Standard_Parts_Catalogue

Page 792 | 2.4 Tensioning with Clamping Mechanisms Toggle Clamps Knee Lever Principle Pneumatic toggle clamps combine the advantages of clamping with the knee lever principle (clamp remains closed even after a loss of pressure) with the capabilities of pneumatic operation. Movement phase 1 The clamping arm opens wide enough that the full surface of the workpiece is exposed, allowing it to be removed or placed into the mechanism without obstruction. Movement phase 2 Even a slight turning of the clamping lever brings the clamping arm with the spindle assembly onto the work­ piece. The arrangement of the three knee joints as shown makes clear that the clamping arm exerts many times the opera- ting force on the lever. However, the toggle clamp is not yet locked in this position; in other words, opposing forces on the clamping arm would open it again. Movement phase 3 When all three joints of the knee lever are in alignment, the maximum clamping force F S is achieved (lever dead point). Movement phase 4 In this position, i.e. the clamping position, the lever dead point is exceeded by a specific amount and the clamping lever is fixed in place by an end stop. This ensures secure locking (self-blocking) of the toggle clamp. The force that can be absorbed by the clamping element in this closed state without lasting deformation is referred to as the retaining force retaining force F H .