Several systems are present on the market for hot-wire cutting works of foamed plastic materials, of the types both with two axes only, and with manny axes under a computerized numeric control; these systems use a heated wire as element for melt-cutting the material.

The wire is subtended in order to obtain a stiffness through a mechanical tensioning that is enough not to determine the possible catenary by flexure during the cutting works.

When it is heated, the wire expands in its length and therefore the system needs a tension compensation.

The two-axes machines, realised with a closed or projecting portal, contain two linear axes that are vertically arranged.

On these axes, the related trolleys (Y axis) are sliding, to which the wire is connected at its ends. The trolleys are moved in synchronism since a torsion bar connectes the two related driving pulleys. The trolleys are then synchronously moved along a Y-stroke, so that they realise trajectories where, in every position, the wire is always parallel to itself.

The second axis (X axis) is hortogonal to the system, and is anyway realised either by a closed- band mat, where the material being worked rests, or by moving the portal structure itself that contains the Y vertical axes; the material in this case rests on a fixed plane.

The systems with multiple axes aim to obtain stretched-wire movements, so that this is not exclusively parallel only but can assume different skews in space.

These machines are realised in a similar way to the former ones, but their linear vertical axes are autonomously moved and they move along the X alignment, each one through a further axis.

The material being worked on the X axis is placed on a fixed plane or is moved by a mat to obtain the longest possible working length.

Such geometric arrangements support the wire through the two hookings. These hookings therefore are never oriented on the same axis with the wire, apart from the condition of a perfectly hortogonal working only.

All this does not allow an intelligent management of the cooling of the wire itself at its ends, since the cooling fans not always are along the same axis of the wire.

This geometry, as regards the wire length, still needs a greater tensioning-compensating length.

Object of the present invention is solving the two above prior-art problems, by providing a system with an innovative cylindric geometry that allows the maximum working flexibility and accuracy with a rational and compact arrangement, suitable for a very high number of applications.

The above and other objects and advantages of the invention, as will appear from the following description, are obtained by a system as claimed in Claim 1. Preferred embodiments and non-trivial variations of the present invention are claimed in the dependent Claims.

The present invention will be better described by some preferred embodiments thereof, given as a non-limiting example, with reference to the enclosed drawings, in which: -Figure 1 is a a perspective view of an embodiment of the system according to the present invention; -Figure 2 is a perspective view of a further embodiment of the system according to the present invention applied to an existing machine; -Figure 3 is a plan view of the system in Fig.

2; -Figure 4 is a side view of a tool that can be applied to the system of the invention; -Figure 5 is a perspective view of the tool in Fig. 4 used for hot-wire cutting; -Figure 6 is a perspective view of the tool in Fig. 4 used for hot-shaped-wire digging; -Figure 7 is a top view of a product worked with the system of the invention; -Figure 8 is a sectional view made along line VIII-VIII in Fig. 7; and -Figure 9 is a sectional view made along line IX-IX in Fig. 7.

With reference to the Figures, the system 1 of the invention is shown that allows performing hot- stretched-wire cutting operations and hot-shaped- wire digging operations for working thermoplastic materials, and in particular foamed materials such as polyurethan. The system 1 of the invention, however, with small constructive modifications, could be applied in a similarly efficient way to all workings where a wire is used for cutting material, such as for example for working marble.

The system 1 comprises a support frame 2, in this case realised vertically resting on feet 5; such support frame 2 vertically supports a framework structure 3 that is oscillating along a fixed vertial axis R passing through the center of the structure 3 itself. This oscillation is obtained, in the embodiment shown, through a support 7 shaped as an arc of a circle that operates as guide for rotating the structure 3, for example by the angle +a,-a shown in Fig. s 1 to 3.

The structure 3 supports two independent vertical axes Y1 and Y2 that can be moved along the framework along the direction of arrows A in Fig. 1 (for example in positions Y1'and Y2'shown as dashed in Fig. 1) and fixed by tighening them on a clamp in order to be arranged by an operator according to the width working needs. To the two vertical axes Y1 and Y2 are respectively connected two ends of the cutting wire 9, through hooking anchors 11,13: in Fig. 1 the wire 9 is shown in two different operating positions. The wire 9 is connected at its end 11 in order to be wound or unwound according to the line to be cut: this allows obtaining a shorter length of the wire 9 and therefore whose range is smaller.

Measuring rows (not shown) help the operator in positioning the vertical axes, in positions that can be both at the same distance, and not at the same distance from the center of the axis R, in order to obtain the maximum operating flexibility.

