Why does squeezing a clothespin make it open?

Squeeze the long ends of a spring clothespin and its gripping ends move apart. The apparent reversal comes from the turning point between them: each wooden half acts as a lever. Your fingers overcome the spring while opening the jaws; releasing the handles lets the spring close them. The spring supplies the closing force, but its relationship to the turning point has not always looked the same.^[1][2]

First, separate the spring from the hinge

David M. Smith’s patent of October 25, 1853, makes those jobs particularly easy to see. In Figure 1, the small letter a marks a hinge joining two levers. The spring C sits above it, between the longer handles. The opening D for cloth and line lies below it. Moving the handles together swings the shorter ends apart; the flared mouth helps the pin pass onto the line.^[1]

Read the drawing from top to bottom rather than treating every metal part as a spring. C pushes the handles apart, a allows the two halves to turn, and the jaws grip on the other side. Smith’s claim concerned the arrangement of the line opening and spring on opposite sides of the hinge. He explicitly excluded a claim to the mere combination of two hinged levers and a spring. The document therefore cannot establish that he invented every spring clamp.^[1]

Then find a spring doing two jobs

Solon E. Moore’s June 28, 1887, patent describes a different arrangement. Its single wire coils at D, and that coil rests in recesses cut into the wooden halves. Moore calls it a movable coiled fulcrum: the support about which the halves turn. Arms E extend from the coil and normally press the jaws closed. Here the spring provides both the closing force and the central support, rather than sitting between handles above a separate hinge.^[2]

The small grooves matter too. Moore’s wire ends sit in transverse grooves on the outside of the wood, while the arms pass along opposite sides of the clamps. His description explains how this placement keeps the spring from moving sideways. Figure 3 isolates the wire so that its coil, long arms and bent ends can be followed without the wood hiding them. Moore also acknowledges earlier coiled-spring pins; his patent claims a particular construction, not all pins with coils.^[2]

The useful comparison is the location of the turning point, not which drawing looks oldest. Both arrangements make squeezing one end open the other, but only Moore’s pictured coil doubles as the fulcrum. The 2010 photograph shows another spring-type pin; it cannot date the design or prove who made it. For the wider routine around that little clamp, our washday story follows the work that remained after washing.^[1][2][3]

Did your household use the squeeze-open pins, the one-piece wooden kind, or both?