From DT Online
Two pivoted links can be joined together such that the output is caused to move in the same direction as the input. These are often known as Push-Pull Linkages.
Features and Uses
They consist of Levers connected with two fixed pivot points. The positions of the pivots can be varied to amplify the output movement, or the force it exerts, whilst its direction remains the same as the input. Links can be extended and extra pivots added to create useful movements.
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