Method to prolong lifetime of diaphragm pump

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.

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;

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