Method and apparatus for the compressive shrinking of textile fabrics

Abstract

 The invention relates to a method and an apparatus for the compressive shrinking of textile fabrics, preferably knitted fabrics, in either tubular or open-width form. In the order as seen in the direction of conveyance of the fabric through the apparatus, the apparatus comprises a fabric steaming and moisturising unit (B) and at least one first compressive shrinking module (C1) with substantially identical first (c1) and second (c2) compressive shrinking sections arranged in series to compressively shrink a respective side of the fabric (24, 24'), each compressive shrinking section (c1;c2) having a fabric support belt (7;13) guided between a fabric support belt deflection roller (9;15) and a heatable fabric belt support roller (10;16). To increase productivity while maintaining the same level of quality, the ratio between the diameter of the fabric support belt deflection roller and the thickness of the fabric support belt of each compressive shrinking section ranges between substantially 6:1 and 4:1, and the ratio between the diameter of the fabric belt support roller and the thickness of the fabric support belt of each compressive shrinking section ranges between substantially 15:1 and 6.5:1.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for the compressive shrinking of textile fabrics such as knitted fabrics, woven fabrics or the like. Such compressive shrinkage is also known in the art as compacting and is performed so as to substantially reduce the amount of shrinkage the material may undergo when the material is exposed after manufacture to processes in which it is moistened or wetted, for example, the process of washing to clean a used garment made from such a material. The material to which the method and apparatus of the present invention relates is generally open-width or tubular in shape as seen in the longitudinal direction of the fabric i.e. the open-width material essentially defines one layer in the flattened condition, whereas the tubular material essentially defines two layers when stretched in the direction transverse to its longitudinal, tubular extension.

Background Art

[0002] A known compacting method and apparatus is described in the following with reference to Fig. 4 and with regard to the processing of tubular fabric, although this description applies substantially equally to open-width fabric, as becomes apparent. The known apparatus comprises a stretching and overfeeding unit A, which is required only if tubular fabric 24 is being processed, a steaming and moisturising unit B, a compacting module C, and a cooling unit D in the order as seen in the direction of passage of the fabric through the apparatus. The stretching and overfeeding unit A for tubular fabric 24 may comprise a tubular expander 1, a tension control roller 2 and an idle return roller 3 and further roller 5. If an open-width fabric material 24' is to be processed, the tubular expander can obviously be bypassed by the fabric 24', which is then fed from a tension control roller 2 via the rollers 3 and 5 into the steaming and moisturising unit B, as indicated by the dashed line in Fig. 4.

[0003] The steaming and moisturising unit B downstream of unit A comprises a steaming box 4, upstream of which there is a spreading roller 6.

[0004] The compacting module C downstream of unit B comprises a first shrinking section c1 and a second shrinking section c2, each of the sections c1 and c2 essentially comprising a fabric support belt in the form of an endless felt belt 7, 13 respectively, said belts being at least partially wound around a respective drawing roller 8, 14, a deflection roller 9, 15, a heated support roller 10, 16 for the belt and a felt belt centering/tensioning roller 103, 104, a sliding sheet or shoe 11, 17, which extends between the respectively associated felt belt and support roller, and a tension control roller 12, 18.

[0005] The cooling unit D is located downstream of unit C in the direction of conveyance of the fabric 24, 24' and comprises a conveyor belt 19 comprising a net or similar, which is conveyed in an endless loop arrangement between a drawing roller 20 and a deflection roller 21, and an air cooling suction box 22 placed between the upper and lower branches of the belt loop.

[0006] In operation of the apparatus as illustrated in Fig. 4, a tubular fabric 24 is fed to the stretching and overfeeding unit A to be threaded onto the tubular expander 1 via the tension control roller 2 and the idle return roller 3. The action of the expander 1 is to transversely stretch the tube to a pre-determined and adjustable width as well as to overfeed it longitudinally until a desired extent is obtained. The expander 1 guides the tubular fabric 24 in this preset condition into the steaming and moisturising unit B.

[0007] As outlined above, in the case of processing an open-width fabric 24' instead of a tubular fabric 24, the stretching and overfeeding unit A is by-passed, as indicated by dotted lines in Fig. 4, and, if desired, the tubular expander 1 is removed from its housing. Thus, the open-width fabric 24' is directly fed to the steaming box 4 via the roller 5 and the spreading roller 6 and then to the subsequent first shrinking section c1 of the compacting module C.

[0008] Independently of the type of fabric 24 or 24' which is to be treated, the action of the steaming box 4 is required to preheat and moisten the fabric, thus causing the fibers thereof to swell and become plastic so as to facilitate and enhance slipping with respect to each other of the individual fabric fibers during the subsequent compaction stage.

[0009] In the compacting module C, the fabric 24 or 24' is first laid open on the upper external side of the endless felt belt 7, which is partially wound around the deflection roller 9, and taken up by the felt belt 7 and, additionally, brought into close contact with it by the sliding sheet or shoe 11, which keeps the fabric pressed against the upper surface of the felt belt 7 during its passage from deflection roller 9 to the heated support roller 10 and beyond. This is achieved because the sliding sheet or shoe extends to between the felt belt 7 and the heated support roller 10.

