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Патент USA US2406284

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Aug. 20, 1946. v
E. R. FITCH
,
' 2,406,284
BRAKE MECHANISM
Filed March 26, 1941
2 Sheets-‘Sheet l
.Il .Il
Aug. 20, 1946.
E, R, FlTcH
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2,406,284,
BRAKE‘ MECHANISM‘
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Filed March 26, 1941.
2 Sheets-Sheet 22 I
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Patented Aug. 20, 1946
2,406,284
UNITED STATES PATENT OFFICE
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2,406384
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BRAKE MECHANISM
Ellery R. Fitch, Pittsburgh, Pa., assignor to Ben
ilk-Westinghouse Automotive Air Brake Com
pany,'Pittsburgh, Pa., a corporation of Delaware
Application March 26, 1941', Serial No. ‘385,355
7 Claims. (Cl, 137-444)
1
2
This invention relates to ?uid pressure ap-V
inherent ‘friction of the valve parts in causing
paratus and more particularly to ?uid pressure
braking systems adapted for use in connection
with automotive vehicles.
such pressure differentials.
that such, pressure. will be. dependent upon .the
sures torall the brakes until a predetermined pres
sure is reached and to thereafter supply different
,
f
It has also been found desirable, in ?uid. pres
sure braking systems under certain conditions of
One of the objects of the present invention is to‘ 5 operation when reducing valves of the above
provide, in a ?uid pressure braking system hav-'
character are used‘to control thepressure to a
ing front and rear brakes, 'a ‘novel arrangement
.' portion. of ‘the brakes, to provide vfor equal pres-g
sures in all of the brakes except at the higher
wherein. the braking“ effects at the’front and‘rear
wheéls'o'f thevehicle bear a predetermined ratio
braking pressures, as it__ has been found by ex
substantially throughout, the range of braking 10 haustive tests that a large percentage of ordi
pressures, the arrangement preferably- being such
nary brake applications are made at relatively‘
low pressures, andan arrangement of this type is
that the braking effect‘ at theiront wheels of the
vehicle will be less thanbut at all times prop-or»
very desirable in insuring that all of the brakes
ti-onal to‘. the'braking reflect secured at the rear
do their share of the work under these conditions.’
wheels of the .vehicle,,such a construction avoid~ 15 At the higher pressures, the reducing valve auto
ing..the possibilitiesof the. frontwheels becom
matically cuts in torsupply different but propor
ing. locked during braking of thevehicle.
tional pressures to the brakes in order to prevent
the possibility of the front wheelbrakes locking
[Another object of ‘the. invention is to provide
and a?fecting the steering of the vehicle. ‘It is
anoveL?uid pressure apparatus in connection
with va'?uidpressu're braking system which is so 20 accordingly another object of the invention to
constituted as to reduce the pressure of the ?uid
provide a ‘combined reducing and quick release‘ ‘
supplied .to the front brakesin such a manner
valve which‘will be effective to supply equal pres~
de'g'reefof pressure applied to, the rear brakes. ‘
_ A further object of the,‘ invention is to provide. 25 but proportional pressures thereto.
‘ ‘
in. a fluid pressureapparatus of the above type,
means controlled by the operator for. rendering
the pressure- at the .front,_,brakes less than but
Yet another object of the invention is to pro
vide, in a control valve'mechanism of the above
proportion'al'te the pressure at: the rear brakes,
v_ pressure‘ release will be substantially proportional
type, means ‘for insuring that small increments of
orfsubstantially equal to the rear brake pressure, 30
from’, all the brake actuators.‘ ‘
depending on operating conditions.
A further obiectis' to provide, in a mechanism
of. the above ,type,,means for effecting a quick 1'8‘:
ducing and release valve with the parts so con
lease of pressure from the front brakes such that,
onyrelease' of the rear'brakes', the front brake
A‘still further object is to provide a hovel re
structed and arranged so as to provide an un
/ _ usually lightweight an'cl'compact structure ca;
pable of ‘ready inspection and repair, and of such
construction; as to be capable of being manufac
pressure will at all times be less than but sub~
stantially proportional to the rear brake pressure.
hired and installed on existing ?uid pressure
I Yet anotherv object of the invention is‘ to pro
braking systems at a relatively low cost.
vide a combined reducing and. quick release valve
Other objectsand features of novelty of the
for controlling. the pressure in some of the v'e-v 40 invention will appear more clearly from the fol
hicle brakes which shall insure a complete ex
lowing detailed description when taken in con-~
haust of fluid pressure. from these brakes when
the rest of. the brakes are released. .
‘
‘Yet another object of the invention is to pro-
vide means for preventing undue-vibration of the
valve parts during operatiom I. .
nection with the. accompanying drawings, illus
trating two embodiments of the invention. It
'
45 is to be expressly understood, however, that the
,
Frictional means of some sort arefsometimejs
used to prevent iunduei vibration'in ,controlvalve's
for ?uid pressure systems, andyunder certain cir-v
cumstances, such means 'havepreviously caused
unnecessary pressure differentials between var
ious'portions of'the' valves; and it is accordingly
anothercbject of ‘the present invention to pro
vide a construction so'cons'tituted as to minimize
the effects of this'addéd friction 'agwen asmthe" 65
drawings are for purposes of illustration only and
are not ‘designed as a de?nition of the limitsof
the invention, ‘ reference I being had for
pose tothe‘appended'claims.
_
v
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The two embodiments of theinvention 1111.15".
trated will be described‘in connection with the
accompanying drawings, wherein similar refer-;
ence characters refer to like parts throughout the
several views, and in which:
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Fig. ljillustrates a diagrammatic arrangement,
2,406,284
'3
connected with the outlet chamber 3| by means:
partly in section, of one form’ of the invention, ,
.7
and.
of an inlet port 4! formed in the partition. Valve
L
mechanism for controllingthe inlet port and the
exhaust port 26 includes a valve'member 42 hav
Fig. 2 illustrates, diagrammatically, partly in
section, another embodiment of the invention.
,Referring ‘more’ particularly to Fig. 1, a ?uid
‘pressure braking system incorporating the pres
ent invention is shown therein as including front
ing an inlet valve 43 'at its upper; end and an:
exhaust valve 44 at the lower‘ end, the inlet Valve‘:
being normally held me position to close theE '
inlet-port- 4-l‘ by~.m,eans of, a valve spring 45in?
andprear brake actuators H3 and M respectively,
a ?uid pressure supplyzreservoir l2, supplied with.
fluid, pressure from any suitable .means, not
terpgsed; between the partition 40 and the ex- '
haust valve. The valve member '42 is of‘ such
length that the valve 44 is normally spaced from
shown, conduits I3, l4, l5, l6 and I‘! for sup-V
. plying fluid under pressure to the front brake ,'
actuators, and conduits I73, l8‘and I9 for supply
ing ?uid under ‘pressure to the; rear brake actu» '
the upper end of the exhaust port 26 when
\the piston is at the upper end of its travel and
the. piston is~normal-.1-y maintained in this posiu
'ators. A brake valve '20, constructedgin'any‘well :_ tion‘by means of! a relatively light spring 46 ~
interposed between the lower end of the piston
known manner, and preferablyofthe, self-lap
and the valve casing, It will be understood from
ping type as disclosed in the" patenttoW. J.
Andres and R. "'S. Sanford, No.‘ 2,113,275; dated
V .the abive that the construction provides a valve
mechanism for connecting conduits l5 and It, so
October‘18, 1938, for Control mechanisrndi‘snppe
sitioned between conduit 13 and conduits l4 and 20 constructed that communication between con
duits I5 and I6 is normallyrpreventedwhile corn‘
I8 respectively, for controlling therflow, of ?uid
duit i6 is normally connected-withatmosphere,
under pressure from the reservoir l2“ to. the; front
‘and rear brake actuators. ‘A manually operable
the result being that, when the brake valve‘ 2c
control lever ‘2|’ is " provided for- operating .‘the
valve 20 in the above. manner. .The pressure of
is‘ in a position to exhaust conduits, M; and’ [a I
as well as the rear brake actuators II, no pres;
fluid suppliedv to the rear brake. actuators“. is
sure is trapped in the brake actuators H! to cause
directly controlled by the. operation of the'bral‘ce
dragging of the brakes._
in the
art.
a
.
‘
.
a
.
description that, on depression of, the pedal 21 ‘of
'
the. brake valve 20fto effect a brakeapplicatiimi
any desired degree of pressure may be supplied
to the rear brake actuators l I dependent on, the;
degree of depression of the pedal 2|, while. the _
same pressure will be supplied to the inlet chamé.
An importantifeature of the presentinvention
resides. in the automatic control of. braking pres~.
sures of the front brake actuators, and this con- > ‘
trol' is effected in such a manner that, on appli
cation‘ of the brake valve 20, the pressure sup.
7 ' plied to the front brake chambersis proportional
. '
It will be readily apparent'from the foregoing
valve 2-0 in (a manner'well known to those skilled _
-} ber 3i! of the reducing valve 22 through conduits '
l4 and I5. Since the valve springjiandthe
pistonspring 46 are only tensioned su?iciently
to. hold the valves and piston in the position
effected by means of acombined pressure reduc
shown, the pressure supplied to the inlet cham
. ing and’ quiclsrelease valve 22 interposed between
conduits '15. and [Band comprising ‘a. casing 123 40 ber 30 acts on the smal'ljarea of the piston in the‘
inlet chamber with the'result that the piston ime
provided-V with an inletipert 24 connected to. con
mediately moves downwardly, thus actuating the‘
duit l5,- an outlet port 25 connected with con
valve 44 to close the exhaust‘port 26', and acting
duit 'It‘and anlegrhaust port 26v connected with
to but less than that supplied by the brake valve
,to~ the7 rear brake actuators.’ This control is
atmosphere. The upper portion of the casing. is‘
provided with a, bore 2,‘! adapted to slidably re
ceive the smaller end of; a double diameter valve
on a further increase in pressure in, the inlet
45
chamber to move the piston away ‘from the inlet
valve 413 and establish communication between,
the inlet chamber 30_ and the outlet chamber 3|;
actuating element or’ piston 28, an enlarged’ bore
in thelower portion of the housing receiving an
enlarged portion 29 of the piston. It will thus
Communication} is thus established betweenthe '
chamber 30 connected, with the inlet- port asj
shown, an outlet chamber 3! connected with the
actuation of the~ valves as described. As the
vpre'ssure'builds up in the outlet‘chamber 3 l., ‘how
brake valve 20 and the front brake chambers NJ)
be apparent that the piston inv cooperationwith I50 as soon'as sufficient pressure has been supplied
to the inlet chamber of the reducing valve‘ to
the casing divides’ the interior of. the.- crasik-ng . into
overcome the springs 45 and 467130 cause the
' ..a'- plurality of chambers, comprising an inlet
outlet’ and exhaust portsand a third’ chamber 55‘ on
ever,the
it will‘be
piston due
understood
to ,fluidthat
pressure
the forces
will be
acting
uni v
' 3.2. ‘Sealing elements 33 and 34 are provided’ on
the small ‘and on’ the enlarged portions respec
tively of the piston, as shown, to prevent-‘the
' equal where equal pressures are supplied to both
ends ofthe piston, due to'the fact that the presa sure acting on the lower endof the pistonacts on
?ow ofiiuid pressure from the inlet and outlet
chambers to'the chamber 32, the latter being. 60 a larger area thanthat acting on the upper end;
of the piston, and the opposing forces acting on,
normally connected withatmosphere by way. of
the
piston will thus balance with the pressure in
an atmospheric'port 3% formed in the casing,
the outlet chamber, being at all times less than
a conduit‘ 35 connected'thereto and exhaust port.
