EMPLOYEE WAS ASSISTING WITH A CONVEYOR BELT REPAIR WITH A LOADER. BELT CLAMPS HAD BEEN PUT ON & CABLE COME ALONGS PULLED UP TO HOLD THE TWO ENDS TOGETHER. EE WAS ON THE CONVEYOR WHEN THE LOADER RELEASED THE PULL ON THE BELT & THE BELT ROLLED BACK PINNING EE'S LEG BETWEEN A ROLLER & THE BELT CLAMP.