Abstract:
An apparatus and method is provided for connecting together sections of a coaxial radio frequency transmission line. The system includes a multiple finger contact radially deformable along its axial length that may be resiliently supported in the radial direction by multiple finger contact spring rings. A hood is provided to catch metallic particles given off by the frictional wear of the contact.

Description:
FIELD OF THE INVENTION 
     The invention pertains to an apparatus and method for connecting together sections of a coaxial radio frequency transmission line. 
     BACKGROUND OF THE INVENTION 
     Various arrangements are known for connecting together two sections of a radio frequency transmission line. In the case of sectional coaxial transmission lines, it is desirable to have a connector that can electrically connect the coaxial inner conductor portions of adjacent sections. 
     One problem with prior connectors is that they sometimes require a relatively high insertion force in order to achieve the desired degree of electrical contact. Another problem is that when the coaxial lines are arranged vertically, a connector can disperse undesirable metallic particles onto the insulator of the conductor. 
     Accordingly, there is a need in the art for a coaxial connector that can provide a relatively low insertion force with a relatively high electrical contact and that can avoid disbursing metallic conductive particles on the insulator. 
     SUMMARY OF THE INVENTION 
     In one aspect of the invention, an apparatus is provided which connects a first coaxial transmission line section to a second coaxial transmission line section. The apparatus comprises an inner conductor body mounted to the first coaxial inner conductor. A connector sleeve is mounted to the inner conductor body, and an annular multiple finger contact element, which has a total axial length and is deformable in the radial direction along the entire total axial length, is mounted to the connector sleeve and surrounds at least a portion of the connector sleeve. At least one annular multiple finger spring ring is disposed between the connector sleeve and the multiple finger contact to resiliently support the multiple finger contact, and the multiple finger contact is insertable into the second coaxial inner conductor in order to provide a contact with the inner conductor. 
     In another aspect of the invention, a multiple finger contact element is provided that has fingers that extend along the total axial length of the contact. 
     In another aspect of the invention, a hood is provided to catch the metallic particles resulting from wear due to movement of the contact. 
     There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
     In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract included below, are for the purpose of description and should not be regarded as limiting. 
     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side sectional view of a connector according to a preferred embodiment of the invention shown connecting two coaxial transmission line sections. 
     FIG. 2 is a side sectional view showing a connector according to the embodiment of FIG. 1 installed on one end of a coaxial transmission line section before connection to a second coaxial transmission line section. 
     FIG. 3 is a detailed cut away cross sectional view illustrating a connector according to the embodiment of FIG.  1 . 
     FIG. 4 is a cross sectional view of an inner conductor body. 
     FIG. 5 is a cross sectional view of a connector sleeve. 
     FIG. 6A is a cutaway side view of a multiple finger contact element. 
     FIG. 6B is a detailed cutaway side view of the multiple finger contact element. 
     FIG. 7 is an exploded view of a connector assembly according to the embodiment of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a connector and method for connecting coaxial transmission line sections, and more particularly for electrically connecting the inner conductors of coaxial transmission line sections. 
     Referring now to FIG. 1, a connector assembly  10  is used to connect a first coaxial transmission line section  11  having a first coaxial outer conductor  12  and a first coaxial inner conductor  14  to a second coaxial transmission line section  15  having a second coaxial outer conductor  16  and a second inner conductor  18 . A flange  20  on the first line section  11  is connected to a flange  22  on the second line section  15  by a bolt or other fastener  24 . This provides a mechanical and electrical connection between the outer coaxial conductors  12  and  16 . 
     An O-ring  26  may be provided in grooves in the flanges  20  and  22  in order to provide a seal against environmental conditions for the interior of the coaxial line sections. An anchor insulator  28  is provided as shown to position the inner conductor  30  in a radially centered position and insulate it from the outer conductors. 
     Positioned in a central bore in the anchor insulator  28  is an inner conductor body  30 . The inner conductor body  30  has a hood extension  31  which is discussed in more detail below. The connector  10  also includes a connector sleeve  32  having annular grooves  33 . A multiple finger contact element  34  generally surrounds a portion of the connector sleeve  32  and multiple finger spring rings  36  are set into the grooves  33  and provide a resilient springback to the multiple finger contact  34 . A bolt  38  attaches the connector sleeve  32  to the inner conductor body  30  as shown. This connection also traps the multiple finger contact  34  in place. 
     FIG. 2 shows the assembly according to FIG. 1 when it is mounted to the first coaxial transmission line section and before the first coaxial transmission line section is connected to a second coaxial transmission line section. The individual line sections, in some embodiments, may be distributed to the end user in this configuration. It will be appreciated that the end user can then connect the line sections together by simply inserting the connector  10  into the second coaxial inner conductor of a second coaxial transmission line section, and tightening the bolts  24  on the flanges  20  and  22 , as shown in FIG.  1 . 
