A Study of human office support in the office environment

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Rochester Institute of Technology

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2-14-2001

A Study of human office support in the office

environment

Norman Fizz

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(2)

ROCHESTER INSTITUTE of

TECHNOLOGY

A Thesis Submitted to the

Faculty

of

The College of

Imaging

Arts and Sciences

in _{candidacy for}the degree of

Masterof Fine Arts

A

Study

of Human Office Support in theOffice Environment

By

Norman Horsch Fizz

(3)

Approvals

Chief Advisor:

Craig McArt

DATE:

Associate Advisor:

Doug Cleminshaw

DATE: 01

lA..--=...-

[S-Associate Advisor:

Kim Sherman

DATE:

'3. I

4- .

0

l

School Chairperson:

Nancy Ciolek

DATE:

3·/

J.

Of

I, Norman H. Fizz, hereby grant permission to the Wallace Memorial Library of

The Rochester Institute of Technology to reproduce my thesis in whole or in part.

Any reproduction will not be for commercial use or profit.

(4)

Copyright

by

Norman H. Fizz

(5)

TABLE

OF

CONTENTS

LIST OF ILLUSTRATIONS V

LIST OFTABLES VII

ACKNOWLEDGMENTS

VIII

GLOSSARY IX

CHAPTERS

I. INTRODUCTION 1

II. RESEARCH 4

III. GOALS 16

IV. CRITERIA 20

V. DEVELOPMENT 26

VI. CONCLUSION 42

APPENDIX 45

(6)

LIST

OF

ILLUSTRATIONS

Figure Page

1.

Standing

and Seated Man Spine Posture 6

2. Relaxed Man Angle Measurements 9

3. Recommended Seat Dimensions 10

4. Serber's Ergomax 13

5. Aeron Chair 13

6. Viennese Designed Sofa-Bed 18

7. Upright 20

8.

Kneeling

21

9.

Reclining

21

10. Fixed Armrest in All Three Positions 22

1 1. ExplodedView of

Padding

and Knockdown Construction 24

12. Seatwith Rocker 27

13. Full-size Plywood "Shaker" Rocker 28

14. Seat Motion Mappedto Paper 28

15. Computer-Aided Design

Rocking

Seat Motion

Map

28

16. Trackand Rail Mechanism 29

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18. Four-BarMechanism 31

1 9. Four-BarSolution 32

20. Profiler 33

21. ProfilerCombined with Four-BarSolution in Reclined Position 33

22. Four-Bar Solution First

Working

Design 34

23.

Seat,

Back and Kneeler/Leg-rest Pin andGroove Paths 35

24. Side View of Mechanisms 36

25. Plywood Parts Cut Pattern 37

26. Tee-nut

Plug

Assemblage 38

27. Back Rest Mechanicsand Fasteners 39

28. Thesis Chair Assembled in Task Position 40

29.

Rocking

Index 41

30. Chairin Show 41

31. Finished Prototype 42

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LIST OF TABLES

Table Page

1. Goals Defined

by

being

the extra

two hands neededto finish the prototype throughoutthe nightand _{early morning}

and Stephen

Schaeffer,

Astrida Schaefferand Carl Nickerson fortheirerudite

understandingand assistance with the written word and mental support.

Finally,

Iwould liketo thank _my parents Sieglinde Field and Grant Fizz III

fortheirnever_ending support.

(10)

GLOSSARY

Ischial:

Pertaining

to the lowest part ofthe

hip

bone,

on which the

body

rests

when sitting.

Ischemia:The restriction of blood flow inthe

body

from an outside pressure.

Necrosis: The

decay

ordeath in

body

tissue.

Seatpan:The part ofa chair which supportsthe

hip

and upperthigh.

Waterfall: The front part ofthe seatpanwherethe seat material curves or rolls

awayfromthe area ofthe thigh behind the knee.

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CHAPTER I

INTRODUCTION

Thisthesis isabout_seating, the problemsit_creates, and a solutionto those

problems.Thischapterwill provide an overview ofour

bodies,

a lookat ourwork

and an analysisofthe problems created. Itwill explain _{my idea for} asolution and

describe howthatsolution wasachieved.The chapterswhichfollowgo into further

detail aboutthe material presented.

PREMISE

Human anatomy has not changed much forthousands of years.

Muscles,

bones, back,

digestive tract, and _physiologyare the same as that in placewhen

wewere a nomadic culture.

During

the pastseveral thousand _years, our_society

and culture evolved

dramatically

froma

highly

mobile _societyto a _sedentaryone.

An imbalance has emerged between our bodies andour workplaces.AsWestern

cultureproceeded towarda service based economy, the number of_{jobs requiring}

lengthy

seated positions at adesk increased.The change has created problems

forourbodiesand lifestyle.

PROBLEM

Sitting

for

long

periods of time _{is contrary}to our physiological need to

move.This has resulted in stress on the

body,

_affecting eating, moods, and

daily

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Types/Examples

Discrepancies between ourbody's _physiologyand the increased seated

time demanded

by

our_societyhave led to back _problems, reduced blood

circulation, muscle

fatigue,

and skin anesthesia. Back problems range from

muscle straintodisc injuries such as disc herniation. Reduced blood flowcauses

numbness and_{tingling, particularly}in the buttocksand thighs. Muscle fatigue

resultsfrom a set of muscles_working _constantlyto retain a position foran

extended_time, much like

holding

one's arm outstraightfora minute or so. Skin

anesthesia comes_{from maintaining} a seated position on soft seatsforprolonged

periodsoftime.These individual problems leadto social problems which will be

explained in more detail later inchapter 2.

OBJECTIVE/HYPOTHESIS

More

body

movement and stimulation in theworkplace would assist in

solving the problem. Aseat could be designed thatpromotes _activityratherthan

restrictsit. Such aseatwould providetheworker with

body

supporttofacilitatethe

work while _minimizingfatigue.

