Powder feeding apparatus

Claim 1

A powder feeding apparatus comprising a holding hopper for holding a powder, a metering hopper for metering the powder fed from the holding hopper, hopper opening-closing means adapted to be selectively held at an opening position at which it opens a discharge opening in the metering hopper and a closing position at which it closes the discharge opening, control means for controlling the hopper opening-closing means so as to discharge the powder in intervals, and smoothening means for substantially smoothening the flow of powder discharged from the metering hopper, said smoothening means including a trough beneath the metering hopper and a vibration generator for vibrating the trough, said trough having a discharge and located downstream of the metering hopper, said vibration generator being operable to smoothen the flow of powder while it is transferred through the trough to the discharge end; said control means comprising timer means for measuring time and user-adjustable means for setting a time period to be measured by the timer means; said control means producing a discharge signal when the time period measured by the timer means elapses to bring the hopper opening-closing means to its opening position so that the intervals of powder discharge can be increased by increasing the time period set in the timer means or decreased by decreasing the time period set in the timer means; weight detecting means for detecting the weight of powder contained within the metering hopper, said weight detecting means being variable to control the amount of powder fed by the metering hopper so that the amount of powder fed by the metering hopper is controlled by both said timer means and said weight detecting means; said powder feeding apparatus further comprising driving means for feeding powder into said metering hopper, and wherein said hopper opening-closing means includes a top shutter and a bottom shutter, and wherein said control means includes means for signalling for the activation of said driving means and signalling for said hopper opening-closing means to position said top shutter in an open position and said bottom shutter in a closed position, said control means further including means for signalling the deactivation of said driving means and the closing of said top shutter upon said weightdetecting means detecting a predetermined weight of powder in said hopper, and said control means further including means for signalling for the opening of said bottom shutter when said period measured by said timer means has elapsed.