GB2148342A - Method and apparatus for compressive shrinkage of textile fabric - Google Patents

Abstract

A fabric 12 is compressively shrunk in a compaction zone formed along a straight path of a flexible belt 16 which defines both straight and curved paths by means of rollers 19,17,20 etc. The fabric 12 is fed into the straight path by a roller 13 in which path it is pressed against the belt 16 by a flexible sheet 22. A rigid support member 23 presses the sheet 22 against the fabric 12. The pressure applied by the member 23 can be varied by adjusting the distance of the member 23 from the belt 16. The presser member 23 may be replaced by an inflatable flexible bladder (68) (Figure 3 not shown). The fabric 12 is then fed towards a second compaction zone 15. The member 23 may be heated to produce steam in the first compaction zone to further reduce friction. The sheet 22 is polytetrafluoroethylene coated fibre glass and is anchored about a bracket 21. <IMAGE>

Description

SPECIFICATION Method and apparatus for compressive shrinkage of textile fabric Background of the invention The present invention concerns a novel method and apparatus for mechanically preshrinking textile fabric webs and particularly knit fabric webs. The apparatus utilizes at least in part a web shrinkage technique illustrated in the applicant's U.S. Patent No. 4,156,955. As illustrated in this patent, a tefloncoated fiberglass sheet is restrained at one end adjacent to a drum-type drier or palmer such that the sheet and free end thereof pass between the drum and a continuous felt belt which passes around the circumference of the drum. The fabric web is permitted to enter the nip formed between the tefloncoated fiberglass sheet and the felt belt and in so doing is caused to be compacted or preshrunk.

Although the above described compressive shrinking arrangement is quite effective and has inherent in its construction and operation large savings in capital investment, nevertheless the degree of shrinkage of textile fabric using this method and apparatus is generally only about six to twelve percent. This is sufficient for some purposes, but there are applications which require more preshrinkage than the described apparatus can provide. It is therefore the purpose of the present invention to describe compressive shrinkage systems which incorporate certain aspects of the system just described; but which allow for either single or double compressive shrinking of the fabric to achieve higher degrees of shrinkage than heretofore achieved.

Summary of the invention In accordance with the present invention, there has been provided an apparatus for mechanically introducing longitudinal compaction into a fabric web comprising, a flexible belt, means for guiding and driving said belt in a curvilinear closed loop path including guide roll and drive roll means which cause curvature of portions of said belt as said belt passes round said roll means, said belt having on the side thereof facing outwardly of said loop a frictional surface adapted to engage the surface of said fabric web, said guide and drive rolls defining together with said belt spaced apart curved portions of belt and relatively straight sections intermediate said curved portions an elongated flexible sheet having a low frictional surface thereon, means for anchoring one end of said flexible sheet adjacent to a curved portion of said belt, means for applying pressure to said sheet against said belt for a distance against a straight section thereof in the direction of movement of said belt, thereby defining a compaction zone between said belt and sheet, means for varying the amount of pressure applied by said pressing means, means for introducing a fabric web into said compaction zone to cause compaction of said web.

In accordance with one aspect of the present invention the means for applying pressure to the sheet to define a compaction zone between the belt and sheet is a flat member capable of being heated and conducting said heat to the sheet to effect the generation of steam and thus to reduce friction between the steam and the fabric passing over the sheet. Another means for applying the aforesaid pressure consists of an inflatable bladder which may contain a heated fluid to effect the same result. The invention further contemplates, if a further degree of compaction is required, the use of a second stage of compaction which in essential respects is similar to the compaction stage depicted in U.S. Patent No. 4,156,955.If this second stage of compaction is used, the apparatus and method of the present invention contemplates using the flexible sheet of the first stage of compaction to transport the fabric web into such second stage in a relatively tensionless state, thus minimizing pull out of the compaction introduced into the fabric by the first stage.

Brief description of the drawing Figures 1 and 2 illustrate a compaction arrangement for textile webs incorporating two stages of compaction in accordance with the present invention; and Figures 3 and 4 illustrate a single stage of compaction incorporating an inflatable means for applying pressure to the flexible sheet in the area of a compaction zone.

