Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
FLOW DIVIDER-COMBINER VALVE
Background of ~he Invention
This invention i5 directed t~ a novel flow control
valve, alld more particularly, is directed to a novel
flow divider-combiner valve.
A flow divider-combiner valve is generally designed
for use with a system which uses a pressurized hydraulic
fluid to drive at least -two hydraulic cylinders, motors,
or the like, one such being driven independently of
the other. Such a valve functions as a flow divider
when a single stream of hydraulic fluid, from a hy-
draulic fluid source, flows through the valve and there-
by is divided into at least two hydraulic fluid streams.
When flow of hydraulic fluid through such a valve is
reversed, the valve functions as a flow combiner to
combine several such hydraulic fluid streams.
For example, such a flow divider-combiner valve is often
used in combination with a wheeled vehicle having at
least two independently driven wheels. Each wheel of
the vehicle is generally driven by a respective hy-
draulic motor. Each hydraulic motor is generally
~..
connected to the combiner side oE such a valve as wellas to the divider side. Independent connections be-
tween the flow-divider side of the valve and the respec-
tive hydraulic motors are made in a manner such that
the flow divider-combiner valve supplies each hydraulic
motor, independently, with hydraulic Eluid. In addi-
tion, independent connections between the flow-cornbiner
side of the valve and the re!spect;ve motors are made
in a manner such that the divider-combiner valve re-
ceives at least two independent streams or flows ofhydraulic ~luid from the separate hydraulic motors.
Thus t the flow divider~combi~er valve e;ther indepen-
dently supplies hydraulic fluid to or independently
receives hydraulic fluid from each such hydraulic motor.
For such a wheeled vehicle, flow of hydraulic fluid
through the valve causes each of the driven wheel~s to
rotate at about the same speed and in the same direc-
tion. When flow of fluid is reversed through the
valve, rotation of the wheels is similarly reversed.
Thus, when equipped with a flow-combiner valve, the
wheeled vehicle does not require a conventional trans-
mission.
It is desirable that the divider-combiner valve cause
the wheels to rotate at about the same speed so that
the wheeled vehicle moves in a linear and predictable
fashion.
Commercially available divider-combiner valves genera~-
ly independently control flow of hydraulic fluid to
each hydraulic motor by being responsive to pressures
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within and thereby accordingly ad~justing or regulating
the flows within the connections, lines or conduits
supplying hydraulic fluid to or receiving hydraulic
fluid from the hydraulic motorsO A problem is encoun-
tered when using such commercially available divider-
com~iner valves, however, when one motor is subjected
to a no load condition (such as when its respective
wheel is on ice) or when the vehicle is turning. ~ost
of the commercially available divider-combiner valves
react to such situations in two ways. E'irst, as to
the no~load condition, conventional divider-combiner
valves generally re~porld to ~uch a con~ition by reduc-
ing flow of hydrau~lc fluid through the no-load motor
and by reducing flow through the other motor as well,
resulting in the slowing down or stopping of the vehicle.
Second, when the vehicle is directed around a corner,
the wheel traversing the greater arc causes its r~espec-
tive motor to act as a pump7 in contrast to the motor
guiding the vehicle through the turn. The motor which
acts as a pump causes a low resistance to flow to be
sensed at the conventional divider-combiner valve con-
nected thereto. The divider-combiner valve responds
by reducing the flow of hydraulic fluid to the motor
guiding the vehicle through the turn. In addition,
when the wheeled vehicle is directed around a corner,
the wheel traversing the greater arc sometimes locks
up, and upon being dragged across the ground by the
wheel traversing the lesser arc, generally gene,rates
skid marks upon the ground, rug or such support sur-
face.
Objects and Summary of the Invention
Accordingly, it is a general object of this inventionto provide a novel divider-combiner valve.
A more speclfic objec-t is to provide such a valve
which, when used with an apparatus such as a wheel.ed vehic]e,
does not react to cause such a vehicle -to stop when one wheel
oE the veh.icl.e is subjected to a no-load condition.
A related object: is to p:rovic1e such a valve which,
when used with such a vehicle, is adapted to substantially avoi.d
a whee1 lock-up condition whiGh otherwise might occur when such
a vehicle is directed around a corner.
~riefly, and in accordance with the foregoing objects,
a Elow divid.er-combiner valve unit will now be summarized.
According to one aspect of the invention a flow divi-
der-combiner valve unit comprises a cavity having first and sec-
ond spaced portions and a cavity portion intermediate the first
and second cavity portions. First and second passageways com-
municate with the first and second cavity portions, and a third
passageway communicates with the intermediate cavity portion.
First and second pressure-responsive elements are individually
movable in the cavity respectively between open positions and
progressively closed positions thereby for controlling fluid
flow between the first and second cavity portions and the first
and second passagewaysO The first and second elements respect--
ively include fourth and fifth passageways providing communica-
tion between the first and second passageways and the cavity.
The fourth passageways are alignable with one of the firs-t and
second
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passageways and the fi:L-th passageway is alignable w:i-th the other
of the firs-t and second passageways for thereby providi.ng the
open positions for enabling substantially unrestricted flow
individually through -the one and through the other of the Eirst
and second passageways. Means are disposed within the cavity
and are cooperatively engagable with the :Eirst and second ele-
men-ts in a :Eirst predetermined inrler position fixed against fur-
ther movemen-t inwardly of -the cavity for individually retaining
the first ~nd second elements substantially in the open positions
untll there is at least a predetermined substantial pressure
difference between fluid pressures in the first and second cav-
ity portions and the intermediate cavity portion~ Means are
disposed within the caivty and are coactable with the retaining
means, permitting movement of the retaining means from the inner
position outwardly of the ca~ity under influence oE the adjacent
press~e--responsive element for enabling the first and second
elements to move substantially independently oE each other toward
the respective closed positions when a predetermined pressure
differential between the intermediate cavity portion and one of
the first and second cavity portions exceeds the predetermined
pressure difference, and for causing the first and second ele~
ments to move substantially in unison when the pressure diEfer-
ential between the intermediate cavity portion and both of the
first and second cavity portions exceeds the predetermined
pressure difference.
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According to another aspect of the invention there is
providedl in combination with a fluid source, a flow divlder
combiner valve unit comprising a cavity having first and second
spaced end por-~ions and an intermecliate por-tion disposed between
the first and second cavity end por-tions. First and second
passageways provide fluid communication between the source and
respective ones of the first and second spaced cavi.ty end
portions. A third passageway provides fluid communication
betwe~en the source and the in-termedi.ate cavi-ty portion. First
and second pressure-responsive elements are individually movable
in the cavity respectively between open positions and progress-
ively closed positions thereby for controlling fluid flow be-
tween the first and second cavity end portions and the first
and second passageways. The first and second elements res-
pectively include Eourth and fifth passageways providing com--
munication between the first and second elements respectively,
inlcuding fourth and fifth passageways providing communication
between the first and second passageways and the cavity. The
fourth passageway is alignable with one of the first and second
passageways and the fifth passageway is alignabl.e with the
other of the first and second passageways for thereby providing
the open positions for enabling substantially unrestricted flow
individually through the one and through the other of the first
and second passageways. Means are disposed within the cavity
and are cooperatively engageable with the first and second
elements for individually retaining the first and second ele-
ments in a first predetermined inner position fi~ed against
r'~
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fur-ther movement inwardly of the cavlty substantially in the
open positions unti:l there is at least a predetermined substan-
tial pressure dif:Eerence between fluid pressures in the first
and second cavity portions and the intermediate cavity portion.
Means are disposed within the cavity and are coactable with
the retaining means for permittlng rnovement of the retaining
means :Erom the inner posit:ion ou-twardly oE the cavity under in-
:EI.uence o:E the adjacent pressure-responsive element fo:r enabling
the first and second elements to move substantially independen-tly
of each other toward the respectlvely closed positions when a
predetermined pressure differential between the intermediate
cavity portion and one of the first and second cavity portions
exceeds the predetermined pressure diference between the inter-
mediate cavity portion and both of the first and second cavity
portions exceeds the predetermined pressure difference.
