Universal Seal and Support Guide for Push-Pull Cable Terminals

The present invention relates to improvements in sealed universal pivot joints for push-pull cable terminal assemblies and is herein illustratively described by reference to the presently preferred embodiments thereof. However, it will be recognized that certain modifications and changes therein with respect to details may be made without departing from the essential features involved.

Flexible push-pull coaxial cables used in a wide variety of remote control applications comprise flexible inner and outer coaxial cable members with suitable terminal fittings on the ends of the respective members. At one or both ends of the cable assembly, the projecting end of the inner cable member carries a rod-like extension fitting that serves as a load coupler that, together with the connected immediately adjoining portion of the center cable, requires both support and guidance, as well as a means to effect a seal around the same and around the cable so that dirt and moisture cannot enter the cable assembly. Such a guiding support and seal means capable of functioning as a universal joint in order to accommodate the variously deflected positions which the load coupler rod may have to assume under operating conditions, must satisfy certain practical requirements as well as the functional ones mentioned. To be commercially practicable, the device must be relatively inexpensive to manufacture, easily assembled, sturdy and durable. In many applications, the cable assembly operates to perform cyclic control functions literally thousands of times within an operating lifespan. Oftentimes, load forces and moment couples reacting on the cable members and fitting assemblies are severe and are imposed during each operating cycle and with the end fittings laterally deflected out of coaxial alignment with the anchored terminal fitting of the outer cable member. It is therefore important to permit the inner cable member and its extension rod fitting to flex as required and yet to protectively limit the degree of flexure so as to minimize fatigue failures as well as maintain the integrity of the cable assembly seals.

A broad object of this invention is to provide an improved guiding support and seal means for coaxial cable assemblies solving the foregoing problems in an economic and practicable manner suitable for commercial use. More specifically, it is an object hereof to provide a readily manufactured and assembled device, and a sturdy and durable wear-resistant device of the nature indicated.

A further object of this invention is to provide such a device, the parts of which are few and simple and may be manufactured as relatively low cost with the necessary degree of dimensional precision so as to provide an effective durable seal without complicating the steps required to assemble the mechanism.

In accordance with the concepts of this invention, the load coupler extension rod of the inner cable member passes through a sliding seal in one end of a support tube. The support tube carries a hollow ball coupler element on its opposite end that is engaged in a tubular socket element on one end of a resilient plastic socket tube through which the inner cable member also passes. With the ball and socket elements thus interengaged, the socket tube is inserted into the open end of a receptacle in a terminal tubular fitting on the outer cable member. The parts fit snugly so that upon completion of such insertion, a seal is formed around the socket tube and also between the ball and socket elements. Close collaring of the installed socket tube socket element precludes its expansion and thereby snugly requires it to retentively hold the support tube. A positive interlock between the inserted socket tube and the tubular terminal fitting securely holds together these components.

Additional features of the assembly comprising the invention will appear more fully as the description proceeds with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view of one end of a push-pull coaxial cable assembly embodying the preferred embodiment of the invention.

FIG. 2 is a transverse sectional view taken on line 2--2 in FIG. 1.

FIG. 3 is an exploded view of the three principal parts that interfit in forming the protective universal seal and joint comprising the preferred embodiment.

FIG. 4 is a fragmentary longitudinal sectional view illustrating limited deflectability of the ball and socket joint and associated components comprising the invention.

FIG. 5 is a fragmentary longitudinal sectional view illustrating a first alternative embodiment of the invention.

FIG. 6 is a fragmentary longitudinal sectional view illustrating a second alternative embodiment of the invention.

FIG. 7 is an exploded view of the second alternative embodiment of FIG. 6.

FIG. 8 is an isometric exploded view of the second alternative embodiment of FIG. 6.

Referring to the drawings, wherein like reference characters designate like or corresponding elements throughout the several views, the push-pull coaxial cable components are illustrated in somewhat simplified form and are or may be conventional, including the flexible multi-strand cable inner member 10 and the wrapped multi-strand cable outer member 12 in which the inner member is received and guided for longitudinal relative sliding movement in the usual manner.

Referring to FIGS. 1 through 4 in particular, the preferred embodiment includes a tubular terminal fitting 14 fixed on the end of the outer member 12 has a threaded cylindrical tip 14a by which it may be anchored with use of lock nuts to a panel or other support (not shown) through which it passes in the usual manner. Inner member 10 projects axially outward from the fitting 14 and carries a rod-like load coupler extension fitting 16 thereon for transmitting load forces through the cable assembly. Rod 16 is swaged at 16a on the end of inner member 10.

The open end of tubular fitting 14 forms a receptacle comprising a substantially cylindrical entrance chamber 14b adjoined through a steeply sloped annular shoulder 14c to a substantially cylindrical elongated intermediate chamber 14d. At the inner end of chamber 14d the receptacle undergoes an abrupt expansion to form an annular locking shoulder 14e and an inner chamber 14f. Longitudinally insertable with a snug conforming fit into the open fitting receptacle is a socket tube 18 including at one end a socket element 18a that fits into the outer chamber 14b, and a cylindrical shank 18b that fits within the intermediate chamber 14d. Shank 18b itself terminates at its inner end in a multiply-slotted portion forming a circumferentially spaced group of resiliently deflectable fingers 18c that carry transversely projecting locking tabs 18d, the tips of which are chamferred at 18d' for ease of entry by inward wedging action against the inner edge of annular shoulder 14c during the insertion process. When the socket tube 18 is fully inserted in the receptacle of fitting 14 the fingers are free to snap outwardly, positioning the locking tabs 18d in direct abutment with the locking shoulder 14e so as to prevent retraction of the socket tube. Being of resilient plastic material, the socket tube also has a degree of surface softness or elastic yield so as to enhance its sealing effect in snug fitting contact with the interior wall of the tubular fitting outer chamber as shown.

In order to provide support and guidance for the cable rod 16, the assembly includes a support tube 20, preferably of metal, such as stainless steel, carrying a seal element 20a on its outer end that effects a sliding seal with the rod 16 passing through it. The opposite end of the support tube 20 carries a tubular ball element 20b that can be inserted by snap action into the socket element 18a before the socket tube 18 is inserted into the fitting 14. Once the socket tube 18 is fully so inserted however, the closely collared socket element 18a cannot expand and thus retentively holds the ball element 20b, yet permitting the support tube 20 to undergo universal tilting or deflection movement relative to the socket tube 18. The degree of deflection permitted in any plane is limited by stop surfaces including a conically reentrant annular end face 18a' on the socket element 18a adapted to bear against a support tube surface, namely the cylindrical outer wall of the support tube 20. This is depicted in FIG. 4 wherein a maximum limited deflection angle of 16.degree. between opposite limits is indicated.

In FIG. 3 the interfittable parts are shown separated. Assembly is effected by first snapping the ball 20b into the socket 18a and thereupon by longitudinally inserting the socket tube 18 into the receptacle of fitting 14 until it is fully inserted and the locking tabs 18d snap outwardly past the locking shoulder 14e to complete the assembly.

An first alternative embodiment is shown in FIG. 5, wherein the parts are similar except, in this case, the resilient fingers with locking tabs are replaced by use of screw threads 18bb formed on the exterior of the socket tube shank portion 18b engageable with matching screw threads 14dd formed on the cylindrical wall of the intermediate chamber.

A second alternative embodiment is illustrated in FIGS. 6 through 8, wherein elements essentially identical to elements of the preferred embodiment are similarly numbered. In this alternative embodiment, a modified socket tube 22 and a cooperable lock ring 24 substitute for the single-piece socket tube 18 of the preferred embodiment. The complemental parts 22 and 24 are more readily moldable with present plastic molding technology than the one-piece socket tube 18 due to the internally divergent-convergent surface form of the latter. The modified socket tube 22 includes a semispherical socket portion 22a having a lap joint surface 22f along its outer rim. The lock ring 24 also includes a lap joint surface 24a which is cooperably engageable with the socket tube lap joint surface 22f to form a two-piece socket element essentially equivalent in function to the single-piece socket element 18a of the preferred embodiment. The lock ring 24 also includes an annular, spherically curved socket surface 24c which is cooperable with the socket portion 22a of the modified socket tube 22 to form the spherical, two-piece socket element. The lock ring 24 further includes an outwardly flanged edge 24b which retentively engages an annular groove 14g in the interior wall of the fitting 14 when the ring 24, socket tube 22 and O-ring 26 are installed in the fitting 14. A conically reentrant stop surface 24d is essentially equivalent in function to the similarly formed end face 18a' of the preferred embodiment.

The modified socket tube 22 further includes a shank portion 22c, deflectable fingers 22d, and locking tabs 22e with chamferred edges 22e', all of which are essentially identical to the corresponding elements of the preferred embodiment.

An elastomeric O-ring 26 is positioned between the sloped annular shoulder 14c of the fitting 14 and a cooperable annular shoulder 22b of the modified socket tube 22. The O-ring 26 exerts axial compressional force to maintain the two-piece socket element parts pressed together as an integral retainer for the ball element 20b of the support tube 20.

The above-described alternative embodiment is particularly adaptable to fabrication according to well-known methods of plastic molding and is thus particularly economical to produce. Moreover, the O-ring 26 and retentively engaged lock ring 24 provide a two-piece socket assembly which is retentively engaged at both ends and resiliently tensioned against disengagement due to longitudinal forces exerted on the support tube 20.

Inasmuch as the interfittable parts are readily formed with precision, the socket tube 18 by a precision plastic molding process and the support tube 20 by a precision dye-casting or forming process (being formed of metal) snug precision fits are readily achieved to form an effective and durable seal. Limited deflectability of the support tube 20 as shown in FIG. 4 protects the cable inner member 10 against undue load stress and undue deflection. The support for the socket tube socket element provided by the terminal fitting 14 assures a continuing seal between the parts even with the parts under load stress in their deflection-limit positions wherein the deflection leverage forces must be borne by the elements carrying the deflection limit stop surfaces described. The entire assembly is manufacturable at low costs on a production basis and very quickly assembled without any special skills required.

These and other aspects of the invention will become evident to those skilled in the art based on the foregoing description of the presently preferred embodiment which are illustrative of the novel concepts and features involved.