U.S. patent application number 16/704425 was filed with the patent office on 2020-04-09 for idler gear for positive displacement gear pump.
This patent application is currently assigned to Viking Pump, Inc.. The applicant listed for this patent is Viking Pump, Inc.. Invention is credited to Michael Robert Crawford, John Howard Hall, Victor Christian Iehl.
Application Number | 20200109710 16/704425 |
Document ID | / |
Family ID | 61193184 |
Filed Date | 2020-04-09 |
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United States Patent
Application |
20200109710 |
Kind Code |
A1 |
Iehl; Victor Christian ; et
al. |
April 9, 2020 |
IDLER GEAR FOR POSITIVE DISPLACEMENT GEAR PUMP
Abstract
One or more techniques and/or systems are disclosed for a gear
pump for low speed transfers of viscous liquid slurries promotes
growth of suspended particles, such as sugar crystals, by avoiding
crushing of the particles. The pump includes a rotor gear in mesh
with an eccentrically mounted idler gear supported on a boss of a
pump head that includes a crescent seal extending into an opening
resulting from the eccentricity of the idler gear relative to the
rotor gear. The idler gear contains a radially extending land on
each tooth profile, symmetrically oriented on adjacently spaced
pairs of teeth. The lands, configured to minimize crushing of
crystals passing through the pump, engage mating rotor teeth for
sealing between inlet and outlet ports of the pump. To promote
crystal growth, the lands cover only 10% to 30% of profile surface
area of each tooth. To minimize gear tooth wear, the lands are
axially staggered between successive adjacent pairs of teeth.
Inventors: |
Iehl; Victor Christian;
(Waterloo, IA) ; Crawford; Michael Robert; (Cedar
Falls, IA) ; Hall; John Howard; (Cedar Falls,
IA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Viking Pump, Inc. |
Cedar Falls |
IA |
US |
|
|
Assignee: |
Viking Pump, Inc.
Cedar Falls
IA
|
Family ID: |
61193184 |
Appl. No.: |
16/704425 |
Filed: |
December 5, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15592458 |
May 11, 2017 |
10514034 |
|
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16704425 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04C 2/14 20130101; F04C
15/06 20130101; F04C 2/101 20130101; F04C 2240/30 20130101; F04C
2/084 20130101; F04C 13/002 20130101; F04C 15/0019 20130101 |
International
Class: |
F04C 15/00 20060101
F04C015/00; F04C 2/08 20060101 F04C002/08; F04C 2/10 20060101
F04C002/10; F04C 13/00 20060101 F04C013/00; F04C 15/06 20060101
F04C015/06; F04C 2/14 20060101 F04C002/14 |
Claims
1. A positive displacement gear pump comprising: a casing defining
a casing interior, the casing comprising an inlet port and an
outlet port for transferring a target fluid though the casing
interior; an external rotor gear supported within an inboard end of
the casing by a rotor shaft, the external rotor gear comprising
radially inwardly oriented teeth; a head positioned at an outboard
end of the casing; and an internal idler gear rotationally
supported on the head about an idler gear axis within the casing
interior, the internal idler gear comprising radially outwardly
oriented teeth, the internal idler gear being operably disposed on
the head in a fixed, radially eccentric, relationship with the
external rotor gear, and at least a portion of the internal idler
gear teeth operably meshing with at least a portion of the external
rotor gear teeth; wherein the idler gear teeth comprise: two
radially oriented surfaces respectively extending between a root
and a tip of the idler gear tooth; a land comprising a
substantially planar surface rising from the radially oriented
surface to a height, the height of the respective land from the
surface being substantially constant along a length of the land,
and the surface of the land configured to engage a meshing rotor
tooth for sealing between the inlet port and the outlet ports of
the pump; and a relief area disposed adjacent to the land, the
relief areas defined by the land, an edge of the idler gear tooth,
and the root and the tip, wherein the relief area transiently forms
a relief volume with the meshing rotor gear tooth, wherein the
relief volume is sized to fit a target solid disposed in the target
fluid.
2. The positive displacement gear pump of claim 1, wherein a
surface area of the land comprises from ten-percent to
thirty-percent of a total surface area the corresponding radially
oriented surface of the idler gear tooth.
