While pulling out of the hole with the 3rd stand of drill pipe and the TDS positioned at 40' above the drill floor, an object fell onto the starboard side of the rotary table. Operations were immediately suspended and the area secured. Upon investigating, it was found that the TDS alignment cylinder clevis pin had sheared, with the nut portion of the clevis backing off the cylinder and subsequently falling onto the drill floor. This nut portion of the clevis weighed 1.4 kg and descended 40', with the nearest person situated 3' away from the initial impact point.