industrial biography-第48节

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pressure　in　fluids；　as　exhibited　in　the　well　known　'hydrostatic

paradox。'　In　his　patent　of　1785；　in　which　he　no　longer　describes

himself　as　Cabinet　maker；　but　'Engine　maker'　of　Piccadilly；　he

indicated　many　inventions；　though　none　of　them　came　into　practical

use；such　as　a　Hydrostatical　Machine　and　Boiler；　and　the　application

of　the　power　produced　by　them　to　the　drawing　of　carriages；　and　the

propelling　of　ships　by　a　paddle…wheel　fixed　in　the　stern　of　the

vessel；　of　which　drawings　are　annexed　to　the　specification；　but　it

was　not　until　1795　that　he　patented　his　Hydrostatic　or　Hydraulic

Press。



Though　the　principle　on　which　the　Hydraulic　Press　is　founded　had　long

been　known；　and　formed　the　subject　of　much　curious　speculation；　it

remained　unproductive　of　results　until　a　comparatively　recent　period；

when　the　idea　occurred　of　applying　it　to　mechanical　purposes。　　A

machine　of　the　kind　was　indeed　proposed　by　Pascal；　the　eminent

philosopher；　in　1664；　but　more　than　a　century　elapsed　before　the

difficulties　in　the　way　of　its　construction　were　satisfactorily

overcome。　　Bramah's　machine　consists　of　a　large　and　massive　cylinder；

in　which　there　works　an　accurately…fitted　solid　piston　or　plunger。　　A

forcing…pump　of　very　small　bore　communicates　with　the　bottom　of　the

cylinder；　and　by　the　action　of　the　pump…handle　or　lever；　exceeding

small　quantities　of　water　are　forced　in　succession　beneath　the　piston

in　the　large　cylinder；　thus　gradually　raising　it　up；　and　compressing

bodies　whose　bulk　or　volume　it　is　intended　to　reduce。　　Hence　it　is

most　commonly　used　as　a　packing…press；　being　superior　to　every　other

contrivance　of　the　kind　that　has　yet　been　invented；　and　though

exercising　a　prodigious　force；　it　is　so　easily　managed　that　a　boy　can

work　it。　　The　machine　has　been　employed　on　many　extraordinary

occasions　in　preference　to　other　methods　of　applying　power。　　Thus

Robert　Stephenson　used　it　to　hoist　the　gigantic　tubes　of　the

Britannia　Bridge　into　their　bed；*

　＇footnote。。。

The　weight　raised　by　a　single　press　at　the　Britannia　Bridge　was　1144

tons。

　。。。＇

and　Brunel　to　launch　the　Great　Eastern　steamship　from　her　cradles。　　It

has　also　been　used　to　cut　bars　of　iron；　to　draw　the　piles　driven　in

forming　coffer　dams；　and　to　wrench　up　trees　by　the　roots；　all　of

which　feats　it　accomplishes　with　comparative　ease。



The　principal　difficulty　experienced　in　constructing　the　hydraulic

press　before　the　time　of　Bramah　arose　from　the　tremendous　pressure

exercised　by　the　pump；　which　forced　the　water　through　between　the

solid　piston　and　the　side　of　the　cylinder　in　which　it　worked　in　such

quantities　as　to　render　the　press　useless　for　practical　purposes。

Bramah　himself　was　at　first　completely　baffled　by　this　difficulty。　　It

will　be　observed　that　the　problem　was　to　secure　a　joint　sufficiently

free　to　let　the　piston　slide　up　through　it；　and　at　the　same　time　so

water…tight　as　to　withstand　the　internal　force　of　the　pump。　　These　two

conditions　seemed　so　conflicting　that　Bramah　was　almost　at　his　wit's

end；　and　for　a　time　despaired　of　being　able　to　bring　the　machine　to　a

state　of　practical　efficiency。　　None　but　those　who　have　occupied

themselves　in　the　laborious　and　often　profitless　task　of　helping　the

world　to　new　and　useful　machines　can　have　any　idea　of　the　tantalizing

anxiety　which　arises　from　the　apparently　petty　stumbling…blocks　which

for　awhile　impede　the　realization　of　a　great　idea　in　mechanical

invention。　　Such　was　the　case　with　the　water…tight　arrangement　in　the

hydraulic　press。　　In　his　early　experiments；　Bramah　tried　the　expedient

of　the　ordinary　stuffing…box　for　the　purpose　of　securing　the　required

water　tightness'　That　is；　a　coil　of　hemp　on　leather　washers　was

placed　in　a　recess；　so　as　to　fit　tightly　round　the　moving　ram　or

piston；　and　it　was　further　held　in　its　place　by　means　of　a

compressing　collar　forced　hard　down　by　strong　screws。　　The　defect　of

this　arrangement　was；　that；　even　supposing　the　packing　could　be　made

sufficiently　tight　to　resist　the　passage　of　the　water　urged　by　the

tremendous　pressure　from　beneath；　such　was　the　grip　which　the

compressed　material　took　of　the　ram　of　the　press；　that　it　could　not

be　got　to　return　down　after　the　water　pressure　had　been　removed。



In　this　dilemma；　Bramah's　ever…ready　workman；　Henry　Maudslay；　came　to

his　rescue。　　The　happy　idea　occurred　to　him　of　employing　the　pressure

of　the　water　itself　to　give　the　requisite　water…tightness　to　the

collar。　　It　was　a　flash　of　common…sense　genius　beautiful　through　its

very　simplicity。　　The　result　was　Maudslay's　self…tightening　collar；

the　action　of　which　a　few　words　of　description　will　render　easily

intelligible。　　A　collar　of　sound　leather；　the　convex　side　upwards　and

the　concave　downwards；　was　fitted　into　the　recess　turned　out　in　the

neck　of　the　press…cylinder；　at　the　place　formerly　used　as　a

stuffing…box　。　　Immediately　on　the　high　pressure　water　being　turned

on；　it　forced　its　way　into　the　leathern　concavity　and　'flapped　out'

