Abstract:
A trimmer head for use with rotary vegetation cutting devices is disclosed. The head has a wear guide that indicates when the body of the trimmer head is worn down and needs replacement. In an embodiment of the invention, the body comprises two plates that are molded to fit together. The plates have bores for holding connecting pins. The connecting pins not only hold the plates together, but also pivotably support cutting blades, by fitting into openings in the blades.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to heads for attachment to rotary vegetation cutting devices. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0002]    [0002]FIG. 1 is an exploded perspective view of a trimmer head according to an embodiment of the present invention.  
         [0003]    [0003]FIG. 2 is a top view of a trimmer head according to an embodiment of the present invention.  
         [0004]    [0004]FIG. 3 is a bottom view of a trimmer head according to an embodiment of the present invention.  
         [0005]    [0005]FIG. 4 is a top view of a bottom plate of a trimmer head according to an embodiment of the present invention.  
         [0006]    [0006]FIG. 5 is a side cut-away view of a trimmer head according to an embodiment of the present invention, taken along line  5 - 5  in FIG. 2.  
         [0007]    [0007]FIG. 6 is a side view of a trimmer head according to an embodiment of the present invention.  
         [0008]    [0008]FIG. 7 is a bottom view of a trimmer head according to an embodiment of the present invention.  
         [0009]    [0009]FIG. 8 is a side cut-away view of a trimmer head according to an embodiment of the present invention, taken along line  8 - 8  as depicted in FIG. 7.  
         [0010]    [0010]FIG. 9 is a bottom view of a top plate of a trimmer head according to an embodiment of the present invention.  
         [0011]    [0011]FIG. 10 is a perspective view of the interior surface of the top plate.  
         [0012]    [0012]FIG. 11 is a perspective view of an embodiment of a trimmer head blade.  
         [0013]    [0013]FIG. 12 is a top view of the blade depicted in FIG. 11.  
         [0014]    [0014]FIG. 13 is a side view of the blade depicted in FIG. 11.  
         [0015]    [0015]FIG. 14 is a cut-away side view of the blade depicted in FIG. 12, taken along lines  14 - 14 .  
         [0016]    [0016]FIG. 15 is a front view of the blade depicted in FIG. 11. 
     
    
     DETAILED DESCRIPTION  
       [0017]    The present invention is a trimmer head, for attachment to a rotary vegetation cutter. It is comprised of a body and blades. In one embodiment, the body is comprised of a top plate, bottom plate, and pins.  
         [0018]    As illustrated in FIGS. 1, 2 &amp;  6 , the top plate,  20 , is a one-piece plate that fits over the bottom plate. A central bore  30  extends through the top plate, and the bore is sized so as to accommodate the arbor or shaft of a trimmer. As illustrated in FIG. 9, the top plate  20  has a first set of pin bores  40 ,  42 , and  44  on its interior surface for holding pins  130 ,  132 , and  134 . The top plate also has a plate coupling well  50 , which fits with the coupling boss  80  of the bottom plate  60  when the top plate  20  and bottom plate  60  are joined together.  
         [0019]    As illustrated in FIG. 1, in an embodiment of the invention the top plate is triangular shaped, although it could also be a number of other difference shapes, including circular, square, or octagonal. etc.  
         [0020]    As illustrated in FIGS. 1, 2,  3 ,  4 ,  5 ,  6 , and  7 , the bottom plate  60  is a one-piece plate that fits with the top plate  20  and pins to form the body of the trimmer head. The bottom plate  60  has a base  70  that extends upwardly from the bottom plate. The base  70  houses a second set of pin bores  90 ,  92 , and  94  that can be aligned with the first set of pin bores  40 ,  42  and  44 . Atop the base is a coupling boss  80  that is shaped and aligned so as to conjoin with the top plate&#39;s coupling well  50 . The central bore  30  extends through the bottom plate.  
         [0021]    On the exterior or bottom surface of the bottom plate is a shaft attachment depression  110  within which is a fastener well  120 . As illustrated in FIG. 10, the attachment depression is essentially the hollow interior of the base  70  and the coupling boss  80 , and in one embodiment of the invention the depression is circular and has a circumference less than the circumference of the coupling boss. Within the attachment depression  110  is the fastener well  120 , which has side wall  122  and fitted opening  124 . The central bore  30  extends through the fastener well.  
         [0022]    As illustrated in the above-referenced figures, in an embodiment of the invention the bottom plate is circular, although it could also be a number of other different shapes, including triangular, scalloped-shape for easy removal by hand, etc.  
         [0023]    The trimmer head is attached to a rotary vegetation cutter by inserting the shaft of the trimmer all the way through the central bore  30 , and by placing a fastener, such as a hex nut or bolt, in the fastener well and securing it to the shaft. The trimmer head is designed to work with many different kinds of trimmers, and therefore different fasteners may be necessary to fit the head to different trimmers.  
         [0024]    As shown in FIGS. 7 and 8, the exterior surface of the bottom plate also may have wear guides  100  and  102 . These wear guides are depressions or indentations, and as the bottom plate wears away from use, the wear guides become shallower and shallower. The user can then decide when to replace the trimmer head based on the depth of the wear guides. Other suitable wear guides could be fashioned from a protrusion that would wear away with use, tire-type treads that would wear down, or a subsurface of a different color that would be apparent when the plate wears down. The wear guide could be placed on any portion of the body that wears down from contact or use, including but not limited to the bottom or side.  
         [0025]    For purposes of this patent, the following definitions apply. “Wear guide” refers to any structure that indicates the deterioration of the body of the trimmer head. “Body” refers generically to any blade-holding piece or pieces, such as the top plate and bottom plate. “Bottom portion” refers to the exterior surface of the bottom plate, or in the case of unibody versions of this invention, the bottom portion of the unibody. “Side portion” refers to any side or lateral portion of the top or bottom plate, and in the case of unibody versions of this invention, refers to any side or lateral portion of the unibody.  
         [0026]    The top plate and bottom plate are held together with pins  130 ,  132 , and  134 , which fit into the first set of pin bores,  40 ,  42 , and  44  and into the second set of pin bores  90 ,  92 , and  94 , as illustrated in FIG. 1. The pins are sized to tightly fit within the pins bores  40 ,  42 , and  44  (described below), so that pins become a part of the top plate.  
         [0027]    The blades  140 ,  142 , and  144  have openings  160 ,  162 , and  164  at one end, and the blades are attached to the body by inserting the pins through the openings and into the first set of pin bores and second set of pin bores, as illustrated in FIG. 1. The blades, which rotate and pivot around the pins with the movement of the shaft, may have serrations  150 ,  152 ,  154  to enhance their cutting ability.  
         [0028]    As shown in FIGS.  11 - 15 , in an alternative blade embodiment,  170 , the blade itself,  190 , is made of metal, but has a plastic overcoat,  180 , as well as an opening  200 , for insertion of the pins.  
         [0029]    The top plate, bottom plate and blades can be made of plastic, and other materials such as aluminum. The pins can be made of metal, such as steel, and also could be made of other materials.  
         [0030]    The top plate and bottom plate can be made by injection molding, or machined using lathes and drill presses. One skilled in the art will appreciate that the present invention can be practiced by other than the described embodiments, which are presented for purposes of illustration and not limitation.