U.S. patent application number 15/311504 was filed with the patent office on 2017-03-23 for reciprocating pump with improved fluid cylinder cross-bore geometry.
The applicant listed for this patent is FMC Technologies, Inc.. Invention is credited to Paul A. Crawford, John D. Morreale.
Application Number | 20170082103 15/311504 |
Document ID | / |
Family ID | 54554878 |
Filed Date | 2017-03-23 |
United States Patent
Application |
20170082103 |
Kind Code |
A1 |
Morreale; John D. ; et
al. |
March 23, 2017 |
RECIPROCATING PUMP WITH IMPROVED FLUID CYLINDER CROSS-BORE
GEOMETRY
Abstract
A reciprocating pump comprising a fluid end housing having a
number of plunger sections, each of which includes a plunger bore
within which a plunger is slidably received, a suction bore within
which a suction valve is positioned, a discharge bore within which
a discharge valve is positioned, and a cross bore chamber which is
located between said bores and is configured as a surface of
revolution. Each of the bores intersects the cross-bore chamber to
thereby define a respective cross curve which is spatially
separated from each adjacent cross curve. In this manner, the
cross-bore chamber defines a single, contiguous surface which
extends around and between all of said cross curves.
Inventors: |
Morreale; John D.; (Houston,
TX) ; Crawford; Paul A.; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FMC Technologies, Inc. |
Houston |
TX |
US |
|
|
Family ID: |
54554878 |
Appl. No.: |
15/311504 |
Filed: |
May 22, 2015 |
PCT Filed: |
May 22, 2015 |
PCT NO: |
PCT/US15/32300 |
371 Date: |
November 15, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62002593 |
May 23, 2014 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04B 19/22 20130101;
F04B 53/22 20130101; F04B 53/162 20130101; F04B 53/1032 20130101;
F04B 53/1025 20130101; F04B 53/16 20130101; F04B 53/007 20130101;
F04B 53/14 20130101; F04B 53/10 20130101 |
International
Class: |
F04B 53/16 20060101
F04B053/16; F04B 53/14 20060101 F04B053/14; F04B 53/10 20060101
F04B053/10; F04B 19/22 20060101 F04B019/22 |
Claims
1. In a reciprocating pump comprising a fluid end housing having a
number of plunger sections, each plunger section including a
plunger bore within which a plunger is slidably received, a suction
bore within which a suction valve is positioned and a discharge
bore within which a discharge valve is positioned, the improvement
comprising a cross bore chamber which is located between said bores
and is configured as a surface of revolution, wherein each of said
bores intersects the cross-bore chamber to thereby define a
respective cross curve which is spatially separated from each
adjacent cross curve, whereby the cross-bore chamber defines a
single, contiguous surface which extends around and between all of
said cross curves.
2. The pump of claim 1, wherein the cross-bore chamber is
configured as an ellipsoid.
3. The pump of claim 2, wherein the ellipsoid comprises a first
axis which is coaxial with a centerline of the plunger bore and a
second axis which is coaxial with at least one of a centerline of
the suction bore and a centerline of the discharge bore.
4. The pump of claim 2, wherein the ellipsoid comprises a first
axis which is coaxial with a centerline of the plunger bore and a
second axis which is parallel to but offset from at least one of a
centerline of the suction bore and a centerline of the discharge
bore.
5. The pump of claim 2, wherein the ellipsoid comprises a first
axis which is parallel to but offset from a centerline of the
plunger bore and a second axis which is coaxial with at least one
of a centerline of the suction bore and a centerline of the
discharge bore.
6. The pump of claim 2, wherein the ellipsoid comprises a first
axis which is parallel to but offset from a centerline of the
plunger bore and a second axis which is parallel to but offset from
at least one of a centerline of the suction bore and a centerline
of the discharge bore.
7. The pump of claim 1, wherein each plunger section further
comprises an access bore which intersects the cross-bore chamber to
thereby define a corresponding cross curve that is spatially
separated from each adjacent cross curve, whereby the cross-bore
chamber defines a single, contiguous surface which extends around
and between all of said cross curves.
