US1849510A - Sucker rod - Google Patents

Description

March 15, 1932. A T M N 1,849,510

SUGKER ROD Original Filed June 11. 1930 INVENTCR ALFRED MORRIS THOMSON A'ITORN EYS Patented Mar. 15, 1932 UNITED STATES PATENT OFFICE ALFRED MORRIS THOMSON, OF NEWARK, NEW JERSEY, ASSIG-NOR TO DARDELET THREADLOGK CORPORATION, OF NEW YORK, N. Y., A CORPORATIONOF DELAWARE SUCKER ROD Application filed .Tune 11, 1930, Serial No. 460,478. Renewed October 1, 1931.

This invention relates to improvements in sucker rods for oil well pumps and the like. The invention has for its principal objects to provide a sectional sucker rod of the type wherein, the rod sections are screw thread coupled which may be made of smaller diameter at the joints than the present standard rods and will at the same time more successfully withstand the large axial, lateral and twisting stresses to which the rod is subjected in use; to provide a sucker rod of the screw thread coupled section type wherein liability of accidental unscrewing of the rod sections is largely reduced and wherein the strength of the screw joint is largely increased; and to provide a screw joint for sucker rod sections so constructed as to eliminate existing failures in standard rods due to pin breakage and throw the bending stresses into the main body portions of the rod sections at opposite sides of the screw thread connection therebetween.

Other objects and advantages of the invention will appear from the following description of the embodiments of the invention illustrated in the accompanying drawings in which Fig. 1 is a view partly in vertical longitudinal section of a portion of a sucker rod shown as it'extends into the well; and Fig. 2 is a similar vew of a modified form of sucker rod also embodying the invention.

While the improvements are shown embodied in sucker rods of the single pin and box type, it will be obvious that the invention is not limited in its application to this type of sucker rod, but may, for example, be embodied in the well known double pin and union type of rod.

Referring to Fig. 1, the rod consists of identical directly coupledrod sections each comprising a main rod-like body portion 10 of circular profile in cross-section having an integral box 11 at its upper end and having an integral pin at its lower end separated from the body portion by an integral collar 12.

The upper section of the pin is non-tapering and comprises a non-threaded portion 9 of substantial length and cylindrical crosssection and an externally threaded portion carrying the external screw thread 13 which may be of any suitable type, the thread shown being the usual V-thread. The lower face of collar 12, is tapered downward and inward to provide a conoidal friction surface portion 14 of the rod section'at the upper end of pin portion 9 facing toward the lower or pin end of the rod section and spaced a substantial distance from the upper end of the pinv thread 13.

The pin extends a substantial distance and at the same time avoids abrupt changes.

of section and longitudinal profile in the pin and the interfitted portion of the box.

The box 11 is formed at its mouth with a downwardly and inwardly tapering conoidal friction surface portion 17 immediately below which is a non-tapered outer portion 8 of the box bore of substantial length and of such diameter as to receive pin portion 9 without "contacting the same. The bore portion immediately below portion 8 is of slightly reduced diameter and non-tapering and is formed with an internal screw thread 18 complementary to pin thread '13. As shown thread18 is a V-thread of the same pitch as thread 13, and engages with thread 13 substantially throughout the length of the threads. The remainder of the box bore is non-threaded and consists of a gradually downwardlyand inwardly tapered bore portion 19 of substantial length spaced radially from portion 1-5 of the pin and a cylindrical lower bore portion 20 of the same diameter as pin portion 16 and into which pin portion 16 projects. The box bore terminates in a bottom or end wall 21 which is preferably dished or conoidal to reduce concentration of breaking stresses at this point, and said bore is of such length that the lower end of the pin does not abut the bore bottom when friction surfaces 14 and 17 are forced tightly together by the screwing of the pin into the box. Surfaces 14 and 17 may be made sufficiently abrupt to the axis of the rod to effectively limit the extent of inward screwing of the pin and still take a strong frictional grip on each other when the coupling is completed. y

A short distance above collar 12 and a short distance below the bottom of the box the rod section is formed with two squared wrenchreceiving portions 22 and 23, respectively. Externally the box is gradually reduced in diameter below its threaded portion.

