GB871101A - Bobbin thread case opener mechanism - Google Patents

Abstract

871,101. Sewing machines. SINGER MANUFACTURING CO. March 15, 1960 [April 6, 1959], No. 9054/60. Class 112 Bobbin case-opener mechanism in a lock stitch sewing machine is characterized in that a pair of stop members, movable in unison toward and away from the axis of rotation of the looptaker, co-operate each with one of a pair of abutment surfaces carried on the bobbin case and disposed on that side of the path of needle reciprocation from which the looptaker beak moves in engaging a needle thread loop, said abutment surfaces being spaced angularly and at different radial distances from said axis of rotation, whereby the movable stops are positioned alternately in engagement with their co-operating surfaces for passage of a thread loop in succession therebetween. The base 11 of the bobbin case is formed with a low radial projection 30 and a high radial projection 31. A curved arm 35, carried on a bracket 38 pivoted on a fixed pin 39, is secured adjustably by a screw and slot connection 41, 42 to an arm 43 also pivoted on pin 39. A forked end 44 of arm 43 embraces a three-lobed cam 45 on the looptaker driving shaft 16, whereby arm 35 is moved toward and away from the shaft. Arm 35 is closest when the looptaker is spreading the needle thread loop, and in this position, Fig. 1, a stop member 36 on arm 35 engages an abutment surface 32 on projection 30 to hold the bobbin case stationary. A second stop member 37 on arm 35 is then spaced from projection 31 to provide a gap for the inward passage of the front limb F of said thread loop. Arm 35 is farthest from shaft 16 when the needle thread take-up is operating, Fig. 5, whereby member 37 engages an abutment surface 33 at the outer end of projection 31 to hold the bobbin case stationary, while member 36 moves clear of surface 32 to provide a gap for the outward passage of thread limb F. It is stated that surfaces 32 and 33 are preferably formed as arcs concentric with pin 39 and are then so dimensioned that member 37 engages surface 33 before member 36 is free of surface 32.