US2874937A

US2874937A - Corrosion-resistant sucker rod and method of constructing same

Info

Publication number: US2874937A
Application number: US548934A
Authority: US
Inventors: Edward F Higgins
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-11-25
Filing date: 1955-11-25
Publication date: 1959-02-24
Anticipated expiration: 1976-02-24

Description

SAME 1955 3 H 5 A 4 32 B 1111M w Z l l/Il/lll/ll/llllfll B B m l 7 2 M Z INVENTOR EDWARD F HIGGINS BY dam/7W Afiomvm E. F. HIGGINS CORROSION-RESISTANT SUCKER ROD AND METHOD CONSTRUCTING Filed Nov. 25,

United States Patent CORROSION-RESISTANT SUCKER ROD AND METHOD OF 'CONSTRUCTING SAME Edward F. Higgins, Kirkwood, Mo.

Application November 25, 1955, Serial No. 548,934

6 Claims. (Cl. 255-28) The present invention relates to sucker rods for oil wells and the like; and particularly to a light weight, corrosion-resisting sucker rod and the method of'constructing same.

Chains of sucker rods, coupled to each other and extending downward for thousands of feet, are used in pumping oil Wells. The great weight of the chain of rods and the alternating motion of pumping have set up severe repetitive stresses, tending to cause fatigue and premature failure. Corrosion has caused a gradual lessening of strength, and its effects are cumulative with the effects of fatigue.

The purposes of the present invention include overcoming all of these problems and providing a sucker rod which is not subject to corrosion, is resistant to fatigue, and is of such light weight as to minimize the power required for pumping and permit the pumping of deeper wells, by the use of longer rod chains than heretofore possible.

A further purpose is to provide a sucker rod formedof light weight material, to whose ends metal fittings are secured by adhesive bonds which develop in shear substantially the full tensile strength of the rod.

A still further purpose is to provide a method for enlarging the ends of glass fiber rods Within internally tapered metal fittings, so as to provide closely mating surfaces for adhesive bonding, and to develop bond-curing pressures reliably.

An additional purpose is to provide a method and means for plugging end cavities in rod ends so enlarged.

Other objects will'be apparent from; this specification and the discussion which follows herein.

In the accompanying drawings (one sheet):

Figure 1 is a view partly in elevation and partly insection of one end of a sucker rod inserted into an end fitting preliminary to their securement to eachother;

Figure 2 is a sectional view taken alongthe plane indicated by line 22 of Figure-l;

Figure 3 is a sectional view somewhat similar to Fig--' ure 1, showing therod end spread taperingly within-the fitting by a simple tool, illustrated partly in elevation and partly in section;

Figure 4 is a somewhat similar sectional view, showing the end fitting completely assembled onto the rod, with a poured-in resin filler plug in place;

Figure 5 is a somewhat similar sectional view illustrating two rods connected end to end, as in use in a chain, further showing an alternate construction utilizing pointed metal filler plugs;

Figure 6 is a sectional view taken along the plane indicated by line 66 of Figure 5.

The adhesive coating on the sucker rod end, shown in the partly elevational view, Figure 1, and inthe cross sectional views Figures 2 and 6, is omittedfrom the sectionalviews Figures 3, 4 and 5;

The principal, member of each suckenrodfassembly.is; 70 an elongated, preferably cylindrical, light weight, corro-- slam-resistant rod, generally; designated 10, of convenient 2,874,937 Patented Feb. 24, 1959 resins commonly utilized. Rods so composed are free from attack by chemicals'present in crude oils which injuriously aiiect the strength of steel rods. The longitu= dinal alignment of thefibers gives them great strength in tension, so their strength-to-weight ratio far exceeds that of common steel. Such rods have also been found to be inherently less susceptible than steel to the effects of fatigue from the reversals of load during pumping operations.

For attachment to each end of such a rod, I provide an end fitting generally designated 11, preferably ma chined from corrosion-resistant steel, and having a rodreceiving end opening 12 of sumcient diameter to accommodate the rod and a surrounding layer of adhesive bond material. The fitting 11 has a sleeve portion 13 enlarged from the end opening 12 taperingly to maximum diameter at an annular end Wall 1-4, said enlargement and annular end wall being defined with reference to a longitudinal axis designated a coincident with the rod axis. The space within such annular tapering enlarged sleeve portion 13, extending from the rod end opening 12 to the annular end wall 14, is referred to hereinafter as the chamber 15; and the inner surface of the sleeve portion 13, utilized for bonding, is referred.

to as the fitting bonding surface 16.

