U.S. patent application number 12/116721 was filed with the patent office on 2009-11-12 for peristaltic pump.
This patent application is currently assigned to Manning Environmental, Inc.. Invention is credited to Dean M. Carroll.
Application Number | 20090280016 12/116721 |
Document ID | / |
Family ID | 41265315 |
Filed Date | 2009-11-12 |
United States Patent
Application |
20090280016 |
Kind Code |
A1 |
Carroll; Dean M. |
November 12, 2009 |
PERISTALTIC PUMP
Abstract
A peristaltic pump uses a length of elastic tube with an inlet
at one end and an outlet at the second end for delivering fluid
material an outlet pressure greater than the inlet pressure. A
support element disposed along the length of elastic tube is in
contact with the elastic tube. A mechanism moves a compression
element into engagement with a segment of the elastic tube thereby
forming a compressed segment with a tube center section and two
folded tube edges wherein at least one surface engaging the folded
tube edges has a contours that reduce stresses in the elastic tube
walls at the folded tube edges increasing pump performance and/or
life of the elastic tube.
Inventors: |
Carroll; Dean M.;
(Georgetown, TX) |
Correspondence
Address: |
FISH & RICHARDSON P.C.
P.O BOX 1022
Minneapolis
MN
55440-1022
US
|
Assignee: |
Manning Environmental, Inc.
Georgetown
TX
|
Family ID: |
41265315 |
Appl. No.: |
12/116721 |
Filed: |
May 7, 2008 |
Current U.S.
Class: |
417/477.3 |
Current CPC
Class: |
F04B 43/1253
20130101 |
Class at
Publication: |
417/477.3 |
International
Class: |
F04B 43/12 20060101
F04B043/12; F04B 45/08 20060101 F04B045/08 |
Claims
1. A perisaltic pump comprising: a length of elastic tube having
tube walls, an inlet at a first end of the elastic tube for
receiving a fluid material at a first pressure, and an outlet at a
second end of the elastic tube for delivering the fluid material at
a second pressure; a support element disposed along and contacting
the length of elastic tube; and a mechanism for moving a
compression element into engagement with a segment of the elastic
tube thereby compressing the elastic tube and forming a compressed
segment with a flattened tube center section and two folded tube
edges, wherein at least one surface of the support element or the
compression element, proximate to the folded tube edges, has
contours that reduce stresses in the tube walls at the folded tube
edges.
2. The pump of claim 1, wherein the mechanism moves the compression
element along the elastic tube thereby moving the compressed
segment from a point proximate to a first end of the segment of the
elastic tube to a point proximate to a second end of the segment of
the elastic tube such that the compressed segment acts to move the
fluid material from the inlet to the outlet of the elastic
tube.
3. The pump of claim 1, wherein the compression element is a roller
that is free to rotate about its axial center and the mechanism
rotates the roller on a radial arm in a plane substantially
orthogonal to a surface of the support element.
4. The pump of claim 3, wherein the roller is cylindrical in shape
between opposing ends and has two end sections each having an edge
surface at a first diameter and a center section with a center
surface at a second diameter disposed over a width dimension
between the two end sections, wherein the first diameter is smaller
than the second diameter.
5. The pump of claim 4, wherein the surface of the support element
corresponding to the width dimension of the roller is substantially
flat.
6. The pump of claim 3, wherein the roller is cylindrical in shape
between opposing ends with a surface at a diameter over a first
width dimension and the support element has two end sections each
with an edge surface at a first level and a center section disposed
between the two end sections and having a center surface raised to
a second level above the first level of the edge surfaces over a
second width dimension smaller than the first width dimension.
7. The pump of claim 4, wherein the support element has two end
sections each with an edge surface substantially mirroring
corresponding edge surfaces of the roller and a center section
disposed between the two end sections and having a center surface
substantially conforming to the center surface of the roller.
8. The pump of claim 1, wherein the contours engaging the folded
tube edges operates to prevent the elastic tube from translating
orthogonal to the length dimension of the elastic tube when the
elastic tube is compressed to pump a fluid.