HOW

The solution involves researching the problem, setting standards,

defining

the specificsfora _solution, and_creating thatsolution.Chapter2 presentsa report

on _my research. It detailsthe subject matter introduced in thischapter. It includes

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anthropometric _{recommendations,} and a presentation ofother solutions. Chapter

3 outlines and organizesthe major goalsto be attained.The needs of the user

shapesthose objectives.The criteriachapter4 setsspecifics such as

dimensions,

shape, etc.,

defining

what is necessaryto attainthe goals listed in chapter3.

Chapter5 explains the process used to

design, develop,

and create a

functioning

prototype seat.Thisseat displayswhat is necessary to diminish harm caused

by

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CHAPTER

II

RESEARCH

This chapter reports on the research undertaken. It detailsthe subject

matterintroducedin thefirst _chapter,

including

ergonomic_{guidelines, the} extentof

the problem, and recommendations.

SEATING PROBLEMS

What arethe negative effects associated with sitting?

Prolonged _sitting creates a_variety of physiological problems.Sincethe

largestand most _costly_seating problems relateto the human

back,

they

serve as

the focus forthisthesis.1

Evidenceshows prolonged _sitting can cause complications _{ranging from}

simple pain to serious health issues. Pain can bea signal offuture health

concerns. Forexample, "An Epidemiological

Study

ofAcute Herniated Lumbar

Intervertebral Discs"

found that "men who spend morethan 1/2 ofthe_{workday in}

acarhave a 3 fold increasein disc herniation."2

Lower back problems aresecond

to heartconditions ascausesforhospitalvisitation, arethe

fifth-ranking

reasonfor

hospitalization,

andare the

third-ranking

reasonforsurgical procedures.3

Thesecomplications, ifnot_affectingaperson

directly,

impactus as a_group

1. Occupational Low Back Pain:Assessment, Treatment, andPrevention.(St.Louis: MosbyYear

Book, 1991), 251.

2.Kelsey, J.L.,"An Epidemiological_StudyofAcute Herniated Lumbar Intervertebral Discs,"Rheum

RehabV\4(1975): 144.

(15)

through shared _costs, _{like group insurance} rates.Back _pain, _especially in the

lumbar _region, causes agreat deal of absenteeism in thework place, anda

resulting lossof productivity.4

The total coststo governmentand

industry

are

staggering.The United Statesgovernment spendsbillionsthrough programssuch

as Medicare and Social

Security

Disiability

forlower back pain alone.Thecostto

industry

canbearound$40billion in a_year,and isnot a recentproblem as we see

in J. Antonakesarticle "ClaimsCosts Of Back

Pain,"

to the effectthat in "1980

Liberty

Mutual paid $217 million_{for compensating} _{lower back pain,} almost$1

million each_working day."5Wesharethese coststhrough social _security

deductions atwork, through taxes, through higher insurance rates, andthrough

higherprices forgoodsand servicesprovided

by

industry.

The current solutionsfor prolonged _sitting problems at workare notthe

best suitedforhumans.Thiscreatesan economic burden fortheemployerand

the country, and possible health risksfortheemployees.

Why

are there_sitting problems?

Several factors lead to thecauses and costs of backpain.This section

focuses onthe clash between our_physiologyand social culture.

Our bodies have not changed _{significantly}since our nomadic ancestors

walked around in search offood.Our genes and the genes of chimpanzeesdiffer

by

lessthan one percent.The difference, genetically, between ourselves andour

ancestors, walkingthe earth 100,000years _ago, isnearnone.6The

body

isa

4. Ibid.,95.

5. Ibid., 106.

(16)

nomadic

design,

meant to travel

by

foot,

and to move throughoutthe day.

Ourculture isdifferent now, and the

daily

environment _{involves inactivity.} _If

wethinkabout our_workday, mostof us would remember_spending it _sitting or

being

confined to a limited space.The reason we sit still is due in part to the

adoption of an erect posture theorem philosophy7

and in partto a focus on the

work

task,

not on the worker.These_attitudes, called Taylorism,8were initiated in

the 1800's. Not until recent times has this paradigm beenchallenged.9

Kyphosis

Seated Man _StandingMan

Figure 1.

Standing

and Seated Man Spine Posture

7._{Taylor, Mark,}"InSearchof an IdealSeatedPosture,"

Workplace Erogonomics July/August (1996):11.

8. Knobel, Lance, Office Furniture (New_York, NY: E.RDutton, 1987), 8. 9.Taylor, Mark,"In Searchof an IdealSeatedPosture,"

[image:16.532.53.440.246.604.2]

(17)

Wethink of_sitting as a relaxed _position, but ittakes a lotof workforour

body

to hold itself up. Here are afewthings _occurring to one's

body

while seated:

To stand or sit erect is a complex

balancing

act (see Figure 1).

"Almost 100 muscles are required to assist a seated workerin _maintaining

balance. This is becausethe spine supports the worker's upper body. The

spine isflexible toallow _movement, but it isthis _very

flexibility

thatmakes it

ill-suitedforsupport. Ifthe spine is not _{supported, there} isa natural

tendency

to

lean forward. This position is known as lumbar kyphosis. Asthe

body

leans

forward,

moretension is placed on the support muscles.Thiscan result in

fatigue, headaches,

and backaches. In addition the bones ofthe spine

(vertebrae)

contain no _nerves, sothe pain _{resulting from} improper_{seating is}

notfelt untilthe delicate discs betweenthe vertebrae have becomeworn."10

Sitting

in the most comfortable chairis notmuch better because it is

stagnant seating. In his article, "Modern Designers Still Can't Makethe Perfect

Chair,"

Doug

Stewart quotes

Mary

Plumb

Blade,

a retired professor of mechanical

engineering at Cooper Union and researcher into theproblem of sitting.

