EP1013384B1 - Method of punching a flat cable - Google Patents

Description

The present invention relates to a method of punching a cable dish. This technique is illustrated for example by patent US-A-4829375.

Flat cables generally include at least one area conductor laterally delimiting an intermediate free zone whose median plane is intended to contain the axis of the punching; the diameter of the punch being the most often less than the width of said free zone.

This punching is intended to produce orifices used as positioning references for subsequent welding operations automatic cable to auxiliary electrical or electronic components such as only connectors, circuits ...

The punching of a flat cable is carried out in the traditional way by positioning by pressing one of its lateral edges against a side secured to a fixed reference guide.

If necessary, a second sidewall disposed opposite the first provides a elastic support against the other lateral edge of the cable so as to compensate for its possible variations in width.

However, the position of the median plane of the free zone depends closely lateral placement of the conductive area which is not strictly invariable along the cable because of the tolerances allowed for its margin while the position of the punching axis is always fixed since it is linked to the tool position.

The lateral offsets of the median plane of the infill free zone are therefore likely to cause punching faults which then takes place offset from the median plane of the free area.

Thus, traditional processes cannot avoid deterioration conductive area during punching, which seriously compromises the cable quality.

In addition, the subsequent operations of connecting the cable to the members auxiliary electrics which use the holes resulting from the punching as reference points, can then lead to short circuits that we can certainly avoid but by performing manual adjustment operations which are laborious and expensive.

The object of the present invention is to solve technical problems posed by traditional punching processes by making the axis of the punching tool with the median plane of the infill free zone whatever are its dimensions and its position on the cable.

• on fait défiler le câble plat dans un guide latéral tout en contrôlant au moyen d'un système vidéo couplé à un calculateur la position d'un plan de référence situé sur la zone conductrice par rapport à l'axe du poinçonnage, et on la compare avec une valeur de consigne correspondant à la position théorique de ce plan de référence par rapport au plan médian de la zone libre intercalaire pour mesurer le décalage de cette zone par rapport à l'axe du poinçonnage,
• on déplace ensuite le câble transversalement et de façon automatique sur une distance correspondant au décalage mesuré par le calculateur de façon à faire coïncider le plan médian de la zone libre avec l'axe du poinçonnage, puis
• on effectue le poinçonnage du câble dans cette dernière position.

This object is achieved in accordance with the invention by means of a method of punching a flat cable comprising at least one conductive zone laterally delimiting at least one intermediate free zone whose median plane is intended to contain the fixed axis of the punching , characterized in that

• the flat cable is run in a lateral guide while controlling by means of a video system coupled to a computer the position of a reference plane located on the conductive zone relative to the axis of the punching, and it is compared with a set value corresponding to the theoretical position of this reference plane with respect to the median plane of the infill free zone to measure the offset of this zone with respect to the axis of the punching,
• the cable is then moved transversely and automatically over a distance corresponding to the offset measured by the computer so as to make the median plane of the free zone coincide with the axis of the punching, then
• the cable is punched in this last position.

According to a specific mode of implementation, one chooses as plan of references the median plane of the conductive area.

According to an advantageous characteristic, the transverse is moved cable by controlling a motor acting on the lateral cable guide.

According to an implementation variant specific to cables comprising two conductive zones consisting respectively of a group of conductors of small section and a group of conductors of larger section, we measure the offset of the infill free zone using the plane as reference plane median of the small section conductor group.

According to another characteristic, the video system notably comprises a camera associated with fiber optic lighting means.

According to yet another variant of implementation, the position is checked of the reference plane on a stripped part of the cable.

Preferably, the position of the reference plane is then checked while longitudinally adjusting the cable.

The method of the invention allows punching in any safety, without risk of damaging the conductors, whatever are their dimensions and their position on the cable as long as this position remains within allowable tolerances.

The method of the invention makes it possible to use as a reference for the determination of the optimal position for punching an intangible plane which is not not mechanically palpable. The positioning of the punching tool is performed based on the actual location of the conductors and not in relation to a edge of the cable.

Punching produces reference holes for connections cables which are thus placed in optimum positions with respect to to drivers, taking into account variations in margin and center distance.

This process is carried out automatically and continuously, which offers very high rates with a very satisfactory level of quality.

• les figures 1A, 1B et 1C, représentent des schémas illustrant les étapes successives de la mise en oeuvre des procédés traditionnels selon l'art antérieur,
• les figures 2A, 2B, 2C et 2D représentent des schémas illustrant les étapes successives de la mise en oeuvre du procédé de l'invention,
• les figures 3A et 3B représentent des vues en coupe d'un câble sur lequel le procédé de l'invention est appliqué,
• la figure 4 représente une vue schématique d'un mode de réalisation de l'installation utilisée pour la mise en oeuvre du procédé de l'invention.

