CA1285751C - Method of intermittent powder coating - Google Patents
Method of intermittent powder coatingInfo
- Publication number
- CA1285751C CA1285751C CA000528597A CA528597A CA1285751C CA 1285751 C CA1285751 C CA 1285751C CA 000528597 A CA000528597 A CA 000528597A CA 528597 A CA528597 A CA 528597A CA 1285751 C CA1285751 C CA 1285751C
- Authority
- CA
- Canada
- Prior art keywords
- powder
- gun
- air
- ejector
- 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 - Lifetime
Links
- 239000000843 powder Substances 0.000 title claims abstract description 79
- 238000000034 method Methods 0.000 title claims abstract description 13
- 238000000576 coating method Methods 0.000 title description 17
- 239000011248 coating agent Substances 0.000 title description 15
- 238000005507 spraying Methods 0.000 claims abstract description 28
- 239000000203 mixture Substances 0.000 claims abstract description 12
- 239000007921 spray Substances 0.000 claims description 17
- 239000007787 solid Substances 0.000 claims description 5
- 238000010586 diagram Methods 0.000 description 4
- 238000009503 electrostatic coating Methods 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 230000002093 peripheral effect Effects 0.000 description 4
- 229940098458 powder spray Drugs 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 2
- 230000000873 masking effect Effects 0.000 description 2
- JHWNWJKBPDFINM-UHFFFAOYSA-N Laurolactam Chemical compound O=C1CCCCCCCCCCCN1 JHWNWJKBPDFINM-UHFFFAOYSA-N 0.000 description 1
- 229920000299 Nylon 12 Polymers 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000007610 electrostatic coating method Methods 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 230000011664 signaling Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
- B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
- B05B7/1404—Arrangements for supplying particulate material
- B05B7/1468—Arrangements for supplying particulate material the means for supplying particulate material comprising a recirculation loop
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B12/00—Arrangements for controlling delivery; Arrangements for controlling the spray area
- B05B12/02—Arrangements for controlling delivery; Arrangements for controlling the spray area for controlling time, or sequence, of delivery
- B05B12/06—Arrangements for controlling delivery; Arrangements for controlling the spray area for controlling time, or sequence, of delivery for effecting pulsating flow
-
- 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
- B05B5/16—Arrangements for supplying liquids or other fluent material
- B05B5/1683—Arrangements for supplying liquids or other fluent material specially adapted for particulate materials
Landscapes
- Application Of Or Painting With Fluid Materials (AREA)
- Electrostatic Spraying Apparatus (AREA)
- Nozzles (AREA)
Abstract
ABSTRACT
The specification describes a method for intermittently spray coating a powder. During spray coating a mixture of a powder and a gas is ejected continuously and constantly from a gun nozzle.
The mixture is discharged by an air ejector through a bypass route.
Intermittent spraying is achieved by intermittent operation of the air ejector. A gun adapted to carry out the method is also described.
The specification describes a method for intermittently spray coating a powder. During spray coating a mixture of a powder and a gas is ejected continuously and constantly from a gun nozzle.
The mixture is discharged by an air ejector through a bypass route.
Intermittent spraying is achieved by intermittent operation of the air ejector. A gun adapted to carry out the method is also described.
Description
12~
The invention pertains to a method and spray guns for the intermittent spray coating of powder.
The methods conventionally used for the intermittent coating of powder include electrostatic coating, screen printing, roll coating, and parasprinkling, but all of them suffer from the following drawbacks:
(1) the outline of the coated pattern is indistinct, (2) the powder adheres to areas where coating is not required, (3) the use of masking is necessary and powder adheres to the masking, (4) low productivity, and (5) complicated maintenance Even the electrostatic coating method which is said to be best among the above-mentioned methods, cannot avoid indistinctly outlining coating patterns as mentioned in (1).
In particular, noncleancut peripheral lines of string- or band-like intermittent coat:ing are serious problems in coated products.
Summar~ oE the Invention As described above, the number of intermittent spray operations is limited and the boundary lines of the patterns are indistinct in the discontinuous string- or band-patterns applied by the conventional intermittent powder spraying methods and guns.
The object of the invention is to increase the number of intermittent spray operations and to provide a method and YCC/ j j ~" ~
,~
guns that can produce cleancut boundary lines in string- or band-like intermittent powder spray coating.
Generally speaking, the present invention provides a method for intermittently spraying solid particulate powder downward onto products wherein, when the solid particulate powder is to be sprayed from a spray nozzle of a gun body whereon the spray nozzle is mounted, a mixture of the powder and air continuously and constantly supplied by a powder pump travels through a first ejector path in the gun body and the nozzle, and when spraying of the powder is to be interrupted, the continuously and constantly supplied mixture is discharged out of the gun body through a bypass within the gun body, which is in close proximity to the spray nozzle branching off from the first ejector path in the gun body and a second ejector path which is connected thereto and in which an air ejector nozzle mounted in the gun body is disposed, and by the air-ejector being intermittently operated, intermittent spraying of the powder from the nozzle is effected.
