Note: Descriptions are shown in the official language in which they were submitted.
1058664
. BACECGROUNI) OF THE INVENTION
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Field Of The Invention-
This invention pertains g¢nerally to brakes and
more particularly to safety d~vices for fluid pressure
operated brakes.
Discussion Of The Prior Art:
- Vehicular hydraulic brake systems typically
includ~ a master cylinder operative in response to force
applied to a brake pedal by the vehicle operator. A
reservoir, usually included as part of the master
cylinder, retains an excess of brake ~ uid to be used in
the system. The brake fluid, being a substantially non-
compressible iluid, acts to distribute pressure throughout
the system when the brake pedal i9 actuated. Factors such
lS as wear on the brake pads or brake ~hoes due to repeated
braking applications ultimately require added amounts of
fluid in the system. Thus, the level of fluid in the
reservoir is gradually lowered as the system requires more
and more fluid. A diaphragm, placcd in the reservoir aids
in limiting contamination of the fluid due to dirt and
other foreign matter which could impede or impain the
~yqtem function and also as the fluid level in the
reservoir i9 lowered, the diaphràgm extends do~nward with
the fluid level so as to corresp dingly displace the
volume of fluid leaving the reservoir.
Fluid level sensors are often used to indicate a
predetermined minimum level of fluid in such reservoirs.
O~e such sensor i~ immersed into the fluid and includes a
float member which follows the fluid level. Shus th~
float must be free to move in the reservoir in order to
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maintain a fixed position relstive to the lowering fluid level.
Diaphragms, ~uch as hereinabove described can interfere with the
movement of the float member and if so will render the sensor
unreliable. Also, with space in the reservoir being limited due
to the presence of the sensor, the diaphragm is limited in its
ability to move correspondingly in order to displace the fluid
leaving the reservoir. Thus, further lowering of the fluid level -
without a corresponding extension of the diaphragm can cause an
undesirable vacuum condition to exist in the reservoir which can
prevent the brake system from drawing further amounts of fluid
from the reservoir. It would be of benefit, therefore, to provide
such a reservoir with a non-vacuum creating and non-float
interfering relationship between the fluid level, the sensor
and the diaphragm so as to avoit the above-mentioned undesirable
conditions.
SUMMARY OF THE INVENTION
This application is a division of Canatian Patent
Application Serial No. 266,160 filed November 19, 1976..
It has been found, that novel solutions to the afore-
mentionet undesirable conditions can be provided. The invention
defined in the parent application provides a brake fluid reservoir
comprising: a main body portion; a cap mounted on the main body;
brake fluid level sensor means mounted on the reservoir and
protruding thereinto for indicating a predetemined minimum level
of brake fluid in the reservoir; the fluid level sensor including
float means for floating on the surface of the brake fluid;
diaphragm mean~ sealingly secured in the reservoir for correspond-
ing movement in response to a decrease in the level of brake fluid
in the reservoir and for separating a brake fluid containlng
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portion of the reservoir from an air containing portion; means
surrounding the float means for malntaining the movement of the
diaphragm from interfering engagement with the movement of the
float means; the brake fluid level sensor means being: an
elongated portion; the float means being movably mounted on the
elongated portion and buoyant in the brake fluid responsive for
maintaining a constant position with respect to the level of the
brake fluld in the reservoir; the means surrounding the brake
fluid level sensor means being: coil means mounted on the sensor
and concentrically spaced around the elongated portion and the
float means for permitting movement of the float relative to the
elongated portion and for maintaining the movement of the -:
diaphragm spaced from the elongated portion and from the float
means.
On the other hand, the invention according to the
present application broadly, provides a brake fluid reservoir
comprising: a~main body portion; a cap mounted on the,main body;
diaphragm means sealingly secured ln the reservoir for corres-
ponding movement in response to a decrease in the level of brake
fluid in the reservoir and for separating a brake fluid contain-
ing portion of the reservoir from an air containing portion;
normally closed interstice means formed in the diaphragm means,
the interstice means being openable for permitting air in the air
containing portion to pa~ into the brake fluid containing portion
unter preselected conditions; and the preselected conditions
being a difference in pressure between the two sides thereof.
