US3731261A

US3731261A - Electrical connector with twisted posts

Info

Publication number: US3731261A
Application number: US00237942A
Authority: US
Inventors: F Spadoni
Original assignee: Litton Systems Inc
Current assignee: Northrop Grumman Guidance and Electronics Co Inc
Priority date: 1972-03-24
Filing date: 1972-03-24
Publication date: 1973-05-01
Anticipated expiration: 1990-05-01

Abstract

An improved electrical connector is disclosed which may be used to connect to a printed circuit board and is adaptable for use with automatic wire-wrapping machines. The terminal posts of the connector have a square cross section as do the holes in the base into which the posts are located. The posts are twisted about 90* to strengthen, straighten and insure a secure lock of the posts in the base.

Description

EJ115166 tates Patent 1 1111 $31,261 Spadoni, Jr. 1 May 1, 1973 54] ELECTRICAL coNNEcTon W1 FOREKGN PATENTS on APPLICATIONS TWISTED POSTS Inventor: Frank G. Spadoni, Jr., Orange,

Conn.

Assignee: Litton Systems, Inc., Beverly Hills,

Calif.

Mar. 24, 1972 Filed:

Appl. No.: 237,942

Related U.S. Application Data Continuation of Ser. No, 760,561, Sept. 18, 1968, abandoned.

References Cited UNITED STATES PATENTS 10/1967 Kinkaid ..339/220 R X 801,232 9/1958 Great Britain ..29/203 R 973,368 10/ 1964 Great Britain... 1,474,721 2/1967 France ..339/184 M Primary Examiner-Joseph H. McGlynn Assistant Examiner-Lawrence J. Staab Attorney-Alan C. Rose et a1.

[57] ABSTRACT 6 Claims, 3 Drawing Figures Patented May 1, 1973' 3,731,261

INVENTOR.

FRANK 6. SPADONI, JR.

JOSEPH H. GOLANT ATTORNEY ELECTRICAL CONNECTOR WITH TWISTED POSTS This is a continuation of application Ser. No. 760,561, filed Sept. 18, 1968 now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an electrical connector and particularly to an electrical connector for use with a printed circuit board and for use with manual or automatic wire-wrapping equipment.

2. Description of the Prior Art In 1958 the Gardner-Denver Company of Grand Rapids, Michigan introduced a punch-card controlled machine that would automatically strip insulation from a solid wire, properly route it on a wiring panel, and then wrap it around the desired terminal post ofan electrical connector. Thus a solderless wrap interconnection is effected quickly and inexpensively. The Gardner-Denver automatic wire-wrapping machine has the capability of terminating over 500 wires an hour thereby reducing wire terminating costs by more than 400 percent over the older manual methods of wirewrapping. In the wire-wrapping process the bare end of an insulated wire is wrapped around a terminal post havingsharp corners. Since the wrapping is done under tension the wire and the terminal post are deformed at the point of contact, i.e., the corners. Hence the wrapped wire is held to the post by the elastic stresses left in the wire and the post. The average pressure between the wire and the post is 30,000 psi; this pressure is more than sufficient to meet the requirements of a gas-tight connection.

With the advent of the automatic wire-wrapping machine however, came structural requirements for the electrical connector which is to be used in conjunction with the machine. A most important requirement is that the electrical connector post must be positioned within a circle of radius 0.010 inches centered at the true position. Another important requirement is that the terminal post of the electrical connector has sufficient strength so that it does not deform or move out of position during a wire-wrapping operation. Other desirable characteristics include having a square cross section post with a dimension of 0.025 inches per side. The wire-wrapping machine is also capable of wrapping on posts spaced from one another as close as 0.100 inches (center to center). Hence to take full advantage of the automatic wire-wrapping machine an electrical connector should have the above mentioned characteristics.

One prior art electrical connector developed for the automatic wiring operation comprised a plastic base with square posts located within square openings in the base. To retain the posts in the base and prevent them from being pushed through the base during wirewrapping the posts were staked"; that is, the posts were pinched on their opposite sides creating an interference dimension larger than the openings within the base. However, several problems arose with the use of such a connector: l the pinching of the post reduced the effective cross section and thereby the resistance to bending in a plane perpendicular to the pinches at a critical location just above the surface of the base a location where bending is most likely to occur; (2), the pinching operation usually caused the terminal posts to misalign so that a further process operation of realigning the posts within the limits required by the wirewrapping machine was necessary; (3), the pinching operation placed stress concentrations in the posts at the pinched area, thereby further weakening the posts. Hence, not only was the connector relatively expensive to manufacture but additionally had the disadvantage of a relatively high rejection rate during its own manufacturing process and a relatively high rejection rate during the automatic wiring operation causing excessive downtime of the wire-wrap machine. Further if one of the posts of the electrical connector broke during the automatic wiring operation the entire connector became a reject and the rewrapping of all the terminal posts of the replacement connector was necessary as there was no method available to remove just the damaged post and replace it.

