Metal tools and implements – making – Blank or process – Cutlery
Patent
1980-02-13
1982-06-22
Parker, Roscoe V.
Metal tools and implements, making
Blank or process
Cutlery
144 34E, 29416, 72203, B21K 1900
Patent
active
043356311
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a method for making shear blade or cutting assemblies. More particularly, the invention relates to a method whereby blade surfaces are first cut on a blank followed by forming the blank into a desired shape before dividing it to form separate blade portions.
BACKGROUND ART
Tree harvesters are in extensive use to hold and cut trees and transport the harvested product to a desired location. Such tree harvesters commonly use a shear blade assembly which has two blade portions each with a cutting edge. The blade portions are urged into opposite sides of a tree in order to sever the trunk for harvesting purposes. The operation and details of such a tree harvester are shown, for example, in U.S. Pat. No. 3,797,539 which issued to Moser et al. on Mar. 19, 1974.
It has become increasingly common to form such shear blade assemblies in a concave, cylindrical or spherical configuration in order to minimize damage to the trees to be cut and to carry cutting loads through the assemblies in a more efficient manner. Such curved blades assemblies are disclosed in U.S. Pat. Nos. 4,069,847 which issued to Wirt on Jan. 24, 1978, and 4,131,145 which issued to Puna on Dec. 26, 1978, and also in Canadian Pat. No. 840,776 which was granted to Brundell and Jonsson AB on May 5, 1970.
Heretofore, such dish-shaped blade assemblies have been manufactured either by depressing a blank to a desired shape, dividing it into first and second portions and then machining cutting edges along the resultant curved edges or by individually making the first and second blade portions from separate pieces of flat plate. The latter method is disclosed briefly in U.S. Pat. No. 3,690,353 which issued to Johnston et al. on Sept. 12, 1972. Where the cutting edges are machined along the curved surfaces, special machining techniques are required to maintain a constant chamfer or beveled edge which is critical to the operation of the curved blades. Where the blade portions of the shear blade assembly are formed separately, there can be some problem with uniformity between portions, as well as duplicate manufacturing operations.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF INVENTION
In one aspect of the present invention, a method for making a shear blade assembly includes cutting first and second surfaces on a blank. Next, a generally concave shape is formed in the blank by depressing the blank and first and second blade portions are formed by dividing the blank along the web.
In manufacturing a shear blade assembly, the first and second surfaces must be precisely and uniformly cut in order to form the cutting edges associated with the blade portions. Where such surfaces are cut along the curvature resulting from and following the step of depressing the blank or individual blade portions, it is difficult to maintain necessary tolerances without special machining operations. The present method allows the cutting edges to be made first and then the blank as a whole to be depressed to a desired, uniform, concave shape across the cutting edges.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a diagrammatic plan view of one embodiment of a shear blade assembly which can be made with the method of the present invention and which is associated with a tree harvester;
FIG. 2 is a diagrammatic cross sectional view of the shear blade assembly of FIG. 1 as it appears at a step of manufacture with one embodiment of the method of the present invention;
FIG. 3 is a diagrammatic cross sectional view of the shear blade assembly of FIG. 1 as it appears during another step of manufacture subsequent to the step shown in FIG. 2;
FIG. 4 is an enlarged diagrammatic cross sectional view of the area associated with the cutting edges of the shear blade during manufacture with the method of the present invention; and
FIG. 5 is an enlarged diagrammatic cross sectional view of the area associated with the cutting edges of the shear blade during manufacture with another embodimen
REFERENCES:
patent: 2016770 (1935-10-01), DeBats
patent: 3690353 (1972-09-01), Johnston et al.
patent: 3797539 (1974-03-01), Moser
patent: 4061167 (1977-12-01), Dunn
patent: 4069847 (1978-01-01), Wirt
patent: 4131145 (1978-12-01), Puna
Webb Arthur A.
Wirt Leon A.
Caterpillar Tractor Co.
Heming William B.
Parker Roscoe V.
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