JPH105475A - Leg body of sewing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain low vibration so that a resonance phenomenon by exciting force of a sewing machine is not generated by constituting a characteristic frequency of a leg body so as to become prescribed time or more of a frequency of the exciting force. SOLUTION: A sewing machine, particularly, an industrial sewing machine is heavy in weight, and since particularly a multi-head embroidering sewing machine or the like reaches even several hundred kilograms, a characteristic frequency inevitably becomes low, and a characteristic frequency of a leg body 5 results in being less than a frequency of exciting force. Therefore, when the sewing machine is operated, since bending of a leg by vertical directional exciting force within working rotating speed and resonance of a translation mode in the longitudinal and lateral direction of the leg body 5 are generated, it becomes a big problem, Then, in order that a resonance phenomenon by exciting force by the sewing machine is not generated, a characteristic frequency of the leg body 5 is constituted so as to become √2 times a frequency of the exciting force. Though a characteristic frequency of the leg body 5 generates resonance in the case of 0.8 times to √2 times, when it is set not less than √2 times, the resonance is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leg of a sewing machine which supports a main body of the sewing machine.

[0002]

2. Description of the Related Art Legs of conventional sewing machines are designed for the basic configuration of the legs for functional reasons and the like, and little consideration is given to the natural frequency of the legs which cause resonance phenomena. It was also difficult to accurately grasp the natural frequency at the stage. For example, in the case of an embroidery sewing machine, the maximum number of rotations of the main spindle is as high as 1000 rotations or more, so that the vertical reciprocating motion of the needle increases the vertical excitation force. In addition, since the feed frame is provided which can move in a plane intersecting the reciprocating direction of the needle, a forward / backward / left / right direction excitation force also acts.

[0003]

However, a sewing machine, especially an industrial sewing machine, has a large weight, and especially a multi-head embroidery sewing machine and the like occupies several hundred kilograms, so that the natural frequency is inevitably low. The natural frequency of the body was lower than the frequency of the excitation force. Therefore, when the sewing machine is operated, the bending of the legs due to the vertical excitation force within the rotation speed used, and the resonance of the translational mode in the front-back and left-right directions of the legs occur, which has been a serious problem.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a low-vibration sewing machine leg which prevents a resonance phenomenon due to a vibration force of the sewing machine from occurring. It is.

[0005]

In order to achieve this object, a leg of the sewing machine according to the first aspect is configured such that the natural frequency of the leg is √2 times or more the excitation frequency. It is characterized by having made it. Resonance occurs when the natural frequency of the leg is 0.8 to √2 times the resonance frequency.
If it is set to √2 or more, resonance does not occur.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in an embroidery sewing machine will be described below with reference to the drawings.

FIG. 1 is a perspective view of an embroidery sewing machine (multi-head embroidery sewing machine). In the embroidery sewing machine 1, as shown in FIG. 1, three sewing machine heads (sewing machine main body) 7 are juxtaposed on the rear side of the upper surface of a leg 5 extending in the left-right direction, and the sewing machine head 7 will be described later. In this manner, the needle carrying the embroidery thread supports the needle bar 11 attached to the lower end, and reciprocates the needle bar 11 up and down (providing a vertical excitation force). The arm 9 faces the arm 9. A well-known thread catcher for catching a thread loop of an embroidery thread formed by a needle extending and moving up and down integrally with the needle bar 11, and entangled the embroidery thread and the lower thread to form a seam. And a bed 17 for accommodating a container (not shown) therein.

A multi-needle case 13 having a large number of needle bars 11 is attached to the end of the arm portion 9 of the sewing machine head 7, and the needle bar case 13 is moved in the left-right direction by a needle bar selection mechanism (not shown). The needle bar for forming an embroidery stitch with an embroidery thread of a desired color is alternatively selectable. Below the leg of the leg 5, a level seat 6 for height adjustment is attached. Here, the needle bar 11 and the balance 10
An upper shaft (not shown) for vertically moving the motor is driven by a drive shaft 8 driven to rotate by a conduction belt 12 connected to a sewing machine motor (not shown).

A table 15 is provided on the leg 5, and the upper surface of the table 15 is set to be flush with the upper surface of the bed 17 of the sewing machine head 7.

On the upper surface of the table 15, a rectangular frame-shaped movable frame 23 for mounting an embroidery frame or a hat frame (not shown) is mounted as a feeder of the embroidery sewing machine.
A Y-axis driving mechanism and an X-axis driving mechanism are fixedly provided in the sewing machine legs. A front-rear moving plate (not shown) reciprocated in the Y direction by the Y-axis driving mechanism, and the X-axis The movable frame 23 is connected via a left / right moving plate (not shown) supported by a shaft driving mechanism so as to be able to reciprocate in the X direction (left / right direction). Therefore, the movable frame 23 is reciprocated back and forth and right and left on the upper surface of the table 15 together with the embroidery frame. Embroidery is performed by reciprocating an embroidery frame on which a work cloth is stretched in a plane perpendicular to the moving direction (Z direction) of the needle to be moved up and down in the left-right direction, the front-back direction, or a synthetic direction thereof. One reciprocation of the needle bar is performed by one rotation of the upper shaft, and the embroidery frame is moved to one side by one rotation of the upper shaft to form a satin stitch, and then moved backward by one rotation of the upper shaft. That is, reciprocation of the embroidery frame is performed by two rotations of the upper shaft.

As the embroidery sewing is performed, the needle bar 11 and the balance 10 which receive power from the sewing machine motor via the drive shaft 8 and the upper shaft reciprocate up and down. As shown in FIG. 7, a vertical excitation force Fz having the same frequency as the rotation frequency of the upper shaft is generated. Further, when the movable frame 23 with the embroidery frame attached thereto reciprocates in the X-axis direction, a lateral excitation force Fx having a frequency of 1/2 of the upper shaft rotation frequency is generated, and the Y-axis direction is generated. When the reciprocating movement is performed, a longitudinal excitation force Fy having a frequency half the upper shaft rotation frequency is generated.

On the other hand, the leg 5 has a natural vibration mode as shown in FIGS. 2 (a) and 2 (b). FIG. 2A shows a natural vibration mode in the front-back and left-right bending directions, and FIG. 2B shows a natural vibration mode in the up-down bending direction.

Here, assuming that the rotation speed of the upper shaft is 1200 rpm, the frequency fz of the vertical excitation force accompanying the vertical reciprocation of the needle bar 11 and the balance 10 is fz = 1200/60 = 2.
Expressed at 0 Hz. In addition, the frequency fn of the horizontal (front-rear, left-right) excitation force accompanying the movement of the movable frame 23 in the X-Y direction.
Is represented by fn = 1200/60/2 = 10 Hz.

FIG. 3 is a resonance curve. Natural frequency: ω0
Resonance occurs when the ratio of the excitation force frequency: ω is less than √2, and when it is 1, the resonance point has the largest amplitude. If the natural frequency of the leg 5 is in this range, that is, less than 14 Hz if the natural vibration mode (a) is a natural vibration mode (forward-backward translation), 28H if the natural vibration mode (b) is a natural vibration mode (a vertical bending).
When it is less than z, a resonance phenomenon occurs. In particular, when the natural vibration mode of (a) is 10 Hz and in the natural vibration mode of (b) is 20 Hz, the natural frequency of the leg 5 and the frequency of the exciting force are one. Large vibrations occur. However, the leg 5 of the present invention performs eigenvalue analysis using the finite element method,
15 Hz in the natural vibration mode whose natural frequency is (a)
In addition, since the natural vibration mode is designed to be 30 Hz in the natural vibration mode (b), the leg 5 does not cause resonance within the range of the number of rotations to be used, and can operate with low vibration.

[0015]

As is apparent from the above description,
According to the leg of the sewing machine according to the first aspect, since the natural frequency of the leg is configured to be √2 times or more of the exciting force frequency, the sewing machine is low without generating resonance. Operation by vibration becomes possible. In addition, resonance can be avoided without excessive rigidity. In other words, it is possible to prevent the legs from becoming unnecessarily strong, and to reduce the weight of the legs, that is, the sewing machine.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an embroidery sewing machine according to an embodiment of the present invention.

FIG. 2 is a natural vibration mode diagram of the embroidery sewing machine.

FIG. 3 is a resonance curve diagram showing a relationship between a frequency ratio and a response magnification.

[Explanation of symbols]

 5 leg 7 sewing machine 11 needle bar 23 movable frame

Claims (1)

[Claims] 1. A sewing machine comprising a sewing machine body forming a stitch by reciprocating movement of a needle, and a leg supporting the sewing machine body, wherein the natural frequency of the leg is √2 times or more the excitation frequency. A leg of a sewing machine, characterized in that it has a configuration such that: