US20090123298A1

US20090123298A1 - Method to prolong lifetime of diaphragm pump

Info

Publication number: US20090123298A1
Application number: US11/937,415
Authority: US
Inventors: Adam M. Koller; Masaaki Kawase
Original assignee: Tetra Laval Holdings and Finance SA
Current assignee: Tetra Laval Holdings and Finance SA
Priority date: 2007-11-08
Filing date: 2007-11-08
Publication date: 2009-05-14
Also published as: JP5527872B2; NO20084087L; JP2009115095A

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.

Description

BACKGROUND OF THE INVENTION

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.
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.
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.
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.
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.
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.
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

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.
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 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.
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.
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.
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.
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.
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

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:

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;

FIG. 2 is a sectional view of an exemplary diaphragm pump; and

FIG. 3 is a sectional view of another exemplary diaphragm pump.

DETAILED DESCRIPTION OF THE INVENTION

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.
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.
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.
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.
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.
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.
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.
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 (¼) of the stroke can be used, the second ¼ of the stroke (adjacent to but not overlapping the first ¼ of stroke) can be used, the third ¼ of the stroke (adjacent to but not overlapping) the second ¼ 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.
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.
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 ½ 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.
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.
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.
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.
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.
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.
All patents referred to herein, are hereby incorporated herein by reference, whether or not specifically done so within the text of this disclosure.
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.

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:

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:

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.