US 2825968 A
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KNIFE BLADE Filed sept. '6; 195e uflnlllllllllw Ill mm I-bWHHHHlIHHL ...IIIHHIIIIM WHHHUIII IN V EN TOR. cr M 541s? United States Patent O M KNIFE BLADE Albert M. Baer, New York, N. Y., assignor to Imperial Knife Associated Companies, Inc., New York, N. Y., a corporation of Rhode Island Application September 6, 1956, Serial No. 608,266
1 Claim. (Cl. 30-355) This invention relates to a knife blade. More particularly, my invention pertains to a knife blade of the type which is employed in the slicing of food such, for example, as a steak knife, a vegetable knife or a carving knife. v
For many years the eld has experienced considerable diiculty in providing a slicing knife which had and could maintain a keen cutting edge. It was possible to so treat the blade and to pick steels of such constitution that the edge was hard and tough. Nevertheless, at the extreme hardness which it was desirable to impart to such blades, there was a tendency toward brittleness. If this tendency was counteracted by having the blade comparatively thick immediately in back of the cutting edge, it was not possible to secure an acute, and therefore extremely keen, edge. On the other hand, if the cutting blade was reduced in thickness immediately in back of the cutting edge as by employing a tapered, e. g., a h-ollow-ground, blade the cutting edge would chip, tear and bend under normal conditions of use. This was particularly, although not exclusively, true of blades which had been brought to a high Rockwell C, e. g., 56 to 6l. These blades, even though tempered, had to be handled with care, especially when they were cutting foods resting on a hard surface.
It has been proposed to make the edge irregular as by the use of either tiny or gross serrations. However, until the present, the cutting edge provided on serrated blades has never been suiciently keen and, indeed such blades do not perform a true shearing action but rather function by means of sawing, i. e., tearing, so that the resulting surface of the food is minutely or grossly scratched and is not as smooth as is desired.
It is the object of the present invention to provide a cutting blade which avoids all of the foregoing defects.
More particularly, it is an object of the present nvention to provide a cutting blade of such character that, even if extremely hard, is so configured that it will not tend to chip, tear or bend if used in an ordinary manner.
It is another object of my invention to provide a blade of the character described which, although particularly thin immediately in back of the cutting edge, is still sufficiently sturdy to reinforce the cutting edge and thereby inhibit chipping, tearing vor bending thereof so that the cutting edge has a long, useful life.
It is another object of my invention to provide a blade of the character described which, although serrated, does not sever by sawing or abrasion and therefore leaves a clean-cut surface.
It is another object of my invention to provide a serrated blade of the character described, each portion of the cutting edge of which shears rather than saws.
Other objects of my invention will be in part obvious and in part will be pointed out hereinafter.
My invention accordingly consists in features of construction, combinations of elements and arrangements of parts which will be exemplified in the knife hereinafter 2,825,968 Patented Mar. 11, s
described and of which the scope of application will be indicated in the appended claim.
In the accompanying drawings, in which is shown one of the various possible embodiments of my invention,
Fig. 1 is a plan view of a knife constructed in accordance with my invention;
Fig. 2 is a similar view of the opposite side of the knife;
Fig. 3 is an enlarged sectional view taken substantially along the line 3 3 of Fig. l; and
Fig. 4 is a highly enlarged view in plan of a fragment of the blade in the vicinity of the cutting edge.
Referring now in detail to the drawings, the reference numeral 10 denotes a roast slicer embodying my invention. Said slicer includes the usual handle 12 in which there is inserted a tang (not shown) of a steel knife blade 14, the tang being secured in a conventional fashi-o-n as by means of a pair of rivets 16. The blade preferably is tempered and has a hardness of about 56 to 61 Rockwell C.
The blade is quite long, as is usual in the art, and its blunt upper edge 18 is curved slightly upwardly, as at 2t), near the tip. The lower longitudinal part of the blade is tapered on both faces, as by hollow-grinding, this consisting in the provision of an outwardly concave section having its upper edge 22 running longitudinally of the blade at approximately the longitudinal center line and its lower edge at the cutting edge 24 of the blade. The degree lof concavity is comparatively slight, the purpose thereof being to have the opposite faces of the blade approximately parallel and very close to one another at the cutting edge whereby a minimum thickness is created at this region while the back of the knife from the blunt upper edge 18 to the edge 22 reinforces the hollow-ground region. The knife is hollow-ground on both sides as will be seen from inspection of Figs. 1-3. The hollow-grinding is performed with the aid of a conventional apparatus and in a conventional manner as, for example, by slowly traversing the blade longitudinally past and in engagement with a properly positioned grinding wheel.
