US 3810280 A
Longitudinal compressive treatments for producing a wide variety of effects in travelling lengths of sheet materials such as textile fabrics, yarns, paper, film, foil and other webs by confining the material against a drive surface by means of a confining surface and driving the material into engagement with a retarder located beyond the trailing edge of the confining surface and also in spaced relation to the drive surface. The retarding surface is provided by material which is essentially inextensible in the machine direction and is provided with a multiplicity of portions which grip and release the passing material. The confining surface is at least in part spaced closer to the drive surface than is the retarder. The forwardly driven material impinges against a column of already compressed material under the trailing portion of the confining surface and under the retarder. The drive surface propels the continuously formed column from beneath the surfaces.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Walton et al.
[ May 14, 1974  METHOD AND APPARATUS FOR LoNorTUmNAL COMPRESSlVE TREATMENT OF FLEXIBLE MATERIAL  Inventors: Richard R. Walton, 10 W. Hill PL,
Boston, Mass. 021 14; George E. Munchbach, Roslindale, Mass.
 Assignee: said Walton, by said Munchbach  Filed: Feb. 16, 1971 ] App]. No.: 115,606
 U.S. Cl. 26/l8.6, 264/282  Int. Cl D06c 21/00  Field of Search 26/l8.6; 264/282  References Cited UNITED STATES PATENTS 2,263,712 1 1/194] Wrigley et al. 26/l8.6 3,0l5,l45 1/1962 Cohn et a]. 26/l8.6 3,260,778 7/1966 Walton 26/l8.6 UX 3,426,405 2/l969 Walton 26/'l8.6 3,452,409 7/l969 Trifunovic et al. 26/l8.6 3,597,8l4 8/1971 Trifunovic 26/l8.6
Primary Examiner-Robert R. Mackey Attorney, Agent, or Firm-William R. Hulbert [5 7] ABSTRACT Longitudinal compressive treatments for producing a wide variety of effects in travelling lengths of sheet materials such as textile fabrics, yarns, paper, film, foil and other webs by confining the material against a drive surface by means of a confining surface and driving the material into engagement with a retarder located beyond the trailing edge of the confining surface and also in spaced relation to the drive surface. The retarding surface is provided by material which is essentially inextensible in the machine direction and is provided with a multiplicity of portions which grip and release the passing material. The confining surface is at least in part spaced closer to the drive surface than is the retarder. The forwardly driven material impinges against a column of already compressed material under the trailing portion of the confining surface and under the retarder. The drive surface propels the continuously formed column from beneath the surfaces.
25 Claims, 24 Drawing Figures rmmmm 14 m4 sum 01 or as PMETED m 14 1914 sum 02 0F 13 PATHEMY 14 m4 saw our 13;
PAIENIEU MAY 1 4 m4 sum 12 or 13 METHOD AND APPARATUS FOR LONGITUDINAL (ZOMPRESSIVE TREATMENT OF FLEXIBLE MATERIAL This invention relates to longitudinal treatment to produce desired effects in thin materials such as woven, knitted and nonwoven fabrics, yarns (which may be a warp of side-by-side yarns), papers, films, foils and other webs and strands of deformable material. The effects obtained include improvements in hand, softness,
cover, thickness, bulk, ability to drape, and extensibility.
At the present time, in spite of numerous attempts over many years by workers in the field, so far as we are aware there are essentially only two compressive treatment processes in commercial use (leaving aside the age-old method of creping by scraping a web from a drum by a doctor blade). These are the. well-known Sanforizing process involving longitudinally compressing the material by the retractive action of thick moving belts which straighten after passing around a roll, and the machines of our earlier work all of which are still in use commercially, some more extensively than others. See U.S. Pat. Nos. 2,765,513; 2,765,5l4, 3,260,778, 3,066,046, 2,761,490, 2,915,109 as well as others.
It has been the purpose of our work over many years to create a machine and process that would go beyond experimentally demonstrating desired effects to provide the key to practical operation, with leeway to tolerate variables that occur. In this way we have been successful, and a number of machines employing different principles we have developed are in operation in mills today.
We have recognized, however, that use of longitudinal treatments of thin materials would greatly increase if there were a practical machine and process which could be used on very wide webs, e.g., feet wide and more; could operate at high speeds, e.g., for papers and nonwovens at speeds of 300 feet per minute and higher; could tolerate a wider range of temperatures, e.g., from ambient up to 200 to 400 F. without affecting the re lationship of the machine elements; would not involve rapid wear of parts so as to operate for needed lengths of time without adjustment; would not require high accuracy of alignment; as a standard machine design, could be used on a wide variety of materials and treatments; would increase the degree of treatment obtained; and which could be simple and capable of operation by personnel of average skill.
It is an object of the present invention to provide a machine and process meeting these needs and capable of producing uniform effects while accommodating variables of the materials such as density, thickness, uniformity, temperature-sensitivity, limpness and prior history.
Other objects are to realize effects not heretofore realized on a practical commercial basis and to make other effects easier to obtain.
Specifically it is an object to provide an improved machine and process that can uniformly alter a web by forces exerted essentially only within its plane.
A very specific object of the invention is to provide a method and means for improving the cover and bulk of textile materials and the hand and texture of such materials as paper and nonwoven products.
The invention concerns machines having opposed members for contacting respective sides of the material, in the case of uniform treatment of webs the members normally being uniform across the width of the travelling web. According to the invention, on one side of the material is located a drive member providing a movable drive surface and on the other side there is a retarder member spaced from the movable drive surface and having a retarding surface to engage the exposed face of and retard the material while the material is exposed to the .drive surface. On the same side as the retarder member is a primary material confining member immediately preceding the retarder member and defining an inlet to the space between the retarder member and the drive surface. The primary member has a preferably smooth confining surface engaging the exposed surface of the material to cause the material to be driven forwardly by the driving surface and is at least in part spaced closer to the driving surface than the retarding surface. The retarding surface is provided with a multiplicity of portions operable successively to grip and release the material thereby to locally retard the material in its passage between the drive surface and the retarding surface, and the retarding surface is further characterized in being essentially nonextensible in the direction of travel of the material.
In one form of the invention we provide a resilient means supporting the retarder member in the direction of the thickness of the material being treated.
In any of the forms of the invention the retarding portions may comprise projections formed of hard grit grains bonded to a non-extensible backing sheet or may be defined by hard metal.
The movable drive surface, according to the invention, may be the surface of a rubber roll, or the knurled surface of a steel roll, or the roughened surface of a travelling belt, or otherwise be provided by a member having suitable frictional material engaging characteristics.
When the machine is adapted to treat compressible materials the drive member and primary member are arranged to drive the material in essentially uncompressed condition to an initial treatment point wherein compression thereof commences prior to its reaching the retarding surface, the confining surface being further positioned to define with the drive surface a passage beyond the initial treatment point, the parts being positioned to slidably confine a compressed column of material in the passage and direct the same forward for exposure to the retarding surface.
For treatment of some materials all portions of the retarding surface which engage the material are spaced at least as far from the drive surface as the portion of the retarding surface which first effectively retards the material. For treating compressible materials, we may use a drive surface comprising a surface having ridges and grooves, the grooves having a component in the direction of travel of the material and providing at the initial treatment point spaces in which the material may initially slide backward relative to the drive surface and compress before leaving the grooves.
In an embodiment for treating compressible materials, the drive surface is of cylindrical form and the retarding surface commences less than 10 arc degrees from the initial treatment point.
ln many cases the member defining the retarding surface may comprise a fabric or be a layer member, the
drive surface being curved and the machine having a bent metal member over the retarder member positioning the retarding surface with respect to the driving surface. In the latter case a backing layer of resilient material may lie over the retarder layer member and in either case the bent metal member may comprise a resilient or non-resilient sheet form metal keeper member over the backing layer.
In other embodiments the retarder member is a sheet form member, and a presser member is provided for pressing toward the drive surface at a point above the region where the primary member ends, the position of the presser member being adjustable backward or forward relative thereto in the direction of travel of the material so as to vary the proportion of force it applies upon the primary member and upon the retarder memher.
The primary member may comprise a sheet of deformation-resistant metal, the body thereof having a first thickness and tapering or stepped to a reduced thickness at its forward edge, the retarder member overlying the primary member and extending downstream over and beyond the trailing edge of the primary member.
In another form of the invention the retarding surface is backed by a layer of a material deformable in the direction of the thickness of the primary member and deformed about the trailing edge of the primary member to position the retarding surface with respect to the drive surface. In this case the machine may include an outer sheet form member of deformation resistant and force-transmitting material overlying the layer, and a presser having a pressing surface engageable with the outer member positioned to transmit pressing forces to a predetermined region beneath the confining surface or beneath the retarding surface or beneath both such surfaces through the thickness of the intervening members. The presser includes mechanism for adjusting backwardly or forwardly the position of engagement of the presser with the outer member in the direction of travel of the material.
In machines for treating compressible materials wherein the material is advanced to an initial treatment point and then through a passage between the confining surface and the drive surface to the retarding surface, the passage may be enlarged in the direction of the thickness of the material to permit creping of the overall sheet of the material, the machine being thereby capable of producing a time-varying densification of the material under the confining surface as the resistance of the column of compressed material varies with the varying stages of crepe formation. In this case the surface defining the enlarged portion of the passage may be continuous with the confining surface or separately formed. Likewise, at least immediately preceding the retarder member, the spacing of the surface defining the enlarged portion of the passage may be substantially greater than the spacing of the confining surface from the drive surface in the region immediately preceding the initial point of treatment, enabling expansion of the material in the direction of its thickness before reaching the retarder. In either case, the spacing of the confining surface from the drive surface within the passage may abruptly increase and the increased spacing extend all the way to the retarder member. Likewise, the confining surface may be provided by more than one member in overlapped relation. The
time-varying densification of the material may alternatively be made to occur by providing an abrupt enlargement in the direction of the thickness of the material of the spacing between the retarding surface and the drive surface immediately downstream of the trailing edge of the confining surface rather than in the aforementioned passage. For some effects abrupt enlargements may be provided both in the passage to the retarding surface and in the region under the retarding surfce.
To achieve other special effects the primary and retarder members may be arranged at an angle to the path of travel of the material, so that the trailing edge of the confining surface and the leading portion of the retarding surface are angularly disposed to the path of travel of the material. This arrangement may be employed both in embodiments wherein the drive member is a roll, in which case the edges define a helical segment upon the surface of the roll, and in embodiments wherein the drive member is planar, as an endless belt. When a belt is employed and the treatment occurs in a planar section thereof, the adjustments of relative pressure between the driving surface and the other surfaces may be made by mechanisms pressing against the back side of the belt.
The invention also features the method of treating a travelling length of flexible material comprising confining the material against a moving drive surface by means of a confining surface so thatrthe material will be driven forward in essentially uncompressed condition to a point of initial treatment and providing a retarding surface on the same side of the material as the confining surface but beyond its trailing edge and in spaced relation to the drive surface. The retarding surface is essentially non-extensible in the direction of travel of the material and has a multiplicity of portions operable to successively grip and release and thereby to locally retard the travelling material, while the confining surface is at least in part spaced closer to the drive surface than is said retarding surface. The forwardly driven material while still uncompressed and beneath and engaged by said confining surface is caused to impinge upon a column of already compressed material at the initial treatment point and is then propelled as a continuously formed column of compressed material from beneath the confining and retarding surfaces.
For treating textiles, the retarding surface may be arranged to nap the surface of the material in the process of retarding it.
The method of the invention is applicable to bulking or softening a length of fibrous material by providing the driving surface with material gripping projections. The material is slippably confined against such driving surface and at least portions thereof pressed into the intervals between the projections by the confining surface; the relationship of the surfaces is maintained such that the driving surface slides with respect to the material so that the projections tend to pull fibers at one side of the material forwardly and out of the intervals while the rough surface has a relatively opposite effect on fibers at the other side of the material.
To achieve certain effects with some materials the method of the invention includes the step of slidably confining the material substantially to its original thickness at a point of initial treatment, and then releasing the compressed material to expand its thickness at a point spaced beyond the point of initial treatment. The
method may include slidably confining the material following the initial treatment point at a spacing greater than the respective spacing at such point with a low friction confining surface prior to exposing the material to the rough retarding surface.
