Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~.2~
ROD GUIDE
This invention relates to well tools and more particularly to rod guides
for sucker rods o~ a rod guide string employed to actuate a pump connected
in the tubing oi the well.
Background of The Invention
Well fluids are pumped from a well fluid producing earth formation
through a tubing string which extends to the surface by a pump connected
to the bottom end of the tubing string. The pump is actuated by a sucker
rod string which is reciprocally moved in the tubing by a drive means located
10 at the surface the sucker rod string alternately being moved upwardly by
the drive rneans and then allowed to move dou!nwardly by its own weight.
In some cases sinker bars may be connected to the lower portions of sucker
rod string to minirl ize ilexing of the sucker rod string due to the downward
pressure of the weight oi the upper portions of the sucker rod string on
15 the lower portions. This ~lexin~ of some portions of ~he sucker ro~string
would cause the rods of the string to cor tact the internal surfaces of the
tubing. Mor~over the tubing itself is not per~ectly strai~h~. In lact it
is somewhat helical or corkscrc w in Sorm so that thc sucker rods even if
the sucker rod string itsel~ were straight would also contact the tubing
20 at various locations along the lenFtll of the tubinR. Such sliding contact
Or thè rods with the tubing would of course cause darnage both to the sucker
rods and thc tubing.
ln order to prevent Sll~ h c ontact oS the sucker rods w ith the tubing
the rocls are convention-llly provided with guides or centralizers which are
25 rigidly secllred to thc~ rods at several longitudinally spaced locations along
each rod.
Some o~ sucll Kuide are o~ thc typc shown in the U. S. Letters Patent
to D. F. Sable No. 3 442 558 which are formed o~ a resilient substance and
which resiliently grip thc rod so that relatively great longitudinal ~o rces
30 must bc exerted thcreon to move the ~uidc- relative to the rod.
O~her rod guides are molded on the rods and are formed of such sub-
stances as are disclosed in Il. i. Letters l atent No. 4 0~ 5 to r. J. ~`arson.
31 2~90~3
Many such molded in piace ~uides are formed of a plastic available
commercially under the trademark Ryton.
The ri~id molded in piace rod guides require that a much greater
force to be exerted thereon before they are displaced on the rod than the
above described ~uides which resiliently grip the rod. The rigid rod guides,
however, are subject to chipping.
Whether provided with rod guides of either oI the above described
types of rod guides, a large proportion of the guides are always in contact
with the internal surfaces of the tubing. As a result, upon reversal of down-
ward movement of the sucker rod string to upward movement, the ~orce
required to move the sucker rod string upwardly no~ only must overcome
the weight of the sucker rod string and its iner~ia plus the force needed
to force upward movement of the coJumn of fluids in the tubing, bu~ aJso
the frictional resistance between the rod guides and the internal surfaces
of the tubing string. Obviously the great upward forces exerted on the sucker
rod string upon each such reversal of downward to upward movement of
the rod string shorten the life of ehe sucker rods. Upon reversal of upward
~downward movement of the sucker rod string, the forces exerted by upper
portions of the rod string on the lower portions are greatly increased where
2 0 the lower portions of the rod string have rod guides rigld therewith. Todecrease such flexing forces in such cases requires the use o~ sinker bars
of considerable weight. This, of course, increases the ~orce which must
be exerted on the sucker rod string to move it upwardly.
Since such rod guides which are rigidly mounted will wear and abrade
at the locations of their sliding contact with the tubing, the guides will
abrade or wear at such locations of their periphery. To provide even wear
along the entire periphery of the rod guides, the sucker rod string must
be rotated through some angle during each cycle of reciprocatory movement
thereof.
Objects of The Invention
Accordingly, it is an object of this invention to provide a rod guide
which does not resist longitudinal movemen~ of ~he rod on which it is mounted
at the initiation of reversal of movement of the rod even though the guide
~g~`~
is in frictional contact with a tubing string throu~h which the rod extends.