the pressure in the inlet'chamber. Itrwil'l' also
33 offa conventional three-way; valve 37, this
65
be
understood‘ that, since there is a relatively
valve normally serving to connect conduit 35'
high pressure acting on theupper end of the pis-_
with exhaust port 36 and serving, when "the valve
ton and a lower pressure acting on the lowerend'
' ‘operating handle 38 is >.m_oved to aposition ‘at.
rightang'les to that shown, to’ disconnect ~con'--.. ‘of the piston in opposition thereto, the ?uid pres
sure forces acting on the piston will balance when.
duits’ 35 and 36 and ‘to connect ‘conduit 14 with.
conduit 35 in ‘such a ‘manner ‘tha‘tQthe' ‘pressure 70 the pressures in the inlet andv outlet chambersv
are inversely proportional to the areas ' of the.
's'upplied-tofc‘onduits l4" and 1:8’ from the source
rbyr'the'brake. valve is IikGWlSeTSLlIJPliEd to ‘the a small and large ends of the'piston. When
chamber '32. The upper portion :of the-pistonjis
ratio of ‘pressures is established, the, force ex,»
ert'ed ,by.springi4?_,;on the piston will tend‘v to.
provided with’ a bore :39; closed at its'lower endv
by a partition ‘40 and this-bore. isadanted tube 75. mere; ihenishn=ynvardlvte glass the, valve 43»;
2,406,284:
5
and both valves will thereafter remain in closed‘
or lapped position until the ?uid’pressure forces
acting on the piston are again unbalanced either
by operation of the brake valve Zllto increase or
decrease the pressure in thetinlet chamber 30 or‘
on leakage of the valves 43 or 44 or in .other
portions of the system. With the valves in lapped
position as described, operation of the ' brake
valve 20 to release the brakes will act to release
?uid pressure directly from the rear brake actu
ators H, at the same time eifecting a reduction
of pressure in the'inlet chamber 30 of the reduc
ing valve which will unbalance the fluid pressure
forces acting on the piston and allow the pres
sure below'the piston in the outlet chamber 3|
to move the piston upwardly, thus opening ex-,
haust valve 44 ‘and permitting ?uid pressure to
exhaust to atmosphere from the ‘ front brake
that the above pressure differential has ‘a very
small value which'is insufficient to _be' detrimental
tov vsatisfactory operation of the brakes.- The
controlling action exerted by the valve 31 on the
operation of the reducing valve 22 under the
direct control of the driver allows him toread-H
ily- adjust the operation of the front wheel
brakes to varying road conditions or load condi
tions of the vehicle without the necessity of leav
10 ing the driver's seat or stopping the vehicle to,
make the adjustment. 7
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Y
It will be cleartfrom the foregoing description
thatv the combined reducing and quickireleas'e
valve heretofore described constitutes a valve of
the so-called self-lapping type provided, with 7in-,
let and exhaust valves which are sequentially opV-'
erated, and which are both maintained in- closed
position when a predetermined relation of pres
sure balance is set up in the valve, and, as it is
chambers l0 through conduits I1 and l6,_outlet
port 25, outlet chamber 3| and exhaust port 26, 20 well known in the art that all self-lappingvalves
of this general nature have a tendency for the
whereupon the valve parts will again return to
moving parts to vibrate during variation of the
lapped position when the pressure in the cham
pressures applied to or released from the valves,
ber 3| is reduced to a value such that the forces
acting in‘ opposite directions on the piston due
damping
undesirable
means
vibration,’
are provided
such means
for minimizing
being illus
to v?uid pressure are balanced.‘ It will be clear
trated in the drawings as including a split ring
from" the foregoing description that the reducing
47 positioned in a groove 48 formed on the piston
valve parts-can be so proportioned that any de
and so constituted asto normally exert a slight
sired ratio of pressures can be obtained between
the ‘inlet chamber and the outlet chamber by
simply varying the ratio of the differential piston
areas.
a
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pressure against the walls of the large bore of
the valve casing’23 was to exert a slight retard;
ing effect on the‘movement of the piston in either
direction. The friction exerted by this ring as
well as the friction between the piston and the
casing and between the sealing rings 335and134
While a brake control mechanism of the type
described adapted to supply lower pressures to
the front brake‘ actuators than those supplied to
the rear brake actuators is extremely desirable 35 and the casing tends'to delay downwardvmovel
ment of the piston to'actuate the valves on ape
when the vehicle is operating‘ on wet or icy pave
plication of pressure to the inlet chamber ‘130
ments, such a control is often unnecessary when
from the brake valve, which causes a slight difé
thevehicle'is operating under good weather con
ferential in pressure between the inlet and outlet
ditions, and in such cases it is desirable to have
maximum braking force available at both the 40 chambers, even when the atmospheric chamber .