The oscillation of the framework 3, on which the two linear axes Yl, Y2 are assembled, creates a constantly-oriented gemoetry of the hookings of the wire 9 on the axis of the framework 3, limited to the framework 3 plane. The total orientation of the hookings for the wire 9 also on the axis of the wire 9 itself is determined as follows.

The vertical axis Y2 moving like a trolley comprises a further partial rotation axis RR; this rotation axis RR is horizontal with respect to the ground. All the above axes R, Y1, Y2 and RR, in addition to the axis X perpendicular to the framework 3, are controlled by a computerized numeric control, schematically shown in Fig. 1 with reference number 15, since it can be immediately and commonly realised by a skilled person in the art.

The vertical axis Yl moving like a trolley also comprises a movement along the rotation direction RR'similar to the axis Y2: such movement is not controlled by a numeric control, but is free on a bearing in a self-aligning way with the movement of the axis Y2.

The hooking of the wire 9 gets an orientation that is on the same axis of the wire 9 itself because it is self-aligned due to the tension of the wire that passes through a guiding rudder placed on the support 13 next to the self-aligning bearing.

It is evident, therefore, that the two hooking anchors 11,13 of the wire 9 at the end remain perfectly oriented along the same axis of the wire 9 itself, solving the venting need for the wire 9: in fact, the common fans placed along the same axis of the wire 9 in order to keep its temperature at a tolerable level go on venting the wire 9 along its axis, guaranteeing an optimum cooling thereof.

The hooking 11 of the vertical axis Y2 contains a wire tensioning and length-compensating system with release and recovery of the wire to and from a coil: such system is built in a common way for a skilled person in the art.

The axis X is realised with a bar 17 with bearing whiskers 19 that can be moved and replaced for different working lengths. The bar 17 moves along a fixed trolley resting on the ground on stable feet 17'.

The axis X can be also realised with two bands clamped on a closed ring (not shown), arranged one next to the other and that can be moved away according to the length being worked, and synchronously handled (as if they made a single variable-width mat).

A different arrangement is possible where the material rests on a fixed table and the axis R with all the framework is driven on the axis X.

The version as described above then provides for a cutting work with a hot stretched wire.

The same system, without losing the material position references, by replacing on the vertical axis Y2 the tensioning and recovering tool 11 for the wire 9 with a digging tool 21, allows performing digging works with a hot shaped wire 9' of the desired shape. The two possible configurations are respectively shown in detail in Fig. s 5 and 6, while Fig. 4 shows the detail of the digging tool 21.

Such tool 21 is composed of a moving box 23 that moves a linear axis Z with a limited stroke, which on its end towards the machine interior, where the material is placed, supports a suitably- shaped rigid wire 9' (as if it were the bit of a tin welder). The heated rigid wire 9' (through an electric supply from small cables 24) performs digging processes according to the interpolated movements of the affected axes, among which also the rotation on the axis RR (to which the tool 21 is coupled in point 25), that allows realising an angle + (3,-f3 as shown in Fig. 6. Such interpolation is completed by a further rotation axis RRR, also under a computerized numeric control. Such axis RRR allows tangentially arranging the shaped wire 9'.

This geometry allows in such case to make it possible to work the material 31 on the affected face 33 or 35, with the chance of undercut penetration into the material 31 itself, as respectively appears from Fig. 8 and 9 referred to the material shown in Fig. 7, and with the chance of performing tangential edge-cuttings.

The system allows, through a suitable software, working bassorilievos with undercut, cube-shaped letterings with tangential outline- working of the bevel (obviously only on the visible side).

For the latter working, first digging and edges are performed, and then the tool 21 is replaced by what is useful for wire-cutting to perform the cutting itself: all this can be obtained without losing material position references.

As shown in Fig. s 2 and 3, the system 1 of the invention can also be added to a currently-marketed machine, whose support frame is shown by analogy with reference 2, in order to make the existing framework 3'hinged to the axis R'and able to be fixed: in this way the framework 3'is not rigid in an hortogonal position, but can be slanted and secured in some way, which makes the system more widely usable. In Fig. 2, reference number 9 shows the wire in position on the system 1 of the invention, while reference number 9"shows the wire in its typical position on a common two-axes machine.

In the plan view in Fig. 3, in order to obtain a skewed working, it is necessary to place the material 41 in a non-hortogonal way: the cutting with wire 9 performs what is needed on a rather short length of material 41.

With the suggested arrangement of the wire in position 9"', the machine can be used as in 43, and therefore for all its length.