MACHINE FOR CUTTING BOARDS, NATURAL LEATHER, RECLAIMED LEATHER, SYNTHETIC AND PLASTIC MATERIALS, FOR PRODUCING SEMI-FINISHED PRODUCTS FOR FOOTWEAR AND THE LIKE

The invention relates to a mechanism (hereinafter referred to as head) and to a machine suitable for the use of said mechanism, to be utilized to cut boards, fiberboards, cellulosic compounds in sheets, natural leather and reclaimed leather, synthetic materials up to a thickness of 10 mm, used above all in the footwear industry to produce soles and heels.

Said mechanism may advantageously be utilized in a numerically controlled machine with three or more axes, destined above all for the footwear market to replace traditional die cutting machines (turning arm and beam), that is, blow presses that utilize dies to cut the aforesaid materials.

The object of the invention is to overcome the drawbacks of current die cutters, including:

• ➢ lengthy delivery times by suppliers of dies;
• ➢ the cost of the dies;
• ➢ the need to produce dies even for small productions or even for individual samples;
• ➢ the difficulty in finding personnel willing to work at the aforesaid die cutting machines.

In addition to the die cutting machines, punching machines (with punches with diameters of 2-2.2 mm) and oscillating blade cutting machines are known, which partly fulfill analogous tasks, but with considerable limitations. Cutting with the punch (the alternate movement of which is produced mechanically) has a low cutting frequency (around 2800 strokes per minute), a short working stroke (max 3 mm) and creates a "knurled" profile which must subsequently be finished; moreover, use of the punch necessarily also requires the use of a corresponding die. As well as creating difficulties in cutting relatively "soft" materials, this also requires continuous movement of the material being processed, with consequent imprecisions in producing the profile. The cut with an oscillating blade (the alternate movement of which is produced pneumatically) has a higher cutting frequency (around 4500 strokes per minute), a shorter working stroke (1-2 mm) and exploits the "saw" effect, with the considerable limitation that in curved profiles a polygonal one is obtained.

There are also other machines that perform cuts with alternate motion mechanisms, produced with different kinematic systems and with tools with different geometries and inferior performances.

A machine having the features as set forth in the preamble of claim 1 is known from US-A-6 131 498.

The object of the invention is a machine and a head to mechanically produce an alternate movement that reaches a high frequency and a working stroke of up to 10 mm. The structure is dimensioned to perfectly cut solid materials such as fiber board and to solve the aforesaid problems, making it possible to produce samples collections immediately and inexpensively without specialized personnel.

The machine in question characteristically comprises:

• a head to control the tool with alternate axial movements at extremely high frequency and with progressive angular positioning to follow the contour of the pieces to be cut;
• means to control movements of the head with respect to the plane of the material to be cut; and
• means to control insertion of the material into the machine and removal of said material from the machine with the cut pieces still held in the material, to be separated subsequently.

To control the tool with alternate axial movements at extremely high frequency and with progressive angular positioning to follow the contour of the pieces to be cut - a head is provided including an element angularly movable about a vertical axis upon programmed control as a function of the profile of the pieces to be cut; in an axial seat of said element a spindle with a tool-holder clamp, coupled rotatingly to said element and sliding axially in said axial seat; a bell-shaped member mounted on top of said spindle and with essentially punctiform axial contact with said spindle; and eccentric means designed to control alternate axial movements at extremely high frequency to said spindle and therefore to the tool.

Said eccentric means comprise: in said bell-shaped member a transverse sliding seat with respect to said axis; and in said transverse sliding seat a slider in turn forming a seat for an eccentric operated in rotation at the aforesaid frequency by a suitably balanced shaft.

Said element will be controlled angularly according to a program to impose on the tool a specific angular rake with respect to the area of the shaped profile in which the tool is instantaneously located during cutting of a piece.

Said axial contact between said bell-shaped member and said spindle may advantageously be produced with a ball, which is interposed axially between facing surfaces of the bell and of the spindle.