32 ‘is directly connected with the brake'valve' to
front and rear brakes. This operating condition
cause operation of the reducing valve to supply
is ‘readily obtainable by the present invention
a pressure to‘ the front brake actuators substan
and under the direct control of the operator, due
tially equal to that supplied to the rear brake
to the provision of the three-way valve 31 actu
ated by the handle 38 for supplying pressure to 45 actuators, so vthat, in an extreme case, it might 1
be possible to have a pressure of thirty pounds,
the atmospheric chamber 32 of the ‘reducing valve
for example, in the inlet chamber 30, and a 'pres- I
which is equal at all‘ times to the pressure sup
sure of twenty-five pounds in the outlet chamber
plied to the rear brake actuators II, it being
3|. A portion of this differential is caused’by
pointed out that, on movement of the valve han
the friction exerted by the above described ele4
dle 38 to a position at right angles to that shown
ments, and another portion of the differential
in the drawings, communication between the
pressure is due to the action of the springs 42
chamber 32 and atmosphere through port 3401.,v
and 45 in opposing operation of the ‘parts ‘to ‘open
conduit 35, valve 31 and exhaust port 36, is cut
the inlet valve 43, and it may be assumed by way
off and communication is established between
conduits 35 and I4, in such a manner that the 55 of example that the pressure differential due to
friction is of the order of three pounds, and the
pressure. in the inlet chamber 30 of the reducing
pressure differential due to the action. of the
valve is the same at all times as the pressure in
springs of the order of two pounds. Assuming
the atmospheric chamber 32. Under this condi
the above pressure values, it is clear that, if the
tion of operation, it will be clear that the oppos
ing forces acting on the piston due to ?uid pres 60 friction were eliminated with the valve operat
ing to give an output pressure substantially equal
sure in chambers 30 and 3|‘ will at all times be
to that of the input pressure, a pressure of thirty
equal when the pressures are equal, with the
pounds in- the inlet chamber would result in a
result that the application of ?uid pressure to
the inlet chamber 30 will actuate the piston to
pressure of twenty-eight pounds in the outlet
move the exhaust valve to closed position and 65 chamber,‘ but that, with the frictional effect
added, the pressure in the outlet chamber‘ cannot
the‘ inlet valve to open position to permit a sub-'
exceed twenty-?ve pounds.‘ It is accordingly’
possible to minimize and practically overcome
the pressure differential caused by frictional re
inlet and outlet chambers of the reducing valve 70 sistance by providing means for establishing‘ a
stantially equal pressure to be supplied to the
front brake actuators. vIt is recognized that a
slight pressure differential will exist between the
due to the force exerted by the valve spring 45
and the piston spring 46, but, as heretofore
pointed out, these springs are of relatively light
connection between the inlet and outlet portions
of the valve mechanism, and this is accomplished
' in the present instance as illustrated in the draw
ings by means of a port 49‘ serving to ‘connect
springs and the valve parts may be‘s'o designed 75 ports 34a and 25, and normally closed at its
construction, and experiments show, that these
'
7
leyyercencl by means .ef'a hall velve ki?uheld vih
hers...! I.- by meshes .ei
lnlaeelley valve spring 5h The springs! is so.
tensione as. to. permit the. valve 59 to open
the pressure in ‘the pert Mieseeeds'the
pressure in the‘ pertz'h bycenameuntiustih
at,’ and :QQILQPJES I :8 and I9;
eiiiit "t; a Prairie wire
tn the irent brake aetuaters
. ,
I e, bymeens. other}: v
excess ef the differential in pressures resulting
fremsthe action of springs. 4.5.‘ ahd 4%, this spring
\. in'th'e ease of. theexample iustcitedbeing
excess of that necessary to hold the valve
10
- .50 hissed-when the 'eliieiehtial aeress the valve
' is equal to two pounds. If 'the valve were setto
quit is, hrelse valve zitqeeheluiis '4 mill?!’ e
eembihesi resiueihs and Quiet; release ~lye =53Z
anel eehdiiits is and. I1‘, theeenstiiietiehei iii?
valve-timing‘substantially similarte that.’ Qi. the
eerrespehding valve shown. in Fig- 1 extent. is?
the: arrangement oi some 0i the. ihieihel hart-‘S
Th
ve. 53. is provided with a cassette whieh.
is
ed into an inlet ehemher 55., an outlet
chamber '56 and an atmospheric eheihber 51 by
theremieht beiseme tendency fer leakage to se
meehsef dehhle diameter ,pieieh 58. sliqeblii
curpast the valve which would tend to move the
me hted. inthe heusies-and provided with e .h'eh
piston upwardly t0 opentthe exhaust valve, and, 15 10w here see whiehiierms apart at iheihlei themorder to preventsuch' leakage, the tension of.
her, 55-. The. inlet chamber is eenneeted with
' ' open at exactly two pounds pressure differential,
the’ valve spring '5! is ‘increased slightly beyond
brake
at by means 9i eehdiiits'i'i'teiid'ilil
this value. 'It is also evident that, on asudden " ' theehtleteherhberéis connected. to, the iiehth else
application of pressure’ to the inletlchamber 3i]
enlistees by means s: eehdhiis its end vu,
a
on operation of the brake valve 2,8; there will‘be 20.
