Apparatus for adjusting two end positions limiting a clamping stroke

Abstract

In a clamping unit, particularly in a chuck with exchangeable jaws, one terminal clamping position is reached during opening when the clamping jaws approach the limit of stability. The other end position is reached during closing when the jaws approach the point where they cannot be moved any further. However, both end positions must be so far removed from the rest position or the stop position that a residual clamping stroke remains which insures safe clamping even then in the terminal clamping positions. The terminal clamping positions are different for chucks of varying sizes, and so are the clamping strokes. To adjust the end positions as well as for determining the attainment of these end positions, an apparatus is provided comprising a transmitter device and a sensor device which reacts to approach or contact. Spacing is changeable with the adjustment of the clamping jaws. In order to prevent accidental erroneous adjustment, at least one specific part of the transmitter or sensor device is associated with each clamping unit and is changed with or made to function with its corresponding clamping unit.