A MACHINE FOR WORKING SLAB EDGES

Technical field

This invention relates to a machine for working slab edges. Background Art

This type of machine, known in the trade as "edge polishing machine", is applicable to the machining of the edges of slabs, and even more specifically to the shaping, roughing and polishing of the slabs made of marble, granite, hard stone or synthetic materials with a high mechanical strength.

This machine allows the working of the edges of slabs used as kitchen worktops, shelves, windowsills or, more in general, surfaces the side edge of which must be modelled according to specific profiles, for example with toroidal, rounded or square cross sections or according to more complex geometries for mainly aesthetic reasons as well as accident prevention purposes.

The edge polishing machines currently know and marketed comprise a supporting frame and a horizontal surface on which the slab to be worked is rested. The surface is provided with a conveyor belt and/or a sliding roller surface, which feed the slab progressively and at a constant speed along a rectilinear path, along which a series of tools are positioned which work, in succession, the edge of the slab.

Each tool usually consists of a grinding wheel or a milling cutter, mounted on a respective head. The first tool holder heads which work the slab are designed for forming the edge and, therefore, the first roughing of the edge of the slab, with removal of excess material.

Continuing along the working path, the slab encounters the milling cutters comprising diamond heads, or made from a material with a very high hardness such as, for example, cemented carbide (known with the trade name of "Widia"), which finish the edge giving it the desired profile.

More specifically, the heads are pressed, for example by pneumatic means, against the two corners of the slab, to abrade the corners, giving the edge the desired profile. The careful balancing between speed of rotation of the milling cutters, properties of the abrasive material and speed of feeding the slab determine the depth of working the profile (that is to say, they determine the quantity of material removed from the edge). Further tool holder heads polish the edge shaped in this way.

In recent years the market has requested slabs of the above-mentioned type having worked edges, that is, shaped, with a very high precision. More specifically, the market requests shapes of the edges with such precision that the placing alongside each other of two slabs guarantees perfect continuity and uniformity of the shapes of the edges.

In other words, placing the two slabs alongside each other, the join between the shaped edges of the two slabs must not be visible, that is to say, the end section of the shaped edge of the first slab must be identical to the initial section of the shaped edge of the second slab.

Such a result is very difficult to obtain using the prior art machines for working slab edges.

In effect, considering, for example, an edge with both the corners bevelled according to respective inclined planes (that is, a shaped edge B having a profile given by three plane surfaces joined by two corners as illustrated in Figure 3), the two end surfaces of the profile (those indicated with the reference S in Figure 3) have dimensions which are not constant along the extension of the edge of the slab if the slab does not have a perfectly constant cross section along its entire extension.

More specifically, the end surfaces of the profile have smaller dimensions at the portion of slab with the smaller thickness and larger dimensions at the portions of slab with greater dimensions. This means that the profiles of two slabs placed alongside each other do not correspond. It should be noted that, precisely because the shaping of the edges affects the corners of the edges, small variations in thickness of the slab considerably amplify the above-mentioned drawback. For this reason, even millimetric variations in thickness of the slab (which can have lengths of a couple of metres), which are difficult to eliminate by grinding the thickness of the slab, can result in incorrectly profiled edges (the differences in dimensions of the surfaces of the profile must be ground manually by the craftsman installer).

Clearly, there is also the above-mentioned drawback in the shaping of edges with profiles different to that explicitly shown by way of an example.

Disclosure of the invention

In this context, the purpose of this invention is to provide a machine for working slab edges that is free of the above mentioned drawbacks.

As part of that technical purpose, the aim of this invention is to propose a machine for working slab edges which is able to make profiles with a constant, or in any case predetermined, cross section, even with slabs not having perfectly constant thicknesses.

Another important aim is that of providing a machine for working slab edges which allows a perfect shaping of the edges without the need for manual intervention for final grinding.

These aims and others, which shall become more readily apparent in the course of the description that follows, are substantially achieved by a machine for working slab edges as described in one or more of the accompanying claims.

Brief description of the drawings

A preferred, non-limiting embodiment of a machine for working slab edges according to this invention is now illustrated by way of a non-limiting example.

With reference to the accompanying drawings:

Figure 1 is a perspective view of a machine for working slab edges according to this invention with some parts cut away to better illustrate others;

- Figure 2 is an enlarged view of a detail of the machine of Figure 1 ;

- Figure 3 shows an example of a shaped edge of a slab; and

- Figures 4 and 5 are schematic views of some operating positions of the detail of Figure 2.

Detailed Description of the Preferred Embodiments of the Invention

With reference to the accompanying drawings, the numeral 1 denotes in its entirety a machine for working slab edges, preferably made of marble, granite or hard stone, natural or synthetic, homogeneous or composite. The machine 1 comprises a supporting frame 2 and a supporting surface 3 on which a slab L is rested having an edge B to be worked. The slab L is moved forward, using feeding members 4, along a working path, preferably rectilinear, defined by the supporting surface 3.

The feeding members 4 comprise, in the preferred embodiment, a belt 5 trained around opposite and motor-driven pulleys.

The feeding members 4 also comprise, in an embodiment not illustrated, a plurality of idle rollers with axes of rotation parallel to each other, parallel to the slab L being worked and transversal to the working path. The rollers constitute mechanical stops which push from the top downwards on the slab in such a way that the slab is kept adherent to the supporting surface during the working.

The forward movement of the slab L on the supporting surface 3 is guided by contact elements 6, designed to contact the edge B of the slab L. The contact elements 6 act along a contact line R against which the edge B of the slab L rests. This ensures a correct positioning of the edge B of the slab L, avoiding accidental movements of the slab which would adversely affect the quality of the working.

As shown in Figure 1 , the contact elements 6 comprise a plurality of cylindrical rollers 7, mounted in an idle fashion on respective vertical axes of rotation and positioned in an ordered row aligned with the above- mentioned contact line . The machine 1 comprises a plurality of tools 8 distributed in succession along the working path P and each rotatable about a respective axis of rotation, at right angles to the contact line R. The tools 8 are designed to perform preliminary working on the edge of the slab to prepare the slab for subsequent finishing work.

The tools 8 are controlled by respective drive means, which place each tool 8 in rotation about the relative axis of rotation and translate it towards and away from the edge B of the slab L. Preferably, the drive means comprise, for each tool 8, an electric motor, for placing in rotation the respective tool about the relative axis of rotation, and a piston, either pneumatic or hydraulic, which pushes the tool 8 against the edge B of the slab L keeping it in contact during the working.

It should be noted that, if the edge B of the slab L does not need preliminary working, the above-mentioned tools 8 can be inactive or even absent.

The machine 1 comprises at least one station 9 for shaping (or profiling) the edge B of the slab L, illustrated in detail in Figure 2 (where the slab being worked has not been illustrated for the sake of clarity).

The shaping station 9 comprises at least one shaping member 10 provided with a shaping tool 1 1 designed to remove material from the edge of the slab.

In the preferred embodiment, the shaping tool 1 1 is a disk-type milling cutter. More specifically, in the accompanying drawings and in this description reference is made to a shaping member 10 designed to make flat rectilinear edges, of the type illustrated in Figure 3; however, in embodiments not illustrated, the shaping member 10 can be of the type designed to make edges different from that described and illustrated, such as, for example, rounded edges, edges with inclined planes, edges with undercuts and any other type of edge which requires removal of material from the edge of the slab.

The shaping station 9 further comprises at least one member 12 for detecting the position of a portion of the edge B of the slab L, the detecting member being operatively placed upstream of the shaping member 10, as illustrated in Figure 2.

In a first embodiment (illustrated in the accompanying drawings) the detecting member 12 is designed to generate a parameter P representing the position of a portion of the edge B of the slab L, more specifically of the portion of edge on which the detecting member 12 is instant by instant. The machine 1 also comprises a control unit UC designed to receive the parameter P representing the position of a portion of the edge B of the slab L and to send a command signal C, as a function of the parameter P, to the shaping member 10 to determine the position of the shaping tool 1 1 , that is to say, for instructing the shaping member 10 regarding the position which the shaping tool 1 1 must adopt.

In this way, advantageously, the shaping of the edge B of the slab L is performed in a precise fashion and is independent of any variations in thickness of the slab L, as will be described in more detail below.

Lubrication and/or cooling means (not illustrated) are provided at least at the shaping station 9 for cooling the milling cutter during its operation. These lubrication and/or cooling means can, for example, consist of spraying nozzles connected to a system for supplying water, which is sprayed on the milling cutter and on the slab during working of the slab.

The detecting member 12 comprises a mechanical feeler pin 13 designed to contact the above-mentioned portion of the edge B of the slab L.

The mechanical feeler pin 13 comprises a contact portion 14, designed to contact the slab L, made of, or coated with a material, for example cemented carbide (known with the trade name of "Widia"), having a greater hardness degree than the material of which the slab L is made, in such a way that it is not cut by the slab being worked and keeps the effectiveness of the feeling pin unchanged.

