Abstract:
Reciprocating or push-pull control cable assemblies have fittings permanently attached, preferable by swaging or other mechanical deformation process, to the ends of a control cable or core that reciprocates within an outer casing. The fittings have a projected width no greater than the inner diameter of the casing. As a result, the entire control cable, with fittings attached, can be pulled through the casing to remove the control cable for inspection, maintenance or replacement. The cable also have a unique combination of ball joint assemblies and excluder seals that effectively exclude contaminants from the interior of the casing.

Description:
FIELD OF THE INVENTION 
     This invention relates to mechanical control assemblies, and more particularly to push-pull or reciprocating cable assemblies suitable for aeronautical applications. 
     BACKGROUND 
     Push-pull control cable assemblies are used for many systems, e.g. aircraft engines, which must be adjusted from a distance or which are located in hostile environments. These controls frequently have a cable that reciprocates within a casing that supports and protects the cable. Fittings are typically attached to both ends of the cable to connect it to a system to be controlled at one end, and to operating levers, pedals and the like at the other end. 
     With existing controls of this type, the entire control cable assembly must be removed for repair or replacement, and the cable itself cannot be thoroughly inspected without removal of fittings permanently attached to each end. When these cables fail, they are normally discarded and replaced. To facilitate inspection, repair and replacement, a control assembly with a reciprocating cable that can be removed from the casing without removing or disassembling the casing would be desirable. 
     SUMMARY OF THE INVENTION 
     This invention provides improved control cable assemblies having control cables mounted within and adapted for reciprocation within an outer casing. A fitting is permanently attached, preferable by swaging or other mechanical deformation process, to at least one end, normally both ends, of the control cable. These fittings have a projected width, i.e. the width in a plane at right angles to the axis of the cable, no greater than the inner diameter of the casing. As a result, the entire control cable, with fittings attached, can be pulled through the casing to remove the control cable for inspection, maintenance or replacement. This simplifies maintenance, and substantially increases the service life of the cable assembly. To facilitate connection to control levers, pedals or the like, or to apparatus to be controlled or operated, couplings or other connecting members may be detachably secured to the fittings by renewable connections such as threaded joints, for example, that allow the couplings to be removed and replaced easily. 
     The invention also provides a unique combination of ball joint assemblies and excluder seals that effectively exclude contaminants from the interior of the casing, which also helps to increase service life. These and other features of the inventive cable are described more thoroughly in the following detailed description. 
    
    
     DRAWINGS 
     FIG. 1 is a fragmentary, partially cutaway plan view of a control cable assembly embodying this invention. 
     FIG. 2 is a cross-sectional view along lines  2 — 2  in FIG.  1 . 
     FIG. 3 is an enlarged cross-sectional view of a ball joint assembly in the control cable assembly illustrated in FIGS. 1 and 2. 
     FIG. 4 is a further enlarged cross-sectional view of an excluder seal in the control cable assembly of FIGS. 1 and 2. 
     FIG. 5 is an end view of the excluder seal in FIG. 4, partially cut away to show parts of the excluder seal in more detail. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a control cable assembly, generally referred to as  10 , embodying this invention. Cable assembly  10  may extend from the cockpit of an aircraft, or another operating area, to an engine compartment or other remote or hostile location. The cable assembly has a control cable  20  adapted for reciprocation within a casing  40 . Casing  40  typically extends through a bulkhead fitting  15  in a wall or other partition between the aircraft cockpit, or other operating area, and the compartment where the engine or other system to be controlled is located. 
     Each end of control cable  20  has an end rod  28  with a threaded end  32  for attaching a connecting member, such as the couplings  38  illustrated in FIG. 1, that attach the end rods  28  to control levers, pedals or the like in an aircraft cabin or other operating compartment, or to an engine or other system to be controlled. The diameter of the end rods  28  is less than the inner diameter of the casing  40 . This allows the control cable  20 , with end rods attached, to be pulled through the casing  40  and removed for inspection, repair or replacement when a coupling  38  has been removed from one of the end rods. In most cases, both ends of the control cable  20  are substantially the same. Thus, the cable can normally be removed in either direction. However, there may be modifications for particular applications, such as differences in the threads on the end rods. 
     The ability to remove control cable  20  from casing  40  permits servicing, maintenance and repairs that were not possible with prior art control cable assemblies, whose central cables could not be removed without removing end fittings that were permanently attached to this control cable by swaging or the like. This is not a problem with the control cables of this invention, however, because the end rods that are permanently attached to the cables can pulled through the casing. Typically, couplings  38  or other connecting members, designed for connections with engines or other systems to be operated or controlled, or to control levers, pedals or the like, are attached to the end rods with threaded or other renewable connections that allow the connecting members to be removed without distorting or damaging either the end rods or the connecting members. Thus, the control cable can be removed from the casing and the connecting members can be replaced or reinstalled when the control cable has been reinstalled or replaced. The ability to remove and reinstall or replace the control cable in this manner reduces the cost of maintaining and repairing the cable assembly  10 , and tends to increase its useable life. 
     The central part of control cable  20  is similar to prior control systems of this sort. It consists of a flexible core  22  of stranded wire covered with an armor construction or cover formed by steel flats  24  wrapped around the stranded wire core  22 . The steel flats protect the stranded wire core from wear, crushing and the like, and support the core if it is placed in compression. As best seen in FIG. 2, the armor is peeled from or left off the end of the core, which is inserted into a cylindrical bore  34  in end rod  28 . The thin cylindrical shell  36  that surrounds bore  34  is then mechanically swaged or compressed to clamp end rod  28  to the bare core  22  on the end of the flexible cable with sufficient compression to maintain a secure connection between the end rod  28  and core  22  when the cable  20  is placed in tension. 
     The central part of casing  40  is also similar to prior control cable assemblies. A stranded wire conduit  42  is wrapped with steel flats  44  that are similar to the flats  24  that form the armor cover on the core  22 . The stranded wire conduit  42  is lined with a polytetrafluoroethylene tube  46  that reduces friction on the control cable  20 . 
     As shown in FIG. 2, casing  40  extends into cylindrical bores  52  in casing caps  48 , and the thin annular shells  54  that surround the cylindrical bores  52  are mechanically swaged to lock the casing caps securely on the casing assembly. Like the swaged connection between the end rod and the central core  22 , this connection provides a robust, dependable connection. The joints between the casing assembly  40  and the casing caps  48  are sealed with a watertight, two piece epoxy sealant to exclude foreign material at these joints. 
     The ends of the cable  20  extend through support tubes  62 , mounted in ball joint housings  74  threaded onto casing caps  48 . As best seen in FIG. 2, the joints between the end rods  28  and cable  20  are preferably located in the central portions of the support tubes  62 . The end rods extend through excluder seal assemblies  110 , described in more detail below, attached to the outer ends of the support tubes. The control cables  20  extend through casing caps  48  into enlarged, substantially spherical knobs  66  at the inner ends of the support tubes  62 . These knobs  66  are enclosed within generally cylindrical ball joint housings  74  that allow the end rods to pivot through at an angle of at least 5° in any direction from the illustrated central position. In other words, the end rod can swivel within a cone having a central angle of 10° or more. As shown in FIG. 3, an inwardly extending shoulder  76  on each housing defines a hole  78  which is slightly larger than the section of the support tube extending through this hole. This allows the support tube and end rod to pivot within the specified limits, but prevents excessive movement which could damage the flexible core within the ball joint. As best seen in FIG. 3, the ends of control cable  20  enter the enlarged knobs on the support tubes through conical bores  68 , which typically have a cone angle roughly equal to the angle of the cone within which the support tubes can pivot. The sides of these conical bores help to support the control cable when the end rods pivot. 
     As also shown in FIG. 3, the enlarged knobs  66  at the inner ends of the support tubes are sealed within ball joint housings  74  by pairs of polytetrafluoroethylene seals  92 ,  96 . Springs  82 , held in place by retaining rings  84  mounted in grooves in the inner walls of the housings, press seals  92  against the spherical ends  66  of the support tubes. The spherical ends of the support tubes press against seals  96 , which are held in place by the inwardly extending shoulders  76  on the end of the housings  74 . Seals  92  and  96  protect the cable assembly from contamination along the surface of the of the support tubes  62 . O-rings  94 ,  98  at the outer corners of seals  92  and  96  seal against the inner walls of the ball joint housings  74  and minimize the potential for contamination at these points. 
     As mentioned above, each end rod  28  extends through an excluder seal assembly  110 , shown in FIGS. 4 and 5. The excluder seal assembly  110  has a U-cup rod seal  114 , commercially available from Shamban Seals, mounted in a nose cap  112  treaded onto the outer end of support tube  62 . Rod seal  114  is energized by a spring  116  which presses against the end of the support tube. The compressed spring  116  presses the U-cup rod seal against end rod  28 , providing a dependable seal at this juncture. 
     The excluder seal assembly also incorporates a pair of knife-like conical brass wiper rings  122 ,  132 , shown in FIGS. 4 and 5 and commercially available from Wynn&#39;s Precision, Inc, Houston, Tex., which act as blades to remove and dispose of foreign matter on the end rod  28 , thereby protecting the U-cup rod seals. Each of these rings has a flange  124 ,  134  at its base or inner end. The wiper rings are held in place by a cushion ring  138  of an elastomeric materials such as nitrile, butyl, fluoroelastomers or PTFE. As shown in FIG. 5, each of the wiper rings  122 ,  132  has a pair of slits or notches  126 ,  136 , spaced 180° degrees apart in the conical wall and oriented so that the slits  126  in the inner wiper ring  122  are not aligned with the slits  136  in the outer wiper ring seal. These slits provide flexibility, allow for expansion, and produce a spring effect resulting in constant contact with the end rod  28 , full circle. When compressed, cushion ring  128  preloads the wiper rings for wiper edge contact with the end rods  28 , and absorb shock and side loads. The seal is self adjusting. The wiper rings lengthen the life of the U-cup seals by keeping foreign material from damaging the lips of the U-cup seals, and provide a secondary seal that further reduces the risk of contamination. 
     The combination of the PTFE/O-ring seals in the ball joint assembly  60  and the spring energized U-cup rod seals and wiper rings in the excluder seal assembly  110  provide increased and dependable protection against contamination from foreign materials entering the cable, thus increasing the anticipated life of the cable assembly. As those skilled in the art will readily appreciate, the removable core assemblies of these inventive cables also facilitate servicing, maintenance and repairs, which increases the anticipated service life still further. Of course, as those skilled in the art will also appreciate, the control cable assembly shown and described herein is merely illustrative. Many modifications to and adaptations of the illustrated assembly may be made within the scope of this invention, which is defined by the following claims.