Patent Abstract:
An electrically powered lawn edger ( 10 ) having a wire wheel ( 26 ) specifically adapted for edging and trench cutting applications. The wire wheel includes pairs of twisted wire brush segments ( 34 ) which are held within a hub ( 32 ) of the wire wheel. The pairs of brush segments are spaced apart radially around a peripheral edge of the hub to produce evenly spaced gaps ( 36 ). The gaps help to prevent the edger from “loading up” with dirt and/or turf when edging or cutting a trench and possibly stalling the edger motor ( 21 ). A washer ( 40 ) having a key shaped boss ( 44 ) keys the wire wheel to an output spindle ( 21   a ) of the motor to prevent slippage of the wire wheel.

Full Description:
TECHNICAL FIELD 
     This invention relates generally to lawn edgers, and more particularly to an electrically powered lawn edger having a removable wire wheel adapted to cut trenches and to edge along concrete and asphalt surfaces without drawing excessive current from an electric motor of the edger, and also to a system for more positively coupling various edging implements to an output spindle of the electric motor while still permitting such implements to be quickly and easily removed and attached to the spindle. 
     BACKGROUND OF THE INVENTION 
     Edgers are used in applications to trim turf growing along a walkway or a driveway where it is desired to produce a clean “edged” appearance to the turf. Such edgers are also often used to cut trenches through turf and into soil to enable cables or wiring to be laid in the soil. 
     Previously developed edgers, however, have suffered from certain drawbacks when the edger has been used with a wire brush wheel. Wire brush wheels presently available typically include a large number of twisted wire brush segments that are not particularly well suited for use with electrically powered edgers. The large number of wire brush segments are prone to “loading up” with soil and/or turf during use, often temporarily stalling the edger. When this occurs, the edger can also “kick” back toward the user, making use of the edger uncomfortable and tiring. 
     Such previously developed wire wheels having a large number of wire brush segments also produce a greater current draw on the electric motor of the edger during use than other cutting implements. This can limit the use of many wire wheels to those edgers having motors sufficiently powerful enough to handle the anticipated current draw that will result when using a wire wheel. If the wire wheel becomes momentarily loaded up or stalled during use, the current drawn by the motor will increase significantly and can potentially damage the edger motor. 
     The problem with excessive current draw with many previously designed wire wheels is further compounded when the edger is used to cut trenches in rocky or stony soil. In these instances, the contact of the wire wheel with stones or rocks increases the risk of loading up or stalling of the motor of the edger, thus increasing the risk of damage to the motor and/or damage to the wire wheel. Stalling can also occur if the wire wheel must cut into hard, compacted soil. 
     Another disadvantage concerning some previously developed edgers is the somewhat inconvenient process of changing edging implements and/or slippage of the edging implement relative to the spindle of the electric motor driving it. Such edgers often incorporate a number of independent washers and/or threaded nuts for holding the edging implement securely to the motor spindle, which makes changing the edging implement a time consuming and inconvenient process. Often some slippage of the edging implement occurs regardless of how tight the user is able to fasten the edging implement onto the spindle. This slippage can reduce the efficiency of the edger and thus lengthen the time and effort required to complete an edging/trenching task. 
     In view of the foregoing, it is a principal object of the present invention to provide an edger having a wire wheel which has a reduced number and novel arrangement of wire brush segments which requires less power to be driven by an electric motor than conventional wire wheels used with electric edgers. 
     It is a further object of the present invention to provide an edger having a wire wheel which is less likely to become momentarily loaded up with soil or turf, or possibly stalled, when digging trenches or edging in hard soil, thereby preventing an unacceptably high current draw by the electric motor of the edger. 
