U.S. patent number RE32,865 [Application Number 07/033,414] was granted by the patent office on 1989-02-14 for fiberglass sucker rod construction.
This patent grant is currently assigned to Fiberflex Products Ltd.. Invention is credited to Stephen D. Clark, Jon B. Freeman, Woodrow T. Rutledge, Jr., Russell P. Rutledge.
United States Patent |
RE32,865 |
Rutledge, Jr. , et
al. |
February 14, 1989 |
**Please see images for:
( Certificate of Correction ) ** |
Fiberglass sucker rod construction
Abstract
A fiberglass sucker rod construction is disclosed comprising a
cylindrical fiberglass rod having a steel connector member
adhesively bonded to each end thereof. The steel connector members
are basically identical in their manner of being affixed to each
end of the fiberglass rod, each connector member having an internal
receptacle defining a series of tapered annular spaces for
receiving an epoxy adhesive material which bonds the fiberglass rod
in the metal connector member, thereby forming a unitary sucker rod
having a male thread connector at one end and a mating female
connector at the other end thereof. The epoxy adhesive cures,
forming a sleeve having a series of annular tapering surfaces
defining annular wedges that are oriented such that tension applied
to the rod causes the wedges to be compressed between the rod and
connector member, resulting in a radially inwardly directed force
to retain the rod in position against such tension. This is a
Reissue of a Patent which was the subject of a Reexamination
Certificate No. B1 4,360,288, dated Dec. 13, 1983, Request No.
90/000,318, Jan. 20, 1983.
Inventors: |
Rutledge, Jr.; Woodrow T. (Big
Spring, TX), Rutledge; Russell P. (Big Spring, TX),
Freeman; Jon B. (Big Spring, TX), Clark; Stephen D. (Big
Spring, TX) |
Assignee: |
Fiberflex Products Ltd.
(Houston, TX)
|
Family
ID: |
26709665 |
Appl.
No.: |
07/033,414 |
Filed: |
April 1, 1987 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
076373 |
Sep 17, 1979 |
04360288 |
Nov 23, 1982 |
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Current U.S.
Class: |
403/268; 174/176;
403/275; 403/267; 403/361 |
Current CPC
Class: |
E21B
17/00 (20130101); E21B 17/04 (20130101); F04B
53/144 (20130101); F16B 3/005 (20130101); F16B
11/008 (20130101); F16B 2200/10 (20180801); Y10T
403/472 (20150115); Y10T 403/473 (20150115); Y10T
403/4908 (20150115) |
Current International
Class: |
E21B
17/02 (20060101); F04B 53/14 (20060101); F04B
53/00 (20060101); F16B 11/00 (20060101); E21B
17/04 (20060101); E21B 17/00 (20060101); F16B
3/00 (20060101); F16B 011/00 (); F04B 047/02 () |
Field of
Search: |
;403/268,275,267,361,266,265 ;174/179,176,186,177 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1072191 |
|
Feb 1980 |
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CA |
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2511809 |
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Sep 1976 |
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DE |
|
1210779 |
|
Oct 1959 |
|
FR |
|
681550 |
|
Oct 1952 |
|
GB |
|
Other References
"Fiberglass Sucker Rods in Beam-Pumped Oil Wells", a paper by D. L.
Watkins & John Haarsma presented to the SPE-AIME in Nov. 1977
and published in the May 1978 issue of Journal of Petroleum
Technology, pp. 731-736..
|
Primary Examiner: Kee Chi; James
Attorney, Agent or Firm: Pravel, Gambrell, Hewitt, Kimball
& Krieger
Claims
The invention having been described, what is claimed is:
1. A sucker rod construction for use in producing oil wells, said
sucker rod construction comprising:
a .[.first.]. connector member .Iadd.having an outer surface and
.Iaddend.being formed to define a rod receptacle having a closed
axially .[.outer.]. .Iadd.inner .Iaddend.end and an open axially
.[.inner.]. .Iadd.outer .Iaddend.end, said rod receptacle having a
plurality of integrally formed axially spaced apart outwardly
converging tapered frusto-conical .[.annular.]. .Badd.annular
.Baddend..Iadd.internal .Iaddend.surfaces, .[.each of said surfaces
having substantially the same taper.]. .Badd.each of said surfaces
having substantially the same taper, .Baddend..Iadd.said outer
surface of said connector member and said internal surfaces
defining between them a rod receptacle wall, said outer surface
being substantially cylindrical laterally adjacent all said
frusto-conical internal surfaces except the one most near said
axially outer open end of said rod receptacle, the outside surface
of the connector member laterally adjacent that one internal
surface most near the said open end having a gradual axially
convergent taper whereby the rod receptacle wall along said one
internal surface is less thick at portions nearer said open end
than at portions nearer and laterally adjacent the axially upper
reach of said one internal surface; .Iaddend.
