Patent ID: 7621514

Claim:
A clamping apparatus, comprising: a clamping case; a shaft mounted in the clamping case for sliding movement in an axial direction of the shaft, wherein said shaft is pushed with a first pushing member; a clamping arm attached to the shaft, wherein a work is disengageably clamped by the clamping arm; a first engaging member disposed within the clamping case; a first retainer, wherein the first engaging member is engaged with the shaft by the first retainer in a first stroke; a first elastic member with a first spring constant and providing a first elastic force, wherein the first elastic force of the first elastic member is transmitted to the shaft through the first retainer in the first stroke, and wherein the first elastic member coaxially receives a first portion of the shaft; a second engaging member disposed within the clamping case; a second retainer slidably disposed in the clamping case, wherein said second retainer is pushed with a second pushing member, and wherein the second engaging member is engaged with the shaft by the second retainer in a second stroke; and a second elastic member with a second spring constant and providing a second elastic force, wherein the second elastic force of the second elastic member is transmitted to the shaft through the second retainer in the second stroke and the second spring constant is larger than the first spring constant, and wherein the second elastic member coaxially receives a second portion of the shaft, wherein said first pushing member is a rod that is aligned with said second pushing member, said second pushing member being a circular protrusion that is detached from said clamping case, and said shaft is actuated by contact with the first pushing member; wherein in a releasing position in which the shaft is not engaged with either the first engaging member and the second engaging member the first engaging member is held in the first retainer, the second engaging member is held in the second retainer and the shaft is adapted to be detachable from the clamping case.