8. The pump of claim 7, wherein the cross-bore chamber is
configured as an ellipsoid.
9. The pump of claim 8, wherein the access bore is generally
aligned with the plunger bore and the suction bore is generally
aligned with the discharge bore, and wherein the access and plunger
bores are oriented at an angle of generally ninety degrees relative
to the suction and discharge bores.
10. The pump of claim 9, wherein the ellipsoid comprises a first
axis which is coaxial with a centerline of the plunger bore and a
second axis which is coaxial with at least one of a centerline of
the suction bore and a centerline of the discharge bore.
11. The pump of claim 9, wherein the ellipsoid comprises a first
axis which is coaxial with a centerline of the plunger bore and a
second axis which is parallel to but offset from at least one of a
centerline of the suction bore and a centerline of the discharge
bore.
12. The pump of claim 9, wherein the ellipsoid comprises a first
axis which is parallel to but offset from a centerline of the
plunger bore and a second axis which is coaxial with at least one
of a centerline of the suction bore and a centerline of the
discharge bore.
13. The pump of claim 9, wherein the ellipsoid comprises a first
axis which is parallel to but offset from a centerline of the
plunger bore and a second axis which is parallel to but offset from
at least one of a centerline of the suction bore and a centerline
of the discharge bore.
14. The pump of claim 2, wherein each of said bores is oriented at
an angle of approximately 120 degrees relative to each other
bore.
15. The pump of claim 14, wherein the ellipsoid comprises a first
axis which is coaxial with a centerline of the plunger bore and a
center point which is located at an intersection of the plunger
bore, the suction bore and the discharge bore.
16. The pump of claim 14, wherein the ellipsoid comprises a first
axis which is coaxial with a centerline of the plunger bore and a
center point which is offset from an intersection of the plunger
bore, the suction bore and the discharge bore.
17. The pump of claim 14, wherein the ellipsoid comprises a first
axis which is parallel to but offset from a centerline of the
plunger bore and a center which is located at an intersection of
the plunger bore, the suction bore and the discharge bore.
18. The pump of claim 14, wherein the ellipsoid comprises a first
axis which is parallel to but offset from a centerline of the
plunger bore and a center which is offset from an intersection of
the plunger bore, the suction bore and the discharge bore.
19. A method of reducing stress concentrations in a fluid end
housing of a reciprocating pump, the fluid end housing having a
number of plunger sections, each plunger section including a
plunger bore within which a plunger is slidably received, a suction
bore within which a suction valve is positioned and a discharge
bore within which a discharge valve is positioned, the method
comprising: forming a cross-bore chamber between said bores, said
cross-bore chamber being configured as a surface of revolution;
wherein each of said bores intersects the cross-bore chamber to
thereby define a respective cross curve which is spatially
separated from each adjacent cross curve; whereby the cross-bore
chamber defines a single, contiguous surface which extends around
and between all of said cross curves.
20. The method of claim 19, wherein said cross-bore chamber is
configured as a spheroid.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention is related to reciprocating plunger
and piston-type pumps which are used, for example, in oil well
service operations. In particular, the invention is related to an
improved cross-bore geometry for the fluid end of such pumps.
[0002] Plunger pumps for the oilfield industry typically include a
power end and a fluid end. The fluid end generally includes a
plunger which is positioned in a plunger bore and is reciprocated
by the power end, an access bore which is located opposite the
plunger bore, a suction valve which is positioned in a suction bore
and a discharge valve which is positioned in a discharge bore. In
operation, the plunger is reciprocated in the plunger bore to
alternately draw fluid into the pump through the suction valve and
then force the fluid out of the pump through the discharge
valve.