"Ifyou don'tmove, you _quicklybegin to lose calciumin yourbones.A chairthat

fits you _{perfectly is probably} damaging.... the

form-fitting

seats in NASA's first

spacecapsulesturned outto be

terribly

uncomfortableon the launch pad."11

Sitting

for

long

periods can causetroubleas well.When you_sit, the tissue

between the bone andseat surface gets compressed.The blood can'tgetto the

softtissue _overlyingthe bone because thevesselsflatten.Thisis called

ischemia,

meaning a lackofblood _supplytoatissue. Ischemia can cause necrosis ordeath

of cells ortissues.The compressedtissue _may resultin pressure on the nerves

and blood vessels with consequent

tingling

and

numbness.12

10. Metzger,EdwardA. 'TheImportanceofLumbar

Support,"

Workplace ErogonomicsJuly/

August(1996):14.

11. Stewart, Doug,"Modern Designers StillCan'tMake

the PerfectChair,"Smithsonianv17(April

1986):104.

(18)

8

Bending

your upper

leg

relativeto the torso rotatesthepelvic

bone,

which

changes thecurve ofthe lowerspine (see Figure 1).13

A good example ofthis

change isshown

by

_{slumping forward. The} change can be feltas the lower back

movesto theconvex position.This posture isthe_{incorrect way}topick _up objects

offthe

floor,

and isa cause of back injuriesas ittends topinch or squeezethe

intervertebral discs. Ifthese discs

herniate,

they

can press againstthe nerves,

resulting in sciatica.

ERGONOMIC RECOMMENDATIONS

Ergonomics engineers_studyand attempt to understand the

body

and how

it relates to the world. Some studies provide guidelines and suggest solutionsfor

the _{seating dilemma.}

Anthropometrics

Thisaspect of ergonomics isaboutthe measurementof _man, or

anthropometrics, as it relatesto _seating and rest.

The human spine

flexibly

supportsthe upperbody. In

doing

this there isan

optimal shapefor itto work properly, a double S-curve.

Looking

atthe

body

from

the side, the shape ofthe spine from the baseofthe skull to the upperribcage is

concave, called lordosis. The thoracicportion isconvex, called kyphosis.The

lumbar region, or small ofthe

back,

returnsto the lordotic posture (see Figure 1).

Poorposture is shown as"Seated

Man"

in figure 1. The lumbarareais no

longerconcave. It reverses shape into kyphosis. This resultsfromthe rotation of

(19)

the pelvic _bone caused

by

sitting. It _actuallyslumps the back.14 Onecan feel the

difference in posture

by

_{standing up} and _sitting down.

Relaxed Man

Figure 2. Relaxed Man Angle Measurements

Figure 2shows some angle measurementsfroma _studyon relaxed men in

space atzerogravity.15

Theangles shown are consideredtobethe natural _resting

place wherethe muscles in the legsand back areequalized. Notice that the legs

are not 90 degrees to the body.The pelvic bone has not rotated andthe lumbar

curve is still lordotic.

Seating

Standards

Recommended dimensionsfortask _seating are shown infigure 3.This

information was compiledfrom Human DimensionsAndInteriorSpace

by

Julius

14. Ibid.

[image:19.532.52.483.127.367.2]

(20)

10

Panero and MartinZelnik16

andthe recommended dimensions forVDToperators

from AT&T Bell Laboratories.17

The prescribed standards are divided into three

parts: _seat, armrests and backrest.

SeatWidth: 16-20 in.

Backrest Width:

|^-14 in. min.-M

Backrest Length: 9 inch min.

Seat-BackAngle: 100-120 deg.

r

ArmrestHeight:

\s

W

Lumba

I

1

I9"1

Lumbar Height: 0 in. SeatLength: 15-19 in. Armrest Distance: 18 in. Seat Angle:

0-7deg. Seat Height: 15-20 in.

I

Figure 3. Recommended Seat Dimensions

Seat

Theseat (sometimes referred toas _seatpan) needsa minimumwidth of 16

inches and a length of 15 to 19

inches,

with a rollover(sometimes referred to as

waterfall) onthe frontedge. This rollover underthe knee jointprevents pain and

circulation losswhich resultsfrom pressure. Seat heightabove thefloor is an

adjustable 15to 20 inches.Theseatpan angle with respecttothe floor is between

0 and 7 degrees.

16.Panero,JuliusandMartin Zelnik. Human DimensionsandInterior Space.(NewYork: Billboard

[image:20.532.53.483.136.412.2]

(21)

11

Armrests

Armrests should be 10inches above the seat and have a minimum

distance of 18 inches apart.

Backrest

A protrusion in the back rest 9 to 10 inchesfrom the seatwill restore a

concave shape

(lordosis)

inthespine.18

The backangle rangesfrom 100

to

120,

relativeto the seat. Backsupport length isa minimum of9 inchesand width isa

minimum of 14 inches.

Recommendations

Professionals at

Steelcase,

an office furniture _{manufacturer,} suggest a

wide range of solutions forproblemsof prolonged sitting. For

instance,

while

sitting, arms need free movement. Ifthe seat back istoo

broad,

itwill blockarm

rotation. People have many sizes and shapes.Thechair needsto accommodatea

variety of _users, and a solution to this isto makethe chairadjustable.19

Moving

Asstated

before,

the

body

is developed formovement. Prolonged static

seated positions can cause

pain.20

Dr. Joseph

Berg,

in a paper on Posture And

The

Sedentary

Man,

affirmed that_{changing seating} posture is very important to

delay

muscle fatigue.21

Therefore,

anyform of

body

support in the workplace

needs toeither provide forchanges in position or provideformotion.

18. _Ibid, 350.

19. "Adjustability's Untapped Potential,"Workplace Erogonomics

May/June (1996):11.

20. OccupationalLow Back Pain:Assessment, Treatment, andPrevention,20.

(22)

12

Rocking

Researcher

Mary

Plumb

Blade,

cited in "Modern Designers Still Can't

Makethe PerfectChair"

by Doug

Stewart,

recommends _rocking as a one ofthe

two bestsolutionsforthe problems associatedwith sitting.22

This motion creates

both exercise and a _calming effect. It providesa greaterrange of movement, the

previouslysuggested solution.

