Gasket for a rotating shaft and a device incorporating such a gasket

A gasket designed to be inserted between:

• a housing with an interior volume filled with liquid lubricant under pressure,
• and a shaft projecting out from said housing and rotating at a certain rotation speed about a longitudinal axis,
• said gasket comprising a first annular sealing lip which is designed to be joined to the housing and placed in sliding rotary contact with the shaft, the first sealing lip being designed to withstand a first lubricant threshold pressure below 1 bar and to permit shaft rotation speeds in excess if 5000 rpm,
• wherein said gasket also has a second annular sealing lip which is also designed to be joined to the housing and to be in sliding contact with the shaft, the second sealing lip being designed to permit shaft rotation speeds in excess of 5000 rpm and to withstand a second threshold pressure, in excess of 5 bar, prevailing in the interior volume of the housing, this second sealing lip being designed so that it can be inserted between the interior volume of the housing and the first sealing lip,
• wherein the second sealing lip delimits, in conjunction with the first sealing lip, a lubricant collecting chamber provided with a discharge passage for the lubricant,
• wherein the gasket also has a calibrated nozzle bypassing the second sealing lip so as to provide direct communication between the interior volume of the housing and the collecting chamber, said calibrated nozzle being formed in a portion of the gasket which supports the second sealing lip,
• and wherein the calibrated nozzle, the second sealing lip and the lubricant discharge passage are so dimensioned that a lubricant pressure prevailing in the collecting chamber is at most equal to said first threshold pressure when the lubricant contained in the interior volume of the housing is at a pressure at most equal to the second threshold pressure.