As is well-known, in the shoe-manufacturing industry for some time now automatic machines for performing the various steps involved in processing of a shoe have become widespread. In this type of machine, the tool, which is supported by a movable arm, is displaced along a predefined path of the shoe part involved in the specific processing step and carries out the desired operation thereon. In order to perform this operation, it is obviously necessary for the machine, before starting the automatic processing cycle, to undergo a prior"learning"step during which the machine is supplied with the co-ordinates of the"basic"profile of the shoe part on which processing is to be carried out as well as a series of magnification ratios which allow the machine, using this basic profile, to reconstruct automatically the working profiles of the whole range of sizes of the shoe which is to be processed.

In order to perform the learning step, in accordance with the latest known technology, the same machine tool which will perform the final processing step is used. For this operation, the working tool is replaced by a plotting probe, the desired shoe part, in its"basic"size, is placed on the workbench and finally the working arm is used to move said probe over a discrete series of points which are conveniently distributed along the working path. This procedure may be performed both with the working arm in"active"operating mode and with the working arm in"passive"operating mode.

In the first case, the operator enters, with a trial and error method,

via the control console of the machine, the co-ordinates of a first point on the travel path, for example using a cartesian system with three perpendicular axes (x), (y) and (z) and gradually refines these values until the plotting probe is located exactly at the desired point. When this point has been reached, said operator also enters the values relating to the transverse inclination (a) and longitudinal inclination (b) which the tool must have in that particular point-and which the machine is not able to reproduce on the plotting probe since these two movements are normally provided with the tool and are therefore removed with the same-and finally enables the machine, or rather the central processing unit mounted on it, to store this information as that relating to POINT 1 of the travel path. The operation is repeated in succession for several successive POINTS along the working path on the shoe part concerned until said path may be considered adequately characterized over a total number of plotting points which, depending on the shoe model being processed, may vary from 10 to 100.

The total number of plotted points must in fact be sufficient so that the machine, by mathematically interpolating the co-ordinates of said points, is able to follow automatically the desired travel path without appreciable errors.

The procedure when the working arm is used in the"passive" operating mode is not very different. In this case, in fact, the operator, after setting up the machine as described above, manually displaces the plotting probe to the desired point, after which the machine automatically "reads"the co-ordinates (x), (y) and (z) of said point, while the operator, in this case also, enters via the control console the values (a) and (b) relating to inclination of the tool. The simplification which is achieved with this second plotting method is in fact only apparent. Owing, in fact, to the considerable mass of the working arm and hence the inertia thereof, its precise positioning at a desired specific point is anything but easy.

Basically, therefore, the two systems are combined, performing a rough

adjustment in the"passive"operating mode and a fine adjustment in the "active"operating mode of the working arm, whereas in any case the adjustment of the inclination is entered by keying-in angular values, which are often preset as a discrete number of predefined angle values, without this inclination being able to be displayed visually in any way to the operator during the plotting operation.

As is obvious from the description provided above, the plotting operation nowadays still constitutes a significantly long and delicate step.

It in fact requires a specialized operator who is able firstly to identify with certainty the optimum number of points to be plotted in order to achieve a good approximation of the working path and at the same time a plotting time which is not excessively long and who is able, secondly, to evaluate, from a simple visual examination of the shoe part, the numerical inclination values which are most suited for the processing of each of said points, without having the possibility of a direct comparison of the position which the tool would assume at that particular inclination. Also an expert operator in any case requires a period of time ranging from 30 to 60 minutes in order to plot a shoe part and this time has a fairly negative effect on production since the operating machine is obviously at a standstill during this operation.

The drawbacks associated with this mode of operation of automatic machines of the known type are such that even today many shoe manufacturers retain a considerable number of non-automatic machines, not only because of their low cost, but more so because, during small-scale processing which is fairly frequent for fashions shoes or women's shoes, the greater processing speed of an automatic machine is unable to compensate for the long learning time which is required in order to start production.

In the market, therefore, there is an urgent need for an automatic machine which is able to allow plotting of working path of a shoe part in a

shorter period time and using a labour force which is not highly specialized.

The object of the present invention is precisely that of meeting this requirement by providing a machine for automatically processing shoe parts which allows the step involving learning of the working path to be performed in a very short period of time, for example of the order of a minute instead of tens of minutes as occurs at present, excluding moreover any entry of data by the operator via the control console.