An elastic system - for example Belleville washers - may be provided to stress the bell-shaped member in order to cancel clearances between the bell-shaped member and said slider connected to the eccentric.

The invention will now be better understood by following the description and accompanying drawing, which shows a non-limiting practical example of the finding. In the drawing:

• Figures 1, 2 and 3 show the machine as a whole in the front, side and top views;
• Figures 4 and 5 show sections according to IV-IV in Figure 5 and V-V in Figure 4 of the head, enlarged with respect to Figures 1 to 3;
• Figures 6, 7 and 8 show detailed views of said head in the sections according to VI-VI in Figure 7, VII-VII in Figure 6 and VIII-VIII in Figure 7;
• Figure 9 shows an exploded perspective view of some components of the mechanism generating alternate motion at extremely high frequency of the tool;
• Figures 10 to 15 separately show a tool usable in the machine according to the previous figures, in the views and sections according to X-X, XI-XI, XII-XII, XIII-XIII, XIV-XIV and XV-XV;
• Figures 16 and 17 show the operating mode of the tool in Figures 10 to 15; and
• Figures 18 to 21 separately show another tool, in different views and sections.

The machine comprises a base 1, preferably made of electrically welded steel, on which a portal 3 slides by means of rails and recirculating ball bearing blocks 2; the motion of the portal 3 may be actuated by means of a recirculating ball screw 4 actuated - via a toothed belt drive 5 - by a brushless motor 6 or the like.

A carriage 8 controlled by a recirculating ball screw 9, operated via a toothed belt 10 by a brushless motor 11, slides on the portal 3 with the recirculating ball bearing rails. The carriage 8 is equipped with a pneumatic piston-cylinder system 12, which is responsible for vertical movement of a head, indicated generically with 13. The head 13 carries the control mechanism of a tool; with the head in the raised position quick replacement of the tool is possible. In Figure 2 the carriage 8 is shown twice in two different positions A, B that it can assume.

The layout to move the portal 3 and the carriage 8 in two orthogonal directions enables the head 13 and the tool to reach every point of a work surface.

The material to be worked - whether in slabs, sheets, rolls or lengths approximately with more or less regular dimensions - is moved by means of two pairs of rollers 14, 15, positioned transversely to the work table at the beginning and at the end thereof, that is at the inlet and outlet of the material. Each of the two pairs of rollers 14, 15 is formed by a roller with fixed axis 14 and a movable roller 15, the latter operated by a pneumatic cylinder 16 acting on a crossbeam 17 connected rigidly at the ends of said roller. The movement of the rollers 14 is obtained via pulleys 18, mule pulleys 19 and a single toothed belt 20 by a brushless motor and relative reduction gear.

The material to be cut, loaded either manually or automatically, is fed by the first pair of rollers 14, 15 at the inlet acting according to the arrow 21 to a stop position and held here until the part thereof affected by the movement of the active members of the machine has been completely cut into the required pieces. Subsequently, said first pair of rollers at the inlet will drive the material under the second pair of rollers, which will exert a pressure on said material contributing toward clamping and transporting it in the direction of the outlet according to the arrow 22.

The head 13 will perform the cut on the pieces on the part on which said head can operate, within the working range of the machine coming between the two pairs of rollers 14, 15. At the end of the slab, sheet or roll, the last part will be clamped only by the second pair of rollers 14, 15, which will operate at the outlet according to the arrow 22 to deliver the final part of the material. Simultaneously, other material may be loaded to perform a further work cycle. The cut pieces are unloaded by being dropped or ejected at the outlet of the machine.

Movements of the various kinematic systems, including those of the head 13 and of the tool are managed simultaneously by a numeric control operating with suitable software.

The machine may have various dimensions, also as working strokes and therefore as general overall dimensions. Several cutting heads may also be mounted in order to obtain higher levels of production.

