Driving gear 2 rotates about fixed axis A and has bevel gear teeth arranged along a logarithmic spiral. Driven bevel pinion 1 is mounted rigidly on shaft 3 and rotates about its fixed geometric axis B. Shaft 3 slides along axis B in guide a. When gear 2 rotates alternately clockwise and counterclockwise at uniform velocity, shaft 3 has reciprocating helical motion at constant velocity along axis B.
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