Another object of the present invention is moreover that of providing an automatic machine for the processing of shoe parts which is also able to achieve, during plotting, automatic storage also of the transverse and/or longitudinal inclination values of the tool, only on the basis of the actual inclination of the various zones of the shoe part being plotted, i. e. without the operator being required to have the additional capability of recognising the numeric value in degrees of the inclination corresponding to the actual inclination of a given zone of the shoe part being processed.

These and other objects are achieved, according to the present invention, by means of an automatic machine for the processing of shoe parts, characterized in that it comprises: -a working station comprising a working arm with several degrees of freedom, said arm having motor means and carrying a processing tool at its free end, said tool being movable with respect to a reference system consisting of three co-ordinates (x), (y) and (z), and preferably having at least two further degrees of freedom for determining the transverse and longitudinal inclination (a) and (b) of the tool; -a plotting station comprising a plotting arm with several degrees of freedom, said arm not having motor means and carrying a plotting probe at its free end, said probe being movable with respect to a reference system consisting of three co-ordinates (x), (y) and (z), and having preferably at least two further degrees of freedom so as to allow the transverse and longitudinal inclination (a) and (b) of the plotting probe, each degree of

freedom of said plotting arm being provided with means for detecting the position of the elements forming the same; and -a central processing unit suitable for reading and storing the data supplied by said detection means during the movement of said plotting probe along a predetermined path and for using said data to operate the motor means of the working arm, so as to move the tool along an identical path.

According to a preferred characteristic feature of the invention, the degrees of freedom of the plotting arm consist of hinged joints and the position detection means are angular encoders which are integral with an element of the joint and moved by the other element of the joint itself.

According to another characteristic feature of the invention, the automatic machine for the processing of shoe parts also comprises a station for detecting the direction and the position assumed in each case by the shoe part being processed.

The invention will, however, now be described more fully in detail, with reference to preferred embodiments thereof, shown solely by way of example in the accompanying drawings, in which: Fig. 1 is a schematic plan view of an embodiment of the automatic machine for processing shoe parts, according to the present invention; Fig. 2 is a schematic, exemplary, side elevation view of the plotting arm of the plotting station, in an embodiment with six degrees of freedom; Fig. 3 is a plan view of the plotting arm shown in Fig. 2; Figs. 4A, B and C are respectively an exploded plan, side and front view of the end of the plotting arm shown in Fig. 2; Fig. 5 is a front elevation view of the machine shown in Fig. 1, in the direction of the arrow V of said figure; Fig. 6 is a side elevation view of the machine shown in Fig. 1, in the direction of the arrow VI of said figure; Figs. 7A and B show a detail, on a larger scale, of the working

station according to Fig. 1, in which two different positions of the working arm with respect to the co-ordinate (x) are shown; Figs. 8A and B are view which are similar to those of Figs. 7 and in which two different positions of the working arm with respect to the co- ordinate (y) are shown; Figs. 9A and B show a detail, on a larger scale, of the working station according to Fig. 5, in which two different positions of the working arm with respect to the co-ordinate (z) are shown; Figs. 10A and B are views which are similar to those of Figs. 8 and in which two different positions of the working arm with respect to the axis of rotation (a) are shown; and Fig. 11 shows, on a larger scale, the working arm according to Fig. 5 in two different working positions (one shown in broken lines) with respect to the axis of rotation (b).

In the embodiment shown in Fig. 1, the automatic machine for processing shoe parts according to the present invention comprises a fixed support frame 1 and a rotating table 2 which is divided into three zones, corresponding to three different working stations 1, II and 11. In workstation I, the operations involving loading/unloading of the shoe parts as well as plotting of the working path are performed; in workstation 11, detection of the direction, position and size of the shoe parts is performed; and finally in workstation 111, actual processing is performed. The shape of the frame 1 is such that the rotating table 2 is able to rotate freely, conveying cyclically the shoe parts being processed from one to another of the abovementioned workstations.

The processing of a new series of shoe parts with the same shape is firstly performed in workstations I and 11; more precisely, in workstation I learning of the working path which the machine will have to follow automatically on all the shoe parts of the same series is performed, while in workstation 11, the direction, the position and the size of the shoe part are

detected. The operation performed in station 11 is repeated for each shoe part being processed since, as will be seen, the direction and position of the shoe part may vary for each individual shoe part being processed. On the other hand, the operation of plotting the working path in station I is performed once only for each series of shoe parts which are characterized by the same shape.

A new shoe part C, or more precisely a pair of said parts, is then inserted into the station I and fixed onto the table 2 by means of conventional clamping grippers and symmetry locating elements or by means of suction cups (not shown) depending on the type. Whereas, in fact, the bottom of a shoe (namely the upper and, in case, the insole, mounted on a form) can be more easily and securely fixed by the camping grippers 3, the sole of a shoe often does not have a consistency and a thickness such as to allow this type of fixing operation and is therefore simply rested on the table 2 and fixed thereon by means of suction-cup devices or the like. These devices are known per se and do not result in a centred and symmetrical orientation of the sole as in the case of the grippers 3 and the locating elements 4, but only allow a stable position of the shoe part to be defined with respect to the fixed system represented by the frame 1, a position which, even if it is not predefined beforehand, is kept unaltered during rotation of the table 2, such that it can be detected by suitable means in the workstation 11. Obviously the abovementioned fixing means are all simultaneously available in all three zones of the rotating table 2 and in each case those means which are best suited for the particular shoe part being processed are activated.

After the shoe part has thus been positioned, the table 2 is rotated in an anti-clockwise direction so as to bring the shoe part into station 11 where the direction, the position and the size of the shoe part are detected. This operation, which is necessary in order to be able to perform the subsequent plotting operation, will be described in detail below for the sake of a logical

description. When the operation of detecting the direction and the position of the shoe part has been completed, the rotating table is rotated backwards in a clockwise direction into the original position, bringing the shoe part back into the workstation I where the operation of plotting of the working path is performed, as will now be described in detail.

This operation is performed by the operator by simply moving along the said path the plotting probe P of an hinged arm 5 connected to the frame 1 in the plotting station 1. Owing to the particular structure of the arm 5, a structure which will be described in detail below, the arm itself has a very small inertia and is well-balanced, such that it follows in a very soft and precise way each smallest movement which is imparted to it by the operator, both with respect to the position co-ordinates (x), (y) and (z) and with respect to the transverse and longitudinal inclinations (a) and (b). The plotting probe P has, in fact, an elongated shape which allows the operator to evaluate precisely and immediately not only the exact position of said probe P with respect to the shoe part, but also its real inclination- irrespective, therefore, of precise knowledge of the analytical value of said inclination-by adapting it to the shape of the shoe part being processed.

During the movement of the plotting probe P on the shoe part being processed, the central processing unit of the machine automatically learns all the data relating to the path followed by the probe P and will therefore be able to reproduce immediately this path using an hinged support arm 6 for a tool, which is fixed to one side of the frame 1 in a suitable position so as to allow processing in the station 111. As can be easily understood, with the use of the hinged arm 5 the whole plotting operation may be performed in a very short period of time-normally less than one minute and frequently only 10-20 seconds-and it is also possible to perform with great ease plotting of working zones which are very incline, have sudden variations in steepness or also are very high (as, for example, frequently occurs during gluing of the soles of sports shoes, where the sole does not have a regular

perimeter, as in conventional soles, but has extensions which project upwards even over a distance of several centimetres), where the tool must consequently perform more than one pass in order to complete the processing operation.

As has already been mentioned above and as is, moreover, fully evident to a person skilled in the art, the plotting step is performed only once for each type of shoe part, the path being then adapted to the different sizes in the same series and to the right-hand and left-hand nature of the shoe part in accordance with predetermined multiplication and/or symmetry ratios. After this first plotting step, therefore, the station I acts exclusively as station for loading and unloading the shoes, until the series being processed has been completed and the basic model of a new shoe part has to be learned.

Once the plotting operation has been so completed, the rotating table 2 is made to rotate in an anti-clockwise direction through 120° such that the first pair of shoe parts being processed is displaced into the station 11, while the station I is freed so as to allow the insertion of a second pair of shoe parts. The automatic processing of the shoe part, the working path of which has been plotted in the station 1, therefore continues in station 11 in which detection of the direction and longitudinal dimension thereof is performed. This detecting operation is performed in a standard manner also on the first pair of shoe parts, despite the fact that said operation had already been previously carried out as seen above, so as to check for any displacements which the shoe part may have undergone during the plotting operation.

When the shoe part is kept in position by the movable grippers 3, this detecting operation is performed, in a manner known per se, precisely by these grippers which already orient the shoe part so as to assume a symmetrical geometric arrangement predefined by the locating elements 4 and send to the central unit a signal corresponding to the length thereof.

