Pumps – Expansible chamber type – Elongated flexible chamber wall progressively deformed
Reexamination Certificate
2000-10-23
2002-12-17
Tyler, Cheryl J. (Department: 3746)
Pumps
Expansible chamber type
Elongated flexible chamber wall progressively deformed
C417S477900, C417S474000
Reexamination Certificate
active
06494693
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to peristaltic pumps for transporting or pumping fluids. More specifically, this invention relates to an improved peristaltic pump using a pumptube comprising a single tube of a relatively rigid and hard fluoroplastic material, preferably relatively rigid and hard polytetrafluoroethylene (PTFE), and a roller strap located between the pressure rollers of the peristaltic pump and the pumptube. The pumping section of the pumptube, which is not directly contacted by the pressure rollers of the peristaltic pump, is pre-formed or shaped into a flaftened cross section with an overall U-shape which approximately conforms to the pumptube passageway in the peristaltic pump. The pressure rollers contact the roller strap and then compress the flattened side of the pumptube and, thereby, effect transport or pumping of the fluid. The use of the strap prevents excessive tube expansion at the output back-pressure, thereby increasing the lifetime of the pumptube. Using the pumptubes and peristaltic pumps of this invention, corrosive, viscous, sensitive, biological, and/or high pressure fluids can be readily handled. Moreover, fluids up to about 50° C. can be pumped at a back-pressure up to about 4 bar; higher operating temperatures may be possible with lower back-pressures. The pumptube and peristaltic pumps of this invention are especially adapted to operate against high back- or counter-pressures.
BACKGROUND OF THE INVENTION
Peristaltic pumps are preferred for certain applications where it is desirable to pump measured amounts of a fluid or to pump a fluid through tubing while avoiding contact between pump components and the fluid being pumped. In a typical peristaltic pump system, a length of tubing is contacted by a series of pressure rollers that rotate in a circular path. The pressure rollers contact and progressively compress a flexible pumptube at spaced intervals against a surface or raceway so as to flatten or locally reduce the cross-sectional area of the fluid passageway in the pumptube. Preferably, the cross-sectional area of the fluid passageway is effectively reduced to zero (i.e., complete occlusion) as each pressure roller moves over the pumping section of the pumptube. As the pressure rollers continue to roll over the pumptube, the successive flattened portions expand or return to the original cross-sectional area due to the resilience of the tube which generates a sub-atmospheric pressure in the fluid passageway to draw the fluid therein.
The efficiency and operating characteristics of a peristaltic pump generally depend on the physical and chemical characteristics of the pumptube. The pumptube generally must have a combination of properties including flexibility, resilience, durability, resistance to creasing, and resistance to adverse chemical or physical effects, since the pump may be used to pump diverse materials including acids, alkali, solvents, toxic, and sterile liquids.
Commercially available peristaltic pumptubes are generally uniformly cylindrical, flexible tubes with a uniform wall thickness which provide a fast recovery rate of the flattened portion to the normal cross-sectional area. Such pumptubes are normally formed from resilient elastomeric materials such as natural rubber, silicone, polychloroprene, and polyvinyl chloride. Such materials, however, have limited resistance to chemical degradation. Moreover, such materials may leach components (e.g., softening agents and the like) into the fluid being pumped and/or absorb components from the fluid being pumped. Thus, the use of pumps using such pumptubes is generally restricted to liquids having minimal degradation effects.
Fluoroplastic tubing, which has good corrosion resistance, generally has been found to lack resilience and tends to crease in use, thereby limiting the life of such tubing. U.S. Pat. No. 3,875,970 (Apr. 8, 1975) attempted to overcome this problem by providing a pumptube having a thin inner tubular portion of a corrosion resistant material (such as polytetrafluoroethylene) and a thicker outer tubular portion of a resilient elastomeric material (such as silicone, polychloroprene, flexible polyvinyl chloride, natural or synthetic rubber). The overall pumptube remained flexible. Although the design of this pumptube reportably extended the life of the tubing, it has not been as successful as desired and its use in commercially available peristaltic pumps appears to be very limited.
In addition, a variety of pumptubes incorporating various geometric configurations, including multiple layered tubes, have been used in peristaltic pumps. U.S. Pat. No. 3,105,447 (Oct. 1, 1963) used a double layered pumptube where both the inner and outer tubes consisted of rubber or an elastomer. The pumptube design allowed a lubricant to be pumped through the space formed between the inner and outer tubes. German Patent 3,322,843 A1 (published Jan. 3, 1985) also provided a double layered pumptube with a particularly soft and elastic inner layer and an impermeable outer layer. The inner layer could be formed of silicone, natural rubber, soft polyvinyl chloride, polyurethane, or fluoroelastomer; the outer layer could be formed of polyvinyl chloride, polyurethane, fluoroelastomer, and certain polyethylenes. The pumptube was flexible and maintained a circular cross-section in the uncompressed state. European Patent Publication 0,470,33 A1 (published Feb. 12, 1992) provided a flexible pumptube with an elastic reinforcing member or members disposed therein to reduce fatigue failure upon repeated compression and recovery of the tubing. U.S. Pat. No. 5,067,879 (Nov. 26, 1991) provided a flexible, single- or multi-layered pumptube having two longitudinally extending notches or groves in the outer surface. The groves were reported to improve the flexing characteristics of the tubing during compression and recovery. Although providing useful and significant advances in the art, each of these just described pumptubes has significant limitations for use in peristaltic pumps, especially for peristaltic pumps for corrosive and other difficult to handle liquids.
More recently, U.S. Pat. No. 5,482,447 provided a double layer pumptube having a inner tube and an outer tube, both of which were preferably polytetrafluoroethylene (PTFE). Although this pumptube was a significant advance over the prior art, the pumptube, largely because of its tube within a tube design, was more costly and difficult to manufacture than desired. Additionally, the pumptube's useful lifetime was not as high as desired when operated against a significant back-pressure.
The present invention provides an improved peristaltic pump and an improved pumptube. Using the peristaltic pump of this invention, a single shaped tube of rigid fluoroplastic material (preferably PTFE) can be used. Thus, many of the advantages obtained in the double layered PTFE pumptubes of U.S. Pat. No. 5,482,447 can be obtained using a significantly simplified pumptube (i.e., single tube construction) as provided herein. The pumptube and peristaltic pump of the present invention are especially adapted for use in systems which develop, or can develop, high back- or counter-pressures. Using the present system, peristaltic pumps can operate continuously to pump liquid against a counter-pressure of at least 4 bar at a flow rate of at least 4 liters per minute (LPM).
SUMMARY OF THE INVENTION
The present invention relates to an improved peristaltic pump using a pumptube comprising. a single tube of relatively rigid and hard fluoroplastic material, preferably relatively rigid and hard polytetrafluoroethylene (PTFE), and a roller strap located between the pressure rollers of the peristaltic pump and the pumptube. The roller strap is an inelastic material such as, for example, a polyester, an aromatic polyamide, or the like. Preferably, the roller strap is an aromatic polyamide because of its reduced tendency to form a “hammock” during operation. One especially preferred aromatic polyamide is KEVLAR™ (DuPont). A KEVLAR™ strap coated with
Cole-Parmer Instrument Company
Liu Han L.
Tyler Cheryl J.
LandOfFree
Peristatic pump does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Peristatic pump, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Peristatic pump will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2981802