Note: Descriptions are shown in the official language in which they were submitted.
~IE~D O~ THE INV~TIO~
The present invention relates to devices useful for
indicating variations in load on reciprocatingly moving parts.
More particularly, the present invention relates to indicating
devices for indica~ing variations in polish rod loads.
BACR~ROUND AND ~UNMaRY OF THB INV~TIO~
Several types of devices which are adapted to provide
indications of the performance of reciprocatingly moving parts
are known in the prior art. For example, U.S. Patent No.
4,509,901 to McTamaney et al. discloses an apparatus for
detecting probl~ms in sucker-rod well pumps, which includes a
first transducer -which is located between an upper end of a
sucker-rod string and a lower end of a cable section. U.S.
Patent No. 3,343,409 to Gibbs discloses a method of determining
sucker rod performance in which a strain-gauge load cell is
connected to a polished rod to measure the polished rod load.
Also, U.S. ~atent No. 4,363,60~ to Mills discloses an apparatus
which generates an electrical signal which is proportional to the
tension in a bridle which supports a string of a sucker rod. The
apparatus includes a load cell between two arms which are
attached to two bridle cables and which place the load cell in
compression, so that the load cell generates an electrical signal
proportional to the Porce needed to spring the cables apart from
each other. The apparatuses of the above-mentioned patents each
have the disadvantage, however, that they involve relatively
complex electrical measurement and/or computation, and thus tend
to be relatively complex and expensive to manufacture.
Other devices are known in the prior art which provide
continuous indications of a weight on a drill bit. ~or example,
U.S. Patent NOr 2,703,908 to Sel~os et al. discloses a weight-on-
bit indicating apparatus which includes a weight responsive
device attached to a line o~ a well drilling rig. The weight
responsive device generates a pressure signal to three diaphragms
which are pressure-balanced such that the weight on a bit o~ the
well drilling rig registers on a gauge. ~lso, U.S. Patent No~
2,696,111 to Conner discloses a drill string weight indicating
apparatus which includes a roller to which force is applied hy
a drill string, a diaphragm which is connected $o the roller and
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which closes a chamber, and a pressure gauge connected to the
chamber to indicate the load on the drill string based on the
pressure in the chamber. These devices have the disadvantage,
however, that they are designed for use with a drill string which
moves slowly past the devices in one direction only. Thus these
devices are of little use in providing an indication of the
variation in load on a reciprocatingly moving part.
One device is known in the prior art which provides an
indication of the pressure in an apparatus, wherein the apparatus
includes a reciprocatinyly moving part. U.S. Patent No.
4,417,236 to Hunq discloses an overload detecting device for a
hydraulic jack which includes a pressure sensitive switch member
having a piston-like member in a housing. The piston-like member
communicates with a duct o the hydraulic jack and is biased in
one direction by a spring. If the pressure in the duct rises
above a predetermined valuel the pressure overcomes the bias of
the spring, and the piston-like member contacts a spring plate
to set off an alarm. One of the disadvantages of this device,
however, is that the device only actuates the alarm when the
pressure in the hydraulic jack rises above a certain level.
Thus, this device is of little use in providing a repeated
indication of reciprocating movement of a part such as a polish
rod~
In view of the above, it is an object of the present
invention to provide an improved device for indicating variations
in load on a reciprocatingly moving part such as a polish rod.
A further object of the present invention is to provide an
indicating device which is relatively simple and inexpensive to
manufacture.
It is a ~urther object of the present invention to provide
a simple, reliable device which will provide an indication of
load variation once during each cycle of the reciprocably moving
part.
It is a further object of the present invention to provide
an indicating device which re~uires relatively minimal technical
sophistication to monitor.
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Yet another object of the present invention is to provide
an indicating device which is subjected to the full load on a
reciprocating moving par~ to more accurately monitor the moving
part.
5It is a further object of the present invention to provide
an indicating device which provides continuous monitoring of a
reciprocably moving part.
