# Patent

## Title
Saw chain drive link with tail

## Abstract

A saw chain for a saw is disclosed. Embodiments include a drive link that may be used in a saw chain, wherein the drive link includes a tail and a concavity that complements a depth gauge of a trailing cutting link, reducing and/or minimizing the drive link's protrusion into a gullet space of the cutting link. Embodiments of the invention may help improve cutting performance and further help reduce kickback potential.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority to U.S. Provisional Patent Application No. 60/863,091, filed Oct. 26, 2006, entitled “SAW CHAIN DRIVE LINK WITH TAIL,” the entire disclosure of which is hereby incorporated by reference in its entirety.


TECHNICAL FIELD
The present invention relates to the field of saw chains, and in particular to a saw chain drive link having a tail adapted to inhibit kickback and to minimize impact to cutting speed.
BACKGROUND
Chain saws typically include an endless saw chain disposed to articulate around a saw bar. The saw chain generally includes various inter-coupled links, such as cutter links, drive links, and tie straps. Cutter links may be provided with a depth gauge in front of and slightly below a following cutting edge to substantially inhibit the cutter from taking an excessive bite or penetration into the wood. Excessive bite can occur particularly when there is contact between the chain at the upper quadrant of the bar nose and the material being cut (when cutting with the nose) or through accidental contact with a nearby branch or the like. Such contact may induce kickback.
Cutting speed is believed to be affected by the length and height and amount of free space in the gaps between the cutting teeth of the cutting links. When this space fills up the cutting teeth are forced away from the kerf bottom, i.e., out of the cutting mode. Particularly during a nose cut, the depth gauge of the cutting link will be pressed into the kerf bottom, thereby compressing the wood which allows the following cutting tooth to penetrate further into the kerf and take an undesired excessive bite that can cause kickback.
Cutting speed is believed to be further affected by the size and shape of the free space or gullet between the cutting teeth and the depth gauge of the cutting links. The gullet is a necessary space required in wood chip formation, transportation and egression from the cutting kerf. The gullet space may be optimized for cutting performance.



DESCRIPTION OF THE FIGURES
FIG. 1 illustrates a side view of a drive link in accordance with various embodiments;
FIG. 2 illustrates a side view of a cutting link coupled to a drive link in accordance with various embodiments;
FIG. 3 illustrates a side view of a cutting link coupled to a drive link in accordance with various embodiments;
FIG. 4 illustrates a partial side view of a cutting link coupled to a drive link in accordance with various embodiments; and
FIG. 5 illustrates a side view of a cutting chain in accordance with various embodiments.



DESCRIPTION OF VARIOUS EMBODIMENTS
In the following detailed description, reference is made to the accompanying drawings which form a part hereof wherein like numerals designate like parts throughout, and in which is shown by way of illustration embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments in accordance with the present invention is defined by the appended claims and their equivalents.
Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding embodiments of the present invention; however, the order of description should not be construed to imply that these operations are order dependent.
The description may use perspective-based descriptions such as up/down, back/front, and top/bottom. Such descriptions are merely used to facilitate the discussion and are not intended to restrict the application of embodiments of the present invention.
For the purposes of the present invention, the phrase “A/B” means A or B. For the purposes of the present invention, the phrase “A and/or B” means “(A), (B), or (A and B).” For the purposes of the present invention, the phrase “at least one of A, B, and C” means “(A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).” For the purposes of the present invention, the phrase “(A)B” means “(B) or (AB),” that is, A is an optional element.
The terms “coupled” and “connected,” along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Rather, in particular embodiments, “connected” may be used to indicate that two or more elements are in direct physical or electrical contact with each other. “Coupled” may mean that two or more elements are in direct physical or electrical contact. However, “coupled” may also mean that two or more elements are not in direct contact with each other, but yet still cooperate or interact with each other.
The description may use the phrases “in an embodiment,” or “in embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present invention, are synonymous.
Embodiments of the present invention may provide an improved drive link (also referred to herein as a center link) having a rearwardly extended trailing guard portion of the drive link, which may be referred to as a tail. The tail may be positioned alongside a depth gauge of a cutting link that shares a common pivotal connection with the drive link. A double thickness of depth gauge and tail may be formed and may more effectively resist penetration into the wood fibers of the kerf bottom (as compared to an elongated single thickness) and may substantially enhance the resistance to excessive penetration of the following cutting link. In various embodiments, the shape of the rearwardly extending tail may be sized to minimize the extension into the (gullet) space between the depth gauge and the tooth of the cutting link.
In various embodiments, the rearward extension of the tail provides further resistance to penetration of the wood fibers, while minimizing negative effects on cutting performance by minimizing that portion of the center link that extends into the gullet of the cutting link, or in other words helping to maximize the gullet opening for enhanced chip flow. In various embodiments, the configuration of the leading and trailing portions of the center link may be cooperatively formed so that the ramp of the leading portion ramps the wood being cut in a direction that projects above the leading edge of the trailing portion, the leading edge of the trailing portion being itself shaped to avoid presenting a corner that might dig into the kerf, while the tail of the trailing portion may be formed to provide an extended edge along the top of the trailing portion. In various embodiments, the drive link may also be relieved in a center area forward of the trailing portion of the center link to provide added chip carrying capacity.
FIG. 1 illustrates a drive link 28 according to various embodiments of the invention. A drive link 28 may have a tail 40 extending rearward from the body of the center or drive link. The tail 40 may reduce kickback by extending somewhat radially as it traverses the nose of a chain saw bar. In addition, the tail 40 may increase the surface area of the drive link 28 that may be engaged in the kickback event thus reducing kickback energies. In addition the length and shape of the tail may be modified to optimize cutting performance.
In various embodiments, the drive link 28 may include a cutout area 29, which may serve to increase the chip carrying capacity of the chain. In various embodiments, the cut out portion 29 may be moved farther forward in the drive link body in order to increase the surface area at the rear portion of the bumper drive link, which may further help reduce the kickback effect.
In some embodiments, the height of a top edge 44 the tail 40 may be less than the height of an upper surface 46 of a depth gauge 22, when such components are traversing the straight runs of the upper and lower bar rails of a guide bar 36. Such height differential may make maintaining the cutter depth gauge easier in that the tail may not obstruct the depth gauge during filing and maintenance.
FIGS. 2-4 are side views of a cutting link and drive link illustrating a respective first position 12 and second position 14 of a portion of a saw chain 16 in accordance with various embodiments of the invention. FIG. 5 illustrates a side view of the end of a guide bar having a saw chain disposed thereon both in the first position and the second position in accordance with various embodiments. The saw chain 16 may include a cutter link 18 having a cutting edge 20 and a depth gauge 22 separated by a gullet 24. The depth gauge 22 may have an upper surface 46 and a rear face 23 that generally faces gullet 24. The cutter link 18 may be coupled with a drive link 28 with, for example, a rivet 30. A longitudinal first centerline 55 may be disposed through rivet 30 and adjacent rivet holes 27 (rearward cutter link rivet hole) and 29 (forward drive link rivet hole.) A second rivet centerline 57 may be disposed perpendicular to the longitudinal first centerline 55 and generally coplanar with the drive link 28. The cutter link 18 and the drive link 28 may be in a first position 12 while traversing on a generally straight run of a bar rail 34 of a bar 36 and may be in the second position 14 while traversing circumferentially around a nose 38 of the bar 36.
In various embodiments, the drive link 28 may include tail 40 that is adapted to extend partway into the upper region 42 of the gullet 24. The tail 40 may have a top edge 44, which in some embodiments may be lower than the upper surface 46 of depth gauge 22 while in the first position 12. The drive link 28 may have a concavity 48 on a trailing edge 50, and may include a forward most portion 49 disposed below and in front of a tip or rearmost portion 41 of the tail 40. In various embodiments, the rearmost portion 41 of tail 40 may be disposed a first distance 116 from the perpendicular second centerline 57, and the forward most portion 49 of concavity 48 may be disposed a second distance 113 from the perpendicular second centerline 57. In various embodiments, the first distance is greater than the second distance such that the forward most portion is closer than the rearmost portion 41 to the perpendicular second centerline 57. In various embodiments, the concavity 48 is sized to reduce the amount of drive link material that protrudes into the gullet 24 of the cutter link, which in turn reduces the impact on the flow of chips through the gullet 24 promoting better cutting performance.
In various embodiments, as the saw chain traverses the nose of the guide bar, i.e. with the saw chain 16 in the second position 14, the drive link 28 and the cutter link 18 may pivot with respect to each other about rivet 30. In doing so, the tail 40 may extend radially outward from a center of nose 38 as the tail traverses the nose. In some embodiments, as the tail 40 traverses the nose 38, a rearward portion 52 of the tail 40 may substantially align (e.g. extend radially from the center of nose 38) with the upper surface 46 of depth gauge 22 at its point of greatest radial extension. Such alignment may present a larger surface area relative to the kerf width which may help resist kickback when traversing the nose 38. In other embodiments, the end of the tail 40 may extend radially further or less than the depth gauge.
FIG. 4 illustrates a detailed breakaway view of a portion of FIG. 2. Various embodiments may include proportions of saw chain components having pre-selected values such that while in the first position 12 it may help maintain performance, and while in the second position 14 kickback is minimized. In one embodiment, the radial tail dimension 102, i.e. the radial distance from the center 54 of the rivet 30 to a tip 41 of the tail 40 and the depth gauge height 104, i.e. distance from the center 54 to the upper surface 46 of the depth gauge 22 may be modified for optimum cutting and kickback prevention. In one embodiment, the radial tail dimension 102 may be substantially equal to the depth gauge height 104. In various embodiments as the depth gauge is filed down, so to may the tip 41, rear portion 52 (which may include tip 41), and/or upper surface 44 so as to maintain generally a desired ratio (e.g. a one to one ratio).
In various embodiments, the tail 40 may extend into the gullet 24 a predetermined amount as indicated as tail extension distance 100, thereby leaving a gullet distance 117. Gullet distance 117 may be held above a minimum in order to enable maintenance and file access. It is also desirable to have gullet distance 117 at a maximum to promote chip flow and maximize performance. In various embodiments the ratio of tail extension distance 100 and the gullet distance 117 may be between 0.06 and 0.43. In one embodiment, the ratio between the extension distance 100 and the gullet distance 117 may be substantially equal to 0.06.
The height of the top edge 44 of tail 40 above the center 54 of the rivet 30 may be indicated as tail height 106, and may be altered as desired to improve performance, decrease kickback and improve maintainability of the chain. In various embodiments the tail height 106 may be a predetermined percentage of the depth gauge height 104 such as, a range of 80-100%. In further embodiments, the tail height 106 may be kept below the height of the depth gauge height 104, which may reduce the need for maintenance (e.g. filing) on the tail throughout the life of the saw chain.
The concavity depth 108 of the concavity 48 may be altered in order to control the amount of material disposed in the gullet 24. The concavity depth 108 may also be a predetermined percentage or multiple of other dimensions of the arrangement. In one embodiment, the concavity depth 108 may be between 50% and 100% of tail extension distance 100. In various embodiments, the concavity depth 108 may be greater than tail extension distance 100. In one embodiment, concavity 48 can be reduced by reducing tail extension distance 100.
In one embodiment, the tip 41 may be measured from the center 54 of the rivet 30, resulting in horizontal tail dimension 116. In various embodiments, for example, with saw chains with a rivet pitch (distance between rivets—not shown) of approximately 0.375′′ the center 54 to tip 41 horizontal tail dimension 116 may be within a range of approximately 0.06′′ to 0.15′′.
In various embodiments, the top edge 44 of the tail 40 and an upper concavity edge 51 of the tail 40 may define an angle 114 which may be in a range substantially between 20° and 80°. In various embodiments this angle may be substantially equal to 60° degrees. In one embodiment concavity 48 can be increased by decreasing tail angle 114 while maintaining tail extension distance 100. In various embodiments, the upper concavity edge 51 may define a concavity angle 110 with the horizontal that may be approximately within a range between 20° and 80°. In one embodiment the concavity angle 110 may be approximately 64°. The top edge 44 of tail 40 may define a top edge angle 119 with the horizontal and may be in a range substantially between 0° and ±3°.
In one embodiment, the concavity may have a bottom facing angled trailing edge 51. In another embodiment, the concavity may have a bottom facing radius trailing edge. Other embodiments may include a bottom facing trailing edge comprised of one or more angled and or radius edges.
In addition to the discussion and illustrations of various embodiments above, it is to be understood, however, that a wide variety of alternate and/or equivalent embodiments or implementations calculated to achieve the same purposes may be substituted for the embodiments shown and described without departing from the scope of the present invention. Those with skill in the art will readily appreciate that embodiments in accordance with the present invention may be implemented in a very wide variety of ways. This application is intended to cover any adaptations or variations of the embodiments discussed herein.

## Claims

1. A saw chain comprising:
a cutting link having a forward cutting link rivet hole and a rearward cutting link rivet hole, and further having an upper cutting edge disposed at a first height relative to a guide bar rail and a depth gauge having a rear face opposing the cutting edge and an upper surface disposed generally at or below the first height, a gullet formed between the cutting edge and the depth gauge;
a drive link having a forward drive link rivet hole and a rearward drive link rivet hole, the drive link coupled to the cutting link via a rivet engaging the forward cutting link rivet hole and the rearward drive link rivet hole, wherein in a first position a longitudinal first centerline passes through centers of the rivet holes and the rivet, the rivet further including a second centerline perpendicular to the longitudinal first centerline and generally coplanar with the drive link,
the drive link including a top edge having a rearmost portion that is generally the closest point to the upper cutting edge of the cutting link and disposed a first distance from the second centerline;
a tail extension distance defined by the distance between the top edge rearmost portion and the depth gauge rear face;
a trailing edge disposed generally below the top edge, a concavity formed between the top edge and the trailing edge, the concavity having a forward most portion disposed below the upper edge rearmost portion and a second distance from the perpendicular second centerline of the rivet, wherein the second distance is shorter than the first distance such that the forward most portion is disposed in front of the upper edge rearmost portion, thereby defining a concavity depth and forming a tail on the drive link;
wherein as the saw chain traverses a straight run of a guide bar the rearmost portion protrudes into the gullet the tail extension distance and the top edge is disposed generally at or below the upper surface of the depth gauge; and
wherein as the saw chain traverses a nose of the guide bar the position of the tail moves relative to the depth gauge.

2. The saw chain of claim 1, wherein the rearmost portion does not move beyond the height of the depth gauge.

3. The saw chain of claim 1, wherein the tail has a radial tail dimension substantially equal to the height of the depth gauge as measured from a common pivot point of the cutting link and the drive link.

4. The saw chain of claim 1, wherein a gullet distance is defined between the rearmost portion and the upper cutting edge, and wherein the ratio of the tail extension distance to the gullet distance is substantially 0.06 to 0.43.

5. The saw chain of claim 1, wherein the concavity has a concavity depth that is between 50% and 100% of a tail extension distance.

6. The saw chain of claim 1, wherein the tail includes a tail angle of between 20 to 80 degrees where the tail angle is measured between the top edge and an upper edge of the concavity.

7. The saw chain of claim 1, wherein the tail has a tail height that is in the range of 80 to 100 percent of a depth gauge height.

8. The saw chain of claim 1, wherein the first distance in a range of approximately 0.06 to 0.15 inches.

9. The saw chain of claim 1, wherein the concavity includes a concavity angle of between approximately 20 to 80 degrees.