U.S. patent application number 12/642006 was filed with the patent office on 2010-06-24 for suction port lock nut with stub buttress threads.
This patent application is currently assigned to WEIR SPM, INC.. Invention is credited to John E. Hawes, Mark D. Matzner.
Application Number | 20100158727 12/642006 |
Document ID | / |
Family ID | 42266398 |
Filed Date | 2010-06-24 |
United States Patent
Application |
20100158727 |
Kind Code |
A1 |
Hawes; John E. ; et
al. |
June 24, 2010 |
Suction Port Lock Nut With Stub Buttress Threads
Abstract
A reciprocating pump assembly having a block body, a cylinder
chamber in the block body, a plunger reciprocatingly disposed in
the block body, an opening in the block body adjacent the cylinder
chamber, and a cover plate in the opening. Threads on the outer
periphery of the cover plate engage threads formed within the
opening. The threaded outer periphery of the cover plate extends
into the cylinder chamber and past the threaded portion of the
opening so that the load on the cover plate transfers from fully
formed threads on the cover plate to threads formed on the
opening.
Inventors: |
Hawes; John E.; (Southlake,
TX) ; Matzner; Mark D.; (Burleson, TX) |
Correspondence
Address: |
BRACEWELL & GIULIANI LLP
P.O. BOX 61389
HOUSTON
TX
77208-1389
US
|
Assignee: |
WEIR SPM, INC.
Fort Worth
TX
|
Family ID: |
42266398 |
Appl. No.: |
12/642006 |
Filed: |
December 18, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61138776 |
Dec 18, 2008 |
|
|
|
Current U.S.
Class: |
417/521 ;
417/437 |
Current CPC
Class: |
F04B 39/125 20130101;
F04B 39/121 20130101; F04B 53/16 20130101 |
Class at
Publication: |
417/521 ;
417/437 |
International
Class: |
F04B 19/00 20060101
F04B019/00; F04B 1/00 20060101 F04B001/00 |
Claims
1. A reciprocating pump assembly comprising: a block body; a
cylinder chamber in the block body; a plunger reciprocatingly
disposed in the block body; an opening in the block body adjacent
the cylinder chamber; threads formed in the opening; a cover plate
in the opening; and a threaded surface on the outer periphery of
the cover plate engaging the threads formed within the opening and
projecting within the block body past the threads on the
opening.
2. The reciprocating pump assembly of claim 1, wherein the threaded
surface on the cover plate includes at least two unloaded threads
that project within the block body past the threads in the
opening.
3. The reciprocating pump assembly of claim 1, wherein the threaded
surfaces on the cover plate comprises a length of loaded threads
that engage the threads in the opening, and a length of unloaded
threads that project within the block body past the threads in the
opening and the length of loaded threads is greater that the length
of the unloaded threads.
4. The reciprocating pump assembly of claim 1, wherein the threaded
surface on the outer periphery of the cover plate includes threads
having a root portion with a curved profile.
5. The reciprocating pump assembly of claim 1, wherein the threaded
surface on the outer periphery of the cover plate comprises a
British Butt threads.
6. The reciprocating pump assembly of claim 1, wherein the threaded
surface on the outer periphery of the cover plate includes threads
having a thread depth that is from about 60% to about 70% of the
thread pitch.
7. The reciprocating pump assembly of claim 1, wherein the threaded
surface on the outer periphery of the cover plate includes threads
having a truncated crest.
8. The reciprocating pump assembly of claim 3, wherein at least
some of the unloaded threads are substantially identical to the
loaded threads.
9. The reciprocating pump assembly of claim 1, wherein the threaded
surface on the outer periphery of the cover plate includes threads
having a rear flank disposed along a path oriented at an angle of
about 45.degree. with respect to the angle of the cover plate
axis.
10. A reciprocating pump assembly comprising: a cylinder block;
cylinder chambers formed in the block; a plunger reciprocatingly
disposed in each cylinder chamber; circular openings in the block
at an end of each chamber; a thread formed in the openings; cover
plates, each having a thread formed on their outer circumference,
at least a portion of the length of the thread being fully formed
and at a maximum depth, the cover plates coaxially coupled into
each opening so that the maximum depth portion of each cover plate
thread engages the portion of each thread in the openings proximate
the ends of each chamber; and part of the maximum depth portion of
each cover plate thread being out of engagement with and further
inward from the thread in the opening.