[0010] Since the compacting action takes place in the known manner particularly on the fabric upper side facing the surface of the support roller 10 on account of the different relative speeds of the felt belt upper and lower sides as the belt moves between the deflection roller 9 and the support roller 10, the fabric being pressed against the felt belt and the influence of the heated support roller, a subsequent and similar compacting treatment is repeated on the opposite fabric side, which is especially required in case of tubular fabric processing, by means of the second shrinking section c2 immediately downstream of and of substantially the same design as the first compacting section c1.

[0011] Thus, the fabric 24 or 24' leaves the first compressive shrinking section c1 via the tension control roller 12 and, in a similar manner as in the first section c1, is fed in the second compressive section c2 onto the endless felt belt 13, which is partially wound around the deflection roller 15, and then carried by the felt belt 13 to between the deflection roller 15 and the heated support roller 16 while being kept in close contact with and pressed against the felt belt 13 by the sliding sheet or shoe 17. The compacting of the other fabric side is therefore effected in the same manner as the first side of the fabric in the first compressive shrinking section c1.

[0012] After the compacted fabric 24, 24' leaves the compacting or compressive shrinking module C, the final cooling and stabilising step is carried out in the cooling unit D, in which the fabric 24 or 24' is conveyed tension-free and in a relaxed state on the upper branch of the revolving net conveyor belt 19, arranged in an endless loop between the drawing roller 20 and the deflecting roller 21, whilst it is traversed by a cool air stream which is sucked through the belt 13 by the air suction box 22. The treated fabric 24 or 24' then leaves the cooling unit D towards a suitable fabric collecting system (not shown).

[0013] The general concept of a method and apparatus as described above is known, for example, from EP-A-0 295 354.

[0014] In fabric manufacture such as the knitted-goods finishing sector, and particularly in the cotton knits field, the production efficiency needs are at least as important as the qualitative implications. In fact, one of the most disadvantageous limitations of such known compacting methods and apparatus as described above is their unsatisfactory working speed, especially if the shrinkage degree of the fabric has to be kept at fully acceptable levels.

Summary of the Invention

[0015] Therefore, it is an object of the present invention to provide a method and apparatus for compressive shrinking or compacting textile fabrics which permit an increased shrinkage degree and/or productivity without any adverse effects on the quality of the product.

[0016] This object is solved according to the present invention by an apparatus comprising the features of claim 1 and by a method comprising the features of claim 17. Advantageous detailed embodiments are described in the respective dependent claims.

[0017] In accordance with the present invention, the provision of special ratios of the diameters of the deflection and fabric support rollers to the thickness of the fabric support belt in each compressive shrinking section of the at least one compressive shrinking module results in the significant advantage of being able to increase the overall rate of treating the fabric without suffering any loss in the quality of compressive shrinkage in the final product since the new arrangement produces an increased compacting or compressive shrinking effect in relation to the speed of passage of the fabric through the compressive shrinking module. Further, if desired, the speed of the machine can be increased to obtain even higher production rates if a lesser degree of shrinkage is acceptable or it can be decreased to obtain an even higher shrinkage degree than normally required. Therefore, while providing a substantially improved relationship between productivity and achievable degree of shrinkage as compared to previously known methods and apparatus, the method and apparatus according to the present invention additionally offers considerable flexibility in terms of the final relationship between productivity and the degree of compressive shrinking.

[0018] This possibility is even further enhanced by providing a modular concept in accordance with a preferred embodiment of the invention, according to which at least one or more substantially identical compressive shrinking modules can be added immediately downstream of the substantially identical first module to effect more compressive shrinking or further increase productivity. Therefore, the final shrinkage quality and production rate primarily depend on the desired running speed of the fabric when the dimension ratios of the deflection and support rollers to the fabric support belt thickness are maintained within the teaching of the present invention.

[0019] The advantageous effects of the present invention are particularly as a result of a carefully determined favourable ratio between the diameters of the deflection and fabric belt support rollers and the fabric support belt thickness because, as compared to prior art systems, the peripheral speed of the external side of the fabric support belt at its portion in contact with the deflection roller is notably higher than that of the same side of the belt that subsequently comes into contact with the surface of the fabric support roller. Naturally, respectively, the diameter of the deflection rollers, the diameter of the fabric support rollers and the thickness of fabric support belts in each compressive shrinking section of a compressive shrinking module are preferably substantially the same.

[0020] The compressive shrinking effect is determined by a deceleration of the fabric, from the point of feeding thereof into the respective compressive shrinking section, throughout the compressive shrinking section itself. To achieve this condition, the fabric follows its carrier - namely the fabric support belt external side on which it lies - which decelerates along its passage around the support roller . The higher the difference is between the speed of the fabric support belt external side in its portion passing around the deflection roller and the speed of the fabric support belt internal side in its subsequently decelerated portion around the fabric belt support roller, the higher is the fabric compressive shrinkage. In other words, the fabric support belt side carrying the fabric under treatment reduces its speed during its passage from being wound around the deflection roller to being wound around the support roller such that the fabric is forced to a greater or lesser extent, depending on requirements, to follow the fabric support belt surface upon which it is supported and, thus, to slow down. Consequently, it undergoes a compressive shrinkage as seen in its longitudinal direction, i.e. the direction of its conveyance, and preferably also under the influence of heat from the heatable support roller. Naturally, this also depends on the extent to which the fabric is maintained in close contact with the fabric support belt to reduce or even eliminate relative movement or slippage therebetween, preferably by the pressing action of a sliding sheet, shoe or equivalently effective means well known in the art.

[0021] Therefore, by applying this concept in a unique way in accordance with the present invention to increase the running speed of the fabric, which reduces the dwell time of the fabric in each compressive shrinking section by means of the particular ratios between the deflection and fabric support roller diameters and the fabric support belt thickness and, preferably, also providing at least a second substantially identical compressive shrinking module to at least double the compressive shrinkage treatment, there results the surprisingly advantageous and significant effect of the present invention that, for the same compressive shrinkage quality, the overall productivity rate of the final product is significantly increased as compared to previously known systems.

[0022] It is apparent that, in accordance with the present invention, the advantageous effects are obtained the less the diameters of both the deflection roller and the fabric support roller are as compared to the fabric support belt thickness. In other words, the fabric support belt, preferably a felt belt, should be as thick as technically possible whilst the deflection and support rollers diameters should be as small as possible in relation to their mechanical performances, for example strength and flexibility. This is realised according to the present invention by a ratio between the diameter of the fabric support belt deflection roller and the thickness of the fabric support belt ranging between substantially 6:1 and 4:1 and a ratio between the diameter of the fabric belt support roller and the thickness of the fabric support belt ranging between substantially 15:1 and 6.5:1.

[0023] In accordance with a preferred embodiment of the present invention, the ratio between the diameter of the deflection roller and the thickness of the fabric support belt ranges between substantially 5.5:1 and 4.25:1 and/or the ratio between the diameter of the fabric belt support roller and the thickness of the fabric support belt ranges between substantially 12:1 and 7.5:1, this representing a further compromise in view of the technical limitations as to the diameters and thicknesses of the respective parts, as discussed in more detail below. More preferably, the ratio between the diameter of the deflection roller and the fabric support belt thickness ranges between substantially 5:1 and 4.5:1 and/or the ratio between the fabric belt support roller and the fabric support belt thickness ranges between substantially 10:1 and 8:1. More advantageously, the ratio between the deflection roller diameter, the fabric support belt thickness and the support roller is substantially 4.5:1:7 and, most advantageously, the ratio between the deflection roller diameter, the fabric support belt thickness and the fabric belt support roller is substantially 4:1:6.5 taking the present technical limitations regarding flexibility, strength, etc. into account. Naturally, however, these ratios can vary between the lowest ratio of 6:1:15 and the highest ratio of 4:1:6.5 as desired in accordance with the particular method or apparatus in which the present invention is put into effect by the skilled person. Any variation within the ratio ranges is possible so long as the lowest and highest ratios as defined herein are not substantially exceeded.

[0024] Another particularly significant advantage of the present invention as compared to known prior art systems results from the fact that the number of rollers in a respective compressive shrinking section can be reduced from at least four rollers to three as a consequence of the particular ratios between the diameters of the deflection and support rollers and the thickness of the fabric support belt. This results in easier guidance and reduced wear of the fabric support belt, a simpler and more compact design of a compressive shrinking section and reduced costs for setting-up and maintenance due to the reduced number of moving or stationary parts.

[0025] Advantageously, at least one and preferably all of the fabric support belts are in the form of an endless belt. In the compressive shrinking sections comprising such an endless belt, the fabric support belt can then be wound around the deflection roller, a drawing roller and the fabric belt support roller for convenient and efficient operation. Further, the fabric belt support roller is in this case arranged to support the fabric and the fabric support belt at a portion of their path of conveyance between the deflection roller and the drawing roller. Most preferably, the endless fabric support belt is at least partially wound around the associated deflection roller, drawing roller and/or fabric belt support roller so that sufficient guidance of the endless belt is provided while minimising wear.

[0026] In accordance with another preferred embodiment of the invention, one or more and, preferably, all of the compressive shrinking sections comprise a sliding sheet or shoe which extends between the associated fabric support belt and the fabric belt support roller and across the width of the fabric as seen in the direction of conveyance thereof. Such a sliding sheet or shoe is arranged to press the fabric against the fabric support belt surface upon the passage thereof between the deflection roller and the fabric belt support roller and beyond. This ensures optimal compressive shrinking since the fabric is then hindered from moving relative to the fabric support belt surface as the path of its conveyance changes in curvature between the deflection roller and the fabric belt support roller where the compression is effected.

[0027] In accordance with another preferred embodiment of the present invention, a stretching and overfeeding unit is arranged upstream of the steaming and moisturising unit to stretch the fabric into an optimally flat condition before it is subject to the compressive shrinking process and to overfeed the material to avoid any elongation therein. Preferably the stretching and overfeeding unit comprises an expander to expand the fabric transversely to its direction of conveyance, the expander being a tubular fabric expander if the fabric is tubular. Additionally, after the steamed and moisturised fabric has been compressively shrunk in the compressive shrinking modules at a relatively high temperature, it can be passed through a cooling unit arranged downstream of the last compressive shrinking module so that it is cooled and stabilised. Preferably, the cooling unit comprises a fabric conveyor belt, the conveyor belt suitably being an endless net or the like, and an air suction box is arranged on the opposite side of the conveyor belt to the fabric to suck cooling air through the belt and fabric.

[0028] Advantageously, one or more and, preferably, all of the compressive shrinking sections comprise a felt belt as the fabric support belt. Textile belts such as felt belts are particularly suitable for the compressive shrinking process as relative movement or slippage between the felt belt and the fabric is avoided to a greater or a lesser extent and the felt belt has a structure which enhances the transfer of moisture, heat and cooling air between it and the fabric.

