Note: Descriptions are shown in the official language in which they were submitted.
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INTRODUCTION AND DESCRIPTION OF THE PRIOR ART
Large areas of central North America are spotted with pumpjacks recovering
underground petroleum fluids for domestic and commercial use; the present invention
provides an important reduction in the amount of energy required to drive the pump jack,
as well as certain other advantages. Most centrally it applies an improved hydraulic
control system to manage the balanced movement of the horseheads, although aspects of
the weighting and geometric placement of the heads and fulcrum beam are also
addressed.
The existing prior art and commercially operating machines are of many
types, spanning many decades, and no attempt to exhaustively itemi~e the less efficient
pump jacks will be made. For this analysis they may be said to t`all into two broad
categories: those using direct mechanical linkages, and those hydraulically driven. The
present invention is of the second type. Advantages including reduced mechanical wear,
and hence maintenance costs, are realized by the use of hydraulics, such as specified in
U.S. patent #3,369,490 (Hawk, 1968), and C~n~ n patents ~906,477 (Maasshoff, 1972);
#921,768 (Maasshoff, 1973); #994,21 1 ((~oldfein, 1976): #1.164.270 (Creamer, 1984);
and #1,193,345 (Creamer, 198~).
The layout of the hydraulics and the geometry of Ihe horseheads and fulcrum
determines how efficient the pump jack is; and the cited jacks have appreciable losses
from their hydraulic systems and balancing geometry. Some use a mechanical control of
the hydraulic system; some have progressed to an electrical: but in all Ihe hydraulic
cylinder ports are blocked in the neutral position, and pressure soars until it reaches a pre-
set by-pass setting, which is very inefficient and hard on the pump, cylinder, and
hydraulic fittings. As well, if the work load increases, the hydraulic system continues to
drive, or drives until a safety cut-off pressure is reached and a sudden total shut-down is
initiated. This can result in long-term inefficient--and eventually damaging--action, if
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there is an unnoticed downhole problem.
The present invention dramatically reduces the friction and heat losses and
wear on the hydraulic parts by providing a variable output pllmp with electrical over
hydraulic over hydraulic valve control of the cylinder driving the pump jack. This allows
a soft shift spool in normal operation (all ports are open in the shit`ting and neutr.ll
positions) greatly increasing efficiency. This is further enhanced by manually adjustable
needle valves which feather the action of the cylinder by controlling the speed of the
hydraulically actuated valve, hence avoiding hydraulic fluid hammering and
instantaneous direction changes which cause energy losses.
Also incorporated are hydraulic compensators that will sacrifice the amount of
fluid output if the work load increases. This is very important in that it gives early
indication of downhole complications by actually slowing down the speed of the jack,
which can be visually noticed by a well operator. This compensation also reduces the
strain on the pump jack and downhole equipment in load-increase situations, saving the
downhole equipment from damage. To the inventor's knowledge no other pump jack is
capable of this feature.
Another advantage of the present invention is that tapping bottom in the well
can be done easily by adjusting proximity switches instead of difficult manual removal of
bolts on a clamp above a stuffing box, as is currently done. As well, normal speed of the
jack motion is easily changed by varying the output of the pump, instead of the
mechanical changing of pulley and belt sizes. Both of these features mean major
advantages in time, convenience~ safety, and maintenance.
Finally, two important and unique safety features are incorporated. One is to
have a positive hydraulic lock that will hold the cylinder in its stopped position
indefinitely until hydraulic pressure is applied to release it. This avoids the problems of
prior safety locks that rely on the all-ports-blocked hydraulic valve to hold the walking
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beam; as the spool wears, this creates an unsate condition ~Secondly, the present
invention can only be stopped by cutting the electrical sllr ply to the control valve; in
other words. a safe and total shutdown. instead of a shut(lown which leaves pressurized
hydraulics or active electrical systems (or both), as past systems have done.
