Protecting unit for an oil field submersible motor

Claim 1

A protective device for a submersible electrical motor adapted to drive a pump located above and of the type utilizing a lubricating oil about the shaft thereof comprising: a hollow housing interposed between and connected to the casings of said pump and said electrical motor; a shaft extension projecting coaxially through said housing to couple the shaft of said Motor to the shaft of said pump; means for dividing said housing into vertically spaced coaxial cylindrical closed upper and lower chambers; said chambers being confined between said extension shafts and the inner wall of said housing; a plurality of cylindrical laterally spaced sleeves concentrically disposed within said lower chamber and sealed to the extremities thereof to provide annular concentric oil reservoirs therewithin, the innermost reservoir being in communication with the interior of said motor; said reservoirs being serially communicative to provide a unitary continuous oil passageway of a length multiple about that of said lower chamber; a flexible cylindrical membrane coaxially received in said upper chamber and sealed at the upper and lower extremities thereof to provide inner and outer pressure zones within said upper chamber; said outer pressure zone communicating with the well fluid surrounding said pump shaft and said inner zone communicating with said outermost oil reservoir in said lower chamber whereby undulation in the volume of oil received in said inner zone incidental to the expansion thereof during energization of said motor is transmitted to the outer pressure zone through said flexible membrane to cause an inverse undulation of an equal volume of well fluid in said outer pressure zone.