Expansion type rubber sleeve used under well

The utility model relates to an expansion type rubber sleeve for underground use, which comprises an air injection pipe and a rubber sleeve, an air injection hole is arranged on the air injection pipe, the rubber sleeve is sleeved on the air injection pipe and covers the air injection hole, the upper end and the lower end of the rubber sleeve are fixed with the air injection pipe in a sealing way, a folding part is arranged on the rubber sleeve, and the folding part is connected with the air injection pipe. And the folding part is folded towards the inner side of the rubber cylinder. One purpose of the utility model is as follows: after the air injection pipe is pressurized and injected, the rubber cylinder is inflated and expanded, so that the folding part of the rubber cylinder can be expanded and the volume of the rubber cylinder can be expanded, and compared with the scheme of elastic expansion only by the rubber cylinder, the volume variation of the device is larger, so that the volume of the contracted