[0003] During operation of the pump, the fluid end is subject to
very high frequency and large magnitude pressure pulsations. These
pressure pulsations generate large stress concentrations at the
intersections of the bores. In cross-bore geometries in which the
bore intersections form relatively sharp edges, these stress
concentrations may cause fatigue cracks to form in the fluid end
proximate the intersections. In some prior art pumps, the
intersecting edges of the bores are machined to have quasi radii
and chamfered features in an attempt to smooth the bore
intersections. Although smoothing the bore intersections in this
manner may reduce the stress concentrations to a certain extent,
the cross-bore geometries of extreme service pumps remain
susceptible to developing excessive stress concentrations due to
the limitations imposed by the current configurations of the bore
intersections.
SUMMARY OF THE INVENTION
[0004] In accordance with the present invention, these and other
limitations in the prior art are overcome by providing a
reciprocating pump comprising a fluid end housing having a number
of plunger sections, each plunger section including a plunger bore
within which a plunger is slidably received, a suction bore within
which a suction valve is positioned, a discharge bore within which
a discharge valve is positioned, and a cross bore chamber which is
located between said bores and is configured as a surface of
revolution. Each of said bores intersects the cross-bore chamber to
thereby define a respective cross curve which is spatially
separated from each adjacent cross curve. In this manner, the
cross-bore chamber defines a single, contiguous surface which
extends around and between all of said cross curves.
[0005] In accordance with one embodiment of the invention, the
cross-bore chamber is configured as an ellipsoid. In this
embodiment, the ellipsoid may comprise a first axis which is
coaxial with a centerline of the plunger bore and a second axis
which is coaxial with at least one of a centerline of the suction
bore and a centerline of the discharge bore. Alternatively, the
ellipsoid may comprise a first axis which is coaxial with a
centerline of the plunger bore and a second axis which is parallel
to but offset from at least one of a centerline of the suction bore
and a centerline of the discharge bore. Alternatively, the
ellipsoid may comprise a first axis which is parallel to but offset
from a centerline of the plunger bore and a second axis which is
coaxial with at least one of a centerline of the suction bore and a
centerline of the discharge bore. Alternatively, the ellipsoid may
comprise a first axis which is parallel to but offset from a
centerline of the plunger bore and a second axis which is parallel
to but offset from at least one of a centerline of the suction bore
and a centerline of the discharge bore.
[0006] In accordance with another embodiment of the invention, each
plunger section further comprises an access bore which intersects
the cross-bore chamber to thereby define a corresponding cross
curve that is spatially separated from each adjacent cross curve.
In this manner, the cross-bore chamber defines a single, contiguous
surface which extends around and between all of said cross curves.
In this embodiment, the cross-bore chamber may be configured as an
ellipsoid. In addition, the access bore may be generally aligned
with the plunger bore and the suction bore may be generally aligned
with the discharge bore, and the access and plunger bores may be
oriented at an angle of generally ninety degrees relative to the
suction and discharge bores. Also, the ellipsoid may comprise a
first axis which is coaxial with a centerline of the plunger bore
and a second axis which is coaxial with at least one of a
centerline of the suction bore and a centerline of the discharge
bore. Alternatively, the ellipsoid may comprise a first axis which
is coaxial with a centerline of the plunger bore and a second axis
which is parallel to but offset from at least one of a centerline
of the suction bore and a centerline of the discharge bore.
Alternatively, the ellipsoid may comprise a first axis which is
parallel to but offset from a centerline of the plunger bore and a
second axis which is coaxial with at least one of a centerline of
the suction bore and a centerline of the discharge bore.
Alternatively, the ellipsoid may comprise a first axis which is
parallel to but offset from a centerline of the plunger bore and a
second axis which is parallel to but offset from at least one of a
centerline of the suction bore and a centerline of the discharge
bore.