It i~ a further object of the present invention to provide
an indicating device which is of rugged construction and thus
10resistant to damaye.
It is a further object of the present invention to provide
an indicating device which is simple to repair when necessary.
A further object of the present invention is to provide an
indicating device which is adjusta~le to compensate for wear on
15the device and ~or variations in a reciprocating movement of a
part.
The above objects as well as other objects not specifically
enumerated are accomplished by an indicating device for
indicating variations in a load on a reciprocatingly moving part
20in accordance with the present invention. The indicating device
of the present invenkion includes reciprocating moving means for
reciprocatingly moving in response to the variations in the load,
indicating means for providing an indication, and switch means
for switching between an open state and a closed state and for
25causing current to flow through the indicating means when the
switch means is in one of the open and closed states, wherein the
reciprocating moving means causes ~he switch means to switch to
the one of the open and closed states once during each cycle of
the reciprocatiny movement of the reciprocating moving means.
30The objects of the present invention are also accomplished
by a polish rod load indicating device which includes a master
piStOll and cylinder enclosing a fluid therebetween, wherein the
master piston and cylinder are connectable to the polish rod such
that one of the master piston and cylinder moves cyclically with
35respect to the other of the master piston and cylinder, a slave
piston arld cylinder enclosing a fluid therebetween which is in
communisation with the fluid enclos~d by the master piston and
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cylindPr, wherein the cyclical movement of the one of the master
piston and cylinder produces a cyclically varying pressure in the
fluids and wherein the cyclically varying pressure in the fluids
causes one of the slave piston and cylinder to move cyclically
S relative to the other of ~he slave piston and cylinder, an
indicator/ and a switch, wherein the indicator produces a polish
rod load indication signal in respons~ to operation of the
switch, and wherein the cyclically moving one of the slave piston
and cylinder operates the switch to cause the indicator to
produce the polish rod load indication signal once during each
cycle of the cyclical movement of the cyclically moving one of
the slave piston and cylinder.
: The ob~ects of the present invention are further
accomplished by a polish rod load indicating device for
indicating variation in a polish rod load, which includes a
toroidally-shaped master piston, a toroidally-shaped master
cylinder cooperating with the master piston to enclose a fluid,
the master piston and cylinder ~eing connected to a portion of
the pump, a slave piston and cylinder enclosing a fluid which is
: 20 in fluid communication with the fluid enclosed by the master
piston and cylinder, wherein the slave piston includes a flange
portion~ is movable between extended and retracted positions
within the slave cylinder, and is spring biased towards the
retracted position, a switch, wherein the switch is movable
between an open position and a closed position and ls spring
biased towards the open position, and an indicator, the indicator
producing an indication when current flows therethrough, wherein
the master piston is cyclically moveable in response to cyclical
movement of the polish rod to produce a cyclically varying
: 30 pressure in the fluids, and wherein the cyclically varying
pressure causes the slave piston to move cyclically between the
extended and retracted positions such that the flange portion of
the slave piston moves the switch to the closed position when the
slave piston is in the retracted position, closing of the switch
causing current to flow through ~he in~icator so that the
indicator provides the indication once during each cycle of the
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cyclical movement of the ma~ter piston to indicate variation in
the polish rod load.
BRIEF DE~CRIPTIOlN OF TIIB CIRI~WING~
The preferred embodim~nts of the present invention will be
described in greater detail with reference to the accompanying
drawings, wherein like members bPar like reference numerals and
wherein:
Fig~ 1 is a partially cutaway side view of the indicating
device of the present invention; and
Fig~ 2 is a diagram of an electrical circuit of the
indicating device o~ Fig. 1.
DE~I!AXLE:l~ DE~: ~Ill?TIO~a OF ~13 PREFE~ R13D E:~BOD~ T
With r~ference to Figs. 1 and 2, an indicating device 10 in
accordance with the present invention includes a master piston
and cylinder arrangement 12, a slave piston and cylinder
arrangement 14, and an indicating circuit arrangement 16 which
includes an indicating circuit 17, as is explained further
hereinbelow.
As is seen in Fi~. 1, the mastex piston and cylinder
arrangement 12 includes a master pi5ton 20 and a master cylinder
2Z. The master piston 20 and the master cylinder 22 are shaped
as right cylindrical toroids, and are especially adapted to
extend around a polish rod 1 of a conventional pump between a
polish rod clamp 2 and a bridle 3 o~ the pump, since the master
piston 20 has a hole 24 therethrough and the master cylinder 22
has a hole 33 therethrough through which the polish rod 1
extends. The polish rod 1, as can be seen in Fig. 1, is tightly
clamped by the polish rod clamp 2, and the polish rod clamp 2
: rests on the ma~ter piston 200 The bridle 3 is pulled upwardly
by portions of the pump which are not shown, and the master
cylinder 22 rests on the bridle 3. Accordingly, as the bridle
3 is pulled upwardly, it also pulls the master cylinder 22, the
master piston 20, the polish rod clamp 2, and the polish rod 1
upwardly, so that the master pi5ton and cylinder bPar the entire
load on the polish rod 1.
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The master piston 20 includes a pair of 0-rings 26,2~3 which
extend along outer and inner surfaces 30,32 of the master piston
20, respectively, and whose function will be described
hereinbelow. The master cylinder 22 is larger than the master
piston 20, and includes a right cylindrical, toroidally-shaped
chamber 34 which extends downwardly therein from an upper surface
36 of th~ master cylinder 22. The chamber 34 i5 formed such that
it is slightly larger than the master piston 20, so that the
master piston 20 is slidably received in the chamber 34 with the
0-rings ~6,28 providing sealing contact between the master piston
22 and outer and inner walls 40,42, respectively, of the chamber
34.
Accordingly, the master piston 20 and the master cylinder
22 together enclose a fluid-tight space 44 which i5 formQd from
a lower portion of the chamber 34 and which is normally filled
with a fluid. In addition, the master cylinder 22 includes a
passageway 46 which communicates the space 44 with a threaded
opening 48 in an outer surface 50 of the master cylinder 22.
As is seen in Fig. 1, the slave piston and cylinder
arrangement 14 includes a slave cylinder 60 and a slave piston
62. The slave cylinder 60 is ~ormed as an elongated, hollow
cylinder which is open at both ends, and includes a threaded
extension 64 extending from a first end ~5 thereof. The threaded
extension 64 is threadably engaged with the threaded opening 48
in the master cylinder 22, and a passageway 66 is formed through
the threaded extension 6~ such that it communicates the
passageway 46 with a space 70 in a chamber 68 in the slave
cylinder 60. The slave cylinder 60 also includes an 0-ring 72
which is fitted on the first end 65 o~ the slave cylinder 60 to
prevent fluid leakage between the master cylinder 22 and the
slave cylinder 60.
The chamber 68 of the slave cylinder 60 includes a first
chamber portion 74 which has a smaller diameter, and a second
chamber portion 76 which has a larger diameter. As can be seen
from Fig. 1, a wall 78 is forme~ in a transition portion of the
chamber 68 between the first and second chamber portions 74,76,
and the space 70 in the chamber 68 is formed by a portion of the
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first, smaller diameter chamber portion 74. The second, larger
diameter chamber portion 76 includes an internally threaded
portion 80 whi~h opens through a second end 82 of the slave
cylinder 60 which is opposite the first end 65, and an elongated,
hollow cylindrical plug 84 having external threads 86 thereon is
threaded into the internally threaded portion 80 of the slave
cylinder 60~ The function and purpose of the plug 84 will be
explained hereinbelow.
