The present invention relates to machines for winding electrical cables and the like.

More specifically, the invention relates to a control system for an automatic winding machine of the type defined in the introductory part of the appended Claim 1.

In order to wind an electrical cable or the like onto the drum or core of a reel having end flanges, one end of the cable to be wound is fixed to the drum. The reel is then rotated about its own axis and a relative translatory motion between the reel and a cable guide is brought about in a direction parallel to the axis of rotation of the reel.

In practice, the perfect formation of adjacent turns on such a reel is hindered by a plurality of factors. The friction of the cable against the drum of the reel, against the underlying and adjacent turns, and against the end flanges may obstruct the running of the cable and give rise to uneven stratification of the turns.

Moreover, the interiors of electrical cables comprise stranded materials which, when they are pulled, tend to twist, imparting a rotation to the cable which can also upset the ordered and regular winding of the cable onto the reel.

Further causes of irregularities in the winding and stratification of the turns are connected with variations in the tension on the cable, the dimensional tolerances of the cable and of the reel, the fact that the flanges of the reel are not precisely parallel, and errors in the devices which control the reversal of the

- relative movement between the cable guide and the reel when the cable reaches the end flanges of the reel.

In order to carry out the winding correctly, the turns of a layer must be arranged side by side as evenly as possible so that the turns of the layer form as compact and uniform a surface as possible to constitute a good support for the next layer of turns. If this does not occur, during the winding of the next layer of turns, the cable may enter any spaces between turns of the preceding layer or be superposed on raised or σver-__ppi_ιg pαrticns of turns of tine preceding layer and may be peπranently deformed under the pressure of the successive layers of turns which may make it difficult subsequently to unwind the cable for use and/or may alter its internal characteristics, possibly compromising its functional characteristics.

When, in the course of the formation of a layer of turns, the cable approaches an end flange of the reel, it must not be jammed between the flange and the last turn wound. If this occurs, it may be difficult subsequently to unwind the cable from the reel for use and the structural and functional characteristics of the cable may be compromised.

In some cases, the inner face of an end flange of each reel onto which the electrical cables are wound has a so-called spiral in which the first turn is wound so that the end of the cable wound on the reel is accessible from the exterior. With these reels, the turns after the first turn have to be wound on the drum or core of the reel in the space between the spiral on one end flange and the other flange. During the formation of subsequent layers of turns the end turn of

each layer which faces the spiral must not fall into the space surrounding the spiral since, if this occurs deformations and stretching may occur which could damage the cable.

Various automatic winding machines with artificial vision control systems have been proposed for winding electrical cables or the like onto reels automatically.

European patent application EP-A-0 129 926 describes a winding machine in which a luminous panel is disposed on one side of the reel and a television camera on the opposite side picks up the silhouette of a portion of the winding in the region of the step formed between the layer of turns being formed and the underlying layer at the point at which the cable is deposited on or supplied to the reel. The television camera is fixed to the cable guide on the axis (the axis x) of the relative motion between the cable guide and the reel and is movable relative to the cable guide in a direction (the axis y) perpendicular to that axis. A microprocessor system analyzes the silhouette of the portion of the winding framed and determines the position of a characteristic point belonging to the turn of the preceding layer onto which the turn being formed is to be deposited. If the position of the characteristic point is displaced from a predetermined position, the control system acts on the motor which controls the relative motion between the cable guide and the reel in order to return the characteristic point to an assigned position. This control is thus based on the indirect observation and the correction of the position of the turn which is being deposited.

European patent EP-B-0 043 368 describes an automatic

winding machine with an artificial vision system comprising an illuminator which projects a light beam onto the reel and a television camera which picks up a portion of the light beam in the region of the last turn wound and, in particular, in the region of the step formed between the layer of turns being formed and the underlying layer. In this machine, the light beam is projected onto the reel and observed by the television camera at an angular position which is markedly offset from the region in which the cable is deposited on or supplied to the reel. According to this patent, the position of the turn being deposited is detected and the relative movement between the cable guide and the reel is regulated so that the angle at which the cable is supplied to the reel is kept precisely and permanently equal to a predetermined constant value.

