Method of mounting an electrical connector on a coaxial cable, and such a connector

A method of mounting an electrical connector on a coaxial cable may include: providing an electrical connector including: a central contact provided with at least one crimping portion; an insulating body including a bearing portion with a top face on which the crimping portion of the central contact bears, at least in part; and at least one empty space adjacent to the side wall of the bearing portion of the insulating body; and crimping the central contact onto the central conductor by using a crimping tool including a bearing surface bearing against the crimping portion of the central contact, the tool being movable into an end-of-stroke position in which the bearing surface of the tool extends at least in part into the empty space and beneath the crimping portion of the central contact.

The present invention relates to a method of mounting an electrical connector on a coaxial cable, to such an electrical connector, and to a tool for implementing the method.

BACKGROUND

European patent EP-B1-0 432 666 discloses an electrical connector for a coaxial cable, the connector comprising an outer sleeve, an insulating body inserted in said sleeve, and a central contact held by means of the insulating body. The central contact has two pairs of crimping tabs for crimping to the central conductor of the coaxial cable. On opposite sides of these crimping tabs, the outer sleeve has openings above and below the central contact that serve to admit crimping tools. Because the outer sleeve has an opening beneath the central contact, the performance of the connector can be affected at radio frequencies (RF).

Patent application GB-A-2 020 919 also discloses an electrical connector for a coaxial cable, that connector comprising a peripheral conductor element in which there is inserted an insulating sleeve secured to a conductive central element. Said element has crimping portions bearing against the insulating sleeve that can act as a support during crimping.

SUMMARY

The invention seeks in particular to improve the method of mounting an electrical connector on a coaxial cable.

The invention thus provides a method of mounting an electrical connector on a coaxial cable, the method comprising the following steps:providing an electrical connector comprising:a central contact extending along a longitudinal axis and provided with at least one crimping portion suitable for being crimped on a central conductor of the coaxial cable;an insulating body comprising a bearing portion having a top face against which at least part of the crimping portion of the central contact bears, said bearing portion having at least one side wall extending substantially along said longitudinal axis, and in particular beneath the top face of the bearing portion;at least one empty space adjacent to the side wall of the bearing portion of the insulating body, at least part of said empty space extending beneath the crimping portion of the central contact, and in particular beneath the top face of the bearing portion;crimping the central contact of the connector onto the central conductor of the cable using a crimping tool having a bearing surface for bearing against the crimping portion of the central contact, the tool being movable during crimping to an end-of-stroke position in which the bearing surface of the tool extends at least in part into said empty space and beneath the crimping portion of the central contact, and in particular beneath the top face of the bearing portion.

By means of the invention, the crimping portion of the central contact can be pressed against the bearing surface of the tool over a stroke of the tool that is relatively long during crimping, since this bearing surface of the tool can move down relatively far compared with the insulating body of the connector.

This makes it possible, in particular, to fold down the deformable branches of the crimping portion of the central contact in reliable manner, and specifically to avoid these branches buckling outwards while crimping is taking place.

In an implementation of the invention, the crimping portion of the central contact has a cross-section that is substantially U- or V-shaped, and in particular the two branches of the U- or V-shape are folded down towards each other during crimping. The above-mentioned empty space may extend in particular at least in part below a plane that is tangential to the base of the U- or V-shape.

Advantageously, the crimping tool includes an opening into which the crimping portion of the central contact engages during crimping, and the bearing surface of the tool presents a cross-section of a shape that flares towards the opening, at least in the vicinity of said opening.

This shape for the bearing surface of the tool makes it possible to cause the crimping portion of the central contact to be folded down progressively.

By way of example, the bearing surface of the tool may have two facing walls that define a flared shape, which two walls may be plane or otherwise, for example they could be curved.

The bearing surface may be formed in a cavity of the crimping tool, the cavity presenting an end wall of cross-section that is substantially m-shaped, for example.

Preferably, the depth of the cavity in the tool is selected to be sufficient to ensure that at the end of the crimping stroke of the tool, the bearing portion of the insulating body is engaged at least in part in said cavity.

As can be observed, the invention makes it possible to avoid having an opening through the connector for passing a crimping tool that is situated beneath the central contact, thus ensuring, in particular, that the assembly of the connector to the coaxial cable presents performance that is satisfactory in the radio frequency range.

Furthermore, at the end of the crimping stroke of the tool, the bearing surface of the tool may present a shape that substantially matches the shape of the side wall(s) of the bearing portion of the insulating body so that, where appropriate, the bearing surface of the tool can oppose any tendency of the bearing portion of the insulating body to spread under the effect of the force exerted by the crimping tool on the insulating body. The tool can thus take up a fraction of the forces to which the bearing portion of the insulating body is subjected, should that be necessary. If so desired, the invention thus makes it possible to use the crimping tool to exert a relatively high force on the crimping portion without damaging the bearing portion of the insulating body situated beneath it.

