GB784358A - Zig-zag sewing machine - Google Patents

Abstract

784,358. Sewing machines. SOC. PER AZIONI FRATELLI BORLETTI. Aug. 8, 1955 [Aug. 6, 1954, Nov. 18, 1954], No. 22846/55. Class 112 Needles, shifting laterally. Relates to a zig-zag sewing machine in which the needle-bar 5, Fig. 1, receives its up and down movement from a crank 3 driven by the arm shaft 1, and its transverse movement from a rod 31 connected to a shaft 29 slidably mounted on a support 25 oscillated through a lever 19 by a cam 16, driven by the arm shaft, the support 25 and shaft 29 being adjustable relative to the rod 31 to regulate the neutral line of the stitches and the amplitude of the transverse movement. According to the invention a second cam is removably mounted on the same shaft as the cam 16 and the lever. 19 can be displaced to selectively engage either cam without displacing the support. As shown in Fig. 3 the second cam 50 which is shaped for a determined cyclic variation of zig-zag sewing is mounted on the hub of the cam 16 and is removably held in position against the action of a spring 57 by a nut 56. Access to the cam is through a window covered by a plate 58. As shown in Fig. 2, the spring-loaded lever 19 is slidably mounted on a shaft 20, and may be displaced by mean of a knob 52, Figs. 1 and 4, a pin 53 on the lever engaging a slot 54 in a plate 55, the slot being shaped to retain the lever in either of two positions. The support 25 carries a pin 24 engaged by a fork 23 on lever 19 and is pivoted at 26 in a support 35 pivotally mounted on a shaft 35<SP>1</SP> and provided with an arm 36 with a forked end engaged by a projection on a member 39 pivoted on a shaft 40. A flexible plate 41 secured to the member 29 carries a knob 42 which may be moved to occupy one of three different positions, each of which results in a different position for the pivot pin 26 and hence the neutral line of the stitches. The rod 31 and a link 44 are pivoted to the shaft 29 at 43 and the other end of the link is pivoted at 45 on a sleeve 46 mounted on the shaft 40 and provided with an arm 47 carrying a knob 49 by means of which the arm may be moved to move the shaft 29 axially and thus vary the amplitude of the zig-zag. Adjustable stops 59 co-operate with a part 61 on the stem of the knob to limit movement thereof. The knob may be pressed against the action of spring 47 to disengage the part 61 from the stop and allow further movement. Besides the positions of engagement with the cams 16, 50, the lever 19 may occupy a third position resting on a bearing surface independent of the cams, in which case it remains motionless. In a modification, Fig. 6, the sleeve 64 rigidly attached to the lever 19 and slidably engaging the shaft 20 has a groove 65 engaged by a pin 66 on a lever 67 mounted on a bush 68 pivoted on a pin 69. A bell crank lever loosely mounted on the bush has an arm 70 coupled to the lever 67 by a spring 76 and a selection arm 71 adapted to be retained in notches 74a, b, c corresponding respectively to engagement of the lever 19 with cam 50, cam 16 and a cylindrical bearing surface 79. In a further modification, Fig. 9, the sleeve 64 is loaded by a spring 76<SP>1</SP>b and has a projection 66<SP>1</SP> engaging a stepped selecting cam 64<SP>1</SP> which is loaded by a stronger spring 76<SP>1</SP>a and is mounted on a shaft 20<SP>1</SP> co-axial with shaft 40 and provided with a knob 72'. In the arrangements of Figs. 6 and 9 the selecting devices can be operated irrespective of the nature of the engagement of the lever 19 with the cams. Movement of the lever will follow automatically when disengagement occurs. Reference has been directed by the Comptroller to Specification No. 736,277.