| 摘要 |
<p>An apparatus for driving arches into the ground for the making of a cultivation tunnel comprises a drum-like body made of a pair of wheels interconnected by three transverse arcuate arch supports and rotatably mounted on a chassis. The ends of the arcuate arch supports are pivoted to the rims of the wheels adjacent the wheel spokes but behind them in the direction of rotation of the wheels. The arch supports are held within the two wheels and forced to diverge from the spokes by a spring mechanism. Each arch support defines an outwardly open trough into which an arch is inserted, being held in the trough by hooks that are resiliently biassed into captive position of the arch in its support. A cam assembly on each arch support and on the chassis forces the arch support to move toward the vertical against the bias of the spring mechanism as the ends of the arch start to touch the ground. Further rotation of the wheels drives the arch ends into the ground. When each support and arch therein stand vertical, bars fixed to the spokes engage the hooks of the support and release them from the support, against their bias, to thus free the arch from its support.</p> |