Description of particular embodiments Referring now to the drawing and initially to Figure 1 thereof a double compaction apparatus 10 constructed in accordance with the principles of the present invention has been illustrated. The apparatus 10 includes a steam chest 11 through which passes a textile fabric web 12, for example, a flattened tubular web of knit fabric which as illustrated is passed over internal spreader. It should be understood that the apparatus can be used advantageously on open width knit fabric (single layer). The steam moistened web passes over a guide roller 13 and thereafter enters the first stage 14 of the double compaction arrangement according to the present invention. The compaction stage 14 comprises a continuous flexible belt 16 which in the illustrated embodiment is of felt. In other applications the belt may be of rubber or any suitable material.The belt 16 passes around rollers 17, 18 and 19, the surface of rollers 17-19 consisting of rubber which frictionally engages the inner surface of the belt 16. Either or both rollers 18 or 19 may be drive rollers to cause movement of the belt 16 in the direction of the arrows. A blanket guiding roll 20 exterior to the belt loop is provided to maintain the belt 16 in a centered relation with respect to adjacent parts.

Adjacent to and below roller 13 is a cylindrical mounting and anchoring bracket 21 to which is affixed one end of a flexible sheet 22 which may be constructed of fiberglass coated with teflon or an equivalent construction. The sheet 22 is wrapped around the bracket 21 and is of sufficient length to extend beneath most of the horizontal section 16' of the flexible belt 16. When the free section 22' of the sheet 22 is supported as illustrated by a flat, rigid sheet support member 23, the member 23 is movable toward and away from the section 16' of belt 16 and may be tightened in a position to bring the end of the sheet 22' essentially into contact with the adjacent surface of the belt 16 by bolts 24, 25 which are permitted vertical movement within slots 26, 27 in a mounting bracket 28.This movement permits the application of different pressures upon sheet section 22' in order to assure that there is no buckling of fabric in the compaction zone.

Heating element 29 causes heating of the support member 23 and of sheet section 22'.

Accordingly, a compaction zone is formed between belt section 16' and section 22' of the flexible sheet through which the web 12 may pass. The web 12 enters this zone after having become frictionally engaged by the lower surface of the belt 16 after first moving around the curved portion 30 of the belt 16 as defined by the curvature of roller 19. As the web 12 proceeds further into the compaction zone defined between the belt section 16' and the section 22' of the flexible sheet, the web 16 is compacted in the direction of its travel according to well-known principles.Since the web has been moistened previously, the heat imparted by heating element 29 as transmitted by section 22' of the flexible sheet causes some of the moisture in the web to be released as steam which provides additional lubrication, although such lubrication will be present because of the teflon coating on the sheet 22. The arrangement thus far described, namely compaction stage 14 may be expected to produce six to twelve percent longitudinal shrinkage or compaction of the web, it being understood that the degree of compaction may be varied to some extent by varying the curvature of roller 19, and the thickness and material of belt 16.

Immediately adjacent to compaction stage 14 is compaction stage 15 which comprises a heated drier drum 31, which is encompassed by a continous felt belt 32, the movement of which in the direction shown by the arrows will cause clockwise rotation of the drum 31. Belt 32 is driven by the drum 31 and such movement of the belt is supported by rollers 33 and 34. Immediately above roller 34 is an anchoring bracket 36 to which is attached at the lower end thereof the end of a flexible sheet 37 of the same construction as sheet 22.

The remainder of sheet 37 is arranged between the drum 31 and the drum facing side of belt 32, and it is the frictional contact of the free end 37' of sheet 37 with drum 31, together with the rotation of the drum which causes attenuation of the sheet 37.

This attenuation, together with the tension in belt 32 and its contact with drum 31, effects a nip area between section 32' of the belt and section 37' of the sheet.

After fabric 12 passes through the nip of compaction stage 14, it proceeds between the belt 32 and flexible sheet 37 around the curvature determined by roller 34 and thence into the nip area between belt section 32', and sheet section 37'. As the web 12 passes through this nip area, it is again compacted.

It will be observed that a very short space 38 exists between the end of sheet 22 and the beginning of sheet 37 and that as the web 12 passes through this space, the tension on the web 12 can be observed. In the illustration, a very slight downward curvature has been illustrated which would be indicative of essentially a tensionless condition in the web 12. If the web 12 were taut in the space 38, this would indicate a condition of longitudinal tension and that at least some of the compaction introduced into the fabric web by compaction stage 14 was being removed or being pulled out.

Referring now to Figure 2, an alternate arrangement according to the present invention has been illustrated. Since the arrangement of Figure 2 uses essentially the same mechanical components as has been described in Figure 1, with the exception of the use of two flexible sheets 22 and 37, the same reference numerals have been used in respect of the same parts or components which appear in Figure 2. In the embodiment of Figure 2, it will be noted that a single sheet 40 is anchored to bracket 21 in the same way that sheet 22 was attached to bracket 21; however, sheet 40 extends lengthwise to pass around roller 41 and the end section 40' thereof extends along drum 31 to lie between the felt belt 32 and the drum.

In the arrangement of Figure 2, therefore, the web 12 is first compacted in a space in the nip area defined between the lower section 16' of the flexible belt 16 and the section 40'3 of flexible sheet 40. Thereafter, web 12 passes along the upper surface (as viewed in Figure 2) of sheet 40 before passing around roller 41 and into the nip area defined by section 40' of the sheet 40 and section 32' of felt belt 32. As the web 12 passes from stage 1 to stage 2 of the compaction arrangement, the web becomes exposed in a space 38' and the degree of tension on the web can be observed. Ordinarily, the web if essentially tensionless will ripple somewhat in this space but since the web is supported by the underlying sheet 40, it will not be affected by the weight of the fabric.Consequently, there will be no tendency for this reason for the shrinkage applied to the fabric in the first stage of the apparatus to be pulled out as the fabric is transported on sheet 40 to the second stage of compaction.

The apparatus of Figure 1 is perhaps to be preferred over the apparatus of Figure 2, since compaction of the fabric is applied in the respective stages to opposite sides of the fabric. That is to say, slippage of the fabric against the respective sheets 22 and 37 will be with respect to opposite sides of the fabric and thus onesidedness may be eliminated. The apparatus of Figure 2 may be for this reason undesirable but nevertheless illustrates the basic principle of the invention that the web is supported essentially throughout its entire length by a flexible compaction sheet as the web passes through two compaction stages. The apparatus of Figure 2 might be used advantageously to preshrink non-tubular fabric where it might be desired to have only one fabric side exposed to slippage ef fects vis-a-vis the flexible sheet 40.

Referring now to Figures 3 and 4, an alternate method and apparatus has been disclosed for effecting pressure upon a flexible sheet which is used to restrict fabric and define a compaction zone. In the apparatus of Figures 3 and 4, a conventional endless rubber belt 50 passes around rollers 51 and 52 (either or both of which may be drive rollers) and about a small diameter roller 53.

Roller 53 is supported for rotation within frame 54 which also mounts rollers 56, 57 and 58. The latter are positioned to bear against the inner surface 50a of belt 50 in order to prevent deflection of the belt in the area encompassed by rollers 56-58.

immediately adjacent to the roller 53 but outside of the closed loop formed by rubber belt 50 is a frame or bracket 59. Contained within frame 59 is a flexible sheet mounting bar 60 which is secured to the frame by pin 61 which prevents rotation of the bar 60 relative to the frame 59. A flexible sheet 62 constructed of teflon-coated fiberglass in accordance with the teachings of U.S. Patent No.

4,156,955, is secured to the bar 60 by passing the end portion 62a thereof around the bar 60, any by securing such end portion 62a against a flattened area of the bar 60a by means of screws 63 and retention plate 64. The remainder of flexible sheet 62 is permitted to pass around the upper portion (as viewed in Figure 3) of belt 50 along the outside thereof adjacent to roller 53. Fabric 65 is admitted between the outer surface 50b, belt 50 and the inner surface 62a of sheet 62 after passing over stretcher 66. In the illustrated embodiment, the fabric is a tubular textile knit material.

Sheet 62 extends adjacent to the outer surface 50b of belt 50 for a distance which in the illustrated embodiment is somewhat beyond the position of roller 57. In the area which extends laterally adjacent to roller 53 to a position approximately adjacent to roller 57, the apparatus forms a compaction zone in which, according to well-known principles, the fabric 56 is compacted. The fabric is frictionally engaged by the outer surface 50b of the rubber belt 50 and after passing around the arc defined by the belt 50 and roller 53, the fabric will be compacted between the belt 50 and the sheet 62.The degree of compaction is a function of the curvature of the belt effected by roller 53 and will occur in the compaction zone between the outer surface 50b and the inner surface 62a of belt 50 and sheet 62 respectively so long as sheet 62 prevents buckling of the fabric in the compaction zone. The means for preventing this will now be described.

Immediately adjacent to the compaction zone is an apparatus consisting of a box beam 67, a retaining member 68 and an inflatable bladder 69.

