Obstruction detection in automatic portal control apparatus employing induction motor power factor
First Claim
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1. An automatic portal operator comprising:
- a portal closing member movable between a closed position blocking a portal and an open position not blocking said portal;
an induction motor mechanically coupled to said portal closing member for controllably moving said portal closing member between said closed position and said open position;
a motor controller electrically coupled to said induction motor for supplying electrical power to said induction motor for controllably moving said portal closing member toward said closing position or toward said open position, said motor controller including a safety operation for supplying electric power to said induction motor to render said portal closing member safe; and
a power factor sensor connected to said induction motor and said motor controller includinga current sensor for generating a current square wave signal having the phase of the current supplied to said induction motor by said motor controller,a pulse stretching circuits connected to said current sensor for generating a extended current square wave signal having a trailing edge a predetermined length of time after the trailing edge of said current square wave signal,a voltage sensor for generating a voltage square wave signal having the phase of the voltage supplied to said induction motor by said motor controller,a clamping circuit connected to said pulse stretching circuit and said voltage sensor for clamping the reading edge of said extended current square wave signal to the leading edge of said voltage square wave signal, thereby producing a clamped extended current square wave signal,an inclusive or circuit connected to said voltage sensor and said clamping circuit for generating a phase output signal when said clamped extended current square wave signal differs from said voltage square wave signal, andan output circuit connected to said motor controller and said exclusive OR circuit for triggering said motor controller to execute said safety operation if the duty cycle of said phase output signal exceeds a predetermined amount.
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Abstract
The present invention is a load sensor for use in an automatic portal operator such as an industrial gate operator. An induction motor is employed to move the gate. The power factor of the AC electric power supplied to the induction motor is monitored. A safety operation is triggered when the power factor indicates the motor load is greater than a predetermined amount, as when an obstruction is encountered by the gate.
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Citations
11 Claims
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1. An automatic portal operator comprising:
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a portal closing member movable between a closed position blocking a portal and an open position not blocking said portal; an induction motor mechanically coupled to said portal closing member for controllably moving said portal closing member between said closed position and said open position; a motor controller electrically coupled to said induction motor for supplying electrical power to said induction motor for controllably moving said portal closing member toward said closing position or toward said open position, said motor controller including a safety operation for supplying electric power to said induction motor to render said portal closing member safe; and a power factor sensor connected to said induction motor and said motor controller including a current sensor for generating a current square wave signal having the phase of the current supplied to said induction motor by said motor controller, a pulse stretching circuits connected to said current sensor for generating a extended current square wave signal having a trailing edge a predetermined length of time after the trailing edge of said current square wave signal, a voltage sensor for generating a voltage square wave signal having the phase of the voltage supplied to said induction motor by said motor controller, a clamping circuit connected to said pulse stretching circuit and said voltage sensor for clamping the reading edge of said extended current square wave signal to the leading edge of said voltage square wave signal, thereby producing a clamped extended current square wave signal, an inclusive or circuit connected to said voltage sensor and said clamping circuit for generating a phase output signal when said clamped extended current square wave signal differs from said voltage square wave signal, and an output circuit connected to said motor controller and said exclusive OR circuit for triggering said motor controller to execute said safety operation if the duty cycle of said phase output signal exceeds a predetermined amount. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An automatic portal operator comprising:
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a portal closing member movable between a closed position blocking a portal and an open position not blocking said portal; an induction motor mechanically coupled to said portal closing member for controllably moving said portal closing member between said closed position and said open position; a motor controller electrically coupled to said induction motor for supplying electrical power to said induction motor for controllably moving said portal closing member toward said closing position or toward said open position, said motor controller including a safety operation for at least stopping said induction motor to render said portal closing member safe; and a power factor sensor connected to said induction motor and said motor controller including a current sensor for generating a current phase signal indicative of the phase of the current supplied to said induction motor by said motor controller, said current sensor including a toroidal coil having an opening through which is passed one wire supplying current to said induction motor, a voltage sensor for generating a voltage phase signal indicative of the phase of the voltage supplied to said induction motor by said motor controller, a manually operable phase reversal means connected a predetermined one of said current sensor or said voltage sensor to selectively invert said phase signal of said predetermined sensor, whereby passage of said one wire through said opening in said toroidal coil in either direction may be accommodated by operation of said phase reversal switch, and a phase comparator circuit connected to said current sensor, said voltage sensor and said motor controller for triggering said motor controller to execute said safety operation if the difference in phase between said current phase signal and said voltage phase signal is less than a predetermined amount. - View Dependent Claims (11)
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10. An automatic portal operator comprising:
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a portal closing member movable between a closed position blocking a portal and an open position not blocking said portal; an induction motor mechanically coupled to said portal closing member for controllably moving said portal closing member between said closed position and said open position; a motor controller electrically coupled to said induction motor for supplying electrical power to said induction motor for controllably moving said portal closing member toward said closing position or toward said open position, said motor controller including a safety operation for at least stopping said induction motor to render said portal closing member safe, and said motor controller further including a means for generating a reversal signal when said portal closing member is moved toward a first of said closed position and said open position and not generating said reversal signal when said portal closing member is moved toward the other of said closed position and said open position; and a power factor sensor connected to said induction motor and said motor controller for triggering said motor controller to execute said safety operation if the power factor of the electrical power supplied to said induction motor indicates the load on said induction motor exceeds a predetermined amount; and means connected to said motor controller and said power factor sensor for setting said predetermined amount of load as a first predetermined amount if said reversal signal is received and as a second predetermined amount if said reversal signal is not received.
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Specification