Felt calendering of fabrics and a machine for performing it

Abstract

 A wet fabric (18) is felt calendered by passing it in a suc­cession and alternately over a plurality of rollers be­longing to a first order and to a second order. An annular felt band (9) recirculating at the same speed of the fabric is maintained in contact with the fabric during the passage of the fabric over the external surface of the heated man­tle of the rollers belonging to one of said two orders (3,5,7) and the felt further embraces an additional heated drying rol­ler (8) before recirculating again on the series of rollers of said order. Alternately, e.g. between a roller embraced by the felt and the next one, the fabric travels on a roller belonging to the other order of rollers, which may also be optionally heated, without being sandwiched thereon by the recirculating felt. The temperature of each roller is sepa­rately adjustable in order to optimize the treatment con­ditions of the fabric, notably temperature and humidity, though being restrained to maintain a dictated speed of the fabric. The finishing characteristics which are obtained and the energy efficiency of the drying process are im­proved in respect to the prior art. A felt calender with these characteristics is also disclosed.

Description

[0001] The present invention relates to woven and knitted fabric finishing techniques and, in particular, to felt calendering of woven or knitted fabric as a last finishing treatment.

[0002] Felt calendering of fabrics is a well known and widely employed technique for giving an attractive luster and feel to the fabric manufactured. Felt calendering may follow other finishing treatments, such as for example a Sanforizing treatment (Sanfor^R is a registered trade mark of Cluett, Peabody & Co. Inc., U.S.A.) or a starching treatment, etc.. In all cases, whether the fabric come from one of these treatments or not, it contains a certain amount of moisture commonly comprised between 20% and 25% by weight. Basically felt calendering consists in passing the wet or purposely wetted fabric over the external surface of the heated man­tle of a large diameter calender roller, commonly having a diameter comprised between 1000 and 2500 millimeters and heated by means of steam or oil circulation, while maintain­ing in contact with the surface of the fabric around the heated mantle of the roller which is embraced for about 320° by the running fabric, a felt recirculating substan­tially at the same speed of the running fabric. The mois­ture transferred from the fabric to the felt during the passage of the fabric on the heated calender roller is con­tinuously evaporated off the recirculating felt by passing the latter on a drying heated roller. The function is that of drying the fabric while holding it as in a sandwich bet­ween the heated calender roller and the embracing recircula­ting felt in order to confer to the fabric the typical feel of such a finishing treatment, which is also known by the name "PALMER".

[0003] The known machines used for this treatment essentially comprise a sturdy frame on which the principal members re­presented by a main large diameter roller having a mantle which may be heated to an uniform adjustable tempe­rature and a second roller with a heated mantle embraced directly by the recirculating felt in order to continuously dry the latter by evaporating the moisture subtracted from the fabric are mounted. Suitable guide and jockey rollers guide the fabric and the recirculating felt which is made by an annular band, typically of a polyester fiber or or wool or of a wool-­polyester mixture, having a thickness of about 5-15 milli­meters. The calender is provided further with pneumatic centering devices as well as with tensioning means, with means for controlling the temperature of the mantle of the rollers as well as with means for rotating the main roller and the dryer roller of the recirculating felt in order to ensure an identical peripheral velocity of both the fab­ric and the felt, in function of the speed of the fabric through treatment stations which precedes the felt calender­ing station which is normally part of an integrated line of treatment stations operating in a continuous mode.

[0004] According to such a known technique, the felt calendering is carried out at a constant temperature which is adjustable by presetting the temperature of the mantle of the main roller. Being the calendering normally part of an integrated process operating in continuous mode which comprises several treatments performed in succession on the running fabric, the speed of the fabric is generally dictated by specific re­quirements of the treatments carried out before the final felt calendering. A consequence of this fact is a somewhat limited ability to adjust the parameters of the felt calen­dering treatment in function of the type of fabric and of the type of treatment to which the fabric is subjected before the final felt calendering for obtaining the best possible result while keeping in consideration that a necessary condition is that of ensuring that the fabric leaves the felt calen­der properly dried, i.e. with a residual moisture content below a maximum limit which commonly is comprised between about 5% and 10% by weight.

[0005] A main objective of the present invention is to provide an improved felt calendering method which permits to carry out this treatment of the fabric under temperature and hu­midity conditions which may advantageously be separately ad­justed in a substantially independent manner and within wide limits.

[0006] A further objective of the present invention is to pro­vide a felt calender capable of implementing the improved felt calendering treatment of the invention.