The end fitting 11 further includes a tip connector portion 17, which, like conventional sucker rods, is externally threaded with reference to the axis a. connector portion 17 is penetrated along the axis a by an axial bore 18, of lesser diameter than the rod 19, which.

communicates with the larger end of the" chamber 15, joining it at the center of the annular end wall 14. The tip connector portion 17 may be rovided with a shoulder 19, at the base of and extending beyond its threads. The outer surface of the sleeve portion 13 is provided with a pair of opposed wrenching flats-13A.

In Figure l the portion of the cylindrical outer surface of the rod 10 which is inserted within the sleeve portion 13 is coated with a layer 20 of adhesive. Such adhesive maybe of the-high-strength rubber-base type If desired, a

which is cured under heat and pressure. coating of such adhesive may also be preliminarily applied to the fitting bonding surface 16 prior to assembly. The problems are: to enlarge the coated portion of the outer surface of the rod against the fitting bonding surface 16' under suflicient pressure to achieve a'strong',

Figure 2 shows'a cross-section taken'through the sleeve portion 13 and the end of the-rod 10 before it is enlarged and bonded. To effect enlargement, a taperingly pointed toolgenerally designated 22 is driven through the fitting bore 18 into the end face- 21 oftherod'lll, as shown in Figure 3. The tool'22 hasa cylindrical shaft 23 of length at least equal to the-length of the bore 18, aset of hexagonal grasping'faces '24 by whichthe tool may be grasped for removal, ablunt'outer end- 25 by which the tool may be pounded into place, an in ward. formed annularshoulder 26 at the .innerend of the shaft 23,.anda tapering.';point.;21 adaptedtopene The tip Figure 1 shows the end of the" trate into the rod along the axis a and spread the rod material to an annularly enlarged cross-section. The volume of the point 27 and its proportions may best be arrived at by test after the size of the chamber and the diameter and material. of the rod 10 have been chosen.

The point 27 enters the end face 21 of the rod 16 along the axis a and spreads the fibers and flows the binder material outward so that the end face 21 becomes annular with respect to the axis a and the rod material adjacent the end face 21 is caused to expand and flow to fill the chamber 15. When the tool 22 has entered the end of the rod 10 sufficiently to bring the tool shoulder 26 into abutment against the annular rod end face 21, expansion and pressure on the adhesive will have reached the extent predetermined by the shape and volume of the point 27. Thus any desired bonding pressure may be achieved consistently.

During the curing of the adhesive, the tool 22 is held in place within the fitting 11 by any one of a variety of means, not shown. Utilizing typical rubber-base adhesives, such bond curing may involve heating to tempera tures of between 300 and 400 F. for periods of thirty minutes to one hour, or such other times and temperatures as may be recommended by the adhesive manufacturer. The tool 22 is then withdrawn, leaving a tapered, substantially conical end cavity designated 28 in the end face 21 of the rod 143.

' To achieve maximum strength and reliability, the end cavity 28 should be filled. A convenient fill is by means of a poured-in resin plug 29, shown in Figure 4. The resin used for such purpose should preferably be akin to the resin binder of the rod material 16, so that it cures firmly Within the tapered cavity 28, and forms in effect an enlarged rod end. However, any type of close-fitting cavity-filling plug will reinforce the end of the rod 10 and prevent its collapse under bearing loads imposed by the taper of the sleeve portion 13. With bearing failure thus prevented, full shear strength of the adhesive layer may be developed.

As an alternative, it may be desired to utilize an inexpensive expendable metal tool which is left in place and serves as a plug. This construction is shown in Figure 5, which illustrates the ends of two adjoining rods connected as part of a rod chain, with their tip connector portions 17 substantially abutting each other and connected by an internally threaded collar 30 which extends between the shoulders 19 of the respective fittings. Except as hereinafter described, the parts and their numbers shown in Figure 5 are identical with the similarly numbered parts heretofore described.

