Note: Descriptions are shown in the official language in which they were submitted.
a~
HYDRAULIC ACTUATOR FOR WELL PI~PS
Technical Field
This invention relates to the field of hydraulic
engineering, and particularly to hydraulic apparatus for
operating subsurface reciprocating pumps.
Background of the Invention
one of the problems faced by modern technology
is that of delivering to the surface of the earth liquids
located in subsurface pockets. It is customary in oil
producin~ areas, for example, to drill a well from the
earth's surface to a depth at which it penetrates into a
natural reservoir of oil. That depth may be several
hundred feet, much too great to permit operation of a
simple suction pump, and a lift pump is installed near the
bottom of the well, and connected by a string of ~ucker
rods with surface apparatus, called a pumping jack, for
causing the pump to reciprocate. Pumping jacks may be
either mechanical, such as the familiar walking beam, or
may be hydraulic. In either case, the pumping jack must
be capable of the considerable stroke reguired, seven feet
for example, and it it must be of sufficient power to move
the string of sucker rods and the column of oil rising
from the pump to the surface. Twelve thousand pounds may
be a reasonable design load for such an apparatus.
Hydraulic pumping jacks of this sort are known,
but suffer from certain imperfections. In the first
place, a limited guantity of the hydraulic fluid - a
liguid -- is usually pumped from a reservoir into a
1--
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hydraulic motox to raise the load, and then allowed to
flow back into the reservoir so that the load descends by
its own weight. Continuous repetition of this cycle
subjects the hydraulic fluid to damage by heating. The
arrangement also subjects the mechanical equipment to
severe shock each time the direction of movement reverses
from upward to downward, and it is further difflcult -to
provide for varying the speed of operation of such equip-
ment.
1~ Brief Summary of the Invention
The present invention comprises a hydraulic
pumping jack and system including a hydraulic actuator, an
accumulator, a hydraulic supply, and valving and control
arrangements, by which the hydraulic fluid is circulated
to afford cooling, the shocks at reversal are cushioned,
and energy is stored during the descent of the load for
use in xaisin~ it again. This is in part accomplished by
desiyning the actuator so that its vertically movable
piston has a lower working surface of area larger than its
upper working surface, and so that a hydraulic chamber
including the lower piston surface is of larger volume
than a chamber including the upper piston surface. The
valving and control arrangements include limit switches
determining the range of travel of the piston, and may
also include means for varying the speed of operation of
the piston in each direction.
Various aspects of the invention are as follows:
In combination:
a hydraulic actua-tor for vertically recipro-
cating a load lncluding a cylinder and a piston moving
vertically in said cylinder between upper and lower limits
--2--
of travel, and first and second ports communicating with
lower and upper closed chambers in said cylinder below and
above said piston, respectively, said piston having a
lower working surface of area larger than its upper work-
ing surface so that said lower chamber.is of larger volume
than said upper chamber;
a hydraulic accumulator;
means for connecting said first port and said
accumulator to a source of hydraulic fluid under pressure;
a receiver for hydraulic fluid; and,
valving means connected to said ports and said
receiver and having a first condition, in which fluid
flowing from said second port to said receiver is enabled
to raise said piston, and a second condition, in which
said flow to said receiver is prevented and said second
port is connected to said first port and said accumulator,
to lower said piston and charge said accumulator.
In combination, apparatus for vertically recip-
rocating a load, comprising:
a hydraulic actuator including a cylinder and a
piston moving vertically in said cylinder between upper
and lower limits of travel, and first and second ports
communicating with lower and upper closed chambers in said
cylinder below and above said piston respectively, said
piston having a lower working surface of area larger than
its upper working surface so that said lower chamber is of
larger volume than said upper chamber;
means for connecting said load to said piston;
a hydraulic accummulator;
means for connecting said irst port and said
-2a-
accumulator to a source of hydraulic fluid under pressure;
means including a first normally closed valve
for connecting said second port to a receiver for hy-
draulic fluidi
means including a second normally closed valve
for connecting said second port to said accummulator and
said irst port; and
control means acting when said piston reaches
said lower limit of travel to open said first valve and
close said second valve to reverse the direction of move-
ment of said piston, an~l acting when said piston reaches
said upper level of travel to close said first valve and
open said second valve to reverse the direction of travel
of said piston and store fluid under pressu~e in said
accumulator.
