FR2696282A1 - Contact head and contact for connectors and method for their manufacture. - Google Patents

Abstract

The invention relates to a contact head. It relates to a contact head, of the type which comprises a flat and elongated body (12), having two large sides which are substantially parallel and substantially equidistant from a central longitudinal axis (13) of the body and at least one small side, the body having a substantially rectilinear slit (14) which opens into the short side, which is substantially parallel to the longitudinal axis and which is formed over only a part of the length of the body so that it terminates at an inner end (16 ) disposed in the body. According to the invention, the slot (14) is placed asymmetrically in the body (12), at a distance from the central longitudinal axis (13) of the head. Application to strips and cable heads of telephone distributors.

Description

The present invention relates to a contact head,

  a contact comprising two heads, and a method of manufacturing

contacts.

  The invention relates more precisely to the contact heads and contacts, including self-stripping, which are used in the connector blocks such as those called "strips" and "heads of cables" in telephony These connector blocks comprise of contact heads, usually grouped by two in a contact, which allow

  the connection of the connecting wires called "garters".

  A telephone splitter may have several thousand such jumper wires or "jumpers", and their connection to the cable heads and sliders must be easy, fast and secure. More precisely, a jumper wire must be connected to a jumper. head contact without applying excessive force, but it must also be sufficiently resistant to tearing; however, the extraction force must not reach excessive values, as it is common for garters to be

disconnected.

  Already known in the strips and cable heads, self-stripping type contact heads, having a slot which opens at the edge of the contact head by a notch V This notch is intended to guide a wire with its insulation so that the insulation is cut by the edges of the slot and that the metal core is tight

  by these edges when the wire is introduced into the slot.

  The slot is formed in the middle of the contact head and, when a connecting wire is pushed into the slot, the two edges thereof move slightly and symmetrically, first elastically and then with some creep (permanent deformation) It was found that, when connecting threads were introduced and then removed a large number of times, the insertion force and the force

  wire extraction gradually decreased.

  Since the users of the connector blocks set a lower limit to the extraction force, the technique usually used to maintain a suitable extraction force after a certain number of

  of maneuvers includes the use of an extractive force

  the first maneuver, obtained for example by using either a thick material

  high-strength material. The strength of ex-

  traction, which is very high at the first maneuver, still has a value significantly higher than the minimum value imposed after a large number of maneuvers, for example

  example one hundred However, as the force of extrac-

  The insertion force is also high and has disadvantages. In fact, it increases the probability of deterioration of the contacts, the tools used or the adjacent parts of the connector blocks.

  and it can deteriorate the metal core of the wire.

  Figure 4 of the attached drawings illustrates graphically

  this problem The lower curve 46 in

  broken indicates the minimum values imposed by some users The upper curve 48 in dashed line indicates the results obtained with a contact commonly used It is noted that the extraction force obtained at the first maneuver is more than five times greater than the minimum value required. value is chosen so that, after one hundred maneuvers, the extraction force is still well above the minimum value required. However, in return, the insertion force

  bonding wire is very high.

  The subject of the invention is the reduction of the insertion force, and therefore of the extraction force of the wires of

  binding, but with the preservation of an extractive force

  sufficiently high after a large number of

  maneuvers, for example a hundred.

  More precisely, the invention is based on the discovery of

  the unexpected fact that, when the slot of a self-stripping contact is formed off-center in the contact head, the pulling force of a wire is not

  decreases only very slowly with the number of maneuvers.

  Although the invention is not limited by any theory, it is believed that the off-center disposition of the slot allows deformation of the contact head over a greater range of elasticity, i.e. deformation. permanent at each maneuver is reduced. More specifically, the invention relates to a contact head, of the type which comprises a flat and elongated body,

  having two large sides substantially parallel and sensi-

  equidistant from a longitudinal central axis of the body

  and at least a small side, the body having a sensory cleft

  a straight line that opens into the short side, which is substantially parallel to the longitudinal axis and is formed on only a portion of the length of the body to terminate at an inner end disposed in the body; according to the invention, the slot is placed

  asymmetrically in the body, away from the longitudinal axis

central dinal of the head.

