Design of Ergonomic Comfort Chair

International Research Journal of Engineering and Technology (IRJET) e ISSN:2395 0056

Volume: 09 Issue: 06 | June 2022 www.irjet.net p ISSN:2395 0072

Design of Ergonomic Comfort Chair

1,2,3,4,5Department of Mechanical Engineering, Bharati Vidyapeeth College of Engineering, Navi Mumbai ***

Abstract- For many people rising from a seating position can be a painful experience due to the inflammation of their joints. To overcome this problem, we have designed a chair that supports a person while sitting down as well as standing up without using any external power source. The design of the chair is based on 2 port bi stable compliant mechanism. Bi stable mechanism are mechanism with 2 stable state and only require force to actuate between these states. The chair is ergonomically designed such that it is comfortable and reduces the stress on the person’s knee while standing on sitting. The chair design of the chair is modelled in Solid works for better graphical representation.

Key Words: Compliant Mechanism, Comfort Chair, Bi stable Mechanism, Tin lid Mechanism.

1. INTRODUCTION

As humanity strive to improve their living condition through various methods, they started to ignore their health. Large populationoftheworldhasstartedtosufferfrombackandkneepainsincetheiryoungyears.Manypeopledon’thaveproper bodyposturewhilesitting.Slowlyitreachesthepoint ofagonizingpainandinsomecases,itincreasestosucha degreethat even painkillers are ineffective. Some elderly people are unable to sit or stand up without any support, this has a negative influenceontheirdailylife.Thesolutiontothisproblemcanbeintheformofan“comfortchair”.Butcomfortchairsfoundon themarketareexpensiveandarebasedonactuatorsandcomplexpneumatic.Theyrequireexternalelectricalenergy.Which is not readily available in many developing countries such as India. Thus, there is a need for a comfort chair based on an energyconceptthatdoesnotrequireelectricenergy.

So, wedecided to build a comfort chairthat will be affordable and durable. This comfort chair will be based on the bi stable compliantmechanism

A. What is a Comfort Chair?

Acomfortchairisa large,comfortablechair,typicallyanarmchair.Ashumansstartedtosecuretheirnecessitieseasily,they startedtofocusonotherluxuriousproductstomaketheirlifecomfortablyonesuchproductisthecomfortchair.Sobasically, itisachairdesignedforthepeoplewhoneedtositinoneplaceforlonghoursfortheirworkorindailylife.

Toperform various activities.Ourcomfortchairisachairthatsupportsapersontostandfromaseatedposition.Itdoesthis by gently pushing a person towards the standing position. It also reduces the stress on the knee while sitting down by reducingthejerkbygivinggentlesupport.Itisparticularlyaimedatpeoplewhohaveconditionsthatleadtoinflamedjoints. Thesepeoplehavedifficultytostandfromaseatedposition.Thecomfortchairgentlypushesthepersonwhoissittingonit to astandingpositionwhentheywanttostand.Thus,beingofgreathelpparticularlytoolderpeople.

B. Targeted Customer Base

In this world, many diseases result in a person suffering from back pain or unable to sit for long hours such as Rheumatoid Arthritis, Bursitis, Avascular necrosis, diffuse idiopathic skeletal hyperostosis and many more [1]. And the approximate population affected by this is huge. As well as there are many more people looking for a comfortable chair to sit, especially peopleworkinginthefieldsuchastheITindustryneedtoworkinthecrampedworkspace.Toavoidthehealthproblem,they need the comfort chair. At the same time, some like to spend their free time in front of the television and it was found that mostpeoplewhilewatchingTValwayskeepbadpostureandthischairisalsoaimedfortheelderlypeoplewhohavetrouble sittingaswellasgettingupfromthechairandneedsupporttodoso.Itisalsoforthepeoplewhoareinthekindofjob they havecontentiouslysitandget upatrapidintervals.

International Research Journal of Engineering and Technology (IRJET) e ISSN:2395 0056

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C. What is a Compliant Mechanism and Why?

A compliant mechanism can be defined as a single piece of the flexibility of its members rather than from rigid body joints alone.Sucha mechanism,withbuilt inflexiblesegments,issimplerand replacesmultiple rigid parts, pin joints,andadd on springs[2].Hence,itcanoftensavespaceandreducethecostsofparts,materials,andassemblylabor.Otherpossiblebenefits ofdesigningcomplianceintodevicesmaybereductionsinweight,friction,noise,wear, backlash,andimportantmaintenance. Therearemanyfamiliarexamplesofcompliantmechanismsdesignedinasinglepiecethatreplacedrigidlinkmechanisms[3].

Wecansimplymanufactureasingle piecefullycompliantmechanismviainjectionmolding,extrusionandrapidproto typing for medium size devices, or using silicon surface micro machining and electroplating techniques for compliant micro mechanisms[4].Althoughacompliantmechanismgivesmul tipleadvantages,itisdifficulttodesignandanalyze.Mostofthe currentcompliantmechanismdesign,however,mustbeperformedwithouttheaidofaformalsynthesismethodandisbased ontheintuitionandexperienceofdesigners.Severaltrialsanderroriterationsusingfiniteelementmodelsareoftenrequired toobtainthedesiredmechanicalperformance.

So, it can be summarized as complaint mechanism have longer life highly flexible comfort to mass produce and have better compactness that general rigid as well as tradition mechanism and the best part it is that this mechanism is highly energy efficient

2. PROBLEM STATEMENT

Formanypeoplesittingaswellasrisingfromaseatedpositioncanbeapainfulexperienceduetoinflammationoftheirjoints. While there are several existing chairs designed to address this problem, most use electrical actuators or complex hydraulic systems. Since electrical power is not available everywhere for the entire day, especially in developing countries, there is a need for a comfort chair that gives support during rising from the chair without using external by changing from lower to upperstablestate.

3. METHODOLOGY

Astherearevarioustypechairsaredesignedforapersonwhoworksformthesamesittingpositionlongtimetoincreasetheir productivity and to reduce low back injuries. The easy chair work on a bi stable statically balanced mechanism to solve this problemwithoutusinganyexternalpower.Themainmechanismoftheeasychairisbelowtheseatingplatform.Thereisapre compressedmetalstripinthebuckledformattachedtopinned pinnedends.ThestripismadeupofAlloysteel.Asthestrip followsthebi stablemechanism,sowhenapersonsitsonachairthestripchangespositionfromuppertolowerstablestate withoutgivinganybumping effecttothebody.Thislowerstatehelpsthepersonto relaxthebody.Duringdesigncomfortof theseat,backrest,handrest,andlegsareconsidered.Forrisingfromthelowerstableposition,themechanismistriggered by applying slight force on the chair arms by arms and strip of the chair helps the person to rise up by changing from lower to upperstablestate.Duetothispersoncaneasilyrisefromthechairwithouttakinganyloadonthebodystablemechanism.The chair is designed to gently propel from a seated position. The chair has 2 stage states 1st when the seat is in an inclined positionandposition2nd whentheseatisinhorizontalposition.

International Research Journal of Engineering and Technology (IRJET) e ISSN:2395 0056

4.DESIGN

4.1. Customer Requirement

Tosatisfyandheightenthecustomersatisfactionwedesignedthecomfortchairwhileanalyzingthefollowingfactors.

Table:1 ConsumerRequirementChart

CustomerNeeds

CustomerRequest Requirements

Itshouldbesafetogetinandgetout(shouldnotslideback).

Safety

Theseatshouldbecomfortabletositinforalongduration. Comfort

Shouldassistinrising

Ease ofEgress/Gettingup

Shouldbeadjustableintermsofweightoftheperson,backsupport,etc. Adjustability

Shouldbeattractive Aesthetics

Shouldbeaffordabletothelowermiddleclass Affordability Shouldbecomforttomanuallymovearound Portability

Shouldhavealifethatiscom parabletoastandardchair. Durable

Fig-1:BasicDesign

Whentheseatisininclinedpositiontheweightofthepersonsittingontheseatactsatthe1stportofthemechanismthusthe mechanismactuatestothe2ndpositions.Whenthepersonsittingwantstostandthearmofthechairactsas2ndportofthe mechanism.Thus,actuatingthemechanismtothefirstpositionaswellaspropellingthepersontowardsthestandingposition [5].

