Low profile connector

Abstract

 An electrical connector (32) for interconnecting overlapped flap multiconductor cables (12, 30) includes a centerbody (38) adapted to be seated in a hole (40) extending through registered cable conductors. The centerbody (12, 30) has first contact fingers (42) extending from one end thereof and second contact fingers (44) extending from the opposite end thereof. Both sets of contact fingers have insulation piercing ends (42d, 44c) for electrically engaging the cable conductors, upon crimping, at mutually spaced locations coaxial with the centerbody (38).

Description

FIELD OF THE INVENTION

[0001] This invention relates to electrical connectors and assemblies and pertains more particularly to apparatus and methods for insulation piercing interconnection of flat cable.

BACKGROUND OF THE INVENTION

[0002] Flat multiconductor cable is in increasing use as a substitute for customary discrete power distribution cables. A typical present installation finds the flat cable extending from power mains to the floor of an office and thereacross beneath carpet tiles into as many branches as are required to energize office outlets. Each branch from the flat cable connected to the power mains occasions a splice or tap connection thereto of a branch cable, itself feeding the outlet. Should it be necessary to lengthen any installed cable, a longitudinally aligned further cable is splice connected thereto.

[0003] For convenience of installation, the several commercial undercarpet wiring systems known at present employ insulation piercing connectors for making such taps and splices. In one system, the tap/splice connector of which is shown in U.S. Patent Application Serial No. 123,490 filed on February 21, 1980, entitled "Electrical Connector", assigned in common herewith, the cables to be connected are first overlapped. A locating hole is then made through the cables in registry with each pair of conductors to be connected and the connector is placed in the hole with its insulation piercing arms facing the exterior sides of the cables. The arms are then crimped upon the cables into electrical connection with the conductors therein.

[0004] In a second known system the cables are placed in abutting relation and a flat elongate connector, shown in U.S. Patent No. 3,960,430, issued on June 1, 1976, is disposed underlyingly across the line of abutment with its longitudinally opposite ends in registry with a conductor of each cable. The ends have insulation piercing contacts which are forced entirely through the cable, emerging at the cable upper side to be crimped back upon the cable into electrical engagement with its conductor.

[0005] In a third known system, a hole is made through overlapped cables and a rivet contact is placed in the hole with its ends extending outwardly of the exterior sides of the cables. The contact is then crimped upon the cables into full rivet configuration, the ends thereof piercing cable insulation and the contact electrically engaging the conductors registered with the hole.

[0006] Common to all of the described approaches is a requirement for a crimping force of substantial magnitude. Thus, rather large floor-supported crimping tools are necessary in each instance, both increasing system installation labor costs and effort expended per cable connection.

SUMMARY OF THE INVENTION

[0007] The present invention has as its primary object the provision of an improved insulation piercing connector.

[0008] A more particular object of the invention is to provide an insulation piercing connector of low profile which simplifies the interconnection of flat multiconductor cables, particularly from a crimping force viewpoint.

[0009] In attaining the foregoing and other objects, the connector of the invention has a body for seating, by expeditious insertion from above, in a hole formed through registered conductors of a pair of flat cables. - The connector has a plurality of individually deformable and perimetrically spaced contact members extending from the body, which electrically interconnects them, and each contact member has opposed insulation piercing end courses, one extending axially with the centerbody and the other spaced outwardly from the body.

[0010] In its particularly preferred embodiment, such connector body is a cylindrical centerbody of spring tempered metal having an opening extending axially therethrough. First contact fingers extend contiguously with the opening in perimetrically spaced relation from one end of the centerbody in such courses that the free ends of the contact fingers reside in a locus exteriorly coaxial with the center body. Second contact fingers extend in perimetrically spaced relation from the opposite end of the centerbody axially therewith and conti^g- uously with the opening.

[0011] In use of the connector, the centerbody is placed in the cable-hole with the first contact finger ends abutting exterior cable insulation. A crimping tool is then applied, one die surface thereof engaging the first contact fingers during crimping. Another die surface is configured to engage the ends of the second contact fingers and, in the course of crimping, to impart individually to the fingers a curvature such that the finger ends become exteriorly coaxial with the centerbody and assume a line of attack with respect to the cable they confront.

[0012] As the finger ends aside each of the cable exterior sides are all in such perimetrically spaced configuration and in line of attack, nominal crimping force effects insulation piercing thereby and gas-tight electrical engagement with the registered conductors. A particularly low profile, i.e., low height of the connector above and below the connected cables, is achieved to permit aesthetic placement of the cable system beneath carpet tiles.

[0013] The foregoing and other features of the invention will be further evident from the following detailed description of the preferred embodiment thereof and from the drawings wherein like reference numerals identify like parts throughout.

DESCRIPTION OF THE DRAWINGS

[0014] 

Fig. 1 is a perspective showing of a known flat multiconductor cable of type for use in undercarpet power distribution.

Fig. 2 is perspective plan view of a partially completed splice of two cables as in Fig. 1 using connectors of the subject invention.

Fig. 3 is perspective elevation of a connector in accordance with the invention.

Fig. 4 is a sectional elevation as would be seen from plane IV-IV of Fig. 3.

Fig. 5 is a bottom plan view of the Fig. 4 sectioned connector.

Fig. 6 is a partial sectional elevation as would be seen from plane VI-VI of Fig. 1.

Fig. 7 is a top plan elevation of a die suitable for engagement with contact fingers 44 of Fig. 1 in the course of connector crimping.

Fig. 8 is a sectional elevation as seen from plane VII-VII of Fig. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS AND PRACTICES

[0015] Referring to Fig. 1, there is shown a known flexible cable assembly 10, including a flexible multiconductor cable 12, an electrically conductive member constituted by flexible metallic shield 14 positioned above the cable 12, and a flexible plastic shield 15 positioned below the cable 12. The multiconductor cable 12, the metallic shield 14, and the plastic shield 15 have about the same width and are flat such that the cable assembly 10 can be installed underneath a carpet (not shown) or some other similar type of floor covering.

[0016] The multiconductor cable 12 contains a plurality of flat electrical conductors 16, 18, 20, which are contained within a casing constituted by a thin sheet 22 of electrical insulation. The insulation 22 is preferably made from a laminate of polyester and polyvinylchloride. The poly vinylchloride is is contiguous with the conductors 16, 18, 20, while the polyester forms the outer surface of the cable 12. The conductors 16, 18, 20, which are made from copper or any other good electrically conductive material, extend side-by-side along the entire length of the multiconductor cable 12.

[0017] In the embodiment shown in Fig. 1, conductors 16 and 20 adjacent to the opposite longitudinally extending edges of the multiconductor cable 12, may be employed as hot conductors, the middle conductor 18 serving as a ground conductor. The ground conductor 18 is permanently connected, both mechanically and electrically, to the metallic shield 14 by a plurality of welds 24 which are arranged at intervals along the length of the cable assembly 10. Indicia, such as color-coded markings 25, may be provided on the insulation 22 above and below the conductors 16, 18, 20 to distinguish them from each other.

[0018] The metallic shield 14 is made from a thin sheet of good electrically conductive metal such as copper. A layer (not shown) of steel preferably overlies shield 14 and further insulation is disposed stripwise between shield 14 and the insulation of the cable. Preferably, the metallic shield 14 and the conductors 16, 18, 20 are made from the same metal to prevent galvanic corrosion between the metallic shield 14 and the ground conductor 18.

[0019] The plastic shield 15 is employed to provide a cushion for the multiconductor cable 12. As such, the plastic shield 15 can be made of any suitable flexible plastic, such as polyester, sufficiently strong to protect the multiconductor cable 12 from abrasion and possible piercing as a result of its installation on a floor, especially if the floor is made from concrete. The plastic shield 15, which may be permanently attached to the multiconductor cable 12 in any suitable manner also inhibits the penetration of the multiconductor cable 12 by any projections extending upwardly from the floor. Preferably, shield 15 is secured to cable 12 insulation by heat-sealing thereof at locations spaced lengthwise of the shield.

[0020] The selective securement of shield 14 to cable 12 at locations mutually spaced lengthwise of the cable gives rise tc successive shield extents which are respectively unsecured and secured to the cable. Thus, the extent of shield 14 downwardly of weld 24 in Fig. 1 is not secured to the cable. The successive extent of shield 14, i.e., adjacent weld 24, is secured to the cable. The next successive shield extent, upwardly of weld 24 in Fig. 1 is again not secured to the cable. This pattern preferably repeats along the cable length, with uniform or nonuniform shield extents, giving rise to redundant electrical connection of shield 14 to cable 12. Electrically conductive means are in registry with each secured shield extent. For example, the body of material comprising weldment 24, extends through the cable insulative casing, opposed terminal portions of the body having electrical connection to the shield and to an exclusive one of the cable conductors.