Hydraulic apparatus for actuating a subsurface
reciprocating pump, comprising, in combination:
I. a hydraulic actuator comprising,
(a) a vertically disposed motor cylinder having
upper and lower ends,
(b) means, including a piston reciprocable in
said cylinder dividing said cylinder into upper
and lower closed chambers, -the volumes of said
chambers varying oppositely with movement of
said piston, said piston havi.ng a lower working
surface of area larger than its upper working
surface so that said lower chamber is of larger
volume than said upper chamber,
(c) a lift rod actuated by said piston, and
(d) upper and lower ports affording communica~
-2b-
4~
tion wlth said upper a~d lower chambers;
II. a hydraulic accummulator;
III. a source of hydraulic fluid under pressure
including a pump and a receiver; and
IV. valving means operable between a ~irst condi-
tion, in which fluid ingress ~rom said pump is
ena~led -to said lower port and said accumulator,
and fluid egress to said receiver is enabled
from said upper port, and a second condition in
which said fluid egress to said receiver is
prevented and fluid flow from said lower port
and said pump to said accumulator and said upper
port is enabled; and,
V. said piston being reciprocable through a range
between upper and lower limits of travel, and
means effective when said piston reaches said
levels of travel to actuate said valving means
~etween said first and second conditions, where-
by to reverse the direction of movement of said
piston.
Various advantages and features of novelty which
characterize the invention are pointed out with particu-
larity in the claims annexed hereto and forming a parthereof. However, for a better understanding of the inven-
tion, its advantages, and objects attained by its use,
reerence should be had to the drawing which orms a
-2c-
I' ` :?
further part hereof, and to the accompanying descriptive
matter, in which there are illustrated and described
certain preferred embodiments of the invention.
Brief Description of the Drawing
In the drawing, in which like reference numerals
indicate corresponding parts throughout the several views,
FIGURE 1 shows schematically a hydraulic system
according to the invention for actuating a subsurface pump
not shown;
FIGURE 2 shows in longitudinal sec-tion a linear
hydraulic actuator according to the invention;
FIGURES 3, 4, and 5 show several valving arrange-
ments for use in the system of FIGURE 1;
FIGURE 6 shows a hydraulic supply suitable for
use in the system of FIGURE 1;
FIGURE 7 shows an electrical schematic for the
system of FIGURE 1 using the valving arrangement of FIGURE
3;
FIGURE 8 is a fragmentary showing of a modifica-
tion of FIGURE 7 using the valving arrangement of FIGURE4; and
FIGURE 9 shows a simplified electrical schematic
using the valving arrangement of FIGURE 5.
Description of the Preferred Embodiment
FIGURE l shows a control sys-tem 19 according to
the invention to compri~e a double acting hydraulic actu-
ator 20, an accumulator 21, a hydraulic supply 22, a
valving arran~ement 23, and a control arrangement 24.
Actuator 20 is shown in more detail in FIGURE 2, supply 2~
is shown in more de~ail in P'IGURE 6, embodiments of valv-
ing arrangement 23 are shown in more detail in FIGURES 3,
4, and 5, and embodiments of control arrangement 24 are
shown in more detail in FIGURES 7 9.
~q~339~0
FIGURE 2 shows actuator 20 to comprise a cylin~
der 30 with a vertical axis 31. A piston 32 is recipro-
cable in cylinder 30 between upper and lower limits of
travel, and includes piston rings 33 and wear rings 34.
