Fundamentals of pneumatic grippers for industrial applications
First commercially available in the 1970s, pneumatic two-finger grippers are the most widely applied today — accounting for more than half of all pneumatic gripper applications. The fingers in these designs slide or swing on pivot points to close like a gate or lobster claw around target objects. They can employ either parallel jaw action or angled finger action. Pneumatic grippers with parallel jaw action: In parallel grippers, the two fingers slide inward and outward — in straight-line motion — on the same axis along tracks in the upper gripper body. Typically, the inward sliding action is what grasps the workpieces or other objects. However, applications abound in which the two fingers slide outward to secure hollow or open workpieces (such as O-rings or cylinders, for example) from their inner diameters. Benefits of these dead-simple grippers abound. The various subcomponents for such grippers are simpler to manufacture than others, making these grippers very cost-effective. In addition, there is one steady gripping force over the entire finger stroke — which simplifies the work associated with applications involving delicate or otherwise pressure- sensitive workpieces. Finally, parallel grippers can be designed to close and open quite wide — even to a couple feet or more.
Video 1: In one common variation, the pneumatic gripper connects via a specialty hose to a compressed air system. The force of compressed air displaces a piston that in turn (through some gear, toggle, or slide linkage) causes the external jaws to actuate through their range of stroke. (Video source: Schunk)
Control of air into a pneumatic gripper is often reliant on preprogrammed grasp-release cycles … or (in more sophisticated applications) feedback from sensors that detect held objects.
Types of pneumatic grippers
Jaw and finger pneumatic grippers are classified by their: ■ Kinematic arrangement, number of fingers, action, and type of mounting ■ Physical size and maximum gripping force ■ Jaw and housing construction — including level of ingress protection
Figure 3: Two-finger parallel grippers in Schunk’s PGN-plus series deliver long jaw strokes and include seals, dirt-resistant round linear guides, and high-strength aluminum-alloy housings to survive dirty industrial environments. (Image source: Schunk)
■ Connectivity to common industrial control networks
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