DESCRIPTION Technical Field

The present invention relates to a method and a plant for drying knitted articles, such as stockings, socks, tights or the like, usually following a wet-steam stretching treatment, during which the articles are placed on an expanding form. Background of the Invention

In plants for checking and stretching knitted articles, and in particular women's tights and stockings, the articles arriving still wet from a dyeing stage are loaded onto special so-called expanding examining forms, hereinafter simply designated as "forms". After a stretching stage which may comprise a wet-steam treatment - said stage further increasing the moisture content of the articles - the latter are dried inside a tunnel where hot air circulates and where they may be subject to irradiation by suitable heat- radiating sources. Such a method and a plant for realization thereof are for example described in Italian Patent No. 01252802 filed on 23/9/91 and in Italian Patent Applications Nos. FI95A-113 and FI95A-114 filed on 24/5/95 by the same owner of the present application, and involve the displacement and heating of relatively large quantities of air, with a notable expenditure of energy. Disclosure of the Invention In order to reduce the duration of the processing cycle and reduce the energy consumption in such a plant, the method according to the present invention envisages that the drying stage after stretching should take place in one or more drying chambers which are sealed shut with the article, still mounted on its form, inside and in which a vacuum sufficient to extract and evaporate the water absorbed by the fabric of the article is produced. The temperature inside one or more of said chambers is kept at a level equal to or higher than the ambient temperature by means of the action of heating elements contained inside the chambers, depending on the lesser or greater quantity of water to be extracted from the fabric. In order to implement this method, the invention envisages a plant for stretching and drying knitted articles, such as stockings, socks, tights or the like, said plant being of the type comprising a multiplicity of forms which can be moved between several operating stations, for example by means of a carousel rotor, a carousel with straight-path sections joined to one another,

etc., each of these forms being designed to receive an article. A loading and inspection station, a stretching station - usually of the wet-steam type -, one or more drying stations and an unloading station are provided. The drying station or each drying station comprise a chamber which can be opened for arrival and departure of the form together with the article to be stretched and can be sealed shut, there also being provided an aspiration means for creating in the closed chamber a vacuum suitable for facilitating elimination of moisture from the article.

In a preferred embodiment of the invention, the chamber or each chamber is formed by two plate-shaped half-shells with a peripheral lip seal, the form passing through and stopping between the two slightly separated half-shells; the half-shells are then brought together in a sealed manner so as to form said chamber and contain a form with the tights during a drying period. Each chamber comprises a suction duct with a valve which can be switched between a condition for connecting the chamber in the closed condition with an aspirator and a condition for connecting said chamber with the environment in order to break the intemal vacuum and allow opening of the chamber.

At least one heater capable of being regulated so as to reach an adjustable working temperature may also be provided inside each chamber; the heater or heaters may be designed to irradiate the article thermally so as to faciliate extraction of the water. Brief Description of the Drawings

The invention will be better understood with reference to the description and the attached drawing which shows a non-limiting embodiment of the invention. In the drawing:

Fig. 1 shows in diagrammatic form a plan view of the working stations of a stretching and drying plant according to the invention;

Fig. 2 shows a side view of a drying chamber, on the line Ill-Ill of Fig. 1;

Fig. 3 shows a side view of a drying half-shell or half-chamber, on the line Ill-Ill of Fig. 2; and

Figs. 4 and 5 show, respectively, a plan view of drying chamber in the direction of the arrows IV-IV in Fig. 3 and a detail, on a larger scale, of the zone indicated by the arrow V in Fig. 4.

Detailed Description of the Preferred Embodiment of the Invention

The stretching and drying plant comprises a carousel turntable, which is of the type described in the prior patent and patent applications mentioned and whose constructional details are not illustrated herein, said

turntable having uniformly distributed over its periphery eight forms 1 , in particular of the folding-book type, which extend vertically. Tights to be stretched or to be dried before folding and packaging may be fitted onto these forms. During rotation of said table in the direction of the arrow F1 , the forms are made to stop in eight stations which comprise: a loading and inspection station A; a stretching station B; drying stations C, D and E; and an unloading station F.

Loading of the tights onto the respective forms 1 is performed in station A, the forms in this station being in an extended condition with the two jambs 1A, 1 B splayed and arranged edge to edge so as to allow simultaneous inspection for checking of the tights.

Between the stations A and B, depending on the type of tights and the known type of form used, the jambs of the form may be closed up in the manner of a book or accordion against one another, in order to reduce the dimensions of the form and facilitate the subsequent stage of unloading of the tights from the form together with the parts of the tights already positioned on top of one another and ready for final folding.

