507 Mechanical Movements - Brown Part 6 pptx

In the ascent of the piston-rod the lower handlewillbe struckbythe pro-jecting tappet, and, being raised, will be-come engaged by the catch and shut the upper eductionandlowersteamvalves

usedin largeblowing andpumpingengines.

In 181 the lower steam- valve and upper

eduction-valve are open, while the upper

steam-valve and lower eduction-valve are

shut; consequently the piston will be

as-cending In the ascent of the piston-rod

the lower handlewillbe struckbythe

pro-jecting tappet, and, being raised, will

be-come engaged by the catch and shut the

upper eductionandlowersteamvalves ; at

the sametime, theupper handle being

dis-engaged fromthecatch,theback weightwill

pull the handleup and opentheupper steam

and lower eduction valves, when the

pis-tonwill consequently descend. 182

repre-sents thepositionof the catchers and

han-dles when the piston is at the top of the

cylinder In going down, the tappet ofthe

piston-rod strikes the upper handle and

throws the catches and handles to the

po-sitionshown in 181

183 and 184 represent a modification of

181and 182,the diagonal catches being

su-perseded by two quadrants

185 Link-motion valve-gear of a

locomo-tive. Twoeccentricsareusedforonevalve,

one for the forward and the other for the

backward movement of-the engine The

extremitiesofthe eccentric-rodsare jointed

toacurvedslotted bar, or,asit istermed, a

link,which can be raised or lowered by an

arrangement ofleversterminatingina

han-asshown

ofleversterminatingatthevalve-stem The

link, in movingwiththeactionofthe

eccen-trics, carries with it the slide, and thence

motion iscommunicatedtothe valve Sup-pose the link raised so that the slideisin

the middle, then the link will oscillate on the pin of the slide, and consequently the

valve will be atrest. Ifthe link is moved

sothat theslideis atoneof itsextremities, thewhole throwof the eccentricconnected

withthat extremitywill be given to it,and

the valveand steam-portswillbeopened to thefull,and it will onlybe toward the end

of the stroke that theywill betotally shut, consequentlythe steamwill have been ad-mittedtothe cylinderduringalmost the

en-tirelength of eachstroke. Butif the slide

is between the middle and theextremity of the slot,as shown in the figure, itreceives only a part of the throw of the eccentric,

and the steam-ports will only be partially opened, and are quickly closed again, so

that the admission of steam ceases some time before the termination of the stroke,

andthesteam isworked expansively, The

nearer the slideistothe middleof the slot the greaterwill be the expansion, andvice versa

186 Apparatusfordisengagingthe

eccen-tric-rod fromthevalve-gear. Bypullingup the spring hand'e belowunttt it catches in

the notch, a, the pinisdisengaged fromthe

gabintheeccentric-rod

MECHANICAL MOVEMENTS.

189

189 Anothermodification of 186.

191 Scroll-gearsforobtaining a gradually

increasing speed.,

192. A varietyof what is known as the

"mangle-wheel." One variety of this was

illustrated by 36. In this one the speed

varies in "every part of a revolution, the

groove, b, d, in which the pinion-shaft is

guided, aswell as the seriesofteeth,being

eccentric tothe axisof the wheel

193. Another kind of mangle- wheelwith

its pinion With this aswell as with that

iuthe preceding figure,althoughthe pinion

continues to revolve in one direction, the

mangle-wheelwillmakealmostan entire

re-volutionin onedirectionandthesameinan

oppositedirection ;buttherevolution ofthe

wheel in one directionwill be slower than

that in the other,owingtothe greater radius

of the outercircleof teeth

194 Another mangle-wheel. In thisthe

onlyone circleof teeth being provided on thewheel With allof thesemangle-wheels

190. A screw-clamp On turning the\

the P'nion-shaft is guided and the pinion

handle thescrewthrustsupward againstthe,

kePt in earby aS> inthewhee1' The

, , , , i K~UC isaid shaft is made with a universal joint,

holder, which, operating as a lever, holds

down the piece of wood or other material whichallowsaPortion of]t to have the v" placed underitonthe other sideof its ful- bratory motionnecessarytokeepthepinion

in gear

195 A mode of driving a pair of

feed-rolls, theopposite surfaces ofwhich require

to move in the same direction The two wheels are precisely similar,and both gear

intotheendlessscrew whichisarranged

be-tween them The teethof one wheel only arevisible, those of the other being on the

backorsidewhichis concealedfromview

196. The pinion, B, rotates aboutafixed axisand givesan irregularvibratorymotion

tothearmcarryingthe wheel, A.

197. Whatiscalled a"mangle-rack." A

continuousrotationofthepinion willgive a reciprocating motion to the square frame

The pinion-shaft must be free to rise and fall, topassroundtheguidesatthe endsof

the rack This motion maybe modifiedas follows: If the squareframebe fixed,and the pinionbefixed uponashaft madewith

a universal joint,the end of the shaftwill

describealine,similar to that shown in the

around

MECHANICAL MOVEMENTS.

Q_

pinion revolves,but does not rise and fall

as in the former figure. The portion of

theframe carrying the rack isjointedtothe

main portion of the frame byrods, so that

when the pinion arrives at the end it lifts

therackbyits own movement, and follows

ontheotherside.

199 Another formof mangle-rack The

lantern-pinion revolves continuouslyinone

direction,and gives reciprocatingmotion to

thesquare frame, whichisguidedbyrollers

or grooves The pinion has onlyteeth in

less than halfof its circumference, so that

while it engages one side of the rack, the

toothlesshalf is directed againstthe other

The large tooth at the commencement of

each rack ismade toinsurethe teethofthe

pinionbeing properlyin gear

200 A mode of obtaining two different

speedsonthe sameshaftfrom one

driving-wheel

201 A continual rotation of the pinion

(obtained throughthe irregularshaped gear

move-reciprocatingmovementtothe rod,A

202 Worm or endless screw and worm-wheel Modification of 30, used when steadiness or greatpowerisrequired

203 Aregular vibratingmovementofthe curvedslottedarmgives avariablevibration

to thestraightarm

204 Anillustrationof thetransmission of rotarymotion fromoneshaft toanother, ar-ranged obliquelyto it,bymeans of rolling

contact

205 Represents a wheeldriven bya

pin-ionoftwoteeth Thepinion consistsin

re-ality of two cams, whichgear with two

dis-tinctseriesofteethonoppositesidesof the wheel, the teethofone series alternating in

position withthose of theother.

206 Acontinuous circular movement of the ratchet-wheel,produced bythevibration

of thelevercarryingtwopawls,oneofwhich engagesthe ratchet-teeth in rising and the

54 MECHANICAL MOVEMENTS.

-ft

208

twowormsand worm-wheels.

208 A pin-wheel and slotted pinion,by

which three changes of speed can be

ob-tained There are three circlesof pins of

equal distanceon the faceof the pin-wheel,

and byshifting the slotted pinion along its

shaft, tobringit in contact with one or the

other of thecircles ofpins, acontinuous

ro-tarymotionofthewheelismade toproduce

threechangesofppeedof thepinion,orvice

versa

209 Representsamodeof obtaining

mo-tion fromrolling contact. Theteethare for

making the motion continuous, or itwould

cease at thepoint of contact shown in the

figure. The forked catch is to guide the

teeth intopropercontact

210 By turning the shaft carrying the

curved slotted arm, arectilinear motion of

variable velocityisgiventothe vertical bar

largewheelgivesan intermittent rotary

mo-tion to the pinion-shaft. The part of the

pinion shown next thewheel is cut of the

samecurve as the plain portion ofthe

cir-cumference of the wheel, and therefore serves as a lock while the wheel makes a

partof a revolution,anduntilthe pin upon

the wheel strikes the guide-piece upon the pinion, when the pinion-shaft commences another revolution

212 What is called the "Geneva-stop, usedin Swiss watches to limit the numbei

of revolutions in winding-up ; the convex curvedpart, a,b,ofthe wheel, B, servingas

thestop.

213 Another kind of stop for the same purpose

214 and 215 Other modifications of the

stop,the operations of which will be easily understood byacomparisonwith212

MECHANICAL MOVEMENTS.

cog-wheelswork alternately into the pinion,

and give slow forward and quick reverse

217and 218 Theseareparts of thesame

movement, which has been used for giving

the rollermotionin

wool-combingmachines.

Therollertowhichwheel,F(218),issecured

is required to make one third a revolution

backward, then two thirds of a revolution

forward, when it must stop until another

length ofcombedfiberisreadyfor

delivery

Thisisaccomplished bythegrooved

heart-cam,C, D, B, e (217), the stud,A,working

inthe saidgroove; from C to D it moves

the roller backward, and from D to e it

moves it forward, the motion being

trans-mitted

through the catch,G,to the

notch-wheel F, onthe roller-shaft, H When the

stud,A,arrives at the point,e, in thecam,a

projection at the back of the wheel which

carries the camstrikes theprojecting piece

on the catch, G, and raises it out of the

notch in the wheel, F, so that, while the

studis traveling in thecamfrome to C, the

catchis

passing over the plain surface

be-tweenthetwonotches inthe wheel,F,

with-out imparting any motion; butwhen stud,

A, arrives at the part, C, the catch has

droppedinanother notch,andis

again ready

tomove wheel, F,and rollerasrequired.

219 Variable circular motion by

crown-wheel and pinion. The crown-wheel is

placed eccentrically to the shaft, therefore

therelativeradius changes

I

220 The twocrank-shafts are

parallelin ;

direction, but not in line with each other,

j

The revolution of either will communicate!

motion to the other with a varyingvelocity,

for the wrist of one crank in the

jdistancefromthe shaftof thelatter.

221 Irregularcircularmotionimpartedto

!wheel, A C isan ellipticalspur-gear

rotat-iingroundcenter,D, andisthedriver Bis

!a small pinion with teeth of thesamepitch,

i

gearing with C. The center ofthis pinion

I

is not fixed, but is carried by an arm or

;framewhichvibratesonacenter, A, sothat

ias C revolves the frame rises and falls to

enable pinion toremainingear withit,

not-withstanding the variation in its radius of contact To keep the teethofCandBin gear to a proper depth, and prevent them

from riding over each other,wheel, C,has attachedtoitaplatewhichextends beyond

it and is furnishedwith a groove, g,n,of

similarelliptical form,forthe reception of a pin or smallrollerattached to thevibrating

armconcentric withpinion, B.

222 If forthe eccentricwheel described

in thelast figurean ordinary spur-gear

mov-ingon an eccentriccenter ofrrotion be

sub-stituted,a simplelinkconnectingthecenter

of the wheel with that of the pinion with

whichitgearswillmaintain proper pitching

of teeth inamore simple manner than the groove

223 An arrangement for obtaining

vari-able circular motion The sectors are ar-ranged on different planes, andthe relative velocitychangesaccordingtotherespective

diameters of the sectors

224 Thisrepresentsan expandingpulley

On turning pinion,d,to the rightorleft, a

similarmotionisimpartedtowheel,c,which,

bymeansofcurvedslotscut therein, thrusts the studs fastenedtoarms ofpulleyoutward

orinward, thus augmenting or diminishing

the sizeofthe

MECHANICAL MOVEMENTS.