EP0027680A1

EP0027680A1 - Coaxial contact assembly for captivating inner pin-socket electrical contacts

Info

Publication number: EP0027680A1
Application number: EP80302242A
Authority: EP
Inventors: David J. Ball; James W. Burger; David Paul Earl Carter
Original assignee: Automation Industries Inc
Current assignee: Automation Industries Inc
Priority date: 1979-10-09
Filing date: 1980-07-02
Publication date: 1981-04-29
Also published as: NO801508L; AU5896980A; JPS5661774A; CA1124349A

Abstract

An electrical contact assembly for terminating two coaxial cables, of which only one (24) is shown, enables the captivation of the inner socket contact (32). The contact assembly comprises a pin assembly and a socket assembly which, in mated condition, are in overlapping conductive relation. The following brief description concerns only the socket part of the assembly. The construction is true to the pin assembly as well. The socket assembly contains dielectric material (50,52) between the housing (40) and the inner conductor (30). The socket housing can admit a coaxial cable at the rear of the housing, the end of the inner conductor of the cable can enter a socket barrel (34), where it is held by a crimp. The end portion (48) of the outer conductor of the cable fits over a barrel (47) on the end of the housing; dielectric material (50) with said housing insulates the socket member from the respective housing and the dielectric within said housing extends underneath the respective end portion (48) of cable outer conductor and provides abutments (56,57) which bar cable inner dielectric from physical contact with the socket contact; ferrule crimp means (60) encircle the sandwich which . is formed at the end of the contact assembly, where crimping of said ferrule captivates the socket contact against the pull of the cable inner dielectric and inner conductor.

Description

This invention relates to multiaxial cables, connectors, and coaxial contact assemblys therefor. More particularly, the invention relates to termination of multiaxial cables, and, especially, to termination of miniature cables through contact assemblys usable in multipin electrical connectors and multicable electrical connectors.
In general, coaxial cables are made up of:

an inner conductor, which may be solid, stranded, balanced line, etc, made from copper, tin plated copper, silver plated copper, copper covered steel, etc; a dielectric material which may be solid, foamed, tape, helical wrap, and like from natural or synthetic elastomers and polymers; an outer conductor (sheath) which usually is braided copper wire or copper strip, which may be bare or plated, and more than one braid may be used. The outer conductor is covered by a protective, electrically insulating jacket which is usually a solid covering made of synthetic elastomer or polymer.