[0007] In accordance with a further embodiment of the invention,
the plunger bore, the suction bore and the discharge bore are
oriented at an angle of approximately 120 degrees relative to each
other. In this embodiment, the ellipsoid may comprise a first axis
which is coaxial with a centerline of the plunger bore and a center
point which is located at an intersection of the plunger bore, the
suction bore and the discharge bore. Alternatively, the ellipsoid
may comprise a first axis which is coaxial with a centerline of the
plunger bore and a center point which is offset from an
intersection of the plunger bore, the suction bore and the
discharge bore. Alternatively, the ellipsoid may comprise a first
axis which is parallel to but offset from a centerline of the
plunger bore and a center which is located at an intersection of
the plunger bore, the suction bore and the discharge bore.
Alternatively, the ellipsoid may comprise a first axis which is
parallel to but offset from a centerline of the plunger bore and a
center which is offset from an intersection of the plunger bore,
the suction bore and the discharge bore.
[0008] The present invention is also directed to a method of
reducing stress concentrations in a fluid end housing of a
reciprocating pump, the fluid end housing having a number of
plunger sections, each plunger section including a plunger bore
within which a plunger is slidably received, a suction bore within
which a suction valve is positioned and a discharge bore within
which a discharge valve is positioned. The method comprises forming
a cross-bore chamber between said bores, said cross-bore chamber
being configured as a surface of revolution, wherein each of said
bores intersects the cross-bore chamber to thereby define a
respective cross curve which is spatially separated from each
adjacent cross curve. In this manner, the cross-bore chamber
defines a single, contiguous surface which extends around and
between all of said cross curves. In accordance with one aspect of
this embodiment, the cross-bore chamber may be configured as a
spheroid.
[0009] Thus, in accordance with the present invention an improved
cross-bore geometry is obtained by creating a cross-bore chamber at
the intersection of the plunger bore, the suction bore, the
discharge bore and, if present, the access bore. The cross-bore
chamber is configured as a surface of revolution which is created
by rotating a two-dimensional curve around a reference axis. For
example, the cross-bore chamber may be configured as an ellipsoid,
a particular case of which is a sphere. By configuring the
cross-bore chamber as a surface of revolution such as an ellipsoid,
the cross-bore chamber provides a single, smooth contiguous
connecting surface between the bores. As a result, the stress
concentrations in the cross-bore geometry are significantly
reduced, and the fluid end is therefore less susceptible to
failure.
[0010] These and other objects and advantages of the present
invention will be made apparent from the following detailed
description, with reference to the accompanying drawings. In the
drawings, the same reference numbers are used to denote similar
components in the various embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a perspective, partial cut-away view of a prior
art plunger pump in which the cross-bore geometry of the present
invention may be incorporated;
[0012] FIG. 2 is a cross sectional view of the fluid end of the
plunger pump shown in FIG. 1;
[0013] FIG. 3 is a cross sectional view similar to FIG. 2 but with
the internal components of the fluid end removed for clarity;
[0014] FIG. 4 is a schematic representation of the cross bore
geometry in accordance with one embodiment of the present
invention;
[0015] FIG. 5 is a perspective, cut-away view of an embodiment of a
fluid end of the present invention having an illustrative cross
bore geometry;
[0016] FIG. 6 is a cross sectional view of the fluid end shown in
FIG. 5;
[0017] FIGS. 7-9 are cross sectional views of additional
embodiments of fluid ends having differing illustrative cross-bore
geometries; and
[0018] FIG. 10 is a cross sectional view of another embodiment of a
fluid end in which the cross-bore geometry of the present invention
may be incorporated.
DETAILED DESCRIPTION OF THE INVENTION
[0019] An example of a prior art plunger pump in which the
cross-bore geometry of the present invention may be incorporated is
shown in FIG. 1. As described more fully in U.S. Pat. No.
7,610,847, which is hereby incorporated herein by reference, the
plunger pump 10 comprises a power end 12 and a fluid end 14. The
power end 12 includes a gear reducer assembly 16 which is driven by
a suitable motor (not shown). The gear reducer assembly 16 drives a
crankshaft 18. The crankshaft 18 is rotatably connected to one end
of a connecting rod 20, the opposite end of which is pivotally
connected to a crosshead 22 that is supported for linear movement
in a corresponding guide bore 24. The fluid end 14 includes a
number of plungers 26 (only one of which is shown in FIG. 1), each
of which is slidably mounted in a respective plunger bore 28 and is
connected to a respective crosshead 22 by a plunger rod 30. In
operation, rotary motion of the crankshaft 18 is converted by the
connecting rod 20 into linear reciprocating motion of the crosshead
22, which in turn reciprocates the plunger 26 in the plunger bore
28.
[0020] The fluid end 14 comprises a laterally extending housing 32
having a number of plunger sections (in this case five) which are
each aligned with a corresponding plunger 26. The middle plunger
section is shown in greater detail in FIGS. 2 and 3. With the
exception noted below, the middle plunger section is similar to the
remaining plunger sections. As described more fully in U.S. Pat.
No. 7,681,589, which is hereby incorporated herein by reference,
the middle plunger section includes a cross bore arrangement
comprising the plunger bore 28, an access bore 34 which is
generally aligned with the plunger bore, a suction bore 36 which is
generally perpendicular to the plunger bore, and a discharge bore
38 which is generally aligned with the suction bore.
[0021] The plunger 26 is positioned in the plunger bore 28 and is
sealed thereto by, e.g., an annular packing 40, which in the
embodiment shown in FIG. 2 is mounted in a stuffing box 42 that is
secured to the housing 32 by a number of cap screws 44. The access
bore 34 is sealed by a plug 46 which is secured to the housing 32
by a first retainer nut 48. A suction valve 50 is positioned in the
suction bore 36 between the plunger bore 28 and an inlet port 52. A
discharge valve 54 is positioned in the discharge bore 38 between
the plunger bore 28 and a pressure tap fitting 56 which is secured
in the discharge bore by a second retainer nut 58. The discharge
bores 38 of the remaining bore sets are sealed by plugs 60 (FIG. 1)
similar to the plug 48 (FIG. 2), and all of the discharge bores are
fluidly connected via a lateral bore 62 to an outlet coupling 63
(FIG. 1). In this manner, all the fluid pumped through the several
plunger sections will be directed through the lateral bore 62 and
exit the pumping unit 10 through the outlet coupling 63.
[0022] As shown in FIG. 1, the inlet ports 52 of the several
plunger sections are connected to an inlet manifold 64 having a
pump inlet 66 which is connectable to, e.g., a source of well
service fluid (not shown). In operation of the plunger pump 10, the
plungers 26 are reciprocated by the power end 12 in the manner
described above. During the suction stroke of each plunger 26, the
suction valve 50 is forced open and fluid is drawn through the
suction bore 36 and into the plunger bore 28. During the discharge
stroke of each plunger 26, the suction valve 50 is forced closed
and the fluid in the plunger bore 28 is forced through the
discharge valve 54 and the outlet coupling 63. Further details of
the operation of the suction valve 50 and the discharge valve can
be found in the aforementioned U.S. Pat. No. 7,681,589.
[0023] The cross bore arrangement of each plunger section is shown
more clearly in FIG. 3, which is similar to FIG. 2 but with the
internal components of the plunger section removed for clarity. As
shown in FIG. 3, the plunger bore 28 and the access bore 34
comprise respective centerlines C.sub.P and C.sub.A which are
coaxial along an axis X, and the suction bore 36 and the discharge
bore 38 comprise respective centerlines C.sub.S and C.sub.D which
are coaxial along an axis Z that is perpendicular to the axis X. In
this embodiment of the fluid end 14, the suction bore 36 intersects
the plunger bore 28 along a first curve 68, and the discharge bore
38 intersects the plunger bore along a second curve 70. As may be
seen in FIG. 3, the curves 68, 70 define relatively sharp edges
between the intersecting bores.
[0024] During operation of the pump 10, the fluid end 14 is subject
to very high frequency and large magnitude pressure pulsations.
