Abstract:
The invention relates to a test method for nozzles composed of ceramic or ceramic-like materials, in which the following method steps are carried out: transfer of ultrasonic vibration to the nozzle by means of a sonotrode placed against the nozzle and thermographic evaluation of the heat evolved in a wall of the nozzle.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the priority of German Application No. 10 2011 007 230.6, filed Apr. 12, 2011, the disclosure of which is hereby incorporated by reference in its entirety into this application. 
       FIELD OF THE INVENTION  
       [0002]    The invention relates to a test method for nozzles composed of ceramic or ceramic-like materials. The invention also relates to a testing device for nozzles composed of ceramic or ceramic-like materials. Finally, the invention relates to a nozzle that is composed of ceramic or ceramic-like material and that has at least one wall. 
       BACKGROUND OF THE INVENTION  
       [0003]    The German unexamined laid-open patent application DE 100 59 854 A1 discloses a thermographic test method in which a specimen surface is excited by the transfer of ultrasound thereto and then evaluated by means of a thermal imaging camera. When ultrasound is transferred to a defective component, the ultrasonic energy is preferentially converted to heat at the defective locations. 
         [0004]    Finding cracks in ceramic nozzles has been found to be problematic in the prior art. Usually, an experienced quality assurance representative uses a small hammer to tap on ceramic nozzles, which always comprise at least one cavity. The sound resulting when the nozzles are tapped on then serves as an indication of cracks and/or defects that may exist in the nozzles. The examination of ceramic nozzles by means of automated, mechanical processes poses great problems, since nozzles composed of ceramic or ceramic-like materials are fragile under conditions of exposure to severe mechanical and/or thermal stresses. 
       SUMMARY OF THE INVENTION  
       [0005]    It is an object of the invention to improve a test method, a testing device, and a nozzle composed of ceramic or ceramic-like material. 
         [0006]    According to the invention, there is provided, to this end, a test method for nozzles composed of ceramic or ceramic-like materials, which includes the following steps: the transfer of ultrasonic vibration to the nozzle, more particularly by means of a sonotrode placed against the nozzle, and the thermographic evaluation of the heat evolved in a wall of the nozzle. 
         [0007]    The thermographic evaluation is then carried out during or after the transfer of ultrasonic vibration by means of an ultrasonic transducer or a sonotrode, or alternatively by means of a loudspeaker, for example. A greater amount of heat is evolved in cracks or defects in the wall of the nozzle, and this heat can then be detected by thermographic evaluation. When ultrasonic vibration is transferred to the nozzle, it has been found, surprisingly, that cracks and defects in the ceramic material are detected effectively and that only those nozzles that are already severely damaged break to pieces as a result of the transfer of ultrasonic energy under test conditions. Thus the test method of the invention makes it possible to detect cracks and defects in nozzles that are composed of ceramic or ceramic-like materials and that comprise at least one cavity and then to assess the detected cracks or defects in order to decide whether these nozzles can be used and, if so, for which application they would be suitable. The transfer of ultrasonic vibration and the thermographic evaluation allow the examination of nozzles to be carried out without having to depend on the experience of a crack detector and also the detection of cracks or defects that are small or hidden from view and do not extend directly to the surface of the nozzle. Such small defects in critical, highly stressed regions of the nozzle can then lead to malfunction of the nozzle during continuous operation. The test method of the invention remedies such a situation and enables the tested nozzles to be provided with a long service life warranty. Nozzles composed of ceramic or ceramic-like materials comprise at least one cavity. The term “cavity” is understood to mean an enclosed space comprising one or more orifices, for example, a swirl chamber or a through-flow passage in a solid stream nozzle comprising an inlet orifice and an outlet orifice. Nozzles composed of ceramic or ceramic-like materials are always fragile on account of the cavity, and the examination of such nozzles always poses problems, since such examination must include an inspection of all the walls of the cavity and also of all additional, fragile components of the nozzle. The invention provides a surprisingly simple remedy for nozzles comprising at least one cavity. 
