The present invention relates generally to drive-cable liners and, more particularly, to a liner for use in centering a drive cable for a weed trimmer or other drive-cable tools.
Drive cables are used by motorized tools, such as weed trimmers, in order to transfer power from a tool's motor to a working part. For example, the drive cable in a weed trimmer transfers power from the motor, down a shaft, and to a cutting tool, which is then caused to rotate. A drive-cable liner is typically used to center the drive cable within the shaft.
Conventional liners are typically formed from a hollow plastic tube having fins extending radially outward along the entire length of the liner. A disadvantage of such liners is that they must meet stringent manufacturing tolerances. On one hand, if the liner is too thin, the drive cable may not remain centered and thus cause vibrations and wear. On the other hand, if the liner is too wide, the liner may not be able to be inserted into the shaft or the fins may buckle thus resulting in the drive cable being off center. Meeting such stringent manufacturing tolerances is expensive and also results in many liners being rejected during the manufacturing process. Typically, such liners require trimming of the outside diameter resulting in wasted raw materials and additional labor costs. Another disadvantage of such liners is that the fins require a lot of material to form and thus further increasing manufacture costs.
Other conventional liners use rubber spacers fitted around a hollow tube. A disadvantage of such liners is that the rubber spacers must be individually fitted onto the hollow tube, which is a labor intensive process. Another disadvantage is that the rubber spacers are difficult to longitudinally align along the hollow tube. And, even when aligned properly, the rubber spacers may move or slide during use. This may result in the drive cable moving off center, thus leading to excessive wear and premature failure.
Many variations to the above described conventional liners exist. Yet they also suffer from many of the same disadvantages.
Accordingly, there is a need for a liner that can be efficiently and cost-effectively manufactured.
The present invention provides a liner for use in centering a drive cable. The liner comprises a hollow tube. A plurality of longitudinally-spaced, annular elements is integrally formed along the hollow tube. In another embodiment, the annular elements are circumferential corrugations. In another embodiment, the outside surfaces of the annular elements are convex. In still another embodiment, the outside surfaces of the annular elements are concave.
In another embodiment, a weed trimmer is provided. A drive unit for providing torque is coupled to a hollow shaft. A cutting unit having a rotatable-cutting member is coupled to the shaft. A liner is disposed concentrically inside the shaft. The liner comprises a hollow tube. A plurality of annular elements is integrally formed along the hollow tube. The outside surface of each of the annular elements urges against the inside surface of the shaft. A drive cable is disposed concentrically inside the hollow tube of the liner. The drive cable is coupled to the drive unit at one end and the rotatable-cutting member at the other end.
In yet another embodiment, a method of manufacturing a liner for centering a drive cable is provided. A hollow cylindrical plastic tube is extruded. A plurality of longitudinally-spaced, annular elements is then formed along the exterior surface of the tube. In another embodiment, the annular elements are formed using a corrugation process.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. Additionally, as used herein, the term “substantially” is to be construed as a term of approximation.
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Liner 100 is positioned in the hollow interior of shaft 30 and has a hollow interior extending along the axial center of shaft 30. Drive cable 32 is positioned generally along the axial center of the hollow interior of liner 100 and extends along the axial center of shaft 30. Liner 100 and drive cable 32 are preferably flexible allowing them to be used in a curved shaft, but need not be. Drive cable 32 is coupled to drive unit 20 at one end and to rotatable-cutting member 42 at the other end. Drive unit 20 may apply torque to drive cable 32, which is transferred to rotatable-cutting member 42. Rotatable-cutting member 42 may thereby be rotated and used to cut or trim grass, vegetation, etc.
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It is understood that the present invention may take many forms and embodiments. Accordingly, several variations may be made in the foregoing without departing from the spirit or the scope of the invention. For example, the liner could be a composite liner, wherein liner 100, 200, or 300 is positioned concentrically around an inner sheath and the drive shaft is positioned concentrically within the inner sheath.
Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.
Number | Date | Country | |
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62073118 | Oct 2014 | US |