FR2640090A1 - DEVICE FORMING AN ECLATOR COMPRISING AN INTERNAL SHAPING IN ELECTRICALLY INSULATING REFRACTORY MATERIAL AND SHOCKWAVE GENERATING APPARATUS, IN PARTICULAR FOR HYDRAULIC LITHOTRITIS, PROVIDED WITH SUCH A DEVICE - Google Patents

Abstract

The invention relates to a device forming a spark gap. This spark gap device comprises a support box 128, in which at least two electrodes 134, 136 are remotely mounted, forming part of an electrical current supply connector of a given device, the distance between said electrodes 134, 136 being sufficient to interrupt the electrical circuit, and a spark generating element 138, such as a spark plug, capable of closing said electrical circuit between the electrodes 134, 136, upon generation of sparks, and is characterized in that at least a portion 154 of the housing 128 is made of an electrically insulating material, for example a plastic material, the internal side walls 156 of which, adjacent to the walls comprising the electrodes 134, 136, are lined by a lining layer 162 of electrically refractory material insulating. The invention makes it possible to manufacture a device forming a spark gap of reduced size with an extended lifespan which is very useful in shock wave generating devices, in particular for hydraulic lithotripsy.

Description

Apparatus forming a spark gap comprising an inner liner of material

  electrically insulating refractory and shock wave generating apparatus, particularly for hydraulic lithotripsy, provided

such a device.

  The invention essentially relates to a spark gap device comprising an inner liner made of an electrically insulating refractory material and a shock wave generator apparatus,

  in particular for hydraulic lithotripsy, provided with such

  operative part. It is known from US Patent No. 2 549 227 an apparatus for generating high frequency shock waves in a liquid for the remote destruction of targets. This apparatus comprises a shock wave generating device formed by a

  truncated ellipsoidal reflector 80 having a cavity 81 constituting

  killing a reflection chamber shock waves of the same truncated ellipsoidal shape. One of the two foci of the ellipsoid is disposed in the chamber opposite the truncated portion, this chamber being filled with a shock wave transmission liquid 83, for example an oil, this chamber being closed by a

diaphragm 82, FIG.

  The shock wave generator device itself usually comprises two electrodes 12, 13 disposed at least partly within the chamber 81, said two electrodes being arranged to generate a discharge or electric arc in the focus

  located in the room opposite the truncated part.

  Means 10, 11 are also provided for selectively delivering an instantaneous voltage to the two electrodes 12, 13 thereby causing the discharge or electric arc between the electrodes generating the shock waves in said liquid contained in the chamber (see FIG. column 7,

line 51 to column 9, line 30).

  In this Rieber document, an electric power generator

  10 is provided, in particular a battery 34, selectively supplying

  Finally, a transformer 33 and a capacitor 11 (see Figure 5, line 64 to column 6, line 26). This capacitor having a capacitance of 1 microfarad can be charged up to a voltage of 15,000 V to generate the arc or electrical discharge between the electrodes selectively at specified intervals

  (Column 4, lines 69-72 and column 9, lines 7 to 9 and 24 to 27).

  The electrodes are made of a highly conductive material, such as copper or brass which is an alloy of

copper (column 5, lines 33-35).

  This apparatus is used in the medical field, in particular for the destruction of tissues (see column 3,

  lines 30 to 64). This device can also be used for

  ration or stimulation of various parts of the nervous system

(column 3, lines 65 to 74).

  This device can still be used for extracorporeal lithotripsy.

  Document FR-A-2,247,195 also describes a similar apparatus

  in which the liquid consists of water (page 3,

lines 23-24).

  Rieber describes a power supply circuit for electrodes

simple design.

  Furthermore, it has been described in document EP-A-0 261 999 of the present applicants, with reference to FIG.

  a power supply connector 12 in electrical current of the electri-

  trodes 6, 8 comprising an intermediate device 28 forming an electric circuit closure gap between the electrodes 6, 8 intermittently, preferably "Spark Gap" type, interposed

  on a conductor 30 for supplying an electrode 6. This arrangement

  intermediate device 28 may be constituted by a housing 32, wherein are spaced apart two intermediate electrodes 34, 36, this distance being sufficient to interrupt the electrical circuit. This electric circuit is closed by the generation of sparks from a spark generator element 38, by

example a candle.

  To avoid premature wear of the electrodes 34, 36, it is intended to sweep the chamber 33 defined by the housing 32 with a gas stream, advantageously a stream of nitrogen or air fed by suitable 40, 42 (see column 5 lines 11 to 44

and Figure 5).

  It turned out in practice that it was necessary to use

  an intermediate device having a housing of a large size because of the significant heating generated by the electric discharges between the electrodes. Despite this

  over-dimensioning, the service life of such an inter-

mediare is short.

  The present invention therefore aims to solve the new technical problem consisting in the provision of a solution for making the devices forming a spark gap or "Spark Gap" type of reduced size while being of a long life, well greater than the usual life of

this type of devices.

  This technical problem is solved for the first time by the present invention in a particularly simple way, little

  expensive, usable on an industrial scale.

