The invention relates to an accumulator head, especially one that is useful in the production of a multi-layer parison which, for example, is used in the formation of a plastic fuel cell or tank, wherein it is desireable to have an inner layer which is impervious to liquid, covered by an outer layer of highly durable shock resistant material.
U.S. Pat. No. 3,386,132 is relevant to the invention in that it shows an accumulator head having an accumulation chamber with an annular inlet that is located in the outer wall of the chamber intermediate opposing ends of the chamber whereat the ring-piston resides when in its fully retracted and extended positions within the chamber.
U.S. Pat. No. 3,298,061 is also relevant in that it shows a solid cylindrical ram or plunger having a mechanism for wiping the outer tip or pushing face of the plunger free of material which has a tendency to cling to the face and create problems. This is found to be especially true with annular, ring-type pistons which are used in accumulator heads where the annular inlet, through which material is fed into the accumulation chamber, communicates with the chamber between opposing ends of the chamber.
Briefly stated, the invention is in an accumulator head having an annular accumulation chamber which has an open, discharge end opposite a closed end that is sealed by an annular ring-piston which is movable axially in the chamber to force, for example, resinous material that has been charged to the chamber, therefrom. A discharge passageway extends from the discharge end of the chamber and leads to a discharge orifice through which material, from the chamber, is forced to form a parison for subsequent blow molding. Means, including an inlet passageway, are provided by which material is charged into the accumulation chamber intermediate the open and closed ends thereof.
The ring-piston, adjacent its tip or pushing face which first encounters material in the chamber, is provided with means for wiping the face and keeping it clean and free of the material being charged to the chamber, such means including an annular groove which is recessed inwardly in the outer circumferential wall or surface of the piston. The annular groove directly opposite the inlet passageway leading to the accumulation chamber, is in communication with a slotted or flat recess which extends from the groove longitudinally of the ring-piston through the pushing face for communication with the chamber, the recess having a longitudinal axis which is generally normal to the plane of the groove. The recess helps in the removal of material which tends to congregate in this particular area of the groove and pushing face of the piston, as the two streams of resinous material, divided upon contact with the ring-piston, are joined together on the backside of the ring-piston farthest from the inlet passageway. The resinous material as it moves from the groove into the chamber, wipes the pushing face of the piston to clean it and remove any material which clings to the piston.