US3695117A

US3695117A - Long stroke pumping unit

Info

Publication number: US3695117A
Application number: US47074A
Authority: US
Inventors: Roy D Ewing; Michael L Rizzone
Original assignee: United States Steel Corp
Current assignee: OILWELL Inc A CORP OF; National Oilwell Varco LP
Priority date: 1970-06-17
Filing date: 1970-06-17
Publication date: 1972-10-03
Anticipated expiration: 1989-10-03

Abstract

An improvement in a long-stroke pumping unit of the type shown in an earlier patent (Kuhns et al. U.S. Pat. No. 3,285,081). The patented unit includes a tower, drums mounted at the top of the tower, and a reversible drive for the drums. Flexible cables suspend a rod string and a counterbalance from the drums to move in opposite directions. Improvement is in attaching the cables to the drums with pivoted levers to prevent detachment caused by overrun at the ends of a stroke and to shorten the moment arms more effectively at the ends of each stroke.

Description

United States Patent Ewing et al.

Oct. 3, 1972 [54] LONG STROKE PUMPING UNIT [72] Inventors: Roy D. Ewing, Richardson; Michael L. Rizzone, Dallas, both of Tex.

[73] Assignee: United States Steel Corporation [22] Filed: June 17, 1970 [21] Appl. No.: 47,074

[52] US. Cl ..74/89.22 [51] Int. Cl ..Fl6h 27/02 [58] Field of Search ..74/89.2; 254/150, 186

[56] References Cited UNITED STATES PATENTS 3,285,081 11/1966 Kuhns et a1 ..74/89.22 2,329,943 9/1943 Robins ..254/186 1,298,372 3/1919 Monk ..254/150 462,993 11/1891 Pfetch ..254/150 I FOREIGN PATENTS OR APPLICATIONS 690,101 7/ 1964 Canada ..254/150 Primary Examiner-Meyer Perlin Assistant Examiner-Wesley S. Ratliff, Jr. Attorney-Walter P. Wood ABSTRACT An improvement in a long-stroke pumping unit of the type shown in an earlier patent (Kuhns et al. US. Pat. No. 3,285,081). The patented unit includes a tower, drums mounted at the top of the tower, and a reversible drive for the drums. Flexible cables suspend a rod string and a counterbalance from the drums to move in opposite directions. Improvement is in attaching the cables to the drums with pivoted levers to prevent detachment caused by overrun at the ends of a stroke and to shorten the moment arms more effectively at the ends of each stroke.

4 Claims, 6 Drawing Figures PATENTEUIIIZU I972 3.695.117

- sum 2 or 3 NWO m wt, v 9m nwmrons nor 0. 5mm; a MICHAEL L. mzzon/s Br Mmflfl/M4 Attorney PATENTED 0B 3 I9 2 SHEET 3 OF 3 LONG STROKE PUMPING UNIT This invention relates to an improved long-stroke pumping unit for oil wells, and the like.

The present invention is an improvement. over the pumping unit shown in Kuhns and Rizzone US. Pat. No. 3,285,081, of common ownership: The patent shows a long-stroke unit which includes-a tower,. a pair of drums mounted on a commonshaft at the top of the tower, and a reversible drive means connected. to the shaft. Flexible cables suspend the sucker rod string and: a counterbalance therefor from the drums. During a.

downstroke of the rod string the cables which suspend the rod string unwind from the drums, while those which suspend the counterbalance wind thereon. This relation is reversed during an upstroke of the rodstring. Near the end of each stroke the unwindingcables meet eccentric portions or ramps at the sides of the drum, whereby their moment arms become shorter. Before the end of the stroke, the drive means is disconnected from the drums and the stroke is finished under momentum of the parts. The weight distribution alone starts the next stroke, before the drive means is applied in the reverse direction.

The unit shown in the patent is efficient and achieves a satisfactory long stroke for the pump without undue mechanical complexities, but there have been diffi'culties. Occasionally the cables overrun the ramps at the end of a stroke and become detached from the drums. While the moment arm of the unwinding cables is shortened at the ends of a stroke, it never becomes zero, and there is always a torque on the drums in the wrong direction to be overcome in starting the next stroke.

