suction ports 38a and 38b are located in recessed grooves 40a and 40b which are formed on the outer circumference of rotating body 24 first and second recessed grooves 40a and 40b are positioned first and second spiral grooves 30a and 30b respectively the center of first recessed groove 40a is regarded as starting end 32a of first spiral groove 30a similarly the center of second recessed groove 40b is regarded as second starting end 32b of second spiral groove 30b the location of suction ports 38a and 38b may not be limited to placement in recessed grooves 40a and 40b instead they are formed in another area on the circumference of rotating body 24 first and second spiral blades 42a and 42b are fitted into grooves 30a and 30b respectively blades 42a and 42b are formed of elastic material and can be fitted into corresponding grooves 30a and 30b by utilizing their elasticity the thickness of each blade 42a or 42b is substantially equal to the width of the corresponding groove 30 each of blades 42a and 42b are movable in the radial direction of rotating body 24 along the corresponding groove 30 the outer circumference of each blade 42a and 42b is closely in contact with the inner circumference of cylinder 20 the space defined between the inner circumference of cylinder 20 and the outer circumference of rotating body 24 and extending from the middle of cylinder 20 to the first discharge side thereof is partitioned into a plurality of.