The shuttle element may be in the form of a so called slug go devil or pipe cleaner swab that forms {HEAD ~ a relatively tight seal} between the paint on one side and {TAIL ~ the auxiliary medium} on the other side, and that scrapes or swabs along the walls of the paint line as it moves along therein so as to clean the paint line 
between
The shuttle element may be in the form of a so called slug go devil or pipe cleaner swab that forms { HEAD ~ a relatively tight seal } between the paint on one side and { TAIL ~ the auxiliary medium } on the other side , and that scrapes or swabs along the walls of the paint line as it moves along therein so as to clean the paint line
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