Note: Descriptions are shown in the official language in which they were submitted.
~ ~ 3~5
This invention relates to a control apparatus, and
in par-ticular a control apparatus for a pump jack.
Canadian Patent Application Serial No. 366,803, filed
by applicant on December 15, 1980, cliscloses a drive for a pump
jack. There are presently avai].able mechanical and electrical
systems for controlling pump jack dri.ves, i.e. for ensuring the
precise turn around of the polished rod at the -top and bottom
of the stroke. Examples o:E such systems are disclosed by U.S.
Patents Nos. 3,075,466, issued -to B. G. Agnew et al on January
29, 1963; 3,363,573, issued to W. S. Jaeger on January 16, 1969;
and 3,939,656, issued to Fl. A. Goldfein on February 24, 1976.
In general, the available mechanl.cal systems include complicated
linkages, and the electrical systems employ sophisticated elec-
tronics.
The object of the present i.nvention l.s to avoici the
drawbacks o:E exi.StincJ systems by prov.iclincJ a relati.vely simple
appara-tus for accurate control o~f the clr:ive of a pump jack.
Accorclingly, the present inverlt:ion relates to a con-
trol apparatus for controll.ing the flow oE hydraulic flu:id from
a pump in a pump jack of the t~pe :includincJ a samson post, a
walking beam p;.votally mounted on the samson post for rotation
around a horizontal axis, a horsehead on one end of the walking
beam for driving connec-tion to a pump, said apparatus comprising
first swi.-tch means for mounting on a fixed position on said pump
jack; second switch means for mounting in a second fixed position
~ ~; s...
on said pump jack; actuating means for mounting on a movable
element of said pump jack for elosing said firs-t switch means
near one end of the walking beam stroke and ~or closiny said
second switch rneans near the o-ther end of said walking beam
stroke; circuit means incorporating said first and second switch
means, said circuit means including relay means for closing by
said first and second swi-teh means at the top and bottom of
said wal]cing beam stroke; valve eontrol means for ac-tuation by
sai.d relay means; cylinder means for controlling operation of
said pump mechanism; and valve means for feeding hydrau.lie fluid
-to said cylinder means, sa.id valve means being controlled by said
valve control means in response to the closing of said first and
second switch means, whereby closing o:E one o:E said first and
seconcl switeh means causes movement of said polished rod in one
direetion, and elosing of the other said swi.teh means eauses
movement of said polished rocl in the opposite di.reetion.
The inventlon wi:Ll now be deser:ibecl :in CJre~ter detail
with referenee to the aecompa.nyincJ clraw.i.rlcJs, wh:ieh illustrate a
preEerrecl embodiment of -the invent.ion, and wherein:
E`igure 1 is a side eLevatl.on view of a pump jaek and
drive of the type on whieh -the eontrol apparatus of the present
invention is used;
E~igure 2 is a eross-sectional view taken generally
along line II II of Figure l;
Figure 3 is a sehematie elevation view of switches
-- 2
and a switch actuator used in the appara-tus of -the present
inven-tion;
Figure 4 is a circuit diagram of a control circuit
for use in the apparatus of the present invention; and
Figure 5, which appears on the second sheet of draw-
ings, is a schematic longitudinal sectional view of a hydraulic
control cylinder for use in -the apparatus of the present inven-
tion.
With reference to Figures 1 and 2, a conven~ional
pump jack includes a walki.ng beam 1 pivotally mounted on the top
of a samson post 2 for rotation around a horizontal axis defined
by a sadclle bearing 3. The samson post 2 .includes four inelined
legs 4 extendi.n~ upwardly Erom a base 5, a top plate 6, and
crossbars 7 e~-tencling between the legs 4 at the :Eront and rea.r
ends oE the post 2. A counterweight 8 is mounted on the rear
end 9 of the walking beam, and a horsehead 10 ls mounted on the
:Eront end 11 oE such b~am. ~ wire line assembly o:r wire :rope
bridal 12 :is eonnected at one end to the horsehead :I.0 and at the
other end to a p~m~p meehanism, incluc1ing pol:i.shed rod 13. The
briclal 12 and rod 13 are intercorlnected by a eonnector 14.
Usually, -the polishecl rod 13 ree:iprocates a sueker rod or pump
rod associated with a downhole pUlTlp (not shown).
The walking beam 1 is driven by hydraul.ic cylinders
15 and 16 connected to -the rear and front ends 9 and 11, re-
spectively of the walking beam. The bottom ends of the hydraulic
-- 3
~3~
cylinders 15 and 16 are pivotally connected to an I-beam 17 by
clevises 18. The I-beam 17 is supported by the crossbars 7.