The bottom end 35 of cylinder 30 is closed by a base plug
36, by which the actuator may be anchored over a subsur-
face reciprocating pump, not shown, and a guide -tube 37
extends coaxially within cylinder 30 from plug 36. Piston
32 slides on tube 37 and is provided with seals 39 which
engage tube 37 as the piston moves. The lower surface 40
of the piston, the inner surface of cylinder 30, base plug
36~ and the outer surface of guide tube 37 define a first
annular hydraulic chamber 41 having a volume which varies,
increasing as piston 32 moves upward. A lower port 42
affords communication with chamber 41.
A lift tube 43 has its lower end 44 threaded
into the top surface 45 of piston 32 and extends coaxially
within cylinder 30 to project upwardly beyond the upper
end 46 thereof. Tube 43 move~ with piston 32, sliding in
a head 47 which is threaded to end 46 and includes an
O-riny 50 for outward sealing, and a seal 51 and a wiper
52 for inward sealing. The upper end 53 of tube 43 is
closed by a plug 54 from which a lift rod 55 projects
downwardly within cylinder 30 -through lift tube 43, guide
tube 37, and piston 32, to project below end 35 of -the
cylinder for connection to a string of sucker rods by
which the subsurface pump is reciprocated. Head 47, the
ou-ter surface of lift tube 43, the upper surface 45 of
piston 32, and -the inner surface of cylinder 30 define a
second annular hydraulic chamber 56 having a volume which
varies oppositely to that of chamber 41, decreasing as
piston 32 moves upward. The maximum volume of chamber 41
--4--
is greater than that of chamber 56, and the working area
of surface 45 of piston 3~ -- that between cylinder 30 and
lift tube 43 -~ is less than the working area of the
bo~tom surface 40 of the pis-ton. A por-t 57 affords com
munication with chamber 56.
An elongated cover 60 is secured on head 47, as
by fasteners 61, to protect the upper end of the motor
against dirt, dust, water, and physical damage $o lift
tube 43 when piston 32 is near its upper limit of travel.
Cover 60 may be transparent if desired. It is equipped
with a pair of limit switches 62 and 63 which form a
portion of the control apparatus for the system. These
may be microswitches, if physical contact with lif~ tube
43 is acceptable, or may be magnetically actuated switches
if it is preferred to avoid physical contact. Upper
switch 62 is normally open, and is located to be closed by
lift tube 43 when piston 32 is at the upper limit of its
travel. It is connected to control arrangement 24 by a
cable 64 (see also FIGURE 1). Limit switch 63 is normally
closed, and is located to be opened by lif-t tube 43 when
piston 32 is at the lower limit of its travel~ it is
connected to control arrangement 24 by a second cable 65.
A third cable 66 interconnects control arrangemen-t 24 and
valving arrangement 23.
Ports 42 and 57 are connected to valving appara-
tus 23 by conduits 67 and 68 respectively. The former is
also connected to accumulator 21, and the latter may in~
clude a thro-ttle valve 69 if desired. Hydraulic supply 22
is connected to valving apparatus 23 by conduits 70 and
71.
A simple embodiment 23a of valving arrangement
23 is shown in FIGURE 3 to comprise first and second elec-
trically operated, normally closed valves 72 and 73. Inthis arrangement, condui~s 67 and 70 are always in commun-
ication. When actuator 74 of valve 72 is elec-trically
energized through a cable 75, the valve opens a channel
between conduit 68 and conduits 67 and 70. When actuator
76 of valve 73 is electrically energized through a cable
77, -the valve opens a channel between conduits 68 and 71.
Cables 75 and 77 comprise cable 66 of FIGUR~ 1.
A slightly more complex embodimen-t 23b of valv-
ing arrangement 23 is shown in FIGURE 4 to comprise anormally cen'cered reversing valve 80 having oppositely
acting actuators 81 and 82 electrically energized through
cables 83 and 84 to move a spool 85 respectively downward
and upward relative to fixed ports 86, 87, and 88 con-
nected to conduits 68, 71, ancl 67, 70 respec-tively. In
this arrangement also conduits 67, 70 and always in com-
munication. When actuator 81 is electrically energized
conduit 71 is isolated and conduit 68 is placed in com-
munication with conduits 67 and 70. When actuator 32 is
eneryized condui-t 68 is placed in communication wi~h con-
dui.t 71. Here cables 83 and 84 compri~e cable 66 of
FIGURE 1.