The invention will be better understood on reading the description which follows, accompanied by the drawings in which:

• FIGS. 1A, 1B and 1C, represent diagrams illustrating the successive stages of the implementation of the traditional methods according to the prior art,
• FIGS. 2A, 2B, 2C and 2D represent diagrams illustrating the successive stages of the implementation of the method of the invention,
• FIGS. 3A and 3B represent sectional views of a cable on which the method of the invention is applied,
• FIG. 4 represents a schematic view of an embodiment of the installation used for the implementation of the method of the invention.

The flat cable section 1 shown in top view in FIG. 1A has at least one conductive area C distributed over ten conductors C1 to C10 of identical dimensions. On this cable, it is planned to perform a punching P axis to make at least one positioning orifice and preferably two punching of axes P1, P2 in the two intermediate free zones located respectively between conductors C1 and C2, on the one hand, and between conductors C9 and C10, on the other hand.

The axes P1, P2 will subsequently be assimilated to the orifices P1, P2.

If the conductors are perfectly positioned on this section of cable, as shown in Figure la, the punching will be done only through free areas and therefore without damaging neighboring conductors.

However, it is frequent that the flat cable, at least on certain sections such as section 11 of FIG. 1B, presents the configuration shown where the left margin is narrower than right margin. It may also be, that the total width of the cable and / or the dimensions of the conductors C1 to C10 or their spacing is modified relative to the arrangement of Figure 1A.

This shift of conductors C1 to C10 to the left which results from tolerances related to the manufacture of the cable, is likely to cause destruction at least partial of conductors C2 and C10 because the position of the tool punching has not changed from Figure 1A.

Indeed, the punching tool ignores the offset of the conductors since it is positioned relative to the only fixed lateral guide G whose side F is kept here in contact with the left lateral edge of the cable under the action of means elastic support A mounted on the right side of the cable opposite side F.

This punching defect has very harmful consequences on subsequent operations of automatic cable connection to one of the components auxiliaries such as a printed circuit R as shown in FIG. 1C.

In fact, circuit R includes conductive zones or tracks C1'-C10 ' and orifices or pins P1 ', P2' intended to be aligned with the orifices P1, P2 resulting from the punching of the section 11 of flat cable of FIG. 1B in view perform an automatic welding operation.

Due to the shift of the conductors to the left and the alignment of the pins P1 ', P2' with the holes P1, P2, the soldering will lead to a short circuit of the tracks C1 'and C2' via the conductor C2 and tracks C9 'and C10' via the conductor C10.

FIG. 2A represents a top view of an identical section of cable 1 to that shown in FIG. 1A, that is to say a section in which the conductors C1 to C10 are arranged perfectly symmetrically with respect to to the median plane of the cable 1 which here coincides with the median plane M of the group of conductors C1-C10 forming the conductive zone.

Punching is carried out in the free zones located respectively between conductors C1 and C2, on the one hand, and C9 and C10, on the other hand, and produces the orifices P1, P2.

Each of the free zones is therefore delimited by two conductive zones adjacent respectively for the free zone P1, the conducting zones C1 and C2-C10 and for the free area P2, the conductive areas C1-C9 and C10.

The theoretical distance Do respectively separating the orifices P1, P2 from median plane M used as the reference plane is determined by a system video coupled to a computer. The calculated or measured value of this distance Do for a perfect cable like that of FIGS. 1A and 2A is taken as the value of set by the computer.

The cable 1 is then run in contact with a lateral guide G having transverse mobility while continuously measuring the position of the midplane M of reference by means of the video system and by determining by means of the calculator the distance D separating the plane M from the axes P1 or P2.

When the position of the plane M is offset on a section 11 of cable and as shown in Figures 1B and 2B to the left relative to the position Theoretical in FIG. 2A, the distance D differs from the set value Do. The comparison between D and Do gives the difference d.

This difference corresponds to the value of the offset of the free zones relative to to the axes of the punchings P1, P2. The difference d is given by the computer which generates then a signal acting on the lateral guide G to automatically move its lateral flank F from a distance d to the right.

This adjustment has the effect of making the median planes of the free areas with the axes of the punches P1, P2.

The following operation consists of punching in this last position shown in Figure 2C.

the cable is then connected to an auxiliary member R in taking care beforehand to align the pins P1 ', P2' of the organ R with the orifices P1, P2 of the cable as shown in Figure 2D.

The offset measurements performed previously make it possible to avoid thus the risk of short circuit.

