Conical screw machine with rotating inner and outer elements that are longitudinally fixed

A method of operating a conical screw compressor or pump, the conical screw compressor comprising:

• an inner element configured to rotate around a first axis;
• an outer element configured to rotate around a second axis, wherein:
• an outer surface of the inner element and an inner surface of the outer element comprise cooperating grooves and teeth that intermesh on rotation;
• the first axis and the second axis are each stationary and the first axis is inclined relative to the second axis;
• and the method comprising:
• using a fixing mechanism to substantially fix a longitudinal position of the inner element along the first axis and to substantially fix a longitudinal position of the outer element along the second axis thereby to substantially fix the inner element and the outer element in a relative longitudinal position;
• and
• rotating the inner element and outer element, wherein
• the conical screw compressor or pump further comprises a housing;
• the fixing mechanism comprises a bearing proximate to a discharge end of the outer element and a further bearing proximate to a suction end of the outer element, wherein the bearing and the further bearing are each located between the outer element and the housing so as to allow relative axial rotation of the outer element and the housing while restricting longitudinal motion of the outer element and the housing;
• the inner element is coupled to a shaft and the fixing mechanism further comprises at least one additional bearing between the shaft and the housing, the at least one additional bearing between the shaft and the housing being configured to allow relative axial rotation of the inner element and the housing while restricting relative longitudinal motion of the inner element and the housing.