EP0300315B1 - Shock wave generator for an apparatus for non-contact disintegration of concrements, present in a body - Google Patents

Shock wave generator for an apparatus for non-contact disintegration of concrements, present in a body Download PDF

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Publication number
EP0300315B1
EP0300315B1 EP88111054A EP88111054A EP0300315B1 EP 0300315 B1 EP0300315 B1 EP 0300315B1 EP 88111054 A EP88111054 A EP 88111054A EP 88111054 A EP88111054 A EP 88111054A EP 0300315 B1 EP0300315 B1 EP 0300315B1
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EP
European Patent Office
Prior art keywords
shock wave
plate
shock
wave generator
generator according
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EP88111054A
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German (de)
French (fr)
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EP0300315A1 (en
Inventor
Georg Dipl.-Ing. Köhler
Arnim Dipl.-Ing. Rohwedder
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Siemens AG
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Siemens AG
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/02—Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/18—Methods or devices for transmitting, conducting or directing sound
    • G10K11/26—Sound-focusing or directing, e.g. scanning
    • G10K11/30—Sound-focusing or directing, e.g. scanning using refraction, e.g. acoustic lenses

Definitions

  • the invention relates to a shock wave generator for a device for contactless crushing of concrements in the body of a living being, which has a liquid-filled housing with an outlet for shock waves and a shock wave source arranged opposite this, as well as means for focusing the shock waves on a focus, between which Shock wave source and the focus is arranged a plate-shaped body, the area located in the propagation path of the shock waves has a smaller cross-sectional area than a shock wave emanating from the shock wave source, so that only part of a shock wave passes through the plate-shaped body.
  • the plate-shaped body is made of a material whose acoustic impedance differs from that of the liquid. Since the cross-sectional area of the area of the plate-shaped body located in the propagation path of the shock waves is smaller than that of the shock wave, part of the shock wave can pass through the plate-shaped body unhindered, while another part of the shock wave passes through the plate-shaped body.
  • the part of the shock wave that passes through the plate-shaped body is multiplied by multiple reflections on the front and rear sides of the plate-shaped body into a sequence of shock wave fronts, the time interval between the shock wave fronts depends essentially on the thickness of the plate-shaped body.
  • a large number of shock wave fronts act on it Concrement, wherein the mechanical stresses generated in the concretion overlap, so that there is an improved shattering effect compared to a single shock wave front.
  • the course of the pressure p over time t occurs in the focus of the shock waves, as is shown qualitatively by way of example in FIG. 1.
  • This is composed of a theoretically infinitely large number of pressure pulses generated by multiple reflections which follow one another at constant time intervals, of which the pressure pulses 2a to 2d are shown by way of example. Their amplitudes decrease in the form of a geometric series.
  • the pressure pulses 2a to 2d are superimposed by a pressure pulse 1 which corresponds to that part of the shock wave that has not passed through the plate-shaped body. 1, the pressure pulse 1 has a time delay compared to the pressure pulse 2a, which occurs when the speed of sound propagation in the liquid is lower than in the plate-shaped body.
  • the pressure pulse 1 is ahead of the pressure pulse 2a.
  • the individual pressure pulses each have a very steep rise and a subsequent, essentially exponential drop, which generally has a so-called undershoot 3, ie a short-term, under certain circumstances, considerable underpressure occurs.
  • the resulting temporal course of the pressure which results from the addition of the pressure pulses, can also have such an undershoot.
  • the invention is therefore based on the object of designing a shock wave generator of the type mentioned in such a way that the time course of the pressure in the focus of the shock wave generator is largely freely selectable and losses due to reflections are avoided.
  • the plate-shaped body is formed from a material whose acoustic impedance corresponds essentially to that of the liquid and in which the sound propagation speed differs from that in the liquid.
  • shock wave behind the plate-shaped body the shock front of which has two parts staggered in time.
  • the time offset depends on the two sound propagation velocities and on the thickness of the plate-shaped body, the time offset being greater the thicker the plate-shaped body and the more the sound propagation speeds differ from one another. If such a shock wave converges in a focus, there is a temporal course of the pressure, as is shown, for example, in FIGS. 2 and 3. In the case of FIG. 2, there is a slight time offset of the parts of the shock wave, so that the pressure over time has two short successive pressure peaks in the focus, while in the case of FIG.
  • the second Pressure peak compensates the undershoot of the first part of the shock wave.
  • the height the pressure peaks depend, moreover, on the cross-sectional area of the corresponding parts of the shock wave, whereby in the case of FIG. 2 the delayed part of the shock wave has a cross-section which is only slightly small compared to the other part, while the cross section of the delayed part of the shock wave in the case of FIG. 3 is significantly less than that of the other part of the shock wave. Since the acoustic impedance of the plate-shaped body essentially corresponds to that of the liquid, it is ensured that no noteworthy reflections occur at the boundaries between the two, so that the shock wave passes through the plate-shaped body essentially without loss.
  • the shock wave source can be designed such that the means for focusing the shock waves are a direct component of the shock wave source.
  • the shock wave source then has e.g. a suitably shaped radiation surface from which already focused shock waves emanate.
  • the shock wave source is such that special means, e.g. Acoustic lenses or reflectors, for focusing the shock waves emitted by them
  • the plate-shaped body can either be arranged between the shock wave source and the means for focusing the shock waves or in the sense of the direction of propagation of the shock waves behind them. It is also possible to provide plate-shaped bodies both between the shock wave source and the means for focusing the shock waves and behind them.
  • the plate-shaped body has at least one opening in its area traversed by the shock wave and this is made centrally in the area traversed by the shock wave.
  • the plate-shaped body has several openings and the shock wave originating from the shock wave source has a circular cross-section, it is expedient if, according to one embodiment of the invention, the plate-shaped body has several in its area through which the shock wave passes Has sector-shaped openings, the tips of which lie on the central axis of the shock wave.
  • the shock wave generator according to the invention has a small overall length.
  • Fig. 1 shows the typical time course of the pressure in the focus of the shock wave generator according to the prior art.
  • a time course of the pressure can normally be used successfully for the destruction of concretions in the body of living beings, deviating time courses of the pressure are desirable in certain cases, as shown by way of example in FIGS. 2 and 3 and with the shock wave generator can not be easily generated according to the prior art.
  • the resulting time course of the pressure shown in FIG. 2 differs from that of FIG. 1 in that only two pressure peaks 4a and 4b immediately following one another are present.
  • the shock wave generator has a shock wave tube 8, which essentially consists of a tubular component 9 filled with a liquid, for example water, which has at its end an outlet opening 10 for shock waves, which is closed by a bellows 11, by means of which the shock wave tube 8 can be acoustically coupled to the body 5 of the living being.
  • the tubular component 9 has a shock wave source, ie it is closed by a flat membrane 12, which is arranged opposite a flat coil 13.
  • a high voltage supply 14 which contains a capacitor 15 which can be charged to, for example, 20 kV by means of a high voltage source 16. If the capacitor 15 is connected to the flat coil 13 by means of suitable switching means 17, the electrical energy stored in the capacitor 15 suddenly discharges into the flat coil 13, which builds up a magnetic field very quickly. A current is induced in the membrane 12, which consists of an electrically conductive material, which is opposite to the current in the flat coil 13 and generates an opposing magnetic field. Due to the force of the opposing field, the membrane 12 is suddenly repelled by the flat coil 13, as a result of which a unipolar shock wave is formed in the liquid in the tubular component 9.
  • this shock wave In order to be able to use this shock wave to destroy the calculus 6, it is focused by means of an acoustic lens 18 mounted in the tubular component 9. This is arranged in the tubular component such that its focal point F coincides with the concretion 6.
  • the shock wave which is coupled into the body 5 of the living being via the bellows 11, gives off part of its energy content to the concrement 6, which is brittle compared to the environment, by exerting tensile and compressive forces thereon, which break it down into several parts, which can be excreted naturally by the living being.
  • a plate-shaped body 19 which is formed from a material, is arranged between the membrane 12 and the focus F, more precisely between the membrane 12 and the acoustic lens 18. in which the speed of sound propagation differs from that in the liquid and its acoustic impedance corresponds substantially to that of the liquid to avoid reflections at the interfaces with the liquid.
  • the plate-shaped body 19 has a cross-sectional area which is smaller than that of the shock wave in its area passing through a shock wave emanating from the membrane, in that it is provided with a central opening 20.
  • a plane shock wave emanating from the membrane 12 passes through the plate-shaped body 19, it has two parts behind it which are staggered in time, the part of the shock wave which has passed through the opening 20 being the part of the shock wave which has the plate-shaped body 19 has passed, leads or lags, depending on whether the speed of sound propagation in the plate-shaped body 19 is lower or greater than in the liquid.
  • the time offset between the parts of the shock wave is greater, the more the sound propagation speeds in the plate-shaped body 19 and the liquid differ from one another and the thicker the plate-shaped body 19 is.
  • shock wave with its temporally offset parts is focused by means of the acoustic lens 18, there is a pressure curve for a small temporal offset between its parts in focus F, as is shown by way of example in FIG. 2, while the temporal curve of the pressure in focus F for a shock wave, the parts of which have a greater time offset, is shown in FIG. 3. 2 and 3, the resulting time course of the pressure is shown in full lines, while the pressure courses associated with the parts of the shock wave that are offset in time are shown in dotted and dashed lines.
  • the amount of pressure that the parts of the shock wave offset in time in focus Incidentally, each generate depends on the cross-sectional areas of the temporally staggered parts of the shock wave before focusing and thus on the cross-sectional area of the area of the plate-shaped body 19 traversed by the shock wave or the cross-sectional area of the opening 20 made therein.
  • both parts of the shock wave have essentially the same cross section before focusing, while in the case of FIG. 3 the trailing part of the shock wave has a small cross section in comparison to the rest of the shock wave.
  • the opening 20 - a variety of other time profiles of the pressure can be created will be realized. It is also possible to arrange the opening 20 eccentrically in the plate-shaped body 19 and to vary its shape.
  • FIG. 5 shows a shock wave generator, which differs from the one described above essentially in that several plate-shaped bodies 21 to 23 are provided between the membrane 12 and the focus F, which, as can be seen from the different hatching, from consist of different materials and have different thicknesses, that is to say they are geometrically different.
  • the plate-shaped bodies 21, 22 and 23 abut one another with their mutually facing surfaces and are accommodated in the tubular component 9 so that they can be rotated relative to one another by means of the actuating levers 24 to 26.
  • the plate-shaped bodies 21, 22 and 23 each have three circular sector-shaped openings 27, 28 and 29 and can be positioned relative to one another by means of the adjusting levers 24 to 26 such that their areas, which are traversed by a shock wave emanating from the membrane 12, at least partially overlap.
  • the plate-shaped bodies 21 to 23 By suitable rotation of the plate-shaped bodies 21 to 23 relative to one another, they can be brought into such a position relative to one another that a unipolar shock wave emanating from the membrane 12 has up to four parts staggered in time behind the plate-shaped bodies 21 to 23. Accordingly, temporal profiles of the pressure can be realized in focus F, as indicated by way of example in FIGS.
  • FIG. 7 shows a time course of the pressure in which the undershoot of the part of the shock wave arriving first at focus F is practically completely compensated by the following parts of the shock wave
  • FIG. 8 shows a time course of the pressure with three successive ones Pressure peaks 31 to 33 shows.
  • FIG. 9 shows a shock wave generator according to the invention which differs from those described above in that its membrane 34 is spherically curved and a correspondingly curved coil 35 is arranged opposite it.
  • the membrane 34 closes a tubular component 36 of frustoconical shape at the larger end thereof.
  • the outlet opening 37, located at the smaller end of the tubular component 36, for the shock waves emanating from the membrane 34 is again closed by a bellows, which bears the reference number 38 and serves for the acoustic coupling of the shock wave generator.
  • a shock wave emanating from the membrane 34 is concentrated anyway in the focus F, which corresponds to the center of curvature of the spherical membrane 34.
  • the membrane 34 also takes over the function of the means for focusing the shock waves.
  • a plate-shaped body 39 Arranged between the membrane 34 and the focus F is a plate-shaped body 39 which is formed from a material whose acoustic impedance corresponds essentially to that of the liquid and in which the speed of sound propagation differs from that in the liquid.
  • the plate-shaped body 39 is spherically curved, its center of curvature coinciding with that of the membrane 34.
  • the plate-shaped body 39 In its center, the plate-shaped body 39 has an opening 34 of frustoconical shape which has such an opening angle that its imaginary tip coincides with the center of curvature of the membrane 34 and the plate-shaped body 39, ie with the focus F.
  • a shock wave generator temporal profiles of the pressure can be realized in focus F, as shown by way of example in FIGS. 2 and 3.
  • the exemplary embodiments relate exclusively to those shock wave generators in which the shock waves are generated by means of a membrane which can be driven in a shock-like manner.
  • the shock wave generator according to the invention can also contain other shock wave sources, e.g. those in which the shock waves are generated by underwater spark discharges, by piezoelectric means or by the impact of a laser beam on a highly absorbent object in the liquid.
  • the plate-shaped bodies in particular with regard to the shape of the perforations, can be designed differently than described in connection with the exemplary embodiments, provided that they are only suitable with regard to their geometric design and their material to produce a shock wave in the manner described which has portions that are offset in time.