Piston rods 19 extend upwardly from the top ends of the
cylinders 15 and 16 to the walking beam 1. The top ends of the
piston rods 19 are pivotally connected to the walking beam 1 by
clevises 20.
The hydraulic cylinders 15 and 16 are operated by a
hydraulic pump 21, which is driven by a prime mover in the form
of a mo-tor 22. Hydraulic fluid is stored in hydraulic ~luid
reservoir 23. The pump 21, -the motor 22 and -the reservoir 23
are mounted on the rear end of the base 5. A V-belt 2~ passes
around pulleys 25 on the motor 22 and the pump 21, respectively.
The pump 21 is controlled by a pump control lever 26
(:Figure 5). Movement of the lever 26 i.n one direction results
in -the flow of fluid -to one cyl.in.der 15, and movemen-t of such
lever in the other d:irection causes :Elow o.E flu:id to the other
cylinder l.6. Movement o.E the lcver 26 is controlled by the
apparatus o.E the presellt .invelltion. Such apparatus will now be
describecl reEerrin~ :Eirst to ~tLcJure 3.
rl~he apparatus lnclucles a pair o.E swi-tches Sl and S2
mountec~ on a vertically oriented bar 27. The switches are
slidable on the bar 27, so -that the vertical positions thereoE
can readily be adjusted. The switches Sl and S2 are locked in
position by bolts 28. The bar 27 is mounted on a fixed portion
of the pump jack such as the I-beam 17.
The swi-tches Sl and S2 are normally open, magnetieal-
ly actuated proximity switches for ac-tuation by a magnet 30,
which is moun-ted on -the polished rod 13 or on another movable
part of the pump ~ack which moves in -the same manner as the
polished rod 13. The switches Sl and S2 may also be mechanical-
ly actuated, i.e. microswi-tches actuated by a lug or bar
instead of -the magne-t 30. Referring to Figure 4 of the drawings,
the switches Sl and S2 are used to actua-te relays 31 and 32,
respectively. When the magnetic field of the magnet 30 causes
closing of the switch Sl, cur:rent is supp].ied to terminal 7a of
the relay 31 c:Loslng con-taet la wl-th eontact 4a, and contact 2a
wi.th contact 6a. The eontaet la is eonneeted to the positive
terminal o.E a 12-volt battery 33 by means o:E an ON/OFF switeh
S7. Curren-t Elows through the contacts la and 4a to a terminal
7a. Thus, power is introdueed into a rel.ay~35 of the relay 31,
so that the .~elay~35 remains :I.n the ~ctuated eond:lt:Lon. In sueh
eond:Ltion, no eurrerlt flows to a terminal 7e oE a eo:Ll 35 wh:ieh
i.s eonneeted to a eontaet 3a oE the rel;~y 3.1. Contaets 2e and
5e o.E the relay 35 are ln the eLose~ eondlt:l.on, allow:LncJ eurrent
to f:Low to a solenoicl 36. Power to the soleno:Ld 36 causes the
pump jaek to move downwardly (i.n the manner de:ser:Lbed herein-
a:E-ter) until the .Eield oE the magnet 30 closes the switeh S2.
When the magnet 30 eauses the switehes to elose, power is
supplied to a terminal 7b of the relay to aetuate a eoil 37
in the relay 32. This aetion eloses eontaets lb-4b and 2b-6b
~,,
~ . I
3~
of -the relay 32, while breaking con-tact lb-3b and 2b 5b. It
will be noted -that in each of the relays, the contac-ts 1-3 and
2-5 are normally closed, and -the contacts 1-4 and 2-6 are
normally open. The ground for the relay 31 is connected -through
terminal 3a to -the con-tacts lb and 3b -to the ground for the re-
lay 32. The breaking of the circuit involving contacts lb and
3b causes a breakdown of the relay 31, thus breaking contacts
la-4a and 2a-6a, making contacts la-3a and 2a-5a. The ground
line for the relay 32 is connected through terminals 8b, 2a and
6a to the ground. Since contact be-tween the -terminals 2a and
6a is broken when power is applied to the terminal 7b, the switch
S2 cannot aEfect -the coil 32 unti] -the swi-tch Sl has again been
closed. With -the relay 31 in the broken down condition, power
is supplied through contacts la and 3a, and terminal 7c oE the
relay 35, coil 3~ of the re].ay 35 to close eontacts 2c-5c and
disconnect contaets 2c-6c. 'rhus, eurrent flows to a seeond
solenoid 39 throucJh contacts 2c ancl 5c, and the direction oE
movement oE the pol:ished roci 13 ls reversed, :i.e. the polished
rod moves upwardly.
