Boots – shoes – and leggings
Patent
1980-02-04
1982-10-19
Gruber, Felix D.
Boots, shoes, and leggings
324166, 324174, 324176, 34087032, G01P 348, G06F 1520
Patent
active
043553648
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to apparatus for sensing the velocity of metallic parts such as gears and particularly to a velocity sensing system in which a frequency modulated (FM) signal is generated as a result of relative motion between the monitored parts and a sensor. Velocities are detectable over a wide range extending on the low end to zero.
2. Background Art
A determination of the speed and direction of motion of a rotating or linearly translating body such as a drive gear or gear rack is obtainable through the use of a number of prior art devices and techniques; for example, electro optical devices, Hall-effect devices and electromagnetic sensors can be used to generate pulses as the part moves past the sensor and the pulses can then be processed to yield the desired data. Optical devices require a relatively clean environment; Hall-effect devices are expensive and often technically complex. These factors would seem to favor the electromagnetic sensors; however, a practical disadvantage of the electromagnetic sensor is its sensitivity to spacing variations between itself and the translating part, and the dependence of signal strength on the speed of the translating part; i.e., since the signal generator in the sensor is responsive to the change in magnetic flux per unit time, very low speeds of translation render the sensor signal substantially useless in the subsequent data processor. Accordingly, electromagnetic sensors are not generally used where speeds at or near zero are to be detected. One approach to wheel or gear speed measurement in which electromagnetic sensor disadvantages are reduced is disclosed in U.S. Pat. No. 4,050,747 issued to Ruhnau et al on Sept. 27, 1977. That device utilizes counters and data registers responsive to positive and negative transitions of a sensor signal to provide a digital speed indication.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF INVENTION
In one aspect of the present invention a velocity sensing system is provided which utilizes a rugged and simple electromagnetic sensor and which has low and zero speed measuring capability. The system comprises an oscillator having a tank circuit which controls the frequency of the oscillator output and a magnetic flux sensitive sensor adjacent the part to define a portion of a flux path which links the part and in which the magnetic flux varies in intensity according to the physical presence of the part. The tank circuit of the oscillator is linked with the flux path so that the electrical tuning of the tank circuit varies as the part passes by the sensor, thus producing an alternating shift in the frequency of the output signal between relatively high and low frequency levels. Part speed is determined as a function of the rate at which the oscillator varies between the high and low frequencies.
In another aspect of the present invention, a part velocity sensing system which provides a digital signal having discrete transitions which occur at a rate in proportion to the speed of the part being measured is provided without the complexity of the multiple counter and register system of prior art U.S. Pat. No. 4,050,747 mentioned above. The velocity sensing system according to this aspect of the invention comprises an oscillator producing a variable frequency signal, a sensor positioned adjacent the part to vary the frequency signal between high and low frequencies as the part or parts pass the sensor, and a detector receiving the signal to produce a digital waveform in which the transitions occur at a rate representing part velocity. Such a system is not only independent of variations in signal strength, but is easily calibrated during startup as well as during normal operations.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 illustrates an embodiment of the invention as applied to the measurement of gear tooth velocity.
FIG. 2 is a graphical representation of certain signal frequencies under various operating conditions of the embodi
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Grebene: The Monolithic Phase-Locked Loop--a Versatile Building Block, IEEE Spectrum 1971, pp. 38, 39.
Normand: Phase Locked Loop with Sample Phase Comparator TLE, (France), Mar. 1981, Note p. 83 for connections of MC 14046.
Caterpillar Tractor Co.
Gruber Felix D.
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