Abstract:
A cutting member is provided for mounting onto a guard for a line trimmer, the cutting member having at least one knife edge for cutting vegetation in concert with the flailing filament(s) of the trimmer. The knife edge is spaced from any planes swept by the flailing filaments. Additionally, the cutting member may be provided with a second knife edge that is positioned to trim excess length of the filament(s), thus ensuring no filament extends beyond the guard while in use.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to line trimmers for trimming vegetation, such as weeds and grass, and, more particularly, to line trimmers having a guard mounted thereon. 
     In the prior art, it is known to mount guards onto line trimmers (as used herein, a “line trimmer” is a hand-held, motorized device having a drive shaft with a rotating cutting head, wherein at least one filament is mounted to the cutting head that is caused to flail upon rotation of the cutting head and used to trim vegetation, such as weeds and grass (e.g., the line trimmer sold under the brand “WEED WHACKER”)). 
     It is also known to provide a cutting edge on the guards of line trimmers. The cutting edge is disposed in, and generally obliquely to, a plane defined by the flailing of the filament, and acts to clip excessive filament length. In this manner, the cutting edge ensures that the length of the filament does not exceed the size of the guard and, upon rotation, does not extend therebeyond. Examples of such cutting edges are shown in U.S. Pat. No. 4,550,499 to Ruzicka, and U.S. Pat. No. 6,052,976 to Cellini et al. 
     In U.S. Pat. No. 5,491,962 to Sutliff et al., a line trimmer is disclosed having both flexible filaments and rigid cutting blades mounted to the rotating head. The rigid cutting blades and the flexible filaments are disposed generally parallel with the flexible filaments being located above the cutting blades; the flexible filaments and the rigid cutting blades are vertically aligned. With two sets of rotating cutting elements in the Sutliff et al. device, vegetation is simultaneously double-cut upon engagement of the blades and filaments and, in effect, mulched. 
     It is an object of the subject invention to provide a line trimmer having a cutting member with at least one rigid knife edge disposed on a guard that is non-rotatably mounted onto the line trimmer. 
     It is also an object of the subject invention to provide a line trimmer having a cutting member with at least one rigid knife edge disposed on a guard, with the knife edge being spaced from a plane defined by the flailing of a filament upon rotation of the cutting head. 
     SUMMARY OF THE INVENTION 
     The aforementioned objects are met by a line trimmer having a guard mounted thereto, with a cutting member having at least one rigid knife edge being disposed on the guard. The line trimmer also includes at least one filament which flails upon rotation of the cutting head. The knife edge is spaced from any plane defined by the flailing filament(s). Advantageously, the knife edge cuts vegetation in concert with the filament(s). As a variation, the cutting member may include a second knife edge which is disposed to pass through the plane(s) defined by the flailing filament(s) so as to trim excess length of the filament(s). Accordingly, the filament(s) will not extend beyond the guard of the line trimmer while flailing. 
     These and other features will be better understood through a study of the following detailed description and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a line trimmer in accordance with the subject invention; 
     FIG. 2 is a bottom plan view of a guard, cutting head and filament of the line trimmer; and, 
     FIG. 3 is a side elevational view of the guard, cutting head, and filament. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIG. 1, a line trimmer is shown and generally designated with the reference numeral  10 . The line trimmer  10 , as is typical in the art, includes a drive shaft  12 , to which is mounted a cutting head  14 , a motor  16  for causing rotation of the cutting head  14 , and a guard  18 . The design and configuration of the drive shaft  12 , the cutting head  14  and the motor  16  are well known in the prior art and any such design and configuration may be used herein. 
     With reference to FIGS. 2 and 3, the cutting head  14  is generally disc-shaped with at least one filament  20  being mounted thereto and extending therefrom. Although a single filament  20  is shown in the FIG. 2, multiple filaments may be used, as is customary in the prior art and shown representatively in dashed lines in FIG.  3 . The filament  20  is mounted to the cutting head  14  using any technique known in the prior art, such as being spool-mounted or threaded directly into the cutting head  14 . 
     Upon rotation of the cutting head  14 , the filament  20  is caused to flail. With the filament  20  flailing, a reference plane R is defined by the sweeping motion of the filament  20 . If multiple filaments  20  are used, each of the filaments  20  sweeps a reference plane R, the multiple reference planes R being coplanar, not coplanar, or a combination thereof. 
     The guard  18  is preferably non-rotatably mounted to the drive shaft  12  and is located in proximity to the cutting head  14 . The guard  18  radiates outwardly from the drive shaft  12  to at least sweep across an arc A. In particular, the guard  18  includes a top portion  22 , which radiates outwardly from the drive shaft  12 , and a skirt  24  which depends downwardly from the top portion  22 . The top portion  22  and the skirt  24  may be formed with various dimensions (i.e., the size of the arc A; the radius of the top portion  22 ; the height of the skirt  24 )—it must be noted that the guard  18  serves to protect a user from rocks, gravel, cut grass, and other debris which are hurled upwardly and/or outwardly from the cutting head  14  during use, so the extent of selected dimensions will dictate the amount of protection afforded by the guard  18 . 
     A cutting member  26  is mounted to the top portion  22 , and, preferably, the cutting member  26  is rigidly mounted to prevent movement thereof. As shown in FIG. 2, the cutting member  26  has a rigid knife edge  28  which extends beyond the top portion  22 . The knife edge  28  may be of any cutting edge design known in the prior art which serves to cut vegetation in addition to the filament  20  as described below (e.g. a tapered edge; a dihedral edge). Preferably, the knife edge  28  (and the cutting member  26 ) are metallic, e.g., steel. 
     The knife edge  28  is located to oppose the movement of the filament  20 . In addition, as shown in FIG. 3, the knife edge  28  is located to be spaced from the reference planes R, and, preferably is disposed to be generally parallel to at least one of the reference plane(s) R. If multiple filaments are mounted to the cutting head  14 , the knife edge  28  is spaced from all of the reference planes R. As a result of this configuration, the flailing filament  20  strikes vegetation against the knife edge  28  resulting in the vegetation being cut both by the filament  20  and the knife edge  28 ; the knife edge  28  acts to second-cut vegetation in a mulching effect. If multiple filaments are used, the vegetation is further cut into smaller parts further enhancing the mulching effect. 
     The cutting member  26  can be mounted to the guard  18  using any technique known to those skilled in the art. Preferably, the cutting member  26  is mounted to a lower surface  29  of the top portion  22  of the guard  18 . Also, the cutting member  26  is formed with a rearwardly-extending moment arm  30  which extends generally in the same direction as the rotation of the cutting head  14 . More preferably, the moment arm  30  is formed to be located in proximity to the cutting head  14 . By extending in the same direction as the rotation of the cutting head  14 , the moment arm  30  counteracts force imparted thereto by the filament  20  (via impacted vegetation). In addition, the largest imparted force is located closest to the cutting head  14 , thus, requiring the most-significant counteraction in proximity thereto. 
     In a preferred arrangement, the knife edge  28  extends beyond an edge  32  which defines one limit of the arc A of the guard  18 . It is also preferred that the knife edge  28  be generally parallel to the edge  32  and be at least coextensive therewith. 
     As an additional variation, the cutting member  26  may be unitarily formed with a second knife edge  34  (preferably, metallic (e.g., steel)) that is disposed inside of the skirt  24  and passes through at least one of the reference planes R. As shown in FIG. 3, the knife edge  28  and the second knife edge  34  may define a L-shape with the cutting member  26  being formed from a unitary piece of metal. The second knife edge  34  is positioned to trim excess length of the filament(s)  20 . In this manner, no filament  20  will flail into, or beyond, the guard  18 . 
     As is readily apparent, numerous modifications and changes may readily occur to those skilled in the art, and hence it is not desired to limit the invention to the exact construction and operation as shown and described, and, accordingly, all suitable modification equivalents may be resorted to falling within the scope of the invention as claimed.