One_study

by

Janice

Pikna,

_using afixed arm rocker, finds rocking benefits

elderlywomen

by

_providing aform of exercise. Encouragementof exercise in this

manner enhances the _qualityof life and decreasespossible health costs.23

The motion of_rocking producesa_calming effect.Bernice Steinbaumwrites

in her book The Rocker:An American Design Tradition:

"Itwould _{be wrong} of usto lookuponthe rocker with nostalgia as _simplya

piece of

Americana,

for it continuesto fulfill needstoday. There's even a

Bostondoctor who prescribes rockersforpatients asan important part of

convalescence".24

Anotherexample appears in Richard Knox'sarticle,"Rockof Aged:Chair's

Sway

May

Soothe

Ailing

Elders,"where he quotesfromthe study,

Rocking

Chair

Therapy

For

Nursing

Home Residents With

Dementia,

presented atthe Eastern

Nursing

Research

Society

in

Rochester, N.Y.,

by Nancy

Watson,

who statesthat

"rocking

forat leastan hourand 10minutes a

day

eases depressionand _anxiety

among elders_{suffering from} Alzheimer's

disease.'25

22. Stewart, Doug,"Modern

Designers,"

104.

23. Pikna,JaniceKuiper,'TheAcuteCirculatory ResponsesofElderlyWomenToUpperand/or Lower_ExtremityExerciseInaSpecially Designed_RockingChair"(MSinNursing, Universityof Wisconsin, Milwaukee, December 1986):77.

24 Steinbaum, Bernice, TheRocker:AnAmerican DesignTradition, (New York:Rizzoh, 1992),10. 25. Knox, RichardA.,"RockofAged:Chair's_{Sway May}Soothe_Ailing

Elders,"

Boston_Sunday

(23)

13

Figure4. Serber'sErgomax.

Left,

_{chair; right,} example positions.

[Reprinted,

by

permission, from Arlyn

Serber,

"American Ergonomics: Press Info,"

chair, as

reproduced in

http://www.americanergonomics.com/press/ergomax.sit;

internet;

Fri,

29 Sept2000. and

"Fig

6 ISOSPS

-Integrated System of Postural

Support,"

positions, as reproduced in Ergomax CB andISOPS: A New Paradigmforthe

BiomechanicsofErgonomic Seating, (a pamphletfrom American Ergonomics

Corporation,

Novato,

CA).]

Tilt Tension

controlsresistancefeltwhen leaningbade

Q)Lumber Height Lumber Depth pad adjustsverticalry41/2 inches, forward 3/4 inch or1 1/4inches

0Arm Angle pivotsindependently 17.5degrees inwardto 15degrees

outward.'

ArmHeight

adjusts_{independently}within 4-trich

range-TiltUmiter limitsrangeof recline.

i ForwardTitt

adjusts seatangle5 degrees forward.

Figure 5. Aeron Chair.

Left,

diagram of7 knobsforadjustment; right, chairfront

and corner.

[Reprinted,

by

permission, from Lee

Sullivan,

diagram on page 8 and

chairs on page

23,

as reproduced in WearIt in Good Health The

Aeron_Chair

by

[image:23.532.57.457.48.273.2] [image:23.532.55.480.403.638.2]

(24)

14

OTHER

SOLUTIONS

Many

chairs designed

today

attemptto resolve back problems

by

other meansthan_{just pushing}the lumbarregion intothecorrect position.Thesolutions range _{from extremely} mechanical backsupport devicescapable of multiple

seating positionsto tilt-forward seats and mobile office arrangements.

Mechanical Backand Multiple

Body

Position Support

There are a great number of mechanical monstrosities of_varying

complexity available to the consumer.

They

all

try

tofind a perfect position of

support forthe body. The most extreme models are listed here. The most mechanical multiposture

body

support isSerber's Ergomax 1700 (see Figure

4).26

The operation ofthis chairiscomplex enough to require aVHS video

explaining the use ofthe device'sstool, traditional, forward

leaning, kneeling,

kneeling

with backsupport, and _reclining positions.Anotherchairthatfalls into

this_{category is}the popularAeron

Chair,

which has seven separate knobsand

leversto adjust posture (see Figure 5).Toease user confusion an eight page how-to

booklet,

one pagediagramand multi-media compact computerdisk isprovided.

Balans Chairs

The Balans

Chairs,

which usea simplerapproach, are described as "U-shaped, backless rocking stools in which the sitterhalfsitsand half

kneels,

thereby

forcing

the spine intoa healthful

posture."27

The

leg

anglesthese chairs

requireare thoseofthe relaxed man in figure3. Someconsiderthischairthe best

26.Null, Roberta_L, Universal Design:CreativeSolutionsfor ADACompliance(Belmont, Califor nia:Professional Publications, 1996), 157.

(25)

15

solution to_{date for providing} the natural lumbarshape oflordosis.As thearticle

"The Balans Chairand its

Semi-Kneeling

Position: An Egronomic Comparison

With Conventional

Sitting

Position"

inthe publication Spine relates, "Studiesofthe

so-called Balans

Chair,

which _{induces sitting} in a_semikneeling _posture, showthat

this posture _actually results in increased muscle _activityoflumbarand cervical

muscles and increased blood flowto the feetcomparedto a standardchair."28

Doug

Stewart in hisarticle_{"Modern Designers Still Can't Make}the Perfect Chair"

notes "when I spend a

day

_{in one,} _my shinssoon ached.Whenever I leaned

forward to talk on _{the phone,} _{my feet fell} asleep.And

fidgeting

was _nearly

impossible."29

Office

Landscaping

Inthe mid-1950sthe theories and application of officedesign started to

change. European designers developed Burolandschaft (office

landscaping)

which shifted _{focus away from} a grid-like arrangement of

desks,

towardan open

layoutwhich followed the movement of paperandthe flow oftasks.30American

designers George Nelsonand Robert Propst

jointly

developed Action Office for

Herman Miller. This system offurnitureadvocated _changing postures with

differenttasks.31

These changes in philosophystarted a reversal of

Taylorism,

refuting its sedentaryworkspace

ideology,

and

increasing

_mobilityof an

employee'stasks.

