(57) Such excavator comprises a supporting column (1) of structural cross section, a hydraulic
pump (2) and associated control box (13) for feeding the hydraulic system, a motor
(3) driving said pump (2), an articulated arm (4), a working tool (5) and a control
system (6) for the arm (4) and the tool (5). A pivot (11) extending with its axis parallel to the vertical longitudinal axis of
the column (1) is mounted on the projection (1d) of the column (1) and the articulated
arm (4) is secured by means of the hinge (16) to the pivot. Such pivot (11) permits
the articulated arm (4) to be rotated through 180° about the axis of the pivot. The
hinges (16) also permit the articulated arm (4) to be lifted. The working tool (5) is mounted at the distal end of the portion (4b) of the articulated
arm (4). All rotary movements of the articulated arm and its portions as well as the
working tool are hydraulically controlled by means of hydraulic rams (12, 4c, 4d and
5a). The motor (3) is an electric motor or an internal combustion engine and may be located
adjacent the column (1) or outside the well (21). The column (1) is secured by means of the brackets (7) to anchoring means (8) or by
means of the guide (1a) to a rail on the wall (20) of the well (21). In this manner the excavator can perform its excavating work within the well by penetrating
gradually more and more thereinto as the depth on the well increases. A plurality
of anchoring means or rails may be mounted at the same depth of the wall of the well
to give the excavator a range of maneuvrability of 360°. This excavator permits to make vertical or inclined wells of any cross section and
shape, particularly-wells of small diameter or of oblong cross-sectional shape which
cannot be made by conventional excavators. Further, this excavator is particularly useful for excavations under difficult working
conditions such as in places that are not easily accessible or cannot be easily supplied
with electric power.
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