GB826538A - Improvements in or relating to the adjustment of the tension of the upper thread of sewing machines - Google Patents

Abstract

826,538. Sewing machines. PFAFF A. G., G. M. Feb. 13, 1958 [Feb. 21, 1957], No. 4688/58. Class 112 A disc-type thread-tensioning device comprises a check spring having its threadengaging portion disposed between a tension-regulating knob and a housing, and anarcuate member which has a threadguiding edge and a thread-deflecting edge and is situated radially outwards of said spring portion in the thread-passing gap between said knob and housing. A supporting member 4, Fig. 2, is secured by a grub screw 6 in a housing 2 provided in the machine frame 1, and is formed with a central bore 7. A shaft has a rear portion 13 secured in bore 7 by a grub screw 20, an intermediate portion 12 of reduced diameter, and a screw-threaded front portion 10. A knob 31 is formed with a tapped boss 32 which screws on to portion 10. A sleeve 24, slidably mounted on portion 12, is formed in front with a radial flange 30, and a cylindrical portion 28 projects from flange 30 to enclose boss 32. Thread-tensioning discs 25, 26, 27 are mounted on sleeve 24 between member 4 and flange 30, and plate springs 29 are mounted on portion 28 between flange 30 and knob 31. A sleeve 33, secured by pins 34 to member 4, is connected by an outwardly flaring portion 35 to an arcuate portion 36 disposed in the gap 48 between knob 31 and housing 2 and formed with a threadguiding edge 37 and a thread-deflecting edge 38. A finger 39 projecting from portion 36 co-operates with a lug 40 on the knob to limit the rotation of the latter, and a second finger 41 serves as a pointer for graduations on the knob. A check spring has a spiral portion 45 mounted on sleeve 33 and anchored thereto by an end portion passing through one of a series of holes 44 therein and a thread-engaging portion 46 which passes through a slot 47 in portion 35 and lies under portion 36. Thread passes over portion 46 on its way to the deflecting edge 38. A member 23 bridging the inner end of sleeve 24 is adap- , ted to be engaged by a pin 18, actuated by a plunger 17 when the presser foot is lifted, to separate the tensioning discs. In a modification, Fig. 4, a hollow shaft 108 secured by a screw 120 in a support member 104, journals a pin 132 secured to a knob 131. The tension discs 25, 26, 27 are mounted on pin 132 between shaft 108 and knob 131. The plate springs 29 are mounted on shaft 108 between an abutment 52 carried by the latter and a plate 123 which is slidably mounted in a longitudinal slot 111 formed in shaft 108 and is in screw-threaded engagement with the screwed end 110 of pin 132. Plunger 17 is arranged to engage end 110 for releasing the thread tension.