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International Research Journal of Engineering and Technology (IRJET) e ISSN:2395 0056

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4.2. Final Design

Thisdesignconsists ofa basicchairmodel witha fewmodificationsforproviding guideways andsupporttothemechanism. Theseatisapartwithahingeprovidedinthefront.Thishingeisinsertedintotheholeprovidedinthechairthisenablesthe seat to be raised and rotated along the hinge. The bi stable mechanism is placed under the seat. The mechanism is inserted intothehingeprovidedinthechair.Thehandleshaftsareinsertedintotheguidesprovidedinthechair.Theguidesconstrain the motion of the handle to one direction. The connecting rod connects the mechanism to the handle converting the rotary motionofthemechanismintolinearmotion.

Fig 2:FinalDesign

Whenapersonsitsonthechairthemechanismwillactuatefromthefirststatetothesecondstate.Thisalsoraisesthehandle. Whenthepersonwantstogetup,hepressesthehandledownward.Thisexertsaforceonthemechanismactuatingitbackto thefirststateaswellaspushingthepersonoutofthechairintoastandingposition.Springsareprovidedsothattheamount of force that needs to be exerted on the handle can be reduced. The spring stores energy when the person is sitting. It also preventsthejerkwhenthemechanismistransitioningfromthefirststatetothesecondstate.

4.3. Essential Parts of comfort Chair

4.3.1 Connecting Rod

Therodonthebi stablemechanismmakesarotarymotionwhenitmovesfromonestatetoanother.Butthehandlecanonly moveinalinearmotion.Theconnectingrodactsthesamewayasaconnectingrodinasingleslidermechanismconvertingthe rotarymotionintolinearmotion.Itismadeofsteel.

Fig-3:ConnectingRod

4.3.2.

International Research Journal of Engineering and Technology (IRJET) e ISSN:2395 0056

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Bi stable Mechanism

Thebi stablemechanismisamechanismwithtwopointsofstabilityandrequiresanexternalforcetomovefromonepointof stabilitytoanother.Thismechanismconsistsoftwoparts,acylindricalpartwithtwoslotsforthebi stablestripsandtwo pre stressedstrips.Thestripsaremadeofalloyspringsteelandthecylindricalholderismadeofmildsteel.

Fig-4:Bi stableMechanism

4.3.3.

Spring

Springisanelasticobjectwhichstocksmechanicalenergy.Inthismechanism,coilspringsareused.Whenapersonsitsonthe chair the displacement caused is stored as mechanical energy in the spring. This also prevents a jerking when the person is sitting as the spring will slow down the motion of the seat towards the horizontal position. The stored energy is used later whentheseatisbeingraisedtherebyreducingtheamountofforcethatneedstobeexertedonthehandleofthemechanism. The spring should be designed such that it provides enough force to assist in raising the seat but the force should not be so greatthatittriggersthemechanismbyitselfsincethatwouldmakethebi stabilityofthemechanismredundant.

Fig 5:Spring

4.3.4. Basic Chair Model

The chair serves as the part main body which holds the entire mechanism collectively. This basic chair model has been modifiedtousea bi stable mechanism.Ahinge isprovidedonthechairforthemechanism.Thishingeultimatelycarriesthe entireforcethat isexerted onthemechanism.Guide ways areprovidedalong the armofthechair tosupport thearm ofthe mechanism.Ahorizontalbaseisalsoprovidedtosupportthespring.Aslotisprovidedforthehingepartoftheseataswellas ahorizontalextrusiontosupporttheseatinahorizontalposition.

