Conveyors: fluid current – With diverse power-driven conveyor – Rotary
Reexamination Certificate
1999-08-13
2001-07-10
Ellis, Christopher P. (Department: 3651)
Conveyors: fluid current
With diverse power-driven conveyor
Rotary
C406S026000, C406S050000, C406S085000, C406S138000, C406S151000
Reexamination Certificate
active
06257804
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a powder metering apparatus for making available powder, in particular for powder coating.
EP 0 412 289 B1 discloses an electrostatic powder coating device, wherein an injector pump delivers coating powder by means of a conveying gas, and wherein an additional metered gas line from a source of compressed air connects to the injector pump. The metered gas line, via which metered gas is supplied to the injector pump, is intended to facilitate adjustment of the amount of conveying air and the amount of metered air to optimal values. While the introduction of metered gas into the injector pump improves controllability of an injector pump with respect to supplying a desired quantity of powder needed in particular for coating, controllability and thus metering capability of the powder quantity do however not reach the accuracy of conventional, rotatably driven metering pumps of the disk type.
DE 4 242 225 A1 discloses a powder varnish pump for producing and metering a powder, which flows under overpressure. In the described powder varnish pump, the actual feed pump is designed and constructed as a metering pump of the disk type. In this pump, one metering disk is arranged for rotation between lateral components. The metering disk has an inlet, which receives a powder-air mixture, and an outlet, which supplies the powder-air mixture to a consumer, i.e., the described coating purpose. The discharge of the powder-air mixture from the outlet of the metering pump occurs by means of compressed air. As a result of the compressed air, it is possible that powder deposits in the interior of the outlet chamber and in particular in the sealing points between the rotating metering disk and the stationary lateral components. The deposit of powder in the described areas increases the wear of the metering pump. Furthermore, the metering pump has an increased torque that may lead to a blocking of the metering pump. Likewise, there is a risk of leakage.
It is therefore the object of the invention to provide a powder metering apparatus with a metering pump known per se, which exactly meters the quantity of powder necessary for the coating, operates with little wear and high reliably, and wherein powder is largely prevented from depositing in particular in its sealing gaps.
SUMMARY OF THE INVENTION
The above and other objects and advantages of the present invention are achieved by the provision of a powder metering apparatus which comprises a metering pump with a metering disk arranged between lateral plates. The metering disk connects to a shaft that mounts a drive, which rotates the metering disk between the lateral plates. The metering disk contains receiving openings or receiving chambers or metering chambers, which receive via an inlet a powder-air mixture for the metering pump. By rotating the metering disk, the mixture is transported to an outlet, from which the powder or powder-air mixture in the openings or chambers of the metering disk is discharged. Furthermore, the powder metering apparatus comprises an injector pump. The outlet of the metering pump connects to the injector pump via a suction tube. A vacuum flow generated in the injector pump and entering the metering pump via a suction inlet opening is used to suck the powder or powder-air mixture out of the outlet or outlet chamber of the metering pump and to supply it accordingly to a consumer.
As a result of combining a disk-type metering pump known per se, which meters with great accuracy, but is subjected to relatively great wear because of the possibility of powder depositing in sealing gaps, and an injector pump whose delivery is adjustable with only relatively little accuracy, and whose reproducibility of the delivery is dependent on numerous factors, such as grain size, pouring density, formation of the fluid bed in the powder feeding device, etc., it is thus possible to accomplish a simple, reproducible adjustment of the delivery. The important variables that influence the delivery, are the rotational speed of the metering pump, the chamber size, and the pouring density. The fact that by means of the vacuum flow, the powder or powder-air mixture is sucked out of the outlet chamber of the metering pump to the application device prevents powder from depositing in sealing gaps between the metering disk and lateral disks bounding the metering disks. This reduces wear of the metering pump considerably.
According to a preferred embodiment of the invention, the injector pump comprises a first control element for controlling the vacuum flow. By means of this first control element the vacuum flow is controlled such that it prevents powder from depositing in the outlet and/or between the metering disk and the lateral plates. The magnitude of the vacuum flow, i.e., the flow rate prevailing in the injector suction tube depends in this instance, among other things, on the geometric dimensions of the injector pump and the suction air stream, which is used to generate the vacuum flow in the suction tube of the injector.
Preferably, a controller is also provided, which facilitates controlling the injector pump in pressure-regulated manner as a function of the rotational speed of the metering pump. This has the advantage that the metering pump and the injector pump can be optimally adapted to each other with respect to delivery, accuracy, and reliable operation with little wear.
According to a further embodiment, the first control element of the powder metering apparatus is arranged upstream of the suction inlet opening of the metering pump. This first control element causes a controlled air stream from a source of compressed air to enter the suction inlet opening in a flow-assisting manner.
Preferably, to assist the conveying action of the injector pump downstream of the injector pump, a second control element is provided, which causes an additional air stream to be introduced in a controllable manner. The additional air stream is used to assist in influencing purposefully the suction air stream of the injector pump and, thus, the vacuum flow with respect to the flow rate.
Preferably a third control element is provided for controlling the air stream supplied to the injector pump. The provision of the respective control elements thus permits adapting and adjusting the flow conditions and thus the operation of the metering pump as well as the discharged powder quantity purposefully and optimally to the respective cases of application.
According to a further development of the powder metering apparatus of the present invention, the first, the second, and the third control element are controllable by means of a controller.
Preferably, the powder-air mixture is generated in a fluid bed in a container of a powder metering apparatus that is connected to the inlet of the metering pump. Preferably, the fluid bed is maintained even along a feed channel that connects the container to the inlet of the metering pump. This ensures a uniform filling of the metering pump. The feed device consists of a container and a feed channel. Both the container and the feed channel comprise a fluid bed, in which an air stream flows into the powder filled in the container and thus converts the powder into a powder-air mixture. This powder-air mixture is necessary, so that the powder is able to flow uniformly.
According to a further development, at least the lateral plates of the metering pump comprise hollow spaces for the flow of a coolant. This ensures that the powder is not overheated inside the pump.
REFERENCES:
patent: 3269428 (1966-08-01), Stockel et al.
patent: 3648901 (1972-03-01), Cade
patent: 3909068 (1975-09-01), Coucher
patent: 4185942 (1980-01-01), Bazan
patent: 4227835 (1980-10-01), Nussbaum
patent: 4391860 (1983-07-01), Rotolico et al.
patent: 4474327 (1984-10-01), Mattson et al.
patent: 4615649 (1986-10-01), Sharpless
patent: 4751948 (1988-06-01), Hertig et al.
patent: 4789569 (1988-12-01), Douche et al.
patent: 5094403 (1992-03-01), Tschumi
patent: 5702209 (1997-12-01), Mauchle
patent: 42 42 225 (1994-
Alston & Bird LLP
Barmag AG
Dilllon, Jr. Joe
Ellis Christopher P.
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