Triaxial cable adds another dielectric material layer over the first outer conductor and adds a second outer conductor over the second dielectric layer. The triaxial cable is protected like a coaxial cable.
All multiaxial cables must be terminated. Most commonly terminations involve the connection of two cable ends to complete a circuit or, in effect, lengthen the cable to reach a more distant location. These terminations involve electrical connectors: which may be for connecting two cables only, or as a contact assembly used in conjunction with wire or other contact assemblies in a multipin or multicable electrical connector.
Coaxial cable because of its complex structure is easily affected by atmospheric conditions and/or electrical interaction of the different materials in the sandwich or conductors and dielectric. The protective jacket, itself a dielectric, also has an effect on the electrical interaction. All these materials have coefficients of expansion and these can be widely different in a given cable. As a result the members of the cable have different length potentials at cable temperatures other than standard temperature.
When the inner conductor is terminated in a pin-socket contact and the inner dielectric, i.e., the cable dielectric adjacent to the inner conductor is not restrained, temperature changes may cause the inner dielectric to expand against the inner pin-socket contact, or even flow over and around the inner pin-socket contact,resulting in undesirable, and even intolerable, electrical changes at the inner pin-socket contact.
The inner conductor does change length with temperature change, tending with increasing length to reinforce the disturbance caused by the inner dielectric length change. When the inner conductors terminated in an inner pin-socket contact shorten, they try to pull the inner pin-socket contact apart.
It is known to place a crimp sleeve over the tail of the housing, the outer conductor extending over the tail, the cable dielectric extending into the housing, and the inner conductor outside of the barrel of the pin (or socket). The sleeve is crimped to fasten these members and to captivate the cable dielectric. It has been found that this procedure does not give satisfactory captivation. The dielectric material is not held tightly enough by the sleeve crimp and the cable dielectric soon shows undesired axial movement, and disturbances in the electrical state at the inner pin-socket contact.
It has been found that the effects of the undesired axial movement of the inner dielectric material can be minimised by a mechanical restraint applied to the inner pin-socket contact.
The invention is directed to a contact assembly for terminating two multiaxial cables, under conditions where the inner pin-socket contact of said contact assembly is substantially captivated against axial movement. The contact assembly comprises a pin housing and a socket housing for overlapped electrically conductive joinder; pin member and socket member located within respective pin and socket housings, for electrical mating; said socket housing and said pin member having abutting dielectric surface relationship when at the_mated condition for stopping forward axial movement at the inner pin-socket contact; said pin member and said socket member each having a barrel for receiving a cable inner conductor to be terminated within said contact assembly, which barrel can be crimped about said inner conductor; each pin housing and socket housing having a barrel portion over which corresponding outer conductors of terminating cables can be positioned; dielectric material inside of each of said pin housing and said socket housing to insulate the respective housing from its said member, said dielectric material essentially filling each said housing and extending beneath the respective outer conductors of said cables and forward to provide abutments at the barrel end of said socket member against forward axial movement of cable inner dielectric and backward movement of inner pin-socket contact, and to provide abutment for the inner dielectric of second cable inner dielectric and to provide dielectric surface at said pin member for aforesaid abutting socket housing-pin member relation; and ferrule crimp means encircling corresponding: socket barrel portion or pin barrel portionl the extending dielectric material; coaxial cable inner conductor and dielectric, when present; whereby crimping said ferrules captivates inner pin-socket contact against rearward pull of cable inner conductor and inner dielectric; and said housing dielectric materials being substantially rigid, with high resistance to cold flow.
An embodiment of the invention is hereafter described with reference to the accompanying drawings, in which Figures 1, la and lb form one complete figure which shows one embodiment of the multiaxial contact assembly of the invention. For clarity in presentation, a miniature contact assembly was enlarged about 20/1, which enlargement forced cutting the drawing into three sections along the longitudinal dimension, to meet space limitations for individual sheets.
The embodiment as shown is suitable for use in conjunction with a multipin connector, for example, the multipin connector of U.S. Patent No. 4,056,298. When used alone to terminate two cables, the embodiment needs protection against physical abuse, such as, a protective encasement, which encasements are well known to the coaxial connector art.
It is pointed out that the drawing shows the contact assembly in a partially mated condition. This has been done to provide more space at the pin-socket contact zone, to show the various members in the zone. It is self-evident, the contact assembly is brought into abutting relation of the pin member and the socket housing member, when the pin and socket are fully mated.
In the figures, the coaxial contact assembly for captivating inner pin-socket electrical contacts of the invention comprises an electrical socket assembly 10 (Figs. 1-la) for mating with an electrical pin assembly 70 (Figs. la-lb). Socket assembly 10 is also referred to as the male assembly and pin assembly 70 is also- referred to as the female assembly.
In Fig. 1, an end portion of a coaxial cable 14 is shown. Coaxial cable 14 is made up of inner conductor 18, inner dielectric material 20, and double braided outer conductor 22 and 24. The protective jacket, not shown, stops outside the-figure. It is to be understood the coaxial cable ends are shown to illustrate the utility of the invention, but are not part of the invention.
Socket assembly 10 comprises (Figs. 1-la) electrical socket member 30 having a pin receiving socket 32 at one end, away from coaxial cable 14, and a barrel 34 at the other end, having a squared rear end 35, for receiving a portion 36 of the inner conductor of the cable 14, when present. The entry 38 (Fig. la) of socket 32 is beveled to ease entrance of the pin 92. Socket barrel 34 is sized so that the inner conductor portion 36 may be crimped within the barrel, holding the conductor 36 and improving electrical contact.
