GB510009A - Improvements in or relating to lockstitch sewing machines - Google Patents

Abstract

510,009. Sewing-machines. UNION SPECIAL MACHINE CO. Jan. 25, 1938, No. 2339. Convention date, Jan. 30, 1937. [Class 112] In order to reduce wear between the raceway 31 of a rotary hook and the rib 39 of the bobbin holder 38, the raceway is made wider than the rib so that side contact is not continuous, and to avoid pinching the needle thread between the rib and the raceway these parts are pressed together during the first half revolution of the hook after catching the loop, the rib floating in the raceway during the remainder of the stitchforming cycle. In the arrangement shown, the rotary hook makes two revolutions to one of the needle-driving shaft and the means for pressing the rib 39 against the side of the raceway 31 when required is actuated by the feed mechanism. The feed-bar 6 is supported by a link 23 from the feed-lift crank and is pivoted to an arm 9 on a rock-shaft 10 which is oscillated through a telescopic link 12 from the feedadvance eccentric, the feed being varied by mechanism as described in Specification 413,120. The bobbin-case cover 50 is provided with a pair of lugs 44, which embrace the end of a fixed arm 45 to prevent rotation of the bobbincase, and with a raised cam surface 55. An arm 60, pivoted to the feed-bar and spring- biassed to swing back when a spring latch 67 is released, has adjustably fixed to it an abutment member 58 which engages the cam surface 55 on the bobbin-case cover during the idle rearward movement of the feed dog to press the rib 39 against the side of the raceway 31.