CN1093023A

CN1093023A - Electrostatic powder applies

Info

Publication number: CN1093023A
Application number: CN 93103560
Authority: CN
Inventors: 盖萨斯·亚施万特·戈帕尔
Original assignee: INTECH EXPORTS
Current assignee: INTECH EXPORTS
Priority date: 1993-04-03
Filing date: 1993-04-03
Publication date: 1994-10-05
Anticipated expiration: 2013-04-03
Also published as: CN1057027C

Abstract

A kind of electrostatic powder coating unit comprises that a spray assembly is positioned at a bend that is hanging the conveyer belt of several article, these article will apply with powder, heat-treat then powder is become a kind of bonding cover layer or its analog that paints character.This spray assembly comprises an apertured impeller around a vertical axis rotation, and the center of the powder directive impeller of the charging from a fixing nozzle is so that the blade on the impeller transmits centrifugal force to powder particle.This impeller and nozzle assembly can be vertical reciprocating the so that powder of spraying can cross on the whole article that is hanging He moving.

Description

Electrostatic powder applies

The present invention relates to a kind of electrostatic powder coated apparatus that is used for, in this process, article at first are coated on powder, and this is owing to spraying these article and realize with this article ground connection and with the powder of charging.Because the suction of static, the powder of this charging is deposited to be covered on the article that will apply.Then, these article that applied powder betransported or are transferred in the baking oven, and in this baking oven, these article are heated so that powder smelting and curing form the diaphragm that one deck is adhered securely.

The electrostatic powder coating unit needs fluidised powder is transported on the spray head, carries out electrostatic charging and is applied on these article from this spray head.In known coating unit (powder paint spray gun), powder in a container by fluidization and with compressed air it is transported to this spray head (rifle) and gets on.Powder is applied to article and gets on an air deflector, the sprayer of a sprayer or other form.This powder is to carry out corona charging or carry out triboelectric charging with high-intensity pointed tip electrode, use separately one of them or both in conjunction with all can, to reach electrostatic charging.Under the momentum effect of suction, strength and the powder self of electrostatic field, these powder particles are sent to these article and have got on.The thin powder that ejects from spray head gets on the surface that a kind of fan-shaped form of qualification is coated to article the plane of these article.But various restrictions are arranged, for example the chemical composition of Faraday cup effect that causes from corona charging (Faraday cage effect) and the powder that causes owing to triboelectric charging.

This powder coating process is manual or automatically, utilization is such as the mechanical device that moves back and forth device, and this depends on the size and the quantity of the article that will be applied in a specified time limit.

Possible alternative for strength powder spraying is to utilize a static fluidized-bed, and article are placed in the fluidised powder bed and go, and applies (do not re-use air powder is delivered to article get on) of just implementing in electrostatic field.This technology also can be craft or automation form.

More than two kinds of known technologies, use the paint spray gun of compressed air strength and the fluidized-bed that uses simple electrostatic attraction, their advantage and restriction are all arranged.But Pneumatic type far is general than fluidized-bed.

It is 200 Grams Per Minutes that the strength coating has best powder throughput usually, but its maximum output valve can reach 500 Grams Per Minutes, and its charge efficiency and the efficient of passing on are low.Apply in order to reach on two opposites of article, two rifles of minimum needs apply from two opposites.Be used to have the workpiece of four faces, will and have turn device with four applicators sometimes.Automatically applicator will be in up-and-down motion to cover the whole height of article.For speed, running time and its height or the shape that cooperates article, when article when being very of short duration in the face of time of applicator, the applicator quantity that use may be for more.Because it usually is that strong vibration takes place lightweight those article that the effect of the little component of the aerodynamic force of dispense powders may make.

Under the situation that fluidized-bed applies, for those article of complicated shape, the Faraday cup effect is a main restriction.Therefore and the thickness of last coat will become and become unacceptable degree for highly being about article more than 50 millimeters further shortcoming is the thickness that applies.

