John Needles' first articulator (1921; patent # 1368408) was a single rotation center instrument that featured the prototype of this instrument's incisal pin and guide mechanism. It is the first "controlling gothic arch" incisal guide with both lateral and protrusive controls. The 2nd design is an adjustable condylar guide instrument, the controls of which are designed to be set by the Needles-House chew-in technique (i.e. a functionally generated path). The incisal mechanism of this articulator was modified by Milus M. House. House's innovation was the offset incisal pin. The lower section was set at an angle of 55 degrees tangent to the arch of closure of the articulator to facilitate smooth movement of the pin past the guiding edges of the "gothic arch" to contact the lower protrusive guide plate.
Dr. Edgar N. Starcke's articles in the Journal of Prosthodontics have more information on the history of articulators.