3. The positive displacement gear pump of claim 1, wherein, one of:
a land is disposed on respective radially oriented surfaces of
respective idler gear teeth; or lands are axially staggered between
successive adjacent pairs of the idler gear teeth.
4. The positive displacement gear pump of claim 1, wherein
respective relief areas are operably spaced apart from the meshing
rotor gear tooth, and wherein the height of the land is equal to or
greater than twenty-thousandths of an inch above the radially
oriented surface of the idler gear tooth.
5. The positive displacement gear pump of claim 4, wherein a total
surface area of respective idler gear teeth with a land comprises a
combination of a surface area of the land and a surface area of the
relief area.
6. The positive displacement gear pump of claim 5, wherein the
surface area of the land comprises from ten-percent to
thirty-percent of the total surface area the radially oriented
surface of the idler gear tooth, and respective idler gear teeth
comprises two relief areas respectively disposed on either side of
the land.
7. The positive displacement gear pump of claim 1, wherein the root
of respective idler gear teeth is situated radially inwardly of the
tip, with respective roots being shared with an adjacent tooth, and
wherein one or: respective lands extend radially between the root
and tip of the tooth; and respective lands extend axially between
respective edges of the tooth.
8. The positive displacement gear pump of claim 1, wherein the head
includes an inner surface containing a boss configured to retain
the idler gear in meshed engagement with the rotor gear.
9. The positive displacement gear pump of claim 8, wherein the
inner surface further comprises a crescent seal configured to seal
a crescent-shaped gap between unmeshed teeth of the idler and rotor
gears.
10. The positive displacement gear pump of claim 8, wherein the
casing interior and the inner surface of the head define a pump
chamber, the pump chamber comprising interior walls in proximity
with the external rotor gear.
11. The positive displacement gear pump of claim 1, wherein the
casing interior and the inner surface of the head define a pump
chamber, the pump chamber comprising interior walls in proximity
with the edge of the idler gear, and the relief volume is defined
by the interior walls of the pump chamber, the root, the tip, the
land, and the meshing rotor gear tooth.
12. An idler gear for use in a positive displacement gear pump
having a casing that defines a casing interior, an inlet port and
an outlet port in fluid communication with the casing interior, a
head, an open outboard end enclosed by the head, a rotor shaft, a
closed inboard end through which a rotor shaft passes, the head and
casing defining a pump chamber, and a rotor gear driven by the
rotor shaft, the rotor gear comprising radially inwardly oriented
teeth, the idler gear comprising radially outwardly oriented teeth,
the rotor gear teeth operably meshing with the idler gear teeth,
the respective gears disposed within the pump chamber for rotation
induced via the rotor shaft, wherein the idler gear comprises:
axially-aligned lands disposed on respective sides of adjacently
spaced pairs of the teeth that sealedly engage the operably meshing
rotor gear teeth to provide a seal between the inlet port and the
outlet ports of the pump, respective lands comprising a height from
a surface of the idler gear tooth that remains substantially
constant along length of the land; and a clearance relief area
disposed adjacent the land on respective idler gear teeth, a
boundary of the relief area defined by the land, a root and tip of
the idler gear tooth, and an edge of the idler gear tooth, and
operably, transiently forming a clearance relief volume with the
meshing rotor gear teeth, the relief volume sized to fit a target
solid in a pumped fluid.
13. The idler gear of claim 12, wherein a surface area of
respective lands comprise from ten-percent to thirty-percent of a
total surface area the surface of the idler gear tooth.
14. The idler gear of claim 12, wherein the lands are axially
staggered between the successive adjacent idler teeth.
15. The idler gear of claim 12, wherein respective relief areas are
operably spaced apart from the meshing rotor gear tooth, and
wherein respective idler gear teeth comprises two relief areas
respectively disposed on either side of the land, and the height of
the land is equal to or greater than twenty-thousandths of an inch
above the radially oriented surface of the idler gear tooth.
16. The idler gear of claim 12, wherein the head comprises an inner
surface containing a boss configured to retain the idler gear in
mesh with the rotor gear.
17. The idler gear of claim 16, wherein the inner surface further
comprises a crescent seal configured to seal a crescent-shaped gap
between unmeshed teeth of the idler and rotor gears.
18. The idler gear of claim 16, wherein the casing interior and the
inner surface of the head comprise a pump chamber, the pump chamber
comprising interior walls in proximity with the external rotor
gear.
