Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1999-03-23
2002-02-19
Williams, Hezron (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207150, C324S165000
Reexamination Certificate
active
06348790
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to magnetic rotation sensors and in particular, to a non-intrusive motor rotation detector for determining the direction of shaft rotation of an electrical alternating current induction motor without requiring physical contact with the motor.
BACKGROUND OF THE INVENTION
Knowledge of the proper direction of motor shaft rotation is essential when integrating today's industrial motors within systems and machines designed to perform particular applications and tasks. Previously, one could view the direction of motor shaft rotation because few motors possessed hidden shafts or shafts covered by a safety guard. However, as time progressed, regulatory requirements, specific applications, and economic considerations required many motor shafts to become hidden in housings, covered with safety guards, or made an integral part of a mechanical assembly. This inhibited visible determination of the direction of motor shaft rotation. Although rotation direction could still be determined by viewing the motor prior to assembly within the machine or by viewing the process results, these methods often proved inadequate for a number of reasons. First, costly equipment may be damaged by reverse operation for any period above a short time interval; viewing the results of a process that takes even a relatively small amount of time to complete may result in irreparable damage to the machine. Moreover, reverse operation of shaft rotation may not be obvious from viewing the results and may inadvertently be accepted as normal. In addition, original equipment vendors may have a need to check rotation of hidden shaft units so that the final manufacturer can install the motor without the cost of re-connecting motors to obtain the proper shaft rotation.
A number of detectors exist in the prior art for determining shaft rotation direction. However, these instruments require electrical connections to the motor. This imposes added cost, time and labor in order to stop the motor, connect the rotation detector, start the motor, determine the rotation, and disconnect the detector, before moving on to the next unit under test.
Consequently, a compact means for providing an indication of the direction of rotation of a motor shaft without incurring the labor and time investment associated with connecting and disconnecting electrical leads and stopping and starting the motor is greatly desired.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved rotation detection sensor for determining the direction of shaft rotations of an electric motor.
Another object of the invention is to provide an improved motor rotation detector that does not require electrical leads connected to the motor or any physical contact with the motor.
Another object of the invention is to provide a leadless motor rotation detector apparatus for determining the direction of shaft rotation of a motor, the motor of the type providing a fluctuating magnetic field when rotating, the apparatus having at least two sensors separated a predetermined distance D
1
from one another, each sensor operable for sensing the magnetic field and generating a corresponding signal having an amplitude and phase associated with the sensed magnetic field; and a processor responsive to the signals for comparing temporal aspects associated with the relative phase of each of the signals to determine a leading signal, the leading signal associated with a corresponding one of the at least two sensors and is indicative of the direction of motor rotation.
A further object of the invention is to provide a small, compact, handheld moisture resistant rotation detection apparatus which senses the phase difference between two signals induced by a fluctuating magnetic field from the rotation of an electric motor shaft and operates on the relative signal phase difference to indicate the direction of the rotation of the motor shaft.
There is provided a compact portable motor rotation detector apparatus for determining the direction of shaft rotation of a motor, the motor of the type providing a fluctuating magnetic field when rotating, the apparatus comprising first and second sensors displaced a predetermined distance D
1
from one another for detecting the fluctuating magnetic field and producing corresponding first and second sensor signal waveforms, each having an amplitude and phase corresponding to the sensed fluctuating magnetic field from each of the corresponding first and second sensors; amplifier circuitry for amplifying the respective first and second sensor signal waveforms; a processor having first and second input channels for receiving the corresponding amplified first and second sensor signal waveforms, wherein the processor includes an algorithm for determining the phase angle between the two signal waveforms to determine the time shift between the first and second signal waveforms for determining a leading signal associated with a corresponding one of the first and second sensors; and output means for providing a control signal indicative of the direction of motor rotation based on the determination of which sensor is associated with the leading signal.
Further objects of this invention, as well as the novel features thereof, will become apparent by reference to the following description, taken in conjunction with the accompanying figures.
REFERENCES:
patent: 3943504 (1976-03-01), Vosicky
patent: 4001689 (1977-01-01), Williams et al.
Aler Mark D.
Gu Jin H.
Andersen Henry S.
ITT Manufacturing Enterprises Inc.
Lombardi Menotti J.
Williams Hezron
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