WO2011058301A1

WO2011058301A1 - Apparatus for providing a flow of a modified gaseous species

Info

Publication number: WO2011058301A1
Application number: PCT/GB2010/002055
Authority: WO
Inventors: Cormac John Devery; Thomas Bickford Holbeche
Original assignee: Linde Aktiengesellschaft
Priority date: 2009-11-13
Filing date: 2010-11-09
Publication date: 2011-05-19
Also published as: GB0919891D0

Abstract

The present invention provides an apparatus for providing a flow of a modified gaseous species for treatment of a treatment region of a human or animal body. The apparatus comprises a first housing (30) in which is located a generator (36) having at least one electrode (44, 46) which can be energised for forming said modified gaseous species. The housing has a configuration which enables it to be held by hand and operated for treating the treatment region, and comprises an inlet port (56) for a flow gas communicating with the generator and an outlet port (58) for the flow of the modified gaseous species from the generator. A second housing (20) is remote from the first housing and has one or more batteries (22) and a signal generator (27, 28) for converting voltage generated by the battery when located in the second housing into a pulsed high voltage signal. A gas passage (50) extends through the second housing connectable to the inlet port and electrical leads (54) apply the pulsed high voltage signal to the said at least one electrode of the generator.

Description

APPARATUS FOR PROVIDING A FLOW OF A MODIFIED GASEOUS SPECIES

FIELD OF THE INVENTION

The present invention relates to an apparatus for providing a flow of a modified gaseous species such as non-thermal gas plasma. In particular the invention is directed towards an apparatus used for treating an oral region of a human or animal body.

BACKGROUND OF THE INVENTION

Systems for the generation of non thermal gas plasma are known and have utility in a number of fields such as industrial, dental, medical, cosmetic and veterinary fields for the treatment of the human or animal body. Non-thermal gas plasma generation can be employed to promote coagulation of blood, cleaning, sterilisation and removal of contaminants from a surface, disinfection, reconnection of tissue and treatment of tissue disorders without causing significant thermal tissue damage. Examples of such treatments are to be found in US 2005/008550 Al , WO 2006/1 16252 A2, US 6 565 558 Bl and US 2009/004620 Al .

It is however important that the treatment region of a body is not excessively heated causing injury, whether by arcing between plasma chamber electrodes or otherwise.

Additionally, there is a requirement that the use of electrical energy in a plasma apparatus is minimised to prolong battery life.

SUMMARY OF THE INVENTION

The present invention provides apparatus for providing a flow of a modified gaseous species for treatment of a treatment region of a human or animal body, the apparatus comprising a first housing in which is located a generator having at least one electrode which can be energised for forming said modified gaseous species, the housing having a configuration which enables it to be held by hand and operated for treating the treatment region, and comprising an inlet port for a flow gas communicating with the generator and an outlet port for the flow of the modified gaseous species from the generator; a second housing remote from the first housing, a battery and a signal generator for converting voltage generated by the battery into a pulsed high voltage signal, a gas passage through the second housing connectable to the inlet port and electrical leads for applying the pulsed high voltage signal to the said at least one electrode of the generator.

Whilst the present invention allows beneficial treatment particular of an oral cavity, for example for teeth cleaning, whitening or stain removal, without the attendant increased tooth porosity associated with known treatment apparatus such as laser treatment or application of hydrogen peroxide, the present invention also allows treatment to be conducted safely with reduced risk of a patient being undesirably exposed to large electrical currents. In this regard, a battery powered apparatus is limited in the voltage which can be generated and can also, given the size and weight of typical batteries be conveniently portable by hand. A 12 V battery is particularly suited in the present apparatus. For example, an A23 battery provides required voltage and yet is only 30mm by 10mm. The battery or batteries may be rechargeable and in this case the apparatus is supplied with a recharging unit.

A flexible hose may connect the first and second housings, the electrical leads and the gas being supplied through the hose. Preferably the hose is sufficiently flexible so that when the first housing is held and operated by hand the hose does not significantly impede application of non thermal plasma in the confined space of an oral cavity and its manipulation in the cavity for treatment of an individual tooth. In this regard, the hose in addition to the first housing should be light weight as well as flexible. It is further preferable that the electrical leads in the hose do not impede manual operation of the first housing and are therefore also light weight and flexible.

A pressure vessel may be connected to the second housing when in use, the pressure vessel having a water capacity of less than 1.5 litres and containing said flow gas under pressure so that when released the flow gas flows from the pressure vessel to the second housing. The configuration of the pressure vessel allows the apparatus to be portable.

Previously known pressure vessels in use for supplying a treatment gas are generally transported for example by trolley and adapted for semi-permanent location in for instance a surgery. Such known pressure vessels may have a water capacity of a 100 litres.

The apparatus may be configured to be packed in a case that can be carried by hand. The case may be a storm case. In one arrangement, the case has internal packaging for locating each of the first housing, the second housing, the pressure vessel and hose for protection during transit.

The generator may comprise a dielectric material, such as quartz, for electrically insulating the or each electrode. Quartz is transparent and does not melt or degrade under the conditions to which it will be subjected in use. Other dielectrics may be used instead of quartz provided they are able to withstand the temperatures that are created in the generator.

In one preferred arrangement, the generator comprises two electrodes and at least one of said electrodes comprises a metallic coating, such as silver paint, on a dielectric substrate. The metallic coating may be connected to the electrical leads by means of a conductive epoxy resin so that said metallic coating can be energised for forming a non thermal plasma in the generator.

The generator may comprise an elongate electrode comprising a copper wire or rod located within a graphite packing which in turn is contained within a dielectric holder, for example made from quartz.

There may additionally be provided a flow sensor for sensing the flow of gas from the gas supply, and a control for receiving an output from the flow sensor and controlling the application of the high voltage pulsed signal to the electrode only once a predetermined mass or volume flow rate of gas has been sensed by the flow sensor.

The apparatus may comprise first switching means for enabling current to be drawn from the source of electrical energy, and second switching means for enabling gas to flow to the reaction generator.

The first switching means and the second switching means may be connected to the control, and the control may be configured so that when the first switching means is operated the control enables current to be drawn from the source of electrical energy only if the second switching means has been operated.

The control may be connected to a valve for controlling the flow of gas into the reaction chamber and when the second switching means is operated, the control is configured to open the valve to allow gas to flow into the reaction chamber.

The apparatus may further comprise a battery monitor for monitoring the energy stored in the source of electrical energy and outputting a signal to the control dependent on said stored energy, wherein the control is configured to allow activation of the apparatus only when said stored energy is above a predetermined amount that is capable of generating a plasma in the reaction chamber.

The housing may include a nozzle for directing the flow of the gaseous species released from the reaction generator.

The battery, high voltage pulse signal generator and plasma generator may be configured to generate a non-thermal plasma at a temperature which is preferably less than about 40°C which is tolerable to a user. At least one of the said electrodes may be insulated from gas in the reaction generator by a dielectric to reduce arcing and thereby limit heating of the species. Said at least two electrodes may be spaced apart one from another in order to generate an electric field in substantially all of said reaction generator. One of said electrodes may be formed around a periphery of the reaction generator. One of the electrodes may be formed by a probe extending into the reaction generator. The probe may be tapered at an end portion thereof to form a point for increasing the generation of plasma in said reaction generator.

The batteries may be rechargeable.

The signal generator is preferably configured to generate a pulsed DC signal for driving said electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more clearly understood reference will now be made to the accompanying drawings, given by way of example only, in which:

Figure 1 is a schematic view of an embodiment of apparatus according to the present invention; and

Figure 2 is a schematic view of some of the components of the apparatus in more detail.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENT

Referring to Figures 1 and 2, apparatus is shown for generating a non thermal plasma which may be in the form of a gas plume emitted from the device. In the embodiment illustrated, the apparatus includes a gas supply 10, a handheld unit (or first housing) 30 and a bench unit 20 (or second housing). The apparatus provides a flow of a modified gaseous species for treatment of a treatment region of a human or animal body. A generator 36 having at least one electrode 44, 46 which can be energised for forming a non-thermal plasma is located in the handheld unit 30. The handheld unit 30 has a configuration which enables it to be held by hand and operated for treating the treatment region. An inlet port 56 is provided in the housing for a flow gas communicating with the generator and an outlet port 58 allows flow of the modified gaseous species from the generator. The bench unit 20 is remote from the first housing, and has located in, for example, a battery compartment one or more batteries and a signal generator for converting voltage generated by the battery when located in the second housing into a pulsed high voltage signal. A gas passage 50 through the second housing is connectable to the inlet port by a hose 52, having a gas conduit 60, and electrical leads 54 for applying the pulsed high voltage signal to the said at least one electrode of the generator. The gas cylinder 12 is provided as the pressure vessel of the gas supply. This is typically a 1 litre or 1.5 litre cylinder filled with helium, which is preferably CP grade helium, i.e. of high purity, suitable for generating a non-thermal plasma for providing a beneficial or therapeutic effect on a treatment region of a human or animal. In this way, the modified gas stream may include hydroxyl radicals (OH) which are effective for stain removal from teeth. It will be understood that the cylinder is not limited to the size or content indicated although the upper limit is preferably less than 1.5 litres so that the apparatus is portable by hand. The cylinder may be provided with an integral pressure regulator 14.

Located external to the cylinder 12 is a flow controller 16. The flow controller 16 may be set to a value of 0.5L/min. A further pressure regulator 18 is located downstream of the flow controller 16. This pressure regulator 18 releases gas flow at a pressure of 0.5bar. An outlet port of the gas supply is connected to an inlet port of the bench unit 20 by a hose 64.

The bench unit 20 includes a battery 22 and energising means 24 electrically connected to the battery 22. The battery illustrated is a 12V battery. The battery may be supplied with a battery charger 21 and a display LED 23. The display LED can indicate the status of the battery, i.e. it informs the user when the available power in the battery 22 is low. The bench unit comprises means for locating the battery or batteries in the unit so that they are placed in contact with electrical connections or terminals. The locating means may comprise a battery compartment shaped to receive the required battery or batteries and a removeable cover for closing the compartment. The bench unit further comprises a gas passage for conveying gas from the gas supply 10 to the handheld unit 30.

The energising means as described in more detail below comprises one or more signal generators which receive energy from the battery and one or more electrodes driven by the generators for energising a plasma in a reaction chamber. The energising means may include a low voltage signal generator 27 in connection with a high voltage generator 28.

In the illustrated arrangement, the signal generators convert the electrical current from a 12V battery into a pulsed output voltage in the range 4 to 6kV at a frequency of 2-10 kHz which is suitable for generation of a non-thermal plasma. A transformer can be used to step up the voltage and enable voltage pulses in the desired range of 4 to 6kV to be generated. In order to produce clear, well defined pulses it is desirable to keep the number of turns and inductance of the windings of the transformer to low levels and to have modest step-up ratios. This approach helps keep the unwanted parasitic elements of leakage inductance and stray winding capacitance to a minimum, both of which contribute to pulse distortion. Because a pulse transformer has low primary winding inductance, the magnetising current that generates the working magnetic flux in the core is substantial, leading to significant stored magnetic energy in the transformer during the pulse record. For an efficient design, this magnetic energy is recovered at the end of the pulse and temporarily held in another form (usually as a charge on a capacitor) ready to generate the next pulse.

The magnetic flux in the core of the transformer must be returned to zero before the next pulse is generated otherwise the flux builds up with successive pulses until the core saturates, at which point the transformer stops working and acts as a short circuit to the drive electronics.

A common method of magnetic energy recovery in switched-node power supply transformers, which may be used in this case, is through the use of a so-called "flyback" winding. This is usually identical to the primary winding and both wound on the core at the same time (a bipolar winding) in order to ensure a high level of magnetic coupling between the two. The flyback winding connects between ground and the reservoir capacitor of the DC supply via a blocking diode.

During pulse generation a fixed voltage is applied to the primary winding and current ramps up building up magnetic flux in the core - this induces an equal and opposite voltage across the flyback winding (but no current flows due to a blocking

diode). Interruption of the primary current at the end of the pulse forces the magnetic field to start collapsing which reverses the induced voltage across the flyback winding and causes current to flow back into the supply capacitor. The flux and current ramp down smoothly to zero ready for the next pulse.

Another suitable transformer configuration is a push-pull design in which two identical bifilar wound primary windings are alternately connected to the DC power supply. The phasing of the windings is such that magnetic flux in the core is generated with opposing directions which each is alternately driven.

A push-pull design also allows stored magnetic energy to be recovered and returned to the supply capacitor in a very similar fashion to the flyback approach, where the blocking diode now becomes an active transistor switch. The same transformer design may be used for either approach. Although the push-pull design requires additional switching transistor and control, it allows the possibility of doubling the change in magnetic flux within the limits of the core by using both positive and negative flux excursions. The flyback design outlined above only allows unipolar flux excursions. For a given flux ramp rate, the push-pull design has the capability to produce a continuous pulse with twice the duration of a flyback version using the same transformer.

A control 25, which may be in the form of a logic circuit is configured to receive a plurality of inputs which are dependent on a condition of the apparatus and selectively supply an output to the energising means, for example signal generator 27 in this example, for energising a plasma in the reaction chamber 36. The control is electrically connected to the switch 31, flow sensor 32 and valve 34 by an electrical 68 running through flexible hose 52. The signal generator may be configured to generate a signal for driving the electrodes which may be a low duty cycle signal in which the energy is provided to the or each electrode for less than 15% of the cycle. In the embodiment illustrated in Figure 1 the power source is a 6kV AC driver. It generates voltages pulses of one millisecond duration every six milliseconds. If desired, a different pulsing regime may be employed. For example, the pulses may be of shorter duration but may be more frequent. In another preferred

embodiment the signal generator may be configured to generate a pulsed DC signal.

The handheld unit 30 is configured by, for example, size and shape and weight such that it can be operated by a user by hand and the resulting plasma easily directed by the user to treat an oral region of a human or animal body. The handheld unit 30 includes a flow sensor 32, a solenoid valve 34, a reaction generator 36 and a nozzle 38. The solenoid valve is located downstream of the flow sensor 32. The reaction generator is located downstream of the solenoid valve 34. The reaction generator is provided with at least one electrode therein. The nozzle 38 is located downstream of the generator 36 and is adapted for directing a plasma plume to a treatment region of a human or animal. Also located within the unit 30 is an on/off switch 31.

As illustrated in Figure 2, the energising means 24 further includes two electrodes 44 and 46 for generating an electric field in the reaction generator 34. In certain configurations a single electrode may be provided or more than two electrodes may be provided. For example there may be two electrodes receiving a driving signal and one electrode being earthed. The signal generator 28 generates the electric signal for driving, i.e., energising the electrodes. A dielectric material, such as quartz, electrically insulates at least one and, preferably both, electrodes. The electrodes may be double quartz dielectric barrier discharge electrodes. At least one of the electrodes may comprise a metallic coating, such as silver paint, on a dielectric substrate. The metallic coating is connected to the electrical leads 54 by means of a conductive epoxy resin 66 so that said metallic coating can be energised for forming a non thermal plasma in the generator.

The electrodes are thus insulated from gas in the reaction generator by dielectric to prevent excessive heating of the plasma caused by continuous or prolonged arcing. Other suitable dielectric materials are ceramic, plastics or glass. Insulating the electrodes reduces the duration of arcing in the reaction generator when an electric current flows from one electrode to another.

Referring to Figure 2, the electrodes 44, 46 are spaced apart one from another in order to generate an electric field shown by field lines 40 in substantially all of the reaction generator 34. In this way, it is possible to increase the formation of plasma since gas in all portions of the generator interacts with the electric field.

One of the electrodes 46 is formed around a periphery of the reaction generator. If the reaction generator is formed from a dielectric the electrode may be embedded in the structure of the wall of the generator or on the outer surface of the wall. If the reaction generator is formed from an electrical conductor, the wall of the plasma generator itself may act as an electrode.

It has been found that plasma generation is promoted if one of the electrodes 44 is formed by an elongate probe extending into the reaction generator. The electrode 44 may comprise a copper wire or rod located within a graphite packing which in turn is contained within a dielectric holder, for example made from quartz. The probe is tapered at an end portion thereof to form a point for increasing the generation of plasma in said generator. In this regard, the density of electric field is increased particularly in the region of the reaction generator proximate the point of the probe. The probe may be electrically insulated along its length with a dielectric.

The apparatus is configured to be packed in a case that can be carried by hand. A storm case is suitable for this purpose as it provides robust protection for the apparatus during transport. The case may have a padded or foam interior and may have shaped compartments for receiving the components of the apparatus.

A method of operating the apparatus will now be described with reference to the drawings.

The control 25 is configured to receive inputs from low battery monitor 23, switches 29 and 31 , and the flow sensor 32. The control outputs to the signal generator 27 and the solenoid valve 34 when prescribed inputs are received by the control. In this regard, the low battery monitor 23 sends a signal to the control indicating whether or not there is sufficient energy stored in the source 22 for energising plasma in the reaction chamber 26. If the source has insufficient energy the control does not allow operation of the apparatus. If the source 22 has sufficient energy, the apparatus can be activated by operation of desk top switch 29 which outputs a signal to the control 25. The hand unit switch 31 is subsequently operated to supply an output to the control 25. The control receives the output from the switch 31 and if the output is positive and provided the switch 29 has been previously operated, the control sends an output to the solenoid valve 34 causing it to open to allow the flow of gas from pressure regulator 18. The flow sensor 32 sends an output to the control 25 if it senses that the flow of gas into the reaction chamber 36 is above a predetermined mass or volume flow rate. If the control receives a positive output from the sensor 32, the control emits a control signal to the energising means 24 thereby allowing the low voltage signal generator to be energised together with the high voltage generator for activating the electrodes 44, 46. Accordingly, a plasma can be energised in the reaction chamber only if gas flow through the reaction chamber is above a predetermined rate.

During operation of the device gas flowing from the pressure regulator 18 passes through the flow sensor 32. The gas flow then continues to pass through the solenoid valve 34 to the reaction generator 36. If the flow rate is the required amount, as predetermined, the electrodes in the reaction generator are activated by the signal generator as part of the energising means 24. The gas is thus energised and forms a gas plasma. The plasma exits the generator 36 and passes through the nozzle 38. The nozzle concentrates the flow of plasma. The user directs the nozzle towards the treatment area. The nozzle may be replaceable.

The present arrangement has a number of advantages. A plasma is not generated in the reaction chamber without sufficient flow of gas. Accordingly, power is not drained from the source unless it can be used for generating a plasma. Sufficient gas must be present in the reaction chamber so that when energised it provides a plume of modified gaseous species capable of delivering a beneficial effect to a treatment region. Secondly, energising the electrodes without sufficient flow of gas can cause arcing which may be transmitted to a human or animal causing injury.

The invention has been described above with respect to a preferred embodiment. As well as in the dental and cosmetic field the device may be used in non medical applications such as for example, the treatment of surfaces by plasma processing. It will be understood by those skilled in the art that changes and modifications may be made thereto without departing from the scope of the invention as set out in the appended claims.

Claims

1. Apparatus for providing a flow of a modified gaseous species for treatment of a treatment region of a human or animal body, the apparatus comprising a first housing in which is located a generator having at least one electrode which can be energised for forming said modified gaseous species, the housing having a configuration which enables it to be held by hand and operated for treating the treatment region, and comprising an inlet port for a flow gas communicating with the generator and an outlet port for the flow of the modified gaseous species from the generator; a second housing remote from the first housing, one or more batteries and a signal generator for converting voltage generated by the battery when located in the second housing into a pulsed high voltage signal, a gas passage through the second housing connectable to the inlet port and electrical leads for applying the pulsed high voltage signal to the said at least one electrode of the generator.

2. Apparatus as claimed in claim 1 , comprising a flexible hose connecting the first and second housings, the electrical leads and the gas being supplied through the hose.

3. Apparatus as claimed in claim 1 or 2, comprising a pressure vessel connected to the second housing, the pressure vessel having a water capacity of less than 1.5 litres and containing said flow gas under pressure so that when released the flow gas flows from the pressure vessel to the second housing.

4. Apparatus as claimed in any of the preceding claims, configured to be packed in a case that can be carried by hand.

5. Apparatus as claimed in any of the preceding claims, wherein the generator comprises a dielectric material for electrically insulating said at least one electrode.

6. Apparatus as claimed in any of the preceding claims, wherein the generator comprises two electrodes and at least one of said electrodes comprises a metallic coating on a dielectric substrate.

7. Apparatus as claimed in claim 6, wherein said metallic coating is connected to the electrical leads by means of a conductive epoxy resin so that said metallic coating can be energised for forming a non thermal plasma in the generator.

8. Apparatus as claimed in any of the preceding claims, the generator comprising an elongate electrode comprising a copper wire or rod located within a graphite packing which in rum is contained within a dielectric holder.

9. Apparatus as claimed in any of the preceding claims, comprising a flow sensor for sensing the flow of gas into the generator, and a control for receiving an output from the flow sensor and controlling application of the pulsed high voltage signal to said at least one electrode only once a predetermined mass or volume flow rate of gas has been sensed by the flow sensor.

10. Apparatus as claimed in any of the preceding claims, comprising first switching means for enabling current to be drawn from the battery, and second switching means for enabling gas to flow to the generator.

11. Apparatus as claimed in claim 10, wherein the first switching means and the second switching means are connected to the control, and the control is configured so that when the first switching means is operated the control enables current to be drawn from the battery only if the second switching means has been operated.

12. Apparatus as claimed in claim 10 or 1 1 , wherein the control is connected to a valve for controlling the flow of gas into the generator and when the second switching means is operated, the control is configured to open the valve to allow gas to flow into the generator.

13. Apparatus as claimed in any preceding claim, comprising a battery monitor for monitoring the energy stored in the battery and outputting a signal to the control dependent on said stored energy, wherein the control is configured to allow activation of the apparatus only when said stored energy is above a predetermined amount that is capable of generating a non thermal plasma in the generator.

14. Apparatus as claimed in any of the preceding claims, including a case in which the apparatus is able to be packed for transportation, said case being configured to be portable by hand.