Coil Wound Elastomer Connector

Abstract

The invention concerns a method of making a connector body comprising a multiplicity of spaced resilient conductive springs disposed within a matrix of elastomeric insulating material defining a body having spaced surface parts between which the springs extend in non-rectilinear paths and at which ends of the springs are exposed. According to the method at least one wire is wound into a coil of spaced turns and the coil is potted in a mass of elastomer. The resulting body is cut through the coil turns to present the spaced surface parts. To facilitate coil formation and potting, the wire may be wound with elastomer strip or sheet spacing and the composite coil then cured to form a bond between contiguous elastomer surfaces and define a coherent matrix. Alternatively the elastomer may be injection or vacuum molded in the fluent state.

Description

This invention concerns electrical connectors and their method of manufacture.

Generally connectors comprise metal contact portions of interfitting male and female forms each having means for connection to a wire and being releasably mountable in an insulating housing. The housing may contain several contacts arranged for respective connection with complementary contacts in a second housing. Certain disadvantageous limitations have been found with such connectors. The trend to minaturization of assemblies, the extensive use of integrated circuits and the construction of complex assemblies such as computers from small circuit modules has further revealed the need for an alternative to the traditional forms of connector which is economic to use and of wide application.

There has been proposed in the U.S. publication Automotive Industries of Dec. 15, 1971, a contact material comprising a conductive elastomer which may be spongy or semi-rigid. In one application wire ends are mounted within respective plastics sleeves and pressed against a diaphragm comprising an elastomer frame containing cells of the conductive elastomer in compressed condition. The cells are larger than the wire ends which are pressed against respective cells. The cells present a large number of contact points to the wire ends and a large number of parallel conductive paths through the cell.

The contact material comprises a mass of fine metallic or conductive particles suspended in the elastomer matrix such that on subjection to pressure, particles are urged into contact along pressure lines to define conductive paths.

The present invention concerns a different form of material comprising a body of elastomeric insulating matrix containing a plurality of spaced resilient conductors extending between spaced surface parts of the body through non-rectilinear paths. An example of such a material is disclosed in German Offenlegenschrift 2,119,567 published Nov. 25, 1971.

According to the present invention a method of manufacturing such a connector material comprises winding a metal wire in a coil of axially spaced turns, potting the coil in a mass of elastomeric insulating material, cutting the resulting body through the turns of the coil to present a body portion with cut surface parts at which are exposed a multiplicity of respective ends of segments of the coil turns.

The wire is suitably of metal having good spring characteristics as well as electrical performance and resistance to degradation, for example phosphor bronze or brass. The wire should be fine in relation to the contact areas with which it is to be used so that within a contact area a large number of contact points are exposed.

The coil may be wound in an appropriate shape to give the desired spring form to the wire segments, for example the segments may be arcuate with a coil of circular section or chevron shaped from a coil or polygonal cross-section.

To facilitate dielectric separation of adjacent turns the coil may be wound from pre-insulated wire. The insulation may for example be of varnish type in order to maintain a thin coating and allow close spacing of adjacent wire turns or a slippery insulating material such as polytetrafluorethylene to facilitate relative movement between adjacent segments in a cut body portion, and between the wire segments and their surrounding insulation.

The invention includes a body of contact material prepared by the above method and comprising a matrix of elastomeric insulating material containing a mass of segmental resilient conductors in spaced insulated relationship extending between spaced surface parts of the body.

In one embodiment each wire segment is contained within an individual sheath or coating of a fine insulating material and the mass of insulated wires is potted within the elastomeric matrix of a second insulating material.