else he eohneeted withatiheshhere by means’
a tendency for the pressure to increase in the
Qf: an exhaust part 69, eehtraily'iormed in ‘the
lever: Wall. ef the valve easineii- ‘As the-ease
9i the valve meehenismlzz shewh in his Lj'the'
atmesnherie chamber 51 may. be alternately jeeh:
eration of the piston '21 to actuate the va1ves43 25. nested, with atmosphere or ‘with the eehgiiiit L9.
and 44, and such actionis prevented by the in
1011
port-L341; and in the port 49 with suftlcient rapid?
ity topermit a considerable volume of air to ?ow
' as the valve .50 with sresuha-nt leg in the op
clusion ofa choke element-‘i2 in thenport 49, the
area ,of which is so small in comparison with the
‘ ' leading
0i e 'eehyehtiehel
tQ-thebreke
three-way
valve through
valve theehe
31 by means
area of the c0hdhits supplying fluid’ pressure ‘to 1
' etmespherie port 5111 and, eenciuit 35 for the p111";
‘ e..f_ ehneperetine handle as serving to, connect eh
the‘ inlet chamber 39 asrto prevent the passage
eese;eeserihedheretefore in connection with the ,
' embodiment shown in Fig. 1. A reduced section
of su?icient'volume of fluid pressure through the
port 49 to prevent a’ rapid build-upof pressure ' '
in the inletch'amber 3G.
e! of the piston 58 is shdelely meuntedihabere
ii? termed in the upper portion Qfthe valve ease
There has thus been provided in'the embodi- ' ins and an enlarged portion is is adaptedte "
merit-of the invention hereinbefore described a 35 slitie in a correspondingly lesser bore “formed
7 novel __and»_ei_?cient_ valve mechanism capable of
in the lower part ef the heusine, sealing-rings
acting es e cembihed reducing velveand quick ' es and 65 being carried hythe pistenih grooves
release valve serving to maintain a pressure “in
6.1 ahdii? ‘formed thereenahd serving to prevent
the front brake actuators H) which is at all
eemmiihieatien respectively between the inlet
times-proportional to but less than the pressure
ehamher island-the. atmespherie chamber 51 and
, in the rear brake actuators I l, except when the
between the outlet chamber 56 and the chamber 7 '
pressurereducing function of the valve is ren- -
vdered ineifeetive by the eperatiehef the operator
controlledrvalve 31, this latter phase of operation
permitting the reducing valve to act to supply
substantially the same pressure to the front
brake eqiheters as is supplied‘ te the rear ‘brake.
eapertee is formed, in the lower wall of the
pisieh for permitting communication between the
‘ inlet ~?chambler 5%;5 and'the outlet chamber 56, the
vflew 0i ,lfluid pressure ‘through this port and
threuehcthe exhaust valve port 60 being con
trolled by means of a valve member l?rhavingan
Means heveialse
' been provided r for
7
7
aetueters;
‘
e?ec’tively clamping out any tendency for vibra
inlet valve 1|, formed on its upper‘ehd and an
exhaust valve 12 formed on its lower end, the
iieh 9f the valve parts as explained herein, and
50 valve member being positioned inrelation to the
' means have further been provided to minimize a 7 piston and'th'e' bore ‘69 by means of a conical
ftheleffrect of the frictional resistance imposed on ' spring :13 interposed between the lower 'facevof,
the piston by this damping means as well as vthe
the :piston. and the upper faceiof the exhaust
7' frictional vresistance of the other .llarts of the
valve >112. ‘In view of" the ‘fact that the present
' system to the end that thepressure in the front
embodiment of the invention contemplates the
brake actuators under thelatter typeuof reducing
transmission of equal pressures to the front and'
valve operationris at all times as nearly vas pos
sible equal to the pressure in the rear brake
‘actuators-
V
r
rear brake chambers :during initial application
of the brakes at relativelylow pressures, it isde
sirable thatvcommunicati'onr be maintained be
V
:Undercsome eenditiens of vehicle operation in 60 tween the inlet and outlet chambers of the valve
connection with‘braking system of the type here
in" described, which are ‘adapted to supply apres- V V 53 during such brake applications, and, in order
5 sure to the front brake actuators less than but
proportionaltothe pressure supplied to the rear
/ brake actuators, it-has, sometimes been found de
65
sirableteheve these vpressuressubstahtielly equal
dining-initialepplieatioh ef the brakes. at rele
‘to eeeQiiiplish ibis ' desirable 1353111?’ the’ Fist-9.1158
is normaiiyh'eleih a dewhwerdhesitien'byiheens
‘of a r atively liehtjsierine'm pesitiened between
the‘hpperiaee ei thepisteh-endtheiipherehd of
the'valvecasing ‘5.4,the tension of this spring be;
ing su?icient .to balance and overcome the sterl
' tively low pressures,- endie havetheprepertienal
sion exerted inithe,opposingcdirection by the .valve
springs. 13 in such 'a' manner that the exhaust
pressure action effective only atpthe higherfbrak
ins pressures, and the form ofthe invention il-p
lustrated in Fig; 2'o‘f 'theidrawmgh
w
' s isse eehst-i
valve 72 isjnoved to 4a=position closingthéupper '
tutedas to tac'coniplishlthis ,des able result. ~:"I‘he
‘7 end :0 the eighaust port :??-while theinlet valve
?uid ‘pressure braking system’ illustrate-d inthe
drawings includes 1 eg?hid 1~pressi1r
is .siieeeéiiremlthe epeer'eiid of the inlet pert
eserveir 1;?
7 adapted to be eenneeted tO'ihe-ieerbieikeeheme
is
6.9 'sh?ieiehtlystehermitliree passageoi i?liisdjullt
sereiessereeomthe-isletehsmberte-theeiitet t
2,406,284
10
9-
chamber and thence to the front wheel brake
actuators through the conduits l6 and 11.