An object of our invention is to provide, in a pumping unit of the type shown in the Kuhns and Rizzone patent, an improved means attaching. the cables to the drums, which means overcomes the foregoing difiiculties.

A further object is to provide pivoted links attaching the cables to the drums, thus overcoming the problem of overrun at the ends of a stroke, as well as shortening the moment arm of the unwound cables to zero.

A further object is to provide improved drums for use in this type of pumping unit, which drums have an asymmetrical ramp construction affording advantageous reversals at the ends of both strokes.

In the drawings:

FIG. 1 is a diagrammatic side elevational view of portions of a pumping unit equipped with our improved cable-attaching means, the parts being shown in the position they occupy just before the cables start to unwind from the ramps during a downstroke of the rod string;

FIG. 2 is a diagrammatic side elevational view of the drum and cable-attaching means shown in FIG. I, the parts being shown in the position they occupy just after the unwinding cable clears the ramp;

FIG. 3 is a view similar to FIG. 2, but showing the parts at the end of a stroke;

FIG. 4 is a view similar to FIG. 1, but showing a modification in which the drum has asymmetrical ramps;

FIG. 5 is a view similar to FIG. 4 but showing the drum from the other side; and I FIG. 6 is a diagrammatic side elevational view of the drum shown in FIG. 1 from the other side.

FIG. 1 shows diagrammatically the upper and lower portions of a tower 10 which may be like that shown in the Kuhns and Rizzone patent. A shaft 12 is journaled in suitable bearings (notshown) atzthe top of the tower and carries a pair of drums 13, only one of which is shown. The major portion of each drum is concentric with the. shaft. A first cable 14 extends around drum 13 and is attached to a vertically movable polished rod 15 at: the-top of a rod string. A secondv cable 16 extends around drum 13 and is attached to a counterbalance l7 whichtravels up and down within tower 10. A reversible drive means (not shown) is connected with shaft 12 to rotate the drums alternately in opposite directions, first clockwise as viewed in FIG. 1 to lower the rod string and raise the counterbalance and next counterclockwise to move the parts the other way. In common with the constructionshown inthe patent, both sides of the drum have eccentric. portions or ramps 19 which the

cables

14 and 16 meet near the ends of each downstroke and upstroke respectively of the rod string. In this form of the invention, the drums are symmetrical, and the two ramps on each are alike. FIG. 6 shows the ramp 19a for cable 16.

Inv accordance with our invention, we pivot a link 21 to the side face of the drum inwardly from the circumference. Shaft 12 also carries small drums 22 at each side of each drum l3.v We terminate the ramp 19 short of both the small drum 22 and the pivotal connection of link 21, whereby the link normally pivots inwardly toward the small drum in the space just beyond the end of the ramp, as FIG. 1 shows. We attach the end of cable 14 to the free end of link 21. Cable 16 is similarly attached to a link 21a at the other side of the drum as shown in FIG. 6.

During the major portion of each downstroke of the rod string, link 21 occupies the position shown in FIG. 1, and cable 14 extends therefrom around the ramp l9 and unwinds from the concentric portion of drum 13, while cable 16 winds on the concentric portion of the drum to raise the counterbalance 17. Near the end of each downstroke the drive means is disconnected from the shaft 12, and cable 14 unwinds from ramp 19. The rod string decelerates as the moment arm of cable 14 becomes progressively shorter, while the moment arm of cable 16 remains constant. The action thus far is similar to that described in the Kuhns and Rizzone patent.

As distinguished from the construction shown in the patent, cable 14 unwinds completely from the ramp 19. FIG. 2 shows the relation of the parts just after the cable has cleared the ramp and the pivotal axis of link 21 is in approximately the three-oclock position with respect to drum 13. Cable 14 is suspended from the drum via link 21, which has pivoted away from the small drum 22. Continued clockwise rotation of drum 13 carries the parts ultimately to the position shown in FIG. 3. All the while the rod string continues to decelerate, as the moment arm of cable 14 becomes shorter and shorter. The pivotal axis of the link reaches approximately the six-oclock position in which the link extends radially of the drum. The moment arm of cable 14 becomes effectively zero, and clockwise rotation of the drum ceases.