  Thus, according to a first aspect, the present invention provides a spark gap device comprising a housing

  support, in which at least two remote elec-

  trodes forming part of a power supply connection of a given device, the distance between said electrodes being sufficient to interrupt the electrical circuit, and a spark generator element, such as a spark plug, capable of closing said electrical circuit between the electrodes, during the generation of sparks, characterized in that said housing is at least partly made of an electrically insulating material, whose internal walls adjacent to the walls comprising the electrodes are lined with a layer of

  liner made of electrically insulating refractory material.

  According to a preferred characteristic of the invention, the lining material is a ceramic or composite material,

  particularly a composite ceramic.

  According to a particularly advantageous embodiment,

  this lining layer is constituted by a sensing cylinder

  coaxial to a plane of symmetry of the case, from

  preferably by the axis of at least one electrode.

  According to another embodiment also particularly

  Advantageously of the invention, the aforesaid housing is constituted by a cylinder, preferably with a central annular radial shoulder, closed at its two ends by two closure elements at least partly electrically conductive.

  to constitute the aforementioned electrodes.

  According to a preferred embodiment, these elements of

  closure include housing for housing electrical pellets

  triply conducting constituents constituting the active parts of

  trodes. According to another advantageous characteristic of the spark gap device according to the invention, it is characterized in that it comprises means for scanning the inside of the housing by

  a gaseous stream, especially air or nitrogen.

  According to a second aspect, the present invention also provides an apparatus for generating shock waves, preferably with ellipsoidal reflector, equipped with such a device forming

spark gap.

  Thus, thanks to the invention, there is obtained a spark gap device also called "Spark Gap" of reduced size compared to gaping devices currently on the market, a longer life, especially in the preferred use in the devices for generating shock waves, preferably with an ellipsoidal reflector, in which the shock waves are generated by electric discharge between two submerged electrodes

in a liquid such as water.

  This is therefore a decisive technical progress,

  unexpected and not obvious to the man of the art.

  Other goals, features and benefits of

  the invention will become clear in the light of the description

  The explanatory text which will follow with reference to the accompanying drawings showing a presently preferred embodiment of the invention given merely by way of illustration and which can not in any way limit the scope of the invention. In the drawings, FIG. 1 is a view schematically showing the essential part of the electrical power supply connection of the electrodes 8, 9 disposed in an ellipsoidal reflector device 4 forming part of an apparatus for generating shock waves, according to a preferred application or use of the invention; and Figure 2 shows in enlarged detail a presently preferred embodiment of a device forming

spark gap according to the invention.

  With reference to FIG. 1, a device forming

  The converter, represented by a general reference number 28, is integrated in the electrical power supply connector 12 of a high frequency shock wave generating apparatus, preferably comprising an ellipsoidal reflector represented by

  a general reference number 4.

  This ellipsoidal reflector 4 is filled with a liquid 2 such as water and is capable of generating shock waves by electrical discharge between at least two electrodes 8, 9 arranged at least partly in a chamber 10 defined by the ellipsoidal reflector 4, these electrodes being fed intermittently with electric current from an electric power source 22 combined with a

high voltage transformer 24.

  This power supply connector 12 comprises an intermediate device 28 for closing the electrical circuit between the electrodes 8, 9 intermittently, preferably of the "Spark Gap" type.

  interposed in the example shown on the conductor 30 of

the electrode 9.

  The other electrode, here electrode 8, can be connected to the earth symbolized by T and include a capacitor 18 capable

  to store a voltage of 10 000 to 20 000 V and having a capacity of

  quotation of 0.5 or I microfarad, this capacitor 18 being interposed on the conductor 20 between the electric power source 22

  - combined with the high voltage transformer 24, and the electrode 8.

  The intermediate device 28 is advantageously constituted by a housing 32, in which are arranged remotely

  two intermediate electrodes 34, 36, this distance being sufficient

  to interrupt the electrical circuit. These electrodes inter-

  34, 36 are normally in electrical connection with the

  electrical power supply conductor 30.

  os05 This electrical circuit is closed by the generation of

  those from a spark generator element 38, for example a candle. Preferably, it is planned to sweep the

  chamber 33 defined by the housing 32 by a gaseous stream, preferably

  a stream of air or nitrogen fed by ducts

  40, 42, which is clearly visible in FIG.

  This device described above is in accordance with that described in FIG. 5 of EP-A-0 261 999 which is explicitly

incorporated herein by reference.

  With reference to FIG. 2, in accordance with the present invention, there is shown a presently preferred embodiment of a spark gap device according to the present invention for which the same reference numerals have been used for identical or like parts. but increased

  , for a better understanding of the invention.

  Thus, the spark gap device according to the invention

  is represented by the general reference numeral 128, the

  The feed electrode is represented by reference numeral 130, and the electrodes are represented by the respective reference numerals 134 and 136 corresponding to the electrodes 34, 36 of Fig. 1. The priming electrode is represented by the number of the electrodes. 138 and is constituted for example by a spark plug, the flushing ducts by a gas stream being represented by

  reference numbers 140 and 142.

