Air compressor using crank mechanism and slotted link
Roberto Magalhães
Air compressor using crank mechanism and slotted link
SYNOPSIS
The purpose of this experiment is to investigate the kinematic movement of a crank and slotted lever quick return mechanism. The investigation aims to show that this is in fact a quick return mechanism and to evaluate the increase in efficiency that this would offer if applied to a machine tool.
INTRODUCTION
Definition of a mechanism
A mechanism is a simplified model, usually in the form of a line diagram, used to reproduce the movement that occurs in a machine. The purpose of this reproduction is to enable the nature of the machine. The purpose of this reproduction is to enable the nature of the motion to be investigated without the hindrance of the various solid bodies which form the elements of the machine. The various parts of the mechanism are called links or elements. Where two links are at
Contact and relative motion are possible, so they are known as a pair. An arbitrary set of links that form a closed chain capable of relative motion and that can be transformed into a rigid structure by the addition of a single link is known as a kinematic chain. To form a mechanism from a kinematic chain, one of the links must be fixed. However, since any one link can be fixed, it follows that there are as many mechanisms as there are links in the chain. The technique of obtaining different mechanisms by fixing the various links in turn is known as inversion.
WORKING PRINCIPLE
Kinematic Pairs
The relative movement between two links in a pair can take different forms. Three types of pairs are known as bottom pairs and these are the ones that occur most frequently: Sliding: as occurs between a piston and cylinder Turning: as occurs with a wheel on an axle Screw movement: as occurs between a nut and bolt All other cases are considered sliding and rolling combinations are called upper pairs. Strictly screw movement is a higher par as it combines turning and sliding. Slider – Crank Mechanism The slider-crank mechanism is well known as the basis of a reciprocating engine. As shown in the diagram below, it consists of three rotating pairs and one sliding pair
Fig. slider-crank mechanism
In the diagram above, link 1 is fixed. If we now fix link 2, this will be considered a
Inverting the mechanism, we obtain the mechanism shown below. This is known as the Whitworth Quick Return Mechanism.
Fig. Air compressor using crank mechanism and slotted link
Fig. slider-crank mechanism
Fig. Air compressor using crank mechanism and slotted link 
