Fluid sprinkling – spraying – and diffusing – Electrostatic type
Reexamination Certificate
1999-10-08
2001-04-17
Brinson, Patrick (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Electrostatic type
C239S708000, C222S137000, C222S631000, C222S260000
Reexamination Certificate
active
06216966
ABSTRACT:
This invention relates to dispensing devices.
The invention has particular application to electrostatic spraying devices for use in applications involving for example air freshening, air purification, insecticide spraying, personal care/hygiene products (e.g. deodorants, cosmetics and perfumes) and medical and quasi-medical products such as nasal and respiratory tract sprays.
The present invention seeks to provide a device which is capable of efficiently delivering material in small amounts and/or in a relatively short duration of time.
EP-A-224352 discloses an electrostatic spraying device for dispensing opthalmically active compounds in discrete measured quantities. In the disclosed device, liquid is supplied to the tip of the nozzle and a potential difference is applied between the nozzle and an electrode spaced from the nozzle so that an electrical field of sufficient strength is provided at the outlet of the nozzle to draw the formulation away from the outlet as one or more ligaments which then break up into droplets. To enable the liquid to be drawn into ligaments, the liquid must be present at the very tip of the nozzle at the time of application of the potential difference. Liquid feed is supplied to the nozzle either from a reservoir of liquid within the device or by drawing the liquid from a separate source using a pipette action.
According to one aspect of the present invention there is provided an electrostatic spraying device comprising a nozzle, means for establishing a column of material to be sprayed within a passage leading to the nozzle outlet such that the leading surface of the column is spaced from the nozzle outlet, means for pneumatically ejecting said column or part thereof from the nozzle and means for applying high voltage to the material so that the spray formed by breaking up of the column on ejection from the nozzle are electrically charged.
According to a second aspect of the invention there is provided a method of electrostatic spraying comprising establishing a column of material to be sprayed within a passage leading to the outlet of a spraying nozzle of the device such that the leading surface of the column is spaced from the nozzle outlet, pneumatically ejecting the column of material or part thereof from the nozzle and applying high voltage to the material so that the spray particles formed by breaking up of the column on ejection from the nozzle are electrically charged.
Preferably the column of material is established in the passage as a discrete slug having a leading surface spaced from the nozzle outlet and a trailing surface to which air, gas or vapour under pressure can be applied to effect ejection of the slug from the nozzle.
According to a further aspect of the present invention there is provided an electrostatic spraying device comprising a nozzle, means for establishing a discrete slug of material to be sprayed within a passage leading to the nozzle outlet (preferably in such a way that the leading surface of the slug is spaced from the nozzle outlet), means for pneumatically ejecting said slug from the nozzle and means for applying high voltage to the material so that the spray particles formed by breaking up of the column on ejection from the nozzle are electrically charged.
Usually the material will comprise a single phase liquid formulation; however, we do not exclude application of the invention to materials in the form of liquid containing suspended solids. The formulation for instance may comprise more than one liquid in admixture—for example, the formulation may comprise an active ingredient such as a nasal decongestant agent, a diluent and other agents such as viscosity and/or resistivity modifying agents. Also we do not exclude the possibility of the material being in the form of pneumatically transportable fluent material other than a liquid, e.g. a powder.
In the device according to said one aspect of the present invention a column, preferably in the form of a discrete slug, of the material to be sprayed is established within the passage so that the column/slug is located with its leading surface (meniscus) spaced from the nozzle outlet. This allows the column/slug to be cleanly ejected from the nozzle outlet since the column/slug undergoes acceleration as it travels towards the nozzle tip and a relatively high velocity can therefore be imparted to the liquid before it reaches the nozzle tip. If for example a liquid is located with its leading meniscus at the nozzle tip prior to being displaced pneumatically, the liquid will have a low velocity at the beginning of the spraying operation and, in these circumstances, we have found that there is a tendency for spray attachment to the nozzle to occur at the beginning of the spraying action. Likewise, because the preferred method and device isolate a slug of the liquid within the passage leading to the nozzle outlet, the slug has a trailing surface and can exit cleanly from the nozzle without any significant tendency for spray attachment to occur, as would be the case for instance where the liquid in the passage is a continuation of, rather than being isolated from, the body of liquid from which it is derived.
Preferably the high voltage is applied to the material at or near to the nozzle outlet.
According to a narrower aspect of the invention there is provided an electrostatic spraying device comprising a nozzle, means for establishing a column of liquid within a passage leading to the outlet of the nozzle such that the leading surface of the slug is located upstream of a reduced cross-section portion leading to the nozzle outlet, means for pneumatically ejecting the slug as a jet from the nozzle and means for applying high voltage to the slug so that the droplets of the spray formed by breaking up of the jet are electrically charged.
Although not limited to any particular range of resistivity, the invention has particular application to low resistivity materials, especially liquids; e.g. liquids having a bulk resistivity of less than about 1×10
7
ohm cm including liquids having a resistivity significantly less than 1×10
4
ohm cm, e.g. 1×10
3
ohm cm and lower.
Preferably the arrangement is such that the jet of material at the point of egress from the nozzle has a diameter no greater than 300 micron and usually no less than about 15 micron. For example, the diameter of the jet at the point of egress may be in the range from about 20 to about 150 micron, more preferably 25 to 125 micron and most preferably 30 to 80 micron.
The nozzle design is preferably such that the surface of the nozzle at the point of egress of the material to be sprayed is not prone to create corona discharge. Thus as disclosed in prior EP-A-510725, bluff-ended nozzles are therefore preferred when the material to be sprayed has low resistivity.
The fluid pressure generated to effect pneumatic ejection of the slug is conveniently produced in response to operation of actuating means by the user and such operation of the actuating means may also be accompanied by priming of the passage leading to the nozzle outlet with the column/slug in preparation for pneumatic ejection. The priming action and fluid compression may occur substantially simultaneously and the arrangement may be such that operation of the actuating means is also accompanied by operation of a high voltage generator associated with the means for applying high voltage to the material to be sprayed whereby all of these operations together with ejection of the column/slug are effected in response to a single operation of the actuating means by the user. For example, the actuating means may normally be in a standby state and the arrangement may be such that operation of the actuating means is initially accompanied by compression of fluid and priming of the passage leading to the nozzle with the slug/column, followed by communication of the compressed fluid with the interior of the passage and by operation of the high voltage applying means so that, as the slug is displaced by the fluid pressure, the slug traverses a contact
Green Michael Leslie
Prendergast Maurice Joseph
Brinson Patrick
Lewis Leonard W.
Nguyen Dinh Q.
The Procter & Gamble & Company
Ulrich Paul M.
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