JPS643513B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to domestic sewing machines, and more particularly to a zigzag mechanism for such machines.

In a conventional zigzag sewing machine, the needle bar moves vertically and horizontally, and the horizontal movement is during the downward movement of the needle caused by the crank and connecting rod, which causes the needle bar to move to a set position. controlled by holding guiding means. When the material to be penetrated by the needle is hard or thick, the torque on the needle bar caused by the resistance during the movement of the needle will be so great that the needle will move laterally from its set position, thereby causing the needle to break. It ends up. Several methods have been suggested to overcome this drawback. For example, the guide means may be reinforced to withstand the torque, the torque lever arm may be shortened, or a universal joint may be used. the current,
By arranging the step motors, which are increasingly used in sewing machines, to obtain a zigzag movement, the holding force of the guide means in the set position is considerably limited. Therefore, it is important to have a structure in which the torque applied to the needle bar when moving the needle is extremely small.

The upper arm of the invention has a crankshaft that is perpendicular to the zigzag movement of the needle. It is an object of the present invention to easily obtain a driving force for the needle bar when the crankshaft including the link and the connecting means are arranged in this way, and in this case, the zigzag movement guiding means can provide the driving force for the needle bar. The goal is to avoid being interfered with. To solve this problem, the connection point between the connecting rod and the needle bar is placed at a point that approximately coincides with the fulcrum of the zigzag movement at the point when the needle penetrates the fabric. The features thus introduced into the sewing machine according to the invention are set out in the characterizing part of claim 1.

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

A sewing machine according to the invention comprises a hollow body having an upper arm. Horizontal pin 10 at the end of the upper arm
There is a needle bar rocking stand 11 attached to the horizontal pin.
swings in a direction perpendicular to the feed direction of the sewing machine. The adjustment of the needle bar rocker, ie the zigzag position, is effected by guide means 12, which is shown as a single block in FIGS. 1 to 4. The connecting rod 13 is connected at a point 14 to a needle bar 15 which is supported on a needle bar rocker. The crankshaft 16 is installed in the main body perpendicularly to the zigzag direction,
Its crank pin 17 is connected to the connecting rod, and when the needle hits the material, force is transmitted from the crankshaft through the connecting rod to the needle bar. This rod is supported at its apex (Fig. 1) at an angle V with respect to the needle bar rocking table.
Therefore, the distance between the torque fulcrum and the force point (referred to as the torque arm for convenience in this specification)
L ₁ is formed. This torque arm and the force of the connecting rod create a torque on the horizontal pin 10 with an amount determined by the resistance to penetration of the material. This torque stresses the guiding means 12, so that the guiding means must be dimensioned to withstand this torque, which may be large.

FIG. 2 shows the same mechanism as shown in FIG. 1, except that the support pin 10 of the needle bar rocker 11 of FIG. is moving to. In FIG. 2, this bearing pin is designated 18. That is, since the torque arm _L1 of FIG. 1 is zero, the needle bar rocker receives no torque from the needle penetration force at this point in the stitch forming process. When the needle penetrates the material, the torque arm
and the guide means 12 becomes somewhat larger with respect to another torque arm L ₂ , but since L ₁ is still small, the horizontal component of the force of the connecting rod stressing the guide means is substantially smaller than in the device shown.

The arrangement of FIGS. 3 and 4 is an alternative modification of the device. In this case, the propulsion force of the connecting rod is obtained by a link system forming an oval-shaped movement track 19. The link system consists of a pin 20 disposed within the body, a link 21 attached to this pin, and a crank arm 22 carrying the crank pin 17. Arm 23
connects the crank pin to the two bearings 24, 25 of the link and to the connecting rod, respectively. crankshaft 1
6 rotates, the crank pin 17 traces a circular orbit 26, the bearing 24 traces an arc, and the bearing 25 traces the aforementioned egg-shaped orbit 19. When this trajectory narrows in the horizontal direction, the angle U between the connecting rod and the needle bar rocking platform becomes smaller than the angle V in FIG. In FIG. 4, the position of the seam formation process is at the ratio L ₁ , L ₂
is the most disadvantageous position. In this case, L ₁ is so small that the force of the connecting rod has only a small influence on the guiding means 12 . This guide means can therefore be dimensioned so that it has to provide a much smaller positioning force than in the case of the device according to FIG. The pin 20 may be provided with an adjustable metal attachment to allow it to move up and down within the body and to easily adjust the height of the needle.

