridges 46' lies parallel to the cross-machine direction, possibly owing to the uniform drag effect of the extended planar faces of the retarding ridges 46'.

The resultant pattern to some extent produces stretch in more than one direction and makes, e.g., toweling potentially more useful and less prone to tear during use.

In the embodiment of Figs. 14 and 15, very wide grooves are employed and the ridges 46"' define the usual retarding passage with sizable depth. In this case the angled ridges 46"' may have additional retarding effect attributable to the friction of the flat planar surfaces of the ridges. The depth of the grooves may be sufficiently great to cause corresponding portions of the web to bubble, and not to be permanently microcreped. Thus, a differential treatment can be obtained across the width of the web. For instance, during pull-out after the creation of the plisse effect shown in Fig.15, assuming that the plisse is not heat set in the material, the portions in the mid part of the grooves will not retain permanent compaction while the portions in the vicinity of the ridges will.

The foregoing suggests that various treatments can be effected over a wide range depending upon the width of the grooves and ridges, the relative spacings, the depth of the grooves and the selection of the material involved.

Still another variation of the invention has to do with the possibility of varying the direction of the ridges and grooves from one section of the retarder to another.

Referring to Figs. 1 6 and 17, in this embodiment grooves of constant width are set at progressively differing angles. In the center region there is a gap, G, between the two sections of the retarding member, the grooves and ridges in one section being sloped in one direction relative to centerline, A, and the grooves and ridges on the other side sloping in the opposite direction. As seen in Fig. 1 7 this provides a converging pattern of the ribs and grooves. In this embodiment the web is fed in direction S and at the retarding member 40a is facially diverted in accordance with the principles previously described. Gap, G, between the two halves of the retarding member, in which no grooves or ribs are provided, gives space for the treated web to emerge from the grooves in that region without interference.

The web in the embodiment of Fig. 1 7 is compressed lengthwise in accordance with principles previously discussed, while being gathered somewhat widthwise, and emerges in direction S for windup.

A novel variation of the useof this retarding member is illustrated in Fig. 18. In this case the direction of the retarding member 40a is reversed relative to the direction of travel of the web. The web is compressed according to the principles described in the machine direction, but the effect of the diverging ridges and grooves is to stretch the web in the transverse direction. For certain webs which are inherently stretchable, this can have the desirable effect of producing softening.

Indeed, it is possible to follow the treatment shown in Fig. 1 7 by the treatment of Fig. 18 to maximize the softening effects upon a web.

The principles of facial diversion of webs in the compressive treatment process can be employed wherever there is a stationary retarding element engaging the treated web. In Figs. 19-21, the so-called bladed microcreper of U.S.' 3,260,778 or 3,426,405, incorporated herein by reference, flexible retarder member 40b has ridges and grooves in its surface set at an angle to the machine direction S as explained above. The retarding blade 56 as used in the microcreper still is employed to apply a significant retarding effect upon the web, but this retarding effect is assisted by the action of diverting ridges 46c.The additional retarding effects of the ribs 46c can permit the relaxation of the forces urging the retarding member 56 into the cavity, or can permit the angle of its working surface 57 to the roll to be lessened, in a manner that can have advantageous effects in certain instances.

As shown in the embodiment in Fig. 20, the web may be subjected to treatment by a second retarding member with ridges and grooves at an angle opposed to the angle of the ridges of this first retarding member. This double treatment, which results in material having four-way stretchability, is similarly applicable to nonbladed microcreping and to the other embodiments discussed above.

It will be further appreciated that other variations in the use of the invention can be employed. The ridges and grooves can be curved instead of straight and may even have re-entrant curves of S form or zigzag configuration to some extent, all for the purposes described above. For variations in the treatment across the width of the web, it should be noted that in certain materials, and with suitable arrangements of the retarding ribs, the highest degree of compaction can occur immediately adjacent retarding edge E, while in a wide groove adjacent to this ridge a region, remote from the retarding edge EL (e.g. next to the lazy edge in Fig. 4) can have less compressional pressure applied and less permanent compression effects. The resulting web can have, where desired, a gradation of treatment. The treatment over wide lands is another example where a differing kind of treatment can be provided. In many instances the web is subjected to twisting and shear effects in its own plane in a manner very unusual, resulting in greater softening and other improved effects.

Claims (21)

Claims

1. A method for longitudinal compressive treatment of a web comprising pressing the web against a driven gripping surface in a drive zone to drive the web forward in a longitudinal direction, and retarding the web in a retarding zone to cause previously compressed material to oppose the progress of the driven untreated material to cause the untreated material to longitudinally compress thereagainst, the improvement comprising, in the retarding region, engaging the face of the web to be retarded by a large multiplicity of retarding ridges with the set ridges distributed across the width of the web, said set of ridges disposed acutely to said longitudinal direction, and said ridges having initial portions disposed to apply resistance forces to the corresponding portions of the web arriving thereat, the resistance force of each ridge having a retarding force component and a diverting force component, said retarding force component being effective to retard the corresponding oncoming portion of web to resist forward travel thereof, and said diverting force component having the effect of at least temporarily diverting the path of travel of said corresponding portion of said web to a direction acute to said longitudinal direction.

