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Патент USA US3037364

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June 5, 1962
'
F. H. TENNIS
3,037,354
HYDRAULIC APPARATUS FOR VARIABLE LOAD SYSTEMS
Filed May 2, 1961
3 Sheets-Sheet 1
RESERVOHZ
ind/MW
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June 5, 1962
3,037,354
F. H. TENNIS
HYDRAULIC APPARATUS FOR VARIABLE LOAD SYSTEMS
3 Sheets-Sheet 2
Filed May 2, 1961
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June 5, 1962
3,037,354
F. H. TENNIS
HYDRAULIC APPARATUS FOR VARIABLE LOAD SYSTEMS
Filed May 2, 1961
3 Sheets-Sheet 3
C
United States Patent
2
1
of hydraulic apparatus of the character described which
enables the power output of a single prime mover to be
3,037,354
very advantageously utilized in automatically effecting
HYDRAULIC APPARATUS FOR VARIABLE
LOAD SYSTEMS
3,037,354
Patented June 5, 1962
_
Francis H. Tennis, Milwaukee, Wis., assign'or to Hydraulic
Unit Specialties ‘Company, Pewaukee, Wis., a corpora“
tion of Wisconsin
Filed May 2, 1961, Ser. No. 107,253
12 Claims. (Cl. 60—52)
This invention relates ot control means for hydraulic 10
apparatus, and refers more particularly to means for in
creasing the cycle of speed of hydraulic apparatus of the
type which normally encounters substantially varying load
forces during its working cycle.
In certain types of equipment, such as front end loaders,
power shovels and the like, a large force must be exerted
during ‘one part of the working stroke or cycle of the ap
slow movement of a hydraulic motor when the same is
heavily loaded and rapid movement of the motor when it
is lightly loaded.
It is also an object of this invention to- provide hydraulic
apparatus whereby the above stated objects can be ob
tained, and which apparatus is nevertheless very simple,
inexpensive and dependable.
Still another object of this invention is to provide a
hydraulic apparatus of the type which comprises pump
means driven by a prime mover, a hydraulic motor, and
a control valve of the open center type for directing hy
draulic pressure ?uid from the pump means either to the
hydraulic motor, for actuation of the same, or to a reser
voir or the like at times when operation of the motor is not
desired, which apparatus incorporates two pumps that are
driven by the prime mover, one of which is at all times
exertion of substantially less force but is desirably accom
plished at relatively high speed. For example, in the case 20 connected with the control valve and the other of which
is connected with the control valve only at times when the
of a power shovel or the like, the earth engaging imple
hydraulic motor is lightly loaded, so as to supplement the
ment must often exert a large force at the beginning of its
output of the ?rst pump at such times and thus cause faster
cycle, when it is breaking dirt loose from a compacted pile,
operation of the motor.
but after “break out” a much smaller force is usually re—
A further object of this invention is to provide a simple
quired to lift or move ‘the loosened dirt, and it then be 25
and inexpensive pilot operated unloading valve for hydrau
comes desirable for the earth engaging implement to oper
lic apparatus of the character described, having a body
ate at a comparatively high speed in order to minimize the
with an inlet and a pair of outlets and incorporating pres
cycle time and expedite the work. Where such a machine
sure responsive valve means for directing pressure ?uid
incorporates hydraulic control and actuating apparatus,
as is now commonly the case, a cycle of this type requires 30 from the inlet to one of the outlets when the pressure at
said one outlet is below a predetermined value, and for
that during the initial phase of the cycle, when the ground
directing such ?uid to the other outlet when ?uid pressure
is being broken loose, pressure ?uid be supplied to the
paratus, while the remainder of the stroke requires the
hydraulic motor which powers the ground engaging im
plement at a relatively high pressure but at a relatively
slow rate, and that during the remainder of the cycle, when
at the ?rs-t designated outlet exceeds said predetermined
value.
In this connection it is another and more speci?c object
of this invention to provide an unloading valve of the
character described having a pressure responsive main
lic motor receives ?uid at a relatively high ?ow rate,
valve member which is movable between normal and un
though not necessarily at as high a pressure.
loading positions and is yieldingly biased toward its nor
Usually the hydraulic apparatus in such a machine is
powered by a single prime mover, such as an internal com 40 mal position, and wherein a pilot valve is provided which
prevents hunting of the main valve member and which
bustion engine, and heretofore it has been conventional to
assures that the main valve member will not move out of
have this prime mover drivingly connected to a single
its normal position at ?uid pressures below said predeter
hydraulic pump which supplied pressure ?uid to the hy
mined value, said pilot valve being adjustable to provide
draulic apparatus. If the pump afforded a relatively high
for regulation of the pressure at which it permits shifting
?ow rate of pressure ?uid, so as to insure comparatively
of the main valve member from one of its positions to
fast movement of the hydraulic motor or motors driven
the other.