English patent GB-B-2 221 227 (Ceat Cavi) describes a winding machine according to the introductory part of the appended Claim 1, having a vision system comprising a laser source which projects onto the reel a light beam which intersects the turns at the point at which the cable is supplied to or deposited on the reel.

In this machine, the processing and control system associated with the vision system also analyzes the image picked up and determines the position of the point at which the cable is deposited within a reference system and regulates the relative motion between the cable guide and the reel on the basis of the deviation detected between the observed position of the deposition point and an assigned position.

In this winding machine, as in that described in

European application EP-A-0 129 926, the control system intervenes to modify the relative motion between the cable guide and the reel only after it has detected that the point at which the cable is supplied to the reel has moved, that is, after the turn being deposited has already overlapped or become separated from the preceding turn.

The correction of the relative motion thus achieved serves to prevent the winding from continuing incorrectly but the winding defect v/hich has already occurred cannot be eliminated.

An object of the present invention is to provide an automatic winding machine of the type specified above, in which the control of the relative motion between the cable guide and the reel can prevent the formation of winding defects.

According to the invention, this object is achieved by means of a control system for a winding machine, the main characteristics of which are defined in the appended Claim 1.

A further subject of the invention is a method of winding a cable or the like evenly onto a reel in a winding machine, the characteristics of which are defined in the appended Claims 9 to 16.

Further characteristics and advantages of the invention will become clear from the detailed description which follows with reference to the appended drawings, provided purely by way of non-limiting example. In the drawings:

Figures 1 and 2 are a front view and a side view, respectively, of a winding machine having a control system according to the invention,

Figures 3 and 4 are a sectioned side view and a front view, respectively, of a reel during the winding of the electrical cable coming from a cable guide; Figure 4 also shows a perpendicular cartesian reference frame x, y fixed to the cable guide,'

Figure 5 is a block diagram of an artificial vision and control system included in the winding machine according to the invention,

Figure 6 is a series of three graphs showing examples of curves of quantities monitored during the operation of the winding machine, as functions of time shown on the abscissa, and

Figure 7 is a perspective view of a reel with a spiral for the deposition of the first turn of the winding on an end flange.

With reference to Figures 1 and 2, in the embodiment illustrated, a winding machine (of known type) comprises a stationary support structure, generally indicated 1. The structure comprises two parallel vertical uprights 2 which have respective feet 2a at their lower ends for bearing on the floor or ground T and are interconnected at their tops by a pair of parallel cross-members 3 and 4.

A reel-holding carriage, generally indicated 5, is movable along the cross-members or guides 3 and 4. The carriage comprises, essentially, two parallel

vertical arms 6 and 7, between the lower ends of which a reel 8 is supported rotatably for the winding of a cable or the like.

The arms 6 and 7 have respective wheels or rollers 6a and 7a (Figures 1 and 2) which can run on the cross-members 3 and 4 of the supporting structure 1 in a guided manner. The arms 6 and 7 are connected to respective internally-threaded sleeves 10 through which the ends of a worm screw 11 extend (Figure 1) , the worm screw being arranged horizontally and being rotatable as a result of the operation of an associated electric motor 12. The arrangement is such that the operation of the motor 12 in one sense of rotation and in the opposite sense can move the arms 6 and 7 of the carriage 5 apart or towards each other, respectively, to enable a reel 8 to be loaded between their lower ends or to be removed therefrom.

During the normal operation of the machine, the motor 12 is de-activated and moves along the supporting structure 1 together with the arms 6 and 7.

A capstan 13 is disposed on the carriage 5 above the electric motor 12 (Figure 1) and a cable 12a , for example, of steel, the ends of which are connected to opposite ends of the stationary support structure 1, is wound thereon.

The capstan 13 is associated with an electric motor 14 which can rotate it in a controlled manner in one sense or the other in order correspondingly to move the carriage 5 to and fro along the cross-members or guides 3 and 4 of the support structure 1.

A further electric motor 15 for rotating the reel 8 is carried by the lower end of the vertical arm 6 of the carriage 5.

