U.S. patent application number 12/020539 was filed with the patent office on 2008-10-23 for rolling diaphragm pump.
Invention is credited to Walter Neal Simmons.
Application Number | 20080260551 12/020539 |
Document ID | / |
Family ID | 39872367 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080260551 |
Kind Code |
A1 |
Simmons; Walter Neal |
October 23, 2008 |
ROLLING DIAPHRAGM PUMP
Abstract
A rolling diaphragm pump includes a housing, a rolling seal
diaphragm disposed in the housing, a piston for driving the
diaphragm, and a valve for regulating the flow of working fluid in
a portion of the housing. A constant differential pressure is
maintained across the diaphragm independent of discharge pressure
of the pump. A method of pumping a viscous medium includes pumping
the viscous medium by maintaining a constant differential pressure
across a rolling seal diaphragm independent of discharge pressure
of the viscous medium, with the diaphragm disposed between the
viscous medium and a working medium and being driven by a
piston.
Inventors: |
Simmons; Walter Neal;
(Durham, NC) |
Correspondence
Address: |
STEPTOE & JOHNSON LLP
1330 CONNECTICUT AVENUE, N.W.
WASHINGTON
DC
20036
US
|
Family ID: |
39872367 |
Appl. No.: |
12/020539 |
Filed: |
January 26, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60886919 |
Jan 26, 2007 |
|
|
|
Current U.S.
Class: |
417/394 ;
92/98D |
Current CPC
Class: |
F04B 45/043
20130101 |
Class at
Publication: |
417/394 ;
92/98.D |
International
Class: |
F04B 45/00 20060101
F04B045/00; F01B 19/00 20060101 F01B019/00 |
Claims
1. A rolling diaphragm pump comprising: a housing; a rolling seal
diaphragm disposed in the housing; a piston for driving the
diaphragm; and a valve for regulating the flow of working fluid in
a portion of the housing; wherein a constant differential pressure
is maintained across the diaphragm independent of discharge
pressure of the pump.
2. The pump of claim 1, wherein the rolling seal diaphragm is top
hat shaped.
3. The pump of claim 1, wherein the constant differential pressure
is between 1 psi and 100 psi.
4. The pump of claim 1, wherein the constant differential pressure
is between 10 psi and 50 psi.
5. The pump of claim 1, wherein the constant differential pressure
is between 10 psi and 20 psi.
6. The pump of claim 1, wherein the discharge pressure is greater
than 1000 psi.
7. The pump of claim 1, wherein the discharge pressure is greater
than 500 psi.
8. A method of pumping a viscous medium comprising: pumping the
viscous medium by maintaining a constant differential pressure
across a rolling seal diaphragm independent of discharge pressure
of the viscous medium, with the diaphragm disposed between the
viscous medium and a working medium and being driven by a
piston.
9. The method of claim 8, wherein the viscous medium is discharged
at a constant flow rate.
10. The method of claim 8, wherein the viscous medium is discharged
at a constant pressure.
11. The method of claim 8, further comprising: regulating the flow
of the working medium.
12. The method of claim 8, wherein the rolling seal diaphragm is
top hat shaped.
13. The method of claim 8, wherein the constant differential
pressure is between 1 psi and 100 psi.
14. The method of claim 8, wherein the constant differential
pressure is between 10 psi and 50 psi.
15. The method of claim 8, wherein the constant differential
pressure is between 10 psi and 20 psi.
16. The method of claim 8, wherein the discharge pressure is
greater than 1000 psi.
17. The method of claim 8, wherein the discharge pressure is
greater than 500 psi.
18. The method of claim 8, wherein the viscous medium comprises a
slurry with a viscosity between 10,000 and 5,000,000
centipoise.
19. The method of claim 8, wherein the viscous medium comprises
aggregate with a maximum lateral dimension of 1/4 inch.
20. The method of claim 8, wherein the viscous medium comprises
aggregate with a maximum lateral dimension of 1/8 inch.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The benefits of U.S. Provisional Application No. 60/886,919
filed Jan. 26, 2007 and entitled "Rolling Diaphragm Pump" are
claimed under 35 U.S.C. .sctn. 119(e), and the entire contents of
this provisional application are expressly incorporated herein by
reference thereto.
FIELD OF THE INVENTION
[0002] The invention relates to a pump and product delivery. More
particularly, the invention relates to rolling diaphragm type
pumps.
BACKGROUND OF THE INVENTION
[0003] In a rolling diaphragm type pump, a small amount of positive
differential pressure is needed to keep the diaphragm in the
correct orientation (convoluted orientation). However, if the
differential pressure is too high, the diaphragm will wear out at a
faster rate or even burst in extreme cases.
[0004] Prior art rolling diaphragm pump designs create a positive
differential pressure by sizing the driving cylinders to match the
diaphragm diameter. This limits the diaphragm size to one that will
match with commercial cylinders. Additionally, the greater the
mismatch, the more the differential pressure will vary with the
pump's output pressure.
[0005] In a prior art rolling diaphragm pump, the differential
pressure across the diaphragm is determined by the pump dimensions
and the working pressure. For a given pump size, the differential
pressure increases as the working pressure increases. This not only
reduces the lifetime of the diaphragms but also limits the maximum
pressure of the pump.
[0006] A dual-unit pump, e.g., a rolling diaphragm piston pump, is
disclosed in U.S. Pat. No. 4,543,044, the entire contents of which
are incorporated herein by reference thereto. The pump is suitable
for pumping an abrasive high-viscosity slurry, and is adapted to
operate at a constant flow rate by means for detecting and
correcting a pressure differential in the two units before the
units switch from the pumping cycle to the filling cycle and vice
versa. The flow of liquids is controlled by valves of the type
which switch the flow to and from the units with essentially no
volume change in the liquid inlet and outlet lines.
[0007] Turning to FIG. 1, a rolling diaphragm pump 10 of the prior
art is shown. Piston 12, which for example may be formed of nylon,
is disposed within a cylindrical housing 13 and seated with respect
to top-hat shaped rubber diaphragm 14. A working fluid 16 such as
oil and a discharge fluid 18 (the fluid that is being pumped) are
shown. A standard hydraulic cylinder 19 (such as a double-rodded
cylinder with a vented top) includes a fluid region 20 such as
having oil therein, rods 22a and 22b, and a vented region 24.
Piston 12 is used to maintain the shape of diaphragm 14. Diaphragm
14 is coupled along its circumference to housing 13 at regions 27
along axis 25b which is normal to axis 25a (along which rods 22a,
22b for example are axially disposed).
[0008] In FIG. 1, P.sub.1 is the discharge pressure of the medium
that is being pumped (e.g., to a packaging machine so that the
medium may be used to fill a chub), P.sub.2 is the pressure of the
hydraulic fluid under piston 12 (e.g., the working fluid pressure),
P.sub.3 is vented to atmosphere and assumed as zero pressure with
respect to atmosphere, and P.sub.4 is connected to P.sub.2 and thus
is the same as the pressure of the hydraulic pressure P.sub.2. In
addition, for the purposes of this analysis, A.sub.1 is the
effective area that pressure P.sub.1 acts upon to produce force in
a direction parallel to axis 25a, A.sub.2 is the effective area
that pressure P.sub.2 acts upon to produce force in a direction
parallel to axis 25a, and A.sub.3 is the internal area of the
hydraulic cylinder 19 about a plane normal to axis 25a. Product is
discharged from pump 10 in direction E. Preferably,
P.sub.1>P.sub.2 in FIG. 1.
[0009] According to the design of pump 10 in FIG. 1, the downward
force is determined by the following Equation 1 below:
F.sub.down=P.sub.1A.sub.1+P.sub.2A.sub.4+P.sub.3(A.sub.3-A.sub.4)
(Eq. 1)
The upward force is determined by Equation 2 below:
F.sub.up=(P.sub.2A.sub.2)+[P.sub.4(A.sub.3-A.sub.4)] (Eq. 2)
Area A.sub.1 is the same as area A.sub.2, pressure P.sub.2 is the
same as pressure P.sub.4, and pressure P.sub.3 is zero pressure
with respect to atmosphere. Thus, the upward force must balance the
downward force as in Equation 3 below:
(P.sub.1A.sub.1)+(P.sub.2A.sub.4)=(P.sub.2-A.sub.1)+[P.sub.2(A.sub.3-A.s-
ub.4)] (Eq. 3)
[0010] This balance can be simplified as shown in Equations 4-6
below:
[ A 1 ( P 1 - P 2 ) ] = [ P 2 ( A 3 - A 4 ) ] - ( P 2 A 4 ) ( Eq .
4 ) [ A 1 ( P 1 - P 2 ) ] = P 2 [ A 3 - ( 2 A 4 ) ] ( Eq . 5 )
.DELTA. P = P 1 - P 2 = ( A 3 - 2 A 4 ) A 1 ( Eq . 6 )
##EQU00001##
[0011] Thus, as shown in Equation 6, .DELTA.P is dependent on
working pressure.
[0012] Pumping high viscosity liquids and slurries at high pressure
and/or at constant pressure or constant flow rate is particularly
difficult. High viscosities slurries, for example, may be between
10,000 and 5,000,000 centipoise, and may be abrasive and include
large particulates such as rocks 1/8 inch in general size. However,
pumping pressures in prior art rolling diaphragm pumps are limited
by the pressure that the diaphragm can withstand. The differential
pressure .DELTA.P varies with discharge pressure P.sub.1 and
therefore if P.sub.1 becomes too high, .DELTA.P can become so high
that the diaphragm integrity is lost and the diaphragm breaks.
[0013] It is desired that the differential pressure .DELTA.P is in
the range of 10 psi to 20 psi so that the diaphragm is maintained
in the correct shape and position, while not being overstressed.
The prior art rolling diaphragm pump permits this but only for a
fixed range of discharge pressure P.sub.1 as will be further
described herein.
SUMMARY OF THE INVENTION
[0014] A rolling diaphragm pump may include a housing, a rolling
seal diaphragm disposed in the housing, a piston for driving the
diaphragm, and a valve for regulating the flow of working fluid in
a portion of the housing. A constant differential pressure may be
maintained across the diaphragm independent of discharge pressure
of the pump. In some embodiments, the rolling seal diaphragm is top
hat shaped. Also, the constant differential pressure may be between
1 psi and 100 psi, between 10 psi and 50 psi, or between 10 psi and
20 psi. The discharge pressure may be greater than 1000 psi or
greater than 500 psi.
[0015] A method of pumping a viscous medium may include: pumping
the viscous medium by maintaining a constant differential pressure
across a rolling seal diaphragm independent of discharge pressure
of the viscous medium, with the diaphragm disposed between the
viscous medium and a working medium and being driven by a piston.
The viscous medium may be discharged at a constant flow rate or
discharged at a constant pressure. The method may further include:
regulating the flow of the working medium. In the method, the
rolling seal diaphragm may be top hat shaped. Also in the method,
the constant differential pressure may be between 1 psi and 100
psi, between 10 psi and 50 psi, or between 10 psi and 20 psi. In
the method, the discharge pressure may be greater than 1000 psi or
greater than 500 psi. Further, in the method, the viscous medium
may be a slurry with a viscosity between 10,000 and 5,000,000
centipoise. Also, the viscous medium may include aggregate with a
maximum lateral dimension of 1/4 inch or aggregate with a maximum
lateral dimension of 1/8 inch.
[0016] In one embodiment of the invention, a rolling diaphragm pump
creates a positive differential pressure through the use of an
adjustable check valve that regulates the flow of a working fluid,
such as oil, between the driving cylinder and the bottom of the
diaphragm by opening when a threshold pressure is met. This
provides control of the differential pressure (.DELTA.P) while
being independent of the discharge pressure (P.sub.1).
Advantageously, an increased pressure range is realized in which
the rolling diaphragm pump can operate, and variable control of
diaphragm stress is permitted.
[0017] In some embodiments, a rolling diaphragm allows continuously
variable control of the differential pressure across the diaphragm,
which is independent of the discharge pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Preferred features of embodiments are disclosed in the
accompanying drawings, wherein:
[0019] FIG. 1 shows a prior art rolling diaphragm pump; and
[0020] FIG. 2 shows an exemplary embodiment of an inventive rolling
diaphragm pump.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Turning to FIG. 2, an exemplary embodiment of an inventive
rolling diaphragm pump 100 is shown. Pump 100 is suitable, for
example, for use in pumping mine roof bolt anchoring compositions,
water-bearing explosives, food products, concrete, fraccing fluids
for oil and gas wells, coal/water slurries, nuclear waste slurries,
asphalt, paint, and filled epoxy resins. However, this list is
non-exhaustive and a variety of high viscosity liquids and slurries
are amendable to pumping in accordance with the exemplary
embodiment.
[0022] Inventive rolling diaphragm pump 100 includes a piston 112,
which for example may be formed of nylon, is disposed within a
cylindrical housing 113, and is seated with respect to a rolling
seal diaphragm 114 such as a top-hat shaped rubber diaphragm. A
working medium 116 such as oil fluid and a discharge medium 118
(the medium that is being pumped) are shown. A standard hydraulic
cylinder 119 (such as a single-rodded cylinder) includes a fluid
region 120 such as having oil therein, and a rod 122. Portion 121
is in communication with housing 113. Piston 112 is used to
maintain the shape of diaphragm 114. Diaphragm 114 is coupled along
its circumference to housing 113 at regions 127 along axis 125b
which is normal to axis 125a (along which rod 122 for example is
axially disposed).
[0023] In FIG. 2, Pt is the discharge pressure of the medium that
is being pumped (e.g., to a packaging machine so that the medium
may be used to fill a chub), P.sub.2 is the pressure of the
hydraulic fluid under piston 112 (e.g., the working fluid
pressure), and P.sub.4 is connected to P.sub.2 and is the pressure
in fluid region 120 and is greater than P.sub.2 by the setting of
check valve 126. In addition, for the purposes of this analysis,
A.sub.1 is the effective area that pressure P.sub.1 acts upon to
produce force in a direction parallel to axis 125a, A.sub.2 is the
effective area that pressure P.sub.2 acts upon to produce force in
a direction parallel to axis 125a, and A.sub.3 is the internal area
of the hydraulic cylinder 119 about a plane normal to axis 125a.
Product is discharged from pump 100 in direction E. Preferably,
P.sub.1>P.sub.2 in FIG. 2, so that diaphragm 114 does not invert
(resulting in accelerated wear of the diaphragm). Moreover,
P.sub.4>P.sub.2.
[0024] Because rod 122 is threadably associated with piston 112,
oil flows around the threads and on top of rod 122 so that A.sub.4
does not effect A.sub.2. Therefore, A.sub.1 is the same as A.sub.2.
The pressure of check valve 126, P.sub.check, is fully adjustable
to suit a given need, the check valve being designed to open when a
threshold differential pressure is met. Thus, a constant pressure
can be created across diaphragm 114 regardless of the pumping
pressure. In other words, regardless of whether the pumping
pressure is 500 psi, 1000 psi, or 10,000 psi, the differential
pressure .DELTA.P, calculated as P.sub.1-P.sub.2, is always the
same. In contrast, the prior art pump 10 would not function
properly at wide ranges of pressures (e.g., 1,000 psi as compared
to 10,000 psi) because the differential pressure .DELTA.P would
increase as P1 increases and become so great as to compromise the
diaphragm. Pump 100 provides constant flow rate or constant
pressure performance. Unlike prior art pump 10, inventive pump 100
advantageously permits pumping of viscous mediums with large
aggregates (1) at high pressure and/or (2) at constant pressure or
constant flow rate over wide pressure ranges. In addition,
inventive pump 100 advantageously may permit longer life of
operation in high pressure usage than rotating or progressive-type
pumps which suffer from substantial wear when pumping media having
large aggregates.
[0025] The theory of operation of exemplary inventive pump 100 now
will be explained. In pump 100, the downward force is determined by
the following Equation 7:
F.sub.down=(P.sub.1A.sub.1)+(P.sub.2-A.sub.3) (Eq. 7)
The upward force is determined by Equation 8 below:
F.sub.up=(P.sub.2A.sub.2)+(P.sub.4A.sub.3) (Eq. 8)
Area A.sub.2 is the same as area A.sub.1, and the check valve
pressure P.sub.check is P.sub.4-P.sub.2. The upward force must
balance the downward force as in Equation 9 below:
(P.sub.1A.sub.1)+(P.sub.2A.sub.3)=(P.sub.2A.sub.1)+(P.sub.4A.sub.3)
(Eq. 9)
This balance can be simplified as shown in Equations 10-12
below:
[ A 1 ( P 1 - P 2 ) ] = ( P 4 A 3 ) - ( P 2 A 3 ) ( Eq . 10 ) [ A 1
( P 1 - P 2 ) ] = A 3 ( P 4 - P 2 ) ( Eq . 11 ) .DELTA. P = P 1 - P
2 = ( P 4 - P 2 ) ( A 3 A 1 ) = P check ( A 3 A 1 ) ( Eq . 12 )
##EQU00002##
Thus, as shown in Equation 12, .DELTA.P is independent of the
working pressure.
[0026] A theoretical performance comparison, based on the above
Equations 1-12, is presented below for an exemplary resin pump
assuming the following: diaphragm area A.sub.1 of 101.6234
in..sup.2, cylinder area A.sub.3 of 8.295768 in..sup.2, rod area
A.sub.4 of 1.484893 in..sup.2, check pressure of 90 psi, diaphragm
diameter 11.75 in., piston diameter 11 in., cylinder diameter 3.25
in., and rod diameter 1.375 in. Table 1 shows the theoretical
performance of the prior art rolling diaphragm pump while Table 2
shows the performance according to the inventive design, with
P.sub.1 being the discharge pressure of the medium that is being
pumped, P.sub.2 being the pressure of the hydraulic fluid under the
piston, and .DELTA.P being P.sub.1-P.sub.2.
