Motors: expansible chamber type – Relatively movable working members with one having motive... – Synchronizing in response to sensed difference in positions
Reexamination Certificate
1998-08-26
2001-01-30
Look, Edward K. (Department: 3745)
Motors: expansible chamber type
Relatively movable working members with one having motive...
Synchronizing in response to sensed difference in positions
Reexamination Certificate
active
06178867
ABSTRACT:
The present invention relates generally to hydraulic or pneumatic control systems and more particularly to methods and apparatus for hydro-mechanically synchronizing the operation of independent actuators or motors regardless of variations in imposed loads, travel, or actuator efficiencies. In particular, the present invention provides synchronization for the hydraulically powered movement of doors associated with aircraft engines.
It is desirable to provide a hydraulic control which assures synchronous motion of a pair of actuators. The present invention creates a hydro-mechanical means to provide reliable synchronous operation of hydraulically or pneumatically powered linear or rotary actuators or motors. It may be applied to systems in which the actuators or motors have equal or unequal displacements, efficiencies, and/or imposed loads, and may even be applied where the strokes of the actuators from stop-to-stop differ or the actuators act in differing directions. Synchronous operation is assured by means of a closed loop, mechanical feedback system and a controller which operates on the hydraulic or pneumatic motive fluid.
Some systems may require the total stop-to-stop stroke of each actuator to be different, or the orientation of each actuator to differ, yet operation to be synchronized so that each remains in step with the other at any given point in its travel range or to reach the stops simultaneously. In this scenario, a ratio other than 1 to 1 between the feedbacks from the individual actuators may be built into the differential sensor device, to provide an appropriate output error signal to the servo valve.
Another advantage inherent in the flexibility offered by the proposed approach is the availability of a number of places in which system gains can be optimized, to maximize the effectiveness of the synchronizer, and to minimize the risk of erratic behavior or unstable transient operation. For instance, over-activity of the controller in response to small travel perturbations can be restrained by inclusion of deadband in the valving, yet quick reaction to significant synchronous operation can be assured by high gains in the throttling loops.
In certain aircraft applications, each inner door, upper or lower, is independently positioned by its own pair of hydraulically powered ram actuators. The actuators are located at either end of the door, each physically isolated from the other. A controller package manages operation of the actuators on each door. In one particular application, each inner door actuator is sized to withstand a tensile stall load of nearly 37,000 pounds and to slew against dynamic loads of 20,200 pounds. Each has a 12.5″ stroke. Extreme loads, long strokes, the large physical separation between these actuators, and the light engine/airframe structure make impractical the use of a mechanical means to assure synchronization. Such a system would simply be too heavy for practical aircraft use.
The present invention provides synchronization while obviating these problems in which direction of actuator travel is detected, differential rate of motion is determined, and correction to restore synchronous operation is established by valves which use the motive flow powering the devices being driven. The valving restricts the supply of motive flow to the faster of the powered devices to limit its rate of travel. The need for the application of large braking forces at the output of the powered devices to control rate of travel is eliminated, as are the inherent heat generation and the deleterious impact on system efficiencies of braking systems. The present invention is a combination comprising: a pair of bidirectional fluid powered actuators; a source of pressurized fluid for operating the actuators; means monitoring the motion of each actuator and providing an indication of a dissimilarity between the motions of the two actuators; and means responsive to a dissimilarity indication for retarding the flow of actuating fluid from the source to the appropriate one of the actuators to diminish the dissimilarity between the motions of the two actuators.
REFERENCES:
patent: 3850081 (1974-11-01), Joelson
patent: 5267438 (1993-12-01), Bunel et al.
patent: 5791860 (1998-08-01), Stockmann
Allied-Signal Inc.
Lazo Thomas E.
Look Edward K.
Palguta Larry J.
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