         [0008]    In a development of the invention, the sonotrode is placed against a connecting region or a chamber region of the nozzle. 
         [0009]    Nozzles composed of ceramic or ceramic-like materials generally consist of a connecting region and at least one chamber region, and an inlet region, by means of which the liquid to be sprayed is conveyed from the connecting region to the chamber region. The connecting region can be composed of, for example, a flange, a circular screw thread, a connecting component for gluing, or the like. The inlet is usually of a tubular shape. The chamber region can comprise, for example, one or more swirl chambers. The most important region to be examined is the inlet region, since this must absorb the greatest stresses not only during the operation of the nozzle but also during fabrication thereof. Therefore, it is not possible to simulate satisfactorily, if at all, the stresses applied to the nozzles during operation by positioning the sonotrode in the inlet region. Rather, the sonotrode is positioned on one of the two portions of greater mass, namely the connecting region or the chamber region, so that oscillation of maximum possible amplitude is induced in the other portion of greater mass, that is to say, in the chamber region or the connecting region, respectively. This then allows the critical inlet region to be tested effectively by means of the test method of the invention. According to the invention, it is preferred to position the sonotrode in the connecting region, since such an approach corresponds most closely to the actual operating conditions. During actual operation, a nozzle is mounted by means of its connecting region on a connecting pipe and vibration caused, for example, by pumps or the fluid flow in the connecting pipe, is transferred from the connecting pipe to the swirl chamber of the nozzle by way of the inlet. 
         [0010]    In a development of the invention, the sonotrode is placed against the peripheral surface of a connecting component, more specifically a connecting flange. 
         [0011]    In this way, ultrasonic vibration can be transferred to the nozzle reliably and without much risk of damage to the nozzle. 
         [0012]    In a development of the invention, the sonotrode is placed against a flat surface in the connecting region or in the chamber region of the nozzle. 
         [0013]    Contact over a flat area between the sonotrode and the ceramic component with interposition of an intermediate component, if appropriate, is preferable for the input of ultrasonic energy because the transfer thereof via point contact can result in damage to both the sonotrode and the nozzle. This can be prevented by providing the nozzle with surfaces showing maximum flatness and having a size that is slightly larger than that of the contact surface of the sonotrode. Advantageously, such a flat surface can be provided in the connecting region or the chamber region of the nozzle in order to achieve a significant examination of the nozzle. 
         [0014]    In a development of the invention, the sonotrode is placed against an external or internal surface of a wall in the chamber region of the nozzle. 
         [0015]    Apart from the transfer of ultrasound via an external surface of the wall of the nozzle, it is also possible to input ultrasonic energy through an internal surface of a wall in the chamber region of the nozzle. 
         [0016]    In a development of the invention, provision is made for the placement of a counterbrace, at a location opposite to the sonotrode, against the internal or external surface of the wall, as appropriate. 
         [0017]    A particularly effective transfer of ultrasonic energy can be achieved by the provision of a counterbrace, which is then positioned in the chamber region, for example, against the internal surface of the chamber wall at a location opposite to the sonotrode. For example, such a counterbrace can be inserted to the swirl chamber through an outlet orifice of the nozzle. 
         [0018]    In a development of the invention, provision is made for pressing the sonotrode against the nozzle during the transfer of ultrasonic vibration, while at least one counterbrace is provided to counteract the pressing force. 
         [0019]    Pressing the sonotrode against the nozzle during the transfer of ultrasonic energy can ensure a particularly effective input of energy. 
         [0020]    In a development of the invention, the counterbrace is positioned at two points of contact on the nozzle. 
         [0021]    In this way, there is formed, together with the sonotrode, a three-point support for the nozzle. Such a three-point support firstly allows the nozzle to be mounted securely in the testing device and secondly it provides only slight obstruction by the points of contact themselves to the vibration being transferred to the nozzle. 
         [0022]    In a development of the invention, a point of contact of the sonotrode and the two points of contact of the counterbrace are located at the corners of a symmetrical planar triangle. 
