AN IMPROVED APPARATUS FOR CONTINUOUSLY DECATIZING OF FABRICS ON A CYLINDER WITH LOCAL STEAM GENERATION

Abstract: In an apparatus for continuously decatizing a fabric (4) on a cylinder (1) at a temperature at least sufficient to avoid condensation, wherein the damp or wet fabric is sandwich-like compressed between said cylinder and a continuous, water-tight carrier web (2), possibly rigid, a high mechanical pressure is applied which is obtained by means of rotatable cylinder (6) having the rotation axis parallel to the central cylinder axis and being strongly pressing against the latter said carrier web while squeezing at the same time the intermediate cloth web. Thus is also obtained a steam sealing action for the completion of which also two rubberized gaskets are preferably provided at both sides of the hot cylinder. The pressure cylinders, except for the first one met by the web, are heated at a high vaporization temperature (160-180 DEG C) if the central hot cylinder is at only about 100 DEG C.

Description: "A!__Ii?PJ? VED_ APPΛRΛJU3- _°_ R ___Q.N_T IJi l0_USL.Y_.DECATIZING_0F The present nvention relates to an improved apparatus for continuously decatizing fabrics on a cylinder ith local steam generation. A method of continuous decatizing is known, as well as the relevant apparatus, for a dimensional conditioning of fabrics by causing them to pass about a very hot rotating steel cylinder, e.g. at a tempera- ture of 160-180°C. From DE-A-3.412.982 it is known to feed the previously damp or wet fabric between said heated cylinder and a water-proof endless (ring-shaped) web or back cloth which is moved forward at the same speed as the hot cyLinder and subjected to a great tensile strength so that it can apply an important pressure onto the fabric in contact with the hot cy¬ linder. The moisture contained in the fabric evapo¬ rates to produce steam. Still according to this prior art, since the watei—proof, extremely taut, is also provided with some elasticity and is larger than the fabric to be treated, the generated steam cannot outflow as it is stopped by the elastic web under tension on one side and, on the other side, by the hot metal cylinder. The steam has thus the tendency to get compressed with augmentation of its pressure untill exceeding, also slightly, the atmospheric value and being able to exert a high temperature action at a greater pressu¬ re than the atmospheric one, as if the fabric were in autoclave. It is also known that the required high tautness for the water proof web, not only to squeeze the fabric, but also to avoid steam leakages, gives rise to a number of inconveniences and to an anomalous wear of the web itself. Furthermore, in spite of high values of web tension, the squeezing pressure on each cm of cloth results to be relatively poor owing to the amplitude of the surface on which squeezing is exerted. For example, with a tensioning or pulling strength of 40.000 kg applied onto the web, if its surface in contact with the cylinder (through the cloth) is of 10.000 cm^ (approximately corresponding to a cloth of 150 cm in height extending in contact with the web along about 70 cm), the squeezing action will be of only 4 kg/cm^. Since at present it has been fully demonstrated that to obtain good results of dimensional condition¬ ing of fabrics the mechanical squeezing is a basic factor, and perhaps the most important, it is an ob¬ ject of the present invention to provide an improved continuously decatizing apparatus through which a strong squeezing can be obtained with a good tightness for steam even without applying high mechanical ten¬ sions on the water-proof web which will have not to be necessarily provided with elasticity. An extremely good continuous decatizing shall be obtained with a watei—proof, inelastic carrier web or back cloth which is only slightly taut and consequently not subjected to wear, even though a very high mechanical pressure is exerted onto the fabric by means of pressing cylin- ders having their axes parallel to the axis of the central decatizing cylinder and the Lateral surface rotating at the same speed of the latter, of the car¬ rier web and of the fabric, being able to press the carrier web against the heated cyLinder while squeezing at the same time the fabric therebetween. Furthermore accordingly to the present inven¬ tion the heat to produce the decatizing steam is pre- ferabLy applied onto the fabric from the outside of apparatus, namely through the same pressing cylinders instead of the inner hot cylinder the temperature of which can be kept at about 100°C to avoid condensa¬ tion. These and additional objects, advantages and characteristics of the apparatus according to the pre¬ sent invention will be clearer from the following detailed description of a preferred embodiment given by way a non-limiting example with reference to the annexed drawings wherein: fIGURE_1 shows a schematic view of an illustra¬ tive apparatus according to the present invention; £Ϊ§UEI_2 shows a similar view of an alternati¬ ve embodiment of figure 1; and FIGURE_3 shows a partial view of the apparatus of Figure 1 l , taken in the direction of arrow H without considering rolls 3, 3a. With reference to the drawings, an endless, ring-shaped water-tight carrier web 2 is continuosly wound, partly but preferably along at least 180°, on a heated metal cylinder 1. A set of rolls 3, 3a-3e causes said carrier web 2, of water-proof material to be fed at the same peripheral speed of cyLinder 1, while keeping the same at the correct position and without practically exerting thereon a pulling act on, except for the minimum necessary to prevent slipping about the feeding rolls themselves, thus ensuring a ring-like running. A fabric 4 to be conditioned, shown by broken lines, upon being previously soaked or at least moistened, gets into contact with both the endless web 2, being larger than the fabric, and cylinder 1, which is heated in a known way, at a temperature sufficient to avoid condensation of at least 100°C, being wound thereabout for the same length as the ring web 2 with which it forms a so-called "sandwich". According to the present invention, about the hot cylinder 2, and namely along the winding length of the said sandwich, with an inelastic web 2 (Fig. 1), there is provided a number or anyway at Least one pair -of pressing cylinders 6 rotatably mounted on respective axes parallel to the axis X-X of cylinder 1. Their axes are pushed against the surface of cylin¬ der 1, placed centrally with respect to them, through known means such as the represented pneumatic or oleo- dinamic pistons 7, but also whichever different means, so as to exert a very high pressure onto the underly¬ ing sandwich. It should be noted that while the axes of c linder-piston 7 have been represented as directed radially with respect to axis X-X of cylinder 1, it is not to be excluded that the pressure is exerted by each cylinder 6 aLong a direction which is possibly different from the perpendicular to the surface of hot cylinder 1, at each generating line of contact between the two cylinders at each moment. The pressure exerted by cylinder 6 has the dual purpose of producing a sensible squeezing of the fabric to be conditioned or decatized and at the same time to seal at the end points A, B of the endless sandwich the steam which would tend to escape owing to its pressure higher than the atmospheric one, which has been generated upon contacting of wet fabric with hot cylinder 1. According to a preferred embodiment of the present invention, the pressing cylinders 6, except for the firstly encountered by web 2 in the direction of winding on cyLinder 1, had been heated themselves and if the latter cylinder is at only 100°C (anti-con¬ densation), it will be the same pressing cyLinder to have also the task of generating the decatizing steam, with temperatures of 160-180°C while transferring from the outside the required vaporisation heat. With such a solution it will not be strictly necessary to heat the carrier web 2 upstream of the zone of contact with cyLinder 1. However, if instead said web is heated, the first cylinder 6 after inlet roll 3 could be pre¬ vented from heating, where no sensible heat Loss from web 2 has been yet experienced. ALL drawbacks are thus avoided which are due to temperature differences between the external surface of web 2 and the internal one, being in contact with the fabric, as well as in the longitudinal direction, with decreasing tempera¬ tures from point A to point B. As mentioned above, according to the present invention the water-proof web does not need to be elastic, but the apparatus with possibly hot, pressu- re cylinders may however show advantages also in this case, :n fact, while the elastic carrier web (e.g. rubberized or si lτcone-based) is capable of retaining the steam by itself, the pressing cylinders 6 of the present invention have however the useful effect of an increased squeezing action on the fabric, which is commonly insufficient if provided by only the elastic feature of the web, as stated before, unless extremely high tensions are exerted, but however in some que- stionable way. In this case, indeed, as the steam has not to be retained at both ends A, B where sealing is ensured by the elastic tension of web 2, even only one pressing cyLinder 6 could reach the purpose sati¬ sfactorily, as shown in figure 2. With reference to figure 1, it should be noted that, in spite of the seal at zones A and B, the steam could however escape from the side ends of cylinder 1. To avoid this, as shown in figure 3, rubberized gaskets 5, 5' are provided at both sides of cylinder 1, near its ends, in a zone preferably comprised bet¬ ween the width of fabric 4 and that of carrier web 2, having a greater width, as stated above. In this way the water-proof web 2, pressed by cylinders 6 against the side gaskets 5, 5' ensures the steam tightness also in an axial direction. It will be seen that in figure 3 only the two end cylinders 6 have been represented, i.e. in correspondence with the generat¬ ing lines A, B of cylinder 1, but obviously additional intermediate pressing cylinders 6 may be provided thus improving the seal along all the peripheral zone of cyl nder 1, where steam is generated.

