Technical Field

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.

Background Art

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

cround.

A list of prior patents which may be of interest is provided

below:

Patent No. Inventor I s s u e Date

2,921,416 P.T. Shanahan 01/19/60

2,993,312 H.L. Holland et al 07/25/61

3,019,568 M.M. Sauers et al 02/06/62

3,122,865 H.W. Rolling 03/03/64

3,238,673 W.F. Thompson 03/08/66

3,648,414 W.F. Thompson 03/14/72

3,800,480 F.J. Keating 04/02/74

U.S. Patent 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 26 & 27 which directly

contact the lawn mower blade 26 and bed plate 28, 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 user during use.

U.S. Patent 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 user to grasp the device at both

ends, making it more difficult to use and accurately position.

U.S. Patent 3,019,568 issued February 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 user

makes the device relatively dangerous to use.

U.S. Patent 3,122,865 issued March 3, 1964, to Rolling 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 user to

grasp the device at both ends, making it more difficult to use and

accurately position.

U.S. Patent 3,238,673 issued March 8, 1966, to W. F. Thomp¬

son 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. Patent 3,648,414 issued March 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. Patent 3,800,480 issued April 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 user 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.

As will be understood from the discussions below, the present

invention overcomes the above detailed deficiencies of the prior art

and substantially improves upon the prior art by providing 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 user using an easily

maneuverable two-hand grasp at opposed ends of the combined

device and drill.

General Discussion of 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 guard which will protect the operator from projectiles created

during the sharpening process, as well as provide a good, gripping

surface for one hand of the user to hold, position and move the

device along the blade in the sharpening process, while the blade is

still in place in its working position on the lawn mower or like

machine.

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, which could limit

its applicability.

It is still a further object of the present invention to provide a

method of sharpening an edge on the blade of a lawn mower, while

it is still attached to a drive member, which is easily implemented and

reduces the risk of injury to the operator.

Accordingly, the present invention in its preferred embodiment

is directed to a blade sharpening device including a guard preferably

with top and side surfaces which extend over the complete axial width

and cover over a substantial amount of the sides of the rotating

sharpening member(s). This guard member not only protects the

user from flying debris or fragments but also provides a safe area for

the user to grasp in several different ways in manipulating the device.

Additionally, a selectively located handle member 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 device further comprises a rotatable

grinding member riding on a shaft member with a shank for

connection to, for example, a portable hand drill for the driving of

the grinding member. The grinding member preferably includes a

longitudinal aperture there through, and grinding surfaces adapted

to grind an edge of desired dimensions on the blade to be sharpened.

The shaft member, which is secured to the grinding member

and has an end thereof adapted for connection with a source of rota-

tional power, such as, for example, a battery or AC powered,

electrical drill, is further associated with securing means for securing

the grinding member through the longitudinal aperture to the shaft

member, and first and second shaft portions adapted for rotation

within a first and second receiving means. The grinding guard

member includes the first and second receiving means and defines a

grinding member cavity therein adapted to allow the grinding

member to be drivingly rotated about the axis of the longitudinal

aperture, when the grinding member is secured by the securing

means to the shaft member and the first and second shaft portions

are received within the first and second receiving means, in a manner

such that a portion of the grinding member is surrounded by the

grinding guard member.

The grinding member includes both a sloped or conically

shaped member as well as an opposed flat member, with the two of

them co-operating together to mutually position and sharpen the

blade. Alternatively, two opposed, sloped or conically shaped

members could be used for dual-edge sharpening, depending on the

type of device or blade being sharpened.

In use the user grips the handle of the drill with one hand and

the other hand grips the housing and/or the handle attached to the

guard or housing. The drill is then activated by depressing the drill ^' s

trigger, and the rotating sharpener is positioned on and moved along

-l i¬ the blade using the guard member to accurately position and move

the device longitudinally along the blade edge, appropriately

sharpening it, while the guard also protects the user from any flying

debris generated in the sharpening process.

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 moved and

positioned by the user using an easily maneuverable, two-hand grasp

at opposed ends of the device and drill. In addition to the particu¬

larly perferred application of lawn mower blades, the device of the

invention 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., particularly for the

latter, where the grinding member includes two, opposed, conically

shaped members.

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:

Figure 1 is a side view of a preferred embodiment of the

invention with the alternate position of the handle member again

being shown in phantom line;

Figure 2 is an axial view from the end the shaft member

adapted for connection with a source of rotational power;

Figure 3 is a cross-sectional side view illustrating the threaded

section and the grinding stop member;

Figure 4 is a perspective view of the over-all embodiment

showing a preferred means of detachably mounting a handle and

threaded means in the grinding guard member for allowing detach¬

able mounting in preferred locations, with the alternate position of

the handle member again being shown in phantom line;

Figure 5 is an exploded view of the device showing a preferred

shaft and grinding member and a preferred mode of securing them

together; and

Figure 6 is an underside perspective view of the preferred

sharpening device illustrated in use on a conventional rotary lawn

mower blade with the sharpening device being completely manually

supported and guided with the exemplary lawn mower blade and

body and the battery power drill all being shown in phantom line.

Exemplary Mode for Carrying Out the Invention

Figure 1 shows the preferred, exemplary embodiment of the

blade sharpening device of the invention with the main elements of

the device including a grinding member, generally indicated by the

numeral 10; a shaft member, generally indicated by the numeral 12;

a grinding guard member, generally indicated by the numeral 14 and

which can be transparent if so desired; and a handle member,

generally indicated by the numeral 16 mounted to an upper, bridging

surface 18. Figure 1 also shows an alternate position (note 16') for

mounting the handle member 16 to an outer, side surface 19 of the

grinding guard member 14. First receiving means 20 and second

receiving means 22 in the housing or guard member 14 for the shaft

12 can also be seen, although, they are better illustrated in Figure 3.