An object of the present invention is to provide t`or an oil-well pump jack
driven by an electric-hydraulic drive system;
the pump jack comprising: a fulcrum beam; on a saddle bearing; the
beam having on one end ~ well-head horsehead with the l`ace tarthe~t from the bearing
being a convex portion ol` a circle circumference whose radius is the distance to the center
of the bearing, and on the other a balance horsehead with a corresponding face similarly
measured from the center of the bearing but extending further downwards in order to
facilitate tapping bottom of the well; well rod linkage connecting the well-head horsehead
with a well-head downhole load; balance rod linkage connecting the balance hor~ehead
with an equalizer; A-leg braces supporting the saddle bearing; and a welded steel base on
a concrete base pad on a gravel pad, supporting the A-leg braces:
the electric-hydraulic drive system comprising: a piston driving the
tulcrum beam; a hydraulic cylinder providing hydraulic fhlid driving the piston; two
input/output ports from the cylinder; a dual counterbalance valve connected to the two
ports; a hydraulic manifold controlling the supply of hydraulic tluid to the cylinder: the
manifold comprising:
two controlled hydraulic fluid output lines, one
communicating with each input/output port through the counterbalance valve; two
pressurized hydraulic fluid input lines, both communicating with a hydraulic fluid
reservoir and isolated from the hydraulic fluid output lines; a hydraulically piloted
hydraulic valve for each fluid output line: a solenoid-controlled hydraulic pilot valve for
each piloted valve; a solenoid controlling each pilot valve; electric control of the
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solenoids; and additional manual control of each pilot valve:
a positive lock on the hydraulic cylinder: ad jus~ahle switching me.lns to
change the direction of tlow of the hydraulic fluid in the manifold at a chosen extent of
the horsehead movement cycle; a pressure relief valve; a back pressure check valve; an
electrically-monitored pressure gauge; a variable-displacement hydraulic pump; an
hydraulic reservoir; an electric motor; a control circuit controlling the electric motor; and
a power circuit to supply electric power to the electric motor;
wherein the equalizer is provided of such weighl as to counterbalance the
downhole load evenly without exerting horizontal forces on the well rod linkage: wherein
this even counterbalancing is arrived at by calculating the moments of gravitational force
of the fulcrum, horseheads, well rod linkage, and downhole load, and by specifying the
radii of the horseheads; wherein engagement of the electric motor engages the pump and
drives the cylinder and hence fulcrum beam and well-head and halancing horseheads;
wherein the electric-hydraulic over hydraulic valves provide soft shift spool in normal
operation, enhanced by manual adjustment; wherein the electric-hydraulic over hydraulic
control, in being two separate hydraulic fluid circuits, provides hydraulic compensation in
the form of sacrifice of fluid output if the work load increases such as by increased
downhole load, so that the system slows down visibly, signalling the operator and
avoiding downhole damage; wherein stopping the horseheads can be done only by cutting
electrical supply to the electric motor, thereby depressurizing the system and effecting a
safe and total shutdown; and wherein the positive hydraulic lock safely holds the cylinder
in its stopped position indefinitely until hydraulic pre~sure is applied to release it.
DETAILED DESCRIPTION OF THE INVENTION
For this description, refer to the t`ollowhlg diagrams, wherein like nulllerals
refer to like parts:
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Figure 1, an embodimenl of the inven~iom ~ide elevatioll;
Figure 2, detail of Figure 1, hydraulic system: block diagram: and
Figure 2A, detail of Figure 2; manifold; block diagram.
In the example of the invented apparatus shown in Figure I, pump jack
indicated generally as 10 is of a type common in the petroleum-pumping industry, and
consists of a fulcrum beam 12 with horseheads on either end, a well-head horsehead 14
and a balance horsehead 16. The precise shape and placement of the horseheads 14 and
16 are specific to this invention, and will be discussed in more detail below.
The elements just described are supported on a saddle bearing 18, in turn
supported by A-leg braces 2(), welded steel base 22. concrete hase pa(l 24. and finally
gravel pad 26.
Hanging t`rom horsehead 14 is well rod linkage indicated generally as 30.
