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APPARATUS FOR CUTTING GRANITE BLOCKS INTO SLABS BY MEANS OF DIAMOND STEEL BAND

Technical field The present invention is concerned with the stone processing field, and particularly an innovative apparatus for cutting granite blocks into slabs and its relevant tool.

The industrial field of the extraction and processing of granite greatly developed over the years and is in continuous evolution, involving and expanding number of applications.

The granite working process starts in a quarry where big stone blocks are extracted and transported in the working facilities, where the working process begins with a first cut of the block into slabs. Then at least one surface of each slab is polished and finally cut to create tile, kitchen tops, decorative slabs and other. The first phase of cutting the block into slabs is a very slow, critical and problematic operation representing a technological challenge for decades.

In fact, the current block cutting technology implies the use of the so called granite gang saw featuring a plurality of parallel steel blades, tensioned inside a large rectangular frame aimed by a slow reciprocating motion guided by a huge crankshaft system. The cut is obtained by an abrasive material, called grit (small cast iron spheres) suspended in an abundant water flow. The moving frame descends vertically guided, digging grooves in the granite, equal to the thickness of the blades with a cutting speed often below 2-3 cm per hour in case of hard materials. The cutting proceeds at an excessively slow speed producing impressive quantities

of mud which requires special recycling treatment.

The difficulty of the process is not limited to the time or cost, in fact the accuracy of the cut has great influences on cost of the subsequent procedures, especially if the resulting slabs does not have enough parallelism because it heavily aggravates the cost of the polishing process by significantly slowing the process as well as increasing the cost of the diamond tools necessary to flatten the slab surface.

Almost all the manufactures of machinery and tools in this field are trying to use diamond tools to improve the efficiency of the granite block cutting process. Among those attempts, the only alternative to the gigantic traditional granite gang saw is the technology using the saw called wire beads wherein the diamond cutting edge is a bead threaded on a wire. The diamond wire, if suitably tensioned and dragged into the material, has proved to reach easily a cutting speed up to four times faster than conventional gang saw, additionally is used with lighter machines and eliminates as well the costly recycling treatments of the mud. This technique, despite some drawbacks and limitations hereinafter described, is becoming successful and is growing rapidly.

Machines with fifty wires have been developed capable of simultaneously cutting big blocks into slabs with cutting speeds up to five times faster than traditional frames. Recently, an innovative machine has been developed wherein the tool features a plurality of tool holders with brazed cutting tips, linked together by a steel wire, sliding at high speed and guided into a guiding blade suitably tensioned and capable to provide to each tool holder an accurate transversal and vertical guide. Each tool holder features brazed diamond cutting tip and cooperates with the guiding blade suitably tensioned giving to the running tool holders a steady vertical

and transversal guide. A close loop guiding ring allows the re-circulation of the tool holders.

Each cutting tip individually proceeds, and is well guided and properly cooled, and transits at an optimal speed, thus permitting a high efficiency and cutting accuracy to be obtained. Prior art

Italian patent application PC 2003 A 000031, filled on July 21st 2003 titled "Apparatus for cutting granite blocks into slabs" illustrates in details this innovative machine. Unfortunately, this machine despite being the most advanced in its field shows some limitations and deficiencies yet to be improved. For example, the return circuit of the tool holders is full of unavoidable discontinuities that create shocks, noise, and wear out the tool holders quickly. Furthermore, should a single tool holder get out of track and loose orientation, the traction wire brakes, thus resulting in a poor system reliability.

Another inherent limitation is the fact that a variation of a distance between the circuits is still problematic in case the operator wants to change the thickness of the slabs because the flywheels and the circuits would require difficult settings. The main object of this invention is to provide a simple and reliable apparatus for cutting granite blocks into slabs wherein a diamond tool cooperates with a guiding blade while transiting inside the granite block.

Another object of this invention is to provide a multi blade apparatus with several circuits capable to easily change the thickness of the slabs resetting the distance between the cutting circuits. A further object of this invention is to provide an apparatus wherein the diamond

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tool is easy to set and replace. Disclosure of the invention

The present invention achieves these and other objects with a granite block cutting apparatus featuring tools comprising of a plurality of tool holders with brazed cutting tips connected together by a close loop connecting means running at high speed inside guiding blades designed to provide to the tool holders an accurate transversal and vertical guide while transiting inside the granite block to according the following claims.

According to a feature of the present invention the apparatus comprises also a devise adapted to change the distance between the circuits, thus permitting the apparatus to achieve a high degree of flexibility.

Brief description of the drawings

The present invention will be now better described by means of the attached figures wherein: - Figure 1 is a front view of the cutting apparatus and its relative belt tool;

- Figures 2A, 2B and 2C are details of the diamond tool used in the apparatus of Figure 1;

- Figures 3 A, and 3B are sectional views of the guiding blades cooperating with the tool of Figure 2 in the cutting area; - Figure 4 is a variant of the belt and the guiding blade according to the present invention;

- Figure 5 is a front view of a variant of a multi tool apparatus which allows to change the distance between the tools.

Best mode of carrying out the invention In Figure 1 is shown a single blade apparatus similar to the one described in the

above- mentioned Italian patent application wherein the close loop tool circulates pulled by the motorized wheel A rotating in the R direction guiding the tool at cutting speed B.

When the tool enters the granite, a straight blade offers to the tool a vertical and transversal guide. The combination of cutting speed B and vertical motion V allows the tool to cut the granite block G laying in a stationary position between the two columns H. The tool is basically comprising a spring steel belt 1 to which are attached a plurality of tool holders 2 by means of a central pin 3.

A sintered, parallelepiped shaped, diamond cutting tip 4 with a truncated conical section is applied to each tool holders. The figure shows also a partial transversal section of the bottom of the guiding blade inside which the tool slides when transiting into the granite.

