Filter assembly for intravenous liquid administration apparatus

Claim 1

A filter for gravity-feed intravenous liquid administration, comprising a plastic filter housing in at least two generally rectilinearly shaped portions bonded together and defining a filter chamber therebetween; an inlet member located generally at a first corner of said housing and an outlet member located generally at a second corner of said housing diagonally opposite said first corner in fluid flow communication with the filter chamber, the inlet member being arranged to be oriented up when so installed for gravity feed of intravenous liquid from the supply, with the outlet member down; a liquid-permeable filter that is gas-impermeable when filled with liquid disposed in the filter chamber across the line of gravity-feed fluid flow through the chamber from the inlet member to the outlet member so that all through flow must pass through the filter, and extending vertically when the pointed member is oriented up; the chamber being divided into two vertically-extending portions, one upstream and one downstream of the filter; a vent in an uppermost portion of the housing when the pointed member is oriented up, in flow communication with the upstream portion of the filter chamber; and a liquid-impermeable gas-permeable porous member extending vertically when the pointed member is oriented up and disposed above the filter across the line of flow through the vent, so that all vent flow must pass through the member, the member passing to the vent flow gas rising to the top of the upstream portion of the filter chamber and restricting such flow to gas to which it is permeable; the inlet member being shaped for attachment to a supply of liquid for intravenous administration; and the outlet member being shaped for attachment to an intravenous liquid administration apparatus, the upper walls of the filter chamber on the upstream side of the filter being arranged to funnel gas rising in the chamber towards the inlet member and vent, and to permit liquid flowing downwardly to spread out over the filter surface, the lower walls on the upstream side of the filter drawing inwardly towards the bottom of the chamber to maintain a uniform flow over the filter surface as the liquid diminishes in volume due to flow through the filter; and the lower walls of the filter chamber on the downstream side being arranged to funnel liquid flowing downwardly in the chamber towards the outlet member.