Coating processes – Direct application of electrical – magnetic – wave – or... – Electrostatic charge – field – or force utilized
Reexamination Certificate
1997-03-20
2001-12-04
Edwards, Laura (Department: 1734)
Coating processes
Direct application of electrical, magnetic, wave, or...
Electrostatic charge, field, or force utilized
C427S483000, C118S620000, C118S624000, C118S627000, C118S629000, C239S704000, C239S707000, C239S708000
Reexamination Certificate
active
06326062
ABSTRACT:
This invention relates to electrostatic spraying devices of the kind comprising an outlet, means for supplying an electrostatically sprayable material to the outlet and high voltage circuitry arranged so that, in use, the material issuing from the outlet forms an electrostatically charged spray.
The present invention is concerned with a device of this kind which affords improved control over spraying, particularly for applications requiring localised deposition of the material being sprayed. Typical applications where such control is required are those involving the application of personal hygiene, personal care, cosmetic, skin treatment and hair care products to the parts of the body—eg eye make-up, fingernail varnish etc.
EP-A-523963 makes reference to deposition localisation of benefit or treatment agents to the hair and/or scalp and discloses a specific embodiment in the form of a brush provided with liquid delivery elements and means for electrostatically charging the liquid. Reference is also made in this patent to an alternative liquid spraying unit with electrostatic charging of the liquid in which proximity sensing means is provided for allowing or causing the unit to operate only when the delivery means are suitably close to the intended target, namely the hair or the scalp. No specific details are disclosed as to how such proximity sensing is to be achieved.
In our prior EP-A-120633, there is described an electrostatic spraying device for use in various applications, including spraying of personal hygiene products, cosmetics, skin treatment formulations and perfumes. In this device, a voltage is developed between the spraying nozzle and earth which is of sufficient magnitude that spraying can be effected at a distance of 2 cm from an earthed surface. Reference is made to developing a field strength at the nozzle such that spraying ceases when the nozzle is not more than a distance of 15 cm away from the earthed surface.
In our prior EP-A-441501 there is described an electrostatic spraying device of the above kind in which an annular shroud of electrically non-conducting material material is mounted adjacent the nozzle such that the shroud becomes electrically charged during use of the apparatus, the shroud being either adjustable or there being a number of different interchangeable shrouds so that by adjustment of the shroud or by interchanging one shroud for another, the shape of the spray may be controlled.
Prior EP-A-501725 discloses an electrostatic spraying device for use in spraying low resistivity liquids such as aqueous, alcohol and aqueous/alcohol based liquids used in personal care products such as deodorants, anti-perspirants, scents and hair sprays. Reference is made to arrangements for attenuating the potential gradient in the vicinity of the orifice of the spraying nozzle with the aim of achieving sufficient potential gradient to promote necking of the liquid ligaments produced from the orifice while reducing the very steep gradients normally associated with pointed nozzle tips which, with low resistivity liquids, tend to give rise to corona discharge from the liquid jet.
According to one aspect of the present invention there is provided a method of applying an agent in spray form to the body by electrostatically spraying the agent on to a selected site of the body using a device having (i) a dispensing outlet from which the agent issues to form an electrostatically charged spray by the application of high voltage to the agent from a voltage source housed within the device and (ii) a portion projecting forwardly of the dispensing outlet in the direction of spraying, on which a potential is established in use to suppress spraying until the forward extremity of the device is brought within a predetermined distance from an earthed target, said method including addressing the body site to be sprayed with the device in such a way that the spraying outlet is sufficiently close to the body site to overcome the suppression of spraying imparted by the potential established on said forwardly projecting portion and thereby allow application of spray to the selected site.
Usually the device will be constructed and arranged so that spraying is suppressed until the spraying outlet is within a range of 20 cm or less (more preferably 15 or even 10 cm) from an earthed target.
Typically the agent applied will comprise be of a cosmetic nature such as personal care products, eg deodorants, antiperspirants, anti-bacterials, perfumes, hair sprays, fresheners, moisturisers and conditioners; and beautifying cosmetics such as lip colouring materials, mascaras, eye shadows, foundation formulas, artificial tanning materials, nail varnishes, nail polishes, nail hardeners etc.
According to a second aspect of the present invention there is provided a device comprising a spraying outlet, means for supplying electrostatically sprayable material to the outlet and high voltage circuitry arranged so that, in use, the material issuing from the outlet forms an electrostatically charged spray, characterised by the provision of a control member on which a voltage of the same polarity as that applied to the material to be sprayed is developed in use, the control member being located forwardly of the outlet in the direction of spraying and arranged in such a way as to attenuate the electric field in the vicinity of the outlet so that spraying from the outlet is suppressed until the forward extremity of the control member is brought within a range of no more than 20 cm from an earthed target to be sprayed.
Thus, in contrast with EP-A-441501 and EP-A-501725 which are respectively concerned with controlling the shape of the spray and with ligament formation, the present invention is concerned with controlling the potential gradient in the vicinity of the outlet so that spraying, and hence deposition of the material, is suppressed until the forward extremity of the control member is brought within a range of no more than 20 cm (more preferably no more than 15 cm, and in many cases no more than 10 cm) from an earthed target.
In one embodiment of the invention the control member comprises a control member of non-conducting material which surrounds the outlet and collects electrical charge leaking from the outlet during the initial application of voltage for spraying of the material (eg. stray corona discharge from the outlet). This approach may be used where the arrangement is such that the time interval between initial application of the spray inducing voltage and the onset of actual spraying allows development of a spray suppressing potential on the control member when the forward extremity of the control member is more than 20 cm from the earthed target.
In an alternative embodiment, the control member may be composed of a semi-insulating material which is coupled to a source of high voltage (preferably said high voltage circuitry) forming part of the device and has sufficient conductivity to permit a potential to be established at a location forwardly of the outlet which is of the same polarity as that applied to the liquid emerging at the outlet.
Thus, the control member serves to prevent spraying from the outlet when the device is remote from the target. In other words, even though the spray inducing voltage may be sufficient in the absence of the control member to allow spraying over a wide range of outlet/target distances extending well beyond 20 cm, the presence of the control member in effect modifies the potential gradient in the immediate vicinity of the outlet to such an extent that the field strength only becomes sufficient to generate electrostatic spraying from the outlet if the latter is within about 20 cm or less from an earthed target. In this way, even with the high voltage generating circuitry operational, the provision of the control member prevents issue of material from the outlet and hence spraying until the device is brought into dose proximity with the surface, eg the face, to be sprayed thereby ensuring deposition of the sprayed material on to a localised surface area.
Green Michael Leslie
Jefferies Andrew
Noakes Timothy James
Prendergast Maurice Joseph
Edwards Laura
Lewis Leonard W.
The Procter & Gamble & Company
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