PROCESS AND APPARATUS FOR THE CONTINUOUS DECATING OF A FABRIC

Abstract: A process for the continuous decating of a fabric continuously fed towards an area provided with a pressurized-steam atmosphere, wherein the area is tightly sealed towards the external environemt, and the fabric under treatment is maintained in the area between at least one back-gray (14) and a cylindrical drum (11) coated with a textile material.

Description: The present invention relates to a process and apparatus for the continuous decating of a fabric. The machines for autoclave-decating operating in alternate-cycle, or batchwise, mode, of the type known from the prior art, perform working cycles essentially constituted by the set of the following main steps: winding of the fabric, and of the back gray, on a beam; charging of the beam to an autoclave; autoclave decating; removal of the beam from the autoclave; unwinding of the fabric and of the back gray from the beam. The winding and unwinding steps take place at suitable stations outside the autoclave. The charging and removal steps require suitable beam-handling units, which considerably contribute to the total cost of the facility and, furthermore, involve an operating time which decreases the production rate. On the other hand, alternate-cycle, or batchwise, autoclave-decating machines are known, wherein the steps of fabric and back gray winding and unwinding take place with the beam being permanently housed inside the autoclave, so as not to require any operations of beam charging to, and removal from, the autoclave, in that the fabric and the back gray can be directly fed from the external station to the beam housed inside the autoclave, and, after the decating step is finished, can be discharged as well from the beam housed inside the autoclave to the external station. Furthermore, from the view point of quality, the batchwise decating in autoclave, as a consequence of the treatment of various layers of fabric wound around a beam causes anyway not negligible problems of uniformity in lent effects between the internal and the external layers of the roll, and between the centre and the selvedges of the fabric. Such a drawback is indeed the problem all manufacturers of decating machines have been unsuccessfully coping with for many years, and is the cause of complaints by the users of such facilities. Moreover, the batchwise decating in autoclave generally requires an operation of preparation of the fabric to be treated, consisting in a pressing, which is carried out on calendering machines. The purpose of such a preparation is to priorily reduce the thickness of the fabric, in order to prevent such a reduction in thickness from subsequently taking place to an excessive extent during the decating operation in autoclave, during which the fabric - due to the fact that many layers thereof are wound on a beam - may undergo irreversible deformations. DE-A-2 024 388 discloses a process and apparatus for the continuous decating of a fabric whereby the fabric is treated with a steam atmosphere under controlled pressure at at least a portion of the treating path. DE-A-1 635 329 also discloses a process and apparatus for continuous decating of a fabric in which feeding and maintaining of the fabric within a pair of back grays or blankets enable the steam to pass through the fabric and the blankets and perform a slight mechanic pressure on the fabric itself. A purpose of the present invention is to provide a continuous decating process, which makes it possible at least the same qualitative results to be achieved, which are presently only achievable by means of the batchwise treatments in autoclave, with the negative aspects of these latter being overcome. A further purpose is to make it possible such a process to be performed in continuous mode, with a simply-structured and simply-operating machine. These, and still further purposes according to the invention are achieved by providing a process for the continuous decating of a fabric according to claim 1. Furthermore, according to the invention, this process is preferably carried out on an apparatus according to claim 3. Characteristics and advantages of a process and of an apparatus for the continuous decating according to the present invention can be better understood from the following exemplifying and non-limitative disclosure also referred to the hereto attached schematic drawings wherein: Figure 1 shows a cross section of an apparatus according to the present invention, according to path I-I of Figure 2, Figure 2 shows a longitudinal view according to path II-II of Figure 1, Figure 3 shows a cross section of another form of practical embodiment of the apparatus of the present invention, according to path III-III of Figure 4; Figure 4 shows a longitudinal cross section according to path IV-IV of Figure 3; and Figure 5 shows a cross section of still a further form of practical embodiment of the apparatus of the invention, similar to that of Figure 1. The process for the continuous decating of a fabric according to the invention comprises the continuous feeding of said fabric kept comprised within a pair of back grays. The fabric, at at least a portion of the treating path is treated with a steam atmosphere under a controlled pressure. The creation of said area containing said atmosphere of pressurized steam is defined by prearranging steam-tight sealing elements peripheral relatively to said area. According to the process of the invention, a change in the pressure of said steam atmosphere is furthermore possible by adjusting the action of said peripheral tight-sealing elements. The process of the invention, as above defined, is practiced, for exemplifying non-limitative