The invention also contemplates a method of treating a travelling length of flexible material including confining the material against a moving drive surface by means of a confining surface so that the material will be driven forward by the drive surface, providing a retarding surface which is essentially non-extensible in the direction of travel of the material and located on the same side of the material as the confining surface but beyond it trailing edge and in spaced relation to said drive surface and wherein the confining surface is at least in part spaced closer to said drive surface than is said retarding surface. We cause the forwardly driven material while still uncompressed and beneath and engaged by the confining surface to impinge upon a column of already compressed material at an initial treatment point beneath the confining surface located upstream of the trailing edge and propel the continuously formed column of compressed material from beneath the surfaces.
In all forms of the invention, the material may be drawn out from the end of the effective retarding surface at a rate greater than the unassisted rate of extrusion from the machine, thereby controllingthe geometry of the passage and the degree of treatment.
The foregoing and other objects, features and advantages of the invention will be apparent from the following detailed description of presently preferred embodiments thereof taken in conjunction with the accompanying drawings wherein:
FIG. 1 is a diagrammatic highly magnified perspective view of a preferred embodiment of the invention;
FIG. 2 is a diagrammatic view of higher magnification than FIG. ll of the action of a projection of the retarding surface upon a fiber or thread;
FIG. 3 is a diagrammatic, highly magnified vertical cross-section of a preferred embodiment treating a knitted fabric and FIG. 4 is a plan view of the fabric at various stages of treatment;with-FIGS. 3 and 4 having the points of treatment aligned;
FIG. 3a diagrammatically illustrates the directions of the forces believed involved at the point of exit of the material from beneath the retarder.
FIG. 5 is a highly magnified cross-section view of a preferred embodiment of the invention including the members defining the effective surfaces; FIG. 5a is a diagrammatic cross-section and force diagram, illustrating forces acting upon the material in FIG. 5; FIG. 6 is a perspective view on a smaller scale of the effective parts of the machine of FIG. 5;
FIGS. 7, 8, 9, and 10 are views similar to FIG. 5 of other embodiments of the invention;
FIG. 11 is a view similar to FIG. 6 illustrating a retarding assembly curved along the axial extent of a drive roll;
4 FIG. 12 may be regarded either as a plan development of the surface of a drive roll, illustrating an embodiment similar to FIG. 1 l or a plan view of a machine employing a planar drive surface;
FIG. 13 is a diagrammatic view illustrating a double action effect of the rough retarding surface in a softening or other such treatment;
FIG. 14 is a diagrammatic view of an overall machine operable according to the invention;
FIG. 15 is a view similar to FIG. 5 of another preferred embodiment;
FIG. 16 is a cross-sectional view similar to FIG. 5 of another preferred embodiment;
FIGS. 17, 17a, and 17b and FIGS. 18, 18a, and 18b are photographs of materials treated according to the invention.
DETAILED DESCRIPTION In FIG. 1 there is diagrammatically shown a driving surface 10 moving in the direction of arrow D, a confining surface 12 and a retarding surface 14. It is assumed for this figure that surface 10 is provided by a moving member and both surfaces 12 and 14 are provided by stationary members, none of which are shown. A web of flexible material 16 to be treated is shown over the moving drive surface 10 and under the confining and retarding surfaces 12 and 14, all of these surfaces having a uniform widthwise extent corresponding to such width of the web as is to be treated uniformly. The degree of magnification of this view will be understood from the fact that the actual thickness of the material is usually less than 0.015 inch and sometimes less than 0.005 inch. Where a curved drive surface is employed, its radius of curvature may be 2 to 6 inches. The degree 'of compression of the material at its various stages is illustrated in a diagrammatic manner by the sections which are intended to represent equal masses of material.
The confining surface is adapted to slippably engage and press the material against the drive surface to confine and drive it forward in region A in longitudinally uncompressed condition to point 0, the initial point of treatment.
