Patent Application
20080011145
In the accompanying drawings, which illustrate an exemplary embodiment of the present invention:
In
A portion of the periphery of slasher disc 14 is shown in
Plate 26 is elongated and flat, having guide slots 28 and 30 in its front and rear edges, respectively. A rounded indentation 32 cooperates with indentation 18 and dowel 20 to fix the tooth in place. The top of plate 26 angles radially inwardly from the front to the back of the plate.
Blade 24 is shaped to have a front surface comprising a first planar side face 34 and a second planar side face 36 that each meet with a planar central face 38 extending generally radially along the front blade surface. Side faces 34 and 36 extend sidewardly and forwardly from central face 38 to side edges 40 and 42, respectively. Edges 40 and 42 extend radially outward to a greater extent than does central face 38, so that the blade face has an inverted trapezoid shaped recess at the top surface. As described below, edges 44 and 46 of the top surface are the primary cutting edges of the blade, and edges 40 and 42 establish the width (or kerf) of the cut. Connection of the side edges 40 and 42 by the cutting edges 44 and 46 is completed by a linear edge segment 45 extending parallel to the disc axis between the cutting edges 44 and 46.
Cutting points 48 and 50 are formed, respectively, by the intersection of edges 40 and 44 on one side and by edges 42 and 46 on the other side. As the slasher disc 14 rotates, points 48 and 50 are first to contact the wood, piercing and shearing wood fibers running longitudinally along log 12 (i.e. perpendicular to the cut of slasher 10). As the disc rotates, shearing continues along edges 44 and 46 which are angled rearwardly and radially inwardly from the points. Specifically, radial inward angling is demonstrated by angle a formed between the central face 60 of the top surface and each of the side faces 58 and 56 thereof within the plane of the front surface central face 38. Angling rearwardly away from the direction of rotation R is demonstrated by angle β formed between the central face 38 of the front surface and each of the side faces 24 and 36 thereof within a plane extending through the blade parallel to the disc axis and normal to the front surface central face 38. Angles αand βare each preferably between 145° and 165° and most preferably about 155°.
Blade 24 is wider and extends further radially than does plate 26, and blade 24 includes various beveled surfaces to provide a smooth transition to plate 26. Specifically cutting or back clearance is provided at the sides of the blade by a beveled surface 52 (
The angle selection is important in making the saw tip durable as well as effective in severing wood fibers. Specifically, the front-to-rear taper (angle π) and the top-to-bottom taper (θ) on the side surfaces, as well as the bevel on the top (angle Γ), allow clearance. The side face angles α and β of the top and front surfaces respectively determine the sharpness of cutting points 52 and 53.
Preferably the tooth width is about 10× to 1× the length of the wood fibers being cut. The resulting chips are large, integral pieces of wood, reducing the heat and binding caused by excessive sawdust. In particular, the tip enables ejection of the chip, and avoids the need for a so-called “raker”, a blunt, non-cutting tooth that clears the area cut by previous teeth.
Blade 24 is configured to fit into a slot in the front of plate 26 and around the sides of the plate. As best shown in
The alternate embodiment depicted in
The use of flat bottom surface 65 which mates with a notch on plate 26, as illustrated in
The following description of Manufacture and Operation applies generally to each of the embodiments described above.
Blade 24 is hard tungsten carbide, made by known techniques. Specifically, blade 24 is made by compressing the ingredients in a mold of the desired form and then sintering to fuse the ingredients using techniques known in the art. Plate 26 is made by investment casting or by traditional wrought manufacturing methods known in the art. Blade 24 is seated in the slots on the front of plate 26 and brazed in place.
When a number of blade/plate assemblies are fixed in the slots of a saw disc, the slasher can be operated by standard techniques to produce a wood product useful in pulp manufacture. Spacing between the teeth can be the same as is used for a given rotational velocity with conventional teeth.
The shape of the blade tip of the tooth of the present invention also has improved strength over those of Applicant's previous patent. The concave or double beveled top surfaces of the prior art tooth blades created reduced thickness, or length, measured rearward (with respect to the direction of disc rotation) from the front surface at a midplane of the tooth. From the figures it should be appreciated that the blade 24 of the present invention is uniform in this dimension across the central face 60 of the top surface from one side face 56 to the other 58. The blade is also uniform in thickness along the central face 38 of the front surface from the bottom surface to the top surface. This avoids weakness along the midplane of the blade tip 24 normal to the disc axis which may lead to premature failure of the part. For example, the tooth of Applicant's U.S. Pat. No. 4,765,217 having concave front and top surfaces was found to have a tendency in some circumstances to break in the center, causing one half of the blade tip to come off the plate.
The chip ejector 68 of the blade tip of the second embodiment acts like a scoop to carry wood chips along the cut for ejection therefrom to prevent chips removed from the body of wood from sliding along the central face 38 of the front surface past the bottom surface 65 where it may become jammed between the plate 26 and the wood on each side of the cut. Such an occurrence causes friction which builds up heat and may cause the saw blade to expand on the outer rim, thereby modifying the tension of the saw blade. The tension of the saw blade is critical for proper operation of the saw blade. The chip ejector helps prevent heat buildup due to friction to keep the saw as cool as possible to maintain a relatively high level of performance. The smooth transition between the curved chip ejector lip and the side faces of the front surface avoids the formation of sharp corners therebetween which may cause chips to become trapped on the front surface and prevent proper ejection from the cut. As explained above, unwanted retention of chips can induce friction and associated problems.
Other embodiments are within the following claims. For example, the saw disc 14 may include integral flanges to support the blade tip, thus avoiding the need for a separate plate such as plate 26. Also, the blade tip may be included on a large disc that can be oriented horizontally to fell standing trees. A cross-cutting saw having a blade disc with generally rounded recesses, as taught in Applicant's U.S. Pat. No. 4,765,217 which is hereby incorporated by reference, may use blade tips as taught in the above detailed embodiments.
Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.