Claims: CLAIMS '• 1. An apparatus for continuously decatizing fabrics (4) on a cylinder (1) at temperature of at least 100°C, sufficient to avoid condensation of lo- caLLy generated steam, wherein the previously moiste¬ ned or soacked fabric (4) is fed between said hot cy¬ linder (1) and a water-tight web (2) continuously wound in an endless fashion between two steam-tight points on cylinder (1), respectively of inlet (A) and outlet (B), the sandwich formed of said web (2) and fabric (4) being fed forward at the same rotation speed of cylinder (1) about its axis (X-X), characte¬ rized by further comprising the application of a high mechanical pressure obtained through one or more cylin¬ ders (6 ) capable of rotating at the same peripheral speed about respective axes which are parallel to each other and to the axis (X-X) of cylinder (1), there been provided means (7) for pushing said press¬ ing cylinders (6) against said cylinder (1) while squeezing at the same time said sandwich formed of said water proof web (2) and fabric (4) between said points (A, B) . 2. AJI apparatus according to claim 1, charac¬ terized in that said pressing cylinders (6) are heated, except for the first of them getting in touch with the said web (2) . 3. An apparatus according to claim 2, charac¬ terized in that said pressing cylinders (6) are heated at a high temperature for vaporization of fabric (4). 4. An apparatus according to anyone of the preceding claims, characterized in that said pushing means (7) are pneumatic or oleodinamic cylindei—piston systems whose action is exerted onto the axes of cylin¬ ders (6) in a direction perpendicular to the surface of cylinder (1 ) . 5. An apparatus according to anyone of the preceding claims, characterized in that said web (2) is essentially without elasticity and the pressing cylinders (6) are at least in number of two, the first and the last of which are respectively coincident with the said points (A, B). 6. An apparatus according to claim 1, charac¬ terized in that said web (2) is of elastic character and acts as a sealing for the steam having a width larger than that of fabric (4), between said points CA, B) there being provided only one pressing cyLinder 7. An apparatus according to anyone of the preceding claims, characterized in that at both sides of cylinders CD, in a zone comprised between the pe- ripheral edges of fabric (4) and web (2), of greater width, two circumferential rubberized gaskets (5, 5 1 ) are applied to said cylinder for sealing the steam in an axial direction, in co-operation with the water-tight web C2).

Inventors: ALBERTO PIETRO, ALBERTO, PIETRO
Applicants: ALBERTO PIETRO, ALBERTO, PIETRO
Application year: 1993
Main classification: D06C7
IPC codes: D06C7, D06C15