WO2009044216A1 - Concentric electrode device and method of producing concentric electrode device - Google Patents

Concentric electrode device and method of producing concentric electrode device Download PDF

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Publication number
WO2009044216A1
WO2009044216A1 PCT/HU2008/000112 HU2008000112W WO2009044216A1 WO 2009044216 A1 WO2009044216 A1 WO 2009044216A1 HU 2008000112 W HU2008000112 W HU 2008000112W WO 2009044216 A1 WO2009044216 A1 WO 2009044216A1
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WO
WIPO (PCT)
Prior art keywords
tube
electrode
inner electrode
conductive material
electrically conductive
Prior art date
Application number
PCT/HU2008/000112
Other languages
French (fr)
Inventor
Ádám RÁCZ
Original Assignee
Racz Adam
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Filing date
Publication date
Application filed by Racz Adam filed Critical Racz Adam
Publication of WO2009044216A1 publication Critical patent/WO2009044216A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/12—Manufacturing methods specially adapted for producing sensors for in-vivo measurements
    • A61B2562/125—Manufacturing methods specially adapted for producing sensors for in-vivo measurements characterised by the manufacture of electrodes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/25—Bioelectric electrodes therefor

Definitions

  • the invention relates to a concentric electrode device, in particular for using as medical diagnostic measuring electrode, and a method of producing such a concentric electrode device.
  • the electrolyte content of the malignous tissues is greater than that of the normal tissues.
  • the two electrodes may behave as a galvanic cell.
  • a pair of concentric electrodes is preferably used the outer electrode of which is typically in the form of a thin tube made of stainless steel, whereas its ion-selective inner electrode is in the form of a body made of a metal of high purity, preferably of at least 99,9999% purity, typically magnesium.
  • the use of a pair of electrodes for the examination of malignities of live tissues is not adversely effected by the fact that the measuring surface of the inner electrode contains not only a single metal, for example magnesium, but in addition to the primary metal, another metal electrically connected to the primary one is also present on the measuring surface.
  • the above concentric electrode device is disclosed, for example, in document
  • This electrode device comprises an outer electrode in the form of a stainless steel tube, and an inner electrode having a measuring surface made of magnesium, said inner electrode being arranged in the outer electrode in an insulated manner, and wherein the inner electrode has an electric output terminal.
  • the inner electrode has a metal tube into which a magnesium body is inserted at its one end, whereas a metal wire forming the electric output terminal of the inner electrode is inserted at its other end.
  • the inner electrode made of magnesium and its metal output terminal are bonded into the metal tube by a conductive adhesive.
  • Document HU 206917 discloses a method of manufacturing electro-chemical sensors made of metal.
  • the method comprises the steps of making a tube from a metal having a higher melting point than that of the metal forming the material of the sensor electrode, filling the tube with a metal powder made from the material of the sensor electrode, melting the powder of the electrode material by heating the device in a closed furnace or a protective gas atmosphere above the melting point of the metal of the sensor electrode, and then cooling the device until the melt becomes solidified, while the vacuum or the protective gas atmosphere is being maintained.
  • a connection with appropriate electric conductivity is established between the melt and then re-solidified metal and the outer metal tube.
  • This manufacturing technology has the basic drawback that production of the electrode is very costly because of the complicated apparatuses, and the material of the outer tube made of the other metal is subject to a substantial thermal stress when melting the metal powder constituting the primary material of the electrode, which adversely affects the productivity.
  • Another drawback of the above mentioned electrode device is that the thermal coefficients of the electrode material and the metal tube are different, therefore while the melted metal powder is cooling down and solidifying, the mechanical bind between the electrode and the surrounding metal tube tends to deteriorate to a significant extent, which might result in the electrode's falling out from the metal tube.
  • a concentric electrode device comprising a tube made of a first electrically conductive material, an inner electrode made of a second electrically conductive material and inserted into the tube at one end of the tube, a wire connected to the other end of the tube, said wire constituting an electric output terminal, and a hollow outer electrode made of a third electrically conductive material.
  • the tube holding the inner electrode is arranged inside the outer electrode in an insulated and concentric manner.
  • the inner electrode is electrically connected along its lateral surface to the inner surface of the tube, and said tube, in turn, is also electrically connected to the output terminal wire.
  • the inner electrode is inserted in the tube in the form of a solid body and secured mechanically therein so that at least a part of its lateral surface is directly and electrically connected to the inner surface of the tube.
  • a method of producing a concentric electrode device comprising the steps of making a tube of a first electrically conductive material; at one end of the tube, inserting an inner electrode in the form of a solid body made of a second electrically conductive material into the tube; mechanically securing the inner electrode inside the tube so that at least a part of the lateral surface of the inner electrode be directly and electrically connected to the inner surface of the tube; electrically connecting an output terminal wire to the other end of the tube; and finally, accommodating the tube holding the inner electrode and the output terminal wire in an insulated and concentric manner inside a hollow outer electrode made of a third electrically conductive material.
  • the electrode device according to the invention may be produced with a much more uniform quality, higher manufacturing productivity and much lower costs.
  • FIG. 1 is a longitudinal cross-sectional view of a preferred embodiment of the concentric electrode device according to the invention.
  • FIG. 2a-e schematically illustrate the basic steps of producing the inner electrode, in a longitudinal cross-sectional view, according to a preferred embodiment of the method of the invention
  • FIG. 3a-c schematically illustrate the basic steps of producing the inner electrode, in a longitudinal cross-sectional view, according to a further preferred embodiment of the method of the invention
  • FIGS. 4a-b are perspective views of two preferred designs of the sensing end portion of the cylindrical tube used in the embodiment of the method illustrated in
  • FIG. 1 a longitudinal cross-sectional view of the concentric electrode device 100 according to a preferred embodiment of the invention is shown.
  • the electrode device 100 comprises a tube 110 made of a first electrically conductive material, an inner electrode 120 made of a second electrically conductive material and inserted into said tube 110 at its one end 112, a wire 130 forming an electric output terminal connected to the other end 114 of the tube 110, and a hollow outer electrode 140 made of a third electrically conductive material.
