Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B43/00—Machines, pumps, or pumping installations having flexible working members
  • F04B43/12—Machines, pumps, or pumping installations having flexible working members having peristaltic action
  • F04B43/1253—Machines, pumps, or pumping installations having flexible working members having peristaltic action by using two or more rollers as squeezing elements, the rollers moving on an arc of a circle during squeezing
  • F04B43/1292—Pumps specially adapted for several tubular flexible members

Definitions

• the present invention relates to a peristaltic pump of the type comprising at least two elastically compressible hose conduits, each having an inlet and an outlet end and mutually identical cross section; a support means for each hose conduit, said support means having a curved surface which is similar for all the hose conduits and which is engaged by the associated hose conduit with at least a portion of the length thereof; at least two synchronously driven rotor units, one for each hose conduit, which are provided with the same number, at least two, of symmetrically arranged and mutually at the same distance from the rotor axis opera ring pressure means for local compression of the hose conduit corresponding to each rotor unit against the curved surface of the associated support means, whereby the number of pressure means on each rotor unit and the extension of said curved surface on the support means of each hose conduit, seen in the longitudinal direction thereof, are mutual ly so adapted that continuously one of the pressure means on each rotor unit compresses the corresponding hose conduit for preventing fluid flow through the
• Peristaltic pumps of this type generates a pulsatile flow in which the pulsation frequency is related to the number of revolutions of the pump. Within certain areas however, a pulsatile flow is utterly disadvantageous. Thus, peristaltic pumps with pulsatile flow have blood-damaging properties
• hemolysis and trombocyte aggregation when they are used fo blood pumping in heart-lung machines and dialysis equipment.
• the object of the present invention is to eliminate said drawbacks and provide a peristaltic pump permitting a non- pulsatile flow.
• This as arrived at according to the invention by that at least the outlet ends of the hose conduits forming part of the pump are joined into a common outlet in a manner known per se; and that the synchronously driven rotor units are angularly displaced relative to each other such that their pressure means operate with phase displacement on each hose conduit, whereby the flow pulsations generated in each hose conduit will at least to a substantial extent neutralize each other at the common outlet of the hose conduits.
• the peristaltic pump according to the invention generates a non-pulsatile flow at constant number of revolutions and is relatively blood compatible. Therefore, the pump is especially suited for control by means of a feed-back circuit and also to be utilized for pumping blood in experimental research on animals, in which requirements for accurate flows and pressure levels and pressure variation configurations should be obtained in combination with low hemolysis. Since the pump through its construction is relatively blood compatible, it is also applicable as a pump in heart-lung machines and dialysis equipment but may find many other applications in laboratories and in the industry.
• each of the conduit branches connected in parallel an approximately sinusoidal flow is generated, said flows being generated symmetrically displaced relative each other and superposed on each other they generate a non-pulsatile flow.
• the pump be controlled by e.g. a normal heart-pressure curve, the pressure curve thus produced by the pump may be brought to almost completely imitate a normal heart-pressure curve.
• the pump permits normal pulsatile as well as constant pressure perfusion and non-pulsatile constant-flow perfusion at the desired flow and pressure levels respectively.
• other pressure configurations such as sinusoidal, triangle, impulse, etc. may be obtained by controlling the pump by means of a functional generator with such curve voltage variations.
• fig. 1 is a perspective view of a peristaltic pump accor ding to the invention and here with three parallel rotor units;
• fig. 2 is a section through fig. 1 perpendicular to the rotor axis;
• fig. 3 and 4 is a plan and side view respectively, of a conduit system running through the peristaltic pump; fig.
• fig. 5 is a principal sketch of the pump and its control units for providing constant pressure or constant flow perfusion
• fig. 6 shows original registrations of pump-generated pressure curves
• fig. 7 is a perspective view of members in a peristaltic pump according to the invention with two parallel rotor units
• fig. 8 is a section through an alternative embodiment of the pump according to the invention
• fig. 9 is a section along the line IX-IX in fig. 8.
• the principal construction of a peristaltic pump means that medium is led through a flexible tubing without bringing any other part of the pump in contact with the medium.
• a pres sure means occludes the tubing against a curved surface on a support means and the pressure means forces the medium ahead during rotation.