~ still more versatile embodiment 23c of valving
arrangement 23 is shown in FIGU~E 5 to comprise a normally
centered reversing valve 90 having oppositely acting actu-
ators 91 and 92 electrically energized through cables 93
and 94 to move a spool 95 respectively downward and upward
relative to fixed ports 96, 97, 98, and 99. When ac-tuator
91 is electrically energized, conduit 70 is placed in com-
munication with a concluit 100, and conduit 71 is placed incommunication with a conduit 101. When ac-tuator 92 is
electrically energized conduit 70 is placed in communica-
-6-
33~1
-tion with conduit 101, and conduit 71 is placed in com-
munication with conduit 100. A second accumula-tor 103 is
always connected to conduit 70.
Conduit 100 is connec~ed, through a check valve
103 bypassed by a normal.ly clcsed throttle valve 104, to
conduit 67, and conduit 101 is connec-ted, through a check
valve 105 bypassed by a normally closed throttle valve
106, to conduit 68. Valve 103 is oriented to prevent
fluid flow from conduit 67 to conduit 100, and valve 105
is oriented to prevent fluid flow from conduit 101 to
conduit 68. A normally closed valve 110 has an actuator
111 energizable through a cable 112: upon energiza~ion,
valve 110 opens a ehannel between conduits 67 and 6~.
Cables 93, 94, and 112 comprise cable 66 of FIGURE 1.
Hydxaulic supply 22 is shown in FIGURE 6 to com-
prise a pressure compensated variable displacement pump
120 driven by an electric motor 121 to draw fluid from a
receiver 122 through a conduit 123, a suction sereen 124
and a conduit 125, and deliver it through a conduit 126, a
ilter 127, a conduit 130, a check valve 131, a conduit
13~, and a throttle valve 133 to conduit 70, a pressure
gauge 134 being provided. Conduit 71 is extended at 135
to discharge fluid to receiver 122. A relief valve 136 is
connected between conduits 132 and 135, as is a starti.ng
valve 137.
An embodiment of control apparatus 24 is shown
in FI~URE 7 to be energized from a source 1~0 of al-ter
nating voltage by a pair of conductors 141 and 142, the
former being the common or ground conductor. In addition
to limit switches 62 and 63, the apparatus includes a fuse
143, single pole single throw switches 144, 145, and 146,
a single pole double throw switch 147 having a switching
contact 150 and two fixed contacts 151 and 152, and a
relay 153 including a winding 154 which actuates an arma-
ture 155 to displace a first movable contact 156 out of
normal engagement with fixed contacts 157 and 160, to
displace a second movable contact 161 into engagement with
fixed contacts 162 and 163, and to displace a third mov-
able contact 164 into engagement with fixed contacts 165
and 166, In this figure, the valving arrangement of
FIGURE 3 is shown schematically.
A circuit may be traced in FIGURE 7 from con-
ductor 142 through fuse 143, conductor 167, switch 144,
conductor 170, switch contacts 150 and 151, and conductor
171 to a junction point 172, from which a ~irst circuit
extends through conductor 173, switch 146, conductor 174,
junction poin-t 175, and conductor 176 to actua-tor 74 of
valving arrangement 23a, and from which a second circuit
extends through conductor 180, switch 145, conductor 181,
junction point 182, and conductor 183 to actuator 76 of
valving arrangement 23a. Conductor 141 is connected
through junction point 184, conductor 185, junction point
186, and conductors 187 and 188 to actuators 74 and 76.
