GB1164258A - Improvements in or relating to Bobbin Case Openers for Rotating Looptaker Lockstitch Sewing Machines. - Google Patents

Abstract

1,164,258. Sewing machines. G. M. PFAFF A.G. 29 July, 1968 [31 July, 1967], No.35991/ 68. Heading D1G. In a sewing machine comprising a rotary hook rotatable at a whole number multiple of each stitch formation, and a bobbin case opener adapted to rotate the bobbin case oppositely to the direction of rotary hook rotation for opening a thread-escape gap, the bobbin case opener is operatively connected to two driving eccentrics, or equivalent mechanical means, one of which rotates synchronously with the rotary hook and the other of which rotates with a reduced whole number ratio thereto. A bed shaft 9, rotating synchronously with the arm shaft, is coupled by gearing 21, 22 to a vertical axis hook body 18 for rotating the latter at twice the speed of shaft 9. The driven gear 21 has a hollow shaft extension which is journalled in the machine frame and receives the lower end of a hollow shaft (17), Fig. 3, frictionally coupled to gear 21 by the head of an internally screwed bush (19) projecting upwardly into shaft (17) to engage a downwardly-projecting screwed stud (20). Upwardlyprojecting lugs (32) on shaft (17) enter apertures (33) in body 18 to couple the latter to shaft (17): A bobbin case 24; journalled in body 18, has a rotation-restraining lug 28 engaged in a notch 30 in the throat plate 29. An eccentric (31) on shaft (17) is embraced by a strap 35 rigid with a finger 36 adapted to cooperate with a lug 37 on bobbin case 24 for turning the latter to open a thread-escape gap between lug 28 and notch 30. An arm 39, projecting from strap 35, is connected by a pivotal link 41 to a bracket 44 rigid with a rod 45 slidable in the machine frame parallel to the direction V of work feed. A bracket 46, rigid with rod 45, is pivotally connected to a pitman 48 embracing an eccentric 49 on shaft 9. The arrangement is thereby such that during the thread loop-manipulating rotation of body 18, a point on finger 36 moves from a position O along a path A to engage lug 37 at a position 4 comparatively slowly along a gentle curve and disengages from lugs 37 at a position 6 comparatively quickly along a sharp curve, and then traces a closed curve D, separated from lug 37, during the succeeding idle rotation of body 18. In a modification, Fig. 4, eccentric 49 is carried by a vertical shaft driven by 1:1 gearing from shaft 9, and is embraced by a pitman pivotally connected to arm 39. In a further modification, Fig. 6, eccentric 49 is carried by a vertical shaft coaxial with the rotary axis of looptaker body 18 and driven by 1:1 gearing from shaft 9, and is embraced by a pitman pivotally connected to a crank arm on the lower end of a vertical shaft, the upper end of which carries a crank arm coupled by a pivotal link to arm 39. In a final modification, Fig. 8, eccentric 49 is carried by a vertical shaft driven by 1:1 gearing from shaft 9, and is embraced by a pitman, the extended arm of which is pivoted intermediately to arm 39 and carries at its free end the finger 36.