PANTOGRAPH MECHANISM

Pantograph is a linkage constituting of five link connected with pin joints to form revolute pairs. It is connected in a manner based on parallelograms so that the movement of one point, in tracing an image, produces identical movements by second point. In order to understand pantograph and its application we need to go through some basic terms associated with mechanisms.

A link is defined as a rigid body having two or more pairing elements which connect it to other link is the frame of the machine and is called the fixed link.

Types of Links:

Rigid : It undergoes no deformation; Example: crank, connecting rod.
Flexible : Partial deformation; Example: springs, belts, ropes
Fluid : Motion is transmitted by this link by deformation.

kinematic pair:The two links or elements of a machine, when in contact with each other, are said to form a pair. If the relative motion between them is completely or successfully constrained (i.e. in a definite direction), the pair is known as kinematic pair.

(a) Lower pair: When the two elements of a pair have a surface contact when relative motion takes place and the surface of one element slides over the surface of the other, the

pair formed is known as lower pair.

(b) Higher pair: When the two elements of a pair have a line or point contact when relative motion takes place and the motion between the two elements is partly turning and partly

sliding, then the pair is known as higher pair. A pair of friction discs, toothed gearing, belt and rope drives, ball and roller etc

kinematic chain :When the kinematic pairs are coupled in such a way that the last link is joined to the first link to transmit definite motion, it is called as kinematic chain

Mechanism is a combination of various links which are capable of having relative motion with respect to one another.
Machine is the combination of number of such mechanisms used to carry out a particular tasks.

Pantograph is used to reproduce to an enlarged or a reduced scale and as exactly as possible the path described by a given point.

It consists of a jointed parallelogram ABCD .It is made up of bars connected by turning pairs.The bars BA and BC are extended to O and E respectively, such that OA/OB =AD/BE

Thus,for all relative positions of the bars, the triangles OAD and OBE are similar and the points O, D and E are in one straight line. It may be proved that point E traces out the same path as described by point D. If a line drawing is traced by the first point D , an identical, enlarged, or miniaturized copy will be drawn by a pen fixed to the point E. Other than that pantograph and its modifications can be used in the following areas.