PLASMA TREATMENT ARRANGEMENT AND METHOD FOR ADAPTING THE SIZE OF A SUPPORT AREA OF THE PLASMA TREATMENT ARRANGEMENT TO THE SIZE OF THE SURFACE TO BE TREATED

Abstract

In a plasma treatment arrangement for carrying out dielectrically impeded plasma discharge onto a surface to be treated having a flat electrode unit (4) which has a treatment side, and a control unit (11) which supplies at least one electrode (19) of the electrode unit (4) with a high-voltage AC potential for a power which is required for plasma generation between the at least one electrode (19) and a counterelectrode which forms a reference potential, wherein the at least one electrode (19) which receives the high-voltage AC potential is shielded with a flat dielectric (7), at least on the treatment side, and wherein the flat electrode unit is designed to reduce the size of its support area on the surface to be treated for the purpose of adaptation to the size of the surface to be treated, the adaptation of the support area of the flat electrode unit (4) becomes possible in an unproblematical manner on account of the control unit (11) having a device (14) for determining the size of the adapted support area and a control device for adjusting the power to be output to the at least one electrode (19) in accordance with the determined size of the support area.

Claims

1. A plasma treatment arrangement for carrying out a dielectric barrier plasma discharge on a surface to be treated, comprising a planar electrode unit (4) that has a treatment side, and a control unit (11) which supplies at least one electrode (19) of the electrode unit (4) with a high-voltage AC potential required for generating a plasma between the at least one electrode (19) and a counter electrode that forms a reference potential, wherein the at least one electrode (19) receiving the high-voltage AC potential is shielded by a planar dielectric (7) at least toward the treatment side and wherein the planar electrode unit is formed to reduce the size of its contact face on the surface to be treated for the adaptation to the size of the surface to be treated, characterized in that the control unit (11) has a device (14) for determining the size of the fitted contact face and a control device for adjusting the power to be output to the at least one electrode (19) on the basis of the determined size of the contact face.

2. The treatment arrangement as claimed in claim 1, characterized in that the planar electrode unit (4) is formed as a stripe with at least one electrode of a given width extending in the longitudinal direction between a first end and a second end, wherein the length of the stripe determines the size of the contact face, and in that the device for determining the size of the contact face contains a detection arrangement (14) for the length of the stripe.

3. The plasma treatment arrangement as claimed in claim 2, characterized in that the detection arrangement (14) is formed to determine the length of the stripe by means of an electrical test signal transported on the at least one electrode.

4. The plasma treatment arrangement as claimed in claim 3, characterized in that the electrode (19) is formed to reflect, at the second end, the electrical test signal coupled in at the first end.

5. The plasma treatment arrangement as claimed in claim 4, characterized in that the detection arrangement (14) contains a frequency generator designed to generate an electrical test signal and an adjustment device for continuously adjusting the frequency of the test signal and a detection device for determining the amplitude of the test signal.

6. The plasma treatment arrangement as claimed in claim 5, characterized in that the frequency generator is formed to generate an electrical test signal in the form of a harmonic wave train.

7. The plasma treatment arrangement as claimed in claim 1, characterized in that the control unit (11) comprises a camera arrangement with at least one camera (30) and an evaluation device for determining the length and/or the area of the electrode unit.

8. The plasma treatment arrangement as claimed in claim 1, characterized in that the electrode unit (4, 40) consists of a plurality of sections (5, 50) with electrodes that are constructed in the same way, between which predetermined separation lines (6) are present, and so the reduction in the size of the contact face is implemented by detaching one or more sections (5, 50).

9. The plasma treatment arrangement as claimed in claim 8, characterized in that the sections (50) carry different codes (22), for which the control unit contains a reader, and in that the connection of the electrode unit (4) to the control unit (11) is envisaged on the section (50) from which one or more sections were detached.

10. A method for adapting the size of a contact face of a planar electrode unit (4) that has a treatment side and is part of a plasma treatment arrangement for carrying out a dielectric barrier plasma discharge on a surface to be treated, to the size of the surface to be treated, wherein a high-voltage AC potential for a power required for generating a plasma between the at least one electrode (19) and a counter electrode that forms a reference potential is supplied to the at least one electrode (19) of the electrode unit (4) by means of a control unit (11), the at least one electrode (19) receiving the high-voltage AC potential is shielded by a planar dielectric (7), at least to the treatment side, and wherein the contact face of the electrode unit (4) is reduced for the adaptation to the size of the surface to be treated, characterized in that the size of the reduced surface is determined by the control unit (11) and the power to be supplied to the at least one electrode (19) is adjusted accordingly on the basis of the determined size of the contact face.

Description

[0033] A first embodiment of a plasma treatment arrangement according to the invention is illustrated in FIGS. 1 to 5. An electrode unit 4 is connected to the housing 1, which is sealed so as to be safe to touch and consists of a housing lower part 2 and housing upper part 3, with electrical contact being established in the process. In the illustrated exemplary embodiment 6, the electrode unit 4 consists of substantially identical sections 5, which are interconnected by way of predetermined separation lines 6. The sections 5 are planar sections which are formed on their upper and lower sides by a dielectric 7, which has passage openings 8 in the illustrated embodiment. The sections 5 have a rectangular form in an exemplary embodiment and have, along their longitudinal edges 9, planar adhesive flaps 10 which are perpendicular to the predetermined separation lines 6 and which allow the electrode unit 4 to be fastened to the surface to be treated, for example the skin of a human or animal body. The section 5 furthest away from the housing 1 is provided with a further adhesive flap 10a that extends parallel to the predetermined separation lines 6.

[0034] The illustration in FIG. 2 shows the housing 1 with a removed housing upper part 3, and so only the housing lower part is visible. A control unit 11 is situated in the housing 1 and, via two high-voltage coils 12a, 12b, introduces two high-voltage signals into the electrode unit 4 via associated lines 13a, 13b. Further, a detection device 14 is situated in the housing 1 and can be used to guide an electrical signal on at least one of the lines 13a, 13b for as long as high-voltage signals are still not guided by this line 13a, 13b.

[0035] In addition to the upright side walls of the housing lower part 2, screw receptacles 15, by means of which the housing upper part 3 can be screwed onto the housing lower part, can be identified in FIG. 2.

[0036] FIG. 3 elucidates a plan view of the arrangement in the housing lower part 2 and a horizontal section through the electrode unit 4. A power supply 16, which supplies the control unit 11 in the housing 1 with voltage, is connectable to the housing 1. A microcontroller 17 generating radio frequency control pulses is situated in the control unit, the control pulses being prepared in a signal shaping stage 18 such that radio frequency pulse trains are available at the outputs of the two high-voltage coils 12a, 12b and respectively have radio frequency oscillations that are significantly damped in terms of amplitude. The repetition frequency of the pulses usually ranges between 1 kHz and 20 MHz. FIG. 3 schematically shows that the output signals of the high-voltage coils 12a, 12b, which are secondary coils of a high-voltage transformer, are each connected to a partial electrode 19a, 19b of an electrode 19. The partial electrodes extend with mirror symmetry in relation to a center line 20 of the sections 5 in the longitudinal direction of the electrode unit 4.

[0037] The width of the partial electrodes 19a, 19b is in each case reduced in stepped fashion in the region of the predetermined separation lines 6. The partial electrodes 19a, 19b are provided with openings 21 circular openings in this case which are flush with the passage openings 8 of the dielectric but have a greater diameter such that the passage openings 8 of the dielectric extend through the electrode 19 and form a passage channel, which even level with the electrode 19 has a wall that is formed by the dielectric 7. This ensures that a fluid, in particular a liquid, can be guided through the passage openings without the liquid coming into contact with the electrode 19. Consequently, the electrode unit 4 is also suitable for placement on a wound on a human or animal skin, with wound secretions being able to be drained through the passage openings.

[0038] The electrode 19 which—as illustrated—may be formed by two or more partial electrodes 19a, 19b is embedded in the dielectric 7 and therefore shielded in a manner safe to touch, in particular toward the surface to be treated. The supply of the electrode with the radio frequency high-voltage potentials leads to the formation of a high-voltage field between the electrode 19 and the surface to be treated, which acts as a counter electrode (ground electrode). The two partial electrodes 19a and 19b are supplied with equal and opposite high-voltage signals, which lead to an aggregate signal of zero. By way of example, this can be effected by virtue of the two high-voltage coils 12a, 12b being driven by identical control signals but being wound in the opposite sense such that signals with opposite polarities form at the output of the two coils. This leads to an amplification of the plasma field in the region of the partial electrodes while the fields are already compensated at some distance such that an impairment of the surroundings by radio frequency signals is significantly reduced.

[0039] Naturally, forming the electrode 19 with two partial electrodes is advantageous in many cases but it is not mandatory for the implementation of the invention. The latter can also be implemented by a single piece electrode 19.

[0040] Further, it is possible for the partial electrodes to be driven such that one partial electrode receives a radio frequency AC voltage signal while the other electrode forms a counter electrode as a ground electrode. This embodiment is expedient if the surface to be treated is not suitable as a counter electrode on account of the material of the body with the surface, for example because there is a lack of the required conductivity. In this case, the partial electrodes need not necessarily be arranged next to one another, as illustrated in FIG. 3, but may also be layered in relation to one another in an arrangement known per se such that there is a dielectric layer between the two electrodes.

[0041] FIG. 4 shows an arrangement in which the electrode unit 4 is formed only by two connected sections 5 such that the electrode unit 4 has a significantly smaller contact area of the surface to be treated (not illustrated) in relation to the electrode unit 4 of FIG. 3.

[0042] So that the control unit does not supply the smaller electrode unit 4 of FIG. 4 with the same electric power as a large electrode unit 4 as per FIG. 3, the size of the contact surface is determined by means of the detection device 14 when the electrode unit 4 is connected to the control unit 11 in the housing 1. To this end, the detection device 14 guides an electrical signal on at least one of the partial electrodes 19a, 19b. The electrical signal of the detection device 14 is reflected at the free end of the partial electrodes 19a, 19b, that is to say at the end-side distant section 5, and so there is a superposition of the transmitted signal and the reflected signal. The detection device 14 can be designed such that it emits a continuous harmonic electrical signal, the frequency (wavelength) of which is adjustable. Then, the frequency is adjusted such that a first-time cancellation of the aggregate signal is detectable. The cancellation is implemented when the length of the electrode unit 4 corresponds to a quarter wavelength. Consequently, the length of the electrode unit 4 can be determined by way of the wavelength set when the aggregate signal is canceled for the first time. Since the length of the electrode unit 4 is proportional to the contact face in the illustrated electrode unit 4, the amplitude of the control signal and hence the electrical power available for the plasma field can be set on the basis of the size of the contact face by the microcontroller 17 as control device of the control unit 11.

[0043] Accordingly, the electrode unit 4 of FIG. 4 is supplied with a different electrical power from that supplying the electrode unit 4 as per FIG. 3. The arrangement arising for the small electrode unit 4 as per FIG. 4 is elucidated in a perspective illustration in FIG. 5.

[0044] It is evident to a person skilled in the art that the illustrated external power supply 16 is not mandatory. It is also possible to set up a stand-alone power supply in the housing which is fed by rechargeable or non-rechargeable batteries, with the radio frequency AC voltage signals being generated in a manner known per se by a chopper or an oscillation circuit driven in pulse-type fashion. Further, it is possible to already supply the control unit 11 with high-voltage signals, but this requires the use of high-voltage-safe lines.

[0045] In a second embodiment of the invention, which is illustrated in FIGS. 6 to 9, the electrode unit 40 once again consists of substantially identical sections 50, which may be constructed in the same way as the sections 5 of the first embodiment. A difference merely consists in the fact that the sections 50 each have a different mechanical code 22 at their respective front edge, which is optionally adjacent to a predetermined separation line 6. The mechanical code arises from the presence or lack of presence of an elevation at four specified positions of the respective front edge of the sections 50. Sensing levers 23 in the housing 1 interact with these mechanical codes 22. The position of the sensing levers is recognized by the detection device 14, which can consequently determine which section 50 is in contact with the control unit 11 in the housing 1. The electrode unit 40 was shortened by detaching at least one section 50 at the end of the electrode unit 4 that is opposite to the section 50 with the end-side adhesive flap 10a. Consequently, the length of the remaining electrode unit 40 can be determined by identifying the section 50 which is in contact with the control unit 11 in the housing 1. Accordingly, the control unit 11 controls the electrical power that is guided to the electrode 19. The electrode 19 is illustrated as a single electrode in this embodiment. Naturally, an electrode 19 may also be formed from two or more partial electrodes 19a, 19b in this embodiment.

[0046] As elucidated in FIGS. 7 to 9, the sensing levers 23 interacting with the mechanical codes 22 are two-arm levers which are mounted so as to be pivotable about a common axis and which have a downwardly offset sensing tip 25 directed at the electrode unit 40. By way of a compressive spring 26 attached from below beyond the pivot 24, the sensing tip 25 is pressed downward onto the face of the section 50 pushed into the housing 1. Only the sensing lever 23 or the sensing levers 23, for which a mechanical code 22 is present on the section 50, is/are lifted at the sensing tip 25, as elucidated in FIG. 8 and FIG. 9.

[0047] It is evident from the comparison of FIGS. 6 and 9 that the long electrode unit 4 of FIG. 6 is encoded by virtue of only the sensing lever 23 situated to the right in figure 6 being lifted, while for the short electrode unit the code which is situated on the penultimate section 50 in FIG. 6 and which has two elevations for the two right sensing levers 23 is effective if the electrode unit 4 only consists of the two last sections 50.

[0048] Lifting of the sensing tips 25 and hence the change in the position of the sensing lever 23 can be detected in conventional fashion, for example by establishing contact at the lever arm distant from the sensing tip 25. The detection by means of a photoelectric barrier 27, as indicated in FIG. 8, is also possible. If only a single photoelectric barrier is present, the interruption of the light beam by one of the levers may also indicate that contact has been established between the control unit 11 in the housing 1 and the electrode unit 4 in order to determine the size at this instant before a high-voltage signal is guided to the electrode 19.

[0049] What is essential within the scope of the present invention is the determination of the size of the electrode unit 4 during or immediately following the establishment of contact between the electrode unit 4 and the control unit 11 on the housing 1.

[0050] In a third embodiment of the invention, which is illustrated in FIGS. 10 to 13, the electrode unit 4 is formed as a helically wound stripe which can be cut at any point in order thus to reduce the usable contact face of the electrode unit 4. The end of the stripe from which a piece has been cut off is inserted into a receiving slot of the housing 1 and can be contacted there by means of a rocker 28, for example by virtue of a metallic cutting contact of the rocker cutting through the dielectric 7 and establishing a conductive contact with the electrode 19 within the dielectric 7. The rocker can be locked by means of a slider 29 such that a high-voltage-safe connection is rendered possible. The housing 1 can be provided with a control unit 11 in the same way as the housing 1 in the above-described embodiments.

[0051] Naturally, the exemplary illustrated form of the electrode unit 4 is not a precondition for the third embodiment since other electrode forms, for example with a linear stripe extending in a straight line, are possible as an electrode unit.

[0052] A camera 30 is provided in the housing 1 as a detection device 14, said camera being directed at the surface of the electrode unit 4 such that the size of the connected electrode unit 4 is determinable by means of image evaluation. It is also essential to this end that the size of the electrode unit 4 is determined after contact with the control unit 11 in the housing 1 has been established.

[0053] In all exemplary embodiments, the electrode unit 4 can be provided with spacer projections 31 formed into the dielectric 7 on its contact face facing the surface to be treated, as a result of which gas spaces in which the dielectric barrier discharge plasma can form are kept clear upon contact with the surface to be treated. FIGS. 12 and 13 elucidate the arrangement of the camera 30 above the upper side of the electrode unit 4.

[0054] It is readily possible to identify that the illustrated exemplary embodiments are respectively combinable in respect of the form of the utilized electrode unit 4 and in respect of the utilized detection devices 14, and that a restriction to the respectively illustrated combination is neither intended nor indicated. The same applies to the embodiment of the housing 1 and the way of establishing contact between the electrode unit 4 and the control unit 11 in the housing 1, which can be implemented in any conventional fashion.

LIST OF REFERENCE SIGNS

[0055] 1 Housing

[0056] 2 Housing lower part

[0057] 3 Housing upper part

[0058] 4 Electrode unit

[0059] 5 Sections

[0060] 6 Predetermined separation lines

[0061] 7 Dielectric

[0062] 8 Passage openings

[0063] 9 Longitudinal edges

[0064] 10, 10a Adhesive flaps

[0065] 11 Control unit

[0066] 12a,b High-voltage coils

[0067] 13a,b Lines

[0068] 14 Detection devices

[0069] 15 Screw receptacles

[0070] 16 Power supply

[0071] 17 Microcontroller

[0072] 18 Signal shaping stage

[0073] 19a,b Partial electrodes

[0074] 20 Center line

[0075] 21 Openings

[0076] 22 Mechanical code

[0077] 23 Sensing lever

[0078] 24 Pivot

[0079] 25 Sensing tip

[0080] 26 Compressive spring

[0081] 27 Photoelectric barrier

[0082] 28 Rocker

[0083] 29 Slider

[0084] 30 Camera

[0085] 31 Spacer projections