U.S. patent application number 13/832539 was filed with the patent office on 2014-09-18 for toothed-lobed gear pump.
The applicant listed for this patent is William D. Flavelle. Invention is credited to William D. Flavelle.
Application Number | 20140271313 13/832539 |
Document ID | / |
Family ID | 50189774 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140271313 |
Kind Code |
A1 |
Flavelle; William D. |
September 18, 2014 |
Toothed-Lobed Gear Pump
Abstract
Toothed gears and lobed gears intermesh to create large volume
pockets in gear sets of a given size. The pockets are larger than
the pockets that exist in current tooth or lobe pumps and provide
the benefit of a pump that better handles shear sensitive liquids.
Preferably, the profiles of the teeth and of the lobes are
involute-shaped to provide rolling contact and a fixed pressure
angle between the teeth and lobes during engagement. The toothed
gears and lobe gears improve upon standard spur and helical gear
designs by omitting alternate teeth on the standard toothed gears
and filling in corresponding gaps on the mating standard lobed
gears. Additional tooth and lobed gear rotors may be added in
tandem as additional pairs of gears to the shafts and
circumferentially offset to provide driving tooth engagement
between at least one pair of the toothed and lobed rotors at every
point around the rotational circumference of the rotors. This spur
gear or helical gear configuration eliminates the need for separate
driving/synchronizing gears.
Inventors: |
Flavelle; William D.;
(Hoschton, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Flavelle; William D. |
Hoschton |
GA |
US |
|
|
Family ID: |
50189774 |
Appl. No.: |
13/832539 |
Filed: |
March 15, 2013 |
Current U.S.
Class: |
418/205 |
Current CPC
Class: |
F04C 2/08 20130101; F01C
11/002 20130101; F04C 2/126 20130101; F04C 2/084 20130101; F04C
2/20 20130101; F04C 11/001 20130101 |
Class at
Publication: |
418/205 |
International
Class: |
F04C 2/08 20060101
F04C002/08 |
Claims
1. A pump, comprising: a housing having an internal cavity that
defines a pumping chamber, an inlet port adapted to allow a fluid
into the pumping chamber, and an outlet port adapted to discharge
the fluid from the pumping chamber; and a gearbox located in the
pumping chamber, said gearbox having a plurality of driving rotors
including first and second toothed gears each having a plurality of
teeth, said plurality of driving rotors also including first and
second lobed gears each having a plurality of lobes wider than the
teeth, said first toothed gear and said first lobed gear being a
first gear set with said first toothed gear mounted to one of a
first rotational axis and a second rotational axis in the pumping
chamber adjacent the first rotational axis, and said first lobed
gear mounted to the other one of the first rotational axis and the
second rotational axis in the pumping chamber, said second toothed
gear and said second lobed gear being a second gear set with said
second toothed gear mounted to one of the first rotational axis and
the second rotational axis in the pumping chamber, and said second
lobed gear mounted to the other one of the first rotational axis
and the second rotational axis in the pumping chamber, the first
toothed gear intermeshed with the first lobed gear in a driving
relationship therebetween, the second toothed gear intermeshed with
the second lobed gear in a driving engagement therebetween, the
teeth of the toothed gears and the lobes of the lobed gears having
an involute shaped profile to provide continuously rolling contact
and a fixed pressure angle between the teeth and lobes during the
driving engagement, wherein one of the first rotational axis and
the second rotational axis is a drive shaft.
2. The pump of claim 1, each of the lobes having a first arcuate
width, each of the teeth having a maximum arcuate width, the first
arcuate width of each lobe being at least double the maximum
arcuate width of each tooth.
3. The pump of claim 2, wherein the first arcuate width of each
lobe is at least thrice the maximum arcuate width of each
tooth.
4. The pump of claim 1, the second gear set being engaged in the
driving relationship therebetween when the first gear set is
disengaged between the first toothed gear and the first lobed
gear.
5. The pump of claim 1, the first gear set being engaged in the
driving relationship therebetween when the second gear set is
disengaged between the second toothed gear and the second lobed
gear.
