Co-axial isolated ground bulkhead receptacle
TECHNICAL FIELD 
     The invention relates to a bulkhead receptacle for electrical connectors and, particularly, to a receptacle of the co-axial BNC series type. 
     BACKGROUND ART 
     Bulkhead receptacles of the co-axial BNC series type typically have one end mounted to an opening in an equipment chassis and the other end configured to receive a BNC type male connector for co-axial cable having a bayonnet slot which locks onto a studded outer connector body of the receptacle. The studded connector body of the receptacle forms the connector ground contact, and an insulated center female contact receives the center male contact of the connector. Known forms of such receiptacles typically have a metal body for mounting the receptable to and forming a ground contact with the equipment chassis. 
     However, in some situation, it is desirable to have the ground contact insulated from the chassis, for example, to form an internal ground contact which is isolated from electromagnetic interference picked up by the chassis. This is known as an isolated RF ground. In one conventional form of isolated ground receptacle, the mounting body is made of an insulator material, such as plastic, with threading for mounting the receptacle to the equipment chassis with a nut and lock washer. However, the plastic insulator body can be deformed or worn down under the pressure of torque applied during mounting to the chassis or when connectors are locked onto the receptacle. The deformation or wear can result in shorting or loss of a good electrical contact. 
     SUMMARY OF THE INVENTION 
     It is therefore a principal object of the invention to provide a co-axial, isolated ground bulkhead receptacle which has a mounting end of high strength and durability and can maintain a proper isolation of the ground contact from the chassis and the center contact, as well as a good electrical connection through the receptacle to the connector ground. It is a further object of the invention to provide a receptacle which can be conveniently manufactured and assembled, and which minimizes the possibility of shorting or loss of good electrical contact. 
     In accordance with the invention, a co-axial, isolated ground bulkhead receptacle has a metal outer connector body, a threaded metal mounting body, an insulator body having a connector end and a mounting end, a central recess for holding a center electrical contact, and a radially located slot for holding an isolated ground contact to form an electrical connection with the connector body and to extend from the insulator body at the mounting end. In a preferred embodiment, the insulator body has three annular rings at its midsection for securing the respective annular flange ends of the connector and mounting bodies and for maintaining them in electrical isolation from each other. The slot in the insulator body and the ground contact have a curvilinear cross-sectional shape so that the ground contact can be mounted with a constant spacing apart from the metal mounting body. Further, the insulator body has splines on its surfaces assembled in contact with the connector body and the mounting body to provide a high resistance to turning under an applied torque. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The above objects and further features and advantages of the invention are described in detail below in conjunction with the drawings, of which: 
     FIG. 1 is a side sectional view of a co-axial isolated ground bulkhead-receptacle in accordance with the invention; and 
     FIG. 2 is a front sectional view of the receptacle of FIG. 1 taken along view line A--A. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following is a detailed description of one preferred form of the invention embodied as a co-axial isolated ground bulkhead receptacle of the female BNC series type. However, it will be understood that the principles of the invention can be equally applied to other forms of co-axial receptacles or electrical connectors. 
     Referring to FIG. 1, metal connctor body 1 has a central opening for receiving a connector for a co-axial cable, and studs 1a which are mated in bayonnet slots formed in the connector (not shown) for securely locking the connector to metal connector body 1. Female contact 6 has slotted end 6a for receiving a center male contact (not shown) of the connector, and is isolated from metal connector body 1 by insulator body 2. Insulator body 2 has a splined surface 2a which is press-fitted against corresponding splines or corrugations on the inner surface of metal connector body 1, so as to secure them fixedly together and prevent turning of the bodies relative to each other under an applied torque, such as when the bayonnet connector is mounted to connector body 1. 
     Insulator body 2 has shoulder portion 2b and a slot, generally indicated at 2c, for mounting isolated ground lug 3. Ground lug 3 has annular ring 3a which fits over the connector end of insulator body 2 (left side of FIG. 1) and is located in position against shoulder portion 2b. During assembly, metal connector body 1 is press-fitted over the connector end of insulator body 2 and presses ground lug 3 against shoulder portion 2b so as to form a good electrical contact therewith. Slot 2c has a tapered wall and ground lug 3 has a corresponding tapered section 3b which are pressed together during assembly. The pressing of the tapered walls results in a spring force applied by ground lug 3 against connector body 1 to form a good electrical contact therewith. 
     At about its midsection, insulator body 2 has three annular rings 2d separated by grooves. One outside ring is used for securing annular flange end 1b of connector body 1, and the other outside ring for annular flange end 7a of metal mounting body 7. The flange ends 1b and 7a are peened over by a spinning tool into the grooves between rings 2d, so as to securely mount the metal connector body 1 and the metal mounting body 7 over the ends of insulator body 2, while the center ring of rings 2d maintains them apart in electrical isolation. 
     Mounting body 7 has threading 7b for mounting the receptacle to an equipment chassis (not shown) by means of nut 5 and lock washer 4. Mounting body 7 also has flat section 7c, known in the industry as a D-flat, which fits into a correspondingly shaped D-hole in the chassis, so as to prevent the receptacle from rotational movement under an applied torque. As seen more clearly in FIG. 2, mounting body 7 is concentric with respect to female contact 6 and insulator body 2. The end of isolated ground lug 3 extends from insulator body 2 beyond mounting body 7, and has a curved cross-sectional shape so that ground lug 3 is spaced a constant distance from metal mounting body 7, thereby preventing any shorting therebetween such as might occur if a conventional flat shaped ground lug is used. Ground lug 3 has hole 3c, and female contact 6 has a cut-away section 6b for facilitating a soldered electrical connection with leads in the chassis in a conventional manner. 
     Female contact 6 has knurled section 6c for making a tight, friction contact when female contact 6 is press-fitted into insulator body 2 during assembly. Insulator body 2 and mounting body 7 have splines or ribbing on their respective mating surfaces which is generally indicated at 7d, for forming a secure fit and preventing insulator body 2 from rotating under torque pressure. 
     The invention as illustrated in the described embodiment has the advantages of high mounting strength and durability through the construction of metal mounting body 7, as well as electrical isolation of ground lug 3 from center contact 6 and the metal mounting body 7. It is simple to manufacture and assemble due to the construction of insulator body 2 for secure mounting of connector body 1 and mounting body 7. Insulator rings 2d of insulator body 2 provide a convenient and secure mounting for the annular flange ends of the respective metal parts while maintaining them in electrical isolation. Further, ground lug 3 has a novel curved cross-sectional shape to minimize possible shorting from the lug to metal mounting body 7, and has a tapered section for pressing the lug into good electrical contact with connector body 1 upon assembly of the receptacle. The receptacle thus has exceptional strength and durability and provides the proper ground isolation and ensures good electrical contact through the respective parts. 
     The above-described embodiment is illustrative of the principles of the invention and is not intended to limit the scope of the invention. Various modifications and substitutions of elements, materials, and equivalent parts may be made without departing from the spirit of the invention. All such modifications and variations are intended to be encompassed within the invention as defined in the following claims.