System for controlling needle positioning drive and thread trimming functions of an industrial sewing machine driven by a continuously coupled dc motor

Claim 2

A digital control system for providing the switching logic necessary to control the automatic driving and angular positional stopping of a sewing machine in selected needle positions responsively to selected input command signals, comprising: a DC motor coupled in continuous driving engagement with the sewing machine; drive controlled rectifiers for applying driving current to said motor; a brake controlled rectifier for applying braking current to said motor; a solid-state control device for turning off said brake controlled rectifier; solid-state pulse-generating means for generating waveform signals related in time to the angular speed and to the angular position of the motor; and solid-state gating means and memory means operative responsively to said selected input command signals and to said waveform signals to enable the triggering of said controlled rectifiers and said solid-state control device in proper time sequence to effect said driving and stopping of said sewing machine in the needle positions selected by said input command signals.

Claim 3

A digital control system for controlling the stopping of a sewing machine from top speed in a selected needle position responsively to a selected stop command signal, said sewing machine being continuously coupled to a single DC driving motor energizable from an AC voltage through drive controlled rectifiers, comprising; a brake controlled rectifier, a brake-release control device, means responsively to said stop command signal for disabling the drive controlled rectifiers and subsequently enabling the brake controlled rectifier to apply braking current to said motor, speed-responsive means and timing means coupled to said speed responsive means for emitting a pulse signal when the decreasing speed reaches a predetermined value, means responsively to said pulse signal for triggering said brake-release control device to turn off said brake controlled rectifier and leave the motor coasting at said predetermined speed, means responsively to said pulse signal for enabling the drive controlled rectifiers, after a time delay, to drive the motor at a predetermined positioning speed, position sensing means responsive to the angular position of the motor shaft and rendered effective, subsequent to said enabling of the drive controlled rectifiers, to emit a position signal, and means responsively to said position signal to disable the drive controlled rectifiers and to subsequently enable the brake controlled rectifier to brake said motor from said positioning speed to standstill with the sewing machine in the selected needle position.

Claim 4

A digital control system for controlling the stopping of a sewing machine from top speed in a selected needle position responsively to a selected stop command signal, said sewing machine being continuously coupled to a single DC driving motor energizable from an AC voltage through drive controlled rectifiers, comprising; a brake controlled rectifier, a brake-release control device, means responsively to said stop command signal for disabling the drive controlled rectifiers and subsequently enabling the brake controlled rectifier to apply braking current to said motor, speed-responsive means and timing means coupled to said speed responsive means for emitting a pulse signal when the decreasing speed reaches a predetermined value, means responsively to said pulse signal for triggering said brake-release control device to turn off said brake controlled rectifier and leave the motor coasting at said predetermined speed, means responsively to said pulse signal for enabling the drive controlled rectifiers, after a time delay, to drive the motor at a predetermined positioning speed, position sensing means responsive to the angular position of the motor shaft and rendered effective, subsequent to said enabling of the drive controlled rectifiers, to emit a position signal, and means responsively to said position signal to disable the drive controlled rectifiers and to subsequently enable the brake controlled rectifier to brake said motor from said positioning speed to standstill with the sewing machine in the selected needle position.

Claim 5

A system as defined in claim 2 wherein the speed-responsive means is a phototachometer which generates a pulse train of frequency related to the motor speed and the timing means is a programmable unijunction transistor connected as a relaxation oscillator with a timing capacitor discharged periodically by said pulse train.

Claim 6

A system as defined in claim 2 wherein the brake-release control device, when triggered, applies voltage from a previously charged capacitor to oppose the braking current to reduce the current through the brake controlled rectifier below its holding current and thus turn it off.

Claim 7

A system as defined in claim 2 wherein the brake-release control device is a normally nonconducting transistor having its collector-emitter path connected directly across the motor armature and its base connected to receive said pulse signal.

Claim 8

A system as defined in claim 2 wherein said position signal is inhibited by a monostable multivibrator for its quasistable period to permit the driving torque to stabilize at the predetermined positioning speed before final braking can be initiated.

Claim 9

A system as defined in claim 2 wherein said speed-responsive and timing means is enabled by a flip-flop which is triggered by the same pulse which triggers the brake controlled rectifier and is disabled by the resetting of said flip-flop by the pulse signal emitted by said speed-responsive and timing means.

Claim 10

A digital control system for providing the switching logic necessary to correlate the starting, running and positional stopping of a sewing machine with the sequential energization and deenergization of solenoids for actuating thread handling devices to perform a thread-trimming function responsively to input command signals, comprising: A DC motor coupled in continuous driving engagement with the sewing machine; drive controlled rectifiers for applying driving current to said motor; a brake controlled rectifier for applying braking current to said motor; a brake-release control device for turning off said brake controlled rectifier; solenoids for actuating thread handling devices; solid-state pulse-generating means for generating waveform signals related in time to the angular speed and to the angular positions of the motor; and solid-state gating and memory means operative responsively to selected input command signals and to said waveform signals to enable triggering of said controlled rectifiers and the brake-release control device and energization and deenergization of said solenoids in proper time sequence to effect said threAd trimming function.

Claim 11

A digital control system for providing the switching logic necessary to correlate the starting, running and positional stopping of a sewing machine with the sequential energization and deenergization of solenoids for actuating thread handling devices to perform a thread-trimming function responsively to input command signals, comprising: A DC motor coupled in continuous driving engagement with the sewing machine; drive controlled rectifiers for applying driving current to said motor; a brake controlled rectifier for applying braking current to said motor; a brake-release control device for turning off said brake controlled rectifier; solenoids for actuating thread handling devices; solid-state pulse-generating means for generating waveform signals related in time to the angular speed and to the angular positions of the motor; and solid-state gating and memory means operative responsively to selected input command signals and to said waveform signals to enable triggering of said controlled rectifiers and the brake-release control device and energization and deenergization of said solenoids in proper time sequence to effect said threAd trimming function.

Claim 12

A system as defined in claim 8 wherein the single input command signal is enabled by a gate which is opened responsively to a proper needle-down position as signaled by a phototransistor receiving light reflected from a reflecting segment.

Claim 13

A system as defined in claim 8 wherein the energization times for the solenoids are controlled by the quasistable periods of monostable multivibrators.