Coaxial cable F connector with improved RFI sealing

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] Other objects will in part be obvious and will in part appear hereinafter.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] FIG. 1 is an exploded perspective view of a first embodiment of the elements of the connector of the invention;

[0014] FIG. 2 is an exploded, side elevational view, in section, of the elements of FIG. 1;

[0015] 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;

[0016] FIG. 3ais an enlargement of the circled portion of FIG. 3 showing one of the elements in an initial configuration, prior to a mechanical forming operation;

[0017] FIGS. 3b-3dare 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;

[0018] FIG. 4 is an exploded perspective view of a second embodiment of the connector;

[0019] FIG. 5 is an exploded, side elevational view, in section, of the elements of FIG. 4;

[0020] 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

[0021] FIG. 7 is the same view as FIG. 6 with the elements in a second position of relative movement.

[0022] 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.

[0023] 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.

[0024] 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 26a, 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 26bof flange 26. Skirt 24 includes annular portion 24a, 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. 3a. The previously mentioned predetermined axial length of spring 16 is such that planar surface 34 is located within annular portion 24awhen the elements are assembled as shown in FIG. 3. After spring 16 is so positioned, annular portion 24ais peened over, i.e., deformed, from its initial, straight configuration of FIG. 3ato 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 26aof flange 26 and annular portion 24aof skirt 24.

[0025] Connector 10 is shown in FIG. 3, and FIGS. 3b-3d, 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 26bof 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.

[0026] Turning now to FIGS. 3b-3d, 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. 3bconnector 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. 3c, nut 12 has been rotated, e.g., a couple of revolutions, thereby moving connector 10 axially upon shaft 56 by the distance indicted as D1 and bringing the end of shaft 56 into contact with surface 26bof 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. 3d. The nut has moved upon the shaft by the distance indicated as D2, although other elements of connector 10 have not moved relative to the shaft. The axial distance by which the nut has moved between FIGS. 3cand 3d, i.e., the difference between distances D1 and D2, is the distance by which spring 16 has been compressed. As the nut travels axially on the shaft, annular portion 24aof skirt 24 bears against end 34 of the spring and compresses the spring as end 32 is held stationary against surface 26aof 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 26bof flange 26.

[0027] 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 72aof 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 72aof post flange 72 and the lower spring surface 84 bearing against surface 78aof 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.

[0028] The same reference numerals are used in FIGS. 6 and 7 for the coaxial cable and its various layers as in FIGS. 3 and 3b-3d. 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.

[0029] 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 72bof post flange 72.

[0030] 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'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.