         [0023]    In this way, it is possible to provide more efficient support of the nozzle in the testing device and, apart from the fact that the nozzle is clamped securely, vibration can propagate to the nozzle in order to achieve reliable test results. The ultrasonic energy must be distributed as uniformly as possible over the wall of the nozzle in order to avoid erroneous measurements. If, for example, the ultrasonic energy were to be concentrated in certain regions of the nozzle following the commencement of the transfer of ultrasonic energy, then said regions will be expected to heat up, even if they contain no defects or cracks or only very small defects or cracks, to a greater extent than other regions in which there is less ultrasonic energy present. The arrangement of the points of contact of the sonotrode and the counterbrace as proposed by the invention is conducive to the prevention of such erroneous measurements or false conclusions. 
         [0024]    In a development of the invention, there is provided a resilient intermediate component between the sonotrode and the nozzle. 
         [0025]    On the one hand, the use of a resilient intermediate component can prevent the ceramic material of the nozzle from being damaged by the sonotrode, and energy can be transferred with only slight loss of ultrasonic energy. On the other hand, a resilient intermediate component can also be used for achieving a match between a contact surface of the sonotrode and an external surface of the nozzle. If, for example, there is no suitable flat surface on the nozzle itself, against which the sonotrode could be placed, it is possible to provide an intermediate component at this location to achieve a match between the mutually opposing surfaces. 
         [0026]    Advantageously, the intermediate component has a modulus of elasticity that ranges from 9,000 N/mm 2  to 19,000 N/mm 2  and is more particularly 14,000 N/mm 2 . 
         [0027]    Such elasticity values have proven to be advantageous in order to achieve an effective excitation of the nozzle at an acceptable loss of ultrasonic energy. For example, hardwood, more particularly beechwood, and also temperature-resistant high performance plastics materials are well-suited for use as an intermediate component. Advantageously, the intermediate component is inserted with its direction of grain extending longitudinally between the sonotrode and the nozzle. 
         [0028]    Advantageously, the intermediate component has a thermal conductivity ranging from 0.1 W/mK to 0.2 W/mK. 
         [0029]    During the transfer of ultrasonic energy, a considerable amount of heat also evolves in the intermediate component and this heat must be removed appropriately in order to prevent destruction of the intermediate component. A suitable relationship between the modulus of elasticity and the thermal conductivity is also conducive to a longer undisturbed test period during the operation of transferring ultrasonic energy. Intermediate components composed of hardwood, more particularly beechwood, have proven to be advantageous for this purpose. For example, it has been found that PVC-plastics, PE-plastics or folded writing paper likewise enable ultrasonic energy to be transferred to the nozzle, but these materials become so hot after a short period that they are destroyed. 
         [0030]    In a development of the invention, provision is made for at least one mirror capable of reflecting thermal radiation to be positioned in the region of the nozzle and for a thermographic evaluation of a mirror image of the nozzle to be carried out. 
         [0031]    In this way, it is possible to evaluate the rear side of the nozzle which is remote from the thermal imaging camera without it being necessary to move the camera itself or to use two cameras. In this way, the test method can be carried out economically, on the one hand, and very rapidly, on the other. This feature is of considerable advantage for the series production of nozzles. 
         [0032]    In a development of the invention, there is provided a curved or bent mirror. 
         [0033]    In this way, it is possible to examine regions of the nozzle that are hidden from view, or for example the complete external wall of the nozzle, by means of a single thermal imaging camera, without having to move this camera or the mirrors. For example, spherical shell-shaped mirrors, parabolic mirrors or bent mirrors having a plurality of flat surfaces inclined at an angle in relation to each other can be used. A distortion of the mirror image of the nozzle as a result of the use of such curved or bent mirrors can either be accepted or, for example, back calculated during the course of the thermographic evaluation. 
         [0034]    In a development of the invention, provision is made for the mirror and/or a thermal imaging camera to be moved during the thermographic evaluation. 
         [0035]    Movement of the mirror or of the camera optionally combined with the provision of bent or curved mirrors can be useful, for example, to make it possible to carry out a particularly accurate examination of nozzles or an overall examination of nozzles having very complicated geometries. 
         [0036]    In a development of the invention, the ultrasonic vibration is transferred at a frequency in the range of 20 kHz. 
         [0037]    At such a frequency, it is possible to carry out a reliable examination of the nozzles without increased risk of damage to the nozzles during the test. 
         [0038]    In a development of the invention, the transfer of ultrasonic vibration is carried out at a power level which ranges from 100 W to 200 W and is more particularly 150 W. 
         [0039]    The transfer of power in the range of from 100 W to 200 W has proven to be sufficient for reliable detection of defects in the ceramic material of the nozzles. At the same time, there is a risk of damage to the nozzles only in the case of nozzles that exhibit severe previous impairment. Thus an acoustic generator having a power level of 500 W is sufficient for carrying out the method of the invention. 
         [0040]    In a development of the invention, a mark is provided on the nozzle prior to the thermographic evaluation using a heat-reflecting coating or by marking the nozzle by means of a heat source. 
         [0041]    When thermal images are captured by the camera, conventional labels or marks on the nozzle are not visible in the image. By contrast, the use of marks on the nozzle provided by a heat-reflecting coating material, for example, by means of a silver paint stick or a pencil or by marking the nozzle by means of a heat source, for example a laser pointer, can render the mark visible in the thermal image and substantially facilitates the evaluation or archiving of the test findings. 
         [0042]    The object of the invention is also achieved by a testing device for nozzles that are composed of ceramic or ceramic-like materials and that comprise at least one cavity, for carrying out the method of the invention, in which testing device there is provided at least one sonotrode for transferring ultrasonic vibration to the nozzle and at least one thermal imaging camera for the thermographic evaluation of the heat evolved in a wall of the cavity of the nozzle. 
         [0043]    Advantageously, the testing device comprises heat-reflecting mirrors, and a mirror image of the nozzle is evaluated by means of the thermal imaging camera. 
         [0044]    In a development of the invention, provision is made for at least one counterbrace to be placed against the nozzle at a location opposite to the sonotrode. 
         [0045]    In a development of the invention, the counterbrace rests against the nozzle at two points of contact that form, together with a point of contact of the sonotrode, a symmetrical planar triangle. 
         [0046]    For example, the counterbrace comprises an approximately V-shaped cutout, and a circular annular connecting flange of the nozzle is accommodated in the V-shaped cutout such that it rests against the counterbrace at two opposing points. A sonotrode is then placed against the periphery of the connecting flange at a location opposite to the counterbrace such that the points of contact form a symmetrical triangle. 
         [0047]    In a development of the invention, a disk composed of resilient material and having a modulus of elasticity that ranges from 9,000 N/mm 2  to 19,000 N/mm 2  and is more particularly 14,000 N/mm 2  is provided between the sonotrode and the nozzle. 
         [0048]    For example, a hardwood disk, more particularly a beechwood disk, can be provided. Advantageously, the wood grain then extends longitudinally between the sonotrode and the nozzle. Disks composed of resilient material, more specifically, wooden disks, having a thickness ranging from 2 mm to 10 mm have proven to be advantageous. It is also possible to use temperature-resistant high performance plastics materials. 
         [0049]    The object of the invention is also achieved by a nozzle that is composed of ceramic or ceramic-like material and that comprises at least one cavity and at least one wall delimiting the cavity, in which nozzle the wall has at least a first flat surface, against which a sonotrode can be placed. 
         [0050]    In this way, ultrasonic energy can be transferred very effectively to the nozzle by way of the first flat surface. Thus the nozzle of the invention is particularly advantageous, since it can be examined for cracks and defects economically and rapidly. 
         [0051]    In a development of the invention, the wall has at least a second flat surface, against which a counterbrace can be placed. 
         [0052]    In a development of the invention, the first surface is disposed on an external or internal surface of the wall and the second surface is disposed at a location opposite to the first surface on an internal or external surface of the wall, respectively. In this way, the sonotrode and the counterbrace can be positioned on the nozzle in a simple manner and an effective transfer of ultrasonic energy to the nozzle can occur during the examination of the nozzles. For example, the first flat surface can be disposed on the external surface of a swirl chamber and the second flat surface can be disposed at a location opposite to the first flat surface on the internal surface of the swirl chamber. 
         [0053]    In a development of the invention, the nozzle comprises a connecting flange in the form of an annular disk, and the periphery of the connecting flange is provided with the at least first flat surface, against which the sonotrode can be placed. 
         [0054]    In this way, nozzles equipped with an annular connecting flange can be designed such that the test method of the invention can be carried out rapidly and effectively. 
         [0055]    In a development of the invention, the nozzle comprises a connecting flange with a connecting screw thread, wherein the first flat surface is disposed in the region of the connecting screw thread and the connecting screw thread is partially discontinued in the region of the first flat surface. 
         [0056]    In this way, an effective transfer of ultrasonic energy to the connecting region can also be ensured in ceramic nozzles having a connecting thread. 
         [0057]    In a development of the invention, the nozzle is provided with a heat-reflecting mark. 
         [0058]    In this way, the mark can also be detected during the process of thermographic image evaluation so that thermographic evaluation or archiving of the test findings is facilitated considerably. 
         [0059]    Additional features and advantages of the invention are revealed in the claims and the following description of preferred embodiments of the invention with reference to the drawings. Individual features of the various embodiments shown can be combined in an arbitrary manner without going beyond the scope of the invention. In the drawings: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0060]      FIG. 1  is a side view of a nozzle of the invention and a testing device of the invention for carrying out the test method of the invention according to a first embodiment, 
           [0061]      FIG. 2  is a rear view of the testing device and the nozzle shown in  FIG. 1 , 
           [0062]      FIG. 3  shows the nozzle shown in  FIG. 1  in a testing device of the invention according to a second embodiment, 
           [0063]      FIG. 4  is an oblique top view of a testing device of the invention according to a third embodiment, 
           [0064]      FIG. 5  is a rear view of the testing device shown in  FIG. 4 , 
           [0065]      FIG. 6  is a side view of the testing device shown in  FIG. 4 , 
           [0066]      FIG. 7  is a top view of the testing device shown in  FIG. 4 , 
           [0067]      FIG. 8  is a rear view of a testing device of the invention according to a third embodiment, 
           [0068]      FIG. 9  is a side view of the testing device shown in  FIG. 8 , 
           [0069]      FIG. 10  is a top view of the testing device shown in  FIG. 8 , 
           [0070]      FIG. 11  is a rear view of the nozzle of the invention shown in  FIG. 1 , 
           [0071]      FIG. 12  is a partially cross-sectional side view of the nozzle shown in  FIG. 11 , 
           [0072]      FIG. 13  is a top view of the nozzle shown in  FIG. 10 , 
           [0073]      FIG. 14  is a partially cross-sectional front view of a nozzle of the invention according to a further embodiment, 
           [0074]      FIG. 15  is a top view of the nozzle shown in  FIG. 14 , and 
           [0075]      FIG. 16  is a side view of the nozzle shown in  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION  
       [0076]    The illustration shown in  FIG. 1  is a side view of a nozzle  10  composed of ceramic material. The nozzle  10  comprises an annular connecting flange  12 , an approximately cylindrical swirl chamber  14 , and an inlet tube  16  adapted to interconnect the connecting flange and the swirl chamber  14 . The swirl chamber is provided with an outlet orifice  18 . 
         [0077]    The nozzle  10  is clamped in a testing device  20  shown only partially in the figure. More specifically, the testing device comprises a sonotrode  22  for the transfer of ultrasonic energy and a counterbrace  24 . The connecting flange  12  is clamped between the sonotrode  22  and the counterbrace  24 . A double arrow  26  signifies the generation of longitudinal vibration by the sonotrode  22 . An arrow  28  denotes a counteracting force applied by the counterbrace  24 . 