The machine is shown in running condition after the treatment has stabilized. It will be appreciated that starting conditions may be quite different. The retarding surface 14 lies along the driving surface 10. The confining surface 12 is at least in part closer to the driving surface than is the retarding surface 14. The retarding surface 14 is rough relative to the confining surface 12 and commenses at T, in this embodiment, within one inch (for textile materials of the order of 0.005 inch to 0.015 inch thick within about one-fourth inch) of the point 0. (In other embodiments e.g., with stiff materials, the initial point of treatment may be nearly coincident with the initial point of the effective retarding surface).
At the point of treatment the longitudinally uncompressed material is driven against a column of temporarily or permanently compressed material, maintained in retarded state by the retarding action of rough retarding surface 14. The material, as it leaves confinement under confining surface 12, is freed to expand at least somewhat, and is able to remain in its expanded condition throughout its transit under retarding surface 14. Through the cooperation of the roughness of that surface, with its relatively large spacing from the drive surface, the retarding action can be maintained with light downward pressure, without danger of causing refeed due to excessive pressure of the web against the drive surface and without undue wear of the retarding surface where wear would cause a detrimental change in the treatment. Advantageously, from the initial area of contact of the retarding surface with the material, the effective retarding surface lies substantially parallel or diverges relative to the drive surface, or at least does not constrict the compressed material or require it to extrude through a minimum passage.
The material illustrated in FIG. 1 is compressible, for instance it could be knitted nylon tricot, or a host of other textile and textile-like products. For many treat ments of such materials the transit of such materials at point T from under confining surface 12 to the retarder surface involves a latent tendency for the material to curl upwardly and back, in response to the dragging action of the confining surface, with resultant balling up and jamming of the material. This tendency is defeated by the location of the initial treatment at a point substantially in advance of the transition to the retarding surface. As shown this is accomplished with an extension of the confining surface through passage B, in which is confined a column of longitudinally compressed material. Thus the initial treatment of the material occurs within the confines of the confining surface 12 where the material is significantly densified, achieving greater columnar strength, and also acquiring a tendency to expand. When this column reaches transition point T at the end of the passage, its strength resists the tendency to buckle, while its newly acquired expansion tendency causes it to expand up against the regarding surface. Densification at least to some degree within the passage B is a critical requirement for numerous textiles which otherwise would not acquire the necessary columnar strength before encountering the retarding surface, while it is essentially non-critical, but in some cases desirable to achieve certain effects, in the case of denser materials already possessing the requisite columnar strength.
According to the present invention, the retarder is substantially rougher than the roughness of the confining surface either before or following the initial point of treatment, and in many instances is preferably rougher than the drive surface, all measured in the direction of travel of the machine.
Preferably for textiles and textile-like materials the roughness of the retarding surface is in the range of 100 to 500 RMS (Root Mean Square microinch) while for' paper and paper-like products the roughness is in the range of 200 to 800 RMS (the particular roughness selected will vary with the relationship of all operating surfaces and the nature of the material and its desired treatment).
In comparison a preferred confining surface has a roughness under 20 RMS and a preferred drive surface for textiles comprising a roll coated with tiny hard particles has a roughness less than I RMS and for papers a roughness less than 130 RMS.
The length of the retarding surface is not critical over a considerable range, being in general longer than the length of such densification passage 8 as is used, or the distance between initial treatment and initial effective retardation. In certain instances, however, especially dealing with treatment of stiff materials and employing roughnesses in the higher part of the range, the length of the retarding surface in region C may be varied as a control for the nature of the treatment obtained. In other instances, e.g., for bulking textiles while minimizing shortening, it is also desired to shorten the retarding surface and have it rougher than would be the case where a substantial amount of longitudinal shortening is affirmatively desired.
A wide variety of materials may be used to provide the retarder projections or retarder surface roughness of the invention. The retarding surface must be essentially non-extensible in the direction of travel of the material in order to perform the proper retarding effect and obtain uniformity and other advantages. For many treatments it is essential that the retarder member also be resiliently supported in the direction of the thickness of the material, which helps to obtain a self-adjusting proper geometry. The elements defining the projections or the roughness preferably comprise hard, wearresistant material. Preferably the material forming the retarder surface has an elongation of less than 5 percent under tensions of 1,000 psi.
Materials, such as filled urethane, which have dense and stable surfaces, exhibit the property of retarding by slip-stick action and with long wearing properties.
