NZ202619A - Electrostatic spraying:liquid container holder opens container seal - Google Patents

Description

Priority Daiefg): .. $■!», % : 71 Complete Spcc-ificeilorj Filed: %'J/i I Class: &.Q&&. &Iq£. .

Publication Date: P.O. Journal F^'o: JeP£/f 202619 Under the provisions of IU6 latiorv 23 (I) the .

Specification has been ante-^ar.-tO |9 if TnT iNr : 5 NOV 1982 ^#17*2 niifals VOX No.: Date: NEW ZEALAND PATENTS ACT, 1953 Divided from No. 191545 COMPLETE SPECIFICATION automatically opening containers appwe, imperial chemical industries plc of Imperial Chemical House, Millbank, London, sw1p 3JF, England, a British Company hereby declare the invention for whichXjg/ we pray that a patent may be granted toxixsc/us, and the method by which it is to be performed, to be particularly described in and by the following statement: - " 1 " (followed by page la) 202619 - i A - —CONTAINERS' FOR USE IN-ELECTROSTATIC SPRAYINC This invention relates to containers, and in particular to containers for use in the electrostatic spraying of liquids. ' , 'Spec < v < c-c«_tx-Ovv.

In our eopend-.i ng Application No 29539/76—(U. S-.— -Setiari—Q12440)—we have described an apparatus for the electrostatic spraying of liquids. This apparatus is of simple construction, with a low power requirement (it has no moving parts and can readily be run off dry cells); it is thus particularly suited for use as a hand held sprayer in applications where large power sources are not readily available: for example, in spraying crops. Electrostatic spraying of crops also has advantages in promoting even coating of plants, with spray being attracted around behind foliage instead of coating only exposed surfaces; and in reducing spray drift, which is at best wasteful and at worst hazardous .to the environment.

Sp <!^o- t. 5" S" S The apparatus disclosed in Application No.—29539/7C comprises essentially a discharge nozzle; an electrode disposed around the nozzle; a container for supplying liquid to be sprayed to the nozzle; and a high voltage generator for applying a high voltage to the electrode, the electrode being earthed. In this way a strong electric field may be produced between the nozzle and the electrode, sufficient to atomise liquid passing through the nozzle.

This apparatus is particularly suitable for the application of pesticides at low or ultra-low volume (typically at a spray application rate in the range 0.5 to 10 litres spray liquid per hectare). Low and ultra-low volume spraying have several recognised advantages, as well as being especially suitable where water is not readily available as a spray diluent, but they also have one disadvantage. Of necessity, they must use relatively concentrated pesticidal compositions. Such compositions frequently have a greater or lesser degree of human 202Jbl<\ MtePtQl toxicity, and for this reason it is desirable that they should be handled as little as possible. A particular danger is the decantation of poisonous liquids into beverage bottles.

A pesticide sprayer, to"provide the best service, must be reliable and adaptable. Desirably it should be able to spray pesticides of several different kinds. Different pesticides come in different formulations, having different electrical properties, and requiring to be sprayed in differing droplet sizes to give optimum effect. In. the apparatus of our New Zealand Patent Specification No. 184555 useful and convenient control over droplet size and spraying properties can be provided by varying the applied voltage; but the size of the nozzle and the relative size and position of the surrounding electrode may also require adjustment to suit the formulation being sprayed. It is often difficult to do this reliably in the field. Also, pesticide sprayers (spray-tanks and spray-lines) normally require careful cleaning between application of different pesticides; otherwise, for example, traces of herbicide may damage crops being sprayed against fungal attack. The need for such cleaning is increased when formulations are to be sprayed electrostatically, since contamination may affect their electrical properties. Thorough cleaning may damage nozzles, leading to incorrect spray application.

The object of the present invention is to provide containers suitable for use in electrostatic spraying apparatus of the kind described in New Zealand Patent Specification No. 184555 which enable a number of the problems outlined above to be mitigated or overcome.

According to the present invention we provide' a container for a liquid to be electrostatically sprayed, suitable for mounting on a holder carrying an incomplete electrical circuit including a high voltage generator, the container having : an orifice for delivering liquid; HAPAtENT OFFICE -5 OCT 1983 ?■ i'! 9 < 1 n L. O y mounting means for locating the container on the holder; an electrical connection having one or more contacts on the -mounting means so placed that when the container is located on the holder by the mounting means, the contact or contacts complete the electrical circuit on the holder; and a seal for closing the orifice prior to location on the holder, which is adapted to be opened by means located on the holder.

