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Sept. 24, 1946., >
Filled May 10, 1945
121-3- ~
Patented Sept. 24, 1946
; ».2,-4os,s0s
Walter :‘Ernst, Mount; Gilead, Ohio, assignor. to
The ‘Hydraulic ‘Development Corporation, Inc",
Wilmington, Del.,, a corporation of Delaware
Application'May 10, 1943, SerialNo. 4861,1283:
(Cl. 60—52‘)
restriction. Both. sides of the ?uid ?ow restric
tion are connected with two opposed substantially
equal areas of a '?uid operable control plunger
adapted whenmoving to vary the delivery'of» the
‘This invention ‘relates to hydraulic systems
andyin particular, to hydraulic control systems
including’ a ?uid-‘pressuresource of. the variable
?uid source, Therefore, any'substantial varia
I-t-is an object’ of-Ithis'?invention ‘tolprovidea
hydraulic system which vincludes areciprocable
tion in the pressure drop across. the fluid, ?ow
plunger and a pressure '?ui'dsourc'e of variable
. restriction will cause‘thev control plunger to vary
delivery.‘ for: supplying; pressure-?uid to said
the delivery ofrrsaid ?uid‘source in such a man
ner that the initial pressure drop is-restored.
plunger, ‘and in which vthe-delivery of the pres
sure-‘fluid sourcez-tosaid plunger 'islcontroll'ed-gaue 10
Structural arrangement"
response to. the-resistance encoun
. } Referring novv'tothe drawing. andto Figure-i
' It'lis anotherobj'ect' to=provide a hydraulic sys
thereof‘ in. particular, the.’ system shown there
tem including a, i?uid operable 'plungereactuated
by a pressure<i-‘lu-idlv source ‘of-variable delivery,
in which a1 ?uid ?ow? "restriction .is interposed be
in comprises a cylinder I having 'reciprocably
mounted therein: a plunger 2 with an advancing
area 3 and a retraction area 4, Connected to-one
end of thecy-linder l is a conduit 5 comprising
a preferably adjustable choke 6 and leading toa
tween the-?uidrsource- and ‘the plunger,v and‘v in
which the.v delivery oilwthel i?uid source is auto;
conduit 1. 'Oneend 0f.- the». conduit ‘Iv communi
matically controlled so i as. -t'o=-hold1' the; pressure
drop. across; said» --restriction-- substantially vcon 20 cates vwith a conduit-8 comprising alcheck Valve
9 and communicating-withtheconduit5;; 'Ilhe
conduit‘ 8 furthermore communicates with a
stant during the working stroke of. said. plunger.
It is-a. further object to provide: a hydraulic
systenrincluding fa. pressure ?uid Source-of." vari‘
four-way valve ' l 0 ‘of any- standard- design-adapt.
ed, whenin one. extreme position, to effect ?uid
from.-.said; ?uidzsouree, ‘in .which: ag?uid’: ?ovv re 25 communication between the pressure line »'_:H I and‘
the line 8 ‘while simultaneously connecting the
striction. is- interposediabetween, ‘said; ?uid. source
conduit. I2, communicatingv with the retraction
and.;said plunger and .ishydraulically:wnn'ected
ableadelivery‘ and-;.-a plunger operable by-?uiid
side of the plunger 2, with-the-.exhaustylinelQ
with control plunger. meansvarying the delivery
of said ?uid sourcein response to variations in
leading to a ?uid-reservoir or tank [4; When the
valve?lroccupies its other extreme position ?uid =
the. pressuredropaacrosssaid restriction.» - >
These; and- other objle‘ctslandlad'viaritages éinthe
communication is established between themes:
invention will‘ appear-more-= clearly Lfrom the Ilfol- '
sure-z line H and the conduit t2, while-‘simulta
neously the conduit: I3 is connected with .the cone
duit 8. When the. valve t0 occupies-its interme
diate or center position, no ?uid passes‘; through
the valve. The check valve 9 in the conduit ?-is
sofarranged as to permit the?ow oi-i?u-id-there
through: from’ the. conduit .= 5 to the~¢four-way: valve
l0, while preventing: the ?ow- of ?uid in the re
lowing; speci?cation in connection. with: i-thev~lac=
companying drawing, in which :
Figure 1,:diagrammatica1lyr illustrates a 'hy- .
drauliesystem. according to the invention;
Figure. 2; shows a hydraulic'system for. con
trnlling'a differentialiplunger .in..:bo'th directions.
