Fluid sprinkling – spraying – and diffusing – Electrostatic type – Pressurized spray material
Patent
1993-10-27
1995-04-11
Hastings, Karen M.
Fluid sprinkling, spraying, and diffusing
Electrostatic type
Pressurized spray material
118627, 118629, 118300, 239323, 239583, 239690, B05B 500
Patent
active
054050901
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The invention relates to an electrostatic spray gun.
BACKGROUND OF THE INVENTION
Electrostatic spray heads are described in U.K. patent specifications Nos. 1 569 707, 2 018 601, 2 030 060 and others, and complete spray units in for example their EPA 0 118 202. Fluid supplied to the head is broken up essentially by the action of a high voltage field to form charged droplets, which are then attracted to and deposit on an earthed target such as a plant crop. The current passing, which is minute and harmless, is supplied for example by dry cells. No impellant gas or mechanical action is involved in transport of the spray.
With the growing concern over discharge of volatiles into the environment, we have sought to develop a gun using replaceable containers and allowing control of a fluid to be sprayed, at low flow rates and low pressures, such as in particular to be a replacement for the widely used aerosol sprays.
SUMMARY OF THE INVENTION
Most broadly the invention provides an electrostatic spray gun comprising a housing for receiving a replaceable collapsible container, a nozzle from which fluid is to be sprayed, means for compressing the container to feed fluid to the nozzle and high voltage means for applying electrostatic potential to the fluid such that the fluid issues from the nozzle in the form of an electrically charged atomised spray, wherein the nozzle forms or is fed by a resealable delivery valve having inner and outer valve members with fluid fed to a gap between them by the compression of the container, from which gap the fluid emerges to form the spray and the gap being closable, desirably with a wiping, fluid-cleaning action, by relative movement of the members.
The collapsible container can be of any suitable form including a simple sachet but will in any event have at least a part of its fluid containing portion flexible walled. Similarly the delivery valve
ozzle may be in any convenient form, separate or combined, whereby if the nozzle is regarded as the part of the gun in which the spray is formed and delivered the valve can constitute the nozzle or simply feed fluid to it.
The valves allow particularly advantageous forms of construction, wherein fluid flow at the low pressures afforded by hand operation and low flow rates of for example up to 20 ml/min that are envisaged, is nevertheless well controlled. Conveniently the gap between the valve members constitutes or is fed by a fluid path of flow-limiting form, suitably an elongate channel of flow-limiting cross section formed between or in one of the valve members. Conveniently further there may then be alternative channels of differing cross sections selectable by the user, or a single channel with different lengths selectable to control passage of the fluid.
Subsidiary concepts applicable to the above or independently in guns broadly as above, that is to say guns comprising a housing for receiving a container, a nozzle from which the fluid is to be sprayed, means for compressing the container to feed fluid to the nozzle and high voltage means for applying electrostatic potential to the fluid such that the fluid issues from the nozzle in the form of an electrically charged atomised spray, are: thus capacities; for example their use within a given space in the gun by means of different container and spacer combinations or their use in a disposable nose section of a gun, such nose section comprising the container and optionally the valve
ozzle also. larger volumes of fluid are required, the use of containers that are of concertina form, especially concertina sachets. Such sachets can be regarded as having successive sachet elements joined centrally with an open area for the container contents to pass from one element to the next. Progressive deformation is very conveniently afforded by such a construction with smooth controlled collapse under axial force and ready maintenance of constant delivery. The sachets may be within a rigid external sleeve and other forms of flexible container so confined are an alternati
REFERENCES:
patent: 3056557 (1962-10-01), Walberg
patent: 3323682 (1967-06-01), Creighton, Jr. et al.
patent: 3409225 (1968-11-01), Maddalozzo et al.
patent: 4066041 (1978-01-01), Buschor et al.
patent: 4136802 (1979-01-01), Mascia et al.
patent: 4557803 (1986-03-01), Owen
patent: 4993645 (1991-02-01), Buschor
Greene Robert H.
Outhwaite Alan C.
Edwards Laura E.
Hastings Karen M.
The Morgan Crucible Company plc
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