Apparatus and method for retaining an insert in an electrical connector

A deformable plastic strip (44') is longitudinally slotted (60) along one edge to define a plurality of laterally separated longitudinal columns (62), cut, and then rolled into a tubular sleeve to form a retention member (44) which is configured to be coaxially driven into an annular passageway (72) formed between an insert (24) and a connector shell (10), engagement of the slotted end portion with an axial shell face (16) causing the columns to axially collapse in accordion like fashion and radially wedge themselves into the passageway whereby to interferencingly retain the insert in the shell.

BACKGROUND OF THE INVENTION 
This invention relates to a separable electrical connector having an 
improved arrangement for retaining an insert within a shell. 
An electrical connector of the type herein includes a dielectric insert 
which is retained in a metallic shell and carries a plurality of 
conductive terminals in electrical isolation from the shell for mating 
with a respective plurality of terminals in a second connector. The 
dielectric insert typically is hard and can either be comprised of a 
thermoset or a thermoplastic material with good dielectric properties for 
circuit isolation. 
Previous approaches for retaining an insert assembly within the shell have 
included upset staking of the shell, metal ring staking, and copper 
mesh/epoxy laminate staking. Each of these offer excellent retention but 
may introduce a conductive path between the insert assembly and shell. In 
"Electrical Connector" U.S. Pat. No. 4,019,799 and "Method of Making 
Electrical Connector" U.S. Pat. No. 4,099,233 issuing to Bouvier, 
respectively, Apr. 26, 1977 and July 11, 1978, and each incorporated 
herein by reference, it has been found that deforming the conductive mesh 
laminate by a crushing action caused the mesh to invade into the bond 
interface between a hard wafer and a resilient grommet whereupon a 
conductive path could be established between the outer row of terminals 
and the shell thereby causing a ground short to exist. 
Other approaches have included epoxy staking, interference fits with epoxy, 
and self-snapping mechanisms, all of which protect against a conductive 
path to the shell but do not offer a good insert retention system. Epoxy 
does not have an internal reinforcement to prevent break up under extreme 
conditions of temperature and pressure. Further, the interference fits 
with epoxy rely on the epoxy to take up sloppy fits due to tolerancing. 
Slippage and loose friction fits could lead to insert pull-out. Self 
snapping mechanisms introduce loose inserts due to tolerancing 
difficulties. 
Another approach has utilized a non-metallic laminate mesh. This offers 
good retention and assures a non-conductive path between the insert and 
shell but is hard to handle and process. 
Provision of a non-conductive insert retention system that would be 
inexpensive, adaptable to a wide range of connector shells having 
different diameters and internal cross-sections, easy to manufacture, easy 
to assemble, and assure the user of insert retention integrity would be 
desirable. 
SUMMARY OF THE INVENTION 
This invention contemplates an electrical connector comprising a metal 
shell that includes an annular groove on its inner wall, a dielectric 
insert having an outer periphery disposed in the shell so that an annular 
passageway is provided between the shell and the insert, and a retention 
arrangement for retaining the insert in the shell. 
In accordance with this invention, a retention member comprised of an 
elongated strip of a deformable thermoplastic material is scalloped along 
its front face by longitudinal slots to provide a plurality of axially 
weakened columns which will collapsingly fold onto one another and stack 
together in accordion like fashion and radially interferencingly wedge 
themselves in the annular pasasgeway when the strip front face engages an 
axial wall at the end of the passageway formed between the insert and the 
shell. The inner wall includes an annular groove which encircles the outer 
periphery and cooperation between axial faces of the groove and radial 
folds requires shear forces to shear the accordion-like folds for the 
insert to be removed.