28. OccupationalLowBackPain:Assessment, Treatment, andPrevention(St Louis: MosbyYear

Book, 1991),27.

(26)

CHAPTER

GOALS

Table 1

lists,

defines,

and categorizesthe objectives developed fromthe

previous research.

They

are presented in orderof priority.

POSITIONS

The

body

support should permitthe usertosit,

kneel,

rock, recline, and

roll.

Drawing

onthe research, it isclearthat _rocking creates movement which benefitsthe body. It is

highly

recommended as a _waytoreduce muscle fatigue

and increasecirculation.

Sitting

ina normaltaskposition allowstheusertoaccess

the desksurface and related work, such ascomputing. Because it isthe most

[image:26.532.57.489.201.486.2]

(27)

17

common _position, it isthe most understood

by

ergonomics engineers and

accepted

by

users.

Kneeling

in the Balans position grantsthe same deskaccess

with the benefitof_opening the angle between the back and

thigh,

thus _providing

lumbar lordosis.

Reclining

also assistswith _openingthe same _angle, _encouraging

circulationand relaxation. _{Periodic shifting between}the two positions_clearly

encourages

body

movement and reduction of muscular

fatigue,

which is

necessary.The inclusionof _rolling assiststhe operator with _moving within the

work environment.

SIZE

The chairneeds to interact withthe under-portion of a deskandfit in small

office spaces.

Designing

the chairto be compact will fitmore limited space

requirements.

Making

the chair able to accommodate large andsmall people

provides proper supportforawide range of users.

INTERFACE

The userinterface should have intuitive operation, require aslittle

instruction as possible, and be transparent. Intuitive operation in that the interface

followsthe logicof the action, sothe user can _{easily grasp}the action requiredto

adjusta position. Forexample, to move the back

forward,

pull _up on the

back;

to

lower

it,

push it down.Thissimplifiestheamount of writtendirections and reduces

possible user confusion.Transparent, in this case, meansthat the userdoes not

(28)

18

not

something

_{with which}_the _user _has_to _interact.

VISUAL

It is desirablethat the chairlook_{warm, playful,} and _exciting to make it

attractiveto potential users.The visual logic or semantics should suggestthat it

moves. An example ofthisstyle isaViennese designed sofa-bed (see Figure6).

Figure6. Viennese Designed Sofa-Bed

[Reprinted,

by

permission,fromAdolf

Krischanitz,

"One-Shaped

Couch,"

furniture,

as reproduced in Wien Mobel (Vienna Furniture).

(Vienna,

Austria: Die

Secession,

1989),

43.]

CONSTRUCTION

Construction ofthe sections

-seat,

back, feet,

andarmrests

-should be

simpleforthe end user.Asimple, modulardesign _naturally pointsto a knockdown

type of construction, withthe _abilityto assemble, disassemble and reassemble a

[image:28.532.70.461.220.443.2]

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19

simple enoughthat the ownercould replace a section,and _easy enoughto

construct, package, and _{ship for}thefactory.

Modular design impliesthat the chair could be customized

by

_simply

changing one partforanother, modified one. For_example, a user who has

scoliosis and requires personalized back _paddingcould changethe backsections

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CHAPTER IV

CRITERIA

This chapter relates_closelyto the previous one.Where the prior chapter

defined

ideals,

this liststhe specifics needed to createthe

body

support.The

section headingsare_{the same,} andfollowthesame order asthe previouschapter

(see Table 1).

POSITIONS

The"thesis"chair should permitthe user_{to sit,}

kneel,

roll, and recline. In

each ofthese positions oractivitiesthe

body

should be ableto rock back and

forth.

Figure 7. Upright

Hip

and backsupport, in an uprightposition, should providetask _seating

(see Figure7).The angles and sizes relateto the ergonomic recommendations

listed earlier(see Figure 3).

[image:30.532.55.186.378.567.2]

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21

Figure 8.

Kneeling

The chair, with kneeand ischialsupport (see Figure

8),

should create

Balans-styleseating.This

kneeling

position should be the largestangle of 135

from backto thigh (see Figure 2).

Figure 9.

Reclining

The chairshould promote _relaxing

by

_supporting _{the calf,}

hip,

thigh, back

and head.The chair, with back reclined and adual purpose

footrest/kneeling

pad

extended (see Figure

9)

atthe appropriate positions (see Figure

2),

providesthis [image:31.532.54.186.43.235.2] [image:31.532.54.257.349.538.2]

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22

Figure 10. Fixed Armrest in All Three Positions

An armrest should be available _{in every} position (see Figure 10).The

placement is7 to 10 inchesabovethe upright seat position as noted in AT&T Bell

Laboratories'

recommended dimensions forVDT operators (see Figure 3).34The

arms should be fixed at this height and notdeviate from thatpoint relativeto the

chairandfloortoassist with _rockingwhile _reclined, providea support_{for changing}

positions, and assist with _getting in and out ofthe

body

support.

SIZE

The footprintshould be lessthan 24 inches wide, and the base mustfit

under mostdesks. The

footrest/kneeling

section shouldtuck underthe seatwhen

not in use to reducethe total space taken _up

by

the

body

support.

Figure 3 shows recommended seatdimensions. Inthis case, the seatpan

[image:32.532.52.304.53.272.2]

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23

heightand seat length need to be atthe lowerend ofthe recommended_sizes, at

15

inches,

to accommodate a greater range of users.

Similarly,

the backrest

length oughttobethe _{higher recommendation,} again to be usable

by

both larger

and smaller people.

INTERFACE

A passive and intuitive interface is preferredforuserinteraction with the

body

support.The numberof moves requiredto change positionsmust be asfew

as possible.The usershouldbe able todo alltheseoperations without

leaving

the

chair. Forexample, to change from atask seated position to a

kneeling

one

should _{only involve} _positioningthe knee pad unit and

kneeling

on it.