An angular-velocity sensor 16 such as a tachometric dynamo or a rotary encoder is associated with the end of the other arm 7 of the carriage 5.

As can better be seen in Figure 2, a cable guide, of known type, generally indicated 17, is fixed to the support structure 1. In particular, the cable guide comprises two output guide rollers, indicated 18 in Figures 1 to 3, between which the cable C to be wound onto the reel 8 extends.

The winding machine shown in Figures 1 and 2 is thus of the type in which the cable guide is fixed and the reel 8 is movable parallel to its axis, relative to the cable guide.

However, as will become clearer from the following, the invention is not limited to this type of arrangement but can also be put into effect in winding machines in which the cable guide is moved parallel to the axis of rotation of the reel.

A laser light source, indicated 20, is carried in a fixed position by the support structure 1. The source directs a laser beam towards the reel 8. The beam is indicated B in Figures 2 and 3. The source 20 has associated optical beam-spreader means by means of which a wide, -thin U tbeam is projected onto the reel 8 and can illuminate the reel 8 and the cable C wound thereon longitudinally from one flange 8a to the other flange 8b throughout the travel of the reel 8 along the

guide cross-members of the support structure 1.

In Figure 4, the line of light projected onto the end flanges of the reel and onto the cable already wound thereon is indicated L.

As can be seen in Figures 2 to 4, the source 20 is arranged in a manner such that the line of light L projected onto the reel 8 intersects the portion Cl of the cable C which is between the cable guide 17 and the reel 8 near the point Q at which the cable C is deposited on or supplied to the reel.

As is shown in Figure 3, the arrangement of the source 20 is such that the beam B intersects the portion Cl of the cable near the point Q at which the cable is deposited on the reel 8 throughout the winding of the cable, that is, for every layer of turns formed on the reel, starting from the innermost layer, shown in continuous outline, and up to the outermost layer, shown in broken outline.

A televisioncamera2L (Figures 2 and 5)which, conveniently, has an interference filter, is fixed on the support structure 1 in a position adjacent and offset from the laser source 20. The television camera 21 is arranged and oriented in a manner such that it frames the line of light L projected onto the reel, onto the cable already wound thereon, and onto the portion Cl of the cable supplied to the reel.

As shown in Figure 5, the television camera 21 is connected to a processing and control system, generally indicated 30, including image-signal processing devices which are arranged to analyze the signals supplied by

the television camera. On the basis of the analysis of the signals, as will be seen, the processing and control system 30 monitors, in particular, the region in which the cable is supplied to or deposited on the reel and, by means of interface circuits 31, regulates the speed of the electric motor 14 which brings about the translatory motion of the reel 8 relative to the cable guide 17.

The sensor 16 is also connected to the processing and control system and supplies it with signals indicative of the speed of rotation of the reel.

Conveniently, the processing and control system 30 is formed with multiple-processor architecture, for example, in the manner described in detail in GB-B-2 221 227.

The hardware of the processing and control system 30 is equipped with a set of software programmes for processing the image signals by known techniques and algorithms including connectivity analysis, analysis of the greyness levels, and the detection of edges and other geometrical characteristics. In particular, the system is arranged to detect and describe the shape of the line L of light which is projected by the source 20 onto the reel and onto the cable in terms of cartesian co-ordinates within a reference frame x, y which is fixed to the television camera 21 and hence to the cable guide 17. The reference frame is shown schematically in Figure 4 and comprises an x axis parallel to the axis of rotation of the reel (and hence to the direction of the relative movement between the reel and the cable guide) and a y axis perpendicular thereto.

The processing and control system 30 is arranged, in particular, to determine, within the reference frame x, y, the co-ordinates of a characteristic point, indicated P in Figures 3 and 4, of the intersection of the light line L with the portion Cl of the cable C, near the point at which the cable is supplied to or deposited on the reel. In particular, the characteristic point may be (for example) the central point of the arc which represents the intersection of the light line L with the portion Cl of the cable C.

If the cable C has a diameter D and the speed of rotation of the reel 8 is -∑ ^"" _- (radians/second) , and provided that there is a minimum space o between adjacent turns in each layer of the winding formed on the reel, (to take account of the dimensional tolerances of the cable) , in operation, the entry point of the cable moves along the reel 8 (that is, parallel to the axis of rotation of the reel) at a velocity

V _Q = (D + <5 ) . Λ /2 TT

The processing and control system 30 controls the motor 14 in a manner such that the relative trans.atia ofthe reel 8 withre-φectto the cable guide 17 normally takes place at the velocity V ^* ₀ .

The co-ordinate x _p of the point P relative to the reference system x, y fixed to the cable guide 17 must therefore remain permanently constant and equal to a value indicated x _Q in Figure 4.

Conveniently, the value x _Q assigned to the point P on the abscissa in the reference frame x, y fixed to the cable guide is different for each layer of turns formed

on the reel 8 and can be determined experimentally beforehand, on the basis of the type and diameter of the cable, and stored in the processing and control system 30.

During the formation of a layer of turns, the processing and control system 30 determines the position x _p (t) and the velocity dx_/dt = V _p (t) of the characteristic point P.

On the basis of the data for the velocity of the point P relative to the axis x fixed to the cable guide, the processing and control system 30 can detect a tendency of the co-ordinate x _p of the point P to deviate from its assigned value _Q and can predict the magnitude of the deviation.

Due to the tolerances of the diameter and the surface irregularities of the cable, the instantaneous velocity of the point P relative to the axis x may be subject to appreciable variations. The processing and control system 30 is therefore conveniently arranged to consider, as the velocity of the point P relative to the axis x, a value obtained from a variable average calculated from a series of instantaneous values.

Naturally, if the cable is wound onto the reel evenly, the average velocity of the point P relative to the axis x is equal to zero.

If the average velocity V _p of the point P detected tends to be other than zero, and hence positive or negative, the processing and control system pilots the electric motor 14 in a manner such as to modify the velocity of the relative translation of the reel 8 with respect to the

cable guide 17 in the manner which will now be described with reference to Figure 6.

In this drawing, the upper graph shows an example of a curve of the velocity V _p of the point P relative to the axis x, as a function of time t shown on the abscissa. The middle graph shows a corresponding curve of the velocity V_ _τ of-the relative translatic- ofthereel 8 relative to the cable guide 17 correspondingly imposed by the processing and control system 30 by means of the electric motor 14 controlled thereby.

As the graphs of Figure 6 show, as long as the velocity V _p of the point P is equal to zero or, in any case, is below a threshold Δ V, the, processing and control system 30 keeps the velocity V„_, of the relative translation at thevalue V' indicated above.

If the speed V of the point P exceeds the threshold A V (at the time t. in the graphs of Figure 6) , the processing and control system 30 reduces the velocity V__ of the relative translation from the value V . This reduction may, for example, be carried out with an initial downward slope (as shown between the times t, and t ₂ in the middle graph of Figure 6) followed by a constant reduction (as shown after the time t~) .

The velocity V _RT of the relative translation is reduced for as long as the velocity V _p of the point P is substantially equal in magnitude to the variation imposed on the velocity of the relative translation, as shown at the time t, in Figure 6.

From the time at which the velocity of the point P started to increase from its assigned value of zero and

up to the time t,, the co-ordinate x _p of the point P is slightly greater than its assigned value ₀ , as shown by the lower graph of Figure 6.

At the time t ₃ , the processing and control system causes a very rapid (theoretically instantaneous) change in the velocity oftherelative translaticnof -the reel relative to the cable guide 17 so that the co-ordinate X _p of the point P returns (theoretically instantaneously) to its assigned value x ₀ .

At this point the correction is completed.

At the start of the winding of the cable on the reel, the first turns are usually formed manually. In this condition, the processing and control system 30 is de-activated. After the first turn or turns have been formed, the reel 8 is brought, by the manual operation of the electric motor 14, to a position relative to the cable guide 17 in which the co-ordinate x _p of the point P is round about its assigned value x _Q .