The above method may be carried out by way of a gun Eor inter-mittently spraying so:Lid particulate powder downward onto products, comprising: a gun body; a first ejector path through the gun body for passing therethrough a mixture of powder and air to be sprayed;
a second ejector path through the gun body having an air ejector therein, which air ejector is mounted within the gun body; a bypass within the gun body connecting the two paths, and a spray nozzle con-nected to the first ejector path with the spray nozzle being mounted on the gun body and in close proximity to the bypass, whereby the air-ejector is intermittently operated to bypass the powder so that intermittent spraying may be effected.
r -2-~ .
sp: ycc `` ~Z~357~;1 13rief Descrip~i n_ f the Drawings Figure I illustrates an intermittent ejection method accord-ing to the invention and shows a front cross section of the basic structure of a gun.
Figure 2 is a front cross section of modification No. 1 of the gun.
Figure 3A is a front cross section of modification No. 2 of tile gun and;
l~igure 313 is a side cross .section of Figure 3A.
~ igure 4 shows a cross section of a gun of the invention to which an electrostatic coating noz%le according -2a-~`,' s~):
1;~ 5~
to a Practical New Device Patent applied for by the present applicant is attached.
Figure 5 shows a front view of a multinozzle gun of the invention.
Figure 6 shows a system diagram of the equipment using a gun according to the invention.
Figure 7 shows a plane view of a discontinuous string-like coating applied by a gun of the invention.
Figure 8 shows a plane view of a discontinuous band-like coating applied by a flat nozzle gun according to theinvention.
Figure 9 shows plane views of two examples of multistripe coating by a multigun according to the invention.
Figure 10 is a system diagram of an intermittent powder coating device equipped with a conventional powder pump.
Figure 11 is a system diagram of an intermittent powder coating device equipped with a conventional pinch valve.
Description of the Prior ~r_ The reason why the outline of a pattern becomes indistinct is explained in the fol:Low:ing. The sequence of intermittent powder coating equipment of the conventional electrostatic type is outlined in Figure 10.
The powder transported by air from a powder pump 93 mounted on a tank 92, i.e. the powder supply source, reaches the gun 81 through a transport pipe 94 and a distributor 95.
The powder is then ejected from a nozzle 85 on the said gun 81 and coated effectively on surface P of the material to be YCC/jj 3 .. ~
coated under the action of a corona pin 89. The coated pattern, however, does not have clear peripheral lines especially in intermittent spray coating, as described above.
In the above-mentioned case, intermittent spraying is carried out by intermittent operation of the powder pump 93 attached to the above-mentioned tank. Accordingly, when periodically interrupting the spraying, the powder pump 93 must be stopped. Thus, air transport of the powder is also stopped, and as a result, the powder sinks to the bottom of the transport pipe 94. When the spraying of the powder from the nozzle 85 is restarted in this state, the fresh powder is air-transported from the tank by once again operating the said powder pump 93. In this case, the aforementioned powder that has settled in the transport pipe 94 is air-transported together with the fresh powder, reaches the gun 81, and is sprayed as ejected from the nozzle 85. Therefore, the density of the powder being sprayed naturally increases and as a result, the coated pattern changes. When stopping this spraying, the aforementioned powder pump 93 (an air ejector is generally used) is stopped again, but the spray stop response is slow because oE the relatively long transport pipe (or hose) between the powder pump and the nozzle, as seen in the said figure; thus the maximum number of intermittent operations is 30 cycles/min and no cleancut outline can be produced, with the end of the coated pattern tailing off. As described above, peripheral lines in string-or band-like intermittent coating become indistinct.
YCC/jj 4 ~' Intermittent spraying can also be performed with the use of a pinch valve in the conventional techniques. Refer to Figure 11. A pinch valve 116 is provided on the air transport pipe 114 immediately before the gun 101. A pinch valve 116 is a device to press or release an elastic tube by means of regulated air pressure applied on said elastic tube, and opens or closes the route of the powder passing through said tube.
When closing said valve, a small amount of powder is trapped inside because of its structural design. Accordingly, it is difficult to close completely and therefore a small amount of air may flow even when the valve is closed. When the operation is started again, the trapped powder is pushed out together with the following fresh powder and is sprayed as ejected from the nozzle 105; thus the density increases. That is, the coated pattern varies between intermittent sprayings and a cleancut peripheral line is difficult to obtain.
As described above, it is difficult to precisely switch on or off the air transportation of the powder by any of the conventional techniques, and the response time for an intermittent signal is also slow; thus it is impossible to avoid indistinctness at the gap between coated patterns in string- or band-like intermittent spraying.