Additionally,

the back rest should lockto sit and unlockto recline.Theseat must rotateforward

and back as _necessarytochange from a seated position to a

kneeling

position.

These operations should need little explanation_{to the user,} and should relate

semanticallyto the

function,

as isthecase when

lifting

a part bringsthe unit up.

VISUAL

The use of bright materials such as brushedaluminum, lightwood, and a

primary-colored seat

fabric,

can provide a playful aesthetic whilethe structure

properembodiesa serious_seating tool, notto be confused with an over-stuffed

recliner.The use of_organic, non-geometric, sweeping lines should provide visual

movement.The Viennese sofa

bed,

with itsvisual cuesto movement, mechanical

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24

Upholstery

PartA'

/"

Tee-_Nuts

Uphoslstery

attached

to plywood with adhesive

Plywood

PartB

Figure 1 1. Exploded View of

Padding

and Knockdown Construction

A fabric andfoam padgluedto a plywood structure make padded support partA. Part B isastructural memberofthe chair. Part Aattachesto Part Bwith bolts and

tee-nuts.

CONSTRUCTION

Sections are built ofindividual partswhich consistof _aluminum, _plywood,

laminate,

etc. andare _{fastened permanently}either with glue, permanent

mechanical

fasteners,

orboth. Infigure 1 1, PartA represents an upholstered

section, such as a _seatpan, backrest orknee pad, exploded into itsconstituent

parts. Part B representsthe structuralframethatsupports and attaches Part Ato

the other components ofthe chair.

Sectionsconsist of major chairunits, likethe seatpan orthe legrest/

kneeling

pad, to reducethe numberofparts andtocreate large manageableparts [image:34.532.55.417.57.326.2]

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25

Final _assemblyof sections intothe completed chair is done

by

the end

user, _using knockdown hardware such ashexagon socket-head_cap

bolts,

or

something similar, and nuts installedwithinthe sections

during

manufacturing.

Figure 1 1 shows Part A

being

attached to Part Bwith two

bolts,

illustrating

this

concept.

Becauseof this modularity, end users can custom orderparts to

supplement orreplace standard componentsforspecific applications such as the

(36)

CHAPTER

V

DEVELOPMENT

With goals set and criteria

determined,

designofthe prototype began. This

process_naturallydivided into _{mechanical, visual,} andfabrication phases.The

mechanical phase involved _{understanding,}

defining

and

designing

the

body

support device. The visual concerned _creatingtwo-dimensional drawings ofthe

shape and aesthetic ofthe chair. Fabrication completedthe processwith afinal

constructionforpresentation.

MECHANICAL

The mechanical _{study included}

developing

a physical solution.This

addressed

body

_position, chair _mechanics, andthe interaction between the

body

and the supportdevice.

Rocking

and

Kneeling

Mechanics

The firstexploration investigated seat angles and

body

position ofBalans

seating.Thisencompassed_goingto localfurniturestores and _{measuring currently}

manufactured products for

kneeling body

support.

Concurrently,

quarter-size models ofdifferent types of _rocking chairswere

made to betterunderstand and recreate the motions involved. These models

included a glider(Canadian rocker), a Shaker style rocker, and single pivot seat

found inthe most popular of swivel chairs.The results indicatedthe Shakerrocker

had the greatest range of motion and provided the properangle fora

kneeling

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27

position attheapex ofthe forward _rocking motion.

The next course of developmentstarted with a suggestion made

during

a

presentation to the thesiscommittee.The ideawasnotto design a whole new

chair, buttocreate atiltmechanism toadd to _existingchairs.Withthechallengeof

designing

a_{tilt mechanism,} an _{understanding}was needed ofthe actual seat

motion

during

rocking.

Rocking

Motion and Path

Curve

Shape

Rocker

placed [image:37.532.55.415.246.441.2]

under seat

Figure 12. Seat with Rocker

The firstattempt at

duplicating

the _rocking motion wasto makea small

curveclose to the underside ofthe seat.Thiswas done

intuitively by drawing

and

cuttingthe curvethatwould approximatethe motion ofthe seat(see Figure 12).

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28

Seat Motion Mapped to

Paper

Pens Joined

to Seat Plane

Figure 13. Full-size Plywood "Shaker"

Rocker

Figure 14.Seat Motion Mapped to Paper

Back

Paths Marked

with Pens

Front

Seat Planes in 7 positions

[image:38.532.49.483.44.301.2] [image:38.532.53.441.345.610.2]

(39)

29

A more empirical method of

understanding

the movement was necessary.

Beforethe second _attempt, afull-size plywood _mock-up was madeto the

dimensions of a Shakerrocker (see Figure 13). The path ofthe seat plane's

motion was drawn on paper (see Figure

14),

_measured, and entered into

MicroStation,

acomputer-aided design

(CAD)

program (see Figure 15).This

definedthe path the seat would follow.

Figure 16. Trackand Rail Mechanism

Left,

arrows pointtowheelsattached_{to seat; center,} arrows pointto the rail

curves the wheels move _upon; _right, complete unit.

Using

CAD,

the curvesthrough whichthe seat moved while _rockingwere

reduced in scale so

they

could be placed undertheseat and become tracks upon

which atest chair would ride (seethe center image of Figure 16).A_matching

plywood

trolly

with wheels was attached tothe seat (seethe left image of Figure

16).

Working

together,these restricted the seat motionto the shape ofthe_track,

so the seat _{successfully followed}the same motion asthe plywood mock-up.

However,

during

a demonstration forthe thesis chairmanthis mechanism

failed,

toppling

me over backwards.A highcenter of_{gravity moving} a large distanceover

a single support pointmade of rails androllers causedthisfailure.

Additionally,

the [image:39.532.63.480.212.350.2]

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30

Body

Positions

Thisdirection wastabled with the _{failure described} on page29. A better

understandingofthe

body

in relationto thesupportdevicewas neededand, using

the thesiscommittee chairman's _advice, afinite definition of an anthropometric

seat and

body

position was created.