We further provide a holder suitable for receiving a container according to the invention which comprises a body carrying a high voltage generator, mounting means complementary to the mounting means on the container provided with one or more electrical contacts complementary to those on the container, and further provided with means for opening the container seal. Throughout this specification, the term 'conducting surface' is intended to include a semi-conducting surface.

According to the invention, the container seal is adapted to be opened when, and preferably only when, located on the holder. Such opening may take place during such location, or subsequently: furthermore, the opening may be actuated mechanically or electrically. Thus, during the action of mounting the container on to the holder, a knife or spike on the holder may cut or pierce a metal foil over the orifice of the container. The container orifice may be sealed by a valve, e.g. a spring-biassed ball valve which is opened during mounting by contact with a detent on the holder.

With such a system the container orifice is automatically closed on removal from the holder which is particularly useful when the container still contains liquid. The same desirable end may also be accomplished by use of an electrostatic valve. Such a valve may be spring-biassed shut, and opened only by application of potential from the high voltage generator when the container is mounted on the holder. The electostatic valve is particularly convenient because the container remains sealed even after being mounted on the holder, until the current is switched OI{\!.2. PATENT OFFICE - 5 OCT 1983 In one aspect of our invention, the spray nozzle forms part of the container rather than of the holder on which it is mounted. Containers of this type are described and claimed in our New Zealand Patent Specification No. 191545.

Preferably means are provided for maintaining one terminal of the high voltage, generator at or near earth potential. Such means may be a conductor for connection to earth, for example, a trailing earth wire dependant from the holder. Where such means are provided, it is preferred that the earthed terminal of the high voltage generator is arranged for connection to the container electrode rather than to the nozzle. Charging of the spray is then by direct contact, rather than by induction, and there is a stronger electrostatic field transporting the spray to its (earthed) target.

If desired, one of the two electrical connections between the contacts on the container and the high voltage generator terminals may be through earth; though a more direct connection is sometimes convenient.

For most efficient operation the container also requires a means of equalising the external and internal pressure during spraying, for example an air vent, or non-rigid walls.

Containers according to the invention may be filled with properly formulated spray liquid by the manufacturer, and after the containers are closed, the spray liquid will remain uncontaiuinated until it is actually sprayed. There is no need to clean spray-tanks (or even spray-lines or nozzles, if the nozzle forms part of the container) to avoid contamination, so different products can be sprayed successively without undue loss of time.

Toxic hazards through handling by operators are minimised; errors by field operators in mixing and dilution procedures are eliminated. After use, the containers according to the invention may be returned to the manufacturer for refilling; or may be discarded. Containers may be made from one or more elements of plastics material by, for example, injection moulding or blow moulding, or a combination of the two. The conducting elements of the •2-°2-6 If -5- 2026!9 containers (nozzle, electrode, contacts and connections) may be provided by metal inserts, or (for all parts except the contacts) by application of conductive metallic coatings or paints to the container surface or by the use of partly-conducting plastics.

It is possible to provide the energy source for the high voltage generator in the holder. It may be preferred however to provide it in. the container.- Containers of this type are described, and claimed in our New Zealand Patent Specification No. 202618.

Such containers may be provided with, a spray nozzle at least part of the surface of which is electrically conductive and an electrode disposed about the nozzle and insulated therefrom, the nozzle and the electrode being disposed to be electrically connected via contacts on the mounting means to opposite terminals of the high voltage generator when the container is located on the holder; but a sometimes convenient alternative is to provide such an electrode, or such a nozzle, or both, on the holder. In a particularly convenient arrangement, the mounting means on the container has three electrical contacts; one for connecting one pole of the power source to a first input terminal of the generator; one for connecting the nozzle to a first output terminal, of N.Z PATE1 the generator; and one for connecting the second pole of the power source and the electrode to a conductor on the holder connected to the second input and output terminals of the generator, and capable of connection to earth.

One suitable form of power source is an electrical storage battery. The amount of electrical energy required to atomise liquid is remarkably low. A typical example may be considered: a vessel containing 500 ml of liquid to be sprayed at a r&te of 0.5 ml per second, with a droplet size of about 100 microns, and a charge to mass -3 ratio of 5 x 10 coulombs per kilogram. The current carried by droplets atomising from the nozzle is thus 2.5 microamperes. The spraying time will be .1000 seconds (just over quarter of an hour) at an input current of, typically, 15 milliamperes, an input voltage of about 10 volts and an output voltage of 20 kilovolts. Thus the required cell rating is only 4 milliampere hours, at about 10 volts. Th.is capacity is considerably less than that of most readily available torch batteries. If the containers are to be discarded after use, batteries of the necessary rating can be made cheaply on a large scale; alternatively, small quickly rechargeable batteries may be used. An example of another form of power source which may be used in the invention is a solar cell. Suitable high voltages for use in the invention range from about 1 to about 30 kilovolts, and most conveniently from about 5 to about 20 kilovolts.

A specific embodiment of the invention will now be described with reference to the drawings, in which: Figure 1 is a perspective view of a container; Figure 2 is an end view of the container of Figure 1; Figure 3 is a vertical section through the container on the line AA of Figure 2; Figure 4 is a plan view of a holder for the container of Figure 1; Figure 5 is a plan view of the collar of the container _ PATENT OFFICE -5 OCT 1983 %plf) I <? ■"> f' O < 1 o U C ! > Figure 6 is a circuit diagram of the circuit formed when the container is mounted on the holder.

Figure 7 is a vertical section through the neck of a second container.

Figure 8 is a vertical section through the neck of a third container.

Figure 9 is a plan view of plate 54 shown in Figure 8. Figures 1 to 6 show .details of the general construction of containers and holders, while Figures 7 to 9 illustrate arrangements for opening of the container seal by the holder.

With reference generally to Figures 1 to 3 and 5, the container comprises a generally flask-shaped body (1) of blow-moulded high density polyethylene, the neck of which is in liquid-tight sealed engagement with a collar (2) injection-moulded from polyacetal. It contains a solution (40) of 10% by weight of an insecticide in an aromatic hydrocarbon solvent. The collar (2) is formed of two concentric cylinders (3) and (4) joined near their ends to form an annulus. Within the inner cylinder (4) is a polyacetal plug (5), whose • external diameter is somewhat less than that of the internal diameter of the cylinder (4). The plug (5) is held in place within the cylinder (4) by outwardly projecting lugs (6). It thus forms, in cooperation with the cylinder (4), an annular channel (7) of capillary dimensions through which spray liquid may pass. The plug (5) is also provided with a. central bore carrying a polythene capillary tube (8) which extends upwardly into the body (1) of the container. The annular nozzle formed by the combination of the plug (5) and the cylinder (.4) is closed against liquid leakage by sealing cap (.9) (shown in position only in Figure 3). Within the container on the upper surface of the collar (2) is carried a 10 volt battery (10).

This battery is specially constructed, and contains sufficient electrical energy to atomise the liquid in the container, w-ith an extra margin of 50% to allow for electrical leakage. The positive pole of the battery (10) is connected to a brass contact stud (.11) on the outer wall of the collar (2) by a strip (.12). of elec- 8 - -r - #02619 trically conductive paint, passing from the battery (10) up over the rim of the collar (2) and down the outside thereof. The negative pole of the battery (.10) is connected, by a similar conductive strip (.13), to a second 5 brass contact stud (.14) . Stud (.14) is also connected, by a similar conductive strip (15), to the rim (16) of the cylinder (3). This rim (16) is itself coated with electrically conductive paint, to form an annular conductor. Similarly, the rim (17) of the inner cylinder 10 (4) is coated with electrically conductive paint to form an annular conductor. The conductive rim (17) is connected by an electrically conductive paint strip (18), passing down the inside of the cylinder (4) and over the top rim of the collar, to a third brass contact stud (19) 15 - on the outside of the collar (2). To prevent current leakage through the spray liquid, the conductive strips (12), (13) and (18) are protected within the body (1) of the container by insulating varnish. A projecting key (20) is also formed on the outside of collar (2). 20 With reference now principally to Figure 4, the holder for the container comprises a body (21) suitable for holding in the hand carrying a variable high voltage generator (22) (233P, 0-20 kilovolts, 200 microamp module, ex Brandenburg Limited). The body (21) is of generally 25 elongated form, and terminates in a ring (23), the inside of which is adapted to receive the collar (2) of the container. A key way (24) corresponds to.the key (20) on the collar (2). Brass contacts (25), (26) and (27) are mounted on the inside of the ring (23) so as to be able 30 to contact studs (.11), (14) and (19) on the container, respectively. Stud (25) is connected by an insulated electrical conductor (.28) to a switch (29), which, in the 'on' position, leads via a conductor (30) to the input . terminal of the high voltage generator (22). Stud (26). 35 is connected via an insulated electrical conductor (31) to a conductor (32) for connection to earth: the conductor (32) is a metal wire with a bared end for trailing " 2026 along the ground. The stud (27) connects, via an insulated electrical conductor (33) to the positive high voltage output terminal (34) of the generator (22). The negative output terminal (.35) of the generator (22) is connected to the earth wire (.32) .

In operation, the container is placed in an upright position, and the sealing cap (.9) removed. The ring (23) of the holder is then placed over the collar (2) of the container, over which it is a push fit, and the two mating parts are pushed together. The ring (23) grips the collar (2) sufficiently tightly to hold the container in position; the key (20) on the container cooperates with the key way (2 4) to hold the container in a position in which the following pairs of contacts touch: (11) and (25); (14) and (26); and (19) and (27). The circuit so formed is shown in Figure 6. The holder is now used to invert the container over the target to be sprayed, and liquid starts to drip from the channel (7). The switch (29) is at once turned to the 'on' position. This permits current flow from the battery (10) via contacts (11) and (25) to the generator (22); and this in turn causes a high potential (conveniently 15 kilovolts) to be conveyed from the terminal (34) via contacts (27) and (19) to the electrically conducting surface (17) of the cylinder (4). Meanwhile the electrically conducting surface (16) of the cylinder (3) is earthed, via contacts (14) and (26) and earth wire (32). An intense electrostatic field is thereby created between the two conducting surfaces (17) and (.16) , which causes liquid emerging adjacent to the surface (17) to atomise, and be projected downwardly as a fine spray, of controlled particle size towards any desired target. As the liquid passes out of the container, through the annular - channel■ (7),. the decreasing pressure within the container is equalised by air passing up through the central capillary tube (.8) . Spraying is stopped by turning off the switch (29) and turning the container mouth upwards.

IO - Jrl - 202619 Various modifications, to the foregoing apparatus will be apparent to those skilled in the art. The container illustrated is intended to be disposable.

However, reusable containers, may also be made, conven-5 iently with rechargeable batteries. For reusable containers, it may be found necessary to make the nozzle and electrode, as well as other electrical connections, of metal rather than merely of a conductive coating or paint; and for this reason such reusable containers are 10 substantially more expensive.

The device described includes a conductor for connection to earth in the form of a trailing bare metal wire. This has the disadvantage that it may become caught up or tangled. The device works best with an I5 earth connection; but it need not be of low resistance.

The conductor for connection to earth may be, for example, a metallised strip along the handle of the holder. When the operator grasps the handle, an electrical pathway to earth is formed through the operator's body. Though this 20 pathway has high resistance, we have found that it is generally adequate. Experiments have shown that, with an arrangement of this kind, the voltage on the container electrode may be up to about one or two hundred volts above that of earth, even when the operator is wearing 25 rubber boots in relatively dry conditions. Such a voltage on the electrode is little different from that of earth, relative to the potential on the nozzle of several thousand volts. The current flowing through the operator is so small that there is no danger to him whatever, nor 30 can he even feel anything.

The apparatus of the invention has been described with particular reference to its use in pesticide spraying, in particular of compositions comprising pesticides in organic liquid carriers, for which .it has 35 special advantages. However, it also has advantages in respect to spraying of coatings or paints, for. example by the home decorator. Holders for the container are f! ^ < i. \J L.. C conveniently adapted for holding in the hand; but they may also be carried on vehicles such as tractors or aircraft, when they may support more than one container.

It may however be preferred to use, in tractors or air-5 craft, a form of the invention in which the spray nozzle is not integral with the container. In this case., a relatively large container can supply several spray nozzles; and electrical power may be supplied from batteries or generators carried in the vehicle.

Figures 7, 8 and' 9 illustrate two closure devices which may be used in the containers of the invention. Both are illustrated in containers in which the spray nozzle is not integral. In Figure 7, the container (40) has a neck (41) in which is mounted a 15 simple mechanical ball valve, comprising a ball (42) urged against a seat (43) by a compression spring (44) mounted against stops (45). Prior to location on the spraying apparatus or holder (46), the ball valve prevents liquid leaving the container (40). On locating the 20 container (40) on the apparatus (46), the ball (42) is forced inwards away from the seat (43) by a finger (47), permitting liquid to flow.from the container (40) into the apparatus (46), for delivery to an electrostatic spray-head (not shown). At the same time, contacts (48) 25 on the mouth of the neck (41) complete an electrical connection in the apparatus (46), permitting the supply of an appropriate high potential to the spray-head.

Figure 8 shows an alternative form of valve in a similar container; this valve is operated electrostatically. 3o The valve comprises a metal plate (50) with a central port (51) mounted in the neck (52) of the container (53).

Below, the plate (.50) is a second plate (54) , shown in plan in Figure 9. It has a central boss (55) which fits within the port (51) of plate (50) and closes it against 35 passa.ge of liquid. Plate (54) has peripheral slots (56) , and is urged against plate (50) by a compression spring (57). Metal plates (50) and (54) are coated, on their 12 - Jr3""- -202619 lower and upper surfaces respectively, with a thin layer of a dialectric (epoxide resin). Contacts (58) and (59) on the outside of the neck (52) are electrically connected via the metal plates (50) and (54). In operation, the 5 container (53) is mounted on a spraying apparatus (not shown) in fluid-tight engagement with a conduit leading to an electrostatic spray-head. Contacts (58) and (59) are thereby connected respectively to the output terminal of a high voltage generator and to the conducting surface 10 of the electrostatic spray-head. A potential of about 20 kilovolts is thus applied to plates (50) and (54).

This potential forces the plates apart by electrostatic repulsion against the action of the spring (57), and liquid flows from the container (53) through the port 15 (51) and slots (56) into the apparatus for delivery to the spray-head. At the same time the spray-head receives a potential appropriate to atomise the liquid being delivered to it. Without the container on the apparatus, the electrostatic valve cannot open, and neither can 20 potential be transmitted to the electrostatic spray-head. 2-1 Aug- 79- *2&2j6 | «( •"> 1 f 1 Q c. vj C. 0 ! J ~ .13 "

Claims (18)

WHAT WE CLAIM IS:

1. A container for a liquid to be electrostatically sprayed, suitable for mounting on a holder carrying an incomplete electrical circuit including a high voltage generator, the container having : an orifice for delivering liquid; mounting means for locating the container on the holder; an electrical connection having one or more contacts on the mounting means so placed that when the container is located on the holder by the mounting means, the contact or contacts complete the electrical circuit on the holder; and a seal for closing the orifice prior to location on the holder, which is adapted to be opened by means located on the holder.

2. A container as claimed in claim 1 wherein the seal is adapted to be re-closed automatically when removed from the holder.

3. A container as claimed in claim 2, wherein the seal comprises a moveable closure element spring-urged against a valve seat, and adapted to be lifted off the valve seat in the act of mounting on the holder by contact with a projection carried on the holder.

4. A container as claimed in either of claims 1 or 2 wherein the seal comprises an electrostatic valve activated by high potential supplied by the high voltage generator carried on the holder.

5. A container as claimed in any of claims 1 to 4 in which the orifice forms part of a conductive spray nozzle.

6. A container as claimed in claim 5, which an electrode disposed around the spray nozz f u ifETfer—carr-ie.s™ or;- -5 OCT 1983

7. A container as claimed in claim 6 wherein the electrode is adapted to be connected to earth when the container is mounted on the holder.

8. A container as claimed in any of claims 1 to 5 which further comprises an electrical power source for the high voltage generator, together with electrical contacts in the mounting means for connecting the power source to the input terminals of the high voltage generator.

9. A container as claimed in any of claims 1 to 8 which comprises an air vent.

10. A holder suitable for receiving a container claimed in any of claims 1 to 9 which comprises a body carrying a high voltage generator, mounting means complementary to the mounting means on the container provided with one or more electrical contacts complementary to those on the container, and further provided with means for opening the container seal.

11. A holder as claimed in claim 10 suitable for receiving a container claimed in claim 3 wherein complementary mounting means on the holder includes a projection for lifting the seal closure element off the valve seat.

12. A holder as claimed in either of claims 10 or 11 which further comprises a conductive nozzle from which spray is atomised.

13. A holder as claimed in any of claims 10 to 12 suitable for receiving a container claimed in any of claims 1 to 7 which comprises a power source for the high voltage generator. ~20l 611 ') O < 1 Q £.U^.O ! / - 15 -

14. A holder as claimed in claim 12 suitable for receiving a container as claimed in claim 8, which further comprises an earthed electrode disposed around the spray nozzle.

15. A holder as claimed in any of claims 10 to 14 provided with a conductor for connection to earth.

16. A holder as claimed in claim 15 wherein the conductor comprises a trailing metal wire.

17. A holder as claimed in claim 15 provided with a handle carrying a conductive strip, thereby to provide a pathway to earth through the operator.

18. Containers substantially as described with reference to any of figures 7 to 9. r- DATED THIS DAY OF 19 A. J. PARK & SON PER of &GENTS FOR THE APPLICANTS N.Z. PATENT OFFICE ','j -5 OCT 1983 I .""V-.--