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(11) | EP 4 246 742 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | METHOD AND APPARATUS FOR IONISING A GAS |
| (57) A method of ionising a gas comprises applying an electric potential to one or more
ionising elements of a gas ionising device (or ioniser 400), sensing electrical characteristics
associated with the gas ionising device, and then using the sensed electrical characteristics
to determine which one of at least two different modes of operation to then use when
operating the gas ionising device to ionise the gas. The ioniser may thus detect in
a start-up phase the type of gas present, which might be nitrogen, air or argon, and
automatically select an appropriate mode of operation. The ioniser (400) may be in
the form of a static eliminator with pointed electrodes (420).
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Field of the Invention
[0001] The present invention concerns a method and apparatus for ionising a gas. More particularly, but not exclusively, this invention concerns a method for ionising a gas and a static eliminator. The invention also concerns an associated control device for use in such a method / apparatus.
Background of the Invention
[0002] Static eliminators are used to control the amount of static charge present on a work piece, for example by reducing the static charge on the work piece to allow the work piece to be handled more easily. Reducing static charges in an environment may additionally or alternatively increase the safety in the environment.
[0003] Static eliminators typically work by applying a high-voltage to electrodes such that they produce a corona discharge on, for example, needle tips of the electrodes. When corona discharge occurs at the needle tips of the electrode and the air surrounding the electrode needles is broken down, positive and negative ions are produced. Corona ionization can be achieved using either AC (alternating current) or DC (direct current) supplies. AC ionizers typically uses one emitter to produce both positive and negative ions, and may be referred to as bipolar emitters. DC ionizers typically use separate positive and negative power supplies that run independently to produce positive and negative ions respectively. The ion emitter(s) may be in the form of one or more emitter pins. A bipolar pin may for example be used to provide both positive and negative ions from a single pin when driven by a high voltage AC waveform such that the bipolar pin produces positive ions while it receives a positive current, and negative ions while it receives a negative current.
[0004] These ions travel in gas environments and combine with oppositely charged static charges thus neutralising the static charge. Thus, static charges are reduced, and at least some of a static charge is eliminated. It will be appreciated that the term "static eliminator" is used in the industry for such static control apparatus and that in use such a "static eliminator" will typically eliminate some or all of the static charge on an object. Thus, a static control apparatus or ionising device does not necessarily need to eliminate 100% of the static charge on an object to be considered, by those skilled in the art, as a "static eliminator". A static eliminator comprising an arrangement of bipolar pins can provide homogenous static control and highly accurate neutralisation of charge at close range. Where it is desired to use a static eliminator at long range (over 150mm), a static eliminator may be arranged with two rows of pins having a single polarity. In this case the pins can either be operated sequentially or in unison to produce positive and negative ions.
[0005] Static eliminators are used in a wide variety of applications, for example in laboratories, cleanrooms, the pharmaceutical industry, the hygiene industry, and in printing and other manufacturing lines. In certain cases, there may be a desire for the same static eliminator to be capable of being used in different applications. In some applications, a static eliminator will be required to operate in ambient air; in others the gas in which the static eliminator operates may be different from air, for example nitrogen and/or an inert environment such as a noble gas - e.g. argon. Dry air typically comprises approximately 78.1 percent nitrogen, 20.9 percent oxygen, 0.9 percent argon, and <0.1 percent of CO2 and other gases, by volume (mole fraction).
[0006] One problem with using a static eliminator in different environments is that arcing or sparking can occur at different voltages in different gases, as governed by Paschen's Law (Paschen breakdown). For example, an ionising device which operates safely in air, could, over time, produce sparks or arcing when operated in a nitrogen, argon or other substantially inert gas. This can be problematic when the composition of gas in which a static eliminator is placed is not known, or when the gas in which the static eliminator is placed changes, because the static eliminator can potentially unexpectedly produce sparks or arcing.
