Description of the Patent for Industrial Invention entitled: "PERFECTED VACUUM DRYER".

In the name of the Company BAGGIO TECNOLOGIE S.R.L. - Via Munara, 7 - 36056 Belvedere di Tezze sul Brenta (Vicenza) - ITALY. DESCRIPTION

The invention concerns a vacuum dryer with continuous evaporation chamber, particularly suitable for drying hides.

It is known that the hides, after the wet tanning treatment, must be properly dried in special drying systems before being submitted to the dry finish treatments.

For this purpose, drying systems called "pasting systems" are widely used, where the hides to be dried are brought to adhere to glass sheets by means of suitable bonding agents, and said glass sheets advance inside a tunnel in which hot air circulates. At the exit of the tunnel the dried hides are detached from the glass sheets and stacked.

The drawbacks of these systems are their high cost, the need to use bonding agents to make the hides adhere to the glass sheets and the high heat losses that entail high operating costs. Vacuum drying systems are also known, in which the hides to be dried are laid on horizontal or vertical plates in an environment where vacuum is successively obtained.

The water contained in the hides evaporates due to the combined action of the vacuum created by special suction units and of the plate heating that is generally obtained through heat exchange with hot fluids.

The main drawback posed by vacuum dryers of the type described is the long drying time, a considerable part of which is constituted by the time necessary for extracting the steam that forms in the evaporation chamber. Therefore operating times become long, thus reducing the dryer's output and increasing operating costs.

A further drawback is constituted by the fact that the steam that forms isn't immediately extracted from the evaporation chamber, which is at least partially saturated with steam, consequently reducing the drying performance of the dryer. Furthermore, the vacuum drying systems of the type described present the

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drawback of having a considerable overall length.

Dryers are also known that carry out a continuous vacuum drying cycle and comprise a pair of horizontal overlapping belts, between which the hides to be dried are positioned. The belts are wound around drums that make them advance while keeping them adherent to each other without sliding, and between them an evaporation chamber is defined, where vacuum is obtained through suction means.

The dryers of the type described carry out the drying process in a continuous cycle, but pose the drawback of their considerable length, which often causes problems for installation in tanneries.

Said considerable length also makes it difficult to install said dryers in line with other machines.

The present invention aims to overcome the drawbacks listed above.

In particular, it is the aim of the present invention to propose a vacuum dryer whose overall length is shorter than the length of equivalent vacuum dryers of known type having the same production capacity.

It is a further aim of the invention to propose a vacuum dryer capable of obtaining on the product to be dried a drying quality at least equal to that offered by the vacuum dryers of known type. It is a further aim of the invention to propose a vacuum dryer whose production costs are lower than those of vacuum dryers of known type having the same production capacity.

The aims described above have been achieved through the construction of a vacuum dryer for drying flexible thin elements, in particular hides, that, according to the main claim, comprises:

- a drying surface on which said hides to be dried are laid;

- a first belt positioned over said hides and in contact with them;

- a second belt positioned over said first belt and in contact with it, in such a way as to make said first belt and said hides adhere to said drying surface; - an evaporation chamber for the evaporation of the water contained in said hides, defined between said drying surface, said second belt and sealing means interposed between the longitudinal edges of said drying surface and of said second belt;

- suction means communicating with said evaporation chamber to make vacuum therein and extract any condensate;

- means for heating said drying surface; and is characterized in that said drying surface corresponds to at least a section of the lateral outside surface of a cylindrical drum provided with a central shaft coupled to driving means suited to set it rotating and supported by bearings fixed to a supporting structure.

According to the preferred embodiment of the invention described herein, the first belt is permeable to steam and water, its structure being defined by a plurality of spirals arranged side by side. The spirals that form the first belt are preferably but not necessarily made of metal and are joined to one another by means of pins arranged parallel to one another and to the generating lines of the cylindrical drum. The evaporation chamber in which the hide to be dried is contained is thus substantially defined by the free volume existing among the spirals and the pins that make up the first belt. The sealing means are constituted by a selvedge in waterproof elastic material present along each side edge of the first belt, in which the ends of the spirals are buried.

The spirals that form the first belt are preferably made of metal, but can also be made of another material, provided that it is rigid and resistant to the oxidation of the chemical substances present in the hides.

According to other embodiments of the invention, the first belt, instead of being formed by spirals, may consist of variously shaped grids, in metallic or non- metallic material, sufficiently rigid, so as not to be deformed when subjected to vacuum, with volume and permeability characteristics suitable for defining the evaporation chamber.

The suction means comprise a vacuum extraction unit arranged outside the dryer and connected to the evaporation chamber through pipes and manifolds fixed to the cylindrical drum. The heating means comprise a plurality of channels made below the side surface of the cylindrical drum, said channels communicating with a heating unit positioned outside the dryer through feeding lines.