     It is still another object of the present invention to provide an edger having a wire wheel which may be quickly and easily removed from an output spindle of the electric motor of the edger so that various edging implements such as edging blades and wire wheel brushes can be more quickly and easily attached to the spindle, and where the edging implement is even more securely held to the spindle to prevent undesired slippage of the edging implement relative to the spindle. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a lawn edger having a wire brush wheel and a means for securing the wire wheel, or virtually any other edging implement, quickly and easily to a spindle of an electric motor of the edger in such a manner that slippage of the edging implement relative to the spindle is prevented. The wire wheel of the present invention incorporates a plurality of wire brush segments which are spaced in desired numbers radially about a hub of the wire wheel. In one preferred embodiment, pairs of wire brush segments are positioned closely adjacent one another, with each pair being spaced evenly from its adjacent pair by a predetermined distance. In this manner the overall number of brush segments is reduced while forming “gaps” between each adjacent pair of brush segments. These gaps help to prevent the wire wheel from getting bogged down or stalled when cutting into hard, compacted soil, which could result when using other conventional wire wheels, and thus preventing the edger motor from drawing excessive current. 
     In the preferred embodiment each twisted wire brush segment comprises a diameter of preferably between about 0.125 inch and 0.5 inch (3.175 mm-12.7 mm). Even more preferably, the diameter of each twisted wire brush segment ranges from about 0.25 inch to 0.375 inch (6.35 mm-9.525 mm). Preferably, the gap between each pair of adjacent wire brush segments is between about 0.5 inch-75 inch (12.7 mm-19.05 mm), and more preferably between about 0.625 inch (15.875 mm), depending on the overall diameter of the wire wheel. These gaps enable dirt and small stones to be readily lifted out by the wire wheel when cutting through hard or highly compacted soil or turf, thus reducing the chance of loading up and stalling of the edger motor. 
     Each of the wire brush segments are secured to a hub having inner and outer plates and a center plate secured therebetween. The brush segments extend outwardly through openings in the center plate. Preferably, the diameter of each of the inner and outer plates is slightly larger than the diameter of the center plate. Between adjacent pairs of wire brush segments the peripheral edges of the inner and outer plates of the hub are narrowed or “crimped in” slightly toward each other. These narrowed areas help to provide support to the brush segments to maintain the brush segments upright during use of the wire wheel. 
     In the preferred embodiment, the hub of the wire wheel includes a keyed opening. The spindle of the motor also includes a cross sectional shape which is such that it requires the wire wheel to be placed on the shaft in a particular orientation. A washer having a key shaped boss is also included. The key shaped boss has a shape, when viewed in cross section, which is designed to fit within the keyed opening of the hub such that the washer is not able to rotate independently of the wire wheel when both are placed on the spindle. A threaded fastening member is then used to secure the wire wheel to the motor spindle. In this manner, both the keyed washer and the wire wheel are prevented from rotating independently relative to the output shaft and to each other. This arrangement further enables the wire wheel to be quickly and easily removed and replaced with another edging implement, such as an edging blade, to suit the needs of a specific edging task. 