[0007] Simply fixing the voltage at which the static eliminator operates to be the highest safe voltage for any gas environment is not a practical option if the same design of static eliminator is to be used in different environments, because the static eliminator would have limited efficiency and/or provide ineffective amounts of ionisation in certain environments. An alternative option would be to provide different control circuitry, for the same design of static eliminator, the control circuitry being modified to suit each associated application, with different set-ups for different gases. That would have the disadvantage of increased manufacturing costs and reduced flexibility. Another option could be to provide a user controlled switch / selection function that enables a user to select the most appropriate mode of operation of a static eliminator. Such a functionality would alleviate the afore-mentioned problems but would rely on the user selecting the correct mode and/or setting the product up correctly and remembering to do this again if ever the gas is changed to a different gas.
[0008] Sparking and/or arcing can cause damage to the static eliminator and/or other products, components or parts of the apparatus / system with which the static eliminator is used. Simply relying on the user to select correctly a mode of operation of a static eliminator may be an unacceptable risk for many applications.
[0009] The present invention seeks to mitigate one or more of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved static eliminator and/or an improved method of ionising a gas.
Summary of the Invention
[0010] The present invention provides, according to a first aspect, a method of ionising a gas. The method comprises applying, during a first phase, an electric potential to one or more ionising elements (e.g. pins) of a gas ionising device. Ionisation of the gas may as a result be caused. There is a step (e.g. also during the first phase) of sensing electrical characteristics associated with the gas ionising device and then using those sensed electrical characteristics to determine which one of two or more different modes of operation in which to use the gas ionising device. The gas ionising device, during a subsequent second phase, then ionises gas in accordance with the mode of operation so determined.
[0011] In embodiments, the electrical characteristics associated with the gas ionising device that are sensed provide information regarding the gas (e.g. the type of gas) of the environment in which the gas ionising device is located. Embodiments of the invention are thus able to improve the safety of gas ionisation, as a result of the method including a step (in the first phase) in which the type of gas is sensed so that the gas ionising device can then be operated (in the second phase) in a mode appropriate to the type of gas sensed. As a result, the risks associated with the gas ionising device being used at too high a voltage for a prolonged period of time and/or in a manner in which sparks or arcing might result, are reduced. This may therefore improve the safety of the method by reducing the probability of sparks being produced or arcing occurring, improve the longevity of the ionising elements, improve the level of control of the ionisation and/or improve flexibility of use of the gas ionising device.
[0012] The gas ionising device has two or more different modes of operation. One of the modes of operation may be a lower voltage mode and another may be a higher voltage mode. For example, it may be that during the first phase the gas ionising device is operated in the higher voltage mode. In an embodiment, the gas ionisation device has two distinct modes of operation (possibly only two): a "low voltage mode" and a "high voltage mode". The "high voltage mode" may be used in the first phase. The method may be performed such that if, during the first phase, a sensed electrical characteristic indicates that the ionising device is in an air environment (or alternatively, is not in an inert gas environment), the "high voltage mode" is then used in the second phase. Alternatively or additionally, the method may be performed such that if, during the first phase, a sensed electrical characteristic indicates that the ionising device is not in an air environment (or alternatively, is in an inert gas environment), the "low voltage mode" is then used in the second phase.
[0013] The timing of the first phase may be such that when the device is in an inert environment, the possibility of sparks being produced, or arcing occurring, is low, for example despite the voltage being high during the first phase. For example the first phase may take under 30 seconds, optionally less the 5 seconds.