[0007] Essentially the felt calendering method of the present invention comprises passing the wet fabric in succession through a plurality of rollers, maintaining a recirculating felt in contact with the surface of the fabric running on the first of said rollers and on each successive roller of odd order of said plurality of rollers, passing the fabric on the second and on each successive roller of even order of said plurality of rollers without being contacted by the re­circulating felt, and adjusting individually the temperature of the mantle of each one of said rollers for achieving desired conditions of temperature and humidity of the fabric during the passage of the latter in succession on the various rol­lers embraced by the recirculating felt.

[0008] Basically, according to the present invention, a phasing of the felt calendering treatment is advantageously introduced in an essentially continuous process thus permitting to in­ dividually adjust the temperature of the distinct felt cal­endering rollers on which the fabric runs in succession and to adjust also the moisture content of the fabric in an es­sentially independent manner before the fabric passes through each successive felt calendering stage. In this way in each stage of the felt calendering treatment it is possible to ac­curately adjust the humidity/temperature "ratio" without the limitation determined by the otherwise unchangeable running speed of the fabric imposing any substantial impediment to the adjustment of such a ratio. The ability of adjusting this ratio between the two fundamental parameters of the treatment together to the ability of actually subjecting the fabric to successive treatment stages wherein this ratio may be sepa­rately adjusted, permits the achievement of a superior look and feel characteristics of the fabric in respect to those commonly obtained by the process of the prior art. A further advantageous aspect of the invention is represented by the fact that the fabric by passing through two orders of rollers during the drying treatment runs in contact with the metal surface of the normally chrome-plated steel mantle of the rollers alternately with the right and the reverse side thereof. This is instrumental to desirably obtain a lustering effect on both faces of the fabric.

[0009] The energy efficiency of the process is also comparably improved in respect to the efficiency of the known process. This may be attributed to the fact that the fabric continues to lose moisture while travelling from a felt calendering roller to the next passing on an intermediate roller (of even order) not embraced by the felt, thus decreasing the total energy required for drying the fabric.

[0010] The different features and advantages of the invention will be more evident through the folLowing detailed de­ scription of a preferred embodiment of the invention in relation to the annexed drawings, wherein:

Figure 1 is a simplified schematic elevation viex of a felt calender made in accordance with the present invention.

Figure 2 is a front view of the felt calender of Fig. 1.

[0011] The following detailed description of the preferred em­bodiment of the invention is purely illustrative and not limitative, being the invention practicable also in different embodiments which may be easily developed by a skilled technician on the basis of the present disclosure.

[0012] In Figures 1 and 2 the felt calender object of the pres­ent invention is globally indicated with 1. The machine has a sturdy steel frame 2 supporting a series of rollers having their axex substantially parallel to each other. A first lower (odd) order of calendering rollers (three in the shown embodiment), respectively 3, 5 and 7, are rotatably mounted at a certain level on the frame 2. A second upper (even) order of calendering rollers (two in the shown em­bodiment), respectively 4 and 6, are rotatably mounted on the frame 2 at a level higher than the level of the rollers of the first order and projectively in an intermediate posi­tion in respect to the distance between the axes of two adjacent rollers of the lower order. A dryer roller 8 for the recirculating felt of the machine is also rotatably mounted on the frame 2.

[0013] All said rollers are commonly rotated so that the pe­ripheral speed of the rollers' mantle is uniform by means of customary transmission organs of the motion generated by an electric motor, according to techniques which are well known to the skilled technician. These transmission organs are not shown in the figures for simplicity's sake. The re­circulating annular felt band 9 runs on free rolls 10, 11, 12, 13, 14, 15, 16 and 17 and besides embracing for about 320° the drying roller 8, the felt embraces for 180°-220° the calendering rollers of the lower (odd) order: 3, 5 and 7. The free running rollers 14, 15, 16, 17 and 10 or only few of them are provided with tensioning means for adjusting the tension of the recirculating felt band 9, in accord­ance with common practices.

[0014] The fabric 18 is correctly positioned by means of the roller 19 20, 21, ..., etc., and travels alternately on the first odd order roller 3 of the lower array of rollers embraced at least partially by the recirculating felt, than on the first even order roller 4 of the upper array of rollers, and so on through the plurality of calendering rollers. Small diameter jockey rollers 22, 23 and 24 are present for adjusting the tension of the running fabric.

[0015] Centering feeler means (not shown in the figures) are used in accordance with common practices for maintaining centered the fabric 18 and the recirculating felt band 9 travelling over the rollers of the machine, which typically have a length of about 2200 millimeters.