SUMMARY OF THE INVENTION The above cited deficiencies in the prior art have been solved by the present invention by providing an improved electrical connector comprising a non-conductive base having a surface and an aperture in the surface, the aperture having a square cross section; a conductive post having a square cross section being partially disposed within the aperture and extending from the base; and the post having a twist for straightening and strengthening said post and for retaining said post in said base.

An object of the present invention is to provide an electrical connector having a strong, straight and properly aligned terminal post.

Another object of the present invention is to provide an electrical connector which is easily manufactured at a relatively low cost.

Still another object of the present invention is to provide an electrical connector which meets and exceeds the requirements imposed by automatic wire-wrapping machines.

A still further object of the present invention is to provide an electrical connector having means for precisely positioning the connector.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of an improved electrical connector having twisted terminal posts.

FIG. 2 is an enlarged perspective view or a portion of the view shown in FIG. 1 illustrating in more detail a twisted terminal post.

FIG. 3 is a plan view of the electrical connector illustrating terminal post ends opposite those shown in FIG. 1 and illustrating a pair of positioning means.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing wherein like referenced numerals designate like or corresponding parts throughout the several views there is shown in FIG. I a preferred embodiment of an improved electrical connector having generally a base 10, locating ears 12 at each end of the base 10 and a plurality of tenninal posts M mounted within the base 10. In more detail the base 10 is a molded generally rectangular shaped body of any suitable material preferably glass filled diallyl phthalate with the locating ears 12 molded integral with the base 10. Each locating ear 12 has a drilled hole 16 which is suitably threaded so as to allow the electrical connector to be mounted to a frame in series with a number of similar electrical connectors for automatic wiring operations to be performed by an automatic wire-wrapping machine as disclosed in co-pending application Ser. No. 760,499, filed Sept. 18, 1968, titled Method of Packing Electrical Connectors and Assembling Same Into a Wire Wrap Machine, now U. S. Pat. No. 3,641,666, issued Feb. 15, 1972, and assigned to the assignee of the present application.

The base is molded with a plurality of apertures 18, one of which is best viewed in FIG. 2, with each aperture having a square cross section at its opening in a top surface 20 of the base 10. As shown in FIG. 1 the apertures are aligned in a column two abreast along the longitudinal axis of the base 10. As mentioned above, a terminal post 14 is located in each of the apertures 18. The terminal posts may be of any suitable material and are preferably formed of phosphor bronze with a gold plating.

Referring now to FIG. 2 there is illustrated an enlarged view of a terminal post 14 located within an aperture 18 of the base 10. As seen the post has a square cross section along most of its length extending from the base 10 and terminating in a pointed structure 22 resembling a four-sidedpyramid. It is noted that along the portion of the post extending immediately away from the surface 20 the post is twisted through 90 (by a device disclosed in co-pending application, Ser. No. 760,404, filed Sept. 18, 1968, titled Device for Twisting and Aligning Terminal Posts of an Electrical Connector, now U. S. Pat. No. 3,580,297, issued May 25, 1971, and assigned to the assignee of the present application) so that while a post surface 24 is adjacent an edge 26 of the square aperture 18 when the terminal post emerges from the base 10, the post surface 24 appears to correspond to an edge 28 of the square aperture as the surface 24 is followed toward the pointed structure 22. Thus, it is seen that surface 24 is twisted through 90 as are each of the other three lateral surfaces of the terminal post 14. It has been found that the twisted configuration provides an electrical connector having terminal posts which obviate the numerous disadvantages of the above mentioned prior art electrical connector.