Descri~tion of the Preferred Embodiment The structure of the gun according to the invention is shown in Figure 1. An ejection route 2 for a mixture PA of a powder and a gas (hereinafter abbreviated as "mixture") is provided inside the gun 1. A connector 8 with a feed hose (or YCC/jj 5 ~.
75:~
pipe) is provided at the entrance of said route, and a nozzle is provided at the other end of said route, as in conventional guns. The difference from conventional guns is that a branched bypass route 3 is provided on said ejection route 2 and is connected with ejection route 4 provided on said bypass route 3 and also inside the gun 1; and an air ejector nozzle 6 is provided on said ejection route 4; and the nozzle tip 6T of said air ejector is positioned approximately at the intersection with said bypass route 3.
In Figure 1, ejection route 2 and ejection route 4 are arranged in parallel with each other, with the directions of ejection flow opposite to each other, but as shown in Figure 2, both routes can be arranged so that they are in parallel, as mentioned above, but ejection flows assume the same YCC/jj 6 ~., 12~
direction (modification 1), or as sho~dn in Figures 3A and 3B, said two routes may be arzanged with a certain angle "u" between them (modification 2) instead of a parallel arrangement. In said figures, "~" is set at 90.
The nozzles of the above-mentioned guns may be provided with a corona pin for electrostatic coating. Figure 4 shows a side cross section of a gun attached to an electrostatic powder coating nozzle according to a Pract cal ~ew Device Patent ~pplication (applied for on Tanuar-J 31, 1930) bv the ?resent applicant. Because the corona pin 28 in sa c nozzl2 is e~bedded in the body of nozzle 27, the annihilation of the corona discharge current due to adhesion of the powder to the corona pin 28, as seen in conventional nozzles, lessens.
The aforementioned nozzle 5 is a general type nozzle, i.e., a type with a circular nozzle hole, even though a flat-type (slit-type) nozzle can also be used.
Moreover, a numDer of the afore~entioned circular nozzles or flat nozzles can be used to make a multipattern coating device in which a single row or several rows of several nozzles are assembled in a frame in order to form a multigun, as shown in Figure 5, and a signalling device to cause these nozzles to eject powder independently is connected to each nozzle.
Figure 6 shows one e~ample of a system diagram for intermittent powder spray coating where the aforementioned gun of the invention is used. The powder feed tank 62 is a fluidized-type (suspension-type) tank and is equippea with a vibrator 78. An air ejector 63 is provided as the powder pump, and an air heater 76 is provided on the air supply pipe 75 for the air ejector. The air-Cransport pipe 6~ for the powder is connected to the gun 51 through a distributor 65. Al air generator 73 for air to be supplied to the air ejector which is installed in said gun and an intermittent switching valve 72 for said _ ~ _ air to be supplied are provided. Said valve is connected to a timer 7~. The discharging side of said air ejector is connected to a back filter 77 via a transport pipe 75. The nozzle 53 of the above-mentioned gun is provided with a corona pin 59 for electrostatic coating, and a high-potential generator oO
is connected to the corona pin.
Actions First, the ac~ion of the gun is described. Refer to Figure l. r~hen a mi~ture P.4 of a powder and a gas is fed into the e,ection route 2 in the gun 1 in order to eject the powder intermittently, said mixture PA travels through the above-mentioned route 2 and is sprayed (PAI) from a nozzle 5 mounted on the end of said route. Then, when air A is fed through the air generator 73 provided outside the said gun into the said gun 1 by opening an intermittent air switching valve 72, air is e,ected (A') from the air ejec~or nozzle 6.
Because the tip 6T of said air ejector is positioned appro~imately at the intersection with the bypass route 3 from the above-mentioned ejection route 2, the gas around the tip is sucked by the action of the air ejector and sent in the direction of ejection. This suction action also e~tends to the said bypass route 3 and the powder ejection route 2, and as a result, the mi~ture P.4~ of powder and gas travelling through the ejection roùte 2 is all suc'~ed in and discharged from the gun 1. That is, the ejection of powder from ehe nozzle 5 is interrupted. Then,when the supply of air A to the above-mentioned air ejector is suspended by closing the above-mentioned intermittent air switching valve 72, the suction action of said air ejector stops, and thus the aforementioned original ejection of powder is resumed, the powder being ejected through the nozzle 5. That is, the ejection of powder from the nozzle 5 can be stopped _ ~ _ 7~1 or started by the inter~ittent sup?ly of air to the air ejector.
When the nozzle S to be mounced on the above-mentioned gun ' is of the general circular type, its discontinuous string-like coated pat.erns are as shown in "C" and "D" of Figure 7.
Figure 8 shows discontinuous band-like patterns that can be obtained bv using a flat (slit) nozzle. As can be seen in said figure, the discontinuous patterns e~`nibit cleancut peri?he;al lines.
When multinozzles are used, various pat.erns can be produced by operating each nozzle independently, as shown in "G" and "H" of Figure 9.
