Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
2000-01-24
2002-06-11
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207240
Reexamination Certificate
active
06404183
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetostrictive transducer with high measurement precision. More particularly, the invention relates to a magnetostrictive transducer which offers simplified construction and improved measurement precision with respect to conventional transducers.
Magnetostrictive transducers are transducers which are usually used to measure a position by using a position marker of the magnetic type.
In particular, a transducer of the above-cited type comprises a tube made of a special alloy which is crossed by a copper conductor to which a current pulse is applied. The copper conductor must carry the current pulse from one end of the alloy tube to the other and return the current pulse to the point of origin in order to close the circuit.
A position marker (permanent magnet) determines the measurement of the position of the work area of the transducer. The field lines of the position marker are perpendicular to the rotational field generated by the current pulse in the alloy tube and also concentrate in the measurement point. In that point, the magnetic fields interact and induce, in the microzone of the structure, a torsional elastic deformation due to a magnetostrictive effect. This deformation is in every respect a torsional mechanical wave which propagates in the two directions of said tube. At one end, propagation of the mechanical wave is damped by adapted damping means, whereas at the opposite end the mechanical wave is detected by means of an inductive pickup and converted into an electrical signal. The time delay between the excitation pulse (current pulse) applied to one end of the tube and the magnetostrictive return represents the position of the position marker (permanent magnet).
Conventional magnetostrictive transducers have the drawback that they have to provide an outgoing path for the current inside the tube (along the copper conductor) and a return path for the same current through a copper conductor which constitutes a closed path together with the copper conductor that carries the outgoing current pulse.
Therefore, since an outgoing path and a return path are required, it is necessary to provide a copper conductor for the outgoing path and a similar conductor, connected thereto, for the return path. This entails constructive difficulties for the magnetostrictive transducer, also in view of the limited dimensions of said transducer.
Moreover, damping of the mechanical wave is very important, since if the wave that propagates toward one end of the tube, opposite to the end where the wave is to be detected, is not damped appropriately, wave reflections can occur which constructively or destructively interfere with the mechanical wave meant to be detected, accordingly interfering with the correct measurement.
Damping of the mechanical wave is entrusted exclusively to the presence of damping elements, such as for example silicone rubber dampers, which allow to damp the mechanical wave along the magnetostrictive tube, but sometimes this solution is not fully satisfactory.
SUMMARY OF THE INVENTION
The aim of the present invention is to provide a magnetostrictive transducer with high measurement precision which can be manufactured with a structure which is simplified with respect to conventional transducers.
Within the scope of this aim, an object of the present invention is to provide a magnetostrictive transducer with high measurement precision in which the mechanical wave is damped in an optimum manner in order to avoid interfering with the measurement provided by the transducer.
Another object of the present invention is to provide a magnetostrictive transducer with high measurement precision in which the external vibrations to which the transducer can be subjected do not affect measurement precision at all or at the most minimally.
Another object of the present invention is to provide a magnetostrictive transducer with high measurement precision which is highly reliable, relatively easy to manufacture and at competitive costs.
This aim, these objects and others which will become apparent hereinafter are achieved by a magnetostrictive transducer with high measurement precision, comprising a containment tube which accommodates a magnetostrictive tube inside which a conducting wire is accommodated, transducer means being provided at one end of said magnetostrictive tube, means for detecting the signal acquired by said transducer means being connected to said transducer means, characterized in that said magnetostrictive tube is connected to said containment tube by conducting means which are suitable to provide electrical continuity between said conducting wire accommodated in said magnetostrictive tube and said containment tube.
REFERENCES:
patent: 3898555 (1975-08-01), Tellerman
patent: 4654590 (1987-03-01), Kitaura
patent: 5070485 (1991-12-01), Nyce
patent: 5804961 (1998-09-01), Castillo et al.
patent: 42 44 204 (1994-06-01), None
Patidar Jay
Sughrue & Mion, PLLC
LandOfFree
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