| 摘要 |
<p>Propulsion apparatus (10) is disclosed for urging a trenching arm (12) forward against the advancing face of an elongate trench being dug by the trenching arm. The propulsion apparatus (10) includes a propulsion member (22) which is engageable with the base wall of the trench such that the trenching arm (12) may be urged forward relative to the engaged propulsion member (22). The propulsion member (22) may then be withdrawn from engagement with the base wall and retracted towards the trenching arm (12) before commencing a further propulsion cycle. The propulsion member (22) is also operable to cooperate with the trenching arm (12) in excavating a starting slot at the beginning of a new trench.</p> |
