Automatic sewing machine

In an automatic sewing machine having

• stitch forming instrumentalities including an endwise reciprocatory needle, the combination comprising
• a drive motor for reciprocating the needle to produce stitches in a workpiece,
• manual means operable to start the drive motor,
• drive means operative to vary the relative position between the needle and the workpiece,
• stitch instruction storage means containing a plurality of randomly addressable storage locations for storing stitch instructions representing the relative positions to form a stitch pattern,
• means for addressing said storage locations in timed relation to reciprocation of the needle,
• position control means responsive to the stitch instruction in the addressed storage location for controlling operation of the drive means between successive stitches in the stitch pattern,
• processing means responsive to the operation of said manual means for sequentially addressing all of said storage locations regardless of reciprocation of said needle to examine the variation of said relative position between successive stitches in said stitch pattern, for selecting one speed from among predetermined maximum permissible speeds depending on the result of the examination, and for starting said drive motor to form said stitch pattern after selection of the maximum permissible speed, and
• speed control means for limiting the actual speed of said drive motor to no more than said selected maximum permissible speed during formation of said stitch pattern.

A method of sewing a workpiece with an automatic sewing machine, the automatic sewing machine having stitch forming instrumentalities including an endwise reciprocatory needle, a drive motor for reciprocating the needle to produce stitches in a workpiece, drive means operative to vary the relative position between the needle and the workpiece, stitch instruction storage means for storing stitch instructions capable of influencing the relative positions to form a stitch pattern, means operative synchronously with reciprocation of the needle for extracting the stitch instruction from the stitch instruction storage means in a predetermined sequence, and position control means responsive to the extracted stitch instruction for controlling operation of the drive means between successive stitches in the stitch pattern, the method comprising the steps in seriatim of:

• scanning all of said stitch instructions stored in said stitch instruction storage means to examine variation of said relative position between successive stitches in a stitch pattern;
• determining a maximum permissible speed depending on the result of said examination;
• starting said drive motor to form said stitch pattern,
• generating permissible speed data related to said maximum permissible speed synchronously with reciprocation of said needle;
• and
• limiting the actual speed of said drive motor to no more than said maximum permissible speed data during formation of said stitch pattern.