Abstract:
A cable linkage comprising a cable partially housed within a sheath and a fitting for securement to a linkage member, a length of cable between the fitting and the sheath being exposed when the cable is extended in use, wherein the fitting has a guide follower arranged to follow a guide so as to substantially inhibit kinking of the exposed length of cable.

Description:
This application claims priority to British Application No. GB 0110457.9 filed Apr. 28, 2001. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a cable linkage. More particularly, the present invention relates to a cable linkage having a guide to inhibit the kinking of the cable when a compression load is applied thereto. 
     The use of cables to enable the remote actuation of devices such as latches and locks on vehicle doors, for example, is well known. 
     In order to simplify the design and installation of cables within doors, it is desirable that sheathed multi-strand flexible cable with a reduced internal friction is used so that the cable may be routed easily around obstacles within the door. Additionally, the use of flexible cables is desirable as slack can be provided along the cable run. This means that in the event of an impact which deforms the door, the deformation is unlikely to cause unwanted actuation due to a tightening of the cable, which would lead to the door becoming unlatched. 
     While flexible cables are effective when required to exert a tensile load, the reduced internal friction of flexible cables results in an intrinsic tendency to kink when called upon to exert a compression load and are unconstrained by an outer sheath, thus preventing actuation of devices connected thereto in this direction. 
     One solution that has been previously proposed in order to overcome this problem provides a rigid end piece to the cable that extends into the cable sheath so that none of the flexible cable is exposed. Thus, this arrangement substantially mitigates the tendency to kink. However, the installation and/or use of such an arrangement is not possible when the end of the cable proximate the device to be actuated has to be routed through a tight angle in order to avoid obstructions, for example, due to the inflexibility of this end of the cable. Furthermore, such an arrangement generally requires an enlarged end to the sheath to accommodate the rigid end piece, which may be undesirable when space is restricted. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to overcome, or at least mitigate, the problems of the prior art. 
     An aspect of the present invention provides a cable linkage comprising a cable partially housed within a sheath and a fitting for securement to a linkage member, a length of cable between the fitting and the sheath being exposed when the cable is extended in use, wherein the fitting has a guide follower arranged to follow a guide means so as to substantially inhibit kinking of the exposed length of cable. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
     FIG. 1A is a side view of a prior art cable linkage. 
     FIG. 1B is a side view of the linkage of FIG. 1A having a compression load exerted thereon. 
     FIG. 2 is a side view of a cable linkage according to one version of the present invention. 
     FIG. 3 is a side view of a cable linkage according to a second version of the present invention. 
     FIG. 4 shows curved elongate projections. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a prior art cable linkage  10  as illustrated comprises a flexible multi-stranded cable  12  housed along the majority of its length by a sheath  14  which permits relative axial movement of the cable  12 . The cable terminates in an end fitting  16  connected to an arm  18  by a pivot pin  20  at one end of the arm  18 . The arm  18  is further pivotally connected at its other end to an input shaft  22  of a door latch, for example. 
     In use, axial movement of the cable  12  relative to the sheath  14  induced by a remote actuator such as a door handle (not shown) is converted into rotational motion of the input shaft  22  which may in turn actuate the door latch. 
     It will, however, be apparent to those skilled in the art that if a compression load is applied to the cable  12  in a direction X and resistance is encountered in rotation of the input shaft  22 , at a certain load, this resistance becomes sufficient to overcome the internal friction of the cable where it is unconstrained by the sheath. This causes the end fitting  16  to pivot about pivot pin  20  and kink as shown in FIG. 1B rather than causing the input shaft  22  to rotate. Clearly, such malfunctioning is unacceptable as it may prevent entry or exit from a vehicle, for example. 
     Turning now to FIG. 2, like numerals have been used for like parts with the addition of the prefix ‘ 1 ’. Thus, only those differences with respect to FIGS. 1A and 1B are discussed in greater detail below. 
     It can be seen that in FIG. 2, the end fitting  116  has been extended beyond the pivot pin  120  connecting it to arm  118  (also known as a linkage member). The end fitting has a finger portion  130  (also known as a guide follower) protruding at substantially right angles from the fitting at the end thereof remote from the exposed cable  112 . In this version, the arm  118  is pivotally secured to a plate  124  by shaft  122  and a guide in the form of a pair of mutually spaced parallel elongate projections  126  and  128  is provided thereon, either side of the finger  130 , to act as a guide for the finger portion  130 . In order to prevent the arm  118  fouling on the elongate projections  126 ,  128  as it pivots, it is preferable that sufficient clearance is provided between the plate  124  and the arm  118 . 
     In use, when a compression load is applied to the exposed cable  112  in the direction X against the resistance in shaft  122 , because the guide causes the end fitting  116  to remain substantially parallel to the longitudinal axis of the exposed cable  112  and as the end fitting  116  is non-rotatably secured to the exposed cable  112 , this arrangement substantially impairs the tendency of the cable to kink. Thus, a flexible cable fitted to the linkage of FIG. 2 is able to transmit a substantially higher compression load by comparison with the prior art cable linkage  10  of FIGS. 1A and 1B. 
     Turning now to FIG. 3, a second version of the invention is illustrated in which like numerals have been used for like parts with the addition of the prefix ‘ 2 ’. Again, only the differences of FIG. 3 in respect of FIG. 2 are discussed in further detail below. 
     It can be seen from FIG. 3 that in this version the spaced guide elongate projections  126  and  128  have been replaced by a slot  228  provided in the cable side of plate  224 . Additionally, the finger  230  has been mounted at the other side of pin  220  on fitting  216  so as to be guided by the slot  228 . It is apparent that this embodiments operates in a similar manner to the embodiment disclosed in FIG. 2 but this arrangement of guide means may be advantageous in certain instances due to space restrictions, for example. 
     It should be understood that numerous changes may be made within the scope of the invention. For example, in an embodiment that requires arm  218  to rotate through a relatively large angle, it may be advantageous for the slot or the elongate projections  126  and  128  to be curved so as to follow a similar arc to that described by pivot pin  120 / 220  in order that the longitudinal axis of the end fitting  216  remains parallel with the longitudinal axis of the cable  212 . Of course, the invention may also be applied to other types of linkage that operate linearly. It should also be appreciated that the present invention has a wide variety of applications in the autolotive and other fields and is not limited to linkages for latching car doors, for example. In preferred embodiments, the cable is of the multi-strand type. However, it should be understood that the invention may also be applied to single strand cables to enable smaller diameter cables of this type to be used in transmitting an equivalent compression load than has hitherto been possible. 
     The aforementioned description is exemplary rather that limiting. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed. However, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. Hence, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For this reason the following claims should be studied to determine the true scope and content of this invention.