In the preferred embodiment the dimensions of the terminal post 14 and the aperture 18 are extremely important in order to fulfill the requirements of the automatic wire wrap machine. The terminal post measures 0.025 inches across one of the side of the square cross section with a tolerance of 10.001 inches. Meanwhile the dimension of the aperture 18 across one of the sides of its square cross section is 0.027 10.0005 inches. It is noted that the automatic wire-wrapping machine is capable of terminating wires around terminal posts as close as 0.100 inches (measured from the center of one aperture to the center of the immediately adjacent aperture in the longitudinal direction of the base 10). Additionally each terminal post is required to withstand an 8-pound force applied in the direction of the surface 20 while having a movement not exceeding 0.020 inches. It has been found for best results, the length of the twist should not exceed 0.060 inches while the twist should not extend from the base more than 0.050 inches. Thus, the length of the twist extending from the base is about twice as great as a side of the square cross-section of the post. The twist is easily made and yet is not so long as to interfere with the wrapping wire during the wire-wrap operation. The twist extends into the aperture and bites into the base to provide a strong anchorage. It is to be noted that while a 90 twist is preferred terminal posts may be twisted from to 95 and still fulfill the requirements of not moving more than 0.020 inches under an 8- pound force and of being properly aligned.

It is recalled that the prior art method of anchoring a terminal post in the base required pinching the square post at opposite faces to create an interference fit with the surface of the base. This had the undesirable effect of reducing the resistance to bending. It is to be noted that in the present invention there is no change of cross section area along the length of the twist of the terminal post. Yet the twisting causes a sufficiently large interference with the base to fulfill the requirements of the automatic wire-wrapping machine. Further there are no stress concentrations created at the twist as was created in the prior art pinching method. In fact the twist seems to harden the material by cold working so that a stronger terminal post is actually achieved whereas the prior art method weakened the post at the location most likely to receive the greatest bending moments. Finally, the twisting process acts to straighten the terminal post so that the end 22 is within the very close tolerance of true position (within a 0.010 inch radius circle); it is imperative that the terminal posts be straight and within the tolerances required.

Still another major advantage achieved over the prior art electrical connector is the ability to remove individual terminal posts that have been damaged so as not to require a rejection of the entire electrical connector. Removal is simply accomplished by placing a tool over a terminal post and twisting in opposition to the original twist so as to remove the twist from the post. The post may then be pushed easily through the base and a new post inserted and twisted into location. It has been found that a number of replacements can be made in the same aperture without excessive damage to the base. In comparison the prior art pinched terminal was not removable without damaging the base.

Referring once again to FIG. 1 several small pegs 30 are located on the surface 20 and may be integral therewith and are spaced along the longitudinal axis of the base 10 to provide in conjunction with raised sides 32 of the base 10 support for a printed circuit board that may be brought down over the terminal posts. The pegs 30 and raised sides 32 provide an air spacing between the board and the surface 20 of the base.

Referring now to FIG. 3, there is illustrated the underside of the base 10 having a surface 40. The apertures 18 which take the form of square openings at the surface 20 take the form of enlarged slots 42 opening to a longitudinal cavity 44 at the surface 40. The terminal posts 14 are bifurcated and disposed within the slots and are adapted to make electrical contact with a terminal end of a printed circuit board receivable in the cavity Disposed at each end of the cavity 44 are

alignment openings

46 and 48 where opening 46 has a square cross section and opening 48 has a circular cross section. The openings are molded into the base during its manufacturing process and serve to offer precise positioning or alignment points for the connector when the connector is aligned for automatic wire-wrapping, as more fully explained in the above mentioned copending application, Ser. No. 760,499, now US. Pat. No. 3,641,666. The dimensions of the alignment openings are for opening 46, 0.062 inches per side, while opening 48 has a 0.062 inch diameter. All location measurements on the connector are made individually from the alignment openings so that each of the apertures 18, for example, are precisely located and without any tolerance buildup.

It is to be noted, however, that positioning or alignment can also be achieved using the cavity 44. Thus an alignment jig having precisely located pins may be used with the

openings

46 and 48 or with the ends of the cavity 44 or alignment ribs may be provided to be used just with the cavity 44. Either system offers an inexpensive solution to a very important alignment problem.

It is understood that the electrical connector herein disclosed is not limited to use with the Gardner-Denver automatic wire wrap machine. The connector may be used with any suitable automatic or semi-automatic wire wrap machine or with manual wire-wrapping tools.

