In-situ blade sharpener

Abstract

A blade sharpening device easily connectable to a source of rotating power, such as a battery powered hand drill, and having a housing, a selectably locatable pitch adjuster and a clamping mechanism means for maintaining the housing and grinding surfaces of the sharpening device at a desired grinding angle. The housing extends completely over the width of the rotatable drums wrapped with grinding surface. By clamping the device directly to the blade and stabilizing the device in this position, the operator has greater control and stability of the sharpener when in use on, for example, a lawn mower blade which is still attached to the lawn mower drive shaft at the underside of the lawn mower housing. This on-site, in-place blade sharpening capability eliminates the necessity of removing the blade for its sharpening, while still allowing easy and safe sharpening of the blade.

Description

CROSS REFERNCE TO RELATED APPLICATION

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

The present invention is directed to blade sharpening devices in general and more particularly to blade sharpening devices suitable for on-site, in-place use on blades which are, for example, attached to a driving member, such as, for example, a lawn mower blade, and even more particularly to such a device which has a safety guard and associated means for allowing the operator to manually control the positioning and movement of the sharpening device. In additional to the preferred, exemplary application of lawn mower blades, the device can be used to sharpen other devices, such as, for further example, garden tillers, shovels, hoes, as well as scythes, cane knives, sweepers, bladed “weed eaters”, bush hogs, etc.

It is often the case with a mechanically powered blade, such as the blade of a conventional rotary mower, that from time-to-time the edge of the blade will require sharpening. The sharpening of the blade edge increases the cutting efficiency of the blade by allowing the edge of the blade to cut the item intended instead of tearing the item as a blunt edge will do.

One problem with maintaining a sharp edge on such a blade is the inconvenience involved in removing the blade from its driving member in order to sharpen the blade on a blade sharpening device, such as, for example, a bench mounted grinding wheel. It would be better, therefore, to have a blade sharpening device which is portable and capable of use on the blade in-place, while the blade remains attached to its driving member.

There are many portable devices known. However there remains problems with such devices due to, inter alia, problems of safety, the ability to monitor the edge sharpening while it is in progress, and accuracy in controlling the angle of the edge being ground since the operator is required to manually hold the device against the blade.

U.S. Pat. No. 2,921,416 to Shanahan discloses a “lawn mower sharpener” in which a power drill is held up-side-down in a cradle-type holder driving a grinding wheel 23, in which the holder includes positioning extensions or protuberances which directly contact the lawn mower blade and bed plate, respectively, causing the device to be directly carried by the blade and its associated structure. Such a device is very limited in its application being confined to use basically only with the lawn mower design illustrated and can be relatively dangerous to use, with the rotating grinder being exposed to the operator during use.

U.S. Pat. No. 2,993,312 to Holland et al discloses a blade sharpening device, which is completely hand manipulated. The sharpener is powered by a portable power tool, and has a wheel type grinding stone rigidly secured to a shaft and a frustro-conically shaped guide which is rotatably mounted on the shaft adjacent to the grinding stone. The shaft is connectable to the chuck of a portable power tool. The wheel and the frustro-conically shaped guide are arranged on the shaft with the smaller end of the guide adjacent to the wheel type stone to present a fixed angular grinding surface to a blade held against the guide. The device includes no guard for the rotating sharpening members, making it relatively dangerous, and no means are provided to allow the operator to grasp the device at both ends, making it more difficult to use and accurately position.

U.S. Pat. No. 3,019,568 issued Feb. 6, 1962 to Sauers et al discloses a lawn mower grinder and sharpener for a reel type lawn mower in which the sharpener is braced (17/18) on one of the lawn mower's basic structural components, i.e. the spacer rod 15. As above, this approach of direct bracing on the lawn mower structure greatly limits the applicability and use of the device. Also, as above, the substantial exposure of the rotating sharpening device to the operator makes the device relatively dangerous to use.

U.S. Pat. No. 3,122,865 issued Mar. 3, 1964, to Kolling discloses a power tool attachment for the sharpening of rotary mower blades. The attachment includes a guide that is spaced from the grinding surface and means for adjusting the spacing between the guide and the grinding surface by disassembling the sharpening device and removing a spacing element, thereby, allowing the use of an unused portion of the grinding surface when a portion of the grinding surface becomes worn. Like Holland et al, the Kolling device includes no guard for the rotating sharpening member, making it relatively dangerous to use, and no means are provided to allow the operator to grasp the device at both ends, making it more difficult to use and accurately position.