[0029] In a further preferred embodiment of the present invention, a fabric tension control roller can be provided in the stretching and overfeeding unit, the steaming and moisturising unit, one or more or, preferably, all of the compressive shrinking modules and/or the cooling unit to provide the optimum tension of the fabric as it is processed in the various units and modules. This maintains a high level of processing quality. Advantageously, the tension control rollers can be automatically controllable by an electronic load cell or the like.

[0030] Naturally, in practising the present invention, there are certain technical limitations. For example, the thickness of the fabric support or felt belt is limited due to the conditions under which it is used. For the purposes of the present invention, the belt thickness preferably lies between 17 and 23 mm. There are several problems limiting the felt belt thickness, such as:

• the belt must be flexible; the smaller the curvature of the rollers, the greater the belt flexibility must be. However, since relatively small diameter rollers can be used in the present invention, the belt thickness is greatly conditioned by its acceptable flexibility;
• an excessive thickness permits the needle-punched layers of a felt belt to slide one over the other until they tend to break off;
• an excessive thickness increases the surface loads which create cracks/chaps and elephant skin-like effects.

[0031] There are also limitations which respect to the roller diameters. For the deflection roller, the main problem limiting the diameter is the deflection roller flexion, particularly in relation to its width. For example, a roller 2400 mm wide as in the case of, for example, open-width knitted fabrics processing, should not have a diameter lower than about 90 mm. A second problem which also relates to the felt belt is that the smaller the deflection roller diameter is, and consequently the greater the curvature is, the more all the felt belt drawbacks indicated above are emphasized.

[0032] With regard to the support roller diameter, there are also limitations. A first reason for not lowering the diameter under a minimum value is to leave enough length for a sliding sheet or shoe to become sufficiently effective between the support roller and the felt belt surface. A second reason is to have a sufficient contact surface for the fabric to undergo a short calendering/smoothing effect after the compressive shrinking treatment.

Brief Description of the Drawings

[0033] Preferred exemplary embodiments of the present invention are now described in more detail in the following with reference to the enclosed drawings, in which:

Fig. 1

shows a schematic side view of an apparatus for the compressive shrinking of textile fabrics according to a first preferred exemplary embodiment of the present invention;

Fig. 2

shows a schematic side view similar to that of Fig. 1 of an apparatus for the compressive shrinking of textile fabrics according to a second preferred exemplary embodiment of the present invention;

Figs. 3a and 3b

show in a schematic side view a detail of the inventive arrangement of a deflection roller and a fabric belt support roller in a compressive shrinking section according to the present invention; and

Fig. 4

shows a schematic side view of an apparatus for the compressive shrinking of textile fabrics according to the prior art.

Description of Preferred Embodiments

[0034] The present invention is now described in more detail with reference to Figs 1, 2, 3a and 3b. However, like parts of the present invention to the method and apparatus described hereinabove with reference to Fig. 4 are designated with the same reference numerals and not necessarily described in further detail here.

[0035] A first preferred exemplary embodiment of an apparatus according to the present invention is described in the following with reference to Fig. 1. The inventive apparatus comprises a stretching and overfeeding unit A, a steaming and moisturising unit B, a compacting module C1 and a cooling unit D in the order as seen in the direction of passage of the fabric through the apparatus.

[0036] The stretching and overfeeding unit A is provided especially if a tubular fabric 24 is to be processed in the inventive apparatus. The stretching and overfeeding unit A comprises a tubular expander 1 and, upstream thereof, a tension control roller 2, which may be automatically controllable by an electronic load cell or the like, and an idle return roller 3. The tubular expander 1 expands the tubular fabric across its width as seen in the direction of conveyance thereof such that it essentially comprises two flat layers when stretched to ensure optimal treatment thereof in the subsequent processing stages. In operation, a tubular fabric 24 is fed to the stretching and overfeeding unit A to be threaded onto the tubular expander 1 via the tension control roller 2 and the idle return roller 3. The expander acts to transversely stretch the tubular material in an adjustable manner to a predetermined width and to overfeed the material longitudinally until a desired extent is obtained. The expander 1 then guides the tubular fabric 24 in this preset condition via a tension control roller 5 into the steaming and moisturising unit B. On the other hand, if an open-width fabric material 24' is to be processed in the inventive apparatus, the tubular expander can be bypassed or even removed. The open-width fabric material 24' is then fed via the tension control roller 5 and a spreading roller 6 directly into the steaming and moisturising unit B, as indicated by the dashed lines in Fig. 1.

[0037] Irrespective of the fabric being a tubular fabric 24 or an open-width fabric 24', the fabric is fed in a predetermined condition into a steaming box 4 of the steaming and moisturising unit B. The steaming box 4 of the steaming and moisturising section B is required to preheat and moisten the fabric 24 or 24' to cause the fibers in the fabric to swell and become plastic. This facilitates and enhances slippage of the individual fabric fibers with respect to each other during the subsequent compacting or compressive shrinking stage.

