Powder paint supply device

Abstract: A fluidized type powder paint tank 1 having a fluidizing chamber 2 for fluidizing a powder paint A and a storage chamber 3 into which the powder paint A in the fluidizing chamber 2 is fed to keep it still. There is also provided a paint supply device for an electrostatic powder painting device having a paint tank (1) for containing a powder paint A and a painting gun 11 coupled to the paint tank (1) through an injector (4) and a hose 10. This device further includes a discharge device 4 for discharging the powder paint A out of the paint tank 1 and a hopper 19 for receiving the powder paint discharged by the discharge device 4. A screw feeder 13 is provided over the hopper 19. With this arrangement, the powder paint A supplied at a uniform rate from the screw feeder 13 is fed into the injector 4.

Description: This invention relates to a paint powder tank for a paint powder application apparatus. Heretofore, a fluidized type paint powder tank has been used as the tank for an electrostatic paint powder application apparatus. In the case of one such paint powder tank, a porous resin plate is provided on the bottom of the tank. Compressed air is supplied into the tank through the porous resin plate to stir and dehumidify the paint powder in the tank. The density of the fluidized paint powder in the tank changes with its amount in the tank. For example, as the amount of paint powder in the tank decreases, i.e. the paint powder level in the tank lowers, the density of the paint powder decreases correspondingly. Thus, if the paint powder in the fluidized type powder tank is drawn out by a discharge device such as an injector, the discharge rate changes according to the paint powder level in the tank, as shown by line a in Fig. 1, and a uniform paint film thickness using a paint gun connected to the injector is not obtainable. It is therefore an object of the present invention to provide a fluidized type paint powder tank in which the paint powder level in the tank has less affect on the discharge rate. FR-A-2215375 cited in the examination of this application discloses a paint powder tank for a paint powder application apparatus, said tank having therein a fluidizing chamber for fluidizing paint powder and a second chamber, said second chamber being in communication with said fluidizing chamber for receiving fluidized paint powder therefrom and being provided with discharge means for discharging paint powder therefrom. In this French specification the second chamber is a fluidizing chamber. In contradistinction the present invention provides a tank as defined in the last but one paragraph characterised in that said second chamber is not a fluidizing chamber and has an opening therefrom at its upper part whereby in use fluidized paint powder received in said second chamber from said fluidizing chamber is able to settle. In the embodiments of the invention disclosed hereinafter the fluidizing chamber is defined in said tank to one side of a partitioning wall therein, said second chamber is defined in said tank to the other side of said partitioning wall in said tank and said chambers communicate with each other at a lower part of said fluidizing chamber. Also in these embodiments, the opening from the second chamber at the upper part thereof communicates with an upper part of said fluidizing chamber which is provided with a vent. Preferably an intermittently operable air purge nozzle or a scraper is provided in said fluidizing chamber for discharging paint powder from said fluidizing chamber into said second chamber. The discharge means for discharging paint powder from said second chamber may comprise a screw extending in said second chamber and rotatable for discharging paint powder from said second chamber through a discharge port thereof. The above-mentioned screw may have an end portion which extends through said discharge port and on which a closure plate is slidably mounted and biassed against said discharge port to close the same. In order that the invention may be well understood, some embodiments thereof, which are given merely by way of example only will now be described with reference to the accompanying drawings, in which: Fig. 1 is a graph showing the relation between the level of the paint in the tank and the discharge rate for a fluidized type paint powder tank as previously mentioned in connection with Figure 1 and a tank embodying the invention; Figs. 2 and 3 are respectively schematic side and plan views of one embodiment according to this invention; and Figs. 4 to 6 are respective side views of three other embodiments according to the present invention. Each of the paint powder tanks 1 illustrated has a fluidizing chamber 2 for moving paint powder A as a fluid, a storage chamber 3 for holding the paint powder A drawn from the fluidizing chamber 2 in a stationary, or settled state and a discharge device 4 attached to the storage chamber 3 for discharging the paint powder A therefrom. The storage chamber 3 is not a fluidizing chamber and has an opening at its upper part, which communicates with an upper part of the fluidizing chamber 2 which is vented by air vent 8, whereby fluidized paint powder received from the fluidizing chamber 2 is able to settle. The paint powder tank shown in Figs. 2 and 3 is provided with a partitioning wall 5 on the righthand side thereof, defining the fluidizing chamber 2 on the left of the wall 5 and the storage chamber 3 on its right. In the fluidizing chamber 2 at the lower part thereof, a porous plate 6 is provided slightly spaced apart from the bottom thereof. Compressed air 7 is fed under the porous plate 6. The fluidizing chamber 2 and the storage chamber 3 communicate with each other at the lower part of the fluidizing chamber 2. An air purge nozzle 9 is provided in the fluidizing chamber 2 at the lower part thereof to discharge the powder paint A in the fluidizing chamber 2 into the storage chamber 3 by intermittently feeding air toward the storage chamber 3. Instead of the air purge nozzle 9, the powder paint A in the fluidizing chamber 2 may be discharged into the storage chamber 3 with a scraper which moves on and along the porous plate 6 toward the storage chamber 3. The bottom of the storage chamber 3 is at a level lower than the bottoms of the porous plate 6 and the tank 1. An injector as the discharge device 4 is mounted at the lower part of the storage chamber 3. A painting gun 11 is connected to the injector 4 through a powder supply hose 10. The embodiment shown in Fig. 4 has the same structure as the embodiment shown in Figs. 2 and 3 except the discharge device 4. The discharge device 4 in this embodiment has the following structure. Namely, a screw 13 rotated by a motor 12 is mounted in the bottom of the storage chamber 3. A discharge port 14 is formed in the side of the storage chamber 3 at the front end of the screw 13. Beside the discharge port 14, there is provided a cylindrical flow straightener 15 having a drop hole in the bottom thereof. Beside the flow straightener 15, a spring housing 16 is provided. A closure plate 18 is slidably mounted on the end of the screw 13 and biassed against the discharge port 14 to close the same by a spring 17 housed in the spring housing 16. By rotating the screw 13 with the motor 12, the powder A at the bottom of the storage chamber 3 is pushed out toward the discharge port 14. The spring 17 is compressed and the plate 18 is moved away from the port 14 by this pushing force, so that the powder is blown out through a gap between the plate 18 and the discharge port 14. The powder thus blown out hits and moves along the inner peripheral surface of the flow straightener 15 and is discharged in uniform amounts into a hopper 19 provided thereunder. An injector 20 is mounted to the bottom of the hopper 19. The powder is fed from the injector 20 into the painting gun 11 through a powder supply hose 10. In the embodiment shown in Fig. 5, a porous plate 6 is provided over the bottom of the tank 1 so as to cover the entire bottom surface. A partitioning wall 5 is provided to divide the space over the porous plate 6 into the fluidizing chamber 2 and the storage chamber 3. A shield plate 21 is provided on the porous plate 6 at its portion located in the storage chamber 3 near its bottom to prevent the air supply from the porous plate into the storage chamber 3. Otherwise, the embodiment shown in Fig. 4 is the same in structure as the embodiment shown in Fig. 1. The tank 1 of the embodiment shown in Fig. 6 has the same structure as that of the embodiment shown in Fig. 5. The discharge device 4 has the same structure as that of the embodiment shown in Fig. 4. In the embodiment shown Fig. 6, the motor 12 for the screw 13 is mounted on the tip of the screw. As shown by line b in Fig 1 a paint powder tank according to this invention can discharge the paint powder at a substantially constant rate irrespective of the paint level in the tank. Thus, the thickness of paint can be kept constant.

