WO1997041353A1

WO1997041353A1 - Orbital peristaltic pump with dynamic pump tube

Info

Publication number: WO1997041353A1
Application number: PCT/AU1997/000242
Authority: WO
Inventors: Joseph Bertony
Original assignee: Pumping Systems Technologies Pty. Limited
Priority date: 1996-04-26
Filing date: 1997-04-18
Publication date: 1997-11-06

Abstract

A peristaltic pump (1) has a flexible tube (2) extending around an inner oscillatory ring (3) and confined by an outer stationary ring. Drive means, e.g. a radial array of hydraulic or piezo-electric actuators, effects the movement of the inner ring (3) to induce peristaltic compression along the tube (2). Reinforcements in the radially-inner and outer portions of the tube wall confine distortion, extension, etc. of the tube to the radially-intermediate portions such that compression of the tube in one region positively induces a corresponding expansion in a diametrically opposite region of the tube and enhances suction at the inlet of the pump. In a relaxed state the tube has an elliptical profile so that compression of the tube induces expansion of the tube to a circular profile in the suction region of the pump.

Description

"ORBITAL PERISTALTIC PUMP WITH DYNAMIC PUMP TUBE"

FIELD OF THE INVENTION

The present invention relates generally to pumps, and more particularly to peristaltic

type pumps.

BACKGROUND OF THE INVENTION

Peristaltic pumps are well known, and typically comprise compression elements such

as pressure rollers which are passed in succession along the length ofthe flexible tube to induce fluid flow through the tube by peristaltic compression. In the past, however, such

pumps have generally been unable to generate sufficient pressure or flow rate to be

effective in many commercial applications. They also require frequent maintenance,

making them problematic even on a small scale, such as in medical applications.

One cause of these problems is that if the flexible tube is formed from a material

sufficiently strong to withstand high internal pressures, then the tube also tends to be

resistant to the required external compression from the pressure rollers. This leads to a requirement for relatively high energy inputs which in turn causes rapid mechanical wear.

On the other hand, when softer and more flexible tubes are used, these have a lower

pressure capacity. Even more significantly, because the tubes by nature need to be flexible,

they have a tendency to collapse on the suction side, particularly after prolonged use. This

characteristic substantially diminishes the performance, efficiency and reliability ofthe

pump.

For these reasons, peristaltic pumps have hitherto been generally confined to low

pressure and low flow rate applications such as in the medical field. Even in this area, however, peristaltic pumps have typically been unable to provide the required

characteristics in terms of performance, efficiency, reliability, consistency and longevity

for use in numerous specialised applications, such as artificial hearts.

It is an object ofthe present invention to provide an improved pump which

overcomes or substantially ameliorates at least some of these disadvantages of the prior art.

DISCLOSURE OF THE INVENTION

Accordingly, the invention as presently contemplated provides a pump comprising a

flexible conduit extending around an inner compression element, a fluid inlet and a fluid

outlet disposed at opposite ends of the conduit, and drive means selectively operable to effect relative rotary oscillation ofthe inner compression element thereby progressively to

induce peristaltic compression along the conduit in a compression plane substantially

normal to the axis of rotary oscillation whereby fluid is displaced from the inlet to the

outlet of the pump, said pump further including peripheral support means operative to

resist longitudinal extension ofthe conduit in the compression plane, such that

compression ofthe conduit in one region by the inner compression element positively

induces a corresponding expansion in a diametrically opposite region ofthe conduit,

thereby enhancing suction pressure at the inlet ofthe pump.

Preferably, the inner compression element comprises a cylindrical compression ring

around which the conduit is looped in a generally circular configuration. The peripheral

support means preferably comprise a flexible substantially inelastic reinforcing element

formed integrally with the outer radial side wall ofthe conduit.

In the preferred embodiment, a series of tensile reinforcing fibres preferably extend

along the outer side wall ofthe conduit adjacent the compression plane to prevent localised extension. Additionally, the peripheral support means preferably include at least one

compressive reinforcing element extending along the inner side wall ofthe conduit to

prevent localised longitudinal compression. Supplementary oblique or cross-ply

reinforcing fibres may also be provided for more precise longitudinal shape control around

the full circumference ofthe conduit.

