[0001] In the technique of washing mechanical pieces, particularly by means of solvents,
it is known to carry out a treatment by ultrasounds. The use of ultrasounds allows
in fact to wash the pieces more thoroughly and in less time.
[0002] The ultrasound transducers used for this purpose fundamentally comprise a pair of
piezoelectric ceramic side-by-side disks, and two metallic resonance bodies applied
on the opposite sides of said pair of disks. An electrically conductive lamina is
interposed between the two disks; an oscillating electric potential, produced by an
electronic oscillator, is applied between said lamina and the two metallic resonance
bodies - possibly with the interposition of two further conductive laminae between
each disk and the metallic resonance body adjacent thereto - said oscillating electric
potential being and apt to cause in the disks, due to their piezoelectric nature,
a vibration phenomenon which is transmitted to the metallic resonance bodies.
[0003] The oscillation frequency is determined by said electronic oscillator circuit at
a preset value, included in the ultrasound field, for instance between 20 and 40 KHz,
and the dimension and shape of the metal bodies is determined so that they may resonate
at that frequency.
[0004] To transmit said ultrasonic frequency to the washing liquid, one of the two resonance
bodies is normally applied against the wall of the washing tank and is fixed onto
said wall by glueing, as shown in figure 1. The wall, which is of thin plate, thus
vibrates together with the resonance body of the transducer and transmits the vibration
to the washing liquid.
[0005] The serious drawback of this system - widely used in these washing plants - is that,
in spite of using highly effective adhesives, after a more or less long period of
use the transducer may disconnect from the wall of the washing tank, thereby requiring
delicate and expensive operations of maintenance and repair.
[0006] To overcome this difficulty, it has also been proposed to form a large hole - substantially
corresponding to the dimensions of a resonance body - into the wall of the washing
tank, and to introduce said body into the washing tank through said hole, fixing it
onto its contour. In this case, the fixing is done by welding along the whole line
of contact between the edge of the hole and the periphery of the resonance body, as
shown in figure 2.
[0007] An arrangement very similar to the one hereabove is described in EP-A2-0.341.505,
which provides moreover for a support ring being fixedly connected, on one hand, to
one of the resonance bodies of the transducer - and precisely, to a frustoconical
body projecting into the washing tank and acting as ultrasound emitter - and on the
other hand, to the wall of the washing tank. Said support ring is, on one side, formed
in one piece with the resonance body or else welded on said body and, on the other
side, it is welded onto the wall of the washing tank (see diagram of figure 3).
[0008] Nevertheless, also these arrangements are not apt to provide fully satisfactory results,
as the welding spots are extremely critical in an environment subject to vibrations,
so that, in the long run, yielding points or cracks may form which are practically
impossible to repair. The arrangement of EP-A2-0.341.505 has the advantage - in respect
of the previous one in which the resonance body is directly welded onto the wall of
the washing tank - that the support ring facilitates mounting as well as welding and,
at the same time, it forms an element apt to damp the vibrations transmitted from
the transducer to the wall; nevertheless, it simply reduces the probabilities of breakage
without definitively solving the problem.
[0009] For this reason, a modification of said arrangement is often preferred, according
to which the transducer is no longer fixed onto the hole of the wall of the washing
tank by welding, but by mechanical means, that is, by locking the contour of said
hole between a shoulder formed on the resonance body and an opposed locking ring also
screwed onto said resonance body. Even this solution has however not been found satisfactory,
as it has the additional drawback that the modified shape of the resonance body -
allowing to form the shoulder - prevents correct transmission of the ultrasounds.
[0010] The object of the present invention is to realize an arrangement for mounting an
ultrasound transducer onto the wall plate of a washing tank, which is apt to fully
eliminate the above mentioned drawbacks, which is easy to assemble and which is very
reliable in the long run. This result is obtained - in a mounting arrangement according
to the introductory part of Claim 1 - thanks to the fact that the wall plate of the
washing tank is provided with a hole of diameter substantially corresponding to that
of the bolt, that this latter crosses in succession, starting from the external part,
a first resonance body and the pair of piezoelectric disks mounted on the outer side
of said wall plate, then the hole in the wall plate, and finally screws into a threaded
dead hole formed in the second resonance body mounted on the inner side of said wall
plate, and that a sealing ring gasket is interposed between said second resonance
body and the inner surface of said wall plate.
[0011] An additional characteristic of the present invention lies moreover in the fact that
the shape of the resonance bodies is planned and determined so that the ultrasonic
frequency mechanical oscillations - of maximum amplitude in correspondence of the
ends of the resonance bodies, particularly in correspondence of the free surface of
the body on the inner side of the washing tank - have a flow such that, as their amplitude
reduces towards the innermost transversal sections, they result of no amplitude at
all just in correspondence of the section coinciding with the wall plate of the washing
tank.
