Centrifugal oil pump for a variable speed hermetic compressor

Centrifugal oil pump for a hermetic compressor comprising:

• a hermetic shell which defines a lubricant oil sump at its bottom;
• a cylinder block in said shell which supports a vertical shaft mounted to a rotor of an electric motor, the shaft having at least one internal oil channel with a lower end at the lower end of the shaft and an upper end with an opening to the shaft exterior at a point between the upper and lower ends of the shaft;
• a
• an upper extension of a pump rotor having an upper part within said shaft lower end and a lower part extending below said shaft lower end and a tubular sleeve attached to a fixed portion of the compressor, said tubular sleeve surrounding at least said lower part of said upper extension external to the shaft;
• said pump rotor having a centrifugation region radially extending beyond the edges of the lower end of said shaft and a nozzle at its lower end that is immersed in the oil sump and in fluid communication with at least an upper radial nozzle that communicates with at least an oil conducting axial channel between the peripheral surface of said portion of the pump rotor external to the shaft and a respective angular sector of the adjacent internal wall portion of said tubular sleeve,
• said oil conducting axial channel communicating with the lower end of said shaft oil channel through at least one dragging duct which is longitudinally provided through the upper extension of the pump rotor.