Bleaching and dyeing; fluid treatment and chemical modification – Fluid treatment – Manipulation of liquid
Reexamination Certificate
2001-11-15
2004-01-27
Stinson, Frankie L. (Department: 1746)
Bleaching and dyeing; fluid treatment and chemical modification
Fluid treatment
Manipulation of liquid
C068S012060, C068S023500, C068S023200, C068S023300, C074S573110, C210S144000
Reexamination Certificate
active
06681430
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to rotatable members that are able to achieve balanced conditions throughout a range of rotational speeds. The present invention also relates to methods and systems for dynamically balancing rotatable members through the continual determination of out-of-balance forces and motion to thereby take corresponding counter balancing action. The present invention additionally relates to methods and systems in which inertial masses are actively placed within a rotating body in order to cancel rotational imbalances associated with the rotating body thereon. The present invention additionally relates to methods and system for dynamic balancing utilizing concurrent control actuator actions.
BACKGROUND OF THE INVENTION
Mass unbalance in rotating machinery leads to machine vibrations that are synchronous with the rotational speed. These vibrations can lead to excessive wear and to unacceptable levels of noise.
It is a common practice to balance a rotatable body by adjusting a distribution of moveable, inertial masses attached to the body. This state of balance may remain until there is a disturbance to the system. A tire, for instance, can be balanced once by applying weights to it. This balanced condition will remain until the tire hits a very big bump or the weights are removed. However, certain types of bodies that have been balanced in this fashion will generally remain in balance only for a limited range of rotational velocities. A centrifuge for fluid extraction, however, can change the amount of balance as more fluid is extracted.
Many machines are also configured as freestanding spring mass systems in which different components thereof pass through resonance ranges during which the machine may become out of balance. Additionally, such machines may include a rotating body loosely coupled to the end of a flexible shaft rather than fixed to the shaft as in the case of a tire. Thus moments about a bearing shaft may also be created merely by the weight of the shaft. A flexible shaft rotating at speeds above half of its first critical speed can generally assume significant deformations, which add to the imbalance. This often poses problems in the operation of large turbines and turbo generators.
Machines of this kind usually operate above their first critical speed. As a consequence, machines that are initially balanced at relatively low speeds may tend to vibrate excessively as they approach full operating speed. Additionally, if one balances to an acceptable level rather than to a perfect condition (which is difficult to measure), the small remaining out-of-balance will progressively apply greater force as the speed increases. This increase in force is due to the fact that F is proportional to r&ohgr;
2
, (where F is the out of balance force, r is the radius of the rotating body and &ohgr; is its rotational speed).
The mass unbalance distributed along the length of a rotating body gives rise to a rotating force vector at each of the bearings that support the body. In general, the force vectors at respective bearings are not in phase. At each bearing, the rotating force vector may be opposed by a rotating reaction force, which can be transmitted to the bearing supports as noise and vibration. The purpose of active, dynamic balancing is to shift an inertial mass to the appropriate radial eccentricity and angular position for canceling the net unbalance. At the appropriate radial and angular distribution, the inertial mass can generate a rotating centrifugal force vector equal in magnitude and phase to the reaction force referred to above.
Many different types of balancing schemes are known to those skilled in the art. When rotatable objects are not in perfect balance, nonsymmetrical mass distribution creates out-of-balance forces because of the centrifugal forces that result from rotation of the object. Although rotatable objects find use in many different applications, one particular application is a rotating drum of a washing machine.
U.S. Pat. No. 5,561,993, which was issued to Elgersma et al. on Oct. 22, 1996, and is incorporated herein by reference, discloses a self-balancing rotatable apparatus. Elgersma et al. disclosed a method and system for measuring forces and motion via accelerations at various locations in a system. The forces and moments were balanced through the use of a matrix manipulation technique for determining appropriate counterbalance forces located at two axial positions of the rotatable member. The method and system described in Elgersma et al. accounted for possible accelerations of a machine, such as a washing machine, which could not otherwise be accomplished if the motion of the machine were not measured. Such a method and system was operable in association with machines not rigidly attached to immovable objects, such as concrete floors. The algorithm disclosed by Elgersma et al. permitted counterbalance forces to be calculated even when a washing machine is located on a flexible or mobile floor structure combined with carpet and padding between the washing machine and a rigid support structure.
U.S. Pat. No. 5,561,993 thus described a dynamic balance control algorithm for balancing a centrifuge for fluid extraction. To accomplish such balance control, balance control actions may place mass at the periphery of axial control planes on the centrifuge. Sensor measurements may be used to assess the immediate balance conditions. In assessing the balance conditions, measurement thresholds may be established to direct the course of balance control. Related sensor responses to balance control actions may be modeled to determine the specific future control actions. The control actions may require multiple control actuators; generally one per axial control plane, although multiple actuators at multiple control planes may emulate additional virtual control planes. The actuators may be actuated independently or concurrently. The advantage to concurrent actuation is reduced time to place the corrective mass and a smoother control trajectory to the balanced state.
With concurrent actuation, it would be ideal if concurrent corrective mass placement actions could be placed continuously and in constant proportion. An actuation system based on the placement of mass on a rotating apparatus from its stationary surroundings, however, does not permit the continuous placement of mass at any desired proportion. A limited amount of mass can be placed at a specific location only once per revolution, and the actuator action is a step action with a minimum resolution. Thus, a different and unique approach must be utilized to overcome these problems, one in which a desired control action is achieved through discretized proportions that closely represent the ideal continuous control action. Additionally, because of the discrete nature of the control actions (i.e., step actions), one must be concerned that an applied set of step actions does not exceed the threshold set for establishing balanced operations. If they do exceed this threshold, a risk may be incurred of jumping directly through the balanced condition and from one unbalanced state to another.
Based on the foregoing, it can be appreciated that a method and system, and program product implementations thereof, are required to coordinate the concurrent multi-actuator control action in order to accomplish as smooth as possible transition of mass to the control planes of the centrifuge and to ensure incremental control actions have the needed resolution to achieve balanced operation. The invention disclosed herein thus addresses these needs and the related concerns.
BRIEF SUMMARY OF THE INVENTION
The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
It is one aspect of the present inventio
Fredrick Kris T.
Honeywell International , Inc.
Lopez Kermit D.
Ortiz Luis M.
Stinson Frankie L.
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