Other advantages and novel features of this lnvention
will become apparent from the following detailed description of
the invention when considered in con~unction with the accompanying
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drawin gQ .
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings wherein like parts are marked alike:
FIG. 1 illustrates a simplified diagrammatic view of
a hydraulic brake sy6tem;
FIG. 2 illustrate6 a cross-sectional side elevation
of a portion of the reservoir of the invention having a raised
fluid level;
FIG. 3 graphically illustrates a cross-6ectional side
elevation of the reservoir of this invention having a loweret
fluid level and a fully extended diaphragm;
FIG. 4 graphically illu~trates a cross-sectional side
elèvation of the reservoir of this invention having
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a further lowered fluid level beyond the full extension
capabilities of the diaphragm;
FlG. 5 illustrates an isometric view of a portion
of the diaphragm including a slit or interstice formed
therein;
FIG. 6 illustrates a cross-sectional side
elevation of a portion of an alternative reservoir of
the invention having a raised fluid level; and
FIG. 7 graphically illustrates a cross-ssctional
side elevation of the reservoir of FIG. 6 having a
lowersd fluid level and a fully extended diaphragm.
pESCRIPTION OF THE PREFERRED EMBODI~n~Nr
- ~eferring now to the drawings, FIG. i generally
illustrates a simplified diagrammatic view of i hydraulic
brake system designated 10. Tandem master cylinder 12
is connected for fluid communication with two brake fluid
reservoirs formed in a single reservoir housing 14.
~owever, inasmuch as the reservoirs are similar, only one
will be shcwn and discussed. Conduit 16 fluidly connects
20 - master cyli~der 12 with front brake wheel cylinders 18
via branch conduits 16a, 16b wherea conduit 20 fluidly
ccnnects the master cylindsr with rsar brake whsel
cylinders 22 via branch conduits 20a, 20b. ~hen force i9
applied to foot pedal 24 by a vshicls operator, the fluid
transmits the pressure to the vehicle brakes.
FIG. 2 illustratQs reservoir housing 14 which
includes main body portion 26 preferably cast of iron or
some other suitable material having side walls 27 which
may be annular or of any ~u~table geometric shape. Top
¢nd 28 terminates at 30 forming an opening whereas bottom
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end 32 terminates st end wall 34 including rQplenishing
port 36 and vent port 38 for fluid com~unication with
master cylinder 12 not shown. Given this basic
configuration it can be seen in ~IG. 2 that the main body
S portion provides an adequate retainer for fluid such as
hydraulic brake fluid 40 as i5 well known.
Cap 42 shown mounted on main portion 26 is
preferably of steel and is formed with a flange portion
44 and a dome-like portion 46. An opening 48 is provided
in the tome-like portion 46 for accom~odating a fluid level
sensor to be discussed later in greater detail. Flange
portion 44 is provided for alig~ment with top end 28 of
main body portion 26 as is weLl known. A vent or port 50
may be provided in cap 42 to communicate the reservoir
to atmosphere.
Diaphragm 52 i8 prefesably of rubber or some
suitable resilient synthetic material. The diaphragm is
sealingly secured in the seservoir at outer pesiphesy 53
between cap 42 and main body portion 26 such as between
top end 28 and flange 44. Diaphragm S2 is convoluted to
permit extension thereof dcwnward into main body portion
26 as is well known. Inner pesiphery 54 is secured between
- cap 42 and the sensor ad~acent opening 48 of the cap.
A novel inclusion in diaphragm 52 i8 provided at
slit os interstice 96 provided in a psrtion of diaphragm
52 insida reservoir 14 in the vicinity of the portion of
the diaphragm secured between flange 44 of cap 42 and top
end 28 of main body portion 26. Slit 96 remains c~osed
due to the inherent resilience of the disphragm matesial
and is provided to open when a substantial pressure
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di~ference exists across diaphragm 52, see FIGS. 2 and 5.
