Patent Application
20050158196
This invention relates generally to pumping systems, and more particularly to peristaltic pumping systems.
Peristaltic pumps are widely used in various applications, including applications in the beverage and pharmaceutical fields, among other fields. Peristaltic pumps generally operate by compressing a flexible tube or channel with one or more heads (or other mechanisms). The head or heads pinch off a portion of the tube or channel (against either a back or an opposing head) and push fluid in the desired direction.
In some applications, a peristaltic pump itself is used over and over again and the tube is frequently replaced, such as when a beverage concentrate is depleted in a beverage system or a medicine is depleted in a pharmaceutical application. In other applications, one tube may be used with the same pump for a relatively long time. In still other applications, the pump itself may be disposable along with the tube.
Although peristaltic pumps offer certain advantages, they do not economically allow for the kind of reproducible and precise flow rates that are often required. In many instances, the inaccuracies result from the tubes, which are made with an extrusion process. The extrusion process results in variations in the inside diameters of the tubes, as well as variations in the thickness of the tube walls. Because of such variations, as tubes are replaced, different flow rates result from the same pump. Also, variations occur from pump to pump (and thus system to system), because of the differences in the tubes, both in disposable tube applications, and in applications where one tube is used for a relatively long time. It is generally not practical to calibrate systems to overcome the variations.
Thus, for example, where a beverage concentrate is to be pumped at a specific flow rate for mixture with water at a given ratio, tube variations result in inaccurate mixture ratios—and hence different quality drinks—from tube to tube. Such beverage systems are often used in restaurants and convenience stores (among other locations), and the variations create unacceptable differences in drink quality from batch to batch in the same location, and from location to location. Similar issues are found in other applications, such as those in the pharmaceutical field.
Another problem with prior art peristaltic pumps is that the pump inlet side of the tube is often attached to a tube fitment that operates as a restriction to free flow to the inlet to the pump.
Therefore, a need has arisen for peristaltic pump and tube system that overcomes the limitations of prior art systems.
In accordance with the teachings of the present invention, methods and apparatus for a molded tube and peristaltic pump are provided which eliminate or substantially reduce the problems associated with prior art systems.
In a particular embodiment, a pump for pumping a material is provided which includes a motor, a molded tube, and one or more compression heads coupled to the motor and adapted to compress the molded tube for pushing the material in a desired flow direction. In one embodiment, the molded tube comprises a first section having a first inside diameter, and a second section having a second inside diameter greater than the first inside diameter. In another embodiment, a fitment is coupled to the second section. Also, the discharge end of the tube may have an inside diameter greater or less than other parts of the molded tube. The molded tube may be an injection molded tube.
In another embodiment of the present invention, a fluid delivery system is provided which includes a peristaltic pump, a molded tube coupled to the peristaltic pump through which the fluid flows, a supply of the fluid coupled to the molded tube upstream of the peristaltic pump, and a dispenser coupled to the molded tube downstream of the peristaltic pump. In one embodiment, the molded tube comprises a first section having a first inside diameter, and a second section having a second inside diameter greater than the first inside diameter. In another embodiment, a fitment is coupled to the second section. Also, the discharge end of the tube may have an inside diameter greater or less than other parts of the molded tube. The molded tube may be an injection molded tube.
Particular applications for the present invention include, without limitation, beverage and pharmaceutical applications.
Also provided is a method of forming a molded tube for a peristaltic pump, which includes providing a core and a fitment, providing a cavity adapted to mate with the core and fitment, injecting material into the cavity for forming the molded tube around at least a part of the core and fitment, and ejecting the molded tube and fitment from the core.
In a particular embodiment, the injected material is a thermosetting elastomer. In one embodiment, the molded tube and fitment are ejected by supplying a gas through the core. In another embodiment, the fitment is formed and then placed on the core. In an alternative embodiment, the fitment is molded in place on the core. In another embodiment, a weakened area may be formed on the molded tube for removing an end of the tube, and, if desired, a removal tab may be formed proximate to the weakened area.
In another embodiment, the fitment has a fitment inside diameter, and the fitment inside diameter is greater than or equal to an inside diameter of a portion of the molded tube not formed around the fitment. In still another embodiment, the molded tube has a discharge end with an inside diameter different than a portion of the molded tube not formed around the fitment.
