Farley, Inc.

Doehler-jarvis Limited Partnership

Robert E Downing

Bobby L Wilson

John P Cestaro

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This disclosure concerns an expendable core for molds such as die casting dies, which core has a central aperture which may be elongated. The outside of this core is provided with a plurality of parallel grooves across the elongated sides of the core parallel to the aperture. These grooves may have corresponding ribs in the central aperture. One and the common end of each of these grooves is provided with a bridging web integral with the core for reinforcing and strengthening the core. The opposite end of the core from these webs may be provided with a printout portion also integral with the core by which the core is supported in the mold or die.

Web reinforced expendable core

The core box has a drag and a cope forming a mold cavity for forming a sand base core. This sand is injected into the cope and the air in the cavity is vented through vents remote or spaced away from where the sand is inserted. These vents are usually in the drag, but may also be in the cope. In each vent adjacent the cavity is a cylindrical cup-shaped plug having slotted perforations in its bottom narrower than the diameter of the sand grains. The diameter of this perforated vent plug is at least 50% greater and preferably at least twice the width of the cavity, slot, or groove at the vent whereby air can be vented along the cavity. Furthermore, the plug having the perforations may be contoured to the groove or that portion of the cavity in which the vent is located so that air can also be vented from the sides of the cavity or groove. These plugs are held in place by sleeves that contact the rim of the cup and extend to the outside of the mold where the sleeves are held in place by overlapping washers or heads of bolts screwed into the mold.

Core box with large diameter vents and plugs

A method for producing high pressure die castings with undercut regions comprises forming an expendable coated core of specific composition, placing it in the die in a die casting machine, injecting molten metal into the die to form the casting and separating the casting from the die and the core from the casting. The composition of the expendable coated core comprises a base sand core held together by a resin binder; a first, bottom, hard refractory coating comprising fused silica and a refractory binder containing at least two of the following additives: a suspension agent, a dispersant, a wetting agent, and an anti-skinning agent; and a second, top, soft, or release coating containing a release material selected from the group consisting of anhydrous powdered aluminum, graphite, talc, titanium dioxide and zircon, and a resinous binder containing at least two different compounds selected from the group of additives consisting of a suspension agent, a dispersant, and an anti-settling agent.

Method of forming a die casting with coated expendable cores

The disclosure concerns a process of producing expendable coated cores for castings comprising mixing sand with a resinous binder, polymerizing the binder, and then washing the resulting bound sand core with an organic solvent to remove unpolymerized residuals from the surface of the core before applying a coating to the core.

Process for washing a casting core

The coatings are for an expendable sand core for die casting dies, which sand core has spaces between its contacting sand grains at least partially filled with resin binder. The first, base, hard, or refractory coating for this core is applied from an aqueous suspension comprising a finely ground refractory of fused silica, a refractory binder, and at least two different compounds selected from the groups of compounds or additives consisting of: (1) a suspension agent, (2) a dispersant, (3) a wetting agent, and (4) an anti-skinning agent. The refractory in the first coating may also include a minor amount, i.e. less than 50%, of another refractory oxide. The amount of binder in the first coating is less than about 15% by weight of the total liquid suspension, and the amount of additives is less than about 1.5% and usually less than 1% by weight of the total liquid suspension. The second, top, soft, or release coating is an organic liquid suspension containing between about 5% and 60% by weight of the whole suspension of particles of a release material selected from the group consisting of anhydrous powdered aluminum, graphite, talc, titanium dioxide, and zircon, and less than about 10% by weight of the total suspension of a resinous binder, less than 15% of at least two additives or different compounds selected from the groups additives and compounds consisting of a suspension agent, a dispersant, and an anti-setting agent.

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Toledo, OH, United States of America

Robert E Downing