Figure. an a diagrammatic illustration lot-a
further: ‘hydraulic . ‘system. according, - to _ ~ the in
vention in: whichthe plunger "to I be.’ controlledais
double; acting, and has; substantially 2 equal. op
>> I
General arrangement
The hydraulic: systemziaccord-ingitoathez. invens
tion substantially. comprises az?uidxsource of;vari-.-.
able "delivel'mgsuch. as a variable delivery pump...
and: a,~?uid; operable plungenqwhile: a fluid; now
verse direction.
The.conduit.’|~'1eads/to a control cylinder. l5‘
having-reciprocably mountedrtherein a plungenl?'
of substantially equalopposed areas l1 and-xiii.
The'plungery I6 is connected to the .?‘ow control
member of a variable‘ delivery. pump: |9wsotliat
rightward ‘movement of. the plunger l6:with re
gard to Figure. 1 decrease; the delivery of. the
pump l9, whereas. leftward vmovement of the.
plunger I6 causes a. spring 20in the springxcham-v
restriction, , such as a -.choke: valve, __ is; interposed 50 ber 2| vto act upon ‘the ?ow control member; of‘
‘ between the, delivery; sideot; the fluid,- source and
at least the advancing sidev ofythe, plunger tozhe
controlled. The arrangement is- rsuchi vthat. the
the pump. l9 sons to ‘increase the deliveryof
the pump Hi. The spring. 20,, which continuously
urges the pump l9 into full delivery position, is
adjustable with regard to its thrustby meansof
delivery-; ofg. the; fluid. source- to; the ra'dvaneinggside '
of the. plunger [must pass. through‘ the. fluid flow 55 an adjustingscrew. 22, The-spring chamber 2|
is hydraulically connected through a conduit 23
with the ?uid tank I4. The fluid tank further
resistance encountered by the plunger 2 during
its advancing movement drops, the plunger 2 will
more communicates through a conduit 25 with
the suction side of the pump I9 and also corn
municates through a conduit 25 with a bore 2%
in an extension of the control cylinder I5. This
bore serves for guiding the control plunger I6.
tend to increase its advancing speed. As a re
sult thereof the pressure in the conduit 21 will
drop to a greater extent than the pressure'in the
conduit 1 so that the pressure acting upon the
area U will overcome the pressure acting upon
the' areav I8 plus the thrust of the spring 20, and
The area I8 of the control plunger I6 is hydraui
will move the plunger I6 right'wardly; “This con
lically connected through a conduit 2'! with the
10 trol will result in a decrease in the delivery of
conduit 5.
It may be assumed that all parts of thesystem
shown in Figure l occupy the position in which
they appear in the said ?gure. If it is now de~
sired to have the plunger 2 perform a working
cycle, the operator shifts the valve In into posi
tion for establishing ?uid connection between the
pressure line II and the conduit 8 while simul—.
taneously connecting the.v conduits I2 and I3 with
each other. Provided the pump I9 has been
started, pressure ?uid delivered by the-pump I9
will now pass through line II, valve I9, conduits
8, ‘I and 6. From there the pressure ?uid will
pass through conduit 5 into the left hand posi
tion of the cylinder]. Here it will act upon the
advancing area 3 of the plunger 2 and move the
'~ - the pump I9 so that the previous ?ow across the
choke 6 and thereby the pressure drop across
the choke will be restored. Therefore the plung
er 2 will again move' at its initial speed, and the
control plunger I6 will maintain its position as
long as no'further variation in the resistance
encountered by the plunger 2 occurs.
