U.S. patent application number 15/978078 was filed with the patent office on 2018-11-15 for planar flow channels for peristaltic pumps.
The applicant listed for this patent is Phillip W. Barth. Invention is credited to Phillip W. Barth.
Application Number | 20180328352 15/978078 |
Document ID | / |
Family ID | 64097664 |
Filed Date | 2018-11-15 |
United States Patent
Application |
20180328352 |
Kind Code |
A1 |
Barth; Phillip W. |
November 15, 2018 |
PLANAR FLOW CHANNELS FOR PERISTALTIC PUMPS
Abstract
A flow channel plate suitable for use with a peristaltic pump
comprises: a planar substrate; a flow channel in the planar
substrate and mechanical strain relief means in the planar
substrate, allowing lateral expansion of the flow channel during
vertical compression of the flow channel. The path of the flow
channel in the flow channel plate may be nonlinear. The flow
channel may be characterized by a Davis-Butterfield cross sectional
shape. A roller pump head comprises: a flow channel plate; a roller
cage; tapered rollers held in position by the roller cage; and a
drive rotor comprising one of a tapered rotor and a rotor having a
radially limited zone of contact on the sloping portions of the
tapered roller. Lower surfaces of the tapered rollers apply force
to the flow channel plate and upper surfaces of the tapered rollers
receive force from the drive rotor.
Inventors: |
Barth; Phillip W.; (Portola
Valley, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Barth; Phillip W. |
Portola Valley |
CA |
US |
|
|
Family ID: |
64097664 |
Appl. No.: |
15/978078 |
Filed: |
May 11, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62505900 |
May 13, 2017 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04B 43/0072 20130101;
F04B 43/1261 20130101; F04B 43/082 20130101; F04B 43/1269
20130101 |
International
Class: |
F04B 43/08 20060101
F04B043/08; F04B 43/00 20060101 F04B043/00; F04B 43/12 20060101
F04B043/12 |
Claims
1. A flow channel plate suitable for use with a peristaltic pump,
the flow channel plate comprising: a planar substrate; a flow
channel in the planar substrate; and mechanical strain relief means
in the planar substrate, allowing lateral expansion of the flow
channel during vertical compression of the flow channel.
2. The flow channel plate of claim 1, wherein the path of the flow
channel in the flow channel plate is nonlinear.
3. The flow channel plate of claim 1 wherein the flow channel is
characterized by a Davis-Butterfield cross sectional shape.
4. The flow channel plate of claim 1, wherein the planar substrate
has a full thickness; and wherein the mechanical strain relief
means comprises holes extending through the full thickness.
5. The flow channel plate of claim 1, wherein the planar substrate
has a full thickness; and wherein the mechanical strain relief
means comprises recesses extending only partway through the full
thickness.
6. The flow channel plate of claim 1 wherein the mechanical strain
relief means comprises a region of elastomeric material.
7. The flow channel plate of claim 1 wherein the mechanical strain
relief means comprises one or more corrugations.
8. The flow channel plate of claim 1 wherein the mechanical strain
relief means comprises a region prone to buckling under lateral
expansion.
9. A disposable kit for an infusion pump, the kit comprising: the
flow channel plate of claim 1; and one or more additional elements;
wherein the flow channel plate and the one or more additional
elements are integrated to form a single assembly.
10. A flow system comprising: the flow channel plate of claim 1;
and one or more additional elements; wherein the flow channel plate
and the one or more additional elements are connected to form a
manifold.
11. The flow channel plate of claim 1, wherein the plate material
comprises one of poly-ether ether ketone, polycarbonate, cyclic
olefin copolymer, polyvinyl chloride with plasticizers, polyvinyl
chloride without plasticizers, polymethyl methacrylate,
polyethylene, high density polyethylene, ultra high density
polyethylene, polyethylene terephthalate, polypropylene, Formlabs
printing resin, other printing resin, silicon, glass, silicone
rubber, polyimide, stainless steel, brass, and bronze.
12. A method of making the flow channel plate of claim 1, the
method comprising at least one of microstereolithography,
stereolithography, three-dimensional printing, lamination,
injection molding followed by lamination, vacuum forming followed
by lamination, lamination around a mandrel, and investment
casting.
13. A roller pump head comprising: a flow channel plate; a roller
cage; tapered rollers held in position by the roller cage; and a
drive rotor comprising one of a tapered rotor and a rotor having a
radially limited zone of contact on the sloping portions of the
tapered rollers; wherein lower surfaces of the tapered rollers
apply force to the flow channel plate and upper surfaces of the
tapered rollers receive force from the drive rotor.
14. The roller pump head of claim 13, further including one of a
collar around the path of the tapered rollers to aid in roller
retention, and a lip on the drive rotor to aid in roller
retention.
15. The roller pump head of claim 13, further including a drive
shaft connected to the drive rotor.
16. The roller pump head of claim 15, further including a thrust
bearing connected to the drive shaft.
17. The roller pump head of claim 16, further including a spring
exerting force on the thrust bearing.
18. The roller pump head of claim 16, further including an
adjustable spring exerting force on the thrust bearing.
19. The roller pump head of claim 13 wherein the drive rotor is
tapered.
20. The roller pump head of claim 13 wherein the drive rotor has a
radially limited zone of contact on the sloping portions of the
tapered rollers.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Patent Application Ser. No. 62/505,900, entitled "Improved
peristaltic pump technologies", filed on May 13, 2017 which is
hereby incorporated by reference as if set forth in full in this
application for all purposes.
BACKGROUND
[0002] Biological systems including tubes or channels such as the
intestines or ureters perform a fluid pumping action called
peristaltic pumping, in which waves of smooth muscle contraction
move along the length of the biological tube. In the remainder of
this disclosure, naturally-occurring peristaltic pumps in
biological systems are referred to as "biological peristaltic
pumps".
[0003] Artificial peristaltic pumps which mimic the action of
biological peristaltic pumps have been developed since 1855. In the
remainder of this disclosure, the term "peristaltic pump" without
the preceding adjective "biological" should be understood as
referring to an artificial peristaltic pump.
[0004] A peristaltic pump, often called a roller pump, is a fluid
pump in which an enclosed flow channel is compressed by roller or
rollers, or by a series of compression blocks or fingers, to propel
a fluid along the channel from a channel entrance to a channel
exit, in rough analogy with the peristaltic pumping action of
biological peristaltic pumps. Advantageously, the fluid being
pumped contacts only the interior surfaces of flow channel, and
complex components such as valves or pistons, which would be
subject to leakage or sliding wear, are avoided.
[0005] The first peristaltic pump, patented in the US in 1855,
employed an elastic tube. Improvements were made but the
peristaltic pump was not widely used before 1932. Currently,
peristaltic pumps are ubiquitous, with uses including hemodialysis,
cardiopulmonary bypass, pharmaceutical manufacturing, drug
infusion, chemical handling, slurry pumping, and general laboratory
use. There are hundreds of manufacturers of peristaltic pumps in
the USA.
[0006] All early versions of peristaltic pumps used soft, round
tubes or hoses, and the use of soft, round tubes or hoses continues
to the present.
[0007] Flow channels for peristaltic pumps having a non-round cross
sectional shape, which herein will be called the Davis-Butterfield
shape, or DB shape, after the inventors, potentially have
performance advantages over a round tube or hose, including low
spallation, low mechanical stress, long channel life, and high
pressure capability. There is, however, a potential drawback of
this shape, regarding lateral expansion of the flow channel under
vertical compression, which has not previously been acknowledged or
discussed. There is, therefore, a need for designs that directly
address this issue, facilitating adoption of such channels in
peristaltic pumps.
[0008] Most existing peristaltic pumps are roller pumps, and most
roller pumps can be called "circumferential roller pumps" as the
peristaltic pump tubing is disposed around a curved path on a rigid
backing member and is driven by rollers which compress the tubing
against the circumference of the curved path. There are, however,
several peristaltic pump designs which can be called "face roller
pumps". In these, the peristaltic pump tubing is disposed on a
planar face of a rigid backing member and is compressed against
that planar face by rollers rolling in a circular path around an
axis perpendicular to the planar face.
[0009] Wearable insulin pumps are a growing market, mainly for use
by Type I diabetes patients, also known as juvenile diabetes
patients. When combined with a blood glucose sensor in an
electronic feedback loop, the result can be called an "artificial
pancreas." A typical wearable insulin pump comprises a small
disposable syringe containing insulin, the syringe being driven by
a stepper motor controlled by electronics, the whole package being
small enough to wear on a belt clip. A typical wearable insulin
pump is the Medtronic Minimed Model 670G. An insulin pump is one
type of infusion pump.
[0010] Every three days the patient or caregiver using a wearable
insulin pump must discard the old syringe to minimize bacterial
contamination, and must refill a new syringe with insulin.
Installing a new syringe is a thirteen-step process, using four
separate disposables. It requires good two-handed manual dexterity,
with several chances for septic contamination. For the many Type I
diabetes patients who are children, this process can be a daunting
task for them and their parents.
[0011] Thus, there exists a need for a compact wearable insulin
pump having a simpler insulin refill process with reduced chances
for septic contamination.
SUMMARY
[0012] The present invention includes a flow channel plate suitable
for use with a peristaltic pump. The flow channel plate comprises:
a planar substrate; a flow channel in the planar substrate; and
mechanical strain relief means in the planar substrate, allowing
lateral expansion of the flow channel during vertical compression
of the flow channel. In one aspect, the path of the flow channel in
the flow channel plate is nonlinear. In another aspect, the flow
channel is characterized by a Davis-Butterfield cross sectional
shape. In yet another aspect, a disposable kit for an infusion pump
comprises the flow channel plate of claim 1 and one or more
additional elements; wherein the flow channel plate and the one or
more additional elements are integrated to form a single
assembly.
