Parallel Motion Linkage
From DT Online
Description
The Parallel Motion Linkage is a special case of Four Bar Chain in which the equal in lengths of opposite sides of the parallelogram ensure that input and output motions remain parallel.
Features and Uses
There are several good examples of these in action. The Pantograph is a parallel motion linkage used by electric trains to pick up power from overhead cables. Another use is the Pantograph used in drawing to copy sketches. Other uses are in containers such as tool boxes and sewing boxes which open up to reveal multiple shelves and containers which need to be held horizontal.
James Watt used a Parallel Motion Linkage to ensure the movements of both the piston and the pump rod in his Beam Engines remained parallel.
Animations
- Examples from Nguyen Duc Thang's YouTube Channel 2100 Animated Mechanical Mechanisms
| Application of Parallelogram Mechanism - self-adjusting step ladder for wharfs. The steps remain horizontal as the water level rises and falls. | Pantograph Mechanism - OABD is a parallelogram and COE lie in a straight line with O a fixed point. Figures traced by pen E and pen C are similar and the scale factor is k.(OE/OC = BE/BD = k = constant) | ||
| Two-Pan Balance - Parallelogram mechanisms are applied for this type of balance. | Two-Pan Balance - Parallelogram mechanisms are applied for this type of balance - the violet sliding mass is moved to balance the pan such that the yellow bar is horizontal. |
