Patent Publication Number: US-4841825-A

Title: Saw chain with wrap-over depth gauge

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to saw chains for chain saws. 
     Chain saw equipment typically used for heavy workload operations, as for example, equipment used in tree falling machines, frequently is of the straddle-chain type. The chain runs on a one-piece non-grooved guide bar, over which the chain links fit as they travel around the bar. The cutting links typically are of relatively large pitch, for example, they may be of of two and one-half inch pitch. This type of chain makes it possible to achieve a complete balance of cutting forces on both sides of the saw bar, which is important for large pitch cutters and allows use of roller chain technology in the chassis portion of the chain. 
     Prior art cutters of this type have experienced deficiencies in service. Such prior art cutters have had side portions, or flanks, connected together by welding a portion of round bar stock between them to create a set spacing. A cutting element is typically mounted on one of the side portions. The welding, however, created a weak point which often caused the cutting element to break away from the flank while experiencing a cutting load. 
     Accordingly, it is a principal object of the present invention to provide a cutting link for a large pitch saw chain that will eliminate the need for any welded portion, thus to eliminate any weak points in the cutter. 
     A further object of the present invention is to provide a cutter of the aforementioned type for use in heavy workload operations which will not be subject to failure under cutting loads. 
     A still further object of the present invention is to provide a cutter of the aforementioned type that will have the advantage of reduced manufacturing cost because fabrication expense associated with welding several components together will be avoided. 
     SUMMARY OF THE INVENTION 
     The cutting chain of my invention includes a plurality of links. Predetermined ones of such links include a cutting portion mounted on one of a pair of spaced-apart, longitudinally-extending planar side portions which are adapted to straddle a guide bar support means. The side portions provide a means for connecting the cutting links to other links in the chain, for example, to roller chain links, which are used to connect the cutters into a continuous loop. 
     The cutting portion comprises a cutting tooth integral with the aforesaid one of the spaced-apart longitudinally-extending side portions. The tooth has a generally transversely-extending cutting edge. The cutting edge extends toward the other of the spaced-apart longitudinally-extending side portions. 
     The longitudinally-extending side portions are interconnected by a cross-piece forwardly of the cutting portion. The cross-piece and the side portions forwardly of the cutting portion form a continuous U-shaped zone. The zone defines a folded-over depth gauge which determines the depth of cut of the cutting portion. 
     A saw chain link having a folded-over depth gauge portion is disclosed in the patent application of Michael D. Harfst, Ser. No. 07/086,640, filed Aug. 18, 1987, now U.S. Pat. No. 4,813,323, issued Mar. 21, 1989. The subject matter of that invention and the instant invention were, at the time the instant invention was made, owned by or subject to an obligation of assignment to the assignee of the instant invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of saw chain cutting apparatus in accordance with the present invention; 
     FIG. 2 is a side elevational view, with parts broken away, of the apparatus of FIG. 1; 
     FIG. 3 is a sectional view taken on line 3--3 of FIG. 2; and 
     FIG. 4 is a sectional view taken on line 4--4 of FIG. 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, saw chain cutting apparatus 10 according to the present invention includes a plurality of links 12, 14 connected to form a straddle chain 16 adapted to ride over a guide bar 18. The chain 16 and bar 18 are of a type suitable for heavy workload operations, as for example, tree falling machines. 
     Links 12 in chain 16 are the cutting links in the chain. Links 12 comprise a pair of spaced-apart longitudinally-extending planar side portions 20, 22 which are adapted to straddle bar 18 as shown. A cutting portion 24 is mounted on portion 22. Cutting portion 24 comprises a cutting tooth 26 formed integrally with portion 22. Tooth 26 has a generally transversely-extending cutting edge 28 which extends across guide bar 18 toward the other side portion 20 of link 12. 
     A cross-piece 30 forming a continuous U-shaped zone 32 interconnects portions 20, 22 forwardly of cutting portion 24. Cross-piece 30 slopes toward guide bar 18 forwardly of cutting tooth 26 such that zone 32 functions as a depth gauge to determine the depth of cut of cutting edge 28. A depending nose tab 34 integral with zone 32 serves to close off a portion of the forward open channel between portions 20, 22, thereby to minimize accumulation and packing of sawdust under zone 32. 
     Side portions 20, 22 provide means for connecting links 12 to inner links 40 which themselves are interconnected by side plates 42 to form chain 16. Each of links 40 comprises a pair of side plates 44 interconnected by rollers 46, which latter are adapted to ride on a center portion 48 of bar 18 as shown. The latter is undercut to form shoulders 50 to accommodate portions 20, 22 of links 12. Links 12 and 40 and side plates 42 are interconnected by rivets 60 having peened-over heads 62, thereby to create the necessary articulation for the chain. 
     In a preferred example rivets 60 are set at a pitch of 21/2 inches. Links 12 are made of 0.250 inch thick heat treated spherodized annealed 4140 steel. The cutter link is made by cutting the desired shape from plate material and subsequently forming it in a punch press die to the desired folded-over configuration. The high point 64 of cutting edge 28 of tooth 26 extends outwardly (upwardly as shown in FIGS. 2, 3 and 4) of the top point 70 of cross piece 30 a distance of 0.24 inch. Cross piece 30 may desirably extend 11/8 inches in a longitudinal direction along zone 32, the slop of zone 32 being 16 degrees toward the center line of chain 16. The height of portions 20,22 is 0.700 inch. Link 12 is four (4) inches long. 
     My integral link, with opposed, substantially parallel, plate sides, provides a four-point support for the cutter as it rides on the rail of the bar 18. The bottom portions of the cutter links 12 under the ends of the four rivets 60 all rest on the shoulders 50 of the bar 18 to provide stability and support for the cutting tooth 26 during operation. 
     My improved saw chain is not limited to an embodiment that runs on a guide bar. The chain can also be wrapped around and secured to the periphery of a disk to form a circular saw. In this case the chassis of the chain is snugly received in a groove in the disk periphery and rotates with the disk. 
     Having illustrated and described a preferred embodiment of my invention, it should be apparent to those skilled in the art that the invention permits modification in arrangement and detail. I claim as my invention all such modifications as come within the true spirit and scope of the following appended claims.