When, on the other hand, the shoe part is simply held in position by suction-cup devices or the like-which, as already mentioned, typically occurs in the case of soles of limited thickness-the direction and the length thereof are detected, in this case also in a manner known per se, by a photocamera or telecamera 7 located above the workstation 11 and able to determine precisely these parameters. For this purpose, the table 2, in the area where the shoe parts are supported, is made of a translucent material and is illuminated underneath such that the profile of the shoe part may be easily detected by means of contrast. In order to obtain a visual field of the photocamera of adequate dimensions, the latter may be arranged at a considerable distance from the rotating table 2 and this would therefore result in an excessive heightwise dimension of the machine and moreover in an awkward position of the photocamera for maintenance purposes. For this reason, according to the invention, it is envisaged that the photocamera 7 is located at the end of an L-shaped tapered reading tunnel 7t which is provided in the angular zone with a mirror 7s arranged at 45° for deviation of the light rays emitted by the shoe part C being detected. With this simple system, the heightwise dimension of the tunnel is halved-without any negative consequence in respect of the widthwise dimension, in view of the fact that the horizontal part of the tunnel 7t does not emerge from the planwise dimensions of the frame 1-while at the same time it is ensured that the vision of the photocamera 7 is not disturbed by light rays which are emitted from the enviroment. The technical methods for detecting the position of the shoe part using the movable gripper system or the television system are widely known to persons skilled in the art and will therefore not be described here in greater detail.

Once detection of the direction, position and size of the shoe part has been performed in the station 11, the rotating table 2 is rotated in an anti- clockwise direction through a further 120°, bringing the first pair of shoe parts being processed into station III, i. e. the working station of the

machine according to the present invention, where finally automatic processing of the shoe parts is performed. The hinged arm 6 may in fact be moved along the desired path owing to the information which the central processing unit of the machine has collecte during the plotting step which took place in station I and during the step for detecting the direction, position and size, performed in station 11.

The processing which takes places in station III and the structure of the hinged arm 6 are obviously variable depending on the specific shoe part handled and the type of processing operation which is to be performed on it and it thus possible to have a machine for gluing bottoms or soles instead of a machine for riveting or for roughening the bottoms or for performing other types of processing operation on shoe parts, all of which are known and may be carried out on the basis of the information received by the central processing unit in stations I and 11 with regard to the working path which the tool will have to follow, of the particular direction and position in each case assumed by the shoe part and finally of its size. It is in fact useful to point out once again that, whereas plotting of the working path in station I is performed once only for each type of shoe part and subsequently station I acts solely as a loading and unloading station, detection of the direction, position and size of the shoe part in station 11 is performed, instead, for each individual shoe part which is processed. In fact, not only the size of the shoe part, but also the direction and position thereof frequently vary when the shoe part is not fixed in a precise position by the grippers 3 and the locating elements 4, but is simply rested on the table 2 in variable positions and directions and retained thereon by the abovementioned suction-cup devices, the function of which is solely that of keeping it in the same position during the whole processing cycle.

The general structure of an hinged arm 5 used in the plotting station I according to the present invention is shown in Figs. 2 to 4. These figures also show in detail the arrangement of the encoders for detecting the

angular position of the individual hinged joints of said arm. In the embodiment shown, which has six degrees of freedom, it therefore comprises a base 8, on which a vertical column 9 is mounted, rotating about its vertical axis d. A first transverse arm 10 is pivotably mounted on the top end of the column 9 about an axis e perpendicular to the axis d. A second transverse arm 11 is pivotably mounted on the free end of the first arm 10, about an axis f parallel to the axis e. The free end of the second arm 11 has, pivotably mounted on it, about a vertical axis c, a bush 12 about an axis b of which, perpendicular to the axis c, a bracket 13 is pivotably mounted. Finally, the top end of the plotting probe P, which is in the form of a thin cylindrical or conical rod, is pivotably mounted on the arms of the bracket 13 and about a horizontal axis a perpendicular to the axis b and the axis c. For greater ease of use, the probe P may be provided with a gripping handle, otherwise and preferably, with an external bush PB coaxial with the cylinder and rotating freely thereon owing to the intervening arrangement of bearings. With this latter arrangement the external bush PB may be held fixed in the operator's hand, while the probe P is free to rotate about its axis during displacement of the probe P itself along the path to be plotted on the shoe part.

The arms 10 and 11 are provided with a balancing system such that the hinged arm 5, or at least a base portion thereof, is always balance, i. e. is in equilibrium whatever its position. The balancing system may be chosen from among those known commercially, for example of the spring or counterweight type. A preferred and also low-cost solution may be obtained by means of use of pneumatic counterpressure cylinder/piston units which are arranged between the column 9 and the arm 10 (indicated by the reference G in Figures 2 and 5) and if necessary between the arm 10 and the arm 11; these types of units are provided with a control system which keeps the same pressure on the two sides of the piston, independently of the position assumed by the latter, therefore perfectly

counterbalancing the weight of the arms in any position.

Owing to this and to the reduced weight of the elements which make up the arm 5-which do not in fact have to withstand any particular stress, in contrast to what happens with the support arm 6 of the working tool, and which therefore may have a particularly slender structure-the displacement of the plotting probe P and its precise positioning along the desired path may be performed with the minimum amount of effort by the operator, thus resulting in the maximum positioning accuracy.

The detection of the positions progressively assumed by the various elements of the hinged arm 5 and their transmission to the central processing unit is obtained owing to the presence of means for detecting the angular position of any hinged joint of the arm 5, consisting of angular encoders 15. As can be clearly seen from the drawings, the body of each encoder 15 is fixed to one of the elements of any hinged joint, whereas the internal rotating part of the said encoder, which is coaxial and integral with an external pulley 16, is rotatably connected, by means of a toothed belt 17, to a pin which is coaxial with the axis of the hinged joint, and fixed to the other element of the hinged joint concerned. Alternatively the encoder is coaxial with the axis of the hinged joint, instead of being offset with respect thereto as shown in the drawings, and in this case the connection to the other element of the hinged joint may be performed directly, i. e. without the aid of the toothed belt.

Thus, for example, the encoder 15 which is designed to detect the angular position of the column 9 is fixed to the base 8 and its pulley 16 is connected, by means of belt 17, to a pin 18 which is coaxial with the axis d and fixed to the column 9. Detection of the angular position of the other hinged joints is performed in an entirely similar manner. Each encoder 15 is electrically connected to the central processing unit which, on the basis of the values received, is able to construct a table of co-ordinates which identify with the maximum precision the working path plotted by the probe

P and the inclinations assumed by the latter along said path.

It is important to emphasize that the working arm 6 which performs processing of the shoe part does not have to have at all a form which is the same as or similar to that described hitherto for the arm 5 supporting the plotting probe P. Once, in fact, the central processing unit has constructed the abovementioned table of co-ordinates of the working path, said table may obviously used for any automatic machine, however formed, provided that said types of machine are all suitable for being operated by means of a co-ordinate based system. It is interesting to note also that not even the structure of the arm 5 shown above, although preferred because of its simplicity, is binding. Any system with a sufficient number of degrees of freedom, however achieved (for example with hinges, slides, ball joints and combinations of these constraints) may be suitable for the purpose, provided that each degree of freedom is provided with a respective encoder able to indicate to the central processing unit the instantaneous position assumed by that particular degree of freedom of the arm during execution of the plotting operation. It is equally obvious that, depending on the type of processing operation, on the degree of sophistication and hence on the cost of the machine, the number of degrees of freedom of the arm 5 may also be different and in particular smaller than that shown above, without thereby departing from the scope of the present invention.

Usefully, the plotting probe P is provided at its free end with a fast- action coupling so as to be able to receive therein probes of varying shapes which are designed to represent in a precise manner the working area of the tool with respect to the action of which the plotting operation is performed.

In this way the operator who performs plotting not only is able to establish with the maximum precision the path which the tool will have to follow, and the inclination thereof, but at the same time will always have visual information relating to the effective working area of the tool itself. This possibility becomes particularly useful in operations where the precision of

the margin of the working zone is of great importance, as occurs for example in carding operations, where an over-estimation or an under- estimation results in an unacceptable deterioration of the upper or respectively in insufficient gluing of the sole.

By way of completion of the present description, operation of the arm 6 supporting the tool U is now described in detail in an embodiment suitable for performing gluing of shoe parts such as soles or bottoms. The various movements of the tool-carrying arm, in order to facilitate understanding, have been shown separately in Figs. 7 to 11 and will now be commented upon below.

It is emphasized firstly that, in the embodiment shown of the machine according to the present invention, a system of polar co-ordinates (x), (y) and (z) has been used, said system allowing the construction of a particularly compact tool support arm.

