Electrical connector
BACKGROUND OF THE INVENTION 
     Commonly known types of quick connect and disconnect electrical connectors comprise two parts. Each part consists of a cylindrical shell having within it insulating inserts which contain mating electrical contacts. As the two parts are engaged electrical contacts are also engaged. The connector parts are provided with keys and keyways to properly orient the connector contacts. A coupling device joins and retains the two parts together. Coupling devices include coupling nuts which are threaded or which are of the bayonet type. The connector shells or housings are generally made from aluminum or steel wherein the parts are extruded or machined. When aluminum is used it is coated with cadmium or other suitable plating. 
     One of the principal uses of quick disconnect electrical connectors is on aircraft where upwards of 100 connectors are used. As with any aircraft component, weight is an important consideration. Obviously, another consideration is the cost of the component. A third consideration is the electrical connector&#39;s ability to remain coupled under vibration occurring during flight. Coupling nuts that are threaded and connect together the two halves of a connector assembly are susceptible to decoupling when subject to vibration. Further, when the coupling nut is partially uncoupled the electrical contacts within the connector are partially coupled and in some instances, the contacts are uncoupled. Obviously, poor or broken electrical connections are undesirable. In an aircraft where there are hundreds of connectors, this type of connector makes it easy to visually identify an electrical connector wherein the coupling nut is not completely threaded to a housing. 
     Accordingly, there has been a need for a light weight, low cost electrical connector assembly that is not susceptible to decoupling when subjected to vibration. 
     SUMMARY OF THE INVENTION 
     This invention provides a low cost, light weight electrical connector that is not susceptible to decoupling when subjected to vibration. Visual examination of the connector will reveal whether or not the coupling nut, retaining the two halves of the connector together, is partially or completely connected. 
     The invention is an electrical connector assembly characterized by a plastic coupling nut 30 and housing 20 that includes on one or the other, an axially extending projection 26 that is mateable with a slot 35 when the coupling nut 30 is threaded to the housing 20 so as to apply axial pressure on the coupling nut. The pressure is applied to the fully mated threads of the coupling nut and housing, this preventing vibration from unthreading the coupling nut. It also provides the advantage that visual inspection of the connector, without uncoupling the connector, immediately identified whether or not the coupling nut is completely threaded upon the housing. The latter advantage is not present in most other connectors of this type because their additional securing mechanism is hidden beneath the coupling nut and cannot be seen. An example of such a prior art connector may be found in U.S. Pat. No. 3,901,574 entitled &#34;Electrical Connector&#34; and issued Aug. 26, 1975 to C. L. Paullus. 
     Accordingly, it is an object of this invention to provide a low cost, light weight electrical connector that is not susceptible to decoupling when subjected to vibration. 
     It is another object of this invention to provide an electrical connector that provides visual indication as to whether or not a coupling nut is completely threaded upon a connector housing. 
     The above and other objects and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings and claims which form a part of this specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of the components of an electrical connector incorporating the objects of the invention. 
     FIG. 2 is a partial cutaway view of one-half of the electrical connector assembly. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings, FIG. 1 illustrates an electrical connector assembly that incorporates the principles of the invention. The electrical connector assembly is comprised of a first shell 10; a second shell 20; a sleeve or coupling nut 30, mounted on one of the shells 10; inserts 40; and a plurality of electrical contacts 27, 47 mounted in the inserts. Preferably, all three pieces are comprised of a firm and resiliently deformable material. A polymeric material can be used and, preferably, the shells 10 and 20 and the coupling nut 30 are comprised of a molded plastic material such as nylon. 
     One-half of the electrical connector assembly includes a shell 20 having a flange 23 and a tubular portion 24 projecting forwardly away from the flange 23. The tubular portion 24 has on the outside surface thereof threads 22. One end of the threads 22 terminates at a forwardly facing shoulder 25. A forwardly extending projection 26 extends from the shoulder 25. The projection 26 has a rounded side 262 and a flat side 261. A portion 29 of the forward facing shoulder 25, adjacent the rounded side 262 of the projection 26, is spaced further from the flange 23 than a portion 28 of the shoulder, adjacent the flat side 261 of the projection 26. On the inside of the tubular portion 24 of the shell 20 there are a plurality of keyways 21. 
     Mounted within the shell 20 is a dielectric insert (not shown) that has mounted therein a plurality of electrical contacts 27 that are connected to a plurality of wires 50. The contacts 27 shown are pin type electrical contacts. 
     The other half of the connector assembly includes a shell 10; a dielectric insert 40; a plurality of electrical contacts 47 mounted within the insert 40; and a coupling nut 30 rotatably mounted on the shell 10. The shell 10 includes threads 14 for receiving a nut 70 (FIG. 2) that retains the coupling nut 30 on the shell 10 and prevents the coupling nut&#39;s (30) removal while allowing the coupling nut 30 to rotate. The insert 40 includes a plurality of keys 11 that are designed to mate with the keyways 21 in the other connector shell 20. The insert 40 has a plurality of axial bores 45. Mounted in each of the bores is an electrical contact 47. The electrical contact 47 shown is a socket type contact that is adapted to engage and mate with the pin type electrical contact 27 in the other connector shell 20. The keys 11 and keyways 21, when engaged, orient the contacts in a predetermined manner for mating. Attached to one end of the socket contacts 47 are a plurality of wires 60 which extend from the connector shell 10. 
     The coupling nut 30 includes, in the front portion, a rearwardly extending notch 35. On one side of the notch 35 there is a rounded projecting portion 352. The other side of the notch 35 includes a flat surface 351 which projects forwardly beyond the forward face 33. The flat side 351 of the notch 35 is adapted to engage the flat surface 261 on the projection 26 of the other shell 20. 
     FIG. 2 illustrates a diagrammatic and partial cutaway view of the one-half of the connector assembly that includes the coupling nut 30. This view particularly illustrates how the additional threaded nut 70 is threaded onto the rear end of the housing 10 to captivate the coupling nut 30 on the shell 10. This view also illustrates the projection of the flat surface 351 and rounded portion 352 beyond the forward face 33 of the coupling nut 30. 
     The electrical connector is coupled together in the following manner to accomplish the objects of the invention. The connector shells 10 and 20 are placed in axial alignment with the keys 11 oriented so that they engage the keyways 21. The threads within the coupling nut 30 are engaged with the threads 27 in the other shell 20 and the coupling nut 30 draws the pin contacts 21 and socket contacts 47 together in mated relationship. As the coupling nut 30 approaches being completely threaded with the connector shell 20 the projection 352 on the coupling nut 30 passes over the projection 26 on the shell 20 and projection 26 snaps into notch 35 and surfaces 351 and 261 engage each other thereby preventing further rotation of the coupling nut 30 relative to sleeve 20. In this embodiment, the portion 29, of the forward facing shoulder 25, on one side of the projection 26 is axially wider than the other portion 28 on the other side of the projection 26. This arrangement operates to exert an axial force on projection 352 of the coupling nut 30 thereby applying an axial force to the engaged threads of the coupling nut 30 and housing 20. The projection 26 engaged in notch 35 and, in some instances, the axial pressure on the engaged threads prevents the connector from being uncoupled during vibration. To remove the coupling nut 30 from the housing 20, an extra amount of rotational force in the opposite direction will be required than as required to thread the coupling nut 30 onto the shell 20. 
     While a preferred embodiment of the invention has been disclosed, it will become 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 corresponding use of other features. For example, the location of the notch 35 and projection 26 may be reversed so that the notch is in the housing and the projection would be on the coupling nut. Also, the location of the male and female type electrical contacts may be reversed. 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.