Technical Field

The invention relates to an apparatus for dyeing edges of leather pieces which is used in the haberdashery-leather industry.

Background of the Invention

One of the basic technological operations in the leather-haberdashery industry is dyeing edges of leather pieces by applying a water-soluble dye on the edges, whereas the quality of the technological operation executed depends on the amount of dye deposited in layers. The objective is to achieve not only colouration of the edge, but also smoothing thereof by applying a thick layer of dye. Said working step is carried out repeatedly in order to provide a sufficiently thick layer of dye. After applying the first layer, the dye applied is usually polished using low-abrasive polishing brushes. When applying each layer of dye, the dye is left to dry-up and then, the next layer is applied. To accelerate said process of drying, driers may be used (60 to 150°C), and to achieve good quality, 3 to 5 separate applications of dye shall be made on one piece, whereby drying is performed after each dyeing step.

WO 2014/045200 Al discloses a machine for dyeing the edge of leather pieces comprising a work surface for the leather to be dyed and a toolhead, movable along the work surface with a numerically controlled axis system. The toolhead carries a tool for dyeing the edges of leather positioned on the work surface. The machine also comprises a vision system 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. 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. Said variable volume chamber comprises a cylinder and a piston sliding in said cylinder.

This known device for dyeing edges of leather pieces does not allow for collecting the residual dye which reduces the efficiency thereof. Furthermore, disassembly of the toolhead is required for cleaning said device.

RO 131550 Al discloses an apparatus for dyeing plane and convex narrow edges of wide belts and strips made of leather or other materials by applying a convex thick dye film, both on a flat and on a convex surface. The apparatus comprises a dyeing device consisting of a dyeing cylinder which is provided with some circular channels of different depth and width which takes over the supply dye or adhesive, a proximity sensor being mounted above it to detect the amount of dye or adhesive in the space above the dyeing cylinder and, in case the amount of dye is not sufficient, it seizes a compressor which starts automatically and pushes the dye from a can into the space above the dyeing cylinder; the apparatus also comprises a steel plate removing, if necessary, the excess of dye from the surface of the dyeing cylinder, said plate being adjusted by means of some screws in order to carry out thick uniform convex film on the edges of a piece without causing leaks on the lateral surfaces of the previously dyed piece.

The size of the dyeing cylinder of the apparatus disclosed in RO 131550 Al is comparatively large which reduces the ability for high-quality dyeing of sharp inner corners and curves of leather pieces. In addition, the presence of channels on the dyeing cylinder impedes washing-up of said dyeing cylinder.

An apparatus for applying dye on edges of leather pieces using a horizontally disposed rotating dye-coated shaft is known. When the dye on the shaft comes into contact with the leather piece, a part of the dye is transferred onto the piece edge. Coating the dyeing shaft with dye is conducted by means of an additional wheel, having a trapezoid cross- section /tapered to an angle of 45 degrees/ which is partly immersed in a bath with dye, whereby the lateral wall thereof rests on the dyeing shaft wall. During rotation, the additional wheel is coated in the bath with dye and the dye thus applied is then transferred onto said dyeing shaft and, therefrom, onto the edge of the leather piece. ("GALLI" S.P.A. Catalogue, 2015.)

The main disadvantages of said known apparatus are as follows: the diameter of the dyeing shaft is not less than 12 - 15 mm which leads to serious problems in two main directions:

1. The amount of dye transferred from the dyeing shaft onto the leather piece is inversely proportional to the dyeing shaft diameter at the same thickness of the dye film thereon. If there are two dyeing shafts - one of them having a diameter of 30 mm, and the other one having a diameter of 7 mm - both of which having a dye film applied with a thickness of 1 mm, the amount of dye transferred from the dyeing shaft having a diameter of 7 mm onto the piece is significantly greater. It is not possible to achieve a diameter of the dyeing shaft which is less than 12 - 15 mm in said known dyeing apparatus. This considerably reduces the amount of dye transferred onto the leather piece which increases the number of dye applications per piece. In order to achieve the required quality when using a dyeing shaft having a diameter of 30 mm, it is necessary to dye one piece 3 to 6 times, and when the dyeing shaft diameter is 7 mm, the piece requires 2 or not more than 3 applications of dye. This is due to the significantly lower force of dye holding /adhesion/ to the dyeing shaft since the area of the shaft itself is smaller at the same thickness of the dye film on the shaft.

2. From the process point of view, it is more difficult to dye pieces with acute inner angles using a larger shaft due to the greater radius and the impossibility to reach the inner areas of the sharp corner.

In addition to the above disadvantages, said apparatus has a complex mechanical structure for actuating the coating shaft and the actuating wheel. There are also considerable difficulties in washing the apparatuses from the dye, due to the large dimensions of the shafts and the baths with dye.

