Method and apparatus for doubling and twisting a yarn by a two-step changeover system

A method for doubling and twisting a material yarn by a two-step changeover system by means of a pot twisting and winding device, wherein said material yarn is fed into said pot by way of a traverse tube being reciprocally displaced upwardly and downwardly along an axial center of said pot during a first step operation so that a yarn package of a primary twisted yarn created from said material yarn is formed upon an inside cylindrical wall of said pot, upon completion of forming said yarn package of said primary twisted yarn, a second step operation starts in which said primary twisted yarn is unwound from said yarn package so as to double with said material yarn supplied through said traverse tube while eliminating the primary twists imparted thereto, and said doubled yarn is twisted simultaneously to said doubling operation;

• and, during the second step operation, upon completion of unwinding of said primary twisted yarn from said yarn package formed in said pot, said second step operation is stopped and said first step operation is commenced again, said first step operation and second step operation being alternately carried out, and changeover from the first step to the second step being controlled such that a bottom end of said traverse tube in said pot is at a position defined by D.sub.2 .gtoreq. L.sub.2 wherein D.sub.2 represents an innermost diameter of said yarn package formed in said pot by said first step operation while L.sub.2 represents a distance between said bottom end of said traverse tube and an upper terminal of an aperture formed from a bottom inside surface of said pot.