11. The reciprocating pump assembly of claim 10, wherein an axial
length of the thread in the openings, relative to an axis of the
opening, is less than an axial length of each cover plate
thread.
12. The reciprocating pump assembly of claim 11, wherein when in a
secured position, an outer end of each cover plate thread is
substantially flush with an outer end of the thread in the
opening.
13. The reciprocating pump assembly of claim 10, further comprising
a smooth cylindrical portion in each opening joining an inner end
of the thread in the opening and wherein part of maximum depth
portion of each cover plate thread is located within the smooth
cylindrical portion.
14. The reciprocating pump assembly of claim 10, wherein the
threaded surface on the outer periphery of the cover plate includes
buttress threads having a truncated crest and rounded root.
15. A pump assembly comprising: a block body; a cylinder chamber in
the block body; a plunger reciprocatingly disposed in the block
body; an opening in the block body adjacent the cylinder chamber;
threads formed in the opening; a cover plate in the opening; a
threaded surface on the outer periphery of the cover plate engaging
the threads formed within the opening and having at least two
unloaded threads projecting within the block body past the threads
on the opening, and a length of loaded threads that exceeds the
length of the unloaded threads.
16. The pump assembly of claim 15, wherein the threads on the cover
plate comprise British Butt threads.
17. The pump assembly of claim 15, wherein the threads on the cover
plate have a truncated crest.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of
co-pending U.S. Provisional Application Ser. No. 61/138,776, filed
Dec. 18, 2008, the full disclosure of which is hereby incorporated
by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates in general to reciprocating
pumps and, in particular, to an improved apparatus for a locking
nut in a reciprocating pump.
DESCRIPTION OF RELATED ART
[0003] In oil field operations, reciprocating pumps are often used
for various purposes. Some reciprocating pumps, generally known as
"service pumps," typically pump service fluids used for downhole
operations such as cementing, acidizing, or fracing a well. These
service pumps may typically operate for relatively short periods of
time, but on a frequent basis such as several times a week. Often
they are mounted to a truck or a skid for transport to various well
sites.
[0004] The oil field reciprocating pumps typically include a
plunger that reciprocates within a cylinder for pumping fluid
through a cylinder. The cylinder generally includes a fluid inlet
and a fluid outlet. An opening in the pump provides access to an
interior of the cylinder. The opening is typically sealed with a
threaded suction cover that can be removed from the cylinder.
SUMMARY OF THE INVENTION
[0005] Disclosed herein is reciprocating pump assembly that
includes a block body, a cylinder chamber in the block body, a
plunger reciprocatingly disposed in the block body, an opening in
the block body adjacent the cylinder chamber, threads formed in the
opening, a cover plate in the opening, and a threaded surface on
the outer periphery of the cover plate engaging the threads formed
within the opening and projecting within the block body past the
threads on the opening. The threaded surface on the cover plate may
include at least two unloaded threads that project within the block
body past the threads in the opening. The threaded surfaces on the
cover plate can have a length of loaded threads that engage the
threads in the opening, and a length of unloaded threads that
project within the block body past the threads in the opening and
the length of loaded threads is greater that the length of the
unloaded threads. The threaded surface on the outer periphery of
the cover plate can include threads having a root portion with a
curved profile. The threaded surface on the outer periphery of the
cover plate may have British Butt threads. The threaded surface on
the outer periphery of the cover plate can include threads having a
thread depth that is from about 60% to about 70% of the thread
pitch. The threaded surface on the outer periphery of the cover
plate can include threads having a truncated crest. At least some
of the unloaded threads can be substantially identical to the
loaded threads. The threaded surface on the outer periphery of the
cover plate may include threads having a rear flank disposed along
a path oriented at an angle of about 45.degree. with respect to the
angle of the cover plate axis.
[0006] Also described is a reciprocating pump assembly that
includes a cylinder block, cylinder chambers formed in the block, a
plunger reciprocatingly disposed in each cylinder chamber, circular
openings in the block at an end of each chamber, a thread formed in
the openings, and cover plates. Where each cover plate has a thread
formed on its outer circumference, at least a portion of the length
of the thread being fully formed and at a maximum depth, the cover
plates coaxially coupled into each opening so that the maximum
depth portion of each cover plate thread engages the portion of
each thread in the openings proximate the ends of each chamber.
Part of the maximum depth portion of each cover plate thread can be
out of engagement with and further inward from the thread in the
opening.
