MXPA97001712A

MXPA97001712A - Electrostat spray device

Info

Publication number: MXPA97001712A
Application number: MXPA/A/1997/001712A
Authority: MX
Inventors: Joyce Cornelius Gay; James Noakes Timothy; Joseph Prendergast Maurice; Jefferies Andrew; Leslie Green Michael
Original assignee: Reckitt & Colman Products Limited
Priority date: 1994-09-07
Filing date: 1997-03-06
Publication date: 1998-07-03

Abstract

The present invention relates to an electrostatic rocker device comprising: (i) a reservoir of a liquid capable of being sprayed electrostatically, (ii) a capillary structure comprising a hollow tube that is formed of a polymeric material that is impervious to liquid, the capillary structure, at one end, comes into contact with the liquid reservoir and, at the other end, ends at a spray tip, the capillary structure being such that, when oriented vertically and with the tip from atomizer upwards, the capillary section is sufficient to transport the liquid to the outlet at the upper end of the tube, and (iii) a means to apply a high voltage to the liquid in order to cause the liquid to project from the tip of the liquid. atomization, as one or more ligations and then disintegrating into a plurality of electrically charged droplets, characterized in that the hollow tube has an internal surface threaded

Description

"ELECTROSTATIC SPRAY DEVICE" The present invention relates to an electrostatic spraying device and, in particular, to an electrostatic spraying device for distributing liquid fragrances such as liquids for air freshening or insecticides, for other applications such as aromatherapy, air purification or for applications of personal care, for example as an inhaler, or an aerosol applicator. Devices for cooling the air where there is a slow release of vapor from a container containing a liquid to cool the air are well known in the art. Electrostatic devices for spraying liquids are also well known in the art. In these electrostatic spraying devices, a liquid is preponderantly extracted by electrostatic forces towards the ligaments that disintegrate in electrically charged droplets. The Patent Number WO-A-93/06937 discloses an electrostatic spraying device for spraying liquids comprising a nozzle in the form of a wick which is brought into contact with a reservoir containing the liquid to be sprayed. The wick is made of a sheet of a resiliently deformable polymeric foam material, the open cell structure and one edge of the sheet is profiled to form a plurality of sites where liquid ligaments can be produced. Patent Number EP-A-0486198 discloses an electrostatic spraying device that incorporates a cartridge containing a liquid, such as a fragrance that produces an oil, to be sprayed through a capillary structure placed vertically, applying a potential electrical to the liquid so that it is attracted through the end face of the capillary structure and sprayed as a plurality of ligaments that disintegrate into droplets. We have now developed an electrostatic spraying device to distribute liquids such as air fresheners, insecticides, oils or aromatherapy liquids for air purification where a specific type of wick is used in combination with liquids of defined characteristics in order to provide controlled atomization of liquid from the tip of the wick. Accordingly, the present invention provides an electrostatic spraying device comprising: (i) a reservoir of an electrostatically sprayable liquid; (ii) a capillary structure comprising a hollow tube having an internal surface and which is formed of a polymeric material that is impermeable to liquid, the capillary structure at one end is brought into contact with the liquid reservoir and at the other end ends in a spray tip, the capillary structure is such that when it is oriented essentially vertically and with the spray tip upwards, the capillary action is sufficient to transport the liquid to the outlet at the upper end of the tube; and (iii) a means for applying a high voltage to the liquid in order to cause the liquid to be projected from the atomization tip as one or more ligaments and then disintegrate in a plurality of electrically charged droplets. The present invention also provides a cartridge for storing a liquid suitable for electrostatic spraying comprising a cartridge body containing a reservoir of a liquid as defined above. A capillary structure as defined above and a means for providing an electrical connection with a high voltage source. The means for providing an electrical connection to a high voltage source may comprise an electrical contact or alternatively the cartridge may be formed at least partially from an electrically conductive or semiconductor material. The electrostatically sprayable liquid that forms the reservoir preferably has a volume resistivity of 2.5 x 10 ^ to 5 x 10 ^ ohm-centimeter, more preferably a volume resistivity of 2.5 to 10 ^ to 2.5 x 10 ^ ohm-centimeter. The Liquid typically has a viscosity that is measured at 20 ° C of 1 to 20 centistokes (1 to 20 x 10 ~ 6 square meters / second), preferably a viscosity of 1 to 10 centistokes (1 to 10 x 10- 6 square meters / second, more preferably from 1.5 to 4 centistokes (from 1.5 to 4 x 10 ~ square meters / second), and still very especially preferred from 2 to 3 centistokes (from 2 to 3 x 10 ~ 6 meters square / second.) The liquid of preference is a liquid to cool the air that is atomized by the electrostatic spraying device to perfum the air where the device is placed, such as a room or corridor.The liquid is electrostatically sprayable, however , it is generally a liquid having a very low non-volatile resinous residue such that a volume of the liquid corresponding at least to the volume of the tank, preferably at least twice the volume of the tank, can be distributed without blocking the tube. In contrast, the non-volatile resinous residue content of the liquid is less than 0.1 percent by weight. The capillary structure used in the present invention comprises a hollow tube that preferably has a smooth outer surface. The hollow tube has a rolled inner surface that is formed of a polymeric material that is impervious to liquid. It will be understood that for a capillary tube to be considered as being screwed, the ratio of the internal perimeter of the tube to the cross-sectional area is 2 / r where r is the radius of a circle having the same cross-sectional area as that of the screwed tube in question. Preferably, the internal perimeter of the tube is equal to or greater than the outer perimeter of the tube. The dimensions of the tube, the material from which it is manufactured and the liquid properties are selected in such a way that when the capillary structure is oriented essentially vertically with the spray tip upwards, the liquid is attracted upwards from the inside of the tube by capillary action to the point of atomization. When an electrostatic charge is applied to the liquid in the reservoir, the liquid in the atomization tip is attracted to the ligaments and then disintegrates in a plurality of electrically charged droplets.