9. The pump of claim 3, wherein the roller is one of a plurality of
rollers that the mechanism rotates into engagement with the elastic
tube.
10. The pump of claim 1, wherein the contours are configured to
increase a useful lifetime of the elastic tube when used to
transport fluid.
11. The pump of claim 1, wherein the contours are adapted in part
in response to a durometer value and/or the wall thickness of a
material forming the elastic tube.
12. The pump of claim 1, wherein the contours are formed by a
smooth transition between levels of two surfaces.
13. A peristaltic pump comprising: a length of elastic tube having
tube walls, an inlet at a first end of the elastic tube for
receiving a fluid material at a first pressure, and an outlet at a
second end of the elastic tube for delivering the fluid material at
a second pressure; a support element disposed along and contacting
the length of elastic tube; and a mechanism for moving a
compression element into engagement with a segment of the length of
elastic tube thereby forming a compressed tube center section and
two folded tube edges within the segment, wherein at least one
surface of the support element surface or the compression element
proximate to the folded tube edges has contours that operate to
shape the folded tube edges to more fully and/or uniformly occlude
the elastic tube and strengthen a seal made by the occlusion in the
elastic tube thereby increasing a pressure and/or a vacuum produced
by the peristaltic pump.
14. The pump of claim 13, wherein the mechanism moves the
compression element along the elastic tube thereby moving the
compressed segment from a point proximate to a first end of the
segment of the elastic tube to a point proximate to a second end of
the segment of the elastic tube such that the compressed segment
acts to move the fluid material from the inlet to the outlet of the
elastic tube.
15. The pump of claim 13, wherein the compression element is a
roller that is free to rotate about its axial center and the
mechanism rotates the roller on a radial arm in a plane
substantially orthogonal to a surface of the support element.
16. The pump of claim 15, wherein the roller is cylindrical in
shape between opposing ends and has two end sections each having an
edge surface at a first diameter and a center section with a center
surface at a second diameter disposed over a width dimension
between the two end sections, wherein the first diameter is smaller
than the second diameter.
17. The pump of claim 16, wherein the surface of the support
element corresponding to the width dimension of the roller is
substantially flat.
18. The pump of claim 15, wherein the roller is cylindrical in
shape between opposing ends with a surface at a diameter over a
first width dimension; and the support element has two end sections
each with a edge surface at a first level and a center section
disposed between the two end sections; and having a center surface
raised to a second level above the first level of the edge surfaces
over a second width dimension smaller than the first width
dimension.
19. The pump of claim 16, wherein the support element has two end
sections each with an edge surface substantially mirroring
corresponding edge surfaces of the roller and a center section
disposed between the two end sections and having a center surface
substantially conforming to the center surface of the roller.
20. The pump of claim 13, wherein the contours are formed by a
smooth transition between levels of two surfaces.
21. The pump of claim 15, wherein the roller is one of a plurality
of rollers that the mechanism rotates into engagement with the
elastic tube.
22. The pump of claim 13, wherein the contours engaging the folded
tube edges operates to prevent the elastic tube from translating
orthogonal to the length dimension of the elastic tube when the
elastic tube is compressed to pump a fluid.
23. The pump of claim 13, wherein the contours are configured to
increase a useful lifetime of the elastic tube when used to
transport fluid.
24. The pump of claim 13, wherein the contours are adapted in part
in response to a durometer value and/or the wall thickness of a
material forming the elastic tube.
Description
TECHNICAL FIELD
[0001] The present invention relates in general to peristaltic
pumps and or tube compression and or roller based pumps.
BACKGROUND
[0002] Peristaltic pumps have been used for many years as a means
of transferring fluid. They are used in many different fields from
medical to industrial.
