ANTI-KICKBACK INSERTABLE CHAIN AND REPLACEABLE TEETH THEREFOR
An anti-kickback saw chain including a plurality of links each having an upstream end and a downstream end relative to a direction of travel of the chain is provided. The anti-kickback saw chain comprises a holding link having a first side and a second side, a replaceable tooth adapted to be removably mounted on the downstream end of the holding link, and a safety drive link. The upstream end of the safety drive link is pivotally connected to the downstream end of the first side of the holding link. The safety drive link includes a safety lobe effective to prevent the tooth from being dislodged from the holding link during chain travel, and a substantially flat upper edge.
This application is a continuation-in-part of U.S. patent application Ser. No. 11/337,294, filed on Jan. 23, 2006, which is incorporated herein by reference.
FIELD OF THE INVENTIONThe present invention is directed to the field of saws, machines for cutting or abrading material and replaceable teeth therefore.
BACKGROUNDA variety of devices exist for cutting or abrading materials including masonry, concrete, metal, glass, wood and stone. These devices can employ various implements for cutting or abrading including chain and rotary blades.
In the timber industry, wood is cut, for example, using chain saws and timber harvesters. The particular chain that is used depends on the area and condition of the wood being cut. Normally, steel cutting links having sharp edges are used to cut wood. However, when there is a danger of the chain impacting metal articles in the wood costly carbide tips can be soldered onto the steel cutting links of the chain. This enables the chain to withstand contact with metal articles in the wood without becoming excessively dull. On the other hand, the soldered carbide tips can become dislodged from the steel cutters upon impact with metal articles in the wood.
The sharp edges of all cutting links of saw chain and rotary blades undergo expected wear over time. In the case of chain saws, worn chain is sharpened in the field or replaced with new or sharpened chain, leading to costly down time during the cutting operation or hazard to the worker sharpening the cutting links by hand.
Some attempts have been made to construct chains with removable cutting inserts of various designs typically from steel. These efforts have generally been unsuccessful. Saw chain having removable cutting inserts is currently not used extensively, if at all. U.S. Pat. No. 2,583,243 discloses saw chain including removable teeth wedged into a slot of a head of a link of the chain. U.S. Pat. No. 2,852,048 discloses saw chain with removable teeth having a T-shaped recess that contacts a T-shaped element of a link of the chain. U.S. Pat. No. 3,547,167 discloses a removable cutting sleeve having a recess that receives a stud of a link of the chain.
Cutting links for wood cutting typically are constructed of stamped and machined metal (e.g., steel) and are permanently affixed to other links of the chain. Previously proposed removable cutting inserts were retained on the cutting links using screws or other means. However, so far as the present inventor is aware, such chains do not employ a safety device, apart from cumbersome fasteners or particular engagement between the cutting inserts and cutting links, for avoiding the dangerous condition of the teeth becoming dislodged during operation of the saw.
Another safety hazard posed by cutting links on a saw chain is what is commonly known as kickback. This refers to what happens when a cutting portion on a saw chain digs excessively into the wood as the cutting link moves over the nose of the saw. Under these conditions, the relationship between the cutting tooth, depth gauge and wood surface may cause the tooth to dig deeply into to the uncut surface. When this happens, the cutter link is thrust in a reactionary backwardly motion causing chain movement to stop momentarily. The energy from the moving chain is then thrust upwardly and rearwardly, so as to propel the saw chain guide bar toward the operator.
Various attempts have been made to prevent the problem of kickback, which are disclosed in the prior art. U.S. Pat. No. 4,425,830 provides for a safety link to be disposed between each cutter link to prevent the cutter link from cutting deeply into the wood when coming around the nose of a saw bar. U.S. Pat. No. 4,133,239 provides a saw chain comprising a safety link having an upstanding cam portion with an upstanding and rearwardly inclined leading edge and a rearwardly projecting tail which pivots outwardly as the chain rounds the nose of a saw blade to provide a reduced effective depth gauge for the cutter link to follow.
The proposed preventative solutions are aimed at providing modified safety links before a cutter link that will allegedly stop the cutter from digging deeply into wood. However, it has yet to be contemplated to prevent the actual rollback movement by the cutter tooth itself, and particularly in a saw chain with replaceable cutter teeth. Therefore, it is desirable to provide a saw chain with easily replaceable teeth that is designed with built in safety features, particularly, preventing chain kickback.
