Abstract:
An F-type connector for mounting to a prepared terminal end of a coaxial cable for threaded engagement of a nut on the connector to a threaded shaft at a port on video equipment to which the coaxial cable is to be electrically connected. In the connector of the present invention, the nut is mounted for limited axial movement with respect to the post, body and compression ring. A coil spring biases the nut toward a rest position with respect to the other elements wherein not more than three revolutions of the nut into engagement with the shaft are necessary in order to bring the post of the connector into contact with the shaft on the equipment, providing a satisfactory coupling. Upon further revolution of the nut, the post and shaft remain in contact as the nut moves axially away from the rest position with respect to the other elements.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to F-type connectors used in CATV applications, and more specifically to structure providing improved engagement of the RFI seal of such connectors against the connector face. 
     The frequencies of RF signals transmitted through coaxial cables to a subscriber TV set are typically in the range of 5 to 40 MHz. This frequency range is plagued with noise ingress that degrades system performance. Studies have shown that the majority of ingress is related to poorly installed F connectors. These connectors are normally mounted upon the end of a coaxial cable for connection to a port on the television set. Connection is usually made by the subscriber in the home via an internally threaded nut of the connector and an externally threaded stub shaft surrounding the port. For fully threaded connection, ensuring the necessary abutment of the RFI seal of the cable against the equipment connector face, the nut must be rotated up to 5 or 6 full revolutions. The typical, non-technical subscriber making the installation often fails to fully tighten the connector for one or both of two reasons: first, the visual performance functions may be obtained with a partial connection and, once the subscriber sees the video operating on the TV screen, it is assumed that the connection is satisfactory, and, secondly, the location of the equipment is often such that the subscriber must reach around and behind the equipment and thus cannot sec the port as the connector is being installed. 
     It is a principal object of the present invention to provide an F-type connector for threaded engagement with a port on a TV set or other equipment receiving RF signals through a coaxial cable to which the connector is mounted wherein a secure RFI seal is obtained in a simplified manner. 
     Another object is to provide an F-type connector having novel and improved features ensuring shielded connection to an input port and which is compatible with an end portion of a coaxial cable which has been prepared in an industry standard manner. 
     A further object is to provide an F-type connector with enhanced ease of proper installation which is compatible with either compression or crimp attachment of the connector to the coaxial cable. 
     Other objects will in part be obvious and will in part appear hereinafter. 
     SUMMARY OF THE INVENTION 
     The connector of the invention is disclosed in two embodiments each having a total of five elements, namely, a body, a nut, a post, a compression ring and a coil spring. The body, nut, post and compression ring are basically the same in structure and function as corresponding elements in conventional F connectors, and are mounted in similar manner upon the end of the coaxial cable. That is, the nut is connected to the flanged end of the post and is freely rotatable, although axially moveable, with respect thereto. The end of the cable is prepared for mounting to the connector by stripping away all covering layers from the central, rigid conductor for a first length, and stripping the braided, shielding layer and outer layer of dielectric material for a second length. The non-flanged end of the post is then forced between the aluminum conducting layer which surrounds the inner layer of dielectric material and the braided layer until the end of the inner dielectric layer and surrounding conducting layer are substantially coplanar with the surrounding, annular surface of the post. The relative axial positions of the nut and post are such that, in the typical case, six or seven full revolutions of the nut are required to bring the annular post surface into contact with the end of the stub shaft surrounding the port on the equipment to which the connector is attached; anything less than full contact of the connector post with the stub shaft, as previously mentioned, provides incomplete shielding and permits noise ingress. 
     In the connector of the present invention, the additional element, i.e., the coil spring, has opposite ends bearing against the underside of the post flange and a portion of the nut. The nut is axially movable to a limited degree with respect to the post (and other elements of the connector) between a first, or rest position, in which it is held by the spring prior to threading the nut onto the shaft, and a second position, wherein the nut is axially displaced by a maximum distance from the rest position. In the rest position, the threaded portion of the nut extends a short way, e.g., one or two thread revolutions, beyond the end of the inner dielectric layer and aluminum conducting layer of the coax cable and the surrounding, annular surface of the post. Thus, when the end of the nut is brought into contact with the end of the shaft, only one or two revolutions of the nut are required to establish contact of the post surface and shaft, thereby providing an acceptable degree of shielding to prevent ingress of noise and degradation of signal at the connector-equipment interface. However, the connector of the invention permits further threaded engagement of the nut and shaft by compression of the spring upon continued rotation of the nut as the latter moves axially with respect to the post. 
     In the first disclosed embodiment, the elements are assembled by inserting the non-flanged end of the post into the connector body until the latter abuts the underside of the flange, then placing the spring in surrounding relation to the body with one end contacting the underside of the flange, outwardly of the body. The nut is then placed over the post flange and spring with the inner end of the threaded portion of the nut contacting the post flange on the surface opposite a first end of the spring and the other, open end of the nut extending past the other end of the spring. This open end of the nut is then deformed, i.e., peened over, to a diameter less than that of the spring, whereby the ends of the spring are captured between the underside of the post flange and the deformed end of the nut. Axial movement of the nut relative to the post in a direction moving the threaded end of the nut away from the post, as when the nut is threaded onto the shaft of the equipment input port, thus compresses the spring. Conversely, when the threaded connection is removed, the spring moves the nut back to its aforementioned rest position with respect to the post. 
     In the second disclosed embodiment, the spring is captured between the underside of the post flange and an integrally formed flange on the inside of the nut, spaced from the threaded portion thereof. In this case, the spring surrounds the post (rather than the body), the elements being assembled by placing the spring within the nut, one end of the spring contacting the ingral flange within the nut, then inserting the post through the nut and mounting the body upon the post below the nut. This embodiment has the advantage that no deforming or peening operation is required in assembly of the elements; however, a non-standard preparation of the end of the coax cable is required due to the spacing of the end of the body from the underside of the post flange. 
    
    
     The foregoing and other features of construction and operation of the invention will be more readily understood and fully appreciated from the following detailed disclosure, taken in conjunction with accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a first embodiment of the elements of the connector of the invention; 
     FIG. 2 is an exploded, side elevational view, in section, of the elements of FIG. 1; 
     FIG. 3 is a side elevational view, with portions broken away, of the elements of FIGS. 1 and 2 in assembled condition, mounted upon one end of a coaxial cable; 
     FIG. 3 a  is an enlargement of the circled portion of FIG. 3 showing one of the elements in an initial configuration, prior to a mechanical forming operation; 
     FIGS. 3 b - 3   d  are side elevational views, with portions broken away, of the assembled elements of the connector with associated coaxial cable end and equipment port, showing three sequential, relative positions of the elements as the connector is threadedly engaged with a shaft on the TV receiver or other such equipment; 
     FIG. 4 is an exploded perspective view of a second embodiment of the connector; 
     FIG. 5 is an exploded, side elevational view, in section, of the elements of FIG. 4; 
     FIG. 6 is a side elevational view, with portions broken away, of the elements of FIGS. 4 and 5 in assembled condition, mounted upon one end of a coaxial cable with certain elements in a first position of relative movement; and 
     FIG. 7 is the same view as FIG. 6 with the elements in a second position of relative movement. 
    
    
     DETAILED DESCRIPTION 
     Elements of the preferred embodiment of the invention are shown in FIGS. 1 and 2, the connector of this embodiment being denoted generally by reference numeral  10 . Connector  10  is made up of a total of five elements, namely, nut  12 , post  14 , coil spring  16 , body  18  and compression ring  20 . Nut  12  includes internally threaded bore  22  at one end and cylindrical skirt  24  which in its initial form is of constant diameter, larger than that of bore  22 , throughout its axial length. Flange  26  at one end of post  14  is integrally attached to stem portion  28 , the flange and stem cooperatively defining constant diameter bore  30 , extending fully through post  14 . Spring  16  has upper and lower surfaces  32  and  34 , respectively, in parallel planes spaced by a predetermined distance, i.e., spring  16  has a predetermined axial length in its undeformed condition. Body  18 , which includes bores  36  and  38  of different diameters, is made of a suitable elastomeric material which is deformable under sufficient applied pressure. Compression ring  20  has an internal bore  39  generally tapering from a larger diameter at one end  40  to a smaller diameter at end  42 . 
     It will be immediately recognized by those skilled in the art that the elements of the connector of the present invention generally duplicate those of prior art F connectors, with the addition of the coil spring. That is, prior art connectors of this type include an internally threaded nut, a flanged post, a deformable body and an internally tapered compression ring. Typically, the post flange is positioned at the inner termination of the nut threads, the body surrounds the stem of the post, and the tapered, internal surface of the compression ring is moved axially on the body to radially compress the latter, thereby tightly engaging the outer layers of the coaxial cable between the body and post. The end of the cable is “prepped” (i.e., portions of the various layers are cut and removed) according to industry standards prior to mounting thereon of the connector. After mounting, the center conductor of the coaxial cable extends forwardly of the connector to enter the opening and the female connector of the port to which the cable is connected. As previously noted, such prior art connectors often require 6 or 7 complete revolutions of the nut in order to achieve fully threaded engagement of the nut (connector) and the port of the equipment to which the cable is electrically connected, and failure to effect such fully threaded engagement degrades the quality of the RFI shield provided by firm engagement of the metal post and the threaded shaft defining the port. 
     Elements of connector  10  are assembled with one another and mounted upon the end of a prepped coaxial cable in much the same manner as prior art F connectors with the notable exception of the inclusion of spring  16 . In the presently described embodiment, after sliding post  14  into bore  36  of body  18  and placing ring  20  upon the body, spring  16  is placed with surface  32  thereof contacting surface  26   a , termed the underside, of post range  26  and the spring encircling portions of body  18  and compression ring  20 . Skirt  24  of nut  12  initially has a uniform inside diameter substantially equal to or slightly larger than the outside diameter of flange  26 . Nut  12  is slid over flange  26  until the inner surface surrounding threaded bore  22  contacts surface  26   b  of flange  26 . Skirt  24  includes annular portion  24   a , having a thickness less than that of the major portion of the skirt and initially having an inside diameter equal to that of the rest of the skirt, as shown in FIG. 3 a . The previously mentioned predetermined axial length of spring  16  is such that planar surface  34  is located within annular portion  24   a  when the elements are assembled as shown in FIG.  3 . After spring  16  is so positioned, annular portion  24   a  is peened over, i.e., deformed, from its initial, straight configuration of FIG. 3 a  to the bent configuration of Figure  3 . As described later in more detail, nut  12  may be moved axially relative to the other elements, causing compression of spring  16  between surface  26   a  of flange  26  and annular portion  24   a  of skirt  24 . 
     Connector  10  is shown in FIG. 3, and FIGS. 3 b - 3   d , mounted upon a terminal end of conventional coaxial cable  44 . Prior to mounting of the connector, cable  44  is prepped by cutting through outer layer  46  of dielectric material, braided metal layer  48 , aluminum layer  50  and inner dielectric layer  52  at a predetermined distance from the end of the cable and removing the end portions of these layers to leave a predetermined length of the central conductor  54  bare. Layers  46  and  48  are then cut through at another predetermined position and the severed slug is removed. The cable is then inserted into the connector with layers  50  and  52  essentially filling bore  30  of post  14 ; and the end surfaces of these layers substantially coplanar with surface  26   b  of flange  26 . The end of post  14  opposite flange  26  is forced between braided layer  48  and aluminum layer  50 , leaving the end portions of layers  46  and  48  positioned in the space between the outside surface of post stem  28  and bore  38  body  18 . Compression ring  20  is then moved, by a conventional compression tool (not shown), axially upon body  18  toward the left as viewed in FIG.  3 . This radially compresses body  18  and grips layers  46  and  48  tightly between the post and body, thereby mounting connector  10  upon cable  44  in an essentially permanent manner. It is again emphasized that the cable is prepped in an industry standard manner and the connector is mounted to the cable in conventional fashion. 
     Turning now to FIGS. 3 b - 3   d , connector  10  is shown in association with an externally threaded stub shaft  56  at a port of a TV receiver or other such equipment. Shaft  56  is hollow and contains female contacts  58  for receiving the end of center conductor  54  of cable  44 . In the position shown in FIG. 3 b  connector  10  has been moved to position threaded bore  22  in alignment with the end of shaft  56 , preparatory to threaded engagement of the connector upon the shaft. In FIG. 3 c , nut  12  has been rotated, e.g., a couple of revolutions, thereby moving connector  10  axially upon shaft  56  by the distance indicted as D 1  and bringing the end of shaft  56  into contact with surface  26   b  of flange  26 . The metal-to-metal contact of shaft  56  and flange  26  provides acceptable RFI shielding and substantially eliminates noise ingress and signal degradation for the user who rotates the connector nut only until it is threadedly engaged with the shaft. However, a more secure connection may be obtained, in the sense that the nut is engaged over a longer axial portion of the shaft, by continued rotation of nut  12  to the position of FIG. 3 d . The nut has moved upon the shaft by the distance indicated as D 2 , although other elements of connector  10  have not moved relative to the shaft. The axial distance by which the nut has moved between FIGS. 3 c  and  3   d , i.e., the difference between distances D 1  and D 2 , is the distance by which spring  16  has been compressed. As the nut travels axially on the shaft, annular portion  24   a  of skirt  24  bears against end  34  of the spring and compresses the spring as end  32  is held stationary against surface  26   a  of flange  26 . It is apparent that as nut  12  is rotated to remove it from shaft  56  the elements will move in reverse order as spring  16  returns to its rest position, moving nut  12  back into contact with surface  26   b  of flange  26 . 
