Feeder-air lock with slide gates

Claim 1

A feeder-air lock, comprising: a substantially vertical passage defining an inside surface through which material can fall; first and second slide gate housings mounted at two different vertical positions along said substantially vertical passage, each of said slide gate housings having a top wall, defining a material inlet, said top wall having an inside surface including a sealing-scraper surface surrounding said material inlet; and having a material outlet below its respective material inlet; and including a slide gate between said material inlet and outlet, said slide gate having a free end and a drive end, wherein the drive end is connected to a mechanical drive which moves its respective slide gate to an extended position, in which the slide gate extends across said slide gate housing to close off said passage, and a retracted position, in which said passage is open, providing a completely smooth, downwardly-extending surface for the dust to pass through; said slide gate having a smooth, flat top surface which seals against said sealing-scraper surface; a bottom surface opposite said top surface; and a supporting rib projecting downwardly from said bottom surface; said slide gate housing having a substantially vertical separator wall, defining a gap between said sealing-scraper surface of said top wall and said separator wall through which the respective slide gate projects; and defining an upwardly-opening slot in said separator wall which provides a cantilever support to said supporting rib as the slide gate moves from its retracted to its extended position; said separator wall defining an inside surface, facing toward the passage, and an outside surface facing away from the passage, wherein said mechanical drive is located outside of said separator wall.