[0038] After passage through the steaming and moisturising unit B as shown in Fig. 1, the fabric 24 or 24' enters the compacting or compressive shrinking module C1. The compacting module C1 comprises first and second shrinking sections c1 and c2. First compressive shrinking section c1 comprises an endless fabric support belt or felt belt 7 which is partially wound around and driven by a felt belt drawing roller 8. A heatable felt belt support roller 10 is provided between the deflection roller 9 and the drawing roller 8 as seen in the direction of conveyance of the fabric 24 or 24' and the endless felt belt 7, but outside the loop of the felt belt 7 such that the belt is also partially wound around the periphery of the heatable support roller 10. Extending along the path of conveyance of the fabric 24 or 24' and the endless felt belt 7 at a partial peripheral surface portion of the deflection roller 9 up to a partial peripheral portion of the support roller 10 is a sliding sheet or shoe 11. The sliding sheet or shoe is arranged such that it extends across the width of and is in close contact with the external side of the fabric 24 or 24' on the felt belt 7 on the one side and, at a downstream portion thereof, the sheet or shoe 11 is also in contact on its opposite side with a partial peripheral surface of the support roller 10. The sliding sheet or shoe 11 thus guides the felt belt 7 and the fabric 24 or 24' along a partial peripheral surface portion of the deflection roller 9 and beyond this to a partial peripheral portion of the heatable support roller 10 to press the fabric 24 or 24' into close contact with the endless felt belt 7 to prevent relative movement between the belt and the fabric and, beyond this, to press the endless felt belt 7 and the fabric 24 or 24' into contact with the partial peripheral portion of the heatable support roller 30. The extent of pressure applied by the sheet or shoe 11 can be adjustable, if desired. In this manner, improved conditions for compressively shrinking the fabric 24 or 24', and especially the external side thereof, in the first compressive shrinking section c1, are provided by the sliding sheet or shoe 11. The fabric 24 or 24' is then guided along a further partial peripheral portion of the heatable support roller 10 to undergo a calendering/smoothing effect after the compressive shrinking treatment.

[0039] After the first side of the fabric 24 or 24' has been treated in this manner in the first compressive shrinking section c1, it leaves the endless felt belt 7 and passes over a tension control roller 12 before it enters the second compressive shrinking section c2 for treatment of the second side of the fabric. The second compressive shrinking section c2 has essentially the same structure and arrangement as the first compressive shrinking section c1 but in the opposite sense so as to treat the other, second side of the fabric opposite the first side treated in the first section c1. Therefore, the second compressive shrinking section also comprises an endless fabric support belt in the form of a felt belt 13. This belt is guided around and driven by a drawing roll 14 and, upstream thereof as seen in the direction of conveyance of the fabric 24 or 24', around a deflection roll 15. The endless felt belt 13 is partially wound around the peripheral surface of the drawing roller 14 and the deflection roller 15 for sufficient guidance while also minimising wear thereof.

[0040] Additionally, a heatable support roller 16 is provided for the felt belt 13 and the fabric 24 or 24' and arranged between the deflection roller 15 and the drawing roller 14 as seen in the direction of conveyance of the fabric, and outside the loop of the endless felt belt 13 such that the fabric 24 or 24' and the belt 13 are wound around a partial peripheral portion of the support roller 16. As in the case of the first compressive shrinking section c1, the second compressive shrinking section in this preferred embodiment of the inventive apparatus is provided with a sliding sheet or shoe 17 which extends across the width of the fabric and between a partial peripheral portion of the deflection roller 15 and a partial peripheral portion of the support roller 16 to press the fabric 24 or 24' against the endless felt belt 13 so that it is in close contact therewith. This prevents relative movement or slippage between the fabric 24 or 24' and the felt belt 13 to a desirably adjustable extent, as in the case of sliding sheet or shoe 11 of the first section c1, as the fabric passes along the curved path between the deflection roller 15 and the support roller 16 to compressively shrink the second side of the fabric in a similar manner as in the first section c1, as described above.

[0041] The fabric 24 or 24' is subsequently preferably subjected to a calendaring/smoothening effect by further partial peripheral portion of the heatable support roller 16 before it leaves least the felt belt 13 and passes over a tension control roller 18 and into the cooling unit D. In the cooling unit D, the fabric 24 or 24' is conveyed along the net conveyor belt 19 and treated in a similar manner as described previously with reference to Fig. 4. The treated fabric 24 or 24' then leaves the cooling unit D via a tension control roller 23 and is supplied to a suitable fabric collecting system (not shown).

[0042] In accordance with the present invention, the apparatus and the related method of compressively shrinking the fabric 24 or 24' is carried out with a ratio between the diameter of the deflection roller and the thickness of the fabric support belt of each compressive shrinking section ranging between substantially 6:1 and 4:1 and a ratio between the diameter of the fabric belt support roller and the thickness of the fabric support belt of each compressive shrinking section ranging between substantially 15:1 and 6.5:1 such that the advantageous effects as previously described in detail are achieved.

[0043] Essentially, the second preferred exemplary embodiment of an apparatus according to the present invention illustrated in Fig. 2 corresponds to that in Fig. 1 but with one additional compressive shrinking module C2 arranged immediately downstream of the first compressive shrinking module C1 and upstream of the cooling unit D. The first compressive shrinking module C1 of the second preferred exemplary embodiment of the inventive apparatus as illustrated in Fig. 2 has the same arrangement of parts with the same reference signs as that illustrated in Fig. 1. Additionally, however, the second embodiment of the inventive apparatus shown in Fig. 2 has a second compressive shrinking module C2 which is substantially identical to the first compressive shrinking module C1 illustrated in Figs. 1 and 2 and comprises a third compressive shrinking section c3 and a fourth compressive shrinking section c4 arranged downstream thereof, the third and fourth sections being provided to respectively further compressively shrink one of the two opposite sides of the fabric 24 or 24' conveyed therethrough. In this manner, the third and fourth compressive shrinking sections respectively operate in a substantially identical manner to the first and second compressive shrinking section c1 and c2 of the first compressive shrinking module C1 of the present invention.

