******* TECHNICAL FIELD The present invention relates to a device for the advancement of a necklace in a machine provided with a diamond tool, for workings in the jewellery field, said device guaranteeing an advancement which is gradual and by a predetermined pitch of a certain necklace, for example a golden necklace, on which one intends to carry out a predetermined finishing and working operation.

The present invention makes it possible to perform the carving of a predetermined drawing in a completely automatic fashion and with the maximum precision.

The device according to the present invention finds a particularly suitable application in the industrial jewellery art field.

BACKGROUND ART Machines for the working and finishing of golden necklaces and similar items are known in the art, that comprise diamond tools, by which the operator in charge of operating said machines sets the necklace in motion manually and decides the advancement speed as the working he is carrying out goes from one stitch to the following ones.

Machines of this type are provided with a suitable rotating drum which consists of a pair of disks mutually coupled by a hub to which said disks are joined.

The disks of which above give way to a route for the sliding of the necklace to be worked and finished that comes from a roll around which it had been previously wrapped.

A suitable tool generally made of a diamond cutter supported by an electric mandrel and rotating at high speed, is located in a predetermined position, above the side of the drum, so as to be able to carry out workings on a given stitch of the

necklace.

Basing on such an operational method, it results to be clear that both the expertise and the deftness of the operator in charge of the diamond tool machine for the accomplishment of the chosen working are of paramount importance.

Therefore, it is obvious that on the basis of the operational methods of the background art, it is impossible to guarantee a total reproducibility of certain workings on each stitch, such a thing affecting the overall quality of the final product and consequently requiring the application of certain handicraft skills to the production of the items detailed above.

DESCRIPTION OF THE INVENTION The present invention aims at overcoming the disadvantages and drawbacks of the prior art, by providing a device for the advancement of a necklace in a machine provided with a diamond tool for workings and finishings in the jewellery field that makes it possible to memorise the dimensions of the stitches of the necklace which is being worked, as well as the forward movements of the necklace itself, by dint of a suitable electronic control, in so doing guaranteeing optimal precision and reproducibility levels of the drawing that one intends to reproduce on each stitch of a given necklace.

This is obtained by putting in practice the features described in the main independent claim.

Dependent claims outline particularly advantageous forms of embodiment of the present invention.

The device according to the present invention is equipped with a stepwise operating motor to each round or fraction of round thereof a predetermined advancement route of the necklace which is subjected to working is made to correspond by a suitable motioning system herebelow described in detail.

By means of a specific control electronics, advantageously of the numeric type, said system makes it possible to fix working parameters for a certain necklace and to carry out an automatic working cycle that is capable of yielding to a final high quality product at the end of a manual working cycle which is necessary in order for the setting of the chosen data to be made, by automatically repeating on each stitch the slit that had been previously set.

According to the present invention, the device object thereof is equipped with sensors that are suitable for constantly monitoring the position and the movement of

the necklace in order to ensure a prompt control of the necklace in whatever moment at whatever stage of the working it is being subjected to.

ILLUSTRATION OF DRAWINGS Other features and advantages of the present invention will be more evident from the reading of the following detailed description given by way of not limiting example, with reference to the drawings in the attached tables, where: -figure 1 shows a side view of the device for the advancement of necklaces according to the present invention; -figure 2 shows a plan view from above of the device shown in figure 1, and -figure 3 shows a cutaway view of a system for the temporary blocking of a necklace, said system belonging to the device object of the present invention.

DESCRIPTION OF A FORM OF EMBODIMENT In the drawings, reference number 10 is given to an automatic machine for the working of a necklace by means of a diamond tool, equipped with a device for the advancement of the necklace itself according to the present invention.

Once necklace 11 to be subjected to working, advantageously a golden necklace, has been suitably unwrapped from a suitable supporting roll (not shown), it reaches a disk clamp 12 shown in detail in figure 3.

With reference to said figure 3, disk clamp 12 consists of a pair of discoidal shells 13,13'joined with a cylindrical element or hub 14 fixed loose so as to be suitable for rotating freely, jointly with the pair of shells 13,13', around an axis A which is perpendicular to the advancement direction X of necklace 11.

The discoidally shaped shells 13,13'are suitably shaped and distanced from each other so as to give way to a groove 15 that acts as a leaning surface for necklace 11, the sides of groove 15 being obtained from the inside perimetral surfaces of said shells 13,13'.

Said inside perimetral surfaces are suitably shaped so as to allow a correct and stable positioning of necklace 11 which, once unwrapped, is laid onto the base surface of groove 15 that is the working surface for diamond tool 16 which is suitable for carrying out a predetermined working of the necklace itself.

According to another aspect of the present invention, disk clamp 12 is devised in such a way that the inside surfaces of said discoidally shaped shells do not result to be parallel with each other, therefore that one of these results to be tilted towards the inside of groove 15 forming a predetermined angle, a suitable piston device 26 being provided, that acts on disk clamp 12 by displacing one of disks 13,13'detailed above so as to narrow the section of groove 15 and block, necklace 11 during the working phase at a predetermined point along a stitch thereof in an intermittent fashion.

According to the present invention machine 10 further comprises an automatic device 40 for the advancement of necklace 11 according to a predetermined pitch.

Device 40 comprises a central body 41 fixed to an element 42 equipped with a pair of vertical holes (not shown) for the vertical positioning of body 41 itself, and with a pair of horizontal holes 43 for the positioning of the unit formed by element 42 together with central body 41 onto machine 10.