The box beam 67 and bladder 69 extend length wise across the width of the fabric to be compacted. The ends of the beam 67 (not shown) are secured to adjacent frame members (not shown), and retainer 68 is slidable along the beam so that it may be positioned to retain bladder 69 in a suitable manner, the function of retainer 68 being to prevent relative movement of the bladder with respect to beam 67. Accordingly, air or other suitable fluid (which may be heated to generate steam from the moistened fabric as it passes through the com paction zone) can enter bladder 69 through fluid connection 70 and the pressure of the fluid within bladder 69 will cause it to expand against the respective opposing surfaces 67a of beam 67 and 62a of sheet 62. The pressure exerted by bladder 69 against sheet 62 should be sufficient to prevent buckling of the fabric in the compaction zone.This pressure can be accurately applied for the purpose for varying conditions, i.e., the speed of compaction, thickness of fabric, etc. so that uniform compaction to the requisite degree results. The support provided by frame 54 and rollers 56-58 provide a low friction (firm) backing support for belt 50 against the pressure exerted by bladder 69 so that the belt 50 will not be deflected by the pressure exerted by bladder 69. In the illustrated embodiment, roller 53 is quite small, and consequently the curvature of the belt 50 around roller 53 is more pronounced than if roller 53 were of a larger diameter. The sharpness of curvature will effect greater compaction in the compaction zone, and therefore it is extremely important that the flexible sheet 62 be maintained firmly and solidly against the fabric as it passes through the compaction zone.The bladder 69 is itself flexible and able to conform to the surface of sheet 52 across the width of the fabric which may vary to some degree depending upon the characteristics of the fabric and compaction which takes place in the compaction zone.

While it is possible for the fabric once it has been subjected to compaction in the apparatus of Figures 3 and 4 to be again subjected to a second stage of compaction as described in connection with Figures 1 and 2, because the curvature of belt 50 around roller 53 is quite great, it is likely that a high percentage of compaction can be achieved in one stage of compaction by using the configuration and apparatus of Figures 3 and 4.

It will be understood that the foregoing description relates to particular embodiments of the invention and is representative. In order to understand the scope of the invention, reference should be made to the appended claims.

Claims (12)

1. An apparatus for mechanically introducing longitudinal compaction into a fabric web comprising, a flexible belt, means for guiding and driving said belt in a curvilinear closed loop path including guide roll and drive roll means which cause curvature of portions of said belt as said belt passes round said roll means, said belt having on the side thereof facing outwardly of said loop a frictional surface adapted to engage the surface of said fabric web, said guide and drive rolls defining together with said belt spaced apart curved portions of belt and relatively straight sections intermediate said curved portions an elongated flexible sheet having a low frictional surface thereon, means for anchoring one end of said flexible sheet adjacent to a curved portion of said belt, means for applying pressure to said sheet against said belt for a distance against a straight section thereof in the direction of movement of said belt, thereby defining a compaction zone between said belt and sheet, means for varying the amount of pressure applied by said pressing means, and means for introducing a fabric web into said compaction zone to cause compaction of said web.

2. The apparatus of claim 1 in which the means for applying pressure is a flat, relatively inflexible member.

3. The apparatus of claim 1 in which the means for applying pressure is an inflatable flexible blad der.

4. The apparatus of claim 1 in which the means for applying pressure is heated to create steam in the compaction zone.

5. The apparatus of claim 1 which further in cludes a heated drier drum, means for causing rotation of such drum, a continuous flexible blanket encompassing most of the circumference of said drum, means for introducing a fabric web between said drum and blanket to cause drying of said web as said web is carried about said drum, said means including a curved portion of the blanket, an elon gated flexible sheet having a low friction surface, means for introducing the free end of said sheet between said blanket and drum and for introducing said web between said flexible sheet and said blanket after said web has passed about the curved portion of the blanket, said blanket and sheet thereafter defining a nip in which further compaction of said web takes place.

6. The apparatus of claim 5 wherein said sheet consists of two parts and one part thereof is anchored adjacent to the means for introducing fabric into the drier drum.

7. The apparatus of claim 6 wherein said sheets are separated by a short distance through which said web can pass without support by either sheet to indicate the degree of longitudinal tension ap plied to said web prior to being subjected to com paction in the second nip area.

8. The method of compacting a fabric web comprising the steps of: passing said web in frictional engagement around a flexible belt in a curved path and then into a straight path, forming a compaction zone in the straight path of said web by pressing the fabric web against a straight portion of the belt by a low friction sheet, applying pressure to said sheet throughout the area of the compaction zone and varying said pressure to ac commodate the speed of travel of said web, the thickness of fabric and the degree of compaction to be achieved.

9. The method of claim 8 which includes the step of generating steam throughout said compaction zone by heating said fabric.

10. The method of claim 8 which includes subjecting said fabric to a second stage of compaction and transporting said fabric in an essentially tension less state from an initial stage of compaction into the second stage of compaction.

11. A method as claimed in claim 8, substantially as described.

12. Apparatus for compacting a fabric web, substantially as described with reference to the drawings.