Model: A01 Screw Kinematic Pair
Reuleaux's use of the term 'lower pair' in the 'A' model series refers to the surface contact or constraint between two bodies. His term 'higher pairs' in the model series 'B' refers to a constraint with a point or line contact as between gear teeth. This model shows the constrained motion of two bodies in which the relative motion is a screw, i.e. a rotary motion with proportional axial displacement. The screw was known to the ancient Greeks as one of the 'simple machines'. It was used by Archimedes [287-212 BCE] and Hero in their machines for pumps and presses.

Francis Moon 2001-00-00

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