Improved shedding arm pin joint structure of plain loom

The utility model relates to an improved opening arm pivoting structure of a plain loom, which comprises an opening arm and at least one connecting rod set, wherein a swing arm is extended from the opening arm. A plurality of fixed parts are arranged on the top surface and/or the bottom surface of the swing arm, or a plurality of fixed holes are punched on the swing arm at equal intervals in a transverse direction. Pivoting parts are formed at one end of each of connecting rods of each connecting rod set. The pivoting parts comprises bearings and pivot shafts. The pivoting sections of the pivot shafts penetrate through the bearings to form pin joint. The pivot shafts are provided with fixing sections for fixing the pivot shafts at the fixing parts or the fixing holes. The dimension of the pivoting parts can be enlarged by using the structural arrangement, so that the pivoting parts are respectively arranged on the left side and the right side of the opening arm. The strength of the pivoting structure of the opening arm can be increased, and the service life is prolonged.