Note: Descriptions are shown in the official language in which they were submitted.
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ELECTRICAL CONNECTOR ASSEMBLY _AVIN~ IMPROVED THREADING
CHARACTERISTICS AND METWOD OF MAKING
TECHNICAL FIELD
This invention relates to electrical connector assemblies of the
type having mateable electrical contacts mounted in connector shells.
More particularly, this invention relates to connector assemt,lies in
5 which a coupling nut is mounted to one shell and includes threads which
- are adapted to mate with threads on the other shell and draw into
mated relationship the contacts in the respective shells.
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BACKGROUND OF THE INYENTION
In the prior art electrical connectors`in this field, as illus-
trated by U.S. Patent 3,227,990, the threads on the coupling nut and
shell are formed on automatic screw machines, for ease in manufacturing
at relatively low cost.
These machines are typically set up to provide a gradually
tapering screw thread, starting from the surface of the ~ember and
gradually building to the desired final thread height.
It is possible to cross-thread the coupling nut on the shell when
lo the threads are manufactured in this way.
When the threads are cross-threaded, there are many disadvantages.
The contacts are not securely mated, leading to poor, and possibly
broken, electrical connection bet~een the contacts. The shells may
separate, from each other, breaking the connection between the contacts.
In some connectors, the cross-threading may allow misalignment of the
shells, which can result in broken contacts. Further, an instance of
cross-threading an assembly can permanently damage the threads, leading
to repeated cross-threading of that assembly.
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_U ~ARY OF TIIE__NV_N r-to N
Accordingly, it i9 an object of the present
invention to overcome the limitations and disadvantages
of the prior art connector assemblies by providing an
electrical connector assembly which resists the cross-
threading of the members.
According to one aspect of the present invention
there is provided an e]ectrical connector assembly
including first and second shel~s, each including mateable
electrical contacts, and a coupling nut mounted on the
first shell and includin~ a first thread adapted to mate
with a second thread carried on the second shell. The
first and second threads have a substantially uniform
height along their respective lengths and each terminate
in a radially-extending surface at the leading thread
edge upon mating.
- According to another aspect of the present invention
there is provided a method of making a mateable electrical
connector assembly including first and second shells adapted
to be held in mated relationship by a coupling nut mounted
to one of the shells and having a thread adapted to mate
with a mating thread on the other of the shells. I~ the
present method the mating threads are formed on the coupling
- nut and the other shell, the threads having a tapered
portion on a leading edge of the thread, and a subsequent
' portion of substantially uniform height, the tapering
portion rising approximately uniformly in height from the
surface of the coupling nut or the other shell respectively
to the uniform height of the subsequent portion of threads.
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At least n port:ion of the tapered portion of at least one
of the threa(ls is removed crea~ing an initial thread
termination which arises abruptly from the surface of the
one coupling nut and the other shell so that the abruptly
rising portion creates a barrier to cross-threading the
coup:Ling nut and shell upon mating.
It has been found that the tapering leading portion of the
threads allows such cross-threading to happen. This leading
tapering or gradually increasinp, inclined portion of the
threads has been removed at least in part and preferably
substantially to leave a blunt, or perpendicularly rising
leading edge to reduced the cross-threading potential.
Other objects and advantages of the present invention
will be apparent to one skilled in the art in view of the
following description and claims, taken in conjunction r~ith
the accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE l is a cross-sect.ior,al view of an electrical connector
assembly.
FIGURE 2 is an enlarged cross-sectional view of a coupl;ng nut
of the prior art, show;ng the tapered threads common to the electrical
connector assemblies of the prior art.
FIGURE 3 is a cross-sectional view of the coupling nut ard shell
of FIGURE 2, taken along the line m-lTT in FIGURE 2, looking in the
direction of the arrows.
FIGURE 4 is a view of the coupling nut shown in FIGURE 3, after
removal of a leading tapering portion of each screw thread.
FIGURE 5 is a cross-sectional view corresponding to FIGURE 3, but
including the coupling nut of the present invention as shown in FIGliRE 4.
FIGURE 6 is a partial cross-sectional view of a coupling nut and
one thread, looking along the line VI-VI of FIGURE l in the direction
of the arrows.
FIGURE 7 is a perspect;ve view of a shell having one thread of the
type preferred in present in~ention for mating with one thread on the
coupling nut.
20FIGURE 8 is a perspective view of the shell and one mating thread
of the type preferred in the present invention.
FIGURE 9 is an end view of the shell of FIGURE 8 looking from the
line IX-IX in the direction of the arrows.
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DETAILED ~ESCRIPTION OF THE DRAWIN~S
FIGURE 1 is a crGss-sectional view of the individual members of
an electrical connector assembly 10 of the present invention. The
assembly 10 includes a first shell 100 which is adapted tG be mated
with a secon~ shell 200. A couplin~ nut 300 is adapted to te mounted
concentricly around the first shell 100 and to be held in place by a
spring 400.
The first shell 100 and the second shell 2CO have mateable
electrical contacts 110, 210, respectively, mounted therein. The
lo contact 110 is of the socket type and the contact 210 is of the pin
type, although any two mateable contacts could be used in the assembly.
The contacts 110, 210 are held within the respective shells 100,
200 by a suitable insert and contact retention system. Several such
systems are well known in the art which retain the contacts in the
proper position and orientation, and the retention system is not
crucial to an understanding of the present invention, so the systems
will not be described in detail. -
The first and second shells are also advantageously provided with
a plurality of spaced mating keys 120 and keyways 220. The keys 120
and keyways 220 are well known in the art and ser~e to allow the shells
to mate only when one shel1 is in a predetermined rotational orienta-
tion with respect to the other shell to make the respective contacts.
A forward portion 130 of the first shell 100 fits within a recess
230 in the forward portion of the second shell 200 when the shells
are mated.
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The second shell 200 has an external thread pcrtion 240 in its
forward portion. The thread portion 240 mates with a complementary
thread portion 340 on the inside of the coupling nut 300. The threads
240, 340 cooperate to draw the first shell 100 and second shell 200
5 together when the shells are mated, and the coupling nut 300 is rotated
with respect to the second shell 200. Such threads will be described
more fully in connection ~ith FIGURES 3-6.
The coupling nut 300 has a rear end 350 with a medial aperture
352 extending therethrough. The rear end 350 has an external, rear-
10 facing surface 354 and an internal, forward-facing annular shoulder 356.
The annular shoulder 356 seats against an enlarged stop (or
shoulder) 150 on the first shell 100 when the connector assembly 10
is put together. The spring (or snap ring) 400 is mounted behind the
rear surface 354 Gf the coupling nut 300 in an arnular sroove 160
15 which extends around the periphery of the shell 100. The coupling nut
is thus captivated in the assembly by the spring 400 in the groove 160
at the rear and the enlarged shoulder 150, but is free to rotate around
~ an axis of the assembly.
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FIGURE 2 is an enlarged cross-sectional vie~ of the electrical
connector assembly lG of FIGURE 1 with the members assembled together.
The coupling nut 300 is mounted to the first shell 100 by the spring
400. The spring 400 is seat~d in the groove 160 and prevents the coup-
ling nut 300 from rearward movement. The coupling nut 300 is limited
in its forward movement with respect to the first shell 100 by the
stop 150, but is allowed to rotate around the a~is of the coupling
nut 300 and the first shell 100.
The threads 240, 340 on the sec;ond shell 200 and the coupling nut
300, respectively, allow the rotation of the coupling r,ut to draw the
second shell 200 into the first shell 100, into a mated relationship.
The mated relationship has the forward portion 130 of the first shell,
within the recess 230 and the contacts 110, 120 mated in electrical
circuit relationship.
Although not shcwn in FIGURE 2, the co~ipling rut 300 and the first
shell 100 are-advantageously provided with a system for resisting de-
coupling rotation of the coupling nut when suojected to vibrational
forces. One such system is described in U.S. Patent 4,109,990 to Knapp
and Waldron.
