WO2014045200A1

WO2014045200A1 - Improved machine and method for dyeing the edge of leather portions

Info

Publication number: WO2014045200A1
Application number: PCT/IB2013/058617
Authority: WO
Inventors: Lapo Governi; Rocco Furferi; Yari VOLPE; Maurizio Toccafondi; Matteo NUNZIATI; Ivan Nikolaev; Andrea TROVATELLI
Original assignee: Officine Maya S.R.L.
Priority date: 2012-09-20
Filing date: 2013-09-17
Publication date: 2014-03-27
Also published as: ITFI20120188A1

Abstract

The machine comprises a work surface (5) for the leather to be dyed and a toolhead (9), movable along the work surface with a numerically controlled axis system. The toolhead carries a tool (11) for dyeing the edges of the leather positioned on the work surface. The machine also comprises a vision system (21) to acquire images of the leather to be dyed positioned on the work surface and a computer that receives the images of the leather and processes the trajectories of the toolhead to dye the edges of said leather. The vision system is positioned over the work surface, while a back-lighting system (31A) is positioned under the work surface (5). The work surface at least partly transparent to the light emitted by the back-lighting system to acquire the images of the leather portions to be dyed.

Description

"Improved machine and method for dyeing the edge of leather portions"

DESCRIPTION

TECHNICAL FIELD

The present invention relates to leather processing. More in particular, the present invention relates to improvements to systems for dyeing leather, in particular destined for the production of leather items, such as bags, belts, footwear or other clothing accessories, or leather articles in general.

p

State of the art

The dyeing process for finishing leather is a process that is performed on all leather portions used to produce articles of various kinds. Leather arriving from the tannery can be cut into the required shape with the aid of cutting dies or in another suitable manner. This cut leaves the edge of the leather rough, i.e. with the natural color of the leather. Therefore, the edge must be finished, coloring it with special paints or inks, both to give the edge the desired color and to form a layer similar to rubber that is pleasing to the touch.

Currently, this process is performed manually in the leather goods industry. Skilled operators hold the leather portion to be finished in one hand and with the other hand dip a small nail-shaped tool into a container filled with paint. The tip of the tool is subsequently passed over the edge of the leather, dyeing it. The leather is then left to dry. Often, the operation must be performed several times to obtain a consistent layer of dye.

This process must have a very high level of finish, in which the dye must be applied uniformly. The greatest difficulty lies in the fact that there must be no smears and stains on the surface of the leather not involved by the dyeing process. This has made it difficult to automate the process. ^!

Pen-shaped tools are known, with which the operator can dye the edge manually without having to dip the tool into the ink, as this is dispensed automatically by pressing a button on the pen. Also with these devices, the dyeing operation is performed manually by a skilled operator.

To make the leather dyeing operation more efficient, a machine and a method that enable a considerably degree of automation have recently been developed. See Italian patent application no. FI2008A000232. - -

The machine described in that patent application comprises in combination: a work surface for the leather to be dyed;

a toolhead, movable along said work surface with a numerically controlled axis system;

a tool carried by said toolhead to dye the edges of the leather positioned on said surface;

a vision system to acquire images of the leather to be dyed positioned on said surface;

a computer that receives the images of the leather and processes the trajectories of the toolhead to dye the edges of said leather.

Although this machine has made the operation of dying the edges of leather portions simpler and more efficient, introducing a substantial degree of automation, the current state of the art still has some limitations. In particular, these concern the method of acquiring images, the way in which the leather is fixed on the work surface and the total productivity of the machine.

Therefore, there is the need to provide an improved machine and method that overcome these limits and drawbacks.

Summary of the invention

According to one aspect, there is proposed a machine for dyeing the edge of leather portions, comprising in combination: a work surface for the leather to be dyed; a toolhead, movable along the work surface with a numerically controlled axis system; a tool carried by the toolhead to dye the edges of the leather positioned on the work surface; a vision system to acquire images of the leather to be dyed that is positioned on the work surface; a computer that receives the images of the leather and processes the trajectories of the toolhead to dye the edges of the leather. The vision system is positioned over the work surface. Characteristically, a back-lighting system is positioned under the work surface to acquire one or more images of the leather portion or portions positioned on the work surface. This latter is at least partly transparent to the light emitted by the back-lighting system. With this arrangement it is possible to acquire images of the leather portions, eliminating or in any case reducing the effect of light sources outside the system. For example, by means of back-lighting it is possible to prevent the acquired images from having effects caused by the reflection or diffusion of light on the surface of the leather. Moreover, the effect of light radiation coming from light sources such as lighting bodies of the room in which the machine is located, windows or the like, is minimized. There is also a reduction in the shadow effect caused by the thickness of the leather, which can cause errors in identification of the real profile or contour of the portions, and therefore in calculation of the trajectories of the dyeing tool.