  In an advantageous embodiment, the slot opens into the short side by a V-notch, and the V-notch is asymmetrical. For example, the asymmetric V-notch is delimited by a first edge of the slot and by a second edge. inclined edge with respect to the second edge of the slot In this case, it is preferable that the edge

  angle of the notch in V is closer to the longitudinal axis

  central tudinal of the body as the first edge of the slit.

  In addition, it is advantageous that, near the inner end of the slot, the body is devoid of

  any noticeable decrease in width.

  In an advantageous embodiment, the thickness of the material of the contact head, along at least part of the edges of the slot and close to them, is less than the thickness of the material of the remainder of the body of

the contact head.

  Advantageously, the contact head comprises, at

  proximity of the inner end of the cleft, a distortion

  localized punctually in the axis of the slit and

beyond its end.

  The invention also relates to a contact comprising two contact heads, each head being of the type which comprises a flat and elongated body, having two large sides substantially parallel and substantially equidistant from a longitudinal central axis of the body and at least one short side, the body having a substantially rectilinear slot that opens into the short side, which is substantially parallel to the longitudinal axis and is formed on only a portion of the length of the body so that it terminates at an inner end disposed in the body , the two heads being parallel to one another, the contact being formed of a flat blank cut and folded about two axes substantially parallel to the central longitudinal axes of the two heads, the two heads being connected by a cheek formed of opposite side to the small side into which the slot opens so that the cheek is distant from the inner ends of the slots in the longitudinal direction; according to the invention, the cheek and the parts of the heads which are adjacent to the cheek have a thickness less than

  the thickness of the body of the contact heads.

  In an advantageous embodiment, the parts of the heads which are aligned on the cheek in direction transverse to the longitudinal direction of the heads have a thickness less than the thickness of the body of the heads of

contact.

  In some embodiments, one of the contact heads is extended, on the side opposite the slot, by a connection member selected from an elastic shank and a

  connecting tab by wire winding.

  It is also advantageous, when one of the contact heads is extended, on the side opposite the slot, by an elastic tail, that this tail has a reduced thickness.

  at least in its near part of the contact head.

  In an advantageous embodiment, the slots of the two heads are placed asymmetrically in the respective body, at a distance from the central longitudinal axis of the

  head, on the opposite side to the cheek.

  The invention also relates to a method for manufacturing said contacts, of the type which comprises the gradual delimitation of a blank in a strip which advances to a series of machining stations ensuring the delimitation of the blank by at least one operation selected in the group of operations

  punching, cutting and piercing.

  In addition, the method further comprises a reduction operation

  thickness of at least the portion of the strip intended for

  form the cheek and fold lines of the contact.

  Preferably, the thickness reduction operation comprises a milling operation of the portion of the strip intended to form the cheek and the fold lines of the

  In an advantageous embodiment, the operation

  The milling section of the part of the band includes an opera-

  longitudinally milling the strip, the strip being displaced along its length and the contacts being formed so that their heads have their longitudinal axis

  oriented in a direction transverse to the band.

  When the method comprises several punching operations performed with several punches, it is advantageous that it comprises the inactive state of different punches or different groups of punches in

  depending on whether one of the contact heads is

  with an elastic tail and a tongue of

winding of wire.

  Other features and advantages of the invention

  tion will become more apparent from the following description,

  with reference to the accompanying drawing in which: Figure 1 is a plan view of a contact head according to the invention; Figure 2 is a plan view of a blank for making a contact having two contact heads according to the invention; Figure 3 is an end view of a contact having two contact heads according to the invention, made with the aid of the blank of Figure 2; and

  Figure 4 is a graph for comparing

  its properties of contacts of the prior art

and contacts according to the invention.

  We first consider a contact head of the prior art and a contact head according to the invention. A contact head of the prior art, used in connector blocks, such as

  rulers and the cable headers of telephone dispatchers

  The longitudinal slot is parallel to the two long sides of the head and opens, on a short side, by a V-notch. The slot and notch are centered on the longitudinal axis of the contact head and the notch is notched. in V

  is symmetrical about this axis.