[0016] The felt calendering rollers belonging to the lower (odd) order 3, 5 and 7 have a diameter generally comprised between 600 and 1200 millimeters, though they may have a larger or smaller diameter. The steel mantle may be heated at a desired constant temperature, which may be independently set for each roller. Commonly the heating of the mantle of the rollers is effected by steam or overheated water or diathermic oil circulation in accordance with customary techniques, alternatively electric heating by means of re­sistors uniformly distributed within the mantle may be em­ployed. The upper (even) order rollers 4 and 6 may have the same diameter of the lower rollers 3, 5 and 7 or a slightly lower or larger diameter thereof. Preferably also the upper roller 4 and 6 may be heated at specific temperatures which may be independently set as for the lower order rollers 3, 5 and 7, and as for the felt drying roller 8. For the pur­poses of the invention it is not strictly necessary that both order of calendering roller be heated. The rollers which are not embraced by the recirculating felt may not be heated. The fabric travelling on these intermediate rollers not embraced by the recirculating felt continues to lose moisture by evaporation. Optionally, by providing means such as for example heat screens or air blowers it is also possible to control within certain limits the loss of mois­ture during the passage of the fabric on each one of said intermediate rollers not embraced by the felt in order to optimize the humidity/temperature ratio in the successive felt calendering stage. An associate advantage is represen­ted by the possibility of easily verifying that the fabric is correctly travelling through the machine because the fabric remains visible when travelling over said intermediate rollers.

[0017] In any case, it has been determined that, the overall de­velopment of the circumferences of the distinct heated rollers of the felt calender of the present invention being equivalent to the development of the circumference of the single calendering roller of a conventional type felt calendering machine, the heat efficiency of the drying process of the fabric for a certain amount of moisture is largely higher for the case of the machine of the present invention because the fabric during the passage on the "intermediate" rollers not embraced by the felt continues to lose moisture more freely than when sandwiched between the roller surface and the felt. This reflects in a remarkable energy saving for the whole calen­dering-drying process. Of course the invention may also be practiced by inverting the order of traversing, through an alternate manner, the series or rolls embraced and not em­braced by the recirculating felt band by the fabric and the relative number of rollers of the two distinct orders, as well as by differently arranging the rollers, e.g. in a vertical succession rather than in a horizontal succession as in the shown example.

Claims

1. A method for felt calendering fabrics comprising pas­sing a wet fabric between the external surface of the man­tle of a rotating roller heated at an adjustable constant temperature and a felt recirculating substantially at the same speed of the fabric and held in contact with the sur­face of the fabric around a portion of the circumference of the heated mantle of the roller, said recirculating felt passing on at least a second drying roller for continuously evaporating off the felt the moisture absorbed from the fabric during the calendering and characterized by
performing the calendering of the fabric in stages by passing the fabric through a plurality of rollers alter­nately belonging to an even and to an odd order of rollers;
maintaining said recirculating felt in contact with the fabric travelling on all the rollers belonging to one of said two orders of rollers and passing the fabric on the rollers belonging to said other order of rollers free from the contact with said recirculating felt; and
individually adjusting the temperature of the mantle of said rollers for setting desired conditions of tempera­ture and humidity of the fabric during the passage of the latter on each roller of said order or rollers in contact with said recirculating felt.

2. A felt calender for finishing treatments of fabrics having a frame supporting rollers having axes parallel among each other and driven in rotation at a substantially uniform peripheral speed and wherein at least one of said rollers has an heated mantle for drying a recirculating an­nular felt band and means for passing a wet fabric between the external surface of the heated mantle of a calendering roller and said felt recirculating at the same speed of the fabric and the maintaining said felt in contact with the surface of the fabric around a portion of the circum­ference of the heated mantle of the calendering roller and characterized by comprising
a first order of a plurality of calendering rollers regularly spaced along a first plane of the frame;
a second order of said calendering rollers disposed on a second plane parallel to said first plane and in an intermediate position in respect to said distance between the rollers of said first order;
means for passing the fabric on the first roller of one of said two orders of rollers and alternately in a suc­cession on all the remaining rollers of said two orders of rollers;
means for maintaining said recirculating felt in con­tact with the surface of the fabric travelling on the heated mantle of all the rollers belonging to one of said two orders of rollers; and
means for heating the mantle of the rollers belonging to at least said latter order of rollers at a constant tem­perature which is separately adjusted for each roller.

3. The calender according to claim 1, wherein all rol­lers of both said two orders are provided with means for heating their mantle at a constant temperature separately adjustable for each roller.

4. The calender according to claim 2, wherein said order of rollers embraced by said recirculating felt is said first order of rollers formed by an odd number of rollers;
the second order of rollers being formed by an even number of rollers smaller by one unity than the odd number of the rollers of the first order.

5. The calender according to claim 4, wherein the fabric embraces said rollers for an angle comprised between 180° and 220°.

Drawing