Modular permanent magnet chuck
A permanent magnet chuck for holding or lifting workpieces is formed of two overlying/underlying flat surfaced chuck layers having a common center of rotation. In each chuck layer an even number of permanent magnet plates radiate from the center of rotation at equal angles with blocks of magnetically soft material between them. The permanent magnet plates are magnetized so that the interposed soft magnet blocks exhibit alternating N-S magnetic polarities. The organization of the permanent magnet plates and soft magnet bodies is matching and complementary so that relative rotation of the chuck layers magnetically activates or de-activates the chuck.
1. A magnetic chuck comprising:
a first chuck layer and a second chuck layer, each of the chuck layers having a common center of rotation, a common periphery, and flat parallel upper and lower surfaces where one of the flat surfaces of one of the chuck layers is the working surface of the chuck for attracting and holding a workpiece;
the first chuck layer comprising an even number of permanent magnet plates, each permanent magnet plate having an inner end at the center of rotation of the first chuck layer and extending radially outwardly to the periphery, each permanent magnet plate having opposed plate surfaces perpendicular to the upper and lower surfaces of the chuck layer, the plate being magnetized with its north magnetic pole (N) and its south magnetic pole at its opposing plate surfaces, and each plate having opposed plate edge surfaces extending from the inner end of the plate to the periphery;
the first chuck layer further comprising a block of magnetically soft material interposed between each pair of magnetized permanent magnet plates around the center of rotation, with the magnetic poles of the plates being oriented so that the magnetically soft blocks are magnetized with alternating N and S polarities around the center of rotation, each block of magnetically soft material being larger than its adjacent permanent magnet plates and each block having opposing magnetically soft block surfaces lying, respectively, in the flat surfaces of the first chuck layer;
the second chuck layer comprising permanent magnet plates and soft magnet blocks that are complementary in shape and position to the permanent magnet plates and soft magnet blocks of the first layer, the first and second chuck layers being assembled in the chuck so that magnetized soft magnet blocks of one chuck layer can overlie magnetized soft magnet blocks of the other chuck layer;
the chuck being activated for magnetic attraction of a workpiece when the first and second chuck layers are positioned with respective overlying/underlying soft magnet blocks of the same magnetic polarity; and
the chuck being inactivated for magnetic attraction of a workpiece when the first and second chuck layers are positioned with respective overlying/underlying soft magnet blocks of opposite magnetic polarity;
whereby the working face of the chuck extends from the center of rotation to the periphery and comprises magnetically soft block surfaces that are each larger than the interposed permanent magnet plate edge surfaces.
2. A magnetic chuck as recited in claim 1 further comprising means for rotating one of the first and second chuck layers between a chuck activated position and a chuck inactivated position.
3. A magnetic chuck as recited in claim 1 in which the first and second chuck layers are of equal thickness.
4. A magnetic chuck as recited in claim 1 further comprising non-magnetic material separating the central edges of the permanent magnet plates of each chuck layer and non-magnetic material spacing the permanent magnet plates in the respective chuck layers.
5. A magnetic chuck as recited in claim 1 in which each chuck layer comprises four soft magnet blocks of the same top and bottom surface area.
6. A magnetic chuck as recited in claim 1 in which comprises six soft magnet blocks of the same top and bottom surface area.
7. A magnetic chuck as recited in claim 1 further comprising:
a non-magnetic frame enclosing the first chuck layer, the frame further enclosing the second chuck layer with its upper surface positioned against the lower surface of the first chuck layer and with the lower surface of the second chuck layer exposed as the workpiece holding surface of the chuck.
8. A magnetic chuck as recited in claim 1 further comprising:
a rotor connected to the upper surface of the first chuck layer;
a non-magnetic frame enclosing the rotor and first chuck layer, the frame further enclosing the second chuck layer with its upper surface positioned against the lower surface of the first chuck layer and with the lower surface of the second chuck layer exposed as the workpiece holding surface of the chuck.
9. A magnetic chuck as recited in claim 8 in which the workpiece holding surface of the chuck consists essentially of surfaces of soft magnet blocks spaced by radial strips of non-magnetic material.
10. A magnetic chuck fixture for holding workpieces of different contact surface areas, the magnetic chuck fixture comprising:
a frame having a magnetic chuck holding body, a workpiece holding surface on the body, and a surface on the body opposite the workpiece holding surface; and
a plurality of individual magnetic chucks as recited in claim 1 contained in the chuck layer holding body, the individual magnetic chucks being spaced in the chuck layer holding body with individual workpiece holding surfaces aligned in the workpiece holding surface of the fixture body, each of the magnetic chucks being individually actuatable for accommodating the contact surface area of a workpiece.
11. A magnetic chuck fixture for holding workpieces of different contact surface areas, the magnetic chuck fixture comprising:
a frame having a magnetic chuck holding body, a workpiece holding surface on the body, and a surface on the body opposite the workpiece holding surface; and
a plurality of individual magnetic chucks as recited in claim 1 contained in the chuck layer holding body, the individual magnetic chucks being spaced in the magnetic chuck holding body with identical individual workpiece holding surfaces aligned in the workpiece holding surface of the fixture body, each of the magnetic chucks being individually actuatable for accommodating the contact surface area of a workpiece.
12. A magnetic chuck fixture for holding workpieces of different contact surface areas, the magnetic chuck fixture comprising:
a frame having a magnetic chuck holding body, a workpiece holding surface on the body, and a surface on the body opposite the workpiece holding surface; and
a plurality of individual magnetic chucks as recited in claim 1 removably attached in the chuck layer holding body, the individual magnetic chucks being spaced in the magnetic chuck holding body with identical individual workpiece holding surfaces aligned in the workpiece holding surface of the fixture body, each of the magnetic chucks being individually actuatable or removable for accommodating the contact surface area of a workpiece.