PANTOGRAPH
Introduction: In 18th century Jesuit Christoph schreiner inventor of the pantograph is a system of mechanical linkages which produces the motion of one point of the linkage at a second point usually at an increase or decrease size this is also called as parallel motion. Pantograph is a current collection device used to collect and transfer electrical energy 25kv from catenary to traction system which is mounted on electrical insulation of the car body top of the roof.
Two type of Pantograph operation (i) spring operated (ii) Air bellow operation most commonly used in railways, because for smooth operation actuated by air either rise or low by help of baby compressor through cam chain mechanism (for rising pantograph above 2.5 bar main pressure is necessary) Lx panto prefer by faiveley under 100kmph metro trains.
Main parts: Base frame, isolator, lower arm, upper arm, main spring, balance rod, self lubrication carbon strip (new size 15mm if it fall back to 6mm will be replaced), compressed air system assembly, damper, MED valve used to prevent raise of pantograph beyond set value, servomotor in spring operation. Specifications: Max extension 1.9M, service extension 1.5M & contact force 70N. Flow of operation:- Auxiliary compressor which deliver air pressure by working compressor through battery at initial stage 0 bar pressure → Pneumatic control unit regulates require air pressure → Pantograph rise.
LOWER PAIR MECHANISM: Basic idea of pantograph used to reduce or increase scale size of shape or configuration, O is a fixed point we have parallelogram ABCD so AB is equal to BC and DA is equal to CB. CD extend to point O, CB extend to point E & point OAE lies in a same straight line (Rigid mechanism with link of dimension is same. Two triangle 1.ODA 2.OEC similar triangle with same angle OD/OC=OA/OE=DA/CE.
Here again A'B'C'D' again forms a parallelogram in second new displacement. In case: AD=20cm A'D' also equal to 20cm. Hence here proved length of link does not change only traces are change, for brief understanding follow up below image.
