Anti-disengagement screw and nut assembly

The invention discloses an anti-disengagement screw and nut assembly, and belongs to the field of rod piece connecting structures in turnout switching devices. The anti-disengagement screw and nut assembly comprises a screw, an opening pin, a nut and a stop ring sleeving the screw. The screw is provided with an external thread and a clamping groove in the axial direction of the screw. The nut is provided with an internal thread matched with the external thread of the screw. A boss matched with the clamping groove is arranged on the stop ring. The nut is fixedly connected with the stop ring through the opening pin. By means of the anti-disengagement screw and nut assembly, after the nut is screwed down, the stop ring and the nut are connected through the opening pin; when a train passes bya turnout, train wheel pairs impact on switch rails, and an expression pull rod bears stress in multiple directions; and since the stop ring is matched with the clamping groove of the screw through the boss, the rotation prob