4.3.5. Seat

International Research Journal of Engineering and Technology (IRJET) e ISSN:2395 0056

Volume: 09 Issue: 06 | June 2022 www.irjet.net p ISSN:2395 0072

Fig:6 BasicChairModel

Theseatisthepartonwhichtheuserwillsit.Itneedstohavebothfunctionalitiesaswellascomfort.Theseatneedstobeable tomovebetweenahorizontalpositionandaninclinedposition.Thus,ametalsheetwithahingeattheendisused.Themetal sheetneedstobestrongenoughtocarrytheweightofthepersonwithoutanydeformation.Thehingeisinsertedintotheslot providedonthechairthatletstheseatrotatealongtheaxisofthehinge.Acushionisalsoprovidedsothatpeoplecansitonit comfortablyforalongduration.

Fig: 7 Seat

Fig:8 Handle

Thehandleconsistsofametalplatethatisweldedtoarodwhichhastappedontheotherend.Therodispassedthroughthe guiding structure of the chair which allows motion only in a single direction. Cushions are provided on the metal plates for bettercomfort.

4.4. Material Selection

While considering the various requirement for bi stable mechanism we shortlisted with two different material we can use theyareasfollows.

International Research Journal of Engineering and Technology (IRJET) e ISSN:2395 0056

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Material Comparison

Properties

Density

Alloyspring steel Titanium Grade2

7.86g/c 4.5

Tensile m3220 g/cm3 Strength GPa 344 Maximum operating 246°C GPa 426.667 temperature 125.5 °C Elasticmodulus GPa Price Rs170/ 105GPa Kg Rs1200/Kg

Table:2 MaterialSelection

AlthoughtheTitaniumgrade2ismoresuitableforcompliantbi stablemechanismduetoitssuperiormechanicalproperties, due to its high cost it is preferred to use alloy spring steel. Although alloy spring steel is comparably cheap and has a good factor of safety. But the lifetime of mechanism and the smoothness of bi stability behavior only go to tolerable limits. this condition has to be compromised. The advantage of allotting spring steel lies in the fact that it is easily available and is consideredasoneofthegreatmaterialsformassproduction.

Thesuitablematerialforthebasicchairmodeliscustomizedasperthecustomerdemand.Thepreferablematerialsarewood, metal, or other strong materials, like stone or Acrylic, Wicker. As for the regular mass production Fiberglass or Polypropylene/MouldedPlasticshouldbefavorable.

Thehandleisthepartthattheuserusestoactuatethemechanism.Theforcethatisexertedonthearmgetstransferredto the mechanismthroughtheconnectingrod.Thehandleonlymoveslinearly.Theguidingstructureonthechairhelpstoguidethis motion.

Cushionsfortheseatarefashionedfrompolyurethanefoam,polyesterfiber,down,cotton,latex,orcotton wrappedsprings.

Forthespringandsingleslidermechanismweselectedarehighcarbon,alloysteel,andstainless steelwires.

5. WORKING

TwoPortBi stableMechanismisBi stablemechanismshavetwostableequilibriumpositions.Theenergylevelislowatboth of the two stable positions. There is an unstable equilibrium position that has a high energy level between the two stable equilibrium positions. Power input is not needed for bi stable mechanisms to maintain any of their two stable positions. Actuation is only necessary to switch from one stable position to another. Because of the high energy in stable equilibrium position,abi stablemechanismwillresistitselfawayfromitsstableequilibriumpositionunderacertainamountofexternal disturbance. When a bi stable mechanism is actuated and driven away from one stable position, it snaps to another stable positionfromtheunstableequilibriumposition.

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Fig:9 EnergyvsPosition[5]

The bi stable mechanism is a mechanism with two stable equilibrium positions. In most planar bi stable mechanisms, the pointandlineofactionoftheactuationforcestoswitchfromstate1tostate2isthesameasthatfromstate2tostate

1.In other words,theyare “single port bi stablemechanisms.For e.g.,inswitch,theline ofactionforactuation between on andoffstateisthesame.

Bi stablemechanismwithtwodifferentportsforactuationiscalleda2 portbi stablemechanism,forexample,theclick clack tin lid mechanism. Consider the click clack tin lid mechanism. The diagram shows how it can be switched between its two stablestates. It hastwo force free stable states (i.e., bi stable)and it can be operatedatthetwo ports. The easy chairisalso basedonsimilarprincipals.

