The invention relates to a tool-holder cylinder and an abrasive unit. In particular, it is a tool-holder cylinder and an abrasive unit used for machining elements made of ceramic and/or stone material, and especially for their surface polishing or lapping.

The invention therefore relates to the field of machine tools.

The currently known abrasive units comprise a support body which usually has two main faces; one is used for attaching to one end of a drive shaft, the other has an abrasive surface, which comes into contact with the workpiece for the actual machining.

The abrasive face may exist, for example, in a continuous form or in the form of a plurality of contiguous and projecting abrasive elements The abrasive body is attached to the shaft by means of a so-called

"foot" bracket integrated at one end of the shaft itself; the combination of these elements forms the grinding head which carries out the grinding on the workpiece.

The second end of the shaft is hinged to an axis that is substantially parallel to the surface to be machined, and around which the shaft itself can oscillate.

The abrasive face of the support body thus describes a trajectory corresponding to an arc of a circle, which is tangential at least in part to the surface to be machined. Lapping and grinding is carried out by successive passes of the abrasive face of the grinding head over the surface of the workpiece.

The workpiece is usually placed on a conveyor belt, which pulls it along a plane tangential to the abrasive face of the tool.

In this case, the shaft around which the oscillating head moves makes an additional movement, known as pivoting, which serves to extend the working area of the tools. This movement consists of an alternating translation of the axis of oscillation perpendicular to the direction of movement of the workpiece and within the plane parallel to that of the workpiece itself.

Moreover, with reference to Figure 13, some known grinding and lapping machines provide that a plurality of abrasive tools 1 , each oscillating about an axis x parallel to the surface of the workpiece, are radially mounted on a support 70 rotating about an axis z perpendicular to the workpiece.

Examples of abrasive tools used in this type of machine are fickerts.

The support body of the fickert has a dovetail coupling with a double taper, which has a first taper parallel to the abrasive face, and a second taper perpendicular to it and in the direction of the abrasive face.

The dovetail coupling allows the fickert to be inserted into the head by means of a radial slide from the centre to the outside of the support.

The attachment must be done from the centre outwards to prevent the fickert from slipping off during machining due to the centrifugal force generated by the rotation of the support around the axis z perpendicular to the workpiece.

Consequently, when the fickert is mounted on the head, the first taper is also oriented radially outwards, while the second is oriented towards the workpiece.

The typical drawbacks of the prior at tools are mainly related to the efficiency of machining and the speed with which it is carried out.

In particular, the following are currently significant drawbacks for the purpose of machining: the frequency of tool changes and the speed with which they can be carried out; the removal capacity of the tool head and the uniformity of machining; the quantity of workpieces that can be machined and their final appearance.

In fact, the fickerts wear out in a short time and are replaced quite frequently, as each abrasive head tackles a fairly large area of the workpiece over a long period of time. The procedure for replacing fickerts attached to the heads is slow and not very easy, as they are removed by sliding in the opposite direction to the slide for the attachment, that is, from the outside inwards.

A possible solution which allows the direction of sliding to be reversed may be to use locking flanges or other interference means which prevent the fickert from slipping out.

However, the saving in terms of time would be useless when considering the time necessary to disassemble and assemble the interference means which holds each fickert in place.

Consequently, the number of parts machined is limited by the extended times needed to perform the machining and by the time needed to replace fickerts and maintain the machines.

Additionally, due to the size of the support and the way the oscillating rods are mounted on it, the bending radius of the tool cannot fall below a minimum length, approximately 20 cm.

Moreover, the movement of the tools is also due to the rotation of support 70 around the axis z perpendicular to the surface of the workpiece, which is the predominant component between the two.

The tools themselves describe a rather wide trajectory oriented parallel to the surface, and cannot adapt to smaller bumps and depressions on the surface of the workpiece.

Consequently, the surfaces of machined materials may have heterogeneous defects due to the lack of versatility and adaptability of the heads.

