Ship's log and speedometer
First Claim
1. Non-contacting apparatus for measuring the revolutions of a rotating shaft comprising:
- bearing means supporting said shaft for rotation about its axis;
a permanent magnet mounted on said shaft with an axis of magnetization oriented substantially transversely with respect to the axis of said shaft;
electro-magnetic sensing means comprising a balanced magnetometer assembly physically spaced from said magnet and adapted to generate a cyclic electrical output signal whose amplitude and polarity are functions solely of the angular position of said magnet; and
means responsive to said output signal for counting and indicating said revolutions.
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Accused Products
Abstract
My invention relates to ship'"'"'logs and speedometers, comprising magnetometers and associated circuitry located inside the hull of the vessel, for accurately sensing, indicating, and recording the revolutions of an external rotator equipped with a small permanent magnet assembly. The rotator with a low-friction bearing arrangement is suitably located outside and below the hull of the vessel so that its rotation accurately registers the movement of the vessel through the water. The elimination of any mechanical or electrical connection between the rotator and the inside sensing components of the magnetometer assembly facilitates removal of the rotator for maintenance and substantially reduces the risk of leaks through the hull of the vessel.
11 Citations
15 Claims
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1. Non-contacting apparatus for measuring the revolutions of a rotating shaft comprising:
bearing means supporting said shaft for rotation about its axis;
a permanent magnet mounted on said shaft with an axis of magnetization oriented substantially transversely with respect to the axis of said shaft;
electro-magnetic sensing means comprising a balanced magnetometer assembly physically spaced from said magnet and adapted to generate a cyclic electrical output signal whose amplitude and polarity are functions solely of the angular position of said magnet; and
means responsive to said output signal for counting and indicating said revolutions.- View Dependent Claims (2, 3, 4, 5, 6)
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7. A ship'"'"'s log for measuring the distance traveled by a vessel through water comprising:
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a rotator assembly adapted to be mounted outside the hull of a vessel and below its water line, said assembly comprising a shaft, low-friction bearing means supporting said shaft, a vaned rotator for turning said shaft in response to movement through the water, and a permanent magnet affixed to said shaft with its axis of magnetization oriented in a plane substantially at right angles to said shaft; a balanced pair of magnetometers adapted to be mounted inside the hull of said vessel substantially in said plane and substantially equidistant from said shaft, said magnetometers being in sufficiently close proximity to said magnet to respond to its magnetic field; electrical circuit means for providing energizing current to said magnetometers and interconnecting them so that their output signals due to said field are added electrically;
said magnetometers and circuit means generating a resultant electrical signal that has cyclic variations which are a direct function of the rotation of said magnet;
phase detection means energized by said circuit means for detecting phase reversals in said signal due to said rotation;digital means for counting and displaying the number of phase reversals with the proper scaling factor, as determined by the pitch of said vaned rotator, thereby to represent the nautical distance travelled by said vessel through the water. - View Dependent Claims (8, 9, 10)
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11. An electrical ship'"'"'s log for indicating the distance travelled by a marine vessel comprising:
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a rotator assembly adapted to be mounted outside the hull of a vessel and below its water line, said assembly comprising a vaned rotator affixed to a shaft, low-friction bearings supporting said shaft for free rotation as said rotator turns due to ship'"'"'s movement through the water, at least one of said bearings being a low-friction thrust bearing, and an annular ring-magnet affixed to said shaft, said ring-magnet being permanently magnetized in a plane substantially at right angles to the axis of said shaft; a serially-connected pair of substantially identical flux-gate magnetometers adapted to be mounted inside the hull of said vessel parallel to each other, said magnetometers being mounted in said plane and symmetrically spaced from said shaft so as to be magnetically coupled to said ring magnet, each of said magnetometers having a pair of additively-connected excitation windings and a differently-connected pair of sense windings mounted on a closed-circuit ferro-magnetic core structure; power supply means providing magnetizing currents to said excitation windings, said power supply means comprising a source of voltage of relatively high frequency and symmetrical waveform, said voltage having sufficient amplitude normally to saturate said cores; phase detection means responsive to signals from said sense windings for generating alternating level transitions each time the net difference in magnetic field strength at the magnetometers caused by said ring magnet changes polarity and exceeds a selected threshold value;
circuit means comprising a digital counter for converting said level transitions into resultant pulses corresponding to the number of turns made by said rotator, shaft and magnet in traversing a unit distance; and
a register augmented by said resultant pulses for logging said displaying the total distance travelled. - View Dependent Claims (12, 13)
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14. Non-contacting apparatus for measuring the number of revolutions made by a rotating shaft comprising:
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a magnet assembly carried by said shaft having an axis of magnetization in a transverse plane intersecting said shaft, an astatically-balanced pair of magnetometers physically spaced from said shaft and symmetrically oriented to respond to magnetic flux from said magnet assembly, said magnetometers having interconnected excitation windings and interconnected sense windings;
a source of AC input signals for energizing said excitation windings;means for deriving AC reference phase signals from said AC input signal; and output means for detecting and indicating cyclically-varying AC output signals from said sense windings;
said output signals having amplitude and phase relations with respect to said reference phase signals which are functions of the angular position of said magnet assembly. - View Dependent Claims (15)
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Specification