Evaporable foam pattern for casting a cylinder block of a two-cycle

Abstract

An evaporable foam pattern for casting the engine block of a two-cycle engine. The pattern has a crankcase end and a head end and a plurality of cylinders extend from the crankcase end toward the head end. A plurality of transfer passages are disposed longitudinally of each cylinder and one end of each transfer passage communicates with the crankcase end, while the second or discharge end of the transfer passage communicates through a transfer port with the cylinder adjacent the head end of the pattern. The pattern is composed of a crankcase section and a head section which are joined along a parting line disposed normal to the axis of the cylinder, with the parting line intersecting the transfer passages adjacent the discharge end of the passages. A portion of the cylinder in the head section located adjacent the parting line is enlarged in diameter and is connected to the cylinder by a plurality of ledges that are disposed between the transfer passages. The pattern also includes an evaporable foam ring which is disposed within the enlarged cylinder portion of the head section and one end of the ring has a plurality of ears which engage the ledges. Recessed edges of the ring extending between the ears bridge the transfer passages and partially define the transfer ports. An adhesive joins the abutting surfaces of the crankcase and head pattern sections, as well as securing the ring in the enlarged cylinder portion of the head pattern section.