An apparatus to close, stretch and nail the flanks of a shoe vamp to a respective insole, in particular in machines for assembling shoe parts, comprising:
- a bed;
- column means operatively mounted to the bed and arranged to rigidly support, in an overturned position, a shoe being worked comprised of a vamp and an insole fitted on a respective shoe last;
- two nailing units operatively mounted to the bed on the opposite sides of the column means respectively, and each arranged to act along a flank of the shoe being worked in order to stretch the vamp on the insole and fasten the vamp edge to the insole through the driving in of nails, wherein each nailing unit comprises:
- a nailing hammer designed to carry out the driving in of nails into the shoe;
- an end plate supporting the hammer;
- a movable block engaging the plate in an oscillatable manner about an axis parallel to the longitudinal extension of the shoe;
- preloading means acting between the end plate and the movable block in order to urge the hammer downwardly according to a predetermined preloading force;
- a guide structure extending at right angles to the longitudinal extension of the shoe and slidably engaging the movable block;
- a supporting plate engaging the guide structure in an oscillatable manner about an axis perpendicular to the longitudinal extension of the shoe;
- a transverse-displacement actuator acting on the movable block to bring hammer from a stand-by position in which it is moved apart sideways from the perimetrical edge of the shoe to a work position in which the lower hammer end acts in thrust relation on the vamp edge folded over the perimetrical edge of the insole in order to stretch the vamp;
- and
- at least a longitudinal-displacement actuator acting between the bed and the column means to move the shoe lengthwise according to a predetermined pitch when the hammer of each nailing unit, after having driven in a nail, comes back to the stand-by position;
- the guide structure of each nailing unit slidably acting on the shoe on the side of the insole, in order to transmit to the hammers the variations in height and inclination encountered on the longitudinal shoe extension during the translation of said shoe upon the action of the longitudinal-displacement actuator.