Description

Die Erfindung betrifft einen Stoßwellengenerator für eine Einrichtung zum berührungslosen Zertrümmern von Konkrementen im Körper eines Lebewesens, welcher ein mit einer Flüssigkeit gefülltes Gehäuse mit einer Austrittsöffnung für Stoßwellen und eine dieser gegenüberliegend angeordnete Stoßwellenquelle sowie Mittel zum Fokussieren der Stoßwellen auf einen Fokus aufweist, wobei zwischen der Stoßwellenquelle und dem Fokus ein plattenförmiger Körper angeordnet ist, dessen im Ausbreitungsweg der Stoßwellen befindlicher Bereich eine geringere Querschnittsfläche als eine von der Stoßwellenquelle ausgehende Stoßwelle aufweist, so daß jeweils nur ein Teil einer Stoßwelle den plattenförmigen Körper durchläuft.The invention relates to a shock wave generator for a device for contactless crushing of concrements in the body of a living being, which has a liquid-filled housing with an outlet for shock waves and a shock wave source arranged opposite this, as well as means for focusing the shock waves on a focus, between which Shock wave source and the focus is arranged a plate-shaped body, the area located in the propagation path of the shock waves has a smaller cross-sectional area than a shock wave emanating from the shock wave source, so that only part of a shock wave passes through the plate-shaped body.

