Basic Link Mechanisms-Ay
Transcript of Basic Link Mechanisms-Ay
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Link is a rigid body paired with other parts of a machine for thepurpose of transmittingforce or motion.
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Classifcation o links : Rigid link -> Which does not undergo any deformation while
transmitting motion.
Flexible link -> Which is deformed appreciably while transmittingmotion with out eecting the function.
Fluid link -> Tube or container capable of transmitting motion bypressure or compression.
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Types o constraints : Completely constrained motion : If the constrained motion is obtained
by its own links.
Successully partially! constrained : If the constrained motion is notcompletely constrained.
"ncomplete constrained : If the motion between the links takes place inmore than one direction.
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#inematic pair : A joint between two links that permits relativemotion. In this links are pairing elements.Classifcation o #inematic pair :
a! $ccording to nature o relati%emotion :• Sliding pair : Which permits relative sliding between its links.
•Turning pair : Which permits only turning motion between links.
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•Rolling pair : Two links are connected in such that one of the link rollsover the other.
•
Scre& pair : The relative motion between the two links is thecombination of sliding and turning.
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rical pair : One of the link in the form of a sphere and it is rotated in a !ed li
b! $ccording to (ature o Contact :• Lo&er pair : Which permits surface contact between two links
while in motion and it is completely constrained. • )ig'er pair : Which permits only point or line contact betweentwo links while in motion and it is incompletely constrained.
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rding to (ature o *ec'anical arrangement o
• Closed pair : Which links of kinematic pair held together mechanically
so as to have a constrained motion. Contact breaks only bydestruction o links!+
• ,pen pair : &lements of a pair that are not held together mechanically
are unclosed pairs.
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#inematic C'ain : It is an assembly of links in which the relativemotion between them e!ists and motion of each relative to the other isdenite.
' ( )p*%Where ' ( +o. of links, p ( +o. of pairs
a! " L .p-/ condition is satised then the link is -ompletely -onstrainedand have specic relative motion.b! " L .p-0 condition is satised then the inematic chain is locked andaccept no relative motion.c! " L .p-1 condition is satised then the inematic chain is
incompletely constrained and relative motion between the links is notdenite.
Fig - a
Fig - b Fig - c
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tures : +o relative motion between the links or it is also called as 'ocked chai
2xamples : /ridges, roof truss, machine frame etc.,
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*$C)"(2 *2C)$("S*#. The arrangement of links withconstrained motion for doing useful
work.
#. The arrangement of links withone link !ed and the motion of
other links connected.
). It modies energy and doesuseful work.
). It modify and transmit motion.
0. A machine is a practicaldevelopment of any mechanism.
0. A mechanism is a working modelof any machine.
%. &!amples 1 $team engine,$haper, $crew jack etc.,
%. &!amples 1 Watch, Typewriter,$pring toys etc.,
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'ever*-rank mechanism 2 'ink 3a4 rotates and link 3c4 oscillates
ersions o a 3uadratic C'ain :
&!amples 1 4eam 2ngine 2 It is used to convert rotary motion to
reciprocating motion of the piston. 5$hown in g*)6
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basic78uickreturn.gif
ithworth 9uick return mechanism:'ever crank mechanism 1
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0. ;ouble -rank mechanism 2 'ink 3b4 and 3d4 make completerevolutions.
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/+ 5att *ec'anism67ouble Le%er mec'anism
Watts7 linkage.gif Watt<s7'inkage7=ear7$uspension.gif
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ering gear mec'anism 67ouble Le%er mec'anism:
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I denotes Instantaneous centre.
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-rank and $lotted 'ever 9uick =eturn>echanism
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