U.S. Patent 2,918,699 — Hall, "High Pressure Press" (tetrahedral press)

Summary

H. Tracy Hall's tetrahedral press patent — the apparatus he designed after leaving General Electric for Brigham Young University, and the first of the two Utah-era press designs that the wiki's Hall page rests on. The patent is filed from Provo and describes the four-anvil geometry by which the press reaches diamond-synthesis pressures.

Useful Claims

• Patent number 2,918,699, titled "High Pressure Press". Application serial no. 731,543, filed April 28, 1958; granted December 29, 1959.
• The face of the patent reads "Howard T. Hall, Provo, Utah, assignor to Research Corporation, New York, N.Y." — Hall's Utah residence is on the instrument, and the assignee is Research Corporation, not BYU and not GE.
• The claimed geometry is four anvils, not one axis: claim 5 covers "four anvil devices each having equilateral triangular faces … whereby the triangular faces of the four anvil devices define a regular tetrahedron." Each anvil is driven by its own hydraulic ram along a line normal to its face.
• The sample sits in a pyrophyllite tetrahedron slightly larger than the anvil faces, so that closing the press extrudes some pyrophyllite between the anvil flanks and, in the patent's words, "a sealing gasket is automatically formed." That self-forming gasket is what lets the press hold pressure without a containment vessel.
• Heating is done in situ: prism-shaped sections are cut from the pyrophyllite tetrahedron to admit metal conductors that pass current through the sample container, so pressure and temperature are applied together.
• The worked example in the specification reports a press with half-inch anvil-face edges and fifty-square-inch ram pistons reaching "pressures of the order of 100,000 atmospheres" in the sample container.

Reliability Notes

Primary tier. A granted U.S. patent is a dated public instrument the USPTO must preserve and is retrievable by number indefinitely, so no archive snapshot is owed. The URL is the issuing body's own PDF of the grant.

Scope, and what it deliberately does not settle. This document is evidence for the tetrahedral press design, its dates, and Hall's Provo address in 1958. It is not evidence for anything about the December 16, 1954 first synthesis at GE, the Belt press, the contested credit around that synthesis, polycrystalline diamond, or the founding of MegaDiamond and Novatek. The cubic press is a separate later patent, recorded at U.S. Patent 3,159,876.

The ram-load figure in the specification's worked example is illegible in the OCR of the grant ("ram loads of about tons"), so it is not quoted here. The 100,000-atmosphere figure is legible and is the only pressure figure this page asserts.

Related Pages

• H. Tracy Hall's Diamond Presses
• U.S. Patent 3,159,876 — Hall, "High Pressure Press" (cubic press)