AU595870B2

AU595870B2 - Method of intermittently spraying powder and a gun therefor

Info

Publication number: AU595870B2
Application number: AU70203/87A
Authority: AU
Inventors: Takashi Watanabe
Original assignee: Nordson Corp
Current assignee: Nordson Corp
Priority date: 1986-02-05
Filing date: 1987-02-04
Publication date: 1990-04-12
Anticipated expiration: 2007-02-04
Also published as: CA1285751C; JPS62180767A; AU7020387A; JPH0615050B2; EP0291534A1; WO1987004643A1

Description

AU-AI-70203/87

PCT

WORLD INTELLECTUAL PROPERTY ORGANIZATION International Bureau a INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 4 (11) International Publication Number: WO 8'q 04643 7/14, 12/06, 5/02 Al (43) International Publication Date: 13 August 1987 (13,08.87) (21) International Application Number: PCT/JP87/00073 (22) International Filing Date: 4 February 1987 (04.02.87) (31) Priority Application Number: 61/023600 (32) Priority Date: 5 February 1986 (05.02.86) (33) Priority Country: JP (71) Applicant (for all designated States except US); NOR- DSON CORPORATION [US/US]; 555 Jackson Street, Amherst, OH 44001 (US), (72) Inventor; and Inventor/Applicant (for US only) WATANABE, Takashi [JP/JP]; 116-8, Niizutsumi, Ohmiya-shi, Saitama 330 (JP).

(74) Agents: OKABE, Masao et al.; No, 209 Fuji Bldg., 2-3, Marunouchi 3-chome, Chiyoda-ku, Tokyo 100 (JP), (81) Designated States: AU, BE (European patent), CH (European patent), DE (European patent), FR (European patent), GB (European patent), NL (European patent), SE (European patent), US.

Published With international search report.

595870 2 SEP 1987 anudmentla"s

I

(54) Title: METHOD OF INTERMITTENTLY SPRAYING POWDER AND A GUN THEREFOR (57) Abstract PA PA Method of intermittently spraying solid particulate powder and gun therefor. In the work of intermitt- 8 ently spraying powder, a mixture of the powder and air PA2 4 continuously and constantly supplied from a powder pump which is a solid particulate powder supply source is spouted from a gun nozzle and during the interruption of the work, the mixture of the powder and air is discharged out of a gun by an air ejector provided in the gun through a bypass br.nchmig off f"iom the path 2 from which the mixture is spouted, thereby interrupting the spout of the mixture from the gun nozzle and by the\ intermittent operation of the air ejector, intermittent PA spraying of the solid particulate powder spouted from the gun nozzle is effected, S WO 87/04643 PCT/JP87/00073 1- 1 SPECIFICATION Method of Intermittently Spraying Powder and a Gun Therefor This invention relates to a method of intermittently spraying solid particulate powder and a gun therefor.

Methods heretofore used as methods of intermittently applying solid particulate powder are of the electrostatic application type, the screen printing type, the roll type, the sprinkling type, etc., but any of these has suffered from the following disadvantages: unclear outline of the applied pattern; adherence of the solid particulate powder to unnecessary portions; the use of masking and adherence of the solid particulate powder onto the masking; reduced productivity; and cumbersomeness of maintenance.

Even the electrostatic application type which is said to be most excellent of the above-mentioned types has not been free from the disadvantage that is, unclear outline of the applied pattern. Particularly in cord-like or band-like, intermittent application, unclear lines of dissection have been a fatal problem to the end products.

Description will hereinafter be made of the WO 804643 PCT/JP87/00073 2 1 reason why such unclearness occurs. The sequence of an electrostatic type apparatus for intermittently spraying solid particulate powder in accordance with the prior art is roughly shown in Figure 10 cf the accompanying drawings. Solid particulate powder airtransported by a powder pump 93 mounted on a tank 92 which is a supply source of solid particulate powder passes through a transport pipe 94 and arrives at a gun 81 through a distributor 95. The solid particulate powder is spouted from a nozzle 85 on the gun 81 and effectively applied onto a surface P to be coated under the action of a corona pin 89. However, the application pattern thereof, particularly in the case of the intermittent spray application, as de cribed above, has been unclear in lines of dissection.