These pressure pulsations generate large stress concentrations at
the bore intersections. In cross-bore geometries in which the bore
intersections form relatively sharp edges, these stress
concentrations may cause fatigue cracks to form in the housing
proximate the intersections. Traditionally, quasi radii and
chamfers have been applied to the bore intersections using hand
tools to obtain some semblance of smoothness. With the advent of
robotics and multi-axis machines, these features can be machined
programmatically. Although smoothing the bore intersections in this
manner may reduce the stress concentrations to a certain extent,
the cross-bore geometries of extreme service pumping units remain
susceptible to developing excessive stress concentrations due to
the limitations imposed by the current configurations of the bore
intersections.
[0025] According to the present invention, an improved cross-bore
geometry has been developed which greatly reduces the stress
concentrations that can lead to fatigue cracks in the fluid end
originating at and propagating from the bore intersections. The
improved cross-bore geometry is obtained by creating a cross-bore
chamber at the intersection of the plunger bore, the access bore,
the suction bore and the discharge bore. The characteristics of the
cross-bore chamber will be described with reference to the
schematic representation shown in FIG. 4. The cross-bore chamber,
generally 72, is configured as a surface of revolution which is
created by rotating a two-dimensional curve 74 around one of the X,
Y or Z axes. In this regard, the X, Y and Z axes are defined as the
reference axes for the surface of revolution. Although in certain
embodiments of the invention the X axis may be coaxial with one or
both of the plunger bore centerline C.sub.P and the access bore
centerline C.sub.A and the Z axis may be coaxial with one or both
of the suction bore centerline C.sub.S and the discharge bore
centerline C.sub.D, these axes do not necessarily have to be
aligned with any of the bore centerlines.
[0026] The two-dimensional curve 74 can have any practical
configuration, provided that it comprises a diameter which is
greater than the diameter of the largest of the plunger bore 28,
the access bore 34, the suction bore 36 and the discharge bore 38.
In the specific embodiment of the invention illustrated in FIG. 4,
the curve 74 is an ellipse which is centered at the origin O of the
X, Y and Z axes. Thus, the surface of revolution defining the
cross-bore chamber 72 has the general shape of an ellipsoid which
is centered about the origin O and is created by rotating the
ellipse 74 about the X axis. In the context of the present
invention, however, the ellipsoid may have any configuration which
is defined by the following standard equation:
x.sup.2/a.sup.2+y.sup.2/b.sup.2+z.sup.2/c.sup.2=1,
where a, b and c are the respective lengths of the semi-principal
axes of the ellipsoid. For example, the cross-bore chamber 72 may
be configured as a sphere by making a=b=c.
[0027] Referring still to FIG. 4, the intersection of each of the
plunger bore 28, the access bore 34, the suction bore 36 and the
discharge bore 38 with the cross-bore chamber 72 defines a
respective cross curve 28a, 34a, 36a and 38a. The particular shape
of each cross curve will of course depend on the shape of the
surface of revolution which defines the cross-bore chamber 72. As
may be seen in FIG. 4, by configuring the cross-bore chamber 72 as
a surface of revolution such as an ellipsoid, the cross-bore
chamber provides a single, smooth contiguous connecting surface
between each of the cross curves. This single, smooth contiguous
connecting surface is created by virtue of the fact that, rather
than intersecting each other, the plunger bore 28, the access bore
34, the suction bore 36 and the discharge bore 38 intersect the
cross-bore chamber 72. Thus, in the present invention the sharp
edge formed by the intersection of, e.g., the discharge bore with
the plunger bore, is eliminated. Instead, the smooth contiguous
connecting surface formed by the cross-bore chamber 72 extends
around and between the cross curves 28a, 34a, 36a and 38a. As a
result, the stress concentrations in the cross-bore geometry are
significantly reduced, and the fluid end is therefore less
susceptible to fatigue crack formation.
