Cable connector
FIELD OF THE INVENTION 
     This invention relates to a connector for a cable, and in particular for a cable which carries an RF signal. 
     BACKGROUND OF THE INVENTION 
     When a cable carrying an RF signal, such as a cable television signal, is disconnected from a television set or a cable box, the RF signal is emitted into the environment unless the connector is properly terminated. If a cable provider is aware of a non-terminated connector, its personnel can attach a terminator to the connector. In the case of a coaxial cable connector, the terminator is attached to the end of the connector to short the center conductor to an outer circumferential conductor with a 75 ohm resistance. 
     As the number of non-terminated emitting connectors increases, the power output from the cable plant must be increased to compensate for the lost power from non-terminated connectors. The signals emitted in the atmosphere can also cause interference with other vital communications sources, such as airport traffic control. If the problem becomes particularly severe, a cable provider must send out a &#34;sniffer truck&#34; to detect RF signals in the environment and order to locate the source of leakage. 
     At a household, such leakage can be caused in a number of different ways. For example, a consumer who is receiving a cable television signal might disconnect the cable from the cable box to the television temporarily if the television is being repaired. Another possibility is that the customer might attach a splitter to the cable box to run a separate cable to a video cassette recorder. Later, the consumer may stop using the recorder, but not remove the splitter. Some people, when they move have been known to is remove the cable all the way to a ground fixture outside the house, thus leaving open the possibility that the signal could be emitted from the ground fixture. It is also increasingly common for cable fixtures to be built into new homes or in remodeled rooms. Fixtures are positioned in the wall similar to telephone fixtures for convenient attachment. If the signal is not properly terminated at each fixture, a signal can be emitted out of any non-terminating fixture. 
     SUMMARY OF THE INVENTION 
     Because of the harmful effects of non-terminated connections to cable operators and to other forms of communication, and because cable operators are not able to conveniently terminate each connector individually, I have developed a connector in which a termination is automatically made when a connector is disconnected from a mating connector. The connector has a switching mechanism for selectively coupling conductors in the connector in response to connecting or disconnecting the connector from a corresponding mating connector. My self-terminating connector is particularly useful in connection with cable systems, but it can also be used in any application, in which a signal is emitted if not terminated. The connector according to the present invention can be manufactured into other products such as cables, splitters, modulators, or wall fixtures; or the self-terminating aspect can be incorporated into an adapter to retrofit an existing connector. 
     A self-terminating connector can be incorporated into either a male or a female connector, such as a common f connector used for cable television. A female f connector has a first conductor including a conductive receptacle for receiving conductor a prong of a male f conductor, and a grounded second conductor. In one embodiment, the first conductor includes a conductor that is movable from a first position, in which the movable conductor couples the first conductor and the second conductor to form an electrical path, to a second position in which the movable conductor does not connect these conductors. The movable conductor may include a spring-biased conducting body. When the female connector is not connected to a male connector, the body is biased to contact a stationary conducting washer which is coupled to the grounded conductor through a 75 ohm resistance. When the male connector is inserted in the female connector, the male prong pushes the spring to move the body out of contact with the washer. As used here, conductor is not limited to any specific range of conductivity, but refers to a member that carries an electrical signal. 
     The self-terminating feature can be used in a male connector. The connector preferably has a mechanical switching mechanism in which the conducting prong is spring biased and has an increased diameter portion which abuts a conducting member to terminate when the male connector is not connected to a female connector. When it is connected, the prong is moved so that the increased diameter portion is separated from the conducting member. 
     A connector according to the present invention may be built into a device, such as cable box, and may be provided in an adapter for connection to a female or a male connector, or at the end of a cable. 
     According to the present invention, a simple and reliable self-terminating connector prevents the harmful problems caused by live, non-terminated connectors, such as interference with other communications systems. The connection terminates automatically when disconnected, meaning that there is no need for additional user/customer action. According to a preferred embodiment, only one of a male and female connection need be modified, while the other may be the same as a prior art connector. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages will become apparent from the following detailed description and from the drawings in which: 
     FIG. 1 is a partial schematic representation of an embodiment of the invention; 
     FIGS. 2 and 3 are partial cross-sectional views of an embodiment of the present invention; 
     FIG. 4 is a close-up view of a receiving cup; 
     FIG. 5 is a partial cross-sectional view of an adapter according to the present invention; and 
     FIG. 6 is a partial cross-sectional view of another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, in an embodiment of the present invention shown in general schematic form, a connector 10 has a first conductor 12 and a second conductor 14 for mating with a corresponding connector. These conductors, which may be coupled to a coaxial cable or a cable box for carrying a cable television signal, are selectively coupled to each other through a 75 ohm resistor with a mechanically actuated switch 16. Switch 16 is preferably actuable automatically in response to the mating action of a connector with a corresponding connector (not shown), and thus the connector can automatically self-terminate. 
