Magnetic workholding device

A switchable permanent electromagnet, comprising:

• external pole means having an inner cylindrical wall defining a cavity with a central axis and a base at the bottom of said cavity, said external pole means including a top surface transverse to said central axis and formed of a ferromagnetic material, said top surface circumscribing a constructive flux receiving annulus;
• reversible magnetic means located in said cavity including a cylindrical core having a magnetic axis aligned with said central axis for establishing a normal magnetic polarity in an inactive state;
• a cylindrical inner pole formed of a ferromagnetic material operatively coupled to said core and inwardly radially spaced from said inner cylindrical wall, said inner pole having a top surface coplanar with said top surface of said external pole means;
• sleeve means interposed between said inner cylindrical wall and said inner pole, said sleeve means formed of a permanent magnetic material and having a magnetic polarity transverse to said central axis and magnetically aligned with said normal magnetic polarity of the core whereby an internal magnetic circuit is established in the inactive state through said reversible magnetic means, said poles, said core and said permanent magnet to the exclusion of said workpiece, said reversible magnetic means being operative to reversing said normal magnetic polarity of said core whereby an external circuit is established with the workpiece.

A switchable permanent electromagnet system, comprising:

• plate means having an upper working surface;
• an array of cylindrical cavities formed in said plate means, each of said cavities being defined by a cylindrical side wall having a opening at said working surface with a central axis and a base wall below said upper working surface transverse to said central axis, said plate means being formed of a ferromagnetic material, said top surface circumscribing a constructive flux receiving annulus surrounding each cavity;
• a cylindrical reversible magnetic core located in said cavities and having an outer cylindrical surface radially inwardly spaced from said cylindrical side wall of an associated cavity defining therebetween an annular recess, said core means having a magnetic axis aligned with said central axis for establishing a normal magnetic polarity in an inactive state;
• solenoid means in said recess operatively surrounding said core means;
• a cylindrical inner pole formed of a ferromagnetic material operatively coupled to said core and inwardly radially spaced from said inner cylindrical wall, said inner pole having a top surface coextensive with said working surface of said plate means;
• sleeve means interposed between said cylindrical side wall and said inner pole, said sleeve means formed of a permanent magnetic material and having a magnetic polarity transverse to said central axis and magnetically aligned with said normal magnetic polarity of the core whereby an internal magnetic circuit is established in the inactive state through said reversible magnetic means, said poles, said core and said permanent magnet to the exclusion of said workpiece;
• channel means in said plate means communicating with said cavities;
• connector means disposed in said channel means and connected at one end to said solenoid means;
• control means connected at said other end of said connector means and operatively connected therethrough with said solenoid means for reversing said normal magnetic polarity of said core whereby an external circuit is established with the workpiece to said constructive annulus, the arrangement being such that said cavities are relatively spaced to define constructive pole areas therearound sufficient to prevent magnetic interference between said magnetic circuits.

A switchable permanent electromagnet system, comprising:

• plate means formed of a ferromagnetic material having a planar working surface;
• an irregularly spaced plurality of cylindrical cavities formed in said plate means defined by cylindrical side walls having openings at said working surface and a central axis orthogonal to said upper working surface and a base located below said working surface;
• a cylindrical reversible magnetic core located in said each of said cavities engaging said base, said reversible magnetic core having an outer cylindrical surface radially inwardly spaced from said cylindrical side wall of an associated cavity, said core means having a magnetic axis aligned with said central axis for establishing a normal magnetic polarity in an inactive state;
• solenoid means in said cavity between said core and said side wall of said cavity;
• a cylindrical inner pole formed of a ferromagnetic material engaging and operatively coupled to said core and inwardly radially spaced from said inner cylindrical side wall, said inner pole having a top surface coextensive with said working surface of said plate means;
• an annular permanent magnetic material mechanically and magnetically coupled between said side wall and said inner pole and having a magnetic polarity transverse to said central axis and magnetically aligned with said normal magnetic polarity of the core whereby an internal magnetic circuit is established in the inactive state through said reversible magnetic means, said poles, said core and said permanent magnet to the exclusion of said workpiece;
• and means for reversibly momentarily energizing said solenoid means for reversing the magnet polarity of said pole.