According to a different aspect, the invention provides a machine for dyeing the edge of leather portions, comprising in combination: a work surface for the leather to be dyed; a toolhead, movable along the work surface with a numerically controlled axis system; a tool carried by the toolhead to dye the edges of the leather positioned on said work surface; a vision system to acquire images of the leather to be dyed that is positioned on the work surface; a computer that receives the images of the leather and processes the trajectories of the toolhead to dye the edges of the leather; a vision system positioned over the work surface. Characteristically, the work surface is removable. The machine can be equipped with more than one interchangeable work surfaces, so that when one work surface is in the machine, with leather portions to be dyed being processed, another work surface can be placed in a drying station and/or in a station for removal of the portions already treated and/or in a station for positioning new portions to be processed.

The removable work surface can also be at least partly transparent to allow back-lighting, with the advantages illustrated above. However, in some embodiments the removable surface may not be back-lit, but illuminated from the same side from which the images are acquired.

According to a further aspect, the invention relates to a machine for dyeing the edge of leather portions, comprising in combination: a work surface for the leather to be dyed; a toolhead, movable along the work surface with a numerically controlled axis system; a tool carried by the toolhead to dye the edges of the leather positioned on the work surface; a vision system to acquire images of the leather to be dyed that is positioned on the work surface; a computer that receives the images of the leather and processes the trajectories of the toolhead to dye the edges of the leather. The vision system is positioned over the work surface. Characteristically, the work surface can comprise a ferromagnetic material. The ferromagnetic material can be positioned inside the work surface or can be applied to a surface thereof. Preferably, the work surface equipped with ferromagnetic properties is advantageously also at least partly transparent and/or removable, to obtain one or more of the advantages illustrated above, achievable with the characteristics of removability and (partial) transparency of the work surface.

With the work surface equipped with ferromagnetic properties it is possible to obtain particularly efficient positioning and fixing of the leather portions on the surface. For example, the work surface can be associated with one or more magnetic blocks, used as spacers between the work surface and the leather to be processed, on which the leather can be positioned and fixed, or a template on which the leather to be dyed is in turn placed and fixed.

In advantageous embodiments the work surface has a flat base surface and one or more raised portions formed on the work surface, the shape of which is determined by the shape of the leather to be dyed. This can be obtained, for example, by thermoforming. The shape of the thermoformed work surface is determined as a function of the shape and of the dimension of the leather portions to be processed. If the work surface has a ferromagnetic material, the leather can be fixed at the raised portions by means of magnets of suitable shape.

If the work surface is at least partly transparent, the ferromagnetic material is distributed or applied so that it does not obstruct correct acquisition of the images of the portions. For example, the ferromagnetic material can be in the form of a fine dispersion of iron filings in a plastic material with which the work surface is formed. In other embodiments the ferromagnetic material can be applied in the form of a mesh with sufficiently fine links, for example with a side of 1-5 mm, in metal wire, to generate a suitable magnetic attraction force, without altering the images of the contours of the pieces of leather to be processed, during the step of acquisition of the images by back-lighting.

According to a further aspect, the invention relates to a machine for dyeing the edge of leather portions, comprising in combination: a work surface for the leather to be dyed; a toolhead, movable along the work surface with a numerically controlled axis system; a tool carried by the toolhead to dye the edges of the leather positioned on the work surface; a vision system to acquire images of the leather to be dyed positioned on the work surface; a computer that receives the images of the leather and processes the trajectories of the toolhead to dye the edges of the leather. The vision system is positioned over the work surface. Characteristically, the toolhead comprises a variable volume chamber containing a dyeing liquid; an actuator for modifying the volume of said variable volume chamber; a dispenser in fluid connection with said variable volume chamber, configured to apply dyeing liquid to the edge of leather to be dyed. The toolhead can be combined with a work surface having one or more of the characteristics described above, for example a work surface that can be back-lit and/or removable and/or provided with ferromagnetic properties.

Advantageously, the dispenser is rotating about an axis of rotation, and the toolhead is equipped with an actuator to control rotation of the dispenser.

In advantageous embodiments, a machine is provided in which the vision system comprises a plurality of image acquisition units of the leather placed on the work surface. In this way, it is possible to acquire images of a relatively extensive surface and then reconstruct, via software, the image projected in the plane of the whole of the work surface.

In some embodiments the computer of a machine according to one or more of the embodiments defined above is programmed to perform the following steps:

acquisition of one or more images with one or more image acquisition units; correction of the geometric distortion of each image acquired, elimination of perspective distortions and conversion of each image to simple orthogonal projections (plan view) of the portion of surface framed;

if necessary merging of the images acquired into a single image;

extraction of external contours and if necessary of internal contours of the leather positioned on the work surface (both external contours and any holes).

According to some embodiments the computer is programmed to perform the following further steps:

vectorization of the contours;

simplification of the contours through conversion of the contours into closed curves, for example closed polylines, each constituted by a plurality of portions consecutive to one another.