6. The pump of claim 1, further comprising a partition wall
extending orthogonally to the first and second rotational axes
between the first gear set and the second gear set for
hydraulically isolation of the fluid.
7. The pump of claim 1, the teeth of said first toothed gear being
angularly offset with relation to the teeth of said second toothed
gear such that a tooth of said first toothed gear is axially
aligned between two teeth of said second toothed gear.
8. The pump of claim 1, said first toothed gear and said second
lobed gear being mounted to the first rotational axis.
9. The pump of claim 1, further comprising radial vanes extending
from the teeth to seal circumferential liquid slip paths between
the toothed gears and the housing and to seal slip paths between
the toothed gears and the lobed gears.
10. The pump of claim 1, further comprising radial vanes extending
from the lobes to seal circumferential liquid slip paths between
the lobed gears and the housing and to seal slip paths between the
toothed gears and the lobed gears.
11. A gearbox of a pump having a housing with an internal cavity
that defines a pumping chamber, an inlet port adapted to allow a
fluid into the pumping chamber, and an outlet port adapted to
discharge the fluid from the pumping chamber, the gearbox located
in the pumping chamber of the housing, said gearbox comprising a
plurality of driving rotors including first and second toothed
gears each having a plurality of teeth, said plurality of driving
rotors also including first and second lobed gears each having a
plurality of lobes wider than the teeth, said first toothed gear
and said first lobed gear being a first gear set with said first
toothed gear mounted to one of a first rotational axis and a second
rotational axis in the pumping chamber adjacent the first
rotational axis, and said first lobed gear mounted to the other one
of the first rotational axis and the second rotational axis in the
pumping chamber, said second toothed gear and said second lobed
gear being a second gear set with said second toothed gear mounted
to one of the first rotational axis and the second rotational axis
in the pumping chamber, and said second lobed gear mounted to the
other one of the first rotational axis and the second rotational
axis in the pumping chamber, the first toothed gear intermeshed
with the first lobed gear in a driving relationship therebetween,
the second toothed gear intermeshed with the second lobed gear in a
driving engagement therebetween, the teeth of the toothed gears and
the lobes of the lobed gears having an involute shaped profile to
provide continuously rolling contact and a fixed pressure angle
between the teeth and lobes during the driving engagement, wherein
one of the first rotational axis and the second rotational axis is
a drive shaft.
12. The gearbox of claim 11, each of the lobes having a first
arcuate width, each of the teeth having a maximum arcuate width,
the first arcuate width of each lobe being at least double the
maximum arcuate width of each tooth.
13. The gearbox of claim 11, the second gear set being engaged in
the driving relationship therebetween when the first gear set is
disengaged between the first toothed gear and the first lobed
gear.
14. The gearbox of claim 11, the first gear set being engaged in
the driving relationship therebetween when the second gear set is
disengaged between the second toothed gear and the second lobed
gear.
15. The gearbox of claim 11, further comprising a partition wall
extending orthogonally to the first and second rotational axes
between the first gear set and the second gear set for
hydraulically isolation of the fluid.
16. The gearbox of claim 11, the teeth of said first toothed gear
being angularly offset with relation to the teeth of said second
toothed gear such that a tooth of said first toothed gear is
axially aligned between two teeth of said second toothed gear.
17. The gearbox of claim 11, further comprising radial vanes
extending from the teeth to seal circumferential liquid slip paths
between the toothed gears and the housing and to seal slip paths
between the toothed gears and the lobed gears.
18. The gearbox of claim 11, further comprising radial vanes
extending from the lobes to seal circumferential liquid slip paths
between the lobed gears and the housing and to seal slip paths
between the toothed gears and the lobed gears.
19. The gearbox of claim 11, said first toothed gear and said
second lobed gear being mounted to the first rotational axis.
20. The gearbox of claim 11, wherein said toothed gears and said
lobed gears are spur-shaped.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] This invention relates generally to gear pumps used for
liquids, and more particularly, to positive displacement gear pumps
that emulate characteristics of lobe pumps.
