DESCRIPTION

Technical Field

This invention relates to an improved machine and method for the combined mechanical and thermal treatment of iabrics to provide effects of dimensional restorability and hand and, in particular, for treating knitted fabrics continuously or discontinuously.

Prior Art

As is well known in the textile industry, it is a strong requirement that a fabric maintains its dimensional stability even after tailoring, wearing and ordinary cleaning and laundering treatments. This applies in particular to knitted fabrics which, by their very nature, tend to lose their dimensional stability more easily than other fabrics.

For this purpose, fabric finishing processes use various devices and treatments to promote the dimensional restorability of the fabric so that this value is as close as possible to the maximum that this will have during the future washing and drying treatments necessary for cleaning an item of clothing tailored with the fabric.

Of the treatments currently possible, those most commonly used are essentially the following:

- run through a free dryer where the open-width, wet or moistened fabric is overfed continuously on a conveyor belt moving through a drying tunnel;

- run through a compactor where the open-width, moistened and heated fabric is continuously forced mechanically to recover its length;

- drying in a tumbler where the fabric in rope form is discontinuously loaded into a rotating tumbler and heated with hot air.

The first and second types of treatment are not particularly effective and, in most cases, both the treatments, performed immediately after one another, are necessary to obtain an acceptable result.

The third type of prior art treatment, that is, tumble drying, is by far the most effective and is normally used as a limit term of reference.

Tumble drying, however, has the serious disadvantages of being discontinuous, with the fabric in rope form, of being possible only on small quantities at a time, with problems of knotting and wringing, of not providing uniform quality and, lastly, of being labour- intensive.

The treatments described above, when applied to knitted fabrics in particular, make it very difficult to eliminate the stresses generated in the fibres in the course of knitting, which means that obtaining a dimensionally recovered and well stabilized fabric can be a problem.

The methods used to help fabric relaxation include vibrating or beating in order to reduce friction between the fibres and between the fibres and other surfaces in contact with them.

Patent documents GB1178270, GB1304733, EP148113A1, EP130342A2, US4219942 describe machines equipped with vibrating conveyor belts for the fabric. The flexibility of the belts in these machines prevents vibrations from being adequately transmitted to the fabric.

Patent document GB2103670 describes apparatus and methods for relieving stresses in fabric which is made up into a roll or bolt preparatory to further processing. In one of the examples described, the fabric is unwound in such a way as to leave a portion of it slack and to lay it on a vibrating plate.

Document GB879483 describes an apparatus in which a damp fabric is made to vibrate using a vibrating grid in a drying zone. The amplitude of vibration imparted to the fabric decreases progressively in the direction of fabric feed.

Document FR1024514 describes a method for stress-relieving a fabric where the fabric is opened out and made to pass on a vibrating support. Alternatively, the fabric may be folded on a vibrating table. To increase the efficacy of the treatment, the fabric may be loaded with weights.

Document US3594914 describes an apparatus comprising at least an inclined vibrating plate on which the fabric slides and is exposed to heating jets.

The solutions cited above are not entirely satisfactory because the vibrations are imparted to fabric surfaces that are in an opened-out form or are moderately pleated. Although this determines a reduction in the friction between the fibres, the accelerations transmitted to them are limited.

In other words, the forces of inertia generated and acting on the fibres are insufficient to dimensionally recover and stabilize the fabric to a good degree.

Patent WO2010064130 to the same applicant as this invention describes a machine in which the fabric is treated partly in the form of a substantially compact mass in a vibrating tub and partly in a drying tunnel. As it feeds through the machine, the fabric is substantially in open-width form.

Although the machine last described above is much more effective than the prior art machines, the applicant has found through experimentation that remarkable improvements can be achieved.

Disclosure of the Invention

This invention therefore has for an aim to provide an improved process for treating fabrics continuously and discontinuously, and which permits drying of a fabric, especially a knitted fabric, while simultaneously obtaining an effect of recovery, swelling and relaxation that improves hand feel and dimensional stability.

This aim is achieved in a machine and a method according to the accompanying claims. The advantages lie essentially in the fact that the treated fabric does not exhibit residual tension due to elastic or plastic deformation which is recovered by the combination treatment and thus does not lead to dimensional instability in the fabric during subsequent processes.

These and other advantages will be better understood from the following description with reference to the accompanying drawings illustrating preferred non-limiting embodiments of the invention.

