The invention relates to an ultrasonic transducer for an ultrasonic flowmeter, having at least one piezoelectric transducer element, having a first holding element and having a second holding element, wherein the at least one piezoelectric transducer element is arranged between the first holding element and the second holding element, and wherein the first holding element, the at least one piezoelectric transducer element and the second holding element are arranged one behind the other along a longitudinal axis.
Ultrasonic transducers of the type in question are known in a multitude from the prior art and are used in ultrasound-based flow or level measurement. The ultrasonic signal is generated by a piezoelectric transducer element.
In many prior art ultrasound transducers, the piezoelectric transducer element is bonded to an ultrasound window through which the ultrasound signals are emitted from the ultrasound transducer into the medium to be measured, or is pressed against the ultrasound window by suitable means. Such an ultrasonic transducer is known, for example, from DE 10 2007 042 663 A1.
In other ultrasonic transducers known from the prior art, the ultrasonic transducers have at least two holding elements between which the piezoelectric transducer element is clamped. Such an ultrasonic transducer is described, for example, in EP 1 181 988 A2. Here, a piezoelectric transducer element is clamped between two holding elements, wherein a tension spring is used for clamping, which is arranged around the piezoelectric transducer element and connects the two holding elements to each other. Each holding element is screwed into the clamping spring. A disadvantage of such a design is that the two holding elements are acoustically coupled to each other directly via the tensioning spring and that, in addition, the shape of the ultrasonic signals generated by the piezoelectric transducer element is influenced.
Accordingly, the object of the invention is to provide an ultrasonic transducer for an ultrasonic flowmeter which minimizes the disadvantages known from the prior art.
According to the characterizing portion of the disclosed features, the task is initially and essentially solved in that at least one pre-tensioning element is provided on the side of the first holding element facing away from the piezoelectric transducer element, and that a connecting element is provided on the side of the pre-tensioning element facing away from the first holding element. The connecting element is used for loading the pre-tensioning element and is also connected to the second holding element. In the loaded state of the pre-tensioning element, a force acts on the first holding element and, via the connecting element, on the second holding element such that the first holding element and the second holding element clamp the at least one piezoelectric transducer element.
When it is said that the connecting element is arranged on the side of the pre-tensioning element facing away from the first holding element, it is meant that at least portions or parts of the pre-tensioning element are arranged on the side of the pre-tensioning element facing away from the holding element. Thus, it is not intended that the connecting element is exclusively located on the side of the pre-tensioning element facing away from the first holding element. According to the invention, however, the pre-tensioning element is arranged in the direction of the longitudinal axis of the ultrasonic transducer between the first holding element and the connecting element or regions or parts of the connecting element. According to the invention, the connecting element is connected to the second holding element so that parts of the connecting element extend past the pre-tensioning element and past the first holding element or through the pre-tensioning element and through the first holding element to the second holding element. According to the invention, the connecting element and the second holding element are connected to each other. By this, it is meant that the connecting element and the second holding element are connected to each other at least in the assembled state of the ultrasonic transducer and in particular in the loaded state of the pre-tensioning element. Possible implementations are described further below in connection with designs according to the invention.
The loading of the pre-tensioning element by the connecting element is to implemented by reducing the distance of the pre-tensioning element in the direction of the longitudinal axis of the ultrasonic transducer to the second holding element, thereby compressing the pre-tensioning element in the direction of the longitudinal axis.
In the loaded state, the pre-tensioning element tends to change to the relaxed state, thereby exerting a force on both the connecting element and the first holding element. The two forces are equal in magnitude, but act in opposite directions. Through the connecting element, the force acting on the connecting element is transmitted to the second holding element, so that the force also acts on the second holding element. As a result, the first holding element and the second holding element clamp the piezoelectric transducer element between them. The degree of clamping here depends on the degree of loading of the pre-tensioning element.
An advantage of the implementation of the ultrasonic transducer according to the invention is that all components necessary for the function are arranged along the longitudinal axis of the ultrasonic transducer. In particular, the fact that the pre-tensioning element is not arranged directly in the region of the piezoelectric transducer element, but is arranged at a considerable distance from the piezoelectric transducer element, considerably reduces the influence of the pre-tensioning element on the shape of the radiated ultrasonic signals.
According to the invention, there are various possibilities for the design of the pre-tensioning element. In a particularly preferred design of the ultrasonic transducer according to the invention, it is provided that the pre-tensioning element is designed in the first holding element. This is reduced, for example, by the fact that the pre-tensioning element is implemented by a material reduction of a part of the first holding element or a special shaping of a part of the first holding element. Thus, a spring-like section is implemented in the holding element. The spring-like section is designed on the side of the first holding element facing away from the piezoelectric transducer element.
In a further preferred design, the pre-tensioning element is designed as a separate spring element. All types of spring elements known from the prior art are suitable for this purpose, for example compression springs, disc springs, wave springs or plate springs.
