Screw powder feeders

摘要

PCT No. PCT/GB85/00456 Sec. 371 Date Jun. 9, 1986 Sec. 102(e) Date Jun. 9, 1986 PCT Filed Oct. 11, 1985 PCT Pub. No. WO86/02337 PCT Pub. Date Apr. 24, 1986.A screw powder feeder has a rotary screw (12) disposed at the base of a hopper (10). The screw (12) comprises a twist drill bit. Powder is discharged into a chamber (18) and picked-up by a flow of gas. The pressure in chamber (18) is varied relative to the pressure in hopper (10) to control the feed rate for a given screw speed. Ultra-low feed rates are made possible by feeding gas into the hopper (10) through the screw (12) and controlling the relative gas pressures such that the pressure in the chamber (18) exceeds the pressure in hopper (10).