Electricity: motive power systems – Motor load – armature current or force control during... – Initial – 'cracking' or 'starting from rest' torque control
Reexamination Certificate
2000-03-24
2001-10-23
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Motor load, armature current or force control during...
Initial, 'cracking' or 'starting from rest' torque control
C318S161000, C139S309000
Reexamination Certificate
active
06307340
ABSTRACT:
PRIORITY CLAIM
This application is based on and claims the priority under 35 U.S.C. §119 of German Patent Application 199 14 131.2, filed on Mar. 27, 1999, the entire disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to a method of starting a power loom equipped with an electric main drive. In such a loom the main drive drives at least one flywheel mass that is coupled to the main drive and is coupled to a main drive shaft by a clutch.
BACKGROUND INFORMATION
It is customary to drive power looms by an electric motor that is connected to an a.c. power supply or a three-phase power supply network. Preferably, pole-switchable or frequency-controlled motors are used. The main power drive is coupled by power transmission means, such as a belt and pulley drive, to a flywheel mass which is coupled to the main drive shaft of the loom, whereby the electric motor drives the flywheel mass. Prior art systems are so constructed that following the switching-on of the main drive, the flywheel mass is first accelerated by the motor to a predetermined rotational speed (called “rpm” herein for brevity). For starting the loom itself, a clutch-brake unit is used for coupling the flywheel mass to the main drive shaft of the loom, so that the rotating flywheel mass starts the loom from a standstill. The performance characteristic of the clutch the “stiffness” or stability of the motor, and the size of the effective flywheel mass, as well as friction resistances determine a very specific rotational speed or rpm progression characteristic on the one hand for the flywheel mass and on the other hand for the main drive shaft of the loom during the loom start-up process. The rpm of the flywheel mass drops substantially after the clutch is engaged and continues to drop until it matches the rpm of the main drive shaft of the loom that is accelerating from a standstill. During this process, the rpm difference between the main loom drive shaft and the flywheel mass involves the “slipping” of the clutch as it is engaged.
Start-up systems for the looms of the type mentioned above must satisfy special conditions in practice. For example, it is necessary that the loom be completely coupled to its power drive before the first beat up of the reed. It can happen during such a coupling operation that the main loom drive shaft is completely coupled to the power drive before the first reed beat-up, but that the instantaneous rotational speed of the loom is too low at the first reed beat-up. As a result, so-called start-up faults are formed in the fabric. Such start-up faults are formed at places where the inserted weft thread is not beat-up with sufficient force against the beat-up edge of the fabric, resulting in an enlarged spacing between neighboring threads. A series of such enlarged spacings resulting from improperly beat-up weft threads may show up as a stripe-type fabric fault. In order to avoid start-up faults that result from insufficient rotational speed in the start-up phase of the loom, it has been customary heretofore to try to construct the loom drive in such a way that it reaches the desired final instantaneous rotational speed if possible by the time of the first beat-up of the reed.
Such a method for starting up a main drive of a power loom is known from U.S. Pat. No. 4,837,485 (Meroth et al.), which issued to the applicant of the present application. The entire disclosure of U.S. Pat. No. 4,837,485 is incorporated herein by reference. While the system and method of U.S. Pat. No. 4,837,485 are effective for achieving the intended objects thereof, there is still room for further improvement. One shortcoming of the method disclosed therein is that it does not call for precisely determining how much the rated rpm of the main power drive, and thus the rpm of the flywheel mass, must be increased in order for the main loom drive shaft to reach the rated operating rpm by the time of the first beat-up of the reed after the main power drive has coupled with the main loom drive shaft. Instead, the prior method generally involves isolating or disconnecting the main power drive from the power supply network during the coupling operation and then reconnecting it to the network with a greater number of motor poles, for example, in order to select a specific rpm that lies between the starting rpm in the coupling operation and the rated rpm for the weaving operation.
SUMMARY OF THE INVENTION
In view of the above it is an object of the invention to provide a method of starting a loom so as to automatically ensure that the rated rpm of the loom is reached by the first reed beat-up. More particularly, the invention aims to provide such a method involving automatically determining the start-up rpm of a flywheel mass that is necessary to accelerate the main drive shaft of a loom to the rated rpm for a weaving operation, following a loom standstill, by the time of the first beat-up of the reed. It is a further aim of the invention to provide such a method that is self-learning, that is, will iteratively determine with increasing accuracy the start-up rpm that is required for the main drive shaft to reach the rated rpm by the time of the first reed beat-up. The invention also aims to overcome or avoid the disadvantages of the prior art, and to achieve additional advantages, as are apparent from the present specification.
The above mentioned objects of the invention have been achieved according to the invention in a method of starting a power loom. The method involves calculating or determining a start-up rpm for a flywheel mass for the start-up operation of the power loom so that the rpm of the flywheel mass and the main drive shaft of the loom are both at approximately the rated operational rpm for the weaving operation at the time the main drive shaft is completely coupled to the flywheel mass, before the time of the first reed beat-up. The method measures the rpm of the main drive shaft of the loom at least at the time of the first beat-up of the reed; determines the deviation of the measured rpm from the rated rpm; evaluates and stores the measured values in the loom control; and calculates a new start-up rpm for the start-up operation, based on the determined values, such that in a subsequent start-up of the loom following a standstill, the speed of the main drive shaft will reach the rated rpm with better accuracy at least by the time of the first beat-up of the reed.
It is significant according to the invention that the rpm of the loom main drive shaft is measured at least at the first beat-up of the reed and the deviation of the measured rpm from the rated rpm is determined. At each new start-up of the loom, the deviation of the measured rpm relative to the rated rpm is evaluated and a new data set with a new start-up rpm is generated and stored to be used for the next subsequent start-up operation. In other words, in each start-up operation, the flywheel mass is accelerated to the respective start-up rpm that was determined in the preceding start-up operation, whereby each successively determined start-up rpm is improved relative to the prior value so as to successively improve the accuracy of getting the main drive shaft up to the rated rpm by the time of the first reed beat-up, without “wasting” time and energy in over-accelerating the flywheel to an excessively high start-up rpm.
Thus, the method according to the invention can be designated as a self-learning method of starting up a loom. With each start-up of the loom subsequent to a fault interruption, data points that map the running-up of the loom rpm from a standstill to the time of the first beat-up or during the course of several beat-ups are generated and stored in the loom control. The actual start-up rpm of the drive motor or of the flywheel mass that is necessary for ensuring that the main drive shaft of the loom will reach the rated rpm at the time of the first beat-up of the next start-up operation is calculated, based on these increasingly accurate data points.
REFERENCES:
patent: 3626992 (1971-
Mueller Herbert
Wagner Arno
Fasse W. F.
Fasse W. G.
Lindauer Dornier Gesellschaft mbH
Ro Bentsu
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