Additionally or alternatively, the peripheral support means may comprise an outer

support ring. In this embodiment, the conduit is preferably disposed between the

oscillating inner compression ring and the outer support ring, which is fixed with respect

thereto. In the preferred embodiment, the radial inner and outer side walls ofthe conduit

remain substantially in constant contact respectively with the inner compression ring and

the outer support ring.

In one embodiment, the drive means include a central drive pinion and a revolving

planetary gear engageable with the drive pinion. The planetary gear is preferably disposed

radially intermediate the drive pinion and the inner compression ring to effect localised

compression ofthe adjacent section ofthe conduit. In this way, rotation ofthe drive pinion

causes the planetary gear to revolve around the central axis of the pinion, which in turn

effects the rotary oscillation ofthe inner compression ring to induce peristaltic compression

along the length ofthe conduit.

In the preferred embodiment, the drive pinion, the planetary gear, and the

surrounding inner compression ring are formed with complementary intermeshing gear

teeth to facilitate the mechanical transmission of drive. In alternative embodiments,

however, the drive surfaces may be essentially smooth, and formed from an elastomeric friction material such as neoprene or rubber. In an alternative embodiment, the drive means may include a radial array of

hydraulic or pneumatic linear actuators, the sequential extension of which induces the

desired rotary oscillation of the surrounding inner compression ring. In an further

alternative embodiment, a radial array of piezo-electric compression elements may be

disposed around a fixed central hub and sequentially extended by the application of electric current from a controller. As a further alternative, the drive means may comprise an eccentric cam assembly.

In the preferred embodiment, the conduit has a circular transverse cross sectional

profile in the fully expanded configuration. It is also prefeπed, however, that the tube is

produced with an elliptical profile in the relaxed condition as manufactured, to minimise

the extent of deformation from the relaxed condition during the cyclic compression and

expansion phases. An elliptical shape advantageously divides the operational flexure into

two opposite phases of bending, in effect halving the maximum extent of deformation from

the intermediate relaxed position.

BRIEF DESCRIPTION OF THE DRAWINGS

Prefeπed embodiments ofthe invention will now be described, by way of example

only, with reference to the accompanying drawings in which:-

Figure 1 is cross-sectional plan view showing a peristaltic pump according to the

invention;

Figure 2 is a cross-sectional view ofthe pump taken along line 2-2 of Figure 1;

Figure 3 is a cross-sectional view similar to Figure 2, showing the variation in cross-

sectional profile ofthe flexible conduit ofthe pump during the cyclic expansion and

contraction phases; Figure 4 is an enlarged cross-sectional view ofthe flexible conduit from the pump of

Figures 1 to 3;

Figure 5 is a side elevation ofthe conduit showing the orientation ofthe primary and

supplementary reinforcing elements in more detail;

Figure 6 is a perspective view ofthe conduit, removed from the pump;

Figure 7 is a cross-sectional view ofthe pump shown in Figure 1, incoφorating a

first form of drive means comprising a planetary gear train, according to the invention; Figure 8 shows a second form of drive means, including an eccentric cam;

Figure 9 shows a third form of drive means incoφorating a radial array of hydraulic

actuators;

Figure 10 shows a fourth form of drive means comprising a radial array of piezo¬

electric compression elements;

Figure 11 is a transverse sectional view showing the elliptical cross-sectional profile

ofthe conduit, in a relaxed configuration as manufactured; Figure 12 is a transverse section showing the conduit of Figure 11 in the compressed

configuration; and

Figure 13 is a transverse section showing the conduit of Figure 11 in the expanded

configuration.

PREFERRED EMBODIMENTS OF THE INVENTION

Referring firstly to Figures 1 to 3, wherein like features are denoted by coπesponding

reference numerals, the invention provides a peristaltic type pump 1 comprising a flexible

conduit or tube 2 extending around an inner compression ring 3. The conduit defines an

inlet 4 and an outlet 5 for the pump. An internal drive mechanism is selectively operable to effect rotary oscillation ofthe inner support ring 3 about a central axis 6, as discussed in

more detail below. The rotary oscillation ofthe inner compression ring 3 about the central

axis 6 induces peristaltic compression along the conduit in a compression plane 8 which is

substantially normal to the axis of rotary oscillation 6. In this way, fluid is displaced from the inlet 4 to the outlet 5 ofthe pump.

