Pumping unit

A pumping unit such as used on an oil well, the unit having a base, an upright sampson post supported on the base, a drum rotatably supported to the sampson post, the drum being rotatable about its horizontal axis, a lever arm pivoted to the base and in a direction to and away from the vertical sampson post, a weight arm pivotally affixed at one end to the upper end of the lever arm, a counterweight affixed to the outer end of the weight arm, a cable extending over the drum having one end secured to the lever arm and the other end hanging in a vertical position from the drum and adapted to be attached to pumping equipment such as an oil well polish rod, a gearbox driven crank arm connected by a pitman arm to the lever arm to pivot the lever arm back and forth towards and away from the sampson post to thereby cause the cable to reciprocate over the drum and a linkage connected to the weight arm to cause it to pivot as the lever arm is pivoted so that the counterweight reacts to offset the weight of pumping equipment attached to the cable.

SUMMARY OF THE INVENTION 
A pumping unit for use in pumping an oil well is provided. While the 
pumping unit may also be used for water wells, it is most particularly 
adapted for pumping oil wells which may be several thousand feet deep as 
compared to the relatively shallower depth of water wells. The pumping 
unit includes a base which is supported on the surface of the earth 
adjacent a well. Mounted on the base is a vertical sampson post, and 
affixed to the top of the sampson post is a drum, in the shape of a wheel, 
which is rotatable about a horizontal axis. A lever arm has a lower end 
pivotally secured to the base adjacent to but spaced away from the sampson 
post, the lever arm being pivotal in a vertical plane to and away from the 
sampson post. A cable is attached to the lever arm and extends over the 
drum and has an end portion which hangs vertically directly over the well 
to be pumped. The lower end of the cable is adapted to be affixed to 
pumping equipment such as a polish rod or the like. The pumping unit 
functions to raise and lower the cable vertically to cause the pumping of 
the well. 
Pivotally attached to the upper end of the lever arm is a weight arm which 
also pivots in a vertical plane. A counterweight is secured adjacent the 
outer end of the weight arm. A stiff arm is hinged at one end to the 
sampson post and at the other end to the weight arm so that as the lever 
arm is pivoted back and forth to and away from the sampson post the weight 
arm is pivoted relative to the lever arm to raise and lower the 
counterweight. A vector force generated by the counterweight is applied to 
the lever arm which in turn is applied to the cable so as to counteract 
and effectively balance the weight of the pumping equipment attached to 
the lower end of the cable. 
The pumping unit is actuated by a mechanism causing the lever arm to pivot 
back and forth to and away from the sampson post. This can be accomplished 
by means of crank arms extending from a gearbox supported on the base. The 
gearbox has a horizontal output shaft which rotates in response to power 
input to the gearbox which may be supplied by an electric motor or by an 
engine. Extending from the outer end of the crank arms are pitman arms 
connecting to the lever arm so that as the crank arms rotate the pitman 
arms are reciprocated back and forth to thereby pivot the lever arm and 
thus the cable to impart vertical pumping action to well pumping 
equipment.

DETAILED DESCRIPTION 
Many oil reservoirs when first penetrated by boreholes have a sufficient 
reservoir pressure to cause fluid therein to flow to the surface. However, 
after some length of time, which may be short or long depending on the 
nature of the reservoir, the pressure of the reservoir decreases to the 
point where fluid is not forced to the surface. Some reservoirs while 
containing large volumes of oil do not have sufficient pressure to force 
the oil to the surface. When oil exists in an underground reservoir and 
insufficient pressure exists to force it to the surface, some means must 
be provided to pump the oil from the reservoir to the earth's surface. 
There are many types of pumps in use, such as electric driven bottom hole 
centrifugal pump, gas lift pumps, etc.; however, the most commonly 
employed type of pumping unit for lifting oil from an underground 
reservoir to the earth's surface is that in which a vertically 
reciprocated pump is positioned in a tubing in the well with a string of 
sucker rods extending to the earth's surface and in which the sucker rods 
are vertically reciprocated to cause pumping action to pump the fluid to 
the earth's surface within the tubing. In the typical arrangement, at the 
surface of the well there is a stuffing box which closes off the tubing 
extending to the earth's surface and a polish rod is reciprocated in the 
stuffing box. A string of sucker rods are attached to the lower end of the 
polish rod, and these extend to a pump within the tubing at the bottom of 
the well. The apparatus which is used to vertically reciprocate the polish 
rod, and thereby the pumping equipment including the string of sucker rod 
and the bottom hole pump, is referred to in the oil industry as an 
"pumping unit". It is to this type of pumping unit that the present 
invention is directed. 