The inner screwed surface of the hollow tube may vary from structures where simple rounded or pointed projections are directed towards the lumen of the tube to more complicated structures where the projections may have interdigital side branches. The inner screwed surface of the tube contributes to the resistance to distortion of the tube during use. A particularly preferred polymeric material from which the capillary structure can be formed is polyacetal, for example polyacetal PA-06010 manufactured by Aubex Corporation. Japan. The polymeric capillary tubes manufactured by Aubex Corporation are manufactured to a very high tolerance of + 5 percent, which is important to maintain uniform flow rates from one device to the next. Other polymeric materials which may also be used are polyethylene, in particular high density polyethylene, polypropylene, polyethylene terephthalate, polyamide, poly (ether ether ketone), poly (ether sulfone) or poly (ether ketone). The capillary structure preferably has an external diameter within the range of 0.1 to 1.5 millimeters, more preferably 0.4 to 0.8 millimeter and still especially preferred of about 0.6 millimeter.

The tip of the capillary structure is preferably flat and shortened at an angle typically of about 45 ° to the axis of the hollow tube. The liquid to be atomized is brought to the spray tip by a passive capillary action. It is then attracted at the tip by electrostatic forces towards ligaments that disintegrate into electrostatically charged droplets. In order for this to happen, the electrical field resistance must be high enough and in order to reduce the voltage required to produce sufficient field strength, the way of supplying the liquid to a steep bank, the form of which is known, is known. intensifies the electric field and from where the liquid is sprayed as a cloud of tiny droplets charged (micrometer). The charged droplets are mutually repellent and have a very large surface area to volume ratio thus resulting in rapid evaporation. The charged droplets try to discharge onto an earth / grounded surface, but remain suspended in the air like a cloud for a period long enough to influence large air spaces. A specific advantage of the present invention is that capillary structures with internal screwed surfaces allow relatively low volumes of electrostatically charged liquids to be sprayed consistently over extended periods of time up to four weeks to eight weeks. Capillary structures with internal screwed surfaces have a significant advantage in relation to capillary tubes with smooth internal surfaces since they are less sensitive to bubble entrapment and, therefore, to the risk of interrupting the electrical continuity through the column. Liquid to the tip. With a flat perforation tube, an air bubble trapped in the tube will tend to separate the column of liquid into two parts, while with the threaded tube there is no possibility, even when a bubble is trapped, that the liquid column is It divides into two parts. In this way, electrical continuity is maintained and the device can continue spraying. In addition, since the threaded tube has a larger surface area in contact with the liquid than the flat perforation tube, the capillary force available to foresee a bubble trapped outside the tube is increased. The means for applying a high voltage to the liquid preferably operates at a potential of two to 25 kV, more preferably at a potential of 8 to 15 kV and especially preferably at a potential of 10 to 12 kV.

In a preferred aspect of the present invention, for example, when the device is to be used to cool the air, the means for applying an electrostatic charge to the liquid can be adapted for intermittent application. In this way, the electrostatic spraying device of the present invention can be operated intermittently, for example, by using an integral synchronizer to change the device to the mode of operation with the application of the electrostatic charge to the liquid. Conveniently, the device of the present invention can be activated at intervals of 1 to 15 minutes, preferably 10 to 12 minutes for a period of 0.5 to 5 minutes, preferably 2 to 4 minutes and more preferably 3 minutes. In this way, when the liquid is a fragrance, the perception of the effect to refresh the air achieved by the fragrance is improved. When the device is in its non-functioning mode, the liquid fills the capillary tube and with the voltage disconnected, the meniscus of the liquid is placed at the open end of the tube but not at the front end of the tube from which the liquid is atomized. When the voltage is applied, the liquid is attracted from the column that fills the tube through the end face of the tube and is atomized from the spray tip of the tube. When the voltage is disconnected, the liquid is retracted - lu ¬ so that the meniscus of the liquid is again placed inside the tube where it is retained by the surface tension forces. The device of the present invention when it is adapted for intermittent use, is particularly advantageous since the liquid product and the batteries have a prolonged duration in comparison with the device that continuously emanate in the fragrance or an insecticide. The present invention also includes within its scope an electrostatic spraying device comprising a cartridge as defined above, a housing wherein the cartridge is adapted to be detachably positioned with the capillary structure extending almost vertically and a high voltage source placed inside the housing for the application of an electrostatic potential to the electrical connection in the cartridge. The high volume source may comprise, for example, a circuit that generates high voltage energized by a low voltage battery. The electrical condition in the cartridge may comprise an electrical contact extending through the base of the cartridge or alternatively the cartridge may be formed at least partially from an electrically conducting or semiconductor material.

A specific advantage of the present invention is that the spray tip is positioned to generally spray, vertically upward without requiring a positive head. Preferably, the cartridge of the present invention is designed so that there is an essentially constant liquid charge and the difference in the level of liquid between the full and near empty levels does not significantly affect the charge of the liquid at the atomization tip . One way to achieve an essentially constant liquid pressure is that the cartridge is of generally flattened configuration with a vertical dimension significantly smaller than its horizontal dimensions so that it can be contacted with a significant amount of liquid, while producing only a small change in the liquid level between conditions completely full and almost empty. Another way to achieve a constant pressure is disclosed in Patent Number WO 95/06521. To refresh the air of a typical room, the supply of 0.3 gram of liquid fragrance per day would provide a satisfactory level of fragrance. A cartridge containing 10 grams of liquid fragrance, therefore, would provide freshness of air for a month.

The present invention will further be described with reference to the accompanying drawings, in which: Figure 1 is a cross section of a capillary structure for use in accordance with the invention; Figures 2A to 2H illustrate cross sections of other capillary structures for use in accordance with the invention; and Figure 3 is a schematic view of an electrostatic spraying device in accordance with the present invention. Referring to the drawings, Figure 1 illustrates in cross-section, a capillary structure that is suitable for use in the present invention. The capillary structure is generally shown at 1 and is a cross section of a hollow polyacetal tube sold by Aubex Corporation of Japan, under number PA-06010. The hollow tube, as shown in cross section has a smooth external surface 2 and an internal surface 3 threaded. The tube has an external diameter of 0.6 mm. Figures 2A to 2H illustrate the cross sections of alternative capillary structures having internal screwed surfaces. As can be seen from these drawings, the internal roughened surfaces can be relatively simple in design, as shown in Figure 2H or more complicated design, as shown in the other Figures. Figure 3 illustrates an electrostatic spraying device comprising a housing 5 consisting of a body portion 65 and a separable cover 7. The housing is divided into two separate compartments, an upper compartment 8 and a lower compartment 9 by means of an internal wall 10. The upper compartment houses a cartridge 11 containing a reservoir of a liquid 12 to cool the air therein. A hollow capillary tube 13 of the type as described with reference to Figure 1 is placed inside the liquid reservoir 12. The liquid for cooling the air moistens the capillary structure 13 by passive capillary action so that the liquid is present in the atomization tip 14 of the capillary structure 13. The base of the cartridge 11 has a connector 15 formed integrally therein. The cartridge rests on the internal wall 10 of the housing immediately above the connector 16 that is formed on the inner wall. A high voltage output is supplied from the high voltage generator circuit 17, energized by a low voltage battery (not shown) through the connections 16 and 15 to the liquid 12 to cool the air. The circuit 17 is controlled by means of a synchronizer 18 which is also housed in the lower portion of the housing. When the sicronizer is connected, the high voltage is applied to the liquid to cool the air 12 contained in the cartridge 11 to effect the electrostatic spraying of the liquid from the atomization tip 14 of the hollow capillary structure 13, the synchronizer, for example, can Operate for three minutes every 15 minutes, that is, four times per hour. When the synchronizer is disconnected, the liquid to cool the air again will moisten the capillary structure 13 so that the atomizing tip 14 contains the liquid to cool the air ready for electrostatic spraying when the synchronizer is then in its connected mode. It will be noted that the circuit has a ground connection through the lower wall of the body 6 of the housing. The cover 7 of the housing is made of an electrically insulating plastic material, such as polypropylene or polyethylene so that the cover does not immediately cause electrostatic spraying to the ground. The liquid for cooling the air contained in the container will fill the viscosity and volume resistivity requirements as defined above. Preferably, the liquid for cooling the air will have a low non-volatile resinous residue of less than 0.1 weight percent, since otherwise any non-volatile material in the formulation will accumulate and interfere with the free flow of the liquid to cool the liquid. air, especially at the spray tip. The liquid to cool the air must also be free of any particulate material, since any of the particles would interfere with the free flow of liquid within the capillary structure. As described above, the liquid for cooling the air rises to the upper open end of the capillary structure 13 by passive capillary action and under the influence of the applied high voltage (which can be negative or positive) that is projected from the tip of atomization as one or more ligaments that disintegrate into particles that repel one with respect to the other to form a cloud of atomized haze. The particles are attracted away from the spray tip tow any of the objects in the vicinity of the device that are at ground potential. It will be noted that the cartridge 11, which contains the liquid to cool the air is relatively flattened and this allows the liquid to cool the air to be attracted to the capillary structure by a passive capillary action, without the height of the liquid in the container having great effect on the operation. When the cartridge is exhausted with the liquid to cool the air, then the cover 7 of the housing can be removed and a new cartridge ready for use inserted.

Claims

R E I V I N D I C A C I O N E S:

1. An electrostatic spraying device comprising: (i) a reservoir of an electrostatically sprayable liquid; (ii) a capillary structure comprising a hollow tube having a coiled internal surface and which is formed of a polymeric material which is impervious to liquid, capillary structure at one end is brought into contact with the reservoir of the liquid and at the other end ends in a spray tip, the capillary structure is such that when it is oriented almost vertically with the spray tip upwards, the capillary section is sufficient to transport the liquid to the outlet at the upper end of the tube; and (iii) a means for applying a high voltage to the liquid in order to cause the liquid to project from the atomization tip as one or more ligaments and then disintegrate in a plurality of electrically charged droplets.

An electrostatic spraying device according to claim 1, wherein the electrostatically sprayable liquid has a viscosity within the range of 1 to 20 centistokes (1 to 20 x 10 ~ square meters per centimeter / second) at a temperature of 20 ° C and a volume resistivity of 2.5 x 10 ^ to 5 x 108 ohms centimeter.

3. An electrostatic spraying device in accordance with claim 1 or claim 2, where the liquid has a viscosity within the scale of 1.5 to 4 centistokes (1.5 to 4 x 10-6 square meters per second) at a temperature of 20 ° C.

4. An electrostatic spraying device according to any one of claims 1 to 3, where the liquid has a volume resistivity of 2.5 x 107 to 2.

5 x 108 ohms-centimeter. An electrostatic spraying device according to any of the preceding claims, wherein the capillary structure has a smooth external surfaces.

6. An electrostatic spraying device according to any of the preceding claims, wherein the liquid is essentially free of any non-volatile resinous constituent.

An electrostatic spraying device according to any of the preceding claims, wherein the capillary structure is formed of polyacetal, polypropylene, polyethylene, polyethylene terephthalate, polyamide, poly (ether ether ketone), poly (ether sulfone) or poly (ether ketone).

8. An electrostatic spraying device according to any of the preceding claims, wherein the capillary structure has an external diameter within the range of 0.1 to 1.5 millimeters.

9. An electrostatic spraying device according to claim 8, wherein the capillary structure has an external diameter within the range of 0.4 to 0.8 millimeter.

10. An electrostatic spraying device according to any of the preceding claims, wherein the tip of the capillary structure is planar and is cut at an angle, typically about 45 ° to the axis of the hollow tube.

11. An electrostatic spraying device according to any of the preceding claims, wherein the means for applying an electrostatic charge to the liquid is adapted for intermittent application.

12. An electrostatic spraying device according to any of the preceding claims, wherein the means for applying a high voltage to the liquid operates at a potential of 2 to 25 kV.

13. A cartridge for the storage of a liquid suitable for electrostatic spraying, the cartridge comprising: (a) a cartridge body containing a reservoir of an electrostatically sprayable liquid; (b) a capillary structure comprising a hollow tube having a coiled inner surface which is formed of a polymeric material which is impervious to liquid, the capillary structure at one end is brought into contact with the liquid reservoir and at the other end ends in a spray tip, the capillary structure being such that when it is oriented almost vertically and with the spray tip at the top, the capillary action is sufficient to transport the liquid to the spray tip; and (c) a means for providing an electrical connection with a high voltage source. A cartridge according to claim 13, wherein the electrostatically sprayable liquid has a viscosity within a scale of 1 to 20 centistokes (1 to 20 x 10 ~ "square meters per second) at a temperature of 20 ° C and a volume resistivity of 2.5 x 10 ^ to 5 x 108 ohms-centimeter 15. A cartridge according to claim 14, wherein the liquid has a viscosity within the range of 1.5 to 4 centistokes (1.5 to 4 x 10). ~ 6 square meters / second) at a temperature of 20 ° C. 16. A cartridge according to claim 14, wherein the liquid has a volume resistivity of 2.5 x 107 to 2.5 x 108 ohm-centimeter. cartridge according to any of claims 13 to 16, wherein the capillary structure has a smooth outer surface 18. A cartridge according to any of claims 13 to 17 wherein the liquid is essentially free of any resinous constituent. non-volatile 19. The cartridge according to any of claims 13 to 18, wherein the capillary structure is formed of polyacetal, polypropylene, polyethylene, polyethylene terephthalate, polyamide poly (ether ether ketone), poly (ether sulfone) or poly (ether ketone). 20. A cartridge according to any of claims 13 to 19, wherein the capillary structure has an external diameter within the range of 0.1 to 1.0 millimeter. 21. A cartridge according to claim 20, wherein the capillary structure has an external diameter within the range of 0.4 to 0.8 millimeter. 22. A cartridge according to any of claims 13 to 21, wherein the tip of the capillary structure is planar and is cut at an angle, typically about 45 °, to the axis of the hollow tube. 23. A cartridge according to any of claims 13 to 22, wherein the high voltage source operates at a potential of 2 to 25 kV. 24. An electrostatic spraying device comprising a cartridge according to any of claims 13 to 23, a housing within which the cartridge is adapted to be removed placed with the capillary structure extending in an essentially vertical direction, and a high source voltage placed inside the housing for the application of an electrostatic potential to the electrical connection in the cartridge. 25. An electrostatic spraying device according to claim 24, wherein the high voltage source comprises a high voltage generator circuit positioned within the housing.