Foldable dielectric insert for a coaxial contact

A coaxial contact (22) for termination to a coaxial cable (200) having a center conductor (208) surrounded by a dielectric material (206) thence a braid (204) and jacket. The coaxial contact (22) has a center contact (24) with a mating portion (42), a conductor attaching portion (46) and a shank (50) extending therebetween. A first substantially semi-cylindrical insert member (160) having an axial recess (170) adapted to receive at least a portion of the center contact (24) is positioned adjacent the center contact (24), A second substantially semi-cylindrical dielectric insert member(162) is adapted to be positioned over the first insert member (160) resulting in a substantially cylindrical dielectric structure (26) that surrounds a portion of the center contact (24). A ferrule (28, 28') is positioned over a portion of the dielectric insert. An electrically conductive shell secures the subassembly together. The shell has a forward cylindrical contact portion (76) and a cable attaching, braid engaging portion (80).

BACKGROUND OF THE INVENTION 
This invention relates to disposing a center contact in a coaxial contact, 
and in particular to a two-piece dielectric insert for positioning a 
center contact in a coaxial contact and for insulating the center contact 
from the surrounding conductive shell. 
Dielectric inserts used to position a center contact in a coaxial contact 
have typically been annular in structure, taking the shape of a cylinder 
with a bore through the center. The center coaxial contact is passed 
partially through the bore and secured. A necessary result is that the 
diameter of the bore must be large enough to accommodate the largest cross 
section of the contact portion passed into or through the bore. 
There is disclosed in U.S. Pat. No. 3,699,504 an open barrel coaxial cable 
terminal including a sleeve formed from a dielectric material having 
resilient buttons for insertion into and snap-in retention in a sleeve 
portion. The sleeve portion of the terminal is freely insertable within 
the inner diameter portion of the dielectric sleeve. 
It would be desirable to have a dielectric insert to position a center 
coaxial contact that does not require passing the center contact through a 
central bore and would provide for a passage through the insert 
commensurate with the varying cross section of the contact to be received 
therein. Such an insert would more accurately align and hold the contact 
in a desired position. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a coaxial contact for termination 
to a coaxial cable having a center conductor surrounded by a dielectric 
material thence a braid and jacket. The coaxial contact has a center 
contact with a mating portion, a conductor attaching portion and a shank 
extending therebetween. A first substantially semi-cylindrical insert 
member having an axial recess adapted to receive at least a portion of the 
center contact is positioned adjacent the center contact. A second 
substantially semi-cylindrical dielectric insert member is adapted to be 
positioned over the first insert member resulting in a substantially 
cylindrical dielectric structure that surrounds a portion of the center 
contact. An electrically conductive shell receives the cylindrical 
structure and secures the subassembly together. The shell has a forward 
cylindrical contact portion and a cable attaching, braid engaging portion.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A connector 20 is shown in FIG. 1 including a receptacle coaxial contact 22 
having a center contact 24 secured therein by a two-piece dielectric 
insert 26 in accordance with the present invention. Coaxial contact 22 
also includes a ferrule 28 and receptacle shell 30. Connector 20 includes 
front and rear dielectric housing members 32,34 and, if shielded, includes 
front and rear shell means 36,38. Coaxial contact 22 may be used in 
conjunction with connector 20 or alone. When used in conjunction with 
connector 20, contact 22 may be secured in connector 20 in accordance with 
the teaching of concurrently filed U.S. patent application No. 07/531,212, 
now U.S. Pat. No. 4,990,104, entitled "Snap-In Retention System For 
Coaxial Contact," the disclosure of which is hereby incorporated by 
reference, or any other known method. 
Center contact 24 shown in FIG. 1 is a pin contact 40. A top view of an 
unterminated pin contact 40 is shown in FIG. 4. Pin contact 40 is 
typically stamped and formed from electrically conductive material such as 
brass stock and has a mating portion 42 with tapered end 44 to facilitate 
mating, a terminating portion 46 in the form of crimp barrel 48 and a 
reduced diameter shank 50 between the mating and terminating portions. The 
difference in diameter between shank 50 and mating portion 42 defines 
rearwardly facing annular shoulder 52. The difference in diameter between 
shank 50 and barrel 46, when crimped, defines forwardly facing shoulder 
54. Shank 50 thus extends between shoulders 52 and 54. 
A plug coaxial contact 22' secured in connector 20' is shown in FIG. 2. 
