Method for electrostatically depositing powder in several different layers on objects

A method of depositing successive layers of powder on objects, the method including providing at least first and second powder depositing booths, conveying objects along a path sequentially through said at least first and second powder depositing booths, electrostatically depositing an underlayer of a first powder in the first booth, and electrostatically depositing a cover layer of a second powder in the second booth, wherein the improvement comprises:

• providing said first powder depositing booth with a first chamber, a second chamber located contiguously upstream of the first chamber with respect to the direction of movement of the objects along said path, and a third chamber located contiguously downstream of the first chamber with respect to the direction of movement of the objects along said path;
• providing the second powder depositing booth with an electrostatic powder depositing chamber and an additional chamber located contiguously upstream of the electrostatic powder depositing chamber with respect to movement of the objects along said path;
• and wherein
• the step of electrostatically depositing the first powder comprises dispersing the first powder in said first chamber of the first booth, diffusing a portion of the powder dispersed in the first chamber into said second and third chambers, and electrostatically charging in the second and third chambers at least part of the portions of the first powder diffused from the first chamber, such that part of the charged portions of the first powder is deposited on the objects in an even thin underlayer as the objects pass through the second and third chambers;
• and
• the step of electrostatically depositing the second powder comprises dispersing and electrostatically charging the second powder in said electrostatic powder depositing chamber of the second booth, diffusing a portion of the second powder into said additional chamber from said electrostatic powder depositing chamber, and electrostatically recharging in said additional chamber of the second booth at least part of the portion of the second powder diffused from said electrostatic powder depositing chamber of the second booth, such that a thin layer of the second powder is applied onto each object exclusively by electrostatic attraction as the object passes through said additional chamber before entering said electrostatic powder depositing chamber of the second booth.