DE1639257B1 - HIGH FREQUENCY PLASMA GENERATOR - Google Patents

Description

The invention relates to a high-frequency plasma ratio for cooling the front gene generator with a cylindrical tube, at the ratorteils present, so that when the main application is Front side the gas to be ionized and on area of the plasma jet generator as surgical whose other end face the generated plasma from cutting instrument this part to touch and flows, an induction coil, one end of which can be used to guide the instrument. It Ground is a high-frequency generator, which then this generator part is also at ground potential the other end of the induction coil and one placed.

between the two ends of the induction coil. Some of those shown in the drawing Lay tap on the induction coil connected to special embodiments of the invention, the entire circuit arrangement between the two look in connection with the following the ends of the induction coil a detailed description of the properties, frequency voltage generated, which is greater than that of the times and advantages of the invention again clearly Generator supplied excitation voltage, and the clear. There are also memory streams from this description of the pipe to the high voltage that advantageously further develops the invention end of the induction coil is connected. 15 embodiments and modifications. It

Shows efficiency, stability and voltage level

are in these known high-frequency plasma F i g. 1 is an overall view of a preferred generator not as desired. The plasma jet torch is also used as a guide,
Ignition requires an auxiliary electrode, which is the reason for F i g. 2 complicated the same plasma torch in an open structure. In addition, the excitation coil 20 state is slightly enlarged,
arranged concentrically around a solid electrode, as shown in FIG. 3 is a further enlarged view of the fact that this electrode is heated inductively within the coil of the plasma jet burner according to FIG

but the efficiency also decreases significantly. The well-known plasma generator also works in a longitudinal section,
A preferred embodiment of the invention, between the high-frequency generator and the pias, which is shown in FIGS. 1 to 3, has a plasma torch are relatively short. burner 10, which has a substantially cylindrical,

The object of the invention is therefore a highly conductive protective housing 12 which is made in one piece frequency plasma jet generator which can be manufactured above 30 aluminum, and a reverse Kind to improve so that the indicated wärtigen section 14, a front section 16, Disadvantages are eliminated, with particular emphasis on the smaller diameter and one of the two simpler ones Handling, simple design, safe conical transition section connecting cuts and has stable operation and good efficiency placed 18. The protective housing 12 has a rear. 35 front opening 20, a front opening 22 and a

These goals are achieved according to the invention in a channel or annular groove 24 (FIG. 3) on the inner surface in

Generator of the above type achieved in that the vicinity of the front end 23.

an end portion of the tube at the gas outlet end from the protective housing 12 contains a high-frequency metal and to the high-voltage coil 30 made of copper, which is a dielectric gas supply end The end of the induction coil is placed that the 40 tube 32, z. B. contains plastic through which Concentric and electrically isolated from a gas generally under pressure in a single tube metallic housing is surrounded, which moves with the direction indicated by an arrow 34 (Fig. 3) Ground end of the induction coil is connected or blown. It should be emphasized, however, den is, and that the gas discharge between the that the coil 30 has no ionizing effect on the both adjacent ends of the tube and housing 45 exerts gas flowing through the supply tube 32, Due to a capacitive coupling between the- The tube 32 is only therefore within the coil and sen both components takes place. arranged concentrically with this in order to

The capacitive coupling is used in this high-penetration structure and a handy form of the To enable frequency plasma jet generator by means of spatial plasma torch. The gas supply pipe Lent design of the high-voltage side achieved, where 50 32 could just as well outside the coil 30 attached the frequency can only be ordered in two by the inductance. The tube 32 consists of a heat th connection point is determined, so that a higher non-conductive material.

Tension can be achieved and stability. The gas supply pipe 32 enters the interior of the

Significantly improved and independent of the plasma itself, protective housing 12 through a central bore 38

gig is. The plasma generator ignites at regulated 55 a plug 40, which is made of a suitable di-

Conditions exist even without the aid of an auxiliary electrical material. The extensive edge

electrode and is because of the between the high of the plug is provided with a groove 42, which the

voltage part and the mass occurring capacity inclusion of a heat-resistant O-ring 44 for

improved in efficiency. For efficiency sealing of the plug against the housing

improvement also contributes significantly to the fact that the wire serves 60 so that its interior is liquid-tight.

Belstrom losses can be kept low. It is also closed while it is however using

In contrast to the well-known, the plasma gas needs a sufficiently large force possible by hand

th arrangement is not borrowed by the high-frequency field, the protective housing 12 from the other

to be passed through. components of the plasma torch 10 to be removed, such as

Because of the formation of the front conduction path 65, this is shown in FIG. 2 is shown.

for the plasma gas as concentric in the housing. The energy of a high frequency generator is about

Running pipe becomes a mathematically clear grasping a coaxial cable 50 (Fig. I and 2) with the head

Bare capacity is formed, and there are clear of the plasma torch, as well as with a coaxial

ORIGINAL INSPECTED

3 4

Grounding cable 52 and a central cable guide quenten high voltage with the front tip of the

54 coupled (Fig. 2). The grounding cable 52 is its electrode tube contributes to the possible accessibility

On the other hand with the grounded rear end 56 that of a power efficiency when using the

Coil 30 connected via a metal sleeve 58, the plasma torch by 90 or more percent at.
The plug 40 passes through a bore 59. 5 Under power efficiency is the ratio of

The sleeve 58 also transmits the outflow from the coolant delivered by the plasma delivery to a workpiece from the interior of the housing in a power to the through the high frequency genera drain pipe 60, the z. B. made of plastic gate to the tank circuit of the plasma torch 10 can be. The coolant outflow is usually understood to be guided power. The nozzle head 90 in the direction shown by an arrow 62 (FIG. 3) is in the embodiment shown by machining to a suitable heat exchanger (not machined or otherwise processed to show a liquid). The metal sleeve 58 has a grounded end to ensure a tight seal with the heat-resistant element 56 of the coil 30 via a short electrical cable 64 O-ring 96 as soon as the inner part is connected. of the plasma torch to its normal position by hand

An elastic wire or spring 56 provides a 15 mounting position in which it is in the

electrical connection of the grounded coil end is held in the housing with a press fit (F i g. 3). The inner one

Area of the sleeve 58 with a point 68 of the housing Dimension and the shape of a bore 92 of the

ses 12 ago. Head 90 as well as the length and shape of the latter

The centrally arranged coaxial cable 54 is electrically determined by the intended use, for world-wide the plasma cloud 108 is provided directly with an intermediate turn 70 or 20, as well as from

a tap on the coil 30, a few turns of the desired power to be generated by the

in front of their earthed end via a metallic mas. The nozzle head can be press fit onto the front

Coolant outflow pipe 72 and a short cable 74 the end 94 of the electrode 82 placed or on

tied together. fixed in the desired position in another way

That turn 70 of the coil to which the short 25 will be, e.g. B. with the help of a suitable binder. Cable 74 is connected, is carried out by experiments determined by calculation so that the exchangers (not shown) are determined by a coolant supply impedance of the coaxial cable 54 with that of the coil over pipe 73 and a coolant pipe 72 in the through agrees to output a low direction shown by arrow 71 on the coaxial cable. The leading standing wave ratio, preferably in the size 30 tube 72 penetrates the plug 40 through the drilling arrangement from 1 to 1.5. The number of tion 75. The supplied coolant is preferential coil windings, the wire thickness and the opening via a connecting sleeve 100 and a meter of the coil are all so desired to bring about a feed tube 102 through its opening 104 Impedance selected, given that it is directly on the nozzle head 90

The front end 80 of the spool is hit at a point 35, as indicated by arrow 106. Ge-84 However, the sleeve 100 and the disconnection can optionally be connected directly to a metallic electrode tube 82. The diameter of the tube 82 is the transfer tube 102 to be removed.

The inner diameter of the gas supply pipe 32 is adapted. In this way, the coolant first arrives

to a good union of the two tubes with the nozzle head 90 in contact, in the When End region 86 of the gas supply pipe 32 to enable the gas to be ionized locally to form plasma. So-

lichen. A stream of gas that is to be ionized then flows into contact with the coolant

is through the central bore 88 of the electrode inner surface of the housing 12 and the outer surface

tube 82 into a generally layered stream of electrode 82, tubes 100 and 102, and des

blown through. Gas supply pipe 32 backwards, the induction

The coil causes the generation of a high frequency coil 30 in which it is completely immersed.

quenten high voltage, which is significantly higher than Finally, the coolant passes through the sleeve

is the reference voltage applied between the rear 58 and the outlet pipe 60 to the heat exchanger.

Coil end 56 and the intermediate turn 70 occurs. back.

The high-frequency chip generated by the coil is therefore the electrode tube, the ceramic one Voltage is drawn from the front end 80 of the coil directly at the 5 ° nozzle head, the high frequency coil, the gas supply the electrode tube 82 via the connecting tube, the coolant line tube and discharge tube as well position 84 transferred. the radio frequency lines and links, and

The front end 94 of the electrode tube is shared with the cylindrical housing by the cooling

a nozzle head 90 is provided, which is cooled from a high-medium.

refractory, dielectric ceramic material, such as 55. The housing 12, which is supported by the cable 66 on the e.g. B. boron nitride or aluminum oxide, the reference voltage is maintained, good thermal conduction and dielectric properties are capacitively coupled to the electrode tube 82 over the coolant. The nozzle head 90 forms a narrow stream, with the housing acting as one plate and the elec- trode channel 92. Such a constriction serves a) the electrode acts as the other plate of a capacitor. to create eddy currents of the gas in the area of the front end of the electrode, at which the gas is locally ionized to plasma by the selected frequency and the induction, and the tive resistance of the plasma generator, and the tive resistance of the plasma generator, b) for Prevention of a backflow phenomenon and the dimensions of the housing and the electrode impact ignition in the opposite direction of the gas flow. tube, as well as the air gap in between. The electrode82 should be made of a material such as 65, which helps determine the size of the capacitive copper, which has good thermal and electrical resistance,
trischo has conductive properties. Not all coolants are designed to develop the

The direct physical coupling of the high-frequency capacity is suitable. Distilled water

5 6

ser would be useful but is not preferred. End 94 of the electrode. This makes the gas partial-preferential a liquid, inert fluorine compound is ionized and a plasma cloud is released used as a coolant. Freon is also introduced spontaneously as 108 without the application of any Suitable for coolant. The cooling liquid must auxiliary equipment for plasma formation, such as this be inert in any case, a low dielectric Kon- 5 is required in known devices. Like it stante, high dielectric strength (i.e. contrary to the sharp-edged formation of the board against arcing, arcing, the electrode end of which can be attributed to the or short circuit), a low viscosity and a local electrical conversion from gas to plasma have good thermal conductivity to go on at the same time.

cool and the capacitive coupling of the electrode io The entry of the gas into the narrow channel 92, wel-

with the housing and a spark rather reduces the gas flow, causes a

to prevent rollover. Mixing or turbulence of the gas in the vicinity

During operation, the cooling liquid flows in the series of the gas ionization area. At the same time

after passing through the supply pipes 73,72,100,102, the narrow channel 92 prevents a reflux of plasma

around the ceramic nozzle head 90 and along the 15 against the gas flow or its non-return ignition

metallic electrode 82, around the entrance.

immersed induction coil 30 and through the sensing If the plasma has a low ionization potential

Generating pipes 58 and 60. Gas is possessed under pressure in tial, such as argon, becomes the plasma cloud

the gas supply pipe 32 is blown as this by 108 have very little heat as it means

the arrow 34 is indicated and flows through the zen- 20 a high frequency high voltage is formed and

central bore 88 of the electrode tube 82 and out it flows into the plasma, if only one

this through the bore 92 of the nozzle head 90 in low high-frequency current. Once this weak

the free atmosphere. ionized plasma but with a material in contact

Which is preferably moved by the high-frequency generator, the moderate conductivity properties Energy generated in a range from 10 to 100 MHz has a high-frequency current from the end 94 Energy is via the coaxial cable 50 in the above-described electrode 82 through the plasma to the flow in the same way with the corresponding parallel conductive material. This condition is under resonance-adjusted tank circuit coupled to prevent coupling of the plasma with a conductor Has inductance-capacitance ratio. The stand.

The tank circuit consists of the coil 80, the electrode 82 30 For operating the plasma torch and for and the metal housing 12. The plasma generator enables the plasma coupling with a suitable must be set so that a standing wave converts workpiece or with air is no special relationship on the coax connection cable, position of the burner required and any which is no greater than 3 to 1, but preferably noble gas or gas or a mixture thereof 1.5 to 1, whereby under the standing wave ratio the dimension 35 without structural change of the burner or the imbalance between the load and replacement of parts of the same are used, the transmission line is to be understood. The induc- The change from one gas to another can tive resistance is intended to be selected for a given without extinguishing the burner and without losing the Frequency should be dimensioned as high as possible (to be carried out- efficiency. The flow of the at least around 1000), so that a high-frequency high-frequency current through the existing plasma voltage on the "hot" or not on the cloud 100 causes the plasma to be heated until The end 80 of the coil 30 which is under tension, there is an almost one hundred percent ionization can be procreated. Once the radio frequency energy has a resistance of about 0.01 ohms per centibei The resonance frequency of the plasma generator reached via the meter, which value when using Coax cable acts on the coil 30, are sultry 45 argon as a plasma gas only slightly higher than that of generated in the tank circuit. Graphite is. In general one can say that the

The coil 30 develops in the tank circuit an inductive amount of heat transferred to the same extent as

activity and between the electrode 82 and the rise as the power expended,

housing 12 creates a capacity with an additional - It is also possible to use the plasma torch

capacity between the coil 30 and the Ge 50 given plasma cloud directly with the atmospheric

housing 12. At a value of the ratio of the in- see air to couple, and if necessary afterwards

ductivity to the capacitance of a smallest conductor with a dielectric. Increases with increased performance

Actance value of 1000 ohms with a selected value also the inclination of the released plasma cloud

drive frequency in the plasma torch is to be coupled with air. Slow gas flows that a

have a 55 smaller flow volume per unit of time between the electrode 82 and the housing 12,

high frequency high voltage generated. increase this willingness to couple the plasma

The high frequency high voltage on the front cloud with the air. The reasons for this phenomenon

The end of the coil is many times higher than the voltage.

Value of the reference voltage in the coil between the kannt.

Connection points 56 and 70. The connection through the dielectric 60 The coupling of the released plasma with non-

tric pipe 32 flowing gas flow is required by the conductors that the plasma cloud first ther-

Induction coil 30 not ionized. The gas flow mixes with the air, which in turn is coupled with

through the tube 32 and through the electrode tube 88 dielectric can be coupled.

flows essentially laminar until it reaches the nozzle head by setting the flow rate appropriately 90 reached. The high frequency energy produced by the plasma gas as well as the size of the high frequency whose end of the coil comes directly to the elec- trode voltage, which abtrode directly to the electrode tube 82 is coupled, causes a local high frequency is, both noble gases and quente Excitation of the gas in the area of the front homely gases with the help of the same plasma torch

ners are ionized in order to interfere with a ceramic material between the inner surface of the Head or with the surrounding air or through the housing 12 and the spaced-apart

Air with a dielectric high efficiency electrode 154 and coil 134 is amazing

degree to achieve. effective, especially at frequencies in the range

The plasma torch 10 according to FIG. 4 indicates an im 5 of 30 MHz or more.

essential cylindrical, conductive protective housing energy is from a high frequency generator via 12, the one-piece design a back a coaxial grounded cable 158 and another wärtigen section 14, a conical transition cable 160 taken. The grounded cable 158 is section 18 and a front section 16 are in turn conductive at the connection point 159 smaller diameter than the rear portion 14 io the housing 12 and with the grounded end 162 owns. The housing 12 has a thread connected to the internal thread of the spool 134. The cable 160 is at the provided rear opening 20 and a front tap 163 with an intermediate turn 164 in Opening 22 in the vicinity of the front housing end 23 is satisfactorily connected, which Winauf. as the penultimate before the earthed coil end. The housing surrounds a hollow 15 at a distance. The exact position of the connec radio frequency coil 134 and a hollow high frequency point of the cable 160 with the coil 134 hangs sequence electrode, which parts are preferably made in one piece largely from the impedance of the coaxial cable are made of brass. The inside of the coil 140 off.

134 and the electrode 154 is connected to the interior of the circuit described forms a tank plasma gas supply pipe 138 connected, the circuit with 20, which is combined from the coil 34, the electrode 154 and a coaxial cable 140 into one piece. A metal housing 12 is assembled. The pouring Gas that arises in the inductivity of the tank circuit indicated by an arrow 142 primarily through flows in the direction shown, passes through the supply coil 134 and in particular through the electrode tube 138 into the interior of the in the area of the inlet 154, which ends in one piece via a brass tube 136 are tightly connected to the tube 138 and are essentially connected via the coil 134. It should be emphasized that the coil 134 extend the entire length of the housing. The capacity the gas flowing through is not ionized and to the tank circuit is mainly between the Plasma reshapes, although it can be assumed, electrode 154 and metal housing 12 are formed that the ionization of the gas that of a voltage although a part of the capacity also between that exposed, the size of which occurs in the flow direction 30 coil 134 and the metal housing 12, increases without ionization to form plasma, which only in the loading The front end 157 of the electrode 154 stands with area of the nozzle head at the outlet end of the burner a narrow passage 170 of the nozzle head 156 in 10 takes place, to a certain extent initiated connection, which is done by hand in the front opening. voltage 130 of the housing 12 is pressed. Therefore, the coaxial cable 140 is in the interior of the housing 35 and the nozzle head 156 can be removed by hand 12 is replaced by a centrally arranged opening 144 of a nozzle head of a different design the rear end 20 of the housing 12 to be closed to plasma of various types and with Verßenden, to produce different properties in this screw-in threaded plug. The front one introduced. The end section of the electrode 154 directed towards the interior of the housing fits very precisely into Front surface 147 of plug 146 presses against 40 a rearwardly directed bore 172 of the nozzle annular disc 148 made of elastomeric head 156. A highly heat-resistant O-ring 174, material. which is arranged in an annular groove 176 of the nozzle head 156. The front surface 149 of the disc 148 is located below and holds the latter in its position of use Pressure on the rear edge 152 of a ceramic solid, but allows its removal by hand. body 150 to the inner wall of the housing 45 The narrow gas passage 170 for the gas flow bileng adapted and therein by the pressure of the disc det a constriction of the same, which serves to 148 is recorded. The coil 134 and the integral 1. vortexing of the gas in the area of the vormit The electrode 154 produced in this way is to be produced in the keg end 157 of the electrode 154 Ceramic body 150 permanently embedded. If at which point is the ionization of the gas alone If desired, the ceramic body 150 including the 50 plasma going on and the coil 134 a high-coil 134 and the electrode 154 generated by the back-frequency high voltage that significantly wärtige opening 20 of the housing 12 pulled out greater than the reference voltage at the rear will. A preferred ceramic material is boron- the end of the coil 134 is, and 2. a flashback nitride, although equivalent ceramics with premature ignition against the direction of the gas flow too borrowed high dielectric strength against 55 prevent.

Be used over high-frequency voltages During operation, gas is under pressure

can. through inlet port 136 into the interior of the spool

It has been found that the use of Ke-134 and the electrode 154 blown like that through

Ramikmaterial is not always necessary and that one arrow 142 is indicated. The gas flow is

Operation without this material is in some cases still preferably essentially laminar. The plasma gas

can be improved. It has been observed that when entering the coil, the reference potential has

that ceramic material under certain conditions and is only ionized at a high voltage,

Power absorbed and therefore with certain operating d. H. reshaped to plasma that is at the front end

frequencies is unsuitable as a dielectric body. 157 of the electrode 154 occurs, although some Conversely, the use of ceramic 65 low ionization of the gas has probably already been

Shem material at relatively low frequencies well beforehand in the course of its passage through the

proven. Coil and the electrode occurs.

The application of an air gap in place of the energy from the high frequency generator is due

the coaxial cable 140 coupled in the manner described in the tank circuit, which consists 154 and the metal case 12 from the coil 134 of the electrode.

The high-tension high-frequency energy, which is directly coupled to the electrode, causes, as mentioned, a local high-frequency excitation or ionization of the plasma gas only in the area of the front end 157 of the electrode. The gas is therefore initially partially ionized until a sudden release of the plasma cloud 108 sets in, without the use of auxiliary devices which initiate the plasma release. The flow rate of gas and the energy supplied by electrode 154 can be coupled to a suitable workpiece or to air to produce a fully ionized plasma. Any noble gas or ordinary gas or a mixture thereof can be used in the manner described above. In principle, the appearance of the plasma formation is similar to that already described in connection with the first embodiment of the invention.

The heat generated in the high frequency coil 134 and / or the electrode 154 is carried away by the flow of the plasma gas as it flows to the nozzle head 156.

The heat generated at the end 157 of the electrode is dissipated into the nozzle head 156 and the ceramic body 150 and finally into the housing 121 , unless it has already been released into the environment by the ceramic body or the head. If there is only an air gap between the housing 121 and the electrode 154 combined with the coil 134 , the heat generated at the front end 157 of the electrode is conducted into the nozzle head and from there to the surrounding air and partly to the housing 121 enclosing it submitted.

The embodiment according to FIG. 4 has the advantage that no cooling liquid is required. This gives greater reliability and reduces the number of components required, as there are no pumps, no heat exchangers, no connecting pipes for conducting the cooling liquid and no liquid-tight O-rings to seal the front and rear openings of the housing 12 . The plasma torch 10 according to FIG. 4 is usually more suitable for surgical purposes than the torch 10 according to FIGS. 1 to 3, since it is smaller, lighter and more manageable than the latter and there is no risk of cooling liquid being deposited in open wounds and since it is possible to exchange the nozzle head to produce the desired shape of a plasma cloud without the cooling liquid being spilled. The efficiency of the air-cooled burner 10 is somewhat better than that of the liquid-cooled burner 10, since the energy requirement of the former is noticeably lower as a result of the lower power losses due to the material surrounding the electrode. The required power can be in the range of about 100 watts or less.

It should be emphasized that the use of a cooling liquid for high-performance burners with performances of 200 watts and above is necessary

is considered. , 6g

Claims (11)

Patent claims: 1. High frequency plasma jet generator with a cylindrical tube, at one end of which the gas to be ionized is supplied and at its other end face the generated plasma flows out, an induction coil, one end of which is connected to ground is a high frequency generator connected to the other end of the induction coil and a Located between the two ends of the induction coil tap connected to the induction coil is, with all the circuitry between the ends of the induction coil one Generates high-frequency voltage that is greater than the excitation voltage supplied by the generator, and the outlet end of the tube to the high voltage end of the induction coil is connected, characterized in that an end section (82) of the tube (32) at the gas outlet end consists of metal and at the high voltage end (84) of the induction coil (30) that the tube (32) is surrounded concentrically and electrically insulated by a metallic housing (12), which is connected to the grounded end (56) of the induction coil (30), and that the Gas discharge between the two adjacent ends (23, 94) of the tube and the housing due to the reason a capacitive coupling takes place between these two components. 2. High-frequency plasma jet generator according to claim 1, characterized in that the electrode tube (82, 154) at the outflow end has a narrowed opening (92, 170) serving as a back-up and backfire prevention device, through which the plasma flows out into the atmosphere. 3. High-frequency plasma jet generator according to claim 2, characterized in that the narrowed opening (92, 170) is located in a removable, thermally conductive, dielectric nozzle (90, 156) . 4. High-frequency plasma jet generator according to one of claims 1 to 3, characterized in that the induction coil (134) and the tube (154) represent a continuous inner channel through which the gas flows continuously. 5. High-frequency plasma jet generator according to one of claims 1 to 4, characterized in that the induction coil (30, 134) and the tube (82, 154) are separated from the metal housing (12, 121) by air, a cooling liquid or a ceramic material. 6. High-frequency plasma jet generator according to claim 5, characterized in that a Cooling liquid is provided, the values of which during operation of the dielectric constant, the dielectric strength, the viscosity and thermal conductivity at least equal to the values of distilled Reach water. 7. High-frequency plasma jet generator according to claim 1, characterized in that the end portion (82, 154) of the tube is outside the field of the induction coil (30, 134) . 8. High-frequency plasma jet generator according to one of claims 1 to 7, characterized in that that the capacitive coupling and the induction coil have such a ratio of have inductive to capacitive reactance that at a selected plasma operating frequency of minimum reactance value is about 1000 ohms. 9. High frequency plasma jet generator according to one of claims I to 8, characterized in that that the position of the tap on the induction coil is chosen so that the coil impedance is adapted to the impedance of the supply lines. 10. High-frequency plasma jet generator according to one of claims 1 to 9, characterized draws that in the supply lines from the RF energy source to the induction coil pipe pieces (59,75) through which a coolant flows. 11. Using the high frequency plasma jet generator according to one of claims 1 to 10 as a surgical scalpel. 1 sheet of drawings