Connector 20' includes front and rear dielectric housing members 32',34' 
and if shielded includes front and rear shell means 36' and 38'. The 
center contact 24 is shown as a receptacle contact 56. A top view of an 
unterminated receptacle contact 56 is shown in FIG. 5. Contact 56 is also 
typically stamped and formed from phosphor bronze stock and has a 
cylindrical barrel 58 formed with cantilever beams 60 extending therefrom 
for receiving therebetween mating portion 42 of a pin contact, a 
terminating portion 62 in the form of a crimped barrel 64, and a reduced 
diameter shank 66 between the cylindrical barrel and crimp barrel. The 
differential diameter between shank 66 and cylindrical barrel 58 defines a 
rearwardly facing annular shoulder 68. The difference in diameter between 
shank 66 and barrel 64, when crimped, defines forwardly facing shoulder 
70. Thus, shank 66 extends between shoulders 68 and 70. 
A drawn conductive ferrule 28, is shown in cross section in FIG. 6A for a 
small diameter cable and a ferrule 28' is shown in cross section in FIG. 
6B for a large diameter cable. While the ferrule in the preferred 
embodiment is a drawn member, such a ferrule could also be stamped and 
formed. Ferrules 28 and 28' are electrically conductive and typically 
manufactured from a copper alloy. Each ferrule has a large diameter 
forward end 76,76', a tapered section 78,78' and a reduced diameter 
cylindrical rear section 80,80'. Each cylindrical section has an annular 
ridge 82,82' of larger diameter than the respective reduced diameter 
cylindrical rear section proximate the free edge 84,84', with free edge 
84,84' defining a cable entry 86,86'. 
The side view of a receptacle shell 30 is shown in FIG. 7. In the preferred 
embodiment, shell 30 is stamped and formed from phasphor bronze strip 
stock. Receptacle shell 30 has a hollow generally cylindrical shape having 
a slotted forward end 90 forming cantilever beams 92. Each beam 92 has an 
arcuate recess 94 proximate distal end 96, collectively forming a reduced 
diameter plug receiving opening 98 best seen in FIG. 8. Typically, plug 
shell 30 is manufactured of stock that has been strip gold plated such 
that the plating is on inner arcuate surfaces 100. The inner surface 100 
of recesses 94 engage and wipe the exterior surface 102 of a plug shell 
104 shown in FIG. 9 as plug and receptacle contacts are mated or unmated. 
Inner surfaces 100 provide redundant points of electrical and mechanical 
contact with the exterior surface of a mated plug shell. Forward end 90 
extends rearward through a retention section 106, described in more detail 
in concurrently filed U.S. application Ser. No. 07/531,212, now U.S. Pat. 
No. 4,990,104 and a rear cylindrical ferrule receiving section 108. A 
portion of section 108 extends rearward forming extension 110 with crimp 
tabs 112 and 114 extending upwardly therefrom. 
Receptacle shell 30 has forward stops 140 formed from a shear line segment 
142 when stop 140 is formed inwardly relative to front end 90. Stops 140 
provide arcuate stop shoulders 144 which assists in positioning insert 26 
upon insertion into shell 30 and prevents over-insertion of insert 26. 
A side view of a plug shell is shown in FIG. 9. Plug shell 104 has a 
hollow, generally cylindrical shape. Shell 104 is typically stamped and 
formed of brass. Shell 104 has a reduced diameter forward end 116 the 
outside surface 118 of which is typically gold plated. Forward end 116 is 
sized such that the outer diameter is receivable within opening 98 of 
forward end 90 of receptacle shell 30. Forward end 116 extends rearward to 
a transition region 120 of conical shape that tapers to a larger diameter 
section 122 that may have a retention section 126 therein. Section 122 
includes ferrule receiving section 128 and insert receiving section 124 
which have substantially the same inside diameter in the preferred 
embodiment and are substantially the same inside diameter as forward end 
90 and ferrule receiving section 108 of receptacle shell 30. Ferrule 
receiving sections 108 and 128 have an inside diameter sized to receive 
the forward end 76 or 76' of ferrules 28 or 28' as best seen in FIGS. 1 
and 2. A portion of ferrule receiving section 128 extends rearward forming 
extension 130 with crimp tabs 132 and 134 extending upwardly therefrom. 
