Note: Descriptions are shown in the official language in which they were submitted.
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1 SLANT HOLE PUMPING UNIT
2 Background of the Invention
3
4 1. Field of the Invention.
The present invention relates generally to well head pumping units and in
6 particular to a pumping unit with a constrained bridle strap.
7
8 1. Descriution of the Prior Art.
9 Well head pumping units are placed over wells for operating down-hole pumps
to whereby oil, water, etc. are extracted and brought to the earth's surface.
The Pauls U.S.
11 Patent No. 4,631,970 discloses a pumping unit with a bridle strap
connecting the drive
12 system thereof with a rod string. The flexible bridle strap transfers the
reciprocating
13 motion of the pumping unit drive system to a vertically reciprocating
motion of the rod
14 string. However, the equalizer beam which connects the drive system to the
bridle strap
assembly in this pumping unit is unconstrained. Thus, the equalizer beam can
damage
16 other components of the pumping unit if tension is released, e.g., if the
rod string breaks.
17 The pumping unit shown in the aforementioned Pauls '970 patent is designed
to equally
1 s divide the rotation of the drive system between the upstroke and
downstroke of the rod
19 string, i.e. 180°/180°. However, in many applications
different upstroke/ downstroke
2o ratios are preferred. For example, relatively high viscosity oil and/or
slant hole
21 applications often necessitate a slower downstroke in order to maintain
tension on the
22 bridle strap assembly.
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The present invention addresses the shortcomings
of the prior art. Heretofore there has not been available a
slant hole pumping unit with the advantages and features of
the present invention.
Summary of the Invention
In the practice of the present invention, a slant
hole pumping unit is provided which includes a base, a
support structure mounted on the base and a drive system
mounted on the support structure. Crank arms are driven by
the drive system and are connected to a bridle strap
assembly through a pitman arm assembly. The bridle strap
assembly is also connected to a rod string. A post assembly
includes a lower end mounted on the base and the support
structure and an upper end mounting a post strap guide. A
constraint link includes a lower end pivotally connected to
the base and an upper end engaging the bridle strap assembly
for constraining the movement thereof through a pivotal arc
defined by the bridle strap assembly.
According to an aspect of the invention, there is
provided a well head pumping unit, which comprises: (a) a
base; (b) a support structure mounted on the base and
extending upwardly therefrom; (c) a drive system mounted on
the support structure; (d) a crank arm connected to the
drive system and rotatable thereby; (e) a pitman arm
assembly pivotally connected to the crank arm; (f) a post
assembly with a lower end connected to the base and an upper
end; (g) a strap guide mounted on said post assembly upper
end; (h) a strap assembly with a distal end adapted for
connection to a rod string and a proximate end; (i) a
constraint link assembly with a lower end pivotally
connected to said base and an upper end, said constraint
link assembly being connected to said pitman arm assembly
2
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distal end in spaced relation from said constraint link
assembly lower end; (j) said constraint link assembly
engaging said strap assembly in spaced relation from said
constraint link assembly lower end; (k) said constraint link
assembly having a constraint link strap guide engaging said
strap assembly; and (1) said strap assembly proximate end
being connected to said base.
Objects and Advantages of the Invention
The principal objects and advantages of
embodiments of the present invention include: providing a
pumping unit for well head applications; providing such a
pumping unit which is adapted for slant hole pumping
applications; providing such a pumping unit which constrains
movement of a bridle strap; providing such a pumping unit
which permits adjustment of the upstroke and downstroke
portions of a drive system cycle; providing such a pumping
unit which can increase reliability in the field; and
providing such a pumping unit which is economical to
manufacture, efficient in operation and particularly well
adapted for the proposed usage thereof.
Other objects and advantages of embodiments of
this invention will become apparent from the following
description taken in conjunction with the accompanying
drawings wherein are set forth, by way of illustration and
example, certain embodiments of this invention.
The drawings constitute a part of this
specification and include exemplary embodiments of the
present invention and illustrate various objects and
features thereof.
3
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Brief Description of the Drawings
Fig. 1 is a side elevational view of a pumping
unit embodying the present invention.
Fig. 2 is a side elevational view of the pumping
unit showing upstroke positions thereof.
Fig. 3 is a side elevational view of the pumping
unit showing downstroke positions thereof.
Fig. 4 is a side elevational view showing a
comparison of constrained and unconstrained equalizer beam
paths of movement and positions.
Fig. 5 is a side elevational view of a constraint
link assembly of the pumping unit.
Fig. 6 is a front elevational view of the
constraint link assembly.
Fig. 7 is a side elevational view of the pumping
unit shown mounted on a trailer in an operating position
thereof.
Fig. 8 is a side elevational view of the pumping
unit shown mounted on a tractor trailer unit in a transport
position thereof.
Fig. 9 is a side elevational view of a pumping
unit comprising a first modified embodiment of the present
invention.
Fig. 10 is a side elevational view of a pumping
unit comprising a second modified embodiment of the present
invention.