In an implementation of the invention, the bearing portion of the insulating body extends substantially entirely beneath the crimping portion of the central contact.

The bearing portion of the insulating body may have a cross-section of a shape that flares downwards, i.e. in a direction substantially opposite to the direction in which the top surface faces.

By way of example, the bearing portion may have at least one side wall that is plane.

In a variant, the bearing portion may have at least one side wall that is not plane, for example a wall that is curved.

In an implementation of the invention, the bearing portion of the insulating body includes at least one side wall with a first plane portion substantially adjacent to the top face of the bearing portion, and a second plane portion beneath the first plane portion and not parallel thereto.

If so desired, the bearing portion may include at least two facing parallel side walls, in particular plane walls.

In an implementation of the invention, the top face of the bearing portion of the insulating body includes a setback arranged to receive at least part of the crimping portion of the central contact, said setback extending in particular substantially parallel to the side walls of the bearing portion of the insulating body.

The insulating body may include a portion, in particular a substantially cylindrical portion, to which the bearing portion is connected, and which has a recess arranged therein to receive at least part of the central contact.

In an implementation of the invention, the insulating body is made of a polymer, in particular a high performance polymer.

The electrical connector may include an outer conducive body provided with a wall surrounding the central contact and the bearing portion of the insulating body, at least in part, said bearing portion resting against said wall of the outer body.

In an implementation of the invention, the depth of the cavity in the crimping tool lies substantially in the range one-half to two-thirds the inside radius of the outer body level with the crimping portion of the central contact.

Advantageously, the outer conductive body includes at least one crimping portion for crimping against at least one of the shielding braid and the outer insulating sheath of the coaxial cable.

In an implementation of the invention, the insulating body of the connector is set back from a crimping central contact of the connector that is used for crimping the shielding braid of the coaxial cable. The central contact of the connector may optionally be provided with an additional crimping portion for crimping to the inner insulating sheath of the coaxial cable.

The invention also provides an electrical connector for mounting on a coaxial cable, the connector comprising:a central contact extending along a longitudinal axis and provided with at least one crimping portion suitable for being crimped on a central conductor of the coaxial cable;an insulating body comprising a bearing portion having a top face against which at least part of the crimping portion of the central contact bears, said bearing portion having at least one side wall extending substantially along said longitudinal axis; andat least one empty space adjacent to the side wall of the bearing portion of the insulating body, said empty space extending at least in part beneath the crimping portion of the central contact.

In an embodiment of the invention, the central contact crimping portion has a cross-section that is substantially U- or V-shaped, with the branches of the U- or the V-shape flaring upwards, for example.

The bearing portion of the insulating body may extend substantially entirely beneath the central contact crimping portion and, where appropriate, may include in its top face a setback extending along the longitudinal axis and arranged to receive the central contact crimping portion, at least in part.

The invention also provides an electrical connector for mounting on a coaxial cable, the connector comprising:an outer conductive body including at least one crimping portion, in particular a portion of U- or V-shaped cross-section, for crimping onto at least one of the shielding braid and the outer insulating sheath of the coaxial cable;an insulating body secured to the outer conductive body; anda central contact held by the insulating body, each branch of the U- or V-shaped crimping portion of the outer body including at least one tooth at its top end, for example, and in particular including a plurality of teeth.

The invention also provides a crimping tool for crimping an electrical connector to a coaxial cable, the tool comprising:an opening in which a crimping portion of the electrical connector is engaged during crimping; anda bearing surface presenting a cross-sectional shape that flares towards the opening, at least in the vicinity of said opening.

The crimping tool need not have any hinged portions, for example.

The invention also provides an assembly of an electrical connector of the invention and a coaxial cable.

MORE DETAILED DESCRIPTION

FIG. 1shows an electrical connector1in accordance with the invention, comprising an outer conductive body2, an insulating body3secured to the outer body2, and a central contact4held by the insulating body3.

The outer body2comprises a cylindrical portion5of longitudinal axis X having a cylindrical portion6of the insulating body3secured therein, and a keying portion8in relief, e.g. formed by tabs projecting from the cylindrical portion5, the keying portion8co-operating with a housing in a complementary electrical connector (not shown).

The outer body2further comprises two crimping portions10and11each of substantially U-shaped cross-section perpendicular to the axis X.