The driving means are of the gear motor type, with variable speed, carried out according to the known art, connected to the central shaft in order to set the cylindrical drum rotating around a horizontal axis defined by the same central shaft.

The advance of the belts takes place owing to the friction due to the contact of the belts with each other and with the lateral outside surface of the drum. Advantageously, the dryer carried out according to the invention, whose drying surface is constituted by the lateral outside surface of the cylindrical drum, has an overall length that is shorter than that of equivalent dryers of known type, and this makes its installation convenient even in the cases where the space available in the tannery is limited.

Still advantageously, the dryer that is the subject of the invention can be carried out with a drum having a small diameter, so that it is possible to install several dryers in line with one another.

This embodiment of the invention further simplifies all installation and transport operations, compared to the solutions where a single drum with large diameter is used, and can be advantageously chosen when the linear overall dimensions of the dryer do not represent a problem. The aims and advantages described above will be highlighted in greater detail in the description of preferred embodiments of the invention, with reference to the attached drawings, wherein:

Figure 1 is side view of the dryer carried out according to the invention;

- Figure 2 is a schematic view of a partial longitudinal section of the dryer shown in Figure 1 ;

- Figure 3 shows a detail of the section shown in Figure 2;

Figure 4 shows a detail of a cross section of the dryer that is the subject of the invention;

Figure 5 shows a construction variant of the detail shown in Figure 4; - Figure 6 shows a detail of the dryer shown in Figure 1 ; Figure 7 shows a detail of Figure 6;

- Figures 8 and 9 are side views of different embodiments of the dryer that is the subject of the invention;

- Figure 10 shows several dryers carried out according to the invention arranged in line.

The vacuum dryer forming the object of the invention is illustrated in a schematic view in Figure 1 , where it is indicated as a whole by 1. It can be observed that it substantially comprises a drying surface 2 visible in greater detail in Figure 6, on which the hides P to be dried are laid, said hides adhering to the drying surface owing to the action of a first belt 3 positioned in

contact with the outside of the hides P themselves.

A second belt 4 positioned in contact with the outside of the first belt 3 keeps the first belt 3 and the hides P adherent to the drying surface 2. It can be observed in particular in the Figures 2, 3 and 6 that the first belt 3 has a structure that is permeable to steam and water, being constituted by a plurality of spirals 3a, preferably but not necessarily made of metal, that are arranged along the width of the first belt 3 and are joined to one another without interruption through pins 3b, visible in particular in Figure 7. These, as shown in Figure 7, are arranged crosswise to the width of the first belt 3 and have substantially the same length as the first belt 3.

The free volume between the spirals 3a contributes to defining the volume of the evaporation chamber indicated by 5 in the detailed view of Figures 3 and 7 which, as can be observed, is thus confined between the drying surface 2, the second belt 4 and the sealing means indicated by 6 interposed between the longitudinal edges of the drying surface 2 and the second belt 4.

The sealing means 6 are constituted by a selvedge 3c present along each one of the edges of the first belt 3, which is obtained by impregnating with waterproof plastic material the ends of the spirals 3a and of the pins 3b coupled with them. Each selvedge 3c is included between the drying surface 2 and the second belt 4 and defines with a sealing effect the evaporation chamber 5 along the side edges of the drying surface 2.

According to the invention, the drying surface 2 corresponds to at least a section 2a of the lateral outside surface 10 of a cylindrical drum 11 provided with a central shaft 12 coupled with driving means suited to set it rotating and supported by bearings 14 fixed to a support structure 15. Preferably, but not necessarily, the driving means set the drum 11 rotating in the counterclockwise direction indicated by the arrow 16, so that on the lateral outside surface 10 of the cylindrical drum 11 it is possible to identify, with reference to Figure 1 , an area C for loading the hides to be dried and an area S for unloading the dried hides, whose loading and unloading directions are indicated by the arrows in Figure 1.

In particular, the loading area C and the unloading area S are positioned at the level of first tightening rollers 19 that, together with a plurality of transmission rollers 19a, wind the first belt 3 in a closed ring and arrange it so that it adheres

to the section 2a of the drying surface 2 of the cylindrical drum 11 , as can be observed in Figure 1.

The section 2a of the drying surface 2 thus corresponds to the section of the lateral outside surface 10 of the cylindrical drum 11 that, as can be observed in Figure 1 , is included between the tangential areas T between the lateral outside surface 10 of the cylindrical drum 11 and the first tightening rollers 19. Outside the first belt 3 and adhering to it for a section of its length on the cylindrical drum 11 , there is the second belt 4 that in turn adheres to the cylindrical drum 11 for a length that is shorter than the length 2a and is wound around second tightening rollers 20 and a plurality of transmission rollers 20a and 19a.

