Agitating – By vibration – By rotary movement of unbalanced-weight shaft
Reexamination Certificate
1999-03-23
2001-04-10
Soohoo, Tony G. (Department: 1723)
Agitating
By vibration
By rotary movement of unbalanced-weight shaft
C366S219000
Reexamination Certificate
active
06213630
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention involves an unbalanced vibrator for compacting concrete components during their manufacture, in particular an unbalanced vibrator having a vibrating table, unbalance shafts arranged on the vibrating table, and electronic motors allocated to the unbalance shafts for driving them, wherein the unbalanced vibrator has a device for the control and/or regulation of the rotational speed and/or the relative phase position of the unbalance shafts.
A device of this type is known, for example, from German utility model DE-U-297 12 242. According to this document, asynchronous three phase a.c. motors are used as electronic motors, and the unbalance shaft control or regulation is accomplished via vector regulators.
It is disadvantageous in this known device that asynchronous machines react relatively sluggishly to the corresponding control or regulation signals. Since, however, even a slight angular displacement of the unbalance shafts in their “neutral position” can lead to an undesired vibration of the vibrating table, this is considered a disadvantage.
Also, from German published patent application DE-A-43 17 351, a comparable vibrating device is known. According to this document, incremental transmitters are provided in order to detect the position that the unbalanced masses have relative to each other. However, these incremental transmitters have a very limited resolution so that the system also has only limited synchronization properties.
In a vibrating device, as is known from German published patent application DE-A-44 07 013, operation is by hydraulic actuators and servo components. These are relatively sluggish, and thus this system is likewise limited in its dynamics. Since the adjustment times are longer, the cycle times are also prolonged, for example, during block manufacturing. Also, the transmitters used in the prior art in order to detect the position of the unbalance shafts are incremental transmitters having only a limited resolution, which has an unfavorable effect, just as the poor dynamics, on the control performance of the device.
SUMMARY OF THE INVENTION
An object of the present invention is thus to provide an unbalanced vibrator in which a most precise regulation can be achieved, wherein the device for control should have a high dynamic and thus achieve a high control performance.
This objective is achieved according to the invention in that the electronic motors of the device are designed as servo-motors having motor regulation electronics, and the device for control and/or regulation of the rotational speed and/or the relative phase position of the unbalance shafts includes sine-cosine transmitters that determine the angular position and rotational speed of the unbalance shafts.
The advantage of this invention consists in that the servo-motors have a higher dynamic than the related asynchronous machines up to now. Furthermore, servo-motors have the advantage of being able to deliver a considerably higher power than the asynchronous machines having like size, so that presently available constructions can be designed so that they are more powerful. At the same time, the peak loading capability, required only for a short time for the adjustment movements, is also more favorable in servo-motors.
The sine-cosine transmitters provided according to the invention can be obtained having, in addition, a resolution that is considerably above that of traditional incremental transmitters. For demanding regulation tasks, sine-cosine transmitters are obtainable having a resolution that is over 65,000 inc./rev. Thus, even the smallest regulation deviations can be detected and can be immediately counterbalanced because of the good dynamics of the servo-motors.
It has also proven to be advantageous with the sine-cosine transmitters to determine the angular position and the rotational speed of the shafts of the electronic motors, and to connect these shafts to the unbalance shafts via a fixed translation ratio. On the one hand, short signal transmission paths can thus be realized, and on the other hand, the electronic motors can be separated from the vibrating table, for example via cardan shafts, etc., so that they themselves are not exposed to any vibrations and ultimately as well, the sine-cosine transmitters are exposed to a smaller mechanical stress.
In a preferred embodiment, the translation ratio between the electronic motor and the unbalance shaft is 1:1, since in this way, the position of the unbalance shaft can be concluded from the angular position of the motor shaft without additional conversion.
It is favorable, with a total of four unbalance shafts, to couple them in de pairs running in opposite directions via toothed (synchronous) belts. Each pair of coupled together shafts thus lies in a horizontal plane and the individual pairs lie above each other in the vertical direction. This arrangement is very compact and favorable for the vibrating force resulting through the unbalance shafts.
The special mechanical connection via the toothed belts has the advantage that the two coupled unbalance shafts can optimally follow a regulation guideline, without slippage occurring for example, as with V-belts, or play, as occurs with toothed gear drives or the like. Slippage of this type or play of this type acts in a disadvantageous manner on the synchronization of the two coupled shafts, which becomes especially noticeable at the operating point in which all centrifugal forces should be removed, in order to have the vibrating table at rest. At this operating point, even the smallest deviations from the synchronization of the coupled shafts become readily noticeable, since they set the vibrating table into slight oscillations.
For cost reasons it is favorable to couple each pair of unbalance shafts to a servo-motor having motor regulation electronics. By the use of only two motors to drive a total of four axles, considerable costs are saved for additional motors and additional power and regulation electronics.
In order to achieve herein as tight a coupling of several motors as possible, it is proposed with two motors to design one as a master drive and the other one as a slave drive.
It has proven to be favorable herein to integrate a position controller, that synchronizes the slave drive, directly into its motor regulation electronics, since this results in short signal run times between the position controller and the rotational speed regulator, which supports a rapid sensing rate of the individual controller, and thus contributes to good regulation dynamics.
Each of the motor regulation electronics therein can have a separate evaluation unit for the sine-cosine transmitter allocated to it, which creates the actual values for the individual controllers. This has the advantage that the computational performance remains reserved for the actual regulation.
This acts in an especially advantageous way, especially in the design of the motor electronics in fully digitalized form, wherein the sensing times are kept extremely short, and preferably less than 75 gsec. Such short sensing times are favorable for a quick dynamic control.
REFERENCES:
patent: 43 17 351 A1 (1994-12-01), None
patent: 44 07 013 A1 (1995-09-01), None
patent: 297 12 242 U1 (1997-10-01), None
Akin Gump Strauss Hauer & Feld & LLP
Masa AG
Soohoo Tony G.
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