The shaft member 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, and plastics having the required torsional strength. In

the preferred embodiment shaft member 12 is constructed of plastic

nylon. 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

(see Figure 6).

In the preferred, exemplary embodiment the shaft end 24 is

three-eighths (3/8") of an inch in diameter in order to fit within the

chuck of an exemplary three-eighths (3/8") inch drill. However, the

invention contemplates all of those methods, well known in the art,

of connecting a shaft to a source of rotational power.

The present invention contemplates the fullest extent of

coverage of the grinding cone member 10 by the grinding guard 14

possible, while still maintaining the blade sharpening capability of the

grinding member 10. Figure 2 shows an axial view from shaft end 24.

It illustrates the preferred exemplary percentage of coverage of the

grinding member 10 by the grinding guard member 14. In this

preferred embodiment, the grinding guard member 14 covers about

eighty (80°) degrees or approximately about twenty five (25%)

percent of the grinding member 10.

Also shown, is a preferred, threaded method of attaching the

handle member 16 to the grinding guard member 14. Although any

known method of rigidly, mounting a handle to a surface is contem-

plated by the present invention, in this preferred embodiment, end

26 of handle member 16 is threaded and grinding guard member 14

includes companionately threaded, alternate bores 28 and 30. These

are more clearly shown in Figure 4.

Figure 3 is a longitudinal cross-section of the preferred,

exemplary embodiment of the invention through the axis of shaft

member 12. It shows a preferred first shaft portion 32, received

within a preferred first receiving means 34, and a preferred second

shaft portion 36, received within a preferred second receiving means

38. In this preferred embodiment first and second shaft portions 32

and 36 are cylindrically shaped and coaxially centered with the

longitudinal axis of shaft member 12. First and second receiving

means 34 and 38 are also cylindrically shaped and coaxially centered

along a common axis, which is located to allow rotational clearance

within grinding member cavity 40 for grinding member 10 mounted

on shaft member 12.

The diameters of the first and second receiving means 34 and

38 are sufficiently larger than the diameters of the first and second

shaft portions 32 and 36, respectively, to allow sufficient clearance for

their rotation when received therein. In this preferred, exemplary

embodiment this clearance is about two thousandths (0.002") of an

inch. Although other means for easing the rotation of first and

second shaft portions 32 and 36 are contemplated, such as inclusion

of bearings, the mere application of a lubricating grease to the shaft

portions and receiving means is simply, less expensive and currently

preferred.

Receiving section 42 of the shaft member 12 is shown adjacent

to the second shaft portion 36. The diameter of the receiving section

42 is smaller than the diameter of the second shaft portion 36 in

order to allow the side 44 of the second shaft portion 36 to operate

as a grinding member stop 45. A preferred means of securing the

grinding member 10 to the shaft member 12 is accomplished by the

combination of receiving section 42, grinding member stop 45,

threaded section 46, and jam nut 48. A washer 61 is also preferably

included. Figure 5 is an exploded view showing their connection.

In this preferred, exemplary embodiment grinding member 10

is constructed of two, opposed, co-operating grinding stones 50 & 58,

one being conical and the other being disc shaped, respectively.

Grinding stone 50 includes a conically shaped grinding surface 52 and

a small, cylindrically shaped grinding surface 54. Grinding stone 58

has a planar grinding surface (like surface 58) on the planar face not

shown in the figure. Alternatively, the disc shaped member 58 could

be replaced by another, opposed, conically shaped grinding stone,

configured as a mirror image of grinding stone 50.

Also illustrated in Figure 5 is a preferred means of imparting

rotational energy from shaft member 12 to grinding member 10. This

is accomplished by shaping the longitudinal aperture 60 of grinding

member 10 to companionately mate with receiving section 42.

Although any shape which will prevent the grinding member 10 from

rotating freely about the receiving section 42 is contemplated by the

invention, in this preferred embodiment a rectangular shape having

opposes arcuate ends is used.

Figure 6 illustrates the blade sharpening device 8 of the

invention in use on the blade 62 of a conventional rotary lawn mower

64. 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 grasping handle

member 16 with one hand 68 and the drill 66 with the other hand 70

as the device 8 is properly positioned and angled on the blade and is

moved longitudinally along with extent of the blade ^' s cutting edge.

This arrangement gives the operator better control over the position

of grinding member 10 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.

The operational position of grinding guard member 14 is also

illustrated. The relatively complete and full coverage of grinding

member 10 by grinding guard member 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. Alternatively, the

guard member can be directly gripped with or without the handle 16

by the user placing his palm and fingers either across or along the

surface 18, whichever may be more comfortable under the

surrounding circumstances.

Thus, in use, preferably after disconnecting the spark plug wire,

the user grips the handle of the drill 66 with one hand 70 and the

other hand 68 grips the guard housing 17-19 and/or the handle 16

attached to the guard or housing. The drill 66 is then activated by

depressing the drill's standard trigger and the rotating sharpener

members 10/58 is positioned on and moved along the blade 62, with

the user using the guard member and drill to accurately position and

move the device along the blade edge (note directional arrows in Fig.

6), appropriately sharpening it, while the guard 14 also protects the

user from any flying debris generated in the sharpening process.

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

exemplar)' 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 modifica¬

tions 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.