Finally, a pair of sliding belts 21 are positioned so that they adhere to the outside of the second belt 4, each at the level of a selvedge 3c, and are wound in a closed ring around third tightening rollers 22 and a plurality of transmission rollers 22a.

The overlapping position of the belts described above enables the hide P, which is positioned at the level of the loading area C as shown in Figure 6, to be included between the drying surface 2 and the first belt 3 that make it advance in the counterclockwise rotation direction indicated by the arrow 16. When the second belt 4 adheres to the outside of the first belt 3, the evaporation chamber 5 is defined, where the hides lose the humidity they have gathered.

Successively, the adhesion of the sliding belts 21 outside the edges of the second belt 4 guarantees better adhesion of the belts to the drying surface 2. The second belt 4 and the sliding belts 21 are preferably made of a flexible material, resistant to high temperatures and to the acids that may be present in the hides P.

As regards the suction means, they can be seen in Figures 1 and 4, where they are indicated as a whole by 8, and they comprise: - a plurality of manifolds 25 fixed to the cylindrical drum 11 ;

- a plurality of sleeves 7, each applied to a corresponding suction hole 7a made in the drying surface 2 near the side edges and communicating with said evaporation chamber 5, as can be observed also in Figures 2 and 3;

- a plurality of first suction pipes 26, each one of which connects a sleeve 7 to the corresponding manifold 25;

- a second suction pipe 27 that connects each manifold 25 to a vacuum extraction unit positioned outside the drum 11 ;

- an on-off valve 28 positioned in the second suction pipe 27.

In particular, the vacuum extraction unit can be of any type, in any case carried out according to the known art and comprising at least one vacuum pump.

The holes 7a made in each side edge of the drying surface 2 are aligned circumferentially.

As can be observed in Figure 2, each on-off valve 28 is of known type, and is provided with actuator means 29 that, for example, can be constituted by cam means cooperating with suitable fixed and adjustable stops applied to the support structure 15.

Obviously, the valves and their operation can be of any type.

According to a construction variant that is shown in Figure 5, the suction means 80 don't comprise manifolds and each sleeve 7 is directly connected to the extraction unit through a second suction pipe 30 intercepted by a valve 40 equipped with actuator means 40a.

In both embodiments, each of the valves 28, 40 serves to automatically intercept the suction flow through the suction holes 7a made in the drying surface 2, when these are outside the evaporation chamber 5 and in communication with the external environment, in particular in the section E included between the loading area C and the unloading area S that can be observed in Figure 1.

The sealing action of the evaporation chamber 5 with respect to the outside, along the generating line of the drum 11 , starts, as can be seen in particular in Figure 6, in the area indicated by G located downstream of the loading area C, where the second belt 4 starts to overlap the first belt 3.

Analogously, the sealing action ends when the second belt 4 leaves the first belt 3 in the area indicated by G' upstream of the unloading area S, as shown in Figure 1. Each on-off valve 28 or 40 is connected to the corresponding external vacuum extraction unit through a condenser unit indicated as a whole by 32 and a first rotary manifold 31 associated with the central shaft 12 of the cylindrical drum 11 , as can be seen in Figure 2.

In particular, the condenser unit 32 comprises a condenser 35 containing a heat exchange fluid 35a in which a heat exchanger coil 36 is immersed.

The heat exchange fluid 35a is circulated between a couple of inlet pipes 37 and outlet pipes 38, each connected to a rotary inlet distributor 39 and outlet distributor 40, respectively, also associated with the central shaft 12, and the coil 36 is interconnected between the pipe 41 connecting in parallel the on-off valves 28 or 40 and the first rotary manifold 31.

In this way the steam that is extracted from the evaporation chamber 5 condenses in the coil 36 and is discharged outside through the first rotary manifold 31. As regards the heating means indicated as a whole by 9 in Figure 2, they comprise an air space 45 obtained under the lateral outside surface 10 of the cylindrical drum 11 and defined by a curved wall 46 arranged inside the cylindrical wall 11.

This is spaced from the lateral outside surface 10 through annular partitions 47 that develop circumferentially to the drum, so that the air space 45 is divided into a plurality of annular channels 48.

One or more delivery ducts 49 and return ducts 50, connected to a heating unit through rotary delivery manifolds 51 and return manifolds 52 enable the heating fluid to circulate in the annular channels 48 of the air space 45. The heating unit with fluid circulation can be any unit of known type, operating with diathermic oil, steam, water or other fluids.

