That patent by Forrest Schultz leaves me a little puzzled. Even the title "Fluid Compressor"; eveyone else seems to agree that Roots blowers aren't 'compressors'. And I fail to see the uniqueness of the "reduced leakage" claim. But I do need to go back and try to better understand his geometric expressions of the rotor shapes- that is, after I consult a dictionary for "hypocycloidal"!