JPS6417685A - Bobbin thread cutting detector in sewing machine - Google Patents

Abstract

PURPOSE: To surely detect the breakage of a bobbin thread by bringing a contact moving member in contact with a part f the bobbin thread to rotate back and force by reciprocative displacing operation at the time of forming the seam, and detecting the operation stoppage of the contact moving member by a sensor equipped oppositely to the contact moving member. CONSTITUTION: The contact moving member 16 supported in the state of being capable of operating horizontally and rotationally in order to detect the presence/absence of the breakage of the bobbin thread in contact with a part of the bobbin thread Y which is contracted and extended to be reciprocatively displaced in the axial direction of a shuttle 5 at the time of forming a seam and the sensor 21 for originating a thread breakage detecting signal by detecting the operation stoppage of the moving member 16 are oppositely equipped under a needle board 1. Thus, the unstable bending and extending operation of the thread Y is converted to the stable rotating operation of the member 16 to precisely detect the operation of the thread to surely detect the presence/absence of the breakage of the thread by the sensor 21 through the member 16 and to eliminate inconvenience of generating an erroneous detection due to the tension fluctuation, or the like of the thread Y.