A well kn wn sensor 56 is provided for mounting on
the reservoir so as to protrude thereinto to indicate a
predetermined minimum level of brake 1uid in the rcservoir.
S ~ain portion 58 of sensor 56 is generally of plastic and
includes a first end 60 having a threaded sxtension 62 for
extending through dome portion 46. Flange 64 secures
inner periphery 54 of diaphragm 52 against dome port~on
46 adjacent opening 48 due to tightening nut 68 threadedly
received by threaded extension 62. An elongated extended
portion 70 extends downward into the reservoir from flange
64 and ~ncludes cavity 72 extending from open first end
60 downward to terminate at cavity end wall 74 adjacent
sensor second end 75, as viewed-in FIG. 2. A well kn~w
lS ~agnetically actuated electric switching element 76 is
secured in cavity 72 by an epoxy filler or the like and
i~ ccnnected to a warning device ~not shown) external to
the sensor 56 by wires 78, as i9 well kn w n. ~ sealing
boot 80 is mounted ad~acent first end 60 to seal the
exposed open first end 60. A pla~tic or other suitsble
~ynthetic material is used to form 8 doughnut-shaped float
82 having opening 84 formed therethrough to be s}idably
accommodated by elongated extended portion 70. Float 82
includes mag~etic elements 66 imbeddet therein to
cooperatingly actuate element 76 when in proximity
tberewith so as to indicate a predetermined minimum level -
of fluid in the reservoir.
A novel inclusion in sensor 56 is provided
comprising a first annular groove 86 formed in the outer
annul~r periphery of flange 46 ad~acent first end 60 and
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a second annular groove 88 in elongated extended portion
to adjacent second cnd 75. Coil spring 90, preferably of
spriDg steel, is substantially of uniform diameter aq it
extends d~nward from first end 92 accommodated by flange
groove 86 and then diminishes in diamet~r at s~cond end 94
to be accommodated by groove 88. The spring is gr~at
enough in both diameter and length to permit fsee movement
of float 82 substantially along the length of extended
portion 70 into ultimate proxim~ty with element 76 so as
to cage float 82 from interferring engagement with
diaphragm 52 as illustrated by FIGS. 2, 3 and 4.
FIG. 3 graphically illustrates a portion of
reservoir housing 14 including the dcwnwardly extended
diaphragm 52 to correspontingly displace the fluid 40
leaving the reservoir. Also, float.member 82 is
illustrated as correspondingly follcwing the fluid level.
~ FIG. 4, graphically illustrates a portion of
reservoir housing 14 including the further downwardly
oxtending diaphragm 52. However, 9ince some of the space
in re~ervoir housing 14 is occupisd by sensor 56, diaphragm
52 is limited in its abil~ty to displace.all or practically
all of the fluid leaving the reservoir. Thus, further
lowering of the level of fluit 40 without a corresponding
displacement by diaphragm 52 can cause an undesirable
vacuum condition to exist in the reservoir. Of course,
such condition can be preselectively controlled in view
of varying the diaphragm paramRters. However, due to the
inclusion of interstice 96 in diaphragm 52 the sealing
: effect of the diaphragm can~be removed under such
conditLon- as th diaphra~= ateecpts to Fxtend douov ~dly
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1058664
ln accordance with the 1uid level. Under these condition~
a potontial vacuum condition can exist in the brake fl~it
containing portion of the reservoir wh&reas the air
containlng portion remains substantially at atmospheric
pressure. Thus a pressur~ differential may exise across
diaphragm 52 sufficient to cause interstice 96 to op~n
thus permitting air to pass therethrough fro~ the air
containing portion of the reservoir to the bxake fluid
containing portion.
