SE448475B - SEWING MACHINE MECHANISM - Google Patents

Description

448 475 is transmitted from the crankshaft to the needle bar via the crank rod. Since this center angle v with the frame and this is stored in the upper end (Fig. 1), a torque arm L1 is formed. This, together with the force in the connecting rod, causes a pivoting moment around the pin 10, the size of which depends on the degree of impermeability of the workpiece. This torque is unfavorable to the adjusting member 12 which must be dimensioned to withstand the torque which may be significant. In Fig. 2 the mechanism is drawn as in Fig. 1 with the difference that the bearing "pin 10 of the frame ll in Fig. 1 is moved from the top to the middle", more precisely to the same "level as point 14. This bearing pin is called in Fig ._y2 18. This means that the torque arm L1 from Fig. 1 is now zero, which means that the needle bar frame does not receive any oscillating moment from the driving force for the penetration of the needle 'at this moment of stitch formation. in relation to a second torque 'Lz, which is the distance between the pin 18 and the member 12, but L1 is still small, therefore the horizontal component of the force from the connecting rod, acting on the adjusting member, becomes considerably smaller than in the device according to Figs. The mechanism shown in Figs. 3 and 4 further improves the device.

The crankshaft is driven here with assistance. of a link system which produces an oval movement 19. The system consists of a pin 20 arranged in the body, on which a link 21 is mounted, and a crank arm 22 which carries a level pin. An arm 23 connects this to bearings 24, 25 on the link resp. the connecting rod. When the crankshaft 16 rotates, the pin 17 describes a circular path 26, the bearing 24 a circular arc 27 and the bearing 25 the oval path 19.

Since this is compressed, in the horizontal direction ', the angle u' between the connecting rod and the needle bar frame becomes smaller than the angle v in Fig. 1. Fig. 1A shows a position in the stitch formation where the ratio L * 1, Lz is most unfavorable. L1 is here very small, which gives an 'insignificant effect of the driving force from the connecting rod on the adjusting member 12. This can therefore be dimensioned for much lower holding force than with a device' according to Fig. 1. The pin 2D can be provided with adjustable. attachment, so that it can be raised and lowered in the frame.

This makes it possible to adjust the needle height in a simple way. i Fig. 5 shows. .the mechanism as a module on a plate frame 28, which can either form part of the upper arm of the machine or be a free-standing part, which is mounted in the arm.

Fig. 4 shows most of the parts of Fig. 4, which show the construction principle of the module. Attached to the crank pin 17 is an arm 29 having a pin 30 which carries a bearing for a slider 31 on a rod 132 which in turn is attached to a wire pick-up 33 which is mounted on a shaft 34 in the module body. The outer end of the arm has a thread guide 35 which in the usual way pulls up the upper thread during single phase of the stitch formation.

The arm is driven by the crank in a vertical pivoting motion; as the crank pin moves in its circular path, the slide piece 31 slides up and down on the rod 32 'while pivoting it back and forth, and follows the pivoting movement.

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Claims (4)

448 475 The adjusting force for the zigzag movement can, as previously mentioned, be reduced in a device according to Fig. 4, in the module, Fig. 5, the zigzag movement is effected by a stepper motor 36 and to this gear and link system connected. A gear 37 acts against a rack 38A, which at one end has an angular recess 39. The rack carries a pin 40 which rests on an extension 41 of the pin frame, which will thereby follow the movement of the rack. The pin is normally held in the apex of the angle as a result of a pair of compression springs 42, 43 acting on the must-facing side of the rod, which are attached to the frame, and the two sloping angular sides 44, 45. the sides when the needle is subjected to a lateral force, but when this ceases the pin returns to the angular tip. A similar actuator is previously described in the Swedish patent publication No. 423. 912. g The mechanism now described is an example of how the invention can be realized. The design of links, angle levers and support points, etc. can of course be varied without the basic idea of the invention being substantially defined in the appended claims. in Patent Claims A zigzag mechanism in a sewing machine with a laterally pivoting needle bar frame (II), a zigzag movement inducing actuator (12), connecting rod (13) coupled to the needle bar (15) in a coupling point (14), which describes an up and down movement, and a crankshaft (16) the extent of which is perpendicular to the zigzag movement, characterized in that an average position in said upward and downward movement of the coupling point is located approximately in the middle of the pivot center (18) of the needle bar frame, and that said coupling center position of the sewing machine's pin tip, as this hits the work material. " 2.; Zigzag mechanism according to claim 1, characterized in that the upper end of the crank is mounted at one end of an arm (23), the other end of which is mounted at a link (21) and which in between "by means of a crank arm ( 22) and the crank pin (17) is in drive connection with the crankshaft Zigzag mechanism according to claim 2, characterized in that the upper end of the connecting rod describes an oval path of movement (19) whose longitudinal axis has an extension in the longitudinal direction of the needle rod. 4. Zigzag mechanism according to claim 2, characterized in that said link (21) has a storage point (20) in the body of the machine with height adjustability, whereby the height position of the needle relative to the gripper is adjustable.