It is advantageous to many treatments that the retarding surface not only have its retarding effect, essential for the application of longitudinal compression to the material, but that it also have a napping effect, by which it is meant that the retarding surface should momentarily interlock with the material locally to the extent that the material is locally deformed. Referring to FIG. 2, which is a fragmentary, diagrammatic, highly magnified cross-sectional view, a projection P of the retarding surface 14 engages a thread or fiber F of the material undergoing treatment and causes it to be separated and deformed from the yarn or bundle Y to which it originally conformed. This effect, multiplied thousands of times over each small area of the material, advantageously contributes to the total treatment, for instance, where it is desired to soften and improve the bulk or cover of nylon knitted fabrics, or to give nonwoven fabrics softeness and a better hand or drape.
Referring to FIGS. 3 and 4 a treatment of knitted nylon tricot, 40 X 40 denier, ten thousandths of an inch thick is illustrated. ln region A the longitudinally uncompressed fabric 16, illustrated by a single chain or wale in the plan view of the face of the fabric in FIG. 4, is driven forwardly to the point 0 of initial treatment. Here it is confronted by a column of longitudinally compressed or densified fabric while it is still confined by a slippable confining surface in region B, in this case by the smooth extension of the confining surface 12. Within the length of one chain loop the fabric is converted from an elongated uniform chain, in which the threads of the yarn are tightly bundled together (region A) to a densifed condition where tht total density of threads is increased while the individual fibers are buckled and bent away from each other, although still retaining a recognizable bundle outline (region B).
After the densified fabric 16a slides to the end of the confining surface 12, it expands and is contacted by the rough retarding surface 14 which has a napping characteristic. Here, in region C, the longitudinally unyieldable roughness of the surface 14 penetrates into the body of the fabric to apply retarding forces sufficient to retard the material and maintain the compressed column in region B. The fabric continues to be driven forward in region C, causing relative movement of the fabric under and past the projections of the retarding surface, the movement under the retarding projections being somewhat analogous to a ratcheting movement.
While this occurs, the retarding surface is also effective to nap the fabric by dislodging individual threads from their bundles and displaying them in a more random condition. The treated fabric 16b has a barely if at all recognizable chain structure, and the fabric (despite being originally formed of straight nylon monofilament) hasnow a soft and textured appearance.
In this example the untreatd fabric may have a thickness of for instance 0.010 inch and the thickness of the treated fabric may range from a slight increase up to 0.020 or 0.030 inch thickness depending upon a number of factors within the control of the operator.
Where it is desired mainly to bulk or thicken a textile, and not to shorten it, advantageously the effective length of the retarding surface 14 is kept short, i.e. oneeighth or one-sixteenth inch in length, and the thickening occurs at the end of the confining surface. The material'is subjected to severe shearing forces at its surfaces, causing actual rearward stretching or even localized tearing of the top surface relative to the bottom surface. These forces and shear distortion are illustrated acting on a section of the material in FIG. 3a. When the material emeges from under such a short extent of retarder it immediately blooms into a bulky form, and has a distinct tendency to roll back in the direction of the curved arrow shown in FIGS. 3 as a result of the oppositely acting forces upon the face and back of the material, such forces and their directions being indicated by the straight arrows.
In important instances it is required that the body of the fabric not be visibly creped, it being desired to achieve treatment of the threads and yarns individually. We have made this possible by the densification of the fabric in region B in which the columnar strength of the fabric is increased while the material is tightly confined at its faces before it is exposed to the retarding surface. With maintenance of this geometry the fabric is resistant to bodily buckling as it is pushed through the successive passages.