thereby, then the necessary pressure could not be obtained
Another speci?c object of this invention is to provide
for driving the hydraulic motor at a slow speed against a
a simple, dependable and inexpensive unloading valve of
heavy load, and it was possible for the prime mover to be
stalled when a heavy load was imposed upon the hydraulic 50 the character described having a body which can be
readily formed from a single casting.
motor, as during “break out” of compacted dirt. On the
It is also a speci?c object of this invention to provide
other hand if the pump provided a low ?ow rate, so as to
an unloading valve having in its body an inlet, a high
insure adequate pressure for slow speed working of heavy
pressure outlet, and an exhaust outlet, and having means
loads, then the entire operation of the apparatus took
the loosened ground is being lifted or moved, the hydrau
place at low speed, with a proportionately long work 55 for communicating the inlet either with the high pressure
outlet or with the exhaust outlet, depending upon the
cycle time.
pressure which obtains at the high pressure outlet, and
With the foregoing in mind it is an object of this inven
which valve also incorporates means for effectively pre
tion to provide hydraulic apparatus of the type having a
venting back ?ow of pressure ?uid from the high pressure
hydraulic motor or motors to which hydraulic ?uid under
pressure is supplied from pump means driven by a single 60 outlet to both the inlet and the exhaust outlet, without
iniposing back pressure on a pump connected with its
prime mover, which apparatus includes means for auto~
in et.
a
matically reducing the rate of ?ow of pressure ?uid to the
With the above and other objects in view which will
hydraulic motor at times when a heavy load is imposed
appear as the description proceeds, this invention resides
upon the motor, and for supplying pressure ?uid to the
in the novel construction, combination and arrangement
hydraulic motor at a normal high rate at times when the
of parts substantially as hereinafter described and more
motor is working against a lighter load, to thus insure that
particularly de?ned by the appended claims, it being
the hydraulic motor is capable of exerting a large force
understood that such changes in the precise embodiment
for “break out” but is nevertheless capable of moving com
of the hereindisclosed invention may be made as come
paratively rapidly at other times, thereby affording a very
short working cycle despite the high force available for 70 within the scope of the claims.
The accompanying drawings illustrate several complete
“break out.”
examples of the physical embodiments of the, invention
Another object of this invention resides in the provision
2,037,354
4
U
constructed according to the best modes so far devised
the unloading valve 17 allows the output of the pump
for the practical application of the principles thereof, and
P—2 to be fed to the control valve by way of a duct 18
in which:
which connects the unloading valve with the duct 15,
and consequently at such times the motor 5 receives
hydraulic ?uid at a high rate of ?ow, equal to the com
FIGURE 1 is a diagrammatic view of a hydraulic
apparatus which embodies the present invention;
FIGURE 2 is a sectional view of an unloading valve
bined output volumes of both pumps.
of this invention shown in its normal position;
However, when the motor 5 is heavily loaded, causing
FIGURE 3 is a view similar to FIGURE 2 but show~
the pressure in the ducts 15 and 18 to rise above said pre
ing the unloading valve in its relief or unloading position;
FIGURE 4 is a view similar to FIGURE 2 but illus
determined value, the unloading valve 17 dumps the out
10 put of pump P-2 into the reservoir 10 by way of a duct
trating a modi?ed form of unloading valve embodying
the principles of this invention, shown in its normal posi
tion; and
FIGURE 5 is a view similar to FIGURE 4, but showing
the modi?ed valve in its relief or unloading position.
Referring now more particularly to the accompanying
drawings, in which like reference characters designate
like parts throughout the several views, the numeral 5
designates generally a hydraulic motor, the operation of
which is governed by a control valve 6 and which is 20
connected for actuation by pressure ?uid from pump
means, generally designated 7, driven by a prime mover
8.
The hydraulic motor 5 is in this case shown as com
prising a double acting cylinder, adapted to actuate the
ground engaging implement (not shown) of an excavat
ing shovel, a front end loader or the like, or to drive
a similar load which at times requires the hydraulic motor
19 which is connected between the unloading valve and
the exhaust duct 11. Under such conditions of heavy
load on the hydraulic motor the pump P—2 consumes only
a negligible amount of power from the prime mover,
since its output ?ows substantially unimpeded to the reser
voir 1t), and consequently substantially all of the power
of the prime mover is available to drive the pump P-l.
Hence the hydraulic motor 5 is driven by hydraulic ?uid
at a high pressure and low ?ow rate dring “break out”
or other heavy load conditions,
When the load upon the hydraulic motor 5 is reduced,
as when a load of earth breaks loose from a pile, and the
unloading valve connects the outlet of pump P-2 into
the pressure system by way of the duct 18, to feed the
combined outputs of the two pumps to the hydraulic
motor, each of the pumps absorbs its respective share of
the power produced by the prime mover.
to exert a large force at very low speed and at other times
It is naturally important that the pump P-l be rated
requires the motor to exert substantially less force but,
for the maximum pressure for which the system is de
30 signed, as limited by the displacement of pump P-1 and
desirably, to move at a relatively fast speed.
