Patent ID: 6203696
Filing Date: 2001-03-20
Classification: B01D,F04B,Y02A,Y10T

Abstract:
A reverse osmosis or filtration system comprising a semi-permeable membrane or filter, a pump arranged to supply all high pressure fluid delivered to the membrane or filter, part of said fluid passing through the membrane or filter as purified or filtered fluid, the remainder of said fluid being a flow of return fluid, which is returned to the pump, the pump being powered only by the return fluid and by an inlet flow of pressurized fluid to be purified or filtered, the pump comprising reciprocable elements bounding a pair of first pressure chambers which alternately receive and exhaust return fluid via control valves to reciprocate the reciprocable elements between extremities of reciprocation, a pair of second chambers also bounded by the reciprocable elements and which alternately receive the pressurized inlet fluid and deliver fluid at high pressure to the semipermeable membrane or filter, the control valves operating at the extremities of reciprocation of the reciprocable elements and being subjected to the pressure of fluid in the first pressure chambers, and a bleed valve permitting limited flow past a said control valve to modify the pressure in a said first chamber whereby to control the timing of operation of the said control valve.