Br;ief Description of the Drawings
The foregoing, as well as other objects, features and
advantages of the invention will become more readily understood
upon reading the following detailed description of the. illus-
trated embodimen-t, together with reference to the drawings,
wherein:
~9 ~
FIG. 1 is a schematic of a hydraulic circuit incorporat-
ing the divider-combiner valve of the invention;
FIG. 2 is a side view, partially in section, of a pre-
ferred embodiment of the flow divider-combiner valve
in accordance with the invention, respectively present-
ing open positions between ~irst and second spaced por-
tions of the cavity and :Eirst and second passageways
through the valve body;
FIG. 3 is a partial view, in section, presenting upward-
ly directed axial ~ovement of the upper pressure-respon-
sive Elow control e-ement within the cavity and subse
quent partial closure of one of the passageways;
FIG. 4 is also a partial view, in section, but present-
ing downwardly directed axial movement of the flow con-
trol element presented in FIG. 3 (within the cavity)
and subsequent partial closure of the passageway;
FIG. 5 is a side view, partially in section, presenting
one fluid-flow situation where the two pressure-respon-
sive flow control elements axially move in unison within
the cavity; and,
FIG. 6 is a side view, partially in section, presenting
another such fluid-flow situation where the two pres-
sure-responsive flow control elements axially move in
unison within the cavity.
B~L~
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Detai3ed Description of the Illustrated Embodiment
Referring to the drawings and initially to FIG. 1, the
novel divider~combiner valve wi]l now be discussed as
it is used in combination with a typical hydraulic cir-
cuit. The hydraulic circuit ;ncludes a fluid source
217 and a pump 23 for drawirlg the hydraulic Eluid from
the source 21 ~via a conduit 25) and for pumping the
fluid forward through a system or hydraulic circuit
~6. Flow of hydraulic fluid through the circuit 26
can be accomplished in any one of at least three dif-
ferent ways.
A well-known schematic representation for a convention-
al, bîased, threc-position solenoid valve, referred
to generally by the reference numeral 27, presents a
Eirst position 29 which permits or causes the hydraulic
fluid to bypass much of the hydraulic circuit 26 and
to be directed back to the fluid source 21 via a con-
duit 31.
A second position 33 of the solenoid valve 27 permitsor causes hydraulic fluid to be directed forward in
the hydraulic circuit 26 via a conduit 35 and into the
flow divider-combiner valve, referred to generally by
the reference numeral 37. With the solenoid valve ~7
in the second position 33, the flow divider-combiner
valve 37 functions as a flow divider, hydraulic fluid
being directed through individual conduits 39, 41 to
individual, respective hydraulic motors 43, 45. Eac~
hydraulic motor 43, 45 is directly coupled to and is
used to drive a respective wheel (wheels not shown).
$
Hydraulic fluid individually exLts each hydraulic motor
43, 45 via a respective conduit 47,49. The hydraulic
Eluid exiting the motors 43, 45 ls combined in a mani-
fold 51 and conveyed orwardwlthin the manifold 51,
through the conduit 31 and ultimately, is conveyed
throu~h the conduit 31 bacl~ into ~he source 21. to com-
plete the flow of h~draulic fluid throu~h the circuit 26.
~en the solenoid valve ~7 i.s set at a third position
53, flow of hydraulic ~luid through much of the divider-
combincr valve 37 and hydra~llic motor 43, 45 portions
of the hydraulic clrcui-t ~6 is reversed and the flow
divider-combiner valve 37 functions as a flow combiner:
whereby hydraulic fluid, which is flowing out of the
divider-combiner valve 37,is directed via the conduit
35, through the conduit 31, and ~ack into the fluid
source 21.
~eferring to FIGo 2, i~ will be seen that khe preferred
embodiment of ~he flow divider-combiner valve 37 of
the present invention is generally cylindrical in shape
and adapted ~o be disposed within a cavity (referred
to generally by the reerence numeral 55) o~ a valve
body 57. The cavity 55.comprises a series of individual
steps 58A, 58B, 58C, and.58D, all of which are concen-
tric with each other. The diameters of the steps 58A,
58B, 58C and 58D progressively decrease moving inwardly
into the cavity 55. .,
The divider-co~biner valve 37 structure presented in
FIGS. ~-6 includes ex~ernal circum~erential threads
59 near the opening or mouth of the cavity 55 so that
the divider-combiner valve 37 can be screwed into mated
threads which have been cut or otherwise formed in the
valve body 57.