a cylindrical fiberglass rod having an end having a uniformly
cylindrical uninterrupted outer surface being received within said
rod receptacle through said .[.inner.]. .Iadd.outer .Iaddend.end
and cooperating therewith to define an annular chamber between said
outer surface of said end of said rod and said outwardly converging
tapered frusto-conical surfaces;
and a body of initially liquid adhesive material filling said
annular chamber that cures to bond to said outer surface of said
end of said rod and to harden to form a plurality of shear and
compression resistant frusto-conical wedges to cooperate with said
frusto-conical surfaces. 2. The sucker rod construction as set
forth in claim 1, including a collet connected to said connector
member adjacent said open axially .[.inner.]. .Iadd.outer
.Iaddend.end of said rod receptacle and having an axial bore
therethrough retaining said end of said rod in coaxial position
within said rod receptacle. 3. The sucker rod construction as
claimed in claim 1, including:
a bore coaxially formed in said .[.first.]. connector member
adjacent said axially outer.]. .Iadd.inner .Iaddend.closed end of
said rod receptacle .[.outwardly.]. .Iadd.axially inward
.Iaddend.of said frusto-conical .[.annular.]. surfaces, said bore
fitting closely with said surface of said end of said rod;
a collet connected to said .[.first.]. connector member adjacent
said axially outer open end of said rod receptacle, said collet
having a passage therethrough coaxial with said rod receptacle,
said passage fitting closely with said surface of said end of said
rod, whereby said bore and said collet support said end of said rod
at axially spaced apart points coaxially within said rod
receptacle. 4. The sucker rod construction as claimed in claim 3,
wherein .[.said first connector member has a cylindrical outer
surface and.]. said collet includes an axially extending tubular
portion having an outside diameter .[.substantially less.].
.Iadd.not greater .Iaddend.than the outside diameter of .Iadd.the
portion of .Iaddend.said first connector member .Iadd.laterally
adjacent said open end of said rod receptacle.Iaddend.. 5. The
sucker rod construction as claimed in claim 3, wherein said collet
and said first connector member are formed of substantially the
same metallic material. .[.6. The sucker rod construction as
claimed in claim 1, wherein said axially inner open end of said rod
receptacle includes an internally threaded portion and said
construction further comprises a collet having an upper portion
threadedly engaged with said threaded portion and a lower axially
extending tubular portion having a passage therethrough
coaxially
aligned with said rod receptacle closely engaging said rod..].
.[.7. The sucker rod construction as claimed in claim 6, wherein
said tubular portion includes an axially upper portion having a
cylindrical outer surface having a diameter less than the outer
diameter of said first connector member, and an axially lower
portion having a frusto-conical outer surface sloping from said
cylindrical outer surface toward said rod..]. .[.8. The sucker rod
construction as claimed in claim 7, wherein said collet includes an
outwardly tapering frusto-conical inner surface positioned
outwardly of said tubular portion..]. 9. A sucker rod, which
comprises:
a .Iadd.first .Iaddend.connector .Iadd.having an outer surface and
.Iaddend..Badd.formed to define a receptacle .Baddend.including an
axially .[.outer.]. .Iadd.inner .Iaddend.closed end and an axially
.[.inner.]. .Iadd.outer .Iaddend.open end, said receptacle
including a plurality of integrally formed axially spaced apart
.Iadd.outwardly converging tapered .Iaddend.frusto-conical internal
surfaces, .[.each of said frusto-conical surfaces having
substantially same angle of taper with respect to the axis of said
connector.]. .Badd.each of said frusto-conical surfaces having
substantially the same angle of taper with respect to the axis of
each said connector.Baddend..Iadd., said outer surface of said
first connector and said internal surfaces defining between them a
rod receptacle wall, said outer surface being substantially
cylindrical laterally adjacent all said frusto-conical internal
surfaces except the one most near said axially outer open end of
said rod receptacle, the outside surface of the first connector
laterally adjacent that one internal surface most near the said
open end having a gradual axially convergent taper whereby the rod
receptacle wall along said one internal surface is less thick at
portions nearer said open end than at portions nearer and laterally
adjacent the axially innermost reach of said one internal
surface.Iaddend., said connector including an integrally formed
threaded coupling member;
.Iadd.a second connector identical to said first connector, a
cylincrical .Iaddend.fiberglass rod including .[.an end.].
.Iadd.distal ends, each .Iaddend..Badd.end .Baddend.having a
uniformly cylindrical uninterrupted outer surface contained within
.[.said receptacle.]. .Iadd.one of said first and second connector
receptacles .Iaddend.and extending through said open end of said
receptacle;
a .Iadd.first .Iaddend.connected to said .Iadd.first
.Iaddend.connector adjacent said open end of said receptacle
.Iadd.thereof.Iaddend., said collet having a passage therethrough
coaxial with said receptacle and closely fitting with said outer
surface of said rod, said collet including a tubular portion
extending axially along said outer surface of said rod, said
tubular portion having an outside diameter .Iadd.not greater
.Iaddend.than the outside diameter of said connector
.Iadd.laterally adjacent said open end of said rod receptacle;
.Iaddend.
.Iadd.a second collet identical to said first collet connected to
said second connector identically as said first collet is connected
to said first connector: .Iaddend.
a quantity of shear and compression resistant adhesive material
bonded to said surface of said .[.rod.]. .Iadd.distal ends of said
rods contained within said receptacles .Iaddend.and filling the
volume about said surface of said rod and bounded by said
.[.receptacle.]. .Iadd.receptacles .Iaddend.and said .[.collet.].
.Iadd.collets.Iaddend.. 10. The sucker rod as claimed in claim 9,
wherein said receptacle includes a bore adjacent said closed end
and closely fitting said surface of said end of said rod. .Iadd.11.
The sucker rod construction as claimed in claim 1, including a
collet connected to said rod receptacle and comprising a coaxially
extending tubular sleeve having an outside diameter not greater
than the outside diameter of the portion of said connector member
laterally adjacent said open end of said rod receptacle, for
fitting closely throughout the sleeve length about a cylindrical
surface of the portion of said rod which proximately extends from
said rod receptacle. .Iadd..[..[.12. The sucker rod construction of
claim 1, wherein said frusto-conical internal surfaces each have
substantially the same angle of
taper..]..]..Iaddend. .Iadd.13. The sucker rod construction as set
forth in claim 1 .Iaddend..[..[.or 12.]..]. .Iadd.wherein the base
frustrums of said outwardly converging tapered frusto-conical
internal surfaces have equal diameters, and wherein said
frusto-conical internal surfaces are axially spaced apart partially
by a cylindrical internal surface of said rod receptacle which has
a diameter equal to the diameter of said base frustrums. .Iaddend.
.Iadd..[..[.14. An assembly which comprises:
a metallic connector member having an outer surface and including a
rod receptacle having an axially inner closed end and an axially
outer open end, said rod receptacle including a plurality of
integrally formed axially spaced apart frusto-conical internal
surfaces, each tapering outwardly convergently, said outer surface
of said connector member and said internal surfaces defining
between them a rod receptacle wall, said connector outer surface
being substantially cylindrical laterally adjacent all said
frusto-conical internal surfaces except the one most near said
axially outer open end of said rod receptacle, the connector member
outside surface laterally adjacent that one internal surface most
near the said open end having a gradual axially convergent taper
whereby the rod receptacle wall along said one internal surface is
less thick at portions nearer said open end than at portions nearer
and laterally adjacent the axially innermost reach of said one
internal surface;
a resin bonded glass fiber reinforced rod including an end having a
uniformly cylindrical uninterrupted outer surface contained within
said rod receptacle and extending through said open end, and
a body of shear and compression resistant adhesive material bonded
to the cylindrical surface of said rod within said rod receptacle
in the form of a plurality of frusto-conical wedges in cooperating
engagement with said frusto-conical internal surfaces of said rod
receptacle..]..]..Iaddend. .Iadd..[..[.15. The assembly of claim
14, wherein said frusto-conical internal surfaces each have
substantially the same angle of taper..]..]..Iaddend. .Iadd.16. The
assembly as set forth in claim .[..[.14 or 15.]..].
.Badd.1.Baddend..Iadd., wherein the base frustrums of said
outwardly converging tapered frusto-conical internal surfaces have
equal diameters, and wherein said frusto-conical internal surfaces
are axially spaced apart partially by a cylindrical internal
surface of said rod receptacle which has a diamater equal to the
diameter of said base frustrums. .Iaddend.
Description
FIELD OF THE INVENTION
The present invention relates to an improved sucker rod
construction, and more particularly to a sucker rod comprising a
fiberglass rod portion epoxy bonded to steel connecting members on
each end thereof.
BACKGROUND OF THE INVENTION
Steel sucker rods have been used for decades in producing oil wells
to actuate petroleum pumps, located in a well bore of a producing,
but not pressurized oil well. A series of sucker rods are connected
together to form a string extending down into the well bore and are
connected to the petroleum pump at one end and to a cyclic or
reciprocating drive mechanism at the well head to actuate the
petroleum pump to cause oil to be pumped up the well bore and into
a pipe line.
Steel sucker rods providing tensile strength to withstand thousands
of cyclic axial forces are inherently heavy, thereby requiring a
sizable reciprocating drive mechanism at the well head to
effectively actuate the pump down in the well bore, which, of
course, requires more energy to operate. In addition, the corrosive
effects of steel contributed significantly to the cost of oil
production, in that steel sucker rods had to be replaced
periodically.
It is therefore an object of the present invention to provide a
sucker rod construction of considerably less weight than its
all-steel counterpart, thereby requiring less energy to
operate.
It is another object of the present invention to provide a sucker
rod construction having improved corrosion resistant
characteristics, thereby greatly extending the useful life
thereof.
It is a further object of the present invention to provide an
improved sucker rod construction having improved elasticity
characteristics, resulting in increased efficiency.
SUMMARY OF THE INVENTION
The present invention is directed to a sucker rod comprising:
(1) A cylindrical fiberglass rod,
(2) A steel connecting member affixed to each end thereof,
(3) A collet positioned about the fiberglass rod and threadedly
engaging each connecting member so as to retain the rod in
functional engagement with each of the connecting members, and
(4) A quantity of adhesive material positioned within an annular
chamber defined by the end of the fiberglass rod inserted into an
axial elongate receptacle of each of the connecting members.
Each of the connecting members receptacles is defined by a series
of outwardly converging tapered surfaces which are filled with the
adhesive material to bond or otherwise steel connector member.
These annular converging surfaces are tapered such that a tension
load along the axis of the fiberglass rod creates a wedge or
cam-like effect to direct a compression force radially inwardly
through the adhesive material toward the rod axis to retain the
fiberglass rod in position within each of the steel connecting
members against such tension load.
.Iadd.The wall of each connecting member laterally adjacent the
tapered internal surface nearest the portion of the rod outside the
receptacle is gradually tapered so that the wall is less thick near
its portion adjacent the receptacle opening than at portions nearer
and laterally adjacent the upper reach of that tapered internal
surface. .Iaddend.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become apparent
upon reading the following detailed description and upon reference
to the drawing, in which:
FIG. 1 is a vertical sectional view of a first connecting member
and fiberglass rod end of the sucker rod of the present invention;
and
FIG. 2 is a vertical sectional view of the second connecting member
and fiberglass rod end of the sucker rod of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings and first to FIG. 1, a sucker rod 10
of the present invention is shown. The sucker rod 10 comprises a
cylindrical rod element 12 (partially shown in FIG. 1 and FIG. 2),
and first and second connector members 14 and 54, respectively. The
first and second connectors members 14 and 54 are basically
identical, except for the gender of their threaded couplings.
Therefore the first connector member 14 and its method of
attachment to the cylindrical rod element 12, will be described in
detail, with the understanding that a like description should also
apply to the second connector member 54 and its method of
attachment to the cylindrical rod element.
As shown in FIG. 1, the first connector member 14 is formed to
define an axial receptacle 16 for receiving a first end of the
sucker rod cylindrical element 12. The axial receptacle 16 is
defined by a series of .Iadd.axially spaced apart
.Iaddend.outwardly converging tapered surfaces 18, .Iadd.as
illustrated, of substantially equal angles of taper, .Iaddend.which
cooperate with the external cylindrical surface of the rod element
12 to further define a series of wedge shaped or tapered annuluses
20 about the rod element when the rod element is in position as
shown. .Iadd.The base frustrums of these outwardly converging
tapered frustoconical internal surfaces, as illustrated, have equal
diameters, and immediately adjacent to the plane of such base
frustrums are cylindrical internal surfaces or lands which have a
diameter equal to the diameter of such base frustrums. .Iaddend.The
connector member 14 includes an external cylindrical surface 22
terminating in an externally threaded end 24 for threadedly
engaging the next successive sucker rod to define a string of
sucker rods for lowering into a well bore. The first connector
member 14 also includes a pair of diametrically opposite flat
surfaces 26 for enabling an oil field operator to attach a standard
sucker rod wrench thereto for connecting and/or disconnecting the
individual sucker rods 10 from one another.
The first connector member 14 includes a chamfered surface 28
located at the end adjacent the rod element 12, the function of
such chamfered surface to be described hereinbelow. An internally
threaded section 30 is located adjacent the chamfered surface 28
for threadedly receiving a first collet 32 therein to align the
cylindrical rod element 12 with the first connctor member 14.
The collet 32 includes a bore 34 therethrough for receiving an end
of the cylindrical rod element 12, and also includes external
engaging threads 36 for engaging mating threads 30 of the first
connector member 14 to retain the collet in position, which in turn
retains the cylindrical rod element 12 in alignment within the
first connector member. The first collect 32 is basically
cylindrical shaped, having an exterior cylindrical surface 38,
terminating at one end in a first chamfered surface 40 and at the
opposite end in a second chamfered surface 42, which second
chamfered surface cooperates with chamfered surface 28 of the first
connector member, the function of which will be described
hereinbelow. The first collet 32 also includes an annular
converging tapered surface 44 integrally formed with the internal
bore 34 therethrough, which functions in a manner identical to the
annular outwardly converging tapered surfaces 18 of the first
connector member 14.
The sucker rod construction of the present invention includes a
sufficient quantity of adhesive material 46 to completely fill the
annuluses 20 defined by the first connector member outwardly
converging tapered surfaces 18 and the outer cylindrical surface of
the rod element 12 for adhering or otherwise interconnecting the
fiberglass rod cylindrical rod element 12 to the steel connector
member 14. Initially in a liquid state, this adhesive material 46
is poured into the connecting member axial receptacle 16. Next, the
fiberglass rod 12 is inserted into the receptacle, displacing much
of the liquid adhesive 46 and forcing it into the annulus
surrounding the rod, where it subsequently cures, forming an
annular wedge which is bonded to the rod and the receptacle tapered
surface 18.
The sucker rod construction of the present invention also includes
a second connector member 54 at the opposite end of the rod element
12 from the first connector member 14. The second connector member
54 is essentially identical to the first connector member;
therefore, the same reference numerals are used to indicate
identical parts on each connector 14 and 54. The difference between
the first and second connector members 14 and 54 is the gender of
their mating threaded connections: the first connector member 14
(FIG. 1) is a male member having an external threaded end 24, and
the second connector member 54 (FIG. 2) incorporates a housing 56
having female internal threads 58 for engaging the externally
threaded end 24 of the first (male) connector member of the next
successive sucker rod.
As best shown in the drawings, the sucker rod construction 10 of
the present invention is formed by positioning the cylindrical rod
element 12 within the first connector member axial receptacle 16,
threadedly inserting the first collet 32 in position about the
cylindrical rod element and into the first connector member. The
end of the rod 12 is in close fitting relation with a blind bore 17
defining the end portion of the receptacle 16. Likewise, the outer
cylindrical surface of the rod is in close fitting relation with
the collet bore 34. Those skilled in the art will readily
appreciate that these spaced points of close fitting engagement
function to align the rod 17 concentric with the collet 32 and
connector member 14.
The cylindrical rod element 12 is held in position within the
connector member 14 or 54 by a body of adhesive material which
fills the annular chamber defined by the cylindrical rod element
exterior surface and the series of connector member outwardly
converging tapered surfaces 18. In constructing the fiberglass rod
sucker rod 10 of the present invention, it is preferable to
introduce a suitable quantity of adhesive material 46, in its
initial liquid state, into the connector member receptacle 16 prior
to the insertion of the cylindrical rod element 12. As
aforementioned, inserting the rod 12 into the receptacle 16 forces
the liquid adhesive into the annular chamber surrounding the rod.
With the rod 12 in position within the connector receptacle 16, the
collet member 32 is next positioned about the rod to threadedly
engage the connector member 14 or 54. As best shown in the
drawings, as the collet 32 is screwed into position, its annular
converging tapered surface 44 serves to compress any residual
liquid adhesive material 46 within the annular chamber and
otherwise squeeze any excess material out into the annulus defined
by the exterior surface of the cylindrical rod 12 and the collet
bore 34.
As shown in the drawings, when the adhesive material 46 cures, it
forms a sleeve having a series of .Iadd.axially spaced apart
.Iaddend.annular tapering surfaces defining a series of annular
wedges positioned between the rod 12 and the receptacle tapered
surfaces 18. This hardened adhesive sleeve 46 forms a bond with the
fiberglass rod 12 to resist the shear force resulting when tension
is applied to the rod, as if to withdraw it from the connector
member. Additionally, tension applied to the rod 12 causes the
annular wedges of cured adhesive material 46 to be forced into
compressive engagement with the rod outer cylindrical surface and
with the connector member tapered surfaces 18 and with the collet
tapered surface 44. This results in a compression force directed
radially inwardly to the center line axis of the rod 12 to compress
the annular wedges of adhesive material 46 against the rod to
retain the rod in position with the connection member against the
action of such tension applied to the rod.
The second connector member 54 is interconnected to the opposite
end of the cylindrical rod element 12 in an identical manner to
form a sucker rod construction 10 having a male connector member 14
at one end thereof and a female connector 54 at the other end
thereof.
In operation, a plurality of sucker rods 10 of the present
invention are interconnected to form a string extending down into
the well bore and are connected to a pump positioned in the oil
bearing region of the well bore at the lower end thereof. The upper
end of the sucker rod string is connected to a device for providing
reciprocating pump action to the sucker rod string, and the sucker
rods are used in the customary manner to actuate the pump to
produce oil from the producing, but otherwise unpressurized oil
well.
The abovementioned chamfered surfaces 40, 42 and 28 on the collet
32 and connector members 14 and 54 provide a gradual taper from the
smaller diameter of the fiberglass sucker rod to the larger
diameter of the connector members, in order to prevent the sucker
rod from binding or otherwise catching the connector member on pipe
or casing joints within the well bore or at the well head as the
sucker rod cycles back and forth within the well bore.
The fiberglass sucker rod construction of the present invention
imparts an elasticity to the sucker rod string not found in
conventional all-steel sucker rods. In a reciprocating environment,
this elasticity inherent in pre-stressed fiberglass, results in an
increased effective stroke length, and an increased stroking force
over that of a steel rod having a comparable surface stroke. This
effect is best illustrated by observing the effect of a rubber band
having a weight affixed to its lower end. As the upper end cycles
through a reciprocating vertical movement of specified stroke
length, it will be seen that the weight at the lower end of the
rubber band experiences a stroke length greater than that of the
upper end of the rubber band. In a cyclic condition, the weight on
the rubber band creates a lower downstroke, due to the elasticity
of the rubber band, and a higher upstroke, due to the resiliency of
the rubber band, than a like weight on a comparable inelastic
material. Obviously, the rubber band illustration results in a much
more drastic effect than a fiberglass sucker rod; however, the
principle is the same and therefore the effect is the same although
on a smaller scale, resulting in increased production from a string
of fiberglass sucker rods as compared to a string of all-steel
sucker rods due to the increased pump stroke that is obtained.
The fiberglass sucker rod of the present invention may also be used
with lighter weight, less expensive surface equipment, because the
sucker rod itself is lighter weight and requires less structure and
less energy to reciprocate a given length of fiberglass rod within
the well bore than a comparable length of all-steel sucker rod.
Additionally, the lighter weight fiberglass sucker rod results in
greater ease of handling for oil field surface crews.
While there has been illustrated and described a single embodiment
of the present invention, it will be appreciated that numerous
changes and modifications will occur to those skilled in the art,
and it is intended in the appended claims to cover all those
changes and modifications which fall within the true spirit and
scope of the present invention.
* * * * *