Brief Description of the Drawings

In the drawings:

- Figure 1 is a schematic perspective view of a machine according to the invention for the discontinuous treatment of a fabric;

- Figure 2 is a photographic image showing the fabric during the step in the process in which it is subjected to vibration;

- Figure 3 is a photographic image showing the fabric in transit towards the drying tunnel;

- Figure 4 schematically illustrates a machine according to the invention for the continuous treatment of a fabric.

Preferred Embodiment of the Invention

Figure 1 illustrates an improved machine according to the invention for the discontinuous, combined mechanical and thermal treatment of a fabric. To better illustrate the essential parts of the machine, the containment walls are not shown.

The machine comprises a rigid, vibrating platform in the form of a cradle 2, and a drying tunnel 4 equipped with at least one hot air distributor 8 fed by a fan 10. A conveyor 7 driven by motor-operated rollers 5,6 is provided for picking up the fabric from one end of the cradel, running it through the tunnel and returning it to the other end of the cradle. According to the invention, the platform-cradle is divided into at least two sections 2a, 2b parallel to the direction of fabric movement, for simultaneously treating as many bolts Tl, T2. Further, the width of each section 2a, 2b is less than the height of the bolts and is preferably adjustable.

That way, during the step in which they are treated in the vibrating cradle, the bolts Tl, T2 are partly in open-width form and partly in rope form, taking on the form of a mass 3 better illustrated in Figure 2, with an efficacy of treatment that is remarkably improved over even that obtainable using the machine of patent WO2010064130.

At one end of the cradle 2 the bolts Tl, T2 are picked up (see Figure 3) by the rollers 5, 6 and by the conveyor belt 7, run through the drying tunnel 4 and then placed in the cradle 2 again.

In the preferred embodiment illustrated in Figure 1, the drying tunnel 4 comprises a first hot air distributor 8 located above the belt 7 and acting substantially on the entire stretch of the bolt lying on the belt. A second hot air distributor 9 may be provided to act from below, through the belt, on the part of the stretch of bolt furthest from the unloading roller 6. The hot air is thus distributed correctly and effectively on the part of the fabric being transported by the belt and, moreover, adherence of the fabric to the unloading roller 6 is guaranteed. To prevent a bolt from falling into the cradle section adjacent to its own during unloading, directional paddles are advantageously provided. A mechanical suspension and vibration system 12 powered by an electric motor 13, elastically supports, and imparts vertical oscillations to, the platform-cradle 2.

The vibrations or oscillations are preferably vertical or have a significant vertical component.

In particular, the amplitude and frequency of the oscillations are induced in such a way that the acceleration imparted to the fabric is greater than gravity, so that the entire mass of the fabric is jolted and not just the part of it that is in direct contact with the platform 2, as in the case of prior art vibrating belt systems.

For example, the peak-to-peak amplitude of the vibrations or oscillations may be between 20 and 60 mm, and the frequency between 5 and 15Hz or, more preferably, between 5Hz and 10Hz.

The heating system 8,9 is preferably of the hot air type, with air partly recirculated, if necessary.

To increase the effectiveness of the treatment the fabric T should initially be in a moistened or wet state.

The fabric is sewn head to tail in such a way as to form a closed loop that moves round continuously within the machine.

The hot air fed into the tunnel 4 by the distributors 8, 9 through the fan 10 and heated by a direct or indirect heating system 15 may be partly recirculated and partly renovated depending on the flow rate set using the extraction fan 1 1.

Figure 4 schematically illustrates an embodiment of the machine for the continuous treatment of knitted fabrics. The bolts of fabric, partly in open-width form and partly in rope form, are fed continuously into a first vibrating platform-cradle 18 which is divided into at least two sections and from there are transferred by a conveyor belt system 70 similar to the one described above into a second platform-cradle 19 passing through a heated tunnel 40, also similar to the one described above. According to the invention, the bolts can be moved alternately between the cradles 18, 19.

The invention achieves considerable technical advantages.

A first advantage is that the relaxation and compacting action induced in the mass of fabric partly in open-width form and partly in rope form accumulated on the platform, combined with the action of the heat applied by the drying system, absorbs most of the residual tensions in the fabric and almost completely recovers deformation, whether elastic or plastic.

This advantage is particularly significant if we consider that fabric stretch is usually more plastic then elastic.

It is also possible to apply to the platforms vibrations whose frequency and amplitude are such as not to simply reduce the friction between the platform and the fabric, and hence the tension created by this, but also to induce in the fabric accelerations that are multiples of gravity acceleration and hence mass forces that are multiples of the fabric's weight in such a way as to make the fibres slide relative to each other and to obtain a considerable compacting and stabilizing effect.