Patent Application
20070089586
Embodiments of the invention relate generally to the field of saw chains, and more particularly to a saw chain configured to reduce vibration.
Saw chains may experience excess vibration, which can be translated to a user. Such vibrations may be caused by a variety of factors, including when the cutter link contacts a portion of an article to be cut that is harder than the surrounding portions. Attempts have been made to minimize vibration. These attempts have focused on using a cutter link and tie strap configuration that allows the cutter links to rock rearwardly in a direction longitudinal to a longitudinal axis of the saw bar.
Embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which:
Various aspects of the illustrative embodiments will be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, it will be apparent to those skilled in the art that alternate embodiments may be practiced with only some of the described aspects. For purposes of explanation, specific materials and configurations are set forth in order to provide a thorough understanding of the illustrative embodiments. However, it will be apparent to one skilled in the art that alternate embodiments may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the illustrative embodiments.
Further, various operations will be described as multiple discrete operations, in turn, in a manner that is most helpful in understanding the present invention; however, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation.
The phrase “in one embodiment” may be used repeatedly. The phrase generally does not refer to the same embodiment; however, it may. The terms “comprising,” “having,” and “including” are synonymous, unless the context dictates otherwise.
Embodiments of the present invention may include a saw chain having cutter links that are configured to allow slight lateral pivoting or rotation in order to allow the cutting tooth to react to various cutting conditions and reduce vibration caused by the saw chain. Embodiments may also include cutter links that have an extended or an exposed toe portion adapted to ride on a rail of a guide bar such that rearward and laterally rotative movement may be allowed.
Saw chain 10 may be adapted to engage a groove or guide 24 of a guide bar 22. Guide 24 may be defined on the outward portion by a pair of rails 26 and 26′ that are spaced apart a sufficient distance to accommodate the width of drive tangs 30 of drive links 18, and enable the saw chain 10 to traverse the guide bar 22 in a cutting operation. The saw chain may be adapted to travel in a direction as indicated with arrow 29.
In one embodiment, cutter links 14/14′ are virtually identical in structure, except one may be a right-hand cutter link and the other the left-hand cutter link. Accordingly, only one cutter link will be discussed with respect to various embodiments, but the disclosed concepts may apply to both cutter links. Cutter links 14 may include an upper portion that has a cutting edge 38 and a depth gage 39 configured to control a depth of cut. In one embodiment, cutter links 14 may also include a lower portion having a heel portion 31 and a toe portion 33. Toe portion 33 may include a protrusion 32 that is adapted to extend below a bottom surface 34 of a corresponding tie strap 16 positioned opposite the cutter links 14.
Protrusion 32 of cutter link 14 may be adapted to be in sliding engagement with rail 26. Protrusion 32 may be further adapted to guide and support the saw chain 10 as it traverses the guide bar 22. The tie strap 16 opposite the cutter link 14 may be sized such that a gap 36 is defined between the bottom surface 34 of the tie strap 16 and the opposite track rail 26′, such that the protrusion 32 is the primary point of normal engagement between the saw chain and the guide bar 22.
In one embodiment, upon making contact with an article to cut, in particular a portion of the article which may be harder or more resistant to cutting, the cutter link 14 may be allowed to pivot about the protrusion 32 in the rearward direction, as illustrated by arrow 40. The gap 36 defined between the tie strap 16 and the rail 26′, opposite the protrusion 32 on the cutter link 14 may allow the cutter link 14 to also pivot laterally toward a central axis 44, as illustrated by arrow 46. Similarly the cutter link 14′ may, upon making contact with an object, pivot in a direction as illustrated by arrow 40′, and as illustrated in
The lateral pivot or rotation of the cutter link 14 may serve to help absorb the impact of a cutter tooth on a resistive material, which in turn may serve to reduce vibration of a saw. Alternate cutter links 14, 14′ etc. may be disposed on opposite sides of a saw chain according to various embodiments of the invention, and may be configured to pivot laterally in alternately opposite directions. The alternating pivoting movement may serve to maintain straight cuts. The lateral pivoting may also serve to provide a narrower kerf and promote more efficient and reduced vibration cutting operation.
In various embodiments of the present invention, the protrusion 32 may be configured to extend below the bottom surface 34 of the tie straps 16 by, for example, limiting the vertical extension of the tie straps 16. One such way of limiting the vertical extension may be, for example, relieving or cutting each tie strap along a bottom edge thereof. Such a configuration may be described as an “in pitch” configuration, in that the centers of the rivet holes of the cutter links 14 may be positioned a standard pitch distance from a center line of the guide bar 22, i.e. the pitch defined by a drive sprocket.
In other embodiments, the cutter links 14 may be configured to have a protrusion that extends below the bottom surface of an otherwise “standard” tie strap 16. Such a configuration may be defined as “over pitch” in that the toe side rivet hole at the cutter link 14 may be configured to “ride” over a pitch distance from the center of the guide bar 22. Embodiments configured with an over pitch design may provide a longer service life.
In one embodiment, the tie strap 116 may have generally square corners 122, which may add to the ease of manufacturability and may also add to the vibration reducing characteristics. In one embodiment, each of the four corners 222 of the tie strap 216 have been given a so-called “VA trim” configuration. This embodiment may also lend itself to ease of manufacture, and reduce material waste. The tie strap 316 may have chamfered corners 322, which may also reduce vibration and improve performance. The tie strap 416 may include filleted corners 422. Other relieved tie strap configurations may be used in other embodiments according the invention.
A method according to embodiments of the invention and according to the various illustrated embodiments, may include:
coupling a cutter link to a tie strap to be located on opposite sides of a central axis of a guide bar, the cutter link having a cutting edge adapted for cutting a kerf, and having a bottom having a heal portion and a toe portion; and
configuring the cutter link and the tie strap such that the bottom of the cutter link extends below a bottom edge of the tie strap.
The method may further include interlinking a plurality of the cutter links to a plurality of the tie straps, the tie straps being symmetrical about a horizontal axis such that they may be interlinked in multiple orientations while still allowing the bottom of the cutter link to extend below the tie strap.
The method may further include using standard cutter links with tie straps adapted to allow a portion of the toe of the cutter link to protrude past the bottom surface of the tie strap and slidingly engage the rail of a guide bar.
The method may further include using standard tie straps and cutter links having an extended portion of the toe such that the extended portion protrudes past the bottom surface of the tie strap and slidingly engages the rail of a guide bar.
Although specific embodiments have been illustrated and described herein for purposes of description of the preferred embodiment, it will be appreciated by those of ordinary skill in the art that a wide variety of alternate and/or equivalent implementations calculated to achieve the same purposes may be substituted for the specific embodiment shown and described without departing from the scope of the present invention. Those with skill in the art will readily appreciate that the present invention may be implemented in a very wide variety of embodiments. This application is intended to cover any adaptations or variations of the embodiments discussed herein. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.