The movement in the horizontal plane is therefore performed along a linear co-ordinate (y) and an angular co-ordinate (x). The movement along the co-ordinate (y), which is shown in Figs. 7A and 7B, is performed by means of an electric motor 21 which causes rotation of an endless screw 22 parallel thereto; a slide nut-screw is then engaged on the screw 22, said nut-screw sliding on the rails 23 (not shown in the drawings) and hang fixed thereto a plate-like support 24 acting as a movable base for the remaining portion of the tool support arm 6. Figures 7A and 7B show two different positions which said working arm 6 is able to assume following displacements along the co-ordinate (y).

The movement along the angular co-ordinate (x), which is shown in Figs. 8A and 8B, is performed by means of an electric motor 25 which is fixed to the plate 24. The motor 25 causes rotation of an endless screw 26 which comprises at its base a universal joint 27; the same endless screw 26 then engages inside a nut-screw 28 which is hinged with the end of a lever 29 which is in turn pivotably mounted at 30 on the plate 24.

Owing to this construction, when the motor 25 causes rotation of the endless screw 26, the lever 29 performs a rotary movement about the centre of rotation 30, whereas the endless screw 26 oscillates about the joint 27, thus resulting in adjustment of the working arm 6 along the angular co-ordinate (x). A second plate-type support 31 is in fact fixed to the lever 29, the remaining part of the tool support arm 6 being mounted on said plate. Figs. 8A and 8B show two different positions which the working arm is able to assume following angular displacements along the co-ordinate (x).

Figs. 9A and 9B then show the movement along the co-ordinate (z); the second plate 31 supports a vertical-axis electric motor 32 which causes rotation of an endless screw 33 which is parallel thereto and which engages inside a nut-screw 34. In this case the nut-screw 34 is fixed to the plate 31 and it is therefore the endless screw 33 which is displaced axially when the motor 32 is actuated. During its displacement, shown in two different positions in Figs. 9A and 9B, the endless screw 33 causes the movement of a vertical slide 35 fixed thereto, to which slide the end part of the working arm 6, i. e. the tool-carrying arm, is fixed.

The further desired movement of the tool U, i. e. the possibility for it to incline both in the longitudinal direction and in the transverse direction with respect to the shoe part being processed, is finally obtained by combining two different rotation movements of the tool and precisely a rotational movement about a vertical axis (a) and a rotational movement about an axis (b) (see Fig. 1 1) inclined, preferably through 25°, with respect to the axis (a) and rotating with the latter. The rotation with respect to the axis (a), consisting of the shaft 38, is performed by the electric motor 36, fixed to the slide 35, while the rotation with respect to the axis (b) is performed by the electric motor 37 fixed to the abovementioned shaft 38.

Since the axis of the tool U is incline with respect to the axis (b) by an angle equivalent to that existing between the axes (a) and (b) it is

possible to determine, as required, the lateral and longitudinal inclination of the tool U with respect to the shoe part being processed, between O° and an angle equal to twice the angle comprised between the axes (a) and (b), as can be seen from Fig. 11. This figure shows, in fact, in solid and broken lines, the two end positions which the tool U is able to assume, following rotation about the axis (b), in each of the angular positions which the axis (b) is able to assume, rotating about the axis (a). It is obvious, therefore, that by rotating the axis (b) and, together therewith, the tool U about the axis (a), the latter is able to assume any position within a cone having its vertex at the point O of intersection of the axes (a) and (b) and angle at the vertex equal to four times the value of the angle between said axes. In the embodiment shown, in which this angle is equal to 25°, this angle therefore has a value of 100° and is such that it comprises the whole range of the angles which the tool must be able to assume during processing of the shoe part.

From the description given above, it can be easily noted how the automatic machine according to the present invention has fully achieved all the predefined objects. It in fact allows the shoe plotting operation to be performed in a very short period of time, normally much less than one minute and therefore does not affect in any way the productivity of the machine. The operation is performed moreover without the operator having to enter any data into the control console of the machine, not even with regard to the inclination which the tool must assume, and moreover this inclination is perfectly visible during the plotting operation, it being constantly indicated by the clearly visible orientation of the plotting probe.

For these reasons, the plotting operation need no longer be performed by personnel specialized also on automatic machines, but may be performed by workers possessing the basic working ability required for conventional operating machines.

The present invention has been described with particular reference to

the specific embodiment shown in the drawings, but it is obvious that the scope of protection thereof extends to all the possible variants within the grasp of a person skilled in the art, provided that it falls within the scope of the claims indicated below.