Classifications

• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14B—MECHANICAL TREATMENT OR PROCESSING OF SKINS, HIDES OR LEATHER IN GENERAL; PELT-SHEARING MACHINES; INTESTINE-SPLITTING MACHINES
  • C14B1/00—Manufacture of leather; Machines or devices therefor
  • C14B1/26—Leather tensioning or stretching frames; Stretching-machines; Setting-out boards; Pasting boards
• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14B—MECHANICAL TREATMENT OR PROCESSING OF SKINS, HIDES OR LEATHER IN GENERAL; PELT-SHEARING MACHINES; INTESTINE-SPLITTING MACHINES
  • C14B1/00—Manufacture of leather; Machines or devices therefor
  • C14B1/58—Drying

Definitions

• the invention relates to a method for fastening hides to drying frames through magnetic attraction and a magnetic system adapted to realize such method.
• One of the essential treatments to which the hides must be subjected after the tanning treatments in order to be workable is drying.
• This treatment is necessary in order to remove the water that the hides have absorbed during the wet working processes and is usually performed using dryers, i.e. apparatus where the wet hides, in contact with heated and dry air, lose the water that they contain and are therefore dried.
• a known drying method envisages spreading the hides to be dried onto perforated frames that are made to transit along a drying tunnel in which the circulation of hot air is maintained.
• the hides are kept spread out firmly constraining their edges to the drying frames.
• the operation through which the edges of the hides are constrained to the drying frame is commonly called“fastening” and it envisages the use of relevant grippers, each of which is provided with a pair of jaws opposing each other that are arranged gripping onto the edge of the hide to be spread out.
• Each gripper is also provided with a projecting pin which is inserted into a hole in the drying frame so that using a plurality of grippers in a variable number as a function of the surface area of the hide to be dried, it is fixed to the frame well stretched out and taut.
• the weakening of the hide is a defect that consists of the localized detachment of the upper part of the hide, called the grain, from the part below.
• This trimming operation implies a reduction in the saleable surface area of hide and therefore wasted material that implies an economic loss for the tanner.
• the magnetic elements are generally disc- or U-shaped with a flat support surface on the hide to be spread out, which is blocked due to the force generated by the magnetic attraction between each element and the underlying frame which comprises a continuous laminar element made of ferromagnetic material.
• the mutual magnetic attraction generated between the magnetic element and the frame generates a friction force between the hide and the frame such as to oppose the sliding of the hide.
• Such friction force depends on the characteristics of the hide and the frame on which it is spread and for a same type of hide and frame it is greater the greater the magnetic force exerted between the magnetic element and the frame.
• the fastening method by means of magnetic elements with a flat surface now described has the advantage of realizing fastening which with respect to fastening with grippers allows the hide to gently slide hence preventing the weakening thereof along the edge.
• a first recognised drawback consists of the fact that, in order to be able to guarantee the grip of the edge of the hide to the frame, the magnetic elements must have a much larger support surface so that the magnetic force that is developed between the magnetic element and the surface of the frame is such as to generate between the hide and the frame a large enough friction force to prevent the sliding of the hide during drying.
• Another drawback consists of the fact that the combination of a large support surface and high magnetic force causes significant permanent deformations of the hide in the areas where the magnetic elements are arranged.
• the present invention intends to overcome the drawbacks described by realizing a method for fastening hides to be dried to drying frames that sets out to significantly reduce the problem of weakening the hide during drying.
• the aims are also reached by a magnetic system for fastening hides, as described in claim 7.
• the use of the method of the invention limits the weakening of the hide during drying and reduces the formation of anti-aesthetic deformations on the edges of the hide.
• this also reduces the economic losses caused by the need to trim the hide.
• FIG. 1 shows an axonometric view of the magnetic system for fastening hides to be dried according to the invention
• Figure 2 represents a detail of Figure 1 ;
• Figure 3 shows an axonometric view of a detail of Figure 2;
• FIG. 4 shows the side view of the section of Figure 2 taken according to the line of trace IV-IV;
• FIG. 5 to 8 each represent in order a sectioned view of an operating step of the method of the invention
• FIG. 9 to 12 show plan and sectional views of different embodiments of holes made in the drying frame.
• the magnetic system for fastening hides onto frames according to the invention is represented in Figure 1 where it is indicated overall by number 1.
• the magnetic system 1 comprises a frame 10 made of ferromagnetic material and a plurality of magnetic bodies 20.
• the frame 10 comprises two panels 11 , 12 made of ferromagnetic material, on which the hide P is spread out and appropriately tensioned through a plurality of magnetic bodies 20 that are arranged in various points along the perimeter edge of the hide P and are constrained to the panels 11 , 12 by magnetic attraction, as will be described in more detail below.
• the panels 11 , 12 are coplanar to each other and are adjacent at a central edge 13.
• the panels 11 , 12 are then spaced out at the central edge 13 through a mutual coplanar movement to both so that the hide P, after being constrained along the perimeter edge by the magnetic bodies 20, is kept stretched out during drying.
• the frame can comprise more than two panels.
• the frame 10 is made of ferromagnetic material and is provided with a plurality of through holes 14.