The solenolcls 36 ancl 39 are connected to a Eour-way
spool valve 40 (Fi~ure 5), which opera-tes a double ac-ting
cyllnder 41. The double actiny cylinder 41 is defined by a
hollow cylinder, closed at each oE its ends 42 and 43, with a
central partition 44 dividing the cylinder into a pair of
chambers 45 and 46. The chambers 45 and 46 are connected to the
-- 6 -
~3~
valve 40 by lines 47 and 48, respectively. The lines 47 and 48
contain valves 49 and 50, respec-tively. A piston Sl is slidably
mounted in ~he chamber ~5, and fluid is introduced into the
chamber 45 on either side of the piston 51 through the lines 47
and 48. The valve 40 opens the line 47 or 48 to a line 52 con-
nected to a source of hydraulic fluid under pressure (no-t shown)
or to a hydraulic fluid reservoir (not shown) via line 53. A
piston rod 54 is connec-ted -to the piston 41 and extends through
the partitlon 44 and the end wall 43 of -the cylinder 41 -to the
pump control lever 26. ~ Eirst adjustable stop 55 is provlded
on the rod 54 between the end wall 43 oE -the cylinder and the
lever 26. A second adjustab].e stop 56 is provided on the piston
rod 54 in the chamber 46 oE the cylinder 41. The posltions of
the stops 55 and 56 can be chancted to adjust the stroke of the
piston 51 in either direction. The lever 26 is connected to the
variable displacement pump 21. The output and dlrection of oil
Elow throucJh the pump 2l. are cJoverrlccl by the dlrection and decJree
oE cleElectlorl o~ the cont~ol lever 26. 'rhe clirection arld deyree
oE deEIection of the control. lever are determined by acljustincJ
the stops 55 and 56 on the pistorl rod 54. The stop 55 controls
the speed oE the pump jack when travellincJ upwardly, and the
stop 56 controls the speed of the pump jack and polished rod 13
when travellin~ downwardly. The acceleration of the rod 13 at
the turn around points in the stroke are determined by the time
required for the cylinder rod 54 to travel the distance between
~3~
the stops 55 and 56. The acceleration time is adjusted by
metering the oil flow into the cylinder ~l using -the valves 49
and 50. The valve ~9 con-trols acceleration at the bottom turn
around, and -the valve 50 con-trols acceleration at the top -turn
around. A spring return system (no-t shown) is used to re-turn
-the piston 51 to the neutral position with respect -to the lever
26.
Referring again to Figure ~ ~f the drawings, a safety
shut-down system is provided, inclu~ding saEety switches S3, S4,
S5 and S6. The swi-tches are normally open and are connected in
parallel to terminal 7d oE a relay 60. Closing of any of the
safety swi-tches applies power to the terminal 7d, causinc3 closing
of contacts ld-4d and 2c1-6d, while breaking contaet betwet-~n
contaets ld-3d and 2d-~d. Thus, eurrent Erom -the hattery 33
Elows through contacts ld and 3d to the terminal 7d, and the
eoil 61 of the relay 60 remains cnergl~zetl to hoLd open eont~ets
2d and ~d. Power to the eontae~ 2e ol thelreLay~35 is :Lnter-
ruptt-~d, and tilus no powt-~r Ls suppLled to elther o tht solt-~noitls
36 and 39. Thus, :L any oE tht sa;Lety swlteht-~s S3-S6 :Ls aetu-
ated, the pUIllp jae]c stops. ~rhe saE~ty swltches S3 and S6 are
commonly part oE cireuits :i.nvolvlng tht-~ hydraulie system. For
examples, the safety switches would be used to de-tect exeess
pressure in the hydraulie system, excess pressure in flow lines,
over travel oE the switching system and low hydraulie fluid. If
no eurrent flows to either of the solenoids 36 and 39, the valve
-- 8 --
3~
40 returns -to the neutral position, -thereby opening both of -the
chambers 45 and 46 to the line 53, i.e~ to the reservoir.
Because piston 51 of the cylinder 4] is spring-centered, the
piston returns to the central position. Thus, -the pump control
lever 26 is also returned to -the central position, causing the
pump jack to stop.