  • the tube 110 holding the inner electrode 120 is arranged concentrically inside the hollow outer electrode 140. Between the tube 110 and the inner surface of the outer electrode 140, there is an insulation 150.
  • An electrically conductive connection is established between the inner electrode 120 and the wire 130 serving as an electric output terminal in such a way that the inner electrode 120 is connected directly to the tube 110 in an electrically conductive manner, and the tube 110 is, in turn, also electrically connected to the wire 130.
  • the inner electrode 120 is inserted into the tube 110 in the form of a solid body having a lateral surface matching to the inner surface of the tube 110, and then said inner electrode 120 is fixed mechanically inside the tube 110.
  • the tube 110 may be made of a conductive material with a melting point substantially the same as or lower than that of the material of the inner electrode 120 (but preferably with a higher strength) on the one part, and it is unnecessary to use a conductive adhesive for securing the inner electrode 120 to the wire 130 inside the tube 110, on the other part.
  • the inner electrode 120 is preferably made of metal, in particular magnesium, but other metals like aluminum, rare-earth metals, gold, silver, platinum, etc. or other non-metallic conductive materials, such as graphite, special plastics, etc. may also be considered for this purpose. Due to the extremely low values of the measurable current intensities in the medical diagnostic applications, it is preferred to use a conductive material of high purity, preferably of a purity of at least 99,9999%, for the inner electrode 120.
  • the tube 110 is preferably made of stainless steel, but in a particular case, it may be made of another metal having good electrically conductivity and substantial mechanical strength, for example gold, platinum, etc.
  • the insulation 150 between the inner electrode 120 and the tube 110 is preferably made of a synthetic resin, for example epoxy resin, or a metal ion curing adhesive, for example an adhesive containing urethane methacrylate or methacrylate esther, but other insulating materials suitable for medical diagnostic applications may also be considered for this purpose.
  • a synthetic resin for example epoxy resin
  • a metal ion curing adhesive for example an adhesive containing urethane methacrylate or methacrylate esther, but other insulating materials suitable for medical diagnostic applications may also be considered for this purpose.
  • the wire 130 which is preferably a metal wire, is electrically connected to the end 114 of the tube 110. Connecting the wire 130 to the tube 110 may be carried out by inserting the wire 130 into the inside of the tube 110, and by securing to the tube 110 directly, for example, by soldering, or indirectly, for example, by externally pressing the tube 110 thereon, as shown in Figure 1. Alternatively, the wire 130 may be secured to the front surface of the end 114 of the tube 110 or to the lateral surface thereof. The section of the wire 130 that extends beyond the tube 110 is covered by an insulation 160.
  • the insulation 160 is preferably made of polyethylene (PE) or other similar insulating plastic.
  • the outer electrode 140 is substantially longer than the inner electrode 120 and the tube 110, and the outer electrode 140 is connected to the respective connector of the measuring instrument without using an additional output terminal member.
  • the projecting section of the outer electrode 140 that extends beyond the inner electrode 120 also serves as the electric output terminal of the outer electrode 140 itself.
  • the outer electrode 140 is preferably made of stainless steel, but other electrode materials with appropriate conductivity may also be used.
  • the long outer electrode 140 which serves as supporting member for the electrode device 100 at the same time, provides the required strength, a good grip and an ease of handling for the electrode device 100.
  • the outer electrode 140 is covered by an insulation 170, preferably made of PE or synthetic resin.
  • the insulation 170 has only one layer, in a particular case, in order to further improve the conductivity properties, the insulation 170 may comprise two or more layers as well. In case of a multi-layer outer insulation, the adjacent layers are preferably made of different insulating materials.
  • the tube 110 holding the inner electrode 120, as well as the wire 130 connected to the tube 110 are arranged concentrically inside the outer electrode 140 by means of the insulation 150, and optionally also the insulation 160.
  • the inner electrode 120, the surrounding tube 110 and the outer electrode 140 have a cylindrical shape
  • said components may also be in the form of (solid or hollow) prisms with a base having a triangular, a quadratic or any other planar shape.
  • a tube is made of a first electrically conductive material, preferably of stainless steel.
  • a solid body made of a second electrically conductive material, for example magnesium is inserted inside the tube at one end thereof, said solid body having a lateral surface matching to the inner surface of the tube.
  • the solid body is then mechanically secured inside the tube so that the solid body be connected, along its lateral surface, directly and electrically to the inner surface of the tube. If necessary, the outer front surface of the solid body is mechanically finished to form the required measuring surface.
  • the solid body thus inserted into the tube constitutes the inner electrode.
  • a wire for example a copper wire, is electrically connected to the other end of the tube.
  • the tube holding the inner electrode and the output terminal wire is concentrically arranged in an insulated manner inside a hollow outer electrode made of a third electrically conductive material, preferably also of stainless steel.
  • the inner electrode is inserted into the tube so that it be connected, along its substantially entire lateral surface, electrically to the inner surface of the tube.
  • a stable conductive connection with good electrical conductivity is created between the outer surface of the inner electrode and the inner surface of the tube.
  • a solid body 210 with slight conicity at its one end portion 212 is made.
  • a blocking member 230 of high strength is inserted into the tube 200 to a predetermined distance D on the side of the tube 200 that is adjacent to the electric output terminal, said blocking member 230 having a lateral surface 232 matching the inner surface 202 of the tube 200, wherein said end portion inserted into the tube 200 has a planar front surface 234 perpendicular to the longitudinal axis of the tube 200.
  • the solid body 210 is inserted into the tube 200 on the open end of the tube 200 so that its conical end portion 212 be in contact with the front surface 234 of the blocking member 230 inside the tube 200.
  • the solid body 210 is pushed against the blocking member 230 by applying a predetermined force F so that the conical end portion 212 entirely fill the empty space remained inside the tube 200 between the solid body 210 and the blocking member 230 due to a plastic deformation of said conical end portion 212.
  • a solid inner electrode is produced that is electrically connected, along its substantially entire lateral surface 214, to the inner surface 202 of the tube 200 and which is mechanically secured inside the tube 200.