A first O-ring 61, located near the outer or ex~erior
surface of the valve body 57 and circumferentially
mounted at ~he opening or mouth o:E the cavity 55, is
urged against ~he threads 59 (at the junction of the
divider-combiner valve 37 and the -valve body 57) by,a
portion of a valve ca~ or retainer 63 in a manner such
that the flrst O~ring 61 seats and thereby seals the
divider-combiner valve 37 into the cavity 55.
A second ~-ring 65, circumferentially carried by the
divider-combiner valve 37, seats against a circum-
ferential portion of ~he inner periphery of the cavity55, is urged outwardly against such circumferential
portion by the divider-combiner valve 37 and ther,eby
seals the first step 58A o the cavity S5 from the
second step 58B. A third O-ring 67 similarly carried
by the divider-combiner'valve 37 and similarly circum-
ferentially urged against different portions of the
inner periphery of the cavity 55 similarly seals off
or isolates the second step 58B from the third step
58C. A fourth O-ring 69 similarly isolates the third
step 58C from the fourth step 58D.
The valve body 57 presented in FIGS. 2-6 includes a
first or upper passageway 71 which permits co~unica-
tion of hydraulic,fluid between the hydraulic fluid
source 21 and the first step 58A of the cavity 55. The
valve body 57 also includes a second or intermediate
passageway 73 which permits similar hydraulic fluid
~ 10 -
communication between the hydraulic fluid source 21
and the second step 58B of the cavity 55. The valve
body 57 further includes a third or lower passageway
75 (presented in FIGS. 2, 5 and 6) which permits com
munication between the hydraulic fluid source 21
and the third and fourth steps 58C and 58D.
It can be appreciated that t:he valve hody 57 can in-
clude a plurality of individual passage.ways at any of
the above-discussed first (or upper), second (or in-
termediate) or third (or lower~ passageways 71, 73 or
75~ which respective~y perm~t fluid co~munication
between the hydraulic fl.uid source 21 and the first,
second and third (and fourth) steps 58A,.58B and 58C
(and 58D) of the cavity 55.
When the divider-combiner valve 37 functions as ~ flow
divider, the second passageway 73 functions as a fluid
input or inlet port for the valve 37,.and the first and
~hird passageways.71, 75 function as fluid output or
outlet port~. When the valve 37 functions as a flow
. combiner~ inlet and outle~ functions of the passage-
ways 71, 73 and 75 are reversed.
The illustrated.embodiment of the valve 37 is disposed
within the cavity 55 along an axis 77; and a valve
housing 79 (static in relation to the valye body 57)
separates the inner working parts of ~he valve,37 .
from the cavity 55. The valve hcusing 79 includes
threads 80 externally circumferentially cut or Dther-
wise formed along a portion of the outer periphery of
the valve housing 79 proximate to the opening or mouth
of the cavity 55. A circumferentlal inner portion of
the retainer 63 includes mated threads 80, the retainer
63 being screwed onto the valve housing 79 at the threads
80, the valve housing 79 thereby being held or otherwise
S urged into the cavity 55 by the retainer 63.
The ~alve housing 79 provides a generally cylindrical
shell, on line with and oriented about the axis 77,
enclos:ing a cylindrical chalmel 81 through which hy-
draulic fluid flows alld.wi~hin w'hich two pressure-
responsive flow con-tro'l elernents 83, 85 snugly fit.
Movement of the flrst and seeond flow control elements
83 r 85 is permitted generally along the axis 77.
Each flow con.trol elemen~ 83, 85 has ~n inner core
portion 87, a plurality of orifices 89, and a plura].ity
of respective ports 91A, 91B. Each respective inner
core por~ion 87 provides each respective flow control
element 83, 85 with a eylindrically-shaped inner void
oriented substantially about the axis,77. Each o'rifice
. 89 forms a cylindrically-shaped void through a portion
of the respective flow control elements 83, 85, each
- orifice 89 being oriented substantially transverse to
~he axis 77 and permitting fluid communication between
a portion of t.he channel 81 and the inner core 87.
Each orifice 89 has a relatively small diameter, as
contrasted agains~ the relatively large diamete.r of
the core portion 87. Each flow control elemen~ 83, 85
has a respective p'lurality of ports 91A, 91B which pro-
vide fluid communication between portions of the channel81 and respective inner portions 87 of the flow control
elements 83, 85. Like ~he orifices89, each port 91A,
91B forms a cylindrically-shaped void through a por~ion
of the respective flow control element 83, 85, each
respective port 91A, 91B being oriented substantially
transverse to t'he axis 77. An individual port 91A,
91B has a greater diameter than an individual orifice
89~ In addition, as -to the upper or the lower flow
con-~rol element 83 or 85, the c~ulati.ve cross-sectional
area of all of the ports 91A or 91B is substan-tially
greater than the cumulative cro~ss-sectional area of all
of the orifices 89.
As an initially empty valve 37, functioning as a flow
divider, is fille~ with hydraulic fluid; hydrau].ic
fluid enters`the cavity 55 via the second or inter-
mediate passageway 73 and flows ~rom the second step
58B (of the cavity 55), through the valve housing 79
via a.first opening 93, and into an intermediate por-
tion 95 of the channel 81. Once in the intermediate
portion 95, fluid flows through the orifices 89 and
into the core portion 87 of each respective flow con-
trol-element 83,-85. Hyd~aulic fluid eventually fills
'each inner core portion 87 and the remainder portions
97, 98 ~of,~he channel 81) and thereafter is caused
to flow out of the channel 81 via the ports 91A, 91B,
and into the first (or upper) and third (or lower)
passageways.71, 75. The first and third passageways 71,
75 are appropriately connected individually to hydraulic
~otors 43, 45 (FIG. 1), as discussed above.
First and second end caps 99, 101 seal respective ends
of the channel 81 thereby isolating the channel 81
frorn the cavity 55. The upwardly oriented or outwardly
extending end cap 99 is not integral with the end
portion of the valve housing 79, but, rather, is urged
against such end portion of the valve housing 79 by a
spacer 103, which itself is biasly engaged and inwardly
urged in~o the cavity 55 by ~he above~discussed cap or
re~ainer 63.
Nor is khe downwardly orlent:ed or inwardly extending
end cap 101, located at the other end portion oE the
~ralve housing 79, integral with ~he valve housing 79.
Rather, the lower end cap 101 i5 urged against the
opposite end portion of the valve housing 79 by the
base 102 of the ca-~:Lty 55.
A first or upper spring 105, preloaded to a pressure
corresponding to about 50 psi and partially restrained
by a first or upper spri.ng guide 107 which is secured
by a bolt 109 to the upper end cap 99, is oriented
along the axis 77 between the end cap 99 and the first
flow control element 83 such that the upper spring 105
urges the upper flow control element 83 away from the
end cap 99. Biasing action of the upper spring 105
upon the upper flow control element 83 is restrained,
however, when the upper spring guide 107 is restrained,
by the head of the upper bolt 109 (FIGS. 2, 4 and 6).
Such a restraint; by the upper spring guide 107 is of a
one-way nature and the spring guide 107 is generally
free to mo~e axially along the axis 77 compressing the
upper spri.ng 105 (FIGS. 3, 5). However, it is.the
action of the first or upper flow control element 83,
acting upon the upper spring guide 107, which compresses
the upper spring 105 (FIGS. 3 and 5).
In a similar fashion, a second or lower spring 111,
also preloaded to a pressure corresponding to abou-t
50 psi, is partially restrained by a second or lower
spring guLde 113 which is secured to the lower end cap
lOl by a second bolt 115. ]:n a manner somewhat similar
to ~.he above discussion, the lower spring 1].l. generally
urges the lower flow control element 85 and the lower
end cap lOl apart but is restrai.ned by the lower spring
guide 113 engaging the head o the lower bolt 115.
Restraint of the lower spring 111 is similar to the
one-way klnd of restraint discussed above in that as
the lower flow control element 85 move.s upwardly away
from the lower spring guide 113,.the lower flow control
element 85 eventually becomes fr~e from in:Eluence of
the lower spring 111 (FIG~ 6). However, the compressive
action of the lower flow control element 85 upon the
lower spring guide 113 comp~esses the lower spring 111.
Whenever the first spring 105 or the second spring 111
is in such a restrained 5 tate (FIG. 2) and while the
upper and lower flow-control elements 83~ 85 respectively
touch the upper and lower spring guides 107, 113, the
ports 91A and 91B of the first .(or upper) and second
(or lower) flow control elements 83 and 85 substantially
line up respectively.with a second and third opening
117 and 119 through the valve housing 79 thereby permit-
. ting flow of hydraulic fluid therethrough and fluidcommunication between respective first and thi~d pas-
sageways 71 and 75 and a core portion 87 of respective
first and second flow control elements 83, 85.
Prior to the present invention, the first and second
springs 105 and lll had been moderately weak springs.
It was not uncommon, in a commercially available
divider-combiner flow valve, to preload end springs to
a presswre corresponding to about 5 psi. Hydraulic
fluid pressures generally encowntered in passagewa~s
71 and 75 can easily cause the flow con-trol elements
83 or 85 to compress such a sprirlg and to restrict,
sometLmes adversely, flow through such passageways
71 or 75.
In addition, the present invention incorporates spring
guides 107 and 113 -to restrain the end springs 105 and
111 and, more importantly, to maintain a substantially
unrestricted flow conditio~ permit~ing hydraul.ic fluid
to generally freely flow ~hrough the passageways 71
and 75. Thus, it is the cooperation between the springs
105, 111 and respective spring guides 107, 113 wh.i.ch
permits fluid flow thrcugh passageways 71, 75 to be
relatively insensitive to operating upsets which other-
wi~e result in fluid pressu~e changes and resultantchanges in flows of hydraulic fluid occurring within
the passageways 71, 75.
A third or intermediate spring 121, preloaded to a
pressure corresponding to about 25 psi, is oriented
~long the axis 77 such that the first flow control
element 83 is bi~sed against the second flow control
element 85.
When the valve 37 functions as a flow divider, it can
be appreciated that the orifices 89 effect a pressure
drop for the hydraulic fluid flowing from the inter-
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media~e portlon 95 (of tlle channel 81) into the hollow
inner cores 87 of the respective flow control elements
~3, 85. Referring to -the :Eirst or upper pressure~
responsive flow control element 83 (FIG. 2), it wi.ll
be appreciated that such a press~.re drop e~ists becau~e
the orifices 89 offer much m~re resistance to flow than
do the ports 91~. ~ecause ~.he orifi.ces 89 o~e.r such
a resistance to flow, a fi.rst pressure di~ferential
exists between a firs~ pressure-responsive swrface 123
and a second pressure-r~sponsi~e surface 125 of the
first flow control element 83.
The orifices 89B (of the second flow control element
85) are similarly responsible for a second pressure
differential acting upon the second flow control ele-
ment 85.
When the valve 37 functions as a flow divider, it will
be appreciated that as fluid pressure in the inter-
mediate portion 95 of the channel 81 causes the sum of
the first and the second pressure differentials to
exceed 25 psi, the upper and the lower springs 105, 111
become compressed by the respective.flow control ele-
ments 83, 85. As the first flow control element 83
compresses the first spring 105, the ports 91A of the
first flow control element 83 move in relation to the
(corresponding) second opening 117 (FIG. 3) and flow
therethrough becomes restricted (to a slight degree).
Likewise, compression of the second or lower spring 111
by the second or lower flow control element 85 similarly
moves the ports 91B (of the second flow control element
85) in relation to the (corresponding) third opening
119 similarly resulting in slight restriction of hy-
~ 17-
draulic fluid therethrough.
