Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Viscosity
Reexamination Certificate
2000-08-31
2002-09-17
Chapman, John E. (Department: 2856)
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Viscosity
C073S024060, C073S064530, C073S03200R, C073S580000
Reexamination Certificate
active
06450013
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to transducers and to resonant structures for transducers, particularly structures which comprise a first member, which may be driven into vibration, and a second member, which may carry a sensing element and is disposed in a medium of which a property is to be measured.
2. Related Art
Various transducers including structures of this general nature are known. In known arrangements, the first and second members are intended to vibrate in antiphase, there being a vibrational node of normally zero displacement at a connection by means of which the vibrating structure is supported. Known arrangements of this kind are disclosed in U.S. Pat. No. 3,712,117 and GB-B-2281621. In these designs, the nodal point is connected to a mechanical datum by a flexible means which is substantially more compliant than the first and second members, Theoretically, in these devices, the amplitude and frequency of vibration, which may be torsional or lateral or longitudinal of the first member are the same as those of the second member carrying the sensing element immersed in the medium, which may be gas, liquid or even solid.
SUMMARY OF THE INVENTION
One important feature of the present invention is the use of a semi-rigid connecting member between the nexus of the first and second members and a support. The semi-rigid member is intended to have a stiffness which significantly affects, and preferably controls, the relative motions of the first and second members. It preferably provides a node which is more rigid than the first and second members. This kind of member can avoid the disadvantage of very compliant mounts, which are generally unable to withstand the high pressures and forces encountered in many industrial applications. Moreover, the stiffness of the connecting member or means may be selected to control the sensitivity of the measuring instrument of which the transducer forms a part.
A further feature of the invention is the use of a re-entrant member or resonator enclosed within a sensing element which preferably forms part of the second member but which may have utility independently of the connecting member mentioned above. Such a re-entrant element is intended to vibrate relative to the sensing element, being constituted preferably by a spring-mass structure, but unaffected by the medium in which the sensing element is immersed. Such a re-entrant element or additional resonator may enable the alteration of the characteristics of the transducer in a simple and reliable manner.
Other features of the invention will be apparent from the description which follows.
REFERENCES:
patent: 3712117 (1973-01-01), Fitzgerald et al.
patent: 4857792 (1989-08-01), Miura et al.
patent: 5723771 (1998-03-01), Miura et al.
patent: 915 792 (1954-07-01), None
patent: 2 281 621 (1995-03-01), None
Patent Abstract of Japan vol. 97, No. 001, Jan. 31, 1997, Abstract of JP 08247917 A (Yamaichi Electron Co Ltd) Sep. 27, 1996.
Chapman John E.
Nixon & Vanderhye P.C.
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