CA1239280A - Apparatus for electrokinetically charging of powder materials - Google Patents

Apparatus for electrokinetically charging of powder materials

Info

Publication number
CA1239280A
CA1239280A CA000473799A CA473799A CA1239280A CA 1239280 A CA1239280 A CA 1239280A CA 000473799 A CA000473799 A CA 000473799A CA 473799 A CA473799 A CA 473799A CA 1239280 A CA1239280 A CA 1239280A
Authority
CA
Canada
Prior art keywords
channel
input
insulating material
powder
pipe
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
Application number
CA000473799A
Other languages
French (fr)
Inventor
Helmut Bauch
Wolfgang Kleber
Dieter Auerbach
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
VEB INFRAROT-ANLAGEN ORANIENBURG
Original Assignee
VEB INFRAROT-ANLAGEN ORANIENBURG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by VEB INFRAROT-ANLAGEN ORANIENBURG filed Critical VEB INFRAROT-ANLAGEN ORANIENBURG
Application granted granted Critical
Publication of CA1239280A publication Critical patent/CA1239280A/en
Expired legal-status Critical Current

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B05SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05BSPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/025Discharge apparatus, e.g. electrostatic spray guns
    • B05B5/047Discharge apparatus, e.g. electrostatic spray guns using tribo-charging

Abstract

ABSTRACT OF THE DISCLOSURE
An apparatus for the electro-kinetic charging of powder-like materials having a pair of supply channels, an input zone for each channel, one for the powder dispersed in a gas flow and one for another gas flow and which are shaped as dual annular nozzles with a pipe-shaped separating wall therebetween acting as an electrostatic ionizing electrode and made from an electrically semi-conductive material having anti-sticking properties and, wherein the adjoining flow chan-nel is formed as an annular channel by a pipe from an insulat-ing material, and a centrally arranged rod, wherein the ratio between rod and pipe diameters is in the range 0.75 to 0.9.

Description

~ 3~

The present invention relates to an apparatus for the electro~kinetic charging of powder-like materials for the purpose of electrostatic coating of objects with such powder.
It can be used in manual as well as automatically operated powder spray devices, also ~n fluidized bed apparatus, as a charging device. For the coating material one may use duro or thermoplastic powders, enamel or similar materials in powder form.
There are spray apparatus known for the electro-static surface coa-ting, in whlch the powder-like coating mate-rial while belng pneumatically forced through an insulating material channel, becomes electrically charged through the frictional effect d~le to the fact that the powder particles contact the wall of the flow channel (for example, German Patent 1,577,757 and 2,203,351).
The disadvantage of such apparatus resides in that it can be operated only wlth a relatively low powder output in order to accomplish an intensive all-around contact of the powder particles with the flow-through channel in order to obtain a charge which is satisfactory from the viewpoint of the technical requirement of the process. In order to increase the powd0r charging, various measures have been undertaken, which were intended to increase the turbulence of the flow, a~d to this effect special turbulence creating means have been inserted (German Laid-Open Application 2,938,606), also propellers, (U.S. Patent 3,905,330) or a blower (German Laid-Open Application 2,209,231) and curved charging pipes (German Laid-Open Application 3,100,002). Furthermore, there are constructive variants known, in which by means of a half-toroid-shaped input sect~on under the use of Coanda effect (German Laid-Open Application 2,713,697) or by means of pro-ducing a helical.-shaped partlcle path (German Laid-Open Appll-:, , ~ 3 ~
ca-tion 2,756,009~ an intensive wall con-tact is accomplished.
- Furthermore, there are electro-kinetic charging devices known, in which the charging of the powder is accom-plished by a combination of a frictional-electric effect with the ionization process caused by it on passive electros-tatic electrodes (East German Patents 106,308 a.nd 113,289 and German Laid-Open Application 3,303,137). ~ccorcling to the latter publications, the pneumatically lntroduced powder is undergo-ing a turbulence effect ln an insulating material pipe caused by a gas flow. The device is in the form of a jet apparatus and includes a pair of inpu-t channels meeting in -the star-ting section of the insulating material channel and, in the region of the combined gas flow, one or more electrostatic ionizin~
- electrodes are provided. Such electrodes are in the form of ; rings embedded into the inner wall of the insulating material pipe or, in the form of axially or radially projecting needle electrodes pro~ecting into the insulating pipe.
There is also a device known ln which in the direc-tion of the flow, behind or in the immediate vicinity of the electrostatic ionizing electrode, a cone-shaped flow-member is arranged for the increasing of the frictional electrical effect (East German Patent 134,841). All the devices which operate with an additional gas flow have one feature in com-mon, namely, that they operate on the principle oE a ~et appa-ratus, whereby the unlform nature of the powder-gas flow introduced by a hose conduit and through an e;ector, becomes effected. The devices having the electrostatic ionizing elec-trodes possess the disadvantage that the ionization process occurs on certain preferred poin-ts and, on these poin-ts, due to the partially high field strengths as a result o.~ the glow discharge, the powder pa~ticles will become sintered or melted onto the electrodes, whereupon the ioniza-tion becomes reduced ~ ~ 3~