2. The method of claim 1 comprising, in a second retarding region, engaging the face of the web retarded in the first said region to a second set of retarding ridges distributed across the width of the web, the ridges in the second retarding region disposed acutely to the longitudinal direction of movement of said web and disposed obtusely as compared to the disposition of said ridges in said first region.

3. The method of claim 1 or 2 comprising engaging the face with ridges that are close together, with the width of grooves between the ridges exceeding the width of the highest point of the ridges so that retarding forces are spread uniformly across the web.

4. A machine for performing the method of claim 1,2 or 3 comprising means to press the web against a driven gripping surface in a drive zone to drive the web forward in the longitudinal direction, and retarding means for retarding the web in a retarding zone to cause previously compressed material to oppose the progress of the driven untreated material to cause the untreated material to longitudinally compress thereagainst;; the improvement wherein said retarding means includes a sheet form retarding member having a working surface disposed to engage the face of a web, said working surface defining a large multiplicity of spaced-apart retarding ridges with the set of ridges distributed across the width of the portion of the web to be retarded, said set of ridges being disposed acutely to said longitudinal direction, and said ridges having initial portions disposed to apply resistance forces to the corresponding portions of web arriving at said ridges, The resistance force of each ridge having a retarding force component and a diverting force component, said retarding force component being adapted to retard the corresponding oncoming portion of web and said diverting force component having the effect of temporarily diverting the path of travel of said portion of web, the aggregate effect of said set of retarding ridges adapted to subject a contacting web to a substantial retarding action.

5. The machine of claim 4 wherein said retarding means comprises a multiplicity of parallel side-by-side ridges set at an acute angle to the longitudinal direction of said web in the range between about 100 and 600.

6. The machine of claims 18 or 19 wherein said ridges are approximately 0.25 mm (.010 inch).

7. The machine of claim 4 wherein said ridges are of the order of 0.25 mm (.010 inch) wide and grooves between said ridges are of the order of 0.25 mm (.010 inch) high and of the order of 1.0 mm (.040 inch) wide.

8. The machine of claim 3 or 4 wherein the ridges have planar surfaces disposed for contact with the web.

9. The machine of claim 7 wherein the ridges have horizontal surfaces and the ridges have leading and trailing edges.

10. The machine of claim 7 wherein the ridges have leading edges and sloped surfaces in a checkmark form, the surfaces extending from an edge at an angle to the plane extent of the retarding member to the base of the next edge.

11. The machine of claim 3 or 4 wherein the ridges are formed by the intersection of portions sloped in opposite directions.

12. The machine of claim 3 wherein the grooves progressively diverge from one another and the ridges between said grooves are at progressively different angles.

13. The machine of claim 11 wherein said grooves diverge progressively from each other from longitudinal center axis of said retarding member.

14. The machine of claim 3 wherein said web is wound up about an axis in which the take up direction corresponds to the longitudinal feed direction.

1 5. The machine of claim 3 wherein the web is wound up about an axis in which the take up direction is at an angle to the longitudinal machine direction.

1 6. The machine of claim 3 wherein the machine comprises a driven roll and a stationary member on the opposite side of the web that defines both the pressing surface and the retarding surface, said web being subjected to retarding while being exposed to the moving surface of the roll which slips forward under it.

1 7. The machine of claim 3 wherein the machine has a blade, said machine comprising a driven roll a stationary member on the opposite side of the web that defines a pressing member, a stationary blade next to the roll surface adapted to divert said web, an extension of said pressing member defining a flexible retarding member having a set spaced-apart retarding ridges on a face thereof to subject said web to a substantial retarding action.

1 8. A retarding member for use according tothe method of claim 1 or 2, said member adapted to be held over a drive roll and pressed thereagainst by pressing means to drive forward in a longitudinal direction a web passing between said member and the surface of said drive roll, said member characterized by a working surface comprised of a set of spaced-apart retarding ridges distributed across the width of the portion of the web to be retarded, said ridges being disposed acutely to said longitudinal direction, and said ridges having initial portions disposed to apply resistance forces to the corresponding portions of web arriving at said ridges, the resistance force of each ridge having a retarding force component and a diverting force component, said retarding force component being adapted to retard the corresponding oncoming portion of web, and said diverting force component having the effect of temporarily diverting the path of travel of said portion of web, the aggregate effect of said set of retarding ridges adapted to subject a contacting web to a substantial retarding action.

1 9. A method of longitudinally compressively treating a web substantially as herein described with reference to and as shown in the accompanying drawings.

20. A machine for longitudinally compressively treating a web substantially as herein described with reference to and as shown in the accompanying drawings.

21. A retarding member for use in loRgitudinally compressively treating a web substantially as herein described with reference to and as shown in the accompanying drawings.