The invention concerns a dryer for yarns wound on reels.

It is known that to dry textile products and in particular reels consisting of yarns wound on spindles, dryers are used, said dryers substantially comprising a tunnel in which the reels are arranged in a vertical position on a supporting surface.

Some dryers use a current of hot air which is blown inside the spindle in order to dry the yarn coming radially out of the reels.

Other dryers adopt a radiofrequency generator which uses two opposed electrodes between which a field is generated that leads to evaporation of the water contained in the yarn.

The choice of one or the other type of dryer depends on technical factors, but also on consolidated habits, hence some users prefer air dryers whereas others prefer radiofrequency dryers. Both types of dryer have their drawbacks, however.

As regards the air dryers, they pose the drawback that the air does not come out uniformly according to the spindle cross sections with different axial heights, and this results in non-uniform drying of the yarn.

Said drawback does not occur in radiofrequency dryers, which dry more uniformly, but nevertheless have the drawback of being more costly for treatment of the same quantity of product and extraction of the same amount of water.

In the attempt to combine the advantages of both types of dryer referred to, at the same time eliminating the drawbacks, dryers have been designed which are provided with air blowing devices and electrodes for the generation of a radiofrequency field, in order to perform combined hot air - radiofrequency field drying.

Said electrodes are arranged parallel to each other and to the longitudinal axis of the reels, which are positioned on a substantially horizontal supporting surface resting on a trolley positioned in the area of the field.

A first drawback of said dryers consists in the fact that the points on the outer surface of the reels are at different distances from the electrodes and consequently the field, being square to the reels, does not cross them uniformly, hence they are not dried uniformly throughout their volume. A further and no less important drawback is represented by the fact that the

trolley, being made of a plastic material, must have sufficient mechanical resistance to withstand the weight of the reels.

The present invention aims to overcome all the drawbacks mentioned above.

In particular a first aim of the invention is to produce a combined air and radiofrequency dryer which, compared to equivalent air and radiofrequency dryers with the same power, dries the reels more uniformly.

A further aim of the invention is to produce a dryer that ensures a drying process which is economically comparable to the hot air dryers belonging to the known art. Last but not least, a further aim of the invention is to produce a dryer with a simpler construction than the equivalent dryers manufactured according to the known art.

The aims described above have been achieved through the implementation of a dryer for yarns wound on reels which, in accordance with the main claim, comprises:

- a drying tunnel which develops mainly along a longitudinal axis;

- a radiofrequency generator connected to a pair of opposed electrodes arranged inside said tunnel to create a radiofrequency field;

- means of support designed to arrange said reels in said radiofrequency field with the longitudinal axis, defined by the spindle on which they are wound, substantially vertical and substantially parallel to said radiofrequency field;

- means for circulation of air inside said reels, comprising at least one tubular duct with mainly longitudinal development positioned inside said tunnel and combined with fans for conveying air taken from the outside;

- manifolds designed to ensure communication between the tubular chamber defined by said tubular duct and the internal volume defined by said spindle of each of said reels, characterised in that at least one electrode of said pair of electrodes is constituted by at least one metallic surface belonging to said tubular duct.

According to the preferred embodiment, which is described below, the tubular duct which conveys hot air inside the reels constitutes the lower electrode of the pair of electrodes that generate the radiofrequency field. Said tubular duct also constitutes the supporting surface for the reels to be dried and is made mobile by resting it on a trolley for insertion into and removal

from the dryer.

According to a construction variant, the tubular duct is fixed and the reels to be dried are arranged on a mobile supporting surface.

The aims listed will be highlighted in greater detail in the description of preferred embodiments of the invention which are presented as indicative and non-limiting examples, with reference to the attached drawings, wherein:

- Figure 1 shows a longitudinal section of the dryer subject of the invention;

- Figures from 2 to 4 show axonometric views of details of the dryer subject of the invention; - Figure 5 shows a detail of the inside of the dryer of the invention in an operating phase;

- Figure 6 shows a cross section of the dryer of the invention in an operating phase.

The dryer subject of the invention is shown in Figure 1 where it is indicated as a whole by 1 and where it can be seen that it comprises a drying tunnel 2 provided in its upper part with a radiofrequency generator 3, connected to a pair of electrodes 4 and 5 inside the tunnel 2 to create a radiofrequency field. Between the upper electrode 4 and the lower electrode 5 means of support 6 are provided which arrange the reels R to be dried with their longitudinal axis X in a vertical position and substantially parallel to the radiofrequency field.