The invention will now be described by way of example with reference to the accompanying partly diagrammatic drawings, in which:

FIG. 1 is a perspective view of a circular section coil of wire potted in a block of elastomeric insulating material;

FIG. 2 is a perspective view of a connector portion cut from the potted coil of FIG. 1;

FIG. 3 is an end view of an alternative connector portion cut from the potted coil of FIG. 1;

FIG. 4 is an end view of a connector portion cut from a potted coil similar to that of FIG. 1, but containing a coil of polygonal section;

FIG. 5 is a fragmentary section of a connector portion similar to that of FIG. 1 and containing a coil of relatively thickly insulated wire;

FIG. 6 is a fragmentary view of part of a contact surface of a coil wound connector portion having discrete contact zones;

FIG. 7 is a perspective view of a coil being wound according to one method;

FIG. 8 is a fragmentary section taken on the line 8--8 of FIG. 7;

FIG. 9 is a perspective view of a coil being wound according to a second method;

FIG. 10 is a section taken on the line 10--10 of FIG. 9;

FIG. 11 is a perspective view of a coil being wound according to a third method;

FIG. 12 is a fragmentary section taken on line 12--12 of FIG. 11;

FIGS. 13 and 14 are fragmentary sections similar to that of FIG. 12 of coils wound according to fourth and fifth methods;

FIG. 15 is a perspective view of a coil being wound in a polygonal cross-section;

FIG. 16 is a fragmentary section similar to those of FIGS. 12 to 14 of a coil wound according to a sixth method;

FIG. 17 is a fragmentary sectional view of a coil being wound on a former to define discrete contact zones;

FIG. 18 is a fragmentary end view of the coil former of FIG. 17;

FIG. 19 is a section of a coil wound to a yet further method; and

FIG. 20 is an end view of a connector made from the coil of FIG. 19 and applied to a pair of back to back printed circuit boards.

In FIG. 1 a cylindrical coil 1 of fine insulated wire is potted in a block 2 of elastomeric insulating material to contain and support the wire turns of the coil in insulated spaced relation in a matrix of elastomer insulating material. Various coil winding and potting techniques for this purpose are described below.

The potted coil 1 may be cut into one or more connector portions 3, for example as shown in FIG. 2, where the coil has been cut in planes 4, 5 extending axially and radially of the coil to define a pair of orthogonal contact faces 4, 5. At each contact face 4, 5 cut ends 6 of the wire turns 7 are disposed in closely spaced array in the elastomer matrix. After cutting, the contact surfaces 4, 5 are suitably cleaned to remove any conductive swarf and surface imperfections and the wire ends 6 are suitably then plated by known pulse plating techniques with contact material such as gold or tin to present contact tips which may project from the elastomer matrix surface 4, 5 and serve to facilitate and improve electrical contact with the wire ends 6. The cut wire turns 7 define arcuate springs supported in the elastomer matrix and extending between the contact faces 4, 5.

In the alternative connector portion 8 of FIG. 3 a coil is cut in a pair of spaced axially extending planes 9, 10 parallel to and equally spaced from a radial plane of the coil to define the connector portion 8. This presents a pair of parallel contact faces 9, 10 at which the wire ends 11 are disposed in opposed identical pattern.

In the embodiment of FIG. 4, a coil has been wound about a polygonal former so that each cut wire segment 12 is of chevron form comprising a pair of relatively inclined rectilinear portions 13, 14 compared with the arcuately curved segments in FIGS. 2 and 3.

In the embodiment of FIG. 5, the wire turns 15 are of insulated wire having a relatively thick coating 16 of insulation such as polytetrafluoroethylene and potted within a surrounding matrix 17 of a more pliable elastomer such as a silicone rubber.

In the embodiment of FIG. 6 a coil is arranged as spaced windings 18 potted in an elastomer matrix and the connector portion cut to present discrete contact zones 19 at spaced intervals within the elastomeric matrix 20.

Although the technique of coil winding is a highly developed art, it will be appreciated that there may be some practical difficulty in potting a closely wound coil into a coherent matrix of elastomer free from air spaces. Although elastomer such as silicon rubber may be prepared from liquid constituents and remain in the liquid phase during a curing period so as to be suitable for injection or vacuum molding, the flow passages through a closely spaced coil particularly of fine wire may render difficult a satisfactory potting in which coil turns are individually contained within the matrix.

