Aerodynamic Trimmer Head For Use In Flexible Line Rotary Trimmers

Abstract

An aerodynamic trimmer head assembly for use in flexible line rotary trimmers including a trimmer head having a curvilinear upper head surface and a shroud having a curvilinear portion extending over the head surface. A plurality of ribs extend downwardly and forwardly in the direction of rotation between the head surface and shroud defining a plurality of channels extending between portions of the upper head surface and shroud along curvilinear paths defined by the ribs. The channels define inlet openings in an upper portion of the shroud and outlet openings about the lower end portion thereof During rotation of the head and shroud, air is drawn downwardly about the drive mechanism, through the channel inlets, into and through the channels and outwardly therefrom at a forward inclination about the line projecting from the housing thereby cooling the drive mechanism of the rotary trimmer and reducing aerodynamic drag on the line.

1 - 69 . (canceled) 
     
     
         70 . A shroud for use on a rotary trimmer with a trimmer head having a housing adapted to be operatively connected to the rotary trimmer to effect rotation of the trimmer head wherein the housing defines at least one opening therein for the passage of a length of line therethrough and has a generally curvilinear upper head surface, said shroud comprising:
 a centrally disposed mounting aperture in an upper portion thereof; an annular curvilinear portion outwardly spaced from said mounting aperture and configured so as to be disposed above and extend along an upper curvilinear head surface of a trimmer head; a plurality of laterally spaced ribs projecting from an underside of said shroud and extending downwardly and forwardly along curvilinear paths in the direction of rotation such that upon said shroud being operatively connected to said housing, said ribs extend between said curvilinear portion of said shroud and the upper head surface from an upper portion of said shroud to a lower end portion thereof so as to cooperate with said housing to define a plurality of air channels extending downwardly and forwardly between portions of said upper head surface and said shroud along said paths defined by said ribs; a plurality of open channel inlets disposed about said mounting aperture in said shroud; and a plurality of open channel outlets disposed about said lower end portion of said shroud such that during rotation of said head and shroud, air is drawn downwardly through said channel inlets, into and through said channels and outwardly therefrom at a forward inclination about the length of line projecting from the housing thereby reducing aerodynamic drag on the line and cooling the drive mechanism of the rotary trimmer.   
     
     
         71 . The shroud of  claim 70  including at least one mounting surface disposed about said aperture for operatively connecting said shroud to said housing for rotation therewith and wherein said channel inlets are disposed about said mounting surface inwardly of said annular curvilinear portion of said shroud. 
     
     
         72 . The shroud of  claim 70  including a plurality of dimples disposed in an outer surface of said curvilinear portion of said shroud. 
     
     
         73 . (canceled) 
     
     
         74 . The shroud of  claim 70  wherein the transverse dimension between said ribs increase and the elevation of said ribs decrease as said ribs extend downwardly and forwardly along said shroud. 
     
     
         75 . The shroud of  claim 70  including a plurality of equidistantly spaced troughs disposed in an outer surface of said annular curvilinear portion of said shroud, said troughs extending downwardly and forwardly along curvilinear paths from an upper portion of said outer surface to a lower portion thereof. 
     
     
         76 . The shroud of  claim 75  wherein said curvilinear paths defined by said troughs replicate the curvilinear paths defined by said ribs. 
     
     
         77 . The shroud of  claim 70  wherein the cross sectional area of each of said channels is substantially constant as said channels extend downwardly and forwardly between portions of said upper head surface and said shroud. 
     
     
         78 . The shroud of  claim 70  wherein said shroud defines inner wall surfaces extending along said channel inlets, each of said inner wall surfaces defining a radius of curvature extending downwardly and outwardly to provide a smooth and gradual directional transition for the air entering said channels through said channel inlets. 
     
     
         79 . The shroud of  claim 78  including a plurality of dimples disposed in an outer surface of said curvilinear portion of said shroud. 
     
     
         80 . (canceled) 
     
     
         81 . The shroud of  claim 78  wherein the transverse dimension between said ribs increase and the elevation of said ribs decrease as said ribs extend downwardly and forwardly along said shroud. 
     
     
         82 . The shroud of  claim 78  wherein the cross sectional area of each of said channels is substantially constant as said channels extend downwardly and forwardly between portions of said upper head surface and said shroud. 
     
     
         83 . (canceled) 
     
     
         84 . (canceled) 
     
     
         85 . (canceled) 
     
     
         86 . The shroud of  claim 81  wherein the cross sectional area of each of said channels is substantially constant as said channels extend downwardly and forwardly between portions of said upper head surface and said shroud. 
     
     
         87 . A shroud for use on a rotary trimmer with a trimmer head having a housing adapted to be operatively connected to the rotary trimmer to effect rotation of the trimmer head wherein the housing defines at least one opening therein for the passage of a length of line therethrough and an upper head surface, said shroud comprising:
 a centrally disposed mounting aperture in an upper portion thereof; an annular body portion outwardly spaced from said mounting aperture and configured so as to be disposed above and extend along an upper head surface of a trimmer head; a plurality of laterally spaced ribs projecting from an underside of said body portion of said shroud and extending outwardly and forwardly along curvilinear paths in the direction of rotation such that upon said shroud being operatively connected to said housing, said ribs extend between said body portion of said shroud and the upper head surface from an upper portion of said shroud to a lower end portion thereof so as to cooperate with said housing to define a plurality of air channels extending outwardly and forwardly between portions of said upper head surface and said shroud along said paths defined by said ribs; a plurality of open channel inlets disposed about said mounting aperture in said shroud; and a plurality of open channel outlets disposed about said lower end portion of said shroud such that during rotation of said head and shroud, air is drawn downwardly through said channel inlets, into and through said channels and outwardly therefrom at a forward inclination about the length of line projecting from the housing thereby reducing aerodynamic drag on the line and cooling the drive mechanism of the rotary trimmer.   
     
     
         88 . The shroud of  claim 87  including at least one mounting surface disposed about said aperture for operatively connecting said shroud to said housing for rotation therewith and wherein said channel inlets are disposed about said mounting surface inwardly of said annular curvilinear portion of said shroud. 
     
     
         89 . The shroud of  claim 87  including a plurality of dimples disposed in an outer surface of said body portion of said shroud. 
     
     
         90 . The shroud of  claim 87  wherein the transverse dimension between said ribs increase and the elevation of said ribs decrease as said ribs extend outwardly and forwardly along said shroud. 
     
     
         91 . The shroud of  claim 87  wherein the cross sectional area of each of said channels is substantially constant as said channels extend outwardly and forwardly between portions of said upper head surface and said shroud. 
     
     
         92 . The shroud of  claim 70  wherein said shroud defines inner wall surfaces extending along said channel inlets, each of said inner wall surfaces defining a radius of curvature extending downwardly and outwardly to provide a smooth and gradual directional transition for the air entering said channels through said channel inlets. 
     
     
         93 . The shroud of  claim 92  including a plurality of dimples disposed in an outer surface of said body portion of said shroud. 
     
     
         94 . The shroud of  claim 92  wherein the transverse dimension between said ribs increase and the elevation of said ribs decrease as said ribs extend outwardly and forwardly along said shroud. 
     
     
         95 . The shroud of  claim 92  wherein the cross sectional area of each of said channels is substantially constant as said channels extend outwardly and forwardly between portions of said upper head surface and said shroud. 
     
     
         96 . The shroud of  claim 94  wherein the cross sectional area of each of said channels is substantially constant as said channels extend outwardly and forwardly between portions of said upper head surface and said shroud.