• the flow thus produced is pulsatile and the average speed thereof substantially proportional to the number of revolutions of the rotor.
• the pressure means 3 in one rotor unit 1 are also displaced relative to the pressure means 3 in another rotor unit 1 such that the totally nine pressure means 3 are positioned symmetrically at an angle of 40 between each pres sure means.
• the conduit system 5 which e.g. by means of screw joints 28 is mounted on the support means, comprises in the embodiment shown three parallel conduit branches 6 of which each and everyone is associated with a rotor unit 1.
• the conduit branches 6 are also joined into a common outlet 7.
• Medium is fed to the outlet while the pressure means 3 define medium-containing spaces 8 in the conduit branches 6, displace said spaces towards the outlet 7 during successive increase of the volume thereof, open said spaces successively towards the out let and close said spaces towards the inlet 9 of the conduit branches.
• the conduit branches 6 of the conduit system 5 are made of elastically compressible hose conduits of similar cross section and each conduit branch 6 engages with at least a portion of its length a curved surface 4 which is the same for all the conduit branches.
• the rotor units 1 are driven synchronously and their symmetrically arranged and mutually at the same distance from the rotor axis 2 operating pressure means 3 permit local compression of the conduit branch corres ponding to each rotor unit 1 against the associated curved surface 4, whereby the number of pressure means 3 on each rotor and the extension of said curved surface 4 for each conduit branch 6, seen in the longitudinal direction thereof, are mutually so adapted to each other that always one of the pressure means 3 on each rotor unit 1 compresses the corresponding conduit branch 6 for preventing fluid flow through the conduit system 5 in a direction opposite to the direction of rotation of the rotor unit 1.
• a first part 10 of the curved surface 4 may be circular in shape, run at a constant distance from the rotor axis 2 and have a length corresponding to or somewhat exceeding the distance between two adja cent pressure means. Thereafter, the circular part 10 may (towards the outlet 7) be transformed into a rear part 11, the distance of which from the rotor axis 2 successively increases towards the outlet 7.
• the rear part 11 of the curved surface 4 is preferably made elliptical, but may also have another shape.
• at least the first 120° of the curved surface 4 defines the circular fore part 10, in which part total compression, i.e. occlusion of the conduit branches is attai ned.
• the gradual release of the pressure means 3 from the curved surface 4 in the elliptical part 11 generates flow oscillations from each rotor unit 1 which are substantially sinusoidal.
• the arc of the curved surface 4 preferably comprises totally about 180° (see fig. 2 ), but of course a longer arc is also possible.
• each conduit branch 6 generates a substantially sinusoidal flow, q 1 , q 2 and q 3 respectively, with a mutual phase displacement ⁇ of 360°/3, i.e. 120°.
• ⁇ 360°/3, i.e. 120°.
• q 1 , q 2 and q 3 may be expressed as:
• p 1 , p 2 and p 3 represent the pressure in each conduit branch 6 and p. the pressure in the outlet 7 .
• R 1 , R 2 and R 3 represent the flow resistance in each conduit branch 6 from the forward, totally occluding pressure means 3 to the common outlet 7.
• R 4 represents the flow resistance at the outlet 7 distally of the connecting point of the three parallel con duit branches, including the prefounded vascular bed. p 4 can be expressed as:
• conduit branches 6 are designed such that R 1 , R 2 and R 3 are small compared to R 4 , wherefore p 4 can be simplified:
• p 1 , p 2 and p 3 can be expressed as:
• the pump In order to be able to control the pump-produced pressure or flow via a negative feed-back circuit and create exact pulse configurations, the pump must produce a uniform and virtually non-pulsatile flow at a constant rotor speed.
• the break-down of red blood cells are usually taken as a measure of such blood damage.
• the major factors causing blood damage when using pumps of so called roller type have been shown to be related to the conduit branch material, the smoothness of the inner surfaces of the conduit branches, too high blood flow velocities, too small conduit branch diameters, too high rotor speed and frequency of conduit branch occlusions. Blood damaging influence of these factors has been minimized in the present pump device 24 by its special design as described below.
• the conduit branches 6 are made of a blood compatible, elastic material, e.g. silicone rubber, with an inner surface covered by an even more tissue compatible material.
• the conduit branches are moulded in one piece with the inlet 9, which is divided at the end of the curved surface, and are drained at the common outlet 7.
• the outlet 7 also comprises a suitable device 12 for registration of the pressure of the medium in the outlet 7 (see fig. 2).
• the device 12, which comprises a pressure meter 25, consists of a side outlet 26 to the outlet 7 with a small diameter in order to as little as possible interfere with the fluid. All conduit branches 6 brought in contact with blood are moulded in such a way that extremely smooth inner surfaces are obtained.
• Flow velocity and the frequency of conduit branch occlusions have been minimized by choosing a relatively large rotor diameter (70 mm in this embodiment) and a large inner diameter for the conduit branches (6 mm), whereby a very low rotor speed is reached.
• the pump gives a very low hemolysis at flows up to about 40 ml/min., more exactly defined ⁇ 0,008 g/l of hemoglobine added to plasma at each passage of the blood through the pump, which is to be compared with a value of > 0,14 g/l with a conventional blood perfusion pump (Harvard Variable Speed Peristaltic Pump, Model 1210) at the one and same given test.
• Fig. 5 is a block diagram of the pump 24 and its control units for constant pressure or constant flow perfusion. Constant flow perfusion is accomplished by setting a switch 13 in position 1 yielding a summation of a signal proportional to the rotor speed and a signal representing the desired blood flow. The resulting signal is fed into a PID-regulator 14.
• the rotor speed signal is obtained from a tacho-generator 15 placed on the drive shaft of the rotor.
• the desired blood flow or blood pressure level can be obtained by manual variation of a reference signal.
• a constant average pressure or constant flow (DC-component) of any desired magnitude can be produced independently of a superimposed pulse pressure (AC-component) .
• this pump is capable of reproducing with great accuracy the normal arterial pulse pressure curve both during the upstroke and the pressure decrease.
• the pressure decrease during the diastolic phase of the pulse pressure curve can, however, not be obtained simply by an immediate stop of the rotor.
• the rotor direction has to be reversed for a very short period of time.
• Such transient backwards rotation is obtained with the aid of a special electronic unit 20 which consists of a highpass-filter in combination with a rectifier.
• the pump 24 is capable of reproducing the normal arterial pressure curve up to a frequency of about 4 Hz by using the normally undamped cardiac pulsations (registered via a separate pressure transducer from a catheter in a systemic artery) as the AC-compo nent in the reference signal.
• Other types of AC-signals can alternatively be applied, e.g. sinusoidal, triangle, impulses, step functions etc., which preferably are obtained from a function generator.
• Fig. 6 illustrates some examples of how the pump 24 described above has been used to reproduce various configurations of pressure curves.
• Panel A the upper curve, shows the normal undamped systemic arterial pressure registered. from a cat's brachial artery with a Statham pressure transducer.
• the lower curve in Panel A illustrates the simulated curve produced by the perfusion pump device. Note the close resemblance between these two curves both for slow respiratory variations and the cardiac induced pulse pressure varia tions.
• Panel B shows how the pump can be used to produce a sinusoidal pressure curve, Panel C a positive and a negative pressure impulse and Panel D a positive and a negative pressure step function.
• the present invention is not limited to the embodiment described above.
• the pump described is made for blood perfusion for experimental research on animals, but the pump may be used for all types of perfusion, not only blood perfusion in heart-lung machines and dialysis apparatuses, but also for perfusion of other flows than blood within all flow areas.
• a modification of the above pump has been constructed for constant flows as small as 1 . 10 -3 ml/min.
• the pump may comprise two or more than three rotcr units 1 and each rotor unit may have two or more than three pressure means 3.
• the conduit system 5 may of course consist of two or more than three conduit branches 6.
• the length of the curved surface 4 may vary and so may also the circular and elliptical parts 10, 11 respectively.
• the rotor units 1 are by means of setting devices 22 and 23 of suitable construction also adjustable laterally, vertically and in various inclined positions relative to the curved surface 4.
• the vertical and lateral adjustment is carried out e.g. with screw devices 22 displaceable in long holes 21 and the inclined position is set preferably by means of screws 23.
• the pump illustrated in fig. 8 and 9 is intended for pumping floor masses. It has two rotor units 1 which cooperate with one conduit branch 6 respectively and which each have two pressure means 3 in the form of radially projecting cam means. The angle therebetween is 180o and the angle between one cam means in one rotor unit and the cam means closest thereto in the other rotor unit is 90°.
• the function of the pump corresponds with the pump illustrated in fig. 1 and 2.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• External Artificial Organs (AREA)
• Reciprocating Pumps (AREA)

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• 1981
  • 1981-05-27 SE SE8103353A patent/SE445943B/sv not_active IP Right Cessation
• 1982
  • 1982-05-27 WO PCT/SE1982/000188 patent/WO1982004291A1/en not_active Application Discontinuation
  • 1982-05-27 EP EP82901642A patent/EP0079921A1/de not_active Withdrawn
  • 1982-05-27 GB GB08302039A patent/GB2115498A/en not_active Withdrawn
  • 1982-05-27 JP JP57501642A patent/JPS58500792A/ja active Pending
• 1983
  • 1983-01-26 NO NO830248A patent/NO830248L/no unknown

Non-Patent Citations (1)

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