507 Mechanical Movements - Brown Part 8 potx

Onvibrating the lever towhich thetwo pawlsare attached, a nearly continuous rectilinear motion is given to the ratchet-bar.. Continuous rotarymotionofthecam a reciprocating motion everyd

271 Onvibrating the lever towhich the

two pawlsare attached, a nearly continuous

rectilinear motion is given to the

ratchet-bar

camgivesareciprocatingrectilinearmotion

tothe rod bearingonitscircumference

273 Rectilinear into rectilinear motion

When the rods,A and B,are brought

to-gether, the rods,Cand D,are thrustfurther

apart, andviceversa

274 An engine-governor. The rise and

para-bolic curved arms, B, on which the

anti-frictionwheels, L, run The rods, F,

con-necting the wheels, L, with the sleevemove

itup anddownthe spindle,C,D

rectilinearmotionto therack

276 Continuous rotarymotionofthecam

a reciprocating motion

everydirection measuredacross its center

277 Col Colt's invention for

obtaining themovementofthe cylinderof a revolving

fire-arm bythe actofcocking the hammer.

Asthehammeris drawnbacktocockit,the dog,#, attached tothe tumbler,actson the

ratchet,b,onthebackof the cylinder. The

dogis held uptothe ratchetbyaspring,c.

278 C.R.Otis's safety-stop for the

plat-form of a hoisting apparatus. A are the stationaryuprights, and Bis theupperpart

of the platform working between them.

Therope,<z,by whichthe platformishoisted,

isattachedbyapin,b,and spring,c,andthe

pin is connected by two elbowleverswith

twopawls,d,whichworkinratchetssecured

totheuprights, A Theweight of the

plat-formandthe tension ofthe rope keep the

pawls out ofgear fromtheratchets in

hoist-ing orlowering the platform, butincase of thebreakage of rope the spring,c,presses down the pin,6, and the attached ends of thelevers,andso presses thepawlsintothe

ratchets and stops the descent of the

plat-MECHANICAL MOVEMENTS.

279

282

281

Clayton'sslidingjournal-box applied tothe

crank-wrist This box consists of two

ta-perliningpiecesand twotaper gibs

adjust-able by screws, which serve at the same

time totighten theboxon thewrist and to

set itouttothe slot inthecross-head as the

boxandwristwear

the alternating motion of the long

hand-lever to the right,motion is communicated

to the short" lever, the endof which is in

wheel Theshortlever has a verylimited

motion uponapin,whichis fixed inablock

ofcast-iron,which is madewith two jaws,

each having a flange projecting inward in

contact with the inner surface of the rim of

the wheel By the upward motion of the

outward endof the short lever,the rim of

thewheelisjammedbetween the endofthe

leverand theflanges of the block, so as to

causefrictionsufficienttoturn thewheel by

the furtherupward movement of the lever

prevented bya common ratchet-wheeland

pawls; as the shortlever ispusheddownit

freesthe wheelandslides freelyoverit.

281 Therevolution of thediskcauses the

lever at the right to vibratebythe pin

mov-inginthe grooveinthe faceof the disk

282 Bytherevolutionofthediskinwhich

isfixeda pinworkingina slot inthe upright

barwhichturnsonacentei near the bottom,

both endsof the bar are madeto traverse,

the toothed sectorproducingalternate

recti-linear motion in the horizontal bar at the

bottom, and also alternate perpendicular

motion of the weight

the racks This is used in working small airpumpsfor scientificexperiments

284 Represents a feeding apparatus for

thebed ofasawing machine Bythe revo-lutionofthecrankatthe lower part of the

figure, alternatemotionis communicated to

the horizontal arm of the bellcrank lever

whosefulcrum isata,near the topleft-hand

corner of the figure. Bythismeansmotion

iscommunicatedtothe catch attachedtothe vertical armof thelever,andthesaidcatch

communicates motion to the ratchet-wheel,

upon the shaftof whichisa toothedpinion,

workinginthe rack attached to the sideof thecarriage. Thefeedisvariedbyascrew

inthebell-cranklever

lathe Byturning the wheel to the right, motionis communicated to the screw,

pro-ducingrectilinearmotion of the spindle in

the endof whichthecenteris fixed

valves in steam engines. The curved toe

on the rock-shaft operates onthe lifter at-tached tothelifting-rod to raisethevalve

287 Pickering's governor Theballsare attachedtosprings theupper endofeachof

which isattached to a collar fixed on the

spindle,and thelowerendtoacollaronthe

sliding sleeve Thespringsyieldinaproper

degree to thecentrifugal forceof theballs, andraisethe sleeve; andas the centrifugal forcediminishes, theydrawthe ballstoward

the spindleand

MECHANICAL MOVEMENTS.

288

recoil,andthelatterareposeor dead-beat

K,iscaused,bytheoscillationofthependulum,

tovibrateupontheaxis,a. Betweenthetwo

escape-wheel, A, the teeth of which come alternately

against the outer surfaceof thepallet, K, and

in-ner surface ofpallet, H In 289these surfaces

are cuttoacurve concentrictotheaxis,a;

con-sequently, during the time one of the teeth is

against thepalletthewheel remains perfectly at

rest. Hencethe name repose or dead-beat. In

288the surfaces are of adiffereent form, not

ne-cessaryto explain, asitcan be understood that

any form not concentric with the axis, a, must

produce aslight recoil ofthewheel duringthe

escape of thetooth,and hencethetermrecoil

es-capement Onthepalletsleavingteeth, ateach

teethslide along the surfaces, c, e,andd, b,and

290. Another kind of pendulum

escape-ment

291. Arnold'schronometerorfreeescapement,

sometimes usedinwatches Aspring, A,is

fix-edorscrewedagainst theplateof thewatchat b.

