Apparatus for measuring depth of a fluid chamber
First Claim
1. Fluid power apparatus comprising:
- a cylinder (2'"'"') having an end surface (14'"'"');
a piston (4'"'"') adapted for axial movement in said cylinder and defining a main fluid chamber (10'"'"') bounded by the piston and said end surface;
a reference chamber (117);
means (121) for fluid communication between said main chamber and said reference chamber;
transducer means (12,
13) which is vibratable located in at least one of said main and reference chambers coupling vibrations of said transducer means with fluid in said main chamber and said reference chamber;
amplifier means (24,
25) having positive feedback and connected with said transducer means for interacting with the fluid in said main and reference chambers to provide respective main and reference oscillation signals (at 42,
43), the frequency of each signal being a function of a dimension of the respective chamber;
information-processing means (44) receiving said main and reference oscillation signals for providing an output signal (at
82) that depends upon the frequencies of both of said oscillation signals and indicative of the location of the piston in the cylinder.
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Accused Products
Abstract
The depth of a cavity or chamber (10'"'"') is measured by using the chamber as the resonator of an electronic oscillator (24) whose oscillations are coupled to fluid in the cavity by transducers (12, 13). Both the variable-depth main chamber (10'"'"') and a reference chamber (117) of fixed depth are measured. Variations in the data obtained from the chambers are caused by factors affecting the velocity of propagation of sound in the fluid. An accurate measurement of the depth of the main chamber is obtained by compensating direct data (at 42) obtained from the main chamber (10'"'"'), using, data (at 43) obtained from the fixed-depth reference chamber (117). In one embodiment an inertance orifice (121) is utilized between the two chambers. The fluid inertance of the orifice, together with the compliance of the fluid in the main chamber (10'"'"'), form a resonant system whose anti-resonant frequency is a measure of the dimensions of the main chamber. (Inertance is the acoustical equivalent of inductance.)
19 Citations
8 Claims
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1. Fluid power apparatus comprising:
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a cylinder (2'"'"') having an end surface (14'"'"'); a piston (4'"'"') adapted for axial movement in said cylinder and defining a main fluid chamber (10'"'"') bounded by the piston and said end surface; a reference chamber (117); means (121) for fluid communication between said main chamber and said reference chamber; transducer means (12,
13) which is vibratable located in at least one of said main and reference chambers coupling vibrations of said transducer means with fluid in said main chamber and said reference chamber;amplifier means (24,
25) having positive feedback and connected with said transducer means for interacting with the fluid in said main and reference chambers to provide respective main and reference oscillation signals (at 42,
43), the frequency of each signal being a function of a dimension of the respective chamber;information-processing means (44) receiving said main and reference oscillation signals for providing an output signal (at
82) that depends upon the frequencies of both of said oscillation signals and indicative of the location of the piston in the cylinder. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification