Fluid sampling device

Claim 1

In combination with a fluid flow conduit and a sampling outlet extending therefrom transversely of the flow of fluid, a sampling mechanism comprising an elongated tubular housing extending into the flow conduit through said sampling outlet, releasable clamp means connected to the sampling outlet for locking the housing in a sampling position, a pair of closure devices mounted at opposite end portions of the housing internally and externally of the flow conduit, a reciprocating plunger slidably mounted in one of said closure devices externally of the flow conduit, said plunger having a transfer passage extending therethrough between opposite ends of the plunger, biased discharge valve means connected to the plunger within the housing for conducting fluid under pressure in one direction only into the transfer passage, a piston assembly connected To the discharge valve means and forming a variable volume pressure chamber within the housing adjacent to the other of the closure devices, biased inlet valve means projecting from said other of the closure devices within the flow conduit for conducting fluid under pressure in one direction only into the pressure chamber upon expansion of the pressure chamber, reciprocating drive means connected to the plunger for reciprocation of the piston assembly causing expansion and contraction of the pressure chamber to alternately intake a sample of the fluid through the inlet valve means upon expansion of the pressure chamber and pressurize said sample and to cause fluid to flow into the discharge valve means upon contraction thereof, a relief valve assembly having a closing bias exceeding the static pressure of the fluid in the flow conduit, and coupling means connecting the pressure relief valve assembly to the plunger externally of the housing for periodically discharging fluid from the transfer passage when the pressure thereof builds up to a predetermined value exceeding said static pressure of the fluid in the flow conduit.