MATERIALS

DESCRIPTION

The present invention relates to a drive pulley for supporting cutting tools of machine tools for processing stone materials.

It is known in the technical sector of machines for processing stone materials to use so-called multi- wire machine tools for cutting blocks into sheets; said machines are generally formed by a column-type support structure having, mounted thereon, two or more pulleys/drums, one of which has a driving function and the others of which are idle, said pulleys/drums having, mounted thereon in a closed loop, the cutting tools of the type consisting of diamond-coated flexible wire, i.e. wires with a steel core onto which sintered diamond beads (metal sleeves) are mounted.

It is also known that said diamond-coated wires are normally prepared in the form of a closed loop and directly installed on the machine, being wound onto a drive pulley/drum provided with a plurality of grooves formed on its annular surface and onto one or more idle transmission pulleys.

In order to prevent slipping of the wires during rotation, the drive pulley is in turn coated with elastomer products which are glued to the metal surface of the pulley itself and then undergo turning in order to obtain the seats required for seating the diamond-coated wires.

Although performing their function, these known pulleys nevertheless have the drawback that, when the elastomer becomes worn as a result of the abrasion produced by the diamond-coated wires, it is required to change the drive pulley which must be disassembled from the machine and replaced with a new pulley already prepared, resulting in significant handling difficulties owing to the size of the pulleys and the consequent prolonged downtime of the machine tool.

In addition to this, the drive pulley must operate simultaneously all the cutting wires with the same speed, being subject to a high frictional force which may cause relative slipping between the pulley and rubber-lined coating, thus resulting in the driving movement not being transmitted to the wire which, instead of rotating, cuts into the drive pulley rotating in contact therewith.

WO 2009/001242 and WO 2009/040870 disclose driven pulleys lined with rubber sheaths for seating the wires; however, in the case of driven pulleys, the problem of relative slipping does not arise since each driven pulley is independent of the other pulleys and it is the wire which transmits the driving movement to the pulley, and not vice versa, the latter therefore rotating always without relative speed with the wire itself.

The technical problem which is posed, therefore, is to provide a drive pulley for cutting wires of machine tools for processing stone materials, which is able to ensure rapid return to the working conditions when the maintenance due to wear of the friction coating of the pulley itself is required and which at the same time is able to prevent relative slipping of pulley and rubber lining which guides the diamond-coated wire.

In connection with this problem it is also required that the pulley should be easy and inexpensive to produce and assemble and should be able to be installed easily also on already existing machines without the need for special adaptation.

These results are obtained according to the present invention by a drive pulley for supporting cutting tools of machine tools for processing stone materials, comprising a body provided on its circumferential surface with radial engaging means extending annularly and parallel to each other, and strips made of material with a high coefficient of friction and provided, on their inner surface, with means for engaging with said pulley means, said strips having on their outer surface seats for receiving the cutting wires.

Further details may be obtained from the following description of a non-limiting example of embodiment of the subject of the present invention provided with reference to the accompanying drawings in which :

Figure 1 shows a schematic view of a machine for cutting stone materials with a drive pulley according to the present invention ;

Figure 2 shows a front/side view (completely round profile) of the drive pulley according to the present invention; Figure 3 shows shows a schematic cross-section along the plane indicated by I-I in Fig. 2 and

Figure 4 shows a schematic cross-section along the plane indicated by IV-IV in Fig. 2. As shown in Fig. 1 and assuming solely for the sake of convenience of the description and without any limitation of meaning a pair of reference axes in a diametral direction X-X and transverse direction Y- Y, respectively, the pulley 20 according to the invention which is mounted on a machine tool 10 for supporting diamond-coated wires 11 wound in a closed loop around idle pulleys 12 comprises essentially :

a body 21 which has, formed on its circumferential surface, annular grooves 22 which are parallel to each other and have a suitable - for example, but not necessarily, trapezoidal cross-section and which are preferably, but not necessarily, continuous and are spaced from each other in the transverse direction Y-Y at a predefined interval.

- strips 30 which are made of elastomer material with a high coefficient of friction and which have a cross-section corresponding to that of the grooves 22 of the pulley so as to form:

• inset seats 31 on the outer surface for receiving the wires 11 and

• projections 32 on the inner surface, said projections 32 having a cross-section corresponding to that of the grooves 22 so as to be able to engaged with them.

Preferably the relative dimensions are such that engagement between the projections 32 and the respective grooves 22 occurs with slight forcing. At the opposite longitudinal ends, each strip 30 has fastening means 34 for performing joining to the other end of the said strip in the longitudinal (i.e. annular) direction and means 35 for performing fixing to the body of the pulley in the transverse (i.e. radial) direction.

Preferably, the means 34 for fastening together the strips are of the interlocking type, for example with a dovetail form or regular profile as shown, and the fixing means 35 consist of mounted plate- like elements 35a provided with eyelets 35b for receiving locking screws 35c which are suitably positioned in order to ensure a distribution which allows the dynamic equilibrium of the pulley to be maintained .

It is therefore clear how the pulley according to the invention is able to provide a solution to the problems of the prior art: since, in fact, all the strips are independent of each other it is possible to perform rapid replacement of the single strips of worn elastomer material without having to disassemble the entire pulley, with a consequent reduction in the maintenance costs and the machine downtime .

Although described in connection with preferred examples of embodiment, it is also envisaged that the pulley may have an annular surface with projections instead of grooves and that correspondingly the strips of polymer material may have grooves instead of reliefs in their bottom surface for engagement with the pulley.

In addition to this, the choice of material for the annular strips may be different from polymer materials, provided that a functionality in accordance with the objects of the present invention is ensured.

Although described in connection with certain constructional forms and certain preferred examples of embodiment of the invention, it is understood that the scope of protection of the present patent is defined solely by the following claims.