Sewing machine

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).