Limit control apparatus
First Claim
1. For use in a control system wherein a processing circuit is operable to receive a commanded direction signal and selectively effect movement of an actuator in accordance therewith subject to a first limit ot travel in a first direction, the combination comprising:
- first limit sensing means connected to the actuator and operable to generate a first limit detection signal characterized by at least one electrical pulse, when the actuator approaches the first limit of travel;
integrating means arranged to receive said first limit detection signal and provide a first integral signal output;
comparator means arranged to receive said first integral signal output and provide a first limit signal when said first integral signal output exceeds a predetermined level; and
logic means arranged to receive said first limit signal and the commanded direction signal, said logic circuit being operable to provide a modified direction signal to the processing circuit, said modified direction signal being indicative of the commanded direction in the absence of said first limit signal, said logic means being operable to modify said commanded direction signal upon receipt of said first limit signal such that said modified direction signal is indicative of the direction opposite said commanded direction during the continuance of said first limit signal.
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Accused Products
Abstract
An actuator control system includes a ballscrew type actuator for controlling the positioning of a valve device. A processing circuit is responsive to direction and drive signals for driving a synchronous stepper motor which is operatively coupled to the actuator. The processing circuit includes a switching device which applies a DC voltage to the motor windings to hold the valve position when it is not being driven. A limit sensing device provides a limit signal when the movable member of the actuator approaches a limit of travel. A limit control circuit responds to the limit signal to alternately reverse the direction signal applied to the processing circuit so long as that signal is representative of the direction in which the limit is being approached.
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Citations
5 Claims
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1. For use in a control system wherein a processing circuit is operable to receive a commanded direction signal and selectively effect movement of an actuator in accordance therewith subject to a first limit ot travel in a first direction, the combination comprising:
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first limit sensing means connected to the actuator and operable to generate a first limit detection signal characterized by at least one electrical pulse, when the actuator approaches the first limit of travel; integrating means arranged to receive said first limit detection signal and provide a first integral signal output; comparator means arranged to receive said first integral signal output and provide a first limit signal when said first integral signal output exceeds a predetermined level; and logic means arranged to receive said first limit signal and the commanded direction signal, said logic circuit being operable to provide a modified direction signal to the processing circuit, said modified direction signal being indicative of the commanded direction in the absence of said first limit signal, said logic means being operable to modify said commanded direction signal upon receipt of said first limit signal such that said modified direction signal is indicative of the direction opposite said commanded direction during the continuance of said first limit signal. - View Dependent Claims (2, 3, 4, 5)
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Specification