     The connector is shown in a second embodiment, denoted generally by reference numeral  60 , in FIGS. 4-7 Connector  60  is formed from the same five elements as connector  10 ,  20  namely post  62 , coil spring  64 , nut  66 , body  68  and compression ring  70 . However, the configurations of post  62  and nut  66  are somewhat different than post  14  and nut  12  of the previous embodiment and the manner of assembly of the two connectors is not the same. In addition to flange  72  and stem  73 , post  62  includes external shoulder  74 , spaced a predetermined distance from surface  72   a  of the flange. Nut  66  includes internally threaded bore  76  and integrally formed, internal flange  78  defining opening  80 . In assembly of the elements, stem  73  of post  62  is passed through spring  64  and nut  66  with the upper surface  82  of the spring bearing against surface  72   a  of post flange  72  and the lower spring surface  84  bearing against surface  78   a  of nut flange  78 . Stem  73  is passed through bore  86  of body  68  until the end of the body contacts shoulder  74 . In this position, as seen in FIG. 6, flange  78  and end portion  88  of nut  66  bears against an abutment surfaces of body  68 . Compression ring  70  is placed over body  68  as in the previous embodiment. 
     The same reference numerals are used in FIGS. 6 and 7 for the coaxial cable and its various layers as in FIGS. 3 and 3 b - 3   d . Cable  44  is again prepped by removing all layers to provide a predetermined length of bare center conductor  54 . However, the axial length of outer dielectric layer  46  and braided layer  48  which are removed is longer than in the “standard” prepped cable of the first embodiment. This is because body  68  bears against shoulder  74  rather than the underside of the post flange in order to place spring  64  in surrounding relation to the post, i.e., in the space between the post and nut, rather than to the body and compression ring. Thus, the present embodiment avoids the assembly operation of deforming or peening over the end of the nut, but has the disadvantage of requiring a non-standard prep of the cable. 
     Connector  60  is shown in FIG. 7 in threaded engagement with shaft  90 . Nut  66  has been rotated a number of times to travel axially on the shaft while compressing spring  64  between nut flange  78  and post flange  72 . Nut  66  has moved an axial distance D with respect to the other elements of connector  60 , and will move the same distance in the opposite direction, under the biasing force of spring  66 , as the connector is removed from the shaft. It is apparent that only a very small amount of axial travel of nut  66  on shaft  90 , i.e., an amount produced by only one or two revolutions of the nut, is required to bring the end of the shaft into contact with surface  72   b  of post flange  72 . 
     From the foregoing it will be seen that the connector of the invention addresses a long standing problem in the art, i.e., the frequent failure of the typical, non-technical user to effect proper installation of an F-type coaxial cable connector to a port (threaded shaft) on video equipment. The structure of the connector is such that positive ground contact between the connector and port and an effective RFI shield are provided with a minimal amount of threaded engagement of the connector and port. The first described embodiment of the connector accommodates a standard cable prep length, saving time in the manufacture of jumpers, as well as enhancing the product&#39;s marketability as an individual connector since it does not require the purchase of non-standard prep tools. The skirt of the nut surrounding essentially the entire connector structure also affords greater ease of use since it provides a larger surface for finger grip, and it extends close to the back of the connector, allowing easier access when the connector is recessed into the back of the equipment. It should also be pointed out that threaded bores  22  and  76  of the two embodiments are of the same diameter, both being intended for threaded connection to the same shaft at the equipment port, i.e., shaft  90  is the same as shaft  56 . This means that flange  26  of post  14  is of larger diameter than flange  72  of post  62 , and the outer surface of nut  12  is larger than that of nut  66 , thereby making manual manipulation of nut  12  easier.