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FIGURE 3 is a cut away view, taken along the line lll-lll in
FIGURE 2. The coupling nut 300 has the threads 340 shown. As shown
in this view, there ~re preferably three sets of threads, each of which
includes a leading edge or start 34l, a tapering portion 342, and a
subsequent portion 343. Of course, the thread system employed could
be modified easily to have more or fewer starts, although three starts,
each spaced l20 around the periphery of the shell, is believed to be
the preferred embodiment, allowing quick coupling and decoupling with-
out steep thread angles or large axial displacements per unit of
radial rotation.
The leading thread edge or start 341 is at the dia~eter of the in~
terior wall of the coupling nut 300. From the start 34l, which is dif-
ficult to locate e~actly, the tapering portion 342 rises gradually,
and preferably uniformly, to the height desired for the subsequ~nt
portion 343 of the threads. The subsequent portion 343 of the threads
are advantageously of uniform height and may extend several revolutions
around the interior wall of the coupling nut.
The form of threads described above is especially suited for
manufacture on automatic screw machines which are well known in the
art.
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FIGURE 4 illustrates the coupling nut 300 in FJGU~E 3, following
the removal of the ta~ered pcrtion 342 from the forward or leading edge
of each thread 340. The tapered portion 342 is ren~ved by a grinding
operation, which advantageous removes the entire tapering ~ortion 342
and leaves the coupling nut flat in this region, with a smooth finish
free from flaws and abrupt terminations. A new leading edge 344 of
the threads is created which preferably extends radially with respect
to the coupling nut and perpendlcular to the thread. Thus, the leading
edge 344 of each thread is approximately perpendicular to the surface
lo of the coupling nut with a sharp correr both where it meets the sur-
face cf the nut and where it meets the full thread height subsequent
portion 343.
The tapering portion 342 which preferably has been removed in its
entirety is shown by a dotted line in FIGURE 4. The removal of sub-
stantially all of the tapEring portion is believed to be the best ap-
proach to prevent cross-mating of threads. Removal of lesser amounts
would accomplish the same function to a lesser extent. It is believed
that removal of the tapered thread portion which is less than 50% of
the full height (e.g. of the portion 343) is desirable, with removal
20 of the tapered thread portion less than 90% is more advantageous.
FIGlJRE 5 shows the coupling nut 300 and the first shell 100,
similar to that shown in FIGURE 3. The coupling nut 3C0 shown in
this view is of the type shown and described in FIGURE 4, with blunt
leading edges 344 on the threads 340.
FIGURE 6 is a cross-sectionOl view of the interior of the coup-
ling nut 300 of the present invention, taken along the line V1-Vl in
FIGURE 1. The blunt, or perpendicularly-extending5 leading edge or
start 344 of the thread 340 and the following thread section 343 of
uniform height are sho~;n.
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FIGURE 7 is a perspective view of a portion of the coupling nut
300. The blunt start 344 and the uniform height portion 343 are shown
for one thread.
F~fiURE 8 is a perspective view of the second shell 200 with threads
240. The threads 240 are also formed in the preferrEd embodiment Gn an
automatic screw machine and initially have an inclined (or tapering)
leading edge which has been machined off. The thread thus has a leading
edge 244 which is blunt and perpendicular tG the shell axis and per-
pendicular to the threads, followed by threads 243 of substantially
~0 uniform height.
FIGURE 9 is an end view of the shell 200, showing three thread
starts 244 which are blunt, followed by three threads 243 of sub-
stantially uniform height.
While a perferred embodiment of the invention has been disclosed,
it will be apparent to those skilled in the art that changes may be
made to the invention as set forth in the appended claims ard, in some
instances, certain f~atures of the invention may be used to advantage
without the correspondinc use of other features. The threads could be
formed in different ways and on different ~achinEry. It may be ad-
vantageous to use a blunt start on less than all of the starts on the
: members, coupling nut and mating shell, and one of the t.wo members
might have conventional ~inclined~ starts while the other member in-
cludes blunt starts.
Accordingly, it is int~nded that the illustrative and descriptive
25 materials herein be used to illustrate the principles of the invention
and not to limit the scope thereof.
