| 摘要 |
The invention relates to a frustoconical drag trowel which is drawn through a pipe or the like to trowel a layer of mortar or other plastic lining material therein. The frustoconical trowel has a small leading end of relatively fixed diameter and a large trailing end which is adapted to be expanded and contracted in a diametral direction. The present disclosure provides a novel means within the large end of the trowel for exerting a resilient expansive force thereagainst. This means comprises a hollow torus adapted to bear against the interior of the large end of the trowel along the perimeter of the torus. The torus is of elastic material but is provided with a winding thereabout for restaining the torus against expansion in the direction of its cross-sectional diameter whereby fluid pressure within the torus causes the same to exert an expansive force in the direction of its circumference and thus urge the large end of the trowel body diametrally outwardly to exert a resilient expansive force within the large end of the trowel.
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