EP1443601B1 - Method of making contact strips for connectors of electrical apparatus - Google Patents

Description

The invention relates to a method of manufacturing contact strips for electrical equipment connectors, said contact strips being obtained by segmentation of a secondary band of contacts made from a metal strip. Recesses are made with a regular initial pitch in the metal ribbon to form a discontinuous central strip of lamellae whose longitudinal ends are attached to two continuous lateral bands of the ribbon, each of said lamellae undergoing a twisting operation about its longitudinal axis to rotate relative to the plane of said ribbon, each lamella further undergoing a bending operation so that each of its two faces has at least one protruding zone to form a contact on one side of said plane. Said twisting and bending operations make it possible to obtain a primary contact strip whose lamellae are substantially spaced at the same regular pitch as the initial pitch of said recesses. The method further comprises a pleating operation of said primary contact strip consisting of forming folds on each lateral continuous strip so as to bring the lamellae together, and also comprises a curing heat treatment operation intended to give the slats hardness properties combined with some elasticity for them to behave like springs.

Such a process is known from the patent document FR2811147 , for which the tape used in the process is not necessarily metallic. In practice, a beryllium-based alloy is often preferred. The Central part of one side of the ribbon is covered with a layer of a metal that is good electrical conductor, for example money. One edge of each lamella is folded hem in the direction in which the conductive layer remains outside, so that the current can pass through the conductive layer between the two contacts of the lamella. The layer must thus have a thickness sufficient to have a suitable conduction section. The covering of the central part of one face of the ribbon with the conductive layer is generally carried out by mechanical plating, and this central portion therefore has less elasticity with respect to the lateral parts of the ribbon after the heat treatment of hardening of the strip. of contact.

In this known method, it is necessary that the lateral portions of the ribbon are not covered by the conductive layer, so that their elastic properties after the heat treatment allow the lamellae to act as springs. It may be noted that this need exists in other types of lamellar contact strips, such as individually manufactured lamellae strips which are shown in FR2339259 . It should be remembered that when a strip of a contact strip is subjected from a connecting element to a pressure perpendicular to the plane of the strip, it must be able to pivot relative to this plane while exerting a return force. elastic against this connection element, to ensure reliable contact.

Furthermore, the pleating operation allows the process to result in contact strips that have a large number of slats per unit length of strip. Because the side portions of the ribbon are not covered, the pleating may be made in one or more plies, for example in a single narrow fold which is folded substantially parallel to the ribbon plane, as shown in the patent FR2811147 previously mentioned. There is therefore no particular difficulty in obtaining by this method a large lamella density over the length of a contact strip.

Although making it possible to produce very satisfactory contact strips in particular in terms of electrical conduction power for the strong currents, in particular the currents of the order of a thousand amperes or higher, which are often present at medium or high voltage, the The subject process of the above mentioned patent has certain disadvantages. Firstly, it turns out that the operation of hemming an edge of each slat is difficult to achieve, especially since the plated metal layer which covers one side of this edge must be sufficiently thick to ensure sufficient electrical conductivity between the two opposite contact zones on each lamella, which is disadvantageous for the manufacturing cost. On the other hand, the mechanical plating operation is relatively expensive in itself, particularly compared to an electrolysis galvanizing operation.

There is a conventional method of manufacturing contact strips implementing a galvanizing operation by electrolysis of strips of contact lamellae. This operation occurs almost at the end of the process, after the slats have been formed in each ribbon, that the ribbons have then been cut to the desired lengths for the contact strips, and that each cut ribbon has subsequently undergone a heat treatment such as than an income to give the slats elastic properties. It is note that the lateral parts of the ribbons do not undergo pleating, and that a final contact strip is formed of two galvanized strips of the same length nested one inside the other as shown in the document of FR2100220 . This makes it possible to double the number of slats per unit length and to achieve the desired slat density for use under strong currents.

With this conventional method, it would not be possible to achieve the same lamella density on a single-ribbon strip of contacts. Indeed, the galvanization taking place after the formation of the lamellae, it is not necessary that these lamellae are too close together, because the metal layer obtained by electrolytic galvanization then has a too uneven thickness especially because of so-called phenomenon of shadows cones affecting the lamellae. A shadow cone is defined as a portion of a slat located behind another slat in the direction of the electric field used for galvanizing. In addition, the more the lamellae overlap in the direction perpendicular to the ribbon, the greater the risk of including air bubbles trapped during galvanizing is important. As it is difficult to clean the ribbons in the galvanizing baths to evacuate the trapped bubbles, there is still a risk of local interruption of the continuity of the metal layer. The conventional solution of nesting pairs of strips of lamellae has been chosen to ensure satisfactory galvanization for each lamella.

