Magnetic clamping arrangement

A magnetic clamping arrangement (10;

• 210;
• 310;
• 410) for holding the arrangement operably clamped against a ferromagnetic surface (6), the arrangement comprising housing means (12) supporting
• (i) magnet means (16;
• 216;
• 316;
• 416) comprising a core (18;
• 218;
• 318;
• 418) having a plurality of limbs (201, 202, 203;
• 2201, 2202;
• 320;
• 4201, 4202) at least one of which comprises a plurality of elongate ferromagnetic elements 26, each element having at least one dimension transversely to its length much smaller than its length, bundled together such that the ends of said elements define a pole face (221, 222, 223;
• 2221, 2222;
• 322;
• 4221, 4222) of the limb and are slidable with respect to each other in a direction to and from the pole face, to effect conforming abutment with a said ferromagnetic surface,
• (ii) flux generating means (24;
• 2241, 2242;
• 324;
• 424, 425) coupled to the core to cause a flux path between the pole faces and said ferromagnetic surface to effect an attachment force between the magnet means and surface, and
• (iii) element bias means (36;
• 236;
• 336;
• 436), disposed between housing means and core, operable absent magnetic flux to define by the locus of the ends of the elements of each limb a quiescent pole face and exert a restoring force on elements of the bundle displaced away from the quiescent pole face,
• the arrangement being characterised by a body (5), having a datum face (8) adapted to be disposed in overlying relationship with respect to said ferromagnetic surface, carrying the housing means (12) movable with respect to the body in a direction to and from the datum face and attachment means (44), including (a) resilient attachment bias means (46) between the body and core, arranged to bias the core elements towards a position in which the pole faces are recessed with respect to the body datum face, and (b) attachment bias override means (48) arranged to permit an override force to be exerted in opposition to the attachment bias, to expose quiescent pole faces un-recessed with respect to the datum face for abutment with the ferromagnetic surface, and in opposition to the element bias means to permit the elements in abutment with the ferromagnetic surface to conform thereto, the attachment bias means being operable, with the core pole faces attached to the ferromagnetic surface by said magnetic flux and absent said override force, to cause the datum face of the body to exert an abutting force against the ferromagnetic surface.