After the blade is hollow-ground or otherwise tapered toward the cutting edge as by flat grinding or by stamping, rolling or molding, the thin cutting edge 24 thereof is scalloped, i. e., provided with a series of end-to-end outwardly concave segments. Although the specic dimensions of these segments are not of critical importance, I have obtained excellent results with segments that are approximately @is of an inch long and approximately IKM of an inch deep. Each segment desirably is of circular conguration although this is not absolutely essential for satisfactory performance of my invention. It thus will be seen that the cutting edge consists of a linear set of spaced cusps 26 linked by short segmentally circular outwardly concave spans 28.
Each of said spans is so treated on one face of the blade, as, for example, by grinding, so as to form an acutely inclined flank 30 whereby the lower edge of the blade is acutely tapered in a chisel like section to cutting sharpness. Preferably the anks 30 of the cutting edge are smoothed after they have been formed to provide the sharpened cutting edge so that any burrs or steel shreds that may be present in said edge are removed. The flanks of adjacent spans meet at the ends of the spans to dene ridges 32 extending from the cusps upwardly toward the edge 18.
It now will be apparent that the cutting edge, instead of being straight, as is conventional in one type of blade, or instead of consisting, as is conventional in another type of blade, of a keen cutting edge interrupted by blunt serrations, has a scalloped cutting edge which is keen over the entire length of every individual scallop. This meansthat when the blade is sliced through material each portion of each concave cutting span slices into rather than tears the material being cut, to leave a at, clean, cut surface.
This type of cutting edge has been found to be far more effective than a straight cutting edge. The irnprovement is believed to be due in part to the increased effective length of cuttingV edge and in part to the differentv angles atwhich successive portions of the edge are presented to the material being cut. When a straight cutting blade is drawn through material the actual cutting is due to the downward movement of the blade, i. e., movement perpendicular to the cutting edge. The aXial translation of the blade does not cause the cutting except insofar as the blade maybe minutely serrated so as to saw through the material. On the other hand, when the blade consists of a scalloped edge in which each scallop is keen and the blade is drawn through material toybeV cut, while the blade is being translated axially, it is also cutting,r the cutting taking place at angles perpendicular to the curved sections of the sharp concave spans.
I also have found' that a blade of the foregoing construction has a longer useful life than a conventional straight cutting blade, this being due, it is believed, to the fact that cutting shifts from point to point along each of the concave cutting spans and further to the fact that the extremely thin sharp cusps are backed up and reinforced by the heavier section of the tapered, i. e., hollow-ground, blade immediately above it and by the heavier section of the hollow-ground blade which backs up the center of the concave cutting spans. In this fashion I am able largely to prevent the chipping, tearing and bending that is inherent in an ordinary straight, cutting blade, and particularly in a hard cutting blade.
It thus will be seen that I have provided `a knife blade which achieves the various objects of my invention and are well adapted to meet the conditions of practical use.
As various possible embodiments might be made of the above invention and as various changes might be made in the embodiment above set forth, it is to be understood that all matter herein described or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.
Having thus described my invention, I claim as new and desire to secure by Letters Patent:
A tempered hard elongated steel knife blade having a. thick blunt upper longitudinal edge and a sharp lower serrated edge, said knife being hollow ground on both faces thereof from a zone between said longitudinal edges and as thick as said upper edge to a thin zone immediately above said lower serrated edge, said serrated edge consisting of a set of spaced pointed cusps linked by short segmentally circular downwardly concave spans, each span being flat ground over its entire length from the thin zone to the sharp lower edge to form on one side of the knife only flanks of chisel-like section which are of uniform contour over the full length of each span and thereby sharpen the lower edge of the knife, the llank of each span intersecting the tlanks of adjacent spans at the ends of each span to define ridges running upwardly from the cusps to the thin zone.
References Cited in the tile of this patent UNITED STATES PATENTS 1,254,563 Anderson Jan. 22, 1918 2,002,812 Hansen May 28, 1935 2,596,851 Hansen May 13, 1952 2,636,267 Whitcomb Apr. 28, 1953 2,671,267 Michalek Mar. 9, 1954 FOREIGN PATENTS 592,234 Great Britain Sept. 1l, 1947