US 6,982,057 B2
Multi-layer rotational plastic molding
Nathan King, Inver Grove Heights, Minn. (US); Jennifer Schwiebert, Maple Grove, Minn. (US); John Morgan, Cedar, Minn. (US); and Gary Engen, Mounds View, Minn. (US)
Assigned to Solar Plastics, Inc., Delano, Minn. (US)
Filed on Nov. 15, 2002, as Appl. No. 10/298,042.
Prior Publication US 2004/0096608 A1, May 20, 2004
Int. Cl. B29C 41/04 (2006.01)
U.S. Cl. 264—255 36 Claims
OG exemplary drawing
 
1. A method for rotation molding an article, comprising the steps of:
introducing a first flowable material into a mold having an insulating member mounted on a mold wall and having a protrusion extending through an aperture in the mold wall;
heating and rotating the mold so as to lay down the first material as a first layer having a thickness small enough so as to form a gap at the insulating member;
removing the insulating member so as to expose the gap;
introducing a second flowable material without opening the mold;
heating and rotating the mold so as to fully cure the second material as a second layer over the first layer and in the gap;
cooling the mold so as to solidify both the first and second layers,
where the second material is introduced into the mold through the aperture.