Assuming that the operator desires to effect an
initial brake application of ten pounds pressure
for checking the speed of the vehicle, it will be
evident that,‘ on movement of the brake valve
operating lever 2| in an amount suf?cient to :es
tablish this pressure in therear brake actuators
through the conduits I8 and [9, a similar pres
sure supplied to the rear brake actuators. In like.
manner, ‘on-operation of the brake valve to effect
a release'of, ?uid pressure from the rear brake
chambers, the corresponding reduction of pres-'
sure in the inlet chamber'55 of the valve 53 will
unbalance the opposing forces acting on the pisr
ton, allowing the pressure in outlet chamber" 56
acting on the lowerface ofthe piston to move,
the piston upwardly, thus moving the exhaust,
sure will be supplied to the inlet chamber 55 of 10 valve upwardly away‘from the exhaust port and
permitting the escape of air from the frontbrake
the reducing valves through conduits I4 and I5,‘
chambers to atmosphere until the pressures act
and, in view of the fact that the inlet valve ‘H is
ing on the differential piston areas are again such
normally opened and the'exhaust valve 12 is
that the valve mechanism laps with the inlet-and
closed, this same pressure will also be supplied to
exhaust valves in‘ closed position.
the front brake actuators through inlet port 69,
In the event substantially equal pressures are
outlet chamber 56 and conduits l6 and I1. With
desired in the front and rear brake actuators,
the-valve 31 so positioned asto connect the at
throughout the range‘of braking pressures, the
mospheric chamber 51 with atmosphere through
operating handle 38 of the control valve 31 is
port 51a, conduit 35 and exhaust port 35, it will
be apparent that, on the establishment of the 20 moved to av position at'rightangles to theQOSl-g
ten pound pressure in both the inlet and outlet
tion shown onlthe drawings, and, as was the case n
chambers of the valve,‘ the forces acting inop
posite directions on the piston’ 58 dueto?uid
in thel mechanism illustrated in Fig. -1 of the
pressure acting on the opposing ends on areas
equal to that of the smaller end willbe equal, '
while an upward force will be exerted due to
the action of ?uid pressure on the annular area
drawings, this operation of the valves acts to con-,
nectthe atmospheric chamber 51 of the reducing
valve with the brake valve in such a manner
thatzthe pressures in the inlet chamber and the
atmospheric chamber of the valve are at all times
equal during the brake application. This being
the case, it is apparent that the differential ac
and, if it is desired to supply a pressure to the 30 tion of the piston is eliminated, and, as there is
no unbalanced ?uid pressure force acting to force
front brake actuators less than but proportional
the-piston upwardly, the inlet valve normally
to that supplied to the rear brake actuators at all
remains open due to the fact that the piston is
pressures of the rear brake actuators above ten
maintained in its downward position by the ac-_
pounds, it will be‘ evident that the tension of the
tion of the piston springlll. If the brake valve is
spring ‘M may be so chosen as to permit upward
now operated toefl'ect a release of ?uid pressure
movement of the piston to effect closure of the
from the brakes, a reduction in pressure will
inlet port 69 by the valve ‘II when a ten pound
corresponding to that presented by the piston
to the atmospheric pressure in the chamber 51,
pressure is established in the, inlet chamber,
whereupon the valve mechanism will- ‘be moved
to a‘ lapped position and both valves will be
closed, A further increase of pressure in the -out-.
let chamber cannot be effected until the pressure
in the inlet chamber is increased by. an amount
occur in the inlet chamber 55 as well as in the
atmospheric chamber 51, and, if the reduction
is sufficiently-rapid, the pressure acting on the
lower face of the piston will tend to force it up»
wardly, closing the inlet valve and thereafter
opening the exhaust valve ‘to exhaust ?uid pres
sure from the front brake actuators directly to
sufficient to move the piston downwardly against
the action of the relatively light valve spring 13, 45 atmosphere, and, as soon as the pressure in the
outlet chamber 56 is reduced su?iciently to- cause
it being pointed out that, when this action occurs,
the force acting upwardly on the piston due to
the piston will again be moved upwardly to close
this pressure to balance the downward forces
the inlet valve before the pressure in the outlet
equal to the airpressure onrthe upper end of the
chamber 56 can increase to a value equal to that
in the inlet chamber, it being understood that the 50 piston and the force exerted by the spring 62, the
valve parts will come to lapped position with
both valves closed. It may be desirable in some
described and on the balance of the lower end
cases to govern the rate 'of pressure ‘reduction
of the piston will move the piston upwardly to
possible in the atmospheric chamber 51 in order
close the inlet valve while the pressure in the
to prevent sudden movement of the piston which
outlet chamber is still less than that in the inlet
chamber. It will thus be apparent that, when 65 will tend to cause vibration of the valve, and this
desirable result can be obtained by the insertionv
the valves are in closedposition, and neglecting
of a choke 15 in the passage 57a.