[0003] 2. Description of Related Art
[0004] Typical spur gear pumps used for pumping hydraulic fluids
generally use a drive gear and an idler gear that mesh proximate
inlet and outlet openings of the pump. As the drive and idler gears
rotate, hydraulic fluid fills the gaps between adjacent spur teeth
and is transferred from the inlet through an intermediate
transition zone to the outlet. Each of the rotors has a plurality
of radially extending, circumferentially-spaced spur teeth with
recesses between the teeth. The teeth on each rotor intermesh with
the teeth of the other rotor in sealing contact with the recesses
of rotors therebetween. The drive gear and idler gear are mounted
for rotation on spaced parallel axis with the gears or rotors
typically enclosed in a housing or casing in sealing relationship
with pumping chamber walls thereof. When there is rotational action
of the spur tooth rotors and displacement of fluid by the mating
teeth thereof, the pump is considered a positive displacement gear
pump.
[0005] Spur gear pumps are well known. For example, U.S. Pat. No.
3,272,140, titled "Metering Pump", to Curry, et al., discloses a
split spur gear pump using rotors with radially arrayed spur teeth
projections that drive one another with inter-projection pockets
between the spur teeth transferring fluid from the inlet to the
outlet. However, spur pumps subject the spurs to fluid milling
action that produces high shearing stress and high pressures. This
milling action is detrimental to shear sensitive liquids, such as
delicate food substances (e.g., salsa, relish, mayonnaise, pasta
sauce, soup).
[0006] For shear sensitive liquids, lobed pumps may be preferred,
with lobed rotors that mesh in opposite direction defining cavities
or pockets between adjacent lobes that can trap and transport
liquid from the inlet port to the outlet port of the pump with a
more gentle pumping action and avoid damage resulting from
excessive agitation. U.S. Pat. No. 5,755,566, titled "Self-Driving
Fluid Pump", to Marsillo, et al., discloses an exemplary lobed pump
for delicate fluids with inter-lobe pockets that can transport
relatively large volumes of product at a time and thus avoid the
excessive milling action arising under spur gear pumps with
relatively small inter-spur tooth pockets. The lobes are
significantly larger than teeth of spur gear pumps to include
larger inter-lobe pockets and thereby provide the ability to better
handle shear sensitive liquids.
[0007] However, it would be even more beneficial to provide larger
volume pockets that are available with typical lobe gear pumps to
even better handle shear sensitive liquids. The invention described
herein by example aims to provide such a benefit as the inventor
has realized the benefit to provide even larger volume pockets in a
gear pump.
[0008] All references cited herein are incorporated herein by
reference in their entireties.
BRIEF SUMMARY OF THE INVENTION
[0009] 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
central features of the claimed subject matter, nor is it intended
for use in determining the scope of the claimed subject matter.
[0010] In accordance with an example of the invention, a pump is
provided with a housing having an internal cavity that defines a
pumping chamber, an inlet port adapted to allow a fluid into the
pumping chamber, and an outlet port adapted to discharge the fluid
from the pumping chamber. The pump also includes a gearbox located
in the pumping chamber. The gearbox has a plurality of driving
rotors including first and second spur toothed gears, each having a
plurality of spur shaped teeth, and first and second lobed gears,
each having lobes wider than the spur teeth. The first toothed gear
and the first lobed gear may be a first gear set with the first
toothed gear mounted to one of a first rotational axis and a second
rotational axis in the pumping chamber adjacent the first
rotational axis, and the first lobed gear mounted to the other one
of the first rotational axis and the second rotational axis in the
pumping chamber. The second toothed gear and said second lobed gear
may be a second gear set with the second toothed gear mounted to
one of the first rotational axis and the second rotational axis in
the pumping chamber, and the second lobed gear mounted to the other
one of the first rotational axis and the second rotational axis in
the pumping chamber.