10Next, the operation of an intermittent powder spray coating system with a gun of the invention to which various types of nozzles can be attached is explained. Refer to Figure 6. The powder tank 62 is a suspension-.ype tank and the uniform disDersion of powder is promoted with a vibrator 7~. The air supplied to the powder pump 63 wnich is mounted on said tank, an air ejector in this figure, is hot-air heated by an air heater 76, A mixture of a powder and a gas conveyed under air pressure by the above-mentioned powder pump 63 is fed continuously and constantly into the gun 51 of the invention through an air transport pipe 64 and then a distributor 65, and is sprayed from a nozzle 55. ~hen periodically lnterrupting said spraying, an intermittent air-~0 switching valve 72 for the air ejector, used to supply air to the gun 5i, is opened in order to feed air into said air ejector in the gun, and the powder-gas mi~xture passing through the said gun 51 is sucked in by the ejector's action, discharged away from the gun 51, and conveyed to an air back filter 77 through an air transport pipe 75. Thus, the powder can be sprayed intermittently from the gun by intermittent operation of the intermittent air-switching valve for the air ejector in the above-mentioned gun.
``~_ ~ _ ~. ~
Experimental data for the above-mentioned system are as follows.
Powder used: nylon 12 and polyethylene, epoxy resin Powder pump: air ejector Air pressure of pump: 0.3 kg/cm2 Transport pipe: powder hose 3/16 Length between distributor and gun: 2.000 mm Gun nozzle diameter: 2.4 mm~
Air pressure of gun air ejector: 0.7 kg/cm2 Electrostatic voltage applied: 17 kV
Conveyor speed: 50 m/min No. of intermittent spray operations: 1,500 cycles/min.
(Note) The number of intermittent spray operations by conventional powder pump (air ejector) at the powder tank was 30 cycles/min at maximum.
Effects of the Invention According to the method and gun of the invention, discontinuous string- or band-like powder coatings with cleancut and uniform outlines can be obtained during high-speed intermittent coating of 30-1,500 cycles/min in an intermittent powder spray coating operation, and powder coatings of band-like clear geometrical patterns can be obtained with a multinozzle gun.
YCC/jj 10 A~
The invention pertains to a method and spray guns for the intermittent spray coating of powder.
The methods conventionally used for the intermittent coating of powder include electrostatic coating, screen printing, roll coating, and parasprinkling, but all of them suffer from the following drawbacks:
(1) the outline of the coated pattern is indistinct, (2) the powder adheres to areas where coating is not required, (3) the use of masking is necessary and powder adheres to the masking, (4) low productivity, and (5) complicated maintenance Even the electrostatic coating method which is said to be best among the above-mentioned methods, cannot avoid indistinctly outlining coating patterns as mentioned in (1).
In particular, noncleancut peripheral lines of string- or band-like intermittent coat:ing are serious problems in coated products.
Summar~ oE the Invention As described above, the number of intermittent spray operations is limited and the boundary lines of the patterns are indistinct in the discontinuous string- or band-patterns applied by the conventional intermittent powder spraying methods and guns.
The object of the invention is to increase the number of intermittent spray operations and to provide a method and YCC/ j j ~" ~
,~
guns that can produce cleancut boundary lines in string- or band-like intermittent powder spray coating.
Generally speaking, the present invention provides a method for intermittently spraying solid particulate powder downward onto products wherein, when the solid particulate powder is to be sprayed from a spray nozzle of a gun body whereon the spray nozzle is mounted, a mixture of the powder and air continuously and constantly supplied by a powder pump travels through a first ejector path in the gun body and the nozzle, and when spraying of the powder is to be interrupted, the continuously and constantly supplied mixture is discharged out of the gun body through a bypass within the gun body, which is in close proximity to the spray nozzle branching off from the first ejector path in the gun body and a second ejector path which is connected thereto and in which an air ejector nozzle mounted in the gun body is disposed, and by the air-ejector being intermittently operated, intermittent spraying of the powder from the nozzle is effected.
The above method may be carried out by way of a gun Eor inter-mittently spraying so:Lid particulate powder downward onto products, comprising: a gun body; a first ejector path through the gun body for passing therethrough a mixture of powder and air to be sprayed;
a second ejector path through the gun body having an air ejector therein, which air ejector is mounted within the gun body; a bypass within the gun body connecting the two paths, and a spray nozzle con-nected to the first ejector path with the spray nozzle being mounted on the gun body and in close proximity to the bypass, whereby the air-ejector is intermittently operated to bypass the powder so that intermittent spraying may be effected.
r -2-~ .
sp: ycc `` ~Z~357~;1 13rief Descrip~i n_ f the Drawings Figure I illustrates an intermittent ejection method accord-ing to the invention and shows a front cross section of the basic structure of a gun.
