Measuring and testing – Volume or rate of flow – By measuring thrust or drag forces
Reexamination Certificate
2000-06-23
2003-08-12
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Volume or rate of flow
By measuring thrust or drag forces
C073S861830, C324S207210
Reexamination Certificate
active
06604434
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for determining the direction or magnitude of rotation, or both, of a rotating magnetic field. More specifically, the present invention determines the direction of rotation of a rotating magnetic field by sensing the changes in polarity of magnetic flux occurring at two locations within the rotating magnetic field and comparing these changes to determine the direction of rotation. In addition, the rate or number of revolutions may also be measured. In one exemplary embodiment of the present invention, a fluid meter is provided that determines the magnitude and direction of a flowing fluid. The kinetic energy of the moving fluid is translated into a rotating magnetic field. Two sensors are placed within the magnetic field to determine the changes in magnetic flux polarity occurring at two different locations within the field. The direction of fluid flow is determined by comparing and interpreting the signals. The volume or rate of flow may also be determined.
BACKGROUND OF THE INVENTION
Conventional devices for fluid measurement are known. In general, such devices may be limited to measuring flow rates or may also be configured for totalizing the volume of fluid flow. While various devices and techniques for fluid measurement have been applied, many utilize a rotating element placed in the path of fluid flow. The kinetic energy of the moving fluid is harnessed to cause an element, such as a turbine, to rotate upon a shaft. Means are provided for detecting the rotational speed of the element and, in some devices, to determine the total number of revolutions. The volume of fluid displaced during one revolution is usually predetermined through calibration or calculations based upon the geometry of the rotatable element and the associated fluid passageway.
Various means exist for detecting the rotations of an element and converting the same into a recordable measurement. Such means include registers that are mechanically or magnetically coupled with the rotating element. U.S. Pat. No. 5,187,989, issued to Bulteau and commonly owned with the present application, discloses one example of an apparatus for detecting the rotation of the spinner of a water meter. In one embodiment, sensors in the form of oscillator circuits are disposed on two opposite radial directions about a disk. The disk is constructed of a non-metallic material but includes a metallized radial sector on the disk. As the disk rotates due to the flow of water through the meter, the oscillator circuits are used to detect the passage of the sector. The number of turns completed by the disk, and thus the flow of fluid through the meter, may then be totaled by associated circuitry to provide a measurement.
Sensors capable of detecting a changing magnetic field created from the rotation of a measuring element have also been applied. U.S. Pat. No. 4,579,008, issued to Bohm et al., discloses a flow meter that uses a plurality of sensors to detect the changing magnetic field created by placing a pair of magnets into the ends, respectively, of oval measuring gears. A plurality of sensing elements are required, and a nonuniform distribution of the sensors is utilized to compensate for the nonuniform rotation of the oval measuring gears.
U.S. Pat. No. 5,530,298, issued to Gerhold, discloses a natural gas volume meter. A magnetic sensor is located in close proximity to a magnet that is mounted upon a rotatable element in the gas meter. As the kinetic energy of the moving gas causes the element to rotate, a single magnet also rotates to create a magnetic field of changing flux. As only a single magnet is utilized, the resolution of this apparatus is limited to one change in magnetic flux, or signal, per each 180 degrees of revolution. Furthermore, specific physical configurations of the sensor and magnet are not taught.
The entire disclosures of the U.S. Patents noted above are herein incorporated by reference into the subject disclosure.
While the above referenced disclosures discuss means for detecting the rotation of an element for measuring the amount of flow, these references do not provide means for determining the direction of flow. In many applications, the ability to determine not only the amount or rate of flow but also the direction of flow would be advantageous.
SUMMARY OF THE INVENTION
The present invention provides for determining both the direction of rotation and magnitude of a rotating magnetic field. In application, the present invention provides for the measurement of certain physical events where the rotating magnetic field is generated in a known relationship to the event. The rotations of the magnetic field, for example, may be created by translating the kinetic energy of a moving fluid. Knowing the volume of fluid displaced per rotation of the magnetic field, the present invention allows for the determination of both the direction of flow and magnitude (rate or volume) of flow.
The present invention provides numerous embodiments for determining the direction of rotation of a rotating magnetic field. Examples will now be provided; others will be apparent to those of ordinary skill in the art using the techniques disclosed herein. In one exemplary embodiment, a method of determining the direction of rotation of a magnetic field includes sensing the change in polarity of magnetic flux encountered at a first point and at a second point located within a rotating magnetic field. The second point is located within the magnetic field at a position that is subsequent in the direction of rotation from the location of the first point. For example, if the magnetic field is rotating counter-clockwise, a change in magnetic flux encountered at the first point would be detected subsequent in time at the second point. In the event the direction of rotation changes from counter-clockwise to clockwise, the change in polarity of magnetic flux encountered at the second point would then be detected subsequent in time at the first point. By comparing the changes in polarity of magnetic flux detected at the first point and the second point, the direction of rotation of the rotating magnetic field may be determined.
Stated alternatively, the first point and second point are located at an angle, or subsequent in the direction of rotation, from one another. For example, assume a first plane is defined by the plane that is coincident with the axis of the rotating magnetic field and the location of the first point. Accordingly, the second point is located within a second plane that is coincident with the axis about which the magnetic field is rotating and positioned such that the second plane and first plane form a positive angle from each other. By way of example only, the angle between the first plane and second plane may be 45 degrees or multiples thereof such as 135, 225, and 315 degrees. Importantly, the angle between the first plane and second plane should be greater than 0 degrees. Otherwise, the change in magnetic flux polarity being detected at the first point and second point will be identical and thereby preclude a determination of the direction of rotation.
The rotating magnetic field may be created by the rotation of a magnet mechanically coupled with a measuring element located in the path of a flowing fluid. By way of example only, the rotating magnet may be connected to a turbine or nutating disk within a fluid meter. Water flowing through the meter causes the magnet to rotate by acting upon the turbine. The magnet may be configured from a variety of shapes. For example, the magnet may be cylindrical in shape and contain four quadrants of polarity within the cylindrical shape.
In another exemplary embodiment, the present invention provides a method of sensing the rotation and direction of a rotating magnetic field as follows. Within the rotating magnetic field, the changes in polarity of magnetic flux are detected at a first point. These changes are used to create a corresponding first stream of electrical pulses that alternate in polarity.
Castleberry Walter
Hamilton David
Scarborough John
Bradley Arant Rose & White LLP
Mack Corey D.
Mixon, Esq. David E.
Neptune Technology Group Inc.
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