Claims: A paint powder tank for a paint powder application apparatus, said tank having therein a fluidizing chamber (2) for fluidizing paint powder and a second chamber (3), said second chamber being in communication with said fluidizing chamber for receiving fluidized paint powder therefrom and being provided with discharge means (4) for discharging paint powder therefrom, characterised in that said second chamber (3) is not a fluidizing chamber and has an opening therefrom at its upper part whereby in use fluidized paint powder received in said second chamber from said fluidizing chamber is able to settle. A tank as claimed in claim 1, wherein said fluidizing chamber (2) is defined in said tank to one side of a partitioning wall (5) therein, said second chamber (3) is defined in said tank to the other side of said partitioning wall (5) in said tank and said chambers (2, 3) communicate with each other at a lower part of said fluidizing chamber (2). A tank as claimed in claim 1 or 2, wherein said opening from the second chamber at the upper part thereof communicates with an upper part of said fluidizing chamber which is provided with a vent (8). A tank as claimed in claim 1, 2 or 3, wherein an intermittently operable air purge nozzle (9) or a scraper is provided in said fluidizing chamber (2) for discharging paint powder from said fluidizing chamber into said second chamber. A tank as claimed in any one of claims 1 to 4, wherein said discharge means (4) for discharging paint powder from said second chamber (3) comprises a screw (13) extending in said second chamber and rotatable for discharging paint powder from said second chamber (3) through a discharge port (14) thereof. A tank as claimed in claim 5, wherein said screw (13) has an end portion which extends through said discharge port (14) and on which a closure plate (18) is slidably mounted and biassed against said discharge port (14) to close the same.

Inventors: KAIJU HARUHISA, YOSHIDA HITOSHI, YOSHIZAKI AKIHISA, YUKIKAWA JUNICHI, KAIJU, HARUHISA, YOSHIDA, HITOSHI, YOSHIZAKI, AKIHISA, YUKIKAWA, JUNICHI
Applicants: MATSUO SANGYO KK, MATSUO SANGYO CO., LTD.
Application year: 1991
Main classification: B05B5
IPC codes: B05B7, B65G53, B05B5, B01J8