The crimping portions10and11comprise respective pairs of fold-down branches10a&10band11a&11brespectively serving to crimp onto the shielding braid15and onto the outer insulating sheath13of a coaxial cable12.

Each of these crimping portions10and11is provided with a respective opening18situated between its two fold-down branches10a&10bor11a&11b, leaving room, during crimping, for a fraction of the shielding braid15or of the outer insulating sheath13to project slightly through the opening18, thus improving anchoring of the shielding braid15and the outer insulating sheath13within the connector.

Each of the branches10a,10b,11a, and11bhas a plurality of teeth19at its end, in particular to surround better the shielding braid15or the outer insulating sheath13.

The insulating body3has a bearing portion20extending along the axis X and connected to the cylindrical portion6, as can be seen inFIG. 3, in particular.

The bearing portion20has a top face22provided with a setback23of axis X arranged to receive a crimping portion25of the contact element4, at least in part, as shown inFIG. 1.

The bearing portion20presents a bottom wall32resting on a cylindrical wall of the outer body2.

In the example described, the bearing portion20has two facing walls27that diverge downwards, each comprising a first plane portion28substantially adjacent to the top face22and a second plane portion29below the first portion28and not parallel therewith.

In a variant, as shown inFIG. 4, the bearing portion20of the insulating body3may have two facing side walls30that are completely plane and that diverge downwards.

In another variant, the bearing portion20of the insulating body20may have two side walls31that are plane and parallel.

In the example described, the insulating body is made of a high performance polymer. Naturally, the invention is not restricted to an insulating body made with this type of material.

The cylindrical portion6of the insulating body3includes a recess33serving to receive one end of the central contact4when the crimping portion25is placed on the top face22of the bearing portion20.

The crimping portion25is of U-shaped cross-section, with two facing branches35that can be folded down towards each other around the central conductor16of the coaxial cable12, during crimping. The branches35flare apart upwards, prior to crimping, as shown in particular inFIG. 6. In a variant, the branches of the U-shape could initially be parallel.

In a variant that is not shown, the crimping portion25could have more than two deformable branches, for example it could have two pairs of facing branches.

The electrical connector1has two empty spaces40formed on either side of the bearing portion20of the insulating body3.

Each empty space40is adjacent to one of the side walls27of the bearing portion20and extends under the crimping portion25of the central contact4as far as the outer conductor2, as can be seen in particular inFIG. 6.

In order to crimp the crimping portion25onto the central conductor16of the coaxial cable12, a crimping tool50is used as shown diagrammatically in cross-section inFIGS. 6 to 8.

This tool50includes a cavity51defining a bearing surface52capable of bearing against the crimping portion25of the central contact4.

At least in the vicinity of an opening53through which the crimping portion25of the central contact4is engaged during crimping, the bearing surface52presents a cross-section that flares downwards.

By way of example, the bearing surface52may comprise two facing curved walls55that join together via an end wall54of the cavity51, which end wall54presents a cross-section that is m-shaped, for example.

In the example described, the shape of the bearing surface52is selected so as to match substantially the shape of at least a portion of the side walls27of the bearing portion20at the end of the stroke of the tool50during crimping, as shown inFIG. 8.

While the central contact4is being crimped onto the central conductor16of the coaxial cable12, the tool50is moved along an axis Y perpendicular to the axis X, as shown inFIGS. 6 to 8.

The downwardly-flared shape of the bearing surface52of the tool50and the relatively great depth of the cavity51enable the branches35of the U-shape of the crimping portion25to be folded down progressively so as to avoid any buckling of these branches35in an outward direction.

The bearing surface52engages in the empty spaces40beneath the crimping portion25after the tool50has moved along a stroke of a certain magnitude, as shown inFIG. 8.

At the end of crimping, as shown inFIG. 8, the branches35have been folded down towards each other around the central conductor16.

In the example described, at the end of the stroke, the tool50exerts a force that may be of the order of 1300 newtons (N) on the assembly constituted by the central contact4and the bearing portion20.

Because the bearing surface52of the tool50serves to limit any spreading of the bearing portion20, said portion can withstand relatively high forces without being damaged.

The bearing surface52of the tool50may be downwardly flared to a greater or lesser extent as a function of the shape of the side walls of the bearing portion20.

As shown inFIGS. 9 and 10, when the bearing portion20has side walls31that are plane and parallel, the bearing surface52of the tool50may flare downwards to a smaller extent, e.g. having two facing walls55that are substantially plane.

Naturally, the invention is not limited to the embodiments described above.

For example, if so desired, at the end of the crimping stroke, the bearing surface of the crimping tool need not match the shape of the side walls of the bearing portion of the insulating body.