Flexible drive shaft liner
View Patent ↗A flexible, rotating drive transmission assembly having a substantially spiral-shaped liner supporting a center, rotatable, flexible shaft. The liner and its center shaft are carried within an outer down-tube. The spiral-shaped liner contains flexible, continuously tapering, elliptical legs that are self-adjusting and allow the liner to be easily inserted into and firmly retained by the outer down-tube. The self-adjusting legs of the liner conform to the inside diameter of the outer down-tube despite internal variations, thus allowing the liner to maintain its central axis or centerline relative to the central axis of the outer down-tube and end components attached to the assembly. The legs provide vibration isolation and absorption by their inherent spring effect. Moreover, grease skived from the inner wall of the outer down-tube, due to the auger effect of the rotating flexible shaft, is uniformly collected in pockets for distribution along the entire length of the outer down-tube.
1. A flexible, rotary drive transmission assembly, comprising a rotatable flexible shaft supported within a central, hollow portion of a cylindrical liner, said liner comprising a plurality of unitary, continuously tapered, flexible, elliptical legs formed from and projecting tangentially from an outer surface thereof thereby defining a boundary line, said boundary line proceeding helically around said outer surface of said cylindrical liner, said liner being carried within an outer down-tube, said legs being disposed in an interference fit with an inner surface thereof, thereby centering and supporting said liner on its intended centerline substantially coaxially with said outer down-tube.
2. A weed trimmer comprising the flexible, rotary drive transmission assembly in accordance with claim 1 .
3. The flexible, rotary drive transmission assembly in accordance with claim 1 , adapted for use in one of the following devices: weed trimmers, hand-held snow blowers, power brooms, lawn edgers, hedgers, pruners, chain saws, blowers/vacuums and automotive applications.
4. The flexible, rotary drive transmission assembly as recited in claim 1 , wherein each of said plurality of tapered, flexible, elliptical legs exhibits both leaf spring and lever spring characteristics.
5. The flexible, rotary drive transmission assembly as recited in claim 4 , wherein said leaf spring characteristic is provided by at least said taper of said plurality of tapered, flexible, elliptical legs.
6. The flexible, rotary drive transmission assembly as recited in claim 4 , wherein said lever spring characteristic is provided by at least said tangential projection of said plurality of tapered, flexible, elliptical legs.
7. The flexible, rotary drive transmission assembly as recited in claim 4 , wherein at least one of said leaf spring and said lever spring characteristics causes said liner to self-center itself in said outer down tube.
8. The flexible, rotary drive transmission assembly as recited in claim 7 , wherein said process of said liner self-centering itself in said outer down tube compensates for tolerance variations in an inner surface of said outer down tube.
9. The flexible, rotary drive transmission assembly as recited in claim 4 wherein at least one of said leaf spring and said lever spring characteristics facilitates vibration reduction in said flexible, rotary drive transmission.
10. The flexible, rotary drive transmission assembly as recited in claim 1 , wherein said plurality of tapered, flexible, elliptical legs comprises three tapered, flexible, elliptical legs.
11. The flexible, rotary drive transmission assembly as recited in claim 10 , wherein a cross-section of said elliptical legs is substantially triangular.
12. The flexible, rotary drive transmission assembly in accordance with claim 1 , wherein each of said plurality of tapered, flexible, elliptical legs comprises a peripheral tip at the distal end thereof, disposed helically around said outer surface of said inner liner.
13. The flexible, rotary drive transmission assembly in accordance with claim 1 , wherein each of said plurality of tapered, flexible, elliptical legs comprises a peripheral tip at the distal end thereof, and wherein each of said peripheral tips defines a spiral path at a respective point of contact along a length of said inner surface of said outer down tube.
14. A flexible liner carried within an outer down tube of a flexible, rotary drive transmission assembly, said flexible liner comprising a cylindrical, hollow inner tube having a plurality of unitary, continuously tapered, flexible, elliptical legs projecting tangentially from an outer surface thereof wherein said legs wind helically along the length of the hollow inner tube centering and supporting a flexible shaft on its intended centerline within the outer down tube, thus preventing parallel misalignment with end components connected respectively to a proximal and a distal end of said flexible shaft, thereby minimizing premature failure of said rotary drive transmission assembly.
15. The flexible liner for a flexible rotary drive transmission assembly as recited in claim 14 , wherein said tapered, flexible, elliptical legs are flexibly self-adjusting, thereby facilitating insertion of said liner into and retention with the outer down-tube.
16. The flexible liner in accordance with claim 15 , adapted for use in one of the following devices: weed trimmers, hand-held snow blowers, power brooms, lawn edgers, hedgers, pruners, chain saws, blowers/vacuums and automotive applications.