Connecting rod telescoping mechanism for screw down gear and screw down gear

The invention discloses a connecting rod telescoping mechanism for a screw down gear and the screw down gear, and aims at solving the problems of inconvenient adjusting of space between two box bodies and high cost of the screw down gear in the prior art. The telescoping mechanism comprises a hollow worm, a first connecting sleeve, a second connecting sleeve and a connecting rod; the first connecting sleeve and the second connecting sleeve are connected with the inner wall of the worm by interference fit; a first key slot is formed in one end of the first connecting sleeve; second key slots are formed in the inner wall of the other end of the first connecting sleeve and the inner wall of the second connecting sleeve; keys adapted to the second key slots are formed in one end of the connecting rod. According to the mechanism, the first connecting sleeve and the second connecting sleeve are arranged at intervals, and the connecting rod slides in the worm during connecting, so that the length of the connecting rod extending out from the box bodies changes, the connecting rod is simply connected with different connecting sleeves during rolling switching, and as a result, the space between the two box bodies of the screw down gear can be simply and conveniently adjusted; in addition, other backup connecting rods are not needed, so that the cost is decreased.