In advantageous embodiments, the computer is programmed to perform customization of the sections of contour to be dyed. Advantageously, the computer can be programmed to reprocess a path of the tool as a function of the customization of the sections of contour to be dyed. Customization of sections of contour to be dyed can be performed through the following steps: _ _ selection, by the operator using a pointer on a monitor, of an initial customization point on a leather contour to be customized;

identification of the curve portion on which said initial point is located;

visualization on said monitor of a cursor that lies on said curve portion which was intersected by the passage of the pointer;

while the operator moves the cursor using the pointer approximately along the contour, calculation of the equations required to constrain the cursor exactly on the contour regardless of the accuracy of movement of the operator and instarit identification of the possible change of curve portion on which the cursor is located, said portion being the one closest to the position of the cursor and consecutive or precedent to the previous curve portion;

repetition of the preceding step until release by the operator of the pointer in a final point of the customized section of contour.

According to a further aspect, the invention relates to a method for dyeing edges or contours of portions of leather or hide, comprising the steps of:

if necessary merging of the images acquired into a single image;

extraction of external contours and if necessary of internal contours of the leather arranged on the work surface (both external contours and any holes).

In advantageous embodiments, the method can comprise the further steps of vectorization of the contours;

According to a further aspect, the method of the invention can comprise step of customization of the sections of contour to be dyed. The customizing of sections of contour to be dyed can take place through the following operations:

selection, by the operator using a pointer on a monitor, of an initial customization point on a leather contour to be customized;

identification of the curve portion on which said initial point is located; visualization on said monitor of a cursor that lies on said curve portion which was intersected by the passage of the pointer;

while the operator moves the cursor using the pointer approximately along the contour, calculation of the equations required to constrain the cursor exactly on the contour regardless of the accuracy of movement of the operator and instant identification of the possible change of curve portion on which the cursor is located, said portion being the one closest to the position of the cursor and consecutive or precedent to the previous curve portion;

Characteristics and embodiments are described hereunder and further defined in the appended claims, which form an integral part of the present description. The brief description provided above identifies characteristics of the various embodiments of the present invention so that the following detailed description can be better understood and so that the contributions to the art may be better appreciated. Naturally, there are other characteristics of the invention which will be described below and will be set forth in the appended claims. It must be understood that the various embodiments of the invention are not limited in their application to the structural details and to the arrangements of components described in the following description or illustrated in the drawings. The invention can be implemented in other embodiments and put into practice in various ways. Moreover, it must be understood that the phraseology and terminology employed herein are purely for descriptive purposes and must not be considered limiting.

Therefore, those skilled in the art will understand that the concept on which the description is based can be used as a basis to design other structures, other methods and/or other systems to implement the various objects of the present invention. Consequently, it is important that the claims are considered as inclusive of those equivalent structures which do not depart from the spirit and from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood by following the description and accompanying drawing, which shows non-limiting practical embodiments of the invention. More in particular, in the drawing: - -

Fig.1 shows a schematic front view of an embodiment of a machine according to the invention;

Figs.2, 3 and 4 show axonometric views of the machine according to the invention, respectively: with the work surface mounted, during removal and removed;

Fig.5 shows an axonometric view of the toolhead carrying the dyeing tool;

Figs.6 to 8 show schematic front views of three possible modes of supporting and blocking the leather on the work surface, and

Figs.9A-9I show explanatory diagrams of the method of processing the images and of processing the leather.

Detailed description of embodiments of the invention

The following detailed description of some exemplary embodiments refers to the accompanying drawings. The same reference numbers, recurring in different drawings, indicate the same or similar elements. The drawings are not necessarily to scale. Further, the following detailed description does not limit the invention. On the contrary, the scope of the invention is defined by the appended claims.

In the whole of the description, reference to "an embodiment" or "some embodiments" or analogous or equivalent wording indicates that a particular characteristic, structure or property described in relation to an embodiment is included in at least one embodiment or example of embodiment of the object described. Therefore, the phrase "in an embodiment" or "in some embodiments", or analogous or equivalent expressions, in various points of the description does not necessarily refer to the same embodiment or embodiments. Moreover, the particular characteristics, structures or properties can be combined in any suitable manner in one or more embodiments.

Fig. 1 schematically shows the general configuration of a machine according to the invention in a possible embodiment. The machine, indicated as a whole with 1, comprises a work surface 5 supported by a load-bearing structure shown schematically at 3. A numerically controlled axis system, indicated as a whole with 7, is associated with the work surface 5 to move a toolhead with a tool according to a plane substantially parallel to the work surface 3. More in particular, the numerically controlled axis system comprises a first horizontal guide 7X on which a toolhead 9 carrying the dyeing tool 11 moves along the numerically controlled axis X, described in more detail below. The guide 7X is in turn movable along two lateral guides 7Y _ defining the numerically controlled axis Y. The letters Mx and My indicate the two motors that control the movement along X and along Y, respectively. Movement of the toolhead 9 along the numerically controlled axes X and Y is controlled by means of a block 13 comprising a CNC system 15 and drives 17. Reference number 19 indicates a computer, for example a PC, which manages operation of the machine and provides the numeric control 15 with the data defining the trajectories of the toolhead 9.

