Selective thread cutting device in a sewing machine

Abstract

A thread cutting device includes a movable knife positioned below a throat plate and movable from a first position to a thread cutting position via a second position for separating the upper fabric thread and the upper needle thread from each other within the range where the movable knife may engage the upper fabric thread and the upper needle thread but may not engage or cut the lower thread. The movable knife includes an engaging portion for engagement with the upper needle thread on the side toward the second position and a cutting edge on the opposite side. The movable knife also includes a thread separating portion for separation of the upper fabric thread and the upper needle thread between the needle hole and the bobbin holder from each other toward the cutting edge and the engaging portion, respectively, when the movable knife moves from the first position to the second position. A fixed knife is positioned below the throat plate for cooperation with the movable knife at the thread cutting position, so that the upper fabric thread can be cut when the movable knife is moved from the second posiiton to the cutting position. A lower thread guide is positioned below the throat plate and operable to selectively move the lower thread existing between the needle hole and the bobbin holder within the range where the movable knife passes when the movable knife moves from the second position to the cutting position, thereby permitting cutting of both the upper fabric thread and the lower thread.