  • the blocking member 230 is removed from the tube 200, and finally, a planar measuring surface is formed by mechanically finishing the end portion 204 of the tube 200 that holds the inner electrode and the outer front surface 216 of the inner electrode.
  • a metal plate 310 is made of the second electrically conductive material outside the tube 300, said metal plate 310 having a thickness d substantially equal to the length of the inner electrode to be produced. Then the metal plate 310 is punched by means of the tube 300, whereby a solid inner electrode is produced inside the tube 300, at one end thereof, said solid inner electrode being electrically connected, along its entire lateral surface, to the inner surface of the tube 300, and being mechanically secured inside the tube 300.
  • punching the metal plate 310 is preferably carried out by over- advancing the front end 302 of the tube 300 to a minimal extent on the other side of the metal plate 310, which causes the solid body 320 cut out from the metal plate 310 to be securely fixed inside the tube 300.
  • the cut-out solid body 320 remaining inside the tube 300 will constitute the inner electrode.
  • a planar measuring surface is formed for the electrode by mechanically finishing the end portion 302 of the tube 300 holding the inner electrode and the outer front surface 322 of the solid body 320 serving as the inner electrode.
  • a tube 300 having a rotationally symmetric shape is made of the first electrically conductive material, and by rotating the tube 300 at a suitable rate and by advancing it with the application of a suitable intensity of force, the metal plate 310 is going to be bored through by the tube 300.
  • a solid inner electrode with a rotationally symmetric shape is made inside the tube 300.
  • a short section of the through-boring end portion 302 of the tube 300 is formed slightly tapered inwardly.
  • Through-boring of the metal plate 310 by means of the tube 300 thus formed actually implements a friction-welding process, wherein a local melting of the metallic material of the tube 300 on the mutually contacting surfaces of the tube 300 and the solid body 320, as well as securing the solid body 320 inside the tube 300 by the required compressive force are both achieved by applying an independent force system, without the use of any external clamping tool, while a direct, electrically conductive connection is established between the solid body 320 and the inner surface 304 of the tube 300 along the substantially entire lateral surface of the solid body 320.
  • the tube 300 is preferably made of a high-strength, hard metal, for example stainless steel, whereas the inner electrode is preferably made of much softer, easily formable metal, for example magnesium.
  • the inner diameter of the tube 300 is, for example 0,9 mm, and its length ranges, for example, from 12 to 15 mm.
  • the wall of the tube 300 at the front end thereof is formed, along a section of a length of approximately 2 to 3 mm, to have an inwardly widening conical profile, wherein the cone angle is in the magnitude of a few degrees.
  • the front end portion 302 of the tube 300 is cut along a plane slightly inclined relative to the plane perpendicular to the longitudinal axis of the tube 300, said inclination preferably having an angle of 5 to 15 degrees, but it is more preferred that said end portion is provided, on a relatively short section thereof, with a cutting edge having a suitable profile, for example a double-wave profile.
  • the boring process is preferably carried out at a rate of approximately 1000 rpm, while the tube 300 is pushed against the metal plate 310 by applying a force of approximately 20 to 30 N, whereby only the outer surface of the solid body forming the inner electrode becomes ductile, or tends to melt, temporarily and locally, whereas the inner part of the solid body still remains in a solid state.
  • a force of approximately 20 to 30 N whereby only the outer surface of the solid body forming the inner electrode becomes ductile, or tends to melt, temporarily and locally, whereas the inner part of the solid body still remains in a solid state.
  • the aforementioned embodiments of the end portion 304 of the tube 300 are illustrated in Figures 4a and 4b in perspective views.
  • the tube 300 having the sloped or profiled end portion is over-advanced beyond the metal plate 310 to an extent that the entire cross-sectional widths of the tube 300 traverses the metal plate 310.
  • the second electrically conductive material is used to make a solid body with a slightly tapered end portion.
  • the solid body is formed so that its lateral surface matches the inner surfaces of the tube.
  • the solid body is completely inserted into the tube with its tapered end portion, and then secured in the tube by externally pressing the tube thereon.
  • the inner surface of the tube is connected to the lateral surface of the inserted solid body in such a way that the solid body is electrically connected along its entire lateral surface to the inner surface of the tube.
  • the solid body thus inserted and fixed constitutes the inner electrode.
  • a planar measuring surface is prepared by mechanically finishing both of the end portion of the tube holding the inner electrode, and the outer front surface of the inner electrode.
  • the planar measuring surface is prepared preferably by smoothing the end portion of the inner electrode and the tube on the measuring side.
  • the smoothing process may be carried out in multiple steps as well, for example by a first coarse smoothing and subsequently, in order to prepare the final planar measuring surface, by a fine polishing.
  • the planar measuring surface may also be prepared by cutting off a short section of the tube holding the inner electrode on the measuring side.
  • the planar measuring surface of the inner electrode is prepared in one step by machining the end portion of the outer electrode and the insulation between the tube and the outer electrode simultaneously, the measurement side, that is, the measuring surface of the complete electrode device comprising both the inner and the outer electrode is produced in a single step.
  • the output terminal wire of the inner electrode is connected to the tube preferably in such a way that it is inserted into the free end of the tube and connected indirectly, for example by soldering, or directly, for example by externally pressing the tube thereon.
  • the output terminal wire of the inner electrode may be connected to the rim or the outer surface of the tube in any known manner.
  • securing the tube holding the inner electrode concentrically inside the hollow, typically pipe-like outer electrode is carried out in a way that the tube - and in a particular case, also the output terminal wire connected thereto - is drawn into the outer electrode in a synthetic resin bath, wherein the synthetic resin is preferably epoxy resin.
  • the synthetic resin bath instead of the synthetic resin bath, other inert material adapted for medical diagnostic use may also be used, provided that said inert material is capable of centering the tube inside the outer electrode after its solidification, and moreover it has an insulating characteristic in its solid state.
  • these materials include, for example, the aforementioned urethane methacrylate-based or methacrylate esther-based adhesives.
  • a plastic centering sheath (not illustrated in the drawings) may be arranged around the tube, wherein said sheath is drawn together with the tube into the hollow outer electrode.