[0013] The present invention further includes a roller pump head
comprising: a flow channel plate; a roller cage; tapered rollers
held in position by the roller cage; and a drive rotor comprising
one of a tapered rotor and a rotor having a radially limited zone
of contact on the sloping portions of the tapered rollers; wherein
lower surfaces of the tapered rollers apply force to the flow
channel plate and upper surfaces of the tapered rollers receive
force from the drive rotor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 (Prior Art) illustrates the basic principle of a
circumferential-roller peristaltic pump.
[0015] FIG. 2A (Prior Art) illustrates a cross section of a soft,
round tube as used in peristaltic pumps, in a relaxed state.
[0016] FIG. 2B (Prior Art) illustrates a cross section of the soft,
round tube of FIG. 2A in a compressed state.
[0017] FIG. 3 (Prior Art) shows the Davis-Butterfield
cross-sectional flow channel shape in uncompressed and compressed
form.
[0018] FIG. 4A (Prior Art) illustrates cross sections of a
Davis-Butterfield flow channel in a relaxed state
[0019] FIG. 4B (Prior Art) illustrates a cross section of a
Davis-Butterfield flow channel in a compressed state.
[0020] FIG. 5 illustrates a semicircular segment of a peristaltic
flow channel according to one embodiment of the present invention,
following a planar path.
[0021] FIG. 6 illustrates a planar flow channel plate according to
one embodiment of the present invention.
[0022] FIG. 7 illustrates a cross section of a face roller pump
head incorporating a planar flow channel according to one
embodiment of the present invention.
[0023] FIG. 8 illustrates a three-dimensional exploded view of a
face roller pump head incorporating a planar flow channel according
to one embodiment of the present invention.
[0024] FIG. 9 illustrates a cross section of a face roller pump
head incorporating a planar flow channel according to another
embodiment of the present invention.
[0025] FIG. 10 illustrates a cross section of a face roller pump
head incorporating a planar flow channel according to yet another
embodiment of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0026] Embodiments described herein include a peristaltic flow
channel and mechanical strain relief features disposed in a planar
fashion suitable for incorporation into a compact face-roller
peristaltic pump. Embodiments further include a face-roller
peristaltic pump incorporating a peristaltic flow channel disposed
in a planar fashion.
[0027] FIG. 1 illustrates the basic principle of a prior-art
circumferential-roller peristaltic pump 10. Flexible tube 1 sitting
within rigid case member 2 contains the fluid to be pumped, and is
compressed by rollers 3 and 4 on arm 5 at regions 6 and 7. If arm 5
rotates clockwise, the rollers 3 and 4 move the compression regions
6 and 7 clockwise, causing fluid to be sucked in at 8 and expelled
at 9.
[0028] In FIGS. 2 through 8 in the present disclosure, the
orientation of flow channels is shown such that a roller or other
compression member can compress the flow channel vertically from
above or below, and such that the lateral dimensions of the flow
channel can increase under vertical compression while the vertical
dimension of the flow channel can decrease.
[0029] Descriptive language in this disclosure and in associated
claims refers to flow channels in the orientations shown in FIGS. 2
through 8, using terms such as upper, lower, top, bottom, lateral,
vertical, width, and height, but that language is a convenience for
purposes of description and explanation of flow channels in those
particular orientations, and is not limiting of the invention, nor
is the orientation chosen a limitation of the invention.
[0030] FIG. 2A shows a cross section taken through a soft, round
tube 20 as used for a traditional peristaltic pump, in its relaxed,
uncompressed state. Lumen 21 in the center of the tube is open or
patent.
[0031] In FIG. 2B the tube is compressed as it would be under a
roller and lumen 21 is almost occluded. The tube is considerably
wider in its compressed state than in its relaxed state, as
indicated by the spacing of the dotted lines 22.
[0032] The word "round" used herein to describe flow channel shapes
connotes flow channels having a lumen which, when viewed from
inside the lumen, has a shape which is concave everywhere, such as
a circle, oval, or ellipse. Flow channel shapes having points,
cusps, tips, or regions which are convex when seen from within the
lumen are non-round.
[0033] FIG. 3, reproduced from FIG. 5 of U.S. Pat. No. 9,683,562,
illustrates a Davis-Butterfield flow channel non-round cross
sectional shape. Such channels can be formed by extrusion or by
lamination of two sheets. Although the figure does not indicate
that any lateral expansion of the flow channel occurs under
vertical compression, in reality, lateral expansion of the
Davis-Butterfield channel must occur when it is compressed
vertically. FIGS. 4A and 4B are accurately scaled drawings which
illustrate cross sections taken through a Davis-Butterfield flow
channel and do take lateral expansion into account. FIG. 4A
illustrates the flow channel in its relaxed, uncompressed state
with an open lumen 41 between shaped walls 42 and 43, each of
uniform thickness, the walls meeting at tips 44 and 45 having a
small radius of curvature and an interior angle approaching 180
degrees. FIG. 4B illustrates the same channel in a compressed
state, when the lumen opening 41 is reduced but not fully occluded.