SUMMARY OF THE INVENTIONIn accordance with one aspect of the present disclosure, an anti-kickback saw chain including a plurality of links each having an upstream end and a downstream end relative to a direction of travel of the chain is provided. The anti-kickback saw chain comprises a holding link having a first side and a second side, a replaceable tooth adapted to be removably mounted on the downstream end of the holding link, and a safety drive link. The upstream end of the safety drive link is pivotally connected to the downstream end of the first side of the holding link. The safety drive link includes a safety lobe effective to prevent the tooth from being dislodged from the holding link during chain travel, and a substantially flat upper edge.
In accordance with another aspect of the present disclosure, a saw chain including a plurality of links is provided. The saw chain comprise a plurality of holding links each having an upstream end and a downstream end relative to a direction of travel of the chain and a first side and a second side, a plurality of replaceable teeth that include a cutting surface, the teeth being adapted to be removably retained on the downstream end of the holding link, and a plurality of safety drive links comprising a straight back edge. The straight back edge is adapted to limit rollback movement of the tooth and prevent kickback of the saw chain.
In accordance with yet another aspect of the present disclosure, a method of preventing kickback in a saw chain with replaceable cutting teeth is provided, including a plurality of links each having an upstream end and a downstream end in a direction of travel of the chain. The method includes the steps of removably mounting a tooth to a holding link having a first side and a second side; pivotally connecting the upstream end of a safety drive link to the first side of the downstream end of the holding link, the safety drive link comprising a straight top edge, and obstructing rollback movement of the holding link with the straight top edge of the safety drive link to maintain a generally flat cutting plane.
In accordance with another aspect of the present disclosure, a powdered metal rivet is provided. The powdered metal rivet includes a first end having a head portion, a second end opposite the first end and comprising a cylindrical tail portion with a uniform diameter, and a doughnut shaped bearing surface positioned between the first end and the second end. The bearing surface of the rivet comprises powdered metal.
In accordance with another aspect of the present disclosure, a method for preventing kickback in a saw chain comprising a plurality of links, each having an upstream end and a downstream end according to a direction of travel of the chain is provided. The method includes removably mounting a removable tooth to a holding link, providing a safety drive link with a generally semi-circularly shaped rivet hole, the rivet hole including a “V” shaped protrusion extending therein, the protrusion having a first angle, molding a powdered metal rivet having a diameter less than the rivet hole, the rivet having a semi-circular shape with a “V” shaped section missing therefrom, the section having a second angle, and pivotally connecting the upstream end of a safety drive link to the holding link, wherein the “V” shaped portion limits the rotation of the holding link.
Referring now to
The safety links, holding links, drive links and other links of the chain, each include a pair of rivet holes 30. Connector or tie straps 34 along the chain each include a pair of rivet holes 30. Rivets 32 are disposed in aligned rivet holes of the holding links, safety links, drive links, and other links, and the connector straps, which pivotally connect the links together.
The holding links and safety links are used with other links of the chain in any standard wood-cutting or other chain design (e.g., plastic or metal cutting). For example, in wood cutting the cutting links (i.e., the holding links of the invention) may be used in full compliment, semi-skip (half skip) and full skip chains, referring to the number of tie straps between cutting links. The 2003 website by Manufacturer's Supply Inc., which is incorporated herein by reference in its entirety, describes the chain designs as follows: full compliment chain has a first cutter, tie strap and another cutter (e.g., right cutter, tie strap, left cutter, tie strap, right cutter, etc.); semi-skip chain has alternating one and two tie-straps after cutters (e.g., right cutter, tie strap, left cutter, two ties straps, right cutter, etc.); and full skip chain has two tie straps after cutters (e.g., right cutter, two tie straps, left cutter, two ties straps, right cutter, etc.). The inventive holding link is suitable for all chain pitches (defined as the distance between three consecutive rivets divided by two), including ¼, 0.325, ⅜, ⅜ extended, 0.404, % and 0.750 inch pitches. The particular chain shown in
The holding links 20 each include a holding or key member 36 having at least one seating surface. The key member 36 shown in
The teeth are inserted onto the chain by pushing each tooth so that the holding member moves into the tooth recess. The holding member front surface 46 may engage the front tooth recess surface 60 (
A function of the saw chain of the present invention is to enable material to be cut or abraded using teeth that are quickly replaceable and yet safe. In this regard, the teeth advantageously engage the holding members without the need for fasteners (e.g., screws). The teeth can be held in place on the holding members in various ways as would be appreciated by those skilled in the art reading this disclosure. The seating surfaces of the holding members and teeth (e.g. seating surface 39 of the holding member and seating recess surface 61) can be tapered as disclosed in the U.S. patent application Ser. No. 10/780,323, which is incorporated herein by reference in its entirety. These “wedge and taper” surfaces inhibit the tooth from moving in a direction opposite to the chain travel direction. The wedge and taper also inhibit movement of the tooth in the chain travel direction. When the teeth are retained on the holding members with the interacting wedge and taper feature, a specialty tool or hammer is used to remove them in the chain travel direction.