To the under side ofthis spring is attached a

smallstop,</,againstwhichrestsuccessively the

spring is fixed a stud, /', holding a lighter and

k, atthe extremity of A, sothat it is freeonbeing

depressed, but in rising wouldlift A On the

axis of the balance is a small stud, a, which

touches the thin springateachoscillationof

bal-ance-wheel Whenthemovementis inthe

direc-tionshownbythe arrow, the stud depresses the

springinpassing, butonreturningraises it and

the spring, A, and stop, d,and thus allows one

tooth ofescape-wheel to pass, letting themfall

immediately to arrest the next. At the same

time,that this tooth escapes another strikes

It willbeunderstoodthatonlyat pointisthe

I freemovementofbalanceopposedduringan os-cillation.

292. Stud escapement, used in large clocks.

|

the otheratthe back The studs are arranged

in the same manner, and rest alternately upon

pallets isanarcdescribedfromF,this isarepose

or dead-beatescapement.

293. Duplexescapement,forwatches, so called

frompartaking of the characters of the spurand crownwheels Theaxis ofbalancecarriespallet,

B,whichateveryoscillationreceivesan impulse fromthecrownteeth. In theaxis,A,of

balance-wheeliscut a notchintowhich the teeth round

theedgeof thewheel successivelyfall aftereach oneofthecrownteeth passes theimpulsepallet, B

294 and 295. A cylinder escapement. 294 showsthe cylinderinperspective,and295shows

part of theescape-wheel ona largescale,and re-presents the different positions taken by

a, b, c,onthewheelrest alternatelyontheinside

andoutsideofcylinder. Tothe top of cylinder

isattached the balance-wheel Thewheelpallets

arebeveledso astokeep upthe impulseof

bal-ance byslidingagainst thebeveled edgeof cylin-der.

296. Lever escapement Theanchororpiece,

B,whichcarriesthepallets,is attachedto lever,

E,C,atoneendofwhich is a notch, E Ona disk secured on the arbor of balanceis fixeda small pinwhich enters the notch at the middle

Thewheelgivesan impulsetoeachof thepallets

givesimpulse to the balance-wheel in opposite

74 MECHANICAL MOVEMENTS.

Anarm, A,carriesthetwopallets,BandC.

298 Anold-fashionedwatch escapement

299 Anold-fashioned clockescapement

escape-ment; 300beingafront elevation, and 301

aside elevation Thepallet is acted upon

by the teeth ofone and the other oftwo

escape-wheelsalternately

which the pallets vibrate,and hence there

isnorecoil.

292 The pins, A, B, of the

escape-wheel are of two different forms, but the

formof thoseonthe right side is the best

is that if oneofthe pins is damageditcan easily be replaced, \vhereas if a tooth is

damagedthewhole wheelisruined

302 Balance-wheel escapement Cisthe

305 A single-pin pendulumescapement,

balance; A, B, are the pallets; and D is

|Theescape-wheelisa very small disk with the escape-wheel singleeccentric pin; itmakeshalfa

revolu-tion forevery beat of the pendulum,giving

theimpulse on the uprightfaces ofthe

pal-303 A dead-beat pendulumescapement, lets,the horizontalfaces ofwhich are dead

The and outer ones This can alsobe adapted towatches

7 MECHANICAL MOVEMENTS.

312

The pallets are formed in an opening ina

plate attached to the pendulum, and the

three teeth of theescape-wheel operateon

One tooth is shown in operation on the

upperpallet.

307 A modification of the above with

long stopping teeth, D and E, A and B

are the pallets

leaving the pendulum, P, free or detached

fromthe escape-wheel, exceptatthetime of

receiving the impulse and unlocking the

wheel There is but one pallet, I, which

receives impulseonlyduring the vibrations

of the pendulum tothe left. Thelever, Q,

locks theescape-wheel until just before the

timeforgiving the impulse,when it is

un-lockedby theclick, C,attached tothe

right,the click, which oscillates onapivot,

willbe pushedasidebythe lever

309 Mudge's gravity escapement The

pallets,A,B,instead ofbeing on onearbor,

areon two, asshown at C The pendulum

plays between the and so

pendu-lum returns thepallet falls with it,and the

weightof thepalletgives the impulse

by the three pins near the center of the escape-wheel, thepalletsvibratingfrom two

centers near the point ofsuspensionof the

by-meansofstops, DandE,onthe pallets.

311 Doublethree-legged gravity

escape-ment Two locking-wheels, A, B, C, and

set wide enough apart toallow the pallets

toliebetween them Theteethof the

stop-tooth, D, on one pallet, and those of the other one by a stop-tooth, E, on the otherpallet.

pallets are lifted alternately by the small wheel,and the stopping is done bythe ac-tion of the stops,A and B, on the larger wheel E and F are the fork-pins which

MECHANICAL MOVEMENTS.

313