Means for circulation of air inside the reels R are also provided, indicated as a whole by 10, comprising a tubular duct 7 with mainly longitudinal development, arranged inside the tunnel 2 and combined with fans 40 for conveying air taken from the outside. As can be seen in Figure 2, manifolds 11 are provided which ensure communication between the tubular chamber 7a, defined by the tubular duct 7, and the internal volume of the spindle Ra of each of the reels R. According to the invention, at least one out of the upper electrode 4 and the lower electrode 5 consists of at least one metallic surface belonging to the tubular duct 7.

In particular, the electrode 5 is constituted by the surface of the tubular duct 7, which is made of sheet metal.

In the preferred embodiment of the invention, the tubular duct 7 also acts as a means of support for the reels R and for said purpose, as can be seen in the detail shown in Figure 3, the upper surface 5 has a plurality of manifolds 11

which consist of through holes 8 delimited by centring collars 9 protruding from the surface 5.

The centring collars 9 are housed inside the spindles Ra of the reels R, when the latter are arranged on the surface 5, in order to prevent movement thereof. The tubular duct 7 is also provided with four support brackets 13 with wheels

14 for positioning it on the supporting structure 15 in the tunnel 2 which will be described below.

In different embodiments, not shown here, the tubular duct can be made totally or partially of plastic, on condition that it is provided with at least one horizontal surface made of conductive material which performs the function of electrode. The tubular duct 7 is arranged on a trolley 12 which, as can be seen in Figure 4, is provided with wheels 12a running on rails for insertion into and removal from the drying tunnel 2. Said trolley 12 is provided with actuator means 19 for raising the tubular duct 7, preferably but not necessarily consisting of manually operated hydraulic jacks.

As regards the tunnel 2, it can be seen from Figures 1 and 5 that in the inside it is provided with a supporting structure 15 for the tubular duct 7. Said supporting structure 15 comprises two upright opposed parallel structures 16, running laterally along the tunnel 2 and intended to support the tubular duct 7.

According to the preferred embodiment, the upright structures 16 are made of metallic material and on their upper surfaces 16b there are two bars of insulating material 17. Each of the upright structures 16 is provided, in an intermediate symmetrical position with respect to its longitudinal axis Y, with two loading cells 18 and, above the latter, two slanting surfaces 16a converging downwards. As can be seen in Figure 6, two contact plates 24 provide the electrical earth connection for the tubular duct 7 as they are made of conductive material; they have an L-shaped cross section, a first side 24a of which is fixed to the lateral structure 2a of the tunnel 2, while a second side 24b rests on the bars of insulating material 17, thus being positioned between the supporting structure

15 and the tubular duct 7 when the latter is inserted in the tunnel 2.

In an alternative version the upright structures are electrically connected to earth and therefore the bars of insulating material and the contact plates are

no longer necessary.

The upper electrode 4, as can be seen in Figures 1 and 6, comprises a metallic laminar body 25 arranged inside the tunnel 2 and above the tubular duct 7 from which it is separated. Said metallic laminar body 25 is preferably, but not necessarily, a flat body defining a longitudinal axis Y' parallel to the longitudinal axis Y defined by the tubular duct 7 when it is in working position.

A plurality of shaped flanges 21 is combined with the upper electrode 4 and each flange consists, as can be seen in Figures 1 and 6, of a disc 21a and an annular body 21 b made of Teflon or another plastic material.

In particular, the disc 21a faces a corresponding reel R, while the annular body

21b faces the upper electrode 4 and is combined with it via elastic means 22, preferably springs, positioned in-between them.

By lowering the upper electrode 4, the annular body 21b can house inside its hole 21 c the free end 23 of the spindle Ra of the respective reel R.

For said purpose, the upper electrode 4 is combined with driving means 30 which move it vertically inside the tunnel 2 and which comprise screw means

31 positioned between the upper electrode 4 and the tunnel 2, and kinematic means 32 for rotating said screw means 31. The screw means 31 comprise at least four nut screws 31a combined with a supporting element 31c for the upper electrode 4.

Each of said nut screws 31a is crossed by a screw 31b arranged with its longitudinal axis X' in a vertical position and having the ends revolvingly combined with supports 33 connected to the structure of the tunnel 2. The kinematic rotation means 32 comprise at least four pinions 32a, each connected to one end of a respective screw 31b, and a chain 32b arranged in a closed circuit on a surface substantially parallel to the surface defined by the upper electrode 4 and engaging with all the pinions 32a.

A gear motor 32c, flanged to a supporting structure 34, is axially coupled to one of the screws 31 b in order to set it rotating around its longitudinal axis.

When the gear motor 32c rotates the screw to which it is coupled, the chain

32b simultaneously rotates all the screws 31b.

In different embodiments of the invention that are not shown here, the gear motor may be provided with an independent pinion that engages in any position with the chain 32b.

As regards the means for circulation of the air, indicated as a whole by 10, as can be seen in Figure 1 , they comprise a fan 40 provided with a delivery inlet 41 which conveys air inside a heating battery 42 of known type, which has an outlet manifold pipe 43 combined with the tubular duct 7 via coupling means 47.

Said coupling means 47 comprise a flange 44 fixed to the outlet manifold pipe 43 which engages, via sealing means 46, with a counterflange 45 connected to the tubular duct 7. In particular, the flange 44 and the counterflange 45 define a contact surface slanting downwards.

The sealing means 46 referred to above preferably, but not necessarily, consist of elastic gaskets.

The other end of the tubular duct 7, which can be seen also in Figure 2, is closed in order to form a tubular air collection chamber 7a from which the flow of hot air, generated by the fan 40 and by the heating battery 42, is sent through the manifolds 11.

As regards the radiofrequency generator 3, it is of the known type and therefore not described. The signal which it generates is preferably at 27.12 MHz. Lastly, air extractor means 50 are provided, comprising a fan 51 which sucks damp air from the inside of the tunnel 2 and discharges it to the outside. Operatively, the reels R are arranged on the manifolds 11 present on the tubular duct 7 with the trolley 12 removed from the tunnel 2. The number of reels R that are loaded corresponds at least to the number of manifolds 11 , so that all the through holes 8 that make up said manifolds 11 are closed.

Once the loading operation has been carried out, the operator inserts the trolley 12 in the tunnel 2 at the level of the supporting structure 15. Operation of the jacks 19 lowers by a few millimetres the tubular duct 7, which rests on the supporting structure 15 with the contact plates 24 positioned in-between them.

The support brackets 13 with wheels 14 belonging to the tubular duct 7 together with the corresponding slanting surfaces 16a present on the supporting structure 15 cause the tubular duct 7 to move forward and downwards, so that the duct 7 rests in a stable manner on the structure 15 and

establishes the electrical earth connection with the plates 24.

Simultaneously, the flange 44 and the counterflange 45 come into contact so as to form, with the help of the sealing means 46 with which they are provided, a continuous tube for conveying hot air into the tubular duct 7. The operator removes the trolley 12 and, via the driving means 30, lowers the upper electrode 4 so that the shaped flanges 21 rest on the reels R plugging the spindles Ra.

Having done this, the operator starts the dryer 1 , so that simultaneously with the generation of the radiofrequency field between the two electrodes 4 and 5, hot air is conveyed inside the tubular duct 7.

The fan 51 extracts the damp air that forms inside the tunnel 2, maintaining the required humidity conditions.

The drying time is set beforehand by the operator and controlled by a control unit not described herein, but of known type, where all the drying parameters are set, for example temperature, humidity, etc.

Subsequently, the operator re-inserts the trolley 12 in the tunnel 2 for extraction of the tubular duct 7 with the dried reels R.

A construction variant of the dryer subject of the invention, which is not shown in the figures, differs from the embodiment just described due to the fact that the tubular duct is fixed inside the tunnel and the reel supporting means consist of a conveyor belt which runs in a closed circuit around the surface of the tubular duct.

In particular, the manifolds are provided on the conveyor belt and consist of through holes, each of them being delimited by a protruding centring collar. During operation, the manifolds must be coaxial with the through holes present on the tubular duct.

The advantage of this variant lies in the construction simplicity of the electrical contacts of the lower electrode and of the connection between the tubular duct and the air conveying means. Furthermore, in said construction variant, the trolley and the actuator means for lifting the tubular duct from the trolley are no longer necessary.

For all the reasons illustrated above, all the described embodiments of the dryer subject of the invention achieve the set aims.

In particular, the use of the tubular duct as electrode allows uniform drying to be obtained compared to the dryers of the known art which combine hot air

and radiofrequency drying.

Furthermore, thanks to the combination of the two drying systems, the aim to keep drying costs low is also achieved; despite the use of the radiofrequency field, said costs are comparable to the costs of hot air dryers. The use of the tubular duct as electrode, support for the reels and conveyor of air into the reels makes the construction of the dryer simpler compared to that of the equivalent dryers belonging to the known art.

In particular, since the trolley is positioned outside the tunnel when the radiofrequency field is operating, it can be made of any material, Furthermore, the user can employ two or more tubular ducts, so that it is possible to load some reels on one duct while other reels are drying, thus reducing down time.

Upon implementation further changes can be made to the dryer of the invention; the resulting construction variants, although not shown in the drawings and not described, will all be considered protected by the present patent, provided that they come within the scope of the following claims.