In a possible embodiment, these data are obtained by means of a vision system comprising, for example, one or more sensors, e.g. cameras, video cameras or other image acquisition systems. The diagram of Fig.l indicates three image acquisition systems 21A, 21B, 21C positioned over the work surface 5. The vision system 21A, 2 IB, 21C acquires the image of the work surface 5 on which portions P of leather to be dyed are positioned. The vision system 21 A, 2 IB, 21 C is interfaced with the computer 19 or any other suitable programmable control unit, which, by means of image processing software, extracts the contour of the single leather portions from the image acquired by the vision system. Moreover, based on the contours extracted the computer 19 calculates the points of the trajectories that the tool 11 must follow to dye the edges of the portions positioned on the work surface. As will be described in greater detail below, the computer 19 can also execute a software for customization of the dyeing trajectories, for example to allow the operator to dye only some portions of the perimeter or contour of the leather portions P positioned and fixed on the work surface 5.

The cameras or other image acquisition means 21 A, 21 B, 21C can be variable in number as a function, for example, of the extension of the work surface 5. In general, a number of image acquisition means or systems can be provided to allow acquisition of images of the entire work surface 5 and reconstruction of an image, projected in the plane, of portions P of leather positioned on the work surface, for the purposes that will be explained below with reference to the methods of processing the images and of managing the dyeing process by means of the numerically controlled system of the machine.

In some preferred embodiments of the invention, a cover, indicated schematically with 23 in Fig. 1, is associated with the work surface 5 and with the vision system 21. The cover 23 can have the function of preventing illumination of the work surface 5 by external light sources.

The work surface 5 is represented planar in Figs.l to 4. However, as shall be clear below, it could also be shaped with a top surface modeled as a function of the shape of the leather portions P to be dyed.

In advantageous embodiments, the work surface 5 is made of a material that is transparent, semi-transparent or translucent to the light emitted by a lighting system 31 carried by the structure 3 and positioned under said work surface 5. As can be seen in particular in Figs.3 and 4, the lighting system 31 can comprise a plurality of fluorescent tubes 31 A or another light source. The work surface, being at least partly transparent to the light radiation generated by the lighting system 31, allows the vision system 21 A, 2 IB, 21C to acquire images of the work surface and of the leather portions P fixed thereon, which are greatly in contrast, with a light background and dark areas corresponding to the leather portions P. These images allow easy and precise extraction of the contour of the edges of the single leather portions P. The system is substantially insensitive to external light sources. Moreover, with a backlighting system of this type, the images acquired by the vision system 21 A, 21 B, 21C are not affected by possible defects caused by phenomena of diffusion or reflection of the light on the upper surface of the leather. The images acquired by the vision system have no reflections or other spurious phenomena that can occur in the case of lighting from above.

In advantageous embodiments, the work surface 5 can be made of ferromagnetic material. In particularly advantageous embodiments, the work surface 5 comprises at least a part of ferromagnetic material. For example, in the case in which the work surface 5 is produced so as to be at least partly transparent to the radiation of the back-lighting system 31 described above, elements made of ferromagnetic material can be incorporated inside it. To avoid generating spurious effects on the images acquired by the vision system 21 A, 2 IB, 21 C, in some embodiments the ferromagnetic material incorporated in the work surface can comprise wires, bars or other linear elements, or a mesh, grid or similar structure. For example, metal mesh with fine links, such as a mosquito net, can be used. The thickness of the metal material is such that it does not form, on the sensors of the vision system, shadows that could compromise the correct acquisition of the images of the back-lit leather portions.

The work surface can, for example, be made of glass. In other embodiments, _ _ the material of the work surface 5 can be a plastic material. The ferromagnetic material can be incorporated in the material of the work surface 5 also in the form of powders suspended in the fluid material before solidification.

As can be observed in Figs. 2 to 4, the work surface 5 can be removable. For this purpose, the load-bearing structure 3 can comprise guides 32 for insertion and removal of the work surface 5. The machine 1 can comprise two or more work surfaces 5 usable alternately. While one work surface 5 is in the machine, with the leather portions P fixed thereon, to perform dyeing of the edges, a second work surface 5 can be placed in a preparation station, where the operator can position the leather portions to be processed in a subsequent work cycle. In some embodiments a drying position can also be provided, in which one work surface 5 can be positioned to remain for the time required for the dye or ink applied along the edges to dry completely.

In some embodiments, the machine 1 can be provided with three work surfaces 5. While a first work surface 5 is located in the machine 1 with the leather portions P positioned thereon to be dyed, a second work surface 5 can be positioned in a preparation or loading position, and a third work surface 5 can be positioned in a drying station.

In some embodiments, not shown, an optionally automatic mechanized system can be provide to transfer the work surfaces through various stations, in one of which the machine 1 is positioned.

Fig.5 shows a possible embodiment of the toolhead 9 and of the tool 11 for dyeing the edges of the leather portions P. The toolhead is shown in an axonometric view with a part removed to show the internal components. In this embodiment, the toolhead 9 comprises a frame 41 provided with shoes (not shown) for sliding on the guide 7X. The frame 41 carries a first actuator, for example an electric motor 43, to control dosing of the dyeing liquid, for example paint or ink, contained in a variable volume chamber provided in the tool 9. The motor 43 can rotate a threaded bar, which engages in a nut screw (not shown) carried by a slide 47 sliding on guides 47 fixed to the frame 41. The slide 45 carries a pusher 49. The movement of the motor 43 controls lifting and lowering of the pusher 49. The pusher can act on a piston-cylinder system that forms part of the tool 11. In Fig. 5 the piston is indicated with 1 1A and the cylinder with 1 IB. The piston-cylinder system forms a variable volume chamber, . - inside which the liquid for dyeing the edges of the leather portions P is contained. In the end part the tool 11 comprises a rotating element 11C carrying a tip 11D. The liquid from the variable volume chamber defined by the piston-cylinder system 1 1 A, 1 IB, and dispensed by means of the thrust generated by the motor 43, is dispensed on the tip 11D. The tip 11D can be made as described in the patent document mentioned in the introductory part of the present description. By rotating the rotating element 1 1C that supports the tip 11D it is possible to distribute the dyeing liquid evenly on the edge of the leather, avoiding accumulations on the surface of the tip 11D. The toolhead 9 can comprise a second actuator, for example an electric motor 51, to rotate the supporting element 11C of the tip 1 ID. A belt 53 and two pulleys 55, 57 transmit the rotation motion from the electric motor 51 to the rotating element 11C.

The electric motors 43, 51 can be interfaced with the computer 19 of the machine 1. The electric motor 43 can advantageously be controlled so as to correctly dispense the amount of dyeing liquid, for example also as a function of the advancing speed of the tool 11 along the contours or edges of the leather to be dyed.

Advantageous embodiments of the machine 1 , of the work surface 5 and of the accessories thereof can be provided to facilitate the operations of positioning and fixing the leather portions P and for subsequent dyeing of their edges.

When the work surface 5 has ferromagnetic properties, magnetic systems can be used to support and block the leather portions P. Support and fixing of the leather portions imply delicate problems related to the type of product and to the type of processing to be performed thereon. In fact, in general the leather portions to be processed can have dimensions and shapes that differ greatly from one another and there are situations in which it is necessary to process, i.e. dye, very small batches of portions, or even single portions. In other situations it may be necessary to dye or process batches with a larger number of pieces or portions that identical to one another.

A first positioning and fixing system of the leather portions P to be processed is described with reference to Fig.6. This figure schematically shows a section of the work surface 5 according to a plane orthogonal to a generically planar surface of the work surface 5. A ferromagnetic material, for example a mesh 61, is contained inside the work surface 5. The ferromagnetic material 61 could also be applied to an outer face of the work surface, for example the lower face, or flush with the upper or lower _ surface of the work surface.

A leather portion P is positioned and fixed on the work surface 5 by means of a plurality of blocks 63, for example cylindrical or prismatic, formed by a magnetic material or containing magnetic material. Due to the ferromagnetic material 61 incorporated in or associated with the work surface 5, the blocks 63 can be positioned and anchored to the work surface 5 in positions determined by the shape of the leather portions to be processed. A template 65, for example made of cardboard, wood, plastic or another material, can be placed over the blocks 63. The template 65 has a shape corresponding to that of the leather portion P to be processed, but has a slightly smaller dimension, so that the edge or contour PC of the portion P to be processed projects slightly, for example by a few millimeters, from the template. In Fig.6 the projection of the leather portion P is exaggerated for greater clarity of representation.

In this way the tool 1 1 can process the contour PC of the portion P without touching the edge of the template 65 avoiding the risk of seepage of the dyeing liquid between the lower surface of the leather portion P and the upper surface of the template.

Use of the template 63 facilitates processing in the case of small production batches of identical portions, as it allows rapid and correct positioning of the portions after the template has been positioned. To retain the template in position it is possible to use plates made of ferromagnetic material 67 to be positioned over the template 65, at the magnetic blocks 63. Further ferromagnetic plates can be placed over the leather portion P.

Fig.7 shows a fixing system advantageously usable for processing very small batches, for which the production of a template is not cost-effective. In this case, the leather portion P is placed directly over a series of magnetic blocks 63. The magnetic blocks 63 can in this case be placed in positions closer to one another, to provide the necessary support along the whole perimeter of the portion. The number of magnetic blocks 63 and their mutual distance can also depend on the stiffness of the leather used. The leather can be fixed to the blocks using ferromagnetic plates 67 placed over the leather portion P at the magnetic blocks 63.

To process larger batches, specifically shaped work surfaces 5 can be produced as a function of the shape of the leather portions P to be processed. Fig. 8 shows, for example, a work surface 5 comprising ferromagnetic material, for example in the form _ of an iron mesh 61 incorporated in the thickness of or emerging from the work surface 5. The upper surface of the work surface 5 is non- planar, differentl from the previous examples, but has one or more raised areas 5A, the shape and dimension of which is dermined by the shape and dimension of the leather portions P to be processed. The raised area 5A is slightly undersized with respect to the portion P, so that this latter projects with its edge or contour PC, for the reasons described previously with reference to the embodiment of Fig.6, where there is the same difference in dimension between the portions P and the template 65.

The work surface 5 of Fig. 8 can have one or more raised portions 5A, the same shape as or differing in shape to one another, as a function of the type of leather portions P to be processed.

In some embodiments the work surface 5 of Fig. 8 can be obtained by vacuum thermoforming. A work surface 5 of planar shape is placed on a mold having a shape corresponding to the raised portions 5 A to be produced on the surface, heated and drawn into the mold, in a manner known to those skilled in the art of thermoforming. It would also be possible to produce the shaped work surface 5 in another way, for example by chip removal.

The computer 19 can be provided with processing programs that allow the operator to optimize and customize processing. In general terms, the vision system 21 A, 21B, 21C acquires one or more images of the work surface 5. The images can be combined with one another to obtain a total image of the work surface, projected correctly on a plane. This image is normally given by a light background with dark areas that correspond to the leather portions P fixed to the work surface P. The operator can use an interface, for example a touch-screen or a monitor with a mouse or other pointing device, to select one or more contour portions for each leather portion to be dyed, so that the dyeing tool 11 is then controlled in its movements to dye only the portions selected by the operator.

The various steps of an operating method that can be performed by the operator and by the program managed through the computer 19 are described below, with reference to Figs. 9A-9I.

The following list of steps defines the operations that from acquisition of the images lead to guiding of the toolhead. To sum up, the system performs the following operations: 1 acquisition of the processing area

2 extraction of the profiles of material

3 customization and artificial intelligence

4 calculation of the tool trajectories

5 execution of processing.

The five operations listed above are illustrated in greater detail below with reference to Figs. 9A-9I.

1 Acquisition of the processing area:

1.1 using the cameras 21 A, 2 IB, 21 C a suitable number of images are acquired. The number of cameras or other sensors or image acquisition systems depends on the dimension of the work surface, on the resolution of the cameras used and on the accuracy required. Each sensor frames a partial area of the surface. The areas are partly overlapped. Figs. 9A and 9B schematically show two half work surfaces, framed by two sensors, with a partial overlapped area. In this example, the portions to be dyed are only present in the second half of the half work surface (Fig.9B);

1.2 in the subsequent step, the image processing system corrects the distortion of each photo, eliminates perspective distortions and converts each image into simple orthogonal projections (plan view) of the framed surface portion;

1.3 subsequently, the framed areas are merged into a single image; this operation does not require the insertion of any noteworthy element of marking or triangulation. Fig.9C shows the results of steps 1.2 and 1.3. 2 Extraction of the material profiles:

2.1 the contours of the leather portions arranged on the work surface are extracted from the image, also taking into consideration internal contours, such as holes or the like. These edges are represented by a series of polylines, see Fig.9D. In substance, the edge or contour is approximated with curve portions, each of which is represented by an equation;

3 customization and artificial intelligence:

3.1 customization of the portions of edge to be dyed is performed through an operator interface. The customization steps will be described in greater detail below;

3.2 subsequently, these paths are reconstructed automatically on all the leather portions having the same shape as the one selected by the operator. Identical leather portions are recognized automatically by the image processing system;

3.3 customization operations can be reiterated until the operator is satisfied; calculation of the tool trajectories:

4.1 To calculate the trajectory of the tool 11 it is necessary to take account of the position and of the cross section of the tool, which has a finite dimension. An offset is thus calculated, which takes account of the position and of the section (thickness) of the dyeing tool 11. From this the trajectory of the center of mass of the tip 11D of the dyeing tool 11 is obtained. Fig.9E shows the contour of the portion P and the trajectory Tl 1 of the center of mass of the dyeing tool 11 ;

4.2 subsequently, the system automatically adds tool exit and entry portions. These are portions for tool approach and withdrawal with respect to the dyeing areas, to ensure that the toolhead 9 approaches the leather gently;

4.3 optimal paths are then calculated for movement of the toolhead 9 from the rest area to the processing area (or from an area in which processing of one leather portion ends toward an area in which processing of a subsequent portion starts) with management of obstacles: the tool 11 must not pass over the various leather portions to avoid or minimize the risk of drops of dye or ink falling from the tool 11 onto the surfaces of the leather portions positioned on the work surface 5, and which could stain the leather;

4.4 finally, the trajectories are converted into commands comprehensible to the control system (whether a dedicated CNC or simply another software component on the main computer, or a hybrid or other type of solution);

execution of processing: processing takes place through real time guiding of the toolhead 9 and of the tool 11 according to previously defined trajectories _ _ and instructions.

The following list of steps defines the operations that allow an operator to customize contour or edge portions to be dyed on each leather portion P. The steps below are a detail of the step indicated with 3.1 in the previous description. The selections are of two types: additive or subtractive. Both operate in the same way. The mode is selected using a button on the touch screen. The steps of the customization procedure can be the following:

1 the first step consists in the selection of an initial customization point. Using a touch screen this can be done, for example, through a "touch" that crosses the profile or contour of the leather to be customized. In other embodiments the pointer of a mouse or of another suitable interface can be used, for example. Fig. 9F shows by way of example the image of a contour Pc of a leather portion P and the pointer M of a mouse of other pointing device operated by the operator. Each internal/external edge is separate from the other and the operations described below can be performed on each edge or contour, both internal and external. Selection of the initial customization point starts the following processing procedure by the program managed by the computer 19: a cursor is created, which lies on the curve portion that was intersected by the passage of the pointer (i.e. a finger on the touch screen or the pointer of the mouse);

2 subsequently, the pointer M is moved approximately and freely along the trajectory of the edge or contour of the leather portion. During movement, the operator can view the result of the operation, for example by coloring of the section of contour followed by the pointer M. In Figs. 9G and 9H, PI indicates the initial point and P2 the current point in which the pointer M is located. In any case, the operator moves the pointer M along the contour C, following it with a certain degree of approximation. The program executed by the computer performs the following operations:

2.1 instant identification of the possible change of segment, i.e. passage of the pointer from one segment of the curve to an adjacent segment. The selected segment is the one closest to the position of the pointer maneuvered by the operator and in any case must be consecutive to or precede the source segment; _

2.2 constraining the cursor to lie on this segment regardless of the real position of the pointer (for example: using information on the x coordinate of the pointer, the y position is reconstructed, so that the cursor is lying on the current segment of the curve that approximates the contour of the image of the leather portion P);

2.3 iteration of points 2.1 and 2.2 until the pointer is released by the operator, allocating, instant by instant, all the changing shapes (sets of points) taken by the selection during editing;

3 after identification of the portion of contour to be dyed, the operator releases the pointer in the point in which customization ends. Fig.9I schematically shows the final result of a customization procedure in which the operator has selected the section of contour PC on the left of the figure, between points PI and P2:

3.1 the computer calculates the final selection and stores any subsequent change;

4 steps 1 to 3 can be repeated for N selections overlappable until the operator is satisfied;

5 the subsequent step consists of real time resolution of the overlaps:

5.1 each time the operator adds a new selection (points 2 to 4), the computer 19 checks if it overlaps the existing one and solves set theory problems of intersection, union and separation (Boolean algebra on open or closed curves) in order to convert the problem into simple form.

With the procedure described, it is possible to acquire images of the single leather portions on the work surface 5, extract the contours, approximate them with curves, customize processing by means of monitor and pointer, identifying portions, areas or sections of contour (both internal and external) of each leather portion to be subjected to dyeing processes. The tool 11 is then controlled to move according to paths optimized for the customized treatment of each leather portion P.

In some embodiments it is also possible to provide two or more tools 11 containing liquids of different colors and optionally to select portions or areas, sections or parts of contour of a single portions, which can be colored with different colors through the selective action of single tools. While particular embodiments of the invention have been described in the foregoing with reference to the accompanying drawings, those skilled in the art will understand that many modifications, changes, additions and omissions are possible without materially departing from the innovative teachings, from the principles and from the concepts set forth above, and from the advantages of the subject matter defined in the appended claims. Therefore, the effective scope of the innovations described must be determined only on the basis of the widest interpretation of the appended claims, so as to comprise all modifications, changes, additions and omissions. Any reference numbers in the appended claims are provided to facilitate reading of the claims with reference to the description and to the drawing, and do not limit the scope of protection represented by the claims. The term "comprising" does not exclude the presence of further elements or steps besides those listed in a claim. The term "a" preceding an element or characteristic does not exclude the presence of a plurality of these elements or characteristics. The term "means" used more than once in a claim does not exclude the possibility that two or more of these means can be implemented through a single element or component. The fact that given characteristics, elements or components are cited in separate dependent claims does not exclude the possibility of at least some of these characteristics, elements or components being used in combination with one another.

Claims

1. A machine for dyeing the edge of leather portions, comprising in combination: a work surface for the leather to be dyed; a toolhead, movable along said work surface with a numerically controlled axis system; a tool carried by said toolhead to dye the edges of the leather positioned on said work surface; a vision system to acquire images of the leather to be dyed positioned on said work surface; a computer that receives the images of the leather and processes the trajectories of the toolhead to dye the edges of said leather; wherein: said vision system is positioned over the work surface; a back-lighting system is positioned under the work surface; the work surface is at least partly transparent to the light emitted by said back-lighting system.

2. The machine according to claim 1, wherein said work surface is removable.

3. The machine according to claim 1 or 2, comprising a plurality of removable and interchangeable work surfaces.

4. The machine according to claim 1, 2 or 3, wherein said work surface comprises a ferromagnetic material distributed at least partly there along.

5. The machine according to claim 4, comprising magnetic members for blocking the leather on the work surface.

6. The machine according to one or more of the preceding claims, wherein said work surface has a flat base surface and one or more raised portions formed on said work surface, the shape of which is determined by the shape of the leather to be dyed.

7. The machine according to claim 6, wherein said work surface is made of thermoformed plastic material.

8. The machine according to one or more of the preceding claims, wherein said work surface contains a mesh made of ferromagnetic material.

9. The machine according to one or more of the preceding claims, wherein said toolhead comprises: a variable volume chamber containing a dyeing liquid; an actuator for modifying the volume of said variable volume chamber; a dispenser in fluid connection with said variable volume chamber, configured to apply dyeing liquid to the edge of leather to be dyed.

10. The machine according to claim 9, wherein said variable volume chamber comprises a cylinder and a piston sliding in said cylinder.

11. The machine according to claim 9 or 10, wherein said actuator comprises an electric motor and a slide operated by said electric motor, movement of the slide causing a variation of the volume of said variable volume chamber.

12. The machine according to claim 9, 10 or 11, wherein said dispenser is rotating about an axis of rotation, and wherein the toolhead is equipped with an actuator to control rotation of the dispenser.

13. The machine according to one or more of the preceding claims, wherein said vision system comprises a plurality of image acquisition units of the leather placed on the work surface.

14. The machine according to one or more of the preceding claims, wherein said computer is programmed to perform the following steps:

- acquisition of one or more images with one or more image acquisition units;

- if necessary merging of the images acquired into a single image;

- extraction of external contours and if necessary of internal contours of the leather positioned on the work surface.

15. The machine according to claim 14, wherein said computer is programmed to perform the following further steps:

- vectorization of the contours;

- simplification of the contours through conversion of the contours into closed curves, for example closed polylines, each constituted by a plurality of curve portions consecutive to one another.

16. The machine according to claim 14 or 15, wherein said computer e programmed to perform customizing of sections of contour to be dyed.

17. The machine according to claim 16, wherein said computer is programmed to reprocess a path of the tool as a function of the customization of the sections of contour to be dyed.

18. The machine according to at least claim 15, wherein said computer is programmed to perform a customization of sections of contours to be dyed through the following steps:

a) selection, by the operator using a pointer on a monitor, of an initial customization point on a leather contour to be customized; b) identification of the curve portion on which said initial point is located; c) visualization on said monitor of a cursor that lies on said curve portion which was intersected by the passage of the pointer;

d) while the operator moves the cursor using the pointer approximately along the contour, calculation of the equations required to constrain the cursor exactly on the contour regardless of the accuracy of movement of the operator and instant identification of the possible change of curve portion on which the cursor is located, said portion being the one closest to the position of the cursor and consecutive or precedent to the previous curve portion;

e) repetition of the step (d) until release by the operator of the pointer in a final point of the customized section of contour.

19. A method for dyeing edges or contours of portions of leather or hide, comprising the steps of:

acquiring one or more images with one or more image acquisition units; if necessary merging of the images acquired into a single image;

extracting external contours and if necessary of internal contours of the leather positioned on the work surface.

20. The method according to claim 19, comprising the steps of:

vectorization of the contours;

simplification of the contours through conversion of the contours into closed curves, for example closed polylines, each constituted by a plurality of curve portions consecutive to one another.

21. The method according to claim 19 or 20, comprising the steps of:

a) selection, by the operator using a pointer on a monitor, of an initial customization point on a leather contour to be customized;

b) identification of the curve portion on which said initial point is located;

c) visualization on said monitor of a cursor that lies on said curve portion which was intersected by the passage of the pointer;

d) while the operator moves the cursor using the pointer approximately along the contour, calculation of the equations required to constrain the cursor exactly on the contour regardless of the accuracy of movement of the operator and instant identification of the possible change of curve portion on which the cursor is located, said portion being the one closest to the position of the cursor and consecutive or precedent to the previous curve portion; e) repetition of the step (d) until release by the operator of the pointer in a final point of the customized section of contour.