EP0806031A1

EP0806031A1 - Ultrasonic generator

Info

Publication number: EP0806031A1
Application number: EP96900234A
Authority: EP
Inventors: Hans-Peter Keller
Original assignee: KKS Keller HP
Current assignee: KKS Keller HP
Priority date: 1995-01-27
Filing date: 1996-01-16
Publication date: 1997-11-12
Also published as: CH692136A5; WO1996023296A1

Abstract

A first embodiment of the proposed ultrasonic generator (1) has an oscillation head (2) of circular cross-section. The face (3) of the oscillation head (2) facing the cleaning fluid is convex. Owing to the refraction behaviour of ultrasonic waves, this shape increases the angle of diffusion of the ultrasonic waves. The surface of the convex face (3) may be smooth, continuous or stepped. The stepped surface helps reduce reflection at the boundary layer between the oscillation head (2) and the cleaning fluid. The oscillation head (2) has a cylindrical recess in the second face into which is inserted a piezoelectric ultrasound transducer (9). A second embodiment of the proposed ultrasonic generator (1) has a plurality of needle-shaped transmission components running parallel to one another and projecting at right angles downwards from a supporting plate. The proposed ultrasonic generator (1) is secured to the bottom or a side wall of a vat.

Description

ULTRASONIC SENSOR OR -GENERATOR

The invention relates to an ultrasound generator or generator according to the preamble of patent claim 1.

The most widespread application is high-energy ultrasound for cleaning objects and products. Ultrasound is mainly used to clean difficult-to-access surfaces of complicated shaped objects. Furthermore, ultrasonic cleaning can also be used if a very high degree of purity is to be generated or if cleaning with other methods is associated with health risks for the staff. Typical examples of objects that are often cleaned with ultrasound are parts of precision mechanics and precision engineering, medical instruments, optical lenses, glass vessels, dentures, jewelry, etc.

The cleaning is carried out by immersing the object to be cleaned in an ultrasonically excited liquid bath. An ultrasonic cleaning system consists of a trough which is filled with cleaning liquid, an ultrasonic transmitter and an electrical generator for feeding the ultrasonic transmitter. Frequencies between 20 and 40 kHz are usually used for the operation of ultrasonic cleaning systems.

According to the current state of the art, various types of ultrasound transmitters are known, but all of them have certain disadvantages.

In all of the embodiments of the ultrasound transmitters that are common today, the sound waves are not transmitted directly from the ultrasound transducer, but through a transmission element to the cleaning liquid.

The transmission element is often plate-shaped. An ultrasonic transducer with a plate-shaped transmission element is also called a surface oscillator. In the case of a surface oscillator, the ultrasonic waves run at right angles to the plate surface. To defy In order to be able to generate a broad distribution of the ultrasonic waves and thereby produce the most uniform possible ultrasonic field, 10 to 20 individual transducers are attached to the plate-shaped transmission element in a regularly distributed manner. The area transducers are attached to the floor or to the walls of the tub. Such surface oscillators are described, for example, by the published documents DT 26 05 898 (date of disclosure August 26, 1976), DE 31 14 657 (date of disclosure January 7, 1982) and DE 41 15 096 (date of disclosure November 12, 1992). The manufacturing and material costs of a surface vibrator are correspondingly expensive. In addition, surface transducers have the disadvantage that the plate-shaped transmission element is much too thin to withstand high ultrasound powers. The individual converters are therefore operated with a maximum of 100 watts each. Nevertheless, the plate-shaped transmission element is destroyed by cavitation after a relatively short time. In order to reduce cavitation corrosion, the published patent application DE 31 14 657 proposes to provide the plate-shaped transmission element with grooves arranged in a grid-like manner. DE 41 15 096 describes a plate-shaped transmission element which is provided with ring beads, in the center of which an ultrasonic transducer is arranged. Further beads are arranged in those areas of the transmission element which are not occupied by ultrasonic transducers. The beads cause interference vibrations, which lead to a reduction in cavitation corrosion. Furthermore, various forms of ultrasound transmitters are known, which are inserted or suspended in the tub. They are also known as diving transducers.

Such immersion transducers can be plate-shaped, for example. They have numerous individual converters built into a tight-fitting, flat housing. The sound is conducted out through one of the two flat sides of the housing. Plate-shaped submersible transducers have the same disadvantages as surface transducers.

Rod-shaped and tubular immersible transducers are also available on the market. The ultrasonic transducer is usually on the front side here a rod-shaped or tubular transmission element. Rod-shaped immersible transducers are described, for example, in the patent documents DE 41 36 897 (publication day 3.9.1992), EP 0 455 837 (publication day 13.5.1992), EP 0 044 800 (publication day 29.1.1986) and in the publication DE 35 34 898 (disclosure date April 9, 1987).

