CA1224982A - Process and device for dispensing electrically conductive liquids - Google Patents
Process and device for dispensing electrically conductive liquidsInfo
- Publication number
- CA1224982A CA1224982A CA000458549A CA458549A CA1224982A CA 1224982 A CA1224982 A CA 1224982A CA 000458549 A CA000458549 A CA 000458549A CA 458549 A CA458549 A CA 458549A CA 1224982 A CA1224982 A CA 1224982A
- Authority
- CA
- Canada
- Prior art keywords
- liquid
- capillaries
- voltage
- droplets
- nozzle
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D1/00—Processes for applying liquids or other fluent materials
- B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
- B05D1/04—Processes for applying liquids or other fluent materials performed by spraying involving the use of an electrostatic field
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D1/00—Processes for applying liquids or other fluent materials
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
- B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
- B05B5/0255—Discharge apparatus, e.g. electrostatic spray guns spraying and depositing by electrostatic forces only
Landscapes
- Electrostatic Spraying Apparatus (AREA)
- Catching Or Destruction (AREA)
- Chemically Coating (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
- Water Treatment By Electricity Or Magnetism (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
- Nozzles (AREA)
- Cultivation Of Plants (AREA)
- Conductive Materials (AREA)
- Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)
Abstract
Process and device for dispensing electrically conductive liquids Abstract The underlying principle of the atomising process is to let the liquid out of an opening at such a low flow velocity that the initially cohesive thread of liquid automatically disintegrates into individual drops. By applying an electric voltage to the thread of liquid it is then possible to generate a cone of droplets and to stabilise the drop size. In practice this is done by passing the liquid through a large number of capillaries which are parallel from the flow-engineering point of view and act as distributing elements. Each of these capillar-ies is enclosed by a concentric protective sheath which is at the same electric potential as the capillaries.
A high voltage, namely a voltage of 10 to 50 kV, applies between the capillaries and earth. The entire device can be designed in a space-saving manner as a portable appliance and has been found to be particularly suitable in agriculture for dispensing aqueous crop protection formulations.
A high voltage, namely a voltage of 10 to 50 kV, applies between the capillaries and earth. The entire device can be designed in a space-saving manner as a portable appliance and has been found to be particularly suitable in agriculture for dispensing aqueous crop protection formulations.
Description
24~
The ;nvent;on relates ~o a process and a device for spray-d;spens;ng electr;cally conduct;ve l;quids hav;ng a specif;c res;stance ~ 104 -Q-.m, ;n part;
cular aqueous crop protect;on agent solutions.
The spray-dispens;ng of liqu;ds, ;n particular of solut;ons or d;spers;ons, under the action of electr;c fields is known from var;ous f;elds of ;ndustry. Exam-ples ~hich may be ment;oned are the coating w;th pa;nts ;n the automot;ve ;ndustry and the large-area application of crop protection agents in agriculture. Crop protec-t;on products are conventionally sprayed over the crops to be treated ;n the form of suspens;ons or emuls;ons dispersed ;n water us;ng nozzles or rotary atom;sers and are depos;ted more or less successfully onto the leaves of the plants~ ;n the ma;n on the upper s;de of the protruding leaves.
In order for the crop protect;on agents to develop the;r optimum act;on, however, ;t is necessary for the product spray also to h;t the underside of 2û the leaves and the stalks. When spray;ng ;n the open air some of the m;st ;s frequently deflected by the w;nd and carried to other plants ~h;ch are not to be treated.
Furthermore, a large proport;on of the mist is lost as it sinks to the ground or drifts away. This was the reason for specifying a process where the dissolved pro-duct is electrostatically atomised at a high-voltage electrode into very fine aerosol droplets carry;ng a h;gh un;polar charge. ~his process ;s more effect;ve ;n depos;t;ng the l;qu;d onto earthed objects, s;nce ~he plants act as counterelectrode to the atom;sing electrode and attract the charged droplets. The process has the disadvantage, however~ that only organ;c liqu;ds having a spec;f;c electr;c res;stance within a certa;n range (about 104 IL .m to 107 IL.m) can be electrostat;cally Le A 22 441 , ' ~,, ~2~
atomised and deposited. In particular, the aqueous solut;ons cannot be processed~ since the;r surface tens;on ;s too high and the;r spec;f;c res;stance (S ~ = 5.7 ~m) ;s too low~
It ;s a further d;sadvantage that the h;ghly charged, very f;ne droplets can only be deposited on the outs;de parts of the plant, espec;ally if the crops are densely planted, and do not penetrate ;nto the electr;c-ally screened ;nner parts of the crop. Furthermore, the 1û amount oF cha~ge of the drops cannot be controlled in fl s;mple manner, s;nce only a h;gh charge on the l;qu;d at the edge of the spray electrode ~;ll produce the atom;s-;ng effect. If the electrode voltage ;s reduced the l;qu;d ;s no longer atom;sed and merely drips off.
Pract;cal exper;ence ;n the appl;cat;on of crop protect;on agents d;ctates the follow;ng requ;rements:
1. Aqueous, non-flammable formulations are prefer-able to organic l;qu;ds.
The ;nvent;on relates ~o a process and a device for spray-d;spens;ng electr;cally conduct;ve l;quids hav;ng a specif;c res;stance ~ 104 -Q-.m, ;n part;
cular aqueous crop protect;on agent solutions.
The spray-dispens;ng of liqu;ds, ;n particular of solut;ons or d;spers;ons, under the action of electr;c fields is known from var;ous f;elds of ;ndustry. Exam-ples ~hich may be ment;oned are the coating w;th pa;nts ;n the automot;ve ;ndustry and the large-area application of crop protection agents in agriculture. Crop protec-t;on products are conventionally sprayed over the crops to be treated ;n the form of suspens;ons or emuls;ons dispersed ;n water us;ng nozzles or rotary atom;sers and are depos;ted more or less successfully onto the leaves of the plants~ ;n the ma;n on the upper s;de of the protruding leaves.
In order for the crop protect;on agents to develop the;r optimum act;on, however, ;t is necessary for the product spray also to h;t the underside of 2û the leaves and the stalks. When spray;ng ;n the open air some of the m;st ;s frequently deflected by the w;nd and carried to other plants ~h;ch are not to be treated.
Furthermore, a large proport;on of the mist is lost as it sinks to the ground or drifts away. This was the reason for specifying a process where the dissolved pro-duct is electrostatically atomised at a high-voltage electrode into very fine aerosol droplets carry;ng a h;gh un;polar charge. ~his process ;s more effect;ve ;n depos;t;ng the l;qu;d onto earthed objects, s;nce ~he plants act as counterelectrode to the atom;sing electrode and attract the charged droplets. The process has the disadvantage, however~ that only organ;c liqu;ds having a spec;f;c electr;c res;stance within a certa;n range (about 104 IL .m to 107 IL.m) can be electrostat;cally Le A 22 441 , ' ~,, ~2~
atomised and deposited. In particular, the aqueous solut;ons cannot be processed~ since the;r surface tens;on ;s too high and the;r spec;f;c res;stance (S ~ = 5.7 ~m) ;s too low~
It ;s a further d;sadvantage that the h;ghly charged, very f;ne droplets can only be deposited on the outs;de parts of the plant, espec;ally if the crops are densely planted, and do not penetrate ;nto the electr;c-ally screened ;nner parts of the crop. Furthermore, the 1û amount oF cha~ge of the drops cannot be controlled in fl s;mple manner, s;nce only a h;gh charge on the l;qu;d at the edge of the spray electrode ~;ll produce the atom;s-;ng effect. If the electrode voltage ;s reduced the l;qu;d ;s no longer atom;sed and merely drips off.
Pract;cal exper;ence ;n the appl;cat;on of crop protect;on agents d;ctates the follow;ng requ;rements:
1. Aqueous, non-flammable formulations are prefer-able to organic l;qu;ds.
2. The drop s;ze should be w;th;n the range from 100 to 250 ~m.
3. The penetrat;on depth of the drops of l;qu;d ;nto the crop stand should be adjustable. For the purposes of the ;nvent;on "penetrat;on depth" is to be understood as mean;ng the area ~h;ch, when v;ewed from above, ;.e.
from the t;p of the plant, ;s covered dur;ng spray;ng.
It might be poss;ble, for example, to vary the penetra-t;on depth by varying the drop s;ze or by vary;ng the drop charge. Heavy, uncharged drops fall to the ground along the shortest path. By contrast, l;ght, h;ghly charged droplets are most h;ghly deflected from the free-fall fl;ghtpath and are attracted by the most protruding parts of the plant~ Both these extreme cases are undes;r-able. On the contrary~ the ;deal ;s a process where the controlled adjustment of the rat;o of drop charge to drop mass ;s poss;ble, s;nce ;n th;s way the zones between the top layers of the stands and the;r bottom Layers can be Le A 22 441 _ 3 _ ~2~
covered.
It is the object of the invention to develop a process uniformly dispensing aqueous liquids in drop form (plus the device required for this purpose) which will satisfy the above-mentioned conditions.
This object is achieved according to the invention which provides a process for dispensing electrically conductive crop protection liquids in droplet form having a specific resistance ~ 104-f~m, characterised in that the liquid escapes from a small exit orifice at a flow velocity so low that, immediately beyond the exit orifice, the liquid forms a cohesive thread which then disintegrates into individual droplets, and in that an electric voltage of at least 500 V relative to ground is applied to the thread of liquid to stablise the drop size and to produce a cone of droplets whose apex angle depends on the level of the voltage.
The flow velocity is preferably adjusted with due regard to the dimensions of the nozzle or capillary via the operating pressure in such a way that the length of the continuous thread of liquid behind the exit opening is 2 to 100 mm, preferably 5-20 mm. In practice this lengith is obtained for a capillary a few millimetres long under a liquid pressure of 0.1 to lO bar, pref-erably 1 to 3 bar.
It has been found that the penetration depth of the show-er of droplets in the case of densely planted crops can be control-led by varying the liquid pressure.
:t.~ ,.! ' -- 3a ~ 498%
The device for carrying out the process for drop dis-pensing liquids is characterised by a large number of nozzle elements which are connected in parallel from a flow-engineering point of view and which consist of capillaries of which each is surrounded by a concentric protective sheath which is at the same electric potential as the capillaries, as well as by a high-voltage generator whose high-voltage output is connected, in a manner permitting conduction, to the liquid flowing through -the capillaries. This protective sheath is sealed at one end by a base plate and forms a pot through the bottom of :~22~9~2 ,4 ~h;ch the cap;llary appears. The l;qu;d to be d;spensed in droplec form is suppl;ed by a stock reservo;r vessel connected to the cap;llary. The po;nt at wh;ch the drop-iet formation takes place, ;re. the end of the cap;l-lary, ;s ~;th;n the pot. The backpressure requ;red forma;nta;n;ng the flow ;s generated by means of a pump wh;ch keeps the stock reservo;r vessel under superatmo~
spher;c pressureO
The ent;re dev;ce can be constructed ;n a space-sav;ng manner. In part;cular, ;t ;s poss;ble to realisea portable droplet dispenser which works according to this prin-c;ple. Accord;ngly, a further development of the ;nven-tion provides for a holder on which the nozzle elements are arranged and wh;ch ;s attached to a rod shaped mounting wh;ch conta;ns a battery-operated h;gh-voltage generator, an a;r pump for generat;ng the backpressure on the cap;llar;es, and a stock reservoir vessel for the l;qu;d to be spray-d;spensed.
Spec;f;c embodiments and further developments of the ;nvent;on are descr;bed ;n the subcla;ms.
The follou;ng advantages are real;sed by the ;nvent;on:
a) It has been found that aqueous solut;ons as well as salt solut;ons and aqueous suspens;ons and emuls;ons are dispensedand deposited on tarqet ob~jects using the new process w;thout problems. As ;s known, l;qu;ds of th;s type cannot be atom;sed by purely electrostat;c means. b) The degree of charge on a drop or the charge/mass rat;o of the drops ;s determ;ned by the level of the appl;ed voltage and can be var;ed w;th;n wide l;m;ts. This makes ;t possible to control the dispensinn characteristics via the P1Pctrir voltaqe.
Th;s advantage - ~h;ch ;s of great ;mportance as regards the appl;cat;on of crop protect;on formulat;ons - can l;kew;se not be real;sed w;th the known purely electrostat;c processes of atom;s;ng l;qu;ds.
c) It ;s a further advantage that the requ;red l;qu;d Le A 22 441 8~
~ 5 --pressures are onLy relat7vely Low. The requ;red back-pressure can be generated by means of pumps of simple design.
d) The process according to the invention can be real;sed ~;thout much hardware. In particular, the device can be constructed in such a compact and space-sav;ng form that portable, eas;ly operated dispensing units are now available for aqueous crop protection formulat;ons.
e) Since only relat;vely large drops with a narrow drop s;ze spectrum are formed in the process, this avo;ds health-damaging aerosols or fine mist (which are a respira-tory danger to people).
Before the ;nvention is descr;bed in more detail by reference to ;llustrative embodiments and drawings, the principle and the underly;ng physics of the new spray-dispensing process will be explained in more detail below.
In the draw;ngs F;gure 1 shows the d;s;ntegrat;on ;nto drops of a liquid thread after ex;t;ng from a caplllary;
Figure 2 shows a cone of spray be;ng produced by apply;ng an electr;c voltage to the thread of l;qu;d;
F;gures 3a and b show how the penetrat;on depth of the cone of droplets is controlled when treating crop stands;
F;gures 4a and b show how the penetrat;on depth of the cone of droplets is controlled o~y varying the direc-t;on of spraying;
F;gures 5a and b show how d;rected jets of droplets can be used to ;ncrease the space charge dens;ty at the target s;te;
. F;gure 6 schemat;cally shows a complete portable dispensing unit;
F;gure 7 shows the holder tspray head) w;th nozzle elements wh;ch ;s used ;n the dev;ce shown ;n F;gure 6;
~5 and Figure 8 shows an ind;v;dual nozzle element.
Le A 22 441 ~2~
~ 6 --A jet of water emerg;ng at a low velocity from a s;mple or;fice nozzle or cap;llary ;s kno~n to d;s;nte-grate ;n a defined manner ;nto drops of a certa;n s;ze~
The smooth part of the jet, or thread of l;quid, ~hich ;s st;ll cohes;ve at the exit point has, after a short ;nit;al sect;on~ period;cally recurr;ng constr;ct;ons wh;ch become deeper w;th increas;ng d;stance from the ex;t open;ng unt;l, f;nally, it separates ;nto ;ndividual drops whose d;ameter is directly related to the diameter of the cohes;ve part of the jet. This process is depic-ted in F;gure 1. Capillary 1, which has a d;ameter of 100 ~um, e~ects a jet of l;qu;d 2 (for example ~ater) wh;ch is at a speed V = 6 m/second and the shape of wh;ch ;nit;ally rema;ns cyl;ndr;cal along a stretch a few cm long, but thereafter shows surface constr;ct;ons 3 which recur at equ;d;stant ;ntervals, all the ~h;le deepening unt;l, f;nally, ;nd;vidual drops 4 become detached from the jet~
The lower lim;t of the veloc;ty range for the emerg;ng l;qu;d ;s reached when a cohes;ve thread of l;qu;d fails to form at the exit open;ng and ;nstead the l;qu;d comes out ;n dr;ps. The upper l;m;t for the ex;t veloc;ty of the l;qu;d ;s reached when the lam;nar flow turns ;nto turbulent flow and the d;s;ntegrat;on ;nto drops of equal size is replaced by an atomising process where the drop size spectrum is widely t,roadened.The disin-tegrat;on of a thread of l;qu;d ;nto drops ~h;ch is descr;bed here ;s referred to as "natural jet-d;s;ntegra-t;on".
3û The d;ameter d of drops 4 wh;ch are the product of natural jet d;s;ntegrat;on can be calculated from the jet d;ameter D and the spac;ng of the constr;ct;ons or the d;s;ntegrat;on wavelength ~ by the follow;ng formula:
d = V 1~5 D2 ~ 89 D
Le A 22 441 _ 7 _ ~ 22 ~ ~ 82 In practice the ~avelength A can be set = 4.5 D. In addit;on to the drops 4, the diameter d of which can be calculated, there is also formed a very small proport;on by volume of secondary satellite droplets 5 ~hose dia-meter d5 is of the order of, for example, d5 = 0.2 d.
If the drops thus produced are followed on their fl;ght-path, for example over a fl;ght of 1 m, ;t ;s observed that a lar~e proport;on of the drops recomb;nes into larger drops 6 and 7. The result ;s that the drops do not have the expected drop s;ze d ~ 189 ~m but have a s;ze ~ith;n the range from 190 to 8ûO ~m, ;.e. far out-s;de the desired range. The recomb;nat;on process wh;ch the drops undergo ;n fl;ght can be demonstrated by photo-graphs.
It has been found, surpr;s;ngly, that the recom-b;nat;on ;nto larger drops can be prevented by apply;ng an eLectric voltage aga;nst earth to the cohes;ve part of the electrically conductive thread of l;qu;d.
The drops are then preserved ;n their or;g;nal size and arrive at the target unchanged, even if the latter ;s a long d;stance away~ Moreover, th;s leads to the forma-t;on of a w;de angled cone which consists of electr;cally charged droplets ~h;ch can be depos;ted ;n a controlled manner onto earthed objects. Th;s process ;s dep;cted ;n F;gure 2. The flo~ cond;t;ons are the same as for the jet d;s;ntegrat;on dep;cted ;n F;gure 1, except that an electric voltage of 10 kV aga;nst ear~h ;s applied to the cohes;ve thread 2 of l;quid. The cap;llary 1 ;s made of electr;cally conduct;ve mater;al, for example metal, and has a rat;o of length to d;ameter of about 50 : 1O The l;qu;d pressure at the cap;llary ;s adjusted to values of 0.1 to 10 bar, preferably w;th;n the range from 1 to 3 bar. Under these cond;t;ons the result;ng thread of l;qu;d at the cap;llary ;s cohes;ve and has a length of 2 to 100 mm, preferably 5 to 20 mm.
Instead of cap;llar;es ;t ;s also possible to use, for Le A 22 441 38;;~
produc;ng the jet, simple or;fice nozzles whose or;fire d;ameter is w;th;n the range from 50 m to 500 m, prefer-ably between 100 m and 200 m. The rat;o between length and ~;dth of su~h an or;f;ce no~zle ;s, for example, 3:1.
The h;gh voltage of 10 to 50 kv gsnerated by the h;gh-voltage apparatus 8 ;s appl;ed to the cohes;ve l;qu;d thread 2 v;a the cap;llary 1. The voltage and the resulting electr;c field have the effect of ;nduc;ng a h;gh-dens;ty electr;c charge at the surface of the con-duct;ve thread of Liquid, the h;ghest surface charge dens;ty ar;s;ng at the end of the thread of l;qu;d, at about locat;on 9. As the drops 4 and 5 become detached they take w;th them some of th;s surface charge. It ;s of cons;derable importance that the l;qu;d ;n th;s pro-cess is conduct;ve ~;th a spec;fic res;stance ~104 ~L.m.No lo~er l;m;t is descr;bed for the res;stance. The l;qu;d can be ;nf;n;tely h;ghly conduct;ve~
In contrast to the fl;ghtpath of the uncharged drops ;n the f;rst section of F;gure 1, ~hich d;ffers only little from the or;g;nal direction of the jet, the flightpaths of the electrically charged drops in Figure 2 are markedly spread out. The lightwe;ght satell;te drops 5 leave the ma;n fl;ghtpath ;mmediately after format;on and then move to~ards the nearest earthed body ;n the environment~ The normal drops formed from the bulk of the emerging l;qu;d do not step out of line until later, and the d;stance between them ;ncreases. The result is the formation of a cone of droplets lO having an apex angle The droplets retain their orig;nal size even over lengths of fl;ght of 1 m or more. The action of the electric field is thus due to two effects, namely prevent;on of recomb;nation ;nto larger drops and the formatîon of a cone of droplets as a result of electrostatic repul-sion. Chang;ng the polarity of the charge does not affect the effects. The apex angle of the cone of droplets can be made small or large, depending on the level of the Le A 2Z 441 _ 9 ~2Z~!382 cap;Llary eject;on velocity tl;qu;d pressure) poss;ble w;th;n ~he allowed range, on the th;ckness of the jet, and on the electric voltage. As a consequence it is poss;ble to depos;t the droplets in a targeted manner. For example, adjustment of the dispensing direction makes ;t poss;ble to treat a s~and;ng crop elther under a flat angle, so that the charged droplets preferent;ally reach the upper parts of the plant, or under a steep angle~ in wh;ch case the droplets are not deposited until they reach the lower parts of the standr In other words, the penetration depth of the droplets can be matched to the particular requirements of any crop stand.
F;gures 3a and b sho~ how the penetration depth of the droplet shower into dense stands can be controlled by vary-ing the l;quid pressure ;n the nozzle and the associatedjet exit veloc;ty~ In sub-frame a, ~ater ;s ejected under a pressure of P1 = 0.6 bar at an average ejection velocity V1 = 5.6 m/s from a no zle 9 having an internal diameter d = 100 ~m. The jet ;s under a voltage of -15 kV wh;ch ;s maintained by the h;gh-voltage apparatus 10.
Beneath the nozzle there are two plants 11 and 12 of a major stand of plants. The he;ght of the plants is 0.5 m.
The d;stance from the plant tip to the nozzle is 0.3 m. The cone of droplets 13 opens up above the plants 11 and 12.
The drops, becom;ng a liqu;d thread of low kinetic energy, are qu;ckly braked through air resistance and are quan-t;tat;vely depos;ted ;n the upper parts of the plants 11 and 1Z under the act;on of Coulomb forcesn In sub-frame b, the shower comes from nozzle 14 under the same voltage, but the pressure ;s 3 bar and the ex;t velocity V2 =
16.8 m/s. In this case, the moving drops are not effec tively braked unt;l the lower part of the plants 15 and 16, uhereafter the forces of electrostat;c attract;on prevail and deposit the drops in this zonen The cone of drop-lets 17 ;s less w;de-angled than cone 13. In both cases (a and b) the drop size and the charge remain virtually Le A 22 441 the same, so that the drops are depos;ted under controlLed cond;t;ons once the free-fall velocity has been braked.
In Figure 4a the nozzle or capillary 18 is arranged above the stand 19 in such a way that the emerg;ng thread of l;qu;d ;nit;ally goes ;n the hor;zon-tal d;rection. The high-voltage generator has been om;tted here~ The cone of droplets produced is braked by the air res;ctance and then deposits at a reduced velo-city ;n the upper parts of the plants of stand 19, so that the penetration depth obtained ;s only lo~. In Figure 4b the dispensing direction has been turned b~ 90 relat;ve to the first position, ;.e. the capillary 21 is in th;s case vertical. The h;gh-voltage source is not drawn ;n, as ;n F;gure 4a. The cone of droplets falls out of the cap;llary 21 and ;nto the stand 22 at a higher veloc;ty than in the arrangement dep;cted in F;gure 4a, s;nce grav;ty acts ;n the same d;rect;on. As a result the penetration depth is higher and the drops are prefer-ent;ally depos;ted in the lower parts of the ind;v;dual plants. It will be read;ly understood that the penetra-tion depth ;s ;nfin;tely var;able by vary;ng the nozzle pos;t;ons between these two extreme pos;tions 1R and 21.
