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EXPERIMENT NO. I

AIM. TO study mechanical actuators.

 THEORY.

An actuator is a type of motor for moin! or controllin! a mechanism or system.It is operated "y a source of ener!y# typically electric current# hydraulic $uid

pressure# or pneumatic pressure# and conerts that ener!y into motion. An

actuator is the mechanism "y %hich a control system acts upon an enironment.

 The control system can "e simple &a '(ed mechanical or electronic system)#

sotl%are*"ased &e.!. a printer drier# ro"ot control system)# or a human or other

a!ent.

Mechanical Actuators

A mechanical actuator functions "y conertin! rotary motion into linear motion

to e(ecute moement. It inoles !ears# rails# pulleys# chains and other deices

to operate. Mechanical elements include the use of lin+a!es# cams# !ears# rac+and pinion# chains# "elt dries# etc.

I. ,inematic chain A four*"ar lin+a!e# also called a four*"ar# is the simplest

moa"le closed chain lin+a!e. It consists of four "odies# called "ars or lin+s#

connected in a loop "y four -oints. enerally# the -oints are con'!ured so the

lin+s moe in parallel planes# and the assem"ly is called a planar four*"ar

lin+a!e.

/ome of its inersions are0

a. 1eam en!ine ". 2oupled locomotie c. Panto!raph d. 3att mechanism.

 The slider cran+ mechanism

A sin!le slider crac+ chain is a modi'cation of the "asic four "ar chain. It consists

of one slidin! pair and three turnin! pairs as sho%n in the '!ure. It has 4

inersions

a. Pendulum pump ". Oscillatin! cylinder en!ine mechanism c. Rotary I2 En!ine

d. 3hit%orth 5uic+ return mechanism

6. 7ou"le slider cran+ chain

A +inematic chain %hich consists of t%o turnin! pairs and t%o slidin! pairs is

+no%n as dou"le slider cran+ chain.

/uch a +inematic chain has three inersions0

a. Elliptical trammel ". /cotch yo+e mechanism c. Oldham mechanism

4. 2am

A cam is a rotatin! or slidin! piece in a mechanical lin+a!e used especially in

transformin! rotary motion into linear motion or ice*ersa... It is often a part of

a rotatin! %heel &e.!. an eccentric %heel) or shaft &e.!. a cylinder %ith an

irre!ular shape) that stri+es a leer at one or more points on its circular path. The

cam can "e a simple tooth# as is used to delier pulses of po%er to a steam

hammer# for e(ample# or an eccentric disc or other shape that produces a

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smooth reciprocatin! &"ac+ and forth) motion in the follo%er# %hich is a leer

ma+in! contact %ith the cam.

 8. ear and !ear train

A !ear or co!%heel is a rotatin! machine part hain! cut teeth# or co!s# %hich

mesh %ith another toothed part in order to transmit tor5ue# in most cases %ithteeth on the one !ear of identical shape# and often also %ith that shape &or at I.st

%idth) on the other !ear. T%o or more !ears %or+in! in tandem are called a

transmission and can produce a mechanical adanta!e throu!h a !ear ratio and

thus may "e considered a simple machine. eared deices can chan!e the

speed# tor5ue# and direction of a po%er source. The most common situation is for

a !ear to mesh %ith another !ear9 ho%eer# a !ear can also mesh %ith a non*

rotatin! toothed part# called a rac+# there"y producin! translation instead of

rotation.

 Types of !ears0 a. /pur !ear ". Helical !ear c. 1eel !ear d. 3orm !ear e. Rac+

and pinion.

:. 1earin!s

A "earin! is a machine element that constrains relatie motion "et%een moin!

parts to only the desired motion. The desi!n of the "earin! may# for e(ample#

proide for free linear moement of the moin! part or for free rotation around a

'(ed a(is9 or# it may preent a motion "y controllin! the ectors of normal forces

that "ear on the moin! parts.

2lassi'cation of "earin!0

a. ;ournal "earin! ". Piot "earin!. c. Thrust "earin!.