LINKAGES

LINKAGES

• A series of rigid links connected by joints.• Usually forms a closed chain

• A mechanical linkage is an assembly of bodies connected to manage forces and movement.

• The movement of a body, or link, is studied using geometry so the link is considered to be rigid.

• The connections between links are modeled as providing ideal movement, pure rotation or sliding for example, and are called joints.

• A linkage modeled as a network of rigid links and ideal joints is called a kinematic chain.

Uses of Linkages

• A LINKAGE IS A MECHANISM IF TWO OR MORE LINKS MOVE WITH RESPECT TO A FIXED LINK.

• LINKAGES CAN:i. Take an Input and produce a different Outputii. Alter the shape of motion (curves)iii. Change velocity, acceleration of motioniv. Apply Mechanical Advantage• Expect a lot of ROTATING, OSCILLATING and

RECIPROCATING

Types of arm connector

• Straight-line linkages• Pivot linkages• Toggle mechanisms

Straight-line linkages

Pivot linkages

4-BAR LINKAGES

• Simplest closed-loop kinematic links

REVERSE MOTION LINKAGE:

• As the top rod moves to the left the bottom rod moves to the right. The bars move in opposite directions. Another way of describing this linkage is the the direction of movement in one rod is reversed in the other rod. The fixed pivot is the centre of rotatio

PARALLEL MOTION LINKAGE:

• As the large rod at the top of the diagram moves to the left the two small rods at the bottom move to the right. All the rods are parallel to each other. EXAMPLE.

CRANK AND SLIDER LINKAGE:

• The rods move forwards and backwards in slider. The fixed pivot anchor the linkages to one place. EXAMPLE.

BELL CRANK LINKAGE:

• This linkage allows horizontal movement to be converted to vertical movement. It also works the opposite way round. A practical example of this is the brake mechanism on a bicycle. EXAMPLE.

Toggle mechanisms

• Toggle mechanisms are commonly used within linkages and serve many purposes.

• These purposes include: transferring rotational motion into linear motion, magnify input loads (due to the mechanical advantage that a toggle mechanism affords), and locking the position of a linkage.

CAM

• A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa.

• The cam can be a simple tooth, as is used to deliver pulses of power to a steam hammer, for example, or an eccentric disc or other shape that produces a smooth reciprocating (back and forth) motion in the follower, which is a lever making contact with the cam.

Followers shape

Working circle

Displacement Diagram

Kuiz 3

• Describe TWO examples where cam is applied in industry.