Method of molding electrical connector insulator

A one-piece, homogeneous electrical connector insulator is disclosed having an integral contact retention cone in each contact passage thereof. The insulator is made by the use of a mold having two core pins for each contact passage, and a suitably formed bushing positioned between the core pins which is removed by etching after the core pins are withdrawn from the molded insulator.

BACKGROUND OF THE INVENTION 
The present invention relates to an electrical connector of the type in 
which the contacts are inserted into and extracted from the rear of the 
connector insulator and, more particularly, to an insulator for such a 
connector embodying integral contact retention cones and a method and 
apparatus for making the same. 
It is desirable in an electrical connector to have the insulator therein in 
which the contacts are mounted formed of a one-piece, homogeneous 
dielectric material. U.S. Pat. No. 4,114,976 to Selvin et al. discloses 
methods for mounting metal contact retention clips in onepiece insulators. 
In one such method, as depicted in FIGS. 1 and 2 of the patent, the 
insulator is molded around a single core pin for each contact passage 
having an aluminum sleeve mounted over the pin. After the core pin is 
removed from the molded insulator, the sleeve is removed by etching with a 
chemical solution. Thus, there is provided in the wall of each contact 
passage an annular groove having shoulders at its opposite ends which 
positively retain a contact retention clip that is snapped into the groove 
through the rear of the contact passage. The core pin has a small-diameter 
forward end which allows a "closed entry" to be formed at the front of the 
passage when the insulator is molded around the pin. The closed entry 
provides an inwardly extending annular flange at the front of the contact 
passage which limits forward movement of the contact therein. In addition, 
if the contact is a socket contact having spring beams, the flange will 
prevent the beams from being damaged when a mating pin contact or 
electrical probe is inserted into the contact passage from the front of 
the insulator. 
U.S. Pat. No. 3,165,369 to Maston and U.S. Pat. No. 3,727,172 to Clark 
disclose electrical connectors utilizing insulators having integral 
contact retention cones in the contact passages thereof. Each contact 
passage and cone therein is formed by the use of a pair of core pins in a 
mold having end regions which are shaped to define the contact retention 
cone when a dielectric material is molded around the pins. After the 
material hardens, the core pins are separated to provide a through passage 
with a contact retention cone directed toward the front of the insulator 
thus formed. In order to provide entry for the contact passage, a second 
insulator must be mounted on front of the first mentioned insulator. The 
second insulator is adhered to the first insulator by a suitable adhesive 
or cement. The resulting two-piece insulator has the disadvantage that the 
boundary line between the front and rear insulator parts produces a 
potential electrical leakage path which could cause shorting between 
adjacent contacts in the insulator. 
It is the object of the present invention to provide a one-piece, 
homogeneous electrical connector insulator embodying integral contact 
retention cones in contact passages having closed entries, and a method 
and apparatus for manufacturing the same. 
SUMMARY OF THE INVENTION 
According to the invention, there is provided a one-piece, homogeneous 
electrical connector insulator embodying integral contact retention cones 
and closed entries by utilizing a two-part separable mold having opposed 
core pins mounted on the two parts separated by a bushing for each contact 
passage to be formed. One of the core pins is dimensioned to define the 
bore in the closed entry of the contact passage and the other core pin and 
adjacent surface of the bushing is shaped to define the cone. The mold is 
filled with a dielectric material which is allowed to harden to form the 
insulator. The mold parts are separated to remove the core pins from the 
thus formed insulator. Thereafter, the bushing is eliminated from the 
insulator, such as by etching.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1 of the drawings in detail, there is shown a 
two-piece prior art electrical connector insulator assembly, generally 
designated 10, comprising a front insulator 12 and a rear insulator 14. 
The rear insulator embodies an integral contact retention cone 16 in the 
contact passage 18 of the assembly. That portion of the contact passage 18 
which is formed in the rear insulator 14 comprises a cylindrical bore 20 
having a forward section 22 opening at the front face 24 of the insulator, 
a second smaller diameter section 26 behind the forward section, and a 
rear larger diameter section 28 opening to the rear face 30 of the 
insulator. The sections 26 and 28 are joined by a tapered transitional 
section 32. The contact retention cone 16 extends forwardly from the wall 
of section 26 of the bore 20. Normally, the cone 16 is longitudinally 
slotted, as indicated at 34, to provide a plurality of forwardly and 
inwardly extending resilient retention fingers 36 which are capable of 
being radially expanded. Typically, four such fingers are formed by the 
provision of four slots in the cone. As explained previously herein, the 
front insulator 12 is adhered to the rear insulator 18 by cement or 
adhesive. A bore 38 extends from the front 40 to the rear 42 of the front 
insulator coaxial with the bore 20. The diameter of the bore 38 is less 
than the diameter of the intermediate cylindrical section 26 of bore 20, 
thus providing a rearwardly facing annular surface in the contact passage. 