This solution, however, has the disadvantage of being relatively expensive. In addition, it is desirable in such a process that the ribbons are cut to the desired length before the nesting of a pair of galvanized ribbons, because it would be more difficult and expensive to cut a pair of ribbons already nested. Thus, the double-ribbon contact strips obtained must have different lengths corresponding to the dimensions of the connectors to which they are intended, which requires having many items in stock to be able to respond quickly to orders. This solution is therefore penalizing in terms of storage cost and delivery time.

The invention aims to overcome the disadvantages of these known solutions, by proposing a particularly less expensive solution in terms of manufacturing and storage while allowing a fast satisfaction of orders.

• ledit ruban métallique est métallisé sur ses deux côtés pour recouvrir au moins ladite bande centrale d'un métal qui est meilleur conducteur électrique que le métal dudit ruban,
• lesdits évidements sont pratiqués dans ledit ruban,
• lesdites opérations de torsion et de cintrage sont appliquées à chacune desdites lamelles,

et en ce qu'il met ensuite successivement en oeuvre les opérations suivantes :

• ladite opération de plissage est appliquée aux deux bandes continues latérales de ladite bande primaire de contacts,
• ledit traitement thermique de durcissement est appliqué à la bande de contacts obtenue suite aux opérations précédentes, pour constituer ladite bande secondaire de contacts,
• ladite bande secondaire de contacts est segmentée en plusieurs bandes de contacts prêtes à être montées sur les connecteurs auxquels elles sont destinées, selon la longueur de bande requise pour chaque connecteur.

For this purpose, the subject of the invention is a method for manufacturing contact strips as introduced in the preamble, characterized in that it first implements the following three steps of operations:

• said metal strip is metallized on both sides to cover at least said central strip of a metal which is better electrical conductor than the metal of said strip,
• said recesses are made in said ribbon,
• said twisting and bending operations are applied to each of said lamellae,

and in that it then successively implements the following operations:

• said pleating operation is applied to both lateral continuous strips of said primary contact strip,
• said curing heat treatment is applied to the contact strip obtained as a result of the preceding operations, to constitute said secondary band of contacts,
• said secondary band of contacts is segmented into several contact strips ready to be mounted on the connectors for which they are intended, depending on the band length required for each connector.

The secondary band of contacts can be obtained from a long ribbon, and be delivered for example in the form of a coil which will be cut into strips of contacts by the customer just before these strips are assembled on their destination connectors .

Advantageously, the metallization of said ribbon is carried out by galvanizing. Galvanization can for example be performed by electrolysis with silver. In known manner, the ribbon to be galvanized may be made of a beryllium-bronze alloy, which has a poor electrical conductivity but good resilience properties after heat treatment. The heat treatment of beryllium-bronze may consist of heating to about 320 ° C for four hours, followed by gradual cooling.

According to a preferred embodiment of the method, the entire surface of said ribbon is covered during the metallization operation. In particular, with an electrolytic galvanizing metallization, it is in the current state of the art less expensive to perform a total galvanization rather than treating only the central band of the ribbon.

According to one embodiment of the method in which the cutting of the recesses of the ribbon is performed by perforation, that is to say by means of a punch and a die fitted into each other to form holes relatively wide, the ribbon metallization operation is performed before said ajourage.

According to a preferred embodiment of the method, during said pleating operation, said slats are brought closer together to be regularly spaced according to a new regular step such that the ratio between the initial pitch and this new step is between 1, 3 and 2. In what follows, we will designate this ratio as the factor of approximation of the slats. There is a range for this ratio in which the new pitch corresponds to a lamellar density large enough to ensure high current performance which is at least equivalent to that of contact strips made by the known methods described above.

Other features and advantages of the manufacturing method according to the invention will appear in more detail in the following, with reference to the accompanying drawings.