It ;s thus possible to control the penetrat;on depth of the cnne of droplets into crop stands by varying the direc-tion in ~hich the liquid is ejected~ Large-area planta-tions can be treated by mov;ng a row of such nozzles across a field parallel to the ground ~drawn arrows)~
S;multaneous use of a large number o~ nozzle elements makes it possible to concentrate the space charge generated by the drops ;n the immediate vicinity of ~he target object. Thus, ;n F;gure 5a, a space charge cloud 23 of high charge density is bu;lt up ;n front of the target object 24 by means of a large number of parallel-orientated nozzles 25. F;gure 5b shows another way of building up a high space charge density by means of a large number of nozzles 26. In this case the nozzles are Le A 22 441 9~2 or;entated ;n such a way that the extens;on of the l;qu;d threads, i.e. the ;n;t;al direct;ons of the jets~ ;nter-sect at the s;te of the space charge 27 and form a power-ful deposit;on f;eld at the target object 28. In this case the dispensing nozzLes are spaced a cons;derable d;stance apart and the jet d;rect;ons are concentrated on one point ;n space.
F;gure 6 shows a complete device which is con-structed in such a compact and manageable form that ;t can be operated by one person as a portable appl;ance.
It cons;s~s of the shower head 29, the liquid-filter 30,the l;qu;d-valve 31, the stock reservo;r vessel 32 for the l;qu;d to be dispensed, a high-voltage generator 33, a battery cas;ng 34 and an a;r pump 35~ All the components are conta;ned ~;th;n a rod-shaped mount;ng 36 made of ;nsulat;ng mater;al. The electr;c system ;s earthed by means of an earth;ng cable 37 whose free end ;s on the ground or electr;cally connected to the object to be treated.
To set the appl;ance ;n opera~;on the a;r pump 35 ;s used to pump a;r ;nto the vessel 32 ~hich ;s partially full of the l;quid to be discharged.A proportion of the capac;ty, for example 30X, ;s left free for the com-pressed air to form an a;r cushionO The pressure in th;s capac;ty is ra;sed to 2 to 3 bar. The valve 38 prevents the L;quid from flow;ng back. The nozzle head 29 is put under h;gh voltage, for example a voltage of 50 kV~ by sw;tch;ng on the h;gh-voltage generator 33 by means of the sw;tch 39 wh;ch closes the pr;mary c;rcu;t. When valve 31 ;s opened the l;qu;d flows out through ~he nozzle head 29 and ;s d;spensed ;n cone form as described above.
The nozz1e or dispensing head 29 is depicted in Fig. 7. In pr;nc;ple ;t cons;sts of a large number of nozzle e1ements wh;ch are connected ;n paralLel from a flow-engineer;ng po;nt of v;ew and are connected to the l;qu;d conta;ner 32 by way of l;ne 44~ ~h;n jets of L;qu;d are very Le A 22 441 ~2;~4~
effic;ently produced us;ng short cap;llary tubes, wh;ch, however, are very sens;t;ve to so;ling and damage on d;rect contact w;th other objects, for example plants.
For th;s reason the capillary ;s here protected by a con-centr;c shea~h. Although the formation of an electr;cf;eld ;s ;nh;b;ted by the screen;ng act;on of the pro-tect;ve sheath - the sheath be;ng at the same potent;aL -the d;spensîng ;s not ;mpaired. The reason for th;s ;s tat that cohes;ve first section of the thread of liqu;d wh;ch projects beyond the edge of the protect;ve sheath ;s, by v;rtue of the fact that the l;qu;d ;s conduct;ve, a sub-st;tute ~or a tip electrode at wh;ch the requ;red f;eld for charg;ng up the drops bu;lds up outs;de the cyl;nder.
In F;gure 7, the cap;llary 47 is ;nserted ;nto the base plate of a pot 48 and thus forms a nozzle element 40 wh;ch ;s pressed ;nto the correspond;ng bores of the dis-pensino head 29.The project;ng edge 42 (the collar of pot 48) l;m;ts the penetrat;on depth. The free end of the cap;llary 47 d;ps ;nto the l;qu;d duct 43 ~h;ch ;n turn ;s connected to the supply tube 44.
S;nce the cap;llar;es 47 can eas;ly become so;led on prolonged use ;n the form of encrusted depos;ts ;t ;s necessary to have a fac;l;ty wh;ch allows the nozzle ele-ments 40 to be replaced s;mply and qu;ckly. For th;s purpose,eve~y nozzle element 40 ;s enclosed by a r;ng 45 made of res;l;ent mater;al and hav;ng a c;rcu~ference greater than the c;rcumference of the holder 41 for the nozzle elements. The r;ng 4~ has a dr;lled hole at the top (F;gure 7) and ;s bolted to the holder 41 on the oppos;te s;de (46). The nozzle element 40 ;s then ;nserted ;nto the holder 41 through the dr;lled hole ;n the res;l;ent r;ng in such a ~ay that the collar 42 of the protect;ve sheath 48 projects beyond the dr;lled hole and thus forms an abutment (see F;gure 8). To replace a nozzle element 40 the r;ng 45 ;s compressed (arrows ;n F;gure 8). As a result the ring 45 ;s deformed and Le A 2Z 441 ~2~ 2 exerts suff;c;ent force on the nozzle element 40 to d~a~
;t out of the socket in the holder 41. Thereafter a new eLemen~ can be ;nserted through the drilled hole ;n the r;ng 45 and be plugged ;nto the correspond;ng orifice of the holder 41. The exchange of nozzle elements can be done by hand ~ithout the use of tools.
The d;ameter of the res;lient ring 45 ;s S to 50 mm, preferably 10 to 30 mm. The length of the holder 41 and the pack dens;ty of the nozzle elements 40 can be adapted to demand. The pack density is onLy l;m;ted by the mutual contact of the components.
The level of the electr;c charge on the drops has a maximum which ;s reached ~hen the electr;c f;eld strength in the env;ronment of the starting points of the jets takes on a value beyond ~hich corona discharg;ng occurs~ The level of the most su;table operating voltage depends on the d;mensions of the apparatus. It must therefore be determ;ned exper;mentally. A s;ngle nozzle element hav;ng a cap;llary w;dth of 1ûO ~um anc1 a very remote counter-electrode tat least 0.5 m away) has a most suitable operat;ng voltage of about 10 kV~ The upper l;mit for the operat;ng voltage ;s about 50 kVo Compared ~ith known dev;ces for generat;ng electr;cally charged mists, the descr;bed device has a great advantage ;n that no counter-electrode ~;th earth potent;al ;s requ;red ;n the ;mmed;ate v;c;n;ty of the nozzle un;t under h;gh voltage. As a result ;t ;s pos-s;ble to use very long ;nsulat;ng sest;ons between the voltage-conduct;ng parts of the set-up. In th;s ~ay ;t ;s poss;ble largely to el;m;nate operating problems due to mo;st a;r or due to so;ling of the ;nsulators. It ;s furthermore of ;mportance that the currents are very lo~
tof the order of ~A), so that the battery used to supply the voltage has a long life and the h;gh-voltage generator can have a h;gh ;nternal res;stance. In th;s ~ay people are not endangered by h;gh voltage.
Le A 22 441
from the t;p of the plant, ;s covered dur;ng spray;ng.
It might be poss;ble, for example, to vary the penetra-t;on depth by varying the drop s;ze or by vary;ng the drop charge. Heavy, uncharged drops fall to the ground along the shortest path. By contrast, l;ght, h;ghly charged droplets are most h;ghly deflected from the free-fall fl;ghtpath and are attracted by the most protruding parts of the plant~ Both these extreme cases are undes;r-able. On the contrary~ the ;deal ;s a process where the controlled adjustment of the rat;o of drop charge to drop mass ;s poss;ble, s;nce ;n th;s way the zones between the top layers of the stands and the;r bottom Layers can be Le A 22 441 _ 3 _ ~2~
covered.
