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United States Patent (113,573,581 72 Inventors John J

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United States Patent (113,573,581 72 Inventors John J United States Patent (113,573,581 72 Inventors John J. Dutko 3,268,047 8/1966 Grygera, et al............... 1121219 North Plainfield; 3,374,410 3/1968 Cronquist, et al............ 3181138 Richard Beck, Morris Plains; Henry A. 3,435,314 5/1969 Bradley........................ 318/138 Seesselberg, South Plainfield, N.J. 3,443,181 6/1969 Tozol, et al................... 318/138 (21) Appl. No. 836,103 3,466,517 9/1969. Leenhouts.................... 318/138 22 Filed June 24, 1969 45 Patented Apr. 6, 1971 Primary Examiner-Oris L. Rader (73) Assignee The Singer Company Assistant Examiner-K. L. Crosson New York, N.Y. Attorneys-Marshall J. Breen and Chester A. William, Jr. 54 SYSTEM FOR CONTROLLING NEEDLE POSITONING DRIVE AND THREADTRMMING FUNCTIONS OF AN INDUSTRIAL SEWNG ABSTRACT: Solid-state digital logic circuitry with gates, MACHINEDRIVEN BY A CONTNUOUSLY memory flip-flops, delay and sensor elements provide a logic COUPLEDDCMOTOR system for controlling the drive and braking currents to a DC 10 Claims, 9 Drawing Figs. motor continuously coupled in driving relation to a sewing machine. In response to certain input commands, a series of (52) U.S.Ch....................................................... 318/266, events are signaled by the logic circuitry to occur automati 12/219,3181466 cally in a predetermined time sequence resulting in a desired 51 int. Cl............................... ......................... H02p3/06 output sewing related function. Silicon controlled rectifiers 50 Field of Search............................................ 112/219; (SCR's) are used to supply driving current to the motor from a 318/265,266, 466 polyphase voltage supply. A single SCR is used to supply Ref Cited dynamic braking current for the motor. The single SCR is 56 eerees Un turned off to terminate a first braking period when a solid UNITED STATES PATENTS state switch operates responsively to a speed sensor to reduce 3,328,658 6/1967 Thompson.................... 318/138 the SCR current below its holding value. Patented April 6, 1971 3,573,581 5 Sheets-Sheet l IN VE TORS John J. Dutko Richord Beck SYYY 26-4Henry A. Seesselberg4s Patented April 6, 1971 3,573,581 5 Sheets-Sheet 2 INVENTORS John J. Dutko Richard Beck Henry A. Sees set berg P%-44 Afrói,), /3-1-1 Patented April 6, 1971 3,573,581 5 Sheets-Sheet 3 222 INVENTORS John J. Dutko L-3 Richard Beck Henry A. Seesselberg WITNESS: ratul- 9-tz.--d- BY -4 Q. Cul AT TORNEY Patented April 6, 1971 3,573,581 -3Ol INVENTORS John J. Dutko Richard Beck Henry A. Seesselberg 'INESS have -e- By 22-4-4), AT(3.1- TORNEY Patented April 6, 1971 3,573,581 5 Sheets-Sheet 5 Illi lllP --2ms |600rpm 8OOrpin 4O Orpm -ms P2 TIME D Fig. 8 John J. D.?h k."VENT ( fl. 8, Richord Beck WITNESS: Henry A. Seesselberg ?lo 1-1- (-(2. By 22 4. & 9 /C-11 AT TORNEY 3,573,581 2 SYSTEM FOR CONTROLLING NEEDLE POSITONENG second monostable multivibrator which inhibits a needle DRIVE AND THREAD TRIMMING FUNCTIONS OF AN down signal sensor for the definite time it is in its quasistable INDUSTRIAL SEWING MACHINEDRIVEN BY A state to permit the drive SCR's to stabilize the driving speed at CONTNUOUSLY COUPLEED DC MOTOR 400 r. p.m. before search is begun. At the time when the second multivibrator reverts to its sta ble state, the needle-down signal sensor is enabled and emits a BACKGROUND OF THE INVENTION pulse which initiates a brake command and the motor is Industrial sewing machines are conventionally driven by dynamically braked to standstill with the needle down. clutch-brake induction motors having inertia flywheels for storing and releasing the kinetic energy to supply accelerating O NEEDLE-UP POSITION torque to the sewing machines. When needle positioning is With the sewing machine at rest in a treadle relaxed needle required, a fixed low speed drive is supplied from an auxiliary down position, the operator may actuate a switch which in motor or from a speed-reducer clutched to the main motor. itiates a command to drive to needle-up position. This switch The mechanical movement associated with the clutching and applies a trigger pulse to a needle-up flip-flop having comple braking of these prior art systems is a constant source of dif 5 ficulty related to inertia delay and wear of the parts. In ac mentary outputs. One output goes low and triggers the drive cordance with the invention shown and described in the control flip-flop to command the drive SCR's to turn on. copending Ser. No. 787,797 filed Dec. 30, 1968 and assigned Simultaneously, the other output goes high and triggers, a to the same assignee as that of the present application, a sew switching transistor to prepare the drive