[0011] In another example of the invention, a gearbox of a pump is
provided, with the pump having a housing with an internal cavity
that defines a pumping chamber, an inlet port adapted to allow
fluid into the pumping chamber, and an outlet port adapted to
discharge the fluid from the pumping chamber. The gearbox may be
located in the pumping chamber of the housing. The gearbox includes
a plurality of driving rotors including first and second spur
toothed gears, each having a plurality of spur shaped teeth, and
first and second lobed gears, each having a plurality of lobes
wider than the teeth. The first toothed gear and the first lobed
gear may be a first gear set with the first toothed gear mounted to
one of a first rotational axis and a second rotational axis in the
pumping chamber adjacent the first rotational axis, and the first
lobed gear mounted to the other one of the first rotational axis
and the second rotational axis in the pumping chamber. The second
toothed gear and said second lobed gear may be a second gear set
with the second toothed gear mounted to one of the first rotational
axis and the second rotational axis in the pumping chamber, and the
second lobed gear mounted to the other one of the first rotational
axis and the second rotational axis in the pumping chamber.
[0012] The spur tooth gears may be rotatably mounted in angularly
offset about a first rotational axis in the pumping chamber. The
lobed gears may be rotatably mounted and angularly offset about a
second rotational axis in the pumping chamber adjacent and
preferably substantially parallel to the first rotational axis. The
first spur toothed gear is intermeshed with the first lobed gear in
a driving relationship therebetween. The second spur toothed gear
is intermeshed with the second lobed gear in a driving engagement
therebetween. While not being limited to a particular theory, the
teeth of the spur toothed gears and the lobes of the lobed gears
may have an involute-shaped profile to provide continuously rolling
contact and a fixed pressure angle between the teeth and lobes
during the driving engagement. Preferably one of the first
rotational axis and the second rotational axis is a drive
shaft.
[0013] The second gear set may be engaged in the driving
relationship therebetween when the first gear set is disengaged
between the first toothed gear and the first lobed gear. Similarly,
the first gear set may be engaged in the driving relationship
therebetween when the second gear set is disengaged between the
second toothed gear and the second lobed gear. The teeth of the
first toothed gear may be angularly offset with relation to the
teeth of the second toothed gear such that a tooth of the first
toothed gear is axially aligned between two teeth of the second
toothed gear.
[0014] The toothed gears or lobed gears can be mounted on either
the drive shaft or the idler shaft, with the drive shaft being one
of the first or second rotational axes and the idler shaft being
the other one of the rotational axes. In some examples of the
invention, the first toothed gear and the second lobed gear may be
mounted to the first rotational axis. In other examples, the first
toothed gear and the first lobed gear may be mounted to the first
rotational axis. In yet other examples, the first toothed gear and
the first lobed gear may be mounted to the second rotational axis.
In still other examples, the first toothed gear and the second
lobed gear may be mounted to the second rotational axis.
[0015] The examples of the invention may include a partition wall
extending orthogonally to the first and second rotational axes
between the first gear set and the second gear set for hydraulic
isolation of the fluid. The examples may also include radial vanes
extending from the teeth to seal circumferential liquid slip paths
between the toothed gears and the housing and to seal slip paths
between the toothed gears and the lobed gears. The examples may
further include radial vanes extending from the lobes to seal
circumferential liquid slip paths between the lobed gears and the
housing and to seal slip paths between the toothed gears and the
lobed gears.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0016] The invention will be described in conjunction with the
following drawings in which like reference numerals designate like
elements and wherein:
[0017] FIG. 1 is a top view, partially in section, of a pump
constructed in accordance with an example of the invention;
[0018] FIG. 2 is a perspective view of the gear mechanism
illustrated in FIG. 1;
[0019] FIG. 3 is a perspective view of another exemplary gear
mechanism of the invention; and
[0020] FIG. 4 is a perspective view of yet another exemplary gear
mechanism of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] The exemplary embodiments of the pump are described with
reference to FIGS. 1-4. While not being limited to a particular
theory, the exemplary embodiments include both spur gears and lobed
gears intermeshed to create larger volume pockets in gear sets of a
given size. The pockets are larger than the pockets that exist in
current lobe pumps and provide the benefit of a pump that better
handles shear sensitive liquids. Preferably, the profiles of the
spur teeth and of the lobes are involute-shaped to provide rolling
contact and a fixed pressure angle between the spur teeth and lobes
during engagement. The involute-shaped profiles prevent the teeth
and lobes from rubbing and sliding against one another during
engagement. Rubbing and sliding increases friction, power
consumption, wear and galling to the meshing spur teeth and lobes.