  A contact head 10 according to the invention comprises a body 12 formed in a metal sheet, delimited by two long sides which are parallel to the central longitudinal axis 13 of the contact head 10 The metal sheet is formed of a metal or alloy of the types usually used for the manufacture of the contact heads A slot 14 is parallel to the long sides of the body 12 and opens at a small side At the end opposite the short side, it ends with an inner end 16 according to the invention , the slot is not formed along the central longitudinal axis 13, but is shifted on one side thereof, right in Figure 1 The slot is bounded by a straight edge 18, formed on the side of the body the narrower, and a second edge 20 which is opposite the edge 18 over part of its length; an inclined edge 22 forms, with the edge 18, a notch that opens on the short side Although there is shown an asymmetrical notch, it can also be symmetrical, as in the known contacts, but this possibility is less advantageous than the asymmetrical position , when used in combination with

the asymmetrical position slot.

  It is noted in FIG. 1 that the edges 18, 20 of the slot are delimited by a thinned portion which bears the reference 24. This thinned portion is formed by locally reducing the thickness of the blank or the strip before

  cleft realization The advantages of this feature

  have already been described in EP-A-0 327 464 of the applicant. This characteristic is only possible, but it is advantageous in combination with the

  asymmetrical positioning of the slot.

  FIG. 1 further indicates the presence of a deformation 26. This deformation is formed along the axis of

  slot 14 and at a short distance beyond its end.

  internality 16, this distance being for example of the order of 1 mm This deformation 26 is not a hole and, in the example shown, it is simply a

  needle mark causing local creep of the material.

  This technical feature further enhances

  elastic deformation properties of the material of the body 12 and, in combination with the asymmetrical positioning of the slot 14, contributes to the reduction of the slope of the curve representative of the reduction of the extraction force as a function of the number of maneuvers, such as indicated more in

  detail in the following with reference to FIG.

  During the manufacturing process of the contact head 10, the stamping or other thinning operation of the region intended to form the zones 24 is carried out before the formation of the slot, which precedes itself.

  the application of the needle punch creating the deformation 26.

  Figure 4, to which reference has already been made, shows

  clearly the advantages of the invention.

  As indicated above, curve 46 indicates the

  limit extraction force requested by users.

  The intersection with the ordinate axis of this curve corresponds to the extraction force considered as minimal so that a wire is not easily torn off the head of a block of connectors. indicates the curve 46, that this force can decrease, since, until the invention, all the contacts made, having a force

  suitable extraction, showed a significant reduction

  aunt force extraction when increasing the number of maneuvers Indeed, as indicated by the curve

  48, the contacts currently used, as they pre-

  feel a strong reduction of the extraction force (the curve 48 is very inclined), are manufactured so that they give, at the first maneuver, a very high extraction force These contacts are formed in general with a thickness of 0 , 8 mm, obtained in a sheet of this

  thickness or by folding a 0.4 mm sheet on it

  Even this phenomenon exists as well when the contacts are retained on the sides by the housing in which they

  are mounted only when they are free.

  This very high extraction force is a disadvantage

  because it requires an insertion force which must also be very high, and very large forces must be applied to the contact head and can

example twist it.

  On the contrary, as shown in curve 50, the invention

  allows the realization of a contact which, at the first maneuver, has an extraction force which is moderately

  greater than the requested force, as indicated by

  section of the curve 46 with the ordinate axis Consequently, the insertion of the connecting son is easy from

  the first maneuver However, thanks to the characteristics

  aforementioned ticks of the invention, the extraction force

  decreases only very slowly with the number of maneuvers.

  Thus, after one hundred maneuvers, the extraction force is still equal to 83% of the value at the first

maneuver.

  It should also be noted that the regularity of this force makes it possible to reduce the thickness of the material used. Thus, the results corresponding to the curve 50 have been obtained with contacts formed in a sheet only 0.6 mm thick. made of the alloy usually used for these contacts (alloy containing about 91% copper and 9% tin, with a phosphorus content less than or equal to 0.35%> This reduction in thickness has advantages not only of cost of the material, but especially of less wear of the tools

  used for making contacts.

  This feature of the invention is all the more important as the contact heads according to the invention have all the other properties required of the contact heads for connector blocks, and in particular the dimensions allowing their use in the strips.

and cable heads.

