US3144778A

US3144778A - Pumping unit with improved flexibly connected beam

Info

Publication number: US3144778A
Application number: US185267A
Authority: US
Inventors: Lott John Edward
Original assignee: AMERICAN Manufacturing CO OF TEXAS
Current assignee: AMERICAN Manufacturing CO OF TEXAS
Priority date: 1962-04-05
Filing date: 1962-04-05
Publication date: 1964-08-18
Anticipated expiration: 1981-08-18

Description

Aug. 18, 1964 J. E. LOTT 3,144,778

PUMPING UNIT WITH IMPROVED FLEXIBLY CONNECTED BEAM Filed April 5, 1962 a Sheets-Sheet 1 JOHN EDWARD LOTT INVENTOR A T TORNE Y Aug. 18, 1964 J. E. LOTT 3,144,778

PUMPING UN IT WITH IMPROVED FLEXIBLY CONNECTED BEAM Filed April 5, 1962 3 Sheets-Sheet 2 FIG. 7. FIG. 1/.

JOHN EDWARD LOTT INVENTOR ATTORNEY Aug. 18, 1964 J. E. LOTT 3,144,778

PUMPING UNIT WITH IMPROVED FLEXIBLY CONNECTED BEAM Filed April 5, 1962 5 Sheets-Sheet 3 FIG. I3.

FIG. I4.

JOHNEDWARD LOTT INVENTOR ATTORNEY United States Patent PUMPING UNIT WITH TMPROVED FLEXIBLY CONNECTED BEAM John Edward Lott, Fort Worth, Tex., assignor to American Manufacturing Company of Texas, Fort Worth, Tex., a corporation of Texas Filed Apr. 5, 1962, Ser. No. 135,267 1 Claim. ((31. 74-41) This invention relates to well pumping units and has reference to an improved spring linkage between the walking beam and the speed reducer. This application is a continuation in part of my copending application, Serial No. 158,518, filed December 11, 1961, now US. Patent No. 3,109,313, which issued November 5, 1963.

The referred to copending application is directed to a 100% geometrically efiicient unit operable in either direction of rotation of the cranks. Generally, the construction of the copending application is comprised of a spring linkage connected with the extending end of the pitmans and coactive with an arcuate surface on the oscillating walking beam. The are of said surface is generated about the axial center of the saddle bearing. While such construction provides 100% geometric efficiency, this linkage, by selecting a fixed direction of rotation of the cranks, can be arranged to effectively reduce the torque variations at the speed reducer. Generally, such reduction of torque variation is accomplished by canting the arc of the rear mule head and thereby favoring the power source by reason of the inherent geometry of the linkage. A longer lever arm is provided during the up stroke when the well load is at its maximum, and a shorter lever arm is provided on the down stroke to aid the lifting of the counterbalance weight.

Accordingly, an object of the invention is to provide a pumping unit wherein torque variations are reduced at the speed reducer by effectively providing a longer lever arm during the up stroke and an effectively shorter arm during the down stroke.

Additional objects include the elimination of certain wearing parts such as the tail bearing, oil seals and flexible lubrication lines.

These and other objects will become apparent from the following description and the accompanying drawings, wherein:

FIGURE 1 is a side elevational view of a pumping unit in accordance with the invention.

FIGURE 2 is an end elevational view of FIGURE 1.

FIGURE 3 is a fragmentary perspective view of the flexible connection of the pitmans with the rear mule head.

FIGURES 4 through 11 are schematic views illustrating one complete revolution of the cranks and show the directions of forces applied to the walking beam by the pitmans.

FIGURES 12 through 15 are also schematic views and illustrate the application of certain formulas hereinafter referred to.

The pumping unit illustrated is conventional with respect to its general construction and includes a base 10, a samson post 11 and a walking beam 12 mounted on the samson post by means of a saddle bearing 13. At the forward end of the walking beam 12 there is a mulehead 14, herein referred to as the forward mulehead, bridle 15 which is attached to the polished rod 16 by a grip 17.

4 3,144,778 Patented Aug. 18, 1964 "ice Mounted on a conventional speed reducer 18 there is a drive pulley 19 on a driven shaft 20 and also a double pitman crank 21 on the crank shaft 22. The pitmans 23 are attached to the cranks 21 by wrist pins 24. Counterweights 25 are mounted on the cranks 21 in the usual manner.

A mulehead 26 with an arcuate bearing plate 27 integral with its body 28 is mounted on the rear end of the walking beam 12 so that its arcuate surface is concentric with a point or points near the saddle bearing 13. As hereinafter described, the purpose of the bearing plate 27 is to make the rear mulehead 26 wider than a conventional mulehead, such as the forward mulehead 14.