U.S. Pat. No. 3,238,673 issued Mar. 8, 1966, to W. F. Thompson discloses a non-portable, blade sharpener having a rotary guide for maintaining the angle of the blade in relation to a rotating, flat, grinding surface, wherein the guide includes protrusions which cause the blade to move radially, in an upward and downward direction, against the rotating grinding surface. This patent is not directly relevant to the field of the invention and does not help to overcome the deficiencies of the prior art discussed above and below.

U.S. Pat. No. 3,648,414 issued Mar. 14, 1972 also to W. F. Thompson discloses a scissor-type blade sharpener and likewise is not directly relevant to the field of the invention and does not help to overcome the deficiencies of the prior art discussed above and below.

U.S. Pat. No. 3,800,480 issued Apr. 2, 1974, to Keating discloses a portable, on-site, in-place blade sharpener which includes an angular drive means mounted in a housing containing an enclosed, dedicated, electric motor, with the device being hand-manipulated by the operator grasping the motor housing 14 by itself or in conjunction with the sharpener housing 19 and moving the device along the blade edge. The angular drive means is connected between the electric motor 21 and a grinding wheel 35 for coupling the rotational energy of the internal motor to the grinding wheel. Such an approach, in which the device rides through a guide plate 11 in flat-face-to-flat-face surface engagement with the underside of the blade and which does not use a multi-purpose electric drill but rather a contained, dedicated motor, is relatively inflexible in its use and relatively expensive. It does not provide freedom of lateral or angular movement, nor the easily controllable and strongly grippable handle of a power drill, all of which can assist in the easy and accurate positioning of the rotating sharpening member on the blade.

U.S. Pat. No. 5,371,977 issued on Dec. 13, 1994 to Liner discloses an on-site, in-place, portable blade sharpening device for lawn mower blades and the like using the standard type portable electric hand drill for power which device is hand-manipulated, adaptable for use with many different lawn mower designs, relatively safe in use, and easily, stably and accurately moved and positioned by the operator using an easily maneuverable two-hand grasp at opposed ends of the combined device and drill.

U.S. Pat. No. 6,666,758 issued on 23 Dec. 2003 to Parrott discloses a general a lawn mower blade sharpening device and a method of sharpening lawn mower blades using the device. The device comprises a motor to produce rotational movement of a flexible drive cable, where a two-sided grinding disk is attached to the drive cable such that operation of the motor rotates the grinding disk at a relatively high speed. The grinding disk is composed of a material suitable for removing metal from the dull mower blade in order to create a sharp edge. Preferably, a universal joint is provided between the flexible cable and the grinder body or grip to provide for maximum maneuverability of the grinding disk. The motor is preferably battery operated, but may also be electrically or gasoline operated. With this device, the lawn mower blade can be sharpened without the need to remove the blades from the mower, as the combination of flexible drive cable and two sided grinding wheel enable the operator to abrade both sides of the cutting blade to create a sharp edge.

The above mentioned inventions can be unsafe since the sharpening mechanisms are exposed and the operators hands are in close proximity to the blade as well as the sharpening surfaces that abrade the edge of the blade. Furthermore, the manual process of holding the sharpening devices against the blade does not allow for uniform sharpening and may result in “kick-back” of the devices if a nick or dent is hit with the sharpening device. Optimally, a need exists for a device that is potable, can be directly clamped to the blade that needs sharpening in-situ, and needs minimal manual manipulation.

BRIEF SUMMARY OF THE INVENTION

It is thus an object of the present invention to provide a portable blade sharpening device for lawn mowers and the like which has a housing which will contain the rotating sharpening segment protecting the operator from projectiles created during the sharpening process and the grinding surface as it moves along the blade. The housing also provides a gripping surface for the operator to hold the sharpening device in position while clamping the device to the blade enabling the operator to have free hands once the device is in the clamped position while the blade is still in place in its working position on the lawn mower or like machine. The grinding surface shall be slidably mounted to an extension rod allowing for the sharpening segment to move along the entire length of the area of the blade that is to be sharpened without have to loosen the clamps or remove the entire housing from the blade.

