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1. A hook system for a sewing machine, comprising: a hook (1) that is mounted for rotation and is drivable by a hook drive in a hook race (5) of a hook race carrier (7), a bobbin case (11) for a lower thread bobbin (13) is located in the hook (1), a guide bearing (21) for a cam support (19) with at least two drive cams (17) located between the hook drive and the hook (1), the drive cams (17) are displaceably guided on the cam support (19) in the guide bearing (21) that is rotatable by a shaft (35) of the drive, and the cam support (19) is displaceable by a bolt (31) located on the shaft (35) eccentrically to an axis (A) of the shaft (35), a sliding block (29) pushed onto the bolt (31), the sliding block (29) being guided in an opening (25) in the cam support (19) for movement back and forth between two parallel guide surfaces (27), and the sliding block including opposing surfaces upon which the parallel guide surfaces act, the at least two drive cams (17) are displaceable in a radial direction in two slots (23) in the guide bearing (21), the drive cams (17) are driven via the sliding block (29) such that during a rotation of the hook (1), in a first position, each of the drive cams (17) is movably located in a respective one of two openings (15) in a back (14) of the hook (1), entering into a positive connection therewith, and at subsequent rotational positions of the hook, one of the two drive cams (17) are each in a single engagement with the hook in a respective one of the openings (15) and the other of the two drive cams is disengaged from the respective one of the openings in order to allow passage of an upper thread between the hook and the bobbin case.
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