Reverse osmosis apparatus employing a reciprocating membrane cartridge

Claim 1

Apparatus for treating liquid by reverse osmosis comprising; a tubular pressure resistant vessel containing a semipermeable membrane cartridge comprising a membrane, a permeate transfer sheet and a spacer sheet all sprially wound around a central permeate collection tube, and providing generally longitudinal channels for passage of feed liquid therethrough, said semipermeable membrane cartridge being of cylindrical configuration and being materially shorter than said tubular pressure resistant vessel, and being of diameter to fit slidably inside said tubular pressure resistant vessel; means for introducing pressurized impure feed liquid into said tubular pressure resistant vessel near one end thereof for longitudinal passage through said semipermeable membrane cartridge; and means for releasing concentrate from said tubular pressure resistant vessel near the other end thereof while maintaining operating pressure therein; in which the improvement comprises: a. means comprising a tube connected to said permeate collection tube of said semipermeable membrane cartridge at an end of said semipermeable membrane cartridge for releasing permeate produced by said semipermeable membrane cartridge from said tubular pressure resistant vessel; b. means attached to an end of said semipermeable membrane cartridge for reciprocating said semipermeable cartridge within said tubular pressure resistant vessel during passage of feed liquid therethrough; and, c. means for providing an effective cross sectional area of the end of said semipermeable membrane cartridge exposed to the pressure of said feed liquid in said tubular pressure resistant vessel substantially the same as the effective cross sectional area of the end of said semipermeable membrane cartridge exposed to the pressure of said concentrate in said tubular pressure resistant vessel; d. whereby the forces exerted by the pressure of feed liquid on one end of said semipermeable membrane cartridge and force exerted by the pressure of concentrate on the other end of said semipermeable membrane cartridge are essentially balanced.