Figure 17.Anthropometric Figure

Ananthropometricfigureofa5th occidentalpercentile male wasmadewith

paper, pivotedat the points indicated in Figure 17.35

Using

the papermodel

became problematic

because,

although the model could be put _{in the seated,}

kneeling,

and _reclining positions, itwasdifficult to visualize wherethe

body

parts

wouldbewhen_moving between positions and when rocking.Thetwo-dimensional

35. _HenryDreyfussAssociates, TheMeasureofManandWomen: HumanFactors in Design (New

[image:40.532.68.269.182.445.2]

(41)

31

experimentwas convertedto _{a computer animation of positions} _with

body

movement (see Appendix).

Alias/Wavefront

Power Animatorassisted in creation

ofthe animation.The animation _{helped illustrate} and provide afinite

measurement and motion path forthe seat_{supports, but did}not

help

with _creating

a mechanical solution.

Figure 18. Four-Bar Mechanism

Each bar

independently

pivots and slidesat arrows.

Mechanical

Engineering

Advice

Withthe need formoreassistance, I was referred

by

thesiscommittee

member Kim Sherman to Kevin

Kockersberger,

Professorof Mechanical

Engineering

at Rochester Institute ofTechnology.

Analyzing

the animation

convertedtotwo-dimensional

illustrations,

he recommended _{experimenting}with a [image:41.532.61.330.183.377.2]

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32

Back Rotation

Fixed Point

Figure 19. Four-Bar Solution

Fixed Point

Seat Motion

Leg

Rest Rotation

With experimentation, afewsolutions were developed. The best (see

Figure

19)

worked wellforthe desired reclining,

kneeling,

and upright

body

configuration, but it didnot rock. Italso presented an issue ofthe

leg

rest/knee

pad

having

to passthrough the

leg

when _changing positions.

The four-bar mechanism andsolution was demonstratedto the advisors.

Several solutionswere considered andjudged impractical.

Working

from a

full-size mechanism such as a profiler wasdetermined asthe nextstep.A profilerisa

[image:42.532.59.395.45.252.2]

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33

Figure 20. Profiler Figure 21. Profiler Combined with Four-Bar

Solution in Reclined Position

(One side ofthe profilerhas been removed

for photo)

Profiler

A profiler was built (see Figure

20)

to hold a seat withthe dimensionsas

shown in Figure 3.The anglesforthe relaxed and

kneeling

positionswere

determined usingthe angles shown in Figure2 asguidelines.The four-bar

mechanism was combined with the profiler(see Figure 21).This produced a

partial _solution, buta full solution needed resolutionsforthe transition_{from sitting}

to

kneeling,

_{for rocking} andfor rolling.

PositionTransition Difficulties

Kneeling Issues

The four-bar mechanism made the lowerlegs captive when

kneeling,

makingthe shift from

kneeling

to _sitting awkward. Userswould have to getoffthe

seat, change_{the position,} and_carefully sitagain, placing their legs in the hole

created betweenthe two outside four-bar mechanisms and

kneeling

pad.This [image:43.532.60.481.43.301.2]

(44)

34

centered on

including

_rotating pads and _redesigning _{the mechanism,} but nonefit

theset standards.

Figure 22. Four-BarSolution First

Working

Design

Rocking

The primary focus returned to _rocking with

kneeling

still unresolved.

By

addinga stretcher and _removing unneeded materialtofabricate rocker_runners,

the profilerbecame thefirstcompleted, working design without _{rolling (see Figure}

22).Thiswas presented to peers and

faculty

with otherdemonstrations ofthe

intended

body

placement and motions.

Rolling

The chief _advisor,

Craig

McArt,

suggested a wheeled cradleto housethe

mechanism.Thiswould allowthe chairto roll and rock while _{maintaining fixed}

[image:44.532.54.312.111.323.2]

(45)

35

Resolving

Kneeling

Issues

At_{this point,}

kneeling

again _became _the

primary focus.Moresketches and

ideaswere developed with poor results.A review of criteria helped provide ideas.

The most

promising

ofthese involved a

kneeling

_pad/legrest_that_was_independent

ofthe four-bar_mechanism,to beattachedto and extend outfromthe bottom of

thechairthrough _{a pin and groove mechanism similar}_{to the} _sofa_{bed in Figure} _4.

Groove Seatpan Pin-A _pin Rotation

6>

Pin-Drop& Lock Points

Groove

Backrest

Rotation

^

Seat Rotation BackRecline

Path

Pin-c

^T

X

_Grooves

0

Kneeler Extend and Retract

Figure 23.

Seat,

Backand Kneeler/Leg-rest Pin and Groove Paths

This ledto a redesign ofthe back andseat _mechanisms,

bringing

the

design more in linewith the original criteria.The four-barsolution waschanged,

keeping

the ideaofthe pivotpoints, to three similarindependent mechanismsfor

the

back,

the seat, andthe leg/knee support (see Figure 23).A mock-upwas [image:45.532.57.443.206.507.2]

(46)

36

Conversion from CADtoAesthetic

The new, _completely_working, prototype was measured and modeled in

CAD. The mechanismswere refined and simplified with thecomputer. Scale plots

were made of themechanisms and usedforthe next_{phase, that} of aesthetic

development.

VISUALIZATION

Backrest

Armrest

Seatpan

Knee/Leg-rest

Figure 24. SideView of Mechanisms

Plotsofthe mechanisms were used as abasisfor

drawing

sideviews ofthe

body

support components (Figure24). Afterseveral

drawings,

the preferred

contour was scanned intothe computer, addedto thecurrentCAD file and refined

to the final appearance.The aesthetic goals andcriteriaset in Chapters II and III

[image:46.532.58.448.224.503.2]

(47)

37

FABRICATION

Constructionofthe prototype required

finding

_materials, _makingcut _plans,

cuttingand _assemblingthe parts._These _{processes occurred}

continuouslyand

simultaneously up to completion.