It is the object of the invention to develop a process uniformly dispensing aqueous liquids in drop form (plus the device required for this purpose) which will satisfy the above-mentioned conditions.
This object is achieved according to the invention which provides a process for dispensing electrically conductive crop protection liquids in droplet form having a specific resistance ~ 104-f~m, characterised in that the liquid escapes from a small exit orifice at a flow velocity so low that, immediately beyond the exit orifice, the liquid forms a cohesive thread which then disintegrates into individual droplets, and in that an electric voltage of at least 500 V relative to ground is applied to the thread of liquid to stablise the drop size and to produce a cone of droplets whose apex angle depends on the level of the voltage.
The flow velocity is preferably adjusted with due regard to the dimensions of the nozzle or capillary via the operating pressure in such a way that the length of the continuous thread of liquid behind the exit opening is 2 to 100 mm, preferably 5-20 mm. In practice this lengith is obtained for a capillary a few millimetres long under a liquid pressure of 0.1 to lO bar, pref-erably 1 to 3 bar.
It has been found that the penetration depth of the show-er of droplets in the case of densely planted crops can be control-led by varying the liquid pressure.
:t.~ ,.! ' -- 3a ~ 498%
The device for carrying out the process for drop dis-pensing liquids is characterised by a large number of nozzle elements which are connected in parallel from a flow-engineering point of view and which consist of capillaries of which each is surrounded by a concentric protective sheath which is at the same electric potential as the capillaries, as well as by a high-voltage generator whose high-voltage output is connected, in a manner permitting conduction, to the liquid flowing through -the capillaries. This protective sheath is sealed at one end by a base plate and forms a pot through the bottom of :~22~9~2 ,4 ~h;ch the cap;llary appears. The l;qu;d to be d;spensed in droplec form is suppl;ed by a stock reservo;r vessel connected to the cap;llary. The po;nt at wh;ch the drop-iet formation takes place, ;re. the end of the cap;l-lary, ;s ~;th;n the pot. The backpressure requ;red forma;nta;n;ng the flow ;s generated by means of a pump wh;ch keeps the stock reservo;r vessel under superatmo~
spher;c pressureO
The ent;re dev;ce can be constructed ;n a space-sav;ng manner. In part;cular, ;t ;s poss;ble to realisea portable droplet dispenser which works according to this prin-c;ple. Accord;ngly, a further development of the ;nven-tion provides for a holder on which the nozzle elements are arranged and wh;ch ;s attached to a rod shaped mounting wh;ch conta;ns a battery-operated h;gh-voltage generator, an a;r pump for generat;ng the backpressure on the cap;llar;es, and a stock reservoir vessel for the l;qu;d to be spray-d;spensed.
Spec;f;c embodiments and further developments of the ;nvent;on are descr;bed ;n the subcla;ms.
The follou;ng advantages are real;sed by the ;nvent;on:
a) It has been found that aqueous solut;ons as well as salt solut;ons and aqueous suspens;ons and emuls;ons are dispensedand deposited on tarqet ob~jects using the new process w;thout problems. As ;s known, l;qu;ds of th;s type cannot be atom;sed by purely electrostat;c means. b) The degree of charge on a drop or the charge/mass rat;o of the drops ;s determ;ned by the level of the appl;ed voltage and can be var;ed w;th;n wide l;m;ts. This makes ;t possible to control the dispensinn characteristics via the P1Pctrir voltaqe.
Th;s advantage - ~h;ch ;s of great ;mportance as regards the appl;cat;on of crop protect;on formulat;ons - can l;kew;se not be real;sed w;th the known purely electrostat;c processes of atom;s;ng l;qu;ds.
c) It ;s a further advantage that the requ;red l;qu;d Le A 22 441 8~
~ 5 --pressures are onLy relat7vely Low. The requ;red back-pressure can be generated by means of pumps of simple design.
d) The process according to the invention can be real;sed ~;thout much hardware. In particular, the device can be constructed in such a compact and space-sav;ng form that portable, eas;ly operated dispensing units are now available for aqueous crop protection formulat;ons.
e) Since only relat;vely large drops with a narrow drop s;ze spectrum are formed in the process, this avo;ds health-damaging aerosols or fine mist (which are a respira-tory danger to people).
Before the ;nvention is descr;bed in more detail by reference to ;llustrative embodiments and drawings, the principle and the underly;ng physics of the new spray-dispensing process will be explained in more detail below.
In the draw;ngs F;gure 1 shows the d;s;ntegrat;on ;nto drops of a liquid thread after ex;t;ng from a caplllary;
Figure 2 shows a cone of spray be;ng produced by apply;ng an electr;c voltage to the thread of l;qu;d;
F;gures 3a and b show how the penetrat;on depth of the cone of droplets is controlled when treating crop stands;
F;gures 4a and b show how the penetrat;on depth of the cone of droplets is controlled o~y varying the direc-t;on of spraying;
F;gures 5a and b show how d;rected jets of droplets can be used to ;ncrease the space charge dens;ty at the target s;te;
. F;gure 6 schemat;cally shows a complete portable dispensing unit;
F;gure 7 shows the holder tspray head) w;th nozzle elements wh;ch ;s used ;n the dev;ce shown ;n F;gure 6;
~5 and Figure 8 shows an ind;v;dual nozzle element.
Le A 22 441 ~2~
~ 6 --A jet of water emerg;ng at a low velocity from a s;mple or;fice nozzle or cap;llary ;s kno~n to d;s;nte-grate ;n a defined manner ;nto drops of a certa;n s;ze~
The smooth part of the jet, or thread of l;quid, ~hich ;s st;ll cohes;ve at the exit point has, after a short ;nit;al sect;on~ period;cally recurr;ng constr;ct;ons wh;ch become deeper w;th increas;ng d;stance from the ex;t open;ng unt;l, f;nally, it separates ;nto ;ndividual drops whose d;ameter is directly related to the diameter of the cohes;ve part of the jet. This process is depic-ted in F;gure 1. Capillary 1, which has a d;ameter of 100 ~um, e~ects a jet of l;qu;d 2 (for example ~ater) wh;ch is at a speed V = 6 m/second and the shape of wh;ch ;nit;ally rema;ns cyl;ndr;cal along a stretch a few cm long, but thereafter shows surface constr;ct;ons 3 which recur at equ;d;stant ;ntervals, all the ~h;le deepening unt;l, f;nally, ;nd;vidual drops 4 become detached from the jet~
The lower lim;t of the veloc;ty range for the emerg;ng l;qu;d ;s reached when a cohes;ve thread of l;qu;d fails to form at the exit open;ng and ;nstead the l;qu;d comes out ;n dr;ps. The upper l;m;t for the ex;t veloc;ty of the l;qu;d ;s reached when the lam;nar flow turns ;nto turbulent flow and the d;s;ntegrat;on ;nto drops of equal size is replaced by an atomising process where the drop size spectrum is widely t,roadened.The disin-tegrat;on of a thread of l;qu;d ;nto drops ~h;ch is descr;bed here ;s referred to as "natural jet-d;s;ntegra-t;on".
3û The d;ameter d of drops 4 wh;ch are the product of natural jet d;s;ntegrat;on can be calculated from the jet d;ameter D and the spac;ng of the constr;ct;ons or the d;s;ntegrat;on wavelength ~ by the follow;ng formula:
d = V 1~5 D2 ~ 89 D
Le A 22 441 _ 7 _ ~ 22 ~ ~ 82 In practice the ~avelength A can be set = 4.5 D. In addit;on to the drops 4, the diameter d of which can be calculated, there is also formed a very small proport;on by volume of secondary satellite droplets 5 ~hose dia-meter d5 is of the order of, for example, d5 = 0.2 d.
If the drops thus produced are followed on their fl;ght-path, for example over a fl;ght of 1 m, ;t ;s observed that a lar~e proport;on of the drops recomb;nes into larger drops 6 and 7. The result ;s that the drops do not have the expected drop s;ze d ~ 189 ~m but have a s;ze ~ith;n the range from 190 to 8ûO ~m, ;.e. far out-s;de the desired range. The recomb;nat;on process wh;ch the drops undergo ;n fl;ght can be demonstrated by photo-graphs.