The control valve 6 is preferably of the well known
the horsepower rating of the prime mover. However, it
open center type, and has a spool 9 that is axially man
ually shiftable between a neutral position and a pair of
will be understood that the two pumps need not be of
peded through the control valve and to a reservoir 10
or other unpressurized source of ?uid, by way of an
exhaust duct 11 connected between the control valve
and the reservoir. When the spool 9 of the control valve
is shifted to one of its operating positions, it communi
cates one end of the cylinder with the pump means via
a duct 12, and connects the other end of the cylinder
with the exhaust duct 11 via a duct 13 to effect move
ly the pump P—2 can be rated for a lower pressure than
pump P—1, since maximum system pressure is never ap
equal displacements. Thus if there is a substantial varia
operating positions spaced to opposite sides of neutral.
tion between the maximum expected load and the normal
When the spool is in the neutral position, pressure ?uid 35 load, and rapid operation of the hydraulic motor is de
is locked in both ends of the cylinder 5 while ?uid from
sired at times when it is lightly loaded, the pump P-Z may
the pump means is allowed to pass substantially unim
have a larger displacement than the pump P-l. Obvious
ment of the work performing element of the cylinder in
one direction. When the spool 9 is shifted to its other
operative position, the duct 13 supplies pump ?uid to said
other end of the cylinder, to eifect movement of its work
performing element in the opposite direction; and the
?uid then being expelled from the cylinder ?ows to the
exhaust duct 11 via the duct 12 and the passages in the
control valve.
Those skilled in the art will understand that the con
trol valve 6 can comprise a bank of open center valves,
each of which is connected with a hydraulic motor to
etfect control thereof, and that the principles of this
invention are as well applicable to apparatus comprising
a plurality of control valves and motors as to a system
having only a single motor and control valve.
It will also
be understood that the double-acting hydraulic cylinder 5
plied by pump P-2.
The unloading valve 17 of this invention has a body
20 that can be formed as a single block-like casting, and
has a bore 21 extending therethrough and three passages
22, 23 and 24» transverse to the bore that open to it at
spaced intervals along it length and extend to the exterior
of the body. The opposite end portions of the bore 21 are
counterbored and closed by plugs 25 and 26 which are
threaded into the counterbores. The intermediate por
tion of the bore accommodates an axially slidable pres
sure responsive main valve member or spool 27.
The passage 22 is an inlet passage which communi~
cates the medial portion of the bore with an inlet port 28
that opens to one side of the body and is adapted to be
connected with the high pressure outlet of a pump cor
responding to the pump P-2, as by means of a duct cor
responding to the duct 16. The passage 23 is a high
pressure outlet passage which communicates the bore 21
with a high pressure port 29 that is located at the side
of the valve body opposite to that to which the inlet port
60 28 opens, The port 29 is adapted to be connected with
a duct, corresponding to the duct 18, in which hydraulic
shown in FIGURE 1 is merely illustrative of any of a
system pressure is manifested. The passage 24 is an
wide variety of hydraulic motor types that can be used
exhaust outlet passage which opens to an exhaust port 30
with the apparatus.
that is located at the same side of the body as the outlet
It is a feature of the apparatus of this invention that 65 port 29 and is connectable to a reservoir or other unpres~
surized ?uid source.
the pump means 7 comprises two pumps P-1 and P~2,
both of which are driven by the same prime mover 5.
It will be noted that the several passages 22, 23 and 24
The inlets of both pumps are connected, as by duct means
open to enlarged diameter portions of the bore, and that
14, with the hydraulic ?uid reservoir It}, but the high
the inlet passage 22 communicates with the bore at a zone
pressure outlet of the pump P—1 is connected directly 70 intermediate the zones at which the bore is respectively
with the control valve 6 by means of a duct 15, while
communicated with the high pressure outlet passage 23
the high pressure outlet of the other pump P-2 is con
and the exhaust outlet passage 24.
nected, via a duct 16, with an unloading valve 17.
The main valve member or spool 27 is biased to a
When pressure in the system comprising the duct 15
normal position in which an axially elongated land 31
and the hydraulic motor 5 is below a predetermined value, 75 thereon blocks communication between the inlet passage
3,037,354.
5
6
?uid pressure in the end portion 34 of the bore to build
up more rapidly, when the pilot poppet 36 is open, than
it can escape through the bleed passage.
‘It is well known that a pressure responsive poppet such
as the pilot poppet 36 tends to open slightly, or “crack”,
at ?uid pressure values below that at which it is intended
to respond. It will be noted that the bleed passage 47 al
lows ?uid that leaks past the pilot poppet, due to its crack
ing, to be conducted out of the end portion 34 of the
bore before the spool can be displaced by such ?uid.
22 and the exhaust passage 24, but in which the spool
permits communication through the bore 21 between the
inlet passage and the high pressure outlet passage 23.