An electrically conductive socket housing 40 (Figs. 1-la) is coaxially aligned around socket member 30 and has a cylindrical nose portion 42, which has a relatively squared end 44. The nose portion 42 extends beyond the entry 38 to socket 32. Socket housing 40 has at its other end a cylindrical barrel (tail) portion 46. Barrel 46 can be inserted underneath an end portion 48 of outer conductor braid 22 to make electrical contact therewith.
Dielectric materials 50 (Figs. 1-la) and 110 (Figs. la-lb) are substantially rigid, insulating materials with high resistance to cold flow, such as, polyester, polyamide, and polyimide.
Dielectric material 50 is positioned in socket assembly 10 between socket member 30 and socket housing 40 to electrically insulate these from each other and, also, socket member 30 from outer conductor 48; dielectric 50 essentially fills aforesaid space. Dielectric 50 extends back beyond socket housing tail portion 46 a substantial distance underneath outer conductor 48, when this is present, so as to underlie a ferrule 60. Dielectric 50 may be in one piece, but normally will consist of more than one piece for greater ease of manufacture and installation. In general, the number of pieces in dielectric 50 is determined by the configuration of the cavity between socket member 30 and socket housing 40. The individual pieces may be formed from the same type of material, or from different materials in the defined class of materials.
Herein, dielectric 50 is fitted as two pieces 52 and 54 (Figs. 1-la). Piece 52 extends out to socket housing end 44 to insulate electrically nose portion 42 from electrical pin 92, when pin 92 and socket 32 are mated.
Dielectric piece 54 extends roughly from the outer end 61 of ferrule 60, at the approximate level of the outer surface of tail portion 46, underneath ferrule 60, end portion 48 of braid 22, tail portion 46 and forward until it abuts rear end 35 of socket barrel 34 at flat end 56. Herein, a shoulder 55 of piece 54 abuts against end 47 of barrel 46, which shoulder 55 restrains piece 54 from movement toward socket barrel 34. Piece 54 is provided with another shoulder 57 against which the inner end of cable inner dielectric 62 can abut in forward axial movement thereof. Ends 56, 57 and the dielectric therebetween bar the inner dielectric 62 from further movement toward the inner pin-socket contact zone and thereby minimise electrical disturbances caused by cable inner dielectric movement.
Socket assembly 10 includes a conductive ferrule crimp means 60. Ferrule 60 encircles: socket housing barrel (tail) portion 46, socket assembly dielectric material 54, end portion 48 of outer conductor 22, cable inner dielectric 62, and that portion of cable inner conductor roughly under ferrule 60. Ferrule 60 is of metal capable of being crimped to fasten together (1) the ferrule, the encircled tail portion, and outer conductor; and (2) the ferrule, outer conductor, and dielectric 54 extending beyond the tail portion. The crimp (2) restrains the inner pin-socket contact against rearward pull of inner dielectric and inner conductor.
An end portion of a second coaxial cable 74 is shown in Fig. lb. Cable 74 is made of inner conductor 76, inner dielectric material 78, and a double braid outer conductor 80 and 82. The protective jacket is outside the figure.
Pin assembly 70 as set forth in Figs. la-lb comprises an electrical pin member 90 having a pin 92 at one end, away from cable 74, and a barrel 94 at the other end for receiving a portion 96 of the inner conductor of cable 74. Pin barrel 94 is sized so that innter conductor portion 96 can be crimped therein, holding inner conductor 96 and improving electrical contact.
An electrically conductive pin housing 100 (Figs. la-lb) is coaxially aligned around pin member 90 and has a cylindrical tapered nose portion 102 having forward end 103, end 103 being divided into a plurality of spring fingers for improving electrical contact with socket nose portion 42. Pin housing 100 has at its other end a cylindrical barrel (tail) portion 106, for insertion underneath an end portion 108 of outer conductor braid 80 and to make electrical contact therewith.
Dielectric material 110 (Figs. la-lb) is positioned in pin assembly 70 between pin member 90 and pin housing 100 to insulate electrically these from each other, and also pin housing 100 from inner conductor 112 (Fig. lb). Dielectric 110 essentially fills aforesaid space. Dielectric 110 extends back beyond pin housing barrel (tail) portion 106 a substantial distance underneath outer conductor 80, when this is present, so as to underlie a ferrule 130.
Herein, dielectric 110 is fitted as three pieces 114,116 and 118 (Figs. la-lb). Piece 114 goes forward to squared end 120 to insulate pin 92 from nose end 44 when the pin and socket are mated.
Dielectric piece 118 extends roughly from the outer end 131 of ferrule 130, at the approximate level of the outer surface of tail portion 106, underneath ferrule 130, end portion of braid 82, tail portion 106, and forward until it abuts the rear end 117 of dielectric piece 116. Piece 118 is provided with a shoulder 119 against which the inner end of cable dielectric 132 abuts in forward axial movement and is barred from further movement toward the inner pin-socket contact zone, thereby minimising electrical disturbance caused by cable dielectric axial movement. Shoulder 120 abutted against end 107 of tail portion 106 helps restrain forward movement of dielectric material 110.
Dielectric 116 runs into dielectric 114, described earlier.
Because of the characteristics of dielectric materials 50 and 110 there is no thermal elongation to force pin 92 and socket 32 apart. Thus inner pin-socket contact is further captivated against axial movement.
Pin assembly 70 includes a conductive ferrule crimp means 130. Ferrule 130 encircles: pin housing barrel (tail) portion 106, pin assembly dielectric material 118, end portion 108 of outer conductor 80, cable inner dielectric 132, and that portion of cable inner conductor roughly under ferrule 130. Ferrule 130 is of metal capable of being crimped to fasten together (1) the ferrule, outer conductor and the encircled tail portion; and (2) the ferrule, outer conductor, and dielectric 118 extending beyond the tail portion. The crimp (2) restrains the inner pin-socket contact against rearward pull of inner dielectric and inner conductor.
Pin assembly 70 is provided with (Fig. la) a stainless steel cylindrical protective sleeve, 140, positioned on the exterior of pin housing 100 to protect the spring fingers at the forward end 103 of pin housing nose portion 102.
ILLUSTRATION: A suitable coaxial cable for termination by the contact assembly of the invention is RG 142/U in size 12 contact in conjunction with a multipin electrical connector. This cable has a solid copper inner conductor; a PTFE dielectric (polytetrafluoroethylene); a braided copper outer conductor; and a FEP protective jacket (fluorinated ethylene propylene). In the contact assembly, the pin and socket members, the pin and socket housings, and the cylinder with spring fingers are made from heat treated beryllium copper alloy. The ferrules are soft beryllium copper alloy. The dielectric material is polyamide.

