Patent Application
20220016649
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The electrohydrodynamic atomization of fluids is increasingly acquiring significance in the field of coating methods. For example, PCT/EP2018/060117 discloses a device which uses electrohydrodynamic atomization e.g. care products such as for example sun block to a body of a person.
Methods for electrohydrodynamic atomization of fluids are known from the prior art.
The electrohydrodynamic atomization is based on the instability of electrically chargeable fluids, in particular fluids which are sufficiently electrically charged under high voltage, in a strong, non-homogeneous electrical field. The fluid is subjected here to a high voltage. The fluid deforms in this context to form a cone, from whose tip a thin stream, a so-called jet is emitted, which jet decomposes immediately afterwards into a spray composed of finely dispersed droplets. Under certain conditions, in the Taylor cone mode, the droplets have a narrow size distribution. Because very high electrical field strengths are necessary for the atomization, function control is advantageous in order to avoid undesired electrostatic charges.
A method for the function control of an electrohydrodynamic atomizer, wherein an electrohydrodynamically atomized fluid, originating from the atomizer, is applied to a body, e.g. a person, in order to coat this body at least in certain areas. The atomizer comprises a fluid tank for storing the fluid and at least one high voltage source for making available a high voltage and at least one pump unit for transporting the fluid. The fluid is delivered to a nozzle arrangement of the atomizer by means of the pump unit. The fluid is atomized electrohydrodynamically at the nozzle arrangement by means of the effect of the high voltage from the high voltage source. A voltage and/or a current at the high voltage source is evaluated in order to acquire a working point of the high voltage source via a current/voltage characteristic curve.
The object of the invention is therefore to make available function control for such devices in order to avoid undesired effects as a result of the electrohydrodynamic atomization.
This object is achieved by means of a method for function control of an electrohydrodynamic atomizer as claimed in claim 1.
In the text which follows, the invention and its advantageous developments and embodiments are explained with reference to the current/voltage characteristic curve from
By way of example, various coating situations are also shown in
In this context, an electrohydrodynamically atomized fluid originating from the atomizer is applied to a body, e.g. a person, in order to coat this body at least in certain areas. The atomizer comprises for this purpose a fluid tank for storing the fluid and at least one high voltage source for making available a high voltage and at least one pump unit for transporting the fluid. The fluid is delivered to a nozzle arrangement of the atomizer by means of the pump unit, wherein the fluid is atomized electrohydrodynamically at the nozzle arrangement by means of the effect of the high voltage from the high voltage source.
For function control there is provision here that a voltage U and/or a current I at the high voltage source are/is evaluated, in order to acquire a working point A1, A2, A3, A4 of the high voltage source via a current/voltage characteristic curve 10.
The electrohydrodynamic atomization uses the effect of a high voltage, as a result of which charges are transmitted to the fluid and from it to the body to be coated. Measurement of current and/or voltage and comparison of this measurement result with a current/voltage characteristic curve (10) permits definitive information to be obtained about the loading of the high voltage source, in particular as to whether a flow of current has occurred and therefore a coated body also again outputs the charges which are applied via the coating. If a desired flow of current occurs when a high voltage is applied, correct coating occurs and there is a return flow of the applied charges to the atomizer. Each combination of a current value and voltage value which can be achieved by means of the system during operation therefore defines a working point in the current/voltage characteristic curve.
In one preferred embodiment there is provision that the evaluated voltage U and/or the current I is a reference voltage proportional to the actual voltage value and/or current value of the high voltage source and/or is a reference current.
Using a reference voltage and a reference current provides the possibility of acquiring values and evaluating them more easily, since no high voltages have to be fed directly to measuring electronics. In this context, a reference voltage and/or a reference current value are/is made available by the high voltage source, said current value being preferably attached during the generation of the high voltage, and said current value does not directly load the high voltage circuit which is used for the atomization.
In one advantageous embodiment, such as is shown e.g. in
The simplest variant of a closed circuit 28 for avoiding undesired charges and for function control of the electrohydrodynamic atomizer 20 is given by the closing of contact by the user's hand. In structural terms, to do this it is necessary to provide, e.g. on a plastic housing, conductive contact elements which are always contacted during normal use. For example, operator control pushbutton keys and corresponding operator control elements are suitable for this.
In particular, in the method there is provision that a multiplicity of working points A0 to A5 are defined on the current/voltage characteristic curve, wherein the acquired actual working point—e.g. corresponding to A3—at the high voltage source is compared with a working point of the characteristic curve A0 to A5, or is acquired at least in a range 11 on the current/voltage characteristic curve 10 between two working points A2, A4.
It is advantageous here that precise classification of the working point A3 is not necessarily required. Instead, it is sufficient to arrange an acquired working point A3 in a range 11 which is defined by setpoint working points A2, A4 which bound a setpoint working range. In this case, e.g. a low current value, which is, however, still sufficient to transport away the charges sufficiently from the coated body, define a first setpoint working point A2, and a high current value which loads the voltage source and therefore causes the absolute value of the high voltage to drop, wherein electrohydrodynamic atomization is still possible, define a second setpoint working point A4, between which the working range 11 of the atomizer lies.
Moreover, there is preferably provision that a working range 11 is defined on the current/voltage characteristic curve, wherein a fault 40 signals if the acquired working point lies outside this setpoint working range 11.
A corresponding status is illustrated in
In the variant illustrated in
An expedient development of the method provides that regular acquiring of the working point is carried out, wherein an acquired working point A3 is compared with at least one previously acquired working point A3′, in order to detect a change in the working point.
Since during operation the working point depends heavily on the direct geometrical influences, such as e.g. the distance of the atomizer 20 from the object to be coated, e.g. the arm 24 in
One development also provides that the acquired working point triggers a defined user information item which is stored in a memory in accordance with the position of the working point on the current/voltage characteristic curve.
Owing to the physical line properties of the user who is included in the circuit for determining the working point there is the possibility of detecting characteristic working points in which a user information item can be retrieved from a memory. For example, direct contact can be brought about between the atomizer and the main surface during a switch-on process by which a characteristic working point occurs, e.g. in the range 13 between the working points A4 and A5 of the high flow of current of the characteristic curve 10 for precisely a said user.
In particular in the method it is also provided that a switch-on curve of the high voltage source is acquired, wherein the switch-on curve ends at a working point.
By acquiring a switch-on curve it is possible to determine what state the electrohydrodynamic atomizer is to be initially operated in. A switch-on curve K1 to the working point A1 states of the fault which is brought about e.g. by the situation according to
By acquiring the switch-on curves—e.g. K1 to K4—it is possible e.g. to implement at an early time a measure which is assigned to the started working point before this working point is reached. For example, the high voltage or the pump can be blocked if a working point A5′ outside the function range is aimed at via the switch-on curve K5.
The switch-on curve K2 at the working point A2, the switch-on curve K3 at the working point A3 and the switch-on curve K4 at the working point A4 in turn constitute possible operating states.
The situation according to
In the situations according to
Comparable objects are provided with the same reference symbols in
The term characteristic curve according to the invention is also to be understood as meaning collections of characteristic data which can be compared with acquired working points in order to carry out the function control according to the invention.
A further preferred embodiment of the method such as can be given e.g. in
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
This application is a Section 371 National Stage Application of International Application No. PCT/EP2019/086281, filed Dec. 19, 2019 and published as WO/2020/127712 A1 on Jun. 25, 2020, and claims priority to German Application No. 102018133439.7, filed Dec. 21, 2018, the contents of both are hereby incorporated by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/086281 | 12/19/2019 | WO | 00 |