     FIG. 3 is a detailed cutaway view showing in cross section the arrangement of the inner conductor body  30 , hood extension  31 , connector sleeve  32 , grooves  33 , and multiple finger contact  34 . FIG. 4 shows the inner conductor body  30 . FIG. 5 shows the sleeve  32  and the grooves  33 . 
     FIGS. 6A and 6B show the multiple finger contact  34  in greater detail. The multiple finger contact  34  is an annular element having a continuous circular band  40  which has an inner diameter just greater than the outer diameter of the rear portion  42  of the connector sleeve. Extending longitudinally outward from this circular band  40  are a plurality of flexible finger elements  44  that are free to flex to change the radial diameter D of the fingers. The finger elements  44  extend from the free ends  46  of the fingers at one axial end of the multiple finger contact element  34  to the circular band at the other axial end of the multiple finger contact  34  as shown in FIG.  6 A. 
     FIG. 6A shows that the finger elements  44  extend along the entire total axial length of the multiple finger contact  34 , because the fingers  44  are separate until they end in the continuous circular band  40 . This provides a significant advantage of to invention, because the multiple finger contact  34  can flex radially at any point or points along its entire axial length. This permits the multiple finger contact  34  to make satisfactory electrical contact with the inner conductor  18 , (FIG.  1 ), while keeping a desirably low insertion force. 
     The multiple finger spring rings  36  can be seen in greater detail in FIG.  7 . The multiple finger spring rings  36  are made from a linear piece of spring stock which has a flat metallic portion, with a plurality of individual finger spring elements bent back from the flat portion. This linear spring element is bent into the C shape shown in FIG.  7  and is then slid into respective grooves  33 . Installation of the multiple finger contact  34  over the multiple finger spring rings  36  presses the multiple finger spring rings  36  so they each form essentially a full circular ring seated within their respective groove  33 . 
     FIG. 7 further shows an exploded view of the components of the connector  10 . In a preferred embodiment, the parts are assembled as follows. First, the multiple finger spring rings  36  are curved into a C shape to fit into grooves  33  of the connector sleeve  32 . The multiple finger contact  34  is then pushed over the small end of the connector sleeve  32  with the free ends  46  expanding over each of the multiple finger spring rings  36  as they are pushed over them. The multiple finger contact  34  now encircles and captivates the multiple finger spring rings  36 , retaining them in the grooves  33 . Correspondingly, the multiple finger spring rings  36  provide an outward radial restoring force in response to compression of the multiple finger contact  34  in the installed condition. To further assemble the connecting device  10 , the subassembly comprising the above elements is set into the end of the inner connector body  30 , FIG. 1, and is bolted in place  38 . The connector body can now be fitted within an anchor insulator  28  (see FIG. 1) and fixed inside the end of the first coaxial inner conductor  14  (see FIG.  1 ). 
     The various components described above can be made of any suitable materials. However, in one preferred embodiment, the inner connector body  30  is made from copper. The connector sleeve  32  is made from aluminum. The multiple finger contact  34  is a brass silver plated item. The multiple finger spring rings  36  are beryllium copper springs. These C-shaped spring rings  36 , as discussed above, are made by bending into a C-shape a linear beryllium copper finger spring which is commercially available. Although two grooves  33  and two spring rings  36  are described in a preferred embodiment, the number of springs  36  and corresponding grooves  33  may be varied to provide suitable spring back. 
     Referring back to FIG. 1, it will be appreciated that the assembly  10  provides an advantageous arrangement for connecting first and second inner coaxial conductors. By virtue of the multiple finger contact  34 , used in combination with the multiple finger spring rings  36 , the connector may be easily slid into the second coaxial inner conductor  18  with a suitably low insertion force. Also, since the multiple finger spring rings  36  resiliently support the multiple finger contact  34  in the radial direction, the combination of the multiple finger spring rings  36  with the multiple finger contact  34  provides suitable contact force to provide a desired electrical connection with the inner surface of the second coaxial inner conductor  16 . 
     In some preferred embodiments, a hood  31  may be provided as shown to trap particles that might occur due to wear from frictional relative contact occurring between the various parts of the connector. In many embodiments, the second coaxial section  15  will be vertically oriented above the first coaxial transmission line section  11 . The conductors  14  and  18  may move axially relative to each other during use of the assembled coaxial line sections. The axial movement may be due to thermal growth from the environment or from power cycling. By virtue of the hood  31 , any metallic particles resulting from wear due to frictional sliding within the various components of the connector will remain trapped within the area defined by the hood  31 , and will not disperse and collect on other areas such as the anchor insulator  28 . This provides an additional advantage of the invention by avoiding undesirable conductive material coming to rest on the insulator, even when frequent axial movement occurs between the inner conductors, due to, for example, thermal changes or power cycling. 
     The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirits and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.