An improved technique is disclosed for adjusting the crankshaft angle of each of a plurality of synchronized tandem-coupled presses with respect to a reference shaft angle. At the start of adjustment, a plurality of first motors that synchronously drive the successive crankshafts during normal press operation are disengaged from the crankshafts and maintained operative with undiminished speed. A plurality of second motors operative at a speed slightly greater than the speed of the reference shaft are thereafter enabled when the angular phase of each crankshaft relative to that of the reference shaft is within a prescribed angular range. Such range is established by means of a synchro-driven control system coupled to the reference shaft and to the crankshaft when the first motor is disengaged from the crankshaft. Once the required angular adjustment is completed, the rotating first motor may be reengaged to the crankshaft to restore normal press operation.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of copending application Ser. No. 396,301, filed Sept. 11, 1973, and entitled "Method of Synchronized Micro-Driving of Synchronous Press Line", which is in turn a Continuation of application Ser. No. 177,757 filed Sept. 3, 1971, also entitled "Method of Synchronized Micro-Driving of Synchronous Press Line".
In the inching of a grinding mill or similar apparatus which is driven by a pair of synchronous motors through fluid actuated clutches, the motors must be angularly alined one with the other in order that the load be shared equally between the motors. The apparatus of the invention connects the field supply to both motor fields and then it connects a zero frequency supply (i.e. a DC supply) to the stator windings of both motors and ramps up or increases the amplitude of the supply. This brings the rotors into alinement without undue oscillation. When the amplitude of the low frequency supply reaches a predetermined level, the clutches are closed or locked and the motors are connected to the load with the rotors in angular coincidence or alinement.
An automatic motion or position control DC servomotor system in which a load-driving axis driven by a DC motor to be controlled in one rotary mechanism is rotated synchronously with, or following the rotation of, a reference axis manually operated or driven by another DC motor. The system comprises a position signal generator producing first sine- and cosine-wave signals corresponding to an angle of rotation of the controlled load-driving axis; a command signal generator producing second sine- and cosine-wave signals corresponding to an angle of rotation of the reference axis; an arithmetic unit processing the first and second sine- and cosine-wave signals and providing a sine-wave feedback voltage output signal; and a driver circuit amplifying the feedback voltage signal and providing a thus amplified signal to the DC motor driving the load-driving axis. When the reference axis is driven by another DC motor, the command signal generator may be a second position signal generator. The command signal and position signal generators each consists of a combination which preferably comprises a sine-cosine potentiometer. The DC servomotor system is suitably applicable to a sewing machine in such manner that the rotating hook shaft is driven by a first DC motor and the arm shaft by a second DC motor, the first DC motor being controlled synchronously with the second one under closed-loop feedback control as stated above.
An apparatus for changing the relative angles of the output shafts of a multiple-motor electric drive. For this purpose, the appropriate synchronous motor is switched to a phase-shifting frequency changer and its relative shaft (mechanical phase) angle is shifted by varying the frequency. The synchronous motor is then switched back to the operating frequency changer. The phase equality of the output voltages of the two frequency changers is monitored by signals derived from logic elements driving the frequency changers. In normal operation, the phase shifting frequency changer is driven by the same digital frequency generator as the operating frequency changer and is only switched to another frequency generator for phase shifting. Transition from one frequency changer to the other is made without shock.
The position of a drive shaft of a printing press is regulated during acceleration of the printing press. A position regulator includes a first integrator and a second integrator connected in tandem with the first integrator. The first integrator provides an output signal corresponding to the integral of the difference between a first position signal indicative of the desired position of the drive shaft and a second position signal indicative of the actual position of the drive shaft. The second integrator responds to the output signal from the first integrator to provide a control signal. A control asrrangement responds to the control signal from the second integrator to accelerate the drive shaft. During acceleration of the drive shaft, the difference between the first and second position signals is driven to a value of zero.
A tandem press system for the high speed manufacture of rotor cores and stator cores of electric motors. The tandem press system includes a rotor press and a stator press arranged in series for stamping out laminations from a web of stock material and pre-assembling them into rotor cores and stator cores, respectively. Structure is provided between the rotor and stator press to maintain control of the web and provide a substantial barrier to transmission of vibrations in the web to the stator press. The rotor and stator presses are capable of shifting from stamping one type of lamination to stamping another type of lamination without any interruption in the operation of the presses.