, ,
the forces exerted on the piston'by the springs 13
As will be seen from the description inthe
and 14, the opposing forces acting on the piston
pressure acting on the annular area heretofore
due to air pressure will be respectively a down
ward force having a value equal to the area of
the'small end. of the piston multiplied by the
pressure in the inlet chamber, and an upward
force having a value equal to the total area of
previous paragraph, operation of the brake valve ’
to effect a brake release results eventually in the
parts of the reducing valve coming to lapped po
sition where both valves are closed, and, since,
under this condition, the pressure in the outlet'
chamber 56 is greater than the pressure in the
the lower end of thelpiston multiplied ‘by the
pressure in, the outlet chamber, the respective‘ 65 inlet chamber 55 by an amount corresponding to
the tension of the piston spring 14, it is consid-'
pressures thus being at all times inversely pro
ered advisable to provide means for substantially
portional to the areas on opposite ends of the
equalizing these pressures, and,’ to thisend, a
piston whenever the valves arein closed position.
connection is provided between the inlet and out- '
It Will be understood that the spring ‘M can be
tensioned to permit substantially equal pressures 70 let chambers which includes a pair of passages
16 and 11 formed in the casing, communication
in the front and rear brake chambers up to any
desired braking pressure and that differential
therethrough between chambers 55 and 56 being
pressures will be obtained at all higher braking
pressures, the pressure in the front brake actu
ators being less than but proportional to the pres
prevented by means of a ball check valve 18 nor
mally resting against a suitable valve seat 19 as
shown
With this arrangement, a slight excess
2,406, 284 1
II
12
of pressure in the chamber saris sufficient to lift
outlet chambersi an? exhaust port ingthe outlet»
the ball Valve from its seat'and allow the pres
sures to substantially equalize in the inlet and,
outlet chambers through the conduits, ‘l1 and 16,
i this construction allowing substantially equal
pressuresrto exist at‘ all times in the inlet‘ and
outlet chambers‘of the reducing valves regardless
of whether the brakes are'being' applied or re
chamber, and a valve‘member carried ‘by-‘said
element having intake and exhaust valve por
leased.
-
'
tions and normally positioned to close said-‘con
necting port, said valve operating- element having
one area subjected to the pressure‘ in the inlet
chamber and a relatively larger area subjected
to the pressure in the outlet chamber, whereby
anrinitial application of the pressure to the inlet
'
Thus‘, the present invention provides a novel 10 chamber will actuate the elementto close-the ex
di?erential braking system having means for
haust port and open the connecting port and
insuring a substantially equal degree of applica
whereby the element will be» operative to actuate
tion~of the front and rear brakes'o'f the vehicle,
the valves to maintain both ports close'd'when
under one condition of operation, and having
the pressures in said inlet and outlet chambers
means under the control of the driver for chang
are substantially inversely proportional to ‘said
ing the operationof the system to insure‘di?er- I
ential braking pressures in certain of_ the ve-nv
hicle brake actuators, while, vin the embodiment
?rst and second areas.
7
2. Fluid pressure reducing valve mechanism
' provided with a casing, a pressure responsive 'ele4
ment movably mounted in the casing and divid~
ings, a novel di?erential braking system, has/been 20 ing the casing into an, inlet chamber, an outlet
of the invention illustrated in‘ Fig.2 of the draw- ,
' provided which is adapted to insure equal brak
7 chamber, and an atmospheric ‘chamber, a port
ing'pressuresin all of’ the brake actuators dur
formed in said movable element'for connecting
said inletan'd outlet chambers,an exhaust port
ferential pressures in the front and rear‘brake'v
in ‘the outlet chamber, valvular ‘means carried
actuators during more severe brake applications, 25 by the element having inlet and exhaust valve
such an arrangement being particularly desirable
members for controlling said ports, ,means for
to insure that the brakes will all do their share
normally maintaining said inlet valve in closed
of their work during normal stopping operations,
position, means for maintaining said exhaust
and at‘the same time to insure against sliding
valve in normally open position, said element be-‘
of the steering wheels of the vehicleiwhen the ve 30' ing provided with an area subjected to a pressure
hicle is operating on slippery pavements. Since
in theoutlet chamber normally greater than the 7‘
a large number of“ normalbrake applications'are
area subjected to the pressure in I the inlet
ingpartial brakeapplications and to insure dif
made at low pressures, it will be evident that the
chamber, whereby in response to a. predetermined ,
latter arrangement will insure that all the brake
pressure supplied to the inlet chamber, the ele
shoes on the vehicle do their share of' the work 35 ment actuates the valvular means ,to maintain
and that the wear on the brake lining will be
a proportionately lower pressure in the outlet
more uniform than would‘ be possible with other i _
types of controL, Itwill also be understood that
the valve device heretofore described. is so con
structed as to eliminate the necessity of install
ing a separate quick release valve on the vehicle
as hasheretofore been necessary.
7
7
.
‘ While there has beenuillustrated and described
only two embodiments of the present invention, it
is to be understood that the same may be utilized
in various ?uid pressuresystems. For example,
1 instead of controlling the degree of braking effect
applied to the front and rear brakes of .a vehicle,
chamber, and means for subjecting the atmos
pheric chamber to the pressure obtaining in the
inlet chamber, whereby the opposing ?uid pres
40 sure forces on’ the element are substantially
equal and the valves are actuated to maintain
the pressures in the inlet and outlet chambers
substantially equal.
_
.
3. Fluid pressure reducing valve mechanism of
the type having a casing provided with an inlet
port, an outlet port and an exhaust port, and
adapted to maintain the pressure supplied to
the outlet port through the valve mechanism at
‘ the present system may‘ well be employed in a.
a value less than but proportional to the pressure
1 tractor-trailer ?uid pressure braking system, 50 supplied to the inlet port, ‘said mechanism includ
whereby the, degree of brake application of the
ing inlet and exhaust valves in the casing for
, tractor and trailer brakes is substantiallyv equal ‘
alternately connecting the inlet and outlet ports ' v
‘ under certain operating conditions, and wherein
and the outlet and exhaust ports, and a pressure
responsive element for operating the valves hav
‘ the tractorbrakes are automatically controlled
1 so that such application is less than but propor
. tional to the degree of application .of the trailer
brakes when the pressure of the ?uid applied in ,
‘ the. system is above a predetermined value, or the
‘ brake control system may be so constituted that.
