And pre-expander detects material taking joint

The utility model discloses a detection material taking joint of a pre-expander. The device comprises an upper pipe fixed on a discharge box of the pre-expander, the upper pipe is communicated with aninner cavity of the discharging box, a middle pipe is fixedly arranged at the end, back to the discharging box, of the upper pipe, a lower pipe is fixedly arranged at the end, back to the dischargingbox, of the middle pipe, an upper disc is fixedly arranged at the end, facing the middle pipe, of the upper pipe, and an upper hole in the axis direction of the upper disc is formed in the upper disc. The two ends of the middle pipe are sleeved with a front middle disc and a rear middle disc respectively, a front middle hole is formed in the front middle disc, a rear middle hole is formed in therear middle disc, the projection of the front middle hole in the axis direction of the front middle disc coincides with the rear middle hole, and a connecting shaft coaxial with the front middle discand the rear middle disc is