Electrostatic spray device

#This invention relates to a portable electrostatic spray device designed for personal use. More particular, this invention is focused on providing improvements to both the electronic circuit and mechanical designs which lead to the reduction/elimination of shock potentials, thereby improving the safety of the device for the user.

#In U.S. Pat. No. 4,549,243, Owen describes a spraying apparatus that can be held in the human hand for applications such as graphic work where it is desired that the area to which the spray is applied can be precisely controlled (Col 1, 11 5-9). Owen acknowledges both the benefits and hazards associated with stored capacitance when he describes that the high voltage circuit has sufficient capacitance that, during use, the desired electrical gradient at the nozzle is maintained between pulses but on the other hand should have a low stored energy, preferably less 10 mJ, so that no safety hazard is presented to the user for example by accidental contact of the user with the nozzle or on contact of the nozzle with an earthed surface (Col 5, 11 52-59). Owen further describes the occurrence of spark discharges and offers a solution to reduce such discharges, “. . . when a nozzle with a high potential applied thereto is brought close to an earthed surface, spark discharges from the nozzle to the earthed surface may occur instead of spraying; it is preferred that the field strength at the nozzle is such that the maximum distance of the nozzle from an earthed surface at which spark discharges occur is less than 5 mm” (Col 6, 11 14-20). Although recognizing the dangers associated with stored capacitance within the device, Owen fails to offer a means of dissipating said capacitance and chooses to try to design around it. The approach of designing around the internal capacitance, limiting to 10 mJ or less, limits the size/quantity of capacitors within the circuitry which in turn limits the ability to hold the output high voltage at a steady value. Further, Owen's electrical gradient design of limiting the distance at which a spark discharge will occur is not a consumer viable solution as it is very likely that a consumer will come in direct contact with the nozzle area (i.e. less than the 5 mm distance) either while the device is in operation or shortly thereafter before stored charge has been dissipated from the device.

#In U.S. Pat. No. 5,222,664, Noakes provides an electrostatic spraying device with the added benefit of a shock suppression by means of high voltage circuitry having a bi-polar output with a frequency no greater than 10 Hz. The system described by Noakes uses an alternating polarity power supply for generation of a high voltage potential. Noakes recognizes for example, where a direct current electrostatic spraying device which is wholly hand held is used (and hence where no other path to ground exists other than through the operator), and if the operator is or becomes substantially isolated from ground (for instance, as a result of standing on a synthetic fiber carpet or wearing shoes having soles of insulating material), during spraying, charge will accumulate on the operator and, if the operator subsequently touches a grounded conductor, he/she will experience an electrical shock (Col 1, 11 46-56). Owen offers a solution for such problem by thus appropriate selection of the frequency (of the high voltage power supply switching between opposite polarities), it is possible to eliminate the sensation of electrical shock by the operator or at least reduce the sensation to a level at which the risk of an accident as a result of an involuntary reaction by the operator is reduced (Col 2, 11 26-30). However, the solution that Noakes sets forth as a means to reduce the potential for the user to build-up a charge and subsequently discharge this charge in the form of a shock is to provide specifications for the switching frequency of the alternating polarity power supply. While this may represent a viable solution for some cases, this does not find application in electrostatic spraying devices that generate high voltage power using a rectifier which use a single polarity output.

#While the specification concludes with claims particularly pointing out and distinctly claiming the present invention it is believed that the same will be better understood from the following description, taken in conjunction with the accompanying drawings, in which:

#FIG. 1 is an exploded isometric view of a hand-held, self-contained electrostatic spraying device having a disposable cartridge;

#FIG. 2 is an assembled isometric view of the device within FIG. 1;

#Referring to FIGS. 1 and 2, a hand-held, self-contained electrostatic spraying device 5 having a disposable cartridge 200 is shown. Disposable cartridge 200 may contain a variety of product, including but not limited to, cosmetics, skin creams, and skin lotions. The product in disposable cartridge 200 may be positively displaced (discussed infra) and powered by gearbox/motor component 10. Gearbox/motor component 10 may be fixed onto a left or first housing 30. The gearbox/motor component 10 can be affixed into place mechanically, adhesively, or by any other suitable technique. Gearbox/motor component 10 preferably comprises a precision motor 10a connected to a gearbox 10b. Power source 20 provides power to the device. An example of a suitable power source 20 includes, but is not limited to, two “AAA” type batteries. The power source 20 provides power to the device through the control circuit 60, the high voltage power supply 40, and then the high voltage contact 50, which contacts the disposable cartridge 200. High voltage power supply 40 is powered and controlled by control circuit 60 (discussed infra). Power-on switch 80 permits the user to cause an interruption between power source 20 and circuit control 60. Power-on switch 80 is designed such that voltage is supplied to the remainder of the circuit only when switch 80 is in the “ON” or closed position. Apply switch 70 permits the user to selectively activate motor 10a, thereby activating the delivery and spraying of the product. Gearbox/motor component 10 has a driver 90 fastened to a shaft (not shown in FIGS. 1 & 2, see FIG. 3) of gearbox 10b, for example, with a set screw (not shown). Driver 90 has a number of protruding fingers, for example, three, which can fit into the matching recesses on the back of actuator 240.

#Referring now to FIG. 4, a first aspect of this invention is directed at defining a spark gap 300 between the charging location 310 (e.g. a point within the open chamber of disposable cartridge 200 and also near high voltage electrode 210 (e.g., conductive shield) and the nozzle exit orifice 280 (e.g. point at which spray exits device 5). In order to minimize the risk of electrical shock in the form of a tactile discharge to the user, it is essential to maximize the distance between charging location 310 and nozzle exit orifice 280. It is currently believed that the prior art fails to teach this important relationship necessary to minimize the risk of electrical shock.

#The preferred spacing between the charging location 310 and nozzle exit orifice 280 is governed by the following relationship: