The present invention relates to a machine for cutting stone blocks with a differentiated movement. In particular, the machine is suitable for cutting stone blocks such as marble, or granite or natural stone in general, using diamond or non-diamond blades.

In fact, not diamond blades but metal blades (iron) are used if the machine has to cut granite, with the interposition of an abrasive mixture (so-called slurry) essentially consisting of metal grit, lime and water. Machines of this type are known, consisting of a load- bearing structure beneath which at least one block to be cut is positioned, such a load-bearing structure comprises a blade frame inside which at least one cutting blade is positioned longitudinally. The machine comprises means for generating an alternate movement in such a longitudinal cutting direction and such a frame is provided with means for moving the blade frame in a vertical direction towards the block to be cut or vice- versa, meaning that the block moves in the vertical direction towards the blade frame, which is fixed.

The blades consist of a metal structure on which diamond plates are positioned which define the hardest portion that cuts the stone blocks. On machines with metal blades, the abrasive mixture determines the cut. The alternate motion generates the cutting of the blocks. A machine of this type is described in patent EP1089859.

Fine powder is created in the grooves created made by the blades which mixes with the water dispensed. It is known that the presence of such a slurry in the cutting section reduces the effectiveness of the blade action, especially towards the centre of the block where the washing action is less energetic; in order to obviate this drawback, blades are made with diamond segments more concentrated towards the centre of the blades. The slurry (suspension of the sawing dust, centesimal in size in water) tends to settle on the bottom of the cut and the washing action of the wash water of the frame does not always ensure proper cleaning of the cut, due to the output motion which is hindered by the presence of the diamond sectors as one moves from the outside of the block towards the centre of the same.

The aforementioned patent EP1089859 proposes to make the blades oscillate about a central point of the blade frame, making the blades themselves travel along particular trajectories to facilitate cutting.

The invention aims to solve the problem in a decidedly more reliable and effective manner, that is, by lifting the end of the blade frame at each inversion of the motion of the same; this allows the flow of water that drags the dust to better outflow to the outside, improving the cleaning of the cut.

One aspect of the present invention relates to a machine for cutting blocks with differentiated movement having the features of claim 1.

The features of the present invention will become more apparent from the following description and from the accompanying drawings, relating to an exemplary non- limiting embodiment, in which: • figure 1 shows a side view of an embodiment of the machine for cutting stone blocks;

• figure 2 shows a top view of the same machine in figure 1 ;

• figure 3 shows a perspective view of a blade frame of the machine according to the present invention;

• figure 4 schematically shows a side view of one of the guides in which the blade frame slides according to the present invention;

• figure 5 is a schematic figure in which the movement of a blade and the relative deformation upon the inversion of the motion is graphically displayed .

With reference to the above figures, a horizontal machine for cutting blocks comprises a load-bearing structure 2 having four columns 21 connected at the top by longitudinal members 22 and cross members 23. Inside the bearing structure there are a frame or blade frame 3 and a base 4 on which the block B to be cut is placed. The blade frame slides on vertical guides placed on such columns 21 so as to be lowered towards such a block.

In one embodiment, the load-bearing structure is supported on or attached to the floor, while the connecting rod/crank system only moves the blade frame, which comprises a fixed part associated to the mentioned vertical guides and a movable part which slides horizontally with respect to the fixed part and it is connected to the connecting rod. The cutting blades are constrained on such a movable part. In another embodiment of the machine, such a load- bearing structure as a whole is horizontally moved in an alternate motion by a connecting rod/crank system 6. In fact, in this embodiment the structure is engaged in horizontal guides placed at the base of the structure itself that allow it to move horizontally.

Such a connecting rod/crank system comprises at least one connecting rod 61 and at least one crank 62 coupled to a flywheel 63 which regularises its motion. The shaft of the flywheel is set in rotation via a belt 64 which connects it to a motor 65.

Such a frame supports the cutting blades, which are arranged longitudinally side by side.

The forward-back movement imparted by the connecting rod/crank system and the simultaneous lowering of the blade frame causes the cutting of the block.

The lowering of the blade frame is imparted by a motor- reducer system positioned on the frame, which imparts the vertical advancement motion to the blade frame.

In a further embodiment, the blocks are positioned on a block carriage rather than on a fixed base, which is raised progressively during the cutting (feeding motion) , while the cutting motion comes from the blade frame .

In order to cool the blades provided with diamond plates or sectors, pure water is sprinkled on the blocks to be cut by means of a suitable system. In frames with abrasive mixture with grit, the sprinkle consists of such a mixture.

The blade frame 3 is a substantially rectangular or quadrangular structure comprising plates 31 having a high flexural rigidity mutually connected by means of two struts 32 called stringers. Appendages 33 are formed on one of the two plates for connection to the connecting rods 61.

The pack of blades supported by this structure is put under tension by a mechanical or hydraulic tensioner which allows tensioning every single blade and maintaining a constant tension during the cutting process .

Two travel end sensors define the limits of the vertical ascent and descent movement of the blade frame. Two encoders are positioned on the frame at two of the four set screws, control the movement of the frame and check that it is parallel. A mechanical system controlled by a sensor checks on both sides of the block that there is no breakage of a block, in which case the device stops the machine in an emergency .

Means are provided on the blade frame which allow the horizontal movement of the frame in guides 4 of the load-bearing structure. In particular, such means comprise sliding blocks 35 that slide in the guides of the load-bearing structure and that allow the horizontal movement of the frame and that are connected to the plates or to the stays by means of arms 36.

Such sliding blocks slide n said guides 4 and are also equipped with wheels 41 which rotate on a lower plane 42 that copies the shape of guides 4. For the lifting motion, wheels 41 operate on the lower guide 42, while for the inverse downward stroke, wheels 41 operate of the upper guide 4T.

Guides 4 (parallel to each other and arranged one on each side of the blade frame) comprise a central main portion 4C and two end portions 4T slightly curved upwards .

In this way, in the end portions of the guides the blade frame is lifted slightly in the final segment of its stroke, before the inversion of the motion.

Such end portions are roughly 5% of the total length of the guides.

Such end portions are comprised between about 30 and 100 mm (50 mm preferred) in length and the lifting is comprised between about 4-15 mm (7 mm preferred) .

This causes the detachment of a length of blade equal to about half the same, as shown in particular in figure 5, thus facilitating the flow of water and thereby of slurry in said length, towards the outlet in the motion direction before the inversion.

Given the camber of the blades, the first segment of the blade will remain in contact with the material and only the final part will lift proportionally; the phenomenon helps the purge of the slurry only from the part concerned, so as to avoid the bouncing of the same towards the centre of the blades themselves.