This is particularly noticeable when machining any ridges on the surface, which are effectively cut by the action of the tools, and the depressions, which cannot be effectively reached by simply sliding the tools across the surface.

The technology has currently remained unchanged and tends to implement the single or multiple grinding head configuration in all cases.

The main aim of the invention is to provide a tool-holder cylinder and an abrasive unit for surface machining of ceramic and/or stone materials which has, due to higher speeds and kinetic energy of the tool, higher removal capacities and processing efficiency than the prior art.

Another aim of the invention is to increase the uniformity and quality of the surfaces of the machined materials. A further aim of the invention is to provide a tool-holder cylinder and an abrasive unit which enables higher production line speeds to be achieved, and thus higher productivity.

A further aim is to provide a tool-holder cylinder and an abrasive unit which is capable of housing abrasive tools of the same type currently in use in the oscillating head, resulting in considerable versatility and ease of installation.

Finally, it is an object of the invention to provide a tool-holder cylinder and an abrasive unit for the surface machining of ceramic and/or stone materials which decrease the machine stoppages due to tool changes because the head supports a higher number of abrasive tools than the prior art.

An object of the invention is therefore a tool-holder cylinder for supporting abrasive tools, designed to be attached to a head of a machine tool for surface machining of ceramic and/or stone materials, wherein the head is configured to rotate about a first axis substantially parallel to a surface to be machined and coinciding with the axis of central symmetry of the cylinder, the cylinder comprising an upper surface, a lower surface, and a side surface parallel to the first axis and on which are formed a plurality of seats designed to house the abrasive tools by means of a dovetail coupling, in particular the seats have a first tapering which extends perpendicularly and away from the first axis, and a second tapering parallel to the first axis.

Additionally, the second tapering can extend towards the lower surface of the cylinder, or towards the upper surface of the cylinder.

The cylinder may further comprise a cavity provided with an opening and configured to house the head of the machine tool, and at least one through-hole on its upper surface. The cavity may have an inner side wall and a bottom wall, opposite the opening and having a diameter smaller than the opening, in particular the inner side wall may comprise a first conical portion, starting from the bottom wall and whose diameter increases in the direction of the opening, and a second cylindrical portion of constant diameter, contiguous to the first portion and ending at the opening.

A further object of the invention is an abrasive unit comprising a tool- holder cylinder of the types described, wherein the head of the machine tool has an upper surface and at least one hole for inserting means for attaching to the cylinder.

The abrasive unit may comprise a plate designed to make contact with the abrasive tools inserted in the seats and provided with a through- hole, coaxial with the hole of the cylinder and the hole of the head, for housing means of attachment to the head. Further, in the abrasive unit according to the invention, the head of the machine tool may have an upper surface and at least one hole for inserting attachment means; in particular, the unit may comprise a spacer, designed to be interposed between the bottom wall of the cavity of the cylinder and the upper surface of the head of the machine tool, and comprising an upper face designed to make with contact the bottom wall of the cylinder, a lower face designed, to make contact with the upper surface of the head and having a diameter greater than the upper face, a side surface, designed to make contact with the first portion of the inner side wall of the cylinder, a first hole, coaxial to the hole of the cylinder, for housing means of attachment to the cylinder, and at least a second hole, for housing means of attachment to the head.

In this case, the abrasive unit may comprise a plate designed to make contact with the upper surface of the cylinder and provided with a through- hole, coaxial with the hole of the cylinder and the first hole of the spacer, for housing means of attachment to the spacer. Another aspect of the invention relates to a machine tool comprising a cylinder of the types described and/or an abrasive unit of the types described.

Finally, another object of the invention is a machine tool comprising a support having at least one head attached to an abrasive unit of the said type, wherein the support is configured to rotate about a second axis perpendicular to the first axis, so as to rotate the at least one head.