One important technical advantage of the present invention is that it includes a molded tube which allows more precise and repeatable flow rates from peristaltic pumping systems than prior art systems. Another important technical advantage of one embodiment of the present invention is that it includes a molded tube which may be formed in combination with a fitment. Still another important technical advantage of the present invention is that it includes a molded tube which may be formed with an increased diameter portion which makes it easier to improve flow rates into peristaltic pumping systems.
Reference is made in the description to the following briefly described drawings, wherein like reference numerals refer to corresponding elements:
As shown in
The head or heads 16 squeeze the tube 18 (against a back or opposing head or heads) and push fluid in the desired direction. In the particular example illustrated in
Although a peristaltic pump with a motor, shaft, and head is illustrated, any peristaltic pump mechanism may be used, including, without limitation, those that squeeze a tube and move fluid in the tube with one or more roller heads, sliding heads, caterpillar mechanisms, wave mechanisms, cams, disks, or other devices. Examples of particular peristaltic pumps are described in U.S. Pat. Nos. 5,413,252 and 5,558,507, which are herein incorporated by reference in their entirety. The incorporation of these examples is illustrative only, and not by way of limitation, and thus is not meant to limit the scope of the invention or to exclude from coverage any other type of peristaltic pump mechanism. For ease in describing any of the various peristaltic pump mechanisms, the squeezing mechanism may be referred to herein as a compression head. Also, although the supply 20 is illustrated as a flexible bag, any source may be used.
The tube 18 of the present invention is molded, and is not extruded as are prior art tubes. In a particular embodiment, the molding process is an injection molding process. Because the molding process allows for very precise tolerances, the kinds of variations found in prior art tubes are substantially or completely eliminated with the molded tube of the present invention. It should be understood that any other suitable molding process may also be used, including, without limitation, compression molding.
The expanded diameter section 32, although not necessary in all embodiments of the present invention, provides a significant advantage over prior art tubes. In particular, by forming the expanded diameter section 32 with an inside diameter greater than that of the main portion of tube 18, the tube fitment 24 (or supply fitment if the tube is coupled directly to the supply) may have an inside diameter equal to or greater than that of the main portion of tube 18, and can be easily coupled to the tube 18 (the tube may also be formed on the fitment, as described below). With such a fitment, flow to the pump inlet side of the tube is not restricted (as the diameter is not diminished), and thus the peristaltic pump is not “starved” and its performance limited thereby. In some prior art systems, tube fitments cause inlet pump flow restrictions, as it is difficult to stretch an extruded tube over a wide tube fitment. The flow restriction issue is particularly important in pumping relatively high viscosity liquids, such as, without limitation, orange juice concentrate, wherein inlet flow restrictions can significantly affect desired flow rates.
The expanded diameter section 32 may be formed in other processes as well, such as, without limitation, with an expansion mandrel inserted into the tube 18. Furthermore, the expanded diameter section may be formed with features, such as, without limitation, shoulders, grooves, or lips, to accommodate the tube fitment 24 (or supply fitment) and enhance the fit between them. However, it should be understood that any approach may be used to couple the tube with a fitment.
The particular core shown in
As shown in
The tube 18 may be ejected from the mold system by any suitable approach. One approach, without limitation, is to inject a gas through a gas port 54, which allows gas (such as, without limitation, air) to flow through the end of the core 40 to eject the molded tube 18.
An air injection pin 56 is fully inserted during the injection process, to prevent the injection material 58 from entering an ejection channel 60. Ejection channel 60 runs from the end of the core 40 to the gas port 54. When the air injection pin 56 is retracted, as shown in
The particular embodiments and descriptions provided herein are illustrative examples only, and features and advantages of each example may be interchanged with, or added to the features and advantages in the other embodiments and examples herein. Moreover, as examples, they are not meant to limit the scope of the present invention to any particular described detail, and the scope of the invention is meant to be broader than any example. For example, and without limitation, although beverage and pharmaceutical applications have been illustrated, the present invention may be used with any other fluid delivery system. And, in general, although the present invention has been described in detail, it should be understood that various changes, alterations, substitutions, additions and modifications can be made without departing from the intended scope of the invention, as defined in the following claims.