The slave piston 62 is an elongated member which fits
slidably within the slave cylinder 60, and it includes a piston
member 90 and an elongated rod 92. ~he piston member 90 includes
a first portion 94 which has a diam~ter which is slightly smaller
than the diameter of the first chamber portion 74 of the slave
cylinder 60l and a second portion 96 which has a diameter which
is slightly smaller than the diameter of the second chamber
portion 76 of the slave cylinder 60, but which is larger than the
diameter of the ~irst chamber portion 740 The piston member 90
also includes sealing means therearound to prevent leakage from
the slave piston and cylinder arrangement. For illustration
purposes, the sealing means is shown as a pair of 0-rings 98,100
which are fitted around an outer surface 102 of the piston member
90, but other sealing means such as a cup-type packing could just
as easily be used. Accordingly, the first portion 94 of the
piston member 90 fits slidably and fluid-tightly within the first
chamber portion 74 of-the slave cylinder 60 such that the piston
member 90 and the slave cylinder 60 form the fluid-tight space
70, and the second portion 96 of the piston member 90 ~its
slidably within the second chamber portion 76 of the slave
cylinder 60. Enclosed in the space 70 is a fluid which is in
fluid communication wikh the ~luid enclos~d by the master piston
20 and the mast~r cylinder 22.
The piston member 90 also includes a threaded hole 104 which
extends through the secsnd portion 96 of the piston member 90,
and the elongated rod 92 is attached to the piston member 90 by
thr~aded engagement of a fir~t threaded end 106 of the elongated
rod 92 with the threaded hole 104. As is shown in Fig. 1, the
elongated rod 92 extends away from the pi~ton member 90 through
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a hole in the plug 84 to a location outside the slave cylinder
60, and includes a second threaded end 108 onto which a threaded
adjustmen~ member 110 having a ~lange portion 112 is threaded.
Also, a spring 114 is arranged in compression inside the second
chamber portion 76 of the slave cylinder 60 between the plug 84
and the second portion 96 of the piston member 90, such that the
slave piston 62 is spring biased toward the left in Fig. 1.
As is seen from Fig. 1, the indicating circuit arrangement
16 o~ the present invention includes a pair of mounts 120,122
which are welded ~o the outside of the slave cylinder 60, and
which support a frame member 124 and ther~.by a circuit box 126.
On one end of the frame member 124 is mounted a switch box 128
which includes a set of first terminal~ 130, a second terminal
132, and a switch member 134 which is pivotally mounted to the
switch box 128 and which is spring biased away from the second
terminal 132. The switch member 134 and the second terminal 132
together form a contact switch. A wire 136 is connected to two
of the first terminals 130, which wire runs into the circuit box
126. Cn the outside of the circuit bo~ 126 is mounted an LED
indicator 138.
As is ~een in Fig. 2, the second terminal 132, the switch
member 134, and ~he ~ED indicator 138 all form part of an
indicating circuit 17 of the present invention. ~s shown, the
indicating circuit 17 is a simple circuit powered by two
batteries 1~0 arranged in serie~, and includes a resistance 142
and the LED indicator 138 arranged in series. As is shown in
Fig. ~, no current can flow through the indicating circuit 17
when the contact switch formed by the second terminal 132 and the
switch member 134 is open. However, current will flow through
the indicating circuit 17 and thus the LED indicator 138 will
light when the sontact swi.tch is closed, i.e., when the switch
member 134 contacts the second terminal 132 as shown in Fig~ 1.
With reference to Figs. 1 and 2, the operation o~ the
indicating device 10 will now be explained. In use, the master
piston 20 and the master cylinder 22 are held between the polish
rod ~lamp 2 and the bridle 3 of a convsntional well pumpO The
bridle 3 moves reciprocably in an up and down manner to pull up
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the polish rod clamp 2, and thereby the polish rod 1, and then
lower it repeatedly, and a cyclically varying force is thus
applied to the master piston and cylinder arrangement which
causes the master piston 20 to move reciprocally or cyclically
with respect to the master cylinder 22. For example, with a pump
stroke of approximately 6~ inches, a force of about 20,000 lbs.
is applied to the master piston and cylinder arranyement during
an upstroke of the pump, while a force of only about 12,000 lbs.
is applied to the master piston and cylinder durin~ a downstroke
of the pump.
