Drum follower plate pump
A follower plate pump is a device for pumping very highly viscous (pasty) media out of containers. Therefore it is often called a drum follower plate pump .
The principle
If you lower a normal suction nozzle of a pump into a highly viscous (pasty) medium, this medium flows in so slowly that the filler nozzle is no longer completely immersed in the medium to be pumped after a short pumping and therefore draws air. To avoid this, a plate, which is tight against the inside of the container due to a soft sealing lip, is placed on the mass in the container. This plate is slowly pushed into the mass, which therefore rises through a hole in the center of the plate into the suction port of the pump. The amount pumped out and the amount pushed up by the follower plate must be exactly the same, which must be ensured by a corresponding control of the follower plate.
Pumping piston pumps or eccentric screw pumps are suitable pumps for such viscous media .
Fundamental problems
In order to eliminate air inclusions when changing the container, a considerable amount of flow must be pressed out of the container. This material is recorded as waste.
The follower plate can lower too quickly, so that the material is squeezed out to the side instead of being conveyed inside.
Dried-on material residues on the edge of the sealing lip of the follower plate can be carried into the material as crumbs, where they can either cause product rejects or a malfunction in the system.
The problem of crumbs and large amounts of waste when changing containers can be eliminated by using specially designed one-way follower plates. The problem of sagging can be solved with a special control, whereby the amount transported in the pump and the advance of the follower plate are automatically and precisely coordinated. If the disposable follower plate is designed in two layers with numerous holes in the lower plate and the cavity is connected to a vacuum pump, the air trapped under the plate can be completely sucked out through the holes. Generous discharge of material, as is unavoidable with conventional drum follower plate pumps, is no longer necessary. This reduces the waste when changing containers by at least an order of magnitude from one kilogram to less than 100 grams. These small amounts of material are found in the cavity of the disposable follower plate.
This device is usually equipped with a scoop pump or an eccentric screw pump. For highly abrasive pasty media (heat-dissipating potting compound with up to 70 percent ceramic filler), however, the usual scoop piston pump has proven to be unsuitable, as it wears out much too quickly. In the meantime, however, a double piston pump has been developed that is much more durable.
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- ↑ European patent EP 1 754 543 B1; US patent US 20070039978A1