[0012] In this way, the piezoelectric disks and the resonance bodies oscillate in contraposition,
leaving the central position - namely the position of connection to the wall plate
of the washing tank - in still conditions.
[0013] Further characteristics and advantages of the arrangement according to the invention
will anyhow be more evident from the following detailed description of a preferred
embodiment thereof, given by way of example and illustrated on the accompanying drawing,
in which:
Figs. 1, 2 and 3 refer to arrangements of known technique, which have already been
described; and
Fig. 4 is an axial section view of an ultrasound transducer mounted on a washing tank
adopting the arrangement according to the present invention.
[0014] As shown, the ultrasound transducer used in the arrangement according to the invention
is formed - in a substantially known manner - of a pair of side-by-side piezoelectric
ceramic disks 2 and 3, and of a pair of metallic resonance bodies 4 and 5. A lamina
6 of electrically conductive material is interposed between the disks 2 and 3, while
two further conductive laminae 7 and 8 are interposed between the disks 2, 3, and
the resonance bodies 4, 5, positioned at the respective sides of said disks.
[0015] The body 4 has an axial threaded dead hole 4a, and the body 5 has an axial through
hole 5a; also the disks 2 and 3 have central holes, equally as the laminae 6, 7 and
8. Said holes are crossed by a bolt 9, the threaded end 9a of which screws into the
dead hole 4a of the body 4, and which is apt to lock all these pieces together.
[0016] According to the present invention, the lateral wall plate 1 of the washing tank
is provided with a hole, which is just sufficient to allow the passage of the bolt
9. To mount the transducer, one therefore proceeds by mounting the resonance body
4 against the inner surface of the wall plate 1, while the disks 2, 3, and the body
5 are mounted externally to said wall plate; the bolt 9 is then introduced through
the hole 5a and into the axial holes of the disks 2, 3, as well as into the hole of
the wall plate 1, and is then thoroughly screwed into the threaded hole 4a.
[0017] Always according to the present invention, a circular groove is formed on the surface
of the body 4 mounted against the inner surface of the wall plate 1, said groove housing
a sealing gasket 10, of the O-ring type, apt to also perform a vibration damping action.
[0018] According to a further characteristic of the present invention, on one hand the excitation
of the disks 2 and 3 is carried out in phase contraposition - thanks to a proper adjustment
of the feed voltage of the laminae 6, 7, 8 - and on the other hand the size and shape
of the resonance bodies 4 and 5 is determined in such a way that the central, nodal,
vibration plane coincides with the contact surface between the body 4 and the disk
2.
[0019] In this way, while the opposed ends of the bodies 4 and 5 vibrate in synchronism,
but in opposite senses, the central zone of the transducer and precisely the surfaces
of the body 4 and of the disk 2 contacting the wall plate 1 remain substantially still,
which means that no vibrations are transmitted to the wall plate 1.
[0020] It is thus evident that:
- on one hand due to the fact that the fixing of the ultrasound transducer is guaranteed
by the through bolt 9, in cooperation with the sealing gasket 10 which also performs
a damping action, with no other locking means and, particularly, with no weld;
- on the other hand due to the fact that the wall plate 1 is practically not subjected
to vibrations;
the fixing of the ultrasound transducer on the wall plate 1 is obtained in the most
efficient manner and is due to last very long. Furthermore, the mounting is extremely
simple and rapid, and the arrangement can also be easily disassembled for replacements
or repair.
1. Mounting arrangement of an ultrasound transducer onto the wall plate (1) of a washing
tank, of the type in which the transducer consists of a pair of piezoelectric ceramic
disks (2,3), subjected to an electric field variable with an ultrasonic frequency,
and of a pair of metallic resonance bodies (4,5), positioned to the sides of said
pair of piezoelectric disks (2,3), these elements being fixed together by means of
a bolt (9) which axially crosses them, characterized in that said wall plate (1) comprises
a hole of diameter substantially corresponding to that of said bolt, in that this
latter crosses a first resonance body (5) and the pair of piezoelectric disks (2,3)
mounted externally to said wall plate (1) of the washing tank, then crosses said hole
in the wall plate, and finally screws into a threaded dead hole (4A) formed in said
second resonance body (4) mounted on the inner side of said wall plate (1), and in
that a sealing and damping ring gasket (10) is interposed between said second resonance
body (4) and the inner surface of said wall plate (1).