[0021] As shown in Fig. 2 the cable assembly 10 is joined to another identical cable assembly 26, having a metallic shield 28, a plastic shield 29, and a multiconductor cable 30 which is joined to the multiconductor cable 12 by connectors 32. It is not necessary to mechanically and electrically connect the lapping ends of metallic shields 14 and 28 to each other and to ground in order that they are properly grounded, inasmuch as the metallic shields 14 and 28 are electrically connected to ground through welds 24, the ground conductor 18 of the multiconductor cable 12, the corresponding one of the connectors 32, the ground conductor of the multiconductor cable 30, and welds 36 which mechanically and electrically connect the ground conductor of the multiconductor cable 30 to the metallic shield 28. Thus, the lapping ends of shields 14 and 28 may be peeled back (Fig. 2) to inspect or observe the cables 12 and 30 or the connectors 32.

[0022] Referring to Figs. 3-5, connector 32 of the present invention has a hollow cylindrical centerbody 38 of outer diameter D, approximating the diameter of hole 40 (Fig. 2) formed through conductors of cables to be joined. Extending from the upper end of centerbody 38, contiguously with axially extending opening 39 therethrough, is a plurality of first contact members or fingers 42, each having a first course 42a running axially with centerbody 38, a second course 42b running radially outwardly of the centerbody and a third or end course 42c exteriorly coaxially with and having ends 42d spaced outwardly of the centerbody and of insulation piercing type. Adjacent ones of fingers 42 are equally spaced at courses 42a by spacing Sl, giving rise to a mutual perimetric spacing relation among the plurality of fingers 42.

[0023] A plurality of second contact fingers 44 extends from the lower end of centerbody 38 axially therewith and contiguously with opening 39, each finger 44 having a lead course 44a and an end course 44b to be deformed in a crimping operation and an end 44c of insulation piercing type including a chamfered surface, i.e. a flat surface tapering radially outwardly of centerbody 38. Adjacent ones of fingers 44 are equally spaced at courses 44a by spacing 82, giving rise to a mutual perimetric spacing among the plurality of fingers 44. While spacings Sl and S2 are of equal measures in the illustrated embodiment, it will be noted that the perimetric spacing S3 between adjacent finger end courses 42c exceeds Sl and S2, based on the different radial locations thereof in the connector uncrimped state, i.e., the article of manufacture state thereof prior to use. As illustrated, connector 32 is preferably constituted as a body of electrically conductive material, such as a spring tempered metal, e.g., beryllium copper or spring steel suitably plated, and contact fingers 42 and 44 are integral therewith. The first and second sets or pluralities of contact fingers 42 and 44 are provided with contact fingers in number at least three, with the successive end courses of each set extending in different arcuate directions (Fig. 5).

[0024] In making the splice connection of cables 12 and 30 in Fig. 2 (wherein the shields are omitted for convenience), the cables are overlapped at ends and longitudinally aligned. Next holes, one shown at 40 are punched through the cables, each hole extending through a longitudinally registered pair of conductors. Connectors 32 are now inserted into the holes conveniently from above the cables, contact fingers 44 leading, until contact fingers 42 engage the insulation of the upper cable. A crimping tool is now applied to each inserted connector, the tool having an upper die member whose die surface is generally flat, engaging each contact finger 42, to displace finger end course 42c in line of attack to the cable insulation. As shown in Fig. 6, insulative layer 22 is pierced with the finger ends 42d penetrating but preferably not piercing through conductor 18. As indicated, the line of attack of insulation piercing is at a generally orthogonal angle with respect to the surface of such insulation.

[0025] The crimping tool lower die member 50 (Figs. 7 and 8) has a die surface 52 adapted to receive contact finger 44 end courses 44b and to impart configuration as indicated in Fig. 6, wherein courses 44a of these fingers are deformed into radially outward configuration so as to support end courses 44b preferably in a substantially othogonal line of attack with respect to the cable undersurface insulation. In the fully crimped connector, finger ends 44c pierce through insulation 46 penetrating, but preferably not piercing through conductor 48 of cable 30. At the opposite side of the assembly, finger end courses 42c pierce through insulation 22, the finger ends 42d penetrating but preferably not piercing through conductor 18 of cable 12, the assembly thus providing gas-tight electrical engagement at opposed sets of locations which are mutually perimetrically spaced. Centerbody 38 preferably electrically engages the conductors further by contact therewith at its cylindrical periphery within the assembly. Thus, the centerbody is exteriorly perimetrically bounded by the conductors.

[0026] In the particularly illustrated embodiment of the connector, the length of fingers 44 and curvature thereof during crimping is such that finger end courses 44b, upon crimping, are located radially outboard of centerbody 38 and radially inboard of finger end courses 42c. Thus, finger end courses 44b are in perimetric spacing of measure greater than S2, their perimetric spacing upon manufacture, and less than the perimetric spacing of finger end courses 42c. A coaxial relationship exists, following crimping, among centerbody 38, finger end courses 42c and finger end courses 44b.

[0027] In achieving such contact finger configuration, die surface 52 of Figs. 7 and 8 is formed to be substantially circular and is recessed in die member 50, having arcuate extent indicated in the sectional showing of Fig. 8 of less than a full semicircle. Such die surface configuration, in cooperation with the spring characteristic of fingers 44, causes the finger end courses to bend around an arcuate locus during crimping, as shown in Fig. 6. such that the end courses thereof face in directions nearly opposite their direction as manufactured (Fig. 4).

[0028] Attendant to the configuration of the foregoing connector, i.e., its provision of first and second pluralities of contact fingers physically independent of one another, save for commonality with the connector centerbody interconnecting such contact fingers, crimping force is substantially lessened as against a full rivet connector. In the forcing of the perimetrically continuous surface of a full rivet connector through insulation, one expends substantial force in the requisite expansion of the surface itself from one radius and perimeter prior to crimping to a larger radius and perimeter upon crimping. Further, from an electrical contact resistance point of view, one achieves improved electrical contact where plural independent contacts are made discretely about a perimeter than in the case where contact results from interdependent portions of an integral contact member engaging a conductor. Thus for a given crimping force, heightened pressure attends connection at a plurality of contact points versus the pressure resulting from such force over a continuous circular surface. Additionally, whereas a full rivet contact can act as a circular punch if overcrimped, thereby fully severing the conductor it engages, the connector of the invention can be overcrimped without such result, since it does not continuously perimetrically confront the conductor but does so in spaced perimetric manner.

[0029] Various changes evident to those skilled in the art may be introduced without departing from the invention. Accordingly, the particularly described and depicted preferred embodiments and practices are intended in an illustrative and not in a limiting sense. The true spirit and scope of the invention is set forth in the following claims.

Claims

1. An electrical connector comprising: a centerbody extending along a predetermined axis and defining an opening therethrough along such axis, a plurality of first contact fingers extending from said centerbody contiguously with said opening and having insulation piercing finger end courses in mutually perimetrically spaced relation and extending coaxially with said centerbody, and a plurality of second contact fingers extending from said centerbody contiguously with said opening oppositely from said first contact fingers and having insulation piercing finger end courses axially aligned with said centerbody.

2. The connector claimed in claim 1 wherein the mutual spacing of said finger courses of said first contact fingers exceeds the mutual spacing of said finger end courses of said second contact fingers.

3. The connector claimed in claim 1 or claim 2 wherein said centerbody is cylindrical, said first contact fingers extending radially outwardly of said centerbody.

4. The connector claimed in claim 3 wherein each such first contact finger includes a first course extending axially with said centerbody and a second course extending generally orthogonally of said predetermined axis and terminating in such first contact finger end course.

5. The connector claimed in any preceding claim wherein each such second contact finger end course includes an end surface tapering radially outwardly with respect to said centerbody.

6. The connector claimed in anypreceding claim wherein said centerbody is a hollow cylinder and wherein said first and second contact fingers are integral therewith.

7. An electrical connector comprising first and second pluralities of contact members having insulation piercing end courses, means for electrically interconnecting said contact members including a body integral therewith and supporting such end courses of said first and second pluralities at respective opposite ends of said body, successive ones of said end courses of each such plurality extending in different arcuate directions.

8. The connector claimed in claim 7 wherein each such contact member plurality comprises at least three contact members.

9. An electrical assembly comprising a first multiconductor cable, a second multiconductor cable overlying said first cable, a plurality of holes extending through respective registered conductors of said first and second cables, and a connector in each such hole, each said connector having a centerbody exteriorly perimetrically bounded by said conductors, a plurality of first contact fingers extending from said centerbody and having insulation piercing end courses in electrical engagement with a conductor of said first cable at locations mutually perimetrically spaced and coaxial with said centerbody and a plurality of second contact fingers extending from said centerbody oppositely from said first contact fingers..and having insulation piercing end courses in electrical engagement with the conductor of said second cable registered with such first cable conductor at locations mutually perimetrically spaced and coaxial with said centerbody.

10. The assembly claimed in claim 9 wherein said centerbody of each said connector is cylindrical, said first contact fingers extending radially outwardly of said centerbody, and wherein each such first contact finger includes a first course extending axially with said centerbody and a second course extending generally orthogonally of said predetermined axis and terminating in such first contact finger end course.

Drawing