Such bias toward its normal position is imparted to the
main valve member by means of a coiled compression
spring 32 in the counterbored end portion 21’ of the bore
that is nearer the exhaust outlet passage 24, and which
spring reacts between the plug 26 and the axially outer
end of the land 31 on the main valve member. A smaller
diameter projecting end portion 33 of the spool, adjacent
However, when the pilot poppet 36 is fully open, the
restriction 49 prevents the full ?ow of ?uid into the bore
to the land 31, serves as a pilot for the spring 32, and
the spring is further guided by having its axially outer
portion received in an inwardly opening well in the plug
from passing through the bleed passage, so that under
those circumstances the spool is moved to its unloading
26.
The body also has a feed back passage 35, controlled 15 position. The bleed passage 47, with its restriction 49,
by a pilot poppet 36, through which pressure ?uid can
?ow from the high pressure outlet passage 23 into the
counterbored end portion 34 of the bore remote from
the spring 32 whenever ?uid pressure in the outlet passage
23 exceeds a predetermined unloading value. When pres 20
sure ?uid is thus introduced into the bore the main valve
member is moved thereby against the bias of the spring
32 to an unloading position in which a land 37 on the
spool blocks communication between the inlet passage 22
and the high pressure outlet passage 23, and in which the
land 31 is out of the restricted portion of the bore between
thus cooperates with the pilot poppet 36 in providing
for stable and accurate operation of the main valve mem- .
ber, insuring that it will shift to its unloading position
at exactly a predetermined pressure value, with no ten
dency to hunt.
The bleed passage 47 opens axially to the end por
tion 21' of the bore in which the spring 32 is located,
so that leakage ?uid cannot be trapped in said end por
tion of the bore to interfere with movement of the spool
25 to its unloading position, and so that a vacuum cannot
be drawn there when the spring shifts the spool to its
normal position.
the inlet passage ad the exhaust passage 24, so that the
The spool may also be provided with a radial bore
output of a pump connected with the inlet passage is di
50 which opens from the bleed passage to a circumfer
rected through the bore to the exhaust passage 24.
ential groove 51 in the spool, so located along the length
The feed back passage 35 is provided by a bore 39 30 of the elongated land 37 as to be at all times situated
in the valve body which extends parallel to the main
between the high pressure outlet passage 23 and the end
bore 21 and which communicates with the high pressure
portion 34 of the bore. Fluid which leaks along the
outlet passage 23, a coaxial counterbore 44} in which the
bore from the high pressure outlet passage is intercepted
pilot poppet 36 is axially slidable, and an obliquely in
at the groove 51 and conducted to the exhaust outlet
clined passage portion 41, which can be drilled from the
passage 24 by way of the radial bore 50, the bleed passage
end portion of the bore 21 before the same is closed by
47, and the radial bore 48, so that such ?uid cannot en
the plug 25, and which communicates the counterbores
ter the end portion 34 of the bore and tend to shift the
4t) and 34. The shoulder de?ned by the junction of the
bore 39 with the counterbore 40 provides an outwardly
facing valve seat toward which the pilot poppet 36 is
biased by a coiled compression spring 42 that surrounds
a reduced diameter coaxial stem 43 on the pilot poppet
and reacts against a plug 44 threaded into the mouth of
the counterbore.
It will be apparent to those skilled in the art that the
biasing force of the spring 42 can be regulated by adjust
ment of the axial depth to which the plug 44 is threaded
into the counterbore 40, and consequently the pilot poppet
spool toward its unloading position or prevent it from
returning to its normal position.
It is important to prevent any ?ow of pressure ?uid
from the high pressure outlet passage 23 to the exhaust
outlet passage 24 when the spool shifts from one of its
positions to another, since such ?ow could produce ,an
undesirable pressure drop in the hydraulic system con
nected with the high pressure outlet 23. The lands 31
and 37 on the spool are therefore so located and spaced
apart on the spool 27 ‘that as the spool shifts from its
normal to its unloading position, and vice versa, it passes
affords accurate control of the ?uid pressure value at
through a transition or intermediate position in which
which the main valve member or spool 27 is moved to
the land 37 blocks communication through the bore be
its unloading position. Lock or jam nuts 45 threaded
tween the inlet passage 22 and the high pressure outlet
onto the outer end portion of the plug 44 hold the latter
passage 23 while the land 31 blocks communication
against displacement out of any position of adjustment
through the bore between the inlet passage and the ex
in which it may be set.
haust outlet passage 24. To prevent injury to a pump
At its end ‘adjacent to the plug 25, the main valve‘ 55 connected with the inlet passage, due to the back pres
member has a reduced diameter end portion 46 which
sure upon the pump that might result from such “dead
serves as a stop abutment that engages the plug 25 to
ending” of the inlet passage, the unloading valve of this
de?ne the normal position toward which the main valve
invention includes a passage 53 in the valve body through
member 27 is biased by the spring 32.
which pressure ?uid can ?ow from the inlet passage to
The axially outer end of the land 37 on the spool 60 the high pressure outlet passage, and a check valve 54
serves as a piston ‘which receives the thrust due to hy
in ‘said passage 53 which blocks ?ow of such ?uid in the
draulic pressure ?uid in the cylinder comprising the
reverse direction.