Fig.10 Click ClackTin lidMechanism[5]

6.MECHANISM

Themechanismisinitiallyinthefirststatepushingtheseattoaninclinedposition.Whenapersonsitsonthechairtheforceis appliedonthemechanismonitsfirstport.Whenthisforceisgreaterthanacriticallimitthemechanismwillactuatetowards the second state and the seat will be in a horizontal position. To prevent a jerk motion when moving from the first state to second spring are positioned below the bi stable strips. This ensures a gradual motion when going from standing to sitting positionbecausespringprovidesa resistingforceaswell asstoring energyforlater use.Thisreducesthestressontheknee whilesittingbymakingitagradualmotion.

When the person wants to stand, he will push the handle of the mechanism downwards while trying to stand. The force applied by the handle will actuate the mechanism on its second port. This force will be supplemented by the force of the © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page2937

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spring.Thespringstorestheenergywhenthepersonissittingandreducestheforcethatneedstobeappliedonthehandle to actuatefromstate2tostate1.Thus,whenthecombinationofforcesappliedonthehandleaswellasthespringforcebecomes equaltocriticalforcethemechanismwillactuatesupportingthepersontomoveintoastandingposition.Themechanismmay carry40%to60%oftheweightofthepersonthusgreatlyreducingthestressonthekneeoftheperson.

7. CONCLUSION

We have designed a chair that can be a great help to people who suffer due to knee pain while sitting or getting up from a chair.Usingthischairwill resultin reducedstressactingonthekneewhichwill reducekneepaininthelongterm.Wehave designedachairthatiseasytomanufacture,haslowcostandisalsohighlycustomizableaccordingtouserrequirement.Thus, webelievethatitisatechnologythatcouldbehighlyusefultoalargeportionofthepopulation.

8. FUTURE SCOPE

Thecomfortlevelcanbeimprovedbyselectingpropercompliantmaterialwithacombinationofdifferentmaterialwhichhas required material properties based on young’s modulus and harmonic analysis. That results in lower vibration during actuation. This proposed chair can be updated with additional functionalities such as fitted with wheels to its legs for easy movementfromoneplacetoanother,thebackpostofthechaircanbeconvertedintoadjustablesothateachandeveryperson can adjust the back post by according to their comfort, height of the chair is customizable to facilitate the users with higher comfortandadditionalfunctionalneedstotheuser

ACKNOWLEDGEMENT

We have immense pleasure in successful completion of this work titled “Comfort Chair Based on Bi Stability Of Pre compressed Strip”. The special environment at Bharati Vidyapeeth College of Engineering that always supports educational activities facilitated our work on this project, special thanks to our principal. We acknowledge the support, guidance and encouragementextendedforthisprojectbyourProjectCoordinatorofMechanicalDepartmentProf.A.S.BongadeandProject guideProf.JaydeepPatilwhorespondedpromptlyandenthusiasticallytoourrequests,despiteofcongestedschedules.

REFERENCES

[1]https://www.unboundmedicine.com/5minute

[2] S. Shuib, A. Halim Kadarman, M. Ikhwan Zaini Ridzwan in” Methodology of Compliant Mechanisms and its Current Developmentsin applica tions”,AmericanJournalofAppliedSciences,4(3):pp159 166,2007.

[3] D.FarhadiMachekposhti,J.LHerder,Maltol,”CompliantJointsandRigid BodyConstantVelocityUniversalJointsToward theDesignofCompliantHomokineticCouplings”,journalofMechanicalDesign,March2015.

[4] A. Pandiyan, A. Gopal,” Design methods for compliant mechanisms used in new age industries”, Istrazivanja a ProjektovanjazaPrivredu,January2016.

[5] T.J.Lassche,G.K.AnanthasureshandJustLHerder“ACompliantTwo PortBistableMechanismwithApplicationtoEasy ChairDesign”https://www.researchgate.net/publication/286780372