In the above case, intermittent spraying has been accomplished'by intermittent operation of the powder pump 93 mounted on the tank 92. Consequently, when the spraying is to be interrupted, the powder pump 93 is stopped. Accordingly, the air-transport of the solid particulate powder is also stopped and the solid particulate powder is deposited on the bottom of the transport pipe 94. In that state, when the spraying of the solid particulate powder from the nozzle 85 is to be re-started, the powder pump 93 is reoperated to air-transport frKh solid particulate powder from the tank. Thereupon, the old solid I

L

WO 87/04643 PCT/JP87/00073 -3- 1 particulate powder deposited in the transport pipe 94 is air-transported with the fresh solid particulate powder, arrives at the gun 81 and is sprayed from the nozzle 85. As a matter of course, the density of the solid particulate powder sprayed becomes higher.

Consequently, the application pattern fluctuates.

When the spraying is to be interrupted, the powder pump 93 (which is usually an air ejector) is again stopped, but since the supply of the solid particulate powder is by way of the relatively long transport pipe (or hose) between the powder pump and the nozzle as seen in Figure 10, the response thereof is slow and the frequency of intermission is limited to 30 times/ min. at greatest and accordingly, clean cut cannot be accomplished and the breaks in the application pattern leave fine trails. In the above-described manner, the lines of dissection in cord-like or band-like intermittent application have become unclear.

There is also a conventional method of effecting intermittent spraying by means of a pinch valve.

Reference is had to Figure 11 of the accompanying drawings. On an air-transport pipe 114, a pinch valve 116 is provided immediately before a gun 101.

The pinch valve 116 is such that the air pressure is increased or decreased from the outside of a resilient tube, that is, the resilient tube is pushed or released, to thereby open or close the interior thereof and open i 3- ;UCi-.-i~ WO 87/04643 PCT/JP87/00073 4 1 or close the path of the solid particulate powder passing through the tube. When this valve is closed, it is usual from the structure thereof that the valve is closed while holding some solid particulate powder therein. Accordingly, it is difficult for the valve to be fully closed and even when closed, some air may flow. When the spraying is re-started, the solid particulate powder held in the valve is forced out with newly fed solid particulate powder and is sprayed from the nozzle 105 and therefore, the density of the solid particulate powder sprayed becomes higher. That is, in the breaks in the intermittent spraying, the application pattern of the solid particulate powder fluctuates and it is difficult to obtain clear lines of dissection.

As described above, in any of the prior-art systems, it is difficult to precisely accomplish the opening-closing of the air-transport of solid particulate powder, and the response time by the signal of intermission is slow and accordingly, unclear breaks in Sthe cord-like or band-like application pattern by intermittent spraying has been unavoidable.

As described above, in the intermittently coated cord or band produced by the prior-art method of intermittently spraying solid particulate powder and the gun therefor, the frequency of intermission has been small and lines of dissection have been unclear.

IWO 87/04643 PCT/JP87/00073 1/6 it ,s the object of the present invention to overcome or substantially ameliorate the above disadvantages.

There is disclosed herein a gun for intermittently spraying a solid particulate powder, comprising: a spout path for passing therethrough a mixture of powder and air to be sprayed; an ejector path having an air ejector therein, and a bypass connecting said two paths, whereby said air-ejector is intermittently operated to bypass said powder so that intermittent spraying may be effected.

There is further disclosed herein a method of intermittently spraying solid pariculate powder, wherein, when the solid particulate powder Is to be sprayed from a spray nozzle, a mixture of the powder and air continuously and constantly supplied by powder pump is spouted through a S spout path in a gun and a nozzle, and when spraying of the powder is to be interrupted, said cohtinuously and constantly supplied mixture Is a 666 discharged out of the gun through a bypass branching off from the spout 0. path in the gun and an ejector path which is connected thereto and in which 0sa an air ejector nozzle is disposed, and by said air-ejector being intermittently operated, intermittent spraying of the powder from said nozzle is effected.

4, 0 A preferred form of the present invention will now be described by s* way of example with reference to the accompanying drawings, wherein: :Fig. Y is a front cross-sectional viewi Illustrating a gun unit a- 2t according to the present invention.

Fig. 2 is a front cross--sectional view of a first modification of the gun of Figure~l.

KLN/ 19681 WO 87/04643 PCT/JP87/00073 -6- 1 Figure 3A is a front cross-sectional view of a second Modification of the gun of Figure 1.

Figure 3B is a side cross-sectional view of the second Modification.

Figure 4 is a cross-sectional view of the electrostatic application nozzle of the Japanese utility model application as attached to the gun of the present invention.

Figure 5 is a front view of the multi-gun nozzle unit of the present invention.

Figure 6 is a block diagram of an apparatus using the gun of the present invention.

Figures 7A and 7B are plan views showing the patterns of intermittent cord-like coating provided by the gun of the present invention.

Figures 8A and 88 are plan views showing the patterns of intermittent band-like coating provided by the gun with a flat nozzle according to the present invention.

Figures 9A and 9B are plan views showing two examples of the pattern of multi-streak coating provided by the multi-gun unit of the present invention.

Figure 10 is a block diagram of an inter'nittent solid particulate powder application apparatus using the powder pump of the prior art.

Figure 11 is a block diagram -f an intermittent solid particulate powder application apparatus using IT' -Illil~--*i-_ WO 87/04643 PCT/JP87/00073 7 1 the pinch valve of the prior art.

The structure of a gun according to the present invention is shown in Figure 1. In the interior of the gun 1, there is provided a spout path 2 for a mixture PA of solid particulate powder and air (hereinafter simply referred to as the mixture).

As is conventional, a connector 8 to a supply hose (or pipe) is attached to the entrance of the path 2 and a nozzle 5 is attached to the other end of the path 2.

The differences from the prior art are that there is provided a bypass 3 branching off from the spout path 2, that the bypass 3 is connected to an eject path 4 which is also provided in the gun 1, that an air ejector nozzle 6 is provided on the eject path 4 and that the end 6T of the air ejector nozzle is located substantially at the point of intersection with the bypass 3.

In Figure 1, the spout path 2 and the eject path 4 are parallel to each other and the directions of these paths are opposite to each other, but alternatively, as shown in Figure 2, the two paths may be parallel to each other and only the directions thereof may be opposite to each other (a first Modification), or as shown in Figures 3A and 3B, the two paths may be provided not in parallelism to each other, but with an angle formed therebetween (a second Modification). In Figures 3A and 3B, the angle "a" WO 87/04643 PCT/JP87/00073 4/6 WO 87/04643 PCT/JP87/0073 8 1 is Also, a nozzle provided with a charging electrode for electrostatic spraying may be used as the nozzle of the gun. Figure 4 shows a side crosssectional view of a gun having attached thereto a nozzle for electrostatic spraying of solid particulate powder disclosed in the Japanese utility model application No. 12535/1986 filed on January 31, 1986.

In this nozzle, a charging electrode 28 is embedded in the body of the nozzle 27 and therefore, it happens less frequently that as in the prior art, solid particulate powder adheres to the electrode 28 to thereby diminish the corona discharge current.

Although the nozzle 5 is of the ordinary type, the circular nozzle hole type, a nozzle of the flat type (the slit type) may also be used.

Also, a plurality of such circular nozzles or flat type nozzles may be arranged in one or more rows as shown in Figure 5 to provide a so-called multi-gun nozzle unit and a transmitter device or a control unit for causing the plurality of nozzles to effect spraying operation discretely can be connected to the nozzle to thereby provide a multi-pattern applying apparatus.

Figure 6 is a block diagram of a powder intermittently spraying apparatus using the gun according to the present invention. A solid particulate WO 87/04643 PCT/JP87/00073 -9- I powder supply tank 62 is of the fluidizing type (the floating type) and is provided with a vibrating device 78 and a blower 79. An air ejector 63 is provided as a powder pump, and air is supplie*d to an air supply pipe 75 for the air ejector from a blower 77 through an air heating device 76. An air-transport pipe 64 for solid particulate powder is connected to a glin 51 through a distributor 65. An air, generator 73 for the air supplied to the air ejector provided 1o within the gun and. an intermittent air opening-closing valve 72 for the supplied air are provided. The valve 72 is connected to a timer 74. The discharge side of the air ejector is connected to a powder recovery device 177 including an air bag filter by a transport pipe 175. A charging electrode 59 for electrostatic Coating, and which is connected to a high voltage ,source 60, is provided on the gun nozzle The operation of the gun will now be described.

Reference is had to Figure 1. In the gun 1 for intermittently spr~aying the solid particulate powder, ri when the mixture PA of solid particulate powder and air is supplied to the spout path 2 in the gun 1, the mixture PA passes through the spout path 2 and is sprayed (PA) from the nozzle 5 attached to the distal end of the path 2. Subsequently, when air A is Supplied into the gun 1 by the opening of the intermittent air opening-closing valve 72 through the air WO 8704643PCT/JP87/00073 F; /R WO 87/04643 PCT/JP87/00073 10 1 generator 73 provided outside the gun 1, the air is spouted from the air ejector nozzle 6 and, since the end 6T of the air ejector nozzle 6 is located substantially at the point of intersection with the bypass 3 from the spout path 2, the air sucks the surrounding gas with the aid of the action of the air ejector and is sent in the direction of delivery of the ejector. Said sucking action also reaches the bypass 3 and the spout path 2 for solid particulate powder and thus, all the mixture PA 2 of the passing solid particulate powder and air is sucked and discharged out of the gun 1. That is, the spout of the solid particulate powder from the nozzle 5 is interrupted.