In the case of rod-shaped and tubular submersible transducers, use is made of the fact that the longitudinal vibrations generated in the transmission element are partially converted into transverse vibrations which originate radially from the transmission element. Only the vibration radially emanating from the transmission element is used.

In order to improve the conversion of the longitudinal vibrations into transverse vibrations, the patent EP 0 455 837 proposes to arrange an ultrasonic transducer on both end faces of the rod-shaped or tubular transmission element. Rod-shaped and tubular immersion transducers are usually suspended in the cleaning liquid next to a tub wall or at a tub corner. They emit ultrasonic waves all around. The result of this is that a large part of the ultrasonic waves hit a tub wall first. The sound waves only reach the object after reflection on the tub wall, which must be cleaned. With this reflection, part of the energy of the ultrasonic waves is absorbed and is no longer available for ultrasonic cleaning. The efficiency of such rod and tubular immersible transducers is correspondingly low.

Finally, the patent specification DE 38 15 925 (publication date April 20, 1989) describes an ultrasound transmitter with a conical transmission element which acts directly on the cleaning liquid. The base of the cone faces the cleaning liquid. The purpose of this design is to achieve a higher resistance of the transmission element to cavitation damage. It has no noticeable influence on the angle of propagation of the ultrasonic waves.

The invention now has the task of an ultrasound to create encoder or generator with one-sided radiation, which has a wide angle of propagation. The object is achieved with the aid of the features according to the invention according to the characterizing part of patent claim 1.

A first embodiment of the proposed ultrasound transmitter has a transmission element with a circular cross section. The transmission element is also referred to below as an oscillating head. The end face of the oscillating head, which is facing the cleaning liquid, is convexly curved. Because of the refraction behavior of ultrasound waves, this shape causes an increase in the angle of propagation of the ultrasound waves. The convex face can have a smooth and steady surface or a stepped surface. The stepped surface serves to reduce the reflection at the boundary layer between the oscillating head and the cleaning liquid. The second face of the oscillating head is flat. The oscillating head has a cylindrical recess on the second end face. A piezoelectric ultrasonic transducer is inserted into this recess. A cylindrical counterpart can also be screwed into the recess for fixing the ultrasound transducer. The proposed ultrasound transmitter is attached to the floor or to a side of a tub.

A second type of embodiment of the proposed ultrasound transmitter comprises a plurality of needle-like transmission elements which are arranged parallel to one another.

The invention is explained below with reference to exemplary embodiments in the drawings. Show it:

FIG. 1 a shows a front view of an oscillating head of an ultrasound transmitter of the first embodiment with a stepped convex end face;

1b shows a section through an oscillating head according to FIG. 1a, an ultrasonic transducer and a cylindrical counterpart;

FIG. 1 c shows a rear view of a counterpart according to FIG. 1 a; 2a shows a section AA through an ultrasound transmitter with an oscillating head according to FIG. 2b shows a rear view of an ultrasound transmitter according to

Fig. 2a;

3 shows a perspective illustration of an ultrasound transmitter according to FIG. 2a;

4a shows a front view of an oscillating head of an ultrasound transducer of the first embodiment with a smooth and continuous convex end face;

4b shows a section through an oscillating head according to FIG. 4a, an ultrasonic transducer and a counterpart;

4c shows a rear view of a counterpart according to FIG. 4b;

5a shows a section B-B through an ultrasound transmitter with an oscillating head according to FIG. 4a; 5b shows a rear view of an ultrasound transmitter according to FIG

Fig. 5a;

6 shows a perspective illustration of an ultrasound transmitter according to FIG. 5a;

7a shows a cross section through a trough with kinked side walls, on the bottom of which a proposed ultrasound transmitter is arranged;

7b shows a cross section through a wall with curved side walls, on the bottom of which a proposed ultrasound transmitter is arranged;

8 shows a longitudinal section through an elongated trough which is equipped with three ultrasound sensors arranged on a line;

Fig. 9 shows a cross section through a tub with kinks

Side walls, each of which has a proposed ultrasound transmitter on two opposite side walls wearing ;

10 shows a cross section through a trough with straight side walls, each of which carries a proposed ultrasound transmitter on two opposite side walls;

11a shows a longitudinal section through an ultrasound transmitter of the second embodiment and FIG. 11b shows a cross section C-C through an ultrasound transmitter according to FIG. 11a.

The propagation of the ultrasound is similar to that of light waves e.g. with the appearance of absorption, reflection, diffraction and refraction. Thanks to the refractive behavior, ultrasonic waves such as light waves can be focused with the help of lenses (converging lenses) or scattered (scattered lenses).

This fact is used in the proposed ultrasound generator 1. The oscillating head 2 of the proposed ultrasound transmitter

1 has a circular cross section. The upper end face 3 of the oscillating head 2 in the drawings, which faces the cleaning liquid 13, is convexly curved (cf. FIGS. 7a to 8). The upper section 4 of the oscillating head 2 thus has an essentially circular segment-shaped cross section (cf. FIGS. 1b and 4b). It therefore acts as a scattering lens, which increases the angle of propagation of the ultrasonic waves.

The lower section 5 of the oscillating head in FIGS. 1 to 8

2 is essentially hollow cylindrical. It has a circumferential flange 6 on its outside, which is used to fasten the oscillating head 2 to the tub 14. The flange 6 is provided with a plurality of non-continuous threaded bores 7, which are regularly distributed over the circumference of the flange 6.

The interior 8 of the lower oscillating head section 5 accommodates a piezoelectric ultrasound transducer 9. The ultrasonic transducer 9 is plate-shaped and circular. In the exemplary embodiments, it has a piezoelectric element 18, which consists of two round, ring-shaped half-plates. In this ultrasonic transducer 9, a ceramic material is preferably used as the piezoelectric material. A circular contact disk 19 is located between the two half-plates. A likewise circular coupling disk 20 is arranged on each of the two flat sides of the piezoelectric element 18. The piezoelectric element 18, the contact disk 19 and the coupling disks 20 are arranged concentrically and all have the same diameter. In order to reduce the lateral propagation of the vibrations, they are also framed with an insulation ring 21. This insulation ring 21 lies with its curved inside against the curved, outer narrow sides of the piezoelectric element 18, the contact disk 19 and the coupling disk 20.

The ultrasonic transducer 9 is fixed in the interior 8 of the lower oscillating head section 5 with the aid of a cylindrical counterpart 10. The counterpart 10 has the same diameter as the interior 8. It is provided with a thread 11 on its curved narrow side. The lower oscillating head section 5 has a matching thread 11 on its inside, so that the counterpart 10 can be screwed into the interior 8 of the lower oscillating head section 5. On its outer end face, the counterpart 10 has four non-continuous cylindrical bores 12. The bolts of a lever-like tool which serves to tighten the counterpart 10 can be inserted into these bores 12. The counterpart 10 must be well tightened so that the ultrasonic transducer 9 has no play. Movements of the ultrasound transducer 9 would lead to noise generation and would also cause the ultrasound transducer 9 to wear out rapidly.

Two different types of training are provided for the oscillating head 2:

In the first type of training (see FIGS. 4a to 6), the convex end face 3 is smooth and continuous. This shape of the convex end face 3 has the disadvantage that when the sound waves strike the interface between the convex end face 3 and the cleaning liquid 13, some of the sound waves is inflected. This reduces the efficiency of the ultrasound transmitter 1.

In the second embodiment of the oscillating head 2 (cf. FIGS. 1 a to 3) an attempt is made to prevent this reflection or at least to reduce it by giving the upper oscillating head section 4 a stepped profile. The step profile is designed such that the thickness of each ring defined by a step 22 corresponds to an integral multiple of half the longitudinal wavelength in the oscillating head material. A plate or layer of this thickness is completely permeable to sound. So there is no reflection.

However, an upper oscillating head section 4 with a step profile corresponds to a "resonance lens" and is therefore only suitable for ultrasonic waves with a low frequency bandwidth. In the case of high frequency bandwidths, the first type of training of the oscillating head 2 is more suitable.

The ultrasound transmitter of the second type of embodiment has a large number of needle-like transmission elements 23 which run parallel to one another (cf. FIGS. 11a and 11b). These transmission elements 23 can be hollow or solid. In the embodiment which is shown in the drawings, they have a round cross section. Furthermore, they are arranged in the longitudinal direction without being offset from one another.

The transmission elements 23 are fixed at one end with the aid of a holding plate 24 and a pressure plate 25. Both the holding plate 24 and the pressure plate 25 are circular in the exemplary embodiment and have the same diameter. The holding plate 24 is provided with a multiplicity of continuous bores 26, which are preferably arranged at regular intervals. The number of bores 26 corresponds to the number of transmission elements 23. The transmission elements 23 have a conical base 27. An end portion 28 of each bore 26 is also conical. It corresponds in shape and size to the conical foot 27 of a transmission element 23. Each transmission element 23 is inserted into a bore 26 in the holding plate 24 such that its foot 27 is conical End portion 28 of the bore 26 is seated. The transmission elements 23 protrude on that side of the holding plate 24 which faces away from the conical end sections 28 of the bores 26. The pressure plate 25 rests on the other side of the holding plate 24. This pressure plate 25 is pressed onto the holding plate 24 by a plurality of screws 29. It holds the feet 27 of the transmission elements 23 in the conical end sections 28 of the bores 26 of the holding plate 24. To hold the screws 29, the holding plate 24 and the pressure plate 25 have threaded bores that are aligned with one another and are preferably arranged near their outer edge. The total thickness of the holding plate 24 and the pressure plate 25 should be a multiple of half the longitudinal wavelength (λ / 2) of the generated ultrasonic waves, so that the ultrasound waves pass through the holding plate 24 and the pressure plate 25 as freely as possible. The ultrasonic transducer 30 is arranged on that side of the pressure plate 25 which faces away from the holding plate 24.

The front faces of the transmission elements 23, seen along the direction of movement of the ultrasonic waves, can be flat or convex. Curved end faces cause additional bundling of the ultrasonic waves.

The transmission elements 23 can be composed of a tube and a solid needle in a further embodiment, not shown in the drawings. The needle is located inside the tube.

The proposed ultrasound transmitter 1 of both types of training is preferably attached to the bottom 15 of a trough 14 (cf. FIGS. 7a to 8). It emits the ultrasonic waves with a wide angle of propagation upwards. The largest part of the ultrasound waves hits the object 16 to be cleaned, which is arranged above the ultrasound transmitter 1. A small part of the ultrasonic waves strikes the tub walls 17 and is reflected by them. However, there is also the possibility of attaching the proposed ultrasound transmitter 1 to the inside of a tub side wall 17 (cf. FIG. 9 and 10). For example, all side walls 17, two opposite side walls 17 or a single side wall 17 can each carry one or more ultrasound transmitters 1. That part of the ultrasonic waves which strikes the object 16 to be cleaned immediately after the first reflection is increased in the present invention by a suitable shaping of the tub 14. Different tub shapes are provided.

FIG. 7a shows a trough 14 with bent side walls 17. In an upper section the side walls 17 run vertically, in a lower section they run obliquely inwards.

The side walls 17 of the tub 14, which is shown in FIG. 7b, are curved inwards in a lower section. In addition to short tubs 14 with only one ultrasound transmitter 1, long tubs 14 are also provided, on the bottom 15 of which two, three or more ultrasound transmitters 1 are fastened (cf. FIG. 8). They are arranged in a line.

The proposed ultrasound transmitter 1 of the first type of training is advantageously operated at frequencies between 25-40 kHz and powers of 1000-1500 watts per ultrasound transducer 9.

The proposed ultrasonic transmitter 1 has significant advantages over the known ultrasonic transmitters provided for ultrasonic cleaning.

In both types of training of the proposed ultrasound transmitter 1, the ultrasound waves propagate largely on one side of the ultrasound transmitter 1, in contrast to the rod or tube vibrators. This on the one hand achieves a good distribution of the ultrasound waves and on the other hand prevents a large one Part of the ultrasonic waves hits the object 16 to be cleaned only after reflection on the tub wall 17. This has the effect that the efficiency of the proposed ultrasonic transmitter 1 is higher than the efficiency of previously known, comparable ultrasonic transmitters. This means that with the proposed ultrasound generator 1, a substantially better cleaning effect is achieved with a certain amount of energy can be than in the known ultrasonic transducers. The ultrasound transmitter 1 of the first type of training causes the ultrasound waves to spread at a wider angle than the known surface oscillators. In the ultrasonic transmitter 1 of the second embodiment, the contact area between the transmission elements 23 and the cleaning liquid 13 is considerably larger than in the known tube or surface vibrators. The transmission of the ultrasound waves from the ultrasound transmitter 1 to the cleaning liquid 13 is consequently considerably more efficient.

In the case of the conventional surface transducers, the individual ultrasonic transducers could not be operated with excessive power because of the small thickness of the plate-shaped transmission element. Up to 100 watts were usual for each ultrasonic transmitter. At higher powers, the plate-shaped transmission element is destroyed after a short time. Thanks to the massive construction of the proposed ultrasound transmitter 1 of the first type of training, its ultrasound transducer 9 can be operated with powers of 1000-1500 watts. A much higher sound pressure can consequently be generated with the proposed ultrasound transmitter 1 of the first design than with the previously known ultrasound transmitters. This is particularly important if the cleaning liquid 13 used is not an aqueous solution but organic solvents. Organic solvents have the advantage that they have a lower viscosity than water. As a result, they get into fine cracks and cracks on the surface of the object 16 to be cleaned. However, organic solvents have the disadvantage that they have a lower density than water and therefore conduct the ultrasound more poorly. In order to generate the same sound pressure in organic solvents as in water, the ultrasound transmitters must be operated at higher powers. This is now easily possible with the proposed ultrasonic transmitter 1.

