The present invention generally relates to an industrial rotary booth for treating tannery leathers by means of spraying covering products in nebulized form such as for example, paints, pigments, resins, oils, paraffins, glues and so on.

In the leathers tanning industry, it is known that spraying equipment or machines are available which are commonly referred to as“booths”, which are adapted to be used to spray various covering products over the leathers such as paints, pigments, resins, oils, paraffins, glues or natural and/or similar chemical products. As it is also known, painting by means of spraying is one of the most important leather finishing operations of the processing cycle of the tanning industry, which provides large spaces to be available in the factory by reason of the extension of the plants with which it is performed.

In the tanning field, painting the leathers in essence consists in covering the grain side (i.e. the more valued and more precious side of the leather) with one or more layers of covering and coloring material, in the form of a thin and uniform elastic film applied by spraying and in a more or less increased quantity, according to the covering capacity to be obtained.

The main risk also associated with painting leathers is apparently the environmental pollution it induces at the workplaces; to eliminate or at least reduce such a risk, there are to be used specific spraying booths, which may essentially be of two types:

- open spraying booths, i.e. provided with open surface on one or more sides;

- closed, airtight spraying booths, i.e. provided with closed surface on all the sides with the exception of “technical” openings which can be reclosed by means of doors or gates, adapted to allow the inlet of the leathers involved in the spraying operations.

A further classification of the spraying booths used in the tanning industry is obtained from the spraying method type performed with them, which may be manual (increasingly less common) or automated (without intervention by personnel).

A typical known plant for spraying leathers generally comprises a conveyor belt for advancing the leathers along a given linear direction, a closed industrial booth inside of which the covering products are deposited by means of related spray guns, and a fume suction and abatement system by means of which the exhalations of the covering products deposited on the leathers are sucked and filtered.

In particular, the known leather painting or spraying plants use a system for sucking the fumes resulting from the paint suspended in the air in the industrial booth, which may be further classified as rotary type (in the circular, or inappropriately-called elliptical, variant) or of alternate type.

Specifically, a common circular rotary booth (shown in figure 1 , where it is indicated with B) has a central shaft N arranged in the spraying chamber S and operatively connected to motorization means M, serving the function of distributing the covering material (color, paint or whatever else) useful for spraying, to the spraying means controlling the compressed air ducts required for operating the same spraying means.

The circular rotary spraying booth B of known type also includes a plurality of bearing arms (usually eight or twelve in number) which are radially arranged and are integral with the driven central shaft M from which they take the rotary movement, while the spraying means in general comprise a plurality of fixed guns which are installed at the ends of the bearing arms and spray the covering material in nebulized form over the surface of leather P to be treated, which in turn is arranged above a conveyor belt (or carpet), generally made with parallel and closely-spaced nylon threads, which has width G and advances along a predetermined linear direction W by using an inverter at a preset speed (usually comprised from 4 to 22 meters/minute).

One, two or sometimes three spray guns may be installed at the end of each bearing arm, each one controlling its own introduction circuit for supplying the covering material which is sucked by a pump arranged to the side of the rotary booth B, while the compressed air circuit provides for the correct nebulization of such a fluid material.

Moreover, there is a reading bar installed upstream of the industrial rotary booth B, which serves the function of determining the position of leather P, the surface thereof and the outline thereof, so that an electronic control unit, which saves the dimensions and shape of leather P, is capable of causing the opening and closing of the spray guns.

The known circular rotary booths are preferable for the effectiveness and efficiency with which they allow the leather spraying treatment to be performed because, by executing a circulation motion (shown with a dotted line in figure 3) along a circumference of radius R and center O integral with that of the central shaft rotating about a vertical axis, each of the spray guns applies the covering material over the leathers according to a curved articulated drawing E (shown in figures 4 and 5) having intersecting rows to form a net, which due also to the number of spraying passages performed by the dispensing guns over the leathers, substantially makes any treatment imperfections due to uneven operations of the spray guns imperceptible to the human eye, and thus avoids stopping the operation of the rotary booth or at least limits the frequency of machine stops. However, in the face of these advantages, the circular rotary booths have the disadvantage of requiring significant spaces in the factory, which are not always available or conceivable by the entrepreneur.