The head 13 - carried by the carriage 8 is movable to reach all points of the work surface positioned between the two pairs of rollers 14, 15 - is better shown in the enlargements in Figures 4, 5, in the enlarged details in Figures 6, 7, 8 and in the perspective view in Figure 9.

The principal requirement of the cutting head is the extremely high frequency alternate movement to which the tool must be set and an angular movability of said tool to remain tangent at all times, that is osculatory with respect to the profile of the cut to be made, during the relative cutting motion between the head and the material to be cut positioned between the aforesaid pairs of rollers 14, 15.

The alternate movement is actuated starting from a rotating shaft 23, which carries an eccentric 23A, which transmits vertical alternate motion to a bell 24 via a cylindrical slider 25. The eccentric 23A is received in the transverse seat 25A of the slider 25 via a roller cage; the slider 25 is constrained to translate coaxially with the bell 24 via sliding and/or rolling bearings 25B; the upper transverse tubular part 24A of the bell 24 has slots 24B to enable the shaft 23 and the eccentric 23A to pass through. In this way motion is split by producing a cylindrical joint, composed of the shaft 23 with eccentric 23A and by the slider 25, and of a prismatic joint instead composed of the slider 25 and the bell 24. In this way rotation of the shaft 23 causes movement of the slider 25 with horizontal motion and of the bell 24 with vertical motion. Connected to the bell 24 is the vertical tool-holder element, susceptible to alternate vertical movement, transmitted by a spindle 26 to the tool 101 clamped on the tool-holder 28. The impact between the tool 101 and the material M to be cut - which takes place with each cycle of vertical motion of the tool-holder element - is absorbed by a ball 29 in hardened steel, which is housed between two seats 30, also in steel and shaped appropriately. The ball 29, by virtue of its geometrical form and of the type of contact produced with the seats 30, withstands the impacts optimally as, in the state of uniaxial and coaxial compression to which it is subjected, it reacts with a triaxial state of compression; this type of reaction makes the ball less deformable and more suitable to withstand impacts. The bottom of the lower seat 30 is shaped to rest on the head of the spindle 26, in conditions that enable easy relative rotation between the two surfaces almost in punctiform contact.

The tool 101, with the tool-holder 28 and with the spindle 26, 26A must be able to rotate. The rotatory motion of the tool is obtained by a toothed pulley 31 fixed to a rotation bushing 32 which is mounted on bearings 33 and inside which the spindle 26 of the tool-holder slides via sliding and/or rolling bearings. The head 26A of the tool-holder spindle 26 is constrained to the bell 24 by means of a flange 34 fixed under the lower part 24C of the bell 24; said head 26A can rotate (Figures 6, 7) thanks to the presence of sliding and/or rolling bearings 35, interposed between the head 26A, the bell 24, 24C and the flange 34. The spindle 26 slides vertically in the rotation bushing 32 via sliding and/or rolling bearings; the rotation motion to the spindle 26 is transmitted via a spider 36 cooperating with longitudinal grooves located in the seat formed in the upper part of the bushing 32.

The eccentric shaft 23 is supported by ball bearings 37 and takes its motion via pulleys 38A, 38B from a variable speed electric motor 39 (asynchronous with frequency converter and/or brushless). In order to decrease the stresses on the two supporting bearings 37 and decrease the vibrations of the cutting head assembly, two suitably dimensioned counterweights 40 are mounted on the shaft 23.

The rotation bushing 32 - which transmits motion to the tool-holder spindle 26 and which is supported by the ball bearings 33 - via the pulley 31 integral with it is moved by an electric motor 42 (stepping and/or brushless motor).

The tool-holder 28, which houses the tool 101 screw fixed with pressure screw 27A, is fixed at the end of the tool-holder spindle 26. The cutting edge of the tool will be shaped and positioned so that it is exactly coaxial with the tool-holder spindle 26 and so that it guarantees tangency to the profile and prevents harmful bending.