Referring to FIG. a non-creping treatment with moderate bulking is achievable with the construction shown. The drive surface l0-is formed by a cylindrical roll 20, of a diameter on the order of 4 inches for treatment of narrow width materials, up to about 1 foot width, and of increased diameter for wider webs. A sandwich of stationary elements extends over the roll from a stationary support not shown, at the left in FIG. 5. This sandwich includes a primary member 22 whose lower surface defines the confining surface 12, a nonresilient fabric member 24 having a coated grit facing (e.g., emery cloth) defining retarding surface 14, and a relatively thick and unyielding keeper sheet 28. A spring steel keeper 26 is inserted between keeper sheet 28 and the member 24 and extends along the back of the latter. It has an unstressed curvature of a radius less than the radius of the roll 20. The entire sandwich extends as a cantilever over the roll and a presser member 30 is adjustably positioned over the sandwich to press it against the roll. As indicated by the arrows the presser member is adjustable toward the roll surface to vary its pressure and it is adjustable relative to the sandwich back and forth in the lengthwise direction of the latter, to vary'the relative point of application of pressure. By the latter adjustment the proportion of downward force applied to the confining surface to the downward force applied to the retarder member beyond primary end 23 is variable in an action we refer to as teeter totter." The forces applied to the confining surface are normally much greater than those applied to the effective retarding member, and an adjustment one way or the other of the presser member of .025 inch in the direction of the travel of the material can have a desirable effect in controllably varying the treatment. Such adjustment affects the degree to which the emery member deforms about the end 23 of the primary. To some extent it also shifts the point M of initial effective contact of the emery with the material to be retarded.
In the embodiment of FIG. 5 the primary member 22 is formed from a sheet of invar metal originally of 0.020 inch thickness, having a slope ground to form a lower surface which causes the forward part of the member to taper from the full thickness down to the end 23 of 0.004 inch over a distance of approximately onequarter inch. The retarding member 24 comprises emery cloth having an uncompressed thickness of about 0.010 inch, and with the rough surface of the emery facing against the top surface of the member 22. The emery extends beyond end 23 a distance e.g., of one-eighth to three-eighths inch depending on the treatment and roughness of the emery chosen. The keeper 26 is a length of spring steel of 0.005 inch thickness, and one-half inch width, bent in the widthwise direction on a radius smaller than the radius of the drive surface, and having its width arranged in the direction of travel of the drive surface.
With application of pressure by the pressure member 28 as shown, in the region of end 23 of the primary, the confining surface 12 is pressed tightly toward the drive surface and effects forward drive of the material 16, without longitudinal compression, up to an initial point of treatment 0 under the confining surface 12. The material is compressed against a column of longitudinally compressed material which is confined by the forward extension of the confining surface. As the material proceeds forward under this tapering extension, the material is able to gradually expand while being channeled forwardly without opportunity to buckle bodily upon itself. When it reaches the end 23 of the primary member it has stabilized as a lengthwise moving column of nearly the same height as the height under the retarding surface. It therefore readily bridges the small space at the end 23 of the primary member and engages the retarding surface 14 at point M while moving nearly parallel thereto. From point M the retarding surface itself resists any tendency of the material to turn up, while at the same time the retarding surface applies retarding forces in the manner described previously.
The effect of the spring keeper member 26 is to maintain the retarding surface in the approximate curvature of the drive surface without at any place permitting the spacing under the retarding surface to narrow down or constrict the column in the region of effective retardation. In fact, with this embodiment, although loading of the pressing edge of presser member 30 may be around 50 pounds per linear inch of presser edge wid'tliwis'e of tlie machineTone can easily raise the f5 ward edge 27 of the spring keeper 26 with one finger, illustrating the relatively light downward forces required while enabling the rough retarding surface to perform its function. With this arrangement therefore the treated material retains substantially its fully expanded thickness throughout the length of the retarding surface.
The fore and aft adjustability of the relative position of the presser member on the sandwich, indicated by arrow L in FIG. 5, enables a control of the pressure applied by the retarding surface 14; through the force transmitting action of rigid keeper 28 and spring keeper 26, increased pressure on the retarding surface has the effect of increasing the over-all retarding force and the degree of treatment.
In FIG. 5 as in the embodiment of FIG. 1, the point of initial treatment is close to the beginning of the retarding surface, for the knitted tricot specifically mentioned this dimension being one-eighth inch or less. In general for treatments where substantial longitudinal compression is desired of densifiable materials, the length of the retarding surface is substantially longer, but not necessarily so where bulking or napping are the effects to be achieved.
In certain instances, as with nylon tricot, the drive surface is heated and transfers heat into the material in region A to prepare it for treatment. After treatment it is desirable to continue application of the heat to set the material in its new form.