The first and the second flow control elements 83, 85
each incLude an L-shaped ~all 127, 129 structurally
integral therewith and ext:endi}lg outwardly therefrom
in the direction of the ot.her flow control element
83, 85. The L-shaped end ~r. tail 127 of the upper flow
control element 83 and the I..-shaped tail 129 of the
lower flow control element 85 are axially inserted
in-to opposite ends of the intel~medlate spring 121, are
adapted to inter~it therein, and are fur~her adapted
to engage at end portions 131 of the L-shaped tails
127, 129 so that the first and second flow control
elements 83, 85 move in un.ison (FIG. 5) when fluid
pressure in the intermediate portion 95 (of the cavity
55) is sufficient to compress the end springs 105, 111
and cause the end portions 131 of opposing tails .127,
129 to touch. And when fluid pressure within the upper
passageway 71 or the lower passageway 75 or both such
passageways 71, 75 ~FIG. 6) is sufficiently greater
than the pressure exer~ed by the intermediate spring
121, the intermediate spring 121 becomes compressed and
the L-shaped tail 127, 129 of one flow control element
83, 85 butts agains~ the other flow control element
at ends 133; and both flow.control elements-83, 85 move
in unison ~FIG. 6) within the channel 81.
When the divider-combiner valve 37 is functioning as a
flow divider and the first or upper passageway 71 is
supplying a hydraulic.motor 43 or 45 which is under
little or no load (as would be the case when such a
hydraulic motor 43 or 45 drives a wheel on ice), the
-1.7A-
no-load hydraulic mo~or ~3 or 45 offers very little
resistclnce to flo~ o.E hydraulic fluid and hydxaulic
fluid pressure resul~ingly drops in the first passage-
way 71. ~Iydraulic fluid pressure in the inner core
87 of the first or upper flow control elemen-t 83 accor-
dingly drops, which results in an increase in the (first)
pressure ~lferen-till (between the first and t'he second
pressure-responsive sur~aces 123 and 125) of the first
or upper flow control element 83. Whereupon, the first
flow control element 83 moves upwardly ln the cavlty 81,
usually compressi~g the upper spring 1~5 (FIG. 3).
However, because the upper spring 105 is relatively
insensitive to most pressures no~mally experienced
within the upper passageway 71, the upper spring 105
is not substantially compressed and flow through the
first or upper passageway 71 is not entirely cut off
(FIG. 3); and if the flow control elements 83, 85.are
acting in unison (FIG. 5), fluid ~low through the
lower fluid passageway 75 is not greatly affected.
When flow of hydraulic fluid i9 reversed through the
divider-combiner valve 37, the present invention pre-
sents substantially the same advantages as to flow of
hydraulic fluid through the passageways 71 and 75.
The flow control elements 83, 85 of the valve 37 are
generally responsive to fluid pressure in the first
(or upper) and third (or lower~.fluid passageways 71,
75, and are adapted to generally adjust flow of hy-
draulic fluid accordingly. ~owever, the various ele-
ments of the novel divider-combiner valve 37 of the
inven~ion act or operate co-operatively to prevent
total cut-off or restriction of hydraulic fluid through
the passageways 71, 75 when the valve 37 is responding
to operating upsets.
8~
Accordingly, -the present in-vention is relativel~ insen-
sitive to system upsets such as would normally be ex-
perlenced when the wheeled vehicle (discussed above)
is on ice or is rotmding a corner. Incorporation of
the valve 37 of ~he present invention within such a
whee]ed vehicle has substantially eliminated the wheel
]ock-up problem discussed above and has significantly
reduced the wheel-dragging problem (addressed above)
experienced when the wheeled vehicle negotiates a curve.
The flow control elements 83, 85 of ~he divider-combiner
valve 37 of the pr~sent invention normally act indepen-
dently at the start o~ operation? eventually act in
unison (FIGS. 5, 6), normally initially act independently
when a system upset arises and eventually again act in
unison sometime thereafter.
What has been illustrated and described herein is a novel
flow divider-combîner valve unit. While the divider-
combiner valve unit of the present invention has beenillustrated and described wi~h reference to a preferred
embodiment, the invention is not limited thereto. On
the contrary, al~ernatives, changes or modifications may
become apparent to those skilled in the art upon reading
the foregoing description. Accordingly, such alterna-
tives, changes or modifications are to be considered
as forming a part of the invention insofar as they f~l
within the spirit and scope of the appended cl~ims.
