Manhole cover maintenance and installation device and maintenance method

The manhole cover maintenance and installation device comprises a support, the support is provided with a threaded column in the vertical direction, the upper end of the threaded column is fixedly connected with a multi-edge rod, the support is provided with a positioning pipe used for limiting rotation of the multi-edge rod, and the multi-edge rod penetrates through the positioning pipe and is in sliding connection with the positioning pipe; the lower end of the threaded column is coaxially connected with an abutting disc, the threaded column is in threaded connection with a moving ring, an annular groove is formed in the lower end of the moving ring in the circumferential direction, the moving ring is rotationally connected with a plurality of moving blocks along the annular groove, and positioning rods are hinged to the sides, away from the moving ring, of the moving blocks. A lifting block is arranged at the end, away from the moving block, of the positioning rod, and a plurality of clamping grooves match