the　bent　edges　of　the　collar；　and；　in　so　doing；　caused　the　leather　to

apply　itself　to　the　surface　of　the　rising　ram　with　a　degree　of

closeness　and　tightness　so　as　to　seal　up　the　joint　the　closer　exactly

in　proportion　to　the　pressure　of　the　water　in　its　tendency　to　escape。

On　the　other　hand；　the　moment　the　　pressure　was　let　off　and　the　ram

desired　to　return；　the　collar　collapsed　and　the　ram　slid　gently　down；

perfectly　free　and　yet　perfectly　water…tight。　　Thus；　the　former

tendency　of　the　water　to　escape　by　the　side　of　the　piston　was　by　this

most　simple　and　elegant　self…adjusting　contrivance　made　instrumental

to　the　perfectly　efficient　action　of　the　machine；　and　from　the　moment

of　its　invention　the　hydraulic　press　took　its　place　as　one　of　the

grandest　agents　for　exercising　power　in　a　concentrated　and　tranquil

form。



Bramah　continued　his　useful　labours　as　an　inventor　for　many　years。

His　study　of　the　principles　of　hydraulics；　in　the　course　of　his

invention　of　the　press；　enabled　him　to　introduce　many　valuable

improvements　in　pumping…machinery。　　By　varying　the　form　of　the　piston

and　cylinder　he　was　enabled　to　obtain　a　rotary　motion；*

　＇footnote。。。

Dr。　Thomas　Young；　in　his　article　on　Bramah　in　the　Encyclopaedia

Britannica；　describes　the　〃rotative　principle〃　as　consisting　in

making　the　part　which　acts　immediately　on　the　water　in　the　form　of　a

slider；　〃sweeping　round　a　cylindrical　cavity；　and　kept　in　its　place

by　means　of　an　eccentric　groove；　a　contrivance　which　was　probably

Bramah's　own　invention；　but　which　had　been　before　described；　in　a

form　nearly　similar；　by　Ramelli；　Canalleri；　Amontons；　Prince　Rupert；

and　Dr。　Hooke。

　。。。＇

which　he　advantageously　applied　to　many　purposes。　　Thus　he　adopted　it

in　the　well　known　fire…engine；　the　use　of　which　has　almost　become

universal。　　Another　popular　machine　of　his　is　the　beer…pump；　patented

in　1797；　by　which　the　publican　is　enabled　to　raise　from　the　casks　in

the　cellar　beneath；　the　various　liquors　sold　by　him　over　the　counter。

He　also　took　out　several　patents　for　the　improvement　of　the

steam…engine；　in　which；　however；　Watt　left　little　room　for　other

inventors；　and　hence　Bramah　seems　to　have　entertained　a　grudge

against　Watt；　which　broke　out　fiercely　in　the　evidence　given　by　him

in　the　case　of　Boulton　and　Watt　versus　Hornblower　and　Maberly；　tried

in　December　1796。　　On　that　occasion　his　temper　seems　to　have　got　the

better　of　his　judgment；　and　he　was　cut　short　by　the　judge　in　the

attempt　which　he　then　made　to　submit　the　contents　of　the　pamphlet

subsequently　published　by　him　in　the　form　of　a　letter　to　the　judge

before　whom　the　case　was　tried。*

　＇footnote。。。

A　Letter　to　the　Right　Hon。　　Sir　James　Eyre；　Lord　Chief　Justice

of　the　Common　Pleas；　on　the　subject　of　the　cause　Boulton　and

Watt　v。　Hornblower　and　Maberly；　for　Infringement　on　Mr。　Watt's　Patent

for　an　Improvement　of　the　Steam　Engine。　　By　Joseph　Bramah；　Engineer。

London；　1797。

　。。。＇

In　that　pamphlet　he　argued　that　Watt's　specification　had　no　definite

meaning；　that　it　was　inconsistent　and　absurd；　and　could　not　possibly

be　understood；　that　the　proposal　to　work　steam…engines　on　the

principle　of　condensation　was　entirely　fallacious；　that　Watt's　method

of　packing　the　piston　was　〃monstrous　stupidity；〃　that　the　engines　of

Newcomen　（since　entirely　superseded）　were　infinitely　superior；　in　all

respects；　to　those　of　Watt；　conclusions　which；　we　need　scarcely

say；　have　been　refuted　by　the　experience　of　nearly　a　century。



On　the　expiry　of　Boulton　and　Watt's　patent；　Bramah　introduced　several

valuable　improvements　in　the　details　of　the　condensing　engine；　which

had　by　that　time　become　an　established　power；the　most　important　of

which　was　his　〃four…way　cock；〃　which　he　so　arranged　as　to　revolve

continuously　instead　of　alternately；　thus　insuring　greater　precision

with　considerably　less　wear　of　parts。　　In　the　same　patent　by　which　he

secured　this　invention　in　1801；　he　also　proposed　sundry　impro