In this latter embodiment I use a combination tool and plug, generally designated 31, having a shaft portion 32 whose outer diameter substantially fills the bore 18 of the tip connector portion 17. The metal plug 31 has a shoulder 33 at its inner end and a tapering point 34 similar in shape and volume to the point 27 of the tool 22. The plug shaft 32 is approximately the length of the bore 18, and its outer end 35 is adapted to be hammered until the shaft 32 is received entirely within the bore 18 and the shoulder 33 abuts against the end face 21 of the rod 10.

Before spreading the rod end with the metal plug 31, I

I insert within the bore 18 some of the rubber-base adhesive to form a plug-retaining adhesive layer 36 extending through the bore 18 and into the cavity 28 which is formed as the plug point 34 is driven into the rod end. A section through the plug point 34 as this operation is completed is shown in Figure 6. If desired, this adhesive layer 36 may be omitted, for when the assembled sucker rods are connected to each other by the internally threaded collar 30, the outer ends 35 of the plugs will be abuttingly adjacent each other and are not free to come loose.

The rod binder material has been described as having a. tendency to flow somewhat under pressure. Both for purposes of this specification and as used in the claims, the term fiowable as applied to the binder material is to be understood as meaning tending to deform plasticall'y, under pressures of the order of magnitude which can be applied according to the method of this invention. For purposes hereof, it is sufiicient that such flow or deformation take place laterally.

Using rods composed of longitudinally aligned glass fibers held together by a resin hinder, the binder will display this fiow tendency regardless of the longitudinal rigidity of the rod. Further, the flow tendency, or lateral deformation, is sufficient for purposes of this invention, even though separating the rod end fibers to form the end cavity 28 is accompanied by some degree of cracking of the binder material. Although cracks may occur in the regions subjected to greatest strain, I have found that there is adequate plastic flow, or fluid deformation, of the material presented against the inner surface of the sleeve portion 13.

Where suchcracking has occurred in the rod end, it will be remedied by filling with the poured-in resin plug 29, as shown in Figure 4. If cracking occurs when using a metal plug 31 as a tool, to form the cavity 23, the plug 31 should be withdrawn and a small amount of resin poured into the cavity 28. The metal plug 31 should be then again driven into the cavity 28, forcing the resin to fill such cracks and to bond the metal plug 31 firmly in place. In such case the resin so added serves instead of the plug-retaining adhesive layer 36 shown in Figure 6.

I have found that using binders which tend to crack somewhat when the rod ends are enlarged, as herein described, the tendency to flow is sufficient to bring the outer surface of the rod end to bear fairly evenly within the tapering inner walls of the end fittings, exerting pressure sufficient for reliable adhesive bonds. Substantially uniform pressures are achieved from the physical dimensions of the rod end, tool point, and chamber size. Other adhesives, such as epoxy resin adhesives, may be used if it is desired to apply lesser pressure than those required for rubber-base adhesives.

,The construction described makes possible the use of corrosion-proof glass-and-plastic rods having a high ratio of strength to weight and inherent resistance to fatigue. Since only a relatively small amount of steel is utilized in the rod fittings it becomes economical to employ corrosion-resistant steel.

Variations in product and method, based on the foregoing disclosure, will occur to those skilled in the art. The present invention should not be construed narrowly, but rather as fully coextensive with the scope of the claims which follow.

I claim:

1. A corrosion-resistant sucker rod assembly comprising a cylindircal rod fabricated of longitudinal structural fibers and corrosion-resistant binder material therefor adapted to flow under pressure, the rod having a taperingly enlarged end including an end face, in combination with a corrosion-resistant metal rod end fitting mounted on the enlarged end of the rod and having a taperingly-enlarged chamber, within which the enlarged rod end is accommodated, further having a bore, of lesser diameter than the rod, opening into the chamber axially, the assembly further comprising an annular layer of adhesive material bonding the outer surface of the enlarged rod end to and within the inner surface of said chamber, together with a plug insertable through and accommodated within said bore, said plug having a tapering point projecting axially into the chamber.

2. A sucker rod assembly comprising a cylindrical rod having a'taperingly-enlarged end, and an end face, in combination with a metal rod end fitting mounted on the enlarged end of the rod and having an annular, taperinglyenlarged' chamber formed with reference to a longitudinal axis coincident with the rod axis within which the enlarged rod end is accommodated-further having a bore of lesser diameter than the rod opening into the chamber axially whereby to afford access to the end face of the rod, together with a metal plug having a cylindrical plug body insertable through said bore and whose length substantially equals the length of said bore, a tapering point proiecting axially into the chamber and adapted to penetrate and spread the rod end, the base of the point having a diameter smaller than the diameter of the plug body, and an annular shoulder therebetween and adapted to come into abutment against the end face of the rod.

3. A sucker rod assembly comprising a cylindrical rod fabricated of longitudinal structural fibers and binder material therefor adapted to flow under pressure, each rod having a taperingly-enlarged end, an end face, and an axial tapered cavity therein, in combination with a metal rod end fitting mounted on said enlarged end of the rod and having an opening, an annular end wall opposite said opening, and an annular, taperingly-enlarged chamber therebetween within which an enlarged rod end is accommodated, the said annular portions being formed with reference to a longitudinal axis coincident with the rod axis, the fitting further having beyond said end wall a tip connector portion and an axial bore therethrough of lesser diameter than the rod and through the annular end wall, the assembly further comprising an annular layer of adhesive material bonding the outer surface of the enlarged rod end to and within the inner surface of said chamber, and an axially aligned plug having a plug body accommodated within said bore and a tapering point accommodated within the tapered cavity in the end face of the rod.

4. A sucker rod assembly comprising a cylindrical rod taperingly enlarged annularly at its ends, and having a substantially conical end cavity within each taperinglyenlarged end, in combination with metal rod end fittings, each having an opening, an annular end wall opposite said opening, and an annular, taperingly-enlarged chamber therebetween within which an enlarged rod end is accommodated, the said annular portions being formed with reference to a longitudinal axis coincident with the rod axis, each fitting having beyond said end wall a tip connector portion and an axial bore of lesser diameter than the rod therethrough and through the annular end wall to establish communication with the chamber, together with an axially aligned plastic plug in each end fitting, each having a cylindrical plug body accommodated 6 within the bore of the end fitting and a tapering point accommodated and adhered within the substantially conical cavity of the rod end.

5. The method of securing the end of a rod composed of longitudinal structural fibers and binder material, within a fitting having an open end, a tubular, taperinglyenlarged chamber thereadjacent, and an inner wall opposite, comprising the steps of applying an adhesive coating, inserting the rod end through the end opening of the fitting, and advancing it to and against the end wall without spreading it, then penetrating the end face of the rod along its axis and pressing the rod material Wedgingly outward so as to create a tapering aperture in the rod end face whereby to expand the rod end taperingly and to compress the adhesive coating between its surface and the inner surface of the fitting, then while so press ing the said rod material, setting the adhesive, and then relieving the pressure and plugging the aperture.

6. The method of spreading the ends of rods composed of longitudinal fibers and binder material, and bonding them adhesively to and within the inner surface of metal tubular rod-end fittings of the type including an inner tapering enlargement, comprising the steps of applying an adhesive layer for joining the outer surface of a rod end to the tapered inner surface of the fitting, inserting the rod end through the end opening of the fitting adjacent the smaller end of the taper and advancing it to the larger end of the taper without spreading it, then driv ing a taperingly-pointed tool through the other end opening of the fitting axially into the center of the end face of the rod, thereby wedging and spreading the rod end taperingly outward, and continuing such wedging and outward spreading until pressure is exerted between the outer surface of the rod end, the inner surface of the litting, and the adhesive layer therebetween, and then, while maintaining the pointed tool in place at which such pressure is exerted, causing the adhesive to be set.

References Cited in the file of this patent UNITED STATES PATENTS 764,943 Guy July 12, 1904 1,246,329 Salberg Nov. 13, 1917 2,059,867 Hinds Nov. 3, 1936 2,453,079 Rossmann Nov. 2, 1948 2,536,388 Murray Jan. 2, 1951 2,705,346 Schlabach et al. Apr. 5, 1955