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 The propulsion member may then be withdrawn from engagement with the base wall and retracted towards the trenching arm before commencing a further propulsion cycle.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

Abstract: Cutting apparatus is described which has teeth mounted on a carrier such as an endless belt or chain for advancement through material to be cut. The cutting apparatus includes a tooth mounting assembly which is supported on the carrier whereby a tooth supported thereby may be moved between an extended position at which the tooth's cutting edge extends beyond a side of the carrier and a stowed position. There may also be provided locking lugs for operatively maintaining the tooth in its extended position.

Abstract: A propulsion apparatus is disclosed for urging a trenching arm forward against the advancing face of an elongate trench being dug by the trenching arm. The propulsion apparatus includes a propulsion member which is engageable with the base wall of the trench such that the trench arm may be urged forward relative to the engaged propulsion member. The propulsion member may then be withdrawn from engagement with the base wall and retracted towards the trenching arm before commencing a further propulsion cycle. The propulsion member is also operable to cooperate with the trenching arm in excavating a starting slot at the beginning of a new trench.

Abstract: A trenching apparatus (10) is for excavating deep trenches in which inground concrete retaining or foundation walls may be formed. The trenching apparatus (10) has a crawler base (11) on which a carrier assembly (14) is pivotally supported by pivots (16) whereby it may be tilted by rams (17) to maintain the platform horizontal. An automatic control device (64) is provided for this purpose. The carrier assembly (14) has a pair of rails (18/19) along which a carriage (21) may move. The carriage (21) supports a sleeve (24) through which a trenching arm (25) may be lowered to excavate a trench section as the carriage (21) is driven along the rails (18/19).