counterbored end portion 34 of the bore. Since such ?uid
The check valve controlled passage 53 comprises a bore
cannot escape back to the high pressure outlet passage
55 which is parallel to the bore 21 and which intersects
23 when the pilot poppet 36 closes, the spool is pro 65 the inlet passage intermediate the bore 21 and the inlet
vided with a coaxial bleed passage 47 by which such en
port 28, a coaxial outwardly opening counterbore 56 in
trapped ?uid can be conducted to the exhaust outlet
which the check valve 54 is slidable, and a passage sec
passage 24 upon closure ‘of the pilot poppet, to allow the
. tion 57 which communicates the bore 21 with the counter
spool to be returned to its normal position by the bias
bore 56. The passage section 57 comprise-s, in effect,
ing force of the spring 32. To this end the spool has a 70 a coaxial inward extension of the high pressure outlet
passage 23. The mouth of the counterbore 56 is closed
radial bore 48 which opens from the bleed passage 47 to
by a plug 58 which also serves to receive the reaction of
the surface of the land 31 and which is so located along
a coiled compression spring 59 by which the check valve
the length of the spool as to be in register at all times
34 is urged toward a closed position engaging the seat
with the exhaust outlet passage 24. The bleed passage
47 also includes a throttling restriction 49 which allows 75 provided by the junction of the bore 55 and counterbore
3,037,354
:1
E
56. The check valve preferably comprises an elongated
poppet which is slidable in the counterbore 56 and ‘which
has an outwardly opening coaxial well 60 therein in
which a substantial portion of the spring 59 is guidingly
received.
In the embodiment of the unloading valve illustrated
cates with the inlet passage and the high pressure outlet
passage; a main valve element in said bore in the body
movable axially ‘back. and forth between a ?rst position
blocking communication through the bore between the
inlet passage and both outlet passages, and a second
position allowing communication through the bore be
in FIGURES 2 and 3, the check valve 54 is intended to
tween the inlet passage and the low pressure outlet pas
open only at times when the main spool is in its interme
sage but blocking communication through the bore be
diate or transition position blocking all communication
tween the inlet passage and the high pressure outlet pas
through the ‘bore between the three passages 22, 23 and 10 sage, said main valve element being responsive to the
24 which open thereto. In the embodiment of the in
pressure of ?uid in said end portion of the bore to be
vention illustrated in FIGURES 4 and 5 the land 37’ on
moved vthereby toward its said second position; biasing
the spool 27’ is of such length that it always blocks com
means in the valve body reacting against the main valve
munication through the bore between the inlet passage
element to hold the same out of its said second position
22 and the high pressure outlet passage 23. Hence the 15 as long as pressure of ‘?uid in said end portion of the
spool 27’ does not have a transition or intermediate posi
bore does not exceed a value corresponding to said pre
tion, since pressure ?uid entering the inlet passage 22
determined value of pressure in the hydraulic system;
must ?ow to the high pressure outlet passage by way of
and check valve means in the check valve passage for
the passage 53 controlled by the check valve ‘54 at all
‘blocking ?ow of ?uid from the high pressure outlet pas
times that the land 31 blocks ?ow of such ?uid through
sage to the inlet passage, but responsive to ?uid pressure
the bore 21 to the exhaust passage 24. In all other re
in the inlet passage which is higher than that in the high
spects the unloading valve illustrated in FIGURES 4
pressure outlet passage to allow ?uid to flow from the
‘and 5 can be identical to that shown in FIGURES 2
inlet passage to the high pressure outlet passage through
and 3.
the check valve passage when the main valve element is
The modi?ed form of unloading valve illustrated in
in its said ?rst position.
FEGURES 4 and 5 has the advantage of a simpli?ed con
2. The unloading valve of claim 1, further character
ized by: a pressure responsive valve element in said feed
struction of the main valve member, as compared with the
back assage normally blocking ?ow of ?uid therethrough
FIGURES 2 and 3 version of the valve, but has the dis
advantage that it provides a slightly less e?icient system
from the high pressure outlet passage to said one end
because of the back pressure which the relief or check 30 portion of the bore, ‘but arranged to open in response to
valve 54 imposes upon a pump connected with its inlet
?uid pressure in the high pressure outlet passage which
passage 22.
is in excess of said predetermined value to permit such
From the foregoing description taken together with
flow of ?uid through the feed back passage.
