Free flight piston
The free-flight piston is a component of high-pressure piston compressors, which are used, for example, to fill diving and breathing protection bottles. It was developed by Bauer Kompressoren.
Causes of development
By Boyle Mariotte's law , the volume of the compressed gas decreases in inverse proportion to its pressure. Most compressors consist of 3 stages, in which the pressure increases fivefold (from 1 bar to 5 bar, from 5 bar to 25 bar, from 25 bar to 125 bar).
The volume (the displacement) of the last stage is therefore 1/225 of the original volume. The cylinder and piston would have to be very small. Due to the design, it has so far not been possible to equip a cylinder of this size with a stable connecting rod. The compression piston is therefore freely movable and not connected to the guide piston. The free-flight piston moves without piston rings in a precisely ground steel bush. Lateral forces that would cause increased wear are thus eliminated.
Noise development
Due to the loose connection between the guide and compression pistons, the compressor produces the typical thumping noise when the two pistons are not positively connected to one another. Once the pressure has built up, there is a connection between the two components and the noise stops.