Patent ID: 6896935

Claim:
A method of electrostatically forming a coating on an inner periphery of a tube that has a cylindrical barrel, a mouth provided on one axial end of the barrel, and a shoulder located between the barrel and the mouth, the method comprising the steps of: preliminarily holding the tube in a holder, and subsequently jetting powder into the container from a spray gun, through an opening disposed on the other axial end of said barrel of the tube held in the holder, wherein a first passage is used to guide to the spray gun a first air stream together with the powder to be jetted, a second passage is used to feed to the spray gun a second air stream that is being supplied with the powder, a third passage is used to suction collect surplus powder through the mouth of the tube, and a fourth passage is used to suction collect surplus powder through the opening of the tube on the other axial end of the barrel of the tube, and wherein at least one of the first to fourth passages is subject to such a feedback control that flow rate and/or internal pressure of the at least one passage are maintained at target levels, the feedback control controlling a regulator based on signals from a sensor such that flow rate and/or internal pressure of the at least one passage are maintained at target levels, the regulator disposed at an intermediate point of the at least one passage and being actuated to regulate the internal pressure in and/or flow rate through the at least one passage, the sensor disposed at an intermediate point of the at least one passage on a downstream side of the regulator and detecting the internal pressure and/or flow rate of the at least one passage.