GB2023965A

GB2023965A - Rod-type ultrasonic oscillating system

Info

Publication number: GB2023965A
Application number: GB7921601A
Authority: GB
Original assignee: SP PK T B MALYKH ELEK MASH PRO
Current assignee: SP PK T B MALYKH ELEK MASH PRO
Priority date: 1978-06-26
Filing date: 1979-06-21
Publication date: 1980-01-03
Also published as: JPS555792A; NL7904967A; DE2914434A1; DE2914434C2; GB2023965B; SU817809A1; FR2430159A1; FR2430159B1

Abstract

The invention relates to an ultrasonic oscillating system having a longitudinal oscillation transducer (1) joined to a quarter-wave member (2). The (1) has a length equal to a half wavelength of the resonance oscillation of the system, and the cross- sections of the transducers (1) and the member (2) are such that the wave impedance of the member (2) does not exceed one fifth of the wave impedance of the transducer (1). <IMAGE>

Description

SPECIFICATION Rod-type ultrasonic oscillating system The invention relates to ultrasonic oscillating systems, and more particularly to rod-type ultrasonic oscillating systems applicable to such fields as ultrasonic treatment as well as vibration motors utilized as drives for electric record playing apparatus.

There is provided a rod-type ultrasonic oscillating system comprising a longitudinal oscillation electromechanical transducer joined with a quarterwave waveguide whose direction coincides with the propagating direction of the oscillations, which transducer has, according to the invention, a length equal to the half-length of the ultrasonic wave of the resonance oscillations of the system, and the crosssection of the quarter-wave waveguide being related to the cross-section of the transducer so that the wave impedance o the waveguide does not exceed a value of 1/5 of the wave impedance of the transducer.

The rod-type ultrasonic oscillating system should preferably comprise the quarter-wave waveguide joined with the transducer in the node oscillation zone.

The disclosed system is advantageous in that the influence of the load on the oscillation amplitude of the transducer is reduced and the gain of the system is increased as high as possible in the presence of large drops of the wave impedances of their thick and thin portions.

The invention will now be described in more detail, by way of example, with reference to the accompanying drawings in which: Figure lisa longitudinal section of a rod-type ultrasonic oscillating system, according to the invention; Figure 2 is a plot illustrating a distribution of the longitudinal oscillations along the length of the system shown in Figure 1, according to the invention; Figure 3 is a partial longitudinal section of a rod-type ultrasonic oscillating system provided with a three-rod quarter-wave waveguide, according to the invention; Figure 4 is a partial longitudinal section of a rod-type ultrasonic oscillating system having a rod waveguide joined thereto in the mode oscillation zone, according to the invention;; Figure 5 is a longitudinal section of the system shown in Figure 4 and having a quarter-wave waveguide in the form of a three-rod structure, according to the invention.

Figure 6 is a top view of the system shown in Figure 5, according to the invention.

A rod-type ultrasonic oscillating system of the invention comprises an electromechanical transducer 1 (Figure 1) joined with a quarter-wave waveguide 2 whose direction of the oscillations. The transducer 1 possesses a quarter-wave length at the resonance frequency of the longitudinal oscillations, while the waveguide 2 has a quarter-wave length and a relationship of its cross-section and the crosssection of a front metallic covering 3 of the transducer 1 is of such a value that the wave impedance of the wave-guide 2 does not exceed a value equal to 1/5 of the wave impedance of the transducer 1. The latter also comprises a back metallic covering 4, piezoelectric elements 5 in the form of rings, a spring-type attachment flange 6, sealing aluminum gaskets 7, contact tabs 8 of a current collector, insulating mica lining 9, and a gasket 10.The above-mentioned components of the transducer 1 are joined together by a bolt 11 that passes through the central holes in the covering 4, flange 6, gaskets 7, lining 9 and tabs 8, said bolt 11 being threaded into a respective seat in the covering 3.

The attachment flange 6 is a thin a spring-type gasket which tends to reduce losses due to attachment; this means that the oscillating system utilizes the so-called diaphragm-type attachment. The sealing aluminum gaskets 7 provide for better acoustic contact between the components of the pack. To attain the same purpose and prevent the covering 4 from being rotated relative to the piezoelectric elements 5, which, being fragile ones, could be broken during the tightening of the bolt 11, there is a gasket 10 made of a thin zinc-plated sheet metal and inserted between the head of the bolt 11 and the covering 4. The contact tabs 8, together with the insulating mica lining 9, are used to connect a power supply circuit (not shown) to the oscillating system.

One of the piezoelectric elements 5 operates in the reverse piezoelectric effect mode and a driving sine voltage is applied to its plates, while the other piezoelectric element 5 operates in the direct piezoelectric effect mode and is a frequencysensitive feedback pickup necessary for maintaining the oscillating system in the resonance mode in the presence of load variations and other disturbances.

Thus, the insulating mica lining 9 provides for electric insulation of the piezoelectric elements 5; note that mica ensures the lowest attenuation of acoustic oscillations in the system.

The quarter-wave waveguide 2 is usually made in one piece with and of the same material as the covering 3; in this case, a drop of the wave impedances means a difference of the cross-sections of the thin and thick portions of the oscillating system, i.e., the cross-sections of the covering 3 and the waveguide 2. Figure 2 is a diagram illustrating a distribution of the amplitudes of the longitudinal oscillations along the length of the oscillating system. In the diagram, the letters A, B, C, D stand for respective points defining certain sections of the oscillating system of Figure 1. The amplitudes are measured on the surface of the oscillating system in the case of the zero load mode. Note that it is not necessary to have a flat (identical over the entire section) distribution of the amplitudes in the section B.There my be a decrease in the amplitude as it approaches the base of the joined waveguide 2, which characteristic is more evident in the system maintained under load.

Figure 3 shows an embodiment of the system of the invention having the joined quarter-wave waveguide 2 implemented as a structure that comprises three rods 12 each inclined to the propagating direction of longitudinal oscillations at an angle a. In this embodiment, an attachment lug 13 is used instead of a spring-type attachment gasket and is disposed in the section designated by the point C of Figure 2, which represents the node oscillation zone.

This embodiment is applicable to a vibration motor for end-type rotation.

Figure 4 shows another embodiment of the oscillating system dealing with the quarter-wave waveguide 2 which is a rod joined with the transducer 1 in the node oscillation zone defined by the point C of Figure 2, in this embodiment, the covering 4 (Figure 4) is made in one piece with the quarter-wave waveguide 2 and has a threaded hole to attach the bolt 11, while the covering 3 has a through central hole to pass the bolt 11. The overall dimensions of the system, as compared with previously described embodiments, is decreased in this case by 1/4 of the wavelength.

Figures 5, 6 show an embodiment of the system suitable for a vibration motor producing end-type rotation. In this embodiment, the node oscillation zone of the transducer 1 includes three inclined rods 12 (a quarter-wave waveguide) disposed over its circumference and each having a length equal to 1/4 of the wavelength of resonance oscillations. Such an embodiment provides for a tangential component of the velocity of the rotor of a vibration motor (not shown) and for centering the rotor as well. The rotor is held in pressure-exerted contact with the end of the oscillating system from above (namely, with the ends of the inclined rods 12), while the bolt 11, designed to thighten up the system components, has a through hole which can accommodate the shaft of the motor.

The rod-type ultrasonic oscillating system operates in the following manner. An alternating voltage produced by a generator (not shown) is applied to a respective contact tab 8 (Figures 1, 2, 3) of one of the piezoelectric elements 5 of the oscillating system.

The frequency of that voltage is maintained at resonance with the frequency of the longitudinal oscillations of the transducer 1. As a result, the latter produces a standing wave of longitudinal oscillations, having loops at the ends of the transducers 1 and a node in the central zone where the transducer 1 is usually fixed by virtue of the spring-type flange 6. Coupling the waveguide 2 (rods 12) to one end of the transducer 1 does not provide for a considerable decrease in the amplitude of oscillations produced by the transducer 1, since the wave impedance of the joined waveguide 2 is considerably less (by a factor of 5 as a minimum) than the wave impedance of the transducer 1.If the joined waveguide 2 has a length equal to 1/4 of the length of the longitudinal wave in the transducer 1, there then occur at the end of the waveguide 2 the oscillations whose amplitude excreeds the amplitude of the oscillations available to the other end of the transducer 1 (the point D) by a factor of times by which the wave impedance of the transducer 1 exceeds the wave impedance of the joined waveguide 2. This relation is held constant within a range ensured by a maximum permissible difference between the cross-sections of the thick and thin portions of the system, an advantage over a conventional stepwise concentrator having a limited impedance drop.This is due to two factors as follows: the waveguide is joined to the transducer in the area which is different from the maximum stress zone; and no stoppage of the oscillations takes plate, though a certain load is available to the working end of oscillating system (at the point A), since the oscillating half-wave transducer 1 is an additional source of oscillation energy providing a higher level of standing wave.

Due to the second factor, the oscillating system features lesser sensitivity to load variations, since a decrease in the amplitude resulted from an increase in the load is compensated for by a greater delivery of the oscillation energy from the store element of the system, namely, from the transducer 1.

In the embodiments dealing with the waveguide coupled in the node oscillation zone (Figures 4, 5, 6), the relationship of wave impedances is of a somewhat limited value since the rods 12 (waveguide 2) are connected at a point corresponding to maximum mechanical stresses. As a result, redistridution mechanical stresses between the thick and thin portions of the system is limited. The sensitivity of the system, related to the load variations, is decreased due to the availability of the oscillation energy storing element which is the oscillating transducer 1.

Claims

1. A rod-type ultrasonic oscillating system, comprising a longitudinal oscillation electromechanical transducer joined with a quarter-wave waveguide whose direction coincides with the propagating direction of the oscillation, the transducer having a length equal to the half-length of the ultrasonic wave of the resonance oscillations of the system, and the cross-section of the quarter-wave waveguide being related to the cross-section of the transducer so that the wave impedance of the waveguide does not exceed a value of 1/5 ofthewave impedance ofthe transducer.

2. A rod-type ultrasonic oscillating system as claimed in claim 1, wherein the quarter-wave waveguide is joined with the transducer in the node oscillation zone.

3. A rod-type ultrasonic oscillating system substantially as herein described with reference to the accompanying drawings.