A MECHANICAL CONTROL CABLE SYSTEM HAVING AN UMBRELLA SEAL

FIELD OF THE INVENTION

The present invention relates to the field of mechanical control 5 systems having sealed tubular housings.

BACKGROUND OF THE INVENTION

A common problem with mechanical control cables is friction and wear resulting from the ingress of contamination into the annular space between the cable and the coaxially surrounding housing. A

10 common solution to the problem is to provide a scraper-type seal at each end of the housing wherein a scraper component slides axially against the moving surface of the cable. Scraper seals increase the friction of the cable system and also may require that the cables have a smooth outer plastic jacket so that a smooth and effective sealing

15 surface is provided and so that the scraper seal is not quickly worn out.

SUMMARY OF THE INVENTION

The present invention is a mechanical control cable system having a tubular housing coaxially surrounding a portion of a length of

20 control cable and incorporating a tubular umbrella seal at one or both ends of the system. The tubular umbrella seal is coaxially affixed at one end to the control cable; the other end of the tubular umbrella seal coaxially surrounds the adjacent end of the tubular housing with coaxial clearance adequate to allow axial motion between the cable and

2.5 housing over the desired range. Because one end of the tubular umbrella seal surrounds the end of the cable housing, it is necessary to attach the housing to a surface or object at a location on the housing beyond the portion of the housing end surrounded by the tubular umbrella seal at the maximum point of cable insertion into the

30 housing.

In a preferred embodiment, the mechanical control cable system incorporates a tubular metal housing having a polymeric tubular liner closely fitted within the housing. The ends of the tubular liner extend beyond the ends of the tubular housing by an amount at least equal to the desired length of axial motion between the cable and housing. The tubular umbrella seal is coaxially attached at one end to the control cable while the opposite end coaxially surrounds the polymeric tubular liner extending beyond the end of the tubular housing.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a cross sectional view of the mechanical control cable system of the present invention incorporating a tubular umbrella seal at both ends of the system. Figure 2 shows a cross sectional view of a preferred embodiment of the present invention wherein the tubular housing has an internal polymeric liner that extends beyond the ends of the tubular housing.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a cross sectional view of the mechanical control cable system 10 of the present invention incorporating a tubular umbrella seal 26 affixed to at least one end of the system. The mechanical control cable system 10 is shown in a straight configuration for convenience; it is acknowledged that these systems normally include at least one significant curve within their total length during conventional use. The system 10 includes a conventional control cable 12 coaxially surrounded by a tubular housing 20. The tubular housing is preferably of wound metal wire construction and may optionally include a polymeric tubular liner. Likewise, the cable may optionally be provided with a polymeric covering. The use of an optional polymeric tubular liner for the tubular housing and the optional polymeric covering for the cable are well known in the art of mechanical control cables.

Control cable 2 has a middle portion 18 that is coaxially surrounded by the tubular housing £0; the first exposed end H and second exposed end 16 of control cable H are exposed beyond the first end 12 and second end 24 respectively of the tubular housing 10. Annular clearance 38 between the control cable H and the inner surface of the tubular housing 20 allows for relatively free axial travel of the control cable H with respect to the tubular housing 20 during normal operation. A tubular umbrella seal 16 is affixed at a first end 28 of the seal to the first exposed end 14 of cable H. A second end 30 of the tubular umbrella seal 26 is of adequate length and inside diameter to coaxially surround the first end 22 of tubular housing ___• The inside diameter of the second end 30 of the tubular umbrella seal 26 should provide for a slight amount of operating clearance 39 around the outside of the first end 2 of the tubular housing 0. The length of this second end 30 of the tubular umbrella seal 16 should be slightly more than the operating length 37 of the mechanical control cable system 10. This operating length 37 is the axial distance the cable H travels during normal operation with respect to the housing 10. The mechanical control cable system .10 may optionally be provided with a second tubular umbrella seal 32 affixed to the second exposed end 16 of control cable 12.

Figure 1 shows the mechanical control cable system 10 with cable 11 fully extended with respect to the tubular housing 10 in the direction of the second end 2Λ of the tubular housing 10. In this configuration the second end 36 of the second tubular umbrella seal 31 coaxially surrounds only a short length 3j> of the second end 14 of tubular housing 20. This short length 5 should be adequate to provide a reasonably good contamination seal and should be at least about 1-2 mm and more preferably at least about 4-5 mm. The first tubular umbrella seal 16 is shown at its closest proximity to the first end 22 of the tubular housing 10. The first end 22 is coaxially surrounded by the second end 30 of the first tubular umbrella seal 26 for a distance corresponding to the normal operating length 37 of the system \__ plus the short length 35.

The mechanical control cable system H) is attached to any appropriate surface or object, such as a bicycle frame, by clamps 4_2

attached to and located near the first end 22 and second end 14 of the tubular housing 10. The clamps 4_1 can be no closer to the actual end of the tubular housing ___ than the distance corresponding to the combined normal operating length 37 plus the short length 35 in order to allow for travel of the tubular umbrella seal 16 with control cable

11-

The tubular umbrella seal may be affixed to the control cable H by a suitable clamp 40 as shown by the first end 18 of the first tubular umbrella seal 16. Clamp 40 may also be a component with an additional function, such as an actuator clamped to the cable at the same point as the first end 18 of the tubular umbrella seal 16. Alternatively the tubular umbrella seal may be secured to the cable H by an adequate interference fit as shown by the first end 34 of the second tubular umbrella seal 32. The tubular umbrella seal may be made of any suitable material that allows it to provide an effective sealing function over the life of the mechanical control cable system 10. While suitable materials include metals, it is believed that preferred materials are formed polymers offering good flexibility, low coefficient of friction and shape memory. Polymers such as polyethylene, polypropylene and polyvinly chloride are believed to be suitable; fluoropolymers such as fluorinated ethylene propylene, PTFE and perfluoroalkoxy are believed to be preferable because of their low friction characteristics. Heat shrink tubings, preferably of PTFE, may also be appropriate if the relative diameters of the cable and housing allow the first end of the tubular umbrella seal to shrink adequately to adhere to the control cable.

Figure 2 shows a cross sectional view of a preferred embodiment of the mechanical control cable system 10 of the present invention. According to this embodiment the tubular housing 10 is provided with a polymeric tubular liner 44 wherein the first end 46 of the tubular liner 44 extends beyond the first end 22 of the tubular housing 10. Annular operating clearance 41 is provided between the control cable \2 and the inner surface of the polymeric tubular liner 44- The first tubular umbrella seal 16 coaxially surrounds only first end 46 of the tubular liner 44 and does not surround the first end 22 of the tubular housing 20. Instead, the second end 30 of the first tubular umbrella

seal 16 may extend up to the first end 22 of the tubular housing 10 during normal operation of the system 10.