purposes, by means of an apparatus which is shown in Figure 1 and 2. The apparatus is essentially constituted by a cylindrical drum 11, the outer surface 12 of which is constituted by an elastic, deformable material, coated by a sleeve 13 of a textile material, above, and around, which, a back gray 14, also of a textile material, of the closed, continuous-loop type, is wound. The drum 11, e.g., horizontally positioned, is rotatably supported by means of two axial hubs, fastened to both of the base ends thereof, and only partially shown in 10, on a support framework (not shown). In correspondence of at least a portion of the unit constituted by said drum 11, sleeve 13 and back gray 14, a steaming chamber, or steaming vat 15 is positioned, and maintained into contact with, adhering to, it, and laterally fastened to the support framework, not shown. Inside said chamber 15, a superheating coil is housed, which is constituted by a set of finned pipes 16 through which steam flows, and furthermore a steam feed pipe 17 by which steam under controllable pressure is delivered, and a condensate-drain pipe 18 are provided, with the chamber 15 being open in its side opposite to said back gray 14. Said steaming vat 15 has, at its wall ends opposite to said back gray 14, a peripheral groove 19 inside which a tight-sealing element 20 is housed, which is given the form of a surface-contact rubbing block, and is pressed against said back gray 14 both transversely and longitudinally relatively to said cylindrical drum 11. The pressure of said rubbing block 20 on said back gray 14 is determined and controlled by means of an inflatable element constituted by an air tube 21, interposed between said rubbing block 20 and said groove 19. The back gray 14 is returned and guided, in the portion of its path wherein it is not wound around the drum 11, on a set of return rolls 22 at least one of which is equipped with a pneumatic or hydraulic device, not shown, known from the prior art, by means of which the tension of the back gray 14 is adjusted, so that this latter can transmit, along the portion of its path wherein it is wound around said cylindrical drum 11, a variable squeezing pressure. Two further motor-driven rolls 23 constitute the drive means by which the back gray 14 is driven and in its turns transmits the motion to the cylindrical drum 11. According to a further form of practical embodiment, referring to Figures 3 and 4, in correspondence of at least a portion of the unit constituted by said drum 11, sleeve 13 and back gray 14, a set of rolls 25 are positioned, with said rolls 25 being coated with a sleeve 26 of an elastic, deformable material, and being rotatably supported, through hubs 27, by side support plates 28; said rolls are steam-heated. Said rolls 25 are positioned into contact with one another, and each second roll is kept into contact with the unit constituted by said drum 11, sleeve 13 and back gray 14 in such a way as to define, as a whole, at least a steaming chamber 29, inside which at least one steam supply pipe 30 delivering steam under a controllable pressure is installed. Each one of said rolls 25 is furthermore equipped with an either pneumatic of hydraulic device, known from the prior art, which is suitable for keeping them compressed against one another, and respectively against said back gray 14. The pressure applied by said rollers 25 to one another, and respectively to said back gray 14 performs a function of longitudinal tight sealing against any escape of the steam delivered by each steam supply pipe 30 housed inside each one of said steaming chambers 29. The side sealing is secured by means of two gaskets 31 of surface-contact rubbing type, each of which is inserted inside a groove 32 provided on each of said side support plates 28. Said gaskets 31 are furthermore kept pressed so as to rest against the base ends of said rolls 25 and of said drum 11 by two inflatable air tubes 33, each of which is interposed between said gasket 31 and said groove 32. The operation of such an apparatus can be easily understood by referring to the hereto attached figures, wherein the fabric 24 is continuously fed by the first drive roll 23 and, supported by the back gray 14, enters the space between the sleeve 13 which coats the drum 11 and the back gray 14 wound around it. While being so positioned, the fabric 24 is guided to run along the portion of circumference of said at least partially wound cylindrical drum 11, up to the outlet, which coincides with the second drive roll 23. The adjustment of the tension of the back gray 14, e.g. carried out as above stated, makes it possible a predetermined pressure of squeezing of the back gray 14 on the fabric 24, interposed between the same back gray and the sleeve 13, to be preset. The thickness of the fabric 24 is compensated for by the deformation and the squeezing of the elastic, deformable material 12. The pressure applied by the rubbing block 20 (Figures 1 and 2), or, respectively, by the rolls 25 (Figures 3 and 4) to the back gray 14 makes it possible a squeezing to be caused, which is addressed to at least limit the escape of the steam respectively fed to the steaming vat 15 by the pipe 17 (Figures 1 and 2), or to the steaming chambers 29 by the steam supply pipes 30 (Figures 3 and 4). The pressure of steam respectively inside the vat 15 or the chambers 29 is partially determined by the pressure respectively applied by the rubbing block 20 or by the rolls 25 to the back gray 14, and partially depends on the characteristics of permeability of the textile material the back gray 14 and the sleeve 13 are made from, wherein each of these latter could be generally named as "back gray". In fact, pressurized