19. A pump, comprising: a casing defining a casing interior, the
casing comprising an inlet port and an outlet port for transferring
a target fluid though the casing interior; a head comprising an
inner surface interior walls, which, in combination with the casing
interior and head inner surface, define a pump chamber; a rotor
gear disposed in proximity with the interior walls inside the
casing interior and operably supported by a rotor shaft, the
external rotor gear comprising radially inwardly oriented teeth;
and an idler gear operably coupled with the head within the casing
interior in a rotationally eccentric arrangement with the rotor
gear, the idler gear comprising radially outwardly oriented teeth,
at least a portion of which operably mesh with at least a portion
of the rotor gear teeth, respective idler gear teeth comprising: a
tip disposed at a radially outward end of the tooth; a root
disposed at a radially inward end of the tooth, the root shared
with an adjacent tooth; two radial surfaces respectively disposed
on either side of the tooth between the root and the tip; a land
portion of the respective radial surfaces, the land portion
operably sealedly engaging with a meshing rotor tooth to seal the
pumping chamber between the inlet port and the outlet ports of the
pump; and a relief portion comprising a relief cut from the land
portion having a depth from the land that is substantially constant
in a radial orientation between the root and the tip, the relief
portion operably spaced apart from the meshing rotor tooth to
operably fit a target solid in a pumped fluid between.
20. The pump of claim 19, respective idler gear teeth comprising at
least two relief portions on each radial surface, the relief
portions respectively disposed on either side of the land portion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
patent application Ser. No. 15/592,458, entitled IDLER GEAR FOR
POSITIVE DISPLACEMENT GEAR PUMP, filed May 11, 2017, which is
incorporated herein by reference.
BACKGROUND
[0002] Positive displacement gear pumps are commonly used to pump
moderate to high viscosity liquids. A typical positive displacement
gear pump includes a rotor gear mounted on a shaft; the rotor gear
contains a plurality of circumferentially disposed, spaced-apart,
radially inwardly directed gear teeth that also extend axially
toward an open end of the pump casing. A head covers the open end
of the pump casing, and the head supports an idler pin to which an
idler gear is mounted eccentrically with respect to the rotor gear.
The idler gear also contains a plurality of gear teeth
circumferentially disposed between successive idler gear roots. In
contrast to the rotor gear teeth, which extend radially inwardly,
the idler gear teeth extend radially outwardly.
[0003] A crescent-shaped seal is disposed radially between unmeshed
teeth of the idler gear and rotor gears, the seal being positioned
within a crescent-shaped gap, generally directly opposite a point
of fully engaged meshing rotor and idler gear teeth. The crescent
seal is necessary to assure sufficient pressure differentials
between an inlet (suction) port and an outlet (discharge) port of
the pump. The idler gear teeth engage an inboard, radially inwardly
curved, portion of the seal, while the rotor gear teeth engage an
outboard, radially outwardly curved, portion of the seal. In
addition, the intermeshing idler and rotor teeth also act as a seal
between the inlet and outlet ports. Thus, sealing effects of the
intermeshing teeth, as well as of the crescent seal, cooperate to
retain desirable pressure differentials between the inlet and
outlet ports.
[0004] Although considerable progress has been made in sealing
technologies related to positive displacement gear pumps,
additional improvements are needed. For example, in pumping of
slurries that include growing particles, such as crystals suspended
in liquid slurries, idler and rotor gear teeth often undesirably
crush the suspended particles.
[0005] Thus, there is a particular need to avoid crushing of
suspended particles, as for example sugar crystals within a sugar
slurry during their movements through a positive displacement gear
pump
SUMMARY
[0006] This Summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description. This Summary is not intended to identify
key factors or essential features of the claimed subject matter,
nor is it intended to be used to limit the scope of the claimed
subject matter.
[0007] This disclosure generally relates to positive displacement
gear pumps involved in the pumping of viscous liquids. More
particularly the disclosure relates to construction of an idler
gear for pumping of slurries containing growing particles retained
in suspension, such as sugar crystals, without crushing the
particles.