[0044] The third compressive shrinking section c3 comprises an endless fabric support belt in the form of a felt belt 27 which is partially would around and driven by a felt belt drawing roller 28 and a felt belt deflection roller 29. A heatable felt belt support roller 30 is provided between the deflection roller 29 and the drawing roller 28 as seen in the direction of conveyance of the fabric 24 or 24' and the endless felt belt 27. The felt belt 27 is therefore also partially would around the periphery of the heatable support roller 30. A sliding sheet or shoe 31 is provided to extend along the path of conveyance of the fabric 24 or 24' and the endless felt belt 27 downstream of a partial peripheral surface portion of the deflection roller 29 guiding the belt and fabric to a partial peripheral portion of the heatable support roller 30 to press the endless felt belt or the fabric 24 or 24' into contact with the heatable support roller 30. A first side of the fabric is compressively shrunk in the third section c3 in a similar manner as in the first section c1 described above.

[0045] Following its passage through the third compressive shrinking section c3, the fabric leaves the endless felt belt 27 and passes over a tension control roller 32 before it enters the fourth compressive shrinking section c4. The fourth section c4 also comprises an endless fabric support belt in the form of a felt belt 33 which is guided around a drawing roll 34 and a deflection roll 35. As in the case of the first, second and third compressive shrinking section c1 to c3, the endless felt belt 33 in the fourth compressive shrinking section c4 is partially wound around the peripheral surfaces of the drawing roller 34 and the deflection roller 35. A heatable support roller 36 for the felt belt 33 and the fabric 24 or 24' is arranged between the deflection roller 35 and the drawing roller 34 as seen in the direction of conveyance of the endless belt 33 and the fabric 24 or 24' such that the fabric 24 or 24' and the endless felt belt 33 are wound around a partial peripheral portion of the heatable support roller 36. The fourth compressive shrinking section c4 is also provided in this preferred embodiment of the inventive apparatus with the sliding sheet or shoe 37 which extends across the width of the fabric 24 or 24' as seen in its direction of conveyance through the fourth section c4 and, as in the case of the sliding sheets or shoes 11, 17 and 31 in the preceding compressive shrinking sections c1 to c3, extends from downstream of a partial peripheral portion of the deflection roller 35 guiding the belt and fabric to a partial peripheral portion of the support roller 36 to press the fabric 24 or 24' against the endless felt belt so that it is in close contact therewith and relative movement or slippage between the fabric 24 or 24' and the endless felt belt is prevented to the desired extent as the fabric 24 or 24' passes along the curved path between the deflection roller 35 and the support roller 36 to compressively shrink the second side of the fabric in a similar manner as in the second section c2, as described above. After leaving its path of conveyance between the support roller 36 and the endless felt belt 33 in the fourth compressive shrinking section c4, the fabric 24 or 24' is passed over a tension control roller 38 and then on to the net conveyor belt 19 in the cooling unit D, as described previously with reference to Fig. 1.

[0046] In accordance with the preferred exemplary embodiments of a method and apparatus according to the present invention described with reference to Figs. 1 and 2, all of the compressive shrinking sections c1 to c4 comprise an arrangement in which the ratio between the diameter of the deflection roller and the thickness of the fabric support belt or felt belt ranges between substantially 6:1 and 4:1 and the ratio between the diameter of the fabric belt support roller and the fabric support belt or felt belt ranges between substantially 15:1 and 6.5:1 so that the previously described advantages in respect of productivity, shrinkage degree and operation flexibility can be achieved. An explanation of determining the advantageous effects of the present invention as a result of the special ratio between the deflection and support roller diameters and the thickness of the fabric support belt is outlined in the following with reference to Figs. 3a and 3b.

[0047] Key elements of the inventive system are illustrated with reference to Fig. 3a and 3b, taking the first compressive shrinking section c1 shown in Fig. 1 or 2 as a representative example for all sections c1 to c4, and defined as follows:

• the thickness T of the felt belt (7);
• the thickness T/2 of the longitudinal central section (72) of the felt belt (7);
• the diameter D1 of the belt deflection roller (9);
• the diameter D2 of the belt support roller (10);
• the revolutions R1 of the belt deflection roller (9);
• the revolutions R2 of the belt support roller (10);
• the speed S of the longitudinal central section (72) of the felt belt (7);
• the speed S1 of the felt belt upper surface (71) wound around the deflection roller (9), particularly from point P1 to point P2;
• the speed S2 of the felt belt upper surface (71) wound around the support roller (10), particularly, from point P3 onwards.

[0048] The relation between the speeds S and S1 is:

R1 being constant for a constant speed S, the greater T is, the more S1 is greater than S. In particular, S1 increases by a factor 1 of T.

[0049] The relation between the speeds S and S2 is:

R2 being constant for a constant speed S, the greater T is, the more S2 is less than S. In particular, S2 decreases by a factor 1 of T.

[0050] The relation between the speeds S1 and S2 is:

Since R1 and R2 are inversely proportional to their respective D1 and D2, the greater T and R1, R2 are (which means the more D1, D2 are smaller) the more S2 is smaller than S1. In particular, S2 decreases by a factor 2 of T.

[0051] Therefore, it may be concluded that the fabric speed difference, in the passage from points P1 and P2 to point P3 onwards, is

Such a speed difference is directly proportional to twice the felt belt thickness and, at the same time, is also inversely proportional to the roller diameters D1 and D2, resulting in as much an increase for a larger T and for a smaller D1 and D2.