Claims

PATENT CLAIMS

1. Ultrasonic transducer (1) or generator, with at least one ultrasonic transducer (9) and with at least one vibrating head (2) emitting the generated ultrasound, which has an upper section (4) on the transducer (9) in a main direction of propagation of the ultrasound can be coupled, characterized in that the upper section (4) can be represented in longitudinal section at least in regions in its (4) contour at least by a convex envelope (3) or envelope (3) and / or in its (4) contour itself convex is.

2. Ultrasonic generator or generator according to claim 1, characterized in that the upper section (4) adjoining plateaus, which in longitudinal section result in the convex envelope or envelope (3), or the convex envelope or envelope (3) resulting steps (22).

3. Ultrasonic generator or generator according to claim 2, characterized in that the extension of a step (22) in the longitudinal direction of the oscillating head (2) or in the main direction of propagation of the ultrasonic waves of any integer multiple of half a longitudinal wavelength of the ultrasonic frequency (EN) in the material of Swinging head (2) corresponds.

4. Ultrasonic generator or generator according to one of claims 2 or 3, characterized in that the steps (22) have extensions or heights which correspond to different integer multiples of half the longitudinal wavelength.

5. Ultrasonic generator or generator according to one of claims 1 to 4, characterized in that the oscillating head (2) is circular in cross section perpendicular to the main direction of propagation of the ultrasound at least in the region of the upper section (4).

6. Ultrasonic transmitter or generator according to one of claims 1 to 5, characterized in that the transducer (9) is circular in cross section and / or is surrounded perpendicular to the main direction of propagation with an insulation ring (21) or jacket.

7. Ultrasonic generator or generator according to one of claims 1 to 6, characterized in that the transducer (9) is arranged in the lower section (5) of the oscillating head (2) and preferably via a coupling disk (20) to the oscillating head (2 ) is scheduled.

8. Ultrasonic generator or generator according to one of claims 1 to 7, characterized in that the transducer (9) in or on the oscillating head (2) with a counterpart (10) can be fixed.

9. Ultrasonic generator (1) or generator according to one of claims 1 to 8, characterized in that the ultrasonic generator (1) or generator means (7) for fastening it to an inner surface (17) of a container (14 ) having.

10. Ultrasonic generator or generator according to one of claims 1 to 9, characterized in that the container (14) has inner walls (17) which at least in regions have an inclination to the base of the ultrasonic generator (1) or generator, so that are reflected back into the interior of the container trimer waves.

11. Ultrasound generator or generator (1) with at least one ultrasound transducer (30) and with a plurality of the transducer heads (23) which emit ultrasound and which can be coupled with respective upper sections to the transducer (30) in a main direction of propagation of the ultrasound (23) each have cylindrical or rod-shaped bodies (23), characterized in that at least one of the oscillating heads (23) has a base surface which can be turned towards the transducer (30) and which, with regard to the cross-sectional area of the cylindrical or rod-shaped bodies of the oscillating heads ( 23) is larger, the transition area between the base area and the essentially cylindrical or rod-shaped body (23) being essentially continuous, for example at least approximately convex or conical, in order to concentrate the ultrasound energy.

12. Ultrasonic transmitter or generator (1) according to claim 11, characterized by a holding body or plate (24) which connects to the ultrasonic transducer (30) in the direction of extension of the oscillating heads (23), the oscillating heads (23) being through the holding body (24) or the holding plate (24) on the transducer (30) can be fixed.

13. Ultrasonic generator or generator according to claim 12, characterized in that the holding body or plate (24) has openings (26) which has at least one to the transition regions of the oscillating heads (23) substantially complementary to the shape To embrace transition areas preferably in a form-encompassing manner.

14. Ultrasonic transmitter or generator according to one of claims 12 or 13, characterized in that the oscillating heads (23) and / or the holding body or plate (24) on the ultrasonic transducer, for example via a one-piece or multi-piece pressure section (29) can be pressed directly or indirectly.

15. Ultrasonic generator or generator according to one of claims 10 to 14, characterized in that the oscillating heads (23) are formed as a whole or individually at their ultrasound radiating ends according to the characterizing part of claim 1 and / or one of claims 2 to 8 .

16. Ultrasonic transmitter or generator according to one of claims 11 to 15, characterized by the features according to at least one of claims 9 or 10.