[0008] In one form of this disclosure, a positive displacement gear
pump includes a casing defining a casing interior. The casing
includes inlet and outlet ports for transferring fluids though the
casing interior. An external rotor gear is supported within an
inboard end of the casing by a rotor shaft. A head is positioned at
an outboard end of the casing, and an internal idler gear is
rotationally supported on the head about an idler gear axis, the
head supporting the idler gear for rotation within the casing
interior. The idler gear is positioned on the head in a fixed,
radially eccentric, relationship with respect to the rotor gear,
having a portion of its teeth meshing with a portion of the rotor
gear teeth. As disclosed, the idler gear has radially outwardly
oriented teeth, while the rotor gear has radially inwardly oriented
teeth.
[0009] The teeth of the idler gear also extend axially, and each
meshing surface of each idler gear tooth contains a radially
oriented land. Adjacently spaced pairs of the teeth define pairs of
symmetrically aligned lands, each of the pair lands spaced by a
root between the spaced teeth. The lands are configured to engage
meshing rotor teeth for sealing between inlet and outlet ports of
the pump. The lands define boundaries of clearance relief volumes
transiently formed between meshing idler gear teeth and rotor gear
teeth to minimize crushing of crystals passing through the
pump.
[0010] In another form of this disclosure, an idler gear is
configured for use in a positive displacement gear pump having a
casing that defines a casing interior, an inlet port and an outlet
port in fluid communication with the casing interior. The idler
gear is farther configured for a positive displacement gear pump
that includes a head, an open outboard end enclosed by the head, a
rotor shaft, a closed inboard end through which a rotor shaft
passes, the head and casing defining a pump chamber, and a rotor
gear driven by the rotor shaft, the rotor gear having radially
inwardly oriented teeth, the idler gear having radially outwardly
oriented teeth, the rotor gear teeth meshed with the idler gear
teeth, with the gears disposed within the pump chamber for rotation
induced via the rotor shaft. The idler gear has teeth that contain
symmetrically oriented, radially extending, lands on each side of
adjacently spaced pairs of the teeth to engage and mesh with rotor
gear teeth for sealing between inlet and outlet ports of the pump.
The lands are configured to provide clearance relief volumes
transiently formed between the meshing idler and rotor gear teeth
to minimize crushing of crystals passing through the pump.
[0011] In yet another form of the disclosure, a method of making a
positive displacement gear pump, having an extelior rotor gear and
an internal idler gear that includes clearance relief volumes
between meshing idler gear teeth and rotor gear teeth to minimize
crushing of crystals passing through the pump, includes modifying
an involute gear tooth profile on a standard idler gear by cutting
a pair of radially oriented clearance surfaces on each tooth
profile of the idler gear to form a radially oriented land on the
profile, the land configured to make direct contact with teeth of
the meshing rotor gear. The method further includes forming the
clearance surfaces to have a depth of 20 to 40 thousandths of an
inch lower than the height of each land. Under the method, each
land is a raised surface, oriented radially along a radially
extending profile of each tooth, and each land extends axially over
a range of 10.degree. 10 to 30% of the total surface area of each
tooth.
[0012] The features, functions, and advantages disclosed herein can
be achieved independently in various other forms or embodiments, or
may be combined in yet other forms or embodiments, the details of
which may be better appreciated with reference to the following
description and drawings. To the accomplishment of the foregoing
and related ends, the following description and annexed drawings
set forth certain illustrative aspects and implementations. These
are indicative of but a few of the various ways in which one or
more aspects may be employed. Other aspects, advantages and novel
features of the disclosure will become apparent from the following
detailed description when considered in conjunction with the
annexed drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a perspective view of an embodiment of the
disclosed positive displacement gear pump.
[0014] FIG. 2 is an elevation of the positive displacement gear
pump embodiment of FIG. 1, as viewed along lines 2-2 of FIG. 1.
[0015] FIG. 3 is an enlarged view of a portion of FIG. 2, with the
head of the pump removed to reveal rotor gear and idler gears
hidden in the view of FIG. 2.
[0016] FIG. 4 is a perspective view of the head not included in
FIG. 3.
[0017] FIG. 5 is a perspective view of several pump elements,
including the rotor gear shaft, the rotor gear, the idler gear, and
the head.
[0018] FIG. 6 is a perspective view that includes details of an
embodiment of an internal idler gear constructed in accordance with
this disclosure.