As best seen in Figures 2 and 3, the conduit is disposed in an annular clearance space

defined between the inner compression ring 3 and a fixed outer support ring 9, configured

such that the inner and outer side walls 11 and 12 ofthe conduit remain substantially in constant contact respectively with the inner compression ring and the outer support ring.

The outer support ring may be integral with or defined by an outer casing for the pump.

As best seen in Figures 4 and 5, the conduit includes a series of flexible substantially

inelastic tensile reinforcing fibres 13 which extend longitudinally within the outer side wall

12 to prevent longitudinal extension of the conduit in the compression plane 8. Similarly,

the conduit includes a series of flexible substantially inelastic compressive reinforcing

elements 14 which run longitudinally along the inner side wall 1 1 to prevent longitudinal

compression (and extension) ofthe conduit in the compression plane 8. It will thus be

appreciated that the bulk ofthe peristaltic compression ofthe conduit is accommodated by

deformation ofthe intermediate sections ofthe side wall. This aπangement of longitudinal

reinforcing fibres in conjunction with the inner compression ring and the support ring

operates such that peristaltic compression ofthe conduit in one region by the inner ring

positively induces a coπesponding expansion in a diametrically opposite region ofthe

conduit. This prevents the conduit from collapsing and enhances suction pressure at the

inlet of the pump. Supplementary oblique or cross ply reinforcing fibres 15 provide

longitudinal shape control around the full circumference ofthe conduit. As best seen in Figure 4, the primary and supplementary reinforcing elements are

sandwiched between surrounding layers 16 of rubber or other suitable elastomeric material

and additional reinforcement. The conduit further includes an inner lining 17 including longitudinally extending ribs 18 which enable the tube more readily to accommodate the

required resilient deformation and subsequent restoration during each compression cycle.

Figure 7 shows a first form of drive means 20 comprising a drive pinion 21 in

engagement with a revolving planetary gear 22. The planetary gear 22 is thus disposed

radially intermediate the central drive pinion and the surrounding inner compression ring 3.

The diameters of the respective gears are configured to effect localised radial compression

ofthe conduit against the inner periphery ofthe outer support ring 9. It should be

appreciated, however, that the outer support ring is optional due to the longitudinal

reinforcing fibres 13 extending along the outer side wall ofthe conduit. Rotation ofthe

drive pinion 21 causes the planetary gear 22 to rotate about its axis and simultaneously to

revolve around the locus 22'. The resultant oscillatory displacement ofthe surrounding inner compression ring 3, progressively induces peristaltic compression along the length of

the conduit in a clockwise direction, when viewing the drawings.

The drive pinion, planetary gear and the inner surface ofthe compression ring are

formed in one embodiment with complementary intermeshing gear teeth to facilitate the

mechanical transmission of drive from a suitable motor and gearbox assembly (not shown).

In an alternative embodiment, however, the gear teeth may be replaced by substantially

smooth drive surfaces, formed for example from an elastomeric material such as rubber, in

which case the drive transmission is essentially frictional. In this case, the materials may be selected so as to allow slippage if a predetermined threshold pressure and hence torque

are exceeded, thereby preventing the pump from being inadvertently overloaded. Figure 8 shows a variation on the embodiment of Figure 7, wherein the planetary

gear 22 is replaced by an eccentric cam 25 fixedly mounted on a central drive shaft 26. In

this case, ball or roller bearings 27 are disposed between the outer surface ofthe cam lobe

25, and the cylindrical inner surface ofthe annular compression ring 3. It will be

5 appreciated that this arrangement induces the same rotary oscillation ofthe compression ring as in the previous embodiment.

Figure 9 shows a further alternative embodiment wherein the drive means take the

form of a radial aπay of hydraulic or pneumatic cylinders or actuators 30, operated via a

pump and centralised controller (not shown). In this embodiment, the rotary oscillation of

l o the inner compression ring is induced by sequential extension ofthe actuators in a

clockwise manner, and the simultaneous retraction ofthe respective diametrically opposed

actuators, as shown. The thrust from the actuators is reacted at the central fixed hub 31. At least three actuators are prefeπed. However, there is no upper limit, subject to size

constraints and the level of control and smoothness of operation desired for the particular

15 application for which the pump is designed. It should also be appreciated that the actuators

need not be double acting since the unidirectional expansion of any selected actuator will automatically cause a coπesponding compression or retraction in the diametrically

opposing actuator, given the constant internal diameter ofthe suπounding compression

ring 3.