The head assembly is contained in two half casings 45 to allow oil mist lubrication and cooling through appropriate passages, and also to restrict noise within the limits established by the provisions of law.

The tool-holder 28 can receive tools of various shapes and can be replaceable to receive various types of tools.

One applicable tool is the one labeled 101 shown in Figures 10 to 15, produced in a suitable material even formed by sintering, with or without a wear-resistant coating. Said tool has a cylindrical body, with conical support for secure fixing, and characteristically the cutting edge of said tool is an arc of circumference, shaped with appropriate rake angles; said tool is subject to a simultaneous patent right. The diameter of the cylindrical body, the radius of the cutting edge, the length thereof and the material may vary according to the material to be cut. Another applicable tool may be the one shown in Figures 18 to 21.

The tool shown in Figures 10 to 15, indicated generically with 101, has a cylindrical body 103 with lateral milling 105 for fixing to the tool-holder; characteristically, it is provided with a partial extension 107, the outer wall thereof having a cylindrical surface as an extension of the surface of the body 103, a scored concave and inclined inner wall 109, to define a cutting edge 111, and elongated triangular lateral faces 113, with clean edges. The cutting edge 111 extends in an arc of circumference lying in the cylindrical surface 107. The tool 101 is housed in the tool-holder 28 inside a misaligned seat, so that the axis of the spindle 26, which is the axis of oscillation of the angular motion imposed on the tool-holder 28, lies on the cylindrical surface of the outer wall 107 of the tool 101.

The two ends of the cutting edge 111 may be limitedly rounded off to connect at the edges with said converging ends.

From the description it is apparent that the angular movement imposed on the spindle 26 determines an angular shift of the cutting edge 111 about the axis of said spindle 26; the cutting edge 111 is moved in the direction of the axis of the spindle 26 with extremely high frequency alternate motion.

The head 13, is moved by the kinematic system with two orthogonal axes and with a program that makes the axis of the spindle 26 follow a trajectory corresponding exactly to the shape of the piece to be obtained by progressive cutting of the material M; in other words, the axis of the spindle 26 describes the profile of the piece to be cut, obtained with a suitable control program of a numeric control machine or the like, (repeated in all areas of the material utilizable to obtain a deformed piece). This results in the successive arcuate cuts, which are made by the cutting edge 111 of the tool 101, being tangent or rather osculatory along the perimetric profile of the piece to be cut, and the cut being defined by a series of partial cylindrical surfaces (see Figures 16 and 17) with a radius equal to the radius of the cutting edge and staggered by an extremely small degree, determined by the extremely high frequency of the alternate axial strokes of the element of the cutting edge, and by the relatively fast movement for productivity requirements of the head with respect to the material, along the profile of the piece to be cut out. A presser 50 is provided to prevent lifting of the material.

When necessary, the cut made - composed of the extremely small cusps created by the successive cuts performed by the tool - may be completed with extreme ease with subsequent operations.

The angular movement of the tool-holder element, and therefore of the tool 101, is progressively imposed by the program to ensure that the cylindrical surface 107 of the tool is always directed so that the profile of the piece to be produced from the material M is osculatory; said profile is closed and may be composed of continuous curvatures that may be concave and convex with radii of curvature that may vary, such as the soles or insoles for footwear.

The tool 201 in Figures 18 to 21 is produced with a chisel cutting edge 203, positioned so that it passes through the axis of the spindle 26 of the tool-holder element. In this case the successive cuts made at the high frequency of the spindle 26 will be tangent to the perimetric profile of the piece to be cut. The result of the cut is inferior to that of the previous type of tool.

It is understood that the drawing only shows an example provided purely as a practical embodiment of the invention, which may vary in forms and layout without however departing from the scope of the concept on which the invention is based. The presence of any reference numerals in the claims with reference to the description and to the drawing does not limit the scope of protection represented by the claims.