Referring to FIG. a (which is adjacent FIG. 12 in the drawings) principal forces which are apparently acting upon the material in the embodiment of FIG. 5 are illustrated. Force F, represents the impact of the material against the column of compressed material at the point of initial treatment. This force is generated through the gripping of the material by the driving surface at points preceding point 0, these forces being transmitted through the uncompressed material. F represents the further driving force attributable to the portion of the driving surface in the region of point 0. It represents the fact that the gripping effect of the drive surface upon the material must be overcome by the retarded column of compressed material in order for compressive treatment to commence and for the drive surface of the roll to slip freely forward under the compressed column. F; has a slight upward component representing the upward wedging effect of the gripping projections of the roll surface as they slide forward.
F represents the confining forces exerted by the confining surface 12. The compressed column of material has a tendency to expand in all directions, an effect which cari be considerable when the material being treated has a resilient consistency. F;, has a slight rearward component representing the drag effect. The smoothness of the confining surface (e.g., roughness less than 20 RMS) and its low coefficient of friction, assisted e.g., by a teflon impregnation, help to keep this drag effect small.
Throughout the exposure of the material to the moving drive surface there is a slight tendency for that surface to pull the material forward, represented by force F This pull is a function of the pressure with which the material presses against the drive surface. As indicated above, e.g., in the discussion of keeper 26, this pressure can be very light, keeping force F, small.
When the compressed column moves from under end 23 of the confining surface, it expands and immediately engages the rough retarding surface 14, whereupon a significant retarding force is applied along that surface. The localized retarding forces at points along the retarding surface are represented by F while the cumulative efiect of the retarding surface downstream beyond that shown is represented by F In this connection it is to be noted that because the retarding surface is essentially non-extensible in the machine direction, its projections remain stationary under the force exerted by the moving material and prevent non-uniform retarding patterns or bunching to occur; this feature also causes the force applied to the projections to produce an upward turning couple, i.e., a forward force on the projection produced by the material, and an equal reaction force acting rearward along the thickness of the emery, this tendency being yieldingly resisted by a vertically resilient support. Note that this turning tendency varies during treatment and produces a self-adjusting effect to provide uniform treatment.
It is found that with the shortness of the treatment zone as mentioned (region B, FIG. 1), the forces can act together to dramatically alter the structure of the material, the degree of treatment varying with the selection and relationship of the various elements. With curved drive surfaces it is to be noted that the limited arcuate extent of the region B assures that the major forces applied by the drive surface preceding or at the point of initial treatment 0 are substantially aligned with the passage under the rough retarding surface, and thus can more readily cause the material to move therethrough without buckling.
In increasing order of the degree of treatment the following retarding surfaces have been employed in the arrangement of FIGS. 5 and 5a for treatment of knitted and other textiles, all of these retarding members being emery cloth sold by Behr Manning of Troy, New York, under the tradename Metalite, having a thickness on the order of 0.010 inch.
description RMS new RMS in use crocus cloth (polishing -130 90-110 cloth with fine abrasive grit) 500 J 200-240 -200 400 J 270-300 230-270 320 J 300-500 230-280 These roughness readings were made with a profilimeter on the abrasive side of these materials, the side which is ordinarily disposed against the material. Durable fabric of essentially inelastic qualities may itself be used. as a retarding surface; one such demonstration employed a tightly woven mesh fabric having a profilimeter reading of 450-650 new, 400-450 used. Metal screening and other materials having the requisite gripping characteristics may also be used.
Another point worthy of mention is the discovery that used emery surfaces which appear worn-out in fact have a very desirable effect and are actually preferred. When new emery surface is employed it is preferable to pre-treat the retarding surface by rubbing toilet tissue or other fibrous material on the emery, to leave a deposit of tiny fibers. We are not fully sure why this has good results, but it is believed that the fibers duplicate the condition, for new emery, of the emery in use, where certain free fibers serve somewhat as a lubricant over the roughest portions of the surface. The lubrieating effect of retained fibers is demonstrated especially in the small region where the emery bends about the end of the primary member. It is usually preferred to have the emery surface lie parallel to the drive surface or to slightly diverge all along its effective length. But in order for the emery to reach its initial point of effectiveness at the desired height, it usually must be