Keyed connector to prevent intermating with a standard connector
This is a continuation of application Ser. No. 767,799, filed Feb. 11, 1977 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to keyed connectors and more particularly to keyed connectors having dimensions similar to but which cannot be mated with standard connectors. 
     2. Description of the Prior Art 
     Long marketed connector systems commonly known as MICRO-RIBBON connectors (a trademark of Bunker Ramo Corp.) are useful for interconnecting two cables, each having a plurality of wires therein. Such connectors, when embodied as either a plug or a receptacle, have an outer shell which retains an inner contact mounting insert. For a plug, the contact mounting insert has a central, upwardly extending tongue formed of parallel contact-retaining walls and end walls spaced a standard length by the retaining walls. A typical receptacle has a contact mounting insert with an aperture therein formed by parallel contact-retaining walls and end walls spaced a standard length by the retaining walls. The contacts on the contact supporting walls of the plug and receptacle align and mate when the units are plugged together. 
     In many applications, some of the connectors have low voltages associated therewith and others have high voltages. It is undesirable to permit a situation to exist in which a low voltage connector can be accidentally joined to a non-compatible high voltage connector. In particular, it is advantageous to prevent the mis-mating of data system connectors with telephone system connectors. In such cases, voltage level differences of up to 110 volts can occur. Also, even if the connectors do no exactly mate, the possibility that a conductive contact adjacent an end portion of one of the connectors might be tipped into contact or at least near to some of the contacts of the other connector poses a problem. Also, the contacts of non-compatible connectors may approach each other if an attempted head-on insertion is made. A high voltage arc may then occur when the high and low voltage contacts come sufficiently close together to permit an arc between them. Also, government requirements exist requiring connectors carrying high voltages to be polarized so that they can intermate only with similarly polarized mating halves and thus cannot short out any low voltage non-polarized connectors. 
     Examples of prior art patents which illustrate the use of keyed plugs and receptacles are Desso et al (U.S. Pat. No. 3,651,444), McDonald (U.S. Pat. No. 3,656,090), Gallagher (U.S. Pat. No. 3,930,705), Bertram et al (U.S. Pat. No. 3,002,175), Wilson (U.S. Pat. No. 3,953,099) and Yopp (U.S. Pat. No. 3,002,176). These patents are not pertinent to this invention since they do not teach the use of the connector system which uses a standard connector dimension but has a contact mounting insert with a contact supporting means which utilizes the keying means of this invention. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide a keyed connector embodied as either a plug or a receptacle which will not mate with a non-keyed standard connector. 
     It is a further object of this invention to prevent a high voltage arc-over between a keyed connector and a standard connector. 
     It is a further object of this invention to prevent any of the contacts of a keyed connector from approaching or making contact with any of the contacts of a non-keyed, standard connector. 
     It is another object of this invention to provide a keyed connector which utilizes a standard shell shape and has other dimensions which are similar to a standard connector. 
     According to the invention, a keyed connector is adapted to prevent connection to a standard connector having a base which retains a contact mounting insert and a standard length contact supporting means defined by end walls which are spaced a standard length by a contact supporting wall. The keyed connector has a contact mounting insert and contact means retained on a base. Keying means are provided adjacent at least one end of the contact supporting means. These keying means begin at a point shorter than one of the ends of the standard length contact supporting means of the standard connector and terminate at a point longer than the end of the standard length contact supporting means of the standard connector. In the case when the connector is a receptacle, the contact supporting means comprises an aperture in the mounting insert and the keying means comprises a slot of width less than the width of the aperture at ends of the aperture. When the connector of this invention is a plug the contact mounting insert comprises a tongue and the keying means comprises an extended end portion at ends of the tongue which has a width less than the width of the tongue. The keying means of the keyed connector of this invention further may have a raised portion which extends beyond a mating insertion end of the contact supporting means. This prevents high voltage arc-over in the event that a high voltage keyed connector is attempted to be inserted into a low voltage standard connector. Furthermore, a standard shaped shell of the keyed connector of this invention may have additional means at front and side locations to enhance alignment of the connectors when mating and to prevent insertion of a keyed plug of this invention into a standard receptacle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a perspective view of a keyed receptacle of this invention adjacent to a non-keyed standard plug; 
     FIG. 1B is a perspective view of a keyed plug of this invention adjacent a standard receptacle; 
     FIG. 2A is a plan view of a standard receptacle of the prior art; 
     FIG. 2B is a plan view of a keyed receptacle of this invention; 
     FIG. 3A is a plan view of a standard plug of the prior art; 
     FIG. 3B is a plan view of a keyed plug of this invention; 
     FIG. 4 is a side view of the keyed receptacle of FIG. 2B; and 
     FIG. 5 is a side view of the keyed plug of FIG. 3B. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIGS. 1A and 1B, a keyed receptacle 10 or keyed plug 12 of this invention carrying a high voltage, for instance, will not mate with respective standard plug 13 or standard receptacle 11 carrying a low voltage. The characteristics of the keyed receptacle 10 and keyed plug 12 which prevent mating with the standard plug or receptacle are more clearly shown in FIGS. 2A through 5 wherein the various dimensions can be compared by use of the vertical dashed dimension lines connecting FIGS. 2A through 5. 