It has been found, surpr;s;ngly, that the recom-b;nat;on ;nto larger drops can be prevented by apply;ng an eLectric voltage aga;nst earth to the cohes;ve part of the electrically conductive thread of l;qu;d.
The drops are then preserved ;n their or;g;nal size and arrive at the target unchanged, even if the latter ;s a long d;stance away~ Moreover, th;s leads to the forma-t;on of a w;de angled cone which consists of electr;cally charged droplets ~h;ch can be depos;ted ;n a controlled manner onto earthed objects. Th;s process ;s dep;cted ;n F;gure 2. The flo~ cond;t;ons are the same as for the jet d;s;ntegrat;on dep;cted ;n F;gure 1, except that an electric voltage of 10 kV aga;nst ear~h ;s applied to the cohes;ve thread 2 of l;quid. The cap;llary 1 ;s made of electr;cally conduct;ve mater;al, for example metal, and has a rat;o of length to d;ameter of about 50 : 1O The l;qu;d pressure at the cap;llary ;s adjusted to values of 0.1 to 10 bar, preferably w;th;n the range from 1 to 3 bar. Under these cond;t;ons the result;ng thread of l;qu;d at the cap;llary ;s cohes;ve and has a length of 2 to 100 mm, preferably 5 to 20 mm.
Instead of cap;llar;es ;t ;s also possible to use, for Le A 22 441 38;;~
produc;ng the jet, simple or;fice nozzles whose or;fire d;ameter is w;th;n the range from 50 m to 500 m, prefer-ably between 100 m and 200 m. The rat;o between length and ~;dth of su~h an or;f;ce no~zle ;s, for example, 3:1.
The h;gh voltage of 10 to 50 kv gsnerated by the h;gh-voltage apparatus 8 ;s appl;ed to the cohes;ve l;qu;d thread 2 v;a the cap;llary 1. The voltage and the resulting electr;c field have the effect of ;nduc;ng a h;gh-dens;ty electr;c charge at the surface of the con-duct;ve thread of Liquid, the h;ghest surface charge dens;ty ar;s;ng at the end of the thread of l;qu;d, at about locat;on 9. As the drops 4 and 5 become detached they take w;th them some of th;s surface charge. It ;s of cons;derable importance that the l;qu;d ;n th;s pro-cess is conduct;ve ~;th a spec;fic res;stance ~104 ~L.m.No lo~er l;m;t is descr;bed for the res;stance. The l;qu;d can be ;nf;n;tely h;ghly conduct;ve~
In contrast to the fl;ghtpath of the uncharged drops ;n the f;rst section of F;gure 1, ~hich d;ffers only little from the or;g;nal direction of the jet, the flightpaths of the electrically charged drops in Figure 2 are markedly spread out. The lightwe;ght satell;te drops 5 leave the ma;n fl;ghtpath ;mmediately after format;on and then move to~ards the nearest earthed body ;n the environment~ The normal drops formed from the bulk of the emerging l;qu;d do not step out of line until later, and the d;stance between them ;ncreases. The result is the formation of a cone of droplets lO having an apex angle The droplets retain their orig;nal size even over lengths of fl;ght of 1 m or more. The action of the electric field is thus due to two effects, namely prevent;on of recomb;nation ;nto larger drops and the formatîon of a cone of droplets as a result of electrostatic repul-sion. Chang;ng the polarity of the charge does not affect the effects. The apex angle of the cone of droplets can be made small or large, depending on the level of the Le A 2Z 441 _ 9 ~2Z~!382 cap;Llary eject;on velocity tl;qu;d pressure) poss;ble w;th;n ~he allowed range, on the th;ckness of the jet, and on the electric voltage. As a consequence it is poss;ble to depos;t the droplets in a targeted manner. For example, adjustment of the dispensing direction makes ;t poss;ble to treat a s~and;ng crop elther under a flat angle, so that the charged droplets preferent;ally reach the upper parts of the plant, or under a steep angle~ in wh;ch case the droplets are not deposited until they reach the lower parts of the standr In other words, the penetration depth of the droplets can be matched to the particular requirements of any crop stand.
F;gures 3a and b sho~ how the penetration depth of the droplet shower into dense stands can be controlled by vary-ing the l;quid pressure ;n the nozzle and the associatedjet exit veloc;ty~ In sub-frame a, ~ater ;s ejected under a pressure of P1 = 0.6 bar at an average ejection velocity V1 = 5.6 m/s from a no zle 9 having an internal diameter d = 100 ~m. The jet ;s under a voltage of -15 kV wh;ch ;s maintained by the h;gh-voltage apparatus 10.
Beneath the nozzle there are two plants 11 and 12 of a major stand of plants. The he;ght of the plants is 0.5 m.
The d;stance from the plant tip to the nozzle is 0.3 m. The cone of droplets 13 opens up above the plants 11 and 12.
The drops, becom;ng a liqu;d thread of low kinetic energy, are qu;ckly braked through air resistance and are quan-t;tat;vely depos;ted ;n the upper parts of the plants 11 and 1Z under the act;on of Coulomb forcesn In sub-frame b, the shower comes from nozzle 14 under the same voltage, but the pressure ;s 3 bar and the ex;t velocity V2 =
16.8 m/s. In this case, the moving drops are not effec tively braked unt;l the lower part of the plants 15 and 16, uhereafter the forces of electrostat;c attract;on prevail and deposit the drops in this zonen The cone of drop-lets 17 ;s less w;de-angled than cone 13. In both cases (a and b) the drop size and the charge remain virtually Le A 22 441 the same, so that the drops are depos;ted under controlLed cond;t;ons once the free-fall velocity has been braked.
In Figure 4a the nozzle or capillary 18 is arranged above the stand 19 in such a way that the emerg;ng thread of l;qu;d ;nit;ally goes ;n the hor;zon-tal d;rection. The high-voltage generator has been om;tted here~ The cone of droplets produced is braked by the air res;ctance and then deposits at a reduced velo-city ;n the upper parts of the plants of stand 19, so that the penetration depth obtained ;s only lo~. In Figure 4b the dispensing direction has been turned b~ 90 relat;ve to the first position, ;.e. the capillary 21 is in th;s case vertical. The h;gh-voltage source is not drawn ;n, as ;n F;gure 4a. The cone of droplets falls out of the cap;llary 21 and ;nto the stand 22 at a higher veloc;ty than in the arrangement dep;cted in F;gure 4a, s;nce grav;ty acts ;n the same d;rect;on. As a result the penetration depth is higher and the drops are prefer-ent;ally depos;ted in the lower parts of the ind;v;dual plants. It will be read;ly understood that the penetra-tion depth ;s ;nfin;tely var;able by vary;ng the nozzle pos;t;ons between these two extreme pos;tions 1R and 21.
It ;s thus possible to control the penetrat;on depth of the cnne of droplets into crop stands by varying the direc-tion in ~hich the liquid is ejected~ Large-area planta-tions can be treated by mov;ng a row of such nozzles across a field parallel to the ground ~drawn arrows)~
S;multaneous use of a large number o~ nozzle elements makes it possible to concentrate the space charge generated by the drops ;n the immediate vicinity of ~he target object. Thus, ;n F;gure 5a, a space charge cloud 23 of high charge density is bu;lt up ;n front of the target object 24 by means of a large number of parallel-orientated nozzles 25. F;gure 5b shows another way of building up a high space charge density by means of a large number of nozzles 26. In this case the nozzles are Le A 22 441 9~2 or;entated ;n such a way that the extens;on of the l;qu;d threads, i.e. the ;n;t;al direct;ons of the jets~ ;nter-sect at the s;te of the space charge 27 and form a power-ful deposit;on f;eld at the target object 28. In this case the dispensing nozzLes are spaced a cons;derable d;stance apart and the jet d;rect;ons are concentrated on one point ;n space.