[0014] Where in this specification the terms "low", "high", "lower" and "higher" are used, these are to be understood to be in relative terms to each other. For instance, it will be understood that a "lower voltage" (or "low voltage") is lower (or low) in the sense that it is lower than the "higher voltage" (or "high voltage") and that a higher/high voltage is higher than a lower/low voltage. The different modes of operation may correspond to different electric potentials (potential differences/voltages). The voltage applied during the first phase may be a higher voltage than the lowest voltage mode (and if there are three or more modes of operation corresponding to different voltages, preferably at a voltage corresponding to or higher than the second highest of those different voltages and possibly at a voltage corresponding to or higher than the highest of those different voltages). A low voltage may thus be of the order of several kV yet still, within the context of the present invention, be consider as a low voltage (when compared to a higher "high voltage"). The gas in which ionisation occurs may be air, or may be an inert gas such as nitrogen, argon or a noble gas. Reference herein to inert gases is an umbrella term encompassing nitrogen, argon and noble gases. Inert is meant to encompass "substantially inert" gases such as nitrogen. The ionisation of the gas is performed by the gas ionisation device, with the gas ionisation device situated in (i.e. surrounded by) the gas.
[0015] The method may include a step wherein the potential difference applied during the first phase is greater than 2.5kV, preferably greater than 4kV and optionally between 5kV and 6.5kV. In embodiments, setting the initial voltage applied to the ionising elements at this level allows enough of a potential difference to enable the sensing to be undertaken quickly and reliably to determine characteristics of the gaseous environment the ionising device is operating in. The reliable and quick nature of this determination means that if it is determined that the static eliminator is operating in an inert gas environment, the second phase can be operated soon after initiation of the first phase, which advantageously reduces the likelihood of sparking.
[0016] The method may include the potential difference applied during the second phase (e.g. in which the electrical characteristics indicate the gas is air) being more than 4kV, preferably more than 5kV. The method may include the potential difference applied during the second phase (e.g. in which the electrical characteristics indicate the gas is air) being between 5kV and 6.5kV.
[0017] It may be that the potential difference applied during the second phase (e.g. in which the electrical characteristics indicate the gas is inert) is lower than the potential difference applied during the first phase. Thus, the gas ionisation device, which may be arranged such that it is operated only for a short time during the first phase, can then safely operate during the second phase, at a lower voltage than the first phase. In certain embodiments, it may be that the potential difference applied during the first phase (e.g. in which the electrical characteristics are sensed) is higher than the potential difference applied during the second phase (irrespective of the mode of operation in which the gas ionisation device is operated). It may be that the potential difference applied during the second phase in which the electrical characteristics indicate the gas is inert may be lower than 6kV, and optionally lower than 4kV.
[0018] The step of sensing electrical characteristics associated with the gas ionising device may comprise obtaining a measurement of an ionising current, for example being a measure of the net ion current (which increases as the amount of ionisation increases). The net ion current can be measured by sensing the current that flows to/from ground (the "ground return current"). The ground return current may be directly sensed by a current sensing element arranged to detect the current flowing to/from ground. The ground return current may be indirectly measured by other means.
[0019] In embodiments, when a first (e.g. "high") voltage is applied to the ionising elements in the first phase, the net ion current is dependent on the gas in which ionisation is occurring and can be measured/calculated and used to determine the type of gas. For example, if, in the first phase, a high voltage is applied in air at a set current, there is a low net ion current. If the high voltage in the first phase is applied in nitrogen (or argon, or another inert/noble gas), there is a higher net ion current, as ionisation is "easier" in Nitrogen according to Paschen's Law. As mentioned above, this can be sensed (i.e. via a current sensor sensing the ground return current), and be used as the basis of a decision on which voltage to apply during the second phase. If the sensed current is indicative of the ionisation occurring in air, then the second phase voltage can be maintained at the first phase voltage to a level which allows ionisation in air with an acceptably low risk of sparks forming. If the sensed current is indicative of the ionisation occurring in nitrogen, then the second phase voltage can be reduced to a lower voltage (e.g. between 3kV and 4kV, and/or 3.5kV) to allow ionisation in nitrogen with an acceptably low risk of sparks forming.
[0020] The measurement of net ion current may additionally be used to monitor and/or control the output of the ioniser during ongoing use - for example during the second phase.
