GB2150644A

GB2150644A - Peristaltic pump

Info

Publication number: GB2150644A
Application number: GB08425648A
Authority: GB
Inventors: Gyula Istok; Zsolt Szabo; Ferenc Vadasz
Original assignee: MUESZERIPARI MUEVEK LAB
Current assignee: MUESZERIPARI MUEVEK LAB
Priority date: 1983-10-10
Filing date: 1984-10-10
Publication date: 1985-07-03
Also published as: HUT35093A; GB8425648D0; FI843886L; DE3434521A1; HU190171B; CH665259A5; DD232528A5; FR2553151A1; FI843886A0

Abstract

A peristaltic pump comprises a flexible walled pipe section (1) resting on a countersupport (2) and periodically compressed and deformed by a single deforming element (3). Upstream and downstream of the pipe section (1) two halves (4) are arranged to work in antiphase. The stroke of the movement of the deforming element (3) is set to be less than the internal diameter of the pipe section (1). One end position of the stroke is at a smaller distance from the countersupport (2) than the outer diameter of the pipe section, while its other end position is at a greater distance from the countersupport than twice the wall thickness of the pipe section (1). <IMAGE>

Description

SPECIFICATION Peristaltic pump The invention concerns a peristaltic pump for transmitting liquids in analytic measuring apparatus or instruments performing chemical or physical measurements.

In laboratory and health care practice liquid pumping devices are already known which operate on the basis of the suction effect due to the expansion or relaxation following a preceding compression of a resilient-walled tube or pipe; a liquid is sucked from a container at a small pressure difference than at a point of the suction pipe section the pipe is pinched or obturated to prevent return flow of the liquid, and by moving a rolling cylinder or by a sequential depression of a plurality of closely juxtaposed plates, the liquid column or section is advanced by the instantaneously operating element itself.

A characteristic of these known constructions is that the position of the obturation for preventing reverse flow of the liquid moves along the longitudinal axis of the tube section participating in the operation together with the liquid column. Hence, the length of the tube section participating in the operation is subjected to the full compressive load that assures liquid transfer, i.e. to the (maximal) deformation load. The relaxation following the clamping or compression determines the amount of liquid sucked up per unit of time; consequently a change in the rate of relaxation decisively influences the amount or volume of liquid transferred, in this case a drop in said rate due to the fatigue of the material of the tube.

An optimal operation of such pumps would in practice require the elasticity of the material of the pump tube to be such that on release from its functionality maximally deformed state preventing return flow of liquid it should instantaneously re-assume its original crosssection. In using peristaltic pumps it is an operational phenomenon that the amount of liquid delivered changes (decreases) with time, and the nominal delivery value is restored by replacing the tube. The change in liquid delivery can unambigously be traced back to material fatigue due to the regular systematic deformation.

Because of the load, the only suitable tubes or pipes are those made of a synthetic material which is capable of large, complex or composite resilient change of shape, which is especially resilient and which is made by a special technology, yet they have a limited life time.

Apparatus based on this principle of functioning consists either of a row of rollers arranged in cylindrical symmetry, or in a plane, or tightly juxtaposed plate bundles.

These solutions have the already mentioned disadvantage.

An ai the invention is to reduce or eliminate the above-mentioned drawback of peristaltic pumps while preserving their advantage, i.e.

to increase the service life of the pipes and the accuracy of the metering or dosing of the pump.

The invention is based on the discovery that the above aim may be attained by entrusting the liquid transfer or transport function to a single deforming element and the correctness of the direction of transport is assured by valve means downstream and upstream of the deforming element. In this way, the advancing of the liquid and the valve operation are separated from each other both in space and in time. It is additionally important from the point of view of increasing the service life of the pipe that the stroke of the deforming element should be adjusted to a value which reduces the deformation load on the pipe section that takes part in the operation.

Accordingly, the invention concerns a peristaltic pump including a periodically actuated deforming element for radially deforming a flexible pipe or a plurality of such pipes, and a support element or counterpiece co-operating with the deforming element. The essence of the invention is that, taken in the direction of flow, before and after the deforming element, it includes two valves operated in antiphase, i.e. in mutually opposite phases; and the stroke of the deforming element is selected to be smaller than the internal diameter of the pipe, preferably but not absolutely essentially, one end position of the stroke being at a distance from the support element or counterpiece which is smaller than the outer diameter of the pipe, while its other end position is farther from the support element or counterpiece than twice the wall thickness of the pipe.

