Apparatus for continuous steaming and dimensional stabilization of continuous fabric webs and relevant method

Abstract: An apparatus for continuous steaming and dimensional stabilization of continuous fabric webs comprises a steaming tunnel (11) through which a conveyor belt (12) runs, which supports and conveys a continuous fabric to be treated (13), the steaming tunnel (11) being provided with an inlet opening (14), an outlet opening (15) and a steam delivering device (16), in which apparatus the inlet opening (14) and the outlet opening (15) are both arranged under the bottom tunnel portion and inside said tunnel, opposite to at least one of said openings a temperature sensor (23) is provided which modulates the emission of steam from the steam delivering device (16). Furthermore, a method is accomplished for the steaming and dimensional stabilization of continuous fabric webs, method which is constituted by the treatment of fabric webs in an air-free atmosphere of saturated steam.

Description: The present invention relates to an apparatus for continuous steaming and dimensional stabilization of fabrics in the form of continuous webs, and to a method using said apparatus. At present, apparatuses are known and used for continuously performing the steaming, the relaxation, the shrinkage and the dimensional stabilization of fabrics in general. Under the generic term "fabrics", both fabrics of weft-warp type and knitted fabrics, as well as even non-woven fabric made from any materials of natural, man-made and synthetic origin, are to be understood. The apparatuses known from tne prior art have the purpose of determining a stabilization of the fabrics without applying any cross and/or longitudinal (i.e., in the machine direction) stresses to the material under treatment. These apparatuses essentially are constituted by a conveyor belt and a tunnel inside which the fabric is caused to run through. The conveyor belt is arranged as a closed ring and has a partially open surface structure, such as constituted by a net, so as to be permeable after receiving the fabric to be treated. The tunnel is assimilable to a steaming tank through which the fabric supporting conveyor belt runs. Under said conveyor belt, a steam delivering device, and over it a roof, or, anyway, a heated condensation preventing cover connected with a sucking hood with a vent fan are respectively provided. Said vent fan also intakes the steam which leaves the tunnel through the inlet and outlet openings of the latter, through which the conveyor belt and the fabric web run, together with a certain air amount from the working premises. Although they effectively treat the fabric and supply it with optimal, natural, stress-free relaxation and shrinkage effects, such a kind at apparatuses known from the prior art unfortunately display the following drawbacks. High steam consumption, because the tunnel must be constantly kept filled with steam and in the mean time there is a continuous escape of steam from said tunnel inlet and outlet openings. In fact, the steam excess is continuously sucked, together with a certain air amount from the working premises, by the sucking hood which is installed over the tunnel and is provided with a vent fan. Continuous steam and air venting to the surrounding atmosphere, with considerably high energy consumption and waste for the treatment and the heating of steam and air from the working premises. Treatment of fabric inside the tunnel with a mixed atmosphere of air and steam, with the treatment temperature being consequently limited at 100°C or slightly higher temperatures, and incomplete and, optimal dimensional stabilization of the fabric. FR-A-2147238 discloses an apparatus according to the preamble of claim 1. EP-A-0297029 relates to a similar apparatus in which a sensor is provided in order to modulate the emission of a fluid. FR-A-1576836 relates to a method for continuously steaming under pressure a fibrous material impregnated with a dye. This method aims at obtaining an improved fixing of the dye. The purpose of the present invention is of providing an apparatus capable of overcoming the above drawbacks, so as to yield a treated fabric which is dimensionally stable, with a minimal energy amount and limited costs. This purpose according to the invention is achieved by providing an apparatus for continuous steaming and dimensional stabilization of continuous fabric webs according to claim 1 and a method according to claim 8. Characteristics and advantages of an apparatus according to the present invention will be better understood from the following exemplifying, non-limitative disclosure made by referring to the schematic sectional elevational view of an embodiment thereof. Referring to the figure, an apparatus is schematically illustrated for the continuous steaming and dimensional stabilization of continuous fabric webs according to the present invention. The apparatus comprises a steaming tunnel (11) having the form of a tank, through which a conveyor belt (12) is caused to run which supports and conveys a continuous fabric web to be treated (13). The steaming tunnel (11) is provided with an inlet opening (14) and an outlet opening (15), both connected with the external environment and arranged at a much lower level than the bottom floor of said tunnel. Inside the steaming tunnel (11) provided is a steam delivering device (16) to supply steam, which is constituted, e.g., by a perforated pipe which receives steam from a central steam generation unit, not shown in the figure, and which extends transversely to the tunnel (11). In the depicted embodiment, such inlet and outlet openings, (14) and (15) respectively, are even downwards oriented. The conveyor belt (12) is endless, is arranged along the bottom tunnel portion on rollers (17) and forms a closed, endless ring around them (as partially shown in the figure) and has a permeable surface structure, e.g., a net-like surface structure. The fabric web (13) to be treated is driven into the interior of the steaming tunnel (11) by means of a motor-driven roller (18) which is installed in the upper portion