Patent ID: 8430640

Claim:
A powder feed apparatus for a powder spraycoating equipment, said powder feed apparatus comprising: a dense phase powder pump including at least one feed chamber for discharging coating powder, a powder intake valve at a powder intake of said at least one feed chamber to aspirate the coating powder during a suction stage; a powder outlet valve at a powder outlet of said at least one feed chamber to discharge the coating powder during a discharge stage; control valves configured to operate the dense phase powder pump; and an electric control unit including at least one computer configured to drive the dense phase power pump by the control valves, and a powder adjusting element configured to control a rate of a powder stream to be moved by the dense phase powder pump, wherein the control unit stores a function t total =t delay +m p C to obtain an open time of the powder intake valve during the suction stage, where t total is a total open time (t total ) of the powder intake valve during the suction stage from an onset of a command to open the powder intake valve to an onset of a command to close the powder intake valve from the control unit, t delay is a response delay time from the onset of the command to open the powder intake valve to an onset of the powder stream into the feed chamber through the powder intake valve which is at least partly open, m p denotes a percentage of the rate of the powder stream to be moved by the dense phase powder pump relative to a maximum possible rate of powder discharge of the dense phase powder pump at a predetermined maximum opening time of the powder intake valve and is adjustable by the powder adjusting element, and C is an equipment constant C, wherein the powder adjusting element has an adjustment range of 0 to 100%, said adjustment range being divided into corresponding 0 to 100% portions of a powder discharge rate of conveyed discharged powder of the dense phase powder pump, where 0% corresponds to the state when, at an end of the response delay time, the coating powder just begins streaming through the powder intake valve of the feed chamber in the suction stage, and 100% corresponds to the maximum possible rate of powder discharge of the dense phase powder pump at the predetermined maximum opening time of the powder intake valve of said at least one feed chamber, and wherein the control unit is configured to control the open time of the powder intake valve as the calculated t total based on the m p set in the powder adjusting element.