Patent Application
20080210056
The invention relates generally to a method and apparatus for blade sharpening. More specifically, the invention provides a method and apparatus for sharpening rotary law mover blades and, in particular, sharpening both clockwise rotating and counter-clockwise rotating blades as well as sharpening both standard and mulching type lawnmower blades.
As civilization has progressed from its primeval beginnings, small groups of people formed mobile communities that worked together to hunt and gather food for themselves. As their knowledge and technology advanced, they became more settled and found ways to cultivate the earth and domesticate animals for their own use and benefit without the need to be constantly on the move. As civilizations advanced further, these groups became larger communities and even large cities for trade, commerce and other activities. These activities generated greater wealth for some individuals such that they could own their own homes and have servants to take care of many, if not all, of the domestic chores such as, but not limited to, washing clothes, cleaning the household, caring for the children, preparing and cleaning up meals and so forth. At some point in time, the exact date being unknown, wealthy home owners decided to hire servants to tend the household yards in order to make more enjoyable use of the property they owned. One of the tasks required to tend the yards was to keep the lawn mowed in a neat and pleasing appearance. At that time, the process for mowing the lawns consisted of hiring a group of servants with hand sickles to cut the lawn by hand. As would be apparent to anyone considering this activity, it was a constant and laborious task to accomplish.
With more advances in technology came manual hand powered lawnmowers and later gasoline powered lawnmowers. It is only in recent history that riding lawnmowers have become available for property owners personal use. While these obvious advances are plain for most individuals to see and appreciate, there have been many more advances that most people are unaware of or take no notice of. These advances include such things as a better means for leveling a power lawnmower desk so as to provide a more even appearance to a cut lawn. Wide, low air pressure filled tires allow a lawn tractor to traverse over most ground surfaces without leaving tire marks in the ground or grass. A better understanding of how to properly cut grass led to a better understanding of the proper blade cutting edge and angle that a lawnmower blade should have. A further advancement was the development of an automatic means for collecting the grass clippings and debris as the lawn was being mowed, typically known as a bagger. This allowed for easy disposal of the clippings and debris and greatly reduced the time for yard maintenance.
As an alternative to collecting the grass clippings and disposing of them, came the development of what is known in the art as mulching lawnmower blades. Mulching lawnmower blades cut the grass into much smaller pieces which, when left back on the ground, decompose quickly and leave their nutrients back into the soil to aid in the growth of new grass. A standard, or non-mulching, clockwise rotating lawnmower blade 1, as shown in
For many people, the use of mulching type lawnmower blades 6 is a preferable alternative as there is no need to spend time and effort to collect and then dispose of the grass clippings and it has the further advantage of returning the nutrients back into the soil for further plant growth.
In addition to the standard clockwise rotating lawnmower blade 1 and the mulching type clockwise rotating lawnmower blade 6, there are also two categories that define the type of lawnmower blade that is utilized in lawnmowers. These are the clockwise rotating lawnmower blades 1 or 6 and the counter-clockwise rotating lawnmower blades 9, of which only the standard blade 9 is shown in
Cutting grass is a very abrasive process. If a user starts with a lawnmower blade, sharpened properly and at the correct cutting angle, as they mow the lawn, the process of cutting grass quickly dulls the sharp cutting edges of the blade. As the cutting edges of the blade becomes duller and duller, instead of cutting the grass the blade starts to tear the grass. This not only leads to an unappealing lawn surface, but can damage the grass thereby increasing the grass' susceptibility to disease.
Consequently, there is a need to sharpen the lawnmower blade or blades on a regular basis. Professional lawn care providers often sharpen their lawnmower blades after every day's use. The same is often true for those individuals responsible for the care of lawns at golf courses and recreational areas such as playgrounds and parks. Individual home owners sharpen their lawnmower blades at their own discretion.
In re-sharpening a lawnmower blade, great care must be taken in a variety of areas. First and foremost is the need for safety. Regardless of the method of sharpening used, care should be taken to securely clamp or hold the lawnmower blade in place so that it does not come loose and injure someone or something. Secondly, if some form of powered sharpening mechanism is utilized, such as bench or disc grinders, there should be a means to trap and arrest any hot sparks resulting from the sharpening process in order to prevent burns or fires. Thirdly, it is important to retain the original angle of the cutting edges of both the primary, 2 and 3, and secondary, 7 and 8, cutting edges in order to maintain the proper grass cutting action. Fourth, when sharpening a lawnmower blade, it is important to maintain the balance of the blade. This means that in re-sharpening a lawnmower blade, all of the cutting edges on a given plane should have the same amount of material removed from them. If not, the high rotary speed of the blade in use can cause the grass to be cut unevenly leading to an unaesthetic appearance. Other areas where care is needed are well known in the art.