In stretching station B the tights are treated with saturated or superheated steam inside a chamber 3. This chamber may be of the type with a sealed closure designed to withstand a pressure greater than atmospheric pressure, for a more effective stretching treatment using saturated steam at a temperature greater than 100°C.

The three following drying stations C, D and E each comprise a drying chamber 5 inside which at each step a form for drying the tights optionally fitted onto it is sealed shut; these chambers form a subject of the present invention and will be described more fully below. The drying chambers are connected by means of pipes 7, a union 9 and a diverter valve 11 to an aspirator 13. In the sealed condition of the chambers 5, by means of this arrangement and a signal to the valve 11 synchronized with the closing of the chambers, a vacuum is formed inside the latter in order to extract or at least facilitate extraction of water present in the fabric of the tights; at the end of the drying period, the valve 11 is switched so as to disconnect the chamber from the aspirator and connect said chamber with the extemal environment, thereby breaking the vacuum inside the chamber and allowing opening of the latter for replacement of the form with the next one by means of rotation of the rotating table by one step.

In another embodiment of the invention, each drying chamber may also be provided with an orifice closed by a remote-controlled valve; in this

case, the aspirator may be left continuously in communication with each drying chamber and, at the end of the drying period, said remote-controlled valve is opened so as to break the intemal vacuum and activation of a washing air stream through each of the chambers, thereby improving removal of the moisture.

In unloading station F, the tights are unloaded from the form, manually or by means of a gripping member of a folding system (not shown).

As will be described more fully below, in order to facilitate drying, the chambers 5 may be fitted internally with drying means, for example two heating plates arranged inside each chamber and arranged on opposite sides of the book-folded form, so as to radiate heat onto the fabric of the tights during the stoppage period of the latter inside the chamber. With the vacuum on, drying of the tights is achieved with little or no heating of the air in contact with the forms, with a low energy consumption and reduced amount of stoppage time of the forms in the various stations, said time being of the order of only a few seconds.

Each drying chamber comprises a fixed half-chamber 15 (see also Figs. 2, 3, 4 and 5) formed by a sheet-metal half-shell with a limited concavity having an approximately rectangular and vertical extension, said concavity having arranged alongside it - upon each forward movement of the rotating carousel - a book-folded type form 1 , as shown in Fig. 3. Said half-chamber 15 is provided with an opening 15B (Fig. 3) to which a pipe 7 for connection to the aspirator 13 is connected. Each drying chamber also comprises a second half-chamber 17, movable in the direction of the double arrow F2 in Fig. 2 so as to be moved away from and towards the fixed half-chamber 15; said second half- chamber 17 is formed by a second half-shell, having a shape similar to, but with a concavity larger than that of, the fixed half-chamber 15. The concavities of the two half-shells are arranged opposite one another and the rectangular opening of each is delimited by a flat edge 15A, 17A. The edge 15A of the fixed half-chamber facing the edge 17A of the movable half- chamber has fixed to it a lip of a flexible seal 18 made of rubber or other resilient material; this seal surounds the entire opening of the two half- chambers. The movable half-chamber 17 is made to slide in the direction of the double arrow F2 on straight guides 19, fixed in a manner not shown to the rotating framework of the carousel table; the displacement in the direction of F2 is obtained by means of a linear actuator 21 , for example by means of a pneumatic jack. In this way the movable half-chamber 17 may

be brought towards the fixed half-chamber 15, thus enclosing the form 1 during a drying period, or moved away from said half-chamber 15 when the rotating table of the carousel displaces the forms by one peripheral step, allowing the exit of a form with the tights at least partially dried and the entry of the next form with the tights to be dried.

A heating plate 23 with an electrical resistance is arranged inside one or each half-chamber 15 and/or 17 (Fig. 5); the resistance or each resistance may receive regulated pulses of current at least when the drying chamber is in the closed condition, so as to raise said plate to a temperature suitable for radiating heat onto the tights mounted on the form 1 ; the heating may also be continuously produced. The arrangement of the plates 23 allows the tights to be irradiated on both sides and thus contributes towards evaporation of the moisture absorbed by the tights.

It is understood that the drawing shows only an example provided by way of a practical demonstration of the invention, the forms and arrangements of said invention being able to be varied without thereby departing from the scope of the idea underlying the invention itself. The presence of any reference numbers in the accompanying claims has the function of facilitating reading of the claims with reference to the description and to the drawing, and does not limit the scope of protection represented by the claims.