While traditional lobe pumps require an external gearbox to
synchronize its pump rotors to one another and to keep the rotors
from rubbing during operation, the examples of the invention
eliminate this need for such an external gearbox.
[0022] The profile of the spur gear rotors and the lobe gear rotors
can be made as an improvement from standard spur and helical gear
designs, for example, by omitting alternate teeth on the standard
spur rotors and filling in corresponding gaps on the mating
standard lobed rotors. In some cases, depending upon gear geometry,
this approach allows the gears to become disengaged from one
another as they rotate. To solve this problem, additional spur
toothed and lobed rotors are added in tandem to the shafts and
circumferentially offset to provide driving tooth engagement
between at least one pair of the spur toothed and lobed rotors at
every point around the rotational circumference of the rotors. With
this configuration, the rotor sets directly drive one another, and
thus do not require a separate gearbox with driving/synchronizing
gears.
[0023] Accordingly, tandem gears overcome the problem of gear
disengagement that previously would require an additional gearbox.
As can be seen in the figures, a spur toothed gear and matching
lobe gear may become completely disengaged in certain rotational
positions. Placing another pair of matching spur and lobed gears in
tandem behind the first pair, with a rotational offset between the
pairs that may be equal to half of the angle between the spurs or
lobes on the rotors, and keying them all to the shafts to lock the
rotational offset provides teeth in mesh in at least one of the
pairs of rotors at all times.
[0024] According to examples of the invention, there is provided a
self-driving fluid pump having male (e.g., spur toothed) and female
(e.g., lobed) rotary members mounted for rotation on spaced
parallel axis. The rotors can be enclosed in a housing or casing in
sealing relationship with cylindrically curved parts thereof, or
they may be mounted on open framework for operation while immersed
in a fluid medium. Each of the male rotors has a plurality of
radially extending circumferentially spaced spur shaped teeth with
recesses between the teeth. Each of the female rotors has a
plurality of radially descending pockets that define
circumferentially spaced lobes, with the pockets forming recesses
between the lobes. The spur teeth on each male rotor intermeshed
with the lobes of the female rotor in sealing contact. Preferably,
each of the rotors has flat parallel sides, although the invention
is not limited by shape of the sides.
[0025] The rotors may rotate in the housing in sealing contact with
opposite interval sides or walls of the housing that define the
pumping chamber thereof. The housing includes two communication
compartments. One compartment may serve as an inlet bore or port to
receive fluid from an external conduit connected to the housing.
The other compartment may serve as an outlet bore or port to expel
fluid under pressure to a discharge conduit as the rotors rotate in
the housing.
[0026] A first set of in tandem rotors may serve as drive rotors
driven by a powered shaft connected to the rotors. Other tandem
rotors intermeshed with the first set of tandem rotors, then serve
as driven rotors coupled to the idler shaft. The rotors are
connected to their respective shafts and rotationally locked to
their shaft via locking pins that extend into and between the
rotors and shafts for locked engagement therebetween. As the spur
teeth of a rotor enter the recesses of its matching lobed rotor,
fluid is pumped between the rotors and out of the outlet
compartment. While the examples of the invention depicted in the
figures and discussed below concentrate on spur gears, it is
understood that the invention covers at least both spur gears and
helical gears. In other words, the tooth gears and lobe gears may
be helical within the scope of the invention, that is, with gear
teeth and lobes at some angle relative to the shaft
centerlines.
[0027] Other advantages, characteristics and details of the
invention will emerge from the explanatory description below with
reference to the attached drawings and examples, however, it should
be understood that the present invention is not deemed to be
limited thereto. To that end, FIG. 1 depicts an exemplary spur
teeth/lobed pump apparatus 10. The pump apparatus 10 includes a
housing 12 and a gearbox or gear mechanism 14 (FIG. 2), preferably
both made of a material (e.g., steel, cast iron, bronze, ceramic,
some combination thereof) compatible with shear sensitive liquids.
