Permanent magnetic lifting device

A permanent magnetic lifting device, comprising:

• a housing, at the bottom of which is a clamping surface for clamping objects;
• at least a fixed magnet, set in said housing relatively fixed to the housing;
• and
• a turnable magnet, set in said housing relatively turnable to said fixed magnet, wherein when said turnable magnet is in a first position relative to said fixed magnet, the magnetic force generated by said fixed magnet and said turnable magnet to said clamping surface is zero magnetic force;
• when said turnable magnet is in a third position relative to said fixed magnet, the magnetic force generated by said fixed magnet and said turnable magnet to said clamping surface is the maximum magnetic force;
• the permanent magnetic lifting device further comprising a positioning mechanism for second position, wherein when the positioning mechanism for second position positions said turnable magnet in the second position relative to said fixed magnet, said fixed magnet and said turnable magnet generate trial clamping magnetic force to said clamping surface for clamping objects, the trial clamping magnetic force being higher than zero magnetic force and lower than maximum magnetic force.