Impellers 1 and 2 rotate about fixed axes A and B and have identical and symmetrically arranged teeth d whose profile is made up of portions of cycle curves. When impellers 1 and 2 rotate, fluid is continuously delivered in the direction of arrows a and b. The suction and discharge chambers are separated by imparting special profiles to impellers 1 and 2. The impellers are driven by two meshing identical gears keyed to the shafts of impellers 1 and 2.
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