| 摘要 |
The interior of a pipe is coated with a uniform thickness of plastic. A fluidized bed of heat-meltable plastic material in particular form is connected to the inlet end of the pipe, while the opposed end of the pipe is made attachable to a source of reduced pressure. A source of compressible fluid is also connected to the inlet end of the pipe. The pipe is preheated and then rotated axially while the compressible fluid flows therethrough. The compressible fluid flowing to the inlet is suddenly terminated while a flow from the fluidized bed is immediately established so that the vacuum at the outlet end of the pipe causes uninterrupted mass flow and pulls a finite pocket of the finely divided plastic into the pipe. The flow of particular plastic material is terminated, while the flow of compressed gas is immediately re-established, thereby pushing the pocket of plastic material into and through the pipe. Timing means associated with the flow from the fluidized bed enables the vacuum source to be removed before the pocket of material arrives at the outlet end of the pipe. This sequence of manipulative steps applies a coating of plastic material on the interior surface of the spinning pipe. The spinning action, together with the elevated temperature of the pipe, enhances the uniformity of the deposited plastic material.
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