The bell tank is a type of equipment for electroplating coating of parts in bulk. The bell tanks are well suited for treatment of moderate batches of small parts (from 5 to 25 kg). Like other equipment for treatment of parts in bulk, they enable to decrease costs by reducing the labor intensity of mounting/demounting of parts compared with treatment on racks.

Design solution and varieties of the bell tanks

Depending on the design features, there are bell tanks with bells of the filling or immersion type.

Filling-type bell tank

The main structural assembly is the bell, which is made in the form of a truncated pyramid with six or eight faces, where the bottom is a large base and the loading hole is a smaller one. The chemically resistant polymers are used to manufacture the tank. The walls and bottom of the bell are not perforated, the working solution and the parts to be treated are only fed through the upper loading hole.
The filling bell is mounted on a stable bed and rotated by a gear motor. The angle of inclination of the bell in the course of treatment of parts is 35-40 degrees relative to the vertical axis of the structure. Through the open top part, the working solution is poured into the container, the parts are fed, the anode is installed, and the flexible cathode is introduced.
To unload the finished parts, it is possible to lower the bell, while the tank is drained through a sieve into a reservoir, which is included in the scope of supply. The treated parts remain on the sieve.

Advantages of the filling-type bell tank

The main advantages of this unit include:

• Small parts can be treated due to the absence of perforations in the walls.
• Compact design.
• Reliability and ease of maintenance.

Some constraints on the use of the filling-type bell tanks are associated with the limitation of the amount of parts, a small volume of electrolyte, a small surface area of the anode and the inability to maintain consistently its elevated temperature.

Immersion-type bell tank

The unit consists of the following main parts:

• tank for electrolyte, welded from polypropylene sheets,
• perforated immersion bell with a drive for its rotation, to be mounted on the shaft. The bell shaft is hinged to the tank body using brackets.

The cathode current lead with a flexible cathode runs along the shaft inside the bell. The length of the flexible cathode is adjustable and fixed with a special clamp.
For models with the lifting capacity of 10 kg and above, the bell is raised and lowered using a mechanism, consisting of a worm gear motor and a crank mechanism.
The unit is equipped with:

• a frame with adjustable supports,
• surface-mounted side exhausters with dampers to regulate the flow of sucked air,
• non-removable folding lids,
• a fixed tray for loading of parts,
• fixed trays for unloading of parts,
• copper (anode) rods on holders,
• a drain pipe with a shut-off valve,
• a control unit.

The immersion bell has the shape of two paired pyramids, which ensures the uniformity of the applied coating and the high quality of treatment. The bell faces are perforated, which ensures the flow of the working solution not only through the upper loading hole, but also through the side walls of the bell.
Unlike the filling bell, this unit uses anodes with an increased area, which enables to maintain the normal conditions of their dissolution.

Standard equipment

• Polypropylene body with the bandage, drain pipe and shut-off valves
• Support frame with adjustable feet
• Submersible perforated bell with rotary drive
• Side exhausts
• Trays for loading and unloading of parts
• Cover lids
• Conducting rod
• Lift mechanism with locking system provision in emergency situations (beginning with the model VK-25)
• Control system

Optional extra

• Replacement bell with perforation from 0.5 mm to 30 mm (depending on the size of the workpiece it is possible to make perforation more than 30)
• Electric heater
• Heat exchanger
• System of mixing the electrolyte
• Periodic or continuous filtration system
• Level sensor
• Temperature sensor
• Automatic temperature control system
• Rectifier unit