A circuit may be traced from contact 152 of
switch 147 -through conductor 190, junc-tion point 191 and
conductor 192 to junction point 193, which is connected by
conductors 194, 195, and 196 to relay contacts 160, 163,
and 166. Relay contact 157 is connected by conductor 197
to junction point 182. Relay contact 162 is connected by
conductor 200 to junction point 175. Relay contact 165 is
connected by conductor 201 to one contact of normally
closed limit switch 63, and junctlon point 191 is con-
nected by conductor 202 to one contact of normally open
limit switch 62. The other contacts of the limit switches
--8--
are connected by conductors 203 and 204 to a junction
poin-t 205, which is connected by a conductor 206 to one
terminal of relay winding 15~. The other terminal of the
relay winding is connected by conductor 207 to junction
point 184.
FIGURE 8 shows the specific comlec~ions of ~he
control apparatus to the valving arrangement 23b of FIGURE
5. Conductors 176 and 183 are connected to irst ter-
minals of actuators 81 and 82, and the other actuator
terminals are connected by conductors 210 and 211 to
junction point 186. Conductors 17& and 210 comprise cable
83 of FIGURE 4, and conductors 183 and 211 comprise cable
84 of FIGURE 4.
FIGURE 9 shows a simplified electrical schema-
tic, applied to the valving arrangement 23c of FIGURE 5.
In addition to limit switches 62 and 63, the components
are a pair of fuses 214 and 215, a power switch 21~ having
terminals 217, 220, 221 and 222, and a relay 223 having a
winding 224 moving an armature 225 to displace movable
contacts 226 and 227 out of normal engagement with fixed
contacts 230 and 231 and into engagement with fixed con-
tacts 232 and 233.
Power is supplied from source 140 to swi-tch con-
-tacts 217 and 222 through conductor 234, fuse 214, and
conductor 235, and through conductor 236, fuse 215, and
conductor 237 respectively. Terminal 220 is connected
through conductor 240, junction point 241, and conductor
242 to one contact of normally open limit switch 62, and
from junction point 241 through conductor 243, junc-tion
point 244, and conductors 245 and 246 to relay contacts
226 and 227 respectively.
3~
Relay contact 233 is connected by a conductor
247 to one con-tact of normally closed limit switch 63.
The other contacts of switches 62 and 63 are connected
through conductors 250 and 251, junction point 252, and
conductor 253 to one terminal of relay winding 224, the
other texminal of which is connected through conductor
254, junction point 255 and conductor 256 to switch con-
-tact 221.
Relay contact 232 is connected by conductor 257,
junc-tion point 260, and conduc-tors 261 and 262 to valve
actuators 92 and 111 respectively. Relay contact 230 is
connected by conductor 263 to valve actuator 91. The
actuator circuits are completed through conductors 264 and
265, junction point 266, and conductor 267, and through
conductor 271, to junction point 270, the latter being
connected by conductor 272 -to junction point 255.
In one embodiment of the invention the range of
travel of piston 32 is 85 inches, which requires the
addition of 4.6 gallons of hydraulic fluid at port 42.
The area of the lower surface 40 of piston 32 is 12.57
square inches, so that with a hydraulic presswre of 1,000
psi a load of more than 12,000 pounds can be lifted. The
area of the upper surface 45 of piston 32 is 7.08 square
inches, and the maximum volume of chambe:r 56 is about 1/3
of the maximum volwme of chamber 41. The size of accumu-
lator 21 if used alone is 10 gallons: if used with a
second accumulator 103 their si~es may be 5 gallons and 4
gallons. Pump 121 may have a rating of 15 gallons per
minute at at maximum pressure of 2500 pounds per square
inch.
1()
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Operation of the Preferred Embodiments
The operation of my system is as follows, refer-
ring generally to E'IGURE 1 and specifically to FIGURES 2,
6, and 7. Switches 144, 145, and 146 are open. Switch
147 is in its "AUTOMATIC" position, in which contact 150
engages contact 152. Motor 121 is driving pump 120, and
hydraulic fluid at a pressure determined by relief valve
136, for example lO00 pounds per s~uare inch, is available
at conduit 70, being indicated at gauge 134 and regulated
by relief valve 136. Piston 32 is at some posikion within
its range of travel, so that switch 62 is open and switch
63 is closed. Lift rod 55 is connected -to the sucker rods
for operating the subsurface pump. Valves 72 and 73 are
closed so that the position of piston 32 in cylinder 30 is
hydraulically fixed.