trigger line for a soft ing machine is continuously and directly coupled to a low-in start. This other output also enables a gate to couple any nee ertia DC motor and all starting, running and stopping of the dle-up pulses emitted by a needle-up position sensor to the sewing machine is controlled by controlling the flow of cur direct set line of the drive control flip-flop so that when a nee rent into and out of the armature of the motor by the gating of dle-up pulse is emitted, the drive control flip-flop resets and its silicon controlled rectifiers (SCR's) and there is no mechani output disables the drive SCR's and commands the brake SCR cal clutching and braking anywhere in the system. In order to 25 to turn on (after and RC delay) and the sewing machine extend the advantages of the direct-coupled drive to the func comes to rest in a needle-up position. tions of automatic needle positioning and automatic thread THREAD TRIM OPERATION trimming, it is necessary to supply a sequencing control which forces certain events to proceed in a logical order responsively This operation requires a specific time sequence of ener to single input commands and it is the purpose of this inven gization of three solenoids (picker, trimmer, and wiper) coor tion to provide such a control. dinated with a specific sequence of needle positions. With the sewing machine at rest in a needle-down position, SUMMARY OF THE INVENTION a normally closed switch is opened by heeling the treadle and In keeping with the solid-state nature of the direct coupled 35 initiates a trimming command by emitting a pulse which is drive system, all logic decisions in the system of the present in passed by a gate, enabled by a needle-down position sensor vention are performed by solid-state digital components which signal, to trigger a flip-flop having complementary outputs. removes at once all possible difficulties associated with One output goes low and triggers a monostable multivibrator mechanical inertia and wear. The logic circuitry employs con which energizes a picker solenoid for the guasistable period. ventional solid-state logic components such as phototransistor 40 When this multivibrator returns to its stable state, it emits a sensors, flip-flops, NAND gates, inverters, and discrete trigger pulse which triggers the needle-up flip-flop and com switching transistors in a circuit which responds to the single mands the sewing machine to drive to needle-up position in input commands of (1) needle-down position, (2) needle-up the same manner as described above for the needle-up com position, and (3) thread trim operation. mand. The high output of the needle-up flip-flop enables a 45 gate which passes the needle-up position sensor signal to NEEDLE-DOWN POSITION trigger a monostable multivibrator which energizes a trimmer The needle-down positioning cycle involves the accurate solenoid for the quasistable period and after an RC delay also stopping of the drive motor in a minimum time from top speed energizes a wiper solenoid for the remainder of the period. driving condition and requires both speed sensing and needle When the multivibrator returns to its stabl, state it resets the down position sensing. The speed sensing is required to 50 needle-up flip-flop to its original state.Te sewing machine is establish a predetermined speed at which it is practical to now at rest in the needle-up position with the bobbin and nee search for the proper stop position. The position sensing is dle thread trimmed and wiped. required to determine the final stop position accurately. It is an object of this invention to provide a solid state digital One logical approach to the positioning problem would be 55 control system for automatically stopping a sewing machine to brake the motor at once to a random stop and then ac with respect to a predetermined desired needle position celerate to a low positioning speed and search for the proper without the use of any electromechanical relays or clutch stop position. This has the disadvantage of requiring too much brake devices. time. The present system is based on different logic which It is a further object of this invention to provide a solid state avoids a random stop and brakes the motor in two discrete 60 digital control system for automatically coordinating the sequential stops. The first braking period is terminated when sequential energization and deemergization of three solenoids the motor reaches a speed slightly above 400 rp.m. This with respect to needle positions as required for automatic requires a speed sensor which, in the present invention, may thread trimming in a sewing machine. be a phototransistor which optically generates a pulse train of It is a still further object of this invention to provide a solid frequency related to the motor speed.
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