The detecting member 12 comprises a transducer 13a for determining the position of the mechanical feeler pin. The transducer 13a (illustrated schematically in Figures 4 and 5) determines the current position of the mechanical feeler pin 13, which being in direct contact with a portion of the edge of the slab, generates or allows generation of the parameter P representing the position of the portion of the edge B of the slab L contacted. The detecting member 12 comprises a device 15, preferably pneumatic, for moving the mechanical feeler pin 13 close to and away from the slab L. It should be noted that in the shaping example described, the feeler pin 13 contacts the edge of the slab L at a corner of the slab, as illustrated schematically in Figure 4.

The shaping member 10 comprises an actuator 16 designed to receive the command signal C for moving the shaping tool 1 1 away from and close to the slab L as a function of the parameter P, that is to say, as a function of the position of the feeler pin 13.

In the preferred embodiment, the actuator 16 is an electric motor preferably of the stepper type.

Preferably, the machine 1 comprises at least a pair of shaping stations 9, in such a way as to allow the simultaneously working on two adjacent corners of the edge B of the slab L.

Preferably, the shaping stations 9 are reciprocally inclined to each other, in such a way that the axes of rotation 1 1 a of the shaping tools 1 1 converge towards the contact line R, as illustrated in Figure 2.

Depending on the type of working, one or both the shaping stations 9 can be active.

Operatively downstream of the shaping stations 9 there are further tools 17 (two tools are illustrated downstream of each shaping station in Figure 2) designed to polish the edge B of the slab L already shaped. More specifically, the tools 17 are each provided with a respective grinding wheel 18.

In a second embodiment (not illustrated), the detecting member 12 and the shaping member 10 are mechanically constrained to each other.

In other words, when the feeler pin 13 moves towards or away from the edge B of the slab L, the shaping member also follows the same movement as the feeler pin 13.

In this embodiment there is a single motor, preferably electric, which serves and moves both the detecting member 12 and the shaping member 10. According to this embodiment, the shaping tool 1 1 can be moved relative to the detecting member 12 for determining the working depth of the edge B. In other words, the shaping tool 1 1 can be moved towards the slab L by a further quantity relative to the detecting member 12. In this way, the shaping tool 1 1 is able to remove material from the edge B of the slab L.

In use, the first embodiment of the machine 1 , and more specifically each shaping station 9 performs the following operations.

When the slab L is moved towards the shaping stations 9, the mechanical feeler pin 13, pushed by the pneumatic device 15, moves close to a portion of the edge of the slab, in the example shown in Figure 4 to the corner of the edge of the slab, until it contacts it.

During this step, the shaping member 10 is in the rest position away from the slab (Figure 4). The transducer of the detecting member 12 generates or allows generation of the parameter P representing the position of the portion of the edge B of the slab L contacted.

The signal is sent to the control unit 13 (Figure 4) which generates and sends the command signal C to the shaping member 10 (Figure 5) for determining the position of the shaping tool 1 1 .

The command signal C is received by the actuator 16 which moves the shaping tool 1 1 towards the edge of the slab. The degree of approach of the tool 1 1 depends on the type of shaping to be performed; in this example the tool 1 1 is moved until touching and moving beyond the corner of the slab (eroding it), in such a way as to make a rectilinear shaping (as illustrated in Figure 3).

Any variations in the thickness of the slab are immediately perceived by the feeler pin which, as described above, allows the depth of working of the tool 1 1 to be adjusted, thus allowing a profile to be obtained always having a constant working thickness (or in any case following perfectly the design form and dimensions of the shaping).

It should also be noted that the contact portion 14 of the feeler pin 13 has dimensions of a few centimetres, that is to say, the portion of the feeler pin which contacts the slab has a contact surface of a few centimetres.

This feature prevents small imperfections of the edge, in particular of the corner, of the slab (which are annulled by the action of the shaping tool 1 1 ) from causing variations to the position of the feeler pin (which would cause an incorrect shaping).

In other words, the contact portion 14 of the feeler pin 13 is insensitive to small irregularities or bevels of the corner or of the edge of the slab.

In use, the second embodiment of the machine 1 extracts the tool 1 1 by the quantity necessary to perform the working of the edge of the slab, in other words by a quantity identical to the depth of the recess to be made on the edge of the slab.

Next, when the slab approaches the shaping station 9, the detecting member 12 together with the shaping member 10 are lowered until reaching the edge of the slab.

In this configuration the tool 1 1 is already positioned at the correct operating level and performs the desired working.

It should be noted that there are the above-mentioned advantages also for the operating method of the second embodiment.