Since the slave piston ~2 and the slave cylinder 60 enclose
in the space 70 a fluid which is in fluid communication with the
fluid enclosed by the master piston 20 and the master cylinder
22, a cyclically varying pressure is produced in both of the
fluids as the master piston 20 moves reciprocally or cyclically
relative to the master cylinder 22. Thus, the cycl.ically varying
pressure in the fluids a~ts to cause the slave piston 62 to move
reciprocally or cyclic~lly against the force of the spring 114,
due to the force exerted on the piston member 90 by the fluids.
20 Th8 slave piston 62 therefore moves repeatedly between a
retract d position wherein the second portion 96 o~ the piston
member 90 is at its leftmost position in the chamber 68 as shown
in Fig. 1 due to the force of the spring 114 acting between the
plug 84 and the second portion 96, and an extended position
wherein khe second portion 96 of the piston member 90 is at its
rightmost position in the chamber 68 due to the force of the
fluids enclosed by the master and slave piston and cylinder
arrangements.
As the slave piston 62 moves cyclically or recipro~ably, the
threaded adjustment member 110 moves rigidly with the slave
pisto~ 62, and thus the flange portion 112 of the threaded
adjustment memb~r 110 moves cyclically left-to-right and right-
to-left in Fig. 1. The flange portion 112 of the threaded
adjustment member llQ thus repeatedly moves the switch member 134
from a spring biased open position to a closed position seen in
Fig. 1 where the switch member 134 contacts the second terminal
132, and then releases the switch member 134 to allow it to
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return to its spring biased open position. Thus, each time the
~lave piston 62 is brought into its retracted position, the
contact switch of indicating circuit 17 is closed, and current
flows through the indicating circuit 17 to light the LED
indicator 138.
As can be appreciated from Fig. 1, turning of the plug 84
relative to the slave cylinder 60 will result in ax.ial movement
of the plug 84 relative to the slave cylinder 60~ due to the
coaction of internally threaded portion 80 and external threads
86. Accordingly, the force of the spring 114 on the piston
member 90 at aIIy given position of the piston member 90 can be
varied by turning the plug 84, and thus the exact left-to-right
location of the extended position of the slave piston 62 can be
precisely set as follows. The plug 84 is first tightened until
the spring 11~ is compressed and the second portion 96 of the
piston member 90 abuts the wall 78. The threaded adjustment
member 110 is then tightened until the flange portion 112 just
closes the switch, iOe., until the switch member 134 just
contacts the second terminal 132. The plug 84 is then backed out
so that the spring 114 is less co-mpressed, but so that the spring
114 is still compressed enough to keep the switch closed. Load
is then applied to the polish rod 1, and the plug 84 is adjusted
until the ~orce sf spring 114 is just high enough to retain the
second portion 96 against the wall 78 at the minimum lvad and
thereby cause the switch to be closed. Consequently, at this
setting of the plug and the spring force the variations in the
load will cause the switch to be repeatedly turned on and off.
Thus, the extended position of the slav~ piston 62 is set during
this final adjustment of the plug 84.
The ability to thus adjust the extended position of th~
slave plston 62 allows a user to set up the indicating device
such that the flange portion 112 of the threaded adjustment
member 110 just closes the contact switch when the slave piston
62 i8 in the retracted positionO The indicating device can
therefore be set up such that the ~ED indicator 138 lights just
once during each cycle of a reciproca~ingly moving part such as
a polish rod of a pump~ and the indicating device is therefore
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able to prvduce an indication of the variation in the polish rod
load. Adjustment of the point at which the contact switch is
closed can also be accomp~ished by turning of the threaded
adjustment washer 110 on the rod 92, which varies the distance
between the piston member 90 and the flange portion 112.
The adjustment features of the present invention allow a
single indicating device to be used with any of a wide range o~
wells, both deep and shallow, since the indicating device can be
adjusted to indicate a wide variation of loads. The indicating
device can also use the adjustment features to compensate for
changes in elasticity of the spring 114, and small losses of
fluid in the master and slave piston and cylinder arrangements.
Accordingly, the adjustment features allow the indicating device
o~ the present invention to be used ~or long periods of time
without repair or replacement.
The indication of load variation in a reciprocatingly moving
part such as a polish rod of a pump, which is provided by the
indicating device of the present invention, is a simple and
reliable indication which can readily be monitored by an operator
who may not have a high level of technological expertise. For
example, when the indicating device of the present invention is
being used with ~ pump which i~ experiencing a desired load
variation, an operator will see a simple cyclical on/off pattern
o~ flashing from the LED indicator of the indicating device. As
long as the on/off pattern of flashing continue~, and continues
at the same frequency, the operator is given a good indication
that the load is varying as desired. If the on/off pattern
stops, i.e., if thP indicator stays on or stays off, or if the
frequency of flashing of the LED indicator changes, the operator
knows that the pump has completely stopped operating, that the
connection between the polish rod and the bridle has somehow
failed, that a rod break has occurred and that the polish rod is
no longer supporting a heavy weight, or that some other abnormal
condition of the pump has occurred. With a little experience
with the indicating device, an operator can quickly recognize the
condition which a particular flashing pattern indicates. Thus,
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the indicating device of the present invention is extremely
simple to monitor.
Additionally, since the indicating device is simple and
rugged in construction, it is subject to only infrequent break
downs, and, when it does ~reak down, it is relatively simple to
repair, since it contains no complex electronics~
It is to be appreciated that the advantages of the present
invention can be obtained through the use of any of a number of
fluids in the master and slave pistons and cylinders. For
example, hydraulic fluid, oil, air, or other fluids may be used.
Also, although the master and slave pistons and cylinders are
shown in the drawings as being made of metalr they could also be
advantageously made of any number of materials, such as plastic,
ceramic, or combinations thereof. It is also to be understood
that the indicating circuit arrangement may be mounted separately
from th~ slave cylinder if desired, and that the slave piston and
cylinder may be separate from the main piston and cylinder with,
~or example, a hose keeping the main and slave piston and
cylinders in fluid communication.
Indicating circuit arrangements which are different from the
one disclosed may be used, and advantages of the present
invention obtained therefromO For example, a circuit which
includes a transistor may be used in the present inventiQn, such
that closing of the contact switch causes the transistor to cut
the flow of curr0nt to the LED indicator, and therefore such that
the LED indicator normally provides a lighted indication, and is
not lit only when the contact switch is closed. Also, the
contact switch of the present invention may be replaced with
another switch such as a magnetic switch, and the LED indicator
may be replaced with another indicator such as a buzzer, a bell,
or a whistle, and advantages obtained therefrom. The indicating
circuit could also be completely replaced by a mechanical
noisemaker which is activated once during each cycle of the slave
piston. Also, the indicating circuit could be modified to allow
graphic recording of the load variation on the polish rod, or to
cause ~hut down of the power supply to the pump whan the load
variation becomes irregular.
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At least some of the advantages of ~he present invention are
also achievable if the slav~ piston and cy]inder arrangement is
arranged in fluid communication with the master piston and
cylinder arrangement through a passageway through the master
piston~ Additionally, the slave piston may be held fixed to the
master piston and cylinder arrangement, and the slave cylinder
may be arranged movably, and some advantages obtained therefrom.
The principles, a preferred embodiment and the mode of
operation of the present invention have been described in the
foregoing specifica~ion. However, the invention which is
intended to be protected is not to be construed as limited to the
particular embodiment disclosed. The embodiment is therefore to
be regarded as illustrative rather than restrictive. Variations
and changes may be made by others without deparrting from the
spirit of the present invention. Accordingly, it is expr ssly
intended that all such variations and changes which fall within
the spirit and scope of the present invention as defined in the
claims be embraced thereby.
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