and, the powder charging falls-off. The electrostatic elec--trodes, -therefore, must undergo a removal of the powder crust developed on -thell) after a c~-tain period of time.
The present invention improves the functional relia-bility of a powder coating apparatus operating with electro-kinetic charging, by providlng a more uniform powder output, as well as an increased and more s-~able powder cllarging, along wi-th the reduction of the cleaning requirement and, as a result, to increase the scope of application of the electro-kinetic powder coating apparatus.
The present inven-tion also prevents the crus-t forma-tion on the elec-trostatic electrodes by improving the shape of the input zone and, by an appropriate input of the materials, as well as to increase the intensity of the charging process.
According to the present invention an apparatus for the el~ctro--kinetic c~larging oE powder shape~ materials ~or the electros-ta-tic coating of ob~ects comprising a firs-t input channel for a powder dispersed in a gas flow and a second input channel for another gas flow, an insulating material flow channel having an input region, said input channels meeting in the input region of said insulating material channel, and a passive electrostatic ionizing electrode, wherein each of said input channels comprise an inlet zone shaped as a pair of annular nozzles, wherein said ~irst inpu-t channel is formed as an inner channel and said second inpu-t channel is formed as an outer annular channel, a pipe shaped separating wall ac-ting as said passive electrostatic ionizing elec-trode separa-ting said inpu-t channels, said ionizing elec-trode is made from an electrically semi-conductive ma-terial having anti-sticking properties and is direc-tly or indirectly connected to ~round pote~tial, and wherein the insulating material flow channel is formed as an annular charlnel made -from an insulating material.
Thus, according to the invention an input zone is provided for each of a pair of supply channels in one of which the powder dispersed in a gas flow is flowing and, in the o-ther, a further gas flow is introduced, which input zone is in the form of a dual annular nozzle, and wherein throu~h the inner channel the powder gas flow and, through the outer annu-lar gap, the second gas flow is introduced and, according to which, a pipe-like separating wall ac-ting as the passible electrostatic ionizing ~lectrode is the separating wall between the two channels. It is made from an electrically semi-conductive material having anti-sticking properties and is, directly or indirectl~ through a measuring and/or control device, connected to ground potential and, the next ad;acent flow channel is formed as an annular channel from an insulat-ing material. Especially suitable is an embodiment, in which the electrostatic ionizing electrode is made from a material which has a specific volume resistance of 104...108 ~m.
Polytetrafluoroaethylene has been found especially suitable with a graphite content of 10-25%.
As a further suitable embodiment for the pipe-like electrostatic electrode, an insulating material with semi-con-ductive coating on its outer surface has been found, which has a specific upper surface resistance of 106...109 ohm tmeasured with a pair of cutting electrodes having a length of lOcm and spaced lcm fxom each other).
In a preferred embodiment of the invention the outer annular-shaped supply channel for the gas flow will taper in a conical fashion, and wherein the generating surface of the channel wall encloses an angle of 5-30 wi-th respect to the axis of the pipe.
The channel made from an insulating materlal and, .

~ ~ 9~ ~

which is adjoining the input zone, ls made preferably from a pipe and a central rod, wherein the rates of the rod diameter to the diame-ter of the pipe is in -the range of 0.75-0.9 tha-t ls, the numbers 0.75 and 0.9 each represents a ra-tio.
r~ e lnvcn~ion will be Eurther descri.bed ~)y wa~ o~
the accompanying drawing which illustrates in sectional view the charging device according to one embodiment of the inven-tion.
Through an input channel l which terminates in an inner annular shaped chamber 4 surrounded by an electrostatic electrode 3, a powder is dispersed in the supply gas and com-ing from a supply container is introduced by means of an ejec-tor. ~n inpu-t channel 2 for a second gas flow is terminating in the outer annular chamber 5.
A pipe-shaped separating wall between the two annu-lar chambers forms the electrostatic electrode 3. ~ccording to the invention it is made from a material having anti-stick-~, ing properties and having a specific volume resistance of 104-~ ~ 10~ ~m. Especially sui-tably ls polytetrafluoroethylene having an additive of 10-25% graphi-te. The Eront portion of the electros-tatic electrode is formed as a shape ed~e. While the inner wall is tapering outwardly, the outer wall is taper-ing inwardly.
The adjoining flow channel ~ is made from a pipe of insulating material 6 and has a centrally arranged rod 7 of the same material therein, wherein the ratio of rod and pipe diameters~ is in the range of 0.75-0.9.
By employing electrically semi--conductive material, it is accomplished that the i.onization is very uniform and will be distributed on t~e front edge. The gas Elowlng through the annular gap which is tapering ln a conical fash-ion, will cause a removal of the powder-gas flow from the ~ ;~3~8~
edges of the electrostatic electrode. AS a result, the region of high field strength in front of the ring shaped electrode edge, will be free from powder particles, so that the ioni~a-tion process (glow or corona discharge) will occur in pure gas and, melting on or sintering of powder particles will be pre-vented. This effect will further be supported by the anti-sticking properties of the polytetrafluoroaeth~lene.
The annular gap-like form of the adjoining flow channel in which very strong electro-kinetic effects will occur due to the combined effect of the two streams having different speeds, will accomplish a very high powder charging as a result of the cooperation between the wall material and the constructive shape of the electrostatic electrode bringing about a uniform distribution of the ionization process and resulting in the aforementioned high powder charging.
It is a further advantage that there will be no undesirable e~ector effects which would undesirably influence the uniform nature of the powder charging.

Claims (6)

  1. THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
    PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

    l. An apparatus for the electro-kinetic charging of powder shaped materials for the electrostatic coating of objects comprising a first input channel for a powder dis-persed in a gas flow and a second input channel for another gas flow, an insulating material flow channel having an input region, said input channels meeting in the input region of said insulating material channel, and a passive electrostatic ionizing electrode, wherein each of said input channels com-prise an inlet zone shaped as a pair of annular nozzles, wherein said first input channel is formed as an inner channel and said second input channel is formed as an outer annular channel, a pipe shaped separating wall acting as said passive electrostatic ionizing electrode separating said input chan-nels, said ionizing electrode is made from an electrically semi-conductive material having anti-sticking properties and is directly or indirectly connected to ground potential, and wherein the insulating material flow channel is formed as an annular channel made from an insulating material.
  2. 2. A device according to claim l, in which the ion-izing electrode is made of a material having a specific volume resistance of 104 to 108.OMEGA.m.
  3. 3. A device according to claim l, in which the ion-izing electrode is made of polytetrafluoroethylene having a graphite content of 10 to 25%.
  4. 4. A device according to claim 2, in which the ion-izing electrode is made of insulating material and an electri-cally semi-conductive layer having a specific surface resis-tance of 106 to 109 ohm is present in the outer surface.
    5, The apparatus according to claim 1, in which an input portion of the outer annular shaped channel is conically tapering in the flow direction, wherein a generating surface of the channel wall of said outer channel forms an angle of
  5. 5°-30° with respect to the axis of the flow channel.
  6. 6. The apparatus according to claim 1, in which the channel made from the insulating material and adjoining the dual annular nozzle is formed from a pipe with a rod centrally arranged therein, wherein the ratio of the rod diameter to the pipe diameter is in the region of 0.75-0.9.
CA000473799A 1984-02-08 1985-02-07 Apparatus for electrokinetically charging of powder materials Expired CA1239280A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DDDDRWPB05D/25992 1984-02-08
DD84259926A DD232595A3 (en) 1984-02-08 1984-02-08 DEVICE FOR ELECTROKINETIC CHARGING OF POWDER-FUSED SUBSTANCES

Publications (1)

Publication Number Publication Date
CA1239280A true CA1239280A (en) 1988-07-19

Family

ID=5554566

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000473799A Expired CA1239280A (en) 1984-02-08 1985-02-07 Apparatus for electrokinetically charging of powder materials

Country Status (13)

Country Link
US (1) US4798338A (en)
JP (1) JPS6182858A (en)
AU (1) AU574426B2 (en)
BG (1) BG45734A1 (en)
CA (1) CA1239280A (en)
CH (1) CH664509A5 (en)
DD (1) DD232595A3 (en)
DE (1) DE3447338A1 (en)
FR (1) FR2559076B1 (en)
GB (1) GB2154475B (en)
HU (1) HU193309B (en)
IT (1) IT1182406B (en)
SE (1) SE456070B (en)

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US4182490A (en) * 1978-02-13 1980-01-08 Nordson Corporation Electrostatic spray gun
DE3420325A1 (en) * 1984-05-30 1985-12-05 Ransburg-Gema AG, St.Gallen SPRAYING DEVICE FOR COATING ITEMS WITH POWDER
DE3529703C1 (en) * 1985-08-20 1986-08-28 Ransburg-Gema AG, St. Gallen Spraying device for electrostatic powder coating
DD271611A3 (en) * 1987-10-27 1989-09-13 Verkehrswesen Hochschule SPRAY GUN WITH ELECTRIC KINETIC POWDER RECHARGE
US5406205A (en) * 1989-11-08 1995-04-11 Bruker Analytische Messtechnik Gmbh Gradient-generation system, nuclear spin tomograph, and process for the generation of images with a nuclear-spin tomograph
JPH0474555U (en) * 1990-11-05 1992-06-30
US5344082A (en) * 1992-10-05 1994-09-06 Nordson Corporation Tribo-electric powder spray gun
DE4240568C2 (en) * 1992-12-02 1996-08-08 Atochem Elf Sa Semiconductive charging electrode
US5843536A (en) * 1992-12-03 1998-12-01 Ransburg Corporation Coating material dispensing and charging system
US5395046A (en) * 1993-10-25 1995-03-07 Nordson Corporation Hand-held spray gun with replaceable handle
US5975090A (en) 1998-09-29 1999-11-02 Sharper Image Corporation Ion emitting grooming brush
US6544485B1 (en) * 2001-01-29 2003-04-08 Sharper Image Corporation Electro-kinetic device with enhanced anti-microorganism capability
US6585935B1 (en) 1998-11-20 2003-07-01 Sharper Image Corporation Electro-kinetic ion emitting footwear sanitizer
US8763936B2 (en) * 2006-06-23 2014-07-01 Terronics Development Company Nozzle assembly and methods related thereto

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DE1577757B2 (en) * 1951-01-28 1973-09-06 METHOD AND DEVICE FOR ELECTROSTATIC COATING OF AN OBJECT WITH PULVERIZED COATING MATERIAL
GB1004246A (en) * 1963-02-22 1965-09-15 British Iron Steel Research Improvements in or relating to the heat treatment of steel
GB1375928A (en) * 1971-03-08 1974-12-04 Tranemo Fargfabrik Ab Electrostatic powder charging and applying apparatus
DE2203351B1 (en) * 1972-01-25 1973-08-23 Schaad Hans J Method and device for coating objects with plastic powder
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JPS52101249A (en) * 1976-02-20 1977-08-25 Tadashi Sakurai Powder painting device
US4071192A (en) * 1976-03-29 1978-01-31 Coors Container Company Tribo-electro-gas-dynamic powder charging apparatus
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DD134841B1 (en) * 1978-03-22 1981-05-27 Peter Dressler Apparatus for electrokinetic coating with powdered and fibrous particles
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Also Published As

Publication number Publication date
JPS6182858A (en) 1986-04-26
US4798338A (en) 1989-01-17
BG45734A1 (en) 1989-08-15
GB2154475B (en) 1987-11-18
FR2559076A1 (en) 1985-08-09
SE8500530L (en) 1985-08-09
GB2154475A (en) 1985-09-11
GB8502137D0 (en) 1985-02-27
SE8500530D0 (en) 1985-02-05
SE456070B (en) 1988-09-05
IT1182406B (en) 1987-10-05
IT8567103A0 (en) 1985-02-05
AU3855785A (en) 1985-08-15
AU574426B2 (en) 1988-07-07
IT8567103A1 (en) 1986-08-05
FR2559076B1 (en) 1989-09-08
DE3447338A1 (en) 1985-08-08
DD232595A3 (en) 1986-02-05
HUT39103A (en) 1986-08-28
HU193309B (en) 1987-09-28
CH664509A5 (en) 1988-03-15

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