Pneumatic grippers with angled finger action: In these grippers, the actuated ends of the fingers are pinned to a fixed pivot point. Upon application of pneumatic power, a piston action and mechanical wedge element cause the fingers to swing closed (or in other variations, open) like French doors. In the open position, the jaws wing outward beyond the gripper body or project straight out. In the closed (typically grasping) position, the tips of the gripper fingers tilt inward to close into a tapered grasping shape. One design caveat when using these grippers is that, unlike parallel-finger types, angled fingers have limited strokes and generate a gripping force that’s variable along the actuation stroke. That said, angled finger grippers under direct piston action can have exceptionally high gripping force — up to 2,300 N or higher. Higher finger Counts: three and four-finger grippers Where two-finger pneumatic grippers are inappropriate to handle an operation’s workpieces, three and four-finger grippers (and even five-finger grippers in specialty humanoid-type robotics applications) can provide better gripping support and stability. To be clear, though: all such grippers are far less common than two-finger grippers … and only three-finger grippers are common in industrial
applications. Their higher level of applicability comes at a cost, but three-fingered grippers can grasp workpieces and other items with more complex or challenging geometry. So-called self-centering three-finger pneumatic grippers include a trio of fingers even spaced (120° apart on a machine chuck) that necessitate finger swap-outs for an operation change. These close inward to grip workpieces at a center point. In contrast, so-called adaptive three-finger pneumatic grippers set two fingers together and the third to oppose them like a thumb. Most common on mobile robotics, such grippers can pick up objects in several ways to accommodate variations on a given workpiece geometry.
Jaw and finger pneumatic grippers can take the form of single and double-action grip types as well. In single-acting grippers, the force of compressed air generates the gripping motion and force. Once the supply is shut off, the fingers return to and stay in their original position thanks to the action of a simple compression spring. In contrast, double-acting grippers require compressed air actuation for both the grip and release motions. In fact, double-acting grippers may be capable of both internal and external gripping as described above.
Common pneumatic- gripper applications
Pneumatic grippers are widely used in industrial settings — especially for automated workcells, assembly and production lines, machine tending associated with advanced manufacturing, hazardous plant areas, and logistics as well as automated warehousing operations. A small but growing array of commercial, recreational, and consumer robotics applications (including mobility bionics) also make use of pneumatic grippers. Consider pneumatic grippers for material handling in food and beverage processing and packaging equipment. Here, the clean operation of pneumatics
Internal gripping and double acting
Though the majority of pneumatic grippers are used for grasping or cradling parts around their exterior (contacting outer object surfaces) internal gripping operations are essential to many assembly applications. Here, the gripper fingers open to grasp objects with hollow geometries from within. In some cases, grippers can be tasked with both external and internal gripping operations — though must be designed to have both capabilities.
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