| CPC B25B 23/108 (2013.01) [B25B 13/065 (2013.01)] | 8 Claims |

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1. An elastic element, comprising:
an inner annular wall;
an outer annular wall connected to and surrounding the inner annular wall; and
a groove formed between the inner annular wall and the at least one outer annular wall;
wherein the elastic element has a closed end formed where the inner annular wall and the outer annular wall are connected, and the groove is provided between the outer annular wall and the inner annular wall in an annular manner;
the inner annular wall comprises at least one protruding portion, the inner annular wall has a height measured from the closed end to an end portion of the at least one protruding portion, the outer annular wall has a height measured from the closed end to an end portion of the outer annular wall, and the height of the inner annular wall is greater than the height of the outer annular wall.
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