  • the part of the output terminal wire of the inner electrode that extends outside the tube is preferably covered by a plastic insulation.
  • the insulation may be drawn onto the wire, for example in the form of a plastic tube.
  • a plastic sheath may be thermo-shrunk onto the wire.
  • the outer electrode comprising the insulated inner electrode inside is covered by an insulation that preferably also provides a mechanical protection.
  • the material of the insulation includes, for example, PE which is shrunk onto the outer electrode by applying heat, but for example, a synthetic resin may also be considered.
  • a multi-layer insulation may also be provided on the outer surface of the outer electrode.
  • the electrode device according to the invention there is a long-lasting, electrically conductive connection providing a very high conductivity between the inner electrode and the surrounding tube.
  • a further advantage of such an electrode device is that the measured current intensity is independent of the extent of intrusion of the device into the material to be measured.
  • the above described method of producing the electrode device allows an extremely high production outcome, while the electrical conductivity properties of the electrode devices have a negligible variance.

Abstract

The concentric electrode device according to the invention is adapted for using as a medical diagnostic measuring electrode. Together with the electrolyte present in the tissues, the device forms a galvanic cell. The electrode device (100) comprises a tube (110) made of a first electrically conductive material; an inner electrode (120) made of a second electrically conductive material and inserted into the tube (110) at one end (112) of the tube (110); a wire (130) connected to the other end (114) of the tube (110), said wire constituting an electric output terminal; and a hollow outer electrode (140) made of a third electrically conductive material. The tube (110) holding the inner electrode (120) is arranged inside the outer electrode (140) in an insulated and concentric manner. The inner electrode (120) is electrically connected along its lateral surface to the inner surface of the tube (110), and said tube (110) is also electrically connected to the output terminal wire (130). The inner electrode (120) is inserted in the tube (110) in the form of a solid body and secured mechanically therein so that at least a part of its lateral surface is directly and electrically connected to the inner surface of the tube (110). The method according to the invention relates to a method of producing such an electrode device.

Description

Concentric electrode device and method of producing concentric electrode device
The invention relates to a concentric electrode device, in particular for using as medical diagnostic measuring electrode, and a method of producing such a concentric electrode device.
In the medical diagnostics it is a well known characteristic of the live tissues that the electrolyte content of the malignous tissues is greater than that of the normal tissues. When two electrodes having different, appropriately selected materials are inserted into a tissue, the two electrodes may behave as a galvanic cell. By (substantially) short-circuiting the electrodes through a measuring instrument, a current characteristic to the extent of malignity of the tissue tends to flow and this current can be measured by the instrument.
In order to carry our the above measurements, a pair of concentric electrodes is preferably used the outer electrode of which is typically in the form of a thin tube made of stainless steel, whereas its ion-selective inner electrode is in the form of a body made of a metal of high purity, preferably of at least 99,9999% purity, typically magnesium.
During former researches it has also been recognized that the use of a pair of electrodes for the examination of malignities of live tissues is not adversely effected by the fact that the measuring surface of the inner electrode contains not only a single metal, for example magnesium, but in addition to the primary metal, another metal electrically connected to the primary one is also present on the measuring surface. The above concentric electrode device is disclosed, for example, in document
HU 206610. This electrode device comprises an outer electrode in the form of a stainless steel tube, and an inner electrode having a measuring surface made of magnesium, said inner electrode being arranged in the outer electrode in an insulated manner, and wherein the inner electrode has an electric output terminal. The inner electrode has a metal tube into which a magnesium body is inserted at its one end, whereas a metal wire forming the electric output terminal of the inner electrode is inserted at its other end. The inner electrode made of magnesium and its metal output terminal are bonded into the metal tube by a conductive adhesive. The above mentioned electrode device has the drawback that due to the use of the conductive adhesive, there is an excessive contact surface area between the inner electrode and the metallic output terminal wire, which results in a significant and hardly controllable instability for the electric conduction.
Document HU 206917 discloses a method of manufacturing electro-chemical sensors made of metal. The method comprises the steps of making a tube from a metal having a higher melting point than that of the metal forming the material of the sensor electrode, filling the tube with a metal powder made from the material of the sensor electrode, melting the powder of the electrode material by heating the device in a closed furnace or a protective gas atmosphere above the melting point of the metal of the sensor electrode, and then cooling the device until the melt becomes solidified, while the vacuum or the protective gas atmosphere is being maintained. In the sensor electrode thus obtained, a connection with appropriate electric conductivity is established between the melt and then re-solidified metal and the outer metal tube. This manufacturing technology has the basic drawback that production of the electrode is very costly because of the complicated apparatuses, and the material of the outer tube made of the other metal is subject to a substantial thermal stress when melting the metal powder constituting the primary material of the electrode, which adversely affects the productivity. Another drawback of the above mentioned electrode device is that the thermal coefficients of the electrode material and the metal tube are different, therefore while the melted metal powder is cooling down and solidifying, the mechanical bind between the electrode and the surrounding metal tube tends to deteriorate to a significant extent, which might result in the electrode's falling out from the metal tube.
It is an object of the present invention to eliminate the above drawbacks and to provide an electrode device operating as a galvanic cell in the presence of electrolyte in the tissues, wherein a long-lasting, stable and electrically conductive connection is established between the electrically conductive inner electrode and the surrounding, electrically conductive tube.
It is another object of the present invention to provide an electrode device capable of measuring always substantially the same current intensity independently of the extent of intrusion into the material to be measured.
Finally, it is an object of the present invention to provide an electrode device that allows a high manufacturing productivity while the electrical conductivity properties of the electrode devices produce only a negligible variance. The above objects are achieved by providing a concentric electrode device comprising a tube made of a first electrically conductive material, an inner electrode made of a second electrically conductive material and inserted into the tube at one end of the tube, a wire connected to the other end of the tube, said wire constituting an electric output terminal, and a hollow outer electrode made of a third electrically conductive material. The tube holding the inner electrode is arranged inside the outer electrode in an insulated and concentric manner. The inner electrode is electrically connected along its lateral surface to the inner surface of the tube, and said tube, in turn, is also electrically connected to the output terminal wire. The inner electrode is inserted in the tube in the form of a solid body and secured mechanically therein so that at least a part of its lateral surface is directly and electrically connected to the inner surface of the tube.
The above objects are further achieved by providing a method of producing a concentric electrode device, the method comprising the steps of making a tube of a first electrically conductive material; at one end of the tube, inserting an inner electrode in the form of a solid body made of a second electrically conductive material into the tube; mechanically securing the inner electrode inside the tube so that at least a part of the lateral surface of the inner electrode be directly and electrically connected to the inner surface of the tube; electrically connecting an output terminal wire to the other end of the tube; and finally, accommodating the tube holding the inner electrode and the output terminal wire in an insulated and concentric manner inside a hollow outer electrode made of a third electrically conductive material.
Compared to the prior art electrode devices, the electrode device according to the invention may be produced with a much more uniform quality, higher manufacturing productivity and much lower costs.
The invention will now be described in detail with reference to the accompanying drawings, wherein:
- Figure 1 is a longitudinal cross-sectional view of a preferred embodiment of the concentric electrode device according to the invention;
- Figures 2a-e schematically illustrate the basic steps of producing the inner electrode, in a longitudinal cross-sectional view, according to a preferred embodiment of the method of the invention; - Figures 3a-c schematically illustrate the basic steps of producing the inner electrode, in a longitudinal cross-sectional view, according to a further preferred embodiment of the method of the invention;
- Figures 4a-b are perspective views of two preferred designs of the sensing end portion of the cylindrical tube used in the embodiment of the method illustrated in
Figures 3a-c, wherein the end portions are shown prior to their boring into the metal plate.
In Figure 1 , a longitudinal cross-sectional view of the concentric electrode device 100 according to a preferred embodiment of the invention is shown. The electrode device 100 comprises a tube 110 made of a first electrically conductive material, an inner electrode 120 made of a second electrically conductive material and inserted into said tube 110 at its one end 112, a wire 130 forming an electric output terminal connected to the other end 114 of the tube 110, and a hollow outer electrode 140 made of a third electrically conductive material. The tube 110 holding the inner electrode 120 is arranged concentrically inside the hollow outer electrode 140. Between the tube 110 and the inner surface of the outer electrode 140, there is an insulation 150.
An electrically conductive connection is established between the inner electrode 120 and the wire 130 serving as an electric output terminal in such a way that the inner electrode 120 is connected directly to the tube 110 in an electrically conductive manner, and the tube 110 is, in turn, also electrically connected to the wire 130.
In order to avoid the costly heat treatment of the inner electrode 120 (i.e. melting and re-solidifying the metal powder of the inner electrode) wherein such heat treatment causes substantial thermal stress to the tube 110, the inner electrode 120 is inserted into the tube 110 in the form of a solid body having a lateral surface matching to the inner surface of the tube 110, and then said inner electrode 120 is fixed mechanically inside the tube 110. Due to this arrangement, the tube 110 may be made of a conductive material with a melting point substantially the same as or lower than that of the material of the inner electrode 120 (but preferably with a higher strength) on the one part, and it is unnecessary to use a conductive adhesive for securing the inner electrode 120 to the wire 130 inside the tube 110, on the other part. The inner electrode 120 is preferably made of metal, in particular magnesium, but other metals like aluminum, rare-earth metals, gold, silver, platinum, etc. or other non-metallic conductive materials, such as graphite, special plastics, etc. may also be considered for this purpose. Due to the extremely low values of the measurable current intensities in the medical diagnostic applications, it is preferred to use a conductive material of high purity, preferably of a purity of at least 99,9999%, for the inner electrode 120. The tube 110 is preferably made of stainless steel, but in a particular case, it may be made of another metal having good electrically conductivity and substantial mechanical strength, for example gold, platinum, etc.
The insulation 150 between the inner electrode 120 and the tube 110 is preferably made of a synthetic resin, for example epoxy resin, or a metal ion curing adhesive, for example an adhesive containing urethane methacrylate or methacrylate esther, but other insulating materials suitable for medical diagnostic applications may also be considered for this purpose.
The wire 130, which is preferably a metal wire, is electrically connected to the end 114 of the tube 110. Connecting the wire 130 to the tube 110 may be carried out by inserting the wire 130 into the inside of the tube 110, and by securing to the tube 110 directly, for example, by soldering, or indirectly, for example, by externally pressing the tube 110 thereon, as shown in Figure 1. Alternatively, the wire 130 may be secured to the front surface of the end 114 of the tube 110 or to the lateral surface thereof. The section of the wire 130 that extends beyond the tube 110 is covered by an insulation 160. The insulation 160 is preferably made of polyethylene (PE) or other similar insulating plastic.
In a preferred embodiment of the electrode device according to the invention, as shown in Figure 1 , the outer electrode 140 is substantially longer than the inner electrode 120 and the tube 110, and the outer electrode 140 is connected to the respective connector of the measuring instrument without using an additional output terminal member. In other words, the projecting section of the outer electrode 140 that extends beyond the inner electrode 120 also serves as the electric output terminal of the outer electrode 140 itself. The outer electrode 140 is preferably made of stainless steel, but other electrode materials with appropriate conductivity may also be used. Thus the long outer electrode 140, which serves as supporting member for the electrode device 100 at the same time, provides the required strength, a good grip and an ease of handling for the electrode device 100.
As shown in Figure 1 , the outer electrode 140 is covered by an insulation 170, preferably made of PE or synthetic resin. Although in the embodiment shown in Figure 1 , the insulation 170 has only one layer, in a particular case, in order to further improve the conductivity properties, the insulation 170 may comprise two or more layers as well. In case of a multi-layer outer insulation, the adjacent layers are preferably made of different insulating materials. The tube 110 holding the inner electrode 120, as well as the wire 130 connected to the tube 110 are arranged concentrically inside the outer electrode 140 by means of the insulation 150, and optionally also the insulation 160. Although it is preferred that the inner electrode 120, the surrounding tube 110 and the outer electrode 140 have a cylindrical shape, said components may also be in the form of (solid or hollow) prisms with a base having a triangular, a quadratic or any other planar shape.
In the foregoing, the generic steps of producing the above described electrode device will be introduced, and then some advantageous technological solutions for inserting and securing the inner electrode will be described. For producing the concentric electrode device, first a tube is made of a first electrically conductive material, preferably of stainless steel. Subsequently, a solid body made of a second electrically conductive material, for example magnesium, is inserted inside the tube at one end thereof, said solid body having a lateral surface matching to the inner surface of the tube. The solid body is then mechanically secured inside the tube so that the solid body be connected, along its lateral surface, directly and electrically to the inner surface of the tube. If necessary, the outer front surface of the solid body is mechanically finished to form the required measuring surface. The solid body thus inserted into the tube constitutes the inner electrode. Next, a wire, for example a copper wire, is electrically connected to the other end of the tube. Finally, the tube holding the inner electrode and the output terminal wire is concentrically arranged in an insulated manner inside a hollow outer electrode made of a third electrically conductive material, preferably also of stainless steel.
It is preferred that the inner electrode is inserted into the tube so that it be connected, along its substantially entire lateral surface, electrically to the inner surface of the tube. Thus a stable conductive connection with good electrical conductivity is created between the outer surface of the inner electrode and the inner surface of the tube.
An alternative embodiment of the method according to the invention will now be described with reference to Figures 2a-e. In this method, subsequently to forming the tube 200, a solid body 210 with slight conicity at its one end portion 212 is made. Next, a blocking member 230 of high strength is inserted into the tube 200 to a predetermined distance D on the side of the tube 200 that is adjacent to the electric output terminal, said blocking member 230 having a lateral surface 232 matching the inner surface 202 of the tube 200, wherein said end portion inserted into the tube 200 has a planar front surface 234 perpendicular to the longitudinal axis of the tube 200.
Subsequently, the solid body 210 is inserted into the tube 200 on the open end of the tube 200 so that its conical end portion 212 be in contact with the front surface 234 of the blocking member 230 inside the tube 200. Now the solid body 210 is pushed against the blocking member 230 by applying a predetermined force F so that the conical end portion 212 entirely fill the empty space remained inside the tube 200 between the solid body 210 and the blocking member 230 due to a plastic deformation of said conical end portion 212. Thus a solid inner electrode is produced that is electrically connected, along its substantially entire lateral surface 214, to the inner surface 202 of the tube 200 and which is mechanically secured inside the tube 200. After forming the inner electrode, the blocking member 230 is removed from the tube 200, and finally, a planar measuring surface is formed by mechanically finishing the end portion 204 of the tube 200 that holds the inner electrode and the outer front surface 216 of the inner electrode. A further embodiment of the method will now be described with reference to
Figures 3a-c. In this method, a metal plate 310 is made of the second electrically conductive material outside the tube 300, said metal plate 310 having a thickness d substantially equal to the length of the inner electrode to be produced. Then the metal plate 310 is punched by means of the tube 300, whereby a solid inner electrode is produced inside the tube 300, at one end thereof, said solid inner electrode being electrically connected, along its entire lateral surface, to the inner surface of the tube 300, and being mechanically secured inside the tube 300. As shown in Figure 3b, punching the metal plate 310 is preferably carried out by over- advancing the front end 302 of the tube 300 to a minimal extent on the other side of the metal plate 310, which causes the solid body 320 cut out from the metal plate 310 to be securely fixed inside the tube 300. The cut-out solid body 320 remaining inside the tube 300 will constitute the inner electrode. Finally, a planar measuring surface is formed for the electrode by mechanically finishing the end portion 302 of the tube 300 holding the inner electrode and the outer front surface 322 of the solid body 320 serving as the inner electrode.
In the above mentioned embodiment of the method according to the invention, it is preferred that a tube 300 having a rotationally symmetric shape is made of the first electrically conductive material, and by rotating the tube 300 at a suitable rate and by advancing it with the application of a suitable intensity of force, the metal plate 310 is going to be bored through by the tube 300. Thus a solid inner electrode with a rotationally symmetric shape is made inside the tube 300. To this end it is preferred, that a short section of the through-boring end portion 302 of the tube 300 is formed slightly tapered inwardly. Through-boring of the metal plate 310 by means of the tube 300 thus formed actually implements a friction-welding process, wherein a local melting of the metallic material of the tube 300 on the mutually contacting surfaces of the tube 300 and the solid body 320, as well as securing the solid body 320 inside the tube 300 by the required compressive force are both achieved by applying an independent force system, without the use of any external clamping tool, while a direct, electrically conductive connection is established between the solid body 320 and the inner surface 304 of the tube 300 along the substantially entire lateral surface of the solid body 320.
In the above mentioned embodiment of the method according to the invention, the tube 300 is preferably made of a high-strength, hard metal, for example stainless steel, whereas the inner electrode is preferably made of much softer, easily formable metal, for example magnesium. The inner diameter of the tube 300 is, for example 0,9 mm, and its length ranges, for example, from 12 to 15 mm. In order to facilitate the through-boring of the relatively soft metal plate 310 by the tube 300, the wall of the tube 300 at the front end thereof is formed, along a section of a length of approximately 2 to 3 mm, to have an inwardly widening conical profile, wherein the cone angle is in the magnitude of a few degrees. In order to make the boring process even easier, the front end portion 302 of the tube 300 is cut along a plane slightly inclined relative to the plane perpendicular to the longitudinal axis of the tube 300, said inclination preferably having an angle of 5 to 15 degrees, but it is more preferred that said end portion is provided, on a relatively short section thereof, with a cutting edge having a suitable profile, for example a double-wave profile. With the above mentioned parameters, the boring process is preferably carried out at a rate of approximately 1000 rpm, while the tube 300 is pushed against the metal plate 310 by applying a force of approximately 20 to 30 N, whereby only the outer surface of the solid body forming the inner electrode becomes ductile, or tends to melt, temporarily and locally, whereas the inner part of the solid body still remains in a solid state. Thus the adverse effects deriving from the significant thermal extension and the subsequent contraction of the solid body inserted in the tube may be prevented.
The aforementioned embodiments of the end portion 304 of the tube 300 are illustrated in Figures 4a and 4b in perspective views. In order to achieve the inclined measuring surface, it is preferred that the tube 300 having the sloped or profiled end portion is over-advanced beyond the metal plate 310 to an extent that the entire cross-sectional widths of the tube 300 traverses the metal plate 310.
In another alternative embodiment of the method (not shown in the drawings) according to the invention, the second electrically conductive material is used to make a solid body with a slightly tapered end portion. In this case, the solid body is formed so that its lateral surface matches the inner surfaces of the tube. In this method, however, the solid body is completely inserted into the tube with its tapered end portion, and then secured in the tube by externally pressing the tube thereon. Thus the inner surface of the tube is connected to the lateral surface of the inserted solid body in such a way that the solid body is electrically connected along its entire lateral surface to the inner surface of the tube. The solid body thus inserted and fixed constitutes the inner electrode. Finally, a planar measuring surface is prepared by mechanically finishing both of the end portion of the tube holding the inner electrode, and the outer front surface of the inner electrode.
In the aforementioned various manufacturing methods, the planar measuring surface is prepared preferably by smoothing the end portion of the inner electrode and the tube on the measuring side. The smoothing process may be carried out in multiple steps as well, for example by a first coarse smoothing and subsequently, in order to prepare the final planar measuring surface, by a fine polishing. The planar measuring surface may also be prepared by cutting off a short section of the tube holding the inner electrode on the measuring side. However, it is preferred that the planar measuring surface of the inner electrode is prepared in one step by machining the end portion of the outer electrode and the insulation between the tube and the outer electrode simultaneously, the measurement side, that is, the measuring surface of the complete electrode device comprising both the inner and the outer electrode is produced in a single step. The output terminal wire of the inner electrode is connected to the tube preferably in such a way that it is inserted into the free end of the tube and connected indirectly, for example by soldering, or directly, for example by externally pressing the tube thereon. Thus a reliable and safe, electrically conductive connection is achieved between the wire and the tube. Alternatively, the output terminal wire of the inner electrode may be connected to the rim or the outer surface of the tube in any known manner.
Preferably, securing the tube holding the inner electrode concentrically inside the hollow, typically pipe-like outer electrode is carried out in a way that the tube - and in a particular case, also the output terminal wire connected thereto - is drawn into the outer electrode in a synthetic resin bath, wherein the synthetic resin is preferably epoxy resin. Instead of the synthetic resin bath, other inert material adapted for medical diagnostic use may also be used, provided that said inert material is capable of centering the tube inside the outer electrode after its solidification, and moreover it has an insulating characteristic in its solid state. These materials include, for example, the aforementioned urethane methacrylate-based or methacrylate esther-based adhesives.
For securing the inner electrode-containing tube concentrically within the outer electrode, a plastic centering sheath (not illustrated in the drawings) may be arranged around the tube, wherein said sheath is drawn together with the tube into the hollow outer electrode.
When the wire is inserted into the tube, the part of the output terminal wire of the inner electrode that extends outside the tube is preferably covered by a plastic insulation. The insulation may be drawn onto the wire, for example in the form of a plastic tube. Alternatively, a plastic sheath may be thermo-shrunk onto the wire.
The outer electrode comprising the insulated inner electrode inside is covered by an insulation that preferably also provides a mechanical protection. The material of the insulation includes, for example, PE which is shrunk onto the outer electrode by applying heat, but for example, a synthetic resin may also be considered. As mentioned above, on the outer surface of the outer electrode, a multi-layer insulation may also be provided.
In the electrode device according to the invention, as described herein, there is a long-lasting, electrically conductive connection providing a very high conductivity between the inner electrode and the surrounding tube. A further advantage of such an electrode device is that the measured current intensity is independent of the extent of intrusion of the device into the material to be measured. The above described method of producing the electrode device allows an extremely high production outcome, while the electrical conductivity properties of the electrode devices have a negligible variance.
In the foregoing, the present invention has been described through various embodiments which merely provide a better understanding of the invention, that is the various embodiments described and illustrated in the drawings should not be understood as limited to the specific embodiments. Accordingly, all possible embodiments of the invention fall within the scope of the invention defined by the appended claims.

Claims

Claims
1. A concentric electrode device adapted for using as a medical diagnostic measuring electrode, wherein said electrode device (100) together with the electrolyte present in the tissues forms a galvanic cell, said electrode device (100) comprising
- a tube (110) made of a first electrically conductive material,
- an inner electrode (120) made of a second electrically conductive material and inserted into the tube (110) at one end (112) of the tube (110), - a wire (130) connected to the other end (1 14) of the tube (1 10), said wire constituting an electric output terminal, and
- a hollow outer electrode (140) made of a third electrically conductive material wherein the tube (110) holding the inner electrode (120) is arranged inside the outer electrode (140) in an insulated and concentric manner, and - wherein the inner electrode (120) is electrically connected along its lateral surface to the inner surface of the tube (110), and said tube (110), in turn, is also electrically connected to the output terminal wire (130), characterized in that the inner electrode (120) is inserted in the tube (110) in the form of a solid body and secured mechanically therein so that at least a part of its lateral surface is directly and electrically connected to the inner surface of the tube (110).
2. The concentric electrode device according to claim 1 , characterized in that the inner electrode (120) is electrically connected along its entire lateral surface to the inner surface of the tube (1 10).
3. The concentric electrode device according to claim 1 or 2, characterized in that the second electrically conductive material of the inner electrode (120) is a high- purity metal, preferably with a purity of at least 99,9999%.
4. The concentric electrode device according to any one of claims 1 to 3, characterized in that the second electrically conductive material is magnesium, aluminum, rare-earth metal, gold, silver or platinum.
5. The concentric electrode device according to any one of claims 1 to 4, characterized in that the first electrically conductive material and/or the third electrically conductive material is stainless steel.
6. The concentric electrode device according to any one of claims 1 to 5, characterized in that an insulation (150) made of synthetic resin, preferably epoxy resin, or other adhesive is arranged between the tube (110) and the outer electrode (140).
7. The concentric electrode device according to any one of claims 1 to 6, characterized in that the section of the output terminal wire (130) of the inner electrode (120) that extends outside the tube (1 10) is covered by a plastic insulation (160).
8. The concentric electrode device according to any one of claims 1 to 7, characterized in that the inner surface of the tube (110) is electrically connected to the output terminal wire (130) of the inner electrode (120) by soldering or by externally pressing the tube (1 10) thereon.
9. The concentric electrode device according to any one of claims 1 to 8, characterized in that the outer electrode (140) is substantially longer than the inner electrode (120).
10. The concentric electrode device according to claim 9, characterized in that the electric output terminal of the outer electrode (140) is formed by the section of the outer electrode (140) that extends beyond the inner electrode (120).
11 . A method of producing a concentric electrode device adapted for using as a medical diagnostic measuring electrode, wherein the electrode device together with the electrolyte present in the tissues forms a galvanic cell, characterized in that said method comprising the steps of:
- making a tube (200, 300) of a first electrically conductive material, - at one end of the tube (200, 300), inserting an inner electrode in the form of a solid body (210, 320) made of a second electrically conductive material into the tube (200, 300),
- mechanically securing the inner electrode inside the tube (200, 300) so that at least a part of the lateral surface (214) of the inner electrode be directly and electrically connected to the inner surface (202, 304) of the tube (200, 300),
- electrically connecting an output terminal wire to the other end of the tube (200, 300), and
- accommodating the tube (200, 300) holding the inner electrode and the output terminal wire in an insulated and concentric manner inside a hollow outer electrode made of a third electrically conductive material.
12. The method according to claim 11, characterized in that the inner electrode is secured in the tube (200, 300) so that it be directly and electrically connected along its entire lateral surface (214) to the inner surface (202, 304) of the tube (200, 300).
13. The method according to claim 12, characterized by the further steps of:
- making a solid body (210) of the second electrically conductive material to have a slightly tapered end portion (212), - inserting a high-strength blocking member (230) into the tube (200), on its side adjacent to the output terminal, to a predetermined distance (D), said blocking member (230) having a lateral surface (214) matching the inner surface (202) of the tube (200), said inserted end portion (234) having a planar front surface perpendicular to the longitudinal axis of the tube (200), - inserting the solid body (210) into the tube (200) at its open end so that the tapered end portion (212) of the solid body (210) contacts with the blocking member (230) inside the tube (200),
- pushing the solid body (210) against the blocking member (230) by exerting a high force (F) thus producing a solid inner electrode that is directly and electrically connected, along its entire lateral surface (214), to the inner surface (202) of the tube (200),
- removing the blocking member (230) from the tube (200), and - preparing a planar measuring surface by mechanically finishing the end portions (204) of the tube (200) containing the inner electrode and the outer front surface (216) of the inner electrode.
14. The method according to claim 12, characterized by the further steps of:
- making a metal plate (310) of the second electrically conductive material, said metal plate having a thickness (d) substantially equal to the length of the inner electrode to be produced,
- punching the metal plate (310) by the tube (300) made of the first electrically conductive material, thus producing a solid inner electrode inside the tube (300) at one end of the tube (300), said inner electrode being directly and electrically connected, along its entire lateral surface, to the inner surface (304) of the tube (300) and
- preparing a planar measuring surface by mechanically finishing the end portion (302) of the tube (300) containing the inner electrode and the outer front surface (322) of the inner electrode.
15. The method according to claim 14, characterized by
- producing a tube (300) with a rotationally symmetric shape from the first electrically conductive material, and
- through-boring the metal plate (310) by rotating the tube (300) at a predetermined rate and by advancing it with applying a predetermined intensity of force (F), thus producing a solid inner electrode with a rotationally symmetrical shape inside the tube (300).
16. The method according to claim 11, characterized by
- making a solid body of the second electrically conductive material to have a slightly tapered end portion,
- fully inserting the solid body into the tube with its tapered end portion ahead, - externally pressing the tube onto the inserted solid body so that the solid body be directly and electrically connected, along its entire lateral surface, to the inner surface of the tube, thereby producing a solid inner electrode inside the tube at one end of the tube, and - preparing a planar measuring surface by mechanically finishing the end portion of the tube containing the inner electrode and the outer front surface of the inner electrode.
17. The method according to any one of claims 11 to 16, characterized by inserting the output terminal wire into the free end of the tube (200, 300) and securing it to the tube (200, 300) by soldering or by externally pressing the tube (200, 300) thereon.
18. The method according to any one of claims 11 to 17, characterized in that insertion of the inner electrode-containing tube (200, 300) concentrically inside the outer electrode is carried out by drawing said tube into the outer electrode in a synthetic resin bath.
19. The method according to any one of claims 11 to 18, characterized by covering the section of the output terminal wire that extends outside the tube (200, 300) by a plastic insulation.
20. The method according to any one of claims 11 to 19, characterized by providing the outer electrode having an insulated inner electrode therein with one or more layer of insulation on its outer surface.
PCT/HU2008/000112 2007-10-05 2008-10-03 Concentric electrode device and method of producing concentric electrode device WO2009044216A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11617883B2 (en) 2020-07-13 2023-04-04 Heraeus Deutschland GmbH & Co. KG Multilayer ring electrode having a plurality of openings

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4184486A (en) * 1977-08-11 1980-01-22 Radelkis Elektrokemiai Muszergyarto Szovetkezet Diagnostic method and sensor device for detecting lesions in body tissues
HU206610B (en) * 1990-01-15 1992-12-28 Lajos Papa Concentric electrode device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4184486A (en) * 1977-08-11 1980-01-22 Radelkis Elektrokemiai Muszergyarto Szovetkezet Diagnostic method and sensor device for detecting lesions in body tissues
HU206610B (en) * 1990-01-15 1992-12-28 Lajos Papa Concentric electrode device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11617883B2 (en) 2020-07-13 2023-04-04 Heraeus Deutschland GmbH & Co. KG Multilayer ring electrode having a plurality of openings

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