Subsequently, when the intermittent air opening-closing valve 72 is closed and the supply of the air A to the air ejector is interrupted, the aforementioned sucking action by the air ejector is interrupted and therefore, the aforedescribed original spout or spray of the solid particulate powder is restored and effected through the nozzle 5. That is, the intermission of the spout of the solid particulate powder from the nozzle 5 is accomplishGd by the intermission of the supply of the air to the air ejector.

Where the nozzle 5 attached to the gun 1 is of the ordinary circular type, the discontinuous cord-like application pattern thereof is as indicated at or in Figures 7A and 7B.

L PCT/JP87/00073 WO 8714643 11 1 Also, the band-like discontinuous patterns in a case where a nozzle of the flat type (the slit type) is used are shown in Figures 8A and 8B. As seen in this figure, lines of dissection of intermission appear clearly.

Where a multi-nozzle is used, each nozzle can be operated singly to cause various patterns to appear as shown at and in Figures 9A and 9B.

Description will now be made of the operation of a solid particulate powder intermittent spray applying apparatus comprising chiefly the gun of the present invention having the various nozzles attached thereto. Reference is had to Figure 6. The solid particulate powder tank 62 is of the floating type and the vibrating device 78 is also added to achieve uniformity of the degree of dispersion of the solid particulate powder. In Figure 6, the air supplied to the air ejector by the powder pump 63 attached to said tank is hot air heated by the air heating device 76.

20 The mixture of solid particulate powder and gas pumped by the powder pump 63 is supplied continuously and constantly to the gun 51 of the present invention through the air transport pipe 64 and through the distributor 65 and is sprayed onto a substrate 80 from the nozzle 55. When the spray is to be interrupted, the intermittent air opening-closing valve 72 for the air ejector which supplies the air into the gun 51 PCT/J P87/00073 WO 87/04643 12 Iis opened to supply the air to the air ejector in the gun, and the mixture of solid. particulate powder and gas passing through the gun is sucked by the action of the ejector and d~ischarged out of the gun 51, and it is delivered into thie recovery device 177 through the air transport pipe 175. Thus, the spraying of the solid particulate powder from the gun can be intermittently accomplished by the intermittent operation of the intermittent air opening-closing valve for the ejector i~n the gun.

The data experimented by the above-described apparatus will be given. below.

Solid particulate powder Nylon 12, polyethylene handled and epoxy resin Powder pump Air ejector Air pressuro of the powder 0.3 kg/cm2 Transport pipe Powder hose 3/16 Length from distributor 2,000 mm to gun Gun nozzle diameter 2.4 Gun ejector air pressure 0.7 )Xg/cm 2 Applied electrostatic 17 Ky voltage conveyor speed 50 r/min.

Frequency of intermA~ssion 10-500 times/rT~n, (Note) The frequency of intermission by the prior-art, powder pump (aIr ejector) on the solid particulate powder tank sidq wtas 30 times/min. Max.

1~ WO 87/04643 PCT/JP87/00073 13 1 According to the method and gun of the present invention, in the intermittent solid particulate powder spray applying work, cord-like or band-like discontinuous coating of solid particulate powder having clear and uniform lines of dissection is obtained under highspeed intermittent application of 30 1,500 times/min., and band-like coating of solid particulate powder in a clear geometrical pattern is provided by the multitype gun nozzle of the gun.

Claims

1. A gun for intermittently spraying solid particulate powder downward onto products, comprising: a gun body a spout path through the gun body for passing therethrough a mixture of powder and air to be sprayed; an 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 spout 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 electrostatic application.

4. A gun according to claim 1, further comprising a plurality of nozzles arranged in a framework.

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 is spouted through a spout 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 rroximity to the spray nozzle branching off from the spout path in the gun body and an 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 6, wherein the frequency of intermission Is 30 times/mln. or more.

7, A gun substantially as hereinbefore described with reference to the accompanying drawings, S.19 681 I V 1 I

8. A method of sprayin1g solid particulate powder substantially as hereinbefore described with reference to the accompanying drawings. DATED this TWENTY-NINTH day of JANUARY 199,0 Nordson Corporation Patent Attorneys for the Applicant SPRUSON FERGUSON 0

9. C .8 0 06 0 0 0* KLN/19681