Patent Application
20050019186
The invention relates generally to resilient tubes used in peristaltic pumps.
Peristaltic pumps are used in a variety of applications in which it is desirable to convey fluid in accurately controllable quantities. Peristaltic pumps typically include a rotary portion that compels the movement of a fluid by peristaltic compression of resilient tubing containing the fluid.
Imaging systems using inkjet printing have become widely known, and are often implemented using thermal inkjet technology. Such technology forms characters and images on a medium, such as paper, by expelling droplets of ink in a controlled fashion so that the droplets land on the medium. The printer, itself, can be conceptualized as a mechanism for moving and placing the medium in a position such that the ink droplets can be placed on the medium, a printing cartridge which controls the flow of ink and expels droplets of ink to the medium, and appropriate hardware and software to position the medium and expel droplets so that a desired graphic is formed on the medium. A conventional print cartridge for an inkjet type printer comprises an ink containment device and an ink-expelling apparatus, commonly known as a printhead, which heats and expels ink droplets in a controlled fashion.
In some inkjet type printers, a peristaltic pump head is used to drive multiple, resilient tubes to convey ink between the containment device and the printhead. Unless the resilient tubes are perfectly aligned parallel to the occlusion of the pump roller, the tubes have a tendency to migrate to a point of lower force during pump operation. Tube migration can result in the tubes bunching together, which can increase the force required to collapse the tubes. The forces applied by bunched tubes can also change the natural restoring force of the tubes. Tube migration can also result in individual tubes moving to one side of the pump or the other, which can also undesirably alter the pumping forces exerted on the tubes.
A variety of approaches to pump design have been presented in an attempt to reduce tube migration. In one example, pumps have been developed in which each tube is located in a separate drive head. While this reduces the likelihood of tube migration, it is comparatively expensive, requiring redundant parts and additional assembly time.
In another approach, the tubes are stretched over respective rollers in such a way as to maintain the tubes under constant tension. This approach is usually used in conjunction with additional mechanisms to maintain precise parallelism between the rollers and the occlusion. Again, although this approach reduces the likelihood of tube migration, it is also comparatively expensive, often requiring additional parts, control systems, and assembly time.
It can be seen from the foregoing that the need exists for a simple, inexpensive, arrangement for securing tubes in peristaltic pumps.
The present invention is directed to a tube component of a pump having a rotary portion that compels the movement of a fluid by peristaltic compression of resilient tubing containing the fluid. The tube component has a plurality of adjacent resilient tubes, with a web interconnecting the adjacent resilient tubes. The web may be offset from the centerline of the tubes so as not to degrade the compressibility of the tubes.
An embodiment of a peristaltic pump assembly 10 in accordance with the principles of the present invention is shown in
As shown in
A pump occlusion 26 partially surrounds the rotor 16. A tube component 28 is secured between the pump occlusion 26 and the rotor 16. The tube component 28 includes a plurality of flexible tubes 30, 32, 34 ganged together with a web 38. The pump occlusion 26 is radially spaced from the rollers 18, and provides a working surface such that rotation of the rotor 16 causes the rollers 18 to compress and collapse the tubes 30-34 against the occlusion 26 to impart motive force to fluid contained within the tubes 30-34 in a known manner. The web 38 prevents movement of the tubes 30-34 during operating of the pump assembly 10.
It is also contemplated that advantages accrue from locating the web 38 outside of the rotary area of pump operation, i.e., outside of the area where the rotors 18 compress the tubes 30-34 against the occlusion 26.
The resilient tubes 30-34 can be formed from any suitable elastomeric material, such as a flexible plastic. The web 38 can be formed integrally with the tubes 30-34, or fabricated separately, then installed onto the tubes 30-34.
The web 38 permits the tubes 30-34 to function essentially as a unit, rather than as three independently variable tubes. Since the tube component 28 can be installed as a unit in the pump assembly 10, the time and complexity of assembling the pump is reduced.
Although the present invention has been described with reference to specific embodiments, those of skill in the art will recognize that changes may be made thereto without departing from the scope and spirit of the invention as defined by the appended claims.