Claims

1. A coaxial contact assembly for captivating inner pin-socket electrical contacts, which contact assembly comprises:

a pin housing (70) and a socket housing (16) for overlapped electrically conductive joinder;

pin member (90) and socket member (30) located with said corresponding housings, for electrical mating;

said pin member and said socket housing having abutting, non-conductive relation when in the mated condition (at 120);

said pin member and said socket member each having a barrel (34,94) for receiving a coaxial cable (14) inner conductor (36,112) to be terminated within said contact assembly;

said pin housing and said socket housing each having a barrel portion (47,106) over which an outer conductor end portion (48,108) of corresponding coaxial cables can be positioned; and

dielectric material (50,110) within each of said pin housing and said socket housing to insulate the respective housing from its corresponding pin or socket member, characterised in that said dielectric material extends beyond the corresponding barrel, beneath the corresponding outer conductor end portion, (48,108) and forward to provide abutments (56,57) at the barrel end of said socket member against forward axial movement of a cable inner dielectric and backward movement of said inner pin-socket contact, and to provide abutments (119,117) for the inner dielectric of a second cable and to provide a dielectric surface (120) at said pin member for aforesaid abutting-socket housing-pin member relation; the assembly including

ferrule crimp means (60,130) encircling corresponding: housing barrel, extended dielectric material, cable inner dielectrical and cable inner conductor,

whereby, when said cables are in position in the contact assembly, crimping said ferrules substantially captivates the inner pin-socket contacts against axial movement;

said housing dielectrics being substantially rigid, insulating materials with high resistance to cold flow.