The tapered friction grip portion 14 extends outward to the cylindrical periphery of collar 12 so that it may be drawn into the correspondingly tapered mouth portion 17 of the box by screwing of thread 13 into thread 18 until the two identically tapered surfaces are tightly gripped. The wedging of these friction grip portions also causes the upper side of the rib of thread 13 to be pressed tightly to the under side of the rib of thread 18. The two adjacent rod sections will, therefore, be held against accidental unscrewing by a large frictional resistance against relative turning after'being fully coupled. The tight frictional fit between portions 16 and 20 also adds to this frictional resistance to unscrewing. I

A further important feature of the described joint is that the tightly interfitted conoidal portions 14 and 17 and the tightly interfitted cylindrical portions 16 and 20 are located at opposite sides of the screw thread connection 13 and 18, each of said pairs of portions being firmly engaged around the rod axis and the axis of the engaged threads at points spaced a substantial distance from opposite ends of the point or area of screw threaded engagement so that lateral and bending forces are taken up thereby and transmitted to the main bodies of the rod sections whereby they are widely distributed and are absorbed by said body portions instead of being imposed largely upon or concentrated in the threaded portions of the rod sections.

The two most frequent causes of rod failure wi h the standard type of rods, accidental unscrewing and pin fracture or breakage of the rod through the threaded parts of the joint, are thus overcome by rods embodying the present invention. By providing the pin end with a fulcrum point in the box or close fit in the box at a point relatively remote from the threaded connection and keeping the pin out of contact with the box between said points, and by providing a telescopic or interfitted contact between the box mouth and the rod section whose pin is fitted in the box at the upper end of the pin remote from the pin thread, lateral cocking or hinge action between the threads which breaks down the threads and fractures the pin is prevented, as is also lateral cooking of the rod sections with a hinge action between the portions 14 and 17 or between the box mouth and collar which imposes breaking stresses upon the pin and box under lateral vibrations and bending stresses, thus overcoming serious and long existing defects in rods of the kinds heretofore used.

The" modified form of rod shown in Fig. 2 has the advantages of the rod above described and additional advantages hereinafter pointed out. This rod comprises identical rod sections each having a cylindrical main body portion 24, two squared wrench-receiving portions 25 and 26, a box 27' at its upper end, and a pin at its lower end separated from themain body portion by an integral cylindrical collar portion 28.

The pin has a non-tapered cylindrical portion provided with an external V-thread 29 and separated from the collar 28 by a cylindrical non-threaded portion 30 of substantial length and less diameter than the collar. Below the threaded portion the pin has a nont-hreaded extension of substantial length comprising a cylindrical portion 31 of substantial length and a terminal conodial portion 32 tapering downward and inward.

The box bore has an intermediate threaded portion provided with a V-thread 33 com plementary to the pin thread and engaged therewith substantially its full length when the sections are fully coupled, as shown. Above and below thread 33 the box bore has cylindrical and non-threaded portions 34 and 35 of such diameters as to receive portions 30 and 31, respectively, of the pin without contacting the same. Below portion 35 the bore is gradually contracted to form a conoidal lower bore portion 36 preferably having a conical bottom or end wall 37, this bore portion having the sametaper as the pin portion 32 and being of such length that the lower end of the pin does not seat on the bottom of the box when the rod sections are fully coupled, as shown.

With the above construction portion 32 may be with certainty forced tightly down into portion 36 by the action of threads 29 and 33, and the reaction between the conoidal surfaces of said portions forces the upper side of the rib of thread 29 tightly against the under side of the rib of thread 33, thus tightly holding the rod sections against ac cidental unscrewing.

The internal diameter of bore portion 34 is the same as the external diameter of collar 28, and the box is of such length that collar 28 is telescoped within the upper end of bore portion 34 when the parts are fully coupled as shown. The engaged portions 28 and 34 and engaged portions 32 and 36 function to prevent breakage and to throw the bending stresses into the main body portions of the rod sections as in the case of portions 14 and 17 and portions 16 and 20 of the rod of Fig. 1. It will be noted, therefore, that in the case of the rod of Fig. 2, also, both points of contact or connection at opposite sides of the point of screw thread engagement or connection are spaced a substantial distance from the engaged threads and that the pin and box are free from contact and radial connection for a substantial distance between the three points of contact, connection or engagement described, and this feature of the construction of the improved rods is deemed advantageous in effectively protecting the threads and pin from the effects of lateral vibrations and bending stresses to which the rods are subjected in use.

It will also be observed that the pin in the construction shown in Fig. 2 is not stretched or placed under tension by the coupling oper ation as is the case with the construction shown in Fig. 1, and this feature of the Fig. 2 construction is highl advantageous, since the full strength of t e pin is retained to withstand the load to which it is subjected by the weight of the rod sections therebelow. This is important, since the factor of safety in sucker rods with respect to ability to take the load of the very long and heavy rods used in deep wells is necessarily very slight.

It will be further observed that, in Fig. 1,

the portions 19 and 15 of the pin and box and portions 8 and 9 thereof are of substantial length as compared with the length of the screw thread connection, so that the two sets of engaged non-threaded port-ions 1620 and 1417 contact at points relatively remote from the opposite ends of said screw thread connection, and this relatively wide spacing between the three points of engagement between the two rod units is an important feature as heretofore pointed out, the units being free from contact at each end of the screw thread connection for a substantial distance, which preferably is about equal to the length of the screw thread connection, as shown. In Fig. 2, it will be observed that a similar wide spacing of the three connections or points of engagement is maintained. This wide spacing as compared with the length of screw thread connection is advantageous in resisting cocking in the screw connection and breakagein or at the ends of said connection, and in distributing the rod flexing stresses in the advantageous manner hereinbefore set forth.

What I claim is:

1. A sucker rod comprising separably with the latter unit between said points except for a screw thread connection between the units that terminates a substantial distance from both of said points and comprises an external thread on the first-mentioned unit and an internal thread on said next unit.

2. A sucker rod comprising separably jointed units wherein, at each joint, one unit is frictionally embraced by the next unit at two longitudinally spaced points and has a direct .screw thread connection with'the latter unit intermediate said points terminating at a distance from each of said points approximately equal to the length of said connection, said two units having a radial clearance therebetween from the ends of said screw thread connection to the points at which the first mentionedunit is embraced by the other unit.

3. A sucker rod comprising separably jointed units wherein, at each joint, one unit is threaded into an axial bore in the adjacent unit and has a cyl ndrical friction surface and a conoidal friction surface telescoped into engagement with complementary friction surfaces of said adjacent unit beyond opposite ends of the screw thread connection between said units, there being a radial clearance'between said units from each end of their screw thread connection for a substantial distance longitudinally of the bore as compared with the length of said connection.

4. A sucker rod comprising two separably jointed units having engaged screw threads connecting the same, said units contacting each other through the medium of telescoped conoidal surface portions thereof at one side of their screw thread connection and through the medium oftelescoped cylindrical surface portions thereof at the other side of said connection, each end of said screw thread connection terminating at a distance from the nearest point of contact of the adjacent telescoped surface portions of the units that approximates the length of said connection, and said units having a radial clearance therebetween from the ends of their screw thread connection to the nearest points of contact between the units afforded by said telescoped surface portions thereof.

5. A sucker rod havingunits arranged in succession with each two adjacent units free from all contact except that between a pair of telescoped conoidal friction surface portions, a pair of telescoped cylindrical friction surface ortions and an intermediate pair of screw t reads the engagement between which threads terminates at two points each located a substantial distance from the nearest point of contact between the adjacent pair of friction surface portions.

6. A sucker rod having threaded units screwed together in succession and free from all contact except that afforded respectively by said threads, the frictional engagement between a pair of telescoped conoidal surface portions of the units beyond one end of their screw thread connection, and the frictional engagement between a pairv of telescoped cylindrical surface portions of the units beyond the opposite end of their screw thread connect-ion, the thread engaged portions of the units being spaced from the adjacent frictionally engaged portions thereof a distance approximating the length of said thread engaged portions.

In testimony whereof I hereunto afiix my signature.

ALFRED MORRIS THOMSON.

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