of said tunnel positioned at the initial portion of the conveyer belt (12). Downstream of the motor-driven roller (18), a fabric web deflection control device (19) is installed, which checks the fabric web (13) feed to the region of deposition of said fabric web on said conveyor belt (12). A long the upper, cover portion and a long the bottom floor of the steaming tunnel (11), upper heated plates and lower heated plates (20) and (21), respectively, are installed in order to act on steam temperature. Furthermore, a long the bottom portion of the tunnel (11) also a vibrator device (22) acting from the bottom on the conveyor belt (12) is installed, e.g., as consisting of a swinging roller. Inside the steaming tunnel (11), just at the inlet opening (14) a first temperature sensor (23) is installed which is operatively connected with the steam delivering device (16) in order to command steam to be emitted, whenever necessary. Inside the interior of the steaming tunnel (11), a second temperature sensor (26) is installed, which is operatively connected with the upper heated plates (20) and the lower heated plates (21), in order to control their regulation. During the operation of the apparatus, the interior of the steaming tunnel (11) is filled with steam by means of the steam delivering device (16), so as to cause the inner tunnel air to escape from said tunnel through the inlet opening (14) and the outlet opening (15). When the tunnel (11) is filled with steam up to the lower level where the temperature sensor (23) is installed, the latter, by detecting, through the temperature, the presence of steam, modulates the emission of steam by said steam delivering device (16) or even stops said steam emission by means of a whatever modulating valve, not depicted, in that way preventing steam from escaping through the inlet opening (14) and the outlet opening (15). Simultaneously, the upper and lower heated plates (20) and (21) respectively, are switched on at such a temperature as to cause steam to reach a predetermined temperature, e.g., comprised within the range of from 100 to 120°C. The function of the heated plates (20) and (21) is also of preventing condensate from forming inside the steaming tank (11). The regulation and switching on of the plates is automatically carried out through an actuator device not depicted in the figure, connected with the second temperature sensor (26) and preset as a function of the treatment requirements. The fabric web (13) is vertically driven from down upwards into the tunnel (11) through the inlet opening (14) by the motor-driven roller (18) and is deposited on the conveyor belt (12). The revolution speed of the motor-driven roller (18) is variable and is automatically regulated through the fabric web deflection control device (19) at its region of deposition on the conveyor belt (12). In that way, a continuous control of fabric web feed is accomplished, with the application of any tensile stresses to it, in particular in the machine direction, being prevented. In order to optimize the operation of the fabric web deflection control device (19), said fabric web deflection control device (19) is accomplished by means of an optical-fibre reading unit (24) which results to be particularly advantageous in an environment saturated with steam, and at a high temperature. In fact, the optical-fibre reading unit (24) detects the distance of the fabric web (13) from a support plate (25) together with which it constitutes the fabric web deflection control device (19). Then it transmits a signal to a converter, not shown in the figure, which consequently acts on the regulation of the revolution speed of the motor-driven roller (18). The fabric web deflection control device (19) results to be particularly advantageous because it makes it possible the fabric web (13) to be overfeeded to the conveyor belt (12) in such a way as to compensate for the reduction in length of the fabric web caused by its longitudinal shrinkage. When necessary, in order to favour the sliding and rearrangement of the fibres and/or yams which constitute the fabric web (13), the vibrator device (22) can be started up which, by acting on the conveyor belt (12), transmits a corresponding vertical vibrational movement to the fabric web (13) during its advancing motion. During the operation, as already mentioned, the temperature sensor (23) performs the function of detecting, through a temperature detection, the presence of steam inside the interior of the tunnel (11) and of automatically regulating the steam emission through the steam delivering device (16). In that way, steam is prevented from escaping from the tunnel into the working premises, and, simultaneously, the steam emission is exactly metered as a function of the amount which is absorbed by the fabric web (13). By means of the apparatus according to the present invention, steam consumption can hence be limited to the strictly necessary for the treatment of the fabric, and the presence can be avoided of any sucking devices, thus any useless wastes and consequent energy costs being eliminated. Furthermore, by means of an apparatus according to the present invention, a further feature is evidenced, which is advantageous from the technological aspect of fabric treatment. In fact, since the steaming treatment is carried out in an apparatus in which no air is present, the fabric undergoes a considerably higher dimensional stabilization than allowed by the traditional steaming processes carried out in apparatuses in which a mixture of air and steam is present. A further advantage of the apparatus disclosed above is the possibility of reaching, inside the steaming tunnel (11), such steam temperatures that the latter will be overheated and saturated. The temperatures of the overheated saturated steam atmosphere can be regulated up to values comprised within the range of from 100 to 120°C, thanks to the presence of the heated plates (20) and (21). Furthermore, the latter feature, as already said, enables the temperature to be more accurately regulated, with undesirable phenomena of steam condensation being prevented.

