Concentric gripper handles parts of different sizes

Paul Boughton
When components of different sizes have to be handled alternately, conventional centric grippers quickly reach their limits. In order to cover the whole spectrum of components, gripper fingers or complete grippers have to be exchanged. However, Schunk is introducing a highly efficient alternative in the form of the innovative PZH-plus Long Stroke Gripper. This features a belt drive that eliminates the need for long-stroke actuators within the gripper, as well as the need to exchange top jaws or grippers.
With patented multi-tooth guidance and a housing made of high-strength aluminium, the new gripper offers high performance in a compact package. Compared to similar grippers, the PZH-plus is claimed to provide a gripping force that is twice as high. In order to achieve a certain stroke and force, smaller gripper sizes can be chosen. It saves space, lowers the energy consumption and capital expenditure. Optionally, the PZH-plus can be reliably monitored via magnetic field sensors or inductive sensors.
A further benefit of the new design is the large central bore that provides for workpiece viewing via a camera, feed-through of material, or the gripping of very long workpieces.
From early 2011 the Long Stroke Centric Gripper will be available in four sizes. At a weight between 1.6 and 33kg, the maximum stroke per finger is 20 to 75mm, and the gripping forces are 250 to 3,800N. The gripper is suitable for internal and external gripping of circular workpieces weighing up to 19.3kg. It is said to be suitable for loading machine tools or for handling wheel rims, cast blanks or other components.
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