Ein solcher Stoßwellengenerator ist in der DE-PS 32 40 691 beschrieben. Dabei ist der plattenförmige Körper aus einem Werkstoff gebildet, dessen akustische Impedanz von der der Flüssigkeit abweicht. Da die Querschnittsfläche des im Ausbreitungsweg der Stoßwellen befindlichen Bereiches des plattenförmigen Körpers geringer als die der Stoßwelle ist, kann ein Teil der Stoßwelle den plattenförmigen Körper ungehindert passieren, während ein anderer Teil der Stoßwelle den plattenförmigen Körper durchläuft. Da die akustische Impedanz des plattenförmigen Körpers von der der Flüssigkeit abweicht, wird derjenige Teil der Stoßwelle, der den plattenförmigen Körper durchläuft, durch Vielfachreflexionen an der Vorder- und Hinterseite des plattenförmigen Körpers in eine Folge von Stoßwellenfronten vervielfacht, wobei der zeitliche Abstand zwischen den Stoßwellenfronten wesentlich von der Dicke des plattenförmigen Körpers abhängt. Außer demjenigen Teil der Stoßwelle, der den plattenförmigen Körper ungehindert passiert, wirken somit eine Vielzahl von Stoßwellenfronten auf das Konkrement ein, wobei sich die jeweils in dem Konkrement erzeugten mechanischen Spannungen überlagern, so daß sich eine gegenüber einer einziger Stoßwellenfront verbesserte Zertrümmerungswirkung ergibt.Such a shock wave generator is described in DE-PS 32 40 691. The plate-shaped body is made of a material whose acoustic impedance differs from that of the liquid. Since the cross-sectional area of the area of the plate-shaped body located in the propagation path of the shock waves is smaller than that of the shock wave, part of the shock wave can pass through the plate-shaped body unhindered, while another part of the shock wave passes through the plate-shaped body. Since the acoustic impedance of the plate-shaped body differs from that of the liquid, the part of the shock wave that passes through the plate-shaped body is multiplied by multiple reflections on the front and rear sides of the plate-shaped body into a sequence of shock wave fronts, the time interval between the shock wave fronts depends essentially on the thickness of the plate-shaped body. In addition to the part of the shock wave that passes freely through the plate-shaped body, a large number of shock wave fronts act on it Concrement, wherein the mechanical stresses generated in the concretion overlap, so that there is an improved shattering effect compared to a single shock wave front.

Bei dem bekannten Stoßwellengenerator tritt im Fokus der Stoßwellen ein Verlauf des Druckes p über der Zeit t auf, wie er in Fig. 1 qualitativ beispielhaft dargestellt ist. Dieser setzt sich zusammen aus einer theoretisch unendlich großen Zahl von durch Vielfachreflexionen erzeugten, in konstanten zeitlichen Abständen aufeinanderfolgenden Druckimpulsen, von denen beispielhaft die Druckimpulse 2a bis 2d dargestellt sind. Deren Amplituden nehmen in der Form einer geometrischen Reihe ab. Den Druckimpulsen 2a bis 2d überlagert sich ein Druckimpuls 1, der demjenigen Teil der Stoßwelle entspricht, der den plattenförmigen Körper nicht durchlaufen hat. Im Falle des zeitlichen Verlaufes des Druckes nach Fig. 1 weist der Druckimpuls 1 gegenüber dem Druckimpuls 2a eine zeitliche Verzögerung auf, die dann auftritt, wenn die Schallausbreitungsgeschwindigkeit in der Flüssigkeit geringer als in dem plattenförmigen Körper ist. Im umgekehrten Falle tritt eine zeitliche Voreilung des Druckimpulses 1 gegenüber dem Druckimpuls 2a auf. Die einzelnen Druckimpulse weisen jeweils einen sehr steilen Anstieg und einen sich daran anschließenden im wesentlichen exponentiellen Abfall auf, der in der Regel einen sogenannten Unterschwinger 3 aufweist, d.h. es tritt kurzfristig ein unter Umständen erheblicher Unterdruck auf. Einen solchen Unterschwinger kann auch der resultierende zeitliche Verlauf des Druckes, der sich aus der Addition der Druckimpulse ergibt, aufweisen. Es gibt Anzeichen dafür, daß der beim Abfall des Druckes im Bereich des Unterschwingers auftretende Unterdruck Schädigungen des ein zu zertrümmerndes Konkrement umgebenden Gewebes durch Kavitationserscheinungen hervorruft. Druckverläufe, die keinen Unterschwinger aufweisen und gleichzeitig zur Zertrümmerung von Konkrementen geeignet sind, können mit dem bekannten Stoßwellengenerator nicht ohne weiteres erzeugt werden. Außerdem ist es infolge der Vielzahl der infolge von Vielfachreflexionen auftretenden Druckimpulse bei dem bekannten Stoßwellengenerator nur in sehr beschränktem Umfang möglich, auf den sich im Fokus ergebenden zeitlichen Verlauf des Druckes Einfluß zu nehmen. Desweiteren ist es von Nachteil, daß die Vielfachreflexionen an den Grenzflächen zwischen dem plattenförmigen Körper und der Flüssigkeit mit Verlusten verbunden sind.In the known shock wave generator, the course of the pressure p over time t occurs in the focus of the shock waves, as is shown qualitatively by way of example in FIG. 1. This is composed of a theoretically infinitely large number of pressure pulses generated by multiple reflections which follow one another at constant time intervals, of which the pressure pulses 2a to 2d are shown by way of example. Their amplitudes decrease in the form of a geometric series. The pressure pulses 2a to 2d are superimposed by a pressure pulse 1 which corresponds to that part of the shock wave that has not passed through the plate-shaped body. 1, the pressure pulse 1 has a time delay compared to the pressure pulse 2a, which occurs when the speed of sound propagation in the liquid is lower than in the plate-shaped body. In the opposite case, the pressure pulse 1 is ahead of the pressure pulse 2a. The individual pressure pulses each have a very steep rise and a subsequent, essentially exponential drop, which generally has a so-called undershoot 3, ie a short-term, under certain circumstances, considerable underpressure occurs. The resulting temporal course of the pressure, which results from the addition of the pressure pulses, can also have such an undershoot. There are indications that the negative pressure occurring in the area of the undershoot when the pressure drops causes damage to the tissue surrounding a concretion to be broken up by cavitation phenomena. Pressure curves which have no undershoot and are at the same time suitable for crushing concrements cannot easily be generated with the known shock wave generator. In addition, due to the large number of pressure pulses occurring as a result of multiple reflections in the known shock wave generator, it is only possible to a very limited extent to influence the temporal course of the pressure that results in the focus. Furthermore, it is disadvantageous that the multiple reflections at the interfaces between the plate-shaped body and the liquid are associated with losses.

Der Erfindung liegt daher die Aufgabe zugrunde, einen Stoßwellengenerator der eingangs genannten Art so auszubilden, daß der zeitliche Verlauf des Druckes im Fokus des Stoßwellengenerators weitgehend frei wählbar ist und Verluste infolge von Reflexionen vermieden sind.The invention is therefore based on the object of designing a shock wave generator of the type mentioned in such a way that the time course of the pressure in the focus of the shock wave generator is largely freely selectable and losses due to reflections are avoided.