[0007] In an optional embodiment, a pump assembly is described
having, a block body, a cylinder chamber in the block body, a
plunger reciprocatingly disposed in the block body, an opening in
the block body adjacent the cylinder chamber, threads formed in the
opening, a cover plate in the opening, a threaded surface on the
outer periphery of the cover plate engaging the threads formed
within the opening and having at least two unloaded threads
projecting within the block body past the threads on the opening,
and a length of loaded threads that exceeds the length of the
unloaded threads.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a side perspective view of a reciprocating pump in
accordance with the present disclosure.
[0009] FIG. 2 is a side partial sectional view of the pump of FIG.
1.
[0010] FIG. 3 is an enlarged side sectional view of a portion of
the valve stop assembly of FIG. 2.
[0011] FIG. 4 is a side sectional view of a retainer nut of the
valve stop assembly of FIG. 3.
[0012] FIG. 5 is an enlarged sectional view of a threaded portion
of the retainer nut.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The apparatus and method of the present disclosure will now
be described more fully hereinafter with reference to the
accompanying drawings in which embodiments are shown. This subject
of the present disclosure may, however, be embodied in many
different forms and should not be construed as limited to the
illustrated embodiments set forth herein; rather, these embodiments
are provided so that this disclosure will be thorough and complete,
and will fully convey the scope of the invention to those skilled
in the art. Like numbers refer to like elements throughout. For the
convenience in referring to the accompanying figures, directional
terms are used for reference and illustration only. For example,
the directional terms such as "upper", "lower", "above", "below",
and the like are being used to illustrate a relational
location.
[0014] It is to be understood that the subject of the present
disclosure is not limited to the exact details of construction,
operation, exact materials, or embodiments shown and described, as
modifications and equivalents will be apparent to one skilled in
the art. In the drawings and specification, there have been
disclosed illustrative embodiments of the subject disclosure and,
although specific terms are employed, they are used in a generic
and descriptive sense only and not for the purpose of
limitation.
[0015] A reciprocating pump assembly 10 is illustrated in FIG. 1 in
a side perspective view. The assembly 10 includes a pump section 12
coupled to a fluid cylinder portion 11. A crankshaft housing 13 is
shown covering the pump section 12 and shielding its components. A
plunger or plunger rod 16 assembly is shown projecting from a side
of crankshaft housing 13 to the cylinder section 11. Stay rods 15
adjacent the rod assembly 16 anchor the cylinder section 11 to the
pump section 10. The cylinder section 11 includes a cylinder block
17 having multiple cylinder chambers 39 (shown in dashed outline).
Each cylinder chamber 39 is shown herein in alternating fluid
communication with a fluid inlet 19 and a fluid outlet 21. Each
cylinder chamber 39 end is capped with a suction cover plate 22. An
opening 18 is formed in the cylinder block 17 configured to receive
a cover plate 22. The pump assembly 10 can easily be mounted to a
trailer that can be towed between operational sites, or to a skid
such as for offshore operations.
[0016] Referring now to FIG. 2, an example of the pump assembly 10
is illustrated in a side sectional view. In this example, a plunger
35 is shown reciprocatingly disposed within one of the cylinder
chambers 39. Although a single plunger 35 is illustrated, each
cylinder chamber 39 may include a corresponding plunger 35. Each
cylinder chamber 39 and plunger 35 comprise what may be referred to
as a plunger throw, thus the pump assembly 10 of FIG. 1 comprises
three plunger throws. Pump assembly 10 embodiments exist having
other than three plunger throws (i.e. a triplex), such as pump
assemblies having four or more plunger throws.
[0017] A rotatable crankshaft 25 is shown within the crankshaft
housing 13 and as will be described in more detail below,
reciprocates the plunger 35 within the cylinder chamber 39 when it
is rotated. The crankshaft 25 includes a main shaft 30 that
connects to and is rotated by a motor (not shown). In one
embodiment, a flywheel gear 24 is illustrated mechanically
connecting to the crankshaft 25. Teeth on the flywheel gear 24 mesh
with teeth on a drive gear 26, and the drive gear 26 is attached to
the motor. A crank pin 28 attaches to the main shaft 30, shown
offset from and substantially parallel to the axis A.sub.X of the
crankshaft 25. An elongated connector rod 27 is depicted having an
end anchored around the crank pin 28 with a bearing surface
therebetween enabling the crank pin 28 to rotate with respect to
the connector rod 27. In the embodiment of FIG. 2, the crank pin 28
is offset from the axis A.sub.X of the crankshaft 25, so when the
crankshaft 25 rotates, the crank pin 28 orbits the axis A.sub.X of
the crankshaft 25. The rotatable connection between the end of the
connector rod 27 and crank pin 28 causes the connector rod 27 to
reciprocate.
