Dc control circuits for direct drive motors continuously coupled to sewing machines for controlling sewing functions

Claim 2

A control system for driving a DC motor continuously coupled to the drive shaft of a sewing machine, the system being energizable from a commercial source of AC voltage and having means for changing the AC voltage to a DC voltage comprising: a. dynamic braking means for continuously braking said motor, having a coil and a pair of normally closed contacts, said coil being connected in series with said motor and said contacts being resistively coupled in parallel with said motor; b. electromechanical braking means mounted on said sewing machine drive shaft for braking said shaft for a predeTermined time interval; c. power transistor means coupled in series with said motor and coil for providing a variable driving DC voltage to said serially connected motor and coil; d. limiting means coupled to said power transistor means for controlling the maximum value of said variable DC voltage; and e. control means coupled to said power transistor means operative in a forward position from a relaxed position for controlling the acceleration of said sewing machine motor and operative when permitted to return from a forward position to said relaxed position to automatically apply said dynamic braking means and said electromechanical braking means.

Claim 3

A control system for driving a DC motor continuously coupled to the drive shaft of a sewing machine, the system being energizable from a commercial source of AC voltage and having means for changing the AC voltage to a DC voltage comprising: a. dynamic braking means for continuously braking said motor, having a coil and a pair of normally closed contacts, said coil being connected in series with said motor and said contacts being resistively coupled in parallel with said motor; b. electromechanical braking means mounted on said sewing machine drive shaft for braking said shaft for a predeTermined time interval; c. power transistor means coupled in series with said motor and coil for providing a variable driving DC voltage to said serially connected motor and coil; d. limiting means coupled to said power transistor means for controlling the maximum value of said variable DC voltage; and e. control means coupled to said power transistor means operative in a forward position from a relaxed position for controlling the acceleration of said sewing machine motor and operative when permitted to return from a forward position to said relaxed position to automatically apply said dynamic braking means and said electromechanical braking means.

Claim 4

A control system for driving a DC motor continuously coupled to the drive shaft of a sewing machine, the system being energizable from a commercial source of AC voltage and having means for changing the AC voltage to a DC voltage comprising: a. dynamic braking means for continuously braking said motor, having a coil and a pair of normally closed contacts, said coil being connected in series with said motor and said contacts being resistively coupled in parallel with said motor; b. electromechanical braking means mounted on said sewing machine drive shaft for braking said shaft for a predeTermined time interval; c. power transistor means coupled in series with said motor and coil for providing a variable driving DC voltage to said serially connected motor and coil; d. limiting means coupled to said power transistor means for controlling the maximum value of said variable DC voltage; and e. control means coupled to said power transistor means operative in a forward position from a relaxed position for controlling the acceleration of said sewing machine motor and operative when permitted to return from a forward position to said relaxed position to automatically apply said dynamic braking means and said electromechanical braking means.

Claim 5

A control system for driving a DC voltage continuously coupled to the drive shaft of a sewing machine according to Claim 1 further including solid state overload protection means coupled to said power transistor means for sensing the current drawn by said motor and causing said variable DC voltage to be reduced to substantially zero upon excess current being drawn by said motor.

Claim 6

A control system for driving a DC motor according to claim 1 further including: a. permanent magnet locating means rotatably mounted on said drive shaft, said magnet being adjustable relative to the angular position of said drive shaft; and b. utilization means cooperating with said permanent magnet locating means for energizing said electromechanical brake means in a preselected angular position of said drive shaft for said predetermined time interval.

Claim 7

A control system according to claim 3 further including: a. a transistor for energizing said electromechanical brake; b. capacitor means charged during the running period of said motor; and c. means responsive to said control means for permitting said capacitor means to discharge through said transistor to turn it on for a predetermined time to energize said electromechanical brake.

Claim 8

A control system according to claim 4 further including: a. relay means; b. transistor means for energizing said relay means during the running period of said motor; c. means responsive to movement of said control means to a relaxed position for preparing a circuit for turn-off of said transistor means to de-energize said relay means; d. said actual turn-off being conditioned responsive to a positioning pulse generated by said permanent magnet sensing means in a predetermined angular position of said drive shaft.

Claim 9

A control system according to claim 5 wherein the deenergization of said relay means initiates the times energization of the electromechanical brake.

Claim 10

A control system according to claim 6 further including means responsive to the energization of the electromechanical brake for inhibiting the application of driving DC voltage to said motor during said energization.

Claim 11

A control system according to claim 7 wherein said drive shaft is stopped in an angular position corresponding with the needle of said sewing machine being positioned needle-down when said control means is in said relaxed position and said drive shaft is stopped in an angular position corresponding with the needle of said sewing machine being positioned needle-up when said control means is momentarily urged to a rearward position from said relaxed position.

Claim 12

A control system for starting, running and braking a DC motor continuously coupled to the drive shaft of a sewing machine and fed from an AC voltage source and having means for changing the AC voltage to a DC voltage comprising, transistor drive means for supplying a controlled variable DC voltage for running said motor, first braking means having an energizing coil, for connecting a dissipative electrical load to said motor to provide dynamic braking, said energizing coil being connected in series with the armature of said DC motor, second braking means including an electromechanical brake for applying frictional forces to the drive shaft for a predetermined time intErval and control means operative in a forward position from a relaxed position for controlling the acceleration of said sewing machine and operative when permitted to return from a forward position toward said relaxed position to automatically energize said first and second braking means.

Claim 13

A control system for starting, running and braking a DC motor continuously coupled to the drive shaft of a sewing machine and fed from an AC voltage source and having means for changing the AC voltage to a DC voltage comprising, transistor drive means for supplying a controlled variable DC voltage for running said motor, first braking means having an energizing coil, for connecting a dissipative electrical load to said motor to provide dynamic braking, said energizing coil being connected in series with the armature of said DC motor, second braking means including an electromechanical brake for applying frictional forces to the drive shaft for a predetermined time intErval and control means operative in a forward position from a relaxed position for controlling the acceleration of said sewing machine and operative when permitted to return from a forward position toward said relaxed position to automatically energize said first and second braking means.

Claim 14

A control system for driving a DC motor having an armature continuously coupled to the drive shaft of a sewing machine, said system being energizable from a commercial source of AC voltage and having means for changing the AC voltage to a DC voltage comprising: a. dynamic braking means for continuously braking said motor, having a coil and a pair of normally closed contacts, said coil being connected in series with said armature and said contacts being resistively coupled in parallel with said armature; b. electromechanical braking means mounted on said sewing machine drive shaft for braking said shaft for a predetermined time interval; c. power transistor means coupled in series with said armature and coil for providing a variable voltage to said serially connected armature and coil; d. first and second transistor driver means connected in series and coupled to said power transistor means; e. control means coupled to said first transistor driver means for limiting the maximum DC voltage provided by said power transistor means; and f. operator actuated control means coupled to said second transistor driver means operative in a forward position from a relaxed position providing a variable DC reference voltage for controlling the acceleration of said sewing machine and operative when permitted to return from a forward position toward said relaxed position to automatically energize said dynamic braking means and said electromechanical braking means.

Claim 15

A control system for driving a DC motor having an armature continuously coupled to the drive shaft of a sewing machine, said system being energizable from a commercial source of AC voltage and having means for changing the AC voltage to a DC voltage comprising: a. dynamic braking means for continuously braking said motor, having a coil and a pair of normally closed contacts, said coil being connected in series with said armature and said contacts being resistively coupled in parallel with said armature; b. electromechanical braking means mounted on said sewing machine drive shaft for braking said shaft for a predetermined time interval; c. power transistor means coupled in series with said armature and coil for providing a variable voltage to said serially connected armature and coil; d. first and second transistor driver means connected in series and coupled to said power transistor means; e. control means coupled to said first transistor driver means for limiting the maximum DC voltage provided by said power transistor means; and f. operator actuated control means coupled to said second transistor driver means operative in a forward position from a relaxed position providing a variable DC reference voltage for controlling the acceleration of said sewing machine and operative when permitted to return from a forward position toward said relaxed position to automatically energize said dynamic braking means and said electromechanical braking means.

Claim 16

A control system for driving a DC motor according to Claim 10 further including: a. permanent magnet locating means rotatably mounted on said drive shaft, said magnet being adjustable relative to the angular position of said drive shaft; and b. utilization means cooperating with said permanent magnet locating means for energizing said electromechanical braking means in a preselected angular position of said drive shaft for said predetermined time interval.

Claim 17

A control system according to claim 11 wherein said permanent magnet locating means is positioned to stop said drive shaft in an angular position corresponding with the needle-down position when said operator actuator control means is in said relaxed position and said permanent magnet locating means is positioned to stop said drive shaft in an angular position corresponding with the needle-up position when said operator actuated control means is momentarily urged to a position rearward from said relaxed position.