Seam forming method and device for sewing machine for embroidery

A method for embroidering a cloth with a pattern having an outer circular arc add an inner opposite line opposed to the outer circular, said method comprising the steps of:

• reading data of at least three points on the outer circular arc of an original pattern;
• reading data of at least two points on the inner opposite line of the original pattern;
• determining, in accordance with the thus read data of said three points, an outer circular arc origin and a radius of an outer circular arc to specify the outer circular arc;
• determining, in accordance with predetermined pitch for a needle location point, needle location points on the specified outer circular arc;
• determining radial bisector passing through the outer circular arc origin and bisecting an angle defined by radial lines connecting the outer circular arc origin to two successive needle location points on the specified outer circular arc;
• determining first intersections between the inner opposite line specified by said data of the two points on the inner opposite line and said each radial bisector;
• judging as to whether the ratio of a distance between the first intersection and the outer circular arc origin to the radius of the specified outer circular arc is less than a predetermined ratio;
• and
• determining the needle location points on the specified inner opposite line in such a manner that they are wholly positioned at the first intersections if said ratio is greater than the predetermined ratio, and that they are alternatingly positioned at the first intersections and second intersections between the radial bisectors and a mid line positioned between the needle location points on the outer circular arc and the first intersections, if said ratio is less than the predetermined ratio.

An apparatus for reading data for a contour of a pattern to be embroidered comprising:

• cursor means manually movable upon an original pattern for indicating a point on the contour of the original pattern so that positional data of the point thus indicated are read in a form of co-ordinate;
• a first manual switch for a straight line for producing a first signal when it is operated after said cursor is positioned;
• a second manual switch for a circular arc for producing a second signal when it is operated after said cursor is positioned;
• a third manual switch for completion of reading of data for producing a third signal, said third manual switch being operated when reading of the data for a pattern to be embroidered is completed;
• and
• judging means for judging that data of the single straight line and single circular arc connected thereto are read when four signal including one first signal, two successive second signals and one third signal are successively generated of four signals including two successive second signals, one first signal and one third signal are successively generated.

An apparatus for embroidering a cloth with a pattern comprising:

• means for reading data of a contour of an original pattern and a direction of movement of a needle or the cloth;
• means for determining the contour of the pattern in accordance with the thus read data and the direction of movement of the needle or the cloth in accordance with a line connecting two needle location points to each other;
• means for determining successive lines oriented in the thus determined direction in such a manner that they are spaced at a predetermined pitch for the needle location point;
• means for determining the needle location points on the specified contour in such a manner that they are positioned at intersections between said successive lines and the specified contour;
• and
• means for moving the needle or the cloth in accordance with said needle location points to embroider the cloth with a pattern.