Finally, the invention also relates to a contact strip for a connector of an electrical apparatus, obtained from a metal strip in which recesses are formed to form a discontinuous central strip of lamellae, said contact strip being metallized. over its entire surface by a layer of a good electrically conductive metal, the longitudinal ends of said lamellae being attached to two lateral continuous strips of said ribbon which are folded in transverse folds, said lamellae being evenly spaced according to a not regular, characterized in that each fold has a height such that the ratio between said regular pitch and said height is between 1.7 and 2.5. The dimensional characteristics of each fold of such a strip of contacts are particularly advantageous in order to allow a relatively simple pleating to be performed and which is not likely to break the conductive metal layer at said lateral continuous bands of the ribbon.

Such a strip of contacts according to the invention is particularly interesting in terms of the performance / cost ratio if it is obtained by a manufacturing method according to the invention.

The Figures 1 to 3 illustrate the steps of an exemplary implementation of the method according to the invention for the manufacture of contact strips with high lamella density.

The figure 3a schematically represents another embodiment of a transverse fold in a strip of slats.

The figure 4 schematically represents a form of lamella suitable so that each of the two faces of the lamella can have two contact zones.

The figure 5 schematically represents a cross-sectional view of a strip of contacts installed in a portion of a connector, formed from a sliver strip such as that shown in FIG. figure 4 .

The figure 6 schematically shows a cross-sectional view of a contact strip similar to that shown in FIG. figure 5 and installed in a portion of a connector which comprises longitudinal locking means of the band.

The figure 6a schematically represents a view in longitudinal section of the device of the figure 6 .

A metal ribbon 9, visible on the figure 1 , is covered on both sides with a layer 15 of a good electrical conductor metal as visible on the figure 1a . In the following, we mean good all-electric conductor that is substantially better conductor than the ribbon metal. At least the central band CS of the ribbon is covered by the layer 15, and regularly spaced recesses 2 are made by perforation in this central band as visible on the figure 2 . These recesses may possibly be practiced before the tape is covered by the layer 15 of good conducting metal, as explained below.

It is assumed for the rest of the description that the entire surface of the ribbon 9 is covered during the metallization operation, and that the recesses 2 are made after the metallization. The metal of the ribbon is for example an alloy of beryllium and bronze, which is a relatively poor electrical conductor, and the metallization consists for example of an electrolytic galvanization in a silver bath. In the case of a galvanization of the entire ribbon, the edges of the ribbon are covered with a layer joining its two faces, as the layer 15s shown on the figure 1a .

Figure 2 , the recesses 2 are formed in the metallized ribbon of the figure 1a with an initial step d ₁ regular in the direction of the longitudinal axis A of symmetry of the ribbon, to form a central band CS discontinuous slats 3, the longitudinal ends 31 and 32 are attached to two continuous lateral strips ES ₁ and ES ₂ of the ribbon. It is preferable that the recesses are sufficiently close to their sizes which are situated here along the longitudinal axis A of symmetry of the tape, in particular to obtain an initial step of ₁ as small as possible for a given blade width D and also to limit the amount of cored material.

Preferably, the width D of each lamella is greater than about 80% of the initial pitch d ₁ , which is to say that the width of a recess at its size is at most equal to about 20% of d ₁ since this width at the size is equal to d ₁ -D. For a given width D of lamella, it is indeed undesirable that the initial pitch d ₁ of the recesses is much larger than D, since this would require the use of a longer metallized ribbon and to increase the width of the recesses. which would be penalizing for the manufacturing cost. In addition, with a pleating operation producing protruding folds on the same side of the ribbon as described below, the height of the folds increases with the initial pitch d ₁ , while it is not desirable to have folds that are too large and could interfere with the mounting of the contact strip on the destination connector.

The two side strips ES ₁ and ES ₂ of the ribbon are notched to the outside of the ribbon so as to form tabs 4 which will be used for the connection of the contact strip with one of the parts of the connector for which it is intended. The slats 3 are here symmetrical about their longitudinal axes A _T that are perpendicular to the longitudinal axis A, but could be considered a drawing which is not perfectly symmetrical by adopting a somewhat dissymmetrical shape of recess.

Conventionally, the slats then undergo a twisting operation about their longitudinal axis to pivot relative to the plane of the ribbon so that the two faces of each slat form two respectively prominent contacts 3A and 3B on each side of this plane, as visible in the first part of the figure 3 . This twisting operation is conventionally accompanied by a bending of the two lateral edges of each lamella according to at least one longitudinal plane perpendicular to the plane of the ribbon, so as to form on each face of a lamella at least one contact zone intended to ensure the flow of current between the lamella and a portion of a connector. In what follows, it is meant that a contact such as 3A or 3B consists of at least one contact zone.

In a manufacturing method according to the invention, it is generally preferable for reasons of cost that the operations of cutting lamellae and tongues, of torsion with bending of the lamellae, then of pleating of the continuous lateral bands of the ribbon, are effected at during a continuous process carried out in the same installation. Indeed, it is less expensive, especially in terms of labor cost, do not have to reinstall or readjust the ribbon between these operations. This is why it is generally preferable that the metallization operation is carried out at the very beginning of the manufacturing process according to the invention.

Moreover, it should be noted that with perforations made in a solid metallized strip as represented in FIG. figure 1a , electrical conduction between the two layers that cover both sides of the ribbon slats is through the ribbon metal thickness only. Indeed, a lamella cut by a punch does not have on its edges a metal layer joining its two surface layers as the layer 15s of the edge of the ribbon visible on the figure 1a . However, the metal of a tape for contact strips is generally not a good electrical conductor. However, since such a ribbon generally has a relatively small thickness, typically between 0.10 and 0.40 mm, the conduction of strong currents can take place once the ribbon has a sufficient surface area for the overall resistance to be achieved. the band of contacts, ie the equivalent resistance between the two series of contacts 3A and 3B of all the lamellae, remains in acceptable values in terms of heating of the lamellae according to the currents to be passed.

If the overall resistance of the contact strip is to be reduced without increasing the surface of the ribbon or reducing its thickness, it may be necessary for the metallization to take place on an already hollow ribbon, that is to say after the slats were cut and possibly twisted and bent. Indeed, the good conductive metal then covers both surfaces and the edges of each lamella. Consequently, in the band of contacts obtained by this method, the current which passes between the two contacts 3A and 3B of a lamella is thus distributed between the thickness of the ribbon 9 and the edges of the lamella, which makes it possible to reduce to some extent the overall strength of the contact strip obtained. However, a metallization carried out at this stage usually involves a substantial additional cost compared to an order of operations in which the metallization is performed at the very beginning of the process, for the reasons mentioned above.

The first part of the figure 3 shows a longitudinal sectional view of the secondary and primary contact strips, in a plane perpendicular to the plane P of the ribbon and passing through its longitudinal axis A. The primary contact strip, obtained after the operation of twisting the strips of the strip of contacts who is represented at the figure 2 , is visible from the right side of the figure 3 . The lamellae 3 are spaced from the same initial pitch d ₁ as the pitch of the recesses 2. In this representation, the tongues 4 are already inclined relative to the plane P of the ribbon, as visible in FIG. figure 5 . The left side of the figure shows the secondary band before its heat treatment, obtained following the pleating of the two lateral continuous strips ES ₁ and ES ₂ of the ribbon so as to bring the strips 3 in a new step d ₂ . It should be remembered that in a manufacturing method according to the invention, the pleating operation mentioned above must take place after the metallization operation of the ribbon, in order to avoid a bad metallization at the portions of the lamellae which overlap each other.

To give an order of magnitude, the initial pitch d ₁ is for example equal to 2.5 mm, and the new step d ₂ corresponding to is equal to 1.7 mm, which amounts to a closeness factor d ₁ / d ₂ lamellae close to 1.5. It can be seen that the lamellae partially overlap each other in the direction perpendicular to the plane P of the ribbon. However, the distance between the edge of one lamella and the surface of the adjacent adjacent lamella must remain sufficient so that this edge does not abut against the said surface when the strip of contacts obtained is installed and compressed between two parts of a connector such as the two parts 11 and 12 shown in FIG. figure 5 . Thus, from a given primary contact band, there is a lower limit not to be crossed for the new step d ₂ . This limit depends in particular on the inclination of the slats relative to the plane of the sliver, the desired elasticity for the slats, as well as the width D and the thickness of the slats. There is therefore a compromise to adopt to have a step d ₂ as small as possible, in order to obtain a high lamellar density that goes with a good conduction capacity for strong currents.