When the plunger has reached the end of its
working stroke, and it is now desired to reverse
20 the plunger 2, the operator shifts the valve In into
position for establishing ?uid connection between
the pressure line II and the conduit I2, while
latter rightwardly. The ?uid expelled ‘by the
plunger 2 from the cylinder I during this right
simultaneously connecting theconduitst and I3
with each other. Pressure ?uid deliveredby the
pump I9 now passes through conduits II and. I2
into the right hand portion of the cylinder I.
Here it acts upon the retraction area 4 of plunger
2, thereby causing the, plunger 2 tomove left
wardly. , The ?uid expelled from ‘the left hand
ward movement ‘escapes through the conduit vI2,
30 portion of the cylinder I_._during- this leftward
the valve I I and the conduit I3 into the tank I4.
movement of the plunger 2 escapes through the
When the fluid delivered by the pump I9 passes
‘through- the-choke valve 6, a pressure drop will
occur across this choke valve‘which pressure drop
will make itself felt on the opposed areas IT and
conduit 5, check valve 9 and conduits .8 and I3
into the tank I4. It will be noticed that during
this retraction stroke the choke 6, is jby-passed
.‘ and therefore is ineffective, so that no speed con
trol is exerted upon the plunger 2 duringits re:
in the conduit ‘I and therefore on the areas I?
traction stroke. However, in general, no speed
of plunger I6 “Will be greater than thepressure
control is necessary during the retraction stroke
in the-conduit 21, and therefore upon‘thearea
of the plunger 2 since, as a rule, no variations in
I8, thevpressure acting on the area I7 Will some
What counteract the spring 20 and slightly re 40 resistance occur during the retraction stroke-of
the plunger 2.
duce the delivery of the pump I9 until the pres
I8 of the control plunger I6. Since the pressure
sure acting on‘ the area I‘! balances the pressure
. When it is desired to bring?the plunger 2 to a
acting on the area I 8 plus the thrust of the spring
2EI.v ' When this balancing» position has been
stop, the valve. I0 is moved-into its neutral posi
reachedjthe flow through the-choke valve 6 and
thereby the pressure drop‘ created thereby will
under‘ ‘normal conditions remain substantially
ard servomotor means, which maybe associated
with the pump. I9, will cause the pump l9 to shift
into substantially neutral or no delivery position.
constant, and the plunger 2 will perform its work
ing stroke at a substantially constant speed.
~ If it should not occur that, for some reason,-the
tion and the pump I9 is either stalled or stand
Second embodiment ‘
Referring ‘now to Figure 2, the structure shown
therein substantially corresponds’ to, the struc
plunger 2 encounters increased resistance,’ this
ture of Figure 1 withzthe exception that addition
will temporarily slow down the movement of the
a1 control means are provided for‘ e?ecting a
plunger 2. As a result thereof the pressure in'the
speed control also during .the1 retractionstroke
lefthand portion of the cylinder I and therefore,
also in the conduit 27 will increase to a greater (71 D1. of the plunger. .To'more clearly indicate v.the
similarity. between Figures 1 and 2, the elements
extent than the pressure in the conduit '1'.’ Con
of Figure 2 corresponding to those of Figure 1
sequently the previously mentioned balancing
have been designated with the same reference
condition will be disturbed, and the plunger it
numerals as inFigure 1 however, with the addi
will be moved leftwardly until the pressure acting
upon the area I'l' will again be balanced-by the 60 tional character-a. The difference between the
pressure acting on the area I8 plus the thrust of
structure of Figure 2 and the structure of Figure
the spring 20. In view. of the thus e?ected left~
1 consists in that the control mechanism associated with the advancing side of the plunger 2a
Ward movement of theplunger E6, the spring 253
is duplicated for the retraction area do. To this
vacts upon the control member of thepump ISso
as to increase the delivery of the pump~ is. in I end the righthand portion of the ‘cylinder la is
view of this increase in the delivery of the pump
connected with a conduit 28 comprisinga choke
I9, the previous flow across the choke 6 will ‘be
2a ‘and leading to the four-‘way ‘valve? Hid;
restored and therefore also the previous pressure
Branching off from the conduit 28-is a conduit
drop across the choke .6. The plunger 2 will con
30 containing a check valve 3| adapted to~allow
sequently resume its previous speed. The control -.
plunger I6 will maintain its new position, i. e.,
hand portion of the cylinder Ia to ‘the check
the thus changed delivery of the pump I9 will now
be maintained as long as the resistance encoun
tered by the plunger 2 .remainsthe same.
valve Illa while preventing the-?ow of» fluid in
the opposite direction.» Also branching on from
the conduit 28 is a'concluit 32 leading‘to the con
the ‘?ow of fluid therethrough fromith‘e'right
If it should occur, that, for some;_reason, the 575 trol-cylinder 33. . The ‘control cylinder 33lha‘s'-re-'
c’iprocablyi mounted-i therein 3a‘ plunger? v‘.341 with
tothati of Figures 1 and 2' so thatnofurther
two" opposed . substantially -equal area 35- andL36.
description thereof Iappears necessary; -
The area ~35” is engagedgby- a spring- 20a =continu-.
ously 'rurgingfthe ‘ plunger 34. 'leftwardly to thereby
tion. is by no. means limited to. the particular
It will be.»understood.that..;the present ins/‘em
cause the plunger 34 to. move the pump: Isa into 5 structureshown inthe drawing, but alsoembraces
any. modi?cation falling within. the; scope of. the
fulldelivery position; Theithrust of the spring
20a is adjustable
a threaded extension mem
Having thus fully described my invention, what
ber 31 comprising a bore 38 for guidance of the
plunger 34. The bore 38 is connected through a
conduit 39 with the tank [4a. The area 36 of 10
I claim as new and desire to secure by Letters
Patent, is:
1. In a hydraulic system, the combination with
a variable delivery source of pressure ?uid, of
a conduit 40 with the conduit 28.
a reversible ?uid motor having a pair of ports
The control of the plunger 2a during its ad- I
and operable in both directions by ?uid sup
vancing movement fully corresponds to the con
plied to said ports from said source, a ?rst ?ow
trol of the plunger 2 during the advancing move
restricting means hydraulically connecting said
the plunger 34 is hydraulically connected through
ment thereof, and therefore the description of the
advancing movement of the plunger 2a appears
source with one of said ports, a second flow re
stricting means connecting said source with the
to be super?uous. However, as previously men
other of said ports, conduit means adapted freely
tioned, in the arrangement of Figure 2 also the
20 to exhaust either of said ports when the other is
retraction stroke of the plunger 2a will be con
being supplied with pressure ?uid from said
trolled as to its speed.
source, yielding means for continuously urging
It may be assumed that the valve Ilia occupies
said ?uid source toward maximum delivery posi
the position in which the pressure line Ila is
tion, a ?rst and a second double acting plunger
in ?uid communication withthe conduit 28 while 25 each having two opposed and substantially equal
simultaneously the conduitla communicates with
areas thereon respectively connected with the
inlet and the outlet of said ?rst and second ?ow
the ‘conduit I3a. Pressure ?uid will then be de
restricting means respectively, said plungers
livered by the pump 19a through the choke 29
being connected to vary the delivery of said ?uid
into the right hand portion of the cylinder la,
thereby causing the 'plunger 2a to move leftward 30 source.