Plug shell 104 has stops 150 formed from a shear line segment 152. Stop 150 
is formed inwardly relative to shell 104 resulting in an arcuate stop 
shoulder 154 which positions insert 26 upon insertion into shell 104 and 
prevents over-insertion of insert 26. 
Two embodiments of a two-piece dielectric insert are shown in FIGS. 3A and 
3B. The major difference between the two embodiments permits one of the 
inserts to accommodate a larger diameter coaxial cable. The FIG. 3A 
embodiment will be described; the same reference number having a prime 
notation will refer to similar structure in the embodiment of FIG. 3B. 
A two-piece dielectric insert 26 is comprised of two substantially 
identical halves 160,162. Halves 160,162 in the preferred embodiment are 
molded of polyolefin and are hingedly interconnected by web 164. Each half 
has a forward portion 166 and a rearward portion 168. Each forward portion 
is substantially semi-cylindrical having a semi-cylindrical channel 170 
coaxially disposed therein. Forward surface 172 is semi-annular in shape 
and engages a stop shoulder 144 or 154 upon insertion of insert 26 into 
shell 30 or 104 respectively. The edge of surface 172 along 
semi-cylindrical side wall 174 may be beveled 176 to facilitate entry of 
insert 26 into a shell. The rear of forward portion 166 is defined by 
inner semi-annular surface 178 concentrically disposed about channel 170 
and outer semi-annular surface 180 also concentrically disposed about 
channel 170. 
The spacing or distance between surfaces 172 and 178 is substantially the 
same spacing or distance between shoulders 52 and 54 of pin contact 40 
(see FIG. 4), or the distance between shoulders 68 and 70 of receptacle 
contact 56 (see FIG. 5). The radius of semi-cylindrical channel 170 is 
substantially the same as or slightly smaller than the radius of shank 50 
of a pin contact 40 or shank 66 of a receptacle contact 56. When halves 
160 and 162 are positioned over each other in the absence of web 164 or 
when the two halves are folded about web 164, the two forward portions 166 
form a cylindrical structure with the two semi-cylindrical channels 170 
forming a centrally located cylindrical bore therethrough. 
Rearward portion 168 extends from and is integral with forward portion 160 
of each half 160,162 between inner semi-annular surface 178 and outer 
semi-annular surface 180. Rearward portion 160 is substantially 
semi-cylindrical having a semi-cylindrical channel 182 coaxially disposed 
therein and extending from semiannular surface 178 rearward. The radius of 
channel 182 is typically larger than the radius of channel 170 as channel 
170 accommodates the shank of a center contact 24 while channel 182 
accommodates the crimped barrel of a center contact 24. When halves 160 
and 162 are folded about web 164 or positioned over each other in the 
absence of web 164, rearward portions 168 form a cylindrical structure 
with two semi-cylindrical channels 182 forming a centrally located 
cylindrical bore therethrough. Rearward portion 168 may be beveled 184 at 
the trailing edge to be received in a tapered portion of a ferrule 28 or 
28'. To accommodate a larger diameter cable, a portion of channels 182 may 
be enlarged to form a larger diameter channel portion 186' to receive the 
dielectric of the cable being terminated to permit the insulative insert 
to overlap the coax cable dielectric. In a preferred embodiment, the 
distance from semi-annular surface 178,178' to semiannular surface 188' is 
substantially the length of the crimp barrel of a center contact between 
shoulder 54 or 70 and rear end 210. 
The outside diameter of the rearward portion, when halves 160,162 are 
folded about web 164, is sized to be closely received within the forward 
end 76,76' of ferrule 28,28' with the leading edge 190,190' of ferrule 
28,28' abutting semi-annular surfaces 180 in the assembled contact to 
position and secure insert 26 in the desired location within shell 30 or 
104. Thus, arcuate stop shoulders 144 and 154 provide a forward stop for 
insert 26 or 26' while surfaces 180 or 180' provide a rear stop for the 
insert. 
Each receptacle contact 22 thus comprises a center contact 24 in the form 
of pin contact 40, a two-piece dielectric insert 26 or 26', a shell 30 and 
a ferrule 28 or 28'. Each plug contact 22' comprises a center contact 24, 
in the form of receptacle contact 56, a two-piece dielectric insert 26 or 
26', a shell 104 and a ferrule 28 or 28'. Plug contact 22' may include an 
insulated tapered lead-in insert 192 (in accordance with concurrently 
filed U.S. patent application Ser. No. 07/521,204, now U.S. Pat. No. 
