Aza Arnold

Born in Smithfield, Rhode Island, he was trained as a machinist during his youth, and in 1809, entered work at Samuel Slater's textile manufacturing equipment plant in Pawtucket.

After a failed venture in woolen blanket production and several years of employment at another Pawtucket factory, he invented a device to separate wool during carding and began to experiment with differential gear trains, possibly inventing the device independently or borrowing the concept from contemporary clockmaking.

After several years administering a manufacturing plant in North Providence, Rhode Island, he moved to Philadelphia to operate a print works.

[2] Arnold left employment at Slater's manufacturing plant to begin producing woolen blankets.

Several years later, he moved to North Providence, Rhode Island, where he established his own textile machinery plant.

[5] In 1822, he incorporated the differential into a roving frame, allowing the bobbins to progressively slow relative to the spindles as it filled.

[6][7] This gear train system was considered impressive by regional engineers, who had initially described the proposal as "impracticable".

[5] Although initially invented in ancient times (attested in the Chinese south-pointing chariot and the Ancient Greek Antikythera mechanism), the first modern differential gears were used by some 18th-century clockmakers, with James White pioneering its first industrial usage in the 1780s in order to adjust the gap between windmill millstones in variable winds.

[6] Even within the United States, many manufacturers refused to pay royalty fees for the differential gear train.

Lowell-associated corporate agents, attempting to defend against patent infringement suits, were unable to find precedence to differential gears' usage in cotton processing in the United Kingdom.