Figure 2 is a front cross section of modification No. 1 of the gun.
Figure 3A is a front cross section of modification No. 2 of tile gun and;
l~igure 313 is a side cross .section of Figure 3A.
~ igure 4 shows a cross section of a gun of the invention to which an electrostatic coating noz%le according -2a-~`,' s~):
1;~ 5~
to a Practical New Device Patent applied for by the present applicant is attached.
Figure 5 shows a front view of a multinozzle gun of the invention.
Figure 6 shows a system diagram of the equipment using a gun according to the invention.
Figure 7 shows a plane view of a discontinuous string-like coating applied by a gun of the invention.
Figure 8 shows a plane view of a discontinuous band-like coating applied by a flat nozzle gun according to theinvention.
Figure 9 shows plane views of two examples of multistripe coating by a multigun according to the invention.
Figure 10 is a system diagram of an intermittent powder coating device equipped with a conventional powder pump.
Figure 11 is a system diagram of an intermittent powder coating device equipped with a conventional pinch valve.
Description of the Prior ~r_ The reason why the outline of a pattern becomes indistinct is explained in the fol:Low:ing. The sequence of intermittent powder coating equipment of the conventional electrostatic type is outlined in Figure 10.
The powder transported by air from a powder pump 93 mounted on a tank 92, i.e. the powder supply source, reaches the gun 81 through a transport pipe 94 and a distributor 95.
The powder is then ejected from a nozzle 85 on the said gun 81 and coated effectively on surface P of the material to be YCC/jj 3 .. ~
coated under the action of a corona pin 89. The coated pattern, however, does not have clear peripheral lines especially in intermittent spray coating, as described above.
In the above-mentioned case, intermittent spraying is carried out by intermittent operation of the powder pump 93 attached to the above-mentioned tank. Accordingly, when periodically interrupting the spraying, the powder pump 93 must be stopped. Thus, air transport of the powder is also stopped, and as a result, the powder sinks to the bottom of the transport pipe 94. When the spraying of the powder from the nozzle 85 is restarted in this state, the fresh powder is air-transported from the tank by once again operating the said powder pump 93. In this case, the aforementioned powder that has settled in the transport pipe 94 is air-transported together with the fresh powder, reaches the gun 81, and is sprayed as ejected from the nozzle 85. Therefore, the density of the powder being sprayed naturally increases and as a result, the coated pattern changes. When stopping this spraying, the aforementioned powder pump 93 (an air ejector is generally used) is stopped again, but the spray stop response is slow because oE the relatively long transport pipe (or hose) between the powder pump and the nozzle, as seen in the said figure; thus the maximum number of intermittent operations is 30 cycles/min and no cleancut outline can be produced, with the end of the coated pattern tailing off. As described above, peripheral lines in string-or band-like intermittent coating become indistinct.
YCC/jj 4 ~' Intermittent spraying can also be performed with the use of a pinch valve in the conventional techniques. Refer to Figure 11. A pinch valve 116 is provided on the air transport pipe 114 immediately before the gun 101. A pinch valve 116 is a device to press or release an elastic tube by means of regulated air pressure applied on said elastic tube, and opens or closes the route of the powder passing through said tube.
When closing said valve, a small amount of powder is trapped inside because of its structural design. Accordingly, it is difficult to close completely and therefore a small amount of air may flow even when the valve is closed. When the operation is started again, the trapped powder is pushed out together with the following fresh powder and is sprayed as ejected from the nozzle 105; thus the density increases. That is, the coated pattern varies between intermittent sprayings and a cleancut peripheral line is difficult to obtain.
As described above, it is difficult to precisely switch on or off the air transportation of the powder by any of the conventional techniques, and the response time for an intermittent signal is also slow; thus it is impossible to avoid indistinctness at the gap between coated patterns in string- or band-like intermittent spraying.
Descri~tion of the Preferred Embodiment The structure of the gun according to the invention is shown in Figure 1. An ejection route 2 for a mixture PA of a powder and a gas (hereinafter abbreviated as "mixture") is provided inside the gun 1. A connector 8 with a feed hose (or YCC/jj 5 ~.
75:~
pipe) is provided at the entrance of said route, and a nozzle is provided at the other end of said route, as in conventional guns. The difference from conventional guns is that a branched bypass route 3 is provided on said ejection route 2 and is connected with ejection route 4 provided on said bypass route 3 and also inside the gun 1; and an air ejector nozzle 6 is provided on said ejection route 4; and the nozzle tip 6T of said air ejector is positioned approximately at the intersection with said bypass route 3.
In Figure 1, ejection route 2 and ejection route 4 are arranged in parallel with each other, with the directions of ejection flow opposite to each other, but as shown in Figure 2, both routes can be arranged so that they are in parallel, as mentioned above, but ejection flows assume the same YCC/jj 6 ~., 12~
direction (modification 1), or as sho~dn in Figures 3A and 3B, said two routes may be arzanged with a certain angle "u" between them (modification 2) instead of a parallel arrangement. In said figures, "~" is set at 90.