The present invention is not limited to the wedge and taper or other design of holding member and teeth. In fact, in one aspect of the invention the holding members do not prevent movement of the teeth in the chain travel direction. Movement of the teeth 18 in the chain travel direction is prevented entirely by the safety lobes 24. This enables very fast replacement of the teeth without the need for a tool (e.g., specialty tool or hammer) which would otherwise be used to remove teeth held in place on the holding members by engagement of tapers and wedges as described in the 10/780,323 patent application.
The teeth 18 alternate right- and left-handed along the chain (i.e., left-handed tooth, right-handed tooth, left-handed tooth, etc.). Referring to
The features of the replacement teeth 18 used on the saw chain of
The upper surface 204 extends generally vertically and the lower surface 206 extends inwardly at an angle γ of, for example, 5°, for providing clearance of the tooth as it cuts through material (e.g., wood). The seating tooth recess surface 61 is tapered in this particular design, e.g., at angle δ (e.g., 3.000 to 3.125 degrees), which engages the correspondingly tapered seating surface 39 on the holder as disclosed in the 10/780,323 application. Any of the surfaces of the holding member and tooth recess may be tapered as disclosed in the Ser. No. 10/780,323 application.
The teeth and/or holding links can be formed of any suitable cutting, abrading or wear-resistant materials. One suitable material is sintered and compacted particulate material, known as powdered metal as disclosed in the Ser. No. 10/780,323 patent application or known to those of ordinary skill in the art. One suitable material for forming abrading teeth is ceramic such as silicon carbide.
Referring to
Referring to
In a method of safely operating saw chain of the first embodiment, the saw is operated to move the chain by powering the motor to rotate the chain upon engagement of the drive links of the chain with the chain saw sprocket and optional sprocket at the end of the guide bar (not shown) in a known manner. Initially the teeth are all new, sharpened or contain a maximum amount of cutting or abrasion material (e.g., sharpened teeth). The saw is used to cut or abrade the intended material. During operation of the saw, at which time the chain rotates around the bar, dislodging of the teeth from the holders in the chain travel direction is prevented by the safety lobes. This ensures safe operation in that the dangerous condition in which whole teeth are dislodged in the chain travel direction is avoided. Breakage of portions of the teeth may be unavoidable, as occasionally occurs in the breakage of soldered tips from steel teeth. However, this condition can be accounted for with proper safety goggles and other conventional safety equipment and procedures. The saw is operated (e.g., shut off) to stop movement of the chain.