the accompanying drawings it will vbe apparent that this
3. The unloading valve of claim 1, further character
invention provides hydraulic apparatus of the type com
ized by: the fact that the valve body has a second bore
prising a hydraulic motor, an open center control valve
therein which opens to one side thereof and provides a
by which the motor is controlled, and pump means driven
by a prime mover, whereby the power developed by the
portion of said feed back passage, and has means at the
inner end of said second bore de?ning a valve seat; a
prime mover can be most advantageously utilized to pro
pressure responsive pilot poppet in said second bore slid
vide for operation of the motor with ?uid at high pres 40 able toward and from engagement with said valve seat;
sure and a low ?ow rate when the motor is heavily loaded
a plug axially adjustably t readed into the outer end por
and with lower pressure ?uid at a higher ?ow rate when
tion of said second bore; and a spring reacting between
said plug and the pilot poppet to bias the latter toward
the motor is more lightly loaded. It will be further
said valve seat with a force depending upon the'position
apparent that this invention also provides a simple, inex
of axial adjustment of said plug, so that adjustment of
pensive and dependable unloading valve by which pres
sure ?uid from a source thereof is directed to a pres
the plug regulates the value of pressure in the high pres
surized hydraulic system when pressure in the system
is below a predetermined value, but whereby such pres
sure outlet passage at which the main valve element is
moved to its said second position.
sure ?uid is dumped to an unpressurized reservoir or the
4. The unloading valve of claim 1, further character
ized by the fact that: the high pressure outlet passage
and the inlet passage open to opposite sides of the valve
like when pressure in the hydraulic system exceeds said
value.
body, and their axes are substantially parallel to one
What is claimed as my invention is:
another; further characterized by the fact that a portion
of the check valve passage extends from the bore to
a hydraulic pump to a pressurized hydraulic system when
pressure of ?uid in the system is below a predetermined 55 ward the side of the valve body to which the inlet pas
sage opens, and is coaxial with the high pressure outlet
value and for diverting pressure ?uid from the pump away
passage; further characterized by the fact that another
from said hydraulic system when pressure of ?uid in the
portion of the check valve passage extends substantially
system exceeds said value, said unloading valve com
parallel to the bore, is intersected by the ?rst designated
prising: a valve body having a vbore therein which is
portion of the check valve passage, and intersects the
adapted to receive a slidable valve element and the ends
inlet passage intermediate the bore and the side of the
of which are closed, and having high pressure and low
1. An unloading valve for directing pressure ?uid from
pressure outlet passages which intersect said bore at zones
that are spaced lengthwise of the bore axis from one an
other and from one end of the bore, and which respec
tively open to a high pressure port in the valve body that
is connectable with a pressurized hydraulic system, and a
low pressure port in the valve body that is connectable
with a ?uid reservoir, said valve body also having an inlet
passage therein which intersects the bore at a zone spaced
lengthwise of the bore axis from said end of the bore
valve body to which the inlet passage opens; and further
characterized by the fact that the check valve comprises
an elongated poppet which is axially slidable in said
other portion of the check valve passage.
5. The unloading valve of claim 1, further character
ized by the fact that the main valve element is movable
to a third position axially remote from said second posi
tion, and in which the main valve element blocks com
70 munication through the bore between the inlet passage
and from the zones of intersection of said outlet pas
and the low pressure outlet passage but allows com
sages with the bore, a feed back passage communicating
with said end portion of the ‘bore and with the high pres
sure outlet passage intermediate the bore and the high
pressure port, and a check valve passage which communi 75
munication through the bore between the inlet passage
and the high pressure outlet passage, so that when the
main valve element is in said third position pressure
?uid need not unseat the check valve and hence does
‘3,037,354
9
not have back pressure imposed upon it by the check
valve, said biasing means in the valve body normally
maintaining the main valve element in its said third
10
the fourth plug and the check poppet to bias the latter
toward its seated position.
8. In a hydraulic system of the type which is driven
by a prime mover and which includes a hydraulic motor
and a control valve having an inlet for hydraulic ?uid
under pressure and by which such ?uid can be directed
ized by the fact that the main valve element has a re
either to the hydraulic motor, for actuating the same, or
stricted bleed passage extending axially therein and which
to an unpressurizedreservoir or the like, means for sup
in all positions of the main valve element communicates
plying hydraulic ?uid under pressure to the motor at a
said end portion of the bore with the low pressure out
let passage, said bleed passage providing for drainage 10 low rate of flow at times when the motor is heavily loaded
‘and at a high rate of ?ow at times when the motor is
of pressure ?uid out of said end portion of the bore at
lightly loaded, so that the motor moves fastest when least
substantially the same rate that such ?uid accumulates
position.
6. The unloading valve of claim 2, further character
lightly loaded and thus advantageously utilizes the power
therein when the pilot poppet is partially unseated but
available from the prime mover, said means comprising:
by reason of its restriction preventing such ?uid from
leaving said end portion of the bore at the rate that it 15 a pair of hydraulic pumps connected with the prime mover
to be driven thereby; means connecting the inlet of each
of said pumps with -a source of unpressurized hydraulic
?uid; means connecting the outlet of one of said pumps
with the inlet of the control valve so that pressurized ?uid
predetermined value and for diverting pressure ?uid from 20 from said one pump is at all times available to the con
trol valve and hence to the hydraulic motor; an unloading
the pump away from said hydraulic system when pressure
enters the same when the pilot poppet is fully open.
