the upper portion of fig3 the volume of the refilling chamber is essentially zero the piston 60 is a reciprocating member or in other words it moves back and forth as schematically illustrated in fig3 it is to be appreciated that while the machine 10 is generally an arrangement of vertical parts fig3 shows the parts laid down horizontally so that the reader can understand how the piston 60 is driven and how it works to fill the can 14 the piston 60 is moved up vertically by an air pump mechanism portion of the machine shown generally at 62 in fig4 and 3 the air pump mechanism 62 is double acting and driven by a combination of valve and air compressor system illustrated respectively at 64 66 in fig3 the compressor system 66 can consist of a shop compressor system conventional air compressor or the like the valve would be well known and easy to obtain off the shelf based on the description set forth here referring to the upper right hand corner of fig3 the valve 64 is first operated to pressurize the left hand side of an air piston 68 in the air pump mechanism 62 arrow 70 generally indicates the direction of airflow at the same time the region to the right of air piston 68 is allowed to vent via the valve mechanism 64 this drives the air piston 68 in the direction indicated by arrow 72 in the upper right hand portion of fig3 the air piston 68 is connected to a shaft 74 that slides through a plate 76 that defines the bottom part of the air pump mechanism 62 similar to the refilling module 40 previously described.