Apparatus for changing the operating stroke of a punch press

Claim 1

Apparatus for changing the operating stroke of a punch press comprising a drive shaft provided with a connecting rod means, a double eccentric for mounting the connecting rod means, said double eccentric being arranged to be driven by the drive shaft and comprising an inner eccentric and an eccentric sleeve, said inner eccentric having a radial bore, said eccentric sleeve having internal teeth, a locking pin guided in the radial bore of the inner eccentric, said locking pin being provided at one end with teeth means cooperating with the internal teeth of the eccentric sleeve, means for spring-loading the other end of said locking pin, a central adjustment spindle means cooperating with the locking pin, wherein through rotation of the adjustment spindle means the locking pin can be displaced against the spring-load out of engagement with the internal teeth of the eccentric sleeve, an axially displaceable bushing surrounding the adjustment spindle means, a slotted plate spring means with which cooperates the axially displaceable bushing, means for selectively fixedly retaining said eccentric sleeve, a drive element means, the plate spring means in its stressed state operatively connecting the inner eccentric with the drive element means, whereby when the locking pin is displaced against the spring-load means the inner eccentric can be rotated with respect to the fixedly retained eccentric sleeve, and therefore the eccentricity of the double eccentric and the drive stroke of the punch press can be adjusted.