For this reason, alternative-type industrial booths with smaller dimensions are then used, which have been on the market for some time; they comprise one or two guides, which are transverse with respect to the translation (or advancement movement) of the leathers on the conveyor belt and on each of which a gun-holder carriage slides; specific motors which are adjustable with inverter and related drive chains or belts, cause the alternating linear movement of the carriages, as suitable pipes bring both the compressed air and the covering fluid material (in general color) required for the operation of the spray guns and the treatment of the leathers therewith.

In the alternative-type industrial spraying booths, each time the carriage moves in transverse direction, the spray guns apply the covering material over the advancing leather, according to stripes (or rows) which are overlapped in variable manner: the width of such stripes is a function of the features of the spraying means (in general, the guns) and/or of the preset parameters but in any case, the presence on the leather of covering material deposited in broad and tilted stripes is easily perceptible by the human eye and affects the quality of the end product to the point that such industrial booths are used sporadically and only for given spraying steps.

On the other hand, the common rotary industrial booths of parallel type (improperly also defined“elliptical”) are based on the same operating principle as the elliptical booths (despite being rotary) because the closed annular trajectory T described by the spraying means during the treatment (see figures 6 and 7 to this end) consists of two central rectilinear and parallel stretches Ki and K2 - exactly defined in the part above the conveyor belt and the leathers progressively stretched out thereon - at which the spraying means operate, and of two curved side stretches Ji and J2 (substantially two half-circles) - defined sideways and outside the conveyor belt and therefore definable as “dead” stretches from a viewpoint of the leather spraying treatment - which mutually link the aforesaid two rectilinear stretches and at which the spraying means are closed and not operative.

The parallel-type rotary spraying booths of the prior art have a rectangular structure and a length (measured in the advancement direction of the leathers on the conveyor belt) having a value between 50% and 1/3 of that of the circular rotary booths.

The parallel-type rotary booths include two gear wheels, joined to each other by means of mechanical drive means (such as a belt or chain) which define the aforesaid trajectory which is closed at parallel rectilinear stretches alternated by arced stretches; one of such wheels is driven, while a plurality of spray guns, to which specific air tubes and tubes for the covering material to be applied are connected, are fastened to the drive means and a central distribution shaft supplies both the air circuits and the circuits of the covering fluid material and/or color dispensed by the spray guns.

In addition to being intrinsically rather complicated from a constructional viewpoint, even the parallel-type industrial booths have the drawback that the transverse movement of the spraying means, combined with the movement of the conveyor belt which advances the leathers, generates a linear drawing L formed by a series of intersecting stripes (or rows) which, similarly to the alternative-type industrial booths, do not provide good results; not surprisingly, these booths have a limited application in the tanning industry, given that they are usually used for depositing the so-called “ground color” on which the layers of permanent color are then deposited with other spraying booths.

On the basis of the operating features provided by the types of booths currently on the market, as already mentioned above, the conclusion is that the circular rotary booths provide the best performance in terms of surface finishing of the leather by means of spraying treatment of a covering material and/or color (such as a paint, for example).

However, such circular rotary booths have the drawback of an excessive volume, which parallel rotary booths (or improperly, elliptical booths) remedy, but while creating the drawbacks mentioned above in terms of quality of the finished product at the end of the spraying treatment on the one hand and the construction complexity thereof on the other.

Therefore, starting from the knowledge and the existence of the above-disclosed drawbacks of the current prior art, the present invention intends remedying the same.

In particular, main purpose of the invention is to provide an industrial rotary booth for the spraying treatment of leathers which has the qualities and advantages both of the circular-type rotary booths and of the parallel-type rotary booths (better, albeit inappropriately, also known as elliptical-type booths in jargon).

In other words, primary purpose of the present invention is to conceive an industrial rotary booth for the spraying treatment of leathers which combines the operating efficiency of a typical circular-type rotary booth with the most reduced dimensions, especially in the extension along the advancement direction of the leathers on the conveyor belt (or carpet) of a parallel-type rotary booth.

Within the scope of such a purpose, it is task of the present invention to create an industrial rotary booth for leather spraying treatment which can also be both installable and operational in factories where the available spaces are more limited and such as to prevent the installation of a traditional circular-type of rotary booth.

It is another task of the invention to indicate an industrial rotary booth for the spraying treatment of leathers which supporting frame has more contained dimensions (when measured in the advancement direction of the leathers on the conveyor belt) with respect to the traditional circular-type rotary booths of which the operating efficiency is to be emulated.

It is a further task of the current invention to provide an industrial rotary booth for leather spraying treatment which comprises a number of spray guns (or of other spraying means usually used for this processing in the tanning industry) which is less than that of the rotary booths of known type, effectiveness, efficiency, quality and speed of the spraying treatment to be carried out being equal.

It is also a task of the invention to materialize an industrial rotary booth for the spraying treatment of leathers which has a largely competitive production cost with respect to the rotary industrial booths of the known art, the factors involved in calculating such a parameter - such as that for the raw materials and for the labor - being equal.

It is a last but least purpose of the current invention to fine-tune an industrial rotary booth for the leather spraying treatment, the construction concept of which is at least comparable to that of the rotary booths of the prior art, it not being superior with respect thereto.

Said purposes are achieved by an industrial rotary booth for leather spraying treatment according to the appended claim 1 , to which reference is made for the sake of brevity of disclosure.

Further detailed technical features of the industrial rotary booth for the leather spraying treatment of the invention are indicated in the corresponding dependent claims.

As later specifically and practically defined, the aforesaid claims are to be intended as an integral part of the present description.

Advantageously, the industrial rotary booth of the present invention has the auxiliary circumference arcs (those lying sideways outside the underlying conveyor belt) of the closed annular trajectory travelled by the spraying means more compressed with respect to one another with respect to what occurs in the circular rotary booths of known type, therefore reducing the volume of such auxiliary and lateral circumference arcs, those at which the spraying means in essence do not operate and do not dispense any fluid covering mixture. The industrial rotary booth of the current invention thus provides a dead (or non- operational) path of the spraying means outside the conveyor belt on which the leathers advance one-by-one, of smaller circumferential length with respect to that of the circular rotary booths of the known art, the best ones in terms of the spray performance profile.

Again advantageously, the industrial rotary booth of the invention has dimensions, along the predetermined linear advancement direction of the leathers on the conveyor belt which are less than those of the known circular rotary booths.

Being equally advantageous, the industrial rotary booth can be designed with a number of examples forming the spraying means (spray guns) which is lower than that of a traditional-type circular rotary booth, re-proposing the same operating advantages thereof: the frequency with which the spraying means are over the leathers to be treated indeed is higher with respect to that of a regular circular rotary spraying booth due to the length of the two auxiliary circumference arcs (external and lateral to the conveyor belt, as mentioned above) which are not useful to treating the leathers.

The above-mentioned advantages are achieved in particular thanks to the fact that the radius of curvature of the main circumference arcs and the radius of curvature of the auxiliary circumference arcs in the industrial rotary booth of the invention, which are all crossed by the spraying means during each individual rotation thereof about a vertical longitudinal axis, in particular take finite values different from zero and different from one another.

Said purposes and advantages will become more apparent from the following description related to a preferred embodiment of the industrial rotary booth for the spraying treatment of tannery leathers of the invention, given by way of indicative and illustrative but non-limiting example, with the aid of the accompanying drawings (already mentioned in part), in which:

- figure 1 is a simplified axonometric view of an industrial rotary booth of the known art;

- figure 2 is a side view of figure 1 ;

- figure 3 is a diagrammatic and explicative plan view of figure 1 ;

- figure 4 is a diagrammatic and explicative plan view of the initial steps of the application method for spraying a covering material over the leathers, executed by the spraying means installed in the circular-type industrial rotary booth of figure 1 ;

- figure 5 is a diagrammatic and explicative front view of the advanced steps of the application method for spraying a covering material over the leathers, executed by the spraying means installed in the circular-type industrial rotary booth of figure 1 ;

- figure 6 is a diagrammatic and explicative plan view of the initial steps of the application method for spraying a covering material over the leathers, executed by the spraying means installed in an industrial rotary booth inappropriately defined elliptical, belonging to the known art;

- figure 7 is a diagrammatic front view of the advanced steps of the application method for spraying a covering material over the leathers, executed by the spraying means installed in the industrial rotary booth of figure 6;

- figure 8 is a diagrammatic and explicative plan view of the initial steps of the application method for spraying a covering material over the leathers, executed by the spraying means installed in the industrial rotary booth

(actually elliptical) of the invention;

- figure 9 is a diagrammatic and explicative front view of the advanced steps of the application method for spraying a covering material over the leathers, executed by the spraying means installed in the industrial rotary booth

(actually elliptical) of figure 8.

The industrial rotary booth of the invention used for the spraying treatment of the leathers P by means of paints, colors or the like, is shown in diagrammatic, illustrative and partial manner in figure 8, where it is indicated as a whole with 1 ; although with the due significant construction differences noted in the continuation, it is comparable to the industrial rotary booth B of the prior art shown in figure 1. According to the provision already acquired from the background art and partially substantiated in figure 1 , the industrial rotary booth 1 comprises:

- a supporting frame, such as a box-like shell (indicated with 2 in figure 1 ) if the industrial rotary booth 1 is closed, which has an inlet 3, through which a leather P is carried into the spraying chamber 3 of the supporting frame 2 which is subjected to a spraying treatment while lying on the upper surface of a conveyor belt (or carpet) adapted to be at least partially received inside the supporting frame 2 and to be advanced along a predetermined linear direction W, and an outlet (not shown) through which leather P just spray-treated is carried outside the supporting frame 2 for a subsequent processing and/or handling thereof;

- spraying means (not shown for simplicity) coupled to the supporting frame 2 inside which they are arranged, adapted to deposit at least one fluid covering mixture in nebulized form on leather P advancing along the aforesaid linear direction W, while the spraying means are placed in rotation along a closed annular trajectory T so that the spraying means take the working condition at two main circumference arcs 4, 5 belonging to the closed annular trajectory T and lying above the conveyor belt, and the rest (or stop or inoperability) condition at two auxiliary circumference arcs 6, 7, which are distinct from the main circumference arcs 4, 5, belonging to the closed annular trajectory T, lying sideways on the outside of the conveyor belt and joining the two main circumference arcs 4, 5 themselves to each other.

According to the invention, the radius of curvature Ri of the main circumference arcs 4, 5 and the radius of curvature Fte of the auxiliary circumference arcs 6, 7 take finite values different from zero and different from one another.

Particularly, the radius of curvature Ri of the main circumference arcs 4, 5 is greater than the radius of curvature R2 of the auxiliary circumference arcs 6, 7. Preferably but not necessarily, the radius of curvature Ri of the main circumference arcs 4, 5 has a value included in the range of 0.5 to 0.9 times the width of the conveyor belt.

In particular, the value of such a radius of curvature Ri of the main circumference arcs 4, 5 is equal to 0.7 times the width of the conveyor belt; this specific value is nominal and in theory, allows booth 1 to achieve the preset objects of the invention while maintaining congruous construction features.

According to the preferred embodiment herein described of the invention, here the closed annular trajectory T has, for all intents and purposes, a plan profile which is substantially elliptical in shape so that the industrial rotary booth 1 of the invention may rightly be properly defined of elliptical-type (but not parallel), like that diagrammatically depicted in figure 6.

If the aforesaid closed annular trajectory T advantageously consists just of an ellipse, the origin of the radius of curvature Ri of the main circumference arcs 4, 5 lies on the minor semiaxis Mi of the ellipse itself (more precisely, it lies in the point in which such a minor semiaxis Mi intersects or touches the ellipse itself) where it coincides with a point Ci which is distinct from center C of the ellipse so that the length of such a radius of curvature Ri is greater than the minor semiaxis Mi of the ellipse.

In detail, the origin of the radius of curvature Ri of the main circumference arc 4 is symmetrically opposite to the origin of the radius of curvature Ri of the opposite main circumference arc 5, with respect to center C of the ellipse.

For its part, the origin of the radius of curvature R2 of the auxiliary circumference arcs 6, 7 lies on the major semiaxis M _m of the ellipse and substantially coincides with one of the focuses C2 of the ellipse itself, so that the length of such a radius of curvature R2 is less than the half of the major semiaxis Mm of the ellipse; also the origin of the radius of curvature R2 of the auxiliary circumference arc 6 is symmetrically opposite to the origin of the radius of curvature R2 of the opposite auxiliary circumference arc 7, with respect to center C of the ellipse.

Figure 8 shows that center Ci of the radius of curvature Ri of the main circumference arcs 4, 5 is moved (or distinct) but aligned, along the predetermined linear direction W, with respect to center C of the closed annular trajectory T (preferably elliptical, as mentioned) travelled by the spraying means in the rotation thereof about a longitudinal axis X in the direction given by arrow F, for instance. For its part, the center C2 of the radius of curvature R2 of the auxiliary circumference arcs 6, 7 is moved (or distinct) but aligned, along a longitudinal direction Z which is orthogonal to the predetermined linear direction W, with respect to center C of the closed annular trajectory T travelled by the spraying means.

With regards to the supporting frame 2, it extends in length A, measured according to the predetermined linear direction W of advancement of each individual and subsequent leather P on the conveyor belt, not more than substantially 4 meters: this aspect highlights the main advantage of the invention, represented by a significant reduction in the volume of the elliptical industrial rotary booth 1 with respect to a traditional circular rotary booth of which it in any case maintains the operating and performance qualities, as shown in figure 9, and makes the rotary booth 1 of the invention particularly adapted to replace, as overall volume, known spraying machines of another type already existing on the market and/or installed in a factory, but less performing from the spraying efficiency profile, to the complete advantage of the productivity and logistics requirements of the end customer.

In greater detail, the spraying means belong to a rotating carousel and are supported by a plurality of bearing arms which, as it can be derived thanks to the aid of figures 1 and 3:

• support the spraying means themselves;

• are contained in the internal spraying chamber 3 defined in the supporting frame 2;

• project radially downwardly, so as to face the conveyor belt below, from a central distribution shaft 8 coupled to the supporting frame 2 and operatively connected with the motorization means 9 which put it into rotation about a longitudinal axis X orthogonal to the linear direction W (and also to the longitudinal direction Z).

Figure 8 also shows that the rotating carousel extends in width D, measured in a longitudinal direction Z orthogonal to the predetermined linear direction W, having a value directly depending on the value of said radius of curvature Ri of the main circumference arcs 4, 5 and therefore, of the width of the conveyor belt.

In a hypothetically static circumstance, the rotating carousel includes two mutually opposed peripheral longitudinal portions adapted to project sideways on opposite sides from the conveyor belt below, on which upper surface the various leathers to be treated are progressively rested and advance.

It is clear that under operating conditions - i.e. during the rotation of the rotating carousel about the vertical longitudinal axis X - such two peripheral longitudinal portions of the rotating carousel change in continuous and consequential, albeit cyclical manner. Conveniently and advantageously, the bearing arms are provided with adjustment means (not shown for illustrative simplicity) serving the function of varying the length of the support arms themselves in relation to the position of the latter in the passage thereof from the main circumference arcs 4, 5 to the auxiliary circumference arcs 6, 7 and vice versa, while the rotating carousel rotates about the longitudinal axis X defined by said central shaft 9.

In light of the description above, it is thus understood that the industrial rotary booth for the spraying treatment of the tannery leathers of the invention achieves the purposes and reaches the advantages mentioned above.

Upon execution, changes could be made to the industrial rotary booth for the spraying treatment of leathers of the current invention consisting of, for example, spraying means of different type from that one described above, as far as only in relation to the preferred embodiment of the industrial booth herein exclusively claimed.

Additionally, other variants of the industrial rotary booth for the leather spraying treatment being claimed, moreover not accompanied by explicative reference drawings, could exist in which the supporting frame has a different construction concept from that shown in the accompanying drawings, for example of open type, which does not invalidate the advantage brought about by the present invention. Finally, it is clear that several other variations could be made to the industrial rotary booth for the spraying treatment of the tannery leathers concerned, without departing from the inherent principles of novelty of the inventive idea, as it is apparent that any materials, shapes and sizes of the details disclosed may be used as needed in the practical actuation of the invention, and they may be replaced with others which are technically equivalent.

Where the construction features and techniques mentioned in the following claims are followed by reference marks or numerals, such reference signs were introduced with the sole goal of increasing the intelligibility of the claims themselves, and therefore they have no limiting effect on the interpretation of each element identified by mere way of example by such reference signs.