         [0078]    The sonotrode  22  is provided with a stamper  36 . A disk  46  composed of beechwood is disposed between the stamper  36  and the connecting flange  12 . The disk  46  serves as a resilient intermediate component and prevents the periphery of the connecting flange  12  composed of ceramic material from being damaged by the stamper  36 . However, the intermediate component causes only an acceptable loss of the transferred sonic power. The beechwood disk  46  has a modulus of elasticity of approximately 14,000 N/mm 2  and a thermal conductivity of 0.16 W/mK. Thus the heat inevitably evolved by the transfer of ultrasonic energy by means of the disk  46  can dissipate effectively toward the ambient atmosphere and does not lead to any destruction of the disk  46 . 
         [0079]    The illustration shown in  FIG. 2  is a rear view of the nozzle  10  and the testing device  20 , that is to say, a view showing the interior of the inlet of the nozzle  10 . The counterbrace  24  comprises an approximately V-shaped cutout  30 , in which the annular connecting flange  12  is accommodated. Thus the connecting flange  12  rests at its periphery against the counterbrace  24  at two points of contact  32 ,  34 . The sonotrode  22  rests by way of a stamper  36  against the periphery of the connecting flange  12  with interposition of the resilient disk  46 . In the region of a flat surface  38  on the periphery of the connecting flange  12 , the stamper  36  of the sonotrode  22  rests against the connecting flange, that is, against the disk  46 . Thus there is a flat region of contact between the stamper  36  and the periphery of the connecting flange  12  via the disk  46 . Taking the center of the flat region of contact of the stamper  36  as its point of contact between the sonotrode  22  and the connecting flange  12 , then it will be seen in  FIG. 2  that the two points of contact  32 ,  34  of the connecting flange  12  on the counterbrace  24  and the point of contact of the stamper  36  of the sonotrode  22  on the flat surface  38  of the connecting flange  12  form a symmetrical planar triangle. 
         [0080]    Thus the testing device  20  of the invention is capable of transferring ultrasonic energy to the connecting region of the nozzle  10  in an effective manner. At the same time, the nozzle  10  is capable of vibrating between the points of contact  32 ,  34  and the stamper  36  such that the ultrasonic energy transferred will be distributed uniformly across the walls of the nozzle  10 . 
         [0081]    Ultrasonic energy having a frequency of about 20 kHz is transferred to the nozzle  10  by means of the sonotrode  22 . Ultrasonic vibration is transferred to the nozzle  10  at a power level of from 150 W to 200 W. By this means, cracks and defects in the walls of the nozzle  10  are caused to heat up to a greater extent than the surrounding material. This heat can be detected by means of, for example, a thermal imaging camera having a sensitivity of 50 mK. 
         [0082]    The illustration shown in  FIG. 3  shows the nozzle  10  described with reference to  FIG. 1  in a partially illustrated testing device  40  according to a second embodiment of the invention. The testing device  40  comprises a sonotrode  22 , which is placed against a flat surface on the top face of the swirl chamber  14 , again with interposition of a resilient disk. A rod-shaped counterbrace  42  is inserted through the outlet orifice  18  of the nozzle  10  and rests on an internal surface of the cover of the swirl chamber  14  at a location opposite to the stamper  36  of the sonotrode  22 . Here again, a flat surface is provided for the purpose of ensuring a flat region of contact between the counterbrace  42  and the nozzle  10 . In order to illustrate the contact of the counterbrace  42  with the internal surface of the swirl chamber  14 , a cross-section of the nozzle  10  is shown in a circular region  44  in  FIG. 3 . 
         [0083]    In the testing device shown in  FIG. 3 , ultrasonic vibration is transferred to the cover of the swirl chamber  14  from outside and can thence propagate across the walls of the nozzle  10 . In the case of the testing device shown in  FIG. 1 , however, the ultrasonic energy is transferred to the connecting flange  12 , whence it can propagate to the walls of the nozzle  10 . As can be seen in the illustrations of the nozzle  10  shown in  FIG. 1  and in  FIG. 3 , the nozzle  10  has two portions of greater mass, namely the connecting flange  12  and the swirl chamber  14 , which are interconnected by the inlet tube  16 . The inlet  16  constitutes a very critical component both during operation and during fabrication of the nozzle, since the material of the nozzle is exposed to maximum stresses at this point. When ultrasonic energy is transferred either to the connecting flange  12 , as shown in  FIG. 1 , or to the region of the swirl chamber  14 , as shown in  FIG. 3 , the inlet is freely accessible for carrying out thermographic evaluation thereof. Thus the test method of the invention makes it possible to achieve reliable and thorough examination of ceramic nozzles, more particularly of the critical inlet  16 . 
         [0084]    The illustration shown in  FIG. 4  shows a further testing device  50  of the invention with the nozzle  10 . As in the case of the testing device  20  shown in  FIG. 1 , the testing device  50  comprises a sonotrode  22  and a counterbrace  24 , between which the connecting flange  12  of the nozzle  10  is clamped. A thermal imaging camera  52 —symbolically illustrated—is also provided, of which the field of view is directed toward the nozzle  10 . Such a thermal imaging camera is likewise present in the testing devices  20 ,  40  shown in  FIGS. 1 to 3  but is not shown in these figures for the sake of clarity. 
         [0085]    The testing device  50  further comprises a heat-reflecting mirror  54  in the form of a spherical shell-segment. The mirror  54  capable of reflecting heat rays extends over a peripheral region of 45°. The viewing direction of the thermal imaging camera  52  is directed toward the mirror  54 . Thus the thermal imaging camera  52  can evaluate the front side of the nozzle  10  located at the front in  FIG. 4  and also, via the mirror image of the nozzle  10  in the mirror  54 , the rear side of the nozzle and its surface located in front in the left half of  FIG. 4 . Furthermore, the spherical shell-shape of the mirror  54  makes it possible to detect and evaluate the underside and the top face of the nozzle  10  by means of the thermal imaging camera  52 . Thus substantially the entire external surface of the nozzle  10  can be evaluated thermographically without having to move the thermal imaging camera  52  or the mirror  54 . In this way, the nozzle  10  can be examined particularly rapidly and thoroughly. The testing device  50  can still be of an economical design, since there is no need to provide any traversing mechanisms for the thermal imaging camera  52 , the sonotrode  22 , the counterbrace  24 , or the mirror  54 . 
         [0086]    Advantageously, the thermal imaging camera  52  is equipped with a wide-angle lens having a detection range of approximately 45°, so that both the nozzle  10  and the mirror  54  can be recorded in a single image. Wide-angle lenses are further characterized by a greater depth of field so that the mirror  54  can be positioned further away from the thermal imaging camera  52 , if appropriate, so as to alleviate any fear of shadows being formed. Thus the thermal imaging camera  52  can capture sharp images of both the nozzle  10  itself and its mirror image in the mirror  54 . 
         [0087]    The illustration shown in  FIG. 5  is a rear view of the testing device  50 , that is to say, a view of the interior of the connecting flange  12  toward the swirl chamber  14 . 
         [0088]    The illustration shown in  FIG. 6  is a side view of the testing device  50 . 
         [0089]    The illustration shown in  FIG. 7  is a top view of the testing device  50 . The range of detection of 45° of the thermal imaging camera  52  and the reflecting angle of the mirror  54 , which is likewise 45°, can be seen in the figure. The range of detection of the thermal imaging camera  52  is in the form of a circular cone in order to make it possible to detect substantially the entire internal surface of the mirror  54 ; see  FIG. 4 . 
         [0090]    The illustration shown in  FIG. 8  is a rear view of a further testing device  60  of the invention, that is to say, a view of the connecting flange  12  of the nozzle  10 . The testing device  60  comprises a thermal imaging camera  52 , a sonotrode  22 , and a counterbrace  24  and it is further provided with two curved mirrors  62 ,  64 . The mirrors  62 ,  64  are composed of a heat-reflecting material and are in the form of aluminum plates, for example. The mirrors  62 ,  64  each comprise a plurality of flat surfaces that are inclined in relation to each other. 
         [0091]    The mirror  64  is placed in a location opposite to the thermal imaging camera  52  and it therefore makes it possible for the thermal imaging camera  52  to detect not only the front side of the nozzle  10  facing the camera but also the rear side of the nozzle  10  that is remote from the camera. Furthermore, the mirror  64  is curved so as to extend approximately concentrically with the inlet of the nozzle  10  such that the nozzle  10  can also be detected and evaluated from above and below. 
         [0092]    As can be seen from  FIG. 10 , the mirror  62  is disposed such that the front side of the nozzle  10  can be detected. Thus the mirrors  62 ,  64  and the thermal imaging camera  52  make it possible to evaluate, thermographically, substantially the entire external surface of the nozzle  10  during the testing procedure except for that side of the connecting flange  12  that is facing the observer in  FIG. 8 . 
         [0093]    The illustration shown in  FIG. 11  is a rear view of the nozzle  10  of the invention, that is to say, a view of the connecting flange  12  directed toward the interior of the swirl chamber  14 . The flat surface  38  on the periphery of the otherwise circular connecting flange  12  can be seen in the figure. As mentioned above, this flat surface  38  is provided for accommodation of the stamper  36  of the sonotrode  22 ; see  FIG. 2 . 
         [0094]    The illustration shown in  FIG. 12  is a partially cross-sectional view of the nozzle  10  shown in  FIG. 11 . On the external surface of the swirl chamber  14  there is disposed a first flat surface  70 , and the stamper  36  of the sonotrode  22  can be placed flat against said surface (see  FIG. 3 ) and is subjected to a pressing force. On the opposing internal surface of the swirl chamber  14  there is provided a second flat surface  72 , and the counterbrace  42  can then be placed flat against said surface and subjected to a pressing force; see  FIG. 3 . 
         [0095]    The illustration shown in  FIG. 13  clearly shows the flat surface  70  of a circular shape on the top face of the swirl chamber  14 . 
         [0096]    In  FIG. 12 , an external surface of the swirl chamber  14  is provided with a mark  74  in the form of a bar code. This mark  74  is applied in the form of a heat-reflecting coating, for example, by means of silver paint or a soft lead pencil. Thus this mark  74  also appears in the thermal image captured by the camera during thermographic evaluation of the nozzle being tested. This considerably facilitates the evaluation and also the archiving of the test findings. 
         [0097]    The illustration shown in  FIG. 14  is a partially cross-sectional front view of a nozzle  80  of the invention. The nozzle  80  comprises a connecting flange  82  provided with a male screw thread  84 , an approximately tubular inlet  86  (see  FIG. 15 ) and two swirl chambers  86 ,  88  that are connected to the connecting flange  82  by means of the inlet  86 . The swirl chambers  86 ,  88  are open to the atmosphere in mutually opposing directions by way of outlet orifices  90 ,  92 . The internal and external surfaces of the swirl chamber  88  shown in a partially cross-sectional view each comprise a flat surface for accommodation of a sonotrode or a counterbrace, respectively. 
         [0098]    A flat surface  94  the periphery of the connecting flange  82  can be seen in the side view of the nozzle  80  shown in  FIG. 16 . The male screw thread  84  is discontinued in the region of this flat surface. The flat surface  94  serves for accommodation of the stamper  36  of the sonotrode  22 ; see  FIG. 1 . In this way, effective transfer of ultrasonic energy is also possible when the connecting flange  82  is provided with a male screw thread  84 . The flat surface  94  can be rectangular, as shown, or alternatively of circular or oval in shape, for example, and it is dimensioned so as to be slightly larger than the stamper  36 .