7. An unloading valve for directing pressure ?uid
from a hydraulic pump to a pressurized hydraulic sys
tem when pressure of ?uid in the system is below a
of ?uid in the system exceeds said value, said unloading
valve body having an inlet ‘and a pair of outlets and having
passage means through which the inlet is communicable
valve comprising: a valve body having an inlet passage
with both outlets; means communicating the inlet in the
opening to one side of the body and adapted to be con
nected with a pump, a high pressure outlet passage paral 25 unloading valve body with the other hydraulic pump;
pressure responsive valve means in said passage means
lel to and spaced in one direction from the inlet passage
in the unloading valve body biased to a normal position
opening to the opposite side of the body and connectable
blocking communication between the inlet and one outlet
with a pressurized hydraulic system, an exhaust outlet
passage parallel to and spaced in the opposite direction
while allowing communication between the inlet and
from the inlet passage, opening to said opposite side of 30 the other outlet, but shiftable against its bias, in response
to ?uid pressure at said other outlet in excess of a pre
the body and connectable with a ?uid reservoir, and a
determined value, to an unloading position at which said
main bore extending through the body normal to said
valve means blocks communication between the inlet
passages and to which said passages open at their inner
and said other outlet while allowing communication be
ends, said body also having a feed back bore parallel to
said main bore and opening to the high pressure outlet 35 tween the inlet ‘and the ?rst designated outlet; means
communicating said ‘other outlet in the unloading valve
passage, a ?rst counterbore coaxial with the feed back
body with the inlet of the control valve so that pressurized
bore and opening to a third side of the body nearer the
?uid from said other outlet is normally available to the
high pressure outlet passage than the exhaust outlet pas
control valve, ‘and hence to the hydraulic motor, to sup
sage, and a feed back passage portion communicating
plement the volume of ?uid supplied by the ?rst hydraulic
said counterbore with the end portion of the main bore
pump; and means communicating said ?rst designated
nearer said third side of the body, said body further
outlet in the unloading valve body with a source of un
having a check valve bore parallel to the main bore and
pressurized hydraulic ?uid, so that only ?uid from said
communicating with the inlet passage, a second counter
one hydraulic pump is supplied to the control valve, and
bore coaxial with the check valve bore and opening to
hence to the hydraulic motor, at times when pressure of
said third side of the body, and a passage portion co
?uid ‘at said other outlet exceeds said predetermined
axial with the high pressure outlet passage communicat
value.
ing the latter with said second counterbore through the
9. In a hydraulic system of the type which is driven
main bore; a main valve member slidable axially in the
by a prime mover and which includes a hydraulic motor
main bore to a ?rst position blocking communication
and a control valve having an inlet for hydraulic ?uid
through the main bore between the inlet passage and
under pressure and by which such ?uid can be directed
both outlet passages while permitting communication be
either to the hydraulic motor, for ‘actuating the same, or
tween the inlet passage and the high pressure outlet pas
to an unpressurized reservoir or the like, means for sup
sage through the second counterbore and said passage
plying hydraulic ?uid under pressure to the motor at a
portion, and to a second position permitting communica
low rate of ?ow at times when the motor is heavily loaded ,
tion through the main bore between the inlet passage and
the exhaust outlet passage, said main valve member hav 55 and at a high rate of flow at times when the motor is
lightly loaded, so that the motor moves fastest when least
ing a restricted bleed passage therein which at all times
lightly loaded and thus advantageously utilizes the power
provides limited communication between said end of the
available from the prime mover, said means comprising:
main bore and the exhaust outlet passage; 21 pair of plugs,
an unloading valve of the type having an inlet and a
one in each end of the main bore; a spring in the other
end portion of the main bore reacting between the ad 60 pair of outlets and comprising pressure responsive valve
means by which ?uid is directed from the inlet to one
jacent plug and the main valve member to bias the latter
of said outlets so long as pressure of ?uid at said one
away from its said second position; a pilot poppet axially
outlet is below a predetermined value, and by which ?uid
slidable in the ?rst counterbore to and from a seated
from the inlet is directed to the other outlet when pressure
position blocking the feed back bore and responsive to
?uid pressure in the high pressure outlet passage to be 65 of ?uid ‘at the ?rst designated outlet exceeds said pre
determined value; a pair ‘of pumps driven by the prime
moved out of said position; a third plug closing the
mover, each of said pumps having a high pressure outlet
mouth of the ?rst counterbore; a spring reacting between
and an inlet connected with a source of hydraulic ?uid;
the third plug and the pilot poppet to bias the latter to
means connecting the high pressure outlet of one of said
ward its seated position; a check poppet in the second
pumps with the inlet of the control valve so that ?uid un
counterbore axially slidable to and from a seated posi
der pressure from said one pump is at all times available
tion blocking the check valve bore and arranged to move
to the control valve and hence to the hydraulic motor;
out of said position in response to ?uid pressure in the in
means connecting the high pressure outlet of the other
let passage which is greater than that in the high pres
pump with the inlet of the unloading valve; and means
sure outlet passage; a fourth plug closing the mouth of
the second counterbore; and a spring reacting between 75 connecting the ?rst designated outlet of the unloading
3,037,354
11
valve with the inlet of the control valve so that ?uid under
pressure of said other pump is available to the control
forth in said cylinder and having a motion transmitting
connection with the valve element by which the valve ele
valve, and hence to the hydraulic motor, to supplement
ment can be moved to said other position thereof in con
the ?uid from the ?rst designated pump, at times when
sequence of the admission of pressure ?uid into the cylin
?uid at said ?rst designated outlet of the unloading valve 5 der; third passage means in the valve body for communi
is below said predetermined value.