The nozzles of the above-mentioned guns may be provided with a corona pin for electrostatic coating. Figure 4 shows a side cross section of a gun attached to an electrostatic powder coating nozzle according to a Pract cal ~ew Device Patent ~pplication (applied for on Tanuar-J 31, 1930) bv the ?resent applicant. Because the corona pin 28 in sa c nozzl2 is e~bedded in the body of nozzle 27, the annihilation of the corona discharge current due to adhesion of the powder to the corona pin 28, as seen in conventional nozzles, lessens.
The aforementioned nozzle 5 is a general type nozzle, i.e., a type with a circular nozzle hole, even though a flat-type (slit-type) nozzle can also be used.
Moreover, a numDer of the afore~entioned circular nozzles or flat nozzles can be used to make a multipattern coating device in which a single row or several rows of several nozzles are assembled in a frame in order to form a multigun, as shown in Figure 5, and a signalling device to cause these nozzles to eject powder independently is connected to each nozzle.
Figure 6 shows one e~ample of a system diagram for intermittent powder spray coating where the aforementioned gun of the invention is used. The powder feed tank 62 is a fluidized-type (suspension-type) tank and is equippea with a vibrator 78. An air ejector 63 is provided as the powder pump, and an air heater 76 is provided on the air supply pipe 75 for the air ejector. The air-Cransport pipe 6~ for the powder is connected to the gun 51 through a distributor 65. Al air generator 73 for air to be supplied to the air ejector which is installed in said gun and an intermittent switching valve 72 for said _ ~ _ air to be supplied are provided. Said valve is connected to a timer 7~. The discharging side of said air ejector is connected to a back filter 77 via a transport pipe 75. The nozzle 53 of the above-mentioned gun is provided with a corona pin 59 for electrostatic coating, and a high-potential generator oO
is connected to the corona pin.
Actions First, the ac~ion of the gun is described. Refer to Figure l. r~hen a mi~ture P.4 of a powder and a gas is fed into the e,ection route 2 in the gun 1 in order to eject the powder intermittently, said mixture PA travels through the above-mentioned route 2 and is sprayed (PAI) from a nozzle 5 mounted on the end of said route. Then, when air A is fed through the air generator 73 provided outside the said gun into the said gun 1 by opening an intermittent air switching valve 72, air is e,ected (A') from the air ejec~or nozzle 6.
Because the tip 6T of said air ejector is positioned appro~imately at the intersection with the bypass route 3 from the above-mentioned ejection route 2, the gas around the tip is sucked by the action of the air ejector and sent in the direction of ejection. This suction action also e~tends to the said bypass route 3 and the powder ejection route 2, and as a result, the mi~ture P.4~ of powder and gas travelling through the ejection roùte 2 is all suc'~ed in and discharged from the gun 1. That is, the ejection of powder from ehe nozzle 5 is interrupted. Then,when the supply of air A to the above-mentioned air ejector is suspended by closing the above-mentioned intermittent air switching valve 72, the suction action of said air ejector stops, and thus the aforementioned original ejection of powder is resumed, the powder being ejected through the nozzle 5. That is, the ejection of powder from the nozzle 5 can be stopped _ ~ _ 7~1 or started by the inter~ittent sup?ly of air to the air ejector.
When the nozzle S to be mounced on the above-mentioned gun ' is of the general circular type, its discontinuous string-like coated pat.erns are as shown in "C" and "D" of Figure 7.
Figure 8 shows discontinuous band-like patterns that can be obtained bv using a flat (slit) nozzle. As can be seen in said figure, the discontinuous patterns e~`nibit cleancut peri?he;al lines.
When multinozzles are used, various pat.erns can be produced by operating each nozzle independently, as shown in "G" and "H" of Figure 9.
10Next, the operation of an intermittent powder spray coating system with a gun of the invention to which various types of nozzles can be attached is explained. Refer to Figure 6. The powder tank 62 is a suspension-.ype tank and the uniform disDersion of powder is promoted with a vibrator 7~. The air supplied to the powder pump 63 wnich is mounted on said tank, an air ejector in this figure, is hot-air heated by an air heater 76, A mixture of a powder and a gas conveyed under air pressure by the above-mentioned powder pump 63 is fed continuously and constantly into the gun 51 of the invention through an air transport pipe 64 and then a distributor 65, and is sprayed from a nozzle 55. ~hen periodically lnterrupting said spraying, an intermittent air-~0 switching valve 72 for the air ejector, used to supply air to the gun 5i, is opened in order to feed air into said air ejector in the gun, and the powder-gas mi~xture passing through the said gun 51 is sucked in by the ejector's action, discharged away from the gun 51, and conveyed to an air back filter 77 through an air transport pipe 75. Thus, the powder can be sprayed intermittently from the gun by intermittent operation of the intermittent air-switching valve for the air ejector in the above-mentioned gun.