[0021] The one or more ionising elements may be electrodes. The one or more ionising elements may be pointed electrodes, for example sharp pins. The one or more ionising elements may be bipolar pins.
[0022] The first phase may be start-up phase. The duration of the first phase may be less than 1 minute, may be less than 10 seconds, may be less than 5 seconds, may be less than 1 second or may be less than 0.1 seconds. In that time, the characteristics sensing takes place to enable the method to proceed with the second phase. The duration of the first phase may be shorter than the duration of the second phase. The duration of the second phase may be more than 1 minute, may be more than 5 minutes and may be more than 10 minutes.
[0023] The gas in which the ionising device is operating may be air. The gas in which the ionising device is operating may be nitrogen (e.g. >90% nitrogen, possibly >95% nitrogen, and optionally >99% nitrogen). The gas in which the ionising device is operating may be an inert gas, for example a noble gas or mixture thereof (e.g. >90% inert gas, possibly >95% inert gas, and optionally >99% inert gas). The gas in which the ionising device is operating may be a mixture of air and an inert gas. The gas may be one of nitrogen, argon, a noble gas not being argon, air, and a mixture of two or more of the foregoing gases. The multiple modes of operation may comprise a mode for a gas which is inert; a mode for air; and optionally a further mode for a different gas or gas mixture. The further mode may for example be in the form of an intermediate mode, which could for example correspond to a mixture of air and inert gas. The potential difference applied for such an intermediate mode may be higher than the potential difference applied for the inert gas, and below the potential difference applied for air. The device may operate using the intermediate mode when the ionising device is in a gaseous environment comprising a mixture of air and inert gas.
[0024] The step of using the sensed electrical characteristics to determine which one of the different modes of operation to use may include comparing the electrical characteristics with one or more threshold values. For example, the net ion current may be compared with a threshold value. In an embodiment, it may be that using the electrical characteristics to indicate that the gas ionising device is operating in air is effected by detecting whether the net ion current is below a threshold current. It may be that using the electrical characteristics to indicate that the gas ionising device is operating in an inert gas (or another gas not being air) is effected by detecting whether the net ion current is above a threshold current (for example the same threshold current). Thus, if the net ion current is below the threshold current, the second phase voltage is maintained at a high level. If the net ion current is above the threshold current, the second phase voltage is set to a lower level (in some embodiments, this being achieved by reducing the voltage to a lower level than as used in the first phase).
[0025] The environment the gas ionisation occurs in may be a sealed environment. The gas ionisation may occur within a hermetically sealed container. The hermetically sealed container may be a glove box or laboratory equipment.
[0026] The method of ionising a gas may be considered as involving a step of ionising a first gas during the second phase. The method may further comprise the step of using the gas ionisation device to ionise a second gas, of a different composition from the first gas. It may for example be that the method comprises repeating steps of the method (including applying an electric potential during a first phase and using sensed electrical characteristics to determine a mode of operation for use in a subsequent second phase) but in relation to the second gas. It may be that the gas ionising device is transferred to another place at which the second gas is present. It may be that the gas ionising device remains in the same place but the gaseous environment surrounding it changes from the first gas to the second gas.
[0027] According to a second aspect of the invention there is provided a gas ionisation device for providing ions (e.g. from a locally present gaseous medium). The gas ionisation device may be configured to perform the method of the present invention as described or claimed herein. The gas ionisation device may, for example, be in the form of a static eliminator. In embodiments, the static eliminator comprises at least one, and preferably multiple, ionising elements. The static eliminator comprises electrical componentry for supplying a first potential difference to the at least one ionising element and sensing the net ion current from the at least one ionising element. The static eliminator comprises a controller for controlling the device. The controller is configured to determine, for example based on the sensed net ion current, the level of the potential difference to be supplied to the ionising elements. The controller may for example be configured to supply a second potential difference (different from the first potential difference) to the ionising elements if the sensed net ion current meets certain, e.g. pre-set, criteria. The controller controls the electrical componentry of the device to supply the potential difference at the appropriate level.
[0028] The static eliminator may comprise a low pass filter for the purpose of removing high frequency components from the ground return current signal. The static eliminator may comprise an analogue to digital converter. The controller may comprise a microcontroller. The static eliminator may comprise a voltage driver. The static eliminator may comprise positive and/or negative high voltage generators. The static eliminator may comprise a net ion current sensing element. The static eliminator may comprise one or more ionising elements, for example in the form of pointed electrodes, bipolar pins or single polarity pins. The static eliminator may, for example, have at least four, and possibly at least seven, and optionally ten or more ionising elements. The ionising elements may form part of a bar-type static eliminator or a spot-type static eliminator. The static eliminator may be a bar-type or spot-type static eliminator. Alternatively or additionally, the static eliminator may be a blower-type static eliminator. The static eliminator may be connected to a set of weighing scales. The static eliminator may be connected by a power supply to the weighing scales such that the power for the static eliminator comes from the weighing scales. The connection from the weighing scales may be a 12v connection or may be a USB connection or other electrical connection. The static eliminator may have a maximum operating voltage more than 5kV, optionally at least 6.5kV, for example 8kV or more.
[0029] According to a third aspect there may be provided a control device comprising the electrical componentry of any other aspect, arranged to perform the method of any other aspect.
[0030] According to another aspect of the invention there is also provided a method of operating a static eliminator, the static eliminator comprising ionising elements, the method comprising the steps of: i) providing an initial voltage to the ionising elements in a first gaseous environment; ii) sensing a net ion current (which may be negative or positive, and may be AC or DC) from the ionising elements; and iii) based on the sensed net ion current, either continuing to provide the first voltage to the ionising elements or providing a second (e.g. lower) voltage to the ionising elements. The static eliminator may comprise electrical componentry for providing electrical current and voltage to the ionising elements and sensing the net ion current from the ionising elements. When using the sensed net ion current to decide whether (or not) to provide the second voltage, it may be that the sensed net ion current is compared and/or analysed to determine one or more properties of the environment. It may be that a maximum permissible voltage is determined for operating the static eliminator in the environment. The second voltage may be chosen from one of two or more pre-set output voltages which are less than the maximum permissible voltage.
[0031] The supplied current may be AC. The above mentioned voltages may, in relation to an AC waveform refer to the RMS (root mean square) voltage, with the peak voltages therefore being higher than the figures quoted.
[0032] It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.
Description of the Drawings
[0033] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:
Figure 1a shows a circuit diagram of a static eliminator according to a first embodiment of the invention;
Figure 1b is a further circuit diagram showing current flow in part of the static eliminator of the first embodiment;
Figure 2 shows a process flow diagram of a method according to the first embodiment of the invention;
Figure 3 shows a bar-type static eliminator with single row of bipolar pins; and
Figure 4 shows a bar-type static eliminator with two rows of fixed polarity pins.
Detailed Description
[0034] An ioniser, in the form of a static eliminator, according to the first embodiment of the invention is arranged to ionise a gas in the environment local to the ioniser by means of an array of high voltage ionising pins. The ioniser is arranged to operate in a first mode of operation suitable for ionising air using a voltage of 5-6.5kV and a second mode of operation suitable for ionising N2 using a voltage of 2-4kV. A controller automatically selects the correct one of the two modes of operation in which to run ioniser based on a sensed ground return current (the current which returns from the ionising elements) and/or a measured/determined net ion current (the difference between the current supplied to the ionising elements and the current which returns via the ground, which leaves the device as ions), which is effectively used to distinguish between whether the gas in the environment local to the ioniser is air or is N2.
[0035] Figure 1a shows a circuit diagram of the static eliminator of the first embodiment. A digital signal representing the sensed ground return current is fed to a digital processor (a microcontroller) 2. The digital signal comes from an analogue/digital converter 1, which receives the analogue signal from a ground return current sensing element10 via a low pass filter 11. The ground return current sensing element 10 may be otherwise known as a net ion current sensing/determining element 10 (given that the sensed ground return current is a measure of the net ion current). The microcontroller 2 controls a voltage driver 3, which in conjunction with positive 4 and negative 5 high voltage generators and a resistive coupling 6, generate a potential difference (voltage) which is applied to ionising elements 7. Ground 12 is also shown in figure 1a. The microcontroller 2 controls a voltage driver 3 to apply either a low voltage for N2 ionisation or a high voltage for ionisation in air on the basis of the value of the digital signal representing the sensed ground return current/sensed net ion current, as will be described in further detail with reference to Figure 2.
[0036] Figure 1b shows a diagram of part of the static eliminator of the first embodiment. A low voltage drive 20 supplies current to a transformer 30. The output from the transformer 30 is connected to a high voltage multiplier 40. The high voltage multiplier 40 supplies a total amount of current (It) to an emitter pin 60. Some of the total current (It) is emitted as ions (Ii) from the emitter pin 60, and some returns (Ip) through a proximity ground line 70. Current enters the system from ground 12 via resister 50. This ground return current is assumed to be substantially equal to the current that is emitted as ions (Ii). It is possible to measure the current across this resistor 50 (or in this line) and have a sufficiently accurate determination of the current emitted as ions (i.e. the net ion current (Ii)).
[0037] Figure 2 is a flow diagram depicting the method of eliminating static using the static eliminator. The static eliminator is turned on (i.e. powered or initialised) and this begins a first, initial start-up, phase 100. During the first phase, an initial current and voltage are applied 100 by the components of the static eliminator to ionising elements 7. The initial voltage is set at 5-6.5kV - i.e. at a high level - which may produce sparks/arcing if left for a prolonged duration in N2 gas, but which is less likely to produce sparks if only used for a short duration. The risk of sparks and arcing being caused at a voltage of 5-6.5kV when operating in N2 for a short duration is minimal. The ground return current from the ionising elements is sensed 200. A sensed high ground return current which is above a threshold - i.e. a high net ion current - implies that the static eliminator is operating in a N2 gas environment, whereas a sensed low ground return current (i.e. a low net ion current) implies that the static eliminator is operating in an air environment. Based on the sensed 200 ground return current, the static eliminator is then operated 300 in a suitable mode determined by the microcontroller 2. If the sensed 200 ground return current implies that the static eliminator is operating in an air environment, the controller 2 maintains the applied voltage at the ionising elements 7 at a high level, namely 5-6.5kV which in this example is the highest possible level for the device. If the sensed 200 ground return current implies that the static eliminator is operating in a nitrogen environment/gas, then the microcontroller 2 operates the ionising elements 7 at a safe level for the implied gas by reducing the voltage to 2-4kV. Thus, based on a sensed/determined internal electrical characteristic within the static eliminator, the microcontroller controls the static eliminator so that the gas ionisation phase occurs at a voltage which does not produce sparks in the gaseous environment of the static eliminator. The gas ionisation phase (second phase) can begin shortly after the device is switched on and may last for many minutes or indeed hours. By contrast, the first phase can last for less than 5 seconds and be considered a boot-up or initialisation stage.
[0038] The static eliminator may also be subjected to a changed gas atmosphere over time, for example if it is moved or if the gas surrounding the static eliminator changes. The static eliminator may repeat the sensing 200 and operation 300 steps periodically. Alternatively or additionally the static eliminator may repeat the sensing 200 and operation 300 steps continuously. In these cases, the sensed 100 ground return current can be from the ionising elements 7 operated at the highest or lowest operating 300 voltage. The static eliminator can repeat the sensing 200 and operating 300 steps on manual request by an operator. In these ways, the static eliminator may be used in a changing environment.
[0039] Thus it will be seen that Figure 2 is a flowchart illustrating one example of a method of ionising a gas, the method comprising the steps of: i) during a first phase, applying 100 an electric potential to one or more ionising elements of a gas ionising device, the gas ionising device having two or more different modes of operation; ii) sensing 200 electrical characteristics associated with the gas ionising device; and iii) using the sensed electrical characteristics to determine which one of the different modes of operation to then use when operating 300 the gas ionising device during a subsequent second phase in which the gas ionising device ionises gas.
[0040] In one embodiment, the static eliminator is used in a hermetically sealed glove box, for example of the type used in a laboratory. The static eliminator is used in the glove box used for weighing goods which would typically be difficult to weigh with analytical balances without static elimination. One example of such goods could be pharmaceutical compounds. Some weighing scales such as analytical balances have a power output, which can provide power to a static eliminator. In one embodiment, the static eliminator is used in a hermetically sealed glove box, for example of the type used in a laboratory. The static eliminator is used to control static charges on a weighing operation on an analytical balance. Without static elimination, static charges on the receptacle and material being dosed into it, would cause measurement errors. One example of such goods could be pharmaceutical compounds, where accuracy of measurement is critical.
[0042] Figure 3 shows a bar-type static eliminator 400 of a type suitable for use in an embodiment of the invention. The static eliminator 400 has ionising elements 420 in the form of multiple spaced apart bipolar pins 420 capable of providing positive or negative ions, depending on the supplied current. The static eliminator need not be in the form of a straight bar as shown in figure 3, but might be curved or shaped to fit within another apparatus (for example a scales/glove box). This device may be used in applications where the piece to be ionised is at a distance of less than 300mm from the emitter pins, for example less than 200mm, less than 150mm from the emitter pins, or less than 100mm from the emitter pins.
[0043] Figure 4 shows a bar-type static eliminator 500 of a type suitable for use in an embodiment of the invention. The static eliminator 500 has ionising elements 520 and 525, in the form of multiple spaced apart sharp pins, where there is one set of pins for negative ions 520 and one set of pins for positive ions 525.This example is particularly well suited to longer-range applications (above 150mm range), and the ionising pins 520 have a higher voltage applied thereto - in the range of 7-8kV or 7-10kV (for air) or 3-5kV (inert gas). The pins are spaced apart by approximately 20mm to reduce the likelihood of sparking.
[0044] The above embodiment concerns using an ioniser in conjunction with weighing scales, which dependent on the materials being weighed/dispensed, may be operating in a nitrogen environment (at which electrical breakdown and sparking can occur at lower voltages than would be the case in air). The embodiment avoids the need for any additional controls that would require the end-user to set the ioniser to the correct settings for use in such an environment. The environment is detected and the ioniser's output is adjusted automatically. This provides a significant benefit to the product's operation, removing the need for setup by the end-user and removing the risk of incorrect set-up. It is often the case that when ionisers are shipped to an end-user, the environment in which they will be used is not clear or is not known in advance. Without the benefit of the presently described embodiments this then would normally require the ability for the output voltage of the ioniser to be set manually onsite at the final installation.
[0045] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.
[0046] It may be that variations of the above embodiments all enable a method of using a gas ionising device to ionise a locally present gas, comprising detecting (preferably by utilising a part of the gas ionising device, or by utilising a part of its operation, that would in any case be present) the type of gas and then operating the gas ionising device in a manner depending on the type of gas so detected.
[0047] The static eliminator might, for example, be a blower-type static eliminator with pointed electrodes for ionising elements.
[0048] The static eliminator may be configured to operate in different gases. The gas may for example be nitrogen, any of the noble gases, air (ambient atmospheric air or treated/conditioned air) or a mixture thereof.
[0049] There may be applications of the invention which require ionisation of air for purposes other than eliminating static electricity.
[0050] There may be more than two modes of operation. For example, there may be the option of operation in an Argon-based environment. Argon has a lower breakdown voltage than Nitrogen and would require lower output voltages (e.g. of the order of 3.5kV, and/or a range of 2 to 4 kV. A variation could therefore be to follow the same process, but starting at an even lower voltage - one suited to Argon - before selecting which one of three difference modes of operation to use.
[0051] Low-purity Nitrogen environments may present a requirement for a more graduated response by the ionising device, with an increased number of output settings to work in the intermediate atmospheres. There may be three or more different modes of operation to accommodate that scenario. It may be that the output voltage of the ioniser is able to be infinitely varied between a minimum and maximum value, with there being no set number of the different modes of operation
[0052] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.
1. A method of ionising a gas, the method comprising the steps of:
i) during a first phase, applying an electric potential to one or more ionising elements of a gas ionising device, the gas ionising device having two or more different modes of operation;
ii) sensing electrical characteristics associated with the gas ionising device; and
iii) using the sensed electrical characteristics to determine which one of the different modes of operation to then use when operating the gas ionising device during a subsequent second phase in which the gas ionising device ionises gas.
2. The method according to claim 1, wherein one of the two or more different modes of
operation is a lower voltage mode, in which the electric potential applied to the
ionising elements corresponds to a low voltage, and another of the two or more different
modes of operation is a higher voltage mode, in which the electric potential applied
to the ionising elements corresponds to a high voltage.
3. The method according to claim 2, wherein the electric potential applied to the ionising
elements during the first phase corresponds to a voltage which is higher than the
low voltage.
4. The method as claimed in any preceding claim, wherein the potential difference applied
during the first phase is more than 4kVolts.
5. The method as claimed in any preceding claim, wherein the potential difference applied
during the second phase in which the electrical characteristics indicate the gas is
air is more than 4kV Volts.
6. The method according to any of claims 1 to 4, wherein the potential difference applied
during the second phase in which the electrical characteristics indicate the gas is
inert is a lower potential difference than is applied during the first phase.
7. The method according to any of claims 1 to 4 or 6, wherein the potential difference
applied during the second phase in which the electrical characteristics indicate the
gas is inert is lower than 5kV.
8. The method as claimed in any preceding claim, wherein sensing electrical characteristics
associated with the gas ionising device comprises obtaining a measurement of the net
ion current.
9. The method as claimed in any preceding claim, wherein the first phase is a start-up
phase and/or the duration of the first phase is less than 1 minute.
10. The method as claimed in any preceding claim, wherein the two or more modes of operation
comprise:
i. a mode for a gas which is inert;
ii. a mode for air;
and
iii. a further mode for a different gas or gas mixture.
11. A method according to claim 10 wherein
the further mode is an intermediate mode, for example for a gas being a mixture of air and inert gas, and
the potential difference applied for the intermediate mode is higher than the potential difference applied for the inert gas, and below the potential difference applied for air.
12. The method according to any preceding claim, wherein the electrical characteristics
indicating that the gas ionising device is operating in air is determined by the net
ion current being below a threshold current, and/or wherein the electrical characteristics
indicating that the gas ionising device is operating in an inert gas is determined
by the net ion current being above a threshold current.
13. The method according to any preceding claim wherein the method further comprises the
step of the gas ionisation device being subjected to a second, different, gas, wherein
the method further comprises the steps of repeating steps i) to iii) for the second
gas.
14. A static eliminator for providing ions, the static eliminator optionally being connected
to a weighing scale, the static eliminator comprising:
i) at least one ionising element;
ii) electrical componentry for supplying a first potential difference to the at least one ionising element and sensing return current from the at least one ionising element; and
iii) a controller for controlling the device, wherein the controller determines, based on the sensed return current, a second potential difference to be supplied to the at least one ionising element and controls the electrical componentry of the device to supply the second potential difference.
15. A control device comprising the electrical componentry of claim 14, arranged to perform
the method of claim 1.