The means for re-sharpening a lawnmower blade are varied and numerous. In one method, a user clamps a lawnmower blade in a vice and utilizes a metal file to hand sharpen the blade. However, this can lead to erroneous and uneven cutting edge angles and cause the blade to become out of balance.
U.S. Pat. Pub. 2004/0142645 published on Jul. 22, 2004 to Harold Maus discloses a rotary lawnmower blade sharpener that can be utilized with a bench grinder to sharpen the primary cutting edges of a lawnmower blade. This sharpening device being distinguishable from the present invention in that there is no means provided for sharpening the secondary cutting surfaces of a mulching type blade as the fixture clamps the lawnmower blade about the center where the secondary cutting edges are located and does not allow the center of a mulching type blade to come in contact with the grinding wheel. In addition, the apparatus, as best understood and described, is only suitable for sharpening either clockwise rotating blades or counter-clockwise rotating blades but not both with the same apparatus.
U.S. Pat. Pub. 2004/0244538 published on Dec. 9, 2004 to Johannes Franzen, et al. discloses an apparatus for sharpening multiple blade knives. This sharpening device being distinguishable from the present invention in that there is no means provided for sharpening the secondary cutting surfaces of a mulching type blade as the fixture clamps the lawnmower blade about the center where the secondary cutting edges are located and does not allow the center of a mulching type blade to come in contact with the grinding wheel. In addition, the apparatus, as best understood and described, is only suitable for sharpening either clockwise rotating blades or counter-clockwise rotating blades, depending upon the relative position of the fixture to the grinding medium, but not both with the same apparatus.
U.S. Pat. No. 4,736,544 issued on Apr. 12, 1988 to Lawrence Greenquist discloses a blade holder for sharpening lawnmower blades. This sharpening device being distinguishable from the present invention in that there is no means provided for sharpening the secondary cutting surfaces of a mulching type blade as the fixture clamps the lawnmower blade about the center where the secondary cutting edges are located and does not allow the center of a mulching type blade to come in contact with the grinding wheel. As shown and described, the apparatus depicts the holder as being utilized to sharpen counter-clockwise rotating blades. In order to utilize the device to sharpen clockwise rotating blades, either the fixture or the grinding wheel must be physically removed and repositioned to the reverse side of the work bench which is a laborious and time consuming process.
U.S. Pat. No. 6,761,623 issued on Jul. 13, 2004 to Wayne Baker discloses an apparatus and method for sharpening blades at a predetermined angle. As disclosed, the blade is mounted on a clamping fixture above a disc grinder, the disc grinder being pivotally mounted at its base. This sharpening device, as best understood by the specifications and drawings, being distinguishable from the present invention in that there is no means provided for sharpening the secondary cutting surfaces of a mulching type blade. In addition, the apparatus is only suitable for sharpening either clockwise rotating blades or counter-clockwise rotating blades, depending upon the relative position of the fixture to the grinding medium, but not both with the same apparatus.
It is, therefore, an object of this invention to provide an apparatus and a method for sharpening both standard and mulching style lawnmower blades to the proper cutting edge angle.
It is a further object of this invention to provide an efficient and easy apparatus and method for sharpening both clockwise rotating lawnmower blades and counter-clockwise rotating lawnmower blades.
It is still a further object of this invention to assure the safety of the user and area by trapping and arresting any sparks generated during the process of re-sharpening a lawnmower blade for easy disposal later.
It is still a further object of this invention to make the process of loading, sharpening all cutting edges and unloading a quick, simple and accurate process for the user.
Other features and advantages of this disclosure will become apparent to one skilled in the art upon examination of the following drawings and detailed description. It is intended that all such additional features and advantages be included within the scope of the present invention.