What is claimed is:

1. An improved electrical connector, comprising:

a non-conductive base having a surface and an aperture in said surface, said aperture having a square cross section;

a conductive post having a square cross section partially disposed within said aperture and extending from said base;

said post being twisted such that said twist extends below said surface into said non-conductive base for strengthening and straightening said post and for retaining said post in said base; i

said non-conductive base having a second surface;

said second surface having connector positioning means including a first and a second opening disposed therein;

said first opening having a square cross section and said second opening having a circular cross section; and

said conductive post located from said first and second openings.

2. An improved electrical connector, comprising:

said post being mechanically deformed such that said deformation extends below said surface into'said non-conductive base for retaining said post in said base;

said non-conductive base having a second surface;

said conductive post located from said first and second openings.

3. An improved electrical connector, comprising:

a non-conductive base having a first surface and a plurality of apertures symmetrically arranged in said first surface, said plurality of apertures having a square cross section a plurality of conductive posts having a square cross section partially disposed within said plurality of apertures and extending from said first surface of said non-conductive base;

said plurality of posts mechanically deformed such that said deformation is below said first surface within said non-conductive base for retaining said posts in said base;

said non-conductive base having a second surface;

said second surface having connector positioning means including a first and a second aperture disposed therein;

said first aperture having a cross section mechanically differing from the cross section of said second aperture for keying the positioning of said non-conductive base; and

said plurality of conductive posts located from said first and second apertures.

4. An improved electrical connector as claimed in claim 3, wherein:

said mechanical deformation of said plurality of conductive posts is a twisting deformation extending into and below said first surface of said non-conductive base.

5. An improved electrical connector as claimed in claim 4, wherein:

said twisting deformation includes a twist between 75 and 95 which deforms said post below said first surface into said non-conductive base for engaging each comer edge of said square post equally against the inner comer surface of said square cross sectioned aperture within said nonconductive base, thus creating equal reaction forces within said post for strengthening and straightening said post during said twisting deformation.

6. An improved electrical connector as claimed in claim 3, wherein:

said first aperture having a cross section mechanically differing from the cross section of said second aperture includes a first aperture with a square cross section and a second aperture with a round cross section.

Claims

1. An improved electrical connector, comprising: a non-conductive base having a surface and an aperture in said surfaCe, said aperture having a square cross section; a conductive post having a square cross section partially disposed within said aperture and extending from said base; said post being twisted such that said twist extends below said surface into said non-conductive base for strengthening and straightening said post and for retaining said post in said base; said non-conductive base having a second surface; said second surface having connector positioning means including a first and a second opening disposed therein; said first opening having a square cross section and said second opening having a circular cross section; and said conductive post located from said first and second openings.

2. An improved electrical connector, comprising: a non-conductive base having a surface and an aperture in said surface, said aperture having a square cross section; a conductive post having a square cross section partially disposed within said aperture and extending from said base; said post being mechanically deformed such that said deformation extends below said surface into said non-conductive base for retaining said post in said base; said non-conductive base having a second surface; said second surface having connector positioning means including a first and a second opening disposed therein; said first opening having a square cross section and said second opening having a circular cross section; and said conductive post located from said first and second openings.

3. An improved electrical connector, comprising: a non-conductive base having a first surface and a plurality of apertures symmetrically arranged in said first surface, said plurality of apertures having a square cross section a plurality of conductive posts having a square cross section partially disposed within said plurality of apertures and extending from said first surface of said non-conductive base; said plurality of posts mechanically deformed such that said deformation is below said first surface within said non-conductive base for retaining said posts in said base; said non-conductive base having a second surface; said second surface having connector positioning means including a first and a second aperture disposed therein; said first aperture having a cross section mechanically differing from the cross section of said second aperture for keying the positioning of said non-conductive base; and said plurality of conductive posts located from said first and second apertures.

4. An improved electrical connector as claimed in claim 3, wherein: said mechanical deformation of said plurality of conductive posts is a twisting deformation extending into and below said first surface of said non-conductive base.

5. An improved electrical connector as claimed in claim 4, wherein: said twisting deformation includes a twist between 75* and 95* which deforms said post below said first surface into said non-conductive base for engaging each corner edge of said square post equally against the inner corner surface of said square cross sectioned aperture within said non-conductive base, thus creating equal reaction forces within said post for strengthening and straightening said post during said twisting deformation.

6. An improved electrical connector as claimed in claim 3, wherein: said first aperture having a cross section mechanically differing from the cross section of said second aperture includes a first aperture with a square cross section and a second aperture with a round cross section.