Many types of pumping units have been suggested, and as an indication of 
the state of the art, reference may be had to the following U.S. Pat. Nos. 
3,211,569; 2,054,655; 2,161,252; 1,979,803; 2,087,785; 3,208,291; and 
4,161,137. This list of patents is by no means exhaustive but is merely 
exemplary of other types of pumping units which have been suggested. 
One requirement of an effective pumping unit is that the total amount of 
energy employed to reciprocate the string of sucker rods in a well be as 
small as possible. In addition, the stress and strain on the pumping unit 
to reciprocate a long string of sucker rods and a column of fluid requires 
that some counterweight mechanism be provided to offset the weight of the 
pumping equipment. The present invention is particularly directed towards 
a type of pumping unit having an improved counterweight action to more 
effectively and efficiently offset the weight of pumping equipment and in 
an arrangement wherein effective pumping action is achieved. Another 
advantage of the present invention is that it provides a pumping unit in 
which a great variety of different lengths of pump strokes may be 
accomplished by rather simple mechanism adjustments while at the same time 
effective counterweight action is achieved. 
Referring first to FIG. 1, the earth's surface is indicated by the numeral 
10. Extending from the earth's surface is a casing 12 in an oil well. Out 
of the casing extends the upper end of a string of tubing 14 and at the 
top of the tubing is a stuffing box 16. Reciprocally received in the 
stuffing box 16 is a polish rod 18, the lower end of which is attached to 
a length of sucker rods (not shown) and at the lower end of the sucker 
rods there a pump is attached (not shown). By reciprocation of the polish 
rod 18, pumping action is achieved and oil, including oil mixed with 
water, is pumped from the subsurface formation and is caused to flow into 
a lead line 20 which connects to a tank battery (not shown) or other means 
of receiving and containing produced petroleum, or to equipment which 
separates the oil and water. A valve 22 is employed to close off the lead 
line 20. 
The elements described to this point are not part of the invention but are 
merely exemplary of typical pumping well to which the present invention is 
applied. The pumping unit which will now be described has the function of 
vertically reciprocating the polish rod 18 to achieve pumping action. The 
pumping unit includes a base 24 typically made of structural members 
resting on the earth's surface 10 adjacent the well casing 12. Supported 
on the front of the base is a vertical sampson post 26 which may be formed 
of a variety of structural members welded or bolted together. At the upper 
end of the sampson post a drum 28 is supported. The drum is positioned to 
rotate about its horizontal axis 30 and may be supported at the upper end 
of sampson post 26 by opposed pillow blocks 32. The drum 28 has a 
peripheral surface 28A adapted to receive a cable 34 thereover. The cable 
may be in the form of a single length cable or, as illustrated, a double 
cable, and the peripheral surface 28A may include grooves formed in the 
drum to receive the double cable. The pumping unit functions by 
reciprocating cable 34 so that the lower end portions 34A which hang 
vertically from drum 28 may be attached to the polish rod 18 by a polish 
rod clamp 36, an item not illustrated in detail but which is well known in 
the industry. 
Supported on the base 24 is a lever arm 38. The lower end is pivotally 
supported to the base such as by the means of pillow blocks 40A and 40B 
which support a horizontal shaft 42 received by the lower end of the lever 
arm. The upper end of the lever arm 38 has attached to it a weight arm 44 
such as by means of a pin 46. Thus the lever arm 38 is pivotal in a 
vertical plane back and forth towards and away from the sampson post 26; 
and in like manner, the weight arm 44 is pivotal in a vertical plane 
relative to the upper end of the lever arm. 
Secured to the outer or lower end of weight arm 44 is a counterweight 48. 
The position of the counterweight on the weight arm 44 may be varied as 
well as the total amount of the weight by means which is typically 
employed in the manufacture of pumping units. 
A cross member 50 is affixed to the sampson post and is supported in a 
horizontal plane. Extending from base 24 to the outer ends of the cross 
member are braces 52A and 52B. Pivotally attached to cross member 50 is a 
stiff arm 54. In the illustrated arrangement the stiff arm 54 consists of 
two parallel members 54A and 54B. Each is pivotally attached to cross 
member 50 by means of a pillow block or similar type bearing arrangement 
56 so that the inner ends of the stiff arms 54A and 54B pivot about a 
horizontal shaft 58. The outer ends of the stiff arms are attached to the 
weight arm 44 by means of a shaft 60. The shaft 60 is in a horizontal 
plane and is bolted to the weight arm 44 so that it can be easily attached 
to different positions of the weight arm. In this way the geometry of the 
weight arm can be effectively adjusted so that the action of the 
counterweight can be varied as necessary to most effectively function to 
counterbalance the weight of the pumping equipment attached to polish rod 
18. In this manner the pumping unit can be adjusted so as to apply a 
substantially constant load on the prime mover utilized to apply energy to 
the pumping unit which will be described subsequently. 
The pumping unit of this invention is particularly adaptable to various 
adjustments. In addition to changing the amount and position of weight 48 
and the point of attachment of the stiff arms to the weight arm 44 to 
change the geometry of action of the counterweight, the length of stroke 
applied to cable 34, and thereby to polish rod 18, may be easily adjusted 
by changing the position of the point of attachment of cable holder 62 to 
the lever arm 38. The cable holder 62 is preferably bolted to the arm 38 
so that it can be moved up and down to various positions as shown in 
dotted outline in FIG. 1. In a preferred arrangement the cable holder 
includes an extension portion 64 which is pivotally secured to the cable 
holder by means of a pin 66. The extension 64 includes a portion which 
receives a loop of the cable 34 so that the cable is in effect doubled, as 
shown in FIGS. 2 and 3, with both ends being attached to the polished rod 
clamp 36. 
The pumping unit can be fabricated primarily of readily available 
structural members such as H beams, channels, T beams, etc. For instance, 
the sampson post 26 can very effectively formed of two spaced apart 
channel members indicated by the letters 26A and 26B in FIGS. 2 and 3 with 
bracing therebetween. To help support the sampson post 26 in the vertical 
position, lateral braces 68A and 68B may be employed. While the components 
of the invention may be constructed in a variety of ways, the invention is 
not directed to such structural details but is directed towards the basic 
concepts of the elements as exemplified in the drawings regardless of the 
particular manner in which they are formed. 
Positioned on base 24 is a gearbox 70 of a type commonly employed on oil 
well pumping units. The gearbox 70 receives input energy to a sheave 72 
connected to a drive shaft 74. By means of gears (not shown) within the 
gearbox 70 speed reduction of the drive shaft 74 is accomplished to drive 
an output shaft 76 which extends in a horizontal plane and to both sides 
of the gearbox. Attached to the opposite ends of drive shaft 76 are crank 
arms 78A and 78B. Pivotally attached to the outer end of the crank arms 
78A and 78B are pitmans 80A and 80B. The outer ends of the pitmans 80A and 
80B are pivotally attached to the lever arm 38 by means of an equalizer 
bar 82. In this manner both the inner and outer ends of the pitmans 80A 
and 80B are supported by bearings. The point of attachment of the 
equalizer bar 82 may be varied up and down on the lever arm so that the 
pumping action of the unit may be adjusted. The length of stroke of the 
pumping unit may be adjusted in this manner as well as by the adjustment 
of the point of attachment of the cable holder 62. 
To provide prime energy to drive the pumping unit an electric motor 84 is 
mounted on base 24 having an output shaft 86 and sheave 88 driving the 
belt 90 which in turn drives the gearbox sheave 72. Motor 84 is exemplary 
and may be replaced by an engine or other prime mover source. 
The pumping unit illustrated and described herein provides an effective and 
economically constructed device for producing vertical reciprocal motion 
to the polish rod 18 to actuate pumping equipment in a well. The pumping 
unit is unique in the great flexibility of arrangements by which the 
length of the pumping unit stroke may be varied and in the geometrical 
action of the coupling of the drive energy to produce reciprocal action so 
as to enable an operator to "fine tune" the pumping unit to the particular 
stroke length and weight of pumping equipment so that the energy required 
by prime mover 84 is substantially constant. In addition, by the 
adjustable features of the pumping unit the shock load placed on the 
gearbox 70, and thus on the prime mover, can be minimized so that the wear 
and tear on these items of equipment are reduced to ensure a longer useful 
life. 
While the invention has been described with a certain degree of 
particularity, it is manifest that many changes may be made in the details 
of construction and the arrangement of components without departing from 
the spirit and scope of this disclosure. It is understood that the 
invention is not limited to the exemplified embodiments set forth herein 
but is to be limited only by the scope of the attached claim or claims, 
including the full range of equivalency to which each element thereof is 
entitled.