Murfey received patents for lubrication technology specifically designed to prevent the overheating of railroad axles known as 'hot boxes.'
On November 15, 1870, Eliza Murfey was granted three additional patents, US 109,237, 109,238, and 109,239, including what is considered her core invention: a system explicitly designed to prevent the phenomenon railroad workers called a 'hot box' — the dangerous overheating of an axle journal caused by insufficient or uneven lubrication, which could lead to seized wheels, broken axles, and derailments.
Hot boxes were among the most feared mechanical failures in nineteenth-century railroading, capable of causing catastrophic accidents on lines carrying both freight and passengers. Murfey's design addressed the root cause by ensuring a continuous, self-regulating supply of lubricant to the bearing surface, reducing friction-driven heat buildup even under variable speeds and loads.
This patent grant represents the culmination of the technical direction she had been pursuing since her first patent in July of that year, refining packing materials and mechanical delivery systems into a targeted safety solution. Her work in this area is credited by later historians and railroad historians as a genuine contribution to reducing derailments attributable to axle failure, placing her invention within the broader nineteenth-century movement toward standardized railroad safety engineering — a field she entered and excelled in despite having no formal engineering credentials or institutional backing, as was typical for women of her generation.