4,990,105, entitled "Tapered Lead-In Insert For A Coaxial Contact", the 
disclosure of which is hereby incorporated by reference). Other than 
insert 192, in the preferred embodiment, air is the only dielectric 
separating center contact 24 from shell 30 or 104 forward of surface 172 
of insert 26. 
Coaxial contacts 22 and 22' may be assembled and terminated to a coaxial 
cable manually or using automated assembly equipment. The assembly 
procedure will be described with reference to the sequence of FIGS. 10A-E. 
FIG. 10A shows a coaxial cable 200 for terminating to a coaxial contact. 
The coaxial contact may be any of the contacts described herein. The 
jacket 202, braid 204 and dielectric 206 of the cable have been removed to 
expose a length of approximately 6.75 mm of the center conductor 208. 
Further, jacket 202 has been removed to expose a length of approximately 
25 mm of the braid. The stripped center conductor 208 is laid into the 
open crimp barrel 48 or 64 of a center contact 24. Preferably, the cable 
dielectric 206 is butted against the rear end 210 of the crimp barrel. The 
center conductor is crimped in the crimp barrel thereby securing the 
center conductor to the coax center contact to complete a mechanical and 
electrical connection therebetween. The coax cable braid 204 is splayed 
and the terminated center contact 24 is passed into cable entry 86 or 86' 
and through a ferrule 28 or 28' appropriate for the diameter of cable 200. 
Alternatively, it may be stated that the ferrule is passed over the center 
contact. 
The ferrule is slid axially along the cable, with cylindrical section 
80,80' between the cable dielectric 206 and the braid 204 to a position 
with the leading edge 190,190' beyond the crimp barrel of the center 
contact as shown in FIG. 10B. 
As shown in FIG. 10C, the center contact 24 is positioned in channels 
170,182 or 170',182' of one half 160 or 162 With the crimp barrel being 
received in channel 182 and with shoulder 54,74 abutting semiannular 
surface 178 and with shank 50,66 received in channel 170, and shoulder 
52,68 abutting forward surface 172. The other half 162 or 160 is 
positioned over the center contact, or if web 164 is present the other 
half is folded at web 164 around the center contact. 
The forward end of the insert is held to maintain the center contact in 
position while the ferrule is slid axially along the cable toward the end 
of the mating contact such that rearward portions of the insert are 
received within forward end 76 of the ferrule until leading edge 190,190' 
engages outer semi-annular surfaces 180,180'. In this position, insert 26 
is prevented from being removed inadvertently from contact 24. Insert 26 
will not slide axially toward the unterminated end of center contact 24 
due to the forward surfaces 172 engaging shoulders 52 or 68. In order to 
be removed, the two halves must be separated from each other to allow 
channels 170 to pass over shoulders 52 or 68. Thus, with insert 26 
partially within ferrule 28,28', the center contact is held centered in 
insert 26 which is in turn centered within the ferrule. 
The cable braid 204 is then smoothed out to surround the smaller diameter 
cylindrical section 80,80' of the ferrule as shown in FIG. 10D. 
The above subassembly 212,212' is then inserted into the ferrule receiving 
end of a shell 30 or 104 until forward surface 172 or 172' engages forward 
stops 140,150, specifically the arcuate stop shoulders 144 or 154 as shown 
in FIG. 10E. This properly positions center contact 40, insert 26,26', 
ferrule 28,28' and subassembly 212,212' within shell 30,104 with center 
contact 24 coaxially centered in the shell. 
As shown in FIG. 10F, tabs 112,114 or 132,134 are then crimped over the 
braid to secure the shell to the subassembly and to complete an electrical 
path from shell 30,104 to braid 204. Crimping the tabs completes the 
assembly of the coax contact with the crimped tabs securing all parts of 
the connector together. The crimped tabs are between the annular ridge 82 
and forward end 76 with the larger diameter of annular ridge 82 preventing 
the crimped tabs from otherwise sliding off cylindrical section 80,80'. 
The completed coaxial contact 22,22' may be inserted into dielectric 
housing means 34,36 if desired. 
While the preferred embodiment has been described employing a crimp 
termination of the center conductor to the center contact and a crimp to 
secure the shell to the ferrule, other known means of termination such as 
soldering could be used. Various metal parts described in the preferred 
embodiment as stamped and formed members could be made in other ways such 
as being machined, or from other known materials suitable for the function 
each provides.