The invention will now be described by way of non-limiting example according to some of its preferred embodiments, with the aid of the attached figures, wherein:

Figure 1 is a plan view of a first embodiment of a tool-holder cylinder forming part of the abrasive unit according to the invention;

Figure 2 is a front view of the tool-holder cylinder of Figure 1 ;

Figure 3A is a cross-sectional front view of the tool-holder cylinder of Figures 1 and 2;

Figure 3B is a cross-sectional front view of an alternative embodiment of the tool-holder cylinder of Figures 1 and 2;

Figure 4 is a section of a flange for attaching the tools to the tool- holder cylinder of Figure 1 ;

Figure 5 is a plan view of the flange of Figure 4;

Figure 6 is a plan view of a second embodiment of a tool-holder cylinder forming part of the abrasive unit according to the invention;

Figure 7 is a front view of the tool-holder cylinder of Figure 6;

Figure 8 is a cross-sectional front view of the tool-holder cylinder of Figure 6;

Figures 9A-9B-9D are perspective views of attachment means for the tool-holder cylinder of Figure 6;

Figure 9C is a perspective view of a tool-holder head that can be attached to the tool-holder cylinder shown in the previous drawings;

Figures 10A-10B-10C are sectional views of the attachment means of Figures 9A-9B-9D; Figure 10D is a cross-sectional view of an alternative embodiment of the means of attachment of the tool-holder cylinder of Figure 10C;

Figures 11 A and 11 B are an overall sectional view of an abrasive unit comprising the elements shown in Figures 6-11 B;

Figure 12 is a perspective representation of a rotating support with five cylinder-holder heads;

Figure 13 is a perspective representation of a rotating support according to the prior art.

Figures 1 -3B show a tool-holder cylinder 100 designed for holding tools, for example fickerts used for grinding.

Such a cylinder 100 is configured to be attached to a rotating head (for example of the type shown in Figures 9C and 11 A and 11 B) of a machine tool, which is rotated about a first axis x.

A further example of rotating heads 71 is shown in Figure 12, wherein a plurality of heads 71 are arranged on a support 70.

This axis x is substantially coincident with the central axis of symmetry of the cylinder 100.

The cylinder 100 has a plurality of faces 110 along its side surface 160, arranged symmetrically with respect to the same axis x, and extending from the upper surface or base 120 to the lower surface or base 130 of the cylinder 100.

The side surface 160, or the faces 110, are arranged substantially parallel to the axis x.

Moreover, according to a preferred embodiment of the invention, the cylinder 100 is at least partially hollow on the inside; its bottom surface 130 has an opening 131 for access to a cavity 132, configured to receive and house the rotating head of a machine tool.

The cylinder 100 is attached to the rotating head by conventional attachment means.

According to a preferred embodiment, such attachment means are one or more screws or bolts, which can be inserted into appropriate first holes 140. The holes 140 may be formed, for example, within the cavity 132 of the cylinder 100, at a distance from the opening 131 such as to house the rotating head of the machine tool inside the same inner cavity 132 (visible in the section of Figure 3). In each face 110 of the side surface 160 of the cylinder 100, a seat

111 is formed for housing an abrasive tool, such as a fickert or similar.

According to a preferred embodiment, each abrasive tool is inserted into each seat 111 by sliding.

The tools can be any type, as the seat can be shaped to accommodate different types of tools in terms of size and shape.

Consequentially, each seat 111 will have an open upper end 112 and a lower end 113, comprising a stop wall for the fickert, or chosen tool, once it is inserted.

Preferably, the seats 111 according to this first embodiment are used for attaching fickerts by means of a dovetail attachment.

The seats 111 have a first transverse taper (visible in Figure 1 ), which proceeds outwards and perpendicular to the axis x, and a second longitudinal taper (visible in Figure 2), which proceeds towards the lower end 113, or towards the lower surface 130 of the cylinder 100, and parallel to the axis x.

In other words, the first tapering extends perpendicularly and away from the axis x.

The orientation of the first taper prevents the centrifugal force due to the rotation of the head 71 around the axis x from causing the fickert to detach, while the orientation of the second taper allows the fickerts to be inserted and removed more quickly from the seats 111.