[0052] From the analysis above, it is apparent that the position of points P2 and P3 is unimportant as to the speed difference S1-S2 and, consequently, to the amount of fabric compressive shrinkage. In fact, in the case in which points P2 and P3 do not coincide (Fig. 3a), the felt belt upper face (71) assumes between the two points a speed S, where S1>S>S2, the same as that of its longitudinal central section (72). Thus, the fabric decelerates gradually from its speed S1 (points P1-P2) through speed S (points P2-P3) to speed S2 (point P3 onwards).

[0053] When points P2 and P3 do coincide (Fig. 3b), the felt belt upper face (71) changes its speed from S1 to S2, where S1>S2, and the fabric decelerates immediately, at the felt belt inversion point P2/P3, from its speed S1 (points P1-P2/P3) to speed S2 (points P2/P3 onwards).

[0054] Therefore, in the inventive apparatus, in order to adjust the distance between the two rollers, particularly, for example, as a result of belt wear and progressive thickness reduction, the support roller can be moved by means of its shaft (101) sliding in the hole (102) in the roller, towards or away from the deflecting roller, from an arrangement in which their spacing is, for example, 1-2 mm greater than the belt thickness (points P2 and P3 do not coincide) to an arrangement in which their spacing equals the belt thickness (points P2 and P3 coincide).

[0055] The reasoning for that are basically for servicing:

• felt belt installation and replacement for maintenance;
• felt belt wear and tear control and limitation during operation;
• felt belt thickness reduction compensation due to wear.

[0056] On the contrary, a situation like that of Fig. 3b stresses the belt wear and tear whilst it does not increase compressive shrinking performance. Such an adjustment is only helpful towards the end of the belt working life in order to recover its thickness loss and utilise it to the fullest possible extent.

Claims

1. Apparatus for the compressive shrinking of textile fabrics, preferably knitted fabrics, in either tubular or open-width form, comprising, in the order as seen in the direction of conveyance of the fabric through the apparatus, a fabric steaming and moisturising unit (B) and at least one compressive shrinking module (C1) with substantially identical first (c1) and second (c2) compressive shrinking sections arranged in series to compressively shrink a respective side of the fabric, each compressive shrinking section (c1;c2) having a fabric support belt (7;13) guided between a fabric support belt deflection roller (9;15) and a heatable fabric belt support roller (10;16), characterized in that the ratio between the diameter of the fabric support belt deflection roller and the thickness of the fabric support belt of each compressive shrinking section ranges between substantially 6:1 and 4:1, and the ratio between the diameter of the fabric belt support roller and the thickness of the fabric support belt of each compressive shrinking section ranges between substantially 15:1 and 6.5:1.

2. Apparatus according to claim 1, characterized in that there is provided at least one further compressive shrinking module (C2) immediately downstream of the first compressive shrinking module (C1), each further compressive shrinking module (C2) comprising a substantially identical arrangement to that of the first compressive shrinking module (C1) with two compressive shrinking sections (c3,c4) arranged in series and each section having a fabric support belt (27,33) guided between a fabric support belt deflection roller (29,35) and a heatable fabric belt support roller (30,36).

3. Apparatus according to claim 1 or 2, characterized in that the ratio between the diameter of the deflection roller and the fabric support belt thickness ranges between substantially 5.5:1 and 4.25:1 and/or the ratio between the fabric belt support roller diameter and the fabric support belt thickness ranges between substantially 12:1 and 7.5:1.

4. Apparatus according to any one of the preceding claims, characterized in that the ratio between the diameter of the deflection roller and the fabric support belt thickness ranges between substantially 5:1 and 4.5:1 and/or the ratio between the fabric belt support roller diameter and the fabric support belt thickness ranges between substantially 10:1 and 8:1.

5. Apparatus according to claim 1 or 2, characterized in that the ratio between the deflection roller diameter, the fabric support belt thickness and the fabric belt support roller is substantially 4.5:1:7.

6. Apparatus according to claim 1 or 2, characterized in that the ratio between the deflection roller diameter, the fabric support belt thickness and the fabric belt support roller is substantially 4:1:6.5.

7. Apparatus according to any one of the preceding claims, characterized in that one or more of the fabric support belts is an endless belt and, in the one or more of the compressive shrinking sections comprising such an endless belt, the fabric support belt is wound around the deflection roller, a drawing roller and the fabric belt support roller, the fabric belt support roller supporting the fabric and the fabric support belt along their path of conveyance between the deflection roller and the drawing roller.

8. Apparatus according to claim 7, characterized in that each endless fabric support belt is at least partially wound around the associated deflection roller, drawing roller and/or fabric belt support roller.

9. Apparatus according to any one of the preceding claims, characterized in that one or more of the compressive shrinking sections comprises a sliding sheet or shoe extending between the associated fabric support belt and the fabric belt support roller to press the fabric against the fabric support belt surface along its passage between the deflection roller and the fabric belt support roller and beyond.

10. Apparatus according to any one of the preceding claims, characterized in that a stretching and overfeeding unit (A) is arranged upstream of the steaming and moisturising unit (B) to stretch and overfeed the fabric and/or a cooling unit (D) is arranged downstream of the last compressive shrinking module to cool the fabric.