In accurately scaling FIG. 4A and FIG. 4B, the channel perimeter
around the interior walls of lumen 41 in FIG. 4A is made equal to
the channel perimeter around the interior walls of lumen 41 in FIG.
4B. Dotted lines 46 indicate that the flow channel undergoes
lateral expansion as it moves from its relaxed state to a
vertically compressed state.
[0034] Thus, whether the flow channel is a round tube, or has a
Davis-Butterfield shape, or has some other shape, the flow channel
undergoes lateral expansion when it is vertically compressed.
[0035] Prior to the present invention, it has been known that the
Davis-Butterfield channel shape may be fabricated by extruding a
shaped profile, or by bonding together two separate sheets such
that the edge of the bonded areas forms the tips of the shaped
profile. The possibility of bonding together two separate sheets
such that the shaped profile of the channel is set within a larger
planar area has not previously been disclosed, and nor has the
issue of fabricating channels which are not straight-line in form
but instead follow a curving path which is generally planar. The
present invention is inspired in part by a realization that the use
of a peristaltic pump flow channel following a curving path, and
situated in planar fashion within a larger planar area, would have
utility advantages which are worth pursuing for wearable insulin
pumps and other uses. But the lateral expansion of the flow channel
under vertical compression is a problem which must be addressed to
use such channels successfully.
[0036] FIG. 5 is a perspective view of a flow channel 50 with
openings 51 and 52 formed by bonding together two separate sheets
such that the channel follows a semicircular path within a plane.
The channel shown has a Davis-Butterfield cross sectional shape
with channel width 54 and channel height 55, and the center of the
flow path follows a semicircle having a radius 53. In one
embodiment, radius 53 has a value of 5 millimeters; in another, 10
centimeters. The edges of channel 50 would be free to expand within
the plane when the channel is compressed vertically if channel 50
were unconstrained in that plane. But if channel 50 were set within
a larger planar area of bonded sheets, its lateral expansion under
vertical compression would be constrained by the presence of
material outside the channel, making its use as a peristaltic pump
channel problematic and leading to early failure of such a channel.
This problem exists whether the channel has a DB-shape as shown, or
a round channel shape, or some other shape.
[0037] That problem of constrained lateral expansion can be
addressed by introducing strain relief means situated outside the
edges of the channel. FIG. 6 illustrates a planar flow channel
plate 60 of the present invention which can be formed by laminating
together two separate sheets of material that include stain relief
means. Flow channel plate 60 includes a flow channel 601 shown as
having a Davis-Butterfield cross sectional shape, and which has a
semicircular portion 68 plus two straight portions 69. The flow
channel has openings 61 and 62. The dimension 63 is called the pump
diameter having a value of, as one example, 10 millimeters or, as
another example, 20 centimeters, and extends from the center of the
flow path on one side of the semicircular path 68 portion of flow
channel 601 to the center of the flow path on the other side. The
flow channel 601 has a channel width 64 and a channel height 65.
Strain relief means 66 permit portions 68 and 69 to expand
laterally in the plane of the device when force is applied from
above and/or below the plane of plate 60, for example by a roller,
to occlude or partially occlude the flow channel 601 during pump
operation. Center hole 67 permits a pump drive shaft to pass
through the plate 60. The openings 61 and 62 connect to further
channel regions, not shown, which may provide a transition from the
Davis-Butterfield cross section (or, in other embodiments, other
cross section) shape to conventional round flow channels which can
then connect to conventional round tubing or fittings. Other
features, not shown, may be present in flow channel plate 60, for
example, through holes or alignment notches, useful for aligning
and attaching the flow plate 60 in a peristaltic pump head, or
laser markings identifying the channel size and shape and device
serial number.
[0038] Strain relief means 66 are shown in FIG. 6 as holes
extending through the full thickness of flow channel plate 60, but
in other embodiments, relief means 66 may comprise recesses
extending partly through the thickness of plate 60, or corrugations
within plate 60, or thinned regions within plate 60, or regions
prone to bucking under lateral expansion within plate 60, or
inserts of separate material within plate 60, or other means of
allowing lateral expansion of the flow channel, or combinations of
any of these.
[0039] The flow channel plate 60 can be formed by laminating
together two separate sheets of material or by other means. For
example, it can be formed by fine-featured three dimensional
printing means known as micro-stereolithography, using a single
printing material or various materials. Other possible means of
fabricating flow channel plate 60 include, but are not limited to,
stereolithography, three-dimensional printing, injection molding
followed by lamination, vacuum forming followed by lamination,
lamination around a mandrel, and investment casting.