The powder sprayer that the purpose of this invention is to provide a kind of non-aerodynamic force, it can reach 1 kilogram/minute with the efficient of the best powder of providing and delivering, even reaches 2 kilograms/minute, so just can substitute several paint spray guns on those ground that will apply big surface area.The invention provides a kind of equipment, therein article can in spraying band, keep one considerable long-time, so just all article surfaces and storewide length (highly) can be exposed in face of the independent applicator.One of this applicator more the characteristics of novelty to be that distance between article and the applicator remains in the powder coated process constant, this is unlike the situation of strength applicator, the distance with article on conveyer belt is constantly to change there.

Owing to be not aerodynamic force, the vibration of the generation of the article that those are little can be avoided basically or fully.

Specifically, the invention provides a kind of electrostatic powder coated apparatus that is used for, comprise a coating room, this coating room has the conveyer belt of a belt shape at an upper portion thereof, it is the bend of encapsulation basically that the part route of this conveyer belt has formed, improvements are to comprise provides a powder spray assembly, thereby this assembly has a vertical axis that is arranged in the rotation of described bend to be suspended on the route that the article that will apply on the conveyer belt are placed in the powder spraying.

According to the present invention, this device no longer is dispensed into the article that will apply with centrifugal force with powder particle with compressed air aerodynamic force and gets on.Powder is provided and delivered under the powerful electrostatic field situation of neither one then by electrostatic charging, and this has just reduced the Faraday cup effect.Moreover the dress band article on the conveyer belt or similar mechanical device are turn-taked around this powder coated assembly so that the distance between them during spraying remains unchanged.Each face of all of article be owing to can both come out it transposition, and article rest on the time of this powder coated zone or spraying band and can reach long enough, thereby increased the flexibility of coating during for the article that apply long vertical stretching.

Like this, the invention provides a kind of automatic powder coating device that real value is arranged, this device is more effective, a big powder throughput is arranged, the space of spray booth is required less, little complicated owing to no longer need to move back and forth device and strength applicator, be little or big no matter all these advantages are applicable to article.

In a concrete most preferred embodiment, this conveyer belt can have two bends, also is above-described S shape.The article that must apply are no longer needed it around rotate position or rotated of vertical axis, thereby obtained stable higher productivity, keeping the high efficiency of operation simultaneously.

Typical electrostatic powder coating unit according to the present invention comprises a confined chamber, wherein the conveyer belt of the belt shape of a motor driving is arranged at the top of this chamber, and a powder coated assembly is arranged at a bend center of ring road, this assembly comprises the impeller of a rotation, and this impeller is rotated with a fixing angular speed and can be reciprocating along its rotation centerline.The impeller of this rotation is admitted by the charged electrostatically powder by a nozzle assembly, and this nozzle assembly then receives fluidised powder by a powder feeding tube road.This nozzle assembly is fixed on the case of an electric insulation.Described impeller is rotating with a fixing speed, and selects a space rate reciprocating in vertical direction according to the article that will apply.According to the height of wanting coated article, the length of described reciprocating vertical stroke also can change thereupon.This haul distance should go out 50 millimeters at least greatly than the total length of described article.

The powder particle that leaves impeller is dispersed on the article that will apply owing to following four kinds of strength:

A) centrifugal force

B) air force

C) electrostatic field suction

D) impulse force

A) centrifugal force

The centrifugal force that is delivered on the powder particle is because due to the rotation of impeller.The radial fins that any slippage in tangential direction is installed in the impeller weakens.

The described powder that has charged is fed into and goes in the impeller of rotation and owing to centrifugal force is radially even injection basically, but without any tangential slippage, this is to reach owing to having disposed an inclined-plane θ 1 who makes progress.The upper limit of angle θ 1 is an angle of repose, and when this angle of repose, the radial motion of powder will be got off by slow, so just can finish gathering then it to be evenly distributed in several fins and going of powder.So the angle of θ 1 will be selected as being lower than this angle of repose, for example be roughly 0 to 30 degree.Reach best powder uniform distribution and unlikelyly cause the excessive angle of gathering to be roughly 10 degree.