2. The contact assembly of claim 1 wherein a protective cylindrical member (140) is affixed to said pin housing to protect a plurality of spring fingers (103) terminating the forward end of said pin housing.

3. A coaxial contact assembly for captivating inner pin-socket electrical contacts, which contact assembly comprises:

an electrical pin assembly (70);

an electrical socket assembly (10) for mating with said pin assembly; characterised by the following construction:

said socket assembly comprises,

an electrical socket member (30) having a pin receiving socket (32) at one end and a barrel (34) at the other end for receiving a portion (36) of the inner conductor (18) of a coaxial cable;

an electrically conductive socket housing (10) coaxially aligned around said socket member (30) having a cylindrical nose portion (44) extending beyond the entry to said socket and a cylindrical barrel portion (42) for insertion underneath, and for making electrical contact with, an end portion (48) of the outer conductor (24) of a coaxial cable;

socket assembly dielectrical material (50) positioned between said socket member and said socket housing for electrically insulating said socket member from said socket housing and said outer conductor of a coaxial cable, and extending back (54) beyond said socket housing barrel portion (47) and forward to abut the rear end (56) of said socket barrel (34) and to bar forward movement of coaxial cable dielectric; and conductive ferrule crimp means (60) encircling: said socket housing barrel portion (47), said backward extending socket assembly dielectric material (54), said end portion (48) of outer conductor (24) of coaxial cable, and inner conductor (18) and dielectric material (54) associated with the end portion of the outer conductor of coaxial cable;

said ferrule means (60) being capable of being crimped to fasten the ferrule, the encircled barrel portion and outer conductor; and the ferrule, outer conductor and extending dielectric material, to captivate inner pin-socket contacts (92,32) from axial movement owing to axial pull of the coaxial cable dielectric material and the inner conductor;

where said pin assembly comprises, an electrical pin member (90) having a pin (92), for entering said socket (32), at one end and a barrel (94) at the other end for receiving end portion (112) of the inner conductor (76) of a second coaxial cable (74);

an electrically conductive pin housing (70) coaxially aligned around said pin member (90) having a cylindrical nose portion (102) for overlapping electrical contact with said socket housing nose portion, and a cylindrical barrel portion (106) for insertion underneath, and for making electrical contact with, an end portion (108) of the outer conductor (82) of a second coaxial cable (74); pin assembly dielectric material (110) positioned between said pin member and said pin housing for electrically insulating said pin member from said socket housing when said pin and said socket are mated, and for electrically insulating said pin member from said pin housing and said outer conductor of second coaxial cable, said pin assembly dielectric material extending back beyond said pin housing barrel portion and forward to provide an abutment (119) for the inner end of second cable dielectric (132) and at said pin member provides insulator contact (120) with said socket housing and pin-socket captivation; and

conductive ferrule crimp means (130) encircling: said pin housing barrel portion (106), said backward extending pin assembly dielectric material (118), said end portion (108) of the outer conductor of second coaxial cable (74), and inner conductor (76) and dielectric material (132) associated with the end portion of outer conductor of second coaxial cable;

said ferrule being capable of being crimped to fasten together the ferrule, the encircled pin housing barrel portion, outer conductor and the ferrule, outer conductor and pin assembly dielectrical material, to captivate inner pin-socket contacts from axial movement owing to axial pull of second coaxial cable dielectric material and inner conductor;

said pin assembly (70) including a protective cylindrical member (140), positioned on the exterior surface of said pin housing, to protect a plurality of spring fingers (102) terminating the forward end of said pin housing;

said pin assembly and said socket assembly dielectric materials being substantially rigid, insulating materials with high resistance to cold flow.