Claims: Apparatus for continuous steaming and dimensional stabilization of continuous fabric webs comprising a steaming tunnel (11) through which a conveyor belt (12) runs, which supports and conveys a continuous fabric web (13) to be treated, said steaming tunnel (11) being provided with an inlet opening (14), an outlet opening (15) and a steam delivering device (16), whereby said inlet opening (14) and said outlet opening (15) are both arranged under the lower portion of the tunnel, characterised in that inside said tunnel, positioned at at least one of said openings, a temperature sensor (23) is provided which modulates the emission of steam from the steam delivering device (16), and in that, positioned at an upper covering portion and/or to a lower portion of said steaming tunnel (11), upper (20) and lower (21) heated plates, are installed. Apparatus according to claim 1, characterized in that said inlet (14) and outlet (15) openings are both directed downwards. Apparatus according to claim 1, characterized in that a motor-driven roller (18) is provided inside said steaming tunnel (11) in its upper portion positioned at an initial portion of said conveyor belt (12). Apparatus according to claim 3, characterized in that said downstream from said motor-driven roller (18) there is installed a fabric web deflection control device (19) which checks the feed of fabric web (13) in said initial portion, or region of deposition of the fabric web on said conveyor belt (12). Apparatus according to claim 4, characterized in that said fabric web deflection control device (19) comprises an optical-fibre reading unit (24) installed on a support plate (25), which detects the distance of said fabric web (13) from said support plate (25) and regulates the revolution speed of said motor-driven roller (18). Apparatus according to claim 1, characterized in that inside the interior of said steaming tunnel (11) a temperature sensor (26) is installed which regulates said upper (20) and lower (21) heated plates. Apparatus according to claim 1, characterized in that on a bottom portion of said steaming tunnel (11) also a vibrator device (22) is installed, acting on said conveyor belt (12), from the lower side thereof. Method for steaming and dimensionally stabilizing continuous fabric webs, the method comprising the steps of: i) conveying and supporting the continuous fabric webs on a conveyor belt running through a steaming tunnel from an inlet opening to an outlet opening of the tunnel, the inlet and outlet openings being both arranged under a lower portion of the tunnel, ii) delivering steam into the steaming tunnel from a steam delivering device connected thereto, to generate a saturated steam atmosphere in the tunnel to treat the continuous fabric webs, iii) modulating the emission of steam from the steam delivering device by means of a temperature sensor positioned inside the tunnel at at least one of the inlet opening and outlet opening, and iv) heating an upper covering portion and/or a lower portion of the steaming tunnel and the saturated steam atmosphere therein by means of upper and/or lower heated plates installed at the upper covering portion and/or the lower portion, respectively, wherein the treatment of the continuous fabric webs is carried out in a steam atmosphere which is free from air and constituted by overheated saturated steam at a temperature comprised within the range of from 100 to 120°C.

Inventors: BERTOLDO FRANCO, BERTOLDO, FRANCO
Applicants: SPEROTTO RIMAR SPA, SPEROTTO RIMAR S.P.A.
Application year: 1993
Main classification: D06B19
IPC codes: D06B19