Vacuum pump with helically threaded cylinders

A vacuum pump comprising:

• a rotatable cylinder having a plurality of axially spaced annular rows of recesses defined in an outer circumferential surface thereof and a plurality of axially spaced smooth lands on said outer circumferential surface thereof, said rows of recesses and said smooth lands alternating with each other;
• an outer stationary cylinder disposed coaxially around said rotatable cylinder and having a helical groove defined in an inner circumferential surface thereof and a helical thread on the inner circumferential surface thereof;
• said recesses having an axial length smaller than a transverse width of said helical thread;
• an inner stationary cylinder disposed coaxially in said rotatable cylinder and having a helical groove defined in an outer circumferential surface thereof;
• and
• means for rotating said rotatable cylinder to move a gas along said helical grooves.

A vacuum pump comprising:

• a rotatable cylinder, said rotatable cylinder having a plurality of recesses defined in both inner and outer circumferential surfaces thereof;
• an outer stationary cylinder disposed coaxially around said rotatable cylinder and having a helical groove defined in an inner circumferential surface thereof;
• an inner stationary cylinder disposed coaxially in said rotatable cylinder and having a helical groove defined in an outer circumferential surface thereof;
• and
• means for rotating said rotatable cylinder to move a gas axially along said helical grooves.