[0018] A cross head pin 31 attaches the connector rod 27 to a cross
head 29 on the end of the connector rod 27 opposite where it
attaches to the crank pin 28. As shown in FIG. 2, the connector rod
27 is substantially horizontally oriented; as the crankshaft 25
rotates, the connector rod 27 will be oblique to horizontal. The
cross head pin 31 allows the connector rod 27 to pivot with respect
to the crosshead 29. The crosshead 29 is shown disposed within a
horizontally oriented crosshead housing 32. Thus as the crank pin
28 orbits with crankshaft 25 rotation, the attached connector rod
27 pivots and moves laterally back and forth within the housing 13
to reciprocate the crosshead 29 within the crosshead housing 32. A
plunger rod 33 is illustrated connected between the crosshead 29
and the plunger 35, thus when the crosshead 29 is reciprocated by
the rotation of the crankshaft 25, the plunger 35 is also
reciprocated within the cylinder chamber 39.
[0019] An example of an inlet valve 41 is depicted within the
cylinder block 17 and controls fluid from the fluid inlet 19 into
the cylinder chamber 39. The inlet valve 41 can open as the plunger
35 reciprocates out of the chamber 39 to introduce fluid into the
chamber 39, and as the plunger 35 reciprocates back into the
chamber 39, the inlet valve 41 closes to isolate the chamber 39
from the fluid inlet 19. As plunger 35 moves longitudinally away
from cylinder chamber 39, the pressure of the fluid inside chamber
39 decreases creating a differential pressure across inlet valve
41, which actuates valve 41 and allows the fluid to enter cylinder
chamber 39 from fluid inlet 19. The fluid being pumped enters
cylinder chamber 39 as plunger 35 continues to move longitudinally
away from cylinder block 17 until the pressure difference between
the fluid inside chamber 39 and the fluid in fluid inlet 19 is
small enough for inlet valve 41 to actuate to its closed
position.
[0020] Fluid in the chamber 39 pressurized by the inwardly
reciprocating plunger 35 is directed to a fluid outlet 21 shown
formed within the cylinder block 17 and adjacent the cylinder
chamber 39. An outlet valve 43 is also shown in the cylinder block
17 set between the fluid outlet 21 and a cylinder block discharge
44. The outlet valve 43 controls fluid from the fluid outlet 21 to
the cylinder block discharge 44. As plunger 35 begins to move
longitudinally towards cylinder block 17, the pressure on the fluid
inside of cylinder chamber 39 begins to increase, and continues to
increase until the differential pressure across outlet valve 43
exceeds a set point. When the set point is exceeded, the outlet
valve 43 opens to allow the fluid to exit cylinder block 17 through
fluid outlet 21. In one embodiment, fluid is only pumped across one
side of plunger 35, therefore pump assembly 10 is a single-acting
reciprocating pump. Valves 41 and 43 can be spring-loaded valves
actuated by a predetermined differential pressure.
[0021] A suction valve stop assembly 51 is illustrated in the
cylinder block 17 adjacent the suction cover plate 22. The suction
valve stop assembly 51 comprises two primary components: a suction
valve stop 53 and suction cover 55. The suction cover 55 is
generally cylindrical in shape and is designed to be mounted
sealingly in opening 18 in the cylinder block 17.
[0022] Additional crank pins 28 may optionally be provided that are
shown illustrated offset from the crankshaft axis A.sub.X and at
different locations around the circumference of the crankshaft 25.
This alternates when fluid is pumped from each cylinder chamber 39
within the cylinder block 17. As is readily appreciable by those
skilled in the art, alternating the cycles of pumping fluid from
each of cylinder chambers 39 helps minimize the primary, secondary,
and tertiary (et al.) forces associated with pump assembly 10.
[0023] Referring now to FIG. 3, illustrated is an enlarged side
sectional view of the suction cover plate 22 coupled to the opening
18 within the cylinder block 17. The suction cover plate 22
includes threads 222 on its outer periphery shown mated with
correspondingly formed threads 172 on the opening 18 circumference.