' ing an area responsive to the inlet pressure, a
greater area responsive to the outlet pressure,
and a third area equal in value to the di?erence
between the ?rst two areas and responsive to
atmospheric pressure.
,
the pressure applied to the tractor brakes ‘is at 60
4. Fluid pressure reducing valve mechanism of
all times less ‘than that applied to, the trailer
the type having a casing provided with an inlet
‘ brakes, except when set by the driverto give
j equal pressures throughout the system- Various
port, an outlet port and an exhaust port connected
with atmosphere, said mechanism including a pair
‘ other changes and modi?cations of the device
of valves in said casing operable for alternately
illustrated may be resorted to, as will be readily 65 connecting said inlet and outlet ports, said outlet
understood by those skilled‘, in the art, without
and exhaust ports and for preventing communi
departing from the spirit of the invention. Ref- ‘
j erence will,‘ therefore, be had to the appended.
claims for a de?nition ofthe limits of the inven
‘
tion.
'
~What is‘ claimed is;
V
'
>
‘
1-. A reducing valve provided with‘a ‘casing hav~
‘ ing a 'movablerelement therein dividing the cas
cation between any of said ports, means for
actuating said valves including a pressure re-.
sponsive element having an area responsive to
the pressure supplied to the inlet port, a second
and larger area responsive to theypressure sup-»
plied to the outlet port and having a thirdarea I
substantially equal in valueto the difference be
‘ ing into inlet-andoutletchambers, a port, in said
tween the ?rst two areas and responsive to vat-
I movable element for connecting ‘said inlet; and;
mospheric pressure, and -means for subjecting
2,406,284
13
14
said third area at will to the pressure supplied to
the inlet port, whereby the valves are actuated
by said element to maintain the outlet pressure
substantially equal to the inlet pressure.
inlet port and another larger‘area. responsive
5. Fluid pressure control valve mechanism of
the type having a casing provided with an inlet
port, an outlet port and an exhaust port con
nected with atmosphere and adapted to connect
the inlet and outlet ports when the pressure sup
plied to the inlet port exceeds the pressure sup 10
plied to the outlet port by a predetermined ratio
to the pressure supplied to the outlet port for
actuating said valve means to establish said con
nection when the pressure differential between
said inlet and outlet ports exceeds a predeter
mined value and to disestablish said connection
in response to a decrease in said pressure differ
ential, a third area on said element normally re
sponsive to atmospheric pressure, means for sup
plying ?uid pressure from said inlet port to said
third area whereby the opposing ?uid pressure
forces acting on said pressure responsive element
and to exhaust ?uid pressure through an exhaust
are equalized, frictional means interposed be
port when the di?erence in the pressure is sup
tween said element and casing for minimizing
plied to said inlet and outlet ports is less than a
' predetermined ratio, said mechanism including 15 oscillating movement of said element, and means
for minimizing the pressure differential between
valvular means in the casing for alternately con
said inlet and outlet ports 'duerto the action of
necting said inlet and outlet ports and for con
necting said outlet port with atmosphere through
said frictional means including a valve for per
mitting the ?ow of ?uid in one direction between
the exhaust port, a pressure responsive element
for actuating said valvular means having one 20 the inlet and outlet port when said last named
pressure differential exceeds a predetermined
area responsive to the pressure supplied to the
inlet port, a second and larger area responsive
value.
.
7 . Fluid pressure control valve mechanism hav
to the pressure supplied to the outlet port and a
ing a casing provided with an inlet port, an out
third area equal to the di?erence between the
let port and an exhaust port and adapted for
?rst two areas and normally responsive to at
serially connecting said inlet and outlet ports and
mospheric pressure, whereby the valves are actu
for connecting said outlet and exhaust ports in
ated to maintain the ratio of pressures between
the inlet and outlet ports substantially inverse , response to variations in the pressure supplied to
said inlet ‘port, said mechanism including valve
to that of the ?rst two named areas, and means
for subjecting said third area to the pressure sup
plied to the inlet port whereby the effective op
posing areas on said element are rendered sub
stantially equal and the pressure supplied to the
outlet port is maintained substantially equal to
that supplied to the inlet port.
6. Fluid pressure control valve mechanism of
the type having a casing provided with inlet and
outlet ports and adapted to supply ?uid pressure
means having inlet and exhaust valves for alter
nately connecting said inlet and outlet ports and
said outlet and exhaust ports, a valve actuating
element responsive jointly to inlet and outlet port
‘pressures for controlling the operation of said
valve means and having a portion of its area _
normally responsive to atmospheric pressure,
whereby said element is actuated to close both
valves when the pressure at the outlet port is less
than the pressure at the inlet port by a predeter
from the inlet port to the outlet port at a pres
sure less than but proportional to the pressure 40 mined ratio, and means for supplying inlet port
pressure at will to said last named area, whereby
supplied to the inlet port, said mechanism in
cluding valve means operable for establishing and
said element is actuated to maintain the valves in I
closed position when the inlet and outlet port
disestablishing a connection between the inlet
pressures are substantially balanced.
and outlet ports, a pressure responsive valve actu
ating element mounted in the casing having one
ELLERY R. FITCH.
area responsive to the pressure supplied to the
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