The initial step d ₁ must be sufficient to be able to cut lamella enough large to be able to bend and form areas whose contact surfaces are satisfactory with the two parts of the destination connector. In addition, it is important to have slats whose width D is sufficient to ensure the desired elastic deflection at the contacts of each slat, since each slat of the contact strip obtained is able to pivot elastically. However, a large blade width will require to some extent to increase the new step d ₂ , which goes against a high density of lamellae. Since it is not desirable that the initial pitch d ₁ be greater than 1.25 times the desired width D for the lamellae, as explained in the commentary to figure 2 there is therefore a compromise to be adopted to limit as much as possible this initial step.

There is an optimal interval for the approximation factor d ₁ / d ₂ , which corresponds to a new step d ₂ sufficiently small to obtain a relatively high density of lamellae, from a band primary contact whose initial pitch d ₁ is large enough to form slats electrically and mechanically satisfactory. A factor of approximation of the lamellae between 1.3 and 2 constitutes an optimal compromise to allow to fully satisfy the technical requirements mentioned above.

The second part of the figure 3 , located under the first part, shows a view from above of the secondary and primary bands of contacts shown in the first part of the figure. The overlapping of the lamellae of the secondary band is clearly visible on the left of the figure. After the pleating operation, the tongues 4 are regularly spaced from the same new step d ₂ as for the slats.

As visible on the first part of the figure 3 , the folds 5 which have been made transversely to the ribbon to bring the lamellae 3 are all prominent on the same side of the plane P of the ribbon, preferably on the same side as that to which the tongues 4 are folded. Thus, the two lateral continuous strips ES ₁ and ES ₂ of the ribbon take a crenellated form with slots separated in pairs by the bottom of a fold 5.

The inner walls of a fold 5 do not touch, so that the bends applied to the continuous side bands of the ribbon during pleating are not likely to break these bands. This characteristic is especially advantageous in the case where the side strips ES ₁ and ES ₂ are covered with a conductive layer 15 as well as the central band CS of the ribbon, because it is mainly at the level of this layer 15 that it can there is a risk of tearing if the folds are formed by pressing one wall against another.

Each ply thus has an interior space forming a cavity 6 open at the plane P of the ribbon. Each cavity has two substantially plane walls which are parallel to each other and perpendicular to the plane of the ribbon for the embodiment of the invention. figure 3 , and also comprises a semi-cylindrical wall which forms the bottom of the cavity 6. The bottom of this cavity thus has a diameter of curvature δ which corresponds to the diameter of the half-cylinder, this diameter δ being also equal here to the distance that separates the two flat walls of the cavity.

Alternatively, it is possible to produce folds for which the two plane walls of a fold are not parallel to each other, for example according to the shape shown on the drawing. figure 3a . In this figure, one of the two plane walls of the fold 5 is perpendicular to the ribbon plane, but this characteristic is not essential and one could also form an angle other than 90 °. The wall which forms the bottom of the cavity 6 partially matches the shape of a cylinder of diameter δ, and therefore has a diameter of curvature equal to δ.

Advantageously, each transverse fold 5 has a height h such that the ratio d ₂ / h between the new regular pitch d ₂ and this height is between 1.7 and 2.5. The height of a fold is measured as the distance between the plane surface of the sideband of the fold side and a plane parallel to this surface which is tangent to the top of the fold, which supposes that each fold is prominent of the same side of the ribbon plane. For example, a fold height equal to 0.85 mm can be obtained for a new pitch equal to 1.75 mm, which gives a ratio d ₂ / h approximately equal to 2. The range specified above is a good compromise to allow tabs 4 sufficiently wide, while obtaining folds high enough to allow to bring the slats 3 according to the new no d ₂ wished. The width of a tongue is considered at the level of the longitudinal fold that it makes it with a lateral continuous band ES ₁ and ES ₂ of the ribbon.

The tongues 4 must have a certain rigidity combined with a certain elasticity, first of all to be able to be engaged in the grooves of a first part 11 of a connector as represented in FIG. figure 5 when mounting the contact strip. Then, the ends of the tongues must press sufficiently against the inclined walls of the grooves 13 to maintain the contact strip bearing against the portion 11. A too small width of the tongues could lead to insufficient maintenance of the contact strip against this part 11 and a risk of disengagement of the band when the two parts 11 and 12 of the connector are disconnected.

