GB2238833A - Peristaltic pump - Google Patents

Abstract

The pump has 8 resiliently deformable plastics membrane (3, Fig. 1) and a plurality of electro-restrictive devices, e.g. piezo-electric devices or solenoids 2, arranged outside the membrane 50 that on application of an electric current via a micro-processor 20, a peristaltic pumping action is achieved. The membrane is in the form of a tube and is assembled by stretching between end mountings (4). Non-return valves 40A, 40B are provided. The pump is portable and can be used to administer doses of a drug at regular intervals to a patient, typically insulin to a diabetic. A heater may be incorporated to control the viscosity and thereby the rate of pumping of the drug. <IMAGE>

Description

PUMP This invention relates to pumps. In particular but not exclusively to pumps capable of delivering a small volume of fluid, such as those pumps used by the medical profession.

Pumps, such as impeller pumps and centrifugal pumps, require a lubricant in between rubbing, moving surfaces.

This lubricant has presented a problem when the pump has been used to deliver certain types of fluid such as sterile liquids, drugs or blood. There has been a risk that the lubricant may in some way contaminate the fluid to be pumped.

Another problem has been the need to flush the pumping system after each delivery of whatever fluid, with a neutral sterilising fluid. This has meant that the pump has not been available for useful work and has required time consuming sterilisation. The present invention provides an improved pump for medical use, for example.

According to the present invention a pump comprises a resiliently deformable membrane which defines a cavity for receiving fluid and means to squeeze the membrane together.

Preferably more than one electro-restrictive device is dimensioned and arranged outside the cavity so that on application of an electric current to one or more of the devices, a pumping action is achieved by selectively forcing together areas of the membrane.

Preferably the membrane is formed from silicon rubber and is in the form of a tube.

The electro-restrictive devices are preferably electro-mechanical solenoids; although they may feasibly be piezo-electric devices arranged so that they are in close proximity with the plastics membrane.

The electro-restrictive devices are preferably arranged in a longitudinal fashion along an elongate section of the deformable plastics membrane and a control means is provided so that they may operate in such a way that a peristaltic pumping action is achieved.

Preferably the use of the elongate plastics membrane in conjunction with the electro-restrictive devices enables a replacable plastics membrane, with suitably formed adapters at its ends, to be used in a pump housing.

When the pump is used to pump a different substance the plastics tube may be removed and disposed of.

Advantageously the deformable plastics membrane is an elongate tube having valve means at either end. This ensures that the force providing the pumping action is always physically isolated from the substance to be pumped. The tube may have sealable adaptors at its ends which may then be directly connected to other equipment, e.g. intraveneous tubes or syringes.

The invention will now be described, by way of example only, and with reference to the drawings in which: Figure 1 illustrates a plan view of a pump; Figure 2 illustrates a plan view of the pump during its pumping cycle; and Figure 3 illustrates the pump in use in a medical environment with a patient shown diagramtically.

Referring to Figure 1, a pump 1 contains 8 pairs of electro-mechanical squeezing elements 2. For the avoidence of doubt and for this embodiment only, the term "electro-mechanical squeezing element" is defined as a solenoid device. Each pair is positioned on opposite sides of a resiliently deformable silicon rubber tube 3.

The tube 3 is inserted when the electro-mechanical squeezing elements are in an off-state. The tube 3 is of such a length that it is held taut within the pump. The deformable plastics tube 3 has a stopper 4 at either end.

The stopper 4 consists of a metal housing 4a adapted to locate the tube within the pump 1 at a particular stretch length. The stopper 4 also has a central section 5 which is formed from a deformable self-sealing material 5, such as polyurethane. In addition to this valves 40 are provided- in the housing at either end. These are nonreturn valves and permit the flow of fluid through the tube in one direction only. The deformable plastics tube may be removed after use, and disposed of.

The pump thus assembled, will now be described in operation with reference to Figures 2 & 3. A patient, indicated at 10, may require a specific dosage of drugs, at a particular time. Intraveneous connections are made from the patient 10, by way of a connecting tube 11, to the pump 1 through the deformable self-sealing material 5 of the tube housing 4 by piercing the material with a hypodermic syringe 13. The other end of the tube 3 is connected to a reservoir 8 by way of a similar connecting tube 18 and a similar hypodermic syringe 19.

Micro-processor 20 controls the amount of current supplied to each pair of the electro-mechanical squeezing elements 2. When this current is applied the squeezing together of each pair of electro-mechanical squeezing elements 2 occurs in such a way that the walls of the tube 3 are forced together and fluid is forced out of the pump at X only, because the non-return valve 40A is open, and valve 40B is closed. When the electro-mechanical squeezing elements are relaxed the resiliantly deformable membrane returns to its previous shape and a partial vacuum is created inside the tube 3, such that a solution of drug 15, contained in the reservoir 8, is sucked through the tube 18; through the syringe 19; through nonreturn valve 40B and then into the tube 3 inside the body of the pump.The drug 15 is then expelled through the tube 3, in the pump, through valve 40A via the tube 11 into the patient.

The electro-mechanical squeezing elements operate such that pair 2a is energized, then pair 2b is energized then pair 2c is energized. When pair 2d is energized, pair 2a is de-energized; when pair 2e is energized, pair 2b is de-energized and so on. This successive energizing and deenergizing of the electro-mechanical squeezers sucks the drug 15 along the length of the plastics tube in a peristaltic pumping action. The action may be very finely controlled by way of the micro-processor 20, so that the electro-mechanical squeezers need not necessarily squeeze the tube to the the whole extent to which it can be deformed. The squeezers, may be therfore partially energized such that only a fraction of the normal volume is delivered.

A heater 30 is used to control the rate of pumping of the drug. The heater reduces the viscosity of the drug to be pumped and hence, in general, makes pumping easier.

Variation may be made without departing from the invention by including a timer at a central processing unit such that automatic clocking of several pumps from a single computer may be effected.

Leakage and blockage detectors also may be provided within the pumn housing.

Although the present invention has been described with specific reference to a pump for delivering a small volume of fluid, the pump may be used to pump any volume or type of fluid if it is suitably scaled.

Claims (11)

1. A pump comprising a resiliently deformable membrane which defines a cavity for receiving fluid and means to squeeze the membrane together.

2. A pump according to claim 1 having a plurality of electro-restrictive devices, dimensioned and arranged outside the cavity so that on application of an electric current to one or more of the devices a pumping action is achieved by selectively forcing together areas of the membrane.

3. A pump according to claim 2 wherein the membrane is in the form of a tube.

4. A pump according to any preceding claim in which the electro-restrictive devices are electro-mechanical solenoides.

5. A pump according to any of claims 1 - 3 in which the electro-restrive devices are piezo-electric devices.

6. A pump according to any preceding claim in which control means is provided so as to activate the electrorestrictive devices in such a way that a peristaltic pumping action is achieved.

7. A pump according to any preceding claim in which the plastics membrane is replacable.

8. A pump according to claim 7 wherein the plastics membrane is adapted to be held taut within the pump housing at a particular stretch length.

9. A pump according to claim 8 wherein the tube has valve at at least one end.

10. A pump according to any preceding claim which is adapted for use by a diabetic.

11. A pump substantially as herein described and with reference to the figures.