HYDRAULIC GRIPPER
HYDRAULIC GRIPPER
Heavy-duty end effector for a mechanical arm
Heavy-duty end effector for a mechanical arm
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The purpose
A mechanical arm is only as useful as the tool at its end. I designed this hydraulic gripper to be that tool: a set of opposing jaws that can grab, hold, and release heavy or irregular objects, mounted to an arm that can be operated directly or remotely.
How it’s built
The gripper hangs from the arm on a pair of clevis lugs, so it attaches with a single pin and can be swapped out without rebuilding the arm. Below the mounting flange, a central body carries everything else. Each jaw pivots at the bottom of the body and is driven by its own hydraulic cylinder, with the hoses routed along the body to keep them clear of the jaws.
The mechanism
Each cylinder is anchored high on the body and connects to an ear just above the jaw’s pivot. When the cylinder pushes, it rotates the jaw closed around that pivot. The clamping force depends on the lever arm, meaning the perpendicular distance between the cylinder’s line of action and the pivot. I placed the anchor and ear points so the lever arm is largest when the jaws are nearly closed, which is exactly when the gripper needs the most force to hold its load.
The jaws
The jaws curve inward so the tips meet under the center of the body, which helps pull an object in and hold it centered under the arm instead of pushing it away. Ribs along each jaw add bending stiffness without making the whole jaw solid, so the jaws stay rigid under load while keeping their weight down.
Modeling
I modeled the full assembly in SolidWorks, including the cylinders, pins, and hose routing, and checked that the jaws could travel their full range without the cylinders or hoses colliding with the body.
What I took from it
A gripper looks simple, but its performance comes down to geometry. Where you place a few pivot points decides how much force reaches the jaw tips and when. Getting that right on paper first meant the cylinders didn’t need to be oversized to make up for poor leverage.
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