cating said cylinder with the service port; and pressure
10. An unloading valve for hydraulic systems com
responsive pilot valve means in said third passage means,
prising: a body having an inlet port connectible with a
arranged to allow ?uid to ?ow through said third passage
source of ?uid under pressure, a service port connectible
means from the service port to said cylinder, at a rate
with a hydraulic motor, and an exhaust port; ?rst passage 10 faster than such ?uid can ?ow out of said restricted outlet,
means in the body for communicating the inlet and service
when pressure at the service port rises above a predeter
ports; a check valve in said ?rst passage means arranged
mined value, to thus cause the piston to effect movement
to block ?ow of ?uid therethrough in the direction from
of the valve element from its said one position to its said
the service port to the inlet port, but to allow ?ow of ?uid
other position.
in the opposite direction through said ?rst passage means; 15
12. An unloading valve for hydraulic systems compris
second passage means in the body for communicating the
ing: body having an inlet port connectible with a source
inlet and exhaust ports; a valve element movable in the
of ?uid under pressure, a service port connectible with a
body between a pair of positions, and adapted to cooper
hydraulic motor, and an exhaust port; ?rst passage means
ate with said second passage means at one of said posi
in the body for communicating the inlet and service ports;
tions to block communication between the inlet and the 20 second passage means in the body for communicating the
exhaust ports while allowing ?uid to ?ow through said
inlet and exhaust ports; a valve element movable in the
?rst passage means from the inlet port to the service port,
body between a pair of positions, and adapted to coop
said valve element in the other of its positions being
erate with said second passage means at one of said posi
adapted to allow communication through said second
tions to block communication between the inlet and the
passage means between the inlet and the exhaust ports; 25 exhaust ports while allowing ?uid to flow through said ?rst
means in the valve body yieldingly biasing the valve
passage means from the inlet port to the service port, said
element toward its said one position; and means in the
valve element in the other of its positions being adapted
valve body responsive to pressure at the service port and
to allow communication through said second passage
operable to effect movement of the valve element from
means between the inlet and the exhaust ports; means in
its said one position to its said other position when pres 30 the valve body yieldingly biasing the valve element toward
sure at the service port rises above a predetermined value.
11. An unloading valve for hydraulic systems compris
its said one position; means in the body providing a ?uid
pressure responsive operator for shifting the valve element
toward its said other position, comprising a pressure cham
ing: a body having an inlet port conncctible with a source
of ?uid under pressure, a service port connectible with a
her having a restricted outlet which leads to the exterior
hydraulic motor, and an exhaust port; ?rst passage means 35 of the body, and a ?uid pressure responsive member mov
in the body for communicating the inlet and service ports;
able in one direction to effect such shifting of the valve
second passage means in the body for communicating the
element in consequence of admission of pressure ?uid into
inlet and exhaust ports; a valve element movable in the
the pressure chamber at a rate faster than it can ?ow out
body between a pair of positions, and adapted to cooperate
of said outlet; third passage means in the valve body for
with said second passage means at one of said positions 40 communicating said pressure chamber with the service
to block communication between the inlet and the exhaust
port; and pressure responsive pilot valve means in said
ports while allowing ?uid to ?ow through said ?rst passage
third passage means, arranged to allow ?uid to ?ow
means from the inlet port to the service port, said valve
through said third passage means from the service port
element in the other of its positions being adapted to allow
to said pressure chamber, at a rate faster than such ?uid
communication through said second passage means be 45 can ?ow out of said restricted outlet, when pressure at the
tween the inlet and the exhaust ports; means in the valve
service port rises above a predetermined value, to thus
body yieldingly biasing the valve element toward its said
ettect movement of the valve element from its said one
one position; means in the body providing a cylinder hav
ing a restricted outlet communicating with the exhaust
port and a pressure responsive piston movable back and
position to its said other position.
No references cited.
Disclaimer
3,037,354.——Fmn0is H. Tenn/is, Milwaukee, Wis. HYDRAULIC APPARATUS FOR
VARIABLE LOAD SYSTEMS. Patent dated June 5, 1962. Disclaimer
?led Aug. 5, 1963, by the assignee, Hydraulic Um't Specialties Com
pany.
Hereby enters this disclaimer to claims 9 and 10 of said patent.
[Official Gazette October 29, 1.963.]
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