Patent ID: 7464763

Claim:
An apparatus for injecting lift gas into a production conduit of an oil well via one or more downhole gas lift flow control devices comprising: a tubular valve housing comprising a flow passage having an upstream end which is connected to a lift gas supply conduit and a downstream end which is connected to the interior of the production conduit; a flapper type valve body which is pivotally connected to the valve housing and is arranged in the flow passage such that if the valve body is pivoted in the open position the valve body is oriented substantially parallel to the flow passage and that if the valve body is pivoted in the closed position the valve body is oriented substantially orthogonal or perpendicular to the flow passage and is pressed against a ring shaped valve seat, thereby blocking passage of fluids through the flow passage; a valve protection sleeve which is slidably arranged in the flow passage between a first position wherein the sleeve extends through the ring-shaped valve seat, whilst the valve body is pivoted in the open position, thereby protecting the valve seat and valve body against wear by the flux of lift gas or other fluids and a second position wherein the sleeve extends through the section of the flow passage upstream of the valve seat, whilst the valve body is pivoted in the closed position, said sleeve having an upstream end and a downstream end; a flow restrictor forming part of the valve protection sleeve, which is dimensioned such that the flux of lift gas or other fluids flowing through the flow restrictor creates a pressure difference which induces the sleeve to move towards the first position; and a first seal ring disposed between the sleeve and the housing upstream of the valve seat; wherein the downstream end of the sleeve includes a tapered section where the outer diameter of the sleeve decreases in the downstream direction, such that the outer surface of the tapered section of the sleeve is pressed against the inner surface of the seal ring when the sleeve is in the first position, thereby providing a fluid tight seal in the annular space between the tapered section of the sleeve and the housing when the sleeve is in the first position and such that said first seal ring only loosely engages the tapered section of the sleeve when the sleeve is in the second position.