GB994629A - Thread winding control mechanism for sewing machines - Google Patents

Abstract

994,629. Sewing machines. SINGER CO. May 11,1964 [May 14,1963],No.19504/64. Heading D1G. In a lock stitch sewing machine in which a bobbin, journalled in a rotary looptaker, may be rotated in order to be wound in situ by needle thread during normal operation of the needle and looptaker, and comprising means for sensing a predetermined amount of thread on the bobbin, the bobbin-rotating means is driven by an electric motor having a drooping load-speed characteristic, and means responsive to the thread-sensing means is operative for increasing the load on the bobbin-actuating means. A looptaker body 30 is carried by a hollow shaft 18 driven by a gear 21, rigid therewith, from the machine bed shaft. A stationary bobbin case 32, journalling the looptaker, journals a bobbin 34. A bobbin-actuating member 50 has a vertical rim 55<SP>1</SP> and is rigid with a shaft 51 journalled in shaft 18. A leaf spring 62, carried by a lever 60, embraces the lower end of shaft 51, whereby, when lever 60 is actuated to raise shaft 51, a pin 58, carried by shaft 51, enters a recess 59 in gear 21, and a pin 53 on member 50 enters a recess 54 in the bobbin. An arm 100, pivoted at 99 on the bobbin case, has an end 102 adapted to be engaged by the thread wound on the bobbin. When the latter is fully wound, a bevelled surface 103 on arm 100 engages rim 55 to depress shaft 51, against the bias of spring 62, to increas the load on the driving motor which is of the series commutator type having a drooping load-speed characteristic. The motor speed thereby falls to provide a signal to the operator. If the signal is disregarded, the increasing load serves to stall the motor.