     Referring to FIGS. 2 and 3, a female f connector 20 is shown respectively disconnected and connected to a male f connector. Connector 20 has a first conductor including a tubular, axial, conductive receptacle 22, and a second conductor including a conductor 24 arranged coaxially and circumferentially around connector 20. Conductor 24 may be threaded and can be used in connection with a known male f connector that has a typical threaded locking nut or a quick-connect arrangement. Conductors 22 and 24 are separated by an electrically insulating material 26. The connector may be electrically coupled to a coaxial cable 60 having conductors 62, 64. 
     Second conductor 24 includes an annular washer 28 that is stationarily mounted in connector 20 so that it surrounds receptacle 22. Washer 28 is coupled to conductor 24 through a 75 ohm resistance. A movable conducting cup 36 is biased against washer 28 with a spring 32 so that a portion of the cup (such as flange 30 which is shown more clearly in FIG. 4) contacts the washer. The cup is electrically coupled to a conductor 34, which in turn is coupled to coaxial cable 60 for carrying a live signal. 
     When connector 20 is not coupled to a male connector, a signal on conductor 34 is electrically conducted through cup 36, washer 28, the 75 ohm resistance, and conductor 24. Thus, the signal is dissipated by the resistance and is not emitted into the environment. 
     Referring to FIG. 3, when a male connector is inserted in female connector 20, a cylindrical male prong 40 is inserted into the tubular conductor 22 (the rest of the male conductor is not shown for clarity, but it would typically have a cylindrical conductor which would fit over the outside of conductor 24, as shown at male end 42 in FIG. 5). When prong 40 is inserted into connector 20, it pushes cup 36, thus compressing spring 32 and breaking the physical and electrical connection between flange 30 and washer 28 that previously coupled the first and second conductors. As a result, an electrical signal can be electrically coupled from conductor 34 through prong 40 without interference from the 75 ohm resistance. 
     Referring to FIG. 4, the connection is shown in more detail and flange 30 is shown more explicitly. Cup 36 has a split spring assembly 41 located centrally in a bottom portion 38. Spring assembly 41, which generally resembles a split opening found in a plastic soft-drink lid, is made sufficiently tight so that it forms a good electrical connection when a male prong is inserted, and so that the spring is compressed when the male prong is inserted. Alternative forms of connection, such as a standard Y-shaped conductive receiver, could also be used at the bottom portion of cup 36. Flange 30 may be omitted so that the cup is cylindrical without a flange. 
     The connector may be used in a number of different ways, including at the end of a cable, on the housing of a cable television box, or in a wall-mounted jack. The self-terminating concept can also be employed in an adapter to retrofit an existing connector. Referring to FIG. 5, a female-to-female adapter has a male end 42 with a center conducting prong 44 and a locking nut 46. The female end 48 is similar to that shown in FIG. 2 and is electrically coupled to the male end. These adaptors can be used to retrofit an existing female connector to form a new self-terminating female connector. For example, one could connect an adapter to each female connector on a splitter so that if one of the multiple output connectors on the splitter is disconnected, the signal would be terminated. The adapter could also convert male to female by having two female ends. 
     A movable conductor could be employed in a self-terminating male connector to terminate at the male end when it is inserted into a typical female f connector. Referring to FIG. 6, male connector 70 has an axial prong 72 and a cylindrical conductor 74 circumferentially mounted relative to the prong for coupling to a coaxial cable 76. Conductor 74 is coupled through a 75 ohm resistance to a stationary member, such as a washer 78. The prong has an increased diameter portion 80 that is spring-biased against washer 78 with coil spring 82 to couple prong 72 and conductor 74. The prong is sized so that when it is inserted into a female receptacle, the increased diameter portion is pushed away from the washer and the electrical connection between prong 72 and conductor 74 is broken. As with the self-terminating female f connector, the self-terminating male connector can be used with a prior art female f connector without having to modify the f connector. 
     Having thus described a preferred embodiment of the present invention, it should be apparent that other modifications and improvements can be made without departing from the scope of the invention as defined by the appended claims. One could employ other types of springs or biasing means, or other mechanical switching means for selectively coupling the two conductors in the connector. Moreover, in some embodiments it may not be necessary for the receptacle in a female connector to be conducting if a good connection can be formed between a prong and a movable conductor. Furthermore, while it is preferable that only one of the male or female be altered for use with a known connector, other arrangements could be used in which both connectors are modified.