Another object is to provide a rod guide assembly havin~lguide body
which is slidably moun~ed on the rod to permit limited longitudinal movemen~
of the rod relative to rod guide mounted thereon.
5StilJ another object is ~o provide a rod guide assembly~ of the type
described9 having longitudinally spaced stops clamped to the rod between
which the ~uide body is mounted.
Another important object o~ the invention is to provide a rod ~uide
which is free to rotate on the rod guide on which it is mounted.
10Still another object is to provide a rod guide assembly, of the type
described, wherein the guide body is provided with external ribs which extend
angularly relative to its central lon~itudinal axis whereby the forces exerted
$hereon by well fluids flowing through the passa~es formed by the ribs tend
to rotate the guide ~ody.
15Ano~her important objec~ is to provide a rod guide~of the type described,
whose body has two or more sections ~o permit rela~ive freedom of movement
of the sections as when one section is in contact with the well tubing ~nd
the other is not.
Brief Descrip~ion Of The Invention
20The rod guide has a pair of stops each of which has a metal clip or
clamp which clamps or compressively forces a plastic liner against a sucker
rod and a guide body slidably mounted on the rod between the~tops. lhe
guide` body may be formed of one or more independently movable sections.
The stops are spaced to permit limited longitudinal movement of the rod
25relative to the guide body, for example, one half inch to one and one half
inches where the guide body is six and a haJf inches in length.
Description Of The Drawings
Additional objects and advantages of ~he invention will be readiiy
apparent from the reading of the following descriptions of a device constructed
in accordance with the invention and reference to the accompanyln~ drawJngs
5 thereof, wherein:
Figure I is a plan view of a sucker rod provided with rod ~uide assem-
blies embodying the invention;
Figure 2 is a plan view of the rod guide; and,
Figure 3 is a perspective view of a stop of the rod guide.
~L21~
Referring now to the drawings, the rod guide assembly 10 embodying
the invention includes a pair of stops 11 and ! la of the t) pe described in
the U. S. Letters Patent No. 3,507,5Z5 to D. E. Sable. Each stop includes
a liner 12 formed of a plastic, such as is commercially available under the
5 trade name Nylon, which when exposed to weJI fluids absorbs such ~luids
and tends to swell.
The liner is slit, as at 13, and is provided with external ~langes 14
and I S at its opposite ends. A metal clip 16 located between the flanges
is bent about the liner compressing it against the rod. Its adjacent
10 ends are welded as at 17.
The stop I la being identical to the stop 11, its elements have been
provided with the same reference nur~rals, to which the subscript a has
been added, as the corresponding elements ol the stop 11. The guide body
20 is slidably mounted on the rod R between the stops 11 and I la and is
~ormed of three identical sections 21a, 21b and 21c. The sections may be
of the same form and construction as the scrapers described and illustrated
in the U. S. Letters Patent to D. E. Sable No3. 3,364,998.
Each of the guide body sections has a central bore of slightly greater
diameter than the diameter of the sucker rod on which it is mounted and has a
longitudinal slot 23 which extends at an angle relative to the central longitu-
dinal axis of the section. The section is made of a somewhat resilient sub-
stance, such as is available under the trademarl; N~lon. The slot 23 is smaller
in width than the diameter of the rod so that as the section is forced onto
the rod through the slot 23, thc opposite portions of the sections are flexed
apart to ~ermit movement of the section onto the rod. The sections are
provided with external spaced ribs 24 which extend longitudinally at an angle
to the central longitudinal axis of the section. The ribs define passages
or channels 25 through which well fluids may flow.
Each section has planar top and bottom end surfaces 27 and 28, respec-
tively, and top and bottom inwardly convergcnt beveled top and bottom sur-
~aces 31 and 32. The ribs also have beveled top and bottom surfaces 34
and 35. The bevelled surfaces of the sections help cam or slide ~he sections
past internal obstructions in tlle tubing and along the internal surfaces of
the well tubing at locations where the tubing is not straight.
In use, each sucker rod is provided with a plurality of the rod ~ uide
assemblies. For example, as shown in Figure 1, the rod R which is twen-
ty-five feet lor)g is provided with three rod guide assemblies. The top and
bottom assemblies 20a and 20c are spaced three feet from the top and bottom
ends, respectively, of the rod and the middle rod guide assembly is located
at the middle of the rod, that is, twelve and a half feet from either end
5 of the rod.
The stops 11 and I la of each rod guide assembly are spaced apart
a distance somewhat greater than the length of the guide body 20 mounted
therebetween on the rod. For example, if the guide body i5 forrned of three
sections each being two inches in length, the distance between the bottom
10end 40 of the upper stop 11 and the top end 41 of the lower stop may be
betwéen six and a half inches to seven and a half inches .
In use, the sucker rod string is made up of a plurality of rods R and~
depending on the depth at which the well fluid producing earth formation
is located, rnay be several thousand feet long.
l SAt the beginning of a downward movement or stroke of the sucker
rod string, as the sucker rod string is allowed to move downwardly, it moves
by gravity downwardly but the ~uides 20 tend to remain stationary being
held against downward movement by the upward force exerted thereon by
well fluids flowing upwardly therepast. Any of the sections which are not
2 0 in contact with the tubing will be rotated by the forces exerted thereon
by the well fluids fJowing through the inclined passages 25 in a counterclock-
wise direction as seen from above. The sections in contact with the internal
surface of the tubing will also tend to rotate in this direction by the frictional
force exerted thereon due to the angular inctination of the ribs relativ
25 to the longitudinal axis of the guide body.
It will be apparent that upon initiation of a downward stroke of the
sucker rod string, the guide bodies on the rods ofier no or very little resis-
tance to the downward movement of the sucker rod string even if one or
more sections of each guide body are in frictional contact with internal
30 surfaces of the well tubing since at the beginning of the downward stroke,
the guide bodies are resting on the top end surfaces 41 of the stops I la.
Each rod must move one half inch or more, depending on the distance
between the end surfaces 40 and 41 of each rod guide assembly, be~ore the
~9~
wei~ht of the rod string must overcome any frictional resistance between
a guide body section and the well tubing. During this intial downward rnove-
ment of the sucker rod string, the resistance to its downward movement
is therefore minimal.
As the bottom surface 40 of each rod guide assembly engages the
top surface 27 o~ i~s ~uide body 207 the rod string has already ~ained down-
ward momentum which will help overcorne any frictional resistance betwen
a rod ~uide body and the internal surfaces of the well tubing.
At the bottom end of a downward stroke o~ the sucker rod string,
all rod guide bodies are in their topmost positions held against fureher upward
movernent by the top stops 11.
Upon reversal ~rom downward movement to upward movement of
the sucker rod strin~, the rod guide bodies again do not impede initial upward
movement of the rods on which they are mounted until the rods have moved
upwardly, a haif inch or more, and the lower stop surfaces 41 engage the
bottom surfaces 28 of the lowermost sections of the guide bodies.
By this time the inertia of ~he tubing string has been overcome so
that the peak upward force which must be exerted on the sucker rod string
is greatly smaller as compared to a sucker rod string having rod guides which
are ri~id with the rod so that not only the inertia of the rod string but also
the f~ictional resistance between the guides and the well tubing must be
simultaneously overcome at the time of reversal from downward to upward
movement o~ the sucker rod string.
It will now be seen that a new and improved rod guide assembly has
been illustrated and described which greatly decreases the stresses and strains
to which a sucker rod string is subjected during its reciprocation in a well
tubing.
It will also be seen that the provision o~ guide bodies which are slidably
and rotatably mounted on a rod for limited longi~udinal movement thereon
provide for uni~orm wear of the guide bodies.
The fore~oing description of the invention is explanatory only and
changes in the detaiis of the con~truction illus~rated may be made by those
skilled in the art, within the scope of the appended claims, without departing
~rom the invention.