A cylindrical recess 44 is formed in the surface 42 coaxial with the bore 
38 providing an annular abutment 46. Thus, the front insulator provides a 
closed entry for the contact passage. 
A pin contact 48 is shown mounted in the contact passage. The pin contact 
has an enlargement 50 in front of the contact retention cone 16. The 
enlargement defines a rearwardly facing annular shoulder 52 which abuts 
the ends of the fingers 36, whereby rearward movement of the contact in 
the passage is limited. Forward movement of the contact in the passage is 
restricted by engagement of a forwardly facing shoulder 54 on the 
enlargement 50 with the annular abutment 46 on the front insulator. As 
well known in the art, the contact may be removed from the rear of the 
insulator by inserting a suitable tool into the rear of the bore 20 to 
deflect the resilient fingers 36 outwardly from behind the shoulder 52. 
The two-piece insulator assembly of the prior art results in added 
manufacturing and assembling costs, and the joint between the front and 
rear insulators thereof provides a potential electrical leakage path. 
FIGS. 2 and 3 illustrate core pins of the type utilized for forming the 
contact bore 20 in the rear insulator 14 of the insulator assembly 
illustrated in FIG. 1. More specifically, there is provided a male core 
pin 60 and female core pin 62. The male core pin comprises a cylindrical 
rod 63 having a tapered forward end section 64 terminating in a front, 
small diameter guide section 66. The female core pin 62 comprises a 
cylindrical rod 68 having a bore 70 therethrough terminating in a tapered 
recess 72 opening at the front 74 of the rod. Four longitudinally and 
radially extending fins 75 are formed on the tapered forward section 64 of 
the male core pin 60. When the tapered section of the male core pin is 
inserted into the forward end of the female core pin, as seen in FIG. 2, a 
conical cavity is formed between the wall of the tapered recess 72 and the 
outer surface of the tapered section 64 of the male core pin. The conical 
cavity is divided into four sections by the fins 75. When a dielectric 
material is molded around the pins, the conical cavity is filled to form 
the contact retention cone 16 illustrated in FIG. 1. After the dielectric 
sets, the two parts of the mold (not shown) on which the core pins 60 and 
62 are mounted, are separated thus providing the rear insulator 14 
illustrated in FIG. 1. 
Reference is now made to FIGS. 4 and 6 of the drawings which illustrate the 
connector insulator 80 of the present invention, which is seen to consist 
of a one-piece, homogeneous molded part. The reference numerals utilized 
in FIGS. 4 and 6 relating to the insulator 80 correspond to those utilized 
in FIG. 1 with the suffix "a" added. 
FIG. 5 illustrates two male core pins 82 and 84 and an etchable metal 
bushing 86 utilized to form the one-piece, homogeneous insulator 80, and 
FIG. 6 illustrates a two-piece, separable mold, generally designated 87, 
in which the core pins and bushing of FIG. 5 are positioned to produce the 
insulator. 
The core pin 82 has a rear cylindrical section 88, a smaller diameter 
cylindrical section 90 in front of the rear section 88, and a still 
smaller diameter cylindrical section 92 joined to the section 90 by a 
frustro-conical section 94 and an annular shoulder 95. The pin 82 
terminates at its forward end in a pointed end or guide 96. 
The core pin 84 has a rear cylindrical section 98, a second smaller 
diameter cylindrical section 100 in front of the section 98 and a forward 
even smaller diameter cylindrical section 102 terminating in a pointed 
guide 104. A radially extending annular shoulder 106 joins the cylindrical 
sections 100 and 102. 
The bushing 86 may be formed of aluminum, zinc or any other metal which is 
readily etched in a chemical solution. The bushing may be formed by die 
casting, cold heading or the like. The bushing comprises a cylindrical 
body 108 having a circular boss 110 extending outwardly from the end 112 
of the body and a generally tapered recess, generally designated 114, 
opening at the opposite end 116 of the body. A cylindrical bore 118 
extends from the flat end surface 120 of the boss 110 to an annular, 
radially extending shoulder 121 forming the bottom of the recess 114. The 
recess is also defined by a frustro-conical surface 122 and a cylindrical 
inner surface 124 adjacent to the end 116 of the bushing. 