The present invention recognizes and addresses the various drawbacks and limitations of the various apparatuses for the sharpening of lawnmower blades of both the clockwise rotating lawnmower blade type and the counter-clockwise rotating lawnmower blade type as well as sharpening both standard type lawnmower blades and mulching type lawnmower blades. Additional objects and features of the invention are set forth in, or will be apparent to those of ordinary skill in the art, from the detailed description that follows. It should be further appreciated that modifications and variations to the specifically illustrated and disclosed features and materials hereof may be practiced in various embodiments and uses of this invention without departing from the spirit and scope thereof. Such variations may include, but are not limited to, substitutions of the equivalent means, features, and materials for those shown or discussed and the functional, or positional reversal of various parts, features or the like.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and together with the description serve to explain the principles of the invention.
In one exemplary embodiment, there is provided an apparatus and method for sharpening both clockwise rotating blades and counter-clockwise rotating blades at the proper angle comprising a base with a blade fixture that is easily and quickly reversible depending upon the type of blade being sharpened. By positioning the blade fixture in a first position on the base the apparatus is ready for sharpening clockwise rotating blades. By repositioning the blade fixture in a second position on the base the apparatus is ready to sharpen counter-clockwise rotating blades.
Simultaneously, there is provided an apparatus and method for quickly and easily sharpening a primary cutting edge of a blade and then quickly and easily changing the angle of sharpening such that a secondary cutting edge of a mulching style blade can be properly sharpened to a proper cutting angle for the secondary cutting edge. This comprises an adjusting wheel, a spring loaded ball detent and an offset pivotable coupling tied to both the handle shaft and the sharpening mechanism. By turning the adjusting wheel, the pivotable offset coupling changes the angle of the sharpening mechanism which allows a user to easily adjust grinding angles between the primary cutting edge and the secondary cutting edge which are typically about one inch difference in height.
A system and a method according to the invention will be described in more detail by with reference to the appended drawings in which:
Reference will now be made in detail to the description of the invention as illustrated in the drawings. Although the invention is described in connection with the drawings, there is no intent to limit the invention to the embodiment or embodiments disclosed therein. On the contrary, the intent is to include all alternatives, modifications, and equivalents included within the scope and spirit of the invention as defined by the appended claims.
The present invention 10 is primarily concerned with a method and apparatus for sharpening lawnmower blades, and in particular, the sharpening of both clockwise and counter-clockwise rotating blades and with both standard type blades and mulching type blades. As depicted in
If the user makes no adjustments to the cutting angle of the sharpening mechanism 19, attempting to sharpen the secondary cutting edges 7 or 8 of the mulching type lawnmower blade 6 will result in an improper angle of the secondary cutting edges 7 or 8 as the secondary cutting edges 7 and 8 are approximately one inch above the plane of the primary cutting edges 2 and 3 thereby changing the angular relationship of the sharpening mechanism 19 to the secondary cutting edge 7 or 8. In its preferred embodiment, to adjust the angle of the sharpening mechanism 19 quickly and easily, in order to sharpen the secondary cutting edges 7 and 8 of a mulching type lawnmower blade 6, a user turns the adjusting wheel 32 which in turn causes the offset pivotal coupling 28 to push outward or pull backward, depending upon the direction the adjusting wheel 32 is turned, which causes the sharpening mechanism 19 to re-angle itself relative to the lawnmower blade 6. Once the sharpening mechanism 19 is set at the correct angle for the secondary cutting edge 7 or 8, the user then powers up the sharpening mechanism 19 and moves the sharpening mechanism 19 along the direction indicated by the arrow 63 to sharpen the secondary cutting edge 7 or 8.
The user then removes the blade clamp 58, rotates the lawnmower blade 6 180 degrees, repositions the lawnmower blade 6 parallel to the blade fixture 20 and abutting the blade stop 61 and re-attaches the blade clamp 58. The user can then power up the sharpening mechanism 19 to sharpen the other secondary cutting edge 7 or 8, turn the adjusting wheel 32 back to its original position and re-sharpen the other primary cutting edge 2 or 3. When the blade sharpening is completed and the sharpened lawnmower blade 6 removed from the blade fixture 20, the spark trap 24 can be removed and the trapped debris properly disposed of.
In the alternate handle design 64 depicted in
The tapered blade fixture adapter 22, shown in
Although the preferred embodiments of the invention has been described using specific terms, devices and drawings, such description is for illustrative purposes only. The words and terminology used are words of description rather than of limitation. It is to be understood that changes and variations may be made by those of ordinary skill in the art without departing from spirit and scope of the present invention, which is set forth in the following claims. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiments contained herein.