According to a preferred embodiment of the invention the valves are also constituted by deforming elements co-operating with but arranged in separation from the supporting counterpiece.

Thus the peristaltic pump according to the invention appreciably reduces the deformation load on the pipe or tube section participating in the operation, increase the service life of the pump or tube and in addition enhances the accuracy of the metering. The use of various tubes or pipes becomes possible and the liquid transport can be changed with pipes of the same dimension. A further advantage of the pump according to the invention is that it enables a gentle, careful conveying of liquids prone to damage, e.g. blood. In the pump according to the invention the maximal load on the pipe is exerted only at the locations of valving. The deforming element itself does not completely compress the pipe, neither does it allow the pipe completely to relax or expand.The limited compression, i.e. de forming loading, of the pipe and the elimination of the final phase of the relaxation which phase in the known pipes has been of an extended duration, all add to the already enumerated advantages and increases the favourable properties of the peristaltic pump.

The invention is described by way of a preferred embodiment illustrated in the drawing the sole figure of which shows schematically a peristaltic pump according to the invention.

For the sake of simplicity, a peristaltic pump consisting of only a single pipe is shown. A flexible pipe 1 is arranged on a supporting element or countersupport 2. A single deforming element 3 is disposed opposite the countersupport and above the pipe 1, but not directly adjacently to, the deforming element 3 a respective further deforming element is disposed, also opposite the countersupport.

These further deforming elements constitute valves 4.

Naturally, in place of the valves 4 formed from deforming elements other valve construtions may be applied. In the preferred embodiment, the non-iliustrated actuating means for the valves is such that the valves operate antiphase, i.e. when one valve 4 opens the other valve closes, and vice versa.

It is an important feature of the peristaltic pump according to the invention that the stroke of the deforming element is determined in such a manner that in its upper dead centre or end position it presses slightly on the pipe 1 bearing against the countersupport 2, while the its bottom dead centre or end position, which is the one illustrated in the drawing, the pipe is not wholly closed. More precisely formulated, the stroke of the deforming. element 3 is smaller than the internal diameter of the pipe and one end position of the stroke is at a distance from the countersupport 2 which is smaller than the outer diameter of the pipe 2, while its other end position is at a distance from the countersupport 2 which is greater than twice the wall thickness of the pipe.

The peristaltic pump according to the preferred embodiment of the invention is as follows.

Assume that the direction of liquid flow is from the let to the right, as seen in the drawing. In the starting position the right hand valve 4 is closed, the left-hand valve is open and the deforming element 3 is in its upper dead centre position. Then the pipe 1 contains liquid up to the right-hand valve 4.

Thereafter, the left-hand valve 4 closes and the right-hand valve 4 opens, and the deforming element 3 is displaced to its bottom dead centre position and squeezes the liquid in the pipe section beneath it out towards the right.

Subsequently, the right hand valve 4 closes and the left-hand one opens while the deforming element moves to its top dead centre or end position. When the pipe 1 relaxes, i.e.

assumes its maximum size permitted by the deforming element 3, a suction effect is exerted on the liquid and the pipe-section beneath it is refilled with liquid. Thereafter, the above-described process is repeated.

Claims

1. A peristaltic pump comprising a flexible pipe, a periodically displaced deforming element for radially deforming the pipe, a countersupport associated with the deforming element for suporting the pipe, two valves respectively disposed upstream and downstream of the deforming element and operated in antiphase relative to each other, the stroke of the displacement of the deforming element being selected smaller than the internal diameter of the pipe and wherein the stroke is so selected that one of its end positions, it is at a distance from the countersupport which is smaller than the outer diameter of the pipe while in its other end position it is at a distance from the countersupport which is farther than twice the wall thickness of the pipe.

2. A peristaltic pump according to claim 1 wherein the valves are constituted by deforming elements co-operating with the countersupport but which are arranged discretely from the periodically displaced deforming element.

3. A peristaltic pump substantially as herein described with reference to and as shown in the accompanying drawing.