Resonant vibrating structure with electrically driven wire coil and vibration sensor
First Claim
1. A resonance vibrating structure including:
- an adjacent external magnet;
wire coil means coupled to said vibrating structure;
electrical power supply means coupled to said coil means to pass electric current through said coil means at the resonance vibrational frequency of said structure;
said wire coil means being positioned on said structure so that when current having the resonance vibrational frequency is passed through said coil means in the presence of said external magnet, an electromagnetic force is exerted on said structure which causes said structure to vibrate at its resonance frequency;
a vibration sensing means positioned on the structure so that the vibration of said structure causes an electrically measurable output from said vibration sensing means proportional to the vibrational amplitude;
said coil means being appropriately sized and positioned with respect to said magnet so that the vibration induced output from said vibration sensing means varies in a predetermined desired manner as the magnetic field is perturbed so that the output can serve as a sensor of relative position between an object perturbing the magnetic field and said coil means;
feedback means coupled to said electrical power supply means and to said vibration sensing means for feedback control, said feedback means providing an output which controls the current through said coil means for exciting the vibration and keeping said resonance vibrating structure vibrating at its resonance frequency even though the resonance frequency may be changing with external ambient conditions such as temperature.
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Accused Products
Abstract
A vibration type sensor can make a noncontacting measurement of position or sense the passage of an object past a point. The sensor has a coil of wire placed on a vibrating structure. A power supply causes current to be passed through the coil at the resonant frequency of the vibrating structure. As an object with an attached magnet approaches the coil, a force is exerted on the current carrying coil thereby exciting the structure at its resonant vibrational frequency. A piezoelectric bimorph is attached to the structure so that it flexes with the structure producing an emf output proportional to the vibrational amplitude. As the object moves, the field strength at the coil, the amplitude of the vibration and the induced emf change. The latter quantity is used to sense the motion of the object. Alternatively, the magnet remains fixed with respect to the coil while a material of high magnetic permeability approaches the coil and magnet combination thereby perturbing the magnetic field and changing the induced emf. This method can be used to obtain a linear variation of sensor output with position or to enable the use of the device as a timing sensor.
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Citations
13 Claims
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1. A resonance vibrating structure including:
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an adjacent external magnet; wire coil means coupled to said vibrating structure; electrical power supply means coupled to said coil means to pass electric current through said coil means at the resonance vibrational frequency of said structure; said wire coil means being positioned on said structure so that when current having the resonance vibrational frequency is passed through said coil means in the presence of said external magnet, an electromagnetic force is exerted on said structure which causes said structure to vibrate at its resonance frequency; a vibration sensing means positioned on the structure so that the vibration of said structure causes an electrically measurable output from said vibration sensing means proportional to the vibrational amplitude; said coil means being appropriately sized and positioned with respect to said magnet so that the vibration induced output from said vibration sensing means varies in a predetermined desired manner as the magnetic field is perturbed so that the output can serve as a sensor of relative position between an object perturbing the magnetic field and said coil means; feedback means coupled to said electrical power supply means and to said vibration sensing means for feedback control, said feedback means providing an output which controls the current through said coil means for exciting the vibration and keeping said resonance vibrating structure vibrating at its resonance frequency even though the resonance frequency may be changing with external ambient conditions such as temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A resonance vibrating structure includes:
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an adjacent external magnet generating a magnetic field; a wire coil means for carrying electrical current having a plurality of turns coupled so as to vibrate as part of said structure; a diaphragm supporting said wire coil and driven into vibration when an electric current is passed through the coil at the resonance frequency of the diaphragm in the presence of a magnetic field due to an electromagnetic force between the current and the magnetic field and vibrating in its lowest resonance mode in which the only node of the vibration exists at the periphery of said diaphragm and an antinode exists near the geometrical center of said diaphragm; said wire coil means being attached so that a portion of each turn exists in the regions of the antinode and node respectively; a vibration sensing means positioned on said structure so that the vibration of said structure causes an electrically measurable output from said vibration sensing means proportional to the vibrational amplitude which increases linearly with the strength of the magnetic field at the position of the current carrying coil near the antinode of vibration; said wire coil means being positioned with respect to the magnet so that the output from said vibration sensing means varies in a predetermined manner as the magnetic field at the site of the coil is changed due to the nearby motion of an appropriately constructed object thereby indicating the relative position between an object perturbing said magnetic field and said wire coil means. - View Dependent Claims (12, 13)
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Specification