[0003] A peristaltic pump is a type of positive displacement pump
used for pumping a variety of fluids. The fluid is contained within
a flexible tube fitted inside a circular pump casing (though linear
peristaltic pumps have been made). A rotor with a number of cams
such as `rollers`, `shoes`, or `wipers` attached to its external
circumference compresses the flexible tube. As the rotor turns, the
part of tube under compression closes (or `occludes`) thus forcing
the fluid in the flexible tube to be pumped through the tube.
Additionally, as the tube opens after the cam passes,
(`restitution`) fluid flow is induced to the pump. This process is
called peristalsis and is used in many biological systems such as
the gastrointestinal tract.
[0004] Peristaltic pumps are typically used to pump clean or
sterile fluids because the pump does not contaminate the fluid, or
to pump aggressive fluids because the fluid does not contaminate
the pump. Some common applications include pumping aggressive
chemicals, high solids slurries and other materials where isolation
of the product from the environment, and the environment from the
product, are critical.
[0005] Higher pressure peristaltic pumps that operate at pressures
up to 16 bar typically use shoes and have casings filled with
lubricant to prevent abrasion of the exterior of the pump tube and
to increase heat dissipation. Lower pressure peristaltic pumps
typically have dry casings and use rollers. High pressure
peristaltic pumps typically use reinforced tubes often called
`hoses` and are often classified as a `hose pump`. Lower pressure
peristaltic pumps typically use non-reinforced tubing and are often
classified as a `tube pump` or `tubing pump`.
[0006] Because the only part of the pump in contact with the fluid
being pumped is the interior of the tube, the inside surfaces of
the pump are easy to sterilize and clean. Furthermore, since there
are no moving parts in contact with the fluid, peristaltic pumps
are inexpensive to manufacture. Peristaltic pumps lack valves,
seals, and glands, which makes them comparatively inexpensive to
maintain compared to other pump types.
[0007] Commonly, a roller that can `roll` along the tube is used to
compress and occlude the tube as it creates less wear, though, a
non-rolling compression method may be used. A number of different
means exist for moving the roller as it compresses the tube. A
rotary system may be used to move the rollers around a
circumference wherein the tube is compressed between a, wall and a
roller. A linear system may also be used to move a roller along a
straight length wherein the tube is compressed between a wall and a
roller. Or a compression method could be used that has sequential
rollers or fingers to compress the tube. Before a roller has moved
its design distance and no longer occludes the tube, a second
roller compresses and occludes the tube so the material does not
flow back. The first roller then lifts from the tube and the second
roller pushes the material through the tube. The first or another
roller then compresses the tube so the second roller may lift
without allowing material to flow back. Any number of rollers may
be used to smooth the flow of material. The speed of this squeezing
action may be varied and the tube size may also be varied. The
pressure the pump generates is directly related to the strength of
the seal created inside the tube. Pressing the roller against the
tube with greater force is one exemplary method. The vacuum the
pump generates may be related to the durometer (stiffness) of the
tube and the force of compression. A greater force will not
increase the vacuum beyond the point of no vacuum leak in the
compressed portion of the tube.
[0008] The "squeeze" force the peristaltic pump generates is a
significant operational parameter. While high squeeze force will
allow stiff fluids to be pumped, it also causes tube degradation
with use. The greater the squeeze force the more severe the tube
deformation and thus the tube will tolerate fewer compression
cycles due to stresses in the material and heat generated by the
deformation. Advances have been made in materials used in tubes
that enable them to be more resistant to wear. Springs have also
been incorporated in some peristaltic pump designs to provide a
more constant force between roller, tube, and compression surface.
A tube that undergoes significant wear will eventually become
non-functional and require replacement.
[0009] There is, therefore a need for a device and method to
improve the usable life of the tube used in peristaltic pumps.
Further, there is a need for a device and method to improve the
performance of a peristaltic pump.
SUMMARY
[0010] The surface interfaces used to compress the tube of a
peristaltic pump are configured to cooperatively reduce the stress
on the tube edges when the tube is flattened causing an occlusion.
One interface is the surface of the compression element and the
other interface is the compression surface the tube is pressed
against by the compression element.