[0040] The material comprising flow channel plate 60 may be one or
more of poly-ether ether ketone (PEEK), polycarbonate, cyclic
olefin copolymer (COC), polyvinyl chloride (PVC) with plasticizers,
polyvinyl chloride without plasticizers, polymethyl methacrylate
(PMMA or Plexiglass.RTM.), polyethylene, high density polyethylene,
ultra high density polyethylene, polyethylene terephthalate (PET or
PETE), polypropylene, Formlabs printing resin, other printing
resin, silicon, glass, silicone rubber, polyimide, stainless steel,
brass, and bronze. The use of other materials is also possible.
[0041] FIG. 7 illustrates a cross sectional view of a face roller
pump head 70, according to one embodiment of the current invention,
incorporating a flow channel plate and tapered rollers. In the
illustrated embodiment, this is flow channel plate 60 having flow
channel 601 shown in FIG. 6. Strain relief means 66 are not shown
in FIG. 7, for simplicity, but should be considered to be present
within plate 60. Base plate 71 has a central hole allowing drive
shaft 72 to pass through it. Drive shaft 72 rotates (as indicated
by arrow 79) around a vertical axis (shown as dotted line C. L.)
driving tapered drive rotor 73, which frictionally drives tapered
rollers 74, which are held in predetermined relative angular
positions by rotating cage 75. Collar 76 and lip 78 both help to
hold the rollers 74 in place radially. Optional shim plate 77 helps
prevent grinding between tapered rollers 74 and flow channel plate
60.
[0042] Rollers 74 are tapered to provide non-grinding rotation on
shim plate 77 over flow channel plate 60, or on flow channel plate
60 if shim plate 77 is not present. If cylindrical rollers instead
of tapered rollers were to be used, it is known that a grinding
action on the pump components would occur. Large cylindrical
rollers are sometimes used in grinding mills.
[0043] In operation, tapered drive rotor 73 has frictional contact
with tapered rollers 74, tapered rotor 73 turning more than twice
as fast as cage 75 which holds tapered rollers 74. For the
approximately 37 degree taper angles of the rollers shown in FIGS.
7 and 8, the drive rotor 73 turns roughly 2.3 revolutions for every
revolution of the cage 75. The rotational speed of the pump head is
defined as the rotational speed of cage 75. A thrust bearing, not
shown, attaches to drive shaft 72 beneath base plate 71 and pulls
downward on drive shaft 72 to provide downward force on tapered
drive rotor 73, which in turn provides downward force on tapered
rollers 74. A spring, not shown, can provide the desired degree of
downward force and may be adjustable. The thrust bearing can be
fixed in position with respect to drive shaft 72, or can be
adjustable in position with respect to the drive shaft to provide a
desired magnitude of downward force. Other means may be used to
provide the desired force on the thrust bearing.
[0044] Drive shaft 72 may be driven directly by a drive motor, such
as a stepper motor or a DC motor, or indirectly, by a gear
connected to a drive motor, by a drive belt connected to a drive
motor, or by other means. Electronics and/or computer controllers
may be connected to a drive motor to control the position and
rotational speed of drive shaft 72. Sensors may be attached to
drive shaft 72 and/or to cage 75 to monitor the angular position of
drive shaft 72 and/or rollers 74. Various other electronics,
sensor, and computers may be used in connection with the use of the
pump head.
[0045] A retention collar, not shown, may be firmly attached to
drive shaft 72 above base plate 71 and extending loosely beneath
cage 75, so that it does not contact the cage nor the other pump
structures when the pump head is fully assembled, but when the pump
head is disassembled, the cage, rollers, rotor, and drive shaft can
be lifted upward as a single assembly. Further, drive shaft 72 may
include (not shown) means, such as a groove or collar, of snapping
downward into a rotatable retention structure such as a
spring-loaded retention structure beneath base plate 71 during pump
head assembly, and of coming quickly out of the retention structure
during pump head disassembly, thus enabling different flow channel
plates to be swapped in and out of the pump head quickly and
easily. A thrust bearing, not shown, may be connected to the
retention structure.
[0046] The cross section view in FIG. 7 shows two tapered rollers
74 directly opposed to each other for illustration purposes, but
this is not typical. Typically there are three tapered rollers 74
in the pump head 70 design spaced 120 angular degrees apart from
each other, and when three rollers are used no cross section can be
taken as in FIG. 7 which would show two rollers directly
opposed.
[0047] FIG. 8 is a three-dimensional rendering, slightly exploded,
of pump head 70. Three tapered rollers 74 can be seen sitting 120
angular degrees apart from one another in cage 75. The tapered
rollers 74 are held in place in cage 75 by axle pins, not shown,
comprising part of cage 75, the axle pins engaging recesses, not
shown, in the ends of the rollers 74. Alternatively, full axles,
not shown, extending through each roller and attached to cage 75,
may be used. The contact between axle pins and roller recesses may
be optimized for low friction, for example by using jeweled
bearings as in watchmaking, by using coatings of diamond-like
carbon on one or both of pins and recesses, or by using ceramic
rollers or ceramic pins. Because the fluid flow path of the
peristaltic pump is separated from the pump head mechanism by the
walls of the peristaltic flow channel, it is also possible to use
lubricants such as oil or grease in the pump head for low friction
operation.
[0048] Cage 75 may be a unitary body into which the rollers can be
snapped into place, or may be an assembly which can be assembled
around the rotors.
[0049] An advantage of the pump head 70 design, as opposed to
previous face-roller pump designs in the prior art, is that little
or no force is exerted on the axle pins or axles by the tapered
rollers. Instead, all of the vertical bearing force coming from
drive shaft 72 is exerted by the tapered rotor 73 on the rollers
74, and by the rollers 74 on the underlying structures 77, 60, and
71. Thus, a much greater force can be safely applied by a thrust
bearing to the drive shaft, enabling much better high pressure
operation than was possible with prior art designs, where the
allowable force magnitude on roller axles limits high pressure
performance. Collar 76 and rotor lip 78 act to contain the tendency
of the rollers to slide radially outward during pump operation.
[0050] In pump head 70, fluid flow in straight sections 69 of the
peristaltic flow channel 601 passes between base plate 71 and
collar 76. Advantageously, one or both of base plate 71 and collar
76 can feature shallow recessed areas such as shallow recessed
areas 79 to avoid vertical pinching of the fluid flow channel in
straight sections 69 between the base plate 71 and the collar 76.
In FIG. 8, shallow recessed areas 79 are present in base plate 71
to serve this purpose. Rollers 74 pass over recessed areas 79
during pump head operation, and recessed areas 79 can be designed
laterally in a manner, not shown, so that roughly half of the
roller bearing area on flow channel plate 60 remains supported by
underlying base plate 71 as the rollers 74 roll over recessed areas
79.
[0051] The pump head 70 is shown in FIG. 8 as having three tapered
rollers 74, but in other embodiments more or less than three
rollers may be used, in rough analogy with the design of thrust
bearings which may have different numbers of tapered rollers.
[0052] An advantage of using more than three rollers is that the
volume of fluid trapped in the flow channel between adjacent
rollers is reduced. When three rollers spaced 120 angular degrees
apart are used, the minimum fluid aliquot which can be expelled
from the pump is the volume trapped in a 120-degree segment of the
flow channel flow channel. When five rollers are used, a 72-degree
segment of the flow channel volume comprises the minimum aliquot.
Thus using a flow channel with a small cross sectional area, and
using as many rollers as feasible, enables the pump head 70 to more
easily compete with the minimum aliquot available from syringe
pumps presently used in wearable insulin pumps.
[0053] The pump head embodiments shown in FIGS. 7 and 8 have drive
shaft 72 pulling on tapered drive rotor 73 from beneath. In other
embodiments, the drive shaft can push on the tapered drive rotor
from above.
[0054] The pump head embodiments shown in FIGS. 7 and 8 use a
tapered drive rotor having contact areas between the rotor 73 and
the tapered rollers 74. The rotor 73 as shown in FIG. 7 has a
radially large contact zone with rollers 74, the zone extending
over the length of the sloping walls of rollers 74 and making
contact with each roller at a broad contact patch.
[0055] In other embodiments, a different rotor may have contact
with rollers 74 along a radially limited zone of contact instead of
the radially larger zone of contact present if a tapered drive
rotor is used.
[0056] FIG. 9 illustrates one such embodiment of the invention, as
pump head 90, much like pump head 70 in FIG. 7, except that tapered
rotor 73 is replaced with a stepped rotor 93. Drive shaft 92
extends upward to first surface 901, and surface 901 extends
radially outward to O-ring gland 905 which holds O-ring 904. Rotor
93 then steps upward to surface 903 which extends radially outward
to roller retention lip 98. For purposes of discussion and in the
claims below, the rotor 93 is considered to include O-ring 904.
[0057] In operation of pump head 90, tension force on drive shaft
92 is transferred to rotor 93, and thence to O-ring 904, which
bears vertically downward on the tapered rollers 74 along a
radially-limited zone of contact 906. The zone of contact
intersects each roller at a small contact patch, not shown, similar
to the contact patch of a rolling automobile tire on pavement. As
is the case with pump head 70, the rotor 93 turns roughly 2.3
revolutions for every revolution of the cage 75 for the value of
angular taper shown.