``~_ ~ _ ~. ~
Experimental data for the above-mentioned system are as follows.
Powder used: nylon 12 and polyethylene, epoxy resin Powder pump: air ejector Air pressure of pump: 0.3 kg/cm2 Transport pipe: powder hose 3/16 Length between distributor and gun: 2.000 mm Gun nozzle diameter: 2.4 mm~
Air pressure of gun air ejector: 0.7 kg/cm2 Electrostatic voltage applied: 17 kV
Conveyor speed: 50 m/min No. of intermittent spray operations: 1,500 cycles/min.
(Note) The number of intermittent spray operations by conventional powder pump (air ejector) at the powder tank was 30 cycles/min at maximum.
Effects of the Invention According to the method and gun of the invention, discontinuous string- or band-like powder coatings with cleancut and uniform outlines can be obtained during high-speed intermittent coating of 30-1,500 cycles/min in an intermittent powder spray coating operation, and powder coatings of band-like clear geometrical patterns can be obtained with a multinozzle gun.
YCC/jj 10 A~
Claims (6)
1. A gun for intermittently spraying solid particulate powder downward onto products. comprising:
a gun body;
a first ejector path through the gun body for passinge there-through a mixture of powder and air to be sprayed;
a second ejector path through the gun body having an air ejector therein, which air ejector is mounted within the gun body;
a bypass within the gun body connecting said two paths; and a spray nozzle connected to said first ejector path with the spray nozzle being mounted on the gun body and in close proximity to the bypass, whereby said air-ejector is intermittently operated to bypass said powder so that intermittent spraying may be effected.
a gun body;
a first ejector path through the gun body for passinge there-through a mixture of powder and air to be sprayed;
a second ejector path through the gun body having an air ejector therein, which air ejector is mounted within the gun body;
a bypass within the gun body connecting said two paths; and a spray nozzle connected to said first ejector path with the spray nozzle being mounted on the gun body and in close proximity to the bypass, whereby said air-ejector is intermittently operated to bypass said powder so that intermittent spraying may be effected.
2. A gun according to claim 1, wherein the nozzle is a flat spray nozzle.
3. A gun according to claim 1. wherein said gun is for electro-static application.
4. A gun according to claim 1, further comprising a plurality of nozzles arranged in a framework.
5. A method for intermittently spraying solid particulate powder downward onto products wherein. when the solid particulate powder is to be sprayed from a spray nozzle of a gun body whereon the spray nozzle is mounted, a mixture of the powder and air continuously and constantly supplied by a powder pump travels through a first ejector path in the gun body and the nozzle, and when spraying of the powder is to be interrupted, said continuously and constantly supplied mixture is discharged out of the gun body through a bypass within the gun body, which is in close proximity to the spray nozzle branching off from the first ejector path in the gun body and a second ejector path which is connected thereto and in which an air ejector nozzle mounted in the gun body is disposed, and by said air ejector being intermittently operated, intermittent spraying of the powder from said nozzle is effected.
6. A method according to claim 5, wherein the frequency of inter-mission is 30 times/min. or more.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61-023600 | 1986-02-05 | ||
| JP2360086A JPH0615050B2 (en) | 1986-02-05 | 1986-02-05 | Intermittent spray application method of powder and granules and its gun |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1285751C true CA1285751C (en) | 1991-07-09 |
Family
ID=12115092
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000528597A Expired - Lifetime CA1285751C (en) | 1986-02-05 | 1987-01-30 | Method of intermittent powder coating |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0291534A1 (en) |
| JP (1) | JPH0615050B2 (en) |
| AU (1) | AU595870B2 (en) |
| CA (1) | CA1285751C (en) |
| WO (1) | WO1987004643A1 (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3811260A1 (en) * | 1988-04-02 | 1989-10-26 | Thomae Gmbh Dr K | TARGETED DELIVERY OF DOSED AMOUNTS OF FINE DISTRIBUTED SOLIDS WITH VENTURI NOZZLE AND CONTROLLED CONTROL |
| AT390251B (en) * | 1988-09-07 | 1990-04-10 | Veitscher Magnesitwerke Ag | METHOD AND DEVICE FOR INTERMITTENTLY SPRAYING ON A PASTOUS MASS |
| US5037247A (en) * | 1989-11-29 | 1991-08-06 | Nordson Corporation | Powder pump with internal valve |
| US5558713A (en) * | 1994-10-31 | 1996-09-24 | The Procter & Gamble Company | Method and apparatus for forming a pulsed stream of particles for application to a fibrous web |
| DE19606214B4 (en) * | 1996-02-20 | 2006-06-01 | Abb Research Ltd. | Method and device for controlling the discharge of a fluidized solid from a container |
| DE59605130D1 (en) * | 1996-02-21 | 2000-06-08 | Elpatronic Ag Bergdietikon | Method and device for applying a coating to an object |
| ITBO20020069A1 (en) * | 2002-02-08 | 2003-08-08 | Paolo Malavasi | EQUIPMENT FOR THE APPLICATION OF POWDER ENAMEL ON ARTICLES, IN PARTICULAR CERAMIC TILES |
| WO2008084095A2 (en) * | 2007-01-11 | 2008-07-17 | Nordson Corporation | Coating of articles with optional pulsing and recycle of coating material |
| KR101044083B1 (en) | 2008-05-09 | 2011-06-23 | (주)엔티시 | Nanoparticle coating device and nanoparticle coating method using the same |
| GB0814174D0 (en) * | 2008-08-02 | 2008-09-10 | Eastman Kodak Co | A method of making solar cells by dry powder printing |
| JP6277039B2 (en) * | 2014-03-31 | 2018-02-07 | 株式会社トップ工業 | Coating apparatus, control method and program |
| KR101877275B1 (en) * | 2014-05-30 | 2018-07-11 | 도요세이칸 그룹 홀딩스 가부시키가이샤 | Shaped paper article, localized-region coating method, and coating device |
| JP6371689B2 (en) * | 2014-11-25 | 2018-08-08 | 株式会社トップ工業 | Coating apparatus, control method and program, and discharge characteristic measuring method |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3558052A (en) * | 1968-10-31 | 1971-01-26 | F I N D Inc | Method and apparatus for spraying electrostatic dry powder |
| US4165134A (en) * | 1977-08-16 | 1979-08-21 | The Continental Group, Inc. | Pneumatic powder flow diverting device |
| DE2849269C2 (en) * | 1978-11-14 | 1980-11-27 | Gema Ag, Apparatebau, St. Gallen (Schweiz) | Process for powder spraying and pneumatic powder spraying device |
-
1986
- 1986-02-05 JP JP2360086A patent/JPH0615050B2/en not_active Expired - Lifetime
-
1987
- 1987-01-30 CA CA000528597A patent/CA1285751C/en not_active Expired - Lifetime
- 1987-02-04 AU AU70203/87A patent/AU595870B2/en not_active Ceased
- 1987-02-04 WO PCT/JP1987/000073 patent/WO1987004643A1/en not_active Ceased
- 1987-02-04 EP EP19870901121 patent/EP0291534A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62180767A (en) | 1987-08-08 |
| WO1987004643A1 (en) | 1987-08-13 |
| EP0291534A1 (en) | 1988-11-23 |
| AU595870B2 (en) | 1990-04-12 |
| AU7020387A (en) | 1987-08-25 |
| JPH0615050B2 (en) | 1994-03-02 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1285751C (en) | Method of intermittent powder coating | |
| US4302481A (en) | Spray method and spray device, particularly for the spray-coating of articles with powder | |
| US5115972A (en) | Spray die for producing spray fans | |
| EP0362548A3 (en) | Apparatus for spraying droplets of hot melt adhesive | |
| US2894691A (en) | Electrostatic deposition | |
| US6217654B1 (en) | Method and equipment for powder spray coating | |
| JPH029468A (en) | Powder recovery device for a powder-coating apparatus or the like | |
| CN111729766B (en) | Vertical strip powder spraying device capable of improving powder coating rate | |
| JP3842324B2 (en) | Coating material spraying equipment | |
| KR970706915A (en) | HIGH PRESSURE JET STRIPPING SYSTEM WITH SUGTION BY INHALATION | |
| CN212309906U (en) | Vertical plate belt powder spraying device capable of improving powder coating rate | |
| CN111729764B (en) | Vertical plate and strip powder spraying device with blowing mechanism | |
| CZ20012015A3 (en) | Process and apparatus for spray extrusion | |
| US4204497A (en) | Electrostatic coating apparatus having conveyor belt, fluidizing and electrostatic means for recirculation of coating particles | |
| US2855245A (en) | Electrostatic deposition | |
| JPS5946159A (en) | Airless spray painting method and gun therefor | |
| JP2004074015A (en) | Coating device and coating method | |
| CN101184555B (en) | Spray gun for powder electrostatic coating | |
| JP3574934B2 (en) | Accelerated air blower in electrostatic powder coating | |
| JPH0156830B2 (en) | ||
| JPH0330853A (en) | Spray apparatus | |
| JPH09253541A (en) | Coating equipment for water-soluble paint | |
| EP1324833B1 (en) | A method for the decorative printing of surfaces, particularly of tiles and the like, and a machine operating in accordance with the method | |
| KR800001711Y1 (en) | Spray nozzle for powder coating with adjustable spray pattern | |
| JPH0857361A (en) | Electrostatic powder coating method and apparatus |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |