US3496516A - Electrical connector - Google Patents

Description

Feb. 17, 1970 B. R. MCCFADDEN 3,496,516

ELECTRICAL CONNECTOR Original Filed Dec. 19, 1965' INVENTOR. BRUCE R. MFADDEN LMx Arrow/var;

United States Patent 3,496,516 ELECTRICAL CONNECTOR Bruce Richard McFadden, Harrisburg, Pa., assignor to AMP Incorporated, Harrisburg, Pa. Continuation of application Ser. No. 331,785, Dec. 19, 1963. This application Jan. 9, 1967, Ser. No. 608,228 Int. Cl. H01r 25/00, 29/00 US. Cl. 33918 3 Claims ABSTRACT OF THE DISCLOSURE A termination for printed circuits utilizing firm insulation boards. The termination being a tab formed from the conductive-metal, printed-circuit lamina itself, which extends over a plughole in the insulation board. Also, the connection between such a tab termination and a resilient metal contact inserted into the plughole, thereby forming an excellent electrical wipe-contact with residual contact pres-sure therebetween.

This application is a continuation of application Ser. No. 331,785, filed Dec. 19, 1963 and now abandoned. The present invention relates to electrical connecting means. More particularly, it pertains to printed circuit to the manner in which the control components of the machine are to be operated. The contact-carrying boards, one of which is usually fixed relative to the machine while the other is moved into and out of cooperating relationship therewith, are positioned in and relatively manipulated by a suitable mechanism as shown, for example, in Patent No. 2,927,295.

' The rows and columns of contact elements on the fixed board typically constitute the terminals of electrical conductors leading from the sensing elements and the instrumentalities'to be controlled in the machine, and on the movable board provide rearrangeable interconnecting plugs or jacks through which the particular circuit connections on the first board may be made. In an average sys tem, several hundred contact elements are located on each board in a minimum area with a minimum space between rows and columns. Not only is the movable board readily rearrangeable, but when the rearrangement would be extensive, it is preferably replaced by another movable board already pre-programmed in the new arrangement.

It will be readily realized that the larger and more complex machines which extensively utilize patchcord systems will often have a number of jumper connections which do not vary when the overall programming is changed for the various different applications of the machine. When these jumper connections begin to number in the thousands then having a patchcord jumper, each with two electrical plug contacts, for each pre-programmed movable patchboard becomes significantly eX- pensive, especially when there is no need to change the jumper connection at all. What is preferably required is an inexpensive jumper that could be inexpensively applied on the fixed board (thereby eliminating the need of a multiple number of jumpers for one connection), a permanent jumper, and one which would not necessitate the redesign of any of the elements of the existing patchcord systems to accommodate its use.

Various prior art devices have been proposed to meet these needs but without providing truly satisfactory solutions. Bus bars proved to be bulky, tended to make poor contact unless soldered or screwed into place, and often required redesigning the existing patchcord systems. Wirewrap and soldered wire jumpers were diflicult and costly to apply, especially in such confined spaces, and often gave rise to shorting due to slack wire. Even a coiled conductive springhas been proposed as a jumper, which appears to be a bulky, probably expensive item, that would tend to make a poor contact.

It is therefore an object of this invention to overcome the objections raised with respect to the prior art by providing a simple, effective jumper device which is permanent and inexpensive to make and apply, and does not require redesign of any existing equipment for its use.

Another object is to provide a versatile jumper device that can be readily applied and used in the confined spaces common to the plugboards employed in patchcord and other systems to jumper two or more plug contacts whether in adjacent holes or not.

Still another object is to provide such a jumper which can be easily mass produced and yet to adapt readily to different design requirements for different plugboard jumper situations.

Yet another object is to provide an assembly where such a jumper maintains gas-tight, mechanically strong connections having a substantially constant low resistance in spite of varying environmental conditions, and further without having a significant current leakage.

An advantage of this invention is the creation of a jumper with integral terminating means made solely by printed circuit techniques without any special termination adapters screwed, soldered, or otherwise aflixed to the jumper.

Another advantage lies in the creation of such a permanent terminating means which is dependable and electrically superior.

Still another advantage is the creation of a printed circuit procedure whereby the baseboard is preformed and the printed circuit applied thereafter instead of forming the printed circuit and then drilling out or otherwise modifying the baseboard. This reversed procedure has the advantage of not subjecting the thin circuitry to the shocks of processing the baseboard and further permits the formation of tabs or other similar circuit overhangs previously though impossible.

Other objects, advantages, and attainments of the present invention will become apparent to those skilled in 1 the art upon a readingof the following detailed description when taken in conjunction with the drawings in which there are shown and described preferred embodiments of the invention; it is to be understood, however, that these embodiments are not intended to be exhaustive nor limiting of the invention, but are given for purposes of illustration in order that others skilled in the art may more fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify it in various forms, each as may be best suited to the conditions of a particular use.

In the drawings: FIGURE 1 is a plan view of a portion of a plugboard illusrating several preferred embodiments of our printed circuit jumper invention with several of the dimensions of this and the following figures exaggerated for emphasis as will become evident from the subsequent discussion, and with the lower portion of an electrical contact (plug) shown, in horizontal section, inserted in the upper left hand plug hole (see line 11 in FIGURE 3).

FIGURE 1A is a simplified embodiment of our invention;

FIGURE 2 is an exploded elevational view taken line 2-2 in FIGURE 1 of the plug and, in cross sect on of a portion of the plug board and of the jumper device;

FIGURE 3 is an elevational view similar to FIGURE 2, except with the plug inserted, taken along line 33 in FIGURE 1; and

FIGURE 4 is a horizontal section of the plug taken along line 4-4 in FIGURE 3.

In the drawings, the lamina jumper device 10, having tab terminating means 12, is illustrated as applied to a preformed baseboard 14, here shown as a plngboard. The electrical contact, or plug, 16 upon insertion into one of the plugholes 18 (which is jumpered by one of the devices engages the tab contact 12, forms it over against the wall of the hole 18 (see FIGURE 2), and establishes a good electrical wipe-contact with the jumper 10 through the tab 12.

In its simplest form, this invention comprises a thin metal electrical jumper 10a fixed to a baseboard 14a and extending between two plugholes 18a having at least one tab portion 12 extending over each of said holes 18a; so that, when a snugly fitting plug 16 is inserted into plughole 18a at either end of the jumper 1011, an effective jumper circuit is thereby completed. See FIGURE 1A.

This novel jumper 10 takes advantage of the simplicity and cost savings inherent in normal printed circuit procedures, and additionally makes the innovation of applying a printed circuit over a preformed baseboard in such a manner that portions of the printed circuit extend unsupported out over cut-away portions of the baseboard (for example, over plugholes 18 in the plugboard 14) and use such an extension as a terminating means 12. Not only was it novel in the art of printed circuitry to form the baseboard prior to the application of the printed circuit, but even more surprising to a person skilled in the art would have been the thought that the delicate tab extensions 12 of such printed circuit jumpers would withstand the insertion of a plug 16 without tearing loose, but even more strinking, as has actually proven to be the case, is the ability to withstand repeated insertions; thereby ensuring non-failure in service and also allowing for repair of the permanent installation if it should become necessary for the plug to be removed for any reason.

The preferred embodiments illustrated in FIGURE 1 may advantageously be prepared by applying a thin copper lamina to the preformed plugboard 14b by any of a number of well known adhesives, for example epoxy resin. A protective coating of tin solder, or other similarly effective substance, may be then placed over the copper to prevent corrosion of the copper and also to enhance the electrical contact properties of the device. A pattern of etch-resist material is placed over the exposed areas of the copper lamina by a standard screening or photographic method and then etched to form the desired jumper devices 10, complete with overhanging tabs 12.

By referring to the more sophisticated preferred embodiments, for example 10b shown in FIGURES 1, 2, and 3, one can more readily appreciate the various patentable features of this invention. In order to maintain an effective electrical connection between the plug 16 and the formed over tabs 12 (as shown in FIGURE 2) under various environmental extremes, it is highly desirable that there is maintained a residual contact pressure between the plug 16 and the tabs 12. This residual contact pressure is attained in this preferred embodiment by employing a plug 16 which has a body portion 20 formed substantially in a circular cylinder with a longitudinal slot 22. This plug 16 has a lead-in taper so that upon insertion into holes 18b the tabs 12 are formed over and the plug 16 is compressed to partially close the slot 22 and thereby build up an outward radially directed pressure against the walls of hole 18b and therefore againstthe tabs 12 wedged therebetween. The plug 16, as illustrated in FIGURES 2 to 4, is already disclosed in an application of my co-worker, John G. Hatfield, Ser. No. 298,002, filed July 25, 1963, which was copending with the parent application of this case and which is now Patent No. 3,288,915, issued Nov. 29, 1966, and is presently being commercially used in the patchcord assemblies disclosed in Patents Nos. 2,882,508 and 2,927,295. This serves to illustrate how the present invention can be used with existing patchcord systems and not require any modification of the various elements thereof.

One aspect of the plug 16 illustrated as having a substantially circularly cylindrical body portion 20 with a longitudinal slot 22, is that when such a plug is inserted into its plughole 18 it exerts not only a longitudinal pull on tabs 12 but also a circumferential shear if the tabs should be oriented close to the slot 22. Clearly this circumferential shear diminishes the further the tab is placed away from this slot 22. Therefore, jumper 10b takes advantage of another design feature of the plug 16, illustrated in FIGURES 2 to 4. Namely, the body portion 20 is flattened into an orienting surface 24 on either side adjacent to the slot 22 in order to provide an orientation of the plug as it is inserted into holes 18b, which in turn have a corresponding flattened shelf 26 in the lower half of each of the holes 18b, thereby giving the hole outline at that point a D-shape. By taking advantage of this orienting means, 24 and 26, it is possible always to have tabs 12 placed sufficiently far away from the slot 22 to avoid most of the detrimental shear action encountered upon the insertion of the plug 16 into the hole 18b. It has been found advantageous to employ two tabs 12 as a safety feature in case one should prove to be faulty (as may happen in mass production). Advantageously, this pair of tabs 12 are spaced from each other and from shelf 26 thereby minimizing the shear on the tabs. If the tabs 12 were located closely adjacent to each other, then the longitudinal pull therealong would be concentrated at one point on the jumper 10, thereby requiring a larger jumper 10 at that point in order to withstand this pull, and there might not be sufficient clearance between the plugholes to allow for the wider jumper surface required to give increased adherence to the plugboard 18 at that point.

Another advantage in using printed circuit tabs 12 as the terminating means for the shunt 10 is that the thickness of these tabs 12 adds very little bulk in the hole 18. This is one of the features mentioned before which avoids the necessity of redesigning any of the elements of the patchcord assembly system. Thus, where two tabs 12 are used, it is better to have them closer together than on opposite sides of the hole. By having these tabs placed at 120 from each other, their effective bulk with respect to a circular plug 16 is substantially reduced and yet the other advantages to be found with this orientation are also attained.

A recital of some of the dimensions of one installation of embodiment 10b will help to illustrate two important points, how strong these tabs 12 are in spite of their dimensional delicacy, and what a surprisingly small jumper surface need be adhered to the plugboard in order to support these tabs. Thus, in one embodiment the jumper is made from what is called in the trade two ounce copper, which has a thickness of approximately 0.0028 of an inch. One standard plugboard 1412 has plugholes 18b spaced 2. quarter of an inch apart with the holes themselves having approximately 0.15 inch diameters. Each tab 12 is approximately 0.04 by 0.03 inch, and though the jumper is close to a fifth of an inch 'wide across its center, yet that portion connecting the two tabs 12 at a plughole 18b is only 0.04 inch wide. Note that extension 28 of the jumper 10b actually overhangs the hole 18b and serves only as an outside visual orien tation to locate the shelf 26 and is not intended to give any added structural support to the jumper 10b.

