Movement No. 120 demonstrates a powerful jaw-closing mechanism using a pair of gear segments — one with external teeth and one with internal teeth — driven by two pinions on a common shaft. Each jaw of the mechanism is attached to one of the two arc-shaped gear segments. One segment has teeth on its outer surface, while the other has teeth on its inner surface. A shaft carries two pinions: one meshes with the external teeth of the first segment, and the other meshes with the internal teeth of the second segment. When the shaft is turned, both pinions rotate simultaneously — one pushing its segment in one direction and the other pulling its segment in the opposite direction. This opposing action brings both jaws together with great mechanical force, or opens them apart depending on the direction of rotation. The combination of internal and external gearing in a compact arrangement delivers exceptional clamping force, making this mechanism well suited for vises, presses, and gripping devices.
120. Each jaw is attached to one of the two segments, one of which has teeth outside and the other teeth inside. On turning the shaft carrying the two pinions, one of which gears with one and the other with the other segment, the jaws are brought together with great force.