The quantity of radial fins Z is to derive from dust gram recommendation (Eckrecommendations):

Z= \frac{{8.5Sin B}_{2}}{1 \frac{d_{1}}{d_{2}}} = 18

And derive from this terraced Pernod husband recommendation (Steppenhoffrecommendations):

Z＝1/3 B ₂＝30

The better mean value of selecting actual use from above numerical value between the two after taking all factors into consideration is:

Z＝（18+30）/2＝24

Wherein, in these formula,

B ₂The angle of outlet of=blade=90 degree

d ₁The internal diameter of=blade part

d ₂The external diameter of=blade part

The better selection that is used for radial blade is fairshaped.

The angular speed of these radial blades be sent to that powder particle gets on and since these powder particles of action of centrifugal force be able on the article that will apply, adhere to down beginning to move radially and obtain enough issuing velocity on the lower surface of described impeller.

B) air force

When the fin on the described impeller that is rotating is made radial spray with air, this will cause producing a pressure below atmospheric pressure at the central part of impeller, and this has produced an axial air stream again.Air is sucked by the space between impeller shaft and the cylindrical casing and is used to transport powder particle and goes to the article that will apply.To be adjustable cause any big vibration so that it will be unlikely to little article to the speed that air leaves impeller, but be enough to overcome described Faraday cup effect.

C) electrostatic field suction

Powder is fed in the described impeller by a nozzle assembly.This nozzle assembly is made up of 32 electrodes, and is connected to a high voltage electric organ, has set up a strong electrostatic field thereby this electric organ produces 100 kilovar negative voltages.Powder just has been recharged during by this strong electrostatic field.These powder that charged are when by the impeller scattering, because the effect of electrostatic attraction and be pushed to further that the article that will apply of ground connection have got on.

Under the situation without any the corona generating electrodes of outside, the described powder that has charged has been able to equably attached to on the article of Faraday cup effect sensitivity.

D) impulse force

The impeller disk is dish-shaped, when powder when sliding on the skewed surface at impeller under the centrifugal action, for powder particle, transmitted a motion component that makes progress.This component that makes progress has transmitted enough impulse forces and has got on the lower surface that helps powder particle to be coated to the article that will apply.

The present invention is further described conjunction with figs. with embodiment.

Brief Description Of Drawings:

Fig. 1 is the floor map that is used for the powder coating device of powder coated small article of the present invention;

Fig. 2 is the side elevation view of device shown in Figure 1;

Fig. 3 is the side elevation view of the magnification ratio of spray booth shown in Figure 2;

Fig. 4 is the plane of the rotary blade shown in Fig. 2 and 3;

Fig. 5 is an impeller shown in Figure 4 cutaway view along the V-V line;

Fig. 6 is the cutaway view that is used for the nozzle assembly of powder charging;

Fig. 7 is used to hang and the part of rotating the device of each article that will apply is analysed and observe, the part elevation;

Fig. 8 is the view of the modification of an impeller shape that is similar to Fig. 3;

Fig. 9 is the view of the device that is similar to Fig. 2 that adopts the impeller of Fig. 8;

Figure 10 is the plane that is used for the modification equipment of article delivery band.

At first consult Fig. 1 to 7, according to device of the present invention, comprise the spray booth 2 of a sealing, this spray booth 2 has a conveyer belt 3 that is driven by motor 4 at an upper portion thereof.This conveyer belt 3 has formed a loop turn 5, is loaded up and is removed at platform 7 places at platform 6 place's article of conveyer belt.For the purpose of drawing was clear, those supports that are used for limiting the conveyer belt track route were left out from figure.The powder coated assembly comprises a rotary blade 8 that is driven by an electric insulation axle 10 by motor 9.This motor 9 and impeller 8 are contained on the bar 11 by the reciprocating mechanism 12 of motor 13 drivings.What extend round axle 10 is nonconducting sleeve 14 that can not rotate, and this sleeve 14 moves in vertical direction with motor 9.On sleeve 14, adorned a nozzle assembly that can not rotate 15.The high-voltage cable 16 that comes from a high voltage electric organ 17 is supplied to nozzle assembly 15 with high voltage.By another root high-voltage cable 19 row's resistor 18 being connected to the electric charge that is used on the nozzle assembly 15 will accumulating on the nozzle assembly selectively discharges.The powdery paints that sprays is stored in the fluidised magazine 20, is transported to impeller assembly 8 places from this magazine 20 by jet-propelled pump 21 suctions and by a pipe 22 by fluidised powder.Powder is projected onto the center 23 of described impeller 8.As shown in Figure 3, this impeller be dish so that powder passing away 27 with respect to the rotation of impeller upwards and outward-dipping going out, the first step with the rotation vertical line be θ 1 at angle, becoming a bigger angle then is θ 2.The powder that is seated in the impeller scatters out owing to the gradient of action of centrifugal force and passage 27 with being become uniform state.This impeller assembly 8 comprises that two dishes become one group, and upper disc 24 has several radial fins or dividing plate 25 as shown in the figure, and lower disc is then as a cover cap 26.Shown in Fig. 3 and 4, fin 25 preferably has a cross section for along with radius increases intilted shape, is thin so that they locate than its inner place in the outer end of impeller.

