Support spindle for windable material coils

A support spindle (1) to engage a tubular winding core (2) for winding and unwinding windable material (3) to form a coil (4), comprising:

• A) a central shaft (5) defining a rotation axis (6) and forming:
• a connecting portion (7) on a rear side (8) of the support spindle (1),
• a supporting portion (9) extending from the connecting portion (8) along the rotation axis (6) towards a front side (10) of the support spindle (1),
• a plurality of cam seats (11) formed in the supporting portion (9),
• B) a plurality of locking bodies (12) arranged radially outside the supporting portion (9) and in contact, by means of cam follower members (13), with the cam seats (11),
• C) a supporting cage (14) connected to the central shaft (5) and forming a plurality of guide seats (15) which accommodate and position the locking bodies (12) so that the locking bodies (12) can slide radially to the rotation axis (6) with respect to the central shaft (5) and rotate about the rotation axis (6) with respect to the central shaft (5),
• wherein the cam seats (11) and cam follower members (13) are shaped so that a relative rotation between the locking bodies (12) and the central shaft (5) about the rotation axis (6), along an angular stroke (16), causes a radial displacement of the locking bodies (12) between a radially inner retracted position, and a radially outer expanded position, for disengaging and engaging the support spindle (1) with the winding core (2),
• wherein the cam follower members (13) form a first convex cam surface (17) in contact with a second concave cam surface (18) of the corresponding cam seat (11).