To put the system in operation, switch 144 is
closed. This completes a circuit from conductor 142
through fuse 143, çonductor 167, switch 144, conductor
170, s~itch contacts 150 and 152, conductor 190, junction
point 191, conductor 192, junction point 193, conductor
194, relay contacts 160, 156, 157, conductor 197, junc-tion
point 182, and conductor 183 to actuator 76 of valve 73,
the circuit being completed through conductor 188, junc-
tion point 186, conductor 185, and junction poin-t 184 to
conductor 141. Valve 73 opens, so that fluid can flow out
of chamber 56 through conduit 68, and fluid from the pump
may enter chamber 41 and displace piston 32 upwards, to
raise lift tube 43 and lift rod 55, the fluid above piston
32 passing through conduit 68, valve 73, and conduit 71 to
receiver 122.
When actuator 20 reaches the top of its stroke,
switch 62 is closed, completing a circuit from junction
~11 =
point 191 through conductor 202, swi-tch 62, conductor 203,
junction point 205, conductor 206, relay winding 154, con-
ductor 207, and junction point 134 to conductor 141.
Relay 153 operates, completing i~s own holding circuit
through contacts 161-3 and switch 63, interrupting at its
contacts 160, 156, 157 the circui-t for valve 73, which
closes, and completing a circuit for actuator 74 of valve
72 through conductor 176, junction point 175, and con-
ductor 200 from relay contact 162, so that valve 72 now
opens. This means tha-t the pressures on surfaces 40 and
45 of piston 32 are made equal, that on surface 40 still
acting to lift -the piston but that on surface 45 now
acting in opposition, to lower the piston. The lifting
force is no longer sufficient to support the weigh-t of the
load on lift rod 55, which according acts through piston
32 to drive liquid out of chamber 41 through conduit 67,
valve 72, and conduit 68 into chamber 56, the rate of
fluid flow and hence the rate of descent of the piston
being adjustable by adjusting valve 69. Back flow of the
liquid from conduits 67 and 70 to supply 22 is prevented
by check valve 131.
Because the volume of chamber 56 is less than
that of chamber 41, a downward movement of piston 32 is
accompanied by exit of a greater volume of liquid at port
42 than can be received at port 57. This excess flows
into accumulator 21, the energy for the resulting increase
in pressure, at both surfaces of the piston, being derived
from the weight of the descending pump stringO
When piston 52 reaches its low~r level of tra-
vel, switch 63 opens the circuit for relay winding 154,and the relay is deen~rgized, interrupting at contact 161
the circuit for actuator 74 of valve 72, which closes, and
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completing at contact 156 the circuit for actuator 76 of
valve 73, which now opens. The hydraulic chambers are now
isolated, chamber 56 being free to empty through valve 73,
and liquid flowing from accumulator 21 through conduit 67
into chamber 41 to raise piston 32. ~ischarge of li~uid
from the accumulator lowers the pressure in conduit 67 -to
the output pressure of pump 120, which now continues to
supply li~uid to conduit 67 and raise piston 32. Upward
movement of the piston allows switch 63 ~o close, but the
relay winding circuit has been opened at contacts 164,
165, 166, and no change in the system occurs at -this time.
When the piston rises to cause closure of switch 62 a
cycle of operation has been completed, and -the cycle is
repeated as long as switches 144 and 152 remain as
described.
Opening of switch 144 deenergizes whichever of
actuators 74 and 76 is currently energized, closing both
valves and locking the piston in its then position. Re-
closing switch 144 restarts the cycle in its upward direc-
tion, regardless of what direction it was moving in whenshut off.