Four longitudinally and radially inwardly extending fins or ribs 126 are 
formed on the interior of the recess 114, the number corresponding to the 
desired number of slots in the contact retention cone of the insulator to 
be formed. Each fin embodies a front longitudinally extending inner 
surface 128, and a rear inwardly and rearwardly extending tapered surface 
130 which terminates at the shoulder 121. 
The diameter of the rear cylindrical section 88 of the core pin 82 
corresponds to the diameter 28a of the bore 20a in the insulator 80. The 
diameter of the cylindrical section 90 of the pin 88 corresponds to the 
diameter of the cylindrical section 26a of the bore 20a. The 
frustro-conical section 94 of the core pin 92 is shaped to define the 
inner surface of the contact retention cone 16a of the insulator 80 while 
the frustro-conical surface 122 of the recess 114 in the bushing 86 is 
shaped to define the outer surface of the cone. The forward cylindrical 
section 92 of the pin 82 is dimensioned to have a sliding fit within the 
bore 118 in bushing 86. 
The diameter of the cylindrical section 100 of the core pin 84 corresponds 
to the diameter of the bore 38a of the closed entry of the insulator 80 
and the forward section 102 of the pin 84 is dimensioned to have a sliding 
fit into the bore 118 in bushing 86. The boss 110 on the end 112 of the 
bushing has a diameter corresponding to the diameter of the cylindrical 
recess 44a in the contact passage of insulator 80. The outer diameter of 
the cylindrical body 108 of bushing 86 corresponds to the diameter of the 
cylindrical section 22a of the contact passage through the insulator. 
Referring again to FIG. 6, the rear section 88 of the core pin 82 is 
fixedly mounted in one part 132 of the mold 87 while the rear section 98 
of the core pin 84 is fixedly mounted in the other part 134 of the mold. 
The core pins are coaxially aligned with each end inserted into the 
bushing 86 disposed between the core pins. When the mold is closed, the 
shoulder 106 on the core pin 84 abuts the flat surface 120 on the end of 
the boss 110 of bushing 86, and the shoulder 95 on the core pin 82 abuts 
the bottom 121 of the recess 114 in the bushing. The frustro-conical 
section 94 of the pin 82 engages the tapered surfaces 130 of the fins 126 
and the forward portion of the cylindrical section 90 of pin 82 slidably 
engages the longitudinally extending inner surfaces 128 of the fins. 
To form the insulator 80, a dielectric material such as plastic is injected 
into the mold, filling the voids therein, including the conical cavity 
formed between the surfaces 94 and 112 to form the contact retention cone 
16. Complete filling of the mold, particularly in the area of the 
aforementioned conical surfaces may be facilitated by providing a vent 
passage 136 in the core pin 88 leading from the surface of the cylindrical 
section 92 to the rear 138 of the pin. Such passage allows the escape of 
any entrapped air and gases from the mold during the injection of plastic 
thereinto. After the plastic is injected into the mold and allowed to 
harden, the two parts 132 and 134 of the mold are separated thereby 
removing the core pins 82 and 84 from the thus formed insulator 80. After 
the plastic insulator has fully cured, the bushing 86 is removed by 
etching in a chemical bath. The resulting insulator construction is as 
shown in FIG. 4. 
It will be appreciated that in practice, the mold 87 will contain a 
plurality of sets of core pins 82, 84 and bushings 86 to form a plurality 
of contact passages in the insulator. It will be further appreciated that 
the method and apparatus of the present invention allows the production of 
one-piece, homogeneous electrical connector insulators embodying integral 
contact retention cones in the contact passages for restricting rearward 
movement of contacts therein, as well as closed entries and thus 
rearwardly facing shoulders in front of the cones for restricting forward 
movement of the contacts in the cavities. Thus, the invention reduces the 
number of parts required for the connector insulator, reduces 
manufacturing and assembly costs, and eliminates a potential electrical 
leakage path which exists in the prior art insulators employing integral 
contact retention cones. 
The term "one-piece, homogeneous insulator" as used in this description and 
the appended claims is intended to mean the hard plastic insulator in 
which the contacts are supported, and excludes elastomeric sealing 
grommets which are often mounted on the front or rear faces of the hard 
insulator. 
Various modifications to the invention will be apparent to those skilled in 
the art. For example, the fins 126 could be provided on the core pin 82 
rather than on the bushing 86. Also, the shape of the surfaces 94 and 122 
may be modified to provide a different configuration to the contact 
retention cone 16a than that shown. Also, the boss 110 on the bushing 
could be eliminated, if desired.