[0058] FIG. 10 illustrates another embodiment of the invention, as
pump head 100, much like pump head 70 in FIG. 7, except that
tapered rotor 73 is replaced with a rotor 103 which has no roller
retention lip similar to lip 98 or lip 78. Drive shaft 103 extends
upward to first surface 1001, and surface 1001 extends radially
outward to O-ring gland 1005 which holds O-ring 1004. Rotor 93 then
terminates its outward radial extension. For purposes of discussion
and in the claims below, the rotor 103 is considered to include
O-ring 1004.
[0059] In operation of pump head 100, tension force on drive shaft
102 is transferred to rotor 103, and thence to O-ring 1004, which
bears vertically downward on the tapered rollers 74 along a
radially-limited zone of contact 1006. As is the case with pump
head 70, the rotor 103 turns roughly 2.3 revolutions for every
revolution of the cage 75 for the value of angular taper shown.
[0060] In other embodiments, not shown, with non-tapered rotors,
the radially-limited zone of contact can be broadened, relative to
zones 906 or 1006, by using an elastomeric band encircling the
rotor, the band surface being angled to follow the tapered surfaces
of the rollers 74 and providing a flat contact area to rotors 74.
For purposes of discussion and in the claims below, a rotor having
an elastomeric band encircling the rotor is considered to include
the elastomeric band.
[0061] For good pump performance it is important to have a non-skid
interface between rotor 73 and rollers 74, or between O-ring 904,
1004 and rollers 74, or between an elastomeric band, not shown, and
rollers 74. A non-skid interface between rollers 74 and plate 60,
or between rollers 74 and shim plate 77, is desirable but less
important, especially for three-day disposable applications.
Non-skid interfaces may be achieved by various means which will
occur to those skilled in pump design.
[0062] The rotor 93, 103 may comprise a stiff material having a
high elastic modulus in order provide adequate downward force on
the rollers 74 through O-ring 904, 1004. O-ring 904, 1004 may be
made of a soft elastomer for low pressure applications. For high
pressure applications, O-ring 904, 1004 may comprise a hard, stiff
material with a tough nonskid outer coating. For example, the
O-ring may comprise a core having the form of a stainless steel
coil spring and a coating layer of polyimide.
[0063] Tapered rotor 73 shown in FIG. 7 has an advantageous
characteristic of being self-centering with respect to tapered
rollers 74 in cage 75, due to one of gravitational force in the
orientation shown and tension applied by other means on the drive
shaft 72, because the tapered surface of rotor 73 bears on the
sloping surfaces of tapered bearings 74. Tapered rotor 73 also has
the advantageous characteristic of being self-leveling with respect
to the tapered rollers 74 in cage 75, due to one of gravitational
force in the orientation shown and tension applied by other means
on the drive shaft 72. The self-centering and self-leveling effects
are much like those which would be expected if a small funnel were
dropped into a larger funnel, both funnels having the same taper
angle.
[0064] The rotor 93 as shown in FIG. 9 has an advantageous
characteristic of being self-centering with respect to the tapered
rollers 74 in cage 75, due to one of gravitational force in the
orientation shown and tension applied by other means on the drive
shaft 92, because the radially limited contact area of rotor 93
though O-ring 95 falls on the sloping portions of the tapered
rollers. Rotor 93 also has the advantageous characteristic of being
self-leveling with respect to the tapered rollers 74 in cage 75,
due to one of gravitational force in the orientation shown and
tension applied by other means on the drive shaft 72. The
self-centering and self-leveling effects are much like those which
would be expected if a small wheel on an axle were dropped
axle-first into a funnel.
[0065] The rotor 103 as shown inf FIG. 10 has an advantageous
characteristic of being self-centering with respect to the tapered
rollers 74 in cage 75, due to one of gravitational force in the
orientation shown and tension applied by other means on the drive
shaft 102, because the radially limited contact area of rotor 103
through O-ring 105 falls on the sloping portions of the tapered
rollers. Rotor 103 also has the advantageous characteristic of
being self-leveling with respect to the tapered rollers 74 in cage
75, due to one of gravitational force in the orientation shown and
tension applied by other means on the drive shaft 72.
[0066] For good performance, force exerted on tapered rollers 74 by
a rotor such as rotor 93 or 103, the rotor having a radially
limited contact area on the sloping portions of tapered rollers 74
through O-ring 904 or 1004, should transmit force though the
rollers to bear near the radial center of flow of the flow channel
601 in flow channel plate 60, to avoid having too little
compression force at the radially inward edge of the flow channel
601 or too little compression force near the radially outward edge
of the flow channel.
[0067] The rotors 73, 93, and 103 have performance advantages over
prior-art rotor structures using flat disks or soft washers used to
drive rolling elements in peristaltic pump heads.
[0068] A rotor comprising a flat disk is unsuitable for use with
tapered rollers because a flat disk would have bearing force only
at small regions on the radially outward top surfaces of the
rollers, and not on the sloping portions of the rollers, thereby
providing too little compressive force on the radially inward
extents of the tapered roller walls. In addition, a flat disk
bearing on the top outward surfaces of tapered rollers, rather than
on the sloping portions of the tapered rollers, has no
self-centering action.
[0069] Prior art has discussed the idea of using a soft washer to
drive tapered rollers but has not described an embodiment which
does so. A rotor comprising a soft washer is unsuitable for use
with tapered rollers in embodiments like those of the present
invention because a soft washer can't provide enough downward
bearing force for high-pressure operation of peristaltic pumps, and
because the radial position of bearing force provided by a soft
washer, onto tapered rollers and thence onto a flow channel such as
flow channel 601, is difficult to predict or control. If a flat,
soft washer were larger in radial extent than the radial extent of
tapered rollers 74 it would not provide a self-centering
action.
[0070] In one embodiment of the present invention, a disposable
flow channel plate, such as plate 60, can be combined with other
components, such as a septum-puncturing receiver for an insulin
cartridge and a flexible tube connected to a hypodermic needle, and
integrated to form a kit comprising a single assembly. Using such a
kit could reduce a patient's insulin filling process from the
thirteen steps typically required for a syringe pump to four steps,
would use only one disposable instead of four disposables, and
require less dexterity, with less chance of septic contamination.
The four steps required when using a kit of the present invention
comprise inserting the kit into place in an opened pump head,
closing the pump head by snapping an assembly of rotor, roller,
cage, and axle into place in an underlying retention structure,
attaching an insulin vial, and running the pump until all air
bubbles exit the attached tubing of the kit.
[0071] A planar flow channel plate such as flow channel plate 60
can be combined in a manifold with other fluidic elements such as
flow channels and valves.
[0072] Multiple parallel flow paths driven by one pump head may be
included in a planar flow channel plate similar to plate 60.
[0073] Multiple planar peristaltic flow channels driven by multiple
pump heads can be formed in a single planar manifold which may
incorporate other fluid elements. Additional fluidic, electronic,
or optical elements may be incorporated in such a planar manifold
and may extend outward above or below the plane of the
manifold.
[0074] A flow channel plate such as flow channel plate 60 of the
preset invention need not be made from a single material. Composite
or laminated combinations of more than one material may be used to
form the flow channel plate without departing from the scope and
spirit of the invention. As one example, the interior walls of a
flow channel in plate 60 may comprise hard material while the
exterior walls of the flow channel may comprise softer material,
providing the advantage of low spalling of interior walls while
providing the advantage of low closing force for the channel in low
pressure applications. As another example, the strain relief means
66 may comprise soft elastomeric regions while the remainder of
plate 60 may comprise a harder material.
[0075] The use of the Davis-Butterfield cross sectional channel
shape is advantageous in the present invention, but is not a
necessity of the invention. A channel having a round cross
sectional shape or other cross sectional shape may be used, with
the consequence that the stain relief means 66 must possibly
accommodate a larger lateral expansion of the flow channel.
[0076] Embodiments described herein provide various benefits. In
particular, embodiments provide for planar flow channel plate
designs that include strain relief features that accommodate
lateral expansion of the flow channel during vertical compression
of the flow channel during operation with peristaltic pumps. This
benefit is likely to be of great value when channels of the DB
shape, providing advantages of low spallation, long service life,
and high pressure pumping capability, are involved, but will be
useful for other channel shapes too.
[0077] The formation of the flow channel plate in a generally
planar shape can allow inexpensive manufacturing for use in medical
disposable devices.
[0078] A planar flow channel plate can also be advantageous in
allowing for rapid interchange of flow channels in a pump head for
uses such as medical disposable use.
[0079] A three-roller pump head with tapered rollers has been
designed to use the planar flow channels in a manner that provides
low stress on the roller axle pins or axles for long service life
of the pump head, either when used with disposable channels or when
used with long-service-life flow channels. The load on the pump
rollers can be adjusted using a spring-loaded thrust bearing
attached to the pump's drive shaft to provide partial or full flow
channel occlusion during use and to adjust the overpressure value
at which desired leakage through the flow channel can occur.
[0080] The benefits discussed are likely to be of great value in
medical applications, such as insulin pumps, and also in many other
applications in manufacturing and in laboratories in general.
[0081] Although the description has been described with respect to
particular embodiments thereof, these particular embodiments are
merely illustrative, and not restrictive.
[0082] It will also be appreciated that one or more of the elements
depicted in the drawings/figures can also be implemented in a more
separated or integrated manner, or even removed or rendered as
inoperable in certain cases, as is useful in accordance with a
particular application.
[0083] Thus, while particular embodiments have been described
herein, latitudes of modification, various changes, and
substitutions are intended in the foregoing disclosures, and it
will be appreciated that in some instances some features of
particular embodiments will be employed without a corresponding use
of other features without departing from the scope and spirit as
set forth. Therefore, many modifications may be made to adapt a
particular situation or material to the essential scope and
spirit.
* * * * *