GB2033173A - Electrical connector assembly having improved threading characteristics - Google Patents

Abstract

An electrical connector assembly 10 having improved threading characteristics for resisting cross-threading includes a first and a second shell 100, 200, each including mateable contacts 110, 210, and a coupling nut 300 mounted to the first shell 100. The coupling nut 300 and second shell 200 have interfitting, mateable threads 340, 240 for drawing the shells and mateable contacts together. The threads have a substantially uniform height and are formed on an automatic screw machine with a gradual incline on the forward, leading thread portion 342, at least a substantial portion of the inclined thread portion 342 then being removed to form a blunt, substantially perpendicularly rising, start 344 for the thread. <IMAGE>

Description

SPECIFICATION Electrical connector assembly having improved threading characteristics and method of making 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 assemblies in 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.

In the prior art electrical connectors in this field, as illustrated 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 and relatively low cost.

These machines are typically set up to provide a gradually tapering screw thread, starting from the surface of the member and gradually building to the desired final thread height.

Unfortunately, it is possible to cross-thread the coupling nut on the shell when the threads are manufactured in this way.

When the threads are cross4hreaded, there are many disadvantages. The contacts are not securely mated, leading to poor, and possibly broken, electrical connection between 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.

Accordingly, it is an object of the present invention to overcome the limitations and disadvantages of the prior art connector assemblies providing an electrical connector assembly which resists the cross-threading of the members.

It has been found that the tapering leading portion of the threads allows such cross-threading to happen.

Therefore, the present invention proposes 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 said shells and having a thread adapted to mate with a mating thread on the other of said shells, the method comprising the step of forming mating threads on the coupling nut and the other shell, said threads having a tapered portion on a leading edge of the thread, and a subsequent portion of substantially uniform height, said 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, characterized in that it comprises the further step of removing at least a portion of said tapered portion of at least one of the threads for creating an initial thread termination which arises abruptly from the surface of the one coupling nut and said other shell, whereby the abruptly rising portion creates a barrier two crossthreading the coupling nut and shell upon mating.

The invention will now be described with reference to the accompanying drawings wherein Figure 1 is a cross-sectional view of an electrical connector assembly.

Figure2 is an enlarged cross-sectional view of a coupling nut of the prior art, showing the tapered threads common to the electrical connector assemblies of the prior art.

Figure 3 is a cross-sectional view of the coupling nut and shell of Figure 2, taken along the line Ill-Ill 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 the 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 Figure 4.

Figure 6 is a partial cross-sectional view of a coupling nut and one thread, looking along the line VI-VI of Figure 1 in the direction of the arrows.

Figure 7 is a perspective view of a shell having one thread of the type preferred in present invention for mating with one thread on the coupling nut.

Figure 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.

Figure lisa cross-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 to be mated with a second shell 200. A coupling nut 300 is adapted to be 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 200 have mateable electrical contacts 110,210, respectively, mounted therein. The 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 serve to allow the shells to mate only when one shell is in a predetermined rotational orientation with respect to the other shell to make the respective contacts.

Aforward 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.

The second shell 200 has an external thread portion 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 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 with 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, rearfacing 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 of the coupling nut 300 in an annular groove 160 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.

Figure 2 is an enlarged cross-sectional view of the electrical connector assembly 10 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 seated in the groove 160 and prevents the coupling 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 axis of the coupling nut 300 and the first shell 100.

The threads 240,340 on the second shell 200 and the coupling nut 300, respectively, allow the rotation of the coupling nut 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 shown in Figure 2, the coupling nut 300 and the first shell 100 are advantageously provided with a system for resisting decoupling rotation of the coupling nut when subjected to vibrational forces. One such system is described in U.S. Patent 4,109,990 to Knapp and Waldron.

Figure 3 is a cut away view, taken along the line Ill-Ill in Figure 2. The coupling nut 300 has the threads 340 shown. As shown in this view, there are preferably three sets of threads, each of which includes a leading edge or start 341, 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 1 20" around the periphery of the shell, is believed to be the preferred embodiment, allowing quick coupling and decoupling without steep thread angles or large axial displacements per unit of radial rotation.

The leading thread edge or start 341 is at the diameter of the interior wall of the coupling nut 300.

From the start 341, which is difficult to locate exactly, the tapering portion 342 rises gradually, and preferably uniformly, to the height desired for the subsequent 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 ofthe coupling nut.

The form of threads described above is especially suited for manufacture on automatic screw machines which are well known in the art.

Figure 4 illustrates the coupling nut 300 in Figure 3, following the removal of the tapered portion 342 from the forward or leading edge of each thread 340.

The tapered portion 342 is removed by a grinding operation, which advantageous removes the entire tapering portion 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 perpen dicularto the thread. Thus, the leading edge 344 of each thread is approximately perpendicular to the surface of the coupling nut with a sharp corner both where it meets the surface of 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 substantially all of the tapering portion is believed to be the best approach 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 then 50% of the full height (e.g. of the portion 343) is desirable, with removal of the tapered thread portion less than 90% is advantageous.

Figure 5 shows the coupling nut 300 and the first shell 100, similar to that shown Figure 3. The coupling nut 300 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-sectional view of the interior of the coupling nut 300 of the present invention, taken along the line VI-VI in Figure 1. The blunt, or perpendicularly-extending, leading edge or start 344 of the thread 340 and the following thread section 343 of uniform height are shown.

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.

Figure 8 is a perspective view of the second shell 200 with threads 240. The threads 240 are also formed in the preferred embodiment on 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 to the shell axis and perpendicular to the threads, followed by threads 243 of substantially 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 substantially uniform height.

While a preferred 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 and, in some instances, certain features of the invention may be used to advantage without the corresponding use of other features. The threads could be formed in different ways and on different machinery.

It may be advantageous to use a blunt start on less than all of the starts on the members, coupling nut and mating shell, and one of the two members might have conventional (inclined) starts while the other member includes blunt starts.

Accordingly, it is intended that the illustrative and descriptive materials herein be used to illustrate the principles of the invention and not to limit the scope thereof.

Claims (6)

1. 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 said shells and having a thread adapted to mate with a mating thread on the other of said shells, the method comprising : the step of forming mating threads on the coupling nut and the other shell, said threads having a tapered portion on a leading edge of the thread, and a subsequent portion of substantially uniform height, said 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, characterized in that it comprises the further step of removing at least a portion of said tapered portion of at least one of th reads for creating an initial thread termination which arises abruptly from the surface of the one coupling nut and said other shell, whereby the abruptly rising portion creates a barrier to cross-threading the coupling nut and shell upon mating.

2. A method according to Claim 1, characterized in that the step of removing a portion of the tapering threads includes removing a portion of the tapering threads on both the coupling nut and the shell.

3. A method according to Claim 1, characterized in that the step of removing the thread portion includes removing the leading inclined portion which is less than one-halfthe height of the subsequent uniform height portion.

4. An electrical connector assembly including first and second shells, each including mateable electrical contacts, and a coupling nut mounted on the first shell and including a first thread adapted to mate with a second thread carried on the second shell, said first and second threads being formed along the steps of the method according to anyone of Claims 1 to 3.

5. A method of making a mateable electrical connector assembly substantially as described with reference to the accompanying drawings.

6. An electrical connector assembly substantially as described and as shown in the accompanying drawings.