Hanging from balance horsehead 16 are corresponding equalizer linkage 40 and from it
equalizer weight 42. Safety fence 4~ surrounds equalizer 42.
Also indicated on Figure I are electric-hydraulic drive system components
such as piston 44 connected to fulcrum beam 12 at the ad justable pivot 1 ~; hydraulic
cylinder 46; hydraulic manifold indicated generally as 48; dual counterbalance valve,
comprising a positive lock, indicated generally as 50; proximity switches 52, upper, and
54, lower; pressure gauge 56; hydraulic pump 58; electric motor 6(); hydraulic reservoir
62; and fluid lines generally indicated as 90 (shown in partial length only~.
Additional components are indicated on Figure 2 and 2A: a block di.lgl~ ol`
~he electric-hydraulic drive system is ~enerally indicated a~ 7() on Figure 2. On Figure 2
can be seen additionally the placement of pressure relief valve 72, manual snubber valve
57, and back pressure check valve 74 on line generally indicated as 9(), and dual
counterbalance valve 80 on isolated second fluid line generally indicated as 92. Figure
2A is an enlarget1lent of the block diagral1l of the hydraulic m,lllit`ol(l 4X~ showillg
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solenoid-controlled valves 76 and 78 and associated manual needle valves 76a and 78a
respectively on line 90.
Refore detailillg lhe operalioll of Ihe appar.~ imrorl.lnl lo note. with
reference to Figure 1, that outer surfaces 14e and 16e respeclively of horsehea(ls 14 and
16 are portions of the circumference of circles measured from bearing 18, and have
different radiuses Rl and R2 respectively. These distances are same as the horizontal
distances D 1 and D2, respectively, between center 100 of saddle bearing 18 and the
horizontal centers of well rod linkage 30 and balance rod linkage 4(). This ensures that
there is no pressure on the linkages from side loading; all the force will be delivered
smoothly in the vertical direction. Horizontal forces c~use wellhe~(l p;lcking to we~r ~nd
can create a hazardous blowout condition; and energy is wasted in the general running of
the system if all the t`orce is not used to vertically drive well rod linkage 30. Accordingly,
in order to deliver any desired specific height, indicated as 3(~x, of vertical stroke in well
rod linkage 30, the outer circumference of well-head horsehead 14 measured between
points 14b and 14c is fashioned equal to at least this distance 30x, plus an extra amount
30y, equal to the distance between points 14a and 14b, to facilitate tapping bottom in the
well without having to make difficult adjustments to the equipment. The circumference of
balance horsehead 16 is fashioned this same amount 30x, measured between points 16a
and 16b, plus the same extra amount 30y, between points 16b and 16c (note that Figure I
is not a scale drawing). Weight of equalizer 42 is calculated, using well-known simple
geometric techniques, from the moments of gravitational force of the (lownhole load (not
shown); well rod linkage 30; balance linkage 40; horseheads 14 and 16; and fulcrum
beam 12.
The apparatus operates as follows. Engagement of electric motor 60, seen on
Figure I, drives pump ~, moving hydraulic fluid (not shown) from reservoir 62 into
primary line 90. As can be seen best with ret`erence to hydraulic ~low block diagram,
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Figure 2, tlui(l is then routed Ihrough marlual v.llve 57, ~o the pre~sure sg.luge 56, an(l
through hack pressllre check valve 74. past pressure releas~ v;llve 72, all(l intO hy(lralllic
manifold 4X. In the enlarged detail of the Inanifold, Figllre 2A, il call be seell ~hat Illlid is
then routed through electrically-controlled solenoid valves 76 and 78 and correspondillg
manual needle valves 76a and 78a, and presses hydraulically on isolaled hydraulic line
92. Although this is not indicated expressly on the simplified schematic of hydraulic
manifold 48 shown on Figure 2, the solenoids 76 and 78 determine the manifold
direction; i.e. pressure is applied alternatingly to line 92a and line 92b. Referril1g agaill to
Figure 2, the pressure can be seen to flow through dual counterbalance valve 80 and then
directly into cylinder 46 to drive piston 44. Ad jll~tahle pr(~imity switches 52 and 54, as
seen on Figure 1, are triggered by position indicator 53 alternatingly during the motion of
fulcrum beam 12, and form electrical connection with solenoid valves 76 and 78 shown
on Figure 2A, to determine the direction of fluid pressure through manifold 48. The
position of switches 52 and 54 is adjustable, which will in turn change the amplitude of
rotation of the horseheads 16 and 14; this adjustment can be used to control tapping
bottom in the well more safely and easily than the changing of clamps and bolts required
in the prior art.
An important feature of this system is the isolation of line 92 from line 90,
allowing a soft shift spool so that all ports in line 92 and dual counterhalance valve 80 are
open in the shifting and the neutral positions. This avoids hydraulic fluid "dead-head"
found in previous mechanical over hydraulic, or electrical over hydraulic systems, in
which pressure rose until it reached a pre-set bypass setting. This was very inefficient and
hard on the pumps, cylinders, and hydraulic fittings. Also note that manual needle valves
76a and 78a in the present invention allow further adjustment to avoid hydraulic fluid
hammering and inefficient installtalleous direction changes, which in previous systellls
caused rod stretch and hammering on mechanical parts such as the cylinder.
A further advalltage of tllis hydraulic over hydr.llllic sy~lelll in reliatioll lo
previous systems is hydraulic compensation, in whicll the .nlnount -f tluid output is
saclificed if the work load h~creases. Thus i~ cylhl(ler 44 hl Figllre 2 resi~cts more strongly
than usual due to a downhole problem (not shown), increased pressure in isolated fluid
line 92 will mechanically affect the action of manifold 4X, allowin~ for a drop in the
amount of fluid and automatic slowdown of the movement of fulcrum beam 12 of Figure
t. This is very advantageous, both as a signalling mechanism to an operator, and to avoid
damage to downhole parts.
The eleclrical system l`or the illustrated example is ~Iraightforwilrd and will
not be diagrammed. lf radius Rl from Figure I is 4 feet I I inches and all otherdimensions are proportional, then an appropriate power supply for this particular size of
pump jack 10 is a 3 horsepower, enclosed, fan cooled motor. Main power supply could
be a 3-phase, 480 volt alternating current, or adapted to suit any available voltage such as
240 volt single-phase. The power circuit has a main disconnecting means, a magnetic
starter, and overload protection.
The correspondhlg control circuit (not diagrammed) is a 1 2()V A.C~. from a 4-1
stepdown transformer. The control starts at the transformer and goes to an on-off switch
located in a control panel. From there it travels to a hand switch installed near the pump.
After this it goes to a pressure switch on the wellhead to monitor wellhead pressure: this
switch will interrupt the control circuit if a preset pressure is reached. If all these are
electrically satisfied then the electric pump, such as pump 60 on Figure 1, starts and
drives the hydraulic system as detailed above. Proximity switches, shown as 52 and ~4 on
Figure 1, are linked by a simple relay (not diagrammed) to solenoids 76 and 78, seen in
Figure 2A in manifold 48. Note that an important safety feature of this set-up is that the
pump jack 10 can only have its motion stopped by cutting electrical supply to the entire
control circuit, for a safe and total shut-down. In other words, the dangerous
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configuratioll used by previous systems in which a fulcr~ be~m i~ mech-lllically locked
while a pressulized hydraulic system i~ still eleclric.llly dl-ivel~ nvoide(l.
A final important safety control of the apparatus is a posilive hydraulic lock,
incorporated in dual counterbalance valve 5() in Figure 1, which holds piston 44 of
cylinder 46 in a stopped position without relying on hydraulic fluid pressure, which has
been used by previous systems and risks a free-falling fulcrum beam in the event of a
hose, valve or fitting leak or break.
The foregoing is by exalllple only, and ll~e scope ol tl~e h~venlion shoul-l be
limited only by the appended claims.
