Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1999-01-21
1999-11-30
Budd, Mark O.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
31032301, 31032318, H01L 4108
Patent
active
059948183
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a device for transferring or transmitting ultrasonic energy into a fluid or pasty medium, and with the further, characteristics particular to this species of invention. A device of this type is known from U.S. Pat. No. 4,016,436.
2. Description of the Related Art
In this known device a wave guide is provided on one side of a tubular shaped cavity resonator which, by means of a piezo-electric transducer, which for its part converts electrical alternating current output signals of an alternating current generator into longitudinal mechanical oscillations, is capable of being brought or excited to resonant longitudinal oscillations. On a flange shaped area on this transducer the cavity resonator is mechanically rigidly connected and acoustically coupled.
In a further device of the above described type (U.S. Pat. No. 5,200,666), which is substantially a functional analog of the first described, respective transducers transmit ultrasound energy at both ends of a tubular resonator, which is designed for conversion of longitudinal oscillations into transverse oscillations.
It is also known (U.S. Pat. No. 4,537,511), to use a tubular cavity resonator, which is closed on both ends and from one side is impinged by ultrasound from a coupled transducer.
In all these devices the length of the tubular cavity resonator is almost always selected to be in a first approximation described according to the equation, frequency in a steel type resonator and with f.sub.r being the mechanical resonance frequency of the wave guide utilized for introduction of ultrasound in the resonator and which is acoustically coupled with the transducer. The oscillation frequency c.sub.0, is here described by the relationship, ##EQU1## in with E being the modulus of elasticity (Youngs modulus) and with .rho. being the specific weight of the resonator material.
In order, in such ultrasound devices, to convert the greatest possible proportion of electrical energy into utilizatable sound energy, it is also known (FR-A-2 354 827 and EP-A-0 044 800), to so attempt to arrange or design the cavity resonator, so that the longitudinal as well also the transverse natural oscillating frequency of its jacket satisfies the resonance conditions.
In such devices the oscillating effective element is constructed as a three dimensional tubular cavity resonator, in which the propagation velocity V.sub.x and v.sub.r, and therewith also the wave lengths .lambda..sub.x and .lambda..sub.r of the oscillations, which are associated with deflection in the direction of the longitudinal axis (x-direction) and radial thereto, are necessarily different. Those respective ultrasound waves, of which the deflection is in the direction of the longitudinal axis (x-direction) of a resonator, of which the axial length is selected to correspond to a whole number multiple of the half wave length (.lambda..sub.x /2), do not contribute to the outward radiation of ultrasound energy, however prevent a buildup of ultrasound energy and facilitate a good even form or shape of the distribution of the ultrasound energy over the total-axial-resonator length, while those ultrasound waves, of which the oscillation form of the resonator corresponds with deflection radial to the resonator-length axis and to its outer surface, mediate an effective radiating out of ultrasound energy in the environment.
Such an arrangement or design, given that the characteristics of the resonator wall material are pre-determined, requires a very precise coordination of the geometric dimensions of the resonator, namely its length L, its outer diameter D.sub.0 and its wall thickness .delta.. This relationship can in the case of pre-determined values of the outer diameter D.sub.0 and the wall thickness .delta. of course be achieved by adaptation or adjustment of the resonator length L, which however as a rule requires time consuming experiments or testing and only then is justifiable, when a subsequently larger number of such devices can be b
REFERENCES:
patent: 4016436 (1977-04-01), Shoh
patent: 4537511 (1985-08-01), Frei
Abramov Vladimir
Alenichev Vyacheslav
Makarov Leonid
Ruhman Andrew
Budd Mark O.
Tech Sonic Gesellschaft Fur Ultraschall-Technologie m.b.H.
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