F;gure 6 shows a complete device which is con-structed in such a compact and manageable form that ;t can be operated by one person as a portable appl;ance.
It cons;s~s of the shower head 29, the liquid-filter 30,the l;qu;d-valve 31, the stock reservo;r vessel 32 for the l;qu;d to be dispensed, a high-voltage generator 33, a battery cas;ng 34 and an a;r pump 35~ All the components are conta;ned ~;th;n a rod-shaped mount;ng 36 made of ;nsulat;ng mater;al. The electr;c system ;s earthed by means of an earth;ng cable 37 whose free end ;s on the ground or electr;cally connected to the object to be treated.
To set the appl;ance ;n opera~;on the a;r pump 35 ;s used to pump a;r ;nto the vessel 32 ~hich ;s partially full of the l;quid to be discharged.A proportion of the capac;ty, for example 30X, ;s left free for the com-pressed air to form an a;r cushionO The pressure in th;s capac;ty is ra;sed to 2 to 3 bar. The valve 38 prevents the L;quid from flow;ng back. The nozzle head 29 is put under h;gh voltage, for example a voltage of 50 kV~ by sw;tch;ng on the h;gh-voltage generator 33 by means of the sw;tch 39 wh;ch closes the pr;mary c;rcu;t. When valve 31 ;s opened the l;qu;d flows out through ~he nozzle head 29 and ;s d;spensed ;n cone form as described above.
The nozz1e or dispensing head 29 is depicted in Fig. 7. In pr;nc;ple ;t cons;sts of a large number of nozzle e1ements wh;ch are connected ;n paralLel from a flow-engineer;ng po;nt of v;ew and are connected to the l;qu;d conta;ner 32 by way of l;ne 44~ ~h;n jets of L;qu;d are very Le A 22 441 ~2;~4~
effic;ently produced us;ng short cap;llary tubes, wh;ch, however, are very sens;t;ve to so;ling and damage on d;rect contact w;th other objects, for example plants.
For th;s reason the capillary ;s here protected by a con-centr;c shea~h. Although the formation of an electr;cf;eld ;s ;nh;b;ted by the screen;ng act;on of the pro-tect;ve sheath - the sheath be;ng at the same potent;aL -the d;spensîng ;s not ;mpaired. The reason for th;s ;s tat that cohes;ve first section of the thread of liqu;d wh;ch projects beyond the edge of the protect;ve sheath ;s, by v;rtue of the fact that the l;qu;d ;s conduct;ve, a sub-st;tute ~or a tip electrode at wh;ch the requ;red f;eld for charg;ng up the drops bu;lds up outs;de the cyl;nder.
In F;gure 7, the cap;llary 47 is ;nserted ;nto the base plate of a pot 48 and thus forms a nozzle element 40 wh;ch ;s pressed ;nto the correspond;ng bores of the dis-pensino head 29.The project;ng edge 42 (the collar of pot 48) l;m;ts the penetrat;on depth. The free end of the cap;llary 47 d;ps ;nto the l;qu;d duct 43 ~h;ch ;n turn ;s connected to the supply tube 44.
S;nce the cap;llar;es 47 can eas;ly become so;led on prolonged use ;n the form of encrusted depos;ts ;t ;s necessary to have a fac;l;ty wh;ch allows the nozzle ele-ments 40 to be replaced s;mply and qu;ckly. For th;s purpose,eve~y nozzle element 40 ;s enclosed by a r;ng 45 made of res;l;ent mater;al and hav;ng a c;rcu~ference greater than the c;rcumference of the holder 41 for the nozzle elements. The r;ng 4~ has a dr;lled hole at the top (F;gure 7) and ;s bolted to the holder 41 on the oppos;te s;de (46). The nozzle element 40 ;s then ;nserted ;nto the holder 41 through the dr;lled hole ;n the res;l;ent r;ng in such a ~ay that the collar 42 of the protect;ve sheath 48 projects beyond the dr;lled hole and thus forms an abutment (see F;gure 8). To replace a nozzle element 40 the r;ng 45 ;s compressed (arrows ;n F;gure 8). As a result the ring 45 ;s deformed and Le A 2Z 441 ~2~ 2 exerts suff;c;ent force on the nozzle element 40 to d~a~
;t out of the socket in the holder 41. Thereafter a new eLemen~ can be ;nserted through the drilled hole ;n the r;ng 45 and be plugged ;nto the correspond;ng orifice of the holder 41. The exchange of nozzle elements can be done by hand ~ithout the use of tools.
The d;ameter of the res;lient ring 45 ;s S to 50 mm, preferably 10 to 30 mm. The length of the holder 41 and the pack dens;ty of the nozzle elements 40 can be adapted to demand. The pack density is onLy l;m;ted by the mutual contact of the components.
The level of the electr;c charge on the drops has a maximum which ;s reached ~hen the electr;c f;eld strength in the env;ronment of the starting points of the jets takes on a value beyond ~hich corona discharg;ng occurs~ The level of the most su;table operating voltage depends on the d;mensions of the apparatus. It must therefore be determ;ned exper;mentally. A s;ngle nozzle element hav;ng a cap;llary w;dth of 1ûO ~um anc1 a very remote counter-electrode tat least 0.5 m away) has a most suitable operat;ng voltage of about 10 kV~ The upper l;mit for the operat;ng voltage ;s about 50 kVo Compared ~ith known dev;ces for generat;ng electr;cally charged mists, the descr;bed device has a great advantage ;n that no counter-electrode ~;th earth potent;al ;s requ;red ;n the ;mmed;ate v;c;n;ty of the nozzle un;t under h;gh voltage. As a result ;t ;s pos-s;ble to use very long ;nsulat;ng sest;ons between the voltage-conduct;ng parts of the set-up. In th;s ~ay ;t ;s poss;ble largely to el;m;nate operating problems due to mo;st a;r or due to so;ling of the ;nsulators. It ;s furthermore of ;mportance that the currents are very lo~
tof the order of ~A), so that the battery used to supply the voltage has a long life and the h;gh-voltage generator can have a h;gh ;nternal res;stance. In th;s ~ay people are not endangered by h;gh voltage.
Le A 22 441
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for dispensing electrically conductive crop protection liquids in droplet form having a specific resistance < 104?m, characterised in that the liquid escapes from a small exit orifice at a flow velocity so low that, immediately beyond the exit orifice, the liquid forms a cohesive thread which then disintegrates into individual droplets, and in that an electric voltage of at least 500 V relative to ground is applied to the thread of liquid to stabilise the drop size and to produce a cone of droplets whose apex angle depends on the level of the voltage.
2. The process according to Claim 1, characterised in that the flow velocity is adjusted on the basis of the dimensions of the nozzle or capillary and on the basis of the chosen operating pressure in such a way that the length of the cohesive thread of liquid behind the exit opening is 2 to 100 mm, preferably 5 - 20 mm.
3. The process according to Claim 1, characterised in that the liquid pressure upstream of the nozzle or capillary is adjust-ed to values of 0.1 to 10 bar, preferably 1 to 3 bar.
4. The process according to Claim 3, characterised in that the penetration depth of the cone of droplets into densely planted crops is controlled by varying the liquid pressure.
5. A device for carrying out the process according to Claim 1, characterised by a large number of nozzle elements which are connected in parallel from a flow-engineering point of view and which consist of capillaries of which each is sur-rounded by a concentric protective sheath which is at the same electric potential as the capillaries, as well as by a high-voltage generator whose high-voltage output is connected in a manner permitting conduction to the liquid flowing through the capillaries.
6. The device according to Claim 5, characterised in that the protective sheath is sealed at one end by a base plate and forms a pot through whose bottom the capillary appears, one end of the capillary being connected to a stock reservoir ves-sel for the liquid and the other ending within the pot.
7. The device according to Claim 5, characterised in that the internal diameter of the capillaries is within the range from 50 to 500 µm.
8. The device according to Claim 5, characterised in that the nozzle elements are exchangeably inserted in a holder and each nozzle element is enclosed by a ring which is made of res-ilient material, is attached to the holder on one side and has, on the opposite side, a drilled hole through which the protec-tive sheath is guided to leave a collar projecting beyond the drilled hole.
9. The device according to Claim 5, 6 or 8, characterised in that the holder holding the nozzle elements is mounted on a rod-shaped mounting which contains a battery-operated high-vol-tage generator, an air pump for generating the backpressure at the capillaries, and a stock reservoir vessel for the liquid to be dispensed in the form of a conical shower of droplets.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3325070.7 | 1983-07-12 | ||
| DE19833325070 DE3325070A1 (en) | 1983-07-12 | 1983-07-12 | METHOD AND DEVICE FOR SPRAYING ELECTRICALLY CONDUCTIVE LIQUIDS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1224982A true CA1224982A (en) | 1987-08-04 |
Family
ID=6203756
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000458549A Expired CA1224982A (en) | 1983-07-12 | 1984-07-10 | Process and device for dispensing electrically conductive liquids |
Country Status (17)
| Country | Link |
|---|---|
| EP (1) | EP0134951B1 (en) |
| JP (1) | JPS6041419A (en) |
| KR (1) | KR850001031A (en) |
| AT (1) | ATE25597T1 (en) |
| AU (1) | AU2950584A (en) |
| BR (1) | BR8403451A (en) |
| CA (1) | CA1224982A (en) |
| DD (1) | DD225350A5 (en) |
| DE (2) | DE3325070A1 (en) |
| DK (1) | DK340384A (en) |
| ES (1) | ES534231A0 (en) |
| HU (1) | HU190315B (en) |
| IE (1) | IE55390B1 (en) |
| IL (1) | IL72346A0 (en) |
| NZ (1) | NZ208830A (en) |
| PT (1) | PT78829B (en) |
| ZA (1) | ZA845344B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5246166A (en) * | 1991-09-30 | 1993-09-21 | Her Majesty The Queen In The Right Of Canada As Represented By The Minister Of Forestry | Spraying apparatus |
| US10618067B2 (en) | 2015-11-09 | 2020-04-14 | Anest Iwata Corporation | Electrostatic spray device and electrostatic spray method |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3522979A1 (en) * | 1985-06-27 | 1987-01-02 | Bayer Ag | METHOD FOR PRODUCING ELECTRICALLY CHARGED SPRAY MIST FROM CONDUCTIVE LIQUIDS |
| US4748043A (en) * | 1986-08-29 | 1988-05-31 | Minnesota Mining And Manufacturing Company | Electrospray coating process |
| DE3707547A1 (en) * | 1987-03-10 | 1988-09-22 | Bayer Ag | METHOD AND DEVICE FOR SPRAYING PLANT PROTECTIVE SOLUTIONS OR DISPERSIONS |
| GB9115275D0 (en) * | 1991-07-15 | 1991-08-28 | Unilever Plc | Colour cosmetic spray system |
| GB9115279D0 (en) * | 1991-07-15 | 1991-08-28 | Unilever Plc | Hair and scalp treatment system |
| GB9115278D0 (en) * | 1991-07-15 | 1991-08-28 | Unilever Plc | Liquid spraying apparatus and method |
| GB9115276D0 (en) * | 1991-07-15 | 1991-08-28 | Unilever Plc | Skin treatment system |
| GB9115277D0 (en) * | 1991-07-15 | 1991-08-28 | Unilever Plc | Spraying system |
| GB9224191D0 (en) * | 1992-11-18 | 1993-01-06 | Unilever Plc | Cosmetic delivery system |
| KR100523559B1 (en) * | 2002-10-11 | 2005-10-25 | 주식회사 바이오리진 | Method of preparing crude saponin from leaves of Panax ginseng for use of food material |
| DE102020115923B4 (en) | 2019-12-23 | 2022-10-13 | crop.zone GmbH | Device for applying contact resistance-reducing media and applying electricity to plants |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IE45426B1 (en) * | 1976-07-15 | 1982-08-25 | Ici Ltd | Atomisation of liquids |
| DE3069773D1 (en) * | 1979-11-19 | 1985-01-17 | Ici Plc | Electrostatic spraying process and apparatus |
| US4489894A (en) * | 1981-02-27 | 1984-12-25 | National Research Development Corporation | Inductively charged spraying apparatus |
| GB2100147B (en) * | 1981-06-17 | 1985-09-25 | Nat Res Dev | Electrostatic spraying |
-
1983
- 1983-07-12 DE DE19833325070 patent/DE3325070A1/en not_active Withdrawn
-
1984
- 1984-06-19 AU AU29505/84A patent/AU2950584A/en not_active Abandoned
- 1984-06-20 HU HU842384A patent/HU190315B/en unknown
- 1984-07-02 PT PT78829A patent/PT78829B/en unknown
- 1984-07-02 AT AT84107625T patent/ATE25597T1/en not_active IP Right Cessation
- 1984-07-02 DE DE8484107625T patent/DE3462440D1/en not_active Expired
- 1984-07-02 EP EP84107625A patent/EP0134951B1/en not_active Expired
- 1984-07-09 IL IL72346A patent/IL72346A0/en unknown
- 1984-07-09 NZ NZ208830A patent/NZ208830A/en unknown
- 1984-07-09 JP JP59140767A patent/JPS6041419A/en active Pending
- 1984-07-10 CA CA000458549A patent/CA1224982A/en not_active Expired
- 1984-07-10 DD DD84265109A patent/DD225350A5/en unknown
- 1984-07-11 BR BR8403451A patent/BR8403451A/en unknown
- 1984-07-11 ES ES534231A patent/ES534231A0/en active Granted
- 1984-07-11 IE IE1785/84A patent/IE55390B1/en unknown
- 1984-07-11 DK DK340384A patent/DK340384A/en not_active Application Discontinuation
- 1984-07-11 KR KR1019840004029A patent/KR850001031A/en not_active Application Discontinuation
- 1984-07-11 ZA ZA845344A patent/ZA845344B/en unknown
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5246166A (en) * | 1991-09-30 | 1993-09-21 | Her Majesty The Queen In The Right Of Canada As Represented By The Minister Of Forestry | Spraying apparatus |
| US5443210A (en) * | 1991-09-30 | 1995-08-22 | Her Majesty The Queen In The Right Of Canada, As Represented By The Minister Of Energy, Mines, Resources And Forestry | Spraying apparatus |
| US10618067B2 (en) | 2015-11-09 | 2020-04-14 | Anest Iwata Corporation | Electrostatic spray device and electrostatic spray method |
Also Published As
| Publication number | Publication date |
|---|---|
| DK340384D0 (en) | 1984-07-11 |
| IE841785L (en) | 1985-01-12 |
| HU190315B (en) | 1986-08-28 |
| JPS6041419A (en) | 1985-03-05 |
| IL72346A0 (en) | 1984-11-30 |
| BR8403451A (en) | 1985-06-25 |
| ES8504494A1 (en) | 1985-04-16 |
| ATE25597T1 (en) | 1987-03-15 |
| KR850001031A (en) | 1985-03-14 |
| IE55390B1 (en) | 1990-08-29 |
| EP0134951A1 (en) | 1985-03-27 |
| NZ208830A (en) | 1988-02-29 |
| DK340384A (en) | 1985-01-13 |
| HUT35556A (en) | 1985-07-29 |
| DE3462440D1 (en) | 1987-04-09 |
| ZA845344B (en) | 1985-03-27 |
| EP0134951B1 (en) | 1987-03-04 |
| DE3325070A1 (en) | 1985-01-24 |
| AU2950584A (en) | 1985-06-13 |
| PT78829B (en) | 1986-07-15 |
| DD225350A5 (en) | 1985-07-31 |
| PT78829A (en) | 1984-08-01 |
| ES534231A0 (en) | 1985-04-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |