US-12628262-B2 - Electrode arrangement

US12628262B2US 12628262 B2US12628262 B2US 12628262B2US-12628262-B2

Abstract

The invention relates to an electrode arrangement for a plasma jet device comprising a first and a second printed circuit board each having an exposed surface of a circuit path serving as electrode and facing the other printed circuit board, a spacer arranged between the first and second circuit board and a plasma cell arranged between the first and second printed circuit board and the spacer wherein the plasma cell has a gas inlet and a plasma outlet. The invention further relates to a plasma head comprising said electrode arrangement.

Inventors

Loic Ledernez
Michael Bergmann
Markus Altenburger

Assignees

FREIBURGER MEDIZINTECHNIK GMBH

Dates

Publication Date: 20260512
Application Date: 20210713
Priority Date: 20200713

Claims (13)

1 . An electrode arrangement for a plasma jet device comprising: a first printed circuit board having a first exposed surface of a first conductive track serving as a first electrode, and a second printed circuit board having a second exposed surface of a second conductive track serving as a second electrode; a spacer sandwiched between and in contact with the first and second printed circuit boards; a plasma cell formed by the first and second printed circuit boards and the spacer wherein the plasma cell has a gas inlet and a plasma outlet; wherein the spacer defines side walls of the plasma cell and a height of the spacer defines a distance between the first and second printed circuit boards and between the first and second electrodes; wherein the first exposed surface of the first conductive track is facing the second printed circuit board and the second exposed surface of the second conductive track is facing the first printed circuit board; wherein the first and the second printed circuit boards have an identical shape and are arranged in a mirrored position flipped by 180 degrees around a longitudinal gas flow axis between the gas inlet and the plasma outlet; wherein each of the first and the second printed circuit boards has a finger shaped projection providing an electrical connection located at a side of the gas inlet.
2 . The electrode arrangement according to claim 1 wherein the spacer is made of plastic.
3 . The electrode arrangement according to claim 1 , wherein the first and second electrodes are laterally spaced apart by the spacer, wherein a first groove is arranged in the first printed circuit board between the first electrode and the spacer and a second groove is arranged in the second printed circuit board between the second electrode and the spacer, further wherein the first groove has a depth being equal to or greater than a thickness of the first conductive track and the second groove has a depth being equal to or greater than a thickness of the second conductive track.
4 . The electrode arrangement according to claim 1 , wherein the first and second printed circuit boards are arranged in parallel to each other.
5 . The electrode arrangement according to claim 1 , wherein the first and second exposed surfaces each comprises a coating.
6 . The electrode arrangement according to claim 1 , wherein the first and second printed circuit boards and the spacer are made of a flexible material.
7 . The electrode arrangement according to claim 1 , wherein the first and the second electrodes are adapted to be connected with a pulsed voltage source such that pulse discharges between the first and the second electrodes are generated.
8 . A plasma head having a first end and an opposite second end comprising: the electrode arrangement according to claim 1 on the first end; a connector for connecting the plasma head with a handle on the second end; and electrical and gas connections from the connector to the electrode arrangement.
9 . The plasma head according to claim 8 having a plasma exiting tip in form of a hollow cylinder.
10 . The plasma head according to claim 9 having a plasma exiting tip consisting of two sheets which are connected to each other at two lateral sides, wherein each of the two sheets comprise a polyimide film, wherein the electrode arrangement is part of the plasma exiting tip.
11 . The plasma head according to claim 8 , wherein the connector comprises a mechanical connector having cylindrical segments arranged coaxially to each other and two electrical connectors extending radially beyond the outer cylindrical surface of the cylindrical segments.
12 . The plasma head according to claim 11 , wherein each of the two electrical connectors is connected to one of the first and second printed circuit boards, wherein the first and second printed circuit boards are connected to build a support extending along an axis of the cylindrical segments.
13 . The plasma head according to claim 12 , wherein a gas connector at a front face of the cylindrical segments is fluidly connected with a hollow of the support.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This is the United States national phase of International Patent Application No. PCT/EP2021/069484, filed Jul. 13, 2021, which claims priority to European Patent Application No. EP 20185527.7, filed Jul. 13, 2020, the entire contents of each of which being hereby incorporated by reference herein. FIELD OF THE DISCLOSURE The present invention relates to an electrode arrangement for a plasma jet device as well as a plasma head comprising an electrode arrangement. BACKGROUND It is known to use non-thermal atmospheric pressure plasma especially in medical devices. The use of non-thermal plasma for dental applications is also known. Non-thermal plasma is generally produced by a gas discharge at atmospheric pressure. Such plasma cannot be produced or sustained over long distances such that the plasma concentrates in a small volume between the electrodes which are arranged in a near proximity. In the small volume between two electrodes, to which is often referred to as plasma cell, prevails a high concentration of plasma particles having a high energy. In order to avoid arcing, which would increase the temperature in the plasma cell due to the high temperatures of the arc, electric barrier discharge devices are often used when it comes to an atmospheric pressure plasma device having a close proximity of the two electrodes. Such a dielectric barrier discharge device having an insulating dielectric material between the two electrodes adding a high electrical resistance in the inter-electrode space, are shown for example in EP 2 936 943 B1 or US 2010/0 125 267 A1. Often the two electrodes are completely encapsulated in a dielectric material, for example a plastic material. WO 2013/109699 A1 discloses system and method for operating an ionizer using a combination of amplitude modulation and pulse width modulation to control the plasma temperature and the type of ions needed for analytic equipment. The ionization source is a dielectric barrier discharge gas ionizer, which has two metal electrodes separated by an insulator. By protecting the electrodes with a ceramic or dielectric, the ionizer will have a longer lifetime and will generate a cleaner plasma. WO 2002/078838 A1 discloses non-thermal plasma reactor for chemical reduction of nitrogen oxide (NOx) emissions in the exhaust gases of automotive engines, particularly diesel and other engines operating with lean air fuel mixtures that produce relatively high emission of NOx. The non-thermal plasma reactor is a dielectric barrier type rector in a multi-cell stack configuration. Two E-shaped dielectric barriers are paired together and are sandwiched by electrodes to form a single cell unit. KR 10 2012 002 6248 A discloses an apparatus for irradiating plasma having a wide irradiation range by generating plasma at normal pressure and having a line array type. The apparatus comprises a substrate stack. The first electrode is formed by strip lines on the surfaces of the multiple substrates of the stack. The second, ground electrode is formed outside the upper and lower substrates and outside the plasma cell. The discharge is induced between the strip lines on the surfaces of the multiple substrates of the stack serving as first electrode and the ground electrode. One drawback of creating plasma in a dielectric barrier discharge device is that a very high excitation frequency of 10 kHz or more is required. Such high excitation frequencies result in a very complex frequency generator having high electrical losses. When powered by a high frequency generator, the plasma reflects some of the supplied power. The reflected energy is the energy supplied by the generator but not converted into plasma. The reflected power is dangerous for the electrical circuitry. It is dissipated in the form of heat, which may result in overheating damages. GENERAL DESCRIPTION The object of the present invention is to provide an electrode arrangement as well as a plasma head with a plasma cell providing stable conditions for igniting plasma in a simple manner. According to one aspect of the present invention, the electrode arrangement for a plasma jet device comprises a first and a second printed circuit board, each having an exposed surface of a circuit path serving as an electrode and facing the other printed circuit board. A spacer is arranged between the first and the second circuit board. A plasma cell is arranged between the first and second printed circuit board and the spacer. The plasma cell has a gas inlet and a plasma outlet. The circuit path is attached to a substrate of the printed circuit board in a common manner. The substrate, which may be generally provided as a plane layer, provides a support for the circuit path (conductive track). The substrate is made of a dielectric material, preferably any common printed circuit board (PCB) material such as FR4—a composite material composed of woven fiberglass cloth with an epoxy resin binder that is f