It is another object of the present invention to provide a blade sharpening device which will increase the operator's control of and accuracy in the positioning of the grinding surface of the sharpening device on the blade during the sharpening process and does not require it to be braced against any part of the housing of the lawn mower or other such structural parts or machinery except for the blade itself so this device could be used on various sizes, models, and configurations of lawnmowers or other devices that utilize a blade. The present invention provides a method of sharpening an edge of the blade of a lawn mower while it is still attached to a drive member. This enables the operator to save time and energy by not having to remove the blade and place it in a separate detached clamp or vice.

Accordingly, the present invention in its preferred embodiment is directed to a blade sharpening device including a housing preferably with top, side, and bottom surfaces which extend over the complete axial width and cover over all of the rotating sharpening segment. The housing not only protects the operator from flying debris or fragments but also provides a safe area for the operator to grasp in several different ways in manipulating the device to secure it to the lawn mower blade. Additionally, a selectively located drive shaft, clamp tightening lever and sharpening segment pitch adjuster, each having a multiplicity of possible positions or locations preferably is also included, further adding to the ease of control and positioning of the device.

The blade sharpening segment within the housing comprises a rotatable grinding member composed of two rotatable drums with a grinding surface such as emery paper securely wrapped around the two rotating drums. One of the drums is connected to a shaft member with a shank for connection to, for example, a portable hand drill for the driving of the grinding member. The shaft member, which is secured to one of the drums has an end thereof adapted for connection with a source of rotational power, such as, for example, a battery or AC powered, electrical drill, is further associated with securing means for securing the drum therein adapted to allow the grinding surface to be drivingly rotated about the longitudinal axis of the drum.

In use, the operator inserts the edge of the blade that needs to be sharpened through a receiving means in the housing and secures the clamp onto the blade which causes the whole sharpening device to be affixed securely to the lawn mower blade still attached to the body of the mower. The operator can adjust the angle of the grinding surface with the pitch adjuster. The operator then uses the drill to rotate the drum to which the drill is attached which causes the grinding surface to rotate freely within the housing of the sharpening device. The operator can re-position the pitch and the blade that is clamped within the housing to maximize the sharpening capability. The use can also manual slide the grinding member along the shaft and across the blade, or a threaded screw-shank mechanism can mechanically cause this action to occur.

The present invention thus provides an on-site, in-place, portable blade sharpening device for lawn mower blades and the like, preferably using the standard type portable electric hand drill for power, which device is hand-manipulated, adaptable for use with many different lawn mower designs, as well as many other devices, relatively safe in use, and easily, stably and accurately aligned and positioned by the operator using an easily maneuverable clamping device and pitch adjuster that allows the operator to only hold the apparatus that is attached to the shank member to cause the rotation of the drum. This allows the operator to have free use of his other hand during the sharpening process. In addition to the particular application of lawn mower blades, the device of the invention can be used to sharpen other devices that have a blade that has a surface large enough to be clamped and have a rotating grinding surface applied to the edge of the blade, such as, for further example, garden tillers, shovels, hoes, as well as scythes, cane knives, sweepers, bladed “weed eaters”, bush hogs, etc

BRIEF DESCRIPTION OF DRAWINGS

For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

FIG. 1 is a front view of a preferred embodiment of the invention with the position of the pitch adjusting member and the shaft connected to the rotatable grinding member and the clamping mechanism;

FIG. 2 is across sectional view from the end opposite the shaft member adapted for connection with a source of rotational power and a blade inserted into the longitudinal aperture;

FIG. 2A is an exploded side view of the device showing a preferred pitch adjuster location and predetermined angle formation slots; and

FIG. 3 is a front perspective view of the preferred grinding member illustrated in use with dual drums wrapped in the grinding surface and the position of the pitch adjuster.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows the preferred, exemplary embodiment of the blade sharpening device 8 of the invention with the main elements of the device including a grinding member 10; a shaft member 12; a housing member 14, which can be transparent if so desired, having an upper plate 71 and a lower plate 72; and a clamping mechanism 16 having a clamping end 27 mounted to an upper plate 71 which is movable in a vertical direction by the clamping mechanism 16. The entire invention can be constructed of any suitable material that has the strength and durability. The preferred material is a composite of man-made organic para-aramid fibers.