For this reason, once the fickerts or other abrasive tools are in position in the seats 111 , they must be attached by means of a special flange 200, shown in Figures 4 and 5. The flange 200 is secured using conventional attachment means. According to a preferred embodiment, such attachment means are screws or bolts, which can be inserted into second holes 150 of the cylinder 100 and pass through third holes 240 of the flange.

The abrasive tools are therefore locked beneath by the stop walls of the lower end 113 of the seats and above by the flange 200.

Advantageously, the use of the flange 200 makes the assembly safer and more solid during use.

Operationally, when actuated, the cylinder rotates around the axis x, set in motion by the head 71 of a machine tool.

The speed of rotation can be varied according to requirements.

The head is arranged with its axis x parallel to the surface to be machined, so that the abrasive tools, connected to the rotating cylinder, carry out material removal in consecutive passes.

In order to facilitate the removal of the cylinder 100 from the head 71 , for example in the event of a seizure with the head 71 , additional holes 250 are formed in the upper surface 120.

These holes 250 are threaded and pass through, so that by inserting screws, of a suitable length greater than the stroke of the holes 250, the cylinder 100 can be separated from the head 71 .

As mentioned above, a machine tool can be equipped with a plurality of rotating heads with an equal number of cylinders, in order to increase the surface machined and reduce the wear of the individual abrasive tools, as shown in Figure 12.

In this case, the machine tool comprises at least one support 70, provided with a plurality of heads 71 rotating about its axis x.

Each axis x lies in a plane essentially parallel to the surface of the piece to be machined (not shown).

The support 70 itself rotates around a second axis z, which is substantially perpendicular to the surface to be machined.

Advantageously, the rotational motions of the support 70 about the axis z, and of the heads 71 about each axis x, occur in such a way that the tangential speed of the tools mounted on the heads is added to the drag speed, that is, the tangential speed of the same point rotating about the axis z.

An example of such a configuration is represented in Figure 12 by the vx and vz vectors of the angular velocity directions. Respectively, the vectors vx and vz refer to the directions of the angular velocities of the support 70 about the axis z, and of the heads 71 about each axis x.

With this configuration, it is also possible to triple the tangential speed of the tools on the surface of the workpiece compared to conventional oscillating heads.

By tripling the speed, the kinetic energy of the tools themselves is advantageously nine times greater than the prior art.

Moreover, since the movement of the tools on the surface of the workpiece is due to the composition of the rotations around the two axes z and x, in a different way to the prior art in which there is an oscillation (compare with the configuration in Figure 13), the approach and engagement that each tool makes with the surface allows it both to adapt to the depressions in the surface of the workpiece, both to avoid cutting the reliefs, but rather to even them out. The degree of gloss of the final product is higher, and the amount of enamel to be used is less than the prior art.

The uniformity of the machining is also due to the fact that the abrasion of the workpiece takes place in a plurality of directions on its surface, thus avoiding leaving more marks in one direction than in others. In addition, this new machining method allows more parts to be machined, that is to say, side by side in parallel rows, than is possible with the prior art.

In fact, the swinging movement, in a conventional manner, can be combined with the two movements already described simply by shifting the axis of rotation z of the support 70, but keeping it parallel to itself. For example, the support 70 may translate periodically over time between a first position, indicated by vector vz1 , and a second position, indicated by vector vz2.

The vz vectors during translation remain parallel to each other over time, indicating that the support 70 translates parallel to the surface of the workpiece.

Thanks to the new configuration described here, the tangential speed of the tools on the surface of the workpiece can exceed 30 m/s.

Preferably, the respective speeds of rotation of the support 70 about the axis z (revolution) and of the heads 71 about each axis x (rotation) are about 420-450 rpm and about 1500 rpm.

The configuration of the support 70 equipped with a plurality of cylinder heads 71 has been described for the first embodiment of the cylinder 100, but it is understood that it can also be used, with the same advantages, with the second embodiment illustrated below.

Figures 6-8 show a second embodiment of a tool-holder cylinder 300 designed for supporting tools, for example fickerts used for grinding.

This cylinder 300 is configured to be attached to a head 71 of a machine tool, which is rotated about an axis x. This axis x is substantially coincident with the central axis of symmetry of cylinder 300.

The cylinder 300 has a plurality of faces 310 along its side surface 360, arranged symmetrically with respect to the same axis x, and extending from the upper surface or base 320 to the lower surface or base 330 of the cylinder 300.

The side surface 360, or the faces 310, are arranged substantially parallel to the axis x.

In each face 310 there is a seat 311, designed for attaching an abrasive tool, provided with an upper end 312 and a lower end 313. Preferably, the seats 311 according to this second embodiment are used for attaching fickerts by means of a dovetail attachment. The fickerts are inserted by simply sliding the dovetail connection into each seat 311 in the direction from the centre outwards.

The seats 311 have a first transverse taper (visible in Figure 6), which proceeds outwards and perpendicular to the axis x, and a second longitudinal taper (visible in Figure 7), which proceeds towards the upper end 312, or towards the upper surface 312 of the cylinder 300, and parallel to the axis x.

In other words, the first tapering extends perpendicularly and away from the axis x. The orientation of the first taper prevents the centrifugal force due to the rotation of the head 71 around the axis x from causing the fickert to detach.

Moreover, according to a preferred embodiment of the invention, the cylinder 300 is at least partially hollow on the inside; its bottom surface 330 has an opening 331 , configured to receive and house the rotating head 71 of a machine tool inside a cavity 332.

The cavity 332 has an inner side wall 333 and a bottom wall 334, located in a position opposite the opening 331 and near the upper surface 320 of the cylinder 300. The diameter of the bottom wall 334 is smaller than the opening 331.

In fact, the side wall 333 of the cavity 332 comprises a first conical portion 335 and a second cylindrical portion 336.

The first conical portion 335 starts at the bottom wall 334 and its diameter increases as it proceeds towards the opening 331. At an intermediate point of the side wall 333, between the opening

331 and the bottom wall 334, the first portion 335 ends, intersecting with the second portion 336, which continues with a constant diameter equal to that of the opening 331 , to the lower surface 330 of the cylinder 300, or to the opening 331 itself. Figures 9A-9D, 10A-10C show sections of further components for attaching the cylinder 300 to the head 71 are shown, namely a plate 8 and a spacer 9. Together, the cylinder 300 and the spacer 9, and optionally the plate 8, form an abrasive unit that can be attached to a head 71 of a machine tool.

The plate 8 has an upper surface 81 , a lower surface 82 and a central through-hole 83 (Figs. 9A, 10A).

The spacer 9 comprises an upper face 91 , a lower face 92, a side surface 90, a first hole 93 in a central position and at least one second hole 94 adjacent to the first hole 93 (Figs. 9B, 10B).

Preferably, the plate 8 and the spacer 9 are circular in shape.

The diameter of the lower face 92 is greater than the diameter of the upper face 91 , so that the side surface 90 has a conical profile.

According to other embodiments, the diameters of the lower face 92 and upper face 91 are identical, thus making the side surface 90 that of a straight cylinder.

The number of second holes may vary, for example five through holes may be provided symmetrically arranged on the upper surface 91 of the spacer 9 with respect to the first hole 93.

Preferably, the first hole 93 is formed in a central portion projecting from the upper surface 91 , to facilitate centring of the components during attachment, as illustrated below.

In the lower surface 92 of the spacer 9, a seat or recess 95 is formed, which is complementary in shape to a portion of the head 71 of Figure 9C.

The head 71 , shown in Figures 9C, 10C and in the assembly of Figure 11 A, has an upper surface 711 , which comprises a projecting portion 710 and holes 714 designed for the insertion of attachment means (not shown), for example screws.

Preferably, the number and arrangement of the holes 714 correspond to the number and arrangement of holes 94 on spacer 9.

In addition, a shoulder 713 having a diameter equal to that of the lower face 92 of the spacer 9 is formed on the head 71 .

The projecting portion 710 of the head 71 is configured to be inserted within the seat 95 of the spacer 9, as shown in Figures 10B and 11 A, 11 B. The shoulder 713 of the head 71 makes contact with the circular crown portion of the lower face 92 of the spacer 9.

Subsequently, the spacer 9 and the head 71 are attached by inserting attachment means 10 into the respective holes 94, 714.

In this way, the assembly formed by the head 71 and by the spacer 9 can be inserted inside the cavity 332 of the tool-holder cylinder 300 through the opening 331.

The upper face 91 of the spacer 9 makes contact with the bottom wall 334, whilst the side surface 90 makes contact with the first conical portion 335 of the side wall 333.

The conical surface of the spacer 9 is more advantageous than the situation wherein two cylindrical, or otherwise straight, surfaces must be coupled to each other, making it easier to insert and remove the cylinder 300 from the head 71

This second embodiment also provides threaded and through holes 350 for the insertion of release screws in the event of the cylinder 300 seizing with the head 71.

At this point, the plate 8 is positioned on the upper face 320 of the cylinder 300 and attached to the spacer 9, by inserting suitable attachment means into the holes 83 and 93, for example a screw or a bolt 10.

In this way, the cylinder 300 is clamped between the plate 8 and the spacer 9, and can be rotated by the head 71.

This design of the tool-holder cylinder 300 can also be used in a multiple-head configuration by means of the support 70 in Figure 12.

The orientation of the second tapering of the seats 311 , in this second embodiment, is reversed with respect to the first embodiment.

Advantageously, this orientation of the second taper prevents the inserted fickerts from slipping out as a result of the centrifugal force developed by the rotation of the support 70 around the axis z.

Figures 10D and 11 B are cross-sectional front views of an alternative embodiment of the head 71 , substantially similar to that described above, but provided with a bearing 715, preferably of the cylindrical roller type, serving as a support.

The spacer 9, the cylinders 100, 300 and their various embodiments, as well as the plate 8, can equally be used, as shown in the assembly in Figure 11 B.

The above description and illustrations of the abrasive unit refer to the second embodiment of the tool-holder cylinder, but with the same components it is also possible to attach a cylinder according to the first embodiment, suitably adapted to receive the spacer in its cavity. In fact, the invention provides for a third embodiment of the tool- holder cylinder (shown in section in Figure 3B), or of the abrasive unit comprising it, wherein the cylinder has the same characteristics as the first embodiment, but the shape of the cavity 332 is as described for the second embodiment. This makes it possible to take advantage of the ease of attachment for the tools, which can be removed and inserted without removing the cylinder from the head 71 , and the ease of attachment of the cylinder itself to the head by means of the conical coupling.

According to a further preferred embodiment, the tools inserted into the seats are held in place not by a flange 200 secured by attachment means inserted into the holes 150 (Figures 1 , 3-5), but by a plate 8 of suitable width, which can be easily secured by means of the central hole 340 in a similar manner to that described for the second embodiment.

Such a plate holds the tools in place on the cylinder, and at the same time attaches the cylinder itself on the rotating head 71.

In this way, the following advantages can be combined: easy and fast insertion and removal of tools in the seats of the cylinder, and of the cylinder itself to the rotating head; easy and fast attachment of tools to the cylinder and of the cylinder itself to the head.

The invention described may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Further, all the details can be replaced by other technically-equivalent elements.

Lastly, the components used, providing they are compatible with the specific use, as well as the dimensions, may vary according to requirements and the state of the art.

Where the features and the techniques mentioned in the following claims are followed by reference signs, the reference signs have been used only with the aim of increasing the intelligibility of the claims themselves and, consequently, the reference signs do not constitute in any way a limitation to the interpretation of each element identified, purely by way of example, by the signs numbers.