ULTRASONIC TRANSDUCER WITH EMITTING ELEMENT

Abstract

An ultrasonic transducer for an ultrasonic flow meter, with a transducer housing, with a transducer element for generating and/or for receiving ultrasonic signals and with an emitting element, the emitting element being exposed to ultrasonic signals at least indirectly from the transducer element and emitting the ultrasonic signals via one end face on one front side of the emitting element into the vicinity bordering the ultrasonic transducer and/or the emitting element picking up ultrasonic signals from the vicinity via one end face on one front side of the emitting element and transmitting them at least indirectly to the transducer element. A good directional action in spite of small dimensions is achieved by the emitting element being connected to the transducer housing via a connecting element and being free standing on its periphery on the front side such that it can oscillate freely on the periphery.

Claims

1. An ultrasonic transducer for an ultrasonic flow meter, comprising: a transducer housing, a transducer element for at least one of generating and receiving ultrasonic signals and an emitting element, the emitting element being exposed to ultrasonic signals at least indirectly from the transducer element and emitting the ultrasonic signals via an end face on a front side of the emitting element into the vicinity bordering the ultrasonic transducer and/or the emitting element picking up ultrasonic signals from the vicinity via the end face on the front side of the emitting element and transmitting them at least indirectly to the transducer element, wherein the emitting element is connected to the transducer housing via a connecting element and is peripherally free standing on the front side such that it can oscillate freely peripherally.

2. The ultrasonic transducer as claimed in claim 1, wherein the emitting element is a plunger having a plunger shaft and a plunger plate, the plunger plate encompassing the end face and the plunger extending at least partially outside the transducer housing.

3. The ultrasonic transducer as claimed in claim 2, wherein the plunger shaft projects at least partially into the transducer housing.

4. The ultrasonic transducer as claimed in claim 2, wherein the plunger shaft is columnar.

5. The ultrasonic transducer as claimed in claim 2, wherein the plunger shaft has a cross section that is one of round, rectangular or polygonal.

6. The ultrasonic transducer as claimed in claim 1, wherein the connecting element is a membrane.

7. The ultrasonic transducer as claimed in claim 6, wherein the membrane is corrugated.

8. The ultrasonic transducer as claimed in claim 2, wherein the plunger shaft has a cross section which tapers away from the transducer element

9. The ultrasonic transducer as claimed in claim 8, wherein the plunger shaft is shaped as an acoustic horn.

10. The ultrasonic transducer as claimed in claim 1, wherein the transducer housing and the connecting element have a one piece construction.

11. The ultrasonic transducer as claimed in claim 1, wherein the transducer housing, the connecting element and the emitting element have a one piece construction.

12. The ultrasonic transducer as claimed in claim 1, wherein the connecting element and the emitting element have a once piece construction.

13. The ultrasonic transducer as claimed in claim 1, wherein the transducer housing, the connecting element and the emitting element are welded to one another.

14. The ultrasonic transducer as claimed in claim 1, wherein an elastic material is provided between the emitting element and the connecting element.

15. The ultrasonic transducer as claimed in claim 1, wherein the connecting element and the emitting element are welded to one another.

16. The ultrasonic transducer as claimed in claim 1, wherein an elastic material is provided between the emitting element and the connecting element.

17. The ultrasonic transducer as claimed in claim 16, wherein the elastic material is formed by at least one O-ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1a shows a classic ultrasonic transducer from the prior art in the static state,

[0022] FIG. 1b shows the ultrasonic transducer which is shown in FIG. 1a in the dynamic state,

[0023] FIG. 2a shows a first configuration of an ultrasonic transducer in accordance with the invention in the static state or in the state of a fundamental mode,

[0024] FIG. 2b shows the ultrasonic transducer shown in FIG. 2a in the dynamic state in a higher oscillation mode,

[0025] FIG. 3 shows a second configuration of an ultrasonic transducer in accordance with the invention with an elastic element,

[0026] FIG. 4 shows a third configuration of an ultrasonic transducer in accordance with the invention in which the plunger shaft is advantageously shaped,

[0027] FIG. 5 shows the ultrasonic transducer from FIG. 4 with a membrane which is made corrugated as the connecting element,

[0028] FIG. 6 shows a fifth configuration of the ultrasonic transducer in accordance with the invention and

[0029] FIG. 7 shows a sixth configuration of the ultrasonic transducer as claimed in the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0030] FIG. 1a shows an ultrasonic transducer 1 which is known from the prior art in a simplified representation. The ultrasonic transducer 1 comprises a transducer housing 2 and a transducer element 3. Ultrasonic signals are generated by the transducer element 3 and via an emitting element 4, made here as an ultrasonic window, are emitted into the vicinity which borders the ultrasonic transducer 1. Emission takes place via the end face 5 of the emitting element 4.

[0031] FIG. 1b shows a dynamic state of the ultrasonic transducer 1. The ultrasonic signals are emitted via the end face 5. As is clearly apparent in FIG. 1b, the end face 5 of the ultrasonic transducer 1 known from the prior art oscillates only centrally since the emitting element 4 is connected to the transducer housing 2 over its entire periphery. By the mechanical boundary condition of fixing the emitting element 4 it is sketched out that the emitting element 4 always has its greatest oscillation amplitude in its central region, the oscillation amplitude decreasing towards the periphery of the emitting element 4.

[0032] FIG. 2a shows an ultrasonic transducer 1 in accordance with the invention. The ultrasonic transducer 1 has a transducer housing 2 and a transducer element 3. The transducer element 3 generates ultrasonic signals and transmits them to an emitting element 4. The signals are then emitted via the end face 5 on the front side 6 of the emitting element 4 into the vicinity which borders the ultrasonic transducer 1. Furthermore, the ultrasonic transducer 1 is also described as a transmitter, but the use of the same ultrasonic transducer 1 as a receiver is also possible. Then, the emitting element 4 via its end face 5 on the front side 6 picks up ultrasonic signals from the vicinity and transmits them to the transducer element 3; this is accomplished here by a piezoelement. Thus, mechanical oscillations which have been picked up without constraint can be converted into electrical signals.

[0033] The emitting element 4 is connected via one connecting element 7 to the transducer housing 2. The connecting element 7 is made as an elastic resonant membrane 1Q.

[0034] The connecting element 7 is connected to the emitting element 4 such that the emitting element 4 on its periphery U is freely standing on the front side 6 and can oscillate freely on its periphery U. This means that the emitting element 4 on its periphery U can move freely and the periphery U of the emitting element 4 in any case is not hampered from moving the entire emitting element 4 at the same time. Because the emitting element 4 is no longer peripherally fixed, it is possible for it to oscillate with its entire end face 5, as a result of which the entire end face 5 can contribute equally to ultrasonic generation and emission. In this way the effective aperture of the ultrasonic transducer 1 is greatly enlarged, with the size of the end face 5 unchanged and without the outside diameter of the ultrasonic transducer 1 having to be increased. This becomes especially clear in the direct comparison of FIG. 1 and FIG. 2. In FIG. 2 an ultrasonic transducer 1 with a distinctly improved directional action results, since parallel wave fronts can be generated over the entire region of the end face 5. This is fundamentally not possible in the ultrasonic transducer 1 according to FIG. 1.

[0035] The emitting element 4, itself, is made as a plunger and has a plunger shaft 8 and a plunger plate 9. The plunger shaft 8 extends into the transducer housing 2, conversely, the plunger plate 9 is located outside the transducer housing 2. This makes it possible for the plunger plate 9 to have even a larger diameter than the inside diameter of the housing 2. Thus, the size of the end face 5 is independent of the dimensions of the transducer housing 2. But, advantages also arise when the end face 5 is chosen not to be greater than the inside diameter of the housing 2; this is due to the freedom of movement of the periphery U of the emitting element 4 in the region of the plunger plate 9.

[0036] FIG. 2a shows how straight, parallel phase fronts of the ultrasonic oscillations which accompany an outstanding directional action can be implemented by the structure.

[0037] FIG. 2b shows the ultrasonic transducer 1 which is shown in FIG. 2a in the dynamic state in a higher oscillation mode which can be excited at the same time with the fundamental oscillation mode. Therefore, two superimposed oscillation modes of the ultrasonic transducer 1 are shown. In the first mode, essentially the membrane 10 is deflected or excited to oscillations, in the second mode essentially the plunger plate 9 oscillates in itself. This is shown exaggerated in the FIG. 2b using the bent plunger plate 9 whose peripheral region U is deflected downward relative to the central region of the plunger plate 9.

[0038] FIG. 3 shows a configuration of the ultrasonic transducer 1 in accordance with the invention in which there are O-rings 12 in the region 11 between the connecting element 7 which is made as a membrane 10 and the plunger plate 9. The O-rings serve in particular not to attenuate the harmonics which have been directly excited by the transducer element 3.

[0039] Furthermore the ultrasonic transducer 1 has a flange 13 for attachment of the ultrasonic transducer 1.

[0040] The natural frequency of the ultrasonic transducer 1 is proportional to the stiffness of the connecting element 7 which is made as a membrane 10. In order to reduce the stiffness of the membrane 10 and to shift the natural frequency of the ultrasonic transducer 1 to lower frequencies, the embodiment of the ultrasonic transducer shown in FIG. 4 has a plunger shaft 8 which is shaped as an acoustic horn 14. The plunger shaft 9 tapers towards its side which is facing away from the transducer element 3. The membrane 10 is connected to the plunger shaft 8 at the site with the smallest diameter. In this way the moveable area of the membrane 10 of the connecting element 7 is structurally enlarged.

[0041] The embodiment of the ultrasonic transducer 1 shown in FIG. 5 differs from the embodiment shown in FIG. 4 in that the membrane 10 is made corrugated. This still further increases the elasticity of the membrane 10 and further reduces the stiffness of the membrane 10 and this results in a fundamental natural frequency which is lower as compared to the embodiment in FIG. 4.

[0042] FIG. 6 shows an ultrasonic transducer 1 in which the membrane is connected not to the plunger shaft 8, but to the plunger plate 9. The plunger plate 9 is still freely standing on its periphery U so that it can oscillate freely.

[0043] FIG. 7 shows another embodiment of the ultrasonic transducer. The membrane 10 is made here such that it seals the entire transducer housing 2. The emitting element 4 is then connected to the membrane 10 on the side of the membrane 10 facing away from the transducer element 3. Between the transducer element 3 and the membrane 10 there is a line element 15 which relays the ultrasonic signals which have been generated by the transducer element 3 via the membrane 10 to the emitting element 4. Therefore, the emitting element 4 is exposed here to the ultrasonic signals indirectly via the line element 15 and the membrane 10 and not directly, as in the configurations of the ultrasonic transducer 1 which are shown in FIGS. 2 to 6.