DESCRIPTION

The present invention relates to a device and a method for making through holes in ceramic slabs.

In particular, the device and the method according to the present invention enable ceramic slabs to be cut that are over 5mm thick, for example comprised between 8 and 12mm, in order to obtain different sizes starting with ceramic slabs of large dimensions. This enables the production of different sizes to be reduced considerably, with consequent saving of production costs and warehouse stock and rough cutting of the ceramic slabs to be avoided, a process that has numerous critical aspects because it produces edges with an irregular cut that are completely unacceptable.

Cutting processes for ceramic tiles are known that involve the use of lasers.

Lasers are used widely for cutting metal sheets. In such processes, the laser beam is focused on the starting point of the cut until a through hole has been made. Subsequently, the laser or the metal sheet are translated in the direction of the cut that it is desired to perform.

This type of process cannot be used for cutting ceramic slabs, because making a through hole and the following cut causes excessive heating of the area surrounding the cutting zone, making the material excessively brittle.

For these reasons, it has been attempted, with little success, to cut ceramic slabs with lasers using the technique called "scribing", which involves making a surface incision with the laser, executing a series of non-through surface holes and then shearing the material mechanically along the incision line. Localized heating is reduced significantly, but this technique is useful only for approximately 3-5mm thicknesses. In the presence of greater thicknesses, the cutting profile that is obtained after shearing is not uniform and squared, but has a rather irregular cutting section.

The object of the present invention is to offer a device and a method for making through holes in ceramic slabs that enables the drawbacks of the currently available processes to be overcome.

One advantage of the present invention is that it permits laser cutting of ceramic slabs, obtaining regular and well squared cutting edges, also in the presence of thicknesses that are greater than 20 mm.

Another advantage of the present invention is requiring significantly reduced cutting time, further avoiding heating the material excessively in the cutting zone.

A further advantage of the present invention is that of limiting the quantity of material to be removed after cutting, by grinding.

Further features and advantages of the present invention will become more apparent in the following detailed description of an embodiment of the present invention, illustrated by way of non-limiting example in the attached figures, in which:

figures 1 ,2,3 show schematically a first embodiment of the device according to the present invention;

figures 4,5,6 show schematically a second embodiment of the device according to the present invention.

The device for making through holes in ceramic slabs according to the present invention comprises a laser source (20), set up for emitting a laser beam (21 ).

Preferably, but not necessarily, the laser source (20) is provided with an Nd:Yag generator, and is driven by the emission of a pulsed beam. The laser source (20) could be of another kind.

Focusing means (30) is set up for focusing the laser beam (21 ) on a preset area or spot (S). The spot (S) can be focused on the surface of a slab (T), or below the surface of the slab (T), or inside the thickness of the slab (T).

The focusing means (30) can comprise one or more lenses (32) and a mirror (31 ). The mirror (31 ) can be used to deflect the beam (21 ) from the source (20) to a lens (32), for example to enable the source (20) to be fitted in a more convenient position or to meet particular constructional needs. The focusing means (30) can be solidly constrained to the source (20), or can be in the shape of a free-standing unit, positioned in such a manner as to intercept the beam emitted by the source (20).

The focusing means (30) can be connected to the source (20) also by optic fibre that transmits the laser beam exiting the source to the focusing means. With this solution, the layout of the machine is simplified significantly.

The focusing means is not disclosed in greater detail because focusing means are components that are present on the market and the essential components thereof are well known.

The device according to the present invention comprises motor means, set up for determining a translation of a slab (T) to be cut and/or of the spot (S) along a cutting direction (X) such that, for a preset interval of time, the corresponding movement between the slab (T) and the spot (S) along the cutting direction (X) is nil. Nil movement between the spot (S) and the slab (T) means that the spot (S) remains localized on a given area of the slab (T) for a sufficient preset time, for example, to make a through hole through the entire thickness of the slab (T). This enables a hole to be made that is substantially in the same conditions in which the slab (T) and laser source (20) are stationary, with the spot (S) stationary in the position in which it is desired to make the through hole. Using motor means configured as disclosed above, however, enables a sequence of holes to be made that are aligned along the cutting direction (X), in an overall significantly shorter time.

In fact, making two successive holes in a condition in which, for each hole, the slab and the source are stationary, requires, after the first hole is made, the slab or the source to move along the cutting direction (X) for the distance corresponding to the distance at which it is desired to make the next hole. In the device according to the present invention, on the other hand, the slab (T) and/or the laser source (20) can move along the cutting direction (X) during making of the hole, approaching the position of the next hole. In this manner, the necessary movement of the slab (T) and/or of the laser source (20) to make the next hole is reduced, requiring significantly less time.

Basically, through driving the motor means, making holes aligned on one another along the cutting direction (X) translates the first spot (S) and the slab (T) along the cutting direction (X), such that they remain stationary in relation to one another for a preset interval of time that is sufficient to make a through hole through the ceramic slab (T). Subsequently, the first spot (S) and the slab (T) translate in relation to one another along the cutting direction (X), to focus the laser beam (21 ) in successive spots (S), aligned on the first spot (S) along the cutting direction (X). For each successive hole, the spot (S) and the slab (T) translate in such a manner as to keep stationary with respect to one another, for a preset interval of time that is sufficient to make a through hole through the ceramic slab (T).

In a first possible embodiment, the motor means comprises a first motor, set up to translate the focusing means (30) along the cutting direction (X). If the source (20) and the focusing means (30) are solidly constrained to one another, the first motor is set up to translate both in a solidly constrained manner. In the embodiment schematized in figure 1 , the focusing means (30) is movable independently of the source (20). In this case, the first motor is set up to translate only the focusing means (30).

The motor means further comprises a rotor (41 ) set up to rotate the beam (21 ) on a plane containing the cutting direction (X). For example, the rotor (41 ) can be connected to the mirror (31 ) to determine the rotation thereof around an axis. As illustrated in figures 1 and 2, the beam (21 ) rotates between a first position, at which the slab (T) drilling step starts, and a second position, in which the slab (T) drilling step stops.

The beam (21 ), during advancement of the focusing means (30), rotates between the first position and the second position, modifying the tilt with respect to the origin direction (A) and with respect to the surface of the slab (T). The beam (21 ), by modifying tilt at the same time as it advances, traces a cone the vertex of which is located inside the spot (S). By adjusting the advancement speed of the focusing means (30) and the rotation speed of the beam (21 ), it is possible to maintain the spot in a preset position and for the time necessary for making the hole. In other words, for each hole, the spot (S) and the slab (T) are maintained stationary with respect to one another, with respect to translation along the cutting direction (X), translating the focusing means (30) along the cutting direction (X) and simultaneously rotating the beam (21 ) on a plane containing the cutting direction (X), in a direction that is opposite the advancement direction of the focusing means (30).

After a first through hole has been made, which is made whilst the beam (21 ) advances along the cutting direction (X) and rotates on a plane containing the cutting direction (X), the beam (21 ), maintaining itself in translation, rotates from the second position to the first position, translating the spot (S) to the position in which the next hole has to be made. The time that elapses between completion of the first hole and the start of the next hole can thus be reduced significantly with respect to the case in which the spot (S) is simply translated for the distance that separates the next two holes. During the movement of the spot from the first hole to the next hole, the source (20) could be switched off.

The drilling process executed by the device according to the present invention thus comprises at least two steps, a drilling step and a positioning step.

During the drilling step, the beam (21 ) performs a movement (X1 ) in a set time and a simultaneous rotation (a1 ), with respect to the central point of the spot (S), at an angular speed that is such as to cancel the speed along the cutting direction (X) of the spot (S) with respect to the slab (T).

During the positioning step, the beam (21 ) performs a movement (X2) in a set time and a simultaneous rotation (a2), in the opposite direction to the preceding rotation (a1 ), such as to take the spot (S) to the next drilling position.

In the embodiment shown in figures 1 ,2,3, the beam (21 ), in the first position, forms an obtuse angle with respect to the origin direction (A) from the source (20), whereas in the second position an acute angle is formed with respect to the origin direction (A). In other words, in the first position the beam (21 ) is tilted in the advancement direction of the focusing means (30), whereas in the second position it is tilted in the opposite direction to the advancement of the focusing means (30).

In a further possible embodiment, the first motor is operational on the slab (T), and is set up to translate the slab (T) along the cutting direction (X) in place of the focusing means (30). The rotor (41 ) is set up for rotating the beam (21 ) on the plane containing the cutting direction (X). Basically, in this alternative embodiment, the source (20) and the focusing means (30) can be maintained stationary and the slab (T) can make the movement along the cutting direction (X). In this case, the advancement direction of the slab (T) is opposite the advancement direction of the focusing means (30) in the preceding solution.

Also in this case, the beam (21 ) rotates between a first position, at which the slab (T) drilling step starts, and a second position, in which the slab (T) drilling step stops.

The beam (21 ), during advancement of the slab (T), rotates between the first position and the second position, modifying the tilt with respect to the origin direction (A) and with respect to the surface of the slab (T). The beam (21 ), by modifying tilt at the same time as it advances, traces a cone the vertex of which is located inside the spot (S). By adjusting the advancement speed of the slab (T) and the rotation speed of the beam (21 ), it is possible to maintain the spot in a preset position and for the time necessary for making the hole. In other words, for each hole, the spot (S) and the slab (T) are maintained stationary with respect to one another, with respect to translation along the cutting direction (X), translating the slab (T) along the cutting direction (X) and rotating the beam (21 ) simultaneously on a plane containing the cutting direction (X), in a direction that is the same as an advancement direction of the slab (T). After a first through hole has been made, which is made whilst the beam (21 ) rotates on a plane containing the cutting direction (X), the beam (21 ), whilst the slab (T) continues to advance, rotates from the second position to the first position, translating the spot (S) to the position in which the next hole has to be made. Also in this case, the time that elapses between completion of the first hole and the start of the next hole can thus be reduced significantly with respect to the case in which the spot (S) is simply translated for the distance that separates the next two holes. During the movement of the spot from the first hole to the next hole, the source (20) could be switched off.

In the embodiment disclosed above, the beam (21 ) rotates between a first position, in which it forms an obtuse angle with respect to the origin direction (A) from the source (20), and a second position, in which it forms an acute angle with respect to the origin direction (A). In the first position, the beam (21 ) is tilted in the opposite direction to the advancement of the slab (T), whereas in the second position the beam (21 ) is tilted in the advancement direction of the slab (T). The two consecutive holes are made in the same manner already disclosed for the embodiment of figure 1 , in which, instead of the focusing means (30) advancing, it is the slab (T) that advances along the cutting direction (X). In other words, for each hole, the spot (S) and the slab (T) are maintained stationary with respect to one another, with respect to translation along the cutting direction (X), translating the slab (T) along the cutting direction (X) and rotating the beam (21 ) on a plane containing the cutting direction (X), in a direction that is the same as an advancement direction of the slab (T).

Also in this embodiment the drilling process comprises a drilling hole and a positioning step.

During the drilling step, the slab (T) performs a movement (X1 ) within a set time, and the beam (21 ) performs a simultaneous rotation (a1 ), with respect to the central point of the spot (S), at an angular speed that is such as to cancel the speed along the cutting direction (X) of the spot (S) with respect to the slab (T).

During the positioning step, whilst the slab (T) performs a movement (X2) in a set time, the beam (21 ) performs a simultaneous rotation (a2), in the opposite direction to the preceding rotation (a1 ), such as to take the spot (S) to the next drilling position.

In figures 4,5,6 a further possible embodiment is illustrated, in which focusing means (30) is provided in which the mirror (31 ), possibly solidly constrained to the lens (32), can translate along the cutting direction (X), without varying tilt with respect to the origin direction (A) of the laser beam (21 ). This embodiment is particularly, but not exclusively, suitable for cases in which the focusing means (30) is solidly constrained to the laser source (20). In such a case, the motor means comprises a first motor, to slide the source (20) and the focusing means (30) along the cutting direction (X). The motor means further comprises a second motor (42), set up to translate the mirror (31 ) along the cutting direction (X), in an advancing and retracting direction. The second motor (42) is set up to implement linear motion of the mirror (31 ).

In this embodiment, during the drilling step the spot (S) can be maintained stationary on the slab (T), translating the mirror (31 ) in the opposite direction to the focusing means (30). Basically, in this embodiment the motor means is set up to drive in advancement along the cutting direction (X) the source (20) and the focusing means (30), and translate in an opposite direction, at the same speed, the mirror (31 ) and possibly the lens (32), between an initial position and a final position. In this manner, the absolute speed of the mirror (31 ) is nil, so that the beam (21 ) and the spot (S) remain stationary. By adjusting the speed and the stroke of the mirror (31 ) and of the lens (32) with respect to the focusing means (30) it is possible to adjust the interval of time in which the beam (21 ) and the spot (S) remain stationary, in order to enable a through hole to be made. After making a hole, during the positioning step, the mirror (31 ) and the lens (32) return to the initial position, advancing in the same direction in which the focusing means (30) advances. When the beam (21 ) and the spot (S) reach the position of the next hole, the mirror (31 ), and possibly the lens (32), slide again at the same speed and in the opposite direction to the focusing means (30), to make the next hole.

In the embodiment of the figures 4,5,6, the first motor could be active on the slab (T) instead of on the laser source (20). During the making of a hole, the mirror (31 ) is in synchronous motion with the slab (T), i.e. the mirror (31 ) moves in the same direction and at the same speed as the slab (T). After the hole has been made, the mirror retracts to the initial position, from which it synchronizes again with the motion of the slab (T) to make the next hole.

Naturally, it would be possible to set up motor means that enables all the movements disclosed above to be combined. For example, it would be possible to translate along the cutting direction (X) both the focusing means (30) and the slab (T), for example to reduce further the time of movement of the spot from one hole to the next hole.

In a further possible embodiment, not illustrated, the motor means comprises a motor of the laser source (20) or of the focusing means (30), set up for translating the laser source (20) or the focusing means (30) along the cutting direction (X), and a motor of the slab (T), set up for translating the slab (T) along the cutting direction (X). In this embodiment, the slab (T) and the focusing means (30) translate with synchronous motion during making of a hole. Subsequently, the focusing means (30) and/or the source (20) can retract with respect to the slab (T), stopping or moving in the opposite direction until the position of the next hole is reached, then resuming synchronous motion with the slab (T) to make the next hole. Also in this case, the time needed to move the spot (S) from one hole to the next hole can be reduced significantly with respect to the time required for the same movement when the movement is performed with a stationary slab (T).

After the through holes have been made, the slab (T) can be sheared along the cutting direction (X) by a device that is known to the person skilled in the art. Owing to the fact that the holes made are through holes, the cutting edge that results from shearing is clean and well squared.

In all the embodiments disclosed, the motors and the rotor (41 ) can be chosen from the different solutions that are available to the person skilled in the art. For example, the advancement motors can be in the form of linear motors, or in the form of rotating motors combined with a linear transmission comprising a rack. The rotor (41 ), for example, can be in the form of an electric motor. A control module can be set up to drive and coordinate the various motors in a manner that is known to the person skilled in the art.