(57) A safety device in working-plateform elevators and the like. The elevator comprises
two interconnected booms (4 and 7), the lower one (4) of which is mounted to a chassis-mounted
stand (3). The working platform or personnel carrier (10) which is connected to the
upper boom, is maintained in position by upper and lower parallel arms (11 and 12).
These arms are interconnected by a link (13). The upper boom movements relative to
the lower boom is controlled by a hydraulic piston-and-cylinder unit (15).
The device is automatically activated upon occurrence of a predetermined angle between
the upper boom (7) of the elevator and ground level or is manually operated via controls
from the platform. The device comprises a linkage system comprising four link arms
(17, 18, 19, 20) interconnecting the hydraulic piston-and-cylinder unit valve with
a segment (21). The latter is actuated either by an abutment member (22) on the upper
boom or by an actuating means operated from the platform. Movement of the segment
resulting from such actuation is transferred via the linkage system to the valve,
and the lower boom is lowered. The safety device ensures that the elevator booms cannot
assume positions beyond the intended operational range of the elevator and that electric
faults and the like cannot prevent lowering of the platform.
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