Patent ID: 7565873

Claim:
A sewing machine comprising: a needlebar to which a sewing needle having an eye is attached; a needlebar vertical movement mechanism which drives the needlebar vertically; a needle swinging mechanism which drives the needlebar so that the needlebar is swingable right and left; a rotating hook having a hook beak which is capable of seizing a loop of a needle thread extending through the needle eye; a lower shaft which rotates the rotating hook in synchronization with vertical movement of the needlebar; a lower shaft gear which is comprised of a helical gear and slidably mounted on the lower shaft; a hook gear comprised of a helical gear capable of mesh engagement with the lower shaft gear and mounted on the rotating hook; a drive force transmission mechanism which supports the lower shaft gear so that the lower shaft gear is axially moveable and transmits rotation of the lower shaft to the lower shaft gear; a cam mechanism which axially moves the lower shaft gear thereby to adjust at least one of a left encounter timing for seizure of the needle thread loop by the hook beak when the needle occupies a left needle location and a right encounter timing for seizure of the needle thread loop by the hook beak when the needle occupies a right needle location; and a machine frame on which are mounted the needlebar, the needlebar vertical movement mechanism, the needle swinging mechanism, the rotating hook, the lower shaft, the lower shaft gear, the hook gear, the drive force transmission mechanism and the cam mechanism.