Note: Descriptions are shown in the official language in which they were submitted.
3~3~ii
This lnven-tion relates to vehicular fluidic brake
systems and particularly to a brake pressure proportioning
valve adapted -to modulate the fluid pressure at one or more
hrake cy]lnders with respect to the Eluid pressure generated
by a fluid pressure source.
The device of the present inven-tion is adapted
to reduce the relative pressuriza-tion of the rear brakes
of a motor vehicle with respect to the pressurization of
the front brakes in the higher ranges of applied brake pres-
sure. This is desirable in view o:E -the fact that a portion
of the weight borne by the rear wheels of the vehicle is
-transEerred to the front wheels of -the vehicle during rapid
deceleration. ~s a result of this weight transfer, the
maximum braking effort of which rear wheels are capable is
reduced and -the maximum braking effort of -the front wheels
is increased. It is therefore desirable to deliver a higher
level of fluid pressure to the front wheels -than to the
rear wheels cduring the high rates of deceleration. This
will avoid premature rear wheel skidding, help main-tain
the vehicle under control and reduce the to-tal distance
re~uired to stop the vehicle.
The front and rear brake cylinders of a vehicle
are ordinarily designed to apply forces to the front and
rear brakes which are of the desired ratio for light braking
or ordinary stopping. During extremely rapid deceleration
or panic brake applications, however, the "buil-t-in" ratio
:is no longer satisfac-tory and the ratio should be changed
for maximum braking efficiency. The grea-ter -the rate of
decelera-tion the greater should be the difference of fron-t
brake pressure to rear brake pressure. While a bare measure-
ment of -the applied brake pressure is not a completely ac-
cura-te index o:E the rate of deceleration of -the vehicle,
.it has been found to be a practical guide which may be use-
:Eully employed in determining the poin-t at which the rela-
tive pressuri.zation of the front and rear brake cylindersshoul.d be altered. The device o:E the present invention
makes use o.E the applied brake pressure for such purpose.
~7,~
~2~3~3~;
The presen-t invention provides a pressure pro-
portioning valve for fluidic systems which comprises an
elonga-ted housing having an inlet por-t and an outlet port
and having an axial lnternal chamber communicating the inlet
port wi-th -the outlet port; an elonga-te piston member con-
~ained by the housing and axially slidable therein having
a first diame-ter defining a body por-tion near -the housing
outlet por-t and having a smaller second diameter which
enters the chamber inlet portion, the pis-ton member having
an external circumferential groove near the housin~ ou-tlet
port de~ining a piston head, the pis-ton member fur-ther having
a bore communicating -the ln:Le-t por-t wi-th the surface of
the piston body portion; seal means within -the housing which
permits axial movement of the piston member in-terposed be-
tween openings of the piston bore, the piston member beingurged toward the inle-t por-t when inlet pressure increases,
valve means retained by the pis-ton annular groove which
cooperates with the piston head such that the flow of fluid
from -the inlet port to the outlet port is restric-ted when
a predetermined inlet pressure valve is reached and adapted
to relieve pressure at the outlet upon a reduction of pres-
sure at the inlet port.
Preferably, the valve means comprises a circular
uni-tary elastomeric valve member having a plurality of cir-
cum~erentially spaced projec-tions on both of i-ts circular
planar surfaces and on its radiall~ outward surEace and
including a flared shoulder directed toward -the inlet port
of the housing, -the projections providing spaces there-
between for the free flow o~ fluid from the inlet port to
-the outlet por-t when the piston member is moved -toward -the
outlet por-t and -the piston head movable agains-t the valve
member to restric-t fluid flow when the pis-ton member is
moved toward the inle-t por-t. The present propor-t:ioning
va:Lve may be manufactured so as -to be particularly suitable
for :in-line installa-tion wi-th o-ther brake components, for
exarnple, for direct "screw-in" ins-tallation -to the outle-t
port oF a master cy]lnder.
~3~5
An embodiment of the invention is illustrated
by way of exampl.e in the drawings, in which:
Figure 1 is a pictorial view of an axial flow
proportioning valve;
Figure 2 is a cross-sectional view -taken along
line 2-2 in Figure 1 and showing the relative positioning
of the valve elements;
Figure 3 is an exploded pictorial showing the
various valve components;
Figure 4 is an enlarged view par-tly in section
and partly in elevation of the valve member;
Figure 5 is a partial -top view of -the val~e member
shown in Figure 4;
Figure 6 is a sectional view taken along line
6-6 in Figure 4; and
Figure 7 is a sectional view taken along line
7-7 in Figure 4.
Referring to Figures 1, 2 and 3, the new improved
proportionlng valve 10 includes a main body 5 having an
externally threaded inlet boss 6 axially projecting there-
from. Threaded into main body 5 opposite -threaded inlet
6 is outlet plug 4.
Within main body 5 is a central chamber or bore
52 communicating with stepped bore 53 which in turn com-
municates w:ith inlet bore 56.
Outlet plug 4 includes an axially projecting cy-
lindrical projection 42 having an outside diame-ter less
-than -the inside diameter of cen-tral bore 52 and extending
axially into the bore. The inside diameter of cylindrical
projec-tion 42 is sufEicient to permit free axial -transla-
-tion o:E piston head projection 22 -therein. ~ combination
bore and slo-t 44 extends diametrically through cylindrical
projection 42 and piston head abutmen-t surEace 43 o:E plug
'I .
Positioned within main body 5 and extending through
central charnber 52, stepped bore 53 and ir~.~.t bore 56 is
stepped piston 25 sliclably received wi-thin bore 53 and Eluid
~2~;373~i
-- 4
inle-t por-tion 26 ex-tending axially through inlet boss 6
and slidably recei.ved wi-thin inlet bore 56. Standard O-
rings 18 and 19 provide hydraulic sealing between pis-ton
25 and the main body 5 preven-ting the flow of fluid into
chamber 14 which is ven-ted to the atmosphere via duct 51.
O-ring 15: is seated in V-groove 54 acting to restrict dirt
and foreign objec-ts from entering atmosphere chamber 14.
Any other flltering means known in the art may also be used.
Stepped piston 25 includes inlet passage 21 ex-
tendin~ from inlet port 20 axially through the piston exit-
ing radially into cen-tral bore 52. Coil spring 16 sur-
rounding piston 25 is compressed between washer 12 and piston
flange 27 biasing pis-ton head 22 toward -the piston head
abu-tment surface 43 of ou-tlet plug 4. Valve member 84 is
positioned about pis-ton 25 in annular pis-ton recess 23 be-
tween flange 27 and piston head 22.
The details of construction for valve member 84
are shown in Figures 4-7. I-t will be seen tha-t valve member
84 has a depending lip 86 which, i.n the free state of valve
member 84~ is inclined angularly ups-tream and radially out-
ward. When valve member 84 is fitted into bore 52 lip 86
is deflec-ted radially inward by engagement of its outer
periphery wi-th bore 52. This prevents the downstream flow
of fluid from bore 52 around lip 86. The outer periphery
of valve member 84 downs-tream of lip 86 is provided with
a plurality of clrcumferentially spaced axially extending
ribs 88 of generally semi-cylindrical cross-sec-tional shape.
~ibs 88 contact the wall of bore 52 downstream of lip 86.
Plston flange 27 lies partly within lip 86 and engages a
plurality of spaced semispherical bosses 90 projec-ting up-
stream from valve member 84. The outer diameter of piston
flange 27 is less than the inner diameter of lip 86, -thereby
permittlng :Eluid to flow through -the spaces between -the
bosses 90. The diameter o:E pis-ton recess 23 on piston 25
is less than the inside cliame-ter of inner peripheral sur-
face 92 of valve member 84 so that an open fluid path exists
from the space be-tween bosses 90 to passage 44 ln ou-tlet
~ ~-p/~
~ ~ ~ ~ J ~
plug 4 when piston 25 is disposed in the posl-tion ill.us-
-trated in Figure 2.
The downstream side of valve member 84 is pro-
vided with a plurality of angularly spaced bosses 94 which
engage -the cylindrical projection 42 of outlet plug 4 and
angularly aligned with ribs 88 thereby providing spaces
-therebetween for f]ow of fluid ups-tream from passage 44
past piston head 22 and outward between cylindr-ical portion
42 and valve member 84 to the spaces between ribs 88. Thus
:L0 the fluid pressure a-t outle-t port 45 also exists at the
outer periphery of lip 86 such tha-t if -the ou-tle-t por-t 45
pressure is higher than the fluid pressure a-t inlet port
20 after valve closure, the outlet pressure will force lip
86 radially inward permi-t-ting reverse flow of fluid from
the outle-t por-t and into chamber 52. It will be seen tha-t
valve member 84 has a rounded valve seat 96 disposed at the
downstream end of its inner peripheral surface 92. Seat
96 engages the piston head 22 upon upstream movement of
piston 25 agai.nst spring 16. In the even-t of such upstream
movement valve member 84 is kept in position through
frictional engagement between depending lip 86 and central
bore 52.
Thus it is seen th~ fluid enters bore 52 via
inlet port 20 and passage 21. From chamber 52 fluid flows
radially inward between bosses 90 of valve member ~4,
axially be-tween the inner peripheral surface g2 of valve
member 84 and recess 23 of pis-ton 25, and into outlet port
45 via passageway 41. Fluid also flows to ou-tlet port 45
through a pa-th radially outward between bosses 94, axially
between cylindrical portion 42 of plug 4 and -the wall of
bore 52 and through bore 44 and passageway 41. This fluid
pa-th remains open until the fluid inle-t pressure a-ttains
a precletermined value. A-t this -time piston head 22 will
close against the valve member sea-t 96. Summing forces
act:ing upon piston 25 when the fluid path is open and
assum:ing that forces act:ing in the upst:ream directi.on is
pos:it:ive we see that:
3~3S
(1) F = PlA 1- S PlA2
where:
F = Resulting force acting upon piston
25 when the fluid path is open.
PlAl = Force resul-ting from the in].et pres-
sure Pl ac-ting on piston area Al.
S = Spring force
PlA2 = Force resulting from -the inlet pres-
sure Pl acting on piston area A2.
Atmospheric pressure does not enter into the equation for
forces on piston 25 since it acts equally on all the system
components and the sys-tem does not employ evacuated cavities.
During periods of brake inactivity, F is negative
and -the valve elements assume the posi-tion shown in Figure
2. So long as F is negative, the fluid path around valve
member 84 remains open and -the outle-t port pressure equals
-the inlet port pressure. However, as the inlet pressure
increases to the extent -that F becomes positive, piston
25 moves upstream until piston head 22 engages seat 96 of
~alve member 84 thereby closing off the fluid path around
valve member 84.
Once valve head 22 of piston 25 closes the fluid
path around valve member 84 the forces acting upon piston
25 become:
1 2 3 S PlA2 - Pl(A3-Al)
where:
F~ = Resulting force acting on piston 25
~ when the fluid path is closed.
P2A3 = Force resul-ting from the ou-tlet port
pressure P2 ac-ting on the piston head
area A3.
Pl(A3-~l) = Force resul-ting from inlet pressure
Pl ac-ting on an area equivalent -to
the piston head area A3 minus the
-the piston area A, when -the piston
head 22 is closed against valve member
seat 96.
35 S = Spring Eorce.
So long as Fl is positive piston 25 moves upstream
and the :Eluid path around valve member 84 will remain closed.
~ 2q~
~ ~ ~,
However, when inlet ~ressure Pl increases such that Fl be-
comes negative, piston 2S moves downstream thereby opening
the fluid path. Equation (1~ then applies. Thus by -the
movement of piston 25 upstream and downstream the working
pressure of -the fluid flowing -through the valve ls propor-
tionecl.
It is to be unders-tood that the form of the inven-
tion shown and descrlbed is to be taken as a preferred ex-
ample of the same, and that various changes in the shape,
size and arrangement of the parts may be made as do not
depart from -the spirit of the invention or the scope of
the following claims.