It is some-times desirable, in setup and adjust-
ment operations, to be able to cause movement of the
piston in a desired sense for a short dis-tance. To accom-
plish this, switch 147 is -thrown into its "MANUAL" posi-
-tion, in which contac-t 150 engages contact 151. Now if it
is desired to raise the piston, switch 145 is manually
closed, completing an energizing circuit for ac-tuator 76
from source 140 -through conductor 142, fuse 143, conducto:r
167, switch 144, conduc-tor 170, switch contacts 150 and
151, conductor 171, junction poin-t 172, conductor 180,
switch 145, conductor 181, junc-tion point 182, and conduc-
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tor 1~3. Valve 73 opens, allowing liquid to pass from
chamber 56 through outlet 68, so that pump pressure can
act in chamber 41 to raise the piston. Opening of switch
145 terminates this operation.
In the same way, when it is desired to lower
piston 32 sligh-tly, swi-tch 147 is placed in its "MANUAL"
position and switch 146 is closed, completing an ener-
gizing circuit for actuator 74 from source 140 through
conductor 142, fuse 143, conductor 167, switch 144, con-
ductor 170, switch contac-ts 150 and 151, conductor 171,
junction point 172, conductor 173, switch 146, conductor
174, junction point 175, and conductor 176. Valve 72
opens, equalizing the pressures on the top and bottom of
the pis-ton, and allowing the load to lower the piston.
Opening of switch 145 terminates this operation.
Operation of the system using -the valving
arrangement of FIGURE 4 will now be explained, referring
also to FIGURES l, 7, and 8. Valve 80 is normally in
center position, in which conduit 68 is isolated so that
the piston is hydraulically locked in position. With
switch 47 in its "~UTOMATIC" posi-tion, closure of switch
144 completes the circuit to conductor 183 described
above, energizing actuator 82 of the valve. This raises
spool 85 to complete a passage between conduits 68 and 71,
enabling flow of fluid from chamber 56 and thus enabling
flow of fluid into chamber 41 to raise the piston. Opera-
tion of switch 62 acts on relay 153 as described above to
deenergize conductor 183, and energiæe conductor 176.
Spool 85 is now lowered past its central position, placing
conduit 68 in communication with conduits 67 and 70 to
allow fluid passage from chamber 41 to chamber 56 and
permit descent of the piston and admission of fluid into
39~
accumulator 21 as before. When switch 63 opens, relay 153
is deenergized -to deenergize conductor 176 and energize
conductor 183, so that the cycle of operation is repeated.
Opening of swi-tch 144 centers spool 85 and hence locks the
piston in position hydraulically.
In the "MANUAL" position of switch 147, opera-
tion of "UP" switch 145 or "DOWN" switch 146 acts -to
energize conductor 183 or conductor 176 as before, acting
through actuator 82 or actuator ~1 to cause valve spool
displacement and resulting piston movement. It will be
apparent that valve 80 of FIGURE 4 is the functional
equivalent of valves 72 and 73 of FIGURE 3.
The operation will now be described of a system
using valving arrangement 23c of FIGURE 5 and the control
arrangement of FIGURE 9, FIGURES 1, 2, and 6 also being
pertinen-t.
5witch 216 is open. Motor lZl is driving pump
120 and hydraulic fluid at a pressure determined by relief
valve 136 is available in condui-t 70 as before. Piston 32
is at some postion within its range of travel, so that
switch 62 is open and switch 63 is closed. Lift rod 55 is
connec-ted to a load, relay 223 is not ener~ized, valve 90
is centered, and valve 110 is closed.
To put -the system in operation switch 216 is
closed. This completes a circuit from source 140 through
conductor 234, fuse 214, conductor 235, switch contacts
217 and 220, conductor 240, junction point 241, conductor
243, junction point 244, conductor 245, relay contacts 226
and 230, and conductor 163 to actuator 91 of valve 90, the
circuit being completed by conductor 265, junction point
266, conductor 267, junction point 270, conductor 272,
junction point 255, conduc-tor 256, switch contacts 221 and
-lS-
222, conductor 237, fuse 215, and conductor 253 to source
140. Valve 90 operates, comple-ting passages from conduit
70 to conduit 100 and from conduit 71 to conduit 101.