The article 28 that apply are suspended on connecting ring 29 places in the conveyer belt 3 and are rotating so that these article are subjected to a uniform powder coated around a vertical axis continuously or off and on.Do not adhere to unnecessary powder 30 on the article and be collected into one in the magazine 31 of 2 bottoms, chamber, the cfentrifugal blower that these powder drive by means of motor 34 or the suction of air exhauster 33 and by airduct 32.Such product air/powder mixture is fed in the cyclone separator 35 and goes.The powder 36 that reclaims is collected in the bottom of this shell separator and is transported in the little cyclone separator 38 by a pipe 39 by jet-propelled pump 37 suctions and goes, and so just powder has been separated again with air.Drop to the sieve cabin bucket 40 from the powder of the separator well of small-sized cyclone 38, the powder back of being sieved is sent back in the warehouse entry bucket 20 herein, has so just kept being used for the cycle of a closure of powder circulation.Being used for replenishing the fresh powder that has been bonded on the coated article can be by in the feeding magazine 20, because this does not become the part of theme of the present invention, therefore needless to say when needs.

As shown in Figure 7, on each connecting ring 29 on the conveyer belt, hang article, when conveyer belt action article then when impeller moves past, connecting ring 29 can rotate, and so just article is rotated those surfaces with the not coated mistake of exposing it to impeller around its center of gravity generation.This be by means of on the connecting ring 29 with swing pinion 48 finish.But this gear have a suspended item 28 suspension hook 50 and and a tooth bar 52 extending round the part route that conveyer belt goes in ring be meshed.This gear, suspension hook and article in this case are all owing to the motion of conveyer belt with respect to tooth bar is rotated.

As we can see from the figure nozzle be can not rotate but can be reciprocating with impeller assembly.This impeller also is free of attachment to high voltage source thereby the voltage above it can float.High-voltage cable 16 is connected to nozzle assembly to set up a powerful electrostatic field and pass the powder that leaves nozzle and with these powder particles chargings, these powder particles eject and enter the center of impeller from nozzle assembly 15 then.In this case, will can not produce the Faraday cup effect.The impeller of dish has guaranteed that with the exit passageway that makes progress the powder particle of discharging has a vertical motion component, and this strength and gravity have the opposite effect and help that powder is attached to complex surfaces.

As shown in Figure 6, nozzle assembly 15 is contained on the clamper 41 and has a conductive pin 45 that is connected to high voltage electric organ 17 and is connected to resistor row 18 by cable 19 by cable 16.Pin 45 also is connected to an inner conductive sleeve pipe 43.Be equipped with in this sleeve pipe 43 between 32 electrode needle 44, these electrode needle and distributing with 10 millimeters of axially spaced-aparts and spaced radial 90 degree each other.This conductive casings enters the nozzle body 46 of an insulation with interference fit.High voltage also is transmitted to electrode stem 42 by means of pin 47.These 32 electrodes 44, conductive casings 43 and powerful emanant electrostatic field of electrode stem 42 assist in generating.This sleeve pipe 43 is preferably made by polytetrafluoroethylene (PTFE) and the conduction that dopes graphite so that it becomes.

Though the circumferential space between sleeve pipe 43 and bar 42 is hollow cylindrical shown in being, it also can have other transverse shapes.For example, it can outwards open with the speed that reduces powder at the port of export towards it and increase powder thus and rest on time in the charging.

Powder by feeding tube road 22 by feeding nozzle assemblies 15 and remain on that a sufficiently long time can reduce too much spraying like this to obtain charging completely in the powerful electrostatic field.

As Fig. 1, the general arrangement shown in 2,3 is used for applying small article for automatically working.When this same powder coating device is used for applying big surface area, can be by the powder circulation of impeller by feeding powder to increase it by a plurality of nozzle assemblies.The number of nozzle that the powder that supply has been charged goes to impeller be can select be unlikely the impairment powder charge efficiency or the efficient of passing on the quantity of the powder that is suitable for carrying out scattering or the powder quantity that will adhere at the appointed time.The article of large volume can be applied by the diameter that increases the conveyer belt bend, and this diameter is to be in proportion with the article that will do powder coated.

Adhere on the article of large volume for the powder that more effectively will charge and from the powder sprayer more a long way off, the speed of the powder of close article will remain unchanged, this is because Fig. 3 and the impeller shown in 5 are replaced to an impeller that has different dish-shaped angle θ 2 and bigger diameter, but has same number of fin.

Have now and consult Fig. 8 and 9 again, show the modification of rotary blade and nozzle assembly.Among Fig. 2 and Fig. 9, similarly Fig. 3 and the shared part of Fig. 8 are used same numbering.

System shown in Fig. 8 and 9, the high voltage supply is to originate from a high voltage electric organ 67, this electric organ 67 is installed in the housing 65 attached to sleeve pipe 14 bottoms.High voltage electric organ 67 has high-frequency of supply of control and comparatively speaking low-voltage by a shielded cable 66 from suitable external motive device.High voltage lead 60 is connected to nozzle assembly 15 with the output of high voltage electric organ and gets on.

Discharging resistor 68 similarly is installed in attached in the housing 65 of sleeve pipe 14 bottoms and be connected on the cable 69, this cable 69 makes the terminal voltage on nozzle assembly 15 come under observation and externally shows, for example shown by a display that is contained on the power set, these power set are what to be fed to this high-voltage power device.

In use, this device is aforesaid to work together, and high voltage is applied on the nozzle assembly 15 by lead 60, is charged when powder contacts during by nozzle assembly and with the electrode that is fixed on nozzle assembly or acusector and central electrode.The Faraday cup effect is avoided basically.

Device shown in Figure 9 has two nozzle assembly 15(for the sake of clarity, and one of them only is shown among Fig. 8), this will make the powder circulation be increased.This can improve the efficient of whole device morely, because it has guaranteed the quantity of powder that can be coated in the unit interval basically.When device was used for applying the article of high surface area, this was a particular importance.In general, for small article, then an independent nozzle assembly just can transport enough coating powders.

Further improvement can be obtained by the conveyer belt form that adopts in the plane shown in Figure 10 on efficient.Schematically show a conveyer belt route 100, the device that has article can move along this route.It is the housing 101 of sealing basically that part conveyer belt route is sent these article to one, and has an import 102 and an outlet 103.In housing 101, the conveyer belt route forms two bends 103 and 104, and each bend is made up of a circular arc passage that is about 270 °.Settled the powder deliverying unit of forming by the impeller of above-mentioned fixing nozzle and rotation in the centre of each bend.So the article of large volume can pass those two bends 103 and 104 and need not rotate with respect to they suspension arrangements on conveyer belt as can be seen, yet they will expose the both sides on their opposite to the impeller that is positioned at each bend center, so just make the both sides of the large piece article that must apply except when article hang over to impel on the conveyer belt to have formed when its route moves no longer need be in coating procedure with respect to outside the rotation of stationary housing 101 does according to having rotatablely moved around they self vertical axis.This advantageous particularly that concerning big part template article, seems, because these template article will apply on its two opposite, but they can not rotate, otherwise thereby its edge part will lean on the above center impeller dish to have problems, the further benefit of not going to rotate such plate-shaped members is because the restriction of conveyer belt speed is caused by indexing mechanism, there has not been indexing mechanism, this restriction just can be left alone, thereby conveyer belt speed can be adjusted to the use that helps high powder circulation and provide one to want the comprehensive of coated article, high output.

Should be noted that when having increased the powder circulation of impeller, accumulate in powder/air concentration that powder in the spray booth should remain on a safety to avoid the danger of any blast.This safety measure has exceeded scope of the present invention, is not therefore given unnecessary details herein.

Claims

1, a kind of electrostatic powder coated apparatus that is used for, comprise a spray booth, this spray booth has the conveyer belt of a belt shape at an upper portion thereof, it is the bend of sealing basically that the part route of this conveyer belt has formed, it is characterized in that, comprise a powder spray assembly is provided, thereby this assembly has a vertical axis that is arranged in the rotation of described bend to be suspended on the route that the article that will apply on the conveyer belt are placed in the powder spraying.

According to the device of claim 1, it is characterized in that 2, said powder spray assembly is applicable to along rotation reciprocating.

According to the device of claim 1 or 2, it is characterized in that 3, a motor on the support that does not rotate makes it to rotate said powder spray assembly by being contained in, this support is again that made it by another motor along its length direction can be reciprocating.

According to the device of claim 3, it is characterized in that 4, the reciprocating amplitude of said support is adjustable.

5, according to the device of claim 1 or 2, it is characterized in that, said powder spray assembly comprises the impeller of a rotation, is flow to the centre of this impeller near having put powder that a nozzle assembly that can not rotate is used for guiding out a charging on this impeller.

According to the device of claim 5, it is characterized in that 6, said nozzle assembly comprises: the pipe of an electrically non-conductive material, the pipe of a conductive material is arranged on the inner surface of this pipe, have the protrusion that extends internally from the tube inner wall of this conductive material; Also has the metallic rod at a center and radially inwardly spaced apart with those protrusion ends; Be used for pipe and bar in above-mentioned are connected to the device of high voltage source in addition, and being used for device to this nozzle assembly of powders into that will apply, described powder is mobile along axially passing through of nozzle assembly in the circumferential space between interior pipe and bar.

According to the device of claim 6, it is characterized in that 7, the part outer surface of said nonconducting pipe is screwed.

8, according to wherein any one device of claim 5 to 7, it is characterized in that said impeller is dish-shaped, this impeller has the powder passing away, and this passage is sideling upwardly and outwardly with respect to rotation.

9, a kind of electrostatic powder coated apparatus that is used for is characterized in that, comprising: it is vertical rotating shaft basically that a powder spray assembly, this assembly have one; Have an impeller and bolt tightly together in this bottom; Nozzle assembly that does not rotate be bearing on the above-mentioned spray assembly and be used for guiding out carried out electrostatic charging powder flow to the center that reaches described impeller; This impeller has two parts, its underpart is dish (spill) inner surface, having what make one with it on this inner surface is radially fin basically, and its top then has the surface of convex and contacts to limit powder passing away several inclinations and radial radiation with the top of above-mentioned fin.

10, according to the device of claim 9, it is characterized in that said impeller is secured on the end of rotating shaft, this rotating shaft is that electrically non-conductive material is made, and this rotating shaft is surrounded by a sleeve pipe that does not rotate, and has then installed said nozzle assembly in the lower end of this sleeve pipe.

According to the device of claim 9 or 10, it is characterized in that 11, the concave inside surface of said impeller comprises the frusto-conical surface in the outside at the frusto-conical surface of an inboard with big top angle and a little top angle that is adjacent to this.

12, according to wherein any one device of claim 1 to 8, it is characterized in that, comprise also that the device that is connected to said spray booth is used for powder unnecessary in the chamber released and in an airtight route, these powder recirculation are delivered in the nozzle assembly and go.

13, according to wherein any one device of claim 1 to 8, it is characterized in that, when the article that will apply the conveyer belt that goes in ring to the small part route by the time, the device that each article is rotated round it self center of gravity is provided.

14, according to claim 1 to 8, wherein any one device of 12 and 13 is characterized in that the route of said conveyer belt is looked from the top, has two bends to form a pair of adjacent bend of S shape, and each bend has a powder spray assembly.