Fluid sprinkling – spraying – and diffusing – Electrostatic type – Induction charging
Reexamination Certificate
2001-06-08
2003-09-02
Hwu, Davis (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Electrostatic type
Induction charging
C239S690000, C239S003000
Reexamination Certificate
active
06612510
ABSTRACT:
The present invention relates to a method of spraying aerosols which are created during the spraying process from a liquid composition located within a container by forcing the liquid through a suitable spray head attached to the container from which it emerges in aerosol form.
The present invention is particularly concerned with the formation of aerosols using domestic aerosols spray devices. Such devices may contain liquid compositions capable of forming aerosols for use in a wide range of applications including disinfectants, paints, antiperspirants, deodorants and insecticides. Reference will be made hereinafter to disinfectant applications but it should be appreciated that the present invention may be of use in connection with many other aerosol applications.
Dispersion of compositions from an aerosol spray device is not ideal as the spray of liquid droplets emerging from the aerosol device is generally propelled by sufficient force to enable the liquid droplets only to travel more or less in a straight line with a relatively small spread angle for a distance perhaps of the order of 1 meter or more. This is because of the restrictions on the design of the spray head including the outlet orifice. During their travel, the liquid droplets will, until they lose momentum, tend to maintain a straight line path although some attraction may take place between individual liquid droplets causing coalescence between one or more droplets, thereby possibly reducing the spread of droplets from a central spray line extending from the spray head.
In the case of a disinfectant product, the aim of the user is to spray an aerosol disinfectant from the spray device in a manner such that the liquid droplets make contact with microorganisms, typically in the form of bacteria, viruses or fungal spores. Microorganisms tend to accumulate on or adjacent to surfaces which are relatively difficult to access, for example, surfaces located behind the pedestals, handles and rims of sinks, showers, toilets or wash basins. A conventional aerosol spray device, when operated so that the spray is directed in the general direction of these inaccessible areas, will result in the liquid droplets encountering the surfaces of objects which lie between the spray device and the inaccessible areas. Accordingly, the liquid droplets will impinge on these objects and will never make contact with the desired target areas. Furthermore, it is difficult to ensure that a spray of, for example, a disinfectant composition will reach into all of the corners, crevices, pits, hollows and other areas of a surface which are difficult to access. With conventional techniques it is therefore difficult to sterilise the surfaces of operating theatres, hospital wards and other institutions.
We have now developed an improved method of spraying compositions which enables the liquid droplets of the compositions to cover and target surfaces more effectively and, in particular, which enables the droplets to target obscured or partly obscured surfaces.
According, to the present invention there is provided a method of improving the spraying of liquid droplets from a spray device onto a surface which method comprises imparting a unipolar charge to the said liquid droplets by double layer charging during the spraying of the liquid droplets from the spray device, the unipolar charge being at a level such that the said droplets have a charge to mass ratio of at least +/−1×10
−4
C/kg, whereby the charged droplets of the liquid are mutually repelled thereby increasing the spread of the droplets from a central spray line extending from the head of the spray device and avoiding coalescence of the droplets, thus providing a more even coverage of the surface which is to be sprayed.
In a particular aspect of the present invention there is provided a method of spraying liquid droplets from a spray device onto a surface which is obscured by an object located between the surface and the spray device so that liquid droplets travelling in a straight line from the spray device to the surface will impinge on said object, the method comprising imparting a unipolar charge to the said liquid droplets by double layer charging during the spraying of the liquid droplets from the spray device, the unipolar charge being at a level such that the said droplets have a charge to mass ratio of at least +/−1×10
−4
C/kg, whereby at least some of the droplets are caused to travel in a path which avoids the object and impinges on the obscured surface.
It will be understood that the object which obscures the surface which it is desired to spray may be a part of the same article as the article possessing the said surface. The invention is thus applicable to the treatment of three dimensional articles where certain surfaces are obscured from View along a particular line of sight. Accordingly, at least a part of the obverse surfaces of articles may be sprayed with liquid droplets using the method of the invention.
It is preferred that the unipolar charge which is imparted to the liquid droplets is generated solely by the interaction between the liquid within the spray device and the spray device itself as the liquid is expelled therefrom. In particular, it is preferred that the manner in which a unipolar charge is imparted to the liquid droplets does not rely even partly upon the connection of the spray device to any external charge inducing device, such as a source of relatively high voltage, or internal charge inducing device, such as a battery. With such an arrangement, the spray device is entirely self-contained, making it suitable for use both in industrial, institutional and domestic situations.
Preferably, the spray device is a domestic pressure-spraying device devoid of any electrical circuitry but which is capable of being hand held. Typically such a device has a capacity in the range of from 10 ml to 2000 ml and can be actuated by hand, or by an automatic actuating mechanism. A particularly preferred domestic device is a hand-held aerosol can.
Preferably, therefore the droplet charge to mass ratio of at least +/−1×10
−4
C/kg is imparted to the liquid droplets as a result of the use of an aerosol spray device with at least one of the features of the material of the actuator, the size and shape of the orifice of the actuator, the diameter of the dip tube, the characteristics of the valve and the formulation of the composition contained in the aerosol spray device being chosen in order to achieve the said droplet charge to mass ratio by double layer charging imparting the unipolar charge to the droplets during the actual spraying of the liquid droplets from the orifice of the aerosol spray device.
As a result of the method of the present invention surfaces which are normally difficult to access or inaccessible to the spray from an aerosol spray device can be contacted by the spray, thereby rendering many operations much more manageable. By way of example, microorganisms such as bacteria located in areas which are normally difficult to access may be easily eliminated in accordance with the method of the invention.
The method of the present invention may be used, for example, to spray an obscured surface of a sink, shower, toilet, washbasin, chair leg, a handle of a door, cupboard or refrigerator, a part of a human body, or a part of a plant with a liquid composition such as a disinfectant or antimicrobial composition. The method of the invention may also be used to improve the targeting of certain products to their intended destination. For example, more effective spraying of hairsprays, antiperspirants, body sprays, waxes and polishes, oven cleaners, starches and fabric finishes, shoe and leather ware products, glass cleaners, paints, lubricants, house plant sprays, antistick compositions, insecticides, herbicides, fungicides, biopesticides, disinfectants, and various other household, institutional, professional or industrial products may be achieved, with a reduction in the amount of product required
Fox Rodney Thomas
Harper Duncan Roger
Harrison Neale
Hughes John Farrell
Whitmore Lindsey Faye
Fish & Richardson P.C.
University of Southampton
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