Valve 110 remains closed. Fluid flows from condui-t 100
through valve 103 to conduit 67, to enter chamber 41 and
move piston 32 upward, fluid flowing out of chamber 56
through conduit 68 and valve 105 to conduit 10l.
When switch 62 closes a circuit is completed
from junction poin-t 241 through conductor 242, switch 62,
conductor 250, junction point 252, and conductor 253 -to
relay winding 224, the circuit being completed through
conductor 254 to junction point 255. Relay 223 op~rates,
interrupting at contacts 226 and 230 th~ energizing cir~
cuit for valve actuator 91 and completing at con-tacts 226
and 232 circuits which may be traced through conductor 257
to junction point 260 and thence by conductors 261 and 262
to valve actuators 92 and 111. Valve 110 operates to
interconnect condui-ts 68~ 101, with conduits 67, 100, and
valve 90 operates past its center position to connect con~
dui-t 70 with conduit 101 and to connect conduit 71 wi-th
conduit 100. However, by reason of check valves 103 and
105 no fluid flow from pump 120 or to receiver 122 -takes
place. At the same time valve 112 operates to intercon-
nect conduits 68, 101 with conduits 67, 100, and the load
on rod 55 acts as previously described to force fluid from
chamber 41 into chamber 56 and accumulator 21.
Operation of relay 223 also completes a holding
circuit for the relay from junction point 241 through con-
ductor 243, junction point 244, conductor 246, relay co~-
-tacts 227 and 233, conductor 247, switch 63, and conduc-tor
251 to junction point 252, whereby to maintain relay oper~
ation when the piston moves downward and switch 62 opens.
-16-
33~
When switch 63 is opened, a-t the bottom of -the
piston travel, the holding circuit for rela~ 223 just
traced is interrupted, and the relay is deenergized, the
circuit to ac-tuators 92 and 111 is opened at relay con-
tacts 226 and 232, and valve 110 closes. ~owever, the
circui-t for actuator 91 of valve 90 is again com~leted at
relay contacts 226 and 230, and valve 90 returns to a
state enabling upward piston movement, so -tha-t the cycle
can con-tinue.
If it is desired to move piston 32 manually,
switch 216 is -turned off but pump operation is continued,
and valves 103 and 105 are open to the desired extent.
Valve 90 is manually operable, and for up movement of
piston 32 valve 90 is operated manually to lower spool 95
with respect to ports 96-99, admitting fluid to conduit 67
through valve 104 and conduit 100 from conduit 70, and
enabling flow of fluid from conduit 68 through valve 106
and conduit 101 to conduit 71, so that piston 32 is
raised. If it is desired to lower piston 32 manually, the
same procedure is followed, except that valve 90 is
operated manually in the opposite sense, fluid from con-
duit 70 flowing through conduit 101, valve 106, and con~
duit 68 to the top of the cylinder, and fluid from the
bottom of the cylinder flowing through conduit 67, valve
104, and conduit 100 to conduit 71. In each case af-ter
manual operation has been completed valve 90 is allowed to
center itself, and valves 104 and 106 are again closed.
The presence of accumulator 103 enables the use
of an accumulator of smaller size at 21, and also enables
the use of a pump 121 of smaller volume rating.
From -the foregoing it will be evident that the
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~3~3~&~
invention comprises a specially designed hydraulic actua-
tor having chambers of different volumes and piston sur-
faces of different areas, in combination with valving
means directing the flow of hydraulic fluid to and from
the actuator chambers and to and from a hydraulic actuator
associated therewith.
Numerous characteristics and advantages of the
inv~ntion have been set forth in -the foregoing descrip-
tion, together with details of the structure and function
of the invention, and the novel features thereof are
pointed out in the appended claims. The disclosure,
however, is illustrative only, and changes may be made in
detail, especially in matters of shape, size, and arrange-
ment of parts, within the principle of the invention, to
the full extent indicated by the broad general meaning of
the terms in which the appended claims are expressed.
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