Electronic sewing machine with a stitch pattern adjusting device

Claim 1

A sewing machine having an electronic memory storing stitch control signals which are sequentially read out in synchronism with rotation of the upper drive shaft of the sewing machine to control the operations of the stitch forming instrumentalities of the sewing machine, thereby to form stitches of a pattern, a number of pattern selecting switches each selectively operated to select a pattern of stitches, each stitch being produced by the needle swinging amplitude and feeding amount predetermined by a selected set of stitch control signals of the memory, comprising stitch adjusting means manually operated to vary at least one of the needle swinging amplitude and the feeding amount per each stitch of the selected pattern, a switch which is closed by one mode of operation of the stitch adjusting means, a capacitor charging circuit including a capacitor and a variable resistor, the value of said variable resistor being determined by another mode of operation of the stitch adjusting means, thereby to determine the time constant of the circuit, a monostable multivibrator producing a signal in a time based on the charging time of the capacitor charging circuit, and a microcomputor including a central processing unit detecting and memorizing the manual operations of the specific pattern selecting switches and the stitch adjusting means, and digitally counting and calculating the signals from the monstable multivibrator, thereby to make the stitch adjusting means effective or ineffective.