Movement No. 144 demonstrates the “Lazy Tongs” — a classic scissor-linkage mechanism made up of a series of crossed levers connected at their midpoints and ends. A short reciprocating rectilinear motion applied to the rod on the right produces a similar but greatly amplified motion at the rod on the left. The crossed lever pairs form a diamond-shaped expanding and contracting lattice: as the right end is pushed inward, the lattice compresses sideways and extends dramatically in the perpendicular direction, multiplying the input displacement several times over. The amplification factor depends on the number of lever pairs in the chain — more pairs means greater amplification. This elegant mechanism was famously used in children’s extending toys, and historically applied in France to salvage machinery for raising sunken vessels, as well as in ship pump systems. Today the same principle appears in scissor lifts, extendable arms, and deployable structures.
144. A system of crossed levers, termed "Lazy Tongs." A short alternating rectilinear motion of rod at the right will give a similar but much greater motion to rod at the left. It is frequently used in children's toys. It has been applied in France to a machine for raising sunken vessels; also applied to ships' pumps, three-quarters of a century ago.