2. In a hydraulic system, in combination with
ly. The ?uid expelled from the left hand por
a variable delivery source of ?uid and a reversible
tion of the cylinder larescapes through the check
?uid operable motor having a pair of ports and
valve 9a, the conduit la and the conduit l3a
operable in both directions by ?uid supplied to
into the tank l4a. If now, for some reason,
the resistance encountered by the plunger 2 dur 35 said ports by said source, a ?rst adjustable choke
valve connecting said source with one of said
ing its retraction stroke should change, the pres
ports, a second adjustable choke valve connect
sure drop across the choke 29 will also change
ing said source with the other of said ports, con
so that the pressure conditions in the control'
duit means associated with said ports and adapted
cylinder 33 will vary accordingly. As a result
freely to exhaust one of said ports when the other
thereof, the plunger 34 will be moved in a man
ner similar to that described above in connec
tion with the plunger I6, and will bring about a ,
corresponding change in the delivery of the pump
Therefore, the initial ?ow of ?uid across
the choke 29, and thereby also the original pres
is being supplied with actuating fluid, yielding
means continuously urging said source toward
maximum delivery position, a ?rst and a second
double acting plunger each having two substan
tially equal opposed areas thereon, said ?rst and
second plungers having their opposed areas re
spectively connected with the inlet and the out
the plunger 2 will be moved at substantially its _
let of said ?rst and second choke valves respec
original speed.
tively, said plungers being connected to vary the
It will be obvious that by varying the setting 50 delivery of said ?uid source.
of the chokes 6, 6a and 29 the desired speed of
3. In a hydraulic system, a reversible ?uid
the plungers 2 and 2a may be varied. It will also
operable motor having a pair of ports, a variable
be clear that by setting the chokes 6a and 29 dif
delivery source of pressure ?uid for selectively
ferently the advancing speed and the retracting “
supplying actuating ?uid to said ports, means
speed of the plunger 2 may be independently con 55 for connecting said source with one of said ports
including a ?rst adjustable restriction, means
Third embodiment _
connecting said source with the other of said
ports and including a second adjustable restric
The system shown in Figure 3 makes use of
tion, a ?rst and a second check valve bypassing
the same principle illustrated in Figures 1 and 2
and similar parts are designated by the same
said ?rst and second restriction respectively, each
of said check valves being adapted to conduct
numerals as in Figure 1, but with the additional
character 0. However, in Figure 3 the plunger
?uid away from said motor but not vice-versa,
adjustable yielding means for continuously urg
40 to be controlled has a piston portion 4| with
ing said ?uid source toward maximum delivery
substantially equal areas 42 and 43. Further
more, the position of the four-way valve I00 and 65 position, a ?rst and a second double acting
plunger having two- substantially equal opposed
the choke 60 has been reversed with regard to
areas thereon associated with said source and
the pump 190. In other words, the delivery of
connected to vary the delivery thereof, said ?rst
the pump [9a to either the area 42 or the area
and said second plungers each having the opposed
43 must always pass through the choke 6a so that
the advancing as well as the retraction stroke of 70 areas thereof respectively connected with the
inlet and the outlet of said ?rst and second ?ow
the plunger 40 is controlled. However, the set?
restrictions respectively.
ting of the choke Ba will equally affect the con
4. In a hydraulic system, in combination with
trol of the plunger 40 in its advancing and re
ae?uid source of variable delivery, a reversible
tracting directions. Otherwise, the operation of
sure drop across this choke will be restored and
the system shown in Figure 3 fully corresponds 75 ?uid motor having a ?rst and a second port, ?rst
and second ?ow restricting means connecting
said source toward maximum ‘delivery position,
said source with said ?rst and second ports re
spectively and each operable to establish‘ a pre
and ?rst and second ?ow controlling means con
nected to vary the delivery of said source and each
comprising oppositely e?ective fluid‘ operable
means connected respectively with the inlet and
determined pressure di?erence between its inlet
and outlet in response to ?uid ?ow toward the
associated port but to permit free ?ow from the
said port, yielding means continuously urging
the outlet of one of said ?ow restricting means. i
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