The automatic processing and control system 30 is then activated and causes the reel 8 to move relative to the cable guide 17 by the distance necessary to make the co-ordinate x _p of the point P coincide with its assigned value x _Q . Naturally, at this stage, the processing and control system does not take account of the velocity V _p of the point P relative to the axis x.

As stated above, the value x _n assigned to the co-ordinate x _p of the point P is different for each layer of turns wound onto the reel. In fact, as can be seen, for example, from Figure 4, the turns of one layer are generally offset from those of the underlying

layer .

The abscissa values assigned to the point P can be predetermined experimentally and stored in the processing and control system,- or may be calculated by the system on the basis of the diameter D of the cable, the distance between the cable guide and the point at which the cable enters the reel, the helix angle {*> of the winding (Figure 4) , and the diameter D_ of the layer.

The diameter of the layer may be calculated on the basis of the average of the co-ordinates on the axis y of homologous characteristic points of the intersections of the light line L with turns already deposited in the layer.

The helix angle P of the winding may be derived from the pitch of the helix which in turn can be derived by averaging the co-ordinates on the axis x of homologous characteristic points of the intersections of the light line L with turns already deposited.

When a layer of turns on the reel is completed and the deposition point of the cable is in correspondence with an end flange, the processing and control system 30 can detect the formation of the first turn of the next layer on the basis of the detection of the co-ordinates cf the characteristic point P on the axes x and y.

As regards the reversal oftherelative translatic- of-the reel withrespectto -the cable guide 17 in order to form a new layer of turns, the processing and control system may conveniently also be arranged to control the reversal in the following manner.

In the course of the formation of a layer of turns, the processing and control system 30 determines the distance between the characteristic point P and the end flange of the reel towards which the point is moving. This is possible because the light line L also intersects the flange.

When the distance between the characteristic point P and the flange decreases to a predetermined value, the control system brings about a controlled reduction in the velocity ofthe relative translatLct of "the reel 8 with respect to the cable guide 17. This involves an increase in the angle ^χ_ at which the cable C is supplied to the reel, until the cable C is made to overlap the last turn deposited in order thus to form the first turn of the next layer. This enables the first turn of the next layer to be formed even without the cable striking the end flange of the reel.

After the formation of the first turn of the new layer has been detected, the control system 30 causes a rapid and controlled movement of the reel 8 relative to the cable guide 17 so as to cause the supply angle X'_ of the cable C to assume a predetermined value with the opposite sign to its previous value. The deposition of the subsequent turns of the new layer is then controlled in the manner described above, naturally with the reel 8 trarislatirig relative to the cable guide in the opposite direction to that in which it moved previously.

The fact that the cable can be made to overlap the last turn deposited in order to start the formation of a new layer of turns without the cable C necessarily being brought into interaction with the end flange of the

reel is of particular interest when the reel has a spiral on the inner face of an end flange for enabling a first turn to be formed in a manner such that the input end of the cable is in any case accessible from the exterior once the winding is completed.

Such a reel is shown in Figure 7. The inner face of the end flange 8a of the reel shown in this drawing has a projection 40 with a scroll-like or spiral external profile on which the input end C ₀ of the cable C is positioned. Starting from the end C _Q , the cable follows the external profile of the projection^wfaichis radiallyspaced from the axis of the reel by a progressively decreasing distance and, after it has completed a turn around this axis, at the point C ₂ ,itisbent and passes onto the core or drum 8c of the reel to form the first turn of the first layer of the winding. The subsequent turns are formed on the core or drum 8c until the flange 8b is reached. The next layer of turns is wound onto the preceding layer from the flange 8b towards the projection 40 on the other flange 8a. The various layers of turns must be confined between the inner face of the flange 8b and the plane of the surface of the projection 40 which faces the flange 8b. In other words, when new layers of turns are started near the projection 40 of the flange 8a, it is important that the cable does not enter the space between the plane of the inner face of the flange 8a and the face of the projection 40 which faces the flange 8b.

Ihe central techniquedescribed above for reversing the winding prevents this problem which might otherwise cause deformations and stretching which could damage the cable.

Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the present invention.