  It was found that it was preferable

  of the inner end of the slit, the body is devoid of any notable decrease in width. For example, it is preferable to avoid an enlargement.

  of the inner end of the slot, or a reduction

  width of the head on the side of the slot that is the narrowest and near the inner end of the

  It has thus been found that a lateral notch reduces

  Knowing the advantageous characteristic of the invention It is possible that an enlargement improves the characteristic of the invention, but it would then require a greater width of the head which is not compatible with the contacts of the invention.

  cable heads and strips.

  We now consider a contact made with

  contact heads according to the invention.

  In the connector blocks used as cable heads or as strips, the contact heads 10 are usually used in pairs. FIG. 2 represents a contact according to the invention, intended for such a block of

  connectors and having two heads.

  In Fig. 2, a first head 26, having a slot 28, is connected by a cheek 30 to a second head 32, having a slot 34. The head 32 is extended, on the

  opposite its slot, by an elastic tail 36 connection.

  The contact is brought to its final shape by folding, as shown in FIG. 3. However, this folding poses the

next problem.

  Obtaining the insertion force and especially the

  desired extraction force with contact heads required

  site some mechanical qualities of the material of the head,

  hardness and tenacity, and the head itself.

  However, in particular, this material used with the thickness necessary for the contact heads is too rigid to easily allow folding along the lines 44 delimiting the cheek. Indeed, it frequently happens that the material breaks during the contact. bending or forming at least one rupture primer at the cheek joint

  Such a primer of rupture is particularly

  annoying because it tends to move away each time a wire insertion force is applied

  at the end of each contact head.

  For this reason, it is desirable that the folding of the cheek 30 can be performed with a reduced force and progressively. For this purpose, according to the invention, the cheek 30 and the parts of the heads 26, 32 which are close to the lines of

  folding 42 have a reduced thickness, facilitating folding.

  This reduction in thickness appears clearly in FIG. 3, which represents a contact made using the blank shown in FIG. 2, the cheek 30 having a thickness

  much lower than heads 26 and 32.

  In the embodiment shown in FIG. 2, this reduction in thickness covers the entire width of the contact heads, as indicated by the references 38 and 40, and on a substantial part of the elastic tail 36. This reduction in thickness is obtained advantageously

  by removal of material by milling over an indi-

  42, in a direction transverse to the longitudinal direction of the contact heads 26, 32. More precisely, during the manufacture of the blank shown in FIG. 2 and before it is cut out, the strip that runs (in the direction of horizontal in Figure 2) undergoes milling before the cutting of the contact heads It is noted that the milling protrudes from the cheek 30 so that the change in thickness does not coincide with the fitting of each head

  contact 26, 32 and the cheek 30 Moreover, preferably

  This connection is slightly rounded instead of forming

A right angle.

  Note also in Figure 2 that the milling 42 is not performed to the end of the elastic tail 36 In this way, it carries, at its outer end facing downwards in Figure 2, a thicker part, which can be advantageously used as a relatively rigid contact part In a variant, this elastic tail 36 is replaced by a single pin allowing the formation of a contact by winding

of wire ("wrapper" contact).

  Thus, the invention relates to a contact as shown in Figure 3 whose cheek and parts

  close to the fold lines at least have undergone a reduction

  thickness which facilitates folding.

  The invention also relates to a method of manufacturing such a contact which has undergone a reduction in thickness, as indicated above. The method comprises a thickness reduction step. Preferably, this reduction in thickness is performed by milling, being given the convenience of this operation However, the invention is not

  not limited to the milling operation alone.

  It has been indicated previously, with reference to the figure

  2, that the contact could have either an elongated tail

  FIG. 36 is a pin allowing connection by winding of wires.

  contact, it is therefore desirable to use only one

  For the purpose of manufacturing both types of contact For this purpose, the method and apparatus described are used.

  with reference to FIG. 5 of the aforementioned document EP-A-

  0 327 464 However, the elastic tail on the one hand and the wire-wound spindle on the other hand are made to

  using a group of punches that are used in combination

  different formations for the formation of the tail,

  either of the wire winding connection tab.

  The tape used for the manufacture of the contacts is formed from the materials usually used, in the thicknesses normally used. In one example, the strip is formed of a material 0.6 mm thick, and the milling removes half of the thickness This is simply an example of contact heads with a width of 4 mm. Of course, these dimensions can vary widely depending on the intended application and depending on the mechanical characteristics.

particulars which are fixed.

  In addition, many variations can be made within the scope of the invention. The various advantageous features which have been described with reference to FIGS. 1 and 2 can be combined with various

ways.

  Although two contact heads 26, 32 have been shown which end at different distances from the cheek, this characteristic is given purely by way of illustration. In fact, the essential characteristics of the invention are on the one hand the asymmetric position of the slot in the contact head, and secondly the reduction of thickness which facilitates the folding of the two contact heads.

  Although the invention has been described in its application

  telephone exchanges, it is not limited to this single application and is

  in particular to other types of self-stripping contact.

  It is understood that the invention has been described and shown only as an illustrative example and that any technical equivalence can be made in its constituent elements without departing from its scope

  as defined in the appended claims.

Claims (8)

  1 contact head, of the type which comprises a flat and elongated body (12), having two large sides substantially   parallel and substantially equidistant from a longitudinal axis   central dinal (13) of the body and at least a small side, the body (12) having a substantially straight slot (14) which opens into the short side, which is substantially parallel to the longitudinal axis and which is formed on a part only the length of the body so that it ends at   an inner end (16) disposed in the body, characterized   in that the slot (14) is placed asymmetrically in the body, away from the central longitudinal axis (13) of the head.   2 Contact head according to claim 1, of the type in which the slot (14) opens into the short side by a notch V, characterized in that the notch V is asymmetrical.   Contact head according to claim 2, characterized   characterized in that the asymmetric V-notch is delimited by a first edge (18) of the slot (14) and a second edge (22) inclined with respect to the second edge (20) of the slot (14).   4 Contact head according to any one of   preceding claims, characterized in that the thick-   the material of the contact head along at least part of the edges (18, 20) of the slot (14) and close thereto is less than the thickness of the   material of the rest of the body (12) of the contact head.   Contact head according to any one of   preceding claims, characterized in that the head   of contact comprises, near the inner end (16) of the slot (14), a deformation (26) localized punctually in the axis of the slot (14) and beyond its end.   6 Contact comprising two contact heads, each head being of the type which comprises a flat and elongated body (12), having two large sides substantially parallel and substantially equidistant from a central longitudinal axis (13) of the body and at least one small side the body (12) having a substantially rectilinear slot (14) which opens into the short side, which is substantially parallel to the longitudinal axis (13) and which is formed on only a part of the length of the body (12). ) so that it ends at an inner end (16) disposed in the body, the two heads being parallel to each other, the contact being formed of a flat blank cut and folded around two axes   (44) substantially parallel to the central longitudinal axes   traux (13) of the two heads, the two heads being connected by a cheek (30) formed on the opposite side to the short side in   which opens the slot (14) so that the cheek is dis-   the inner ends of the slots in the longitudinal direction, the contact being characterized in that the cheek (30) and the parts of the heads (38, 40) which are adjacent to the cheek (30) have a thickness less than   the thickness of the body (12) of the contact heads.   7 Contact according to claim 6, characterized in that the portions of the heads (38, 40) which are aligned on the cheek (30) in a direction transverse to the longitudinal direction of the heads have a thickness less than   the thickness of the body (12) of the contact heads.   8 contact according to one of claims 6 and 7,   characterized in that the slits (14) of the two heads are asymmetrically placed in the respective body (12), at a distance from the central longitudinal axis (13) of the head, the opposite side to the cheek (30).   9 Method of manufacturing contacts according to one   any of claims 6 to 8, of the type which comprises   the gradual delimitation of a blank in a band that   advance to a series of machining stations ensuring the   at least one operation selected from the group of punching, cutting and piercing operations, characterized in that it further comprises a thickness reduction operation of at least the portion of the strip intended to form the plays (30) and the lines of folding (44) of the contact.   A method according to claim 9, characterized in that the thickness reduction operation comprises a milling operation of the web portion for forming the cheek (30) and fold lines (44) of the contact.