Nach der Erfindung wird diese Aufgabe dadurch gelöst, daß der plattenförmige Körper aus einem Werkstoff gebildet ist, dessen akustische Impedanz im wesentlichen der der Flüssigkeit entspricht und in dem die Schallausbreitungsgeschwindigkeit von der in der Flüssigkeit abweicht. Infolge der voneinander abweichenden Schallausbreitungsgeschwindigkeiten in dem plattenförmigen Körper und in der Flüssigkeit liegt somit hinter dem plattenförmigen Körper eine zeitliche Verzögerung zwischen demjenigen Teil der Stoßwelle, der den plattenförmigen Körper durchläuft, und demjenigen Teil der Stoßwelle, der sich ausschließlich in der Flüssigkeit ausbreitet, vor, wobei der Teil der Stoßwelle, der den plattenförmigen Körper durchläuft, dem übrigen Teil der Stoßwelle entweder nach- oder voreilt, je nachdem, ob die Schallausbreitungsgeschwindigkeit in dem plattenförmigen Körper geringer oder größer als die in der Flüssigkeit ist. Es liegt somit hinter dem plattenförmigen Körper eine Stoßwelle vor, deren Stoßfront zwei zeitlich zueinander versetzte Teile aufweist. Dabei hängt der zeitliche Versatz von den beiden Schallausbreitungsgeschwindigkeiten und von der Dikke des plattenförmigen Körpers ab, wobei der zeitliche Versatz um so größer ist, je dicker der plattenförmige Körper ist und je stärker die Schallausbreitungsgeschwindigkeiten voneinander abweichen. Läuft eine solche Stoßwelle in einem Fokus zusammen, ergibt sich dort ein zeitlicher Verlauf des Druckes, wie er beispielsweise in den Fig. 2 und 3 dargestellt ist. Im Falle der Fig. 2 liegt ein geringer zeitlicher Versatz der Teile der Stoßwelle vor, so daß der zeitliche Verlauf des Druckes im Fokus zwei kurz aufeinanderfolgende Druckspitzen aufweist, während im Falle der Fig. 3 ein vergleichsweise großer zeitlicher Versatz vorliegt, so daß die zweite Druckspitze den Unterschwinger des ersten Teiles der Stoßwelle kompensiert. Die Höhe der Druckspitzen hängt übrigens von der Querschnittsfläche der entsprechenden Teile der Stoßwelle ab, wobei im Falle der Fig. 2 der verzögerte Teil der Stoßwelle einen gegenüber der anderem Teil nur geringfügig kleiner Querschnitt aufweist, während der Querschnitt des verzögerten Teiles der Stoßwelle im Falle der Fig. 3 erheblich geringer als der des anderen Teiles der Stoßwelle ist. Da die akustische Impedanz des plattenförmigen Körpers im wesentlichen der der Flüssigkeit entspricht, ist sichergerstellt, daß an den Grenzen zwischen beiden keine nennenswerten Reflexionen auftreten, so daß die Stoßwelle den plattenförmigen Körper im wesentlichen verlustfrei durchläuft.According to the invention, this object is achieved in that the plate-shaped body is formed from a material whose acoustic impedance corresponds essentially to that of the liquid and in which the sound propagation speed differs from that in the liquid. As a result of the differing speeds of sound propagation in the plate-shaped body and in the liquid, there is a time lag behind that part of the shock wave that passes through the plate-shaped body and that part of the shock wave that only propagates in the liquid behind the plate-shaped body. the part of the shock wave that passes through the plate-shaped body either leads or lags the remaining part of the shock wave, depending on whether the speed of sound propagation in the plate-shaped body is lower or greater than that in the liquid. There is therefore a shock wave behind the plate-shaped body, the shock front of which has two parts staggered in time. The time offset depends on the two sound propagation velocities and on the thickness of the plate-shaped body, the time offset being greater the thicker the plate-shaped body and the more the sound propagation speeds differ from one another. If such a shock wave converges in a focus, there is a temporal course of the pressure, as is shown, for example, in FIGS. 2 and 3. In the case of FIG. 2, there is a slight time offset of the parts of the shock wave, so that the pressure over time has two short successive pressure peaks in the focus, while in the case of FIG. 3 there is a comparatively large time offset, so that the second Pressure peak compensates the undershoot of the first part of the shock wave. The height the pressure peaks depend, moreover, on the cross-sectional area of the corresponding parts of the shock wave, whereby in the case of FIG. 2 the delayed part of the shock wave has a cross-section which is only slightly small compared to the other part, while the cross section of the delayed part of the shock wave in the case of FIG. 3 is significantly less than that of the other part of the shock wave. Since the acoustic impedance of the plate-shaped body essentially corresponds to that of the liquid, it is ensured that no noteworthy reflections occur at the boundaries between the two, so that the shock wave passes through the plate-shaped body essentially without loss.

Im Falle der Erfindung kann die Stoßwellenquelle so ausgebildet sein, daß die Mittel zum Fokussieren der Stoßwellen unmittelbarer Bestandteil der Stoßwellenquelle sind. Die Stoßwellenquelle weist dann z.B. eine geeignet geformte Abstrahlfläche auf, von der bereits fokussierte Stoßwellen ausgehen. Falls die Stoßwellenquelle so beschaffen ist, daß besondere Mittel, z.B. akustische Linsen oder Reflektoren, zum Fokussieren der von ihr ausgesandten Stoßwellen erforderlich sind, kann der plattenförmige Körper entweder zwischen der Stoßwellenquelle und den Mitteln zum Fokussieren der Stoßwellen oder im Sinne der Ausbreitungsrichtung der Stoßwellen hinter diesen angeordnet sein. Außerdem besteht die Möglichkeit, plattenförmige Körper sowohl zwischen der Stoßwellenquelle und den Mitteln zum Fokussieren der Stoßwellen als auch hinter diesen vorzusehen.In the case of the invention, the shock wave source can be designed such that the means for focusing the shock waves are a direct component of the shock wave source. The shock wave source then has e.g. a suitably shaped radiation surface from which already focused shock waves emanate. If the shock wave source is such that special means, e.g. Acoustic lenses or reflectors, for focusing the shock waves emitted by them, the plate-shaped body can either be arranged between the shock wave source and the means for focusing the shock waves or in the sense of the direction of propagation of the shock waves behind them. It is also possible to provide plate-shaped bodies both between the shock wave source and the means for focusing the shock waves and behind them.

Nach Varianten der Erfindung kann vorgesehen sein, daß der plattenförmige Körper in seinem von der Stoßwelle durchlaufenen Bereich wenigstens eine Durchbrechung aufweist und diese mittig in dem von der Stoßwelle durchlaufenen Bereich angebracht ist.According to variants of the invention, it can be provided that the plate-shaped body has at least one opening in its area traversed by the shock wave and this is made centrally in the area traversed by the shock wave.

Soll der plattenförmige Körper mehrere Durchbrechungen aufweisen und besitzt die von der Stoßwellenquelle ausgehende Stoßwelle einen kreisförmigen Querschnitt, ist es zweckmäßig, wenn nach einer Ausführung der Erfindung der plattenförmige Körper in seinem von der Stoßwelle durchlaufenen Bereich mehrere kreissektorförmige Durchbrechungen aufweist, deren Spitzen auf der Mittelachse der Stoßwelle liegen.If the plate-shaped body has several openings and the shock wave originating from the shock wave source has a circular cross-section, it is expedient if, according to one embodiment of the invention, the plate-shaped body has several in its area through which the shock wave passes Has sector-shaped openings, the tips of which lie on the central axis of the shock wave.

Besonders vielfältige Variationen des zeitlichen Verlaufes des Druckes im Fokus sind möglich, wenn zwischen der Stoßwellenquelle und der Austrittsöffnung mehrere plattenförmige Körper aufeinanderfolgend angebracht sind, deren von der Stoßwelle durchlaufene Bereiche einander zumindest teilweise überdecken, wobei die plattenförmigen Körper geometrisch unterschiedlich ausgebildet sein und aus unterschiedlichen Werkstoffen bestehen können. Zusätzliche Variationen des zeitlichen Verlaufes des Druckes im Fokus sind möglich, wenn die plattenförmigen Körper gegeneinander verdrehbar sind. Ein weitere Variante der Erfindung sieht vor, daß die plattenförmigen Körper mit ihren einander zugewandten Flächen aneinander anliegen. Durch diese Maßnahme weist der erfindungsgemäße Stoßwellengenerator eine geringe Baulänge auf.Particularly diverse variations of the pressure over time in the focus are possible if several plate-shaped bodies are successively attached between the shock wave source and the outlet opening, the areas through which the shock wave passes at least partially overlap one another, the plate-shaped bodies being of different geometries and made of different materials can exist. Additional variations in the time course of the pressure in the focus are possible if the plate-shaped bodies can be rotated relative to one another. Another variant of the invention provides that the plate-shaped bodies with their mutually facing surfaces lie against each other. As a result of this measure, the shock wave generator according to the invention has a small overall length.

In dem Artikel "Acoustic lens design" in ULTRASONICS, Band 7, Nr. 2, April 1969, Seiten 98 bis 100, ist im Zusammenhang mit in Wasser zu verwendenden akustischen Linsen dargelegt, daß diese aus einem Material bestehen sollten, dessen akustische Impedanz der von Wasser möglichst genau entspricht, um Reflexionen zu minimieren, daß die Schallausbreitungsgeschwindigkeit in dem Linsenmaterial von der von Wasser stark abweichen sollte, um einen hohen Brechungsindex zu erhalten, und daß es einfach möglich sein sollte, die Linse in der erforderlichen Form herzustellen. Eine Anzahl von denkbaren Linsenmaterialien ist unter Angabe der akustischen Impedanzen und Schallausbreitungsgeschwindigkeiten aufgeführt.In the article "Acoustic lens design" in ULTRASONICS, Volume 7, No. 2, April 1969, pages 98 to 100, it is stated in connection with acoustic lenses to be used in water that they should consist of a material whose acoustic impedance is of water corresponds as closely as possible to minimize reflections, that the speed of sound propagation in the lens material should differ greatly from that of water in order to obtain a high refractive index and that it should be easily possible to manufacture the lens in the required form. A number of conceivable lens materials are listed, with details of acoustic impedances and sound propagation speeds.

Die Erfindung ist anhand der beigefügten Zeichnungen dargestellt. Es zeigen:

Fig. 1
den zeitlichen Verlauf des Druckes im Fokus eines Stoßwellengenerators nach dem Stand der Technik,
Fig. 2 und 3
Beispiele für den zeitlichen Verlauf des Druckes im Fokus eines erfindungsgemäßen Stoßwellengenerators,
Fig. 4
in schematischer Darstellung einen Längsschnitt durch einen erfindungsgemäßen Stoßwellengenerator,
Fig. 5
in schematischer Darstellung einen Längsschnitt durch einen weiteren erfindungsgemäßen Stoßwellengenerator,
Fig. 6
einen Schnitt entsprechend der Linie VI-VI in Fig. 5,
Fig. 7 und 8
Beispiele für den zeitlichen Verlauf des Druckes im Fokus des Stoßwellengenerators nach den Fig. 5 und 6, und
Fig. 9
in schematischer Darstellung einen Längsschitt durch einen erfindungsgemäßen Stoßwellengenerator.
The invention is illustrated with reference to the accompanying drawings. Show it:
Fig. 1
the time course of the pressure in the focus of a shock wave generator according to the prior art,
2 and 3
Examples of the time course of the pressure in the focus of a shock wave generator according to the invention,
Fig. 4
a schematic representation of a longitudinal section through a shock wave generator according to the invention,
Fig. 5
a schematic representation of a longitudinal section through a further shock wave generator according to the invention,
Fig. 6
5 shows a section along the line VI-VI in FIG. 5,
7 and 8
Examples of the time course of the pressure in the focus of the shock wave generator according to FIGS. 5 and 6, and
Fig. 9
a schematic representation of a longitudinal section through a shock wave generator according to the invention.

Die Fig. 1 zeigt den typischen zeitlichen Verlauf des Druckes im Fokus des Stoßwellengenerators nach dem Stand der Technik. Obwohl ein solcher zeitlicher Verlauf des Druckes normalerweise mit Erfolg zur Zertrümmerung von Konkrementen im Körper von Lebewesen verwendet werden kann, sind in bestimmten Fällen davon abweichende zeitliche Verläufe des Druckes wünschenswert, wie sie beispielhaft in den Fig. 2 und 3 dargestellt sind und mit dem Stoßwellengenerator nach dem Stand der Technik jedenfalls nicht ohne weiteres erzeugt werden können. Der in Fig. 2 ausgezogen dargestellte resultierende zeitliche Verlauf des Druckes unterscheidet sich von dem nach Fig. 1 dadurch, daß lediglich zwei zeitlich unmittelbar aufeinanderfolgende Druckspitzen 4a und 4b vorhanden sind. Ein solcher zeitlicher Verlauf des Drukkes kann bei bestimmten Arten von Konkrementen mit höherer Zuverlässigkeit zu deren Zertrümmerung führen, da das Konkrement durch die erste Druckspitze 4a zunächst in einen Spannungszustand versetzt wird, der es zwar "erschüttert", aber noch nicht zu seiner Zertrümmerung führt, dem sich dann durch die zweite Druckspitze 4b ausgeübte Spannungen überlagern, die um so sicherer zur Zertrümmerung des Konkrementes führen. Der in Fig. 3 ausgezogen dargestellte resultierende zeitliche Verlauf des Druckes unterscheidet sich von dem nach Fig. 1 dadurch, daß der in Fig. 1 vorhandene Unterschwinger 3 im wesentlichen fehlt. Ein zeitlicher Verlauf des Druckes ohne Unterschwinger ist deshalb wünschenswert, weil der im Bereich des Unterschwingers auftretende, unter Umständen erhebliche Unterdruck zu Kavitationserscheinungen und damit zu Schädigungen an dem das Konkrement umgebenden Gewebe führen kann.Fig. 1 shows the typical time course of the pressure in the focus of the shock wave generator according to the prior art. Although such a time course of the pressure can normally be used successfully for the destruction of concretions in the body of living beings, deviating time courses of the pressure are desirable in certain cases, as shown by way of example in FIGS. 2 and 3 and with the shock wave generator can not be easily generated according to the prior art. The resulting time course of the pressure shown in FIG. 2 differs from that of FIG. 1 in that only two pressure peaks 4a and 4b immediately following one another are present. Such a course of the pressure over time can lead to the destruction of certain types of calculus with greater reliability, since the calculus is first put into a stressed state by the first pressure peak 4a, which "shakes" but does not yet lead to its destruction, which is then superimposed by the stresses exerted by the second pressure peak 4b, which lead to the destruction of the concrement all the more reliably. The resulting time course of the pressure shown in FIG. 3 differs from that of FIG. 1 in that the undershoot 3 present in FIG. 1 is essentially missing. A time course of the pressure without an undershoot is desirable because the underpressure that occurs in the area of the undershoot, which may be considerable, can lead to cavitation and thus damage to the tissue surrounding the concrement.

In Fig. 4 ist ein erfindungsgemäßer Stoßwellengenerator zum Zertrümmern eines in einem Körper 5 eines Lebewesens befindlichen Konkrementes 6, z.B. eines Steins in einer Niere 7, dargestellt. Der Stoßwellengenerator weist ein Stoßwellenrohr 8 auf, das im wesentlichen aus einem mit einer Flüssigkeit, z.B. Wasser, gefüllten rohrförmigen Bauteil 9 besteht, das an seinem Ende eine Austrittsöffnung 10 für Stoßwellen aufweist, die durch einen Balg 11 verschlossen ist, mittels dessen das Stoßwellenrohr 8 an den Körper 5 des Lebewesens akustisch angekoppelt werden kann. An seinem anderen Ende weist das rohrförmige Bauteil 9 eine Stoßwellenquelle auf, d.h., es ist durch eine ebene Membran 12 verschlossen, der gegenüberliegend eine Flachspule 13 angeordnet ist. Um Stoßwellen erzeugen zu können, ist eine Hochspannungsversorgung 14 vorgesehen, die einen Kondensator 15 enthält, der mittels einer Hochspannungsquelle 16 auf z.B. 20 kV aufgeladen werden kann. Wird der Kondensator 15 mittels geeigneter Schaltmittel 17 mit der Flachspule 13 verbunden, entlädt sich die in dem Kondensator 15 gespeicherte elektrische Energie schlagartig in die Flachspule 13, die sehr schnell ein magnetisches Feld aufbaut. In der Membran 12, die aus einem elektrisch leitenden Werkstoff besteht, wird ein Strom induziert, der dem Strom in der Flachspule 13 entgegengerichtet ist und ein magnetisches Gegenfeld erzeugt. Durch die Kraftwirkung des Gegenfeldes wird die Membran 12 von der Flachspule 13 schlagartig abgestoßen, wodurch sich in der in dem rohrförmigen Bauteil 9 befindlichen Flüssigkeit eine unipolare Stoßwelle ausbildet. Um diese Stoßwelle zur Zerstörung des Konkrementes 6 nutzbar machen zu können, wird diese mittels einer in dem rohrförmigen Bauteil 9 angebrachten akustischen Linse 18 fokussiert. Diese ist in dem rohrförmigen Bauteil derart angeordnet, daß ihr Brennpunkt F mit dem Konkrement 6 zusammenfällt. Die Stoßwelle, die über den Balg 11 in den Körper 5 des Lebewesens eingekoppelt wird, gibt einen Teil ihres Energiegehaltes an das im Vergleich zur Umgebung spröde Konkrement 6 ab, indem sie Zug- und Druckkräfte auf dieses ausübt, die es in mehrere Teile zerlegen, die von dem Lebewesen auf natürlichem Wege ausgeschieden werden können.4 is a shock wave generator according to the invention for Shattering a concretion 6 located in a body 5 of a living being, for example a stone in a kidney 7. The shock wave generator has a shock wave tube 8, which essentially consists of a tubular component 9 filled with a liquid, for example water, which has at its end an outlet opening 10 for shock waves, which is closed by a bellows 11, by means of which the shock wave tube 8 can be acoustically coupled to the body 5 of the living being. At its other end, the tubular component 9 has a shock wave source, ie it is closed by a flat membrane 12, which is arranged opposite a flat coil 13. In order to be able to generate shock waves, a high voltage supply 14 is provided which contains a capacitor 15 which can be charged to, for example, 20 kV by means of a high voltage source 16. If the capacitor 15 is connected to the flat coil 13 by means of suitable switching means 17, the electrical energy stored in the capacitor 15 suddenly discharges into the flat coil 13, which builds up a magnetic field very quickly. A current is induced in the membrane 12, which consists of an electrically conductive material, which is opposite to the current in the flat coil 13 and generates an opposing magnetic field. Due to the force of the opposing field, the membrane 12 is suddenly repelled by the flat coil 13, as a result of which a unipolar shock wave is formed in the liquid in the tubular component 9. In order to be able to use this shock wave to destroy the calculus 6, it is focused by means of an acoustic lens 18 mounted in the tubular component 9. This is arranged in the tubular component such that its focal point F coincides with the concretion 6. The shock wave, which is coupled into the body 5 of the living being via the bellows 11, gives off part of its energy content to the concrement 6, which is brittle compared to the environment, by exerting tensile and compressive forces thereon, which break it down into several parts, which can be excreted naturally by the living being.

Um den zeitlichen Verlauf des Druckes im Fokus F des Stoßwellengenerators beeinflussen zu können, ist zwischen der Membran 12 und dem Fokus F, genauer gesagt zwischen der Membran 12 und der akustischen Linse 18, ein plattenförmiger Körper 19 angeordnet, der aus einem Werkstoff gebildet ist, in dem die Schallausbreitungsgeschwindigkeit von der in der Flüssigkeit abweicht und dessen akustische Impedanz zur Vermeidung von Reflexionen an den Grenzflächen zu der Flüssigkeit im wesentlichen der der Flüssigkeit entspricht. Der plattenförmige Körper 19 weist in seinem von einer von der Membran ausgehenden Stoßwelle durchlaufenden Bereich eine Querschnittsfläche auf, die kleiner als die der Stoßwelle ist, indem er mit einer mittigen Durchbrechung 20 versehen ist. Durchläuft eine von der Membran 12 ausgehende ebene Stoßwelle den plattenförmigen Körper 19, weist sie hinter diesem zwei Teile auf, die zeitlich gegeneinander versetzt sind, wobei derjenige Teil der Stoßwelle, der die Durchbrechung 20 durchlaufen hat, demjenigen Teil der Stoßwelle, der den plattenförmigen Körper 19 durchlaufen hat, vor- oder nacheilt, je nachdem, ob die Schallausbreitungsgeschwindigkeit in dem plattenförmigen Körper 19 geringer oder größer als in der Flüssigkeit ist. Dabei ist der zeitliche Versatz zwischen den Teilen der Stoßwelle um so größer, je stärker die Schallausbreitungsgeschwindigkeiten in dem plattenförmigen Körper 19 und der Flüssigkeit voneinander abweichen und je dikker der plattenförmige Körper 19 ist. Wird die Stoßwelle mit ihren zeitlich zueinander versetzten Teilen mittels der akustischen Linse 18 fokussiert, ergibt sich für einen geringen zeitlichen Versatz zwischen ihren Teilen im Fokus F ein Druckverlauf, wie er beispielhaft in Fig. 2 dargestellt ist, während der zeitliche Verlauf des Druckes im Fokus F für eine Stoßwelle, deren Teile einen größeren zeitlichen Versatz aufweisen, in Fig. 3 dargestellt ist. Dabei ist in den Fig. 2 und 3 der resultierende zeitliche Verlauf des Druckes jeweils ausgezogen dargestellt, während die zu den zeitlich gegeneinander versetzten Teilen der Stoßwelle gehörigen Druckverläufe punktiert bzw. strichliert angedeutet sind. Die Höhe des Druckes, die die zeitlich gegeneinander versetzten Teile der Stoßwelle im Fokus jeweils erzeugen, hängt übrigens von den Querschnittsflächen der zeitlich zueinander versetzten Teile der Stoßwelle vor der Fokussierung und damit von der Querschnittsfläche des von der Stoßwelle durchlaufenen Bereiches des plattenförmigen Körpers 19 bzw. der Querschnittsfläche der in diesem angebrachten Durchbrechung 20 ab. So weisen im Falle der Fig. 2 beide Teile der Stoßwelle vor der Fokussierung im wesentlichen den gleichen Querschnitt auf, während im Falle der Fig. 3 der nacheilende Teil der Stoßwelle einen in Vergleich zum übrigen Teil der Stoßwelle geringen Querschnitt aufweist.In order to be able to influence the time course of the pressure in the focus F of the shock wave generator, a plate-shaped body 19, which is formed from a material, is arranged between the membrane 12 and the focus F, more precisely between the membrane 12 and the acoustic lens 18. in which the speed of sound propagation differs from that in the liquid and its acoustic impedance corresponds substantially to that of the liquid to avoid reflections at the interfaces with the liquid. The plate-shaped body 19 has a cross-sectional area which is smaller than that of the shock wave in its area passing through a shock wave emanating from the membrane, in that it is provided with a central opening 20. If a plane shock wave emanating from the membrane 12 passes through the plate-shaped body 19, it has two parts behind it which are staggered in time, the part of the shock wave which has passed through the opening 20 being the part of the shock wave which has the plate-shaped body 19 has passed, leads or lags, depending on whether the speed of sound propagation in the plate-shaped body 19 is lower or greater than in the liquid. The time offset between the parts of the shock wave is greater, the more the sound propagation speeds in the plate-shaped body 19 and the liquid differ from one another and the thicker the plate-shaped body 19 is. If the shock wave with its temporally offset parts is focused by means of the acoustic lens 18, there is a pressure curve for a small temporal offset between its parts in focus F, as is shown by way of example in FIG. 2, while the temporal curve of the pressure in focus F for a shock wave, the parts of which have a greater time offset, is shown in FIG. 3. 2 and 3, the resulting time course of the pressure is shown in full lines, while the pressure courses associated with the parts of the shock wave that are offset in time are shown in dotted and dashed lines. The amount of pressure that the parts of the shock wave offset in time in focus Incidentally, each generate depends on the cross-sectional areas of the temporally staggered parts of the shock wave before focusing and thus on the cross-sectional area of the area of the plate-shaped body 19 traversed by the shock wave or the cross-sectional area of the opening 20 made therein. Thus, in the case of FIG. 2, both parts of the shock wave have essentially the same cross section before focusing, while in the case of FIG. 3 the trailing part of the shock wave has a small cross section in comparison to the rest of the shock wave.

Durch geeignete Wahl des Werkstoffes und der Dicke des plattenförmigen Körpers 19 sowie des Verhältnisses des Querschnittes des von der Stoßwelle durchlaufenen Bereiches des Körpers 19 zum Querschnitt der Stoßwelle - im Falle des beschriebenen Ausführungsbeispieles also der Durchbrechung 20 - kann eine Vielzahl von anderen zeitlichen Verläufen des Druckes realisiert werden. Außerdem besteht die Möglichkeit, die Durchbrechung 20 exzentrisch in dem plattenförmigen Körper 19 anzuordnen und in ihrer Gestalt zu variieren.Through a suitable choice of the material and the thickness of the plate-shaped body 19 and the ratio of the cross section of the area of the body 19 traversed by the shock wave to the cross section of the shock wave - in the case of the exemplary embodiment described, the opening 20 - a variety of other time profiles of the pressure can be created will be realized. It is also possible to arrange the opening 20 eccentrically in the plate-shaped body 19 and to vary its shape.

In der Fig. 5 ist ein Stoßwellengenerator dargestellt, der sich von dem zuvor beschriebenen im wesentlichen dadurch unterscheidet, daß mehrere plattenförmige Körper 21 bis 23 zwischen der Membran 12 und dem Fokus F vorgesehen sind, die, wie anhand der unterschiedlichen Schraffur erkennbar ist, aus unterschiedlichen Werkstoffen bestehen und unterschiedliche Dicken aufweisen, also geometrisch unterschiedlich ausgebildet sind. Die plattenförmigen Körper 21, 22 und 23 liegen mit ihren einander zugewandten Flächen aneinander an und sind mittels der Stellhebel 24 bis 26 gegeneinander verdrehbar in dem rohrförmigen Bauteil 9 aufgenommen.5 shows a shock wave generator, which differs from the one described above essentially in that several plate-shaped bodies 21 to 23 are provided between the membrane 12 and the focus F, which, as can be seen from the different hatching, from consist of different materials and have different thicknesses, that is to say they are geometrically different. The plate-shaped bodies 21, 22 and 23 abut one another with their mutually facing surfaces and are accommodated in the tubular component 9 so that they can be rotated relative to one another by means of the actuating levers 24 to 26.

Wie aus Fig. 5 in Verbindung mit Fig. 6 erkennbar ist, weisen die plattenförmigen Körper 21, 22 und 23 jeweils drei kreissektorförmige Durchbrechungen 27, 28 und 29 auf und können mittels der Stellhebel 24 bis 26 so zueinander positioniert werden, daß sich ihre von einer von der Membran 12 ausgehenden Stoßwelle durchlaufenen Bereiche zumindest teilweise überdecken. Durch geeignetes Verdrehen der plattenförmigen Körper 21 bis 23 gegeneinander können diese in eine solche Lage relativ zueinander gebracht werden, daß eine von der Membran 12 ausgehende unipolare Stoßwelle hinter den plattenförmigen Körpern 21 bis 23 bis zu vier zeitlich gegeneinander versetzte Teile aufweist. Demzufolge können im Fokus F zeitliche Verläufe des Druckes realisiert werden, wie sie in den Fig. 7 und 8 beispielhaft angedeutet sind, wobei analog zu den Fig. 2 und 3 der resultierende zeitliche Verlauf des Druckes wieder ausgezogen und die zu den einzelnen zeitlich gegeneinander versetzten Teilen der Stoßwelle gehörigen zeitlichen Verläufe des Druckes wieder punktiert bzw. strichliert dargestellt sind. Dabei ist in Fig. 7 ein zeitlicher Verlauf des Druckes dargestellt, bei dem der Unterschwinger des zuerst am Fokus F eintreffenden Teiles der Stoßwelle durch die folgenden Anteile der Stoßwelle praktisch vollständig kompensiert ist, während die Fig. 8 einen zeitlichen Verlauf des Druckes mit drei aufeinanderfolgenden Druckspitzen 31 bis 33 zeigt.As can be seen from FIG. 5 in connection with FIG. 6, the plate-shaped bodies 21, 22 and 23 each have three circular sector-shaped openings 27, 28 and 29 and can be positioned relative to one another by means of the adjusting levers 24 to 26 such that their areas, which are traversed by a shock wave emanating from the membrane 12, at least partially overlap. By suitable rotation of the plate-shaped bodies 21 to 23 relative to one another, they can be brought into such a position relative to one another that a unipolar shock wave emanating from the membrane 12 has up to four parts staggered in time behind the plate-shaped bodies 21 to 23. Accordingly, temporal profiles of the pressure can be realized in focus F, as indicated by way of example in FIGS. 7 and 8, with the resultant temporal profile of the pressure being drawn out again analogously to FIGS. 2 and 3 and offset in time relative to the individual Parts of the shock wave associated temporal profiles of the pressure are again shown in dotted or dashed lines. 7 shows a time course of the pressure in which the undershoot of the part of the shock wave arriving first at focus F is practically completely compensated by the following parts of the shock wave, while FIG. 8 shows a time course of the pressure with three successive ones Pressure peaks 31 to 33 shows.

In Fig. 9 ist ein erfindungsgemäßer Stoßwellengenerator dargestellt, der sich von den zuvor beschriebenen dadurch unterscheidet, daß seine Membran 34 sphärisch gekrümmt und dieser gegenüberliegend eine entsprechend gekrümmte Spule 35 angeordnet ist. Die Membran 34 schließt ein rohrförmiges Bauteil 36 von kegelstumpfförmiger Gestalt an dessen größerem Ende ab. Die an dem kleineren Ende des rohrförmigen Bauteiles 36 befindliche Austrittsöffnung 37 für die von der Membran 34 ausgehenden Stoßwellen ist wieder durch einen Balg, der die Bezugsziffer 38 trägt und zur akustischen Ankopplung des Stoßwellengenerators dient, verschlossen. Infolge der beschriebenen Ausbildung des Stoßwellengenerators sind besondere Mittel zur Fokussierung der von der Membran 34 ausgehenden Stoßwellen überflüssig, da sich eine von der Membran 34 ausgehende Stoßwelle ohnehin in dem Fokus F, der dem Krümmungsmittelpunkt der sphärischen Membran 34 entspricht, konzentriert. Die Membran 34 übernimmt also auch die Funktion der Mittel zum Fokussieren der Stoßwellen. Zwischen der Membran 34 und dem Fokus F ist ein plattenförmiger Körper 39 angeordnet, der aus einem Werkstoff gebildet ist, dessen akustische Impedanz im wesentlichen der Flüssigkeit entspricht und in dem die Schallausbreitungsgeschwindigkeit von der in der Flüssigkeit abweicht. Der plattenförmige Körper 39 ist wie die Membran 34 sphärisch gekrümmt, wobei sein Krümmungsmittelpunkt mit dem der Membran 34 zusammenfällt. In seinem Zentrum weist der plattenförmige Körper 39 eine Durchbrechung 34 von kegelstumpfförmiger Gestalt auf, die einen solchen Öffnungswinkel besitzt, daß ihre gedachte Spitze mit dem Krümmungsmittelpunkt der Membran 34 und des plattenförmigen Körpers 39, d.h. mit dem Fokus F, zusammenfällt. Mit einem solchen Stoßwellengenerator können im Fokus F zeitliche Verläufe des Druckes realisiert werden, wie sie in den Fig. 2 und 3 beispielhaft dargestellt sind.FIG. 9 shows a shock wave generator according to the invention which differs from those described above in that its membrane 34 is spherically curved and a correspondingly curved coil 35 is arranged opposite it. The membrane 34 closes a tubular component 36 of frustoconical shape at the larger end thereof. The outlet opening 37, located at the smaller end of the tubular component 36, for the shock waves emanating from the membrane 34 is again closed by a bellows, which bears the reference number 38 and serves for the acoustic coupling of the shock wave generator. As a result of the described design of the shock wave generator, special means for focusing the shock waves emanating from the membrane 34 are superfluous, since a shock wave emanating from the membrane 34 is concentrated anyway in the focus F, which corresponds to the center of curvature of the spherical membrane 34. The membrane 34 also takes over the function of the means for focusing the shock waves. Arranged between the membrane 34 and the focus F is a plate-shaped body 39 which is formed from a material whose acoustic impedance corresponds essentially to that of the liquid and in which the speed of sound propagation differs from that in the liquid. Like the membrane 34, the plate-shaped body 39 is spherically curved, its center of curvature coinciding with that of the membrane 34. In its center, the plate-shaped body 39 has an opening 34 of frustoconical shape which has such an opening angle that its imaginary tip coincides with the center of curvature of the membrane 34 and the plate-shaped body 39, ie with the focus F. With such a shock wave generator, temporal profiles of the pressure can be realized in focus F, as shown by way of example in FIGS. 2 and 3.

Die Ausführungsbeispiele betreffen ausschließlich solche Stoßwellengeneratoren, bei denen die Stoßwellen mittels einer stoßartig antreibbaren Membran erzeugt werden. Der erfindungsgemäße Stoßwellengenerator kann jedoch auch andere Stoßwellenquellen enthalten, z.B. solche, bei denen die Stoßwellen durch Unterwasser-Funkenentladungen, auf piezoelektrischem Wege oder durch Auftreffen eines Laserstrahles auf ein in der Flüssigkeit befindliches, stark absorbierendes Objekt erzeugt werden. Ebenso können die plattenförmigen Körper insbesondere hinsichtlich der Gestalt der Durchbrechungen anders als im Zusammenhang mit den Ausführungsbeispielen beschrieben ausgebildet sein, sofern sie nur hinsichtlich ihrer geometrischen Ausbildung und ihres Werkstoffes geeignet sind, auf die beschriebene Weise eine Stoßwelle hervorzubringen, die zeitlich gegeneinander versetzte Anteile aufweist.The exemplary embodiments relate exclusively to those shock wave generators in which the shock waves are generated by means of a membrane which can be driven in a shock-like manner. However, the shock wave generator according to the invention can also contain other shock wave sources, e.g. those in which the shock waves are generated by underwater spark discharges, by piezoelectric means or by the impact of a laser beam on a highly absorbent object in the liquid. Likewise, the plate-shaped bodies, in particular with regard to the shape of the perforations, can be designed differently than described in connection with the exemplary embodiments, provided that they are only suitable with regard to their geometric design and their material to produce a shock wave in the manner described which has portions that are offset in time.

Claims (9)

  1. Shock wave generator for a device for contactless disintegration of concretions (6) in the body (5) of a living being, which generator has a housing (9, 36), filled with a fluid, with an outlet opening (10, 37) for shock waves and a shock wave source (12, 13, 14, 34, 35), arranged lying opposite the latter, and also means (18) for focussing the shock waves onto a focal point (F), in which case a plate-like body (19, 21, 22, 23, 39) is arranged between the shock wave source (12, 13, 14, 34, 35) and the focal point (F), the area of which plate-like body, located in the propagation path of the shock waves, has a smaller cross-sectional area than a shock wave originating from the shock wave source (12, 13, 14, 34, 35) so that in each case only one portion of a shock wave passes through the plate-like body (19, 21, 22, 213 (sic), 39), characterised in that the plate-like body (19, 21, 22, 23, 39) is formed of a material with an acoustic impedance substantially corresponding to that of the fluid and in which material the acoustic propagating speed deviates from that in the fluid.
  2. Shock wave generator according to claim 1, characterised in that the plate-like body (19, 21, 22, 23, 39) has at least one opening (20, 27, 28, 29, 40) in its area through which the shock wave passes.
  3. Shock wave generator according to claim 2, characterised in that the opening (20, 40) is provided centrally in the area of the plate-like body (19, 39) through which the shock wave passes.
  4. Shock wave generator according to claim 2, characterised in that a shock wave originating from the shock wave source (12, 13, 14) has a circular cross section and the plate-like body (21, 22, 23) has in its area through which the shock wave passes several circular sector-shaped openings (27, 28, 29), the tips of which lie on the central axis of the shock wave (12).
  5. Shock wave generator according to one of the claims 1 to 4, characterised in that provided between the shock wave source (12, 13, 14) and the outlet opening (10) in succession there are several plate-like bodies (21, 22, 23) the areas of which, through which the shock wave passes, overlap each other at least in part.
  6. Shock wave generator according to claim 5, characterised in that the plate-like bodies (21, 22, 23) are formed so as to be geometrically different.
  7. Shock wave generator according to claim 5 or 6, characterised in that the plate-like bodies (21, 22, 23) consist of different materials.
  8. Shock wave generator according to one of the claims 5 to 7, characterised in that the plate-like bodies (21, 22, 23) can be twisted in relation to each other.
  9. Shock wave generator according to one of the claims 6 to 8, characterised in that the plate-like bodies (21, 22, 23) rest against each other with their facing surfaces.
EP88111054A 1987-07-23 1988-07-11 Shock wave generator for an apparatus for non-contact disintegration of concrements, present in a body Expired - Lifetime EP0300315B1 (en)

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DE8710118U DE8710118U1 (en) 1987-07-23 1987-07-23
DE8710118U 1987-07-23

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DE8710118U1 (en) 1988-11-17
DE3869861D1 (en) 1992-05-14
JPH0446731Y2 (en) 1992-11-04
US4972826A (en) 1990-11-27
EP0300315A1 (en) 1989-01-25
JPS6417217U (en) 1989-01-27

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