Disclosure of the Invention

An object of the invention is to provide an apparatus for dyeing edges of leather pieces which ensures transferring of a larger amount of dye onto the leather piece per one application thus reducing the number of applications and, as a result of this, significant reduction in the duration of the whole process step is achieved.

Another object of the invention is to simplify the dyeing shaft actuating structure. An apparatus for dyeing edges of leather pieces according to the present invention comprising a vertically arranged dyeing head having a dyeing shaft connected to a motor through a coupling, and a controller. The dyeing head comprises said dyeing shaft and an eccentric pump, having a common rotation axis and connected to each other by means of a channel-and-tube system for supplying dye to said dyeing shaft by said eccentric pump. The dyeing shaft is provided with a plate for controlling the thickness of the dye film on said dyeing shaft and said plate is arranged perpendicularly to the rotation axis and tangentially to the lateral surface of the dyeing shaft. Said eccentric pump includes an eccentric cylinder closed at the top by the bottom of a dye tank, wherein an opening for supplying dye to the eccentric pump is formed. A pin mechanism and a process plug are mounted on the lateral side of said eccentric cylinder and said pin mechanism consists of a sleeve closed at its one end, said sleeve accommodating a spring and a spring-loaded pin; and said process plug comprises an opening connected to a channel-and-tube system inlet for supplying dye to the dyeing shaft.

Advantageously, the dyeing shaft of the apparatus has a diameter of 6 mm to 8 mm. Preferably, said plate for controlling the thickness of a dye film on the dyeing shaft is provided with a screw for adjusting the plate position.

In one preferred embodiment, the lower part of the dyeing head is encompassed by a housing, wherein a shaft is incorporated in the bottom part and said shaft is provided with a radial bearing sleeve for dyeing shaft bearing.

In advantageous embodiments, said coupling connecting the- dyeing head to said motor is a magnetic coupling comprising magnets for the dyeing shaft being arranged radially and incorporated into a holder which is attached to the dyeing shaft axis, and magnets for the motor also being arranged radially and incorporated into a second holder which is attached to the motor axis, whereby both holders have an equal number of magnets arranged one above the other. There is a panel of a nonmagnetic material between both holders on which the dyeing head is positioned so that both holders are positioned one above the other.

Preferably, said second holder with the magnets, said motor provided with a motor driver, an electrical power supply source, and said controller are accommodated in a box and said panel of a nonmagnetic material closing the top of the box.

In other preferred embodiment the lower part of the dyeing head, the coupling and the motor are encompassed in a vertically arranged tube which tube, in the lower end thereof, is fixedly attached to a base accommodating the motor driver and the controller.

Preferably, the motor for actuating said dyeing shaft is a step motor or a DC motor. Said controller is connected to a power supply source and to said motor driver.

In one preferred embodiment of the invention, the controller is a single-board microprocessor system.

The advantages of the apparatus for dyeing edges of leather pieces according to the invention are as follows: The dyeing shaft diameter is significantly smaller which ensures the transfer of a greater amount of dye onto the leather piece per one application and, as a result of this, the number of applications of dye onto the piece reduces which leads to significant reduction of the duration of the whole process step. On the other hand a dyeing shaft with a smaller diameter ensures easier and high-quality dyeing of pieces having acute inner angles since such type of a shaft is able to reach the inner areas of the acute angle. Both basic parts of the apparatus - the electrical part with the motor and the dyeing head - are completely separated to provide for unhindered washing of the dyeing head at each change of the dye colour, without disassembling the dyeing head members. The magnetic coupling allows for sealing the apparatus electrical part, including the motor and the controller, whereby increasing many times the apparatus reliability. Furthermore, the dyeing shaft actuating structure is simplified.

Brief Description of Drawings

Figure 1 is a schematic diagram of an embodiment of a dyeing apparatus according to the invention;

Figure 2a is a schematic representation of a dyeing shaft illustrating the principle of formation of a dye film onto the dyeing shaft;

Figure 2b is a schematic representation of the dyeing shaft illustrating the principle of dye transferring from the dyeing shaft onto a piece to be dyed;

Figure 3 is a longitudinal section of the dyeing apparatus according to the invention;

Figure 4 is a transverse section along the A-A line of Figure 3 which passes through the eccentric pump;

Figure 5 a is a longitudinal section of the dyeing apparatus illustrating a schematic representation of the magnetic coupling;

Figure 5b is a transverse section of the magnetic coupling passing through the magnet plane;

Figure 6 is a front view with a partial vertical section of the apparatus for dyeing edges of leather pieces;

Figure 7 is a front view with a partial longitudinal section of another possible embodiment of the apparatus for dyeing edges of leather pieces according to the invention, whereby the lower part of the dyeing head, the magnetic coupling and the motor are encompassed by a vertically arranged tube;

Figure 8 is a perspective side view of the apparatus shown in Figure 7 with a partial longitudinal section.