A clamp 29 with bolts 30 threaded intothe bearing plate 27 at its upper end provides an attachment for depending spring steel actuating plates 31 perforated at their upper ends to receive the bolts 30. The plates 31 are in side-by-side relation, but a single plate, not shown, may be employed. The plates 31 are similarly perforated at their lower ends to receive other bolts 32 by means of which the plates are clamped between the two halves of an equalizer beam 33 which connects the two pitmans at their upper ends. The equalizer beam 33 could be combined with the two pitmans 23 into a solid inverted U-shaped member, but in order to relieve stresses created by slight misalignments of the cranks it has been found to be advantageous to connect the equalizer beam 33 to the pitmans by means of spring steel plates 34 held to the ends of the equalizer beam 33 by clamps 35 and bolts 36 through matching holes in the plates, and likewise to the upper ends 37 of the pitmans 23 by bolts 38 through holes in the lower ends of the plates 34.

The arcuate surface of the bearing plate 27 is generated about a point 39, or multiple of points, not shown, above the axis of the saddle bearing 13 as indicated by the dash line arrow 40. Thus, the rear mulehead 28 is canted downwardly and inwardly relative to the saddle bearing 13, whereas the forward mulehead 14 has its arcuate surface generated about the axis of said bearing in the usual manner. As will become apparent, when the rear mulehead 28 is so canted, it is necessary that the cranks 21 rotate counterclockwise as viewed in FIGURE 1. In FIGURE 1 the arrow lines 41 and 42 indicate the extreme inclination of the walking beam 12 at the ends of the pumping stroke.

In the operation of the pumping unit, schematically illustrated in FIGURES 4-11, inclusive, which show progressively one complete revolution of the crank 21, it is apparent that during the downstroke of the pitman 23, which is equal to the lift of the polished rod 16, the effective lever arm of the walking beam 12, indicated by the arrow line 43, is substantially longer than the lever arm on the upstroke indicated by arrow line 44 in FIGURE 10. This gives the power source a mechanical advantage during that part of the cycle requiring the greater effort.

This difierence results also in a slower lift stroke on the pump and a faster return stroke which improves the operation of the pump and reduces wear. Further, it can be seen from the diagrams that the direction of the force exerted by the pitman 23 during its downstroke is approximately normal to the theoretical lever arm 43 for a large part of the cycle as shown by its closely parallel relation to the perpendicular 45.

On the other hand, during the upstroke of the pitman 21, if it were pivotally connected in the conventional manner to give the same mechanical advantage in the downstroke as shown in FIGURES 4-7, it would make the very disadvantageous angle :1 (FIGURE with the lever arm 43 instead of the advantageous angle b with the theoretical lever arm 4-4 which results when the canted mulehead 26 is employed.

The advantage gained by the use of the canted rear mulehead 26 is further proven by the following formulas applied to FIGURES 12 to 15, inclusive, in which FIG- URE 12 represents the unit with the canted mulehead on the upstroke of the pitman and FIGURE 13 represents the same unit on the downstroke of the pitman.

IN FIGURE 12 Dowlzstroke PT 11 (F YR) F --U D CB P1 P1 R 2E1 IN FIGURE 13 U pstroke EQUATING PTU=PTD Now assume following well conditions, and solve for counterbalance and peak torque:

= 8600 X 24 06,400 in lbs.

UNIT PEAK TORQUE Downstroke PT =206,400 [6000 XggJQi 205,400 1 72,800 33,500 in lbs.

Upstroke PT :10,000 X 24206,400=33,600 in lbs.

Applying similar formulas to FIGURES l4 and 15, representing conventional unit having corresponding dimensions, but in which a rigid pitman 46 is pivotally attached to the walking beam, We have:

PT= [10300-8000]? ECB= 6000+ 2000=8000# in lbs. (Upstrolre or downstroke) Thus, by comparison, the invention requires only approximately of the power required for a comparable conventional pumping unit. Additionally, a smaller and therefore less expensive speed reducer may be used.

The invention is not limited to the construction herein shown and described, but may be made in various ways within the scope of the appended claim.

What is claimed is:

In a beam type pumping unit:

a beam pivotally mounted for oscillation in a vertical plane,

forward and rear muleheads mounted on the ends of said beam, said muleheads having outer generally vertical arcuate surfaces, the arcuate surface of said rear mulehead being generated about at least one point above the axis of oscillation of said beam,

a crank beneath said rear mulehead, said crank having an extending end rotatable about the remaining end, said crank rotating in a direction such that said extending end moves upwardly when on the side of rotation adjacent said forward mulehead,

a pitman journalled on the extending end of said crank and extending upwardly therefrom, and

flexible means connected at the upper end of and extending over the arcuate surface of said rear mulehead and connected with the upper end of said pitman.

References Cited in the file of this patent UNITED STATES PATENTS 1,888,530 Goble Nov. 22, 1932 1,945,774 Goble Feb. 6, 1934 3,005,353 Gallaway Oct. 24, 1961