Patent ID: 6923130

Claim:
A sewing machine, comprising an arm ( 1 ); a base plate ( 3 ); a needle ( 6 ), which is mounted in the arm ( 1 ) drivably in up and down reciprocation, for guidance of a needle thread ( 20 ); a hook ( 8 ), which is mounted in a hook-bearing case ( 11 ) in the base plate ( 3 ), rotatable by a vertical hook-driving shaft ( 10 ) in a direction of rotation ( 48 ); a transmission shaft ( 12 ), which is drivably lodged in the base plate ( 3 ); a step-up gear ( 13 ), which is disposed between the transmission shaft ( 12 ) and the hook-driving shaft ( 10 ), for actuation of the hook-driving shaft ( 10 ) at twice the speed of the transmission shaft ( 12 ); a bobbin case ( 21 ) housed in the hook ( 8 ) freely rotatably in relation thereto, wherein the bobbin case ( 21 ) houses a bobbin ( 29 ), is provided with a lifter cam ( 31 ), has a stopping rib ( 22 ) which cooperates with a stopping cam ( 23 ) that is stationary relative to the base plate ( 3 ), preventing the bobbin case ( 21 ) from rotating in the direction of rotation ( 48 ); a case lifter ( 33 ), which comprises a lifter lever ( 32 ) that is applicable to the lifter cam ( 31 ), a sensing lever ( 40 ) loaded by a spring ( 43 ), and a lifter shaft ( 34 ), which is pivotably mounted in the hook-bearing case ( 11 ), non-rotatably joining to each other the lifter lever ( 31 ) and the sensing lever ( 40 ); and a case-lifter drive mechanism ( 38 ), which comprises an axial cam disk ( 39 ), which is non-rotatably connected to the transmission shaft ( 12 ) and directly drivable thereby for rotation at a speed that is only half the speed of the hook ( 8 ), and which comprises a frontal cam face 42 , against which is pressed the sensing lever ( 40 ).