Modes for Carrying Out the Invention

Referring to Figure 1, a schematic diagram of an apparatus for dyeing edges of leather pieces is shown, said apparatus includes a vertically arranged dyeing head 1 having a dyeing shaft 4 connected to a step motor 2 by means of a magnetic coupling 3. According to Figure 1, Figure 3 and Figure 4, the dyeing head 1 comprises: said dyeing shaft 4 and an underlying eccentric pump 5 which have a common rotation axis 6 and are connected to each other by means of a channel-and-tube system 7 for supplying dye to said dyeing shaft 4 by said eccentric pump 5.

Referring to Figure 2a and Figure 2b, a diagram for dye applying from the dyeing shaft 4 onto the edge of a leather piece 10 is presented. The dyeing shaft 4 is equipped with the following: a channel 11 of the channel-and-tube system 7 for supplying dye to said dyeing shaft 4; a plate 12 for adjusting the thickness of the dye film on the dyeing shaft 4 and said plate 12 is arranged perpendicularly to the rotation axis 6 and tangentially to the lateral surface of the dyeing shaft 4; said plate 12 is provided with a screw 15 for adjusting the position of the plate 12; and a canal 13 for removing the excess of dye from the surface of the dyeing shaft 4. Said channel 11 and said plate 12 are attached to a bearing plate 14.

The dyeing shaft 4 of the dyeing head 1 has a diameter of 6 mm to 8 mm.

Referring to Figure 3 and Figure 4, there is shown the eccentric pump 5 which includes an eccentric cylinder 17 with an eccentrically arranged rotation axis 6, common for the dyeing shaft 4 and the eccentric pump 5. The top of the eccentric cylinder 17 is closed by the bottom of the dye tank 8 wherein an opening 18 for supplying dye to the eccentric pump 5 is formed. A pin mechanism 19 is mounted on the lateral side of said eccentric cylinder 17 which pin mechanism 19 consists of a sleeve 20 closed at its one end,^ said sleeve accommodating a spring 21 and a spring-loaded pin 22. Also, process plug 23 is mounted in the lateral wall of the eccentric cylinder 17 which comprises an opening 24 connected to the channel-and-tube system 7 inlet for supplying dye to the dyeing shaft 4.

The lower part of the dyeing head 4 is encompassed in a housing 25, wherein a shaft 27 is incorporated in the bottom part thereof having a radial bearing sleeve 26 for dyeing shaft bearing and said housing 25 is provided with a foot 28.

The channel-and-tube system 7 for supplying dye from the dye tank 8 to said dyeing shaft 4 comprises consecutively connected tubes 29, 30, 31 and the channel 11 ending with a nozzle (not shown) (Figure 1 and Figure 3).

Referring to Figure 1, Figure 5a and Figure 5b, there is shown the magnetic coupling 3 connecting the dyeing shaft 4 to the step motor 2. The magnetic coupling 3 consists of four pieces of magnets 35 for the dyeing shaft arranged radially and incorporated in a holder 37, being attached to the dyeing shaft axis 6, and four pieces of magnets 36 for the step motor 2 arranged radially and incorporated in a second holder 38, being attached to the motor axis. W 201

There is a panel 39 of a nonmagnetic material between both holders 37 and 38 (Figure 1). The dyeing head 1 is positioned on the panel 39 of a nonmagnetic material so that the magnet holder 37 of the dyeing shaft 1 is arranged coaxially above the second holder 38 of the step motor 2.

In other embodiments, the magnets in each of the holders may be minimum two pieces in each holder, and the maximum number depends on the size of the magnetic coupling (the magnets may be 3, 4, 5, etc. in each holder). Both holders have an equal number of magnets arranged one above the other.

Referring to Figure 6, the panel 39 of a nonmagnetic material closes the top of a box 40, accommodating said second holder 38 with said magnets 36, said step motor 2, a motor driver 41 for controlling of said step motor 2, an electrical power supply source 42 and a controller 43 for controlling the apparatus, being connected to the power supply source 42 and to the motor driver 41, as shown in Figure 1. The controller 43 is a single-board microprocessor system for controlling the operation of the whole apparatus. In other embodiments, said controller may be a microprocessor system of another known type.

