Sewing – Special machines – Embroidering
Utility Patent
2000-06-19
2001-01-02
Nerbun, Peter (Department: 3741)
Sewing
Special machines
Embroidering
C112S475190, C700S138000
Utility Patent
active
06167824
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a sewing machine capable of forming a pattern that determines a sewing speed of a sewing device for each stitch or a plurality of stitches based on stitch points in a sewing area of a work holder.
2. Description of Related Art
A conventional sewing machine capable of embroidering includes a stitch formation mechanism that forms a stitch by synchronizing a needle and a loop taker, an embroidery frame that holds a work cloth detachably, and an embroidery frame driving mechanism that mounts the embroidery frame thereon and moves it in two different directions. The stitch formation mechanism and the embroidery frame driving mechanism are driven based on sewing data that specifies the movement direction and movement amount of the embroidery frame for each stitch of an embroidery pattern, so that the pattern is embroidered on the work cloth attached to the embroidery frame.
During sewing, the embroidery frame starts moving at the time the needle comes out from the work cloth, and stops moving at the time the needle penetrates the work cloth. In other words, while the needle is positioned above the work cloth, the embroidery frame is moved for one stitch.
A sewing machine capable of embroidering is designed to hold the embroidery frame at one end and move it in the two different directions. Just after the embroidery frame stops, damping of oscillations of the embroidery frame caused by the change of inertia begins. It takes some time (damping time) until the damping is substantially completed.
When the damping continues, the needle may not penetrate the work cloth at a designated stitch point, which deteriorates the quality of sewing. Because of the damping, the embroidery frame oscillates 1-2 mm in some cases. If the needle penetrates the work cloth under this condition, the embroidery pattern is not formed correctly. Therefore, it is necessary to set the sewing speed of the stitch formation mechanism in consideration of the damping time as well as the moving time of the embroidery frame.
FIG. 14
is a time chart showing a correlation between the height of the needle point and the movement amount of the embroidery frame. In this chart, t1 is the time taken from the start point where the embroidery frame starts to move to the point S where the frame stops moving, and t2 is the time taken from the point S where the damping occurs to the point d where the damping is substantially settled. In this case, it is necessary to set the sewing speed (the speed the needle bar is driven) so that the time in which the point of the needle is positioned above the work cloth is (t1+t2) or more.
The conventional sewing machines are generally provided with at least two embroidery frames, a large size and a small size. An operator changes them according to the size of the work cloth: the large frame is used for embroidering a large pattern on a comparatively large cloth, and the small embroidery frame for embroidering a small pattern on a comparatively small cloth.
However, the large frame is less stiff than the small frame. If the frames are moved at the same speed for the same distance, as shown in
FIG. 15
, time t3 that is the damping time for the large frame, indicated with a solid line, becomes longer than time t4 that is the damping time for the small frame indicated with a chain line. Furthermore, the conventional sewing machines set the sewing speed for the large frame and the longer damping time so as to ensure an adequate damping time no matter which frame is used. When the small frame is used, the embroidery frame is moved at a slower speed than the embroidery frame could be moved.
The sewing machine capable of embroidering for home use especially, which is designed to hold the embroidery frame at one end and move it in the two different directions, has the following problem regardless of the size of the embroidery frame: when the distance between the connecting portion of the frame to be connected to the embroidery device and a stitch point to be positioned in the embroidery frame becomes longer, the damping time at the stitch point is apt to lengthen, under the influence of the deflection due to inertia during moving.
To maintain the quality of sewing using conventional sewing machines, the sewing speed should be set in consideration of the longest damping time to occur in the embroidery frame. In other words, embroidering proceeds with the sewing speed in consideration of the longest damping time even in a stitch point where the damping time is very short. Therefore, it is impossible to raise the overall speed.
SUMMARY OF THE INVENTION
The invention provides a sewing machine with a pattern forming function that can increase the overall sewing speed and maintain the quality of sewing.
In various exemplary embodiments, a sewing machine according to the invention capable of forming a pattern on a work cloth may include a stitch formation device that forms a stitch by synchronizing a needle and a loop taker, a work holder that holds the work cloth, a work holder driving device that moves the work holder in two different directions holding the work holder at one end, the work holder being detachably attached the driving device on a connecting portion thereof, a calculating device that calculates a distance between the connecting portion and a stitch point based on sewing data, a speed determination device that determines a sewing speed of the stitch formation device so that the sewing speed decreases as the distance increases and increases as the distance decreases, and a controller that controls the stitch formation device based on the sewing speed determined by the speed determination device.
In conventional sewing machines, there exists a problem that when the distance between the connecting portion of the embroidery frame to be connected to the embroidery device and a stitch point to be positioned in the work holder becomes longer, the damping time at the stitch point is apt to lengthen, under the influence of the deflection due to inertia during moving.
For various exemplary embodiments of the sewing machine according to the invention, the calculating device calculates a distance between the connecting portion and a stitch point based on sewing data. The speed determination device determines a sewing speed of the work holder driving device so that the sewing speed decreases as the distance increases. Then, the controller controls the stitch formation device based on the sewing speed determined by the speed determination device.
Therefore, the sewing speed for each stitch created by the stitch formation device can be set as fast as possible based on the distance between the connecting portion and the stitch point so that while the needle is above the work cloth, the work holder can be moved for a stitch and the damping is substantially settled. Thus, the quality of sewing can be maintained and the overall sewing speed can be increased, thereby reducing the sewing time.
In an exemplary embodiment of the sewing machine according to the invention, the speed determination device calculates a predetermined number of speed data for a predetermined number of stitch points and determines the sewing speed for the predetermined number of stitch points by the minimum value among the predetermined number of speed data
Therefore, as the sewing speed is determined every predetermined number of stitches, the stitch formation device can follow the change of the speed. Further, as the speed of the stitch formation device is not changed too frequently, it can perform sewing smoothly.
In another exemplary embodiment of the sewing machine according to the invention, the sewing machine capable of forming a pattern on a work cloth may include a stitch formation device that forms a stitch by synchronizing a needle and a loop taker, a work holder that holds the work cloth, a work holder driving device that moves the work holder in two different directions holding the work holder at one end, the work holder being detachably attached
Brother Kogyo Kabushiki Kaisha
Nerbun Peter
Oliff & Berridg,e PLC
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