Controllable rotary brake

A controllable rotary brake, comprising:

• two non-magnetically permeable isolating rings, spaced apart from each other in an axial direction, wherein each of the non-magnetically permeable isolating rings has a bottom wall, and an even number of penetrating holes are formed on the bottom wall;
• a shaft, rotatably inserted in the two non-magnetically permeable isolating rings, adapted to pivot relative to the two non-magnetically permeable isolating rings;
• an even number of magnetic field generating portions, two ends of each of the magnetic field generating portions are tightly fitted to the corresponding penetrating holes of the two non-magnetically permeable isolating rings;
• at least one resistance disc, sleeved on the shaft, spaced apart from one of the non-magnetically permeable isolating rings;
• at least one magneto-rheological fluid layer, filling between the at least one resistance disc and one of the non-magnetically permeable isolating rings, wherein the at least one magneto-rheological fluid layer contacts the at least one resistance disc and one end of each of the magnetic field generating portions;
• and
• two ring-shaped members, wherein a number of the at least one resistance disc is two, the two ring-shaped members are disposed in the two non-magnetically permeable isolating rings, each of the two ring-shaped members is tightly fitted to a notch of each of the resistance discs, and the shaft is adapted to drive the two resistance discs to pivot relative to the two ring-shaped members.