Once it is determined by the user that one or more teeth should be replaced, such as due to damage or wear of the teeth, the safety link is pivoted out of a path of an adjacent tooth needing replacement. Referring to
The saw chain of the present invention may include various modifications that would be apparent to those of ordinary skill in the art in view of this disclosure. In this disclosure like components are given like reference numbers throughout the several views. As shown in
Referring to
Referring to
In the design shown in
In the tooth replacement procedure shown in
Saw chain kickback most frequently occurs when depth gauge or raker 26 and/or tooth 18, positioned at the upper quadrant of the bar nose, dives too deeply into a piece of wood, suddenly transferring power forward. The tooth 18 is then caused to roll backward, stopping the rotation of the chain, which violently transfers energy and momentum of the saw toward the operator of the saw chain. The present embodiment prevents such movement by limiting the backward movement of tooth 18. As displayed in
Particularly, in
Additionally,
Alternatively, or in addition to the above anti-kickback mechanisms, the safety drive link 25 may include a pair of rivet holes and corresponding rivets adapted to further limit the rotation of the holding link. Rather than the traditional circular holes 30, the rivet hole 322 that connects the safety drive link to the holding link, may be generally semi-circular shaped with a “V” shaped portion protruding into the hole. (See
The present rivet formation method is environmentally friendly in that oil does not have to be continuously fed into the rivet. As the rivet warms up, small amounts of oil are placed exactly where they are supposed to be. Previously, channels have been stamped into the links to allow oil to get to the captured area between the barrel of the rivet and the matching hole in the safety drive link. Allowing oil to reach this area is one argument for having larger clearances between the barrel and the hole in the safety drive link.
An additional advantage of powdered metal rivets is that the particle hardness of the material can be very high (about 50-65 Rockwell C), while the apparent hardness may remain low (about 30-45 Rockwell C), the later which lends itself to the forming process of making a rivet head.
The rotation limiting “V” portion in rivet 324 comprises an angle θ1 that is greater than angle θ2 of the generally triangular portion in rivet hole 322. Additionally, it is preferred that rivet hole 322 comprise a larger diameter than the rivet 324, to include clearance for the rivet to rotate. Generally, the best clearance, or tolerance, that current methods can achieve in cold or hot heading is 0.003-0.004 thousandths of an inch. To achieve tighter clearances and therefore less chain wear for traditional rivets, the entire rivet would require machining. However, the rivet 324 presented herein provides a clearance (tolerance) of within 0.001 thousandths of an inch. Therefore, when rivet 324 is inserted into rivet hole 322, the rivet is allowed limited rotation, but the available rotation is less than 360 degrees.
It is further provided that an anti-kickback saw chain including a plurality of links each having an upstream end and a downstream end relative to a direction of travel of the chain is provided that includes a holding link, a replaceable tooth adapted to be removably mounted on the downstream end of the holding link, and a safety drive link having a generally semi-circularly shaped rivet hole, wherein the upstream end of the safety drive link is pivotally fastened to the downstream end of the holding link by a rivet. The rivet is adapted to limit rotational movement of the holding link. The rivet hole further includes a generally “V” shaped protrusion extending into the rivet hole comprising a first angle. The rivet comprises a generally semi-circular shape with a “V” shaped section missing from the circle. The slice comprises a second angle, wherein the second angle is greater than the first angle. The rivet hole has a greater diameter than the rivet to provide rotational clearance (tolerance), which may be about 0.001 thousands of an inch. The rivet includes a head portion, a tail portion, opposite the head portion, and a bearing disposed between the head and tail portions. The bearing is generally doughnut shaped and includes a bearing surface. The bearing surface comprises powdered metal. The bearing surface is designed to accept at least one of oil, grease, and resin impregnation. The anti-kickback saw chain further includes a second rivet capable of sealing the oil in the bearing. The rivet preferably comprises a particle hardness of about 50-65 Rockwell C and an apparent hardness of about 30-45 Rockwell C.
Many modifications and variations of the invention will be apparent to those of ordinary skill in the art in light of the foregoing disclosure. Therefore, it is to be understood that, within the scope of the appended claims, the invention can be practiced otherwise than has been specifically shown and described
Claims
1. An anti-kickback saw chain including a plurality of links each having an upstream end and a downstream end relative to a direction of travel of the chain comprising:
- a holding link having a first side and a second side;
- a replaceable tooth adapted to be removably mounted on the downstream end of said holding link; and
- a safety drive link, wherein said upstream end of said safety drive link is pivotally connected to the downstream end of the first side of said holding link, said safety drive link including a safety lobe effective to prevent said tooth from being dislodged from said holding link during chain travel, and a substantially flat upper edge.
2. The anti-kickback saw chain of claim 1, wherein said safety lobe is disposed near said downstream end of said safety drive link.
3. The anti-kickback saw chain of claim 1, wherein said flat upper edge is adapted to decrease the range of motion and limit rollback movement of the holding link.