In the coil winding method of FIG. 7, several wires 21 are wound in flat turns 22 at spaced intervals 23 axially of a cylindrical former 24 with an interleaving 25 of elastomeric sheet material. As shown in FIG. 8, the wire turns 22 tend to embed in the elastomeric layer 25 beneath them in the coil and elastomer extrudes or deforms into the inter-wire spaces so that consecutive turns of the elastomer layer 25 contact each other through these spaces, for example at 29. After winding, the elastomer layers may be transformed into a coherent matrix by a method dependent on the characteristics of the elastomer being used.

Generally an adhesive bond may be obtained between abutting elastomer surfaces by coating a surface or the surfaces of the elastomer layer 25 with an appropriate adhesive before winding into the coil and after winding allowing the adhesive to set or cure. The radial pressure due to coil winding is sufficient to effect adequate bonding of the adhesive and the coil may be heated to effect or increase the rate of curing.

If the elastomer layer 25 is silicone rubber then the surfaces of the layer may be wetted by uncured silicone rubber in liquid state, curing being effected after winding by heat treatment to cause a coherent bond between the touching layers, in the spaces 23 between the wire turns 22.

If the elastomer layer is of partially cured butyl rubber, the coil winding pressure is sufficient with the application of heat to effect coherent bonding on curing. A similar effect may be obtained with other partly cured rubbers embodying a cross-linking agent such that bonding will be effected under the coil pressure and application of heat. So called B-stage polyurethane may be bonded in a similar way.

An alternative approach is to utilize an appropriate solvent to soften the surfaces of the elastomer layer before winding and after winding to evaporate the solvent by heating.

In the embodiment of FIGS. 9 and 10, a double layer coil 30 is wound in a similar manner to the single layer coil of FIGS. 7 and 8 but with sets 31, 32 of spaced wires and associated layers 33, 34 of elastomer started from diametrically opposite locations of the coil former 35. As seen in FIG. 10 the wires 31 of alternate layers of the composite winding are staggered longitudinally of the coil in relation to the wires 32 of intermediate layers so that in section a wire of any layer is aligned radially of the coil with the space between adjacent wires in the adjacent layer or layers. This accentuates the tendency for the elastomer layers 33, 34 to extrude into and completely fill the interwire spaces under the coil winding pressure and facilitates the formation of a coherent voidless matrix of elastomer encasing the wire turns.

In the embodiment of FIGS. 11 and 12 a multi-layer coil 35 is helically wound from a single wire 36 and an elastomer strip 37 arranged side-by-side so that adjacent turns of wire 36 are spaced axially of the coil by the elastomer strip 37. As seen in FIG. 12, successive windings 38, 39, 40, 41 are stepped axially of the coil so that wire turns 36 in one layer abut the elastomer strip 37 in the adjacent layers. Suitably the elastomer strip 37 is wider than the wire diameter so that the wire receiving spaces between adjacent turns of the elastomer strip 37 in one layer are totally bridged by the elastomer strip 37 in the adjacent layer.

In the embodiment of FIG. 13, which is similar to that of FIGS. 11 and 12, layers of the coil or successive windings 42, 43 are interleaved by layers 44 of elastomer sheet wound in a concentric coil. In this case the intervening coils of elastomer strip 37 need not be wider than the wire diameter and may allow closer pitching of the wire turns.

FIG. 14 shows a further embodiment in which a coil is wound in successive layers 45, 46, 47 similar to that of FIGS. 11 and 12 but the elastomer strip 48 is of round cross-section of larger diameter than the intervening wire 49. This allows bridging of the inter-wire spaces by the alternate layers of the elastomer strip 48 which under the coil winding pressure will deform substantially to fill the spaces and maintain the wires in insulating spaced relation.

FIG. 15 shows the winding technique disclosed in FIG. 7 applied to the winding of a polygonal section coil 50 on a polygonal former 51.

FIG. 16 shows a fragmentary coil section in which insulated wire 52 is wound in a multi-layer coil with the turns of adjacent layers 53, 54 and 54, 55 leading in opposite directions. Adjacent turns 56, 57 in each layer are spaced apart so that a multi-layer mesh is formed as viewed radially of the coil. With windings of this form there is adequate flow space 58, 59, 60 through the coil for effective potting of the turns 52 by injection or vacuum molding techniques using an uncured elastomer resin. To facilitate this the core 61 may be formed with flow passageways, not shown, through which the resin may pass for radial flow through the coil mesh and filling of the coil spaces 58, 59, 60.

In the embodiment of FIGS. 17 and 18, a coil core 62 is provided with radially projecting spacers 63 arranged in axially spaced groups 64, the spacers 63 of each group 64 being circumferentially distributed around the core 62. First coils 65 are wound by any of the above described techniques between the adjacent groups 64 of spacers 63 of spaced pairs of groups 64. The spaces 66 between adjacent first coils 65 being filled with elastomer by winding or potting to the radial level of the first coils 65. Second coils 67 are then wound over these elastomer fillings and the corresponding spaces 68 over the first coils 65 are elastomer filled. In this way a composite coil may be built up in which groups 65, 67 of closely spaced wire turns are spaced apart in the elastomer matrix for manufacture of a connector of the kind shown in FIG. 6.

When cutting a connector matrix from the potted coil of FIGS. 17 and 18, the contact surfaces are cut in the spaces 69 between adjacent spacers 63 of the groups. As a result any spacer 63 remaining within a connector matrix can be contained within the matrix remote from the contact faces.

In winding a composite coil by this technique it is possible to shield the groups of wire turns from each other by disposing metal foils within the elastomer. For example a foil tape may be wound above and below each coil layer and annular foil spacers provided at axially spaced intervals between coils. The annular foil spacers may replace the groups of spacers show in FIG. 18.

In the embodiment of FIGS. 19 and 20 a coil 70, FIG. 19, wound by one of the above techniques is provided with an outer coil layer 71 of spring wire of enhanced spring characteristics compared with the inner coil turns 72. After potting the composite coil a connector body is formed by removing the coil core 73 and cutting a segment from the coil along the broken lines 74 to define a generally C-spring form having a pair of spaced contact faces 75, 76 from which the ends 77 of the outer spring turns are suitably cut back. In use as shown in FIG. 20 a pair of back to back printed circuit boards 78 having conductive paths 79 on their remote faces are clamped together between the contact faces 75 the mechanical clamping action is essentially due to the outer spring turns 71 which urge the contact faces against the boards 78 and the conductive paths 79.

In the embodiments described above, use has been made of a core for the coil winding which may be formed of cured elastomer for bonding in the matrix on potting the coil windings. Alternatively a rigid core may be used and removed after potting the coil.

Although the embodiments have been wound with conventional round wire, wire of any section may be used. Where an elongated section is used it may be arranged with its longer axis extending radially of the coil so that the winding segments are bent against their maximum stiffness.

Claims

What is claimed is:

1. A method of manufacturing a connector body comprising a multiplicity of spaced resilient conductive springs disposed within a matrix of elastomeric insulating material defining a body having spaced surface parts between which the springs extend in non-rectilinear paths and at which ends of the springs are exposed, said method comprising the steps of winding a plurality of wires into individual coils of flat turns at spaced intervals axially of a cylindrical former, interleaving a sheet of elastomeric material in a manner so as to be common to the plurality of wires, said elastomeric material being wound in a coil disposed between each turn of the individual coils of said wires, bonding adjacent layers of the elastomeric sheet material through the interwire spaces to form a coherent matrix, and cutting through the coil turns to define the connector body with cut portions presenting the spaced surface parts.

2. A method as claimed in claim 1, in which two sets of several wires each associated with a respective sheet of elastomeric insulating material are wound into a composite coil as alternating layers, the wires of one set being staggered longitudinally of the coil in relation to those of the other set so that a wire in any layer lies between adjacent wires in the adjacent layer or layers.

3. A method as claimed in claim 1, in which uncured or partly cured elastomer is wound into the coil and curing is then completed to effect bonding between adjacent layers of the elastomer.

4. A method as claimed in claim 1, in which elastomer strip or sheet having an adhesive or solvent surface coating is wound into the coil and subsequently set or cured or evaporated to bond adjacent layers.

5. A method as claimed in claim 1, in which a vulcanizable elastomer is wound into the coil and is subsequently vulcanized to bond adjacent layers.