ADD System for LRV pantographs
By means of a cylinder-pressure gas unit
arranged in a drive chain and rocking lever, the ADD enables
the pantograph to lower abruptly to avoid damages at the
overhead-line and the pantograph.
Description of Function
The control of the ADD is effected via an electrical signal that is activated in case of horizontal impacts on the collector head.
During initial state the single-action cylinder is retracted. When the ADD responds, the gas generator is activated. The released gas streams into the cylinder and thus extends the piston with the piston rod. The air on side of the piston rod can exhaust through a vent opening at the cylinder. After extension of the cylinder it is retracted again slowly and temporally delayed by external force effect. This is made possible by a permanent vent opening at the cylinder. Due to the gas generator, first the pressure in the cylinder is that high that despite exhausting air from the cylinder the piston remains fully extended and keeps the pantograph in lowest position against the force of the main tension spring.
The movement "Retraction of the Cylinder" and "Extension of the Spindle Drive" are temporally aligned in a way that the pantograph will not leave lowest position.
In addition to the short lowering time of the pantograph a further advantage is that conditional on the system, the pantograph can be re-activated.
If in case of response of the ADD action no or only slight damages to the catenary wire and the pantograph occur it is possible to release the pantograph again via the spindle drive. Thus there is the possibility at least when driving slowly, to run back the vehicle to the next stop or the next depot.