It is to be noted that the apparatus in Figure 1 features flywheels with horizontal rotation axes while the blade moves vertically (V) in a plane perpendicular to those axes, as a result, belt 1 is required to rotate of ninety degrees from horizontal immediately before (input) and after (output) the belt transits into the guiding blade.

This rotation is performed by X and Y rollers.

Figure 2A shows an enlarged view of the described tool while figure 2B shows more clearly by means of a sectional view how the tool and the guiding blade are built.

In particular it is shown how the belt 1 partially enters in a longitudinal slot on the upper surface of the tool holder 2 to which is attached by means of a central pin 3.

The tool holder is sketched in a isometric view where it is possible to note the upper slot with width T, lightly thicker than the connecting belt 1, in the tool holder

central portion L while the slot features width S slightly larger in the outer sections to facilitate a free deflection of the belt while winding on the flywheels and or on the directional sheaves A shown in fig 2C. The slot T splits the tool holder 2 upper portion of the tool holder tool in two surfaces 16.

The guiding blade is typically composed by a three layer sandwich out of which two are external elements 5 and 6 and one is internal element 7, all connected by connecting pins (not shown in the Figure). It is to be noted that the height of the connecting central element 7 is reduced compared to the side elements 5 and 6, thus defining a cavity 17 located in the bottom area of the guide featuring a rectangular cross-section inside which, as better described hereinafter, the belt 1 transits. Element 7 allows the bottom ends of elements 5 and 6 to feature two support tips 15 intended to cooperate with the corresponding surfaces 16 of each tool holder. The combined effect of belt 1 running inside the cavity 17 of the guiding blade and the tool holder surfaces 16 sliding against the blade tip 15 offers the transiting tool holders and their cutting tip a double vertical and transversal guide securing a good quality cut. It is important to point out that if each cutting tip is axially coupled to the corresponding tool holder, each cutting tip will contact the granite frontally as well as on both sides.

With some materials, the cutting tip are intentionally applied with a small offset to allow the cutting edge to stick out more from one side than the other one. Installing the tool holders in such arrangement according to a left-right sequence, it is obtainable a cutting tool where each cutting tip cuts frontally and on one side only

thus minimizing the pulling friction.

Figure 2C shows the typical groove shape of the sheaves and driving flywheels of the tool. It is to be noted that the tool is dragged only by belt 1 as the tool holder and its cutting tips are externally protruding. In Figure 3 it is shown a section of the belt tool and guiding blade assembly. In particular, there are shown the belt 1, the tool holder, the cutting edge 4, the guiding blade made by a three layer sandwich with two external side elements 5 and 6 and an internal element 7, the thickness of which is slightly greater than that of the belt 1. Said three elements are connected together for example by a plurality of connecting means 8 A and 8B. More in details the internal element is actually composed of an upper layer 7 and an internal strip 10 featuring the identical thickness. Strip 10 defines an internal passage inside the guiding blade for the supply of cooling liquid through the cut outs 12 and 13 which channels the fluid from the central passage 9 toward the running tool holders. The cooling fluid is supplied from both sides of the blade as shown by arrow 14. Top portion of Figure 3 shows how the sandwiched guiding blade is connected to the machine frame and tensioned along direction A. If observed from the bottom, the guiding blade features to side guiding edges 15 adapted to cooperate with the tool holder surfaces 16 as well as a central slot 17 which is adapted to house and guide the portion of belt 1 extending from the top edge 16 of the tool holders (only a portion of the belt 1 is engaged inside the cavity 17 of the guiding blade).

In Figure 4 there is shown a structural variant of belt 1 in which the belt features protrusions 20 arranged at the position where tool holders 2 are applied. This design allows the belt 1 to face less stress when winding on the flywheels as shown in Fig. 2C.

Figure 5 shows a variant of the apparatus which is different from that shown in Figure 1 in that the blades are arranged vertical. In this multi blade apparatus, the flywheels A, Cl, C2 etc., features horizontal rotating axes while the blade moves transversally on a plane parallel to these axes, belt 1 does not require a ninety degrees rotation. This design allows to build an apparatus with a fixed frame and wherein the piece G moves toward the guiding blades. The main advantage of this design is the possibility to create a multi blade machine where it is easy to change the distance between the blades. The operation of the apparatus is identical to what described in the above- mentioned Italian patent application and is based on mounting the diamond cutting tips on a plurality of tool holders connected by a close loop steel belt also acting as a transversal guide and driving element. A tensioning frame is provided onto which parallel blades are mounted and individually tensioned, each offering a vertical and transversal rigid, as well as lubricated guide for the running tool holders. The combined effect of the rotation of the motorized drum and the relative motion between the frame and the stationary guiding blades allows the cutting tip to proceed individually well guided, cooled and at an optimal running speed thus achieving maximum efficiency and cutting accuracy. From what is described above it is evident that the present invention reaches the aimed objects and particularly it has the following advantages:

- The belt is representing a simple and reliable tool holder driving means

- The belt is suitable for cooperating with the guiding blade giving to each tool holders an optimal transversal guide;

- The tool is well guided and descends in a well defined plane, allowing a good quality slab in terms of superior allowances;

- Maintenance is greatly simplified as the belt can be easily disassembled, the damaged tool holder can easily be individually replaced and the diamond cutting tips can easily be connected to the tool holders;

- The apparatus does not require the use of cast iron grit and produces a much smaller amount of mud which is easier to recycle with a big advantage to the environment.

Of course the described embodiments are presented only as an example and it is possible to apply modifications from a field expert, still remaining within the inventive area protected and defined by what above-described and hereinafter claimed.