The patchcord system in which this particular jumper with the above dimensions was to be used had a normal working voltage of 50 volts or less. However, these jumpers are spaced by at least 0.04 inch from each other between adjacent holes and have been actually tested to have a minimum voltage breakdown of 1.20 kilowatts. Thousands of test readings showed this jumper device to have a plug to plug average resistance reading of less than a milliohm, and even under the most severe testing conditions this resistance was rarely doubled. Furthermore, it was found that one tab of this installation was completely sufiicient both electrically and mechanically, and a second tab was needed only as an added safety feature to increase on a mass production basis an already surprisingly high reliability. Three or more tabs could have been used, but in the illustrated embodiment having the above dimensions additional tabs were found unnecessary and bulky and therefore impractical.

The other preferred embodiments of FIGURE 1 illustrate various modifications to jumper b. For example, jumper 10b is shaped to extend between two opposingly oriented plugholes 18b, and jumper 100 is a mirror image of 10b in order to jumper two reversed opposingly oriented plugholes 18 and still leave the minimum clearance from the first. Jumpers 10d and 10e show another suggested shape. Jumper 10] illustrates how two or more remotely located plugholes might be advantageously jumpered by the present invention.

I claim:

1. In an electrical assembly the combination comprising a firm insulation board having a substantially cylindrical hole therein; an electrical contact mounted in said hole and having a body portion formed of a conductive spring metal and having a longitudinal slot therein to permit compression thereof, a thin fragile lamina of conductive metal having a thickness typical for printed circuitry, said lamina being fixed to said insulation board and having tab portions extending down into said hole in good electrical wipe-contact with said body portion of said contact and wedged between said body portion and the walls of said hole, said body portion being naturally slightly larger than the space left within said hole by said tab portions and being shaped to exert a residual contact pressure against said tab portions, means for orienting said contact within said hole, said tab portions being disposed in said hole in positions substantially removed circumferentially from said longitudinal slot.

2. In a plugboard assembly the combination comprising a plugboard having a plurality of holes therein; electrical contacts mountable in said plugboard holes, each having a resilient cylindrical body portion with a longitudinal slot therein, thereby being adapted to exert a residual pressure against the walls of said plugboard hole; means for rotatively orienting the insertion of said contacts within said plugboard holes; a thin metallic jumper device fixed to said plugboard, extending between two adjacent plugboard holes and spaced from any conductive elements, other than electrical contacts mounted in the two adjacent holes, sufficiently to avoid voltage breakdown therebetween, and spaced from any contacts mounted in said two adjacent holes sufiiciently to avoid mechanically dislodging said device from said plugboard except for two tabs which extend radially in over part of each of said two adjacent holes which tabs are oriented such that insertion of said contact into one of said holes will engage the tabs respective at substantially from either side of said longitudinal slot thereby wedging said tabs in good electrical wipe-contact between said cylindrical portion of said contact and the walls of said plugholes.

3. A combination as described in claim 2 wherein said jumper device is generally about 0.003 of an inch thick, is spaced from any conductive elements other than electrical contacts mounted in the two adjacent holes by at least 0.040 inch and is spaced from the contacts mounted in said adjacent holes by about 0.005 to 0.010 inch.

References Cited UNITED STATES PATENTS 1,939,130 12/1933 Mills 33917 2,502,291 3/1950 Taylor 33917 2,958,064 10/1960 Swengel 33917 3,105,729 10/1963 Rosenthal et al. 33918 3,142,783 7/1964 Warren 317101 3,189,868 6/1965 Hatfield 369252 MARVIN A. CHAMPION, Primary Examiner P. A. CLIFFORD, Assistant Examiner U.S. Cl. X.R. 33917

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