Figure 7 and Figure 8 show another embodiment of the apparatus for dyeing edges of leather pieces according to the invention. The members of the dyeing head 1, the magnetic coupling 3 and the motor 2 are the same as in Figures 1-5, except for the following: the lower part of the dyeing head 1, the coupling 3 and the motor 2 are encompassed in a vertically arranged tube 44 which, in the lower end thereof, is fixedly attached to a base 45 accommodating the power supply source 42, the driver 41 and the controller 43.

The principle of operation of the apparatus for dyeing edges of leather pieces according to the invention is as follows:

The dyeing shaft 4 is actuated by the step motor 2 controlled by the controller 43. Other types of electrical motors with controlled revolutions also may be used for actuating the dyeing shaft 4. The motion from the step motor 2 to the dyeing shaft 4 is transmitted by the magnetic coupling 3, as shown in Figure 1, Figure 5a and Figure 5b. The magnets in both holders 37 and 38 are oriented so as to attract mutually (Figure 5a). When rotating, the step motor 2 rotates also the holder 38 with the four magnets 36 of the step motor 2. As a result of the attraction between magnets 35 and 36 of both holders, the holder 38 of the dyeing shaft 4 also rotates in the same direction and with the same speed. Thus, the motion is transmitted from the step motor 2 to the dyeing shaft 4 in a completely contact-free way.

The distance between both holders 37 and 38 is determined based on the thickness of the panel 39 of the nonmagnetic material, the thickness of the dye tank bottom and the air gaps required for the free rotation of both holders. This distance may not be greater than 5 mm so as to ensure transmission of sufficient torque. If the distance is greater, the attraction force decreases and the torque transmitted between both holders decreases dramatically.

Principle of operation of the eccentric pump 5. When the dyeing shaft 4 rotates about the rotation axis 6, the eccentric cylinder 17 rotates as well. Due to the eccentrically arranged rotation axis 6, the eccentric cylinder 17 begins to rotate so that point "A" (Figure 4) on the lateral wall of the eccentric cylinder 17 moves along the inner wall of the dye tank 8 in the direction specified by an arrow in Figure 4. The dye enters in the eccentric pump 5 through the supply opening 18. When moving, the eccentric cylinder 17 closes the supply opening 18 and the dye having entered the pump 5 is pushed from the eccentrically moving cylinder 17 towards the pin mechanism 19. The spring-loaded pin 22 of the pin mechanism 19 follows the outline of the eccentric cylinder 17 closing the volume enclosed between point A of the eccentric cylinder 17 and touch point of the spring-loaded pin 22 with the eccentric cylinder 17 in a certain moment, and does not allow the dye to pass behind the spring-loaded pin 22. Thus, the pressure within said volume between point "A" of the eccentric cylinder 17 and the spring-loaded pin 22 of the pin mechanism 11 increases. The pressure generated pushes the dye through the channel-and-tube system 7 inlet to the dyeing shaft 4. The actions described are executed repeatedly.

Referring to Figures 2a and 2b, the principle of forming the dye film 9 with, the required thickness on the coating shaft 4 is shown. The fresh dye enters in the channel 11 of the channel-and-tube system 7 and after flowing out from the channel 11, the dye adheres to the dyeing shaft 4 which rotates in the direction shown in Figure 2a and Figure 2b. The dye is entrained by the dyeing shaft 4 and, through the adjustment plate 12, forms a film 9 of dye onto said dyeing shaft 4, while the excess of dye is removed and, through the canal 13 for removing the excess of dye, is discharged towards the dye tank 8. The film thickness on the dyeing shaft 4 is determined based on the distance between the dyeing shaft 4 and the plate 12, whereas this distance is adjusted by the adjustment screw 15. When screwing up the adjustment screw 15, the distance between the adjustment plate 12 and the dyeing shaft 4 increases, whereby the dye film 9 on the dyeing shaft 4 increases.

When the dye film 9 with the required thickness is formed on the dyeing shaft 4, the leather piece 10 approaches the dyeing shaft 4, moving in the direction specified by an arrow in Figure 2b. When the leather piece 10 touches the dye film on the dyeing shaft 4, as a result of the adhesion /adhesion force/, the dye is transferred from the dyeing shaft 4 onto the leather piece 10. The adhesion of the dye to the piece 10 shall be greater than the adhesion to the dyeing shaft 4 so that the dye may be transferred from the dyeing shaft 4 onto the leather piece 10. Since the adhesion force of the dye depends also on the area to which it adheres - the smaller the area of the dyeing shaft 4 /its diameter, respectively/, the smaller the adhesion force thereto and, therefore, the ability of the shaft to hold the dye on itself.

As seen from the disclosure, the smaller the diameter of the dyeing shaft, the easier the dye will be transferred onto the piece. The dyeing shaft 4 of the apparatus according to the invention has a diameter of 6 mm to 8 mm /the diameters of the existing apparatuses are as twice as big/.