The document discusses the four bar chain mechanism. It consists of four rigid links connected in the form of a quadrilateral by four pin joints. One link is fixed while the others move. It is the simplest closed loop linkage with three moving links, one fixed link, and four pin joints. This mechanism allows for the conversion of rotary motion to reciprocating motion as seen in devices like the beam engine. Variations of the four bar chain can create different mechanisms and complex linkages can be formed by combining multiple four bar chains. Recent uses include steering mechanisms for human powered vehicles and improved robot hand designs.

1. The Four Bar Chain
Mechanism
PREPARED BY
MILAN MAKWANA
190043119046

2. The Four Bar Chain
• It is much preferred device for
mechanization and control of motion due to
its simplicity and versatility
• It consist of four rigid links which are
connected in the form of a quadrilateral by
four pin joint.
• Fig shows link 1 is fixed and other links are
in motion.

3. The Four Bar Chain
• It is impossible to have a four bar linkage if length of one of the link is greater
than the sum of the other three.
• A variety of useful mechanism can be formed from a four link mechanism
through slight variation such as changing the character of the pairs,proportion of
links and many complex link mechanism can be formed formed from
combination of two or more such four link mechanism

4. Flexibility in four bar chain
• Is the simplest of all closed loop linkage
• Have three moving link , one fixed link and 4 pin joints
• There is only one constraint another linkage , which
defines a definite motion

5. Inversions of four bar chain
• Beam engine
• Watts indiacator mechanism
• Connecting rod of locomotive

6. Beam engine
• A part of mechanisms of a beam engine which consists
of four links , is shown In fig
• In this mechanism when the crank rotates about the
fixed centers A the lever oscillates about a fixed centre
D.
• The end E of the lever CDE is connected to a piston rod
rod which reciprocates due to the rotation of the crank.
• In other words, the purpose of this mechanism is to
converts rotary motion into reciprocating motion

7. Watts indicator mechanism
• A WATT'S indicator mechanism which consist of four links, the
four links are A, AC, CE and BFD. The displacement of the link
BFD is directly proportional to the gas or steam pressure, this
pressure of gas/steam used act on the indicator plunger.
complete/clear lines indicates the position at starting time of
mechanism and the dotted lines represents the position when
the gas/steam pressure acts on indicator plunger.
• The link E used move upwards when indicator plunger raises
by the help of gas pressure, and the remaining links used to
change there position according pressure act on indicator
plunger.

8. Connecting rod of locomotive
• In this there is four links A,B,C,D link
AB is fixed and link DC is connecting
rod
• Link AD is driver and link CB is
driven.

9. Latest advancements in four bar chain in HPVC
ground vehicle
• The steering mechanism for human power vehicle
• Where the tire has to rotate equal angle with or some preferred angle more than
handle
• The two pairs of equal links are selected to design and fabricate the steering
mechanism for HPV obeying grass off criterion.

10. Four bar chain in robotics
• To improve the operating performance of robots end-effector, a humanoid robot
hand based on coupling four-bar linkage was designed.
• An improved transmission system was proposed for the base joint of the thumb.
• a prototype of the humanoid robot hand was produced by a three-dimensional
printer, and a kinematics simulation example and the workspace solving of the
humanoid robot hand were carried out.

11. Thank you.