     The edger of the present invention thus enables a wire wheel to be used to edge closely adjacent to areas such as concrete, paving stones, asphalt, etc., or to cut trenches in soil without experiencing the loading up or stalling caused by other wire wheels driven by electric edger motors. The wire wheel of the present invention requires less power than traditional wire wheels, thus enabling the wire wheel to be used with edgers having less powerful electric motors. The keyed design of the opening in the hub of the wire wheel, together with the keyed washer, enables the wire wheel to be held securely to the motor spindle while still enabling the wire wheel to be quickly and easily removed when changing edging implements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various advantages of the present invention will become apparent to one skilled in the art by reading the following specification and subjoined claims and by referencing the following drawings in which: 
     FIG. 1 is a perspective view of an edger incorporating a wire wheel in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is a plan view of an outer side of the wire wheel shown in FIG. 1; 
     FIG. 3 is a perspective view of the wire wheel shown in FIG. 2; 
     FIG. 4 is a plan view of the inner side of the wire wheel shown in FIG. 1; 
     FIG. 4 a  is a cross-sectional view of the wire wheel in accordance with section line  4   a — 4   a  in FIG. 2; 
     FIG. 5 is a perspective view of a keyed washer used to key the wire wheel to the motor spindle of the edger; 
     FIG. 6 is a plan view of the keyed washer of FIG. 5; 
     FIG. 6 a  is a side view of the keyed washer of FIG. 5; 
     FIG. 7 is a cross sectional side view of the keyed washer of FIG. 6 taken in accordance with section line  7 — 7  in FIG. 6; 
     FIG. 8 is a plan view of an outer washer used to help secure the wire wheel to the motor spindle; 
     FIG. 9 is a cross sectional side view of the washer of FIG. 8 taken in accordance with section line  9 — 9  in FIG. 8; 
     FIG. 10 is a plan view of the wire wheel assembled onto the motor spindle; 
     FIG. 11 is a partial cross sectional side view of the wire wheel, the keyed washer and the outer washer secured to a portion of the motor spindle, taken in accordance with section line  11 — 11  in FIG. 10; 
     FIG. 12 is a partial cross sectional side view of the assembly of FIG. 10 taken in accordance with section line  12 — 12  in FIG. 10; and 
     FIG. 13 is a perspective view of a cutting blade adapted for use with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1, there is shown an edger  10  in accordance with a preferred embodiment of the present invention. The edger  10  includes a main handle portion  12 , a secondary handle portion  14 , an elongated, tubular neck portion  16 , and an edging assembly  18  coupled to the neck portion  16 . The edging assembly  18  includes a housing  20  within which is disposed an electric motor  21  (indicated in phantom) having a spindle (i.e., armature shaft)  21   a . A pair of wheels  22  operationally coupled to the housing  20  support the entire edger assembly  18  to permit rolling movement along a surface such as a driveway or sidewalk. A shroud  24  secured to the housing  20  partially encloses a wire wheel  26  which is coupled to the spindle  21   a  so as to be driven thereby. The electric motor  21  is actuated by a manual trigger  28  at the main handle portion  12  to permit on/off control of the electric motor  21 . A guide wheel assembly  30  assists the user in moving the edger  10  closely adjacent the edge of a walkway or driveway. 
     While the edger  10  is shown in FIG. 1 without a rechargeable battery pack, it will be appreciated that the edger  10  could readily be modified to incorporate such a rechargeable power source to enable the edger  10  to be used when an AC power source is not readily available. If a removable, rechargeable battery pack is included, then an AC/DC converter could also be incorporated for use with the edger  10  to enable the edger to be powered by either an AC or DC power source. It will be appreciated, however, that incorporating such an AC/DC power converter would require the tool to be double insulated to meet existing safety standards, as is well known in the art. 
     Referring now to FIGS. 2,  3  and  4 , the wire wheel  26  is shown in greater detail. Referring specifically to FIG. 3, the wire wheel  26  includes a hub  32  which is preferably formed from metal or aluminum, such as by molding or stamping. The hub  32  includes an outer plate  32   a , an inner plate  32   b  and a center plate  32   c  sandwiched between the inner and outer plates  32   b  and  32   a , respectively. The center plate  32   c  is preferably slightly smaller in diameter than the inner and outer plates  32   b  and  32   a , respectively. The plates  32   a ,  32   b  and  32   c  are secured together by welding or other suitable conventional fastening elements. The center plate  32   c  includes a plurality of radially spaced apart openings  32   c   1 . A twisted wire brush segment  34  extends through each opening  32   c   1 . The brush segments  34  are formed from thin steel wire strands (which are twisted to form a relatively rigid brush segment). Each brush segment  34  comprises an overall diameter of preferably between about 0.125 inch-0.5 inch (3.175 mm-12.7 mm), and more preferably between about 0.250 inch-0.375 inch (6.35 mm-9.525 mm). The overall length of each brush segment  34  may vary considerably, but is preferably between about 1.0 inch-1.5 inches (25.4 mm-38.1 mm), and more preferably about 1.25 inches (31.75 mm). In the preferred embodiment  28  brush segments  34  are provided, but it will be appreciated that a greater or lesser number could be used depending on the diameter of the hub  32 . 