[0011] As the tube of a peristaltic pump is compressed, its
non-compressed cross-section shape changes from substantially
circular to substantially rectangular. When the tube is being
compressed, the compressed edges where the tube walls make a
180-degree fold develop significant stress and degradation due to
wall flexure. Embodiments herein shape the interface surfaces to
make the folding of the tube at its compressed edges more gradual,
thus reducing the stress in the tube walls.
[0012] In one embodiment, the compression surface remains flat
while the engaging compression element surface is shaped to
gradually recede from the tube allowing a space for the wall fold
to assume a lower stress shape.
[0013] In another embodiment, the compression element surface is
substantially flat and the compression surface is shaped to
gradually recede from the tube again allowing for the wall fold to
assume a lower stress shape.
[0014] In yet another embodiment, both the compression element
surface and the compression surface are shaped to gradually recede
from the tube allowing the wall fold to assume a symmetrical lower
stress shape on either side of the tube opening thereby further
reducing stress and improving tube life.
[0015] In the embodiments herein, the compression element may be a
roller, a shoe, or a wiper device. If a shoe or wiper device is
used as the compression element, the tube most likely would require
surface lubricant to reduce frictional wear and stress.
[0016] The details of one or more embodiments are set forth in the
accompanying drawings and the description below. Other features,
objects, and advantages of the invention will be apparent to one
skilled in the art from the description and drawings.
DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a drawing showing an embodiment of a shaped roller
and a flat wall with a compressed tube;
[0018] FIG. 2 is a drawing showing an embodiment of a shaped wall
and a flat roller with a compressed tube;
[0019] FIG. 3 is a drawing showing an embodiment of a shaped roller
and a shaped wall with a compressed tube; and
[0020] FIG. 4 is a side view of portions of a peristaltic pump
illustrating the compression element and the mechanism for moving
the compression element.
[0021] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0022] In the following description, numerous specific details are
set forth to provide a thorough understanding of the embodiments
described herein. However, it will be obvious to those skilled in
the art that the embodiments may be practiced without such specific
details. In other instances, well-known elements may be shown in
block diagram form in order not to obscure the description of the
embodiments in unnecessary detail. For the most part, details
concerning detailed dimensions and the like have been omitted
inasmuch as such details are not necessary to obtain a complete
understanding of the embodiments and are within the skills of
persons of ordinary skill in the relevant art.
[0023] In the following, the term `roller` for the purposes of this
document will be understood to mean any structure used to create a
compression point in a tube compression pump. These structures
include but are not limited to rolling, sliding and or stationary
structures. The term compression surface is understood to be a
structure that the roller is pressing against to create a
compression point including but not limited to rolling, sliding and
or stationary structure.
[0024] Refer now to the drawings wherein depicted elements are not
necessarily shown to scale and wherein like or similar elements are
designated by the same reference numeral through the several
views.
[0025] FIG. 1 illustrates roller 100 compressing tube 105 against
support element 106 forming contours 103 according to one
embodiment. Line 107 indicates the interface formed when the
interior walls touch when sufficiently compressed. The roller 100
is cylindrical in shape with a center section with center surface
101 at a first diameter disposed between two edge sections with
edge surfaces 108 at a second diameter. The roller 100 has a center
surface 101 that is substantially flat and is formed of a suitable
material (e.g., rubber, plastic, or metal). A contour 102 is
designed to smoothly transition between the center surface 101 and
the edge surfaces 108 to minimize stress in the edges 103 of tube
105. As the roller 100 engages and flattens tube 105 in its center
area 104, the contours 102 allow the edges 109 of the compressed
tube 105 to assume a low stress shape while the center of the tube
opening (indicated by line 107) is flattened forming an occlusion
that in turn enables fluid material in the tube 105 to be
transported from an intake to an output of tube 105. It is
understood that it is within scope of the present invention to have
the diameter of the edge sections assume other values after they
have extended sufficiently to form surfaces 108.
[0026] Roller 100 has a shape defined by contour 102 that is a
reciprocal to the assumed shape of a compressed tube 105. The shape
of contour 102 may be varied to optimize compression and such
variations are considered to be within the scope of the present
invention. A contour shape may be achieved by various methods such
as a pliable (self forming) layer that acquires a desired shape due
to stresses from the compression and/or a rigid shape and such
variations are considered to be within the scope of the present
invention.
[0027] FIG. 2 illustrates the effect of roller 200 compressing tube
105 against support element 206, which has a center surface 208 at
one level and edge surfaces 205 disposed at a lower level. Contours
202 allow contours 209 in tube 105 to occur when tube 105 is
compressed by roller 200 according to one embodiment. Line 207
represents when the interior tube walls touch when sufficiently
compressed. The surface of roller 200 is formed of a suitable
material (e.g., rubber, plastic, or metal) and is shaped to have a
flat surface 201 designed to compress tube 105. As the roller 200
engages and flattens tube 105 in its center area 204, the contours
202 allows the edges 203 of the compressed tube 105 to assume low
stress shapes while the center of the tube (defined by line 207)
opening is flattened forming an occlusion that in turn enables
fluid material in the tube 105 to be transported from an intake to
an output. It is understood that it is within scope of the present
invention to have the level of the edge sections assume other
values after the edge sections of the support element 206 have
extended sufficiently to form surfaces 205.
[0028] Support element 206 has a shape defined by contours 202 that
form contours 209 when tube 105 is compressed. The shape of contour
202 may be varied to optimize compression and such variations are
considered to be within the scope of the present invention. A
contour shape may be achieved by various methods such as a pliable
(self forming) layer that acquires a desired shape due to stresses
from the compression and or a rigid shape and such variations are
considered to be within the scope of the present invention.
[0029] FIG. 3 illustrates a roller 300 compressing tube 105 against
a support element 306 forming contours 309 according to embodiments
herein. Roller 300 and support element 306 each have contours (302
and 303) which reduce the stress from compression in tube 105. The
roller 300 is cylindrical in shape with a center section with
center surface 301 at a first diameter disposed between two edge
sections with edge surfaces 308 at a second diameter. Center
surface 301 is substantially flat and is formed of a suitable
material (e.g., rubber, plastic, or metal). Support element 306 has
a center section with a center surface 304 at one level and edge
sections with edge surfaces 305 disposed at a lower level. When
roller 300 compresses tube 105, both contours 302 on roller 300 and
contours 303 on support element 306 allow the edges 309 of the
compressed tube 105 to assume low stress shapes while the center of
the tube opening 307 is flattened forming an occlusion that in turn
enables fluid material in the tube 105 to be transported from an
intake to an output of tube 105.
[0030] FIG. 4 is a side view of portions of a peristaltic pump 400
suitable for practicing embodiments described herein. A length of
tube 401 is supported in a circular arc configuration with inlet
403 and outlet 402. Compression elements 406 and 405 are shown
engaging and compressing tube section 401 against a surface of
support element 409 over segments 407 and 408. As rotor 404 moves
as shown by the arrow, compression element 405 will disengage from
segment 407 of tube 401 and compression element 406 will engage and
compress segment 408 of tube 401 such that at least compression
element 406 maintains a seal in tube 401 preventing back flow of
fluid. Material in tube 401 will be moved by peristalsis in the
direction of movement of the compression elements 405 and 406 and
will be delivered to outlet 402. By contouring compression elements
405 and 406 and/or surfaces of support 409, the stresses in tube
401 may be significantly reduced during the pumping process.
[0031] The contour shapes may vary to optimize compression and such
variances are considered to be within the scope of the present
invention. A contour shape may be achieved by various methods such
as a pliable (self forming) layer that acquires the contour shape
due to stresses in the compression or a rigid shape and such
variances are considered to be within the scope of the present
invention.
[0032] A number of embodiments of the invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention. Accordingly, other embodiments are within
the scope of the following claims.
* * * * *