[0028] Referring to FIGS. 5 and 6, an embodiment of the invention
is shown in which the cross-bore chamber 72 comprises a spherical
configuration. In this embodiment, the plunger bore centerline
C.sub.P and the access bore centerline C.sub.A are coaxial with the
X axis and the suction bore centerline C.sub.S and the discharge
bore centerline C.sub.D are coaxial with the Z axis. As may be seen
especially in FIG. 5, the spherical configuration of the cross-bore
chamber 72 forms a single, smooth contiguous connecting surface 76
between and around the cross curves 28a, 34a, 36a and 38a. In this
embodiment, the bore with the largest diameter is the suction bore
36, and the sphere defining the cross-bore chamber 72 comprises a
diameter which is larger than the diameter of the suction bore. In
this as in other embodiments of the invention, the shape and size
of the surface of revolution which is used to form the cross-bore
chamber 72 may be determined empirically for a particular
cross-bore geometry in order to provide desired stress and flow
characteristics for the fluid end.
[0029] Further illustrative and non-limiting embodiments of the
cross bore geometry of the present invention are shown in FIGS.
7-9. The cross bore geometry shown in FIG. 7 is similar to that
shown in FIG. 6. In the embodiment shown in FIG. 7, however, the X
axis is offset from the plunger bore centerline C.sub.P and the
access bore centerline C.sub.A, which in this case are coaxial. In
this example, where the cross-bore chamber 72 is defined by a
sphere having a diameter of 8.50'', the X axis is offset in the Z
direction 0.50'' from the plunger bore centerline C.sub.P toward
the suction bore 36.
[0030] In the embodiment of the cross-bore geometry shown in FIG.
8, the X axis is coaxial with the plunger bore centerline C.sub.P
and the access bore centerline C.sub.A, but the Z axis is offset
from the suction bore centerline. C.sub.S and the discharge bore
centerline C.sub.D, which in this instance are coaxial. In this
example, where the cross-bore chamber 72 is defined by a sphere
having a diameter of 8.50'', the Z axis is offset in the X
direction 0.20'' from the discharge bore centerline C.sub.D toward
the access bore 34.
[0031] In the embodiment of the cross-bore geometry shown in FIG.
9, the X axis is offset from the plunger bore centerline C.sub.P
and the access bore centerline C.sub.A, which in this instance are
coaxial, and the Z axis is offset from the suction bore centerline
C.sub.S and the discharge bore centerline C.sub.D, which in this
case are also coaxial. In this example, where the cross-bore
chamber 72 is defined by a sphere having a diameter of 8.50'', the
X axis is offset in the Z direction 0.50'' from the plunger bore
centerline C.sub.P toward the suction bore 36, and the Z axis is
offset in the X direction 0.20'' from the discharge bore centerline
C.sub.D toward the access bore 34.
[0032] Another example of a fluid end in which the cross-bore
geometry of the present invention may be incorporated is shown in
FIG. 10. The fluid end of this embodiment, generally 14', is
described more fully in U.S. Pat. No. 8,147,227, which is hereby
incorporated herein by reference. As shown in FIG. 10, the fluid
end 14' comprises a Y-shaped cross bore arrangement in which the
access bore is omitted and the plunger bore 26, the suction bore 36
and the discharge bore 38 are oriented approximately 120.degree.
from each other.
[0033] In accordance with the present invention, a cross-bore
chamber (not shown) may be machined into the fluid end to provide
the advantages described above. As in the previous embodiments, the
cross-bore chamber may comprise a surface of revolution, such as an
ellipsoid, which is centered at the origin O of the X, Y and Z
reference axes. In addition, the X axis may be either aligned with
or offset from the plunger bore centerline C.sub.P, and the origin
O of the reference axes may be located at or offset from the
intersection of the plunger bore centerline C.sub.P, the suction
bore centerline C.sub.S and the discharge bore centerline
C.sub.D.
[0034] It should be recognized that, while the present invention
has been described in relation to the preferred embodiments
thereof, those skilled in the art may develop a wide variation of
structural and operational details without departing from the
principles of the invention. Therefore, the appended claims are to
be construed to cover all equivalents falling within the true scope
and spirit of the invention.
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