[0019] It should he understood that the drawings are not
necessarily to scale, and that disclosed embodiments are
illustrated only schematically. It should be further understood
that the following detailed description is merely exemplary and not
intended to be limiting in application or uses. As such, although
the present disclosure is, for purposes of explanatory convenience,
depicted and described in only the illustrative embodiments
presented, the disclosure may be implemented in numerous other
embodiments, and within various other systems and environments not
shown or described herein.
DETAILED DESCRIPTION
[0020] The claimed subject matter is now described with reference
to the drawings, wherein like reference numerals are generally used
to refer to like elements throughout. In the following description,
for purposes of explanation, numerous specific details are set
forth in order to provide a thorough understanding of the claimed
subject matter. It may be evident, however, that the claimed
subject matter may be practiced without these specific details. In
other instances, structures and devices are shown in block diagram
form in order to facilitate describing the claimed subject
matter.
[0021] Referring initially to FIGS. 1-3, a positive displacement
gear pump 10 includes a case or casing 12, having interior walls
that define a casing interior 14. The pump case 12 includes a pump
inlet port 16 and an outlet port 18 to accommodate transfers of
liquids through the casing interior 14 of the gear pump 10. As an
enlarged view of a portion of FIG. 2, FIG. 3 provides an internal
view of the disclosed positive displacement gear pump 10, revealing
a so-called external rotor gear 20 supported within an inboard end
22 of the casing 12 through which a rotor shaft 24 passes. The
rotor shaft 24 drives the rotor gear 20 via a motor, not shown. The
rotor gear 20 includes a plurality of radially inwardly oriented
teeth 26 (FIG. 3).
[0022] Referring now also to FIG. 4, a pump head 28, adapted to he
bolted to the casing 12, is configured to close an outboard,
otherwise open, end 29 of the casing 12. An internal idler gear 30
(FIG. 3) is configured to be mounted for rotation on an idler pin
58 supported on a boss 56 that extends from an interior surface 54
of the head 28. The idler gear 30 is driven by the rotor gear 20
about an idler gear axis 32 (FIGS. 2 and 3). The head 28 thus
supports and retains the idler gear 30 in mesh with the rotor gear
20 for rotation of the idler gear about the idler gear axis 32. For
this purpose, the idler gear 30 has a plurality of radially
outwardly oriented teeth 34, a portion of which mesh with a portion
of the inwardly oriented teeth 26 of the rotor gear 20. The rotor
gear 20 rotates about a separate rotor gear axis 36 (FIGS. 2 and
3), and is thus offset from the idler gear axis 32 to provide for
rotational eccentricity between the rotor gear 20 and the idler
gear 30. In the described embodiment, the casing 12 may also
include a relief valve assembly 35, as shown in FIGS. 1 and 2, and
as will be appreciated by those skilled in the art.
[0023] FIG. 5 illustrates physical relationships of various
elements of the pump 10 that are absent from the view of FIG. 2,
including the head 28, rotor gear 20, and rotor shaft 24, the rotor
shaft being directly connected to the rotor gear 20 for driving
rotation thereof. The radially inwardly oriented teeth of the rotor
20 define a plurality of circumferentially spaced rotor teeth 26
that extend axially into a pump chamber 70 (FIG. 3). The pump
chamber 70 is defined by the casing interior 14, essentially the
interior walls of the casing 12, as, well as the head 28, which
encloses an outboard end 29 of the casing 12. As such, the rotor
gear 20 and the idler gear 30 are eccentrically positioned with
respect to one another within the pump chamber 70.
[0024] In this disclosure, the term "tooth" refers to a single gear
tooth of either the rotor gear or the idler gear. In this
disclosure, the term "teeth" refers to a plurality of gear teeth of
either the rotor gear or the idler gear, or both in the case of
meshing teeth. Moreover, the disclosed gear pump 10 need not be
portrayed exclusively in the orientation shown in the drawings. For
example, the inlet port 16 may have a 90.degree. orientation with
respect to the outlet port 18, instead of the 180.degree.
orientation depicted. Additional variations of elements and
components may apply within the context of this disclosure.
[0025] Referring now also to FIG. 6, the idler gear 30 includes the
plurality of radially outwardly 0 liented idler teeth 34 disposed
between alternating idler roots 38. In contrast to the depicted
radially inward taper of the inwardly oriented rotor teeth 26, the
idler teeth 34 taper outwardly, as they extend radially away from
the roots 38. Further, the circumferentially disposed rotor teeth
26 are separated by spaces 27 (FIG. 5), which receive the idler
teeth 34 within the casing interior 14 of the pump 10 as shown in
FIG. 3. At the top of the pump 10, the idler gear teeth 34 fully
intermesh with the rotor gear teeth 26, and each meshing surface 42
of each tooth 34 has a total surface area (FIG. 6), as further
referenced below.
