Movable pole extension for a magnetic clamping apparatus and magnetic clamping apparatus having such movable pole extension

1. A movable pole extension for a magnetic clamping apparatus ( 1 ) for holding a ferromagnetic workpiece (P), comprising:

a fixed pole member ( 5 ) extending in a predetermined longitudinal direction (X-X) and

at least two pole members ( 6 , 7 ) coupled to said fixed pole member ( 5 ), said at least two pole members ( 6 , 7 ) being movable relative to said fixed pole member ( 5 ),

holder means ( 8 ) operably coupled to said fixed pole member ( 5 ), wherein said holder means ( 8 ):

are movable in said predetermined longitudinal direction (X-X) between a first operating position (P 1 ) and a second operating position (P 2 ) and

operate on said at least two movable pole members ( 6 , 7 ) to hold them in mating contact with said fixed pole member ( 5 );

wherein said holder means ( 8 ) include a hollow member ( 9 ) in slidably mating relationship with said fixed pole member ( 5 ), said hollow member ( 9 ) being able to hold at least one portion ( 5 A) of said fixed pole member ( 5 ) by a form fit between complementary profiles;

wherein said hollow member ( 9 ) comprises an end wall ( 9 A) with side walls ( 9 B) extending therefrom in said longitudinal direction (X-X) to contain said at least one portion ( 5 A) of said fixed pole member ( 5 ).

2. The movable pole extension as claimed in claim 1 , wherein said at least two movable pole members ( 6 , 7 ) are each movable in different directions relative to said predetermined longitudinal direction (X-X).

3. The movable pole extension as claimed in claim 1 , further comprising an abutment means ( 10 ) for urging said holder means ( 8 ) to slide in said longitudinal direction (X-X) between said first operating position (P 1 ) and said second operating position (P 2 ), thereby limiting the stroke of said holder means ( 8 ) relative to said fixed pole member ( 5 ).

4. The movable pole extension as claimed in claim 1 , wherein said fixed pole member ( 5 ) has a receptacle ( 11 ) that defines at least two curved surfaces ( 12 , 13 ) relative to said predetermined longitudinal direction (X-X) and a bottom ( 14 ), said at least two movable pole members ( 6 , 7 ) being each in slidably mating contact with one respective surface of said at least two surfaces ( 12 , 13 ).

5. The movable pole extension as claimed in claim 4 , wherein said at least two curved surfaces ( 12 , 13 ) are oriented in opposite directions, converging towards said bottom ( 14 ).

6. The movable pole extension as claimed in claim 1 , further comprising elastic means ( 17 ) operating on said at least two movable pole members ( 6 , 7 ) for holding said at least two movable pole members ( 6 , 7 ) in contact with said fixed pole member ( 5 ).

7. The movable pole extension as claimed in claim 6 wherein said elastic means ( 17 ) include at least one spring interposed between said at least two movable pole members ( 6 , 7 ) and said fixed pole member ( 5 ).

8. The movable pole extension as claimed in claim 1 , wherein said fixed pole member ( 5 ) has fastener means ( 15 ) for fixation thereof to a clamping plate ( 2 ) of said magnetic clamping apparatus ( 1 ).

9. The movable pole extension as claimed in claim 1 , wherein said holder means ( 8 ) and said fixed pole member ( 5 ) have a circular plan shape.

10. The movable pole extension as claimed in claim 1 , wherein said holder means ( 8 ) and said fixed pole member ( 5 ) have a polygonal or elliptic plan shape or a polygonal shape with rounded corners.

11. A magnetic clamping apparatus comprising:

a frame adapted to contain a plurality of pole pieces, each of said plurality of pole pieces having a ferromagnetic pole member which defines a clamping surface,

at least one of said plurality of pole pieces is designed to be associated to a movable pole extension ( 4 ),

said movable pole extension ( 4 ) comprising:

a fixed pole member ( 5 ) extending in a predetermined longitudinal direction (X-X) and

at least two pole members ( 6 , 7 ) coupled to said fixed pole member ( 5 ),

said at least two pole members ( 6 , 7 ) being movable relative to said fixed pole member ( 5 ),

holder means ( 8 ) operably coupled to said fixed pole member ( 5 ), said holder means ( 8 ) being movable in said predetermined longitudinal direction (X-X) between a first operating position (P 1 ) and a second operating position (P 2 ) said holder means operating on said at least two movable pole members ( 6 , 7 ) to hold them in mating contact with said fixed pole member ( 5 ),

wherein said holder means ( 8 ) at least partly act as a collector for a magnetic flux generated by said magnetic apparatus ( 1 ) and said holder means ( 8 ) include a hollow member ( 9 ) in slidably mating relationship with said fixed pole member ( 5 ), said hollow member ( 9 ) being able to hold at least one portion ( 5 A) of said fixed pole member ( 5 ) by a form fit between complementary profiles.

12. The movable pole extension as claimed in claim 11 , wherein said fixed pole member ( 5 ) has at least two planar surfaces inclined to said predetermined longitudinal direction (X-X), said at least two movable pole members ( 6 , 7 ) being each in slidably mating contact with one respective inclined surface of said fixed pole member.

13. The movable pole extension as claimed in claim 12 , where at least two curves surfaces ( 12 , 13 ) define respective sliding surfaces ( 12 A, 13 A) for said at least two movable pole members ( 6 , 7 ), said respective sliding surfaces ( 12 A, 13 A) being oriented in opposite directions.

14. The movable pole extension as claimed in claim 13 , wherein each of said respective sliding surfaces ( 12 A, 13 A) forms an angle of 40° to 50°, preferably 45°, relative to said predetermined longitudinal direction (X-X).

15. The movable pole extension as claimed in claimed 12 , comprising elastic means ( 17 ) operating on two movable pole members ( 6 , 7 ) for holding said at least two movable pole members ( 6 , 7 ) in contact with said fixed pole member ( 5 ).

16. A magnetic clamping apparatus comprising a frame adapted to contain a plurality of pole pieces, each of said plurality of pole pieces having a ferromagnetic pole member which defines a clamping surface, characterized in that at least one of said plurality of pole pieces is designed to be associated to a movable pole extension ( 4 ), said movable pole extension ( 4 ) comprising:

a fixed pole member ( 5 ) extending in a predetermined longitudinal direction (X-X) and

at least two pole members ( 6 , 7 ) coupled to said fixed pole member ( 5 ), said at least two pole members ( 6 , 7 ) being movable relative to said fixed pole member ( 5 ),

holder means ( 8 ) operably coupled to said fixed pole member ( 5 ), wherein said holder means ( 8 ):

are movable in said predetermined longitudinal direction (X-X) between a first operating position (P 1 ) and a second operating position (P 2 ) and

operate on said at least two movable pole members ( 6 , 7 ) to hold them in mating contact with said fixed pole member ( 5 ).

17. A movable pole extension for a magnetic clamping apparatus ( 1 ) for holding a ferromagnetic workpiece (P), comprising:

a fixed pole member ( 5 ) extending in a predetermined longitudinal direction (X-X) and—at least two pole members ( 6 , 7 ) coupled to said fixed pole member ( 5 ), said at least two pole members ( 6 , 7 ) being movable relative to said fixed pole member ( 5 ), holder means ( 8 ) operably coupled to said fixed pole member ( 5 ), wherein said holder means ( 8 ):—are movable in said predetermined longitudinal direction (X-X) between a first operating position (P 1 ) and a second operating position (P 2 ) and—operate on said at least two movable pole members ( 6 , 7 ) to hold them in mating contact with said fixed pole member ( 5 ); wherein said fixed pole member ( 5 ) has a receptacle ( 11 ) that defines at least two curved surfaces ( 12 , 13 ) relative to said predetermined longitudinal direction (X-X) and a bottom ( 14 ), said at least two movable pole members ( 6 , 7 ) being each in slidable mating contact with one respective surface of said at least two surfaces ( 12 , 13 ); wherein said at least two curved surfaces ( 12 , 13 ) are oriented in opposite directions, converging towards said bottom ( 14 ).

18. A removable pole extension for a magnetic clamping apparatus ( 1 ) for holding a ferromagnetic workpiece (P), comprising:

a fixed pole member ( 5 ) extending in a predetermined longitudinal direction (X-X) and

at least two pole members ( 6 , 7 ) coupled to said fixed pole member ( 5 ),

said at least two pole members ( 6 , 7 ) being movable relative to said fixed pole member ( 5 ), holder means ( 8 ) operably coupled to said fixed pole member ( 5 ),

said holder means ( 8 ) being movable in said predetermined longitudinal direction (X-X) between a first operating position (P 1 ) and a second operating position (P 2 ), said holder means operating on said at least two movable pole members ( 6 , 7 ) to hold them in mating contact with said fixed pole member ( 5 ),

wherein said holder means ( 8 ) at least partly act as a collector for a magnetic flux generated by said magnetic apparatus ( 1 ) and said holder means ( 8 ) include a hollow member ( 9 ) in slidably mating relationship with said fixed pole member ( 5 ), said hollow member ( 9 ) being able to hold at least one portion ( 5 A) of said fixed pole member ( 5 ) by a form fit between complementary profiles;

wherein said at least two movable pole members ( 6 , 7 ) are each movably in different directions relative to said predetermined longitudinal direction (X-X); and

wherein said hollow member ( 9 ) comprises an end wall ( 9 A) with side walls ( 9 B) extending therefrom in said longitudinal direction (X-X) to contain said at least one portion ( 5 A) of said fixed pole member ( 5 ).