Another style of liquid volumetric piston filling machine is a high-speed machine set up for automatic operation. Its construction features and the way it operates are quite different from the small machines just described. It’s principles of operation, however, are similar.

During operation an air cylinder that is located above the container filling head controls the flow of product into and out of the measuring chamber. As the air cylinder starts its upward travel, the fluid valve and filling valve are opened, permitting fluid from the center to supply tube to flow into the measuring chamber. As the air cylinder reaches the top of its stroke, the fluid and filling valves are shut off. Small air cylinders or electric solenoids control the fluid and filling valves. Either is acceptable, but air cylinders usually require fewer parts.

As the air cylinder is actuated for its downward stroke, the fluid valve opens, allowing the liquid product to be transferred from the measuring chamber into the container. After the air cylinder reaches the bottom of its stroke, the fluid valve closes, sealing the measuring chamber. This operation is necessary because on many machines the air cylinder will remain in its discharged position for a short time as it progresses around the machine.

As in all piston-type filling machines, the amount of product measured for each container is controlled or regulated by the length of the piston stroke. In the high-speed machine this is also true. However, in this particular machine, the piston stroke is regulated by changing the stroke of the air cylinder that powers the measuring piston.

In mechanically actuated models, the measuring cylinder and fluid control valve are both attached directly to the side of the product hopper. However, both are actuated by separate mechanisms. As in other piston filling machines, the stroke of the piston on this machine is adjustable. In this particular model, the piston stoke length is varied by changing the location of the cam follower track. If required, the cam follower track can be also being positioned to control the up and down travel and can be slower in one direction than in the other.

When the filler is running, a container is placed beneath the fluid control valve. At the proper time, the valve is shifted to the discharge position and the piston is forced down by the cam follower as it follows the track slope. After it reaches the bottom of its stroke, the fluid control valve is shifter to the fill position, and the piston is forced up, drawing in fluid from the product hopper.

Auger Feed Pumps

Auger feed pumps are volumetric filling machines that do not have a positive means of measuring the product. This does not mean that the pump has no control over the liquid product. An auger feed pump does measure that product. However, it doesn’t have a separate measuring chamber as the piston fillers have to measure the amount of product being dispended to each individual container.

The unit is constructed with a bulk product hopper located immediately above the pump. The pump housing is coupled to the hopper by a separate mounting flange. In this way different pumps can be easily interchanged so the filler can handle different types and amounts of products. The pump drive motor is positioned above the hopper and is connected to the pump by a short drive shaft. If necessary an agitator can be placed in the hopper to keep the liquid mixed, and prevent any solid particles from settling.

The amount of product dispensed by the pump is regulated by three things: pump size, pump speed, and number of shaft revolutions (or duration of operation). Each of these items affects the amount of product placed in each container. Of these items, usually only pump speed and number of revolutions directly affect the filling process. Normally, pump sizes are not changed for the different liquids being handled if the containers are the same size.

Volumetric-Displaced Machines

Volumetric-displacement liquid filling machines are used for a number of filling applications. Their construction and operating features leave them in a class all their own. Compared to other filling machines that control the amount of liquid being placed in a container in a very rigid restricted manner, volumetric-displacement filler control seems rather loose. However, controls that regulate the fluid flow just like in the other machines can be added.

The most unusual feature of the machine is how the fluid is measured before it is placed in the container. As shown, a circular plate with the container filling spouts attached is located above the filling section of the machine. The circular plate rotates beneath a stationary disc called the metering plate. The slot in the stationary disc aids in metering the fluid flow.

During operation, fluid is admitted to the slot through a connection in the sealing plate placed above the metering plate. As the container filling spout passes beneath the slot, fluid is allowed to flow into the container. Fluid flows into the containers as long as the spout is beneath the open part of the disc. When the filling spout moves away from the opening, the fluid flow stops.

The filling rate can be changed by adjusting the amount of product supplied by the pump, the rotational speed of the filling head, and the length of the filling slot. (The slot can be made wider to accommodate larger filling spouts.) Of the many ways of changing the amount of product in that is placed in the container, adjusting the rotational speed of the filling head, and the amount of product supplied by the pump are the easiest.