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Detailed Description of the Preferred Embodiments
I. Introduction and Environment
As required, detailed embodiments of the present
invention are disclosed herein; however, it is to be
understood that the disclosed embodiments are merely
exemplary of the invention, which may be embodied in various
forms. Therefore, specific structural and functional
details disclosed herein are not to be interpreted as
limiting, but merely as a basis for the claims and as a
representative basis for teaching one skilled in the art to
variously employ the present invention in virtually any
appropriately detailed structure.
Referring to the drawings in more detail, the
reference numeral 2 generally designates a pumping unit
embodying the present invention. The pumping unit 2 uses a
bridle strap assembly 24 and other components which are
similar to those shown in U.S. Patent No. 4,631,970.
II. Pumping Unit 2
The pumping unit 2 includes a base 4 which mounts
a support structure 6 extending upwardly therefrom. The
support structure mounts a drive system 8 with
counterweights 7. The drive system 8 rotates a pair of
crank arms 10. A pair of pitman arms 12 have proximate ends
12a connected to the crank arms 10 and distal ends 12b. The
base can be supported on any suitable foundation, such as
the piers 5. The base can also comprise or be mounted on a
vehicle, such as a trailer or truck bed.
A post assembly 14 includes a length-adjustable
rear post leg 16 with a proximate end 16a pivotally
connected to the support structure 6 and a distal end 16b.
4a
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The post assembly 14 also includes a front post leg 18 with
a proximate end 18a pivotally connected to the base 4 in
proximity to a base front 4a and a distal end 18b. The post
leg
4b
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1 distal ends 16b, 18b mount a strap guide assembly 20 which comprises a
roller 22
2 rotatable on a horizontal, transverse rotational axis. A bridle strap
assembly 24 includes
3 proximate and distal ends 24a,b and is placed over the roller 22.
A constraint link assembly 26 includes a lower end 26a pivotally mounted on
the
base 4 adjacent to its front end 4a and an upper end 26b pivotally connected
to the pitman
6 arm distal ends 12b and to the bridle strap assembly proximate end 24a. The
constraint
7 link assembly 26 has a generally triangular configuration as shown in Fig. 6
with a pair of
8 side members 26c, a equalizer beam 26d at its upper end 26b and a brace 26e
extending
9 between and connected to the side members 26c.
11 II. Operation
12 In operation, the pumping unit 2 functions in a manner similar to the
pumping unit
13 disclosed in U.S. Patent No. 4,631,970, except that the constraint link
assembly 26
14 constrains the equalizer beam 26d to a predetermined arc of movement 28
defined by the
pivoting motion of the constraint link assembly 26. Fig. 4 shows an equalizer
beam 26d
16 path of movement describing an arc 28 when constrained by the constraint
link assembly
1'7 26 with various equalizer beam 26d positions designated 26p. Positions of
the equalizer
18 beam 26d if it were not so constrained are designated 26p'.
19 By adjusting the length and end locations of the constraint link assembly
26 with
respect to the other components of the pumping unit 2, a variety of stroke
profiles can be
21 accommodated for particular applications. In particular, the division
between upstroke
22 and downstroke can be adjusted to ratios of, such as
208°/152°. For example, lower
23 upstroke speeds may be desirable to reduce power requirements and reduce
the
24 acceleration forces on the rod string. The downstroke can have a faster
speed, which
increases the leverage of the counterweights 7 and reduces the counterbalance
weight
26 required on the crank arm to achieve the necessary counterbalance effect on
the rod
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1 string.
2 Faster upstroke and slower downstroke can be accomplished by reversing the
3 rotational direction of the crank arms 10. Such operating characteristics
may be desirable
4 to compensate for relatively slow rod string fall (downstroke) speed, which
can result
from relatively high viscosity liquids (e.g., oil) being pumped or a slant
hole well
6 configuration.
'7 The pumping unit 2 can be mounted on a trailer 30b of a tractor-trailer rig
30 for towing
8 by a tractor unit 30a. (Figs. 7 & 8).
9
l0 II. First Modified Embodiment Pumping Unit 102
11 A first modified embodiment pumping unit 102 is shown in Fig. 9 and
includes
12 the bridle strap assembly proximate end 24a being connected to the base 4
with the
13 equalizer beam 26d functioning as a constraint link assembly guide roller.
Greater stroke
14 length, i.e. up to twice the crank arm swing diameter, can be achieved with
this
configuration.
16
17 II. Second Modified Embodiment Pumping Unit 202
18 Fig. 10 shows a pumping unit 202 comprising a second modified embodiment of
19 the present invention wherein the pitman arm distal ends 12b are connected
to the
2o constraint link assembly 26 intermediate its lower and upper ends 26a,b.
Stroke
21 amplification is thus achieved based upon a ratio defined by the placement
of the bridle
22 strap assembly proximate end 24a with respect to the constraint link
assembly lower and
23 upper ends 26a,b. In this configuration the second modified embodiment
pumping unit
24 202 functions as a four bar linkage system.
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It is to be understood that while certain forms of the present invention have
been
2 illustrated and described herein, it is not to be limited to the specific
forms or
3 arrangement of parts described and shown.
4
7