DETAILED DISCUSSION OF THE INVENTION 
Referring now to the drawings, FIG. 1 illustrates a metallic connector 
shell 10 a dielectric insert 24, an insert retention member 44, and an 
insert tool 70 each coaxially aligned for assembly along a central axis. 
The insert and shell have complementary cross-sections such that when the 
insert is fitted into the shell, an axially extending annular passageway 
72 is formed for receiving the insert member (See FIG. 4). The shell and 
insert are generally cylindrical and of one piece but are shown in section 
for clarity of description of the insert retention. 
The shell 10 is open at each of its opposite axial ends and includes a 
forward mating end 11, a rearward entry end 13, an inner wall 12, an 
annular groove 19 disposed within the inner wall, and a radial flange 20 
extending radially inward from the inner wall. The annular groove 
comprises a first axial face 16 disposed in a plane generally 
perpendicular to the central axis and facing rearwardly, a flared 
frusto-conical axial face 18 facing forwardly, and an annular wall 14 
extending between the faces and generally coaxially extending relative to 
the inner wall. The flange 20 includes an endwall 22 that faces rearwardly 
and provides a stop which limits inward axial insertion of the insert into 
the shell. 
The insert 24 is typically comprised of polypheniline sulfide such as 
commercially available under the trade name Torlon, and includes a front 
face 28, a rear face 26, and a plurality of passages 30 extending between 
the faces for receiving an electrical contact (not shown) therein for 
mating. The cross-section of the insert is stepped and includes a first 
surface 34 defining an outer periphery, a second surface 40 extending 
radially outward from the outer periphery to define a collar 32, and a 
third surface 42 extending radially inward from the outer periphery to 
define a shoulder 41 leading to an inward recess, each of the surfaces 
being generally coaxially defined relative to the central axis of the 
insert. The collar 32 includes a rear face 36 facing rearwardly, and a 
front face 38 facing forwardly and adapted to abut endwall 22 of the 
radial flange. The second surface 40 of the insert which defines the outer 
periphery of the collar is adapted to clearance fit against the inner wall 
12 of the shell 10 so as to position the rearwardly facing end wall 36 of 
the collar medially of the annular groove 19 which will encircle it when 
the insert is within the shell. As shown, a pair of cylindrical inserts 
are bonded together into a single member with the bond interface indicated 
at 31. 
The retention member 44 is formed into a tubular sleeve from a flat sheet 
of a thermoplastic material, the sleeve having a forward portion 46 
substantially thinner than a rearward portion 48 with a front face 50 
being scalloped by slots 60 extending therefrom towards its to a rear face 
52. 
Retention member 44 is comprised of a material that would be resiliently 
deformable and not be crackable, have good properties of elongation, shear 
strength and high temperature capability. Such a material is a 
thermoplastic such as would include a polyether sulfone and a 
polyetherimide. 
The insertion tool 70 includes a body 68 and a cylindrical mandrel 64 
extending to a front action surface 66 adapted to engage the rear face 52 
of the retention member 44 whereby to drive the retention member into the 
annular passageway 72 formed between the inner wall of shell and the outer 
periphery of the insert when the insert is inserted within the shell. 
FIG. 2 shows a cross-section of the retention member 44 such as would be 
seen looking along lines II--II of FIG. 3. The retention member has 
generally parallel top and bottom faces for each of its forward and 
rearward portions 46, 48, the rearward portion being the thicker of the 
two and defining a forwardly facing endwall 54 which is adapted to engage 
the shoulder 41 on the insert whereby to trap the rearward portion of the 
two piece insert. 
FIG. 3 shows the retention member 44 as being formed from an 
elongated-continuous strip 44' of non-conductive thermoplastic material. 
As the strip is advanced in the direction "A" a plurality of slots 60 
which extend perpendicularly from its front face 50 inwardly towards its 
rear face 52 are formed to define a plurality of laterally separated 
weakened axial columns 62 which are adapted to collapse upon a sufficient 
external force being placed on them. The strip is first slotted and then 
severed into strip portions each which define the retention member 44. The 
severing could be perpendicular to the front and rear faces of the strip 
44 whereby form a rectangular shape having lateral endfaces 56, 58, as 
shown, or at an acute angle to the front and the rear endfaces whereby to 
form a parallelogram shape (not shown). Following each severing, depending 
on the shape or configuration desired, the respective lateral endfaces are 
wrapped around and brought into abutment with one another to form a 
tubular sleeve having a cross-section sized for insertion into the annular 
passageway. The shape of the slots 60, while being shown as having a 
U-shaped root, could be otherwise. 
FIG. 4 shows the insert 24 clearance fit within the shell 10 with the front 
face 38 of its collar 32 abutting against the endwall 22 of the radial 
flange 20 whereby to position the insert therewithin so that the annular 
groove encircles the collar. The axially extending annular passageway 72 
is formed between the outer periphery of the insert and the inner wall 12 
of the shell. The retention member 44 is inserted inwardly into the 
passageway 72 from the rearward entry end 13 of the shell. The difference 
between the distance between endwall 54 of the rearward portion 48 and the 
front face 50 of the forward portion 46 and the distance between the 
shoulder 41 of the insert and the axial face 16 of the shell defines a 
collapsible volume which is adapted to collapse in accordion like fashion 
whereby to radially wedge itself within the annular groove 19. 
While rear face 36 is shown as being substantially at a right angle, a 
chamfer (i.e., tapered) surface would also work). 
FIG. 5 shows the result of continued insertion of the retention member into 
the passageway. The front face 50 is driven into engagement with the 
rearwardly facing axial face 16 of the annular groove 19. Further external 
force causes the columns 62 to collapse in an accordion-like fashion 
whereby to fold over themselves and have portions thereof driven radially 
upward as the column folds stack. Portions of the folded accordion are 
interferencingly wedged within the annular groove and around the insert 
whereby to engage the insert and shell. When the endwall 54 abuts the 
shoulder 41 of the insert 24, the assembler knows that the insert staking 
operation is complete. 
Because of the accordion-like portion being formed by a plurality of radial 
column folds and disposed between axial faces and in the annular groove, 
insert withdrawal can only come about as a result of shear forces 
sufficient to shear the folds.