• Each magnetic body 20 is housed in a corresponding through hole 14 and constrains an area of the hide P to the frame 10 by the force generated by the magnetic attraction between each magnetic body 20 and the perimeter edge 14a of the corresponding through hole 14 in which it is housed.
• the magnetic body 20 is comprised of a sphere that cooperates with the perimeter edge 14a of the through hole 14 in which it is housed, as can be observed for example in Figure 4.
• the magnetic body 20 may also have a partially curved surface or may also be delimited by a polygonal surface and thus assume the shape of a prism.
• the panels 11 , 12 that are used to make the frame 10 are comprised of commercial perforated sheets in which the holes 14 are obtained by shearing and have a circular profile, as can be observed in particular in Figures 3 and 4.
• Each magnetic body 20 constrains the hide P to the frame 10 by the friction that tends to prevent the hide P sliding on the frame 10 and that is generated between the hide P and the perimeter edge 14a of the through hole 14 because of the mutual magnetic attraction between the magnetic body 20 and the frame 10.
• the hide P is withheld by the friction that tends to contrast the sliding thereof and is generated by the magnetic attraction between the magnetic body 20 and the perimeter edge 14a of the hole 14, in addition to the mechanical contrast of the hide P against the aforesaid perimeter edge 14a of the hole 14.
• the diameter of the sphere that constitutes the magnetic body 20 and the diameter of the hole 14 shall be selected appropriately to ensure the best synergistic effect between friction and the mechanical contrast described.
• Such synergistic effect implies that the magnetic bodies 20 of the spherical type and corresponding holes 14 that house them, also of a small diameter, can exert a constraining effect on the hide P equal to the one exerted by known magnetic disc elements having much larger diameters.
• the magnetic body 20 is configured to be partially housed in the corresponding through hole 14 so as to be partially projecting from at least one surface of the frame 10, as can be seen in Figure 4.
• Such projection is particularly advantageous for the removal of the magnetic system 1 at the end of the hide P drying treatments as the projecting part of the magnetic bodies 20 offers the operator a gripping area that facilitates the detachment thereof from the frame 10.
• the object of the invention is also a method for fastening hides to be dried onto frames through magnetic attraction.
• the method of the invention that uses the magnetic system 1 comprises the operating steps shown by way of example in Figures 5 to 8.
• the method of the invention operatively provides for arranging the frame 10 made of ferromagnetic material that can be observed in Figure 5 to define a support plane of the hide P to be dried that is spread onto the frame 10, as shown in Figure 6.
• the hide P can be spread onto the frame 10 manually by the operators or semi-automatically, for example by robots or other devices.
• the hide P After being spread out, the hide P is constrained to the frame 10 by means of a plurality of magnetic bodies 20, as shown in Figures 7 and 8, which are arranged along the perimeter edge of the hide P as can be observed in Figure 1 .
• the frame 10 is provided with a plurality of through holes 14 of a circular shape so that each magnetic body 20 is housed in a corresponding through hole 14 and constrains the hide P to the frame 10 by the force generated by the magnetic attraction between each magnetic body 20 and the perimeter edge 14a of the corresponding through hole 14.
• the magnetic body 20, as previously indicated, is preferably comprised of a sphere and the through hole 14 has a circular shape and truncated cone profile and these geometric configurations of the magnetic body 20 and of the through hole 14 allow a very strong constraining force of the hide P to the frame 10 to be realized.
• the operation of arranging the magnetic bodies 20 along the edge of the hide P is facilitated by their spherical configuration as, when the magnetic bodies 20 are arranged on the hide P, each of them is spontaneously“recalled” by the perimeter edge 14a of the most proximal hole 14 and is housed therein.
• each magnetic body 20 is partially housed in the corresponding through hole 14 and therefore partially projects from at least one surface of the frame 10.
• the area of the magnetic body 20 projecting from the frame 10 can easily act as a reference for gripping by robotized means of various kinds and types, possibly provided with magnetic or magnetizable means and possibly controlled by a processor for the automatic application/ detachment of the magnetic bodies 20 to/from the frame 10.
• each hole may also be realized according to the variants represented in Figures 9 to 12 in each of which each hole is represented with a plan view which highlights the shape thereof and with a sectional view which highlights the profile thereof.
• Figure 9 One variant embodiment is represented in Figure 9 in which the hole 24 has a circular shape and a truncated cone profile.
• the use of the magnetic system of the invention by reducing and limiting the formation of anti-aesthetic deformations of the hide with respect to the prior art, reduces the need to have to trim the perimeter edge of the hide and therefore reduces processing waste.
• the fastening method of the invention allows the fastening elements to be quickly removed thus reducing working times.

Landscapes

• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Treatment And Processing Of Natural Fur Or Leather (AREA)
• Drying Of Solid Materials (AREA)
• Portable Nailing Machines And Staplers (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
• Magnetic Treatment Devices (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=63579667

Family Applications (1)

Country Status (5)

Cited By (1)

Citations (4)

Family Cites Families (10)

• 2018
  • 2018-06-18 IT IT102018000006393A patent/IT201800006393A1/it unknown
• 2019
  • 2019-05-30 KR KR1020207033063A patent/KR102484561B1/ko active IP Right Grant
  • 2019-05-30 WO PCT/IB2019/054485 patent/WO2019243925A1/en unknown
  • 2019-05-30 EP EP19734900.4A patent/EP3790998B1/en active Active
  • 2019-05-30 CN CN201980040929.8A patent/CN112292465B/zh active Active

Patent Citations (4)

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