| dc.description.abstract | The purpose of this project is to increase cobblestone productivity of our country
Ethiopia, so that it reduces the fatigue of the workers, create goodworking conditions,
increase customary satisfaction and perform uniform tasks. To come into reality, the
project uses direct observation, primary and secondary sources. A quick return
mechanism is an apparatus to produce a reciprocating motion in which the time taken
for travel in return stroke is less than in the forward stroke. It is driven by a circular
motion source (typically a motor of some sort) and uses a system of links with three
turning pairs and a sliding pair. A quick-return mechanism is a subclass of a slider crank linkage, with an offset crank.
Quick return is a common feature of tools in which the action is performed in only one
direction of the stroke, such as shapers and powered saws, because it allows less time
to be spent on returning the tool to its initial position.
Quick-return mechanisms feature different input durations for their working and return
strokes. The time ratio of a QR mechanism is the ratio of the change in input
displacement during the working stroke to its change during the return stroke. Several
basic types of mechanism have a QR action. These types include slider-crank and
four-bar mechanisms. A project on QR mechanism design, within a first course on the
theory of mechanisms, has been found to be effective for exposing students to
concepts of mechanism design and analysis. This paper reviews basic QR
mechanisms, presents a project problem and solution examples, and discusses the
value of inclusion of such project problems within theory-of-mechanism courses | en_US |