A variation in which a second pre-tensioning element is provided is also particularly preferred. The second pre-tensioning element is preferably arranged adjacent to the first pre-tensioning element in the direction of the longitudinal axis of the ultrasonic transducer. If it is stated that the first pre-tensioning element and the second pre-tensioning element are arranged adjacent to each other, then this can be implemented by the two pre-tensioning elements being arranged directly adjacent to each other, in particular being in touching contact. However, it is also possible for the two pre-tensioning elements to be arranged next to one another at a distance from one another, i.e. for there to be an intermediate space between the two pre-tensioning elements. Particularly preferably, both pre-tensioning elements are designed identically.
According to the invention, the connecting element is provided for loading the pre-tensioning element. At the same time, the connecting element is connected to the second holding element. There are now various ways of implementing the connecting element.
In a particularly preferred design, the connecting element is implemented by a sleeve. In one variation, the sleeve is implemented with a closed surface. In an alternative variation, the sleeve has recesses in its surface, in particular in its lateral surface.
For fastening the sleeve to the second holding element, it is provided in a first variation that the sleeve is connected to the second holding element via additional fastening elements. In one variation, these additional fastening elements are designed as latching elements. For this purpose, a latching recess is provided in the sleeve, and a corresponding latching projection is designed in the second holding element. In a further design, this can also be implemented in reverse, so that the latching recess is implemented in the second holding element and the latching projection in the sleeve.
In a further variation, the additional fastening elements are implemented as screws. Preferably, the sleeve and the second holding element then have corresponding recesses with a mating thread corresponding to the thread of the screw, so that the screws can be screwed into the recesses and thus fasten the sleeve. Since the fastener is designed to load the pre-tensioning element, the sleeve must be fitted in such a way that it loads the pre-tensioning element. Thus, the sleeve encloses the pre-tensioning element as well as the first holding element and the piezoelectric transducer element.
In order to be able to implement fine adjustment of the pre-tensioning element, a particularly preferred variation of the ultrasonic transducer according to the invention is characterized in that the sleeve is designed to be screwed onto the second holding element. For this, the sleeve preferably has an internal thread at its end facing the second holding element, and the second holding element preferably has a corresponding mating thread. Depending on how far the sleeve is screwed onto the second holding element, the pre-tensioning element is loaded to a greater or lesser extent.
In an alternative design of the ultrasonic transducer according to the invention, with which fine adjustment of the pre-tensioning element can also be implemented, it is characterized that the connecting element is designed in a T-shape with a T-roof and a T-rod. The T-shaped connecting element has a thread at its end of the T-bar facing away from the T-roof. The second holding element has a connecting element receptacle with a corresponding mating thread. Moreover, in this design of the ultrasonic transducer according to the invention, it is implemented that the pre-tensioning element, the first holding element and the at least one piezoelectric transducer element each have a recess through which the T-bar of the T-shaped connecting element is passed. The pre-tensioning element is then brought into the loaded state by screwing the T-shaped connecting element into the second holding element. Depending on how far the connecting element is screwed into the second holding element, the bias of the biasing element can be adjusted.
Various variations are provided for implementing the T-roof of the T-shaped connecting element. In a first variation, the T-roof is configured as a closed disc. In an alternative variation, the T-roof is implemented by a disc having recesses. In all variations, the T-roof is designed in such a way that uniform loading of the pre-tensioning element is implemented.
In an alternative variation, the connecting element is implemented by a connecting rod and a nut. The connecting rod is connected to the second holding element. In such a design, the pre-tensioning element, the first holding element and the at least one piezoelectric transducer element also each have a recess through which the connecting rod is guided. At its end facing away from the second holding element, the connecting rod has a thread onto which the nut can be screwed. Screwing the nut onto the threaded rod brings the pre-tensioning element into the loaded state. The degree of loading can also be finely adjusted here by the degree to which the nut is screwed onto the connecting rod.
As explained, the connecting rod is connected to the second holding element. In a first variation, the connecting rod is non-detachably connected to the second holding element. This is implemented, for example, by welding the connecting rod and the second holding element together. In an alternative design, the connecting rod and the second holding element are manufactured in one piece, i.e. are made from a single workpiece. When reference is made to an undetachable connection, it is meant that the connection is not detachable without destroying the arrangement, in particular that special force is required to detach the connection.
In an alternative variation, the connection between the second holding element and the connecting element is designed to be detachable. Here, in one variation, it is provided that the connecting rod has a thread at its end facing the second holding element and that the second holding element has a recess with a mating thread, so that the connecting rod can be screwed to into the holding element. In an alternative variation, the holding element and the connecting rod are connected to each other by a bayonet lock. In a third variation, the connecting rod and the second holding element are connected to each other by a snap-in connection.
In detail, there are now a large number of possibilities for designing and further developing the ultrasonic transducer according to the invention. In this regard, reference is made to the description of particularly preferred embodiments in conjunction with the drawings.
In the illustrated embodiment of
In the further figures, the pre-tensioning elements 7 are shown in alternative embodiments. In
The figures also show various designs of the connecting element 9. In the embodiment shown in
Further embodiments of the connecting element 9 are implemented in
In
Number | Date | Country | Kind |
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10 2022 107 092.1 | Mar 2022 | DE | national |