A stepwise motor 17 is joined with one end of central body 41,, whereas inside the central body itself a sliding block 18 is located, which is linked with motor 17 by a ball bearing screw 20.

At one end of sliding block 18, on the side from where this protrudes from central body 41 towards diamond tool 16, a jack 21 is centred, and this is set in motion by a piston 25; at the free end of said jack 21 a plate 22 is located, said plate supporting a hook 23 which is suitable for accomplishing the advancement thereof during the working phase.

The operational phase consists of the steps detailed herebelow.

The operator in charge of machine 10 correctly positions and blocks central body 41 and sledge 42 with respect to machine 10, basing on suitable coordinates chosen by himself.

At the initial phase of the working cycle, a"zero"retreat position is marked for the sliding block 18.

A suitable sensor 24 memorises said"zero"position and the coordinates taken from it are memorised by a suitable electronic logics and set for the calibration of advancement device 40 according to the invention.

This means therefore that the control logics associated with device 40 is bound to calculate the displacements of necklace 11 along advancements direction X, accounting for said coordinates.

After that, sliding block 18 is displaced forward towards diamond tool 16 and

jack 21 ends up finding itself in a lowered position in order for the hook 23 to be capable of gripping onto a stitch of necklace 11.

Once the stitch has been hooked to the necklace, sliding block 18 is moved backwards by a translation covering a predetermined distance, said distance generally corresponding to the length of a single stitch, or to a multiple of said length; at the same time the diamond tool 16 carries out the working of the upper surface of necklace 11, which is held firm by disk clamp 12.

According to a form of embodiment of the present invention, once the working of a given stitch or of several adjacent stitches of necklace 11 has been accomplished, piston 25 acts on jack 21 taking it to its raised position.

After that sliding block 18, which is now disengaged from necklace 11, is now capable of being taken back to its initial position, which is suitable for hooking another stitch and starting a new working cycle.

According to the present invention, the first working cycle on a stitch or on more successive stitches is carried out manually by the operator in charge of machine 10.

In fact the operator is able to set the working parameter values which are necessary for the execution of a desired specific working.

Once the first cycle has been completed in a fully manual fashion, it is possible to carry on with the working in a completely automatic way, on the basis of the data collected by the sensors and set by the operator during said first cycle.

It ought to be stressed in fact that the movement of the necklace by a predetermined stretch which equals the length of one or more consecutive stitches depending on the chosen operational modalities, is directly linked with the number of rotations made by the rotor of stepwise motor 17.

Said motor 17 in fact makes it possible for necklace 11 to be set in motion according to a predetermined pitch, on account of the fact that every rotation or fraction thereof of the motor causes an advancement of the necklace by a precise stretch which is measured by the logics control using an initial position as the bearing point.

Device 40 according to the present invention is equipped with a further series of sensors which are connected with said control logics, that make it possible to monitor the correct functioning of the device itself.

A sensor is provided on supporting plate 22 of hook 23 which is capable of

engaging necklace 11, said sensor being capable of interacting with the edge of disk clamp 12 and of spotting the exact position of said hook 23.

Another sensor supplies a representative signal of the raised or lowered position of jack 21 and, therefore, of the hooked or not hooked state of necklace 11. A further sensor fulfills the task of emergency sensor, operating and blocking the functioning of the machine whenever the sliding block 18 gets too close to diamond point 16 beacuse of the risk jack 21 runs of hitting said point.

As it was mentioned above, the functioning of disk clamp 12 is caused by a piston 26 that acts towards misaligning one of the two discoidally shaped shells 13, 13'from the other.

In fact piston 26 operates on disk clamp 12 in order to alternately block and unblock necklace 11 which is positioned inside groove 15 so as to make the working with diamond tool 16 viable.

By means of piston 26 and the traction on the necklace exerted by stepwise motor 17 it is possible to keep necklace 11 at the right tension during the working phase with tool 16 involving a given portion of the stitch itself.

According to the present invention, piston 26 is equipped with a sensor by which the control logics is capable of determining its exact position.

According to the invention, another sensor is further provided in order for it to adjust the raising stroke of the electrohub and therefore to make it possible to accomplish a correct positioning of diamond tool 16 with respect to necklace 11 that is bound to be subjected to working.

According to a further feature of the invention, machine 10 is provided with an electronic control logics by which all components of the machine are adjusted and synchronised.

This feature makes it possible to automatically perform all the working cycles that follow the first cycle which is itself manually carried out by the operator.

Such a control logics is provided with a data interrogation and setting interface and it comprises a screen equipped with a display keyboard by which the operator defines and memorises the displacements necessary for the accomplishement of a given incision.

For example, the operator sets the dragging distances of the necklace, the moment when to lower or raise the jack, the moment when the diamond tool must cut and not cut, the"zero"point calibration, and so on.

According to a particularly advantageous form of embodiment of the present invention, it is possible to set an execution programme according to which machine 10 automatically performs workings that differ from stitch to stitch according to one or more previously chosen sequences.

The invention has been described particularly according to one of its forms of embodiment, according to which the"stepwise"positioning of the necklace along a cartesian axis is electronically controlled so as to be capable of being reproduced with extreme precision in a continuous fashion.

It is nevertheless evident that the invention is not limited to the form of embodiment herein detailed, but that it comprises all the modifications and variants that may well be taken into consideration, without stepping out of its scope, said scope being defined by the claims.

By way of example, there are found to fall into the scope of the present invention some of its forms of embodiment according to which displacements along the other two cartesian axes are also electronically controlled in such a way as to be capable of being reproduced on a continuous basis.