     FIGS. 2A and 2B show side by side relationships between a prior art receptacle 11 and the keyed receptacle 10 of this invention. The keyed receptacle 10 has a keyed shell 14 and a keyed receptacle insert 15. A plurality of contacts 17 are arranged on parallel contact retaining walls on either side of an aperture 16 within the insert 15 in a fashion similar to prior art receptacles. Narrowed or reduced width end slots 19a,b at either end of the aperture 16 close out or block the wider ends 20a,b of a contact supporting tongue 21a of a plug insert 21 in the standard plug 13 shown in FIG. 3A. Shoulders 22 at which a width reduction occurs between the aperture 16 and slots 19a,b are positioned such that they define a length between shoulders less than the standard length of the aperture 23 of a prior art receptacle 11 or length of the tongue 21a of a prior art plug 13 to prevent insertion of standard plug 13. On the other hand, the outer ends of the slots 19a,b extend beyond ends 33a  or 33b of the aperture 23 in a prior art receptacle 11 as shown in FIG. 2A and beyond the ends 20a,b of the prior art plug tongue 21a shown in FIG. 3A to receive the polarized plug 12 with its extended end portions 32a and 32b. Slots 19a,b include recesses 40a,b to accept raised portions 34a,b of plug 12. 
     The shell 14 of the receptacle of this invention has end keys 25a,b,c,d and side keys 26a,b shaped as convex outer bends in the shell 14 of the receptacle 10. These keys prevent mating with the standard plug 13 of FIG. 3A, even if the plug 13 is tipped in an attempt to insert one end of the plug in. 
     As shown most clearly in FIG. 4, the extensions or raised end portions 18a and 18b are provided at the slots 19a and 19b of FIG. 2B. These raised end portions begin at the shoulders 22 and extend to the outward ends of the receptacle 10. The projection of such raised portions prevents accidental arc-over of high voltages between the keyed receptacle 10 and a non-keyed plug 13 as shown in FIG. 1A. 
     Referring now to FIGS. 3A and 3B, a keyed plug 12 of this inventon will be compared to a non-keyed plug 13 of the prior art. The keyed plug 12 has a keyed plug shell 27 and a keyed tongue 28a on an insert 28. A plurality of contacts 30 are arranged in parallel rows on parallel walls of the tongue 28a. Insert extensions 31a and 31b extend from the ends of the tongue 28a and include ends 32a and 32b which protrude beyond ends 33a and 33b of aperture 23 in the standard receptacle 11 to prevent insertion of the polarized plug 12 into the standard receptacle 11 shown in FIG. 2A. On the other hand, extensions 31a,b, which begin at shoulders 37, are positioned such that they space the beginning points of the narrowed inserts 31a,b at a point less than the ends 20a,b of the tongue 21a of the prior art plug 13 or the ends 33a,b of the aperture 23 in the prior art receptacle 11 to receive the polarized receptacle 14. The base of insert 28 includes recessed end portions 41a,b to accept the raised portions 18a,b of the insert of receptacle 10. 
     As shown most clearly in FIG. 5, the extensions 31a,b have raised portions 34a,b which project above the top face of the tongue 28a. This prevents high voltage arc-over when an attempt is made to mate the keyed plug 12 with a non-keyed receptacle such as 11 shown in FIG. 2A. 
     End keyways 35a,b,c,d and side keyways 36a,b are provided on the shell 27 of plug 12 in order to mate with the corresponding keys 26a,b and 25a,b,c,d of the keyed shell 14 of receptacle 10 of FIG. 2B. These keys have an outward convex bend of slightly greater dimension than the corresponding keys of the receptacle 10 to permit smooth insertion thereover. 
     With the receptacle 10 and plug 12 of this invention, incorrect mating with standard plugs and receptacles is prevented by use of the narrowed slots 19a,b or the lengthened extensions 31a,b. Furthermore, the keys 25a,b,c,d and 26a,b of the shell 14 of receptacle 10 prevent mating of shell 14 with the shell of the standard plug 13 and prevent engagement of the end contacts by tipping of the plug 13. The raised, projecting portions 18a,b or 34a,b prevent high voltage arc-over between keyed and non-keyed connectors when a head-on insertion is attempted in addition to aiding in the separation of end contacts when the receptacle or plug is tipped towards the other connector part. 
     Typical dimensions for the slots 19a,b of the receptacle 10 of this invention is 0.09 inches nominal as compared to the width of the aperture which is about 0.16 inches. The additional height added by the projecting raised ends 18a,b or 34a,b is about 0.035 inches. Such elevation will prevent arc-over up to voltages of at least 1,000 volts. The above dimensions can be compared to the end-to-end length of the contact supporting tongue of the standard plug insert which is about 2.29 inches. 
     Although various minor modifications may be suggested by those versed in the art, it should be understood that we wish to embody within the scope of the patent warranted hereon, all such embodiments as reasonably and properly come within the scope of my contribution to the art.