Material

The material choices werebased _primarilyon aesthetics.Severalelements

were sampled and testedforstrength and durability. The final selectionswere

aluminum forthemechanical _pieces, a Baltic birchsheet plywood forthe actual

structure, taperedhexagonal head boltswithembeddedTee-nuts and sockethead

capscrewsfor

fastening,

and Formica laminate as a bright durable outer coating.

Collecting

the materials involved

finding

suppliers, _orderingand purchasing.The

availabilityof supplies influenced the scheduleof work.

Cutting

and Construction

Chair_Leg

Arm Support

[image:47.532.56.433.416.632.2]

Knee/Legrest Part

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38

Parallel tothis, the computer models were arranged intotwo-dimensional

patternsforchair parts and plotted full-size on paper(see Figure25).This paper

was attachedto Masonite and used to create templatesfora router.

The plywood was laminatedtogetherand the templates were attached.

Using

the _guiding

templates,

the plywood was cut

by

a router.Then the Formica

was attachedto the chair parts and trimmed, again with a router.

Plug

parts

Wooden Dowel

Completed plug is

glued

into hole in

part

Figure26. Tee-nut

Plug

Assemblage

Thenext _stepinvolvedmakingTee-nutplugsfor

fastening

knockdown bolts.

These consisted of aTee-nut gluedand nailed into hollowed dowel (see Figure

26). Holes were drilled in the stretcher, carriage, arms, and

leg-body

supportsfor

the plugs and bolts.The plugs were inserted and glued. Casterswere addedto

[image:48.532.55.391.218.507.2]

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39

assembled and measurements weretaken to make the mechanical pieces.

Figure 27. Back Rest Mechanicsand Fasteners

Hexagon Socket-Head

Cap

Screws are countersunk andfasten the back to the

rodswhichsupportthe plywood backrest.Attheright arethegroovesin whichthe

rods moveto recline the backrest.

The aluminum rod was cut _usinga _milling machine and metal lathe. These

rodswerethen addedto the prototype and usedto

lay

outthe plywood_upholstery

supports.The rodsand plywood were drilled and fastenedwith socket-head _cap

screws (see Figure

27)

and Tee-nutsas in Figure 1 1.

The exposed wood, otherthan where_{the upholstery}would be affixed, was

sanded and sealed.

Using

the plywood section ofthe seatpan,

knee/leg

pad, and

backrest,

the cushion fabricwas cuttosize.Thefabricwas sewn togetherand

stuffed with _{upholstery foam.} Hand stitching finished the cushion, which wasthen

[image:49.532.56.344.75.307.2]

(50)

40

[image:50.532.59.368.72.330.2]

Assembling

Figure 28. Thesis Chair Assembled in Task Position

Withthe completion of_{the parts, the} chairwas assembled andtested (see

Figure 28). Itworked exceptforsomeslippage wherethe rocker

leg

contactedthe

carriage.Thisproblem was solved

by

_{creating index} pins, (see Figure

29)

as

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41

Carriage

L

Sectional View

BottomofRocker

ConvexIndex

-Carriage Expanded Isometric View

Figure 29.

Rocking

Index

Thefemaleconcave hole in the bottom ofthe rockermoves overthe male convex

indexpin inthe carriagesection, much likeonelink in abicyclechain _moving over itsgear.Thisstopsthe rocker_{from sliding} or_changing position.

Figure30. Chair in Show

Displayedwith explanations of positions and movement inthe background.

The final prototype was displayed in the Rochester Institute of

Technology

[image:51.532.57.300.301.590.2]

(52)

CHAPTER

VI

CONCLUSION

Figure 31. Finished Prototype

Left,

3/4view oftaskseat_position; upper_right, sideviewof kneelerposition; lower

right, side view of reclined position.

SUMMARY

There are health risksassociated with prolonged sitting.These risks range

from poor bloodcirculation, muscle

fatigue,

and lifestyle

inhibiting

backpain to a

higherriskfor herniated discs in thespine._{A primary}causeisstatic

body

_support,

which occurs in the workplace.This affects everyone

by

increasing

costs for

health care and

increasing

risk of

injury

for manyof us.

The prototype (see Figure

31)

developed here isa solution.

First,

it uses [image:52.532.60.476.130.433.2]

(53)

43

the recommendationsset forth

by

human factors specialists.These include

prescribed seatdimensionsand multiple

body

positions.

Second,

_{the thesis chair,}

through rocking, eliminates _stagnation, which isa _primarycause of all the

problems listed.

CRITIQUE

Even though thedesign of the thesischair has fulfilled thegoals set in

Chapter

2,

it needs more _studyto resolve some unforeseen _safety

hazards,

to

develop

better _mechanisms, andto measure itseffectivenessfor enhancing

health. Most ofthese matterswere noted

during

athesiscommittee critique atthe

exhibit.

Safety

Some unanticipated _safety matters give riseto possible

bodily

injury. The

extremities are most

likely

to be endangered. For

instance,

a _shearing action

betweenthe arm rests/supports andchair legsoccurs when rocking.The open

groovesfor pivoting the seatpan and the backrest can pinch or crushfingers.

Two less hazardous issuesconcern a weakness _resulting in a left-to-right

motion in the arms and a potential with the inner

body

support for rocking over

backwards.These predicaments can be fixed withthe addition of a cross piece

placed behindthe seat and between the arms.

Furtherdevelopment

More development isrecommendedto explore improvementsforthe thesis

(54)

44

place. Research into differentmaterialsto reduce size and weight isadvised.

Some empirical

testing

would be useful in

determining

the levelof health

improvementthis prototype provides.

FINAL REMARKS

Thisthesis definesthe problem with stagnant_seating and providesa

designsolution toalleviate harm.The prototype illustrates that solution.With

some_{further study} and _{modification,} thischair would provide a design reference

(55)

APPENDIX

(56)

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