Advantageously, for each transverse fold 5 satisfying the interval specified previously for the ratio d ₂ / h, the ratio h / δ between the height h of the fold and the diameter of curvature δ of the bottom of the cavity 6 of the fold is preferably between 2,4 and 3,2. When the side strips ES ₁ and ES ₂ of the ribbon are covered with a conductive layer 15, an h / δ ratio in the range specified above makes it possible in particular to have sufficiently large curvatures to avoid the risk of breaking these sidebands during pleating. For example, for equal fold height at 0.85 mm, it is possible to have a diameter of curvature equal to 0.3 mm, which gives a ratio h / δ approximately equal to 2.8.

On the figure 4 is schematically represented a lamella shape somewhat different from a more conventional form of lamellae such as those of the contact strip of the figure 2 . The blade 3 has a constriction 7 at its middle portion along the longitudinal axis A symmetry ribbon, in the same way that some achievements of the state of the art as the patent document CH590570 . This lamellar form is suitable for after twisting of the strip about its axis A _T and the bending of its side edges to form the contacts, the middle portion of the sipe can not be in contact with a portion of a connector such as the part 11 or 12 visible on the figure 5 . Thus, each of the two faces of the lamella has two contact zones such as Z ₁ and Z ₂ located on either side of said middle portion symmetrically with respect to the axis A.

Figure 5 , a strip of contacts formed from a ribbon strip such as that represented on the figure 4 , is installed in a first part 11 of a connector. The contact strip is shown schematically in a cross-sectional view of a strip in a plane perpendicular to the plane of the strip. The first portion 11 comprises two longitudinal grooves 13 which are provided to block the tongues 4 of the contact strip once it is installed. In addition, each groove 13 is deep enough so that the folds 5 of the two continuous lateral strips ES ₁ and ES ₂ of the ribbon do not abut against the bottom of the groove when the contact strip is compressed between the two parts 11 and 12 of the connector. Between his two throats longitudinal 13, the first portion 11 of the connector comprises a flat longitudinal or cylindrical surface 20 against which the contact 3B of the underside of the strip is maintained supported when the tabs 4 are installed in the grooves. The two end portions 21 and 22 which laterally delimit the longitudinal surface 20 with respect to the two longitudinal grooves 13 may constitute lateral displacement stops for the contact strip. Indeed, in case of friction force in the direction transverse to the contact strip, especially when connecting or disconnecting the two parts 11 and 12 of the connector, the contact strip tends to move laterally. In the case where the tabs 4 are not rigid enough to limit this movement, the folds 5 of a continuous lateral band ES ₁ or ES ₂ can abut against an end portion 21 or 22 and prevent further movement.

The contact 3A of the upper face of the strip is able to press against a second portion 12 of the connector as soon as the two parts 11 and 12 are connected together. This second portion 12 is shown in dashed lines in its connection position. It clearly appears that each contact 3A or 3B consists of two contact zones such as zones Z ₁ and Z ₂ for contact 3A. The contact surface between a face of a lamella and a portion of a connector is thus substantially increased with respect to a more conventional embodiment in which each face of a lamella has a single contact zone. Thus, the contact resistance between a contact 3A or 3B and a connector portion 12 or 11 respectively can be substantially reduced.

Figure 6 , a strip of contacts similar to that shown on the figure 5 is shown partially and schematically by a cross-sectional view. The connector portion which holds the strip comprises longitudinal locking means of the strip, which may be advantageous for some relatively marginal embodiments. These means consist of crenellations 14 which correspond to shallower areas of the longitudinal groove 13, the bottom of a crenel 14 then being formed by the bottom of the groove 13. The bosses of these slots are intended to be closer of the plane P of the ribbon than are the bosses of the folds 5 once the band is in place. Thus, in the event of a large force on the strip of contacts in the longitudinal direction, if tabs of the strip slip into their holding grooves 13, folds 5 will abut on slots 14 and prevent further longitudinal displacement Of the band. For such an embodiment, it is not necessary to have as many slots 14 in the grooves 13 as folds 5 in the associated contact strip, a small number of slots distributed over the length of the strip may be sufficient.

On the figure 6a is schematically represented a longitudinal sectional view of the device of the figure 6 according to plan P '. As for the device of the figure 5 , the bottom of the groove 13 is sufficiently far from the folds 5 to not touch them when the contact strip is compressed. It is clear that the folds 5 can abut on the sides of the crenellations 14 in case of longitudinal displacement of the strip.

Thus, with a realization as illustrated by the Figures 6 and 6a for the first connector portion 11 which supports the contact strip, the The strip may be nested in this connector portion by being securely locked in the longitudinal direction. This of course implies locking in rotation of the band if the connector has a cylindrical shape.

Claims (10)

1. A method of fabricating contact strips for electrical device connectors by segmenting a secondary strip (1) of contacts fabricated from a metal ribbon (9) in which openings (2) are formed with an original pitch (d₁) to form a discontinuous central strip (CS) of blades (3) whose longitudinal ends (31, 32) are attached to two continuous edge strips (ES₁, ES₂) of said ribbon and each of said blades is twisted about its longitudinal axis (A_T) to pivot relative to the plane (P) of said ribbon and bent so that each of its two faces has at least one projecting area (Z₁, Z₂) to form a contact (3A, 3B) on one side of said plane, said twisting and bending producing a primary contact strip (10) whose blades (3) are spaced at substantially the same regular pitch as the original pitch (d₁) of said openings (2), the method further including pleating said primary contact strip (10) by forming pleats (5) on each continuous edge strip (ES₁, ES₂) to move said blades (3) closer together, the method also including a hardening heat treatment to impart hardness to said blades combined with some elasticity so that they function as springs, which method is characterized in that it begins with the following three steps:

   a) said ribbon (9) is metal-plated on both sides to cover at least said central strip (CS) with a layer (15) of a metal that is a better electrical conductor than the metal of said ribbon,

   b) said openings (2) are formed in said ribbon (9), and

   c) each of said blades (3) is twisted and bent,
   and in that it then includes the following successive operations:

   d) the two continuous edge strips (ES₁, ES₂) of said primary strip (10) of contacts are pleated,

   e) said hardening heat treatment is applied to the contact strip obtained after the foregoing operations, to produce said secondary contact strip (1), and

   f) said secondary contact strip is segmented into a plurality of contact strips ready to be mounted on the connectors for which they are intended with a strip length as required for each connector.
2. A fabrication method according to claim 1, characterized in that said ribbon (9) is metal-plated by galvanization.
3. A fabrication method according to either claim 1 or claim 2, characterized in that all of the surface of said ribbon (9) is covered during the metal-plating operation.
4. A fabrication method according to any of claims 1 to 3, characterized in that said ribbon is metal-plated before said openings (2) are punched in the ribbon.
5. A fabrication method according to any of claims 1 to 4, characterized in that, during said pleating operation, said blades (3) are moved closer together so as to be regularly spaced with a new regular pitch (d₂) such that the ratio between the original pitch (d₁) and the new pitch (d₂) is from 1.3 to 2.
6. A fabrication method according to claim 5 in conjunction with claim 3, characterized in that said pleats (5) are formed in two continuous edge strips (ES₁, ES₂) of the ribbon on the same side of the plane (P) of the ribbon and each pleat has a height (h) such that the ratio between the new regular pitch (d₂) and said height (h) is from 1.7 to 2.5.
7. A fabrication method according to claim 6, characterized in that each pleat (5) is formed with a transverse cavity (6) whose section in the longitudinal direction (A) has straight portions and portions with a substantially constant radius of curvature and the bottom of said cavity has a curvature diameter (δ) such that the ratio between the height (h) of a pleat and the diameter (δ) is from 2.4 to 3.2.
8. A contact strip for connecting a medium-voltage or high-voltage electrical device, obtained from a metal ribbon (9) in which openings are made to form a discontinuous central strip (CS) of blades (3) and the whole of the surface of said contact strip is plated with a layer (15) of a metal that is a good electrical conductor, longitudinal ends (31, 32) of said blades are attached to two continuous edge strips (ES₁, ES₂) of said ribbon that are bent with transverse bends (5) and said blades are regularly spaced with a regular pitch (d₂), which contact strip is characterized in that said pleats protrude from the same side of the plane (P) of the ribbon and each pleat has a height (h) such that the ratio between said regular pitch (d₂) and said height (h) is from 1.7 to 2.5.
9. A contract strip according to claim 8, characterized in that each pleat (5) is formed with a transverse cavity (6) whose section in the longitudinal direction

   (A) has straight portions and portions with a substantially constant radius of curvature and the bottom of said cavity has a curvature diameter (δ) such that the ratio between the height (h) of a pleat and the diameter (δ) is from 2.4 to 3.2.
10. A contact strip according to either claim 8 or claim 9, obtained by a fabrication method according to any of claims 1 to 5.

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