11. Apparatus according to claim 10, characterized in that the stretching and overfeeding unit (A) comprises an expander to expand the fabric transversely to its direction of conveyance.

12. Apparatus according to claim 11, characterized in that the expander is a tubular fabric expander (1).

13. Apparatus according to any one of the claims 10 to 12, characterized in that the cooling unit (D) comprises a fabric conveyor belt such as a net and an air suction box arranged to suck cooling air through the conveyor belt.

14. Apparatus according to any one of the preceding claims, characterized in that one or more of the compressive shrinking sections comprises a felt belt as the fabric support belt.

15. Apparatus according to any one of the preceding claims 10 to 14, characterized in that a fabric tension control roller is provided in the stretching and overfeeding unit (A), the steaming and moisturising unit (B), the one or more compressive shrinking modules (C) and/or the cooling unit (D).

16. Apparatus according to claim 15, characterized in that the one or more tension control rollers are automatically controllable by electronic load cells or the like.

17. Method of compressive shrinking of longitudinal tubular or open-width textile fabric such as knitted fabric, comprising the steps of:

a) guiding said fabric through a steaming and moisturising unit (B) to heat and moisten the fabric by steam;

b) supplying the heated and moisturised fabric to the inlet side of at least one compressive shrinking module (C1) with first (c1) and second (c2) compressive shrinking sections arranged in series, each compressive shrinking section comprising a fabric support belt guided between a fabric support belt deflection roller and a heatable fabric belt support roller ;

c) treating the fabric in the first compressive shrinking section (c1) by laying it on an upper external side of the fabric support belt on the deflection roller, maintaining the fabric in close contact with the fabric support belt and introducing the fabric in this state between the fabric support belt and the heated fabric belt support roller to compressively shrink it; and

d) immediately after its treatment in the first compressive shrinking section (c1), treating the fabric in the second compressive shrinking section (c2) in a manner substantially identical to the treatment in the first section but in an opposite sense so as to repeat the identical treatment on the opposite side of the fabric;
characterized by

e) carrying out compressive shrinking steps c) and d) with a ratio between the diameter of the fabric support belt deflection roller and the thickness of the fabric support belt of each compressive shrinking section ranging between substantially 6:1 and 4:1 and a ratio between the diameter of the fabric belt support roller and the thickness of the fabric support belt of each compressive shrinking section ranging between substantially 15:1 and 6.5:1.

18. Method according to claim 17, characterized by further treating the fabric, immediately after its treatment in the first compressive shrinking module (C1), in at least one further compressive shrinking module (C2) in a manner substantially identical to the treatment in the first module (C1) according to steps c) and d), each further compressive shrinking module comprising a substantially identical arrangement to that of the first module with two compressive shrinking sections arranged in series and each having a fabric support belt guided between a fabric support belt deflection roller and a heatable support roller.

19. Method according to claim 17 or 18, characterized by feeding the fabric prior to step a) to a stretching and overfeeding unit (A) to stretch it transversely to the direction of conveyance of the fabric to a pre-determined width and overfeeding it longitudinally to an adjustable extent.

20. Method according to any one of the preceding claims 17 to 19, characterized by carrying out a cooling and stabilisation of the fabric in a cooling unit (D) after step f) by conveying the fabric on a revolving conveyor belt such as a net and sucking cooling air across the fabric on the conveyor belt by means of an air suction box.

21. Method according to any one of the preceding claims 17 to 20, characterized by carrying out step e) at a ratio between the diameter of the deflection roller and the fabric support belt thickness ranging between substantially 5.5:1 and 4.25:1 and/or a ratio between the fabric belt support roller diameter and the fabric support belt thickness ranging between substantially 12:1 and 7.5:1.

22. Method according to any one of the preceding claims 17 to 21, characterized by carrying out step e) at a ratio between the deflection roller diameter and the fabric support belt thickness ranging between substantially 5:1 and 4.5:1 and/or a ratio between the fabric belt support roller diameter and the fabric support belt thickness ranging between substantially 10:1 and 8:1.

23. Method according to any one of the preceding claims 17 to 20, characterized by carrying out step e) at a ratio between the deflection roller diameter, the fabric support belt thickness and the fabric belt support roller diameter of substantially 4.5:1:7.

24. Method according to any one of the preceding claims 17 to 20, characterized by carrying out step e) at a ratio between the deflection roller diameter, the fabric support belt thickness and the fabric belt support roller diameter of substantially 4:1:6.5.

25. Method according to any one of the preceding claims 17 to 24, characterized by maintaining in one or more of the compressive shrinking sections the fabric in close contact with the fabric support belt by means of pressing it against the belt during its passage between the deflection roller and the fabric belt support roller and beyond by means of a sliding sheet or shoe extending between the associated fabric support belt and the fabric belt support roller in the respective compressive shrinking section.

26. Method according to any one of the preceding claims 17 to 25, characterized by controlling the tension of the fabric along its path of conveyance by means of one or more tension control rollers or the like.

27. Method according to any one of the preceding claims 17 to 26, characterized by using in one or more of the compressive shrinking sections an endless fabric support belt, preferably a felt belt, and guiding the endless belt around the deflection roller, a drawing roller and the fabric belt support roller, and supporting the fabric and the belt by means of the fabric belt support roller along their path of conveyance between the deflection roller and the drawing roller in the respective compressive shrinking section.

28. Method according to claim 27, characterized by winding the endless belt at least partially around the deflection roller, the drawing roller and/or the fabric belt support roller.

Drawing