One-piece multipole plate for a magnetic holding apparatus, process for making such plate and magnetic apparatus using such plate

1. A magnetic holding apparatus for holding ferrous workpieces, comprising a frame ( 2 ) adapted to contain a plurality of pole pieces ( 13 ), each of said plurality of pole pieces ( 13 ) having a ferromagnetic pole member which defines the holding surface part ( 13 A), a solenoid ( 3 ) located around a reversible magnet ( 4 ) and a plate ( 11 ), said plurality of pole pieces ( 13 ) extend from said plate ( 11 ) and are formed of one piece with said plate ( 13 ), wherein said plate ( 11 ) is associated with the frame ( 2 ) in a plate position so as to define a holding surface ( 12 A) of said apparatus ( 12 ) in which the pole pieces ( 13 ) are not visible.

2. A magnetic holding apparatus as claimed in claim 1 , wherein said plurality of pole pieces ( 13 ) are connected with each other by a connecting portion ( 11 A) of said plate ( 11 ), so that said plurality of pole pieces ( 13 ) are partially short-circuited during activation of said magnetic apparatus.

3. A magnetic holding apparatus as claimed in claim 2 , wherein:

each pole piece of said plurality of pole pieces ( 13 ) has at least one face adapted to define a holding surface ( 13 A) and

the section of said connecting portion ( 11 A) is less than 30% of the area of said at least one face adapted to define said holding surface ( 13 A).

4. A magnetic holding apparatus as claimed in claim 3 , wherein said connecting portion ( 11 A) has a thickness (S′) equal to the residual dimension between the thickness (S) of the plate ( 11 ) and a first depth (H) of said plurality of grooves ( 15 , 18 ).

5. A magnetic holding apparatus as claimed in claim 3 , wherein said connecting portion ( 11 A) has a thickness (S′) equal to the residual dimension between the thickness (S) of the plate ( 11 ) and said first depth (H) of said plurality of grooves ( 15 , 18 ) as measured from a surface ( 13 B) opposite said holding surface ( 13 A) to the holding surface ( 13 A) and a second depth (h) of said plurality of grooves ( 15 , 18 ) as measured from said holding surface ( 13 A) to said surface ( 13 B) opposite said holding surface ( 13 A).

6. A magnetic holding apparatus as claimed in claim 1 , wherein said plate ( 11 ) comprises a plurality of grooves ( 15 , 18 ) which are adapted to define the periphery of each of said plurality of pole pieces ( 13 ) and to form said connecting portion ( 11 A) for connection of said plurality of pole pieces ( 13 ) to each other, said plurality of pole pieces ( 13 ) have a circular plan section, said grooves ( 15 , 18 ) being circumferential grooves, whose center (C) is at the center of each pole piece ( 13 ).

7. A magnetic holding apparatus as claimed in claim 1 , wherein said plate ( 11 ) comprises a plurality of grooves ( 15 , 18 ) which are adapted to define the periphery of each of said plurality of pole pieces ( 13 ) and to form said connecting portion ( 11 A) for connection of said plurality of pole pieces ( 13 ) to each other, at least one of said plurality of grooves ( 15 , 18 ) extends parallel to an axis (X) of a reference system (X-Y) with orthogonal Cartesian axes (X-Y) and at least one second of said plurality of grooves ( 15 , 18 ) extends parallel to another axis (Y) of said reference system (X-Y) with orthogonal Cartesian axes (X-Y).

8. A magnetic holding apparatus as claimed in claim 1 , wherein each of said plurality of pole pieces ( 13 ) comprises a first through hole ( 14 ), said first through hole ( 14 ) extending through the thickness (S) of said plate ( 11 ).

9. A magnetic holding apparatus as claimed in claim 8 , wherein said first through hole ( 14 ) has threads for receiving the shank of a pole extension.

10. A plate ( 11 ) for a magnetic clamping apparatus ( 12 ), said apparatus ( 12 ) having a plurality of pole pieces ( 13 ), said plurality of pole pieces ( 13 ) extend from said plate ( 11 ) and are formed of one piece with said plate ( 13 ) said plate ( 11 ) comprises a plurality of grooves ( 15 , 18 ) which are adapted to define the periphery of each of said plurality of pole pieces ( 13 ) and to form a connecting portion ( 11 A) for connection of said plurality of pole pieces ( 13 ) to each other

wherein said plurality of pole pieces have a circular plan section, said grooves ( 15 , 18 ) being circumferential grooves, whose center (C) is at the center of each pole piece ( 13 ).

11. A plate as claimed in claim 10 , wherein each of said plurality of pole pieces ( 13 ) comprises a first through hole ( 14 ), said first through hole ( 14 ) extending through the thickness (S) of said plate ( 11 ).

12. A plate as claimed in claim 11 , wherein said first through hole ( 14 ) has threads for receiving the shank of a pole extension.

13. A plate as claimed in claim 10 , wherein:

each pole piece of said plurality of pole pieces ( 13 ) has at least one face adapted to define a holding surface ( 13 A) and

the section of said connecting portion ( 11 A) is less than 30% of the area of said at least one face adapted to define said holding surface ( 13 A).

14. A plate as claimed in claim 10 , wherein said connecting portion ( 11 A) has a thickness (S′) equal to the residual dimension between the thickness (S) of the plate ( 11 ) and a first depth (H) of said plurality of grooves ( 15 , 18 ).

15. A plate as claimed in claim 10 , wherein said connecting portion ( 11 A) has a thickness (S′) equal to the residual dimension between the thickness (S) of the plate ( 11 ) and said first depth (H) of said plurality of grooves ( 15 , 18 ) as measured from a surface ( 13 B) opposite said holding surface ( 13 A) to the holding surface ( 13 A) and a second depth (h) of said plurality of grooves ( 15 , 18 ) as measured from said holding surface ( 13 A) to said surface ( 13 B) opposite said holding surface ( 13 A).