One product advertised by Day's new company was a range of valveless air compressors, built under licence from the patentee Edmund Edwards.
Shortly after the introduction of the new engine one of Joseph Day's workmen, Frederick Cock, patented a modification which enabled it to become genuinely valveless.
An additional port lower in the cylinder wall allowed the skirt of the piston to control the inlet phase thus doing away with the check valve and giving rise to the classic three-port layout.
The development of his engine then passed to his licence holders in America, whose royalties restored his finances sufficiently to allow him to launch a spectacular new venture after the First World War.
His obscurity was so complete that a mere five years after his death, the Science Museum made a public appeal for biographical information about him – with no apparent result.