U.S. patent application number 11/937415 was filed with the patent office on 2009-05-14 for method to prolong lifetime of diaphragm pump.
This patent application is currently assigned to TETRA LAVAL HOLDINGS & FINANCE, S.A.. Invention is credited to Masaaki Kawase, Adam M. Koller.
Application Number | 20090123298 11/937415 |
Document ID | / |
Family ID | 40623868 |
Filed Date | 2009-05-14 |
United States Patent
Application |
20090123298 |
Kind Code |
A1 |
Koller; Adam M. ; et
al. |
May 14, 2009 |
METHOD TO PROLONG LIFETIME OF DIAPHRAGM PUMP
Abstract
A method for operating a diaphragm-type piston pump prolongs the
life of the diaphragm. A pump has a predetermined pump volume
defined by a length of a piston stroke. The pump having a variable
drive. The method includes drawing a first volume of liquid into
the pump through a first portion of the piston stroke. The first
volume of liquid is less than the pump volume. The first volume of
liquid is expelled from the pump through a reverse motion through
the first portion of the piston stroke. A second volume of liquid
is drawn into the pump through a second portion of the piston
stroke. The second volume of liquid is less than the pump volume.
The second volume of liquid is expelled from the pump through a
reverse motion through the second portion of the piston stroke. At
least portions of the first and second portions of the piston
stroke are different from one another.
Inventors: |
Koller; Adam M.;
(Minneapolis, MN) ; Kawase; Masaaki; (Edina,
MN) |
Correspondence
Address: |
Levenfeld Pearlstein LLC (Tetra Pak)
2 North LaSalle Street, Suite 1300
Chicago
IL
60602
US
|
Assignee: |
TETRA LAVAL HOLDINGS & FINANCE,
S.A.
Pully
CH
|
Family ID: |
40623868 |
Appl. No.: |
11/937415 |
Filed: |
November 8, 2007 |
Current U.S.
Class: |
417/53 |
Current CPC
Class: |
F04B 43/04 20130101 |
Class at
Publication: |
417/53 |
International
Class: |
F04B 43/02 20060101
F04B043/02 |
Claims
1. A method for operating a diaphragm-type piston pump, the pump
having a predetermined pump volume defined by a length of a piston
stroke, the pump having a variable drive, the method comprising the
steps of: drawing a first volume of liquid into the pump through a
first portion of the piston stroke, the first volume of liquid
being less than the pump volume; expelling the first volume of
liquid from the pump through a reverse motion through the first
portion of the piston stroke; drawing a second volume of liquid
into the pump through a second portion of the piston stroke, the
second volume of liquid being less than the pump volume; and
expelling the second volume of liquid from the pump through a
reverse motion through the second portion of the piston stroke,
wherein portions of the first and second portions of the piston
stroke are different from one another.
2. The method in accordance with claim 1 wherein the first and
second volumes of liquid are equal.
3. The method in accordance with claim 1 wherein the step of
drawing the second volume of liquid immediately follows the step of
drawing the first volume of liquid.
4. The method in accordance with claim 1 including the steps of:
drawing a third volume of liquid into the pump through a third
portion of the piston stroke, the third volume of liquid being less
than the pump volume; and expelling the third volume of liquid from
the pump through a reverse motion through the third portion of the
piston stroke, wherein the second and third portions of the piston
stroke are different from one another.
5. The method in accordance with claim 4 wherein the third portion
of the piston stroke is different from the first portion of the
piston stroke.
6. The method in accordance with claim 5 wherein the first, second
and third portions of the piston stroke are carried out in
succession.
7. The method in accordance with claim 1 wherein the steps of
drawing the first volume of liquid into the pump and expelling the
first volume of liquid from the pump are carried out repeatedly for
a first predetermined period of time and the steps of drawing the
second volume of liquid into the pump and expelling the second
volume of liquid from the pump are carried out repeatedly for a
second predetermined period of time following the first
predetermined period of time.
8. The method in accordance with claim 7 including the steps of:
drawing a third volume of liquid into the pump through a third
portion of the piston stroke, the third volume of liquid being less
than the pump volume; and expelling the third volume of liquid from
the pump through a reverse motion through the third portion of the
piston stroke, wherein the steps of drawing the third volume of
liquid into the pump and expelling the third volume of liquid from
the pump are carried out repeatedly for a third predetermined
period of time following the second predetermined period of
time.
9. The method in accordance with claim 1 wherein the steps of
drawing the first volume of liquid into the pump and expelling the
first volume of liquid from the pump are carried out repeatedly for
a first predetermined number of strokes and the steps of drawing
the second volume of liquid into the pump and expelling the second
volume of liquid from the pump are carried out repeatedly for a
second predetermined number of strokes following the first
predetermined number of strokes.
10. The method in accordance with claim 9 including the steps of:
drawing a third volume of liquid into the pump through a third
portion of the piston stroke, the third volume of liquid being less
than the pump volume; and expelling the third volume of liquid from
the pump through a reverse motion through the third portion of the
piston stroke, wherein the steps of drawing the third volume of
liquid into the pump and expelling the third volume of liquid from
the pump are carried out repeatedly for a third predetermined
number of strokes following the second predetermined number of
strokes.
11. The method in accordance with claim 9 wherein each the first
and second predetermined number of strokes is greater than one.
12. The method in accordance with claim 10 wherein each the first,
second and third predetermined number of strokes is greater than
one.
13. The method in accordance with claim 9 wherein the first volume
of liquid and second volumes of liquid are substantially equal.
14. The method in accordance with claim 10 wherein the first,
second and third volumes of liquid are substantially equal.
15. The method in accordance with claim 1 wherein portions of the
first and second portions of the piston stroke overlap.
16. The method in accordance with claim 1 wherein no portions of
the first and second portions of the piston stroke overlap.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention is directed to a diaphragm fill pumps.
More particularly, the present invention is directed to a method of
operating diaphragm fill pumps to increase the lifetime of the
diaphragm.
[0002] Form, fill and seal packaging machines are well known in the
art. These machines are widely used in the food packaging industry
for forming a package, filling the package with a liquid or solid
food (or a mixture of liquid and solid foods), and sealing the
package after filling. In many such machines, piston pumps are used
to move or transport product (e.g., food product) from, for
example, a storage tank to individual packages. These pumps use a
flexible diaphragm between the piston and the food product to
maintain separation between the product and the pump driving
elements. Piston-type pumps are used because they provide the
requisite control over the flows and flow rates of the product.
[0003] The diaphragm is positioned between the piston and the
cylinder wall to isolate the product from the close proximity
piston and cylinder wall surfaces. The diaphragm, which is referred
to as a rolling diaphragm, is positioned at the product end of the
piston and extends to (and is sealed at) the cylinder wall. Because
the diaphragm is a flexible material, it "moves" with the pump and
provides the necessary volumetric changes to allow moving or
driving the product.
[0004] The entire assembly is driven by a servo-motor to maintain
strict control over the movement of the piston and thus the volume
of product pumped. Moreover, use of a servo-motor allows for easily
varying the pump volumes to accommodate changing container volumes
and product mixes.
[0005] One drawback to this arrangement is that the pump volume is
often considerably larger than the actual pumped volume. For
example, a 2 liter pump may be used to pump volumes of between 200
ml and 1000 ml. While this, in an of itself is not problematic, for
any given volume, the charge/recharge stroke of the piston follows
the same motion profile, including the start and stop (or top and
bottom dead center) positions.
[0006] Because the diaphragm is positioned between the stationary
cylinder wall and the moving piston, it is subject to wear by
virtue of the rubbing of the surfaces. Due to the piston following
the identical motion profile for a given volume, there is an
increased or concentrated area for wear at certain regions of the
diaphragm.
[0007] Accordingly, there exists a need for a method for increasing
the lifetime of the diaphragm in a diaphragm pump. Desirably, such
a method distributes the wear inherent in an operating pump cycle
over a larger region of the diaphragm. More desirably, such a
method also reduces the wear on other parts within the pump system.
More desirably still, such a method is readily carried out with few
or no changes to the pumping system components.
BRIEF SUMMARY OF THE INVENTION
[0008] A method for operating a diaphragm-type piston pump prolongs
the life of the diaphragm. A pump has a predetermined pump volume
defined by a length of a piston stroke. The pump has a variable
drive such as a servo-motor.
[0009] The method includes drawing a first volume of liquid into
the pump through a first portion of the piston stroke. The first
volume of liquid is less than the pump volume. The first volume of
liquid is expelled from the pump through a reverse motion through
the first portion of the piston stroke.
[0010] A second volume of liquid is drawn into the pump through a
second portion of the piston stroke. The second volume of liquid is
also less than the pump volume. The second volume of liquid is
expelled from the pump through a reverse motion through the second
portion of the piston stroke. The pump stroke is such that portions
of the first and second portions of the piston stroke are different
from one another.
[0011] In this manner, different regions of the diaphragm are
stressed (e.g., different regions of the diaphragm are flexed)
which prolongs the life of the diaphragm. The pump can be operated
such that the piston moves through a third portion of the piston
stroke (at least portions of which are different from the first and
second stroke portions) to draw and expel a third volume of
liquid.
[0012] The determination of when to change the portion of the
stroke through which the pump operates can be by time, by the
number of strokes, or using any of a variety of other factors. It
is anticipated that the volumes of liquid pumped (e.g., the first,
second and, if used, the third volumes of liquid) will be
substantially equal to one another.
[0013] It is contemplated that the system can be operated such that
portions of the (first, second and if used, third) piston strokes
overlap, or that the system is operated such that no portions of
the piston strokes overlap.
[0014] The present method distributes the wear inherent in an
operating pump cycle over a larger region of the diaphragm and
reduces the wear on other parts within the pump system. The method
is readily carried out with few or no changes to the pumping system
components, by effecting changes in control system logic.
[0015] These and other features and advantages of the present
invention will be apparent from the following detailed description,
in conjunction with the appended claims.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0016] The benefits and advantages of the present invention will
become more readily apparent to those of ordinary skill in the
relevant art after reviewing the following detailed description and
accompanying drawings, wherein:
[0017] FIG. 1 is a perspective view of a form, fill and seal
packaging machine having a diaphragm-type piston pump the operates
using a method to prolong the life of the diaphragm in accordance
with the principles of the present invention;
[0018] FIG. 2 is a sectional view of an exemplary diaphragm pump;
and
[0019] FIG. 3 is a sectional view of another exemplary diaphragm
pump.
DETAILED DESCRIPTION OF THE INVENTION
[0020] While the present invention is susceptible of embodiment in
various forms, there is shown in the drawings and will hereinafter
be described a presently preferred embodiment with the
understanding that the present disclosure is to be considered an
exemplification of the invention and is not intended to limit the
invention to the specific embodiments illustrated.
[0021] It should be further understood that the title of this
section of this specification, namely, "Detailed Description Of The
Invention", relates to a requirement of the United States Patent
Office, and does not imply, nor should be inferred to limit the
subject matter disclosed herein.
[0022] Referring now to the figures and in particular to FIG. 1,
there is shown a form, fill and seal packaging machine 10 that is
configured to store a series of carton blanks in a flat, folded
form, erect the blanks into a tubular form, fold and seal the
bottom flaps of the carton, fill and seal the cartons as they move
through the machine. The form, fill and seal packaging machine 10
can be such as that disclosed in Katsumata, U.S. Pat. No.
6,012,267, which patent is assigned to the assignee of the present
invention and is incorporated herein by reference.
[0023] A typical filling machine 10 includes a carton magazine 12
for storing the flat, folded carton blanks. The filling machine
includes a carton erection station 14 that receives the cartons in
the flat, folded form, and opens or erects the cartons into the
tubular form. The tubular formed cartons are then bottom sealed at
a bottom sealing station 16. The cartons then traverse through a
series of stations including a filling station 18 at which product
is filled into the carton, and a top sealing station 20 for sealing
the top of the carton after filling. Other stations can include one
or more sterilization stations 22 and a fitment or closure station
(not shown) for positioning and securing a closure package (such as
a spout and cap combination) to the carton. The overall operation
of the 10 machine is controlled by a controller 26.
[0024] Referring to FIG. 2, the filling station 18 includes one or
more valves 28 for initiating and terminating flow of product to
and from a piston-type pump 30. The pump 30 includes a piston 32
that reciprocates within a cylinder 34, defined by cylinder walls
36. As set forth above, because it is desired to minimize the
number of surfaces that contact the product P (e.g., food), at
least one diaphragm 38 extends across the product side 40 of the
cylinder 34 to isolate the product from the space between the
moving piston 32 and the stationary cylinder wall 36. The diaphragm
38 arrangement is of a rolling-type in which the diaphragm 38 rolls
with the movement of the piston 32. In such an arrangement, the
diaphragm 38 is mounted to the cylinder wall 36 (typically by a
bead 42 secured within a mechanical joint 44) to define a
peripheral seal about the wall 36. The piston 32 is located
"behind" the diaphragm 38 and the product inlet and outlet (i.e.,
the product side 40) are located "in front" of the diaphragm 38. In
this arrangement, the diaphragm 38 essentially isolates the piston
32 from the product. The diaphragm 38 defines a product or pumping
end or chamber 46.
[0025] As will be appreciated from the figures, a gap 48 is present
between the cylinder wall 36 and the piston 32 to accommodate the
diaphragm 38. In order to minimize head loses and maintain the
highest control of the amount of product pumped, it is desirable to
maintain the gap 48 as small as possible. However, because of the
nature of the moving piston 32 (and that the piston 32 may not
always move in a fully concentric manner) there is the potential
for wear on the diaphragm 38. The wear is exacerbated,
specifically, localized and concentrated when the piston 32 follows
the same motion profile for each of the charge (intake) and
discharge strokes of the pump 30.
[0026] A set forth above, in a typical installation, the pump 30
volume (or capacity) often greatly exceeds the actual pumped volume
(the volume of liquid that is moved). Accordingly, a large portion
of the pump 30 stroke goes unused. For example, it is not unusual
to have a pump 30 with a 2 liter (2000 ml) capacity pumping volumes
of between 200 ml and 1000 ml.
[0027] In effort to reduce the wear on the diaphragm 38 and the
pump 30 components, the present method of operation uses a varying
stroke cycle to pump the liquid product. That is, the stroke is
viewed as a series of portions, and different portions of the
stroke are used. For example, if a pump has a capacity of 2 liters
and the volume of product to be pumped is 500 ml, there are four
discrete pump (or stroke) portions. That is, the first one-fourth
(1/4) of the stroke can be used, the second 1/4 of the stroke
(adjacent to but not overlapping the first 1/4 of stroke) can be
used, the third 1/4 of the stroke (adjacent to but not overlapping)
the second 1/4 can be used, and so on. Moreover, there is an
infinite number of stroke portions if the portions are allowed to
overlap, for example, where the second stroke portion begins in the
middle of the first stroke portion. Essentially, the pumping stroke
can start or stop at any point along that length of the pump stroke
so along as the travel (of the portion) is sufficient to displace
the desired volume of product.
[0028] In an exemplary mode of operation, in a first day of a
production run of say 24 hours, the first 50 percent of the pump
stroke may be used (for a pump having a capacity that is twice as
large as the pumped volume), and in the net day of production run,
the second 50 percent of the pump stroke may be used. The exact
durations of use and percentages of use of the cylinder volume will
vary depending upon the pump volume, the pumped volume, the ratio
of the two, and the desired variation scenario.
[0029] In another operating scenario, it may be desired to use a
staggered starting position from one period to the next (e.g., one
day to the next). For example, if the pumped volume is 1/2 of the
pump volume, then a first stroke may use the first 50 percent (what
corresponds to 0 percent to 50 percent) of the pump volume or
stroke, the second stroke may overlap the first stroke and use the
next 10 percent increment (or 10 percent to 60 percent) of the pump
volume or stroke, the third stroke may overlap the first and second
strokes and use the next 10 percent increment (or 20 percent to 70
percent) of the pump volume or stroke, the fourth stroke may use
the next 10 percent increment (or 30 percent to 80 percent) of the
pump volume or stroke, and so on. The same or a different
incremental change scenario can be used throughout or
intermittently.
[0030] It will be understood that the pumped volume percentage need
not be 25 percent or 50 percent of the pump capacity, but can be
any percentage (less than 100 percent) as desired.
[0031] It is anticipated that the variation in the pump stroke can
be set or determined based upon time, machine operating time,
number of pump strokes, or any other measurable characteristic, or
the variation can be random. Although it is envisioned that the
pumped volume will be the same for each operation of the pump, it
will be readily understood that the pumped volume can also
vary.
[0032] It will be appreciated that the flexibility of the pumping
system 30 requires that the drive 50 for the pump 30 permit
accurate, distinct and discrete strokes. In a present system 30,
the drive 50 is a servo-controlled or servo-motor which permits
precise control over the stroke (movement) of the motor 50 and
accordingly the pump piston 32. It is to be understood that other
precision drives known or not known are included within the scope
of the present invention.
[0033] It will also be appreciated that the machine controller 26
will be used to control the precise movement of the motor 50 and as
such the pump piston 32. Those skilled in the art will recognize
the manner in which such a controller 26 is programmed to control
this movement.
[0034] In the present disclosure, the words "a" or "an" are to be
taken to include both the singular and the plural. Conversely, any
reference to plural items shall, where appropriate, include the
singular.
[0035] All patents referred to herein, are hereby incorporated
herein by reference, whether or not specifically done so within the
text of this disclosure.
[0036] From the foregoing it will be observed that numerous
modifications and variations can be effectuated without departing
from the true spirit and scope of the novel concepts of the present
invention. It is to be understood that no limitation with respect
to the specific embodiments illustrated is intended or should be
inferred. The disclosure is intended to cover by the appended
claims all such modifications as fall within the scope of the
claims.
* * * * *