How Does a Piston Filler Work?

Piston filling machines are commonly used in industries where products need to be accurately measured and dispensed into containers by volume. While piston fillers can handle liquids both thick and thin, they are often seen packaging products that are high viscosity, including jams, gels and pastes. In addition, partial strokes of the piston during a fill cycle allow for a single machine to fill a variety of container sizes. Below we look at the piston filler in more depth to understand how this versatile machine works so well for a variety of industries and packagers.

To understand how a piston filling machine works to fill containers, packagers should simply become familiar with the different components of the equipment. The piston filler includes a cylinder, piston, nozzle, three-way valve and often a hopper or tank, though product may be brought in straight from a bulk container.

The cylinder and piston work together to pull product from the bulk supply. As the piston retracts from the cylinder, the product is pulled into the cylinder from the bulk supply, be that the hopper or tank. While this process takes place, the three-way valve is closed at the fill nozzle port, stopping product from moving from the cylinder into the nozzle or nozzles. Once the cylinder is filled with product, the piston will begin to push back into the cylinder, releasing the product through the nozzles and into the container. During the reentry of the piston into the cylinder, the three-way valve will open to allow product to run through the nozzles but block additional product from entering the cylinder from the bulk supply.

As the volume of the cylinder never changes, this process allows for highly accurate volumetric fills. The same volume of product is flowing into and out of the cylinder during each cycle. While the piston size can be changed to allow for different fill volumes, a single piston can also fill a range of containers by using fractional or multiple strokes of the piston. For instance, a sixteen-ounce container can be filled using a sixteen-ounce piston. But by utilizing a half a stroke of the piston with each cycle, the machine could also fill eight-ounce bottles.

Nozzle types for the piston filler can also vary to meet the specific needs of the project at hand. A thin nozzle may be used for bottles with a small opening or projects dispensing small amounts of product. On the other hand, piston fillers can handle not only thick products, but products with large particulates, such as the fruit pieces found in jellies and jams. Wide mouth, or large nozzles would be used for this type of project to assure the particulates get into the containers.

Piston fillers may include other components such as control panels for automatic production, foot switches for semi-automatic machines and options such as drip trays or neck locators. However, understanding the basic components described above helps the user of the piston filler understand how the piston filler works to provide consistent and accurate volumetric fills. From jars of sauces or tubes of cosmetics to bottles of many other liquid products, piston fillers provide a reliable and efficient packaging solution for many different businesses in a range of industries.