  According to the present invention, the housing 128 is at least

  partly made of electrically insulating material, in particular

  a plastic part, such as polymethacrylate, that is to say here the central part 154, whose side internal walls 156, adjacent to the electrodes 134, 136, are lined by a lining layer 162 of electrically insulating refractory material, preferably a ceramic or composite material, in particular a ceramic composite material. Any electrically insulating ceramic material that is well known to those skilled in the art can be used. According to a preferred embodiment, this lining layer 162 is constituted by a cylinder substantially coaxial with the plane of symmetry of the housing, itself essentially formed by a cylinder substantially coaxial with the axis of symmetry of the housing 128.

  which preferably passes through the axis of symmetry of at least one

trode 134, 136.

  According to a preferred embodiment of the invention, the active part 135, 137 of the electrodes 134, 136 is in the form of a pellet clearly visible in FIG.

  at the electrode 134, 136, respectively, for example by brazing.

  According to a particular embodiment, this pellet 137 is embedded in a housing respectively referenced

  150, 152 of the housing defining the spark gap device 128.

  The central piece 154 of the housing 128 may be, according to a particular embodiment, constituted by a paraLlepiped or by a central radially inner shoulder 170 annular cylinder. The central portion 154 is closed at its two ends 154a, 154b by two closure members 172, 174, comprising housings 150, 152 for the active parts 135, 137 of the refractory alloy of the electrodes 134, 136. A closure element, such as that the element 172 may comprise a cavity 176 for the fixation of

the priming electrode 138.

  According to a preferred embodiment, as shown, the closure elements 172, 174 are made of an electrically conductive material such as a metal and therefore constitute the electrodes 134, 136 themselves. These electrodes 134, 136 are naturally electrically connected to the electrical conductor 130 of FIG. 1 of the invention. In addition, the spark generator element 138 has its free end 138a which penetrates into a central orifice 180 of the electrode 134 and 182 of the active part, so as to be flush with the free surface 135a of the part

  active 135, as clearly visible in FIG.

  The electrodes 134, 136 may be made of brass

  or copper and the same for pellets 135, 137.

  We understand that thanks to this structure, we obtain all the decisive technical advantages previously stated, in

  particular a very significant reduction in the size of the

  sitif forming spark gap 128, thanks to the presence of the liner

  internal 162 refractory alloy while obtaining an increase

  longevity of the spark gap device. Also, the combination of this liner with active portions 135, 137 of the electrodes 134, 136 in the form of a tablet further improves the longevity of this

spark gap device.

  It should be noted that the closing elements 172, 174

  constituting in practice the electrodes 134, 136 can be solidified

  darisés by any appropriate means to the central portion 154 of the housing 128, in particular removably or not removable manner according to the choice of those skilled in the art depending on the advantages

  respective of the removable or non-removable nature of the housing.

  The invention thus covers all the means constituting technical means of the means described as well as their various combinations.

Claims (8)

  Apparatus forming a spark gap comprising a support housing (128), in which are mounted remotely at least two   electrodes (134, 136) forming part of a power supply   electrical current (12) of a given apparatus, the distance between said electrodes (134, 136) being sufficient to interrupt the electrical circuit, and a spark-generating element (138), such as a spark plug, capable of closing said electrical circuit between the electrodes (134, 136), during the generation of sparks, characterized in that at least a portion (154) of the housing (128) is made of an electrically insulating material, for example a plastics material , whose lateral internal walls (156) adjacent to the walls comprising the electrodes (134, 136) are lined by a lining layer   (162) of electrically insulating refractory material.   2. Apparatus forming a spark gap according to claim 1, characterized in that the electrically refractory material   insulation is a ceramic or composite material, in particular a composite ceramic.   3. Apparatus forming a spark gap according to claim 1 or 2, characterized in that the lining layer (162) above is constituted by a cylinder substantially coaxial with a plane of symmetry of the housing (128), preferably passing through the axis of at least one electrode (134, 136).   4. Apparatus forming a spark gap according to one of the claims   1 to 3, characterized in that the aforesaid housing (128) is   constituted by a cylinder, preferably with a radially annular shoulder   inner wire (170), closed at both ends (154a, 154b) by   two closure elements (172, 174).   5. Apparatus forming a spark gap according to claim 4, characterized in that the aforementioned closure elements (172, 174) comprise housings (150, 152) for accommodating active parts   (135, 137) electrodes (134, 136).   6. Apparatus forming a spark gap according to claim 4 or 5, characterized in that the aforementioned active parts are made in the form of a solilarized pastiLLe to the electrode   by any appropriate means, for example by brazing.   7. A device according to one of the claims   cations, characterized in that it comprises means (140, 142) for scanning the inside of the housing (128) by a   gaseous stream, especially air or nitrogen.   8. Apparatus for generating shock waves, preferably an ellipsoidal reflector, characterized in that it is equipped with a spark gap device as defined according to any one   claims I to 7, said shock waves being generated by   electric discharge between two electrodes immersed in a liquid such as water.