Low noise producing lawn mower blade
BACKGROUND OF THE INVENTION 
     The invention relates to rotary mower blades of the type including vanes for creating air movement to lift grass into position for being cut by the blade and for blowing the cut grass into a bag. 
     It is becoming more and more popular to cut grass with mowers having the capability to bag the grass clippings. In order to increase the efficiency of the bagging capabilities of these mowers, they are often provided with blades having relatively large vanes or paddles for creating the necessary air flows. 
     However, these existing mower blades are very noisy in operation and often exceed new noise limits soon to be imposed by industry and/or various governmental bodies. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a novel mower blade for use with bagging mowers. 
     A broad object of the invention is to provide a bagging mower having a blade which generates a relatively low level of noise. 
     A more specific object is to provide a mower blade having vanes for creating an air flow sufficient for lifting grass to be cut and for bagging the cuttings and to provide air pressure relief passage means for reducing the pressure of the air ahead of the vanes. 
     These and other objects will become apparent from reading the ensuing description together with the appended drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a perspective view of a mower blade having vanes comprising lift wings and paddles embodying the principles of the present invention. 
     FIG. 2 is an elevational view showing the relationship of one end of the blade to a mower housing shown in section. 
     FIG. 3 is a top plan view of the blade end and housing shown in FIG. 2 with a portion of the housing broken away to reveal the blade end. 
     FIG. 4 is a perspective view variant of the vane illustrated in FIGS. 1-3. 
     FIG. 5 is a perspective view of a blade end having a vane comprising only a lift wing. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, therein is shown a mower blade 10 comprising a flat central section 12 fixed medially of its opposite ends to a vertical spindle 13 and having its opposite ends joined to opposite end portions 14. Each of the end portions 14 is formed to define, as considered relative to the direction of rotation of the blade indicated by the arrows, a first leading flat portion 16 sharpened to define a cutting edge 17, a lift wing 18 joined to and angled upwardly in trailing relationship to the portion 16, a second leading flat portion 20 joined to the wing 18 in trailing relationship thereto, and a fin 22 joined to and angled upwardly in trailing relationship to the portion 20 and terminating in a trailing edge portion 23. The flat portion 20 and fin 22 cooperate to define a paddle, which cooperates with the lift wing 18 to define a vane. 
     In accordance with a first embodiment of the present invention, the flat portion 20 of the paddle is shaped and joined to the lift wing 18 and fin 22 such as to define a recess 24 which extends inwardly between the wing and fin generally toward the spindle 13 from the outermost extremities of the end section 14. The recess 24 serves as an air pressure relief passage which serves to substantially reduce the pressure profile as would occur in front of the fin 22 during rotation of the blade 10 in the absence of the recess 24. 
     Referring now to FIGS. 2 and 3, it can be seen that the outermost surfaces of the end portions 14 of the blade 10, as considered from the cutting edge 17 to the fin 22, are spaced increasingly inwardly toward the spindle 13 from a skirt 24 of a blade housing 26 to thereby cooperate with the recess as a pressure relief passage. 
     Referring now to FIG. 4, therein is shown a variant of the paddle wherein a second flat portion 28 is substituted for the previously described flat portion 20 and differs from the latter in that it is not configured to define a recess between the wing 18 and fin 22, but rather is provided with a plurality of perforations or holes 30 which serve as air pressure relief passages. 
     Referring now to FIG. 5, therein is shown a variant of the end portion 14 of the blade wherein the paddle is omitted and a plurality of perforations or holes 32 are provided in the first flat portion 16 so as to provide pressure relief passage means for the pressure profile created by the lift wing 18. 
     While the recess 24, perforations 30 and perforations 32 have all been illustrated as occurring separately, it is to be understood that any combination of the three ways of providing air pressure relief may be employed. 
     The operation of the invention is thought to be evident from the foregoing description and, for the sake of brevity, no further description of the operation is given.