Design Theories of Single-Edged Blade for Japanese Rotary Blades

Abstract

In this paper, the design theories for the single-edged curve of Japanese rotary blades were obtained by the geometrical analysis.
1) Shapes of blade cross-sections of the lengthwise blades were observed, and it was conjectured that the decreasing tillage resistance of single-edged blades are more advantageous than double-edged ones.
2) The cross-section of lengthwise blade is usually designed on the radius direction of the edged curve, the actual shape of blade cross-section in the soil exists on the trochoid locus curve of the blade motion.
3) The forming process of lengthwise blade portion was observed in the production-line of Japanese rotary blades. The result was that the blade cross-section in the radius direction of edged curve might be of uniform thickness with single-edge which gives the decreasing resistance, due to reasonable relief angle between the blade and the material to be cut.
4) The theoretical analysis for examining angle-operations of blade which has a round cornered edge with radius r, was presented. The calculated equations of actual cutting angle ε₁ and actual relief φ of the lengthwise are obtained as follows:
ε₁=tan^-1[2L₁tan(ε₀/2)-(t¹-t²)tan(β+α-90){(M-r)tan(ε₀/2)+r}/2L₁[(M-r)tan(ε₀/2)+r]√1+tan²(β+α-90)]
φ=tan^-1{(t¹-t²)tan(β+α-90)/2L₁√1+tan²(β+α-90)}
5) The changing range of angle β and the actual cutting angle ε₁ at the lengthgwise blade with single-edge are presented by the graphs, shown in Fig. 7. These graphs are used to obtain the relationships between the actual cutting angle with tillage conditions and design factors, for designing the lengthwise blades of Japanese rotary blades.