nice book

1. Theory of Mechanisms & Machines
Course Project
Title of the Project:
QUICK RETURN MECHANISM

2. INTRODUCTION
 A quick return mechanism is a mechanism that converts rotary
motion into reciprocating motion at different rate for its two strokes.
When the time required for the working stroke is greater than that of
the return stroke, it is a quick return mechanism. It yields a
significant improvement in machining productivity. Currently, it is
widely used in machine tools, for instance, shaping machines,
power-driven saws, and other applications requiring a working
stroke with intensive loading, and a return stroke with non-intensive
loading.

3.  This mechanism is made of a driving crank and of a driven slider crank in
the considered configuration the fixed pivot of the driven crank is located
on the outside of the circle on which the end of the driving crank moves
this leads to an alternated motion of the slider crank

4.  The angular speed of the driven crank is variable .the duration of the motion for its
part corresponding to the blue arc is shorter than the one related to the red arc
.this is why this device is named as the quick return mechanism ,which was used in
crank shaper with the slow part or the stroke being used for the working time of
the tool and the quick part for the non productive time

5. THEORY
 If we go for the classification of the mechanism then we have simple
mechanism, Means the mechanism with four links whereas the
mechanism with more than four links as known as “compound
mechanism” as we know that mechanism is used that for
transformation of the motion.

6.  When the mechanism has to do specific task it will became a machine in
that case every component should has to design to perform specific tasks
according to the requirement there are various type of mechanism
including, Double crank mechanism, Single slider crank mechanism, Crank
shaper mechanism, but among all the mechanism the common thing is
that all of them are linkage

7. HISTORY
 Whitworth quick return mechanism was developed by the British manufacturer Sir
Joseph Whitworth around 1840.He was a machine tool builder and he sensed that
speed of cutting tool on the shaping machines in his factory were not quick
enough. So he adopted an inversion of the slider crank mechanism and fixed the
crank. In the resultant mechanism backward stroke was faster than the forward
stroke hence this mechanism speeded up the return of the cutting tool to the
beginning of the cutting stroke thus saving time.

8. Working of mechanism:
 Working stroke- theta2 =α
 Return stroke- theta1= β
 Working > Return

𝑇𝑖𝑚𝑒 𝑜𝑓 𝑤𝑜𝑟𝑘𝑖𝑛𝑔 𝑠𝑡𝑟𝑜𝑘𝑒
𝑇𝑖𝑚𝑒 𝑜𝑓 𝑟𝑒𝑡𝑢𝑟𝑛 𝑠𝑡𝑟𝑜𝑘𝑒
=
𝛼
𝛽
=
𝛼
360 𝑜−𝛼
Fig.1.2- working
.
2
Working stroke
1
Return stroke

9. advantages of quick return mechanism
 Whitworth quick return mechanism is a device where reciprocation
motion in forward stroke is slower then the return stroke
 Quick return mechanism A reciprocating motion, for operating the
tool of a shaping machine etc, in which the return is made more
rapidly than the cutting stroke, so as to reduce the idling time.

10. disadvantages of quick return mechanism
 As we know that Quick-Return Mechanism consist of various components these
are used to transformation of motion and they have relative motion with each
other due so some disadvantages will occur.
 As we know that in all type of mechanisms in the common thing is that all of that
are linkages and balancing of linkage is also big problem.
 As there is faster motion in the piston it causes the heat which results in loss of
energy via heat
 And another type of disadvantage is friction in the slider and in piston
 More power is required to work the mechanism as the normal.

12. CONCLUSIONS
 A quick return mechanism is an apparatus that converts circular
motion (rotating motion following a circular path) into reciprocating
motion (repetitive back-and-forth linear motion) in presses and
shaping machines, which are utilized to shape stocks of metal into
flat surfaces, throughout mechanical engineering.

13. REFERENCES
 WWW.Wikipedia.COM
 TCSME.ORG
 Transactions of the Canadian Society for Mechanical Engineering, Vol. 33, No. 3,
2009
 WWW.YOUTUBE.COM