[0026] Referring now specifically to FIG. 6, eight teeth 34,
identified herein as 34A through 34H, are symmetrically and
circumferentially positioned about the axis 32 of the idler gear
30. This disclosure, however, is not limited to only eight teeth,
as there may be more or less teeth than as described herein,
depending on size of gear pump. Each meshing surface 42 of each
tooth 34A through 34H contains a corresponding raised land 40,
referenced herein as 40A through 40H, in correspondence with a
specific tooth. Each land, farther described below, is a radially
extending surface configured to intermesh with rotor gear teeth 26.
Right and left axial edges 48 (A through H) and 50 (A through H) of
the lands respectively define boundaries of left and right
clearance surfaces 44 (A through H) and 46 (A through H),
juxtaposed on each side of each land. Rather than contact with or
engage intermeshing rotor gear teeth 26, the clearance surfaces 44,
46 are configured to provide clearance relief volumes 80 (FIG. 3)
between the intermeshing teeth 26 of the rotor 20 and teeth 34 of
the idler gear 30, to avoid crushing of particles suspended within
liquids that flow through the gear pump 10, for example, sugar
crystals suspended within a liquid sugar slurry.
[0027] As disclosed, each land 40 constitutes a proud or raised
surface on each tooth 34 that extends 20 to 40 thousandths of an
inch above the pair of clearance surfaces 44 and 46 that extend
across each tooth 34. Each land 40 extends radially between a root
38 and a tip 52 (A through H) of each tooth. Adjacently spaced
pairs of meshing surfaces 42 of each tooth 34, such as those of
teeth 34G and 34H have axially aligned lands 40, such as the lands
40G and 40H'. Successive adjacent pairs of meshing surfaces 42,
such as those of teeth 34F and 34G also have symmetrically aligned
lands, such as 40F and 40G', although the latter lands 40F, 40G'
may be axially staggered with respect to the lands 40G and 40H', as
depicted, to minimize gear tooth wear. Since each tooth has two
sides, primes are used to distinguish between the counterclockwise
side of any particular tooth from its clockwise side. Thus, the
land 40H' is situated on the counterclockwise side of tooth 34H,
and is thereby distinguished from land 40G (a non-prime referenced
element) situated on the clockwise side of tooth 34G. For reference
purposes, it will be noted that the clockwise side of tooth 34H is
hidden from view in FIG. 6.
[0028] With respect to minimizing gear tooth wear, it also should
be pointed out that the idler gear 30 will normally have fewer
teeth 34 than the rotor gear 20. As such, the two gears, turning at
different speeds, will interact in a manner so that each rotor
tooth 26 will contact an idler tooth land 40 in a different
position upon each rotation. This operational aspect will tend to
further minimize tooth wear.
[0029] To avoid crushing of particles, the lands 40, as disclosed,
cover only 10% to 30% of meshing surfaces 42 of each tooth 34, with
a total meshing surface defined by the area of a land 40 and the
areas of its associated clearance surfaces 44, 46. In the disclosed
embodiment, each meshing surface 42 comprises two clearance
surfaces spaced by a single land, and each land extends over at
least 90% of the radial distance between the root 38 and the tip 52
of the meshing surfaces of each tooth.
[0030] Finally, referring again to FIGS. 3 and 4, a crescent seal
60 extends from the interior surface 54 of the head 28. The
crescent seal 60 is fixedly supported on the head 28 to close a
crescent-shaped gap 62 that exists between transiently unmeshed
idler and rotor gear teeth 34, 26 (at bottom of idler gear 30 in
FIG. 3). The eccentric relationship between the idler gear and the
rotor gear give rise to the gap 62, as well as the need for sealing
the gap to maintain desired pressure differentials between inlet
and outlet ports, as those skilled in the art will appreciate.