Figures 3A and 3B show sectional views of another cable 1 to nine drivers. This cable comprises a first conductive zone constituted a group of conductors C1, C2 of large section and a second zone conductor consisting of seven conductors C3-C9 of smaller section.

We choose as the reference plane, the median plane M of the second zone conductor C3-C9 and the optimum position of the P axis of the punching for a perfect cable (Figure 3A). This optimum position corresponds here in the median plane of the infill free zone located between the first and second conductive areas. Once this choice has been made, the punching tool is immobilized on the P axis. The video system equipped with a camera and coupled to the computer measures then the width L of the second conductive zone C3-C9 and determines the position of its median plane M as well as the distance Do, separating it from the fixed axis P.

The distance Do is entered in the computer as a set value. The cable 1 is then run in contact with the flank F of the lateral guide G which is likely to move transversely while continuously controlling the position of the reference plane M with respect to the axis P.

This position corresponds to a distance D which can vary on certain sections of the cable due in particular to the manufacturing tolerances relating to margins and deviate from the original position.

Any variation of the distance D with respect to the set distance Do corresponds to an offset of the median plane of the infill free zone with respect to the P axis of the punching (see Figure 3B).

The computer constantly compares the value of D observed by the video system with setpoint Do.

When the difference (D-Do) is not zero, the computer determines then the gap d and sends a control signal to the lateral guide G cooperating with the elastic support means A for moving the cable over a distance d, in the opposite direction of this gap.

This transverse movement of the cable has the effect of resetting the plane median of the free area in between with the fixed axis P of the punching tool on FIG. 3B, the distance D is greater than Do and the difference d is positive, which controls the stroke d to the left of the lateral guide G and the movement of the cable 1 in the same direction under the action of the support means A until the edge left side of the cable comes into contact with the side F.

If applicable, when checking the position of the reference plane M and the calculation of D is carried out on a stripped zone whose surface is restricted, one will also adjust the longitudinal position of the cable so as to wedge and center the video system optical field on the bare area. It is possible to choose one edges of the bare area as a longitudinal reference.

FIG. 4 represents a schematic view of an installation allowing the implementation of the process of the invention qualified as punching assisted by video.

This installation includes sets of x rollers intended for transfer automatic and continuous flat cable 1 between two storage coils X, Y.

Cable 1 from coil X runs in a lateral guide G in front a video camera V associated with fiber optic lighting means (not apparent).

The guide G comprises a stepping motor T actuating the flank F intended coming into contact with the lateral edge of the cable 1 and which cooperates with means elastic support A arranged opposite (see Figures 3A, 3B).

The punching tool PA is mounted immediately downstream of the system video and thus works on a perfectly positioned cable.

A cable tensioning roller Z is arranged downstream of the PA tool so that both control and measurement operations as well as punching are carried out on a perfectly flat cable. The process is monitored by a control station K equipped with a screen E. The camera V, the guide G and the punching PA are controlled by the computer S.

The control station K is located downstream of the PA tool and is also equipped U video cameras.

Claims (7)

1. A method of punching a flat cable (1) having at least one conductor zone (C) defining laterally at least one intermediate empty zone whose midplane is designed to contain the fixed punch axis (P), the method being characterized in that:

   the cable is caused to pass flat through a lateral guide (G) while using a video system coupled to a computer to monitor the position (D) relative to the punch axis (P) of a reference plane (M) situated in the conductor zone, and it is compared with a reference value corresponding to the ideal position (Do) for said reference plane (M) relative to the midplane of the intermediate empty zone so as to measure the offset (d) of said zone relative to the punch axis;

   thereafter the cable (1) is displaced transversely and automatically through a distance corresponding to the offset (d) as measured by the computer so as to cause the midplane of the empty zone to coincide with the punch axis (P); and then

   the cable is punched in this position.
2. A method according to claim 1, characterized in that the reference plane (M) is selected as being the midplane of the conductor zone (C).
3. A method accordion to claim 1 or 2, characterized in that the cable is displaced transversely by controlling a stepper motor acting on the lateral guide (G) of the cable.
4. A method according to any preceding claim, characterized in that when the cable has two conductor zones (C) respectively constituted by a group of smaller-section conductors and by a group of larger-section conductors, the offset (d) of the intermediate empty zone is measured by taking as the reference plane (M) the midplane of the group of smaller-section conductors.
5. A method according to any preceding claim, characterized in that the video system comprises in particular a camera (V) associated with optical fiber lighting means.
6. A method according to any preceding claim, characterized in that the position of the reference plane (M) is monitored over a stripped portion of the cable.
7. A method according to any preceding claim, characterized in that the position of the reference plane (M) is monitored while adjusting the cable (1) longitudinally.

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