It can be observed that the rotary delivery manifolds 51 and return manifolds 52, as well as the first rotary manifold 31 , and also the rotary inlet and outlet manifolds 39 and 40, are all associated with the central shaft 12. As regards in particular the rotary manifolds, they are of known type, for example the second rotary return manifold 52 that can be observed in Figure 2 comprises a fixed annular body 52a, provided with a hole 52b for connection to the return duct 50 and externally coupled with the central shaft 12 through lateral sealing means 52c. The annular body 52a thus defines an annular channel 52d communicating with the outside through a hole 52e made in the central shaft 12 that communicates with an axial duct 12a obtained in the shaft itself. Analogously, other axial ducts 12b, 12c, 12d and 12e made in the central shaft 12 respectively connect the rotary manifolds 51 , 31 , 39, 40. According to a different embodiment of the dryer that is the subject of the invention, not illustrated in the figures, an intermediate belt is interposed

between the hides P and the first belt 3, to prevent the impression of the spirals 3a and the pins 3b from being left on the hides. In practice, when the drum 11 is set rotating in the counterclockwise direction indicated by the arrow 16, a first operator places a hide P at the level of the loading area C and introduces it following the direction indicated by the arrow in Figure 1 , between the cylindrical drum 11 and the first tightening roller 19. The hide P is thus positioned between the drying surface 2 and the first belt 3 inside the evaporation chamber 5 defined between them and follows the drum 11 during rotation. The hides P are loaded one after the other without interruption and dry up while covering the arc of circle that corresponds to the section 2a of the drying surface 2.

During rotation of the drum 11 , the extraction unit creates vacuum inside the drying chamber 5 and at the same time extracts the steam and condenses it in the condenser unit 32.

In particular, it can be observed in Figure 7 that the pins 3b joining adjacent spirals 3a to each other define in the drying chamber 5 channels 5a parallel to the generating lines of the cylindrical drum 11 , along which the condensate and the steam are sucked at the sides of the drum 11 towards the suction holes 7.

It can be observed in Figure 6 that the radius of the cylindrical drum 11 , indicated by 60, defines the area G downstream of the loading area C where the second belt 4 overlaps the first belt 3 and where the sealing action of the drying chamber 5 towards the outside starts. Obviously, the situation illustrated in Figure 6, which takes place at the level of the area G downstream of the hide loading area C, is symmetrically repeated at the level of the area G' that can be observed in Figure 1 upstream of the unloading area S, when the second belt 4 leaves the first belt 3 and is no more in contact with it. At the level of these areas G and G' there are the counteracting means that operate the actuator means 29 of the valves 28 or 40 to intercept the suction flow through the suction holes 7a since these, beyond the areas G and G', communicate with the outside. Suction in the drying chamber 5 thus takes place along the whole arc defined by the surface of the drum 11 included between the areas G and G'.

A construction variant of the dryer that is the subject of the invention can be observed in Figure 8 and differs from the embodiment described above only due to the fact that in this case the hides P are loaded through a loading conveyor belt 70 positioned at the level of the loading area C upstream of the first tightening roller 19 and are unloaded through an unloading conveyor belt 71 positioned at the level of the unloading area S downstream of the corresponding first tightening roller 19.

A further construction variant that can be observed in Figure 9 differs from the embodiment just described and represented in Figure 8 due to the fact that in this case it has a composite loading conveyor belt, indicated as a whole by 72, that provides for loading the hide P to be dried in a position R away from the loading area C, positioned for example opposite the latter. On the basis of what has been described, it is clear that the dryer that is the subject of the invention, in all the construction variants shown and described, achieves all the set aims.

In particular, the dryer in its whole occupies, longitudinally, a smaller space compared to the known dryers, said space substantially corresponding to the diameter of the cylindrical drum 11 , increased by the space occupied by any operators and/or any loading/unloading conveyor belts. Furthermore, it has been demonstrated that the dryer of the invention has the characteristics of a continuous vacuum dryer and therefore, by properly adjusting heating of the lateral outside surface 10 of the drum, its rotation speed and the degree of vacuum created in the evaporation chamber 5, it is possible to vary the output of the dryer according to the user's needs. The dryer that is the subject of the invention can be built in any size and this may depend on both construction and production needs. In this regard, if the length of the dryer doesn't represent a problem for the tannery, it will be possible to arrange more than one dryer carried out according to the invention, made with drums with smaller diameter, in such a way as to simplify construction, transport and assembly of the dryer itself.

A solution of this kind is illustrated in Figure 10, where three dryers carried out according to the invention, each one indicated as a whole by 1 , are arranged in line.

It can be observed that the intermediate dryer is connected to the dryers that precede and follow it by means of connection belts indicated by 73, 74,

respectively, for the transfer of the hides P.

It is clear that according to this principle any number of dryers can be connected in line.

Furthermore, any variations that should be made to the dryer that is the subject of the invention, although not described and not shown in the attached drawings, but nonetheless falling within the scope of the following claims, must all be considered protected by the present patent.

In the cases where the technical characteristics illustrated in the claims are followed by references, these have been added only with the aim to facilitate the comprehension of the claims themselves and therefore said references do not have any limiting effect on the degree of protection to be granted to each element they identify only by way of example.