Pumps – Expansible chamber type – Elongated flexible chamber wall progressively deformed
Patent
1997-03-06
1998-12-08
Vrablik, John J.
Pumps
Expansible chamber type
Elongated flexible chamber wall progressively deformed
F04B 4312
Patent
active
058460640
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to peristaltic pumps and constitutes an improvement in their design and consequent performance capabilities.
BACKGROUND ART
Peristaltic pumps move fluids (liquids, suspensions and gases) by the axially progressive radial deformation of an elastic duct or element, of enclosed cross-section, usually in the form of annular tube, having as essential measurements a bore-size and a wall thickness.
Hitherto, the radial deformation has taken the form of a localised compression of the element, flattening it so that one flattened section of the wall is brought into fluid-tight contact with the radially opposite section of the wall. The compression may be effected by one or more rollers, sliding shoes or oscillating fingers, but the operation is identical: the sealed section is progressed a certain distance along the axial dimension, by suitable movement or succession of the operating members.
This pushes the contents ahead of the compressed section along the element and the restitution of the elastic material behind the compression draws in more fluid to be expelled in turn by a succeeding compression.
This arrangement has at least four drawbacks, which limit the range of performance of such pumps in terms of volume, pressure and duration.
A. It is a general characteristic of elastomers which forms the elastic duct or element, that the destructive effect of rapidly and frequently applied stresses and strains, necessary to the operation of a peristaltic pump, varies directly with their thickness and/or hardness. The requirement in the standard form of peristaltic pump that the elastic element should restitute from a flattened condition, against the force of atmospheric pressure, implies that the wall of the element be substantial in thickness or hardness and that either must increase directly with the bore-size of the element. Thus increasing flow-rate requirements, needing larger bores, lead inevitably to thicker and/or harder walls and shorter operating life.
B. In a standard arrangement, the regions of the wall of the element at the radial extremes of the compression, where the walls are being folded sharply, are subjected to very large concentrations of stresses and strains to ensure that the seal formed by the compression is complete across the whole width. This further promotes the breakdown of the elastomer at these particular locations.
C. As the elastic element of a standard peristaltic pump experiences the pumping pressure on its inside, increasing pressure requirements necessitate either yet thicker (or harder) walls, or external reinforcements that militate against the operation.
D. A further drawback of a standard design is that the radial load on the drive-shaft is unbalanced over at least a part of the shaft's revolution, making heavy demands on the bearings of rotating parts and their supporting structures.
DE 3833833 discloses a peristaltic pump which overcomes some of these problems by providing an inner flexible membrane within a rigid outer body. The mechanism for expanding the membrane uses a cam which acts an ball bearings which in turn push out rings thus expanding the flexible membrane.
The mechanism for expanding the inner membrane is complex, requiring many elements and detailed assembly. This creates a peristaltic pump which is complicated and expensive to both assemble and repair if necessary.
Therefore, there is a need for a peristaltic pump that avoids or reduces some or all these problems and limitations.
DISCLOSURE OF INVENTION
Broadly, the present invention provides a peristaltic pump which employs an elastic-walled pumping element of enclosed cross-section and means of causing radial deformations in it progressively along its axis. It is therefore a true peristaltic pump and shares with the standard design the advantages that the operating mechanism is isolated from the fluid being pumped by the wall of the element, and that it has neither glands nor valves.
By the present invention there is provided a peristaltic pump having a tubular el
REFERENCES:
patent: 2695694 (1954-11-01), Seinfeld
patent: 3233553 (1966-02-01), Chanton
patent: 3279388 (1966-10-01), Roudaut
patent: 3433171 (1969-03-01), Corneil
Metameric Limited
Vrablik John J.
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