2. Mounting arrangement as in claim 1), wherein said second resonance body (4) has a
circular groove onto its surface contacting the inner surface of the wall plate (1)
of the washing tank, said groove partially housing said sealing and damping gasket
(10).
3. Mounting arrangement as in claim 1), wherein the size and shape of said resonance
bodies (4,5) are determined so that a central, nodal, vibration plane substantially
coincides with the contact surface between said second resonance body (4) and the
wall plate (1) of the washing tank.
1. Befestigungsanordnung für einen Ultraschall-Wandler an einer Wandungsplatte (1) eines
Waschtanks, von der Art, bei der der Wandler aus einem Paar von piezoelektrischen
Keramikscheiben (2, 3) besteht, die einem elektrischen Feld, das mit einer Ultraschallfrequenz
variabel ist, unterworfen sind, und einem Paar von metallischen Resonanzkörpern (4,
5), die an den Seiten des Paares von piezoelektrischen Scheiben (2, 3) positioniert
sind, wobei diese Elemente miteinander durch einen Bolzen (9), welcher diese axial
kreuzt, verbunden sind, dadurch gekennzeichnet, daß die Wandungsplatte (1) eine Bohrung
mit einem Durchmesser, der im wesentlichen demjenigen des Bolzens entspricht, aufweist,
daß dieser einen ersten Resonanzkörper (5) und das Paar der Piezoelektrischen Scheiben
(2, 3), die außerhalb der Wandungsplatte (1) des Waschtanks montiert sind, kreuzt,
sodann die Bohrung in der Wandungsplatte kreuzt und schließlich in einer Gewindesacklochbohrung
(4A), die in dem zweiten Resonanzkörper (4) ausgebildet ist, der auf der Innenseite
der Wandungsplatte (1) montiert ist, schraubt, und daß eine Dicht- und Dämpfungsringdichtung
(10) zwischen dem zweiten Resonanzkörper (4) und der Innenfläche der Wandungsplatte
(1) angeordnet ist.
2. Befestigungsanordnung nach Anspruch 1), wobei der zweite Resonanzkörper (4) eine kreisförmige
Kerbe auf seiner Fläche hat, die die Innenfläche der Wandungsplatte (1) des Waschtanks
berührt, wobei die Kerbe teilweise die Dicht- und Dämpfungsdichtung (10) aufnimmt.
3. Montageanordnung nach Anspruch 1, wobei die Größe und die Form der Resonanzkörper
(4, 5) derart sind, daß eine zentrale Knotenvibrationsebene im wesentlichen mit der
Kontaktfläche zwischen dem zweiten Resonanzkörper (4) und der Wandungsplatte (1) des
Waschtanks übereinstimmt.
1. Dispositif de montage d'un transducteur d'ultrasons sur la plaque de paroi (1) d'un
bac de lavage, du type dans lequel le transducteur consiste en une paire de disques
en céramique piézoélectriques (2, 3), soumis à un champ électrique variable avec une
fréquence ultrasonore, et en une paire de corps de résonance métalliques (4, 5), positionnés
sur les faces de ladite paire de disques piézo-électriques (2, 3), ces éléments étant
fixés les uns aux autres au moyen d'un boulon (9) qui les traverse axialement, caractérisé
en ce que ladite plaque de paroi (1) comprend un trou d'un diamètre correspondant
sensiblement à celui dudit boulon, en ce que ce dernier traverse un premier corps
de résonance (5) et la paire de disques piézo-électriques (2, 3) montés extérieurement
sur ladite plaque de paroi (1) du bac de lavage, puis traverse ledit trou dans la
plaque de paroi, et se visse enfin dans un logement à fond plein taraudé (4a) formé
dans ledit second corps de résonance (4) monté sur la face interne de ladite plaque
de paroi (1), et en ce qu'un joint annulaire d'étanchéité et d'amortissement (10)
est disposé entre ledit second corps de résonance (4) et la surface interne de ladite
plaque de paroi (1).
2. Dispositif de montage selon la revendication 1, dans lequel ledit second corps de
résonance (4) comporte une gorge circulaire sur sa surface contactant la surface interne
de la plaque de paroi (1) du bac de lavage, ladite gorge logeant en partie ledit joint
d'étanchéité et d'amortissement (10).
3. Dispositif de montage selon la revendication 1, dans lequel la taille et la forme
desdits corps de résonance (4, 5) sont déterminées de manière qu'un plan de vibration
central, nodal, coïncide sensiblement avec la surface de contact entre ledit second
corps de résonance (4) et la plaque de paroi (1 ) du bac de lavage.