From the housing 12 projects an inlet port 16 through which fluid
matter is admitted into the pump apparatus 10, and an outlet port
18 for discharging the pumped matter. The housing 12 includes a
main casing 20 that is integrally formed with the inlet bore 16 and
the out let bore 18. The main casing 20 includes walls 22 having
cylindrically curved portions 24 thereof that internally forms a
cavity defining a pumping chamber 26 therein. The main casing 20
may include a top cover and a bottom cover that sealingly enclose
the pumping chamber 26 as would readily be understood by a skilled
artisan. Preferably, the top and bottom covers may be mounted on
respective sides of the main casing 20 by using suitable fasteners
such as bolts and/or screws (not shown). In another example, one of
the top or bottom covers may be integrally mounted to the main
casing 20. It is understood that one of the covers further includes
an aperture to accommodate a driving shaft that is coupled to gears
within the pumping chamber 26, as will be described in greater
detail below.
[0028] Referring to FIGS. 1 and 2, the gearbox 14 located in the
pumping chamber 26 includes a plurality of male and female rotors
having different shapes. For example, the male rotors are spur
toothed gears 28 having a plurality of spur teeth 30. The female
rotors may be lobed gears 32, each having a plurality of lobes 34.
As can best be seen in FIG. 2, each lobe 34 is significantly wider
than each spur tooth 30. In particular, each lobe 34 may be twice
or thrice the width of each spur tooth 30.
[0029] In the examples depicted by the drawings, the gearbox 14
includes at least two pairs of meshed gears with each pair
including a spur tooth gear 28 and a lobe gear 32. For example, a
first pair of meshed gears includes a first lobed gear 36 adjacent
a first spur tooth gear 38 and intermeshed in a driving engagement
therebetween. Continuing, a second pair of meshed gears includes a
second lobed gear 40 adjacent a second spur toothed gear 42
intermeshed in a driving engagement therebetween. The form of the
spur teeth and lobes may be involute-shaped to provide continuously
rolling contact and a fixed pressure angle between the spur teeth
and lobes during the intermeshed driving engagement. It is
understood that additional gear sets (e.g., pairs of tooth and lobe
gears), including third, fourth and fifth sets may be placed in
tandem with the first and second gear sets.
[0030] Still referring to FIGS. 1 and 2, the first and second lobed
gears 36, 40 are understood to be generally identically shaped lobe
gears 32 mounted in tandem about a first shaft 44, with the first
and second lobed gears rotationally offset. Similarly, the first
and second spur toothed gears 38, 42 are understood to be generally
identically shaped spur toothed gears 28 attached in tandem to a
second shaft 46 with a rotational offset between the gears.
Preferably, the second lobed gear 40 is rotationally offset from
the first lobed gear 36 at an angle equivalent to half the angle
between the lobes on the first lobe gear 36, for example, 60
degrees for a three lobed gear. Similarly, the second spur toothed
gear is rotationally offset from the first spur toothed gear 38 at
an angle equivalent to half the angle between the spur teeth of the
first spur toothed gear, for example, 60 degrees for a three
toothed gear. This offset enables the maintenance of a continuous
engagement between the gears as they rotate. For additional
clarity, the lobes 34 of the second lobed gear 40 are also
identified as reference number 35.
[0031] The lobed gears 36, 40 preferably are rotationally locked
against the first shaft 44, which is shown by example as a drive
shaft. Similarly, the male spur toothed gears 38, 42 preferably are
rotationally locked to the second shaft 46, which is shown by
example as an idler shaft. Between the shafts 44, 46, preferably
one of the shafts is the drive shaft and the other shaft is the
idler shaft. It is understood that the current invention is not
limited to either configuration, as the pump apparatus 10 works
equally well regardless of which shaft is the drive shaft or the
idler shaft. The gears 36, 38, 40, 42 are keyed to their respective
shaft 44, 46 with pins 48 slip-fitted into matching channels of the
gears and shafts to at least rotationally lock the gears to the
shafts, as would readily be understood by a skilled artisan.
[0032] While the examples of the invention depict the lobed gears
as coupled to the first shaft 44 and the spur toothed gears coupled
to the second shaft 46, it is understood that the invention is not
limited to the placement of any lobed gear or any spur toothed gear
on any one particular shaft. For example, the spur toothed and
lobed gears may alternatively be placed on either one of the shafts
44, 46 as long as one of each corresponding spur toothed gear and
lobed gear are placed to form a pair of rotors, with one spur
toothed gear and one lobed gear in a meshed relationship
therebetween. In other words, a spur toothed gear 28 and a lobed
gear 32 may be mounted in tandem to the first shaft 44, with each
gear intermeshed with a corresponding lobed gear 32 and a spur
toothed gear 28 mounted in tandem to the second shaft 46.
[0033] While not being limited to a particular theory, the spur
teeth 30 of the toothed gears 28 and the lobes 34 of the lobed
gears 32 have an involute-shaped profile to provide continuously
rolling contact and a fixed pressure angle between the teeth and
lobes during the driving engagement. With teeth of other shapes,
the relative speeds and forces rise and fall as successive teeth
engage, resulting in vibration, noise and excessive wear. The
exemplary embodiments of the invention preferably use teeth and
lobes having the involute shape so that the relative rates of
rotation are constant while the teeth and lobes are engaged, and
further, the engaging gears always make contact along a single
steady line of force.
[0034] The exemplary embodiments depicted by the figures show each
gear having either three spur teeth 30 or three lobes 34. However,
it is understood that the gears of the invention are not limited to
any specific number of teeth/lobes. In some cases, depending upon
gear geometry, gears may become disengaged from one another as they
rotate. For example, in FIGS. 1 and 2, the first lobed gear 36 and
first spur toothed gear 38 are a first gear set (e.g., at least a
pair of gears) shown at a snapshot of rotation disengaged and thus
not in driving engagement with each other. However, the second
lobed gear 40 is angularly offset from the first lobed gear 36, and
the second spur toothed gear 42 is angularly offset from the first
spur toothed gear 30. As can be seen in FIGS. 1 and 2, a second
gear set of the second lobed gear 40 and the second spur toothed
gear 42 are engaged therebetween when the first gear set is
disengaged. With this arrangement, the angular offset of the second
gear set to the first gear set enables continuous engagement
between the drive gears coupled to the drive shaft and the idler
gears coupled to the idler shaft as the gear sets rotate. In this
manner, the tandem gears overcome the problem of gear disengagement
encountered in some geometries. Accordingly, by placing a second
set of gears in tandem behind a first set of gears, and keying them
all to their respective shafts with a rotational offset
therebetween as shown, the gearbox 14 always has separate teeth and
lobes in mesh in at least one of its set of gears.
[0035] FIG. 3 depicts a gearbox 60 similar to the gearbox 14 shown
by example in FIGS. 1 and 2. The gearbox 60 adds a wear plate 62 as
a partition wall between the first and second gear sets, with the
wear plate 62 fitting within the pumping chamber 26 of the housing
12 to hydraulically isolate fluid material on either side of the
wear plate 62. The wear plate 62 may also further reduce milling
action exerted on the pump fluids and has the effect of
transforming the pump into separate pumping devices operating in
parallel and sharing common inlet and outlet ports 16, 18. In this
manner, the flow of fluid delivered into the pumping chamber 26
from the inlet port 16 is separated into two groups with one group
passing on each side of the wear plate 62. The pump fluid is
combined at the outlet port 18 for exit from the housing 12. The
wear plate 62 also increases the pump efficiency in terms of
pressure and displacement by eliminating fluid cross-flow between
the gear sets during operation. Like the other components of the
apparatus 10 discussed herein, the wear plate 62 is preferably made
of steel, but it is understood that the wear plate may be made of
materials, including cast iron, bronze, ceramic, steel, plastic,
resin, or some combination thereof, that maintain the operability
of the plate in the pumping chamber 26.
[0036] FIG. 4 depicts another example of a gearbox 70 that fits in
a pumping chamber 26 of the pump housing 12. The gearbox 70 is
similar to the gearboxes 14, 60 described above. In particular, the
gearbox 70 includes a plurality of rotors including first and
second spur toothed gears 72, 74, each having a plurality of spur
teeth 76. The plurality of driving rotors also includes first and
second lobed gears 78, 80, each having a plurality of lobes 82.
Each of the lobes 82 is wider than the spur teeth 76. Preferably,
the lobed teeth are at least double the width of each spur tooth.
In other words, each lobe has an arcuate width at least double the
arcuate width of each spur tooth. Similar to the spur toothed gears
28 described above, the spur toothed gears 72, 74 are rotatably
mounted and angularly offset about a first rotational axis (e.g.,
idler shaft 46). In addition and similar to the lobed gears 32
discussed above, the lobed gears 78, 80 are rotatably mounted and
angularly offset to each other about a second rotational axis
(e.g., drive shaft 44). The drive and idler shafts 44, 46 are
adjacent and substantially parallel to each other. The spur toothed
gears 72, 74 are intermeshed with corresponding first and second
lobed gears 78, 80 in driving rotational engagement therebetween.
Like the spur teeth 30 and lobes 34 described above, the spur teeth
76 and lobes 82 preferably have an involute-shaped profile to
provide continuously rolling contact and a fixed pressure angle
between the teeth and lobes during driving engagement.
[0037] Still referring to FIG. 4, the spur teeth 76 and the lobes
82 include radially extending wipers or vanes 84 that seal liquid
slip paths (e.g., radial running clearance areas) that typically
exist between the outer ends of the spur teeth and lobes and the
case bore defined by the pumping chamber 26. While not being
limited to a particular theory, the radially spaced vanes 84 are
disposed within and extend out of respective vane slots 86 formed
in the spur teeth 76 and lobes 82. The vanes 84 may also extend
within the spur teeth/lobes toward the respective axle or shaft 44,
46. Centrifugal force and/or an outward bias that may be provided
by, for example, springs 88 within the vane slots 86, urge each
vane 84 radially outward into contact with the walls of the pumping
chamber 26. During rotation of the gears 72, 74, 78, and 80, the
vanes 84 may also be urged radially outward into contact with an
engaging gear, as can be seen, for example, in FIG. 4. It is
understood that gear rotation is required for centrifugal force to
urge the vanes 84 outward, while compression springs 86 may be
preferred to urge the vanes outward regardless of the rotation.
[0038] Preferably, the housing, gears, shafts, wear plate, vanes
and springs discussed by example herein are made of metal or other
hard, durable material, as readily understood by a skilled artisan.
For example, the housing, gears, wear plate, shafts, vanes and
springs are preferably made of steel, cast iron, bronze, ceramic,
or some combination thereof. The wear plate and vanes may also be
made of a resin, rubber or polypropylene. It should be understood
that the springs may most preferably be formed of a material
capably strong and resilient to function as a biasing member.
[0039] During operation, fluid is drawn from the inlet port 16 into
an increasing volume defined by the pumping chamber 26, the gears
and any wear plate that may be included within the gearbox. After
entering the inlet port, the fluid is transported circumferentially
around the outside of the rotors in the pockets formed by the gear
28, 32 and the housing bore walls. The transported fluid is then
displaced by the teeth and lobes coming into mesh and discharged
through the outlet port 18 and out of the housing 12. During the
rotation of the gears, the vanes 84 are extended, preferably to the
bore walls of the pumping chamber 26 to help seal radial clearance
slip paths, and during intermeshing, the vanes 84 are extended to
compress against centrifugal force and/or a biasing member into the
surface of the meshed gear.
[0040] It is understood that the spur toothed/lobed gear pump
described and shown are exemplary indications of preferred
embodiments of the invention, and are given by way of illustration
only. In other words, the concept of the present invention may be
readily applied to a variety of preferred embodiments, including
those disclosed herein. While the invention has been described in
detail and with reference to specific examples thereof, it would be
apparent to one skilled in the art that various changes and
modifications can be made therein without departing from the spirit
and the scope thereof. For example, the number and material of the
spur or helical teeth, lobes, gears, wear plate and vanes described
may be altered without departing from the scope of the invention.
Without further elaboration, the foregoing will so fully illustrate
the invention that others may, by applying current and future
knowledge, readily adapt the same for use under various conditions
of service.
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