20 In a particularly prefeπed embodiment, the maximum extent of travel, as well as the maximum threshold pressure, are pre-set to prevent over pressurisation ofthe system. In

this way, the maximum extent of orbital off-set may be predetermined to facilitate the

pumping of live specimens such as fish, without risk of damage. The same principle can

be applied on a smaller scale to prevent damage to blood cells in medical applications. Figure 10 shows a further variation in drive means, wherein the hydraulic or

pneumatic actuators of Figure 9 are replaced by a radial aπay of piezo-electric compression

elements 35. In this embodiment, instead of an hydraulic or pneumatic pump, a control voltage is applied sequentially to the compression elements by a centralised

microprocessor controller (not shown) whereupon the compression elements sequentially

expand to induce the desired rotary oscillation ofthe compression ring. This form ofthe

invention is especially suitable for use on a miniature scale, for example in medical

applications, wherein the minimum number of moving parts, relatively low power

requirements and small size may be used to particular advantage,

As best seen in Figures 2, 3 and 4, the conduit has a generally circular cross-sectional profile in the fully expanded configuration. It is prefeπed, however, that the tube is formed

with an elliptical profile in the relaxed condition as manufactured so as to reduce the extent

of displacement and deformation during each compression phase. In terms ofthe pumping

cycle, the conduit is shown fully compressed in Figure 12 and fully expanded in Figure 13.

The elliptical profile ofthe conduit in the relaxed condition as shown in Figure 11

coπesponds to the configuration ofthe conduit midway through a compression phase. It

will thus be appreciated that the elliptical shape effectively divides the operational flexure

into two opposite (i.e. tensile and compressive) phases of bending, rather than a single

phase of twice the magnitude as would occur in a conventional conduit of circular cross-

sectional profile when relaxed. This in effect halves the maximum extent of deformation

from the relaxed or equilibrium condition.

More particularly, the conduit is formed on an elliptical mandrel having a minor axis X and a major axis Y as shown in Figure 11. If the internal diameter ofthe conduit in the fully expanded circular condition is D, (see Figure 13) then the following relationships apply:

X = P_ ; and

2

Y = Xx 7' o s

The significance of these mathematical relationships is that the inner circumference

ofthe conduit (when viewed in transverse cross-section) does not substantially change,

despite variations in the cross-sectional profile during the compression and expansion

cycles. This in turn minimises internal stress and fatigue.

Advantageously, the pump according to the present invention is applicable to a wide

variety of fluids and sluπies with abrasive, coπosive or generally contaminate

characteristics. It also has the capacity to be set up to generate a reasonable flow rate with

only minimal compression. It is therefore able to accommodate relatively large particle

size and may even be used to transfer live specimens, such as fish, between storage tanks.

The invention is also well adapted for use in medical applications due to the minimal

number of moving parts, the high efficiency, low power consumption, and the possibility

of miniaturisation. More particularly, the invention provides a simple, inexpensive, and

effective mechanism for ensuring full expansion ofthe peristaltic conduit which has the

effect of enhancing the suction pressure and hence the overall efficiency of the pump. It

also enables the performance parameters ofthe pump to be calibrated to within closer

tolerances. Furthermore, because it is prevented from collapsing, the service life ofthe

conduit is substantially increased, thereby enhancing reliability and reducing maintenance

costs. Accordingly, in many respects the invention represents a commercially significant

improvement over the prior art. Although the invention has been described with reference to specific examples, it

will be appreciated by those skilled in the art that the invention may be embodied in many

other forms. For example, instead of inducing rotary oscillation ofthe inner compression

ring within the surrounding conduit, the same effect could be achieved by oscillating the

conduit or the outer support ring and fixing the inner ring with respect thereto, the relative

displacement being the significant factor. Moreover, the inner compression element need not comprise a ring, but could include a series of discrete elements cooperating to perform

effectively the same rotary oscillation function.

Claims

' CLAIMS :-

1. A pump comprising a flexible conduit extending around an inner compression

element, a fluid inlet and a fluid outlet disposed at opposite ends of the conduit, and drive

means selectively operable to effect relative rotary oscillation ofthe inner compression

element thereby progressively to induce peristaltic compression along the conduit in a

compression plane substantially normal to the axis of rotary oscillation whereby fluid is

displaced from the inlet to the outlet ofthe pump, said pump further including peripheral

support means operative to resist longitudinal extension ofthe conduit in the compression

plane, such that compression ofthe conduit in one region by the inner compression element

conduit, thereby enhancing suction pressure at the inlet of the pump.

2. A pump according to claim 1, wherein the inner compression element comprises a

cylindrical compression ring and wherein the conduit is disposed in a circular configuration

around an outer periphery thereof.

3. A pump according to claim 1 or claim 2, and wherein the peripheral support means

comprise a flexible substantially inelastic tensile reinforcing element effectively integral

with an outer side wall ofthe conduit to prevent localised extension thereof in response to

rotary oscillation ofthe compression element.

4. A pump according to claim 3, wherein the peripheral support means include a

plurality of tensile reinforcing fibres extending along the outer side wall of the tube

adjacent the compression plane.

5. A pump according to claim 4, wherein the peripheral support means include a

compressive reinforcing element extending along the inner side wall ofthe conduit adjacent the inner compression ring to prevent localised compression ofthe inner side wall

of the conduit.

6. A pump according to any one ofthe preceding claims, wherein the conduit includes

supplementary oblique or cross-ply reinforcing fibres for overall shape control.

7. A pump according to any one ofthe preceding claims, wherein the peripheral support

means comprise a fixed outer support element or ring suπounding the conduit.

8. An pump according to claim 7, wherein the conduit is disposed between the inner

compression ring and the outer support ring.

9. A pump according to claim 8, wherein the inner and outer side walls ofthe conduit remain substantially in constant contact respectively with the inner compression ring and

the outer support ring.

10. A pump according to any one ofthe preceding claims, wherein the drive means

include a central drive pinion and a revolving planetary gear engageable with the drive

pinion, the planetary gear being disposed radially intermediate the drive pinion and the

inner compression ring and configured to effect localised compression of an adjacent

portion ofthe conduit, whereby rotation ofthe drive pinion causes the planetary gear to

revolve around the pinion, thereby to effect rotary oscillation ofthe inner compression

ring.

1 1. A pump according to claim 10, wherein the drive pinion, the planetary gear and the

inner compression ring are formed with complementary intermeshing gear teeth to

facilitate mechanical transmission of drive.

12. A pump according to claim 10, wherein the drive surfaces ofthe drive pinion, the

planetary gear and the suπounding inner compression ring are essentially smooth, and

formed from an elastomeric material to facilitate frictional transmission of drive.

13. A pump according to any one of claims 1 to 9, wherein the drive means include a

plurality of hydraulic or pneumatic linear actuators, disposed in a radial array around a

fixed central hub and extending outwardly to engage the inner periphery ofthe inner

compression ring, whereby sequential extension ofthe actuators induces relative rotary

oscillation ofthe compression element.

14. A pump according to any one of claims 1 to 9, wherein the drive means comprise a

plurality of piezo-electric compression elements, disposed in a radial array around a fixed

central hub and extending outwardly to engage the inner periphery ofthe inner

compression ring, whereby sequential extension ofthe compression elements induces

relative rotary oscillation ofthe inner compression element.

15. A pump according to any one of claims 1 to 9, wherein the drive means include an

eccentric cam rotatable about a central axis to effect relative rotary oscillation ofthe inner

compression element.

16. A pump according to any one ofthe preceding claims, wherein the conduit is initially

formed with an elliptical internal cross sectional profile in a relaxed condition as

manufactured, to reduce the extent of maximum deformation during each compression and

expansion cycle.

17. A pump according to claim 16, wherein the elliptical profile ofthe conduit is defined

by a minor axis X and a major axis Y, determined by the relationships :-

X = D ; and

2

Y = X x 7° ⁵ where D is the nominal internal diameter ofthe conduit when fully expanded to a circular

cross sectional profile.

18. A pump according to claim 16 or claim 17, wherein the elliptical profile ofthe

conduit is determined such that the internal circumference in transverse cross section does

not substantially alter despite variations in cross-sectional profile during the peristaltic

compression cycles.

19. A pump substantially as hereinbefore described, with reference to the accompanying

drawings.