In the alternative, FIG. 6 illustrates reservoir
housing 14a which includes main body portion 26a preferably
of cast iron or some other suitable material hav~ng side
walls 27a which may be annular os of any suitabls gaometric
~hape. Top end 28a terminates at 30a forming an opening
whereas bottom end 32a term~nates at end wall 34a including
replenishing port 36a and vent port 38a fos communication
oi' fluid 40a with master cylinder 12 not shown.
Cap 42a shown mounted on main portion 26a is
preferibly of steel ant is formed with a flange portion 44a
and a tome-like postlon 46a. Flange portion 44a i9 provided
for slignment with top end 28a of main body portlon 26a as
i~ well known.- A vent or port 50a may be provided in cap
42a to communicate the reservoir to atmosphere.
Diaphsagm 52a iB preerably of rubber or somo
suitable sesilient synthetic material. The tiaphragm i~
8eslingly secured in the seservoir at outer periphsry 53a
between cap 42a and main body portion 26a such as between
top end 28a and flange 44a. Diaphragm 52a is convoluted
to permit extension thereof downward into main body portion
26a as i5 well known.
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A novel inclusion in diaphragm 52a is provided at
slit or interstice 96a provided in a portion of diaphragm
52a inside reservoir 14a in the vicinity of the portion
of the diaphragm secured between flange 44a of cap 42a and
top end 28a of main body portion 26a. Slit 96a remains
closed due to the inharent resilionce of the diaphragm
material and is provided to open when a substantial
pressure difference exists across diaphragm 52a.
FIG. 7 graphically illustrates a portion of
reservoir 14a including fully downwardly extended diaphragm
52a. However, in certain instances such as where the
number of permissible convolutions in the diaphragm may
be limited due to space limitations or other factors in
the reservoir, diaphragm 52a is limited in its ability to
di~place all or practically all of the fluid leaving the
reservoir. Thus, further lowering of the level of fluid
40a without a corresponding displacement by diaphragm 52a
can cause an undesirable vacuum condition to exist in the
reservoir. Of course, as stated before, such condition
can be preselectively controlled in view of varying the
diaphragm parameters. However, due to the inclusion of
lnterstice 96a in tiaphragm 52a, the sealing effect of
the diaphragm can be removed under such conditions as
the diaphragm attempts to extend d~nwardly in accordanca
2S with the fluid level. Unter these conditions 8 potential
yacuum condition can exist in the brake fluid containing
portion of the reservoir whereas the air containing portion
re~ains substantially at atmospheric pressure. Thus, a
pressure differential may exist across diaphragm S2a
sufficient to cause interstice 96a to open thus permitting
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air to pass therethrough from the air containing portion
of tho reservoir to the braks fluid containing portion.
In operation, the braks fluid level in th~
reservoir is gradually lowered as the system requires
additional amounts of fluid due to factors such as wear on
thc brake pads or shoes. Diaphrag~ 52 gradually extends
townwardly with the fluid level so as to correspondingly
displace the volume of fluid lsaving the reservoir.
As the fluid level decreases, float member 82
correspondingly moves downwardly along extended portion 70
of sensor 56, Due to the caged relationship of float
member 82 with respect to diaphragm 52, the float member
is permitted to move downwardly along extended portion 70
without experiencing interferring engagement with
downwardly moving diaphragm 52.
Once the tiaphragm is fully extended downwardly
into the reservoir, an undesirable pressure differential
across the diaphragm is avoidsd due to the flexibl~ and
resil~ nt nature of the diaphragm material to permlt
opening of inter9tice 96 thus permitting atmospheric air
to pass therethrough into the brake fluid containing
portion from the ais containing portion. Onca the pressure
differential across the diaphragm diminishes, the
resilience of the diaphragm material permits the interstlce
to close.
The foregoing has described a novel brake fluid
seservois capable of providing a ncn-vacuum creating and
non-float interferring relationship between the fluit
level, sensor snd diaphragm'therein.
Obviously, other modifications and variations of
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the present lnvention are possible in the light of the
above teachings. It i9 therefore to be understood that
within thc scope of the appended claims the invention
may be practiced othen~ise than as specifically describsd,
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