FIG. 5 shows the mechanism as a module in the platform frame 28, which can form part of the upper arm of the sewing machine or can be a separate part attached to the upper arm. Most of the elements of FIG. 4 can also be seen in FIG. 5, which shows the design principles of the module. An arm 29 on the crank pin 17 has a pin 30 which carries the bearing of a slider 31 which slides on a rod 32 which is fixed to a cam balance 33 mounted on an axle 34 in the frame of the module. Thread guide 35 at the end of the arm
usually picks up the needle thread during one phase of the seam forming process. The arm is driven by a crankshaft and vibrates in the vertical direction. When the crank pin moves along a circular path, the slider 31 moves to the rod 32.
The arm follows the oscillatory motion by sliding up and down along the axis, causing it to swing back and forth.

As mentioned above, the adjustment force required for the zigzag movement can be reduced in the device shown in FIG. In the module of FIG. 5, the zigzag motion is achieved by a step motor 36 and a gear link system connected thereto. The pinion 37 meshes with a rack 38 having a bent recess 39 at one end. The rack carries pin 40,
This pin is inserted into the extension 41 of the needle bar rocking base, so that the needle bar rocking base moves in accordance with the movement of the rack. The pin typically has two beveled edges 44,
45 and a pair of compression springs 42, 43 fixed to the needle bar rocker on the opposite side of the rack, it is held at the bottom of the bent recess. However, when the needle is subjected to a force from a side force, the pin may slide upwardly along one of the edges. When the force disappears, the pin returns to the bottom of the recess. Similar guide means have already been described in Swedish Patent Publication No. 423,912.

The mechanisms described above illustrate how to implement the invention. It will be appreciated that the configuration of links, knee levers, fulcrums, etc. may be varied without departing from the inventive concept as generally defined in the appended claims.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a needle bar mechanism in which the needle bar is supported at the top; Figure 2 is a diagram of a mechanism in which the needle bar is centrally supported; Figure 3 is a diagram in which the connecting bar is oval shaped. FIG. 4 is a schematic diagram of the same mechanism as in FIG. 3 in a different position; FIG.
FIG. 2 is a perspective view of such a mechanism. 11...Needle bar rocking table, 12...Guiding means, 13
...Connecting rod, 14...Connection point, 15...Needle bar, 1
6...Crankshaft, 17...Crank pin, 18
... Pin, 19 ... Oval motion trajectory, 20 ... Pin, 21 ... Link, 22 ... Crank arm,
23...Arm.

Claims (1)

[Scope of Claims] 1. A needle bar rocking base 11 that can freely swing laterally, a guide means 12 that is connected to the needle bar rocking base 11 and provides a zigzag movement, and a needle bar 15 at a connecting point 14. In a zigzag mechanism of a sewing machine, which has a connecting rod 13 that is connected to the needle bar 15 and gives reciprocating motion in a vertical direction to the needle bar 15, and a crankshaft 16 that extends in a direction perpendicular to the zigzag motion, the reciprocating motion of the connecting point A zigzag sewing machine characterized by having a zigzag mechanism whose center position substantially coincides with a fulcrum 18 of a needle bar oscillating table. 2. The zigzag sewing machine according to claim 1, wherein the center position of the connection point corresponds to the position of the tip of the needle when it comes into contact with the sewing material. 3. The zigzag sewing machine according to claim 1, wherein the upper end of the connecting rod is attached to a crank pin 17 that projects from a crank arm that rotates around a crankshaft 16. 4. Needle bar rocking base 11 that can freely swing laterally, guide means 12 that provides zigzag movement, and connection point 1
The connecting rod 13 is connected to the needle bar 15 at 4 and has a connecting rod 13 that reciprocates in the vertical direction, and a crankshaft 16 that extends in the direction perpendicular to the zigzag movement,
In a zigzag sewing machine having a zigzag mechanism in which the center position of the connecting point in the reciprocating movement substantially coincides with the fulcrum 18 of the needle bar rocking table, the upper end of the connecting rod 13 moves around a pin attached to the main body of the sewing machine. It is attached to one end of an arm 23 connected to a link 21, and the arm 23 is drivingly connected to the crankshaft 16 by a crank arm 22 that rotates around the crankshaft 16 provided in the main body of the sewing machine and a crank pin 17. A zigzag sewing machine according to claim 1, characterized in that: 5 The upper end of the connecting rod draws an egg-shaped motion trajectory 19,
A zigzag sewing machine according to claim 4, characterized in that its longitudinal axis extends in the longitudinal direction of the needle bar. 6. The link 21 has a pin 20 provided on the main body of the sewing machine, and the pin 20 is adjustable in the vertical direction, so that the height of the needle can be adjusted with respect to the hook of the sewing machine. A zigzag sewing machine according to claim 4.