As shown, the threads 222 extend the entire width of the suction
cover plate 22 and exceed the axial distance of the threads 172 of
the opening 18. Accordingly, some portion of the threads 222 on the
cover plate 22 do not engage threads 172 on the opening 18.
Pressure within the cylinder chamber 39 exerts a force against an
inner surface 23 of the cover plate 22, which transmits from cover
plate threads 222 to the opening threads 172. The threads 222 that
do not engage the opening threads 172 will not receive/transfer a
load to the threads 172, and thus are referred to herein as
unloaded threads 224. The threads 222 engaged with threads 172 can
undergo a load and are referred to as loaded threads 223.
[0024] An arrow F illustrates the direction of the force applied to
the cover plate 22 by the cylinder 39 pressure. Most of a load
transferred between engaged threads concentrates on the first 2-3
threads adjacent the applied load; which in the example of FIG. 3
are the loaded threads 223 adjacent the unloaded threads 224. Since
the first 2-3 of the loaded threads 223 are in roughly the middle
portion of the plate threads 222, the thread depth is substantially
constant, unlike the thread depth at either terminal end of the
plate threads 222. The process by which threads are formed results
in a thread depth typically being less at the terminal ends of a
thread than at the thread middle portion. Thread depth is typically
minimal at the terminal ends of the thread and increases to a fully
formed thread having a maximum depth until reaching the opposite
terminal end. In one exemplary embodiment, the loaded threads 223
transferring the load from the cover plate 22 to the cylinder block
17 are fully formed and at substantially the maximum depth. This
minimizes a stress concentration within the threads 222 that might
occur if the portion of the threads 222 directly adjacent the inner
surface 23 were engaged with the opening threads 172. FIG. 3
provides an example of engaging threads in the inner portion of the
thread 222 length to prevent loading on an end of the thread 222
length where the thread may not be fully formed. Preferably,
unloaded threads 224 comprise at least the first two threads of the
combined set of threads 223, 224. Unloaded threads 224 have the
same form as loaded threads 223. The length of the loaded threads
223 is greater than the length of unloaded threads 224, preferably
at least twice.
[0025] The diameter of the opening 18 reduces along a curved
profile 174 or fillet past the inner surface 23 of the suction
cover plate 22 adjacent to the suction cover 55, where the profile
174 has a defined radius. In one embodiment the radius ranges from
about 10% to about 30% of the distance between the opening 18 front
and the shoulder formed by the profile 174. An advantage provided
by the profile 174 is it better distributes stress loading in the
area of the cylinder block 17 where the opening 18 necks down to
the suction cover 55. Unloaded threads 224 are located within a
smooth cylindrical portion of opening 18 and do not touch the wall
of opening 18
[0026] FIG. 4 provides a side sectional view of an example of the
suction cover plate 22. The cover plate 22 is shown with threads
222 on its outer periphery and a socket 224 formed into the cover
plate 22. The socket 224 is shown coaxial with the cover plate axis
A.sub.P; the socket 224 can be profiled to receive a wrench for
installing the cover plate 224 into the opening 18.
[0027] An example of the threads 222 is depicted in a side cross
sectional view in FIG. 5. As shown, the threads 222 each include a
root portion 226 that is curved for distributing forces along the
curve rather than allowing a stress concentration that can occur if
the cross section of the thread root defined an angle. The threads
222 include a load flank 228, shown optionally disposed angled at
about 7.degree. with respect to the cover plate axis A.sub.P and a
crest 230 that is truncated rather than elongated. Crest 230
appears flat in a sectional view. The rear flank 232 of the threads
222 extends from the crest 230 to the root 226 along a path that is
at an angle oblique to the cover plate axis A.sub.P. The angle
between the rear flank 232 and cover plate axis A.sub.P can be
around 45.degree. in one exemplary example. In one embodiment, the
threads 172 on the opening 18 may be shaped and profiled as
described in the embodiment of FIG. 5, and may be described as a
British Butt Thread. An advantage of employing the threads as
depicted in FIG. 5 for use with the present device is reduced
stress concentrations at the thread root, thereby reducing fatigue
and enhancing component useful life.
[0028] While the invention has been shown in only one of its forms,
it should be apparent to those skilled in the art that it is not so
limited, but is susceptible to various changes without departing
from the scope of the invention.
* * * * *