TABLE-US-00001 TABLE 1 P.sub.1 (psi) P.sub.2 (psi) .DELTA.P (psi)
100 95.02009 4.979909 200 190.0402 9.959817 300 285.0603 14.93973
400 380.0804 19.91963 500 475.1005 24.89954 600 570.1205 29.87945
700 665.1406 34.85936 800 760.1607 39.83927 900 855.1808 44.81918
1000 950.2009 49.79909 1100 1045.221 54.77899 1200 1140.241
59.75890 1300 1235.261 64.73881 1400 1330.281 69.71872 1500
1425.301 74.69863 1600 1520.321 79.67854 1700 1615.342 84.65845
1800 1710.362 89.63836 1900 1805.382 94.61826 2000 1900.402
99.59817
TABLE-US-00002 TABLE 2 P.sub.1 (psi) P.sub.2 (psi) .DELTA.P (psi)
100 92 8.0 200 192 8.0 300 292 8.0 400 392 8.0 500 492 8.0 600 592
8.0 700 692 8.0 800 792 8.0 900 892 8.0 1000 992 8.0 1100 1092 8.0
1200 1192 8.0 1300 1292 8.0 1400 1392 8.0 1500 1492 8.0 1600 1592
8.0 1700 1692 8.0 1800 1792 8.0 1900 1892 8.0 2000 1992 8.0
[0027] As evident from Table 1, in the prior art design the
.DELTA.P is dependent on the working pressure, while in the
exemplary inventive design .DELTA.P is independent of the working
pressure.
[0028] A theoretical performance comparison, based on the above
Equations 1-12, also is presented below for an exemplary catalyst
pump assuming the following: diaphragm area A.sub.1 of 44.17875
in..sup.2, cylinder area A.sub.3 of 8.295768 in., rod area A.sub.4
of 1.484893 in..sup.2, check pressure of 35 psi, diaphragm diameter
7.75 in., piston diameter 7.25 in., cylinder diameter 3.25 in., and
rod diameter 1.375 in. Table 3 shows the theoretical performance of
the prior art rolling diaphragm pump while Table 4 shows the
performance according to the inventive design, with P.sub.1 being
the discharge pressure of the medium that is being pumped, P.sub.2
being the pressure of the hydraulic fluid under the piston, and
.DELTA.P being P.sub.1-P.sub.2 as in the examples above.
TABLE-US-00003 TABLE 3 P.sub.1 (psi) P.sub.2 (psi) .DELTA.P (psi)
100 89.24147 10.75853 200 178.4829 21.51706 300 267.7244 32.27559
400 356.9659 43.03412 500 446.2074 53.79265 600 535.4488 64.55118
700 624.6903 75.30971 800 713.9318 86.06824 900 803.1732 96.82677
1000 892.4147 107.5853 1100 981.6562 118.3438 1200 1070.898
129.1024 1300 1160.139 139.8609 1400 1249.381 150.6194 1500
1338.622 161.3779 1600 1427.864 172.1365 1700 1517.105 182.895 1800
1606.346 193.6535 1900 1695.588 204.4121 2000 1784.829 215.1706
TABLE-US-00004 TABLE 4 P.sub.1 (psi) P.sub.2 (psi) .DELTA.P (psi)
100 91.90837 8.091632 200 191.9084 8.091632 300 291.9084 8.091632
400 391.9084 8.091632 500 491.9084 8.091632 600 591.9084 8.091632
700 691.9084 8.091632 800 791.9084 8.091632 900 891.9084 8.091632
1000 991.9084 8.091632 1100 1091.908 8.091632 1200 1191.908
8.091632 1300 1291.908 8.091632 1400 1391.908 8.091632 1500
1491.908 8.091632 1600 1591.908 8.091632 1700 1691.908 8.091632
1800 1791.908 8.091632 1900 1891.908 8.091632 2000 1991.908
8.091632
[0029] A suitable diaphragm 114 may be a rolling seal diaphragm
obtained for example from Bellofram Corporation, of Newell, W. Va.
Exemplary diaphragms and methods of use are disclosed in U.S. Pat.
Nos. 3,137,215 and 3,373,236, each of which is incorporated herein
by reference thereto.
[0030] While various descriptions of the present invention are
described above, it should be understood that the various features
can be used singly or in any combination thereof. Therefore, this
invention is not to be limited to only the specifically preferred
embodiments depicted herein.
[0031] Further, it should be understood that variations and
modifications within the spirit and scope of the invention may
occur to those skilled in the art to which the invention pertains.
Accordingly, all expedient modifications readily attainable by one
versed in the art from the disclosure set forth herein that are
within the scope and spirit of the present invention are to be
included as further embodiments of the present invention. The scope
of the present invention is accordingly defined as set forth in the
appended claims.
* * * * *