Magnetic device for gripping and clamping a workpiece in a machining unit or machining line
A magnetic device for gripping and clamping a workpiece in a machining unit or on a machining line including a magnetic plate having a distribution of high-energy permanent-magnet modules, which can be electrically activated. An auxiliary workpiece-holder plate made of ferromagnetic material rests on a main surface of the magnetic plate and has a top surface shaped in a way complementary to a surface of the workpiece that rests thereon. The workpiece rests on the top surface of the auxiliary workpiece-holder plate only in points corresponding to some supporting pads, while the facing surfaces of the workpiece and auxiliary workpiece-holder plate are kept slightly set apart from one another for most of their extension.
1. A magnetic device for gripping and clamping a workpiece in a machining unit or on a machining line, said device comprising;
a magnetic plate including a distribution of high-energy permanent-magnet modules, which can be electrically activated, said plate having two plane and opposite main surfaces, giving out onto which are the poles of said permanent-magnet modules;
an auxiliary workpiece-holder plate, made of ferromagnetic material, having a base surface resting on a main surface of the magnetic plate and a top surface for receiving the workpiece thereon;
means for precise referencing in position of the workpiece on the auxiliary workpiece-holder plate,
said referencing means
comprising at least two locating pins carried by said workpiece-holder plate and having axes orthogonal to said main surface of the magnetic plate, said locating pins being prearranged for being received within seats formed in the workpiece so as to enable a precise referencing of the position of the workpiece with respect to the auxiliary workpiece-holder plate in the plane of the main surface of the magnetic plate,
said auxiliary workpiece-holder plate having a top surface shaped in a way complementary to the surface of the workpiece that is to rest thereon; and
said top surface of the auxiliary workpiece-holder plate having a plurality of supporting pads for resting of corresponding portions of the bottom surface of the workpiece in such a way that the bottom surface of the workpiece and the top surface of the auxiliary workpiece-holder plate are kept slightly set apart from one another for most of their extension.
2. The magnetic device according to claim 1 , further comprising a covering shroud for protection of the magnetic plate, having a metal-sheet structure made of non-ferromagnetic material, with a top wall resting on the main top surface of the magnetic plate and having an opening, the boundary of which follows the perimeter of the base surface of said auxiliary workpiece-holder plate so as to enable said auxiliary workpiece-holder plate to project through said opening.