     The brush segments  34  are arranged closely adjacent one another in pairs such that “gaps” or spaces, designated by dimensional arrow  36  (FIG.  2 ), are formed radially about the hub  32 . At these gaps  36 , the peripheral edges  38   a  and  38   b  of the plates  32   a  and  32   b , respectively, of the hub  32  are “crimped” or narrowed slightly, as best seen in FIGS. 3 and 4 a . This crimping is advantageous because it provides additional support to the brush segments  34  to further help keep them upright and rigid during use of the wire wheel  26 . The gaps  36  are important because they provide space for the removal of dirt and vegetation churned up as the wire wheel  26  digs through dirt and turf. This helps to prevent the wire wheel  26  from becoming momentarily stuck in the soil and/or turf, thus causing the edger motor  21  to draw excessively high current. It has been found that the distance of the gap  36  may vary considerably, but for a wire wheel  26  having a hub with an outer diameter of about 4.7 inches (119.4 mm ), and wire brush segments  34  each having a diameter of about 0.25 inch (6.35 mm), and with the wire brush segments  34  being arranged in pairs as illustrated in FIG. 2 with a slight spacing of about 0.125 inch (3.175 mm) between each one of the brush segments  34 , the length of each gap  36  is preferably about 0.5 inch-0.75 inch (12.7 mm-19.05 mm), and more preferably about 0.625 inch (15.875 mm). The brush segments  34  are captured within the hub  32  by looping through apertures formed in the peripheral edge of the center plate  32   c  in conventional fashion. 
     It will also be appreciated that while the wire wheel  26  has been illustrated as having pairs of brush segments  34  spaced around the periphery of the hub  32 , that a greater or lesser number of brush segments  34  could be grouped together around the hub  32 . For example, groups of three brush segments  34  could be disposed around the hub  32  periphery rather than groups of two. Using groups of three or more brush segments  34 , however, would reduce the space available to form the gaps  36  (assuming the diameter of the hub  32  remained the same), which would reduce the ability of the wire wheel  26  to resist “loading up” or stalling during use. 
     Referring further to FIGS. 2 and 3, the outer plate  32   a  includes a circular aperture  32   a   1  while the center plate  32   c  can be seen to include an aperture  32   c   2  having a “kermit eye” shape. Referring to FIG. 4, the inner plate  32   b  is illustrated as also having a kermit eye shaped aperture  32   b   1  which is aligned over the aperture  32   c   2  in the center plate  32   c.    
     Referring now to FIGS. 5-7, a keyed washer  40  is illustrated. The keyed washer  40  is used to lock the wire wheel  26  to the spindle  21   a  of the motor  21 . In this regard it will be appreciated that the spindle  21   a  of the motor  21  has two flattened or shaved surfaces along a distal portion of its length to impart a double “D” shape to at least the distal portion when it is viewed in cross section. This shape is identical, but just slightly smaller than, an aperture  42  having a double D shape formed in the keyed washer  40 . In this manner, the keyed washer  40  can only be inserted onto the spindle  21   a  in one of two possible orientations (180° from one another) and the double D configuration prevents rotation of the keyed washer  40  independently of the spindle  21   a.    
     With further reference to FIGS. 5-7, the keyed washer  40  also includes a raised boss portion  44  on a first surface  46  thereof. A second (i.e., rear) surface  48  is generally flat except for the area defining the double D shaped aperture  42 . The boss portion  44  is illustrated also having a “kermit eye” shape, but it will be appreciated that virtually any other shape could be incorporated that accomplishes the function of keying the keyed washer  40  to the wire wheel  26 , as will be described further momentarily. The boss portion  44  has a height, as indicated by dimensional arrows  50  in FIG. 6 a , which is sufficient to at least partially engage within the keyed aperture  32   c   2  in the center plate  32   c  (FIG.  3 ). The keyed washer  40  is preferably made from metal or other suitably strong material. 
     When the keyed washer  40  is secured to the spindle  21   a  of the electric motor  21  of the edger  10 , the washer  40  is not only keyed to the spindle  21   a  but is also keyed to the wire wheel  26 . Therefore, the keyed washer  40  is not able to rotate independently of the spindle  21   a  nor independently of the wire wheel  26 . 
     Referring now to FIGS. 8 and 9, an outer or clamping washer  52  is illustrated. The outer washer  52  is also shaped in the double D configuration and includes a double D shaped aperture  54  just slightly larger in dimensions than the spindle  21   a  of the motor  10 . When inserted over the spindle  21   a , the outer washer  52  is keyed to the spindle  21   a . The washer  52  is also preferably made from metal or another suitably high strength material. 
     Referring now to FIGS. 10-12, the wire wheel  26  is shown in partial cross section assembled to the spindle  21  a of the motor  21 . During assembly, the keyed washer  40  is first inserted over the spindle  21   a . The keyed washer  40  is inserted such that the boss portion  44  is facing outwardly toward the terminal end of the spindle  21   a . Next the wire wheel  26  is placed onto the spindle  21   a  such that the boss portion  44  engages with the kermit eye shaped apertures  32   b   1  and  32   c   2  in the inner plate  32   b  and center plate  32   c , respectively, of the hub  32 . At this point the wire wheel  26  will be keyed to the keyed washer  40 , which is in turn keyed to the spindle  21   a . Thus, neither the wire wheel  26  nor the keyed washer  40  will be able to move independently of the spindle  21   a  nor independently of each other. 
     The outer washer  52  is then placed onto the spindle  21   a  and it fits partially within the circular aperture  32   a   1  in the outer plate  32   a . Next, a suitable fastening element (not shown) is threaded into an internal threaded bore  54  in the spindle  21   a  to secure the washers  40  and  52  and the wire brush  26  thereon. It will be appreciated, however, that the spindle  21   a  could comprise an external threaded surface and a threaded nut could be incorporated instead. Once assembled, the wire brush wheel  26  and the washers  40  and  52  are keyed to the spindle  21   a , thus eliminating any possibility of slippage of the brush wheel  26  during operation of the edger  10 . 
     With brief reference to FIG. 13, a cutting blade  60  particularly adapted for use with the edger  10  is shown. The cutting blade comprises a central portion  62  also having a kermit eye shaped aperture  64 , and opposing end portions  66 . The opposing end portions each include a “step”  68  and a plurality of teeth  70 . The teeth  70  are arranged along a slight arc. An aperture  72  is formed in each opposing end portion at a point inwardly toward the aperture  64  so as to be approximately above a tooth  70   a  nearest aperture  64 . Apertures  72  form a convenient means for indicating the degree of wear of the opposing end portions  66  to indicate to the user when the blade  60  needs replacement. When replacement is needed, the loss of material of the blade  60  at the opposing ends  66  will reach apertures  72 , thus providing an indication that the blade  60  needs to be replaced. At this point, all but the two teeth  70   a  nearest the kermit eye shaped aperture  64  will be worn away. 
     The edger  10  and the wire brush wheel  26  thus form an easy to use means for digging trenches, edging lawns, cleaning cracks in pavement or paving stone walkways or driveways, without damaging the surface being cleaned. The spacing of the wire brush segments  34  of the wire wheel  26  further serve to reduce the loading on the electric motor  21  of the edger  10  and to help prevent stalling of the wire wheel  26  during use of the edger. The reduced number of brush segments  34  and the manner in which the brush segments are arranged on the hub  32  enable the wire wheel  26  to be driven by less powerful electric motors and further to help prevent damage to the electric motor by reducing the risk of stalling. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification and following claims.

Technology Classification (CPC): 0