The weight of the counterbalance next acts through cable 16 to start rotating drum 13 counterclockwise for the ensuing upstroke of the rod string. Link 21 commences to pivot back toward the small drum 22 and cable 14 winds first on the ramp l9 and subsequently on the concentric portion of drum 13. After counterclockwise rotation is underway, the drive means is reconnected to shaft 12 to drive it in the opposite direction from before. The reversal at the end of the upstroke of the rod string is accomplished in like fashion; hence we do not repeat the description.

FIGS. 4 and show a modification in which the drums 25 are asymmetrical. FIG. 4 shows the drum from the side to which is connected the cable 14 leading to the rod string. We have omitted the ramp altogether from this side of the drum, although we could use a short-length ramp. We pivot a link 26 to the side of drum 25 adjacent the circumference. We rely on the link alone to shorten the moment arm of cable 14 as each downstroke of the rod string nears its end. The rod string is of considerable length and can readily stretch to overcome the abruptness with which the parts would otherwise stop. FIG. 5 shows drum 25 from the side to which is connected the cable 16 leading to the counterbalance'l7. This side of the drum has a relatively long ramp 27 and a link 28 pivoted at the end of the ramp, as in the first embodiment. The counterbalance does not stretch like the rod string; hence we need the ramp to decelerate the parts at the end of an upstroke of the rod string.

From the foregoing description it is seen that our invention affords a long stroke pumping unit which overcomes difficulties encountered with the unit shown in the Kuhns and Rizzone patent, yet retains all the advantages. Since the cables are attached to the drums through pivoted levers, they never become detached by reason of overrunning the ramps. Also the moment arms are effectively shortened to zero at the .end of each stroke.

We claim:

1. In a pumping unit which includes a tower, a drum rotatably supported on said tower, reversible drive means operatively connected with said drum, first and second cables connected to said drum for winding thereon or unwinding therefrom, a rod string attached to said first cable, and a counterbalance attached to said second cable whereby rotation of said drum unwinds one cable and winds the other and thus moves said rod string through downstrokes and upstrokes and simultaneously moves said counterbalance in the opposite direction from said rod string, the combination therewith of improved means connecting said cables to said drum and controlling forces which said cables exert on said drum at the conclusion of each stroke, said connecting means comprising links pivoted at one of their ends to opposite sides of said drum, said cables being attached respectively to the other ends of said links, said drum at the conclusion of a downstroke and an upstroke of said rod string rotating to positions in which said first cable and said second cable respectively unwind completely from said drum and have effectively zero moment arms opposing rotation of the drum to start the ensuing stroke in the opposite direction, said links hanging downwardly from their pivots when the cables to which they are attached unwind cogipletely from said drum.

. A combination as defined in claim 1 in which said drum has a ramp on at least one side, from which ramp said second cable unwinds as said rod string approaches the conclusion of an upstroke to shorten the moment arm of said second cable gradually.

3. A combination as defined in claim 2 in which said drum has ramps on both sides.

4. A combination as defined in claim 2 in which said drum is asymmetrical and has a ramp only on the side from which the second cable unwinds.

Claims

1. In a pumping unit which includes a tower, a drum rotatably supported on said tower, reversible drive means operatively connected with said drum, first and second cables connected to said drum for winding thereon or unwinding therefrom, a rod string attached to said first cable, and a counterbalance attached to said second cable whereby rotation of said drum unwinds one cable and winds the other and thus moves said rod string through downstrokes and upstrokes and simultaneously moves said counterbalance in the opposite direction from said rod string, the combination therewith of improved means connecting said cables to said drum and controlling forces which said cables exert on said drum at the conclusion of each stroke, said connecting means comprising links pivoted at one of their ends to opposite sides of said drum, said cables being attached respectively to the other ends of said links, said drum at the conclusion of a downstroke and an upstroke of said rod string rotating to positions in which said first cable and said second cable respectively unwind completely from said drum and have effectively zero moment arms opposing rotation of the drum to start the ensuing stroke in the opposite direction, said links hanging downwardly from their pivots when the cables to which they are attached unwind completely from said drum.

2. A combination as defined in claim 1 in which said drum has a ramp on at least one side, from which ramp said second cable unwinds as said rod string approaches the conclusion of an upstroke to shorten the moment arm of said second cable gradually.