The shaft 12 may be constructed of any material which has sufficient torsional strength to rotate and carry the grinding member 10. Suitable shaft constructing materials include metals, such as steel, fiberglass, and plastics having the required torsional strength. In the preferred embodiment shaft member 12 is constructed of a man-made organic para-aramid fiber. The shaft member 12 includes an external shaft end or shank 24, which is adapted for connection with a source of rotational power, such as, for example, a battery or AC powered hand drill 66. The invention contemplates all methods, well known in the art, of connecting a shaft to a source of rotational power. The grinding member 10 rotates freely around an imaginary axis 80 located in a longitudinal aperture 81. The grinding member 10 can slide freely in a horizontal direction along the shaft 12. The shaft 12 may be threaded so when a rotational force is applied, the grinding member 10 mechanically moves horizontally along the shaft 12. Also, it is contemplated that a directional horizontal force applied by the operator on the pitch adjuster 20 shall cause the grinding member 10 to move horizontally along the shaft 12.

The housing 14 can be pre-cast or formed in a C-channel form with a first end plate 42 and a second end plate 43. The present invention 8 contemplates the fullest extent of coverage of the grinding member 10 by the housing 14, with additional horizontal space to allow for the grinding member 10 to slide along shaft 12 for the length of the blade 62 to be sharpened while still maintaining the blade sharpening capability of the grinding member 10. The longitudinal aperture 81 formed by the C-channel housing 14 allows for a blade 62 to be inserted through the longitudinal aperture 81 into the housing 14 and come to rest against the grinding member 10 through which imaginary axis 80 runs.

FIG. 2 shows an axial view opposite from the shaft end 24. Also shown, is a preferred, threaded method of attaching the clamping mechanism 16 to the housing 14 and the pitch adjuster 20. Although any known method of rigidly, mounting a clamp to a surface is contemplated by the present invention, in this preferred embodiment, clamping end 27 of clamping mechanism 16 is threaded and first end plate 42 of housing 14 includes companionately threaded, alternate bores 48 and 49. Likewise, it is contemplated in this invention that the clamping end may be located on second end plate 43. Similarly, any known method of rigidly, mounting a pitch adjuster 20 to a surface is contemplated by the present invention, in this preferred embodiment, pitch adjuster 20 is rotatably affixed, such as by a ball-and-socket means to grinding member 10. Pitch adjuster 20 penetrates first end plate 42 and can be secured in any individual slot of a series predetermined slots 45 which determines the angle 46 that is formed between the blade 62 and the grinding member 10. Likewise, it is contemplated in this invention that the pitch adjuster 20 may be located on second end plate 43. FIG. 2A is an exploded view of the first end plate 42 which may also depict second end plate 43.

In the preferred, exemplary embodiment grinding member 10 is constructed of two, opposed, co-operating drums 50 & 58. First drum 50 includes a shaft 24 and second drum includes an attachment for the pitch adjuster 20. Grinding surface 25, such as emery paper, is wrapped around first drum 50 and second drum 58 to form a circular band 52 so as to allow its free rotation initiated by the application of the drive member 66 attached to the drum 50. Frictional forces cause the underside of grinding surface 25 to remain frictionally affixed to the first drum 50 and the second drum 58 while rotating along with the rotation of first drum 50. Frictional forces also cause the grinding surface 25 to cause second drum 58 to rotate. Pitch adjuster 20 is in a fixed position attached second drum 58 by a ball-and-socket, or similar means of connection.

FIG. 3 illustrates the blade sharpening device 8 of the invention in use on the blade 62 of a conventional rotary lawn mower. It shows the blade sharpening device 8 connected to a source of rotational power, in this case a conventional portable drill 66. The sharpening device 8 is controlled by the operator by housing 14 with the operator securing the clamping mechanism 16 to the blade 62 by using a threaded tightening mechanism at clamping end 27. The clamping end is turned by the operator which lowers the causes an arm 73 to move in the vertical direction, raising or lowering the upper plate 71, which is movably attached to the housing 14 onto the blade 62 and securing the blade 62 between the upper plate 71 and the lower plate 72 of the housing 14. Next, the operator positions the pitch adjuster 20 against the edge of the blade 62 that needs sharpening. When the device 8 is properly positioned and angled on the blade, the operator can attach to source of rotational power 66 to the shaft mechanism 12. This arrangement gives the operator better control over the position of housing 14 on blade 62 by providing dual control locations and does not require the sharpening device be braced or supported on the machinery or housing which carries the blade 62, but is supported by the blade 62 itself

The operational position of housing 14 is also illustrated. The relatively complete and full coverage of grinding member 10 by housing 14 affords the operator protection from flying debris created during the sharpening process and also provides a handy surface upon which the lower part of the hand and the side of the little finger can be rested.

In additional to the preferred, exemplary application of lawn mower blades, the device can be used to sharpen other devices, such as, for further example, garden tillers, shovels, hoes, as well as scythes, cane knives, sweepers, bladed “weed eaters”, bushhogs, etc.

It is noted that the embodiment described herein in detail for exemplary purposes is of course subject to many different variations in structure, design, application and methodology. Because many varying and different embodiments may be made within the scope of the inventive concept(s) herein taught, and because many modifications may be made in the embodiment herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.

Claims

1. A blade sharpening device, comprising:

a grinding member having a rotatable grinding surface adapted to grind an edge of desired dimensions on a blade;

a shaft member, secured to said grinding member, having an end thereof adapted for connection with a source of rotational power; securing means for securing said grinding member to said shaft member;

a housing defining a receiving means comprising an upper plate and a lower plate between which said blade may be inserted and a grinding member cavity therein adapted to allow said grinding member to rotate about an axis of a longitudinal aperture, when said grinding member is secured by said securing means to said shaft member in a manner such that said grinding member is surrounded by said housing;

a clamping mechanism, attached to said housing, having a means for adjusting said upper plate to compress said blade against said lower plate to immobilize said blade during an application of said rotating grinding surface against said edge of said blade.

2. The blade sharpening device of claim 1, wherein said clamping mechanism is detachable and includes a means for allowing said clamping mechanism to be mounted in more than one location on said housing.

3. The blade sharpening device of claim 2, wherein said clamping mechanism is detachably mountable perpendicularly to and parallel to said axis of said longitudinal aperture of said grinding member.

4. The blade sharpening device of claim 1, wherein said clamping mechanism includes a cylindrical bore and a cylindrical portion which are companionately threaded.

5. The blade sharpening device of claim 1, wherein said grinding member slides horizontally along said shaft by a manual means of applying a directional force to a pitch adjuster attached to said grinding member.

6. The blade sharpening device of claim 1, wherein said grinding member moves horizontally along said shaft by a mechanical threaded shank.

7. The blade sharpening device of claim 1, wherein a pitch adjuster is affixed to said grinding member to allow for a preferred angle to be formed between said grinding surface and said edge of said blade.

8. The blade sharpening device of claim 1, wherein said grinding member includes a circular band of grinding surface that defines a formed aperture through which a first cylinder and a second cylinder, spaced at a predetermined distance so as to secure said circular band of grinding surface in a taught position and causing said axis of said longitudinal aperture to be centered between said first cylinder and said second cylinder.

9. The blade sharpening device of claim 8, wherein said means for securing said grinding member to said shaft member is adapted to allow the detachable securing of said first cylinder and said second cylinder.

10. A method of sharpening a blade of a lawn mower or the like while said blade remains attached to a drive member of said lawn mower or the like, said method comprising the steps of:

(a) attaching a blade sharpening device to an electrically powered, portable, multi-purpose, multi-use power source producing rotating movement, such as a portable power drill, which device includes:

a grinding member having a rotatable grinding surface adapted to grind an edge of desired dimensions on a blade;

a shaft member, secured to said grinding member, having an end thereof adapted for connection with a source of rotational power; securing means for securing said grinding member to said shaft member;

a housing defining a receiving means comprising an upper plate and a lower plate between which said blade may be inserted and a grinding member cavity therein adapted to allow said grinding member to rotate about an axis of a longitudinal aperture, when said grinding member is secured by said securing means to said shaft member in a manner such that said grinding member is surrounded by said housing;

a clamping mechanism, attached to said housing, having a means for adjusting said upper plate to compress said blade against said lower plate to immobilize said blade during an application of said rotating grinding surface against said edge of said blade.

(b) grasping the housing of said sharpening device in one hand and said portable power source in the other;

(c) adjusting the location of the housing to allow the grinding member access to said edge of said blade;

(d) positioning said grinding member on said blade in a desired location;

(e) securing said clamping mechanism on said blade in said desired location;

(e) initiating transmission of rotational power from said source of rotational power to said shaft and said grinding member; and

(f) moving said grinding member along said shaft across said blade while said grinding member is in contact with said blade and while the position of said blade sharpening device is controlled said secured clamping mechanism.