4. The anti-kickback saw chain of claim 1, further including a tab extending outwardly from the first side of the downstream end of said holding link.
5. The anti-kickback saw chain of claim 4, wherein said tab is positioned on said holding link to contact the top of said safety drive link and limit rollback movement by the holding link.
6. The anti-kickback saw chain of claim 1, wherein said safety drive link includes an upstream and downstream rivet hole, said upstream rivet hold being generally semi-circular shaped with a “V” shaped portion protruding into said hole, said portion having a first angle.
7. The anti-kickback saw chain of claim 6, further including a rivet having a generally semi-circular shape with a “V” shaped section missing from said circle, wherein said section comprises a second angle.
8. The anti-kickback saw chain of claim 7, wherein said rivet is configured to mate with said rivet hole and secure said safety link to said holding link.
9. The anti-kickback saw chain of claim 8, wherein said first angle is less than said second angle.
10. The anti-kickback saw chain of claim 1, wherein said tooth is removably mounted to said holding link without a fastener.
11. The anti-kickback saw chain of claim 1, further including a safety lobe, extending higher than a depth gauge on said holding link.
12. A saw chain including a plurality of links, said saw chain comprising:
- a plurality of holding links each having an upstream end and a downstream end relative to a direction of travel of the chain and a first side and a second side;
- a plurality of replaceable teeth that include a cutting surface, said teeth being adapted to be removably retained on the downstream end of said holding link; and
- a plurality of safety drive links comprising a straight back edge, wherein said straight back edge is adapted to limit rollback movement of said tooth and prevent kickback of the saw chain.
13. The saw chain according to claim 12, wherein said plurality of holding links each include a tab extending outwardly from the first side of the downstream end of said holding link.
14. The saw chain according to claim 13, wherein said tabs are positioned on said holding links to contact the straight back edge of said safety drive links pivotally connected to said holding links on said first side and limit rollback movement of the holding links.
15. A method of preventing kickback in a saw chain with replaceable cutting teeth, including a plurality of links each having an upstream end and a downstream end in a direction of travel of the chain, comprising the steps of:
- removably mounting a removable tooth to a holding link having a first side and a second side;
- pivotally connecting the upstream end of a safety drive link to the first side of the downstream end of said holding link, said safety drive link comprising a straight top edge; and
- obstructing rollback movement of said holding link with said straight top edge of said safety drive link to maintain a generally flat cutting plane.
16. The method of claim 15, wherein said rollback movement is further obstructed by a tab located on the first side of said holding link.
17. The method of claim 15, wherein said safety drive link is pivotally connected to said holding link by mating a rivet hole with a complementary rivet, said rivet hole being generally semi-circularly shaped with a “V” shaped protrusion extending therein, said protrusion having a first angle and said rivet being generally semi-circularly shaped with a “V” shaped section missing from said circle, said section having a second angle, wherein said first angle is less than said second angle.
18. The method of claim 17, wherein mating said rivet hole with said rivet further obstructs rollback movement by said holding link.
19. A powdered metal rivet comprising:
- a first end having a head portion;
- a second end, opposite said first head, comprising a generally cylindrical tail with a uniform diameter; and
- a doughnut shaped bearing surface positioned between said first end and said second end, said bearing surface comprising powdered metal.
20. A method for preventing kickback in a saw chain comprising a plurality of links, each having an upstream end and a downstream end according to a direction of travel of the chain, said method comprising the steps of:
- removably mounting a removable tooth to a holding link;
- providing a safety drive link with a generally semi-circularly shaped rivet hole, said rivet hole including a “V” shaped protrusion extending therein, said protrusion having a first angle;
- molding a powdered metal rivet having a diameter less than said rivet hole, said rivet having a semi-circular shape with a “V” shaped section missing therefrom, said section having a second angle, larger than said first angle; and
- pivotally connecting the upstream end of the safety drive link to said holding link, wherein said triangular portion limits the rotational movement of said holding link.
Type: Application
Filed: Nov 16, 2010
Publication Date: May 26, 2011
Inventor: David A. Szymanski (St. Mary's, PA)
Application Number: 12/947,165
International Classification: B23D 57/02 (20060101); B26D 1/46 (20060101); B27B 33/14 (20060101); F16B 19/04 (20060101);