Blow molding a closed plastic drum including two speed compression molding of an integral handling ring

A method of molding a closed one-piece 55 gallon plastic drum having an integral handling ring at a head end thereof and comprising the steps of:

• providing an axially divided blow mold forming space halves in an open position and having an interior surface of the desired dimensions and shape of the drum to be molded which includes a cylindrical body portion and a head portion on one end of the body portion and connected thereto by a transition area, and having an articulating section to form by compression a solid handling ring integrally extending axially and radially outward from the transition area of the drum, the mold being further shaped to provide an outside curved surface of a predetermined radius on the transition area of the drum so that the outside cylindrical surface of the drum is in a tangential plane in close proximity to a tangential plane along an outer surface of the handling ring;
• extruding a heated plastic parison between the open blow mold halves;
• performing a first blowing operation of the parison, while closing the blow mold halves and while maintaining the mold articulating section in open position a predetermined axial distance of at least approximately 2.65 inches from a closed position, under a predetermined pressure of 30-60 PSI to completely expand the parison into the shape of the inside surface of the mold and to completely fill the open mold articulating section and form an open handling ring, the first blow-molding operation continuing for about 2 seconds after the mold halves are closed to ensure that the parison is completely expanded inside the mold and completely fills the open articulating section during the first blow-molding operation;
• performing a second blowing operation under a predetermined pressure of 15-40 PSI to stabilize the expanded parison inside the closed mold;
• closing the mold articulating section during the second blowing operation in a first sequence in which the mold is closed approximately 70 percent at a predetermined speed and in a second sequence in which the mold is closed the remaining 30 percent at a predetermined slower speed of approximately 10 percent of the speed of closing during the first sequence while compressing the blow-molded open handling ring into a solid handling ring integral with the drum and forming with extruded plastic an inside curved surface on the transition area of the drum in the form of a double ogee with 3 predetermined radii;
• and
• performing a third blowing operation after the mold articulating head section is completely closed at a predetermined pressure of 90-110 PSI for a sufficient time to allow cooling of the molded plastic drum.