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Method and apparatus by which the interior of a pipe is coated with a uniform thickness of plastic. A source of heat-meltable plastic material in particular form is connected at a location upstream of the inlet end of the pipe, while the opposed end of the pipe is made attachable to a reduced pressu

Method and apparatus by which the interior of a pipe is coated with a uniform thickness of plastic. A source of heat-meltable plastic material in particular form is connected at a location upstream of the inlet end of the pipe, while the opposed end of the pipe is made attachable to a reduced pressure. A source of compressible fluid is also connected at a location upstream of the inlet end of the pipe. The pipe is preheated and then rotated axially while a charge of powdered plastic is forced through the pipe by the compressible fluid. The powdered plastic which flows through the pipe is a finite pocket of the finely divided plastic, which is smaller in volume respective to the volume of the pipe being coated.

대표청구항 ▼

Method of powder coating the interior of a tubular element with a synthetic plastic resin material comprising the steps of: (1) preheating the element to a temperature in excess of the fusion temperature of a synthetic plastic resin powder; (2) rotating the preheated element about its longitudinal a

Method of powder coating the interior of a tubular element with a synthetic plastic resin material comprising the steps of: (1) preheating the element to a temperature in excess of the fusion temperature of a synthetic plastic resin powder; (2) rotating the preheated element about its longitudinal axis at a speed which enables any subsequently fused plastic resin material to spread into a continuous film; (3) measuring powdered synthetic resin material to provide a single charge of powdered material which is sufficient for coating the entire interior surface of the preheated element; (4) placing the single charge into a container which has an inlet opposed to an outlet; closing said inlet and said outlet with a closing member; (5) placing said container within an enclosure, communicating said enclosure with one end of the preheated element by connecting a flow conduit to said enclosure at a location downstream of said charge and connecting the other end of said flow conduit to one end of the preheated rotating element; (6) connecting a supply of compressed air to said enclosure at a location upstream of said container; (7) flowing compressed air from said supply, into said enclosure, and into said inlet of said container, thereby placing a pressure differential across the container; (8) opening said inlet and said outlet by using the pressure differential across the container to cause the closure members at the container inlet and outlet to be moved to an opened position, whereupon flow of compressed air occurs through said container, and the single charge is formed into a pocket which moves in advance of the air flowing from the supply; (9) flowing the compressed air from said supply, through said enclosure, and through said element at a rate which moves the entire charge from the container located within said enclosure in advance of the flowing air to push the charge into said rotating preheated element as a pocket of powder, so that the powder contained within the pocket contacts the interior wall surface of the rotating preheated element and is fused into a coating in a single pass of the pocket through the element; and, (10) cooling the coated element to a temperature below the fusion temperature of the plastic.