Dartmouth Engineer - The Magazine of Thayer School of EngineeringDartmouth Engineer - The Magazine of Thayer School of Engineering

Inventions: Cashew Nut Sheller

Richard Couch ’64 Th’65 and Professor Robert Dean


Richard Couch and Robert Dean
Richard Couch, right, and Ephraim Aniebona work on their BE project, “Decortication of Cashew Nuts.” Photograph courtesy of Thayer School Archives.

On the second floor of Cummings Hall is a display of all the patents awarded Thayer’s faculty, students and staff during the last five decades. First on the wall: U.S. Patent 3,605,843, granted to Professor Emeritus Robert Dean and Richard Couch ’64 Th’65. The official paperwork doesn’t describe how an explosive idea for shelling cashews was thwarted by the Cold War.

Couch, then a BE student, saw an opportunity to engineer a solution to a big problem facing a nascent African cashew industry—how to shell the cashews—while on a trip to the continent.

Shelling cashews is complicated because the nuts are in the same family as sumac and poison ivy. The oil inside the shell is toxic and will burn the skin of the workers. Moreover, shelling by hand doesn’t capture the oil, a profitable commodity with a ready market in the auto industry.

Couch decided to design a machine that could shell the cashews while keeping the oil and nut apart. He returned to Dartmouth and began work on a shelling machine under Dean’s tutelage.

Couch’s idea: a controlled explosion. As the patent abstract explains: “The explosive opening of the nutshell results from a technique in which the nut initially is subjected to a compressed gas for a time interval during which the internal pressure of the nut is raised. The nut then is exploded rapidly, to a lower pressure which fractures the shell and separates the shell from the kernel. The nuts are isolated and exploded individually and in rapid, continuous succession. As each nut is exploded, both its kernel and shell are ejected from the machine along different trajectories and are collected and sorted separately and automatically, thus avoiding any contact between the separated shells and kernels.”

“Dick ran experiments—he put nuts in a canister and found that 200 PSI worked fine,” recalls Dean. The two were awarded the patent in 1971.

Their next step, building a prototype, proved insurmountable. The stumbling block wasn’t technical, but simple economics. USAID, the federal agency that invests in ideas to improve the lives of the world’s poorest people, initially liked their idea. Six months later a USAID official told them that their machine was a casualty of the Cold War. It turns out that the Russians were the primary buyers of African cashews, and the U.S. government didn’t want to fund anything that could be seen as helping the Russians.
The idea was shelved.

Forty-six years after Dean and Couch were awarded their patent, the cashew shelling business is unchanged. More than 60 percent of the world’s cashews are processed in India by hand, according to The Guardian.

“We did as much as we could, but we had no money for the project,” says Dean, who along with Couch, a Thayer Overseer, went on to a successful career as an engineer-entrepreneur. “I’m pretty sure it will work.”

—Lee Michaelides

Categories: Inventions

Tags: entrepreneurship, faculty, patent, projects, students

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