[0031] A method of making a positive displacement gear pump having
an exterior rotor gear and an internal idler gear that includes
clearance relief volumes between meshing idler gear teeth and rotor
gear teeth to minimize crushing of crystals passing through the
pump may include modifying an involute gear tooth profile of a
standard idler gear by re-machining or cutting a pair of radially
oriented clearance surfaces on each tooth profile of the idler gear
to form a radially oriented land on the profile, the land
configured to make direct contact with teeth of the meshing rotor
gear. The method further includes forming the clearance surfaces as
reliefs; having a depth of 20 to 40 thousandths of an inch lower
than the height of each land. In accordance with this method, each
land is formed of a raised surface along a radially extending
profile of each tooth, and each land axially extends over a range
of 10% to 30% of the total surface area of each tooth.
[0032] The method also provides that when the idler and rotor gears
are meshed, the clearance surfaces cooperate with the rotor gear
teeth to form transient clearance relief volumes between meshing
idler and rotor gears.
[0033] While only certain embodiments have been described,
alternative embodiments and various modifications will be apparent
from the above description to those skilled in the art. For
example, although the pump as described and shown herein is a
unidirectionally rotating pump, the pump may be configured to
rotate in both directions; i.e., such that the intake or suction
port may become the outlet or discharge port, and vice versa. In
addition, although the suspended particles within the liquids being
pumped have been described as growing crystals of the type involved
in sugar slurries, the described pump may also accommodate
microspheres and polymers suspended in liquids. In such cases, the
described idler gear structure will operate to minimize any
crushing or damage to such particles as caused by shear forces
associated with the pumping action. These and other alternatives
may be considered equivalents, and as such may fall within the
spirit and scope of the present disclosure.
[0034] The disclosed positive displacement gear pump 10 may enable
a variety of operations with reduced risks of crushing particles,
such as emerging or growing crystals within a sugar slurry being
transferred by pumping action. Even more broadly, such disclosed
idler gear structures may be employed in a variety of industrial
and service pumps that include transfers of microspheres and
polymers suspended in liquids.
[0035] The word "exemplary" is used herein to mean serving as an
example, instance or illustration. Any aspect or design described
herein as "exemplary" is not necessarily to be construed as
advantageous over other aspects or designs. Rather, use of the word
exemplary is intended to present concepts in a concrete fashion. As
used in this application, the term "or" is intended to mean an
inclusive "or" rather than an exclusive "or." That is, unless
specified otherwise, or clear from context, "X employs A or B" is
intended to mean any of the natural inclusive permutations. That
is, if X employs A; X employs B; or X employs both A and B, then "X
employs A or B" is satisfied under any of the foregoing instances.
Further, At least one of A and B and/or the like generally means A
or B or both A and B. In addition, the articles "a" and "an" as
used in this application and the appended claims may generally be
construed to mean "one or more" unless specified otherwise or clear
from context to be directed to a singular form.
[0036] Although the subject matter has been described in language
specific to structural features and/or methodological acts, it is
to be understood that the subject matter defined in the appended
claims is not necessarily limited to the specific features or acts
described above. Rather, the specific features and acts described
above are disclosed as example forms of implementing the
claims.
[0037] Also, although the disclosure has been shown and described
with respect to one or more implementations, equivalent alterations
and modifications will occur to others skilled in the art based
upon a reading and understanding of this specification and the
annexed drawings. The disclosure includes all such modifications
and alterations and is limited only by the scope of the following
claims. In particular regard to the various functions performed by
the above described components (e.g., elements, resources, etc.),
the terms used to describe such components are intended to
correspond, unless otherwise indicated, to any component which
performs the specified function of the described component (e.g.,
that is functionally equivalent), even though not structurally
equivalent to the disclosed structure which performs the function
in the herein illustrated exemplary implementations of the
disclosure. In addition, while a particular feature of the
disclosure may have been disclosed with respect to only one of
several implementations, such feature may be combined with one or
more other features of the other implementations as may be desired
and advantageous for any given or particular application.
Furthermore, to the extent that the terms "includes," "having,"
"has," "with," or variants thereof are used in either the detailed
description or the claims, such terms are intended to be inclusive
in a manner similar to the term "comprising."
[0038] The implementations have been described, hereinabove. It
will be apparent to those skilled in the art that the above methods
and apparatuses may incorporate changes and modifications without
departing from the general scope of this invention. It is intended
to include all such modifications and alterations in so far as they
come within the scope of the appended claims or the equivalents
thereof.
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