steam respectively delivered by the vat 15 and the chambers 29 through their open walls opposite to the drum 11 must be capable of relatively easily flowing through the back gray 14, in order to reach the fabric 24, and the underlying sleeve 13. As a practical matter of fact, a certain, limited, steam amount must be capable of flowing, by capillarity, partially through the back gray 14, partially through the fabric 24 and partially through the sleeve 13, in order to purge any air conveyed by said elements as they respectively enter the vat 15 or the chambers 29. As above said, also the sleeve 13 may be given the general name of "back gray", and, for a better understanding thereof, an exemplifying practical embodiment thereof can be seen in Figure 5, wherein to same parts of the apparatus same reference numerals correspond. In this case, the sleeve 13 is given the shape of a continuous, closed loop partially guided along the elastic, deformable material 12 of the cylindrical drum 11, and partially on return rolls 22, also provided with a tension adjustment device (not shown in the figure). It results thus clear how the sleeve can be generally regarded as a first, inner back gray 13, at least partially surrounding the external surface, constituted by an elastic, deformable materal 12, of the cylindrical drum 11. In this case, the back gray 14 will be defined as a second, outer back gray 14. The advantages of a continuous, under-pressure decating process according to the invention can be summarized as follows: uniformity of treatment in both the longitudinal and the transversal directions of the fabric; the fabric is no longer undergoing the decating treatment while being wound as a number of layers, with the faults due to permanent deformations being eliminated; the operations of preparation of the fabric to be submitted to decating are get rid of; and the idle times are eliminated, with the production rate being increased, and the operating costs being decreased.

Claims: Process for the continuous decating of a fabric (24) whereby the fabric is treated with a steam atmosphere under controlled pressure at at least a portion of the treating path and is fed and maintained comprised within a pair of back grays (13,14), characterised in that it comprises the presetting of steam-tight sealing elements peripheral relatively to said portion of the treating path treated with pressurized steam atmosphere. Process according to claim 1, characterised in that it comprises an adjustment of the action of said peripheral sealing elements by associated inflatable elements. Apparatus for the continuous decating of a fabric (24) comprising a cylindrical drum (11), the outer surface of which is constituted by an elastic deformable material at least partially coated with a first inner back gray (13) of a textile material, above which said continuous fabric (24) is fed with said cylindrical drum (11), and said first inner back gray (13) being externally at least partially covered and surrounded by a second outer gray back (14) of a textile material to which the shape of a continuous closed loop is given, and which is provided with its own drive means, whereby at, at least, one portion of the contact zone between said cylindrical drum (11) coated with said inner gray (13) said fabric (24) and said outer back gray (14), a chamber (15,29) is positioned, which contains a pressurized steam atmosphere, whereby the chamber (15,29) extends at least over the whole width of the fabric (24), and being equipped with pressure-tight sealing elements (20, 31) peripheral with respect to said at least one portion, characterised in that said peripheral pressure-tight sealing elements (20,31) are rubbing-block elements, associated with at least one inflatable element (21,33). Apparatus according to claim 3, characterised in that said first inner back gray (13) coating said elastic deformable material is a sleeve. Apparatus according to claim 3, characterised in that said at leat one chamber (15,29) is provided with a steam feed pipe (17,30) delivering pressurized steam and with a condensate drain pipe (18). Apparatus according to claim 3, characterised in that inside said at least one chamber (15,29) a superheating coil (16) is provided, through which steam flows. Apparatus according to claim 3, characterised in that said peripheral pressure-tight sealing elements are of the type of surface-contact rubbing elements (31), respectively positioned longitudinally to said cylindrical drum (11), and transversely to surround said cylindrical drum (11). Apparatus according to claim 3, characterised in that said at least one chamber (29) is defined by a set of revolving rolls (25) positioned into contact with one another, with each second roller thereof being kept into contact with said second outer back gray (14). Apparatus according to claim 8, characterised in that inside said at least one chamber (29) at least one steam feed pipe (30) delivering pressurized steam is provided. Apparatus according to claim 8, characterised in that said revolving rolls (25) are externally coated with an elastic deformable material (26) and are internally heated with steam. Apparatus according to claim 8, characterised in that said set of revolving rolls (25) constitute a steam pressure sealing element longitudinal relatively to said cylindrical drum (11). Apparatus according to claim 8, characterised in that said set of revolving rolls (25) and said cylindrical drum (11) are equipped with side tight-sealing elements of surface-contact rubbing type.

Inventors: DALLA VECCHIA, GINO
Applicants: SPEROTTO RIMAR S.P.A.
Application year: 1988
Main classification: D06C7
IPC codes: D06B1, D06F87, D06B3, D06C15, D06C7