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29, 1946.
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' J, sMlsKo
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2,410,132
LINE PRESSURE VALVE
Filed April 20, 1944
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Patented Oct.
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2,410,132
A
ESSUBE VALVE
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' .Iohn, j’siiiiskiiil Q ‘vasiiingmi; D401.) assigns}, 5y‘
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‘ _ inesnc assignments, tofl‘he B; FJGoodrich Coin;
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Q .1 .~ rApplication 1,151.20, 1941, serial No. 5313991».
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(01. 188-152)‘
The present invention relates to improvements
in‘ hydraulic brake systems,; beingwspeci?cally
concerned with line pressure valve structures
used in combination with the retracting means
brake systems and the like" characterized by a
for the brake shoes for controlling the brake shoe .
the construction, combination and arrangement
reduction in restriction to flow and accelerated
closing at a predetermined pressure.
clearance and rapidity ofbrake application. and
release.
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These and other objects and advantages re
siding in the present invention, and pertaining to
of parts will be more fully understood mm a
consideration ofthe following speci?cation and
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Line pressure valves of the type now inuse'in
annexed claims.
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hydraulic brake systems are of;the> poppet con
In the drawing, wherein. one form of the in
struction. In practice it has been found thatthis 10 vention‘is
illustrated in connection with its use
type of valve builds up substantial resistance to
in combination with hydraulic brake systems, ’
the return-?ow of oil from the actuating cylinder
Fig. 1 is an end elevational .view of the valve,
on the brake prior to closing and trapping a pre
Fig.‘ 2 is across-sectional view taken on, line
determined ?uid pressure in the brakes. 7-, The in
of Fig. 1, and .
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crease in restriction of the fluidrreturning from it) II-II
_Fig. 3 is' a diagrammatical illustration» of the
they actuating cylinder on, the. brake unduly pro
line pressure valve in combination with a hy:
longs brake release and the retracting action of
'draulic brake system.
the brake.
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In the illustrated form of the» invention, the
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According to the present invention,_it is pro
posed to substitute in lieu of ‘the poppet valve 20 valve H3 consistsof tWo cast portions l2 and J4.
The section l2 has a chamber 15in which the
heretofore used in combination with the hydrau
piston 46 is supported for movement and urged
lic brake system a valve whichis characterized
downwardly, as viewed in_Fig. 2, by a spring l8
by the fact that its movement fromfully open to
acting against the head of the piston J6 atone
fully closed is exceptionally rapid, nptwithstande
ing the fact that it is pressure -ac_tuated;,and~be¢ 25 end andagainst. the spring seat 20. at the opposite
‘end. 1 he. tension of the spring} I8 is’ regulated
cause of this characteristic materially ,lleducesthe
through, an adjustment bolt 22, ' actingv against
time interval during braking application andthe
the spring seat 20 and held in position of adjust
reduction of line pressure within thegbgralgesgtov a
predetermined value following brake release. “In
construction and function ‘the preferred formpf
valve is characterized by the fact'that the, pre
loading of the valve'which determinestheg-hold
ing pressure within the brake is counteracted by
ment through the lock nut 24. x
r
_ Cast sections l2 and [4 have threaded engage
ment at 26, and when tightly screwed together
engage with the peripheral portion 28 of .the
flexible diaphragmBDy
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In the illustrated embodiment the end of. the
fluid pressure distributed , over a- relativelygjlarge
piston I6 is shown ?at, as at 32, and when in the
area with the pressure inthe brake inexcess of 35 position shown in Fig. 2 forces the diaphragm 30
the.predetermined-holding pressure.‘ .As the ‘pres
against the complementary flat surface 34 of the
sure ' drops withingthe brake, following‘ brake , re,
casting l4 de?ned betweenthe port 36 and the
lease, this large area is effective to hold the valve
recess>39 concentric with the port 36 and into
‘substantially Wide open ,until .- the pressure has
droppedjust short of the predetermined holding 40 which the connection38 communicates. To fa
cilitate machining, the Y-surfaces32- and 34 are
pressure, atwhich-time the diminishing ?owof
preferably flat and parallel to each other, but it
‘fluid asdthe pressure drops e?ects a sudden redis
will be understood that complementary surfaces
tribution of the pressure" within. the valve from a
other than'?at may be employed with similar
relatively large area- to a, relatively‘small area,
a
thus accomplishinglan acceleration of thevalve
Communicating with the port 316 is a connec
as the line 'pressureapproaches the predeter
tion 40 through which the valve may becon
mined value and-provides the-desired- clearance
nected tov the brake operating cylinder, as shown
results.
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between the brake shoes and the brake drum.- .
in Fig. 3, through the‘line 42. The'connection
Thusv one of the objects of the} present invene
38 couples the line 44 with the cylinder 46,,which
tion is to provide an improved line pressurevalve 50 may
contain a piston actuated from the brake
in combination with the retracting means of 1 the
pedal 48 or other conventional structure found
in hydraulic brake systems, such as a control
hydraulic brake.
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Another object is to provide in combination
with a hydraulic brake system an improved, line
valve and the like.
value.
A still further object of the invention is to pro
ing mechanism usually in the form of springs,
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pressure valve for reducing the timeyintervalbef 5.5 »In operation the valve l0 is inserted in the
hydraulic‘ System between the brake and the
tween ‘brake __release and the reduction of the
source of operating pressure. As it is well un
holding pressure in the brakes to a predetermined
derstood in the art, the brake shOe has retract
which in the case of a radial brake, for example,
vide an improved line pressure valve for hydraulic 60
3
2,410,132
tend to draw the brake shoe radially inward on
brake release to provide clearance between the
brake drum and the brake shoe. In a hydraulic
brake system this retracting action of the brake
shoe functions to force the hydraulic ?uid from
the operating cylinder or its equivalent back'
through the line'. The clearance between the .
brake drum and the brake shoe can. be controlled
by limiting the amount of brake .fluid_displaced
from the brake actuating cylinder. This func-J 10
tion is performed by the line pressure valve In
which may be adjusted to change the tensioning
of the spring l8 to close the port 36 to maintain
a predetermined pressure within the brake. As
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tern having brake elements moved relative to each
other on brake application and release, retract
ing means for providing clearance between said
elements upon brake release, a brake chamber
having a movable wall actuating one of said ele
ments and against which said retracting means
reacts, a source of hydraulic pressure, and a con
duit extending between said brake chamber and
said source through'which a hydraulic ?uid ?ows
toward the brake chamber upon brake applica
tion and in the opposite direction toward said
source upon brake release, a line pressure valve
for maintaining a predetermined pressure in said
chamber to regulate the clearance between said
the brake shoe wears in service the clearance may 15 brake elements located in said conduit and char
be adjusted by increasing the tension of the
acterized by its rapid action reducing the interval
spring I8 to provide the higher pressure necessary
between brake release and the reduction to line
to take up the additional clearance due to wear.
pressure within the brake to a minimum, com
The function just described with reference to the
prising a movable-valve part of relatively large
valve I0 is similarly performed by line pressure 20 area, a valve seat for said valve part, a port of
valves now in use of the poppet type.
relatively small area opening through said seat
The improved’ performance of the valve [0 over
and communicating with that portion of said con
the poppet type, in the combination disclosed, is
duit extending to said brake chamber, said mov
due to its nonrestricting characteristics and ac
able valve part having a face complementary to
celerating. ability as the pressure within the brake 25 said seat and imposed over the entire area there
approaches the predetermined holding pressure.
of, means'continuously stressing said valve part
‘For the reason that the brake actuating pres
toward-said seat to close said port to con?ne ?uid
sure is substantially‘ greater than the holding
under pressure in- said chamber, said valve part
pressure, at the time of brake application hydrau
having a large area as compared to the area of
lic ?uid entering the valve l0 ‘through the con 30 said port subjected to hydraulic ‘pressure with
nection‘ 38 readily displaces the diaphragm 30 and
said valve part held open by pressure in said
piston l6 ‘from ‘the surface 34>surrounding the
brake chamber immediately following brake re
port 36, with the result that ?uid freely ?ows
lease, a second port communicating with that por
through the valve I0 into the brake cylinder 50
tion of said conduit extending to said source, a
through the line 42. The brake cylinder 50
common chamber into‘ which said ports open, a
throughmembers 52 urge the brake shoes 54 out
wall of - said common chamber being de?ned by
wardly against the tension of the retracting
said valve parts, ‘hydraulic pressure from said
springs 56. The brake drum is indicated at 58.
source acting against said. valve parts to move it
Following brake release the high pressure in the
from its seat-to enable ?uid to ?ow between said
brake continues to hold the valve l0 fully open 40 ports, said‘ valve part in its closed position having
as the hydraulic fluid returns through the line
only a relatively small area subjected to the pres
42 and connection 46, and port 36, into the line
sure in- said ‘brake chamber, whereby following
44. .In view of the large area of the diaphragm
brake release said valve part is fully open except
30 and the piston l6, vthe pressure within the
when pressure in said brake chamber has been
brake experiences no diiliculty in resisting the ac
reduced to» the predetermined line pressure at
tion of the spring l8 and maintaining the valve
which point the valve part rapidly closes against
l0 fully open with the restriction to ?ow main
‘pressure distributed over only the area of said
tained at a minimum. vThis condition exists
?rst port.
throughout substantially the entire return ?ow
2. In combination with a hydraulic brake sys
of the hydraulic ?uid from the brake even though 50 tem‘having brake elements moved relative to each
the pressure in the brake is rapidly dropping and
other on brake application and release, retracting
the flow of- ?uid through the valve in is rapidly
means forproviding clearance between said ele
diminishing. This fully open condition of the
ments upon-brake release, a ?uid motor actuating
valve [0 and lack of restriction will maintain due
one of said elements, a pressure source and a con;
to the large area subjected to the pressure in the
duitv for ?uid ?ow in communication with said
brake until just short of the closing of the valve
?uid motor and said pressure source, a pressure
H] to maintain the predetermined holding pres
valve in‘ said conduit maintaining a pressure
sure in the’ brake. The closing action results from
higher than atmospheric between said pressure
thediminishing flow of hydraulic ?uid through
valve and said ?uid motor, said pressure valve
the valve 10 and the decreasing pressure which 60 having a movable part of relatively large area, a
permits the surfaces 32 and 34 to approachv each
valve seat for said valve part, a port of relatively
other, but still being separated so as to permit
small area in said valve seat in communication
the large area to be subjected to the'line pressure.
with said ?uid motor, said movable valve part
The pressure area is reduced to the area- of the
having a face complementary to said valve seat,
port 36 and the stress of the spring I8 is more 65 means for-stressing said valve part to said seat to
than adequate to maintain the predetermined
maintain pressure in said ?uid motor, a chamber
pressure in the valve parts in the closed position
eircumscribing said seat in communication with
shown in Fig. 2.
said movable valve part, and a port in said cir~
Having thus described my invention, what I
cumscribing chamber communicating to said
desire to secure by Letters Patent and claim is: 70 pressure source.
1. In combination with a hydraulic brake ‘sys
JOHN SMISKO.
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