Harvesters – Cutting – Cutter members
Reexamination Certificate
1999-05-12
2001-02-06
Will, Thomas B. (Department: 3671)
Harvesters
Cutting
Cutter members
C056S017500, C056SDIG001
Reexamination Certificate
active
06182430
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to lawnmower blades, and more specifically, a replaceable insert for a rotary lawnmower blade.
2. Description of the Related Art
In the past, the sharpening of a mower blade required the removal of the entire blade. Once the blade was removed, a new edge could be ground or filed onto the blade. The blade would then have to be remounted onto the shaft. This procedure is difficult and time consuming. Various types of replaceable cutters have been proposed to avoid the resharpening and eventual loss of the rotary blade. Such replaceable blades have presented problems of one type or another with regard to the requirement of complex fabrications, strength of the replaceable cutter, weakened resistance to damage by foreign objects, and costs. In addition, there is the difficulty associated with stabilizing the blade in light of significant centrifugal forces, which fatigue the fasteners, bolts, rivets, etc. between the separable cutting edge and the main blade assembly.
Another problem with the blade assemblies of the prior art having separable cutting edges, is that the force of impact with an obstruction such as a rock or a root causes undue strain on the fasteners connecting the separable edge to the main blade assembly.
Related art blades having separable cutting edges sometimes require 5 horse power or more simply to rotate the blade due to the weight of the cutting edge attachments. Similarly, the separable cutting edge of the prior art is typically thicker and the blade assembly, to which the cutting edge is attached, requires larger bolts due to the lack of a stabilizing recess, which further increases the weight and thus the required horsepower. Finally, the problem with having a separable cutting edge retained by fasteners alone, as opposed to by a recessed shoulder, is the additional trouble involved with changing the blades, and the tools required to do so properly.
The present invention addresses the above problems that are evident in the following patents:
U.S. Pat. No. 4,229,933 issued October 1980 to Bernard discloses a separable mower blade having a slotted hole on the mower blade for reception of a bolt. The blade and stem are constructed so as to allow easy removal of the blade. However, Bernard does not disclose a recess and shoulder on the main blade assembly for reception of the cutting blade, and therefore, the bolt carries the load created by the spinning of the assembly, rather than the walls of the recess carrying the load.
U.S. Pat. No. 3,327,460 issued September 1964 to Blackstone teaches a blade assembly for a rotary mower that includes separable cutting blades but not inserts per se.
U.S. Pat. No. 5,303,535 issued April 1994 to Smith shows a mower blade with a separable cutting surface but no outside shoulder to counteract centrifugal force as in the present invention, and it requires large bolts requiring tools, to hold the cutting surface in place.
U.S. Pat. No. 5,467,586 issued November 1995 to Lin et al. teaches a replaceable cutting blade having multiple parts including a cover plate, multiple fasteners, but no outside shoulder.
U.S. Pat. No. 4,712,364 issued December 1987 to Oxley discloses a quick attachable and detachable mower blade assembly. U.S. Pat. No. 2,932,147 issued June 1957 to J. T. Beeston, Jr. shows an expendable cutting blade for a rotary mower. U.S. Pat. No. 2,898,725 issued August 1959 to J. F. Roesel discloses a rotary mower blade assembly having retractable blades. U.S. Pat. No. Re. 31,542 issued March 1980 to Hetrick shows a safety attachment for lawn mowers. British Pat. No. GB 2 036 524 to Houle, published July 1980 to Houle teaches a safety blade made from comminuted waste rubber.
U.S. Pat. No. Des. 357,691 issued April 1995 to Bryant illustrates a design patent for a one-piece lawn mower blade.
U.S. Pat. No. Des. 289,524 issued April 1987 to Andersson et. al. shows another design not suggestive of the present invention.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a lawnmower blade solving the aforementioned problems is desired.
SUMMARY OF THE INVENTION
The invention is a lawnmower blade replaceable cutting edge insert for a rotary lawnmower, disposed upon a support member at each end of a main blade which is, of course, rotatable about a central axis. Of particularly concern is the blade's lower surface, i.e., the one facing the ground. The blade lower surface has a substantially rectangular recess within a front, outside corner of the support. The recess is defined by a back shoulder, a blunted front edge, an inside shoulder, and an outside shoulder, opposite the inside shoulder. The outside shoulder extends from the back shoulder along a portion of the outside edge, but does not extend all the way to the blunted edge, so as to form an insert release passage along the outside edge.
Two threaded preset Allen bolts protrude from the floor of the recess. The bolts are permanently locked into position so the bolt heads remain above the recess floor a dimension substantially equivalent to the recess depth. The bolts are not specifically designed to carry the blade load. The back and outside shoulders of the recess provide most of the force necessary to retain the insert against rotational and centrifugal forces of the blade.
A cutting edge insert having substantially the same profile as the recess slides in and out of the recess, maintaining an interference-type friction fit between the preset bolt and the floor of the recess. The insert has a featheredge that transitions into a razor-sharp cutting edge along its bottom surface. The cutting edge cantilevers slightly over the blunted edge. The insert has a release tab receivable within the insert release passage so as to form an outer-most segment of cutting edge. The release tab is flush with the outside edge of the support, enabling a user access so that he or she can use the tab to easily tap the insert out of position when it is ready to be replaced. Moreover, the passage enables an extension of the cutting edge all the way to the outside edge of the blade support. The insert itself is shorter in length than the recess so that it can be slid in and out of its cutting position with the aid of a slotted hole in the insert which acts as a guide, just as the recess acts as a track.
As the lawnmower is started, the outside shoulder and bolts simultaneously provide a retaining centripetal force against the insert. The back shoulder provides a retaining force against the insert in a direction normal to a longitudinal axis of the blade assembly.
To change the cutting edge insert, its release tab is tapped lightly to disengage the insert from the outside shoulder until the hole on the slotted hole lines up with the preset bolt, at which point the insert can be removed from the recess. A new insert can then be hand-placed onto the recess, and similarly slid into place.
Accordingly, it is a principal object of the invention to provide simplicity in maintaining a razor sharp lawnmower blade that is always in balance during operation of the lawnmower.
It is another object of the invention to provide a cutting edge insert for a lawnmower blade assembly that can be lightly tapped in and out of place on the blade assembly while the motor is off, and one that requires no special tools, fasteners, or knowledge to change or to install.
It is a further object of the invention to provide inserts that are interchangeable on the lawnmower blade assembly, i.e., there is no right or left insert.
Still another object of the invention is to provide a lawnmower blade insert such that there would not be a need to remove the main blade assembly to sharpen the cutting edge.
REFERENCES:
patent: Re. 31542 (1984-03-01), Hetrick
patent: D. 289524 (1987-04-01), Andersson et al.
patent: D. 357691 (1995-04-01), Bryant
patent: 2869311 (1959-01-01), Beeston, Jr.
patent: 2898725 (1959-08-01), Roesel
patent: 2932147 (1960-06-01
Blarek James A.
Nemke David A.
Litman Richard C.
Petravick Meredith C.
Will Thomas B.
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