GB2289512A

GB2289512A - Cleaning tubular elements

Info

Publication number: GB2289512A
Application number: GB9509791A
Authority: GB
Inventors: Lawrence Ralph Dawson; John Frederick Spangler
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-05-16
Filing date: 1995-05-15
Publication date: 1995-11-22
Also published as: GB9509791D0; GB9409785D0

Abstract

In a method and apparatus for cleaning tubular elements such as cannulated medical instruments, cleaning fluid is passed through the element and is pulsed at a frequency in or below the audible range by means of a pump (15). Bubbles of air or another gas may be added to the stream of cleaning fluid to produce a more vigorous cleaning action, the gas being pressurised by a compressor (25) and added to the fluid at a valve (33). Means for dispersing the gas in the fluid, such as an impeller, may also be provided. <IMAGE>

Description

Cleaning Tubular Elements This invention relates to a method and apparatus for cleaning tubular elements. In particular this invention relates to the cleaning of cannulated medical instruments, for example endoscopes.

Many instruments used in the medical field comprise passageways, which will require regular cleaning if the instrument is to be reused without the risk of passing infection to subsequent patients. One such instrument is an endoscope whose complex and expensive construction can usually house one or more passageways, generally running the full length of the instrument.

Endoscopes usually have a diameter of about 5-15mm and a length of between 0.4 and 2m. Nearly always, endoscopes are constructed in a manner which allows the distal end to be directed or driven as it is passed through the passageways of the human body, for example the alimentary canal. To provide the operator with the necessary feedback to control the instrument and to conduct operations, video cameras or video camera chips are often incorporated into the distal end.

These endoscopes have a variety of purposes, for example they can be used to clear passageways, discharge or suck up fluids, or even be used to position catheters or sampling devices which are passed through the body of the endoscope. Of course all these operations will inevitably mean that body fluid or tissue will contaminate the inside of the instrument. Since these devices are too expensive to be disposable, they have to be thoroughly cleaned and decontaminated before being reused.

Generally speaking, the process of cleaning the passageways of these instruments so that they can be safely reused involves four separate stages. These are: (a) cleaning to remove the debris; (b) disinfecting; (c) rinsing; and (d) drying.

t is very important that the initial cleaning stage removes all traces of debris, for example body fluid or tissue, that might be present in the passageways of the instrument. If they are not cleaned thoroughly, the disinfection of the instrument will be incomplete because the presence of debris will obstruct and prevent the disinfectant from reaching certain areas and the debris itself may not be susceptible to adequate disinfecting.

Traditionally, tubular elements such as endoscopes have been cleaned by passing a brush along the length of the tube or passageway to dislodge the debris. The debris can then be flushed out with a pressurised fluid, for example by connecting the passageway to a tap of a water supply. There are a number of disadvantages with this method. For example, there is the risk of damaging or puncturing the passage walls of the endoscope with the brush. This can result in costly repairs, especially if cleaning fluid is able to come into contact with and damage the expensive electrical components within the distal end of the endoscope.

There is also the possibility with this technique that not all of the debris will be removed.

Another known method of cleaning medical instruments is to immerse them in an ultrasonic bath while flushing pressurised cleaning fluid through the passageways of the instrument. Although the ultrasonic vibrations do produce quite an effective cleaning action, they can also damage the instrument, in particular to the expensive high-tech electrical components that might be present. For this reason, ultrasonic cleaning is preferably avoided for endoscopes.

Viewed from a first aspect, the present invention provides a method of cleaning a tubular element by passing a cleaning fluid through the element wherein the fluid is pulsed at a frequency in or below the audible range.

Viewed from a second aspect the invention provides apparatus for cleaning a tubular element including means for providing a pulsed flow of cleaning fluid wherein the frequency of the pulses is in or below the audible range.

We have found that the invention provides an improved cleaning action whilst avoiding the disadvantages of the prior art systems discussed above.

Preferably the pulsing effect is produced by a linear pump although other methods, for example by constricting the supply, or perhaps by providing vibrating or oscillating valves, are also envisaged.

The pulses are generated at a frequency in or below the audible range, i.e. below about 17 kHz. In preferred embodiments the frequency is between 20-500 Hz, and ideally between 50-250 Hz. The most convenient frequency to use is twice the frequency of the local electrical mains supply, i.e. 100 Hz (or 120 Hz in the U.S.A.), since this avoids the extra cost of electrical regulating circuits.

During the pulsing, the pressure in the cleaning fluid will vary between a minimum pressure of substantially zero and a maximum value of, for example, 2 bar. Obviously the upper pressure limit is governed by the nature of the debris to be removed and the type of cleaning fluid being used. It was found that when using water or a water based fluid as the cleaning fluid, a maximum value of 2 bars of pressure was sufficient to remove body fluid and tissue from the inside passageways of an endoscope.

In order to produce a more vigorous cleaning action, in preferred embodiments bubbles of gas, which may be air, are introduced into the pulsing stream of cleaning fluid. Preferably these bubbles are well dispersed in the fluid and preferably they are introduced intermittently. It is believed that ideally the gas is released when the pressure in the cleaning fluid is at its minimum value, i.e. between the high pressure pulses, so that each pressure wave can help to dispense the gas and force the gas against and under the debris.

In preferred embodiments this is achieved by using a compressor which increases the pressure in the gas supply until the gas pressure can overcome the force of a spring means in addition to the hydrostatic pressure of the pulsing cleaning fluid, both of which tend to urge an inlet valve for the gas shut. Obviously, this will result in bubbles of gas being introduced into the fluid stream when the hydrostatic pressure of the cleaning fluid is at a low or minimum value. A good cleaning effect for endoscopes has been found to occur when gas is released after every few pulses of the cleaning fluid, say every second or third pulse, as it seems that the surface of the valve tends to oscillate slightly with the cleaning fluid pulses, creating a better dispersion of bubbles. Thus, in a preferred embodiment the values of the pressures generated by the spring means, the pulsing fluid and the gas are arranged such that the gas pressure causes the valve to open after at least two fluid pulses, and preferably three.

This may be achieved by gradually increasing the pressure of the gas, either continuously or in steps, until the pressure overcomes the force of the valve spring means and the hydrostatic pressure of the cleaning fluid.

The gas may disperse itself to some extent in the fluid, but preferably means for dispersing the gas in the cleaning fluid is provided. This may take the form of any suitable means which sufficiently mixes the cleaning fluid and bubbles of gas, and preferably comprises an impeller.

The impeller preferably includes a plurality of helical or screw-type vanes. The impeller rotates under the force of the fluid incident on it which causes the gas to be dispersed in the fluid. Other configurations of vanes on the impeller which provide suitable dispersion are also envisaged, such as straight vanes which are disposed at an angle with respect to the fluid flow.

The means for dispersing the gas may also comprise means for directing the fluid and gas flow onto the impeller, which preferably includes a plurality of vanes aligned longitudinally along the direction of flow such that the flow is divided into more than one stream, for example into four.

Preferably, a further means for directing the flow is provided on the downstream side of the impeller which serves to stabilise the fluid flow.

Conventionally, medical instruments such as endoscopes are disinfected by a process of immersing the instruments in a bath of disinfectant and allowing them to stand for a period of time to let the chemical reactions take place. The disinfecting fluid is usually syringed or squirted through the passageways to ensure that no air bubbles are present. This is because air bubbles would prevent the disinfectant from coming into contact with certain areas of the instrument, thus creating a risk of spreading infection to the next patient.

Afterwards they are rinsed to remove disinfectant, usually with water or other suitable rinsing fluid.

They are then hung up and allowed to drain until dry.

Viewed from another aspect, the present invention provides a method and apparatus which is capable of cleaning, disinfecting, rinsing and drying tubular elements.

After the tubular element has been cleaned as mentioned above, the preferred apparatus is used to flush disinfectant through the tubular element, by selecting a supply of disinfectant to be pumped by the fluid pump of the apparatus. Once all the gas bubbles have been removed, the pump is switched off to allow the disinfectant to stand as required.

When this stage is complete, a rinsing fluid is then selected and pumped through the tubular element or instrument to remove all traces of the disinfectant. In most cases the rinsing fluid may be the same as the initial cleaning fluid.

Finally, in preferred embodiments, the tubular element is dried by selecting gas from the compressor (which was previously used to introduce the gas bubbles during cleaning as described above) to blow the moisture from the internal passageways.

A preferred embodiment of the present invention will now be discussed by way of example only and with reference to the accompanying drawings, in which: Fig. 1 shows a perspective view of a preferred embodiment of the invention; Fig. 2 shows a functional block diagram of the internal components of the device of Fig. 1; Fig. 3 shows two graphs illustrating variations of pressure with respect to time; Fig. 4 shows a cross-sectional view of an impeller for use with the present invention; and Fig. 5 shows an end view of the impeller of Fig. 4.

A preferred housing of the cleaning apparatus 1 is shown in Fig. 1. Along the top edge of the housing is arranged a series of output nozzles 3. These can be connected to an endoscope or other tubular element via a length of flexible tubing (not shown). In the embodiment of Fig. 1 there are six nozzles to allow a number of instruments to be connected simultaneously.

On the front of the apparatus 1 is located a control panel 5, with which the operator can select the fluid and/or air combination as required. A timer and perhaps flow restrictors can also be incorporated in the control panel 5 if so desired. Inlet ports 7 and 9 are provided to supply the apparatus 1 with the chosen fluid and air.

Numeral 11 denotes the electrical main supply lead.

Fig. 2 shows a functional block diagram of the internal components of the preferred embodiment.

Cleaning fluid for example, is drawn up into the apparatus 1 via a filter 13 by a fluid pulser pump 15.

As mentioned previously the pump 15 is preferably a linear piston pump as this produces strong well defined pulses. The pump 15 ideally operates on both positive and negative parts of the mains AC cycle to give a pulse frequency of 100 or 120 Hz.

Once the cleaning fluid exits the pump 15, it passes along a fluid circuit 21 through a valve 17 and a restrictor 19 towards an output manifold 23 on which are located the output nozzles 3 shown in Fig. 1.

In the embodiment illustrated in Fig. 2, a supply of air can be introduced to the fluid circuit 21 to provide a more vigorous cleaning action. Air or another suitable gas is pressurised by an air compressor 25 and forced along an air circuit 31 through a valve 27 and a restrictor 29 towards the fluid circuit 21. Located at the junction between the fluid circuit 21 and the air circuit 31 is a valve 33.

The valve 33 preferably has a spring or resilient member to urge it closed, so that it shuts off the supply of air to the stream of pulsing fluid. In addition, there is hydrostatic pressure from the fluid in the circuit 21 which also acts to shut valve 33.

Since the fluid is being pulsed, the pressure that acts on the fluid circuit side of the valve 33 will oscillate between a maximum and minimum value as pulses traverse across the valve opening. The air in circuit 31 has to reach at least a pressure that can overcome the valve shutting forces from both the spring and the fluid pressure if it is to escape into the fluid stream.

Obviously the air pressure needs to reach at least a minimum value corresponding to the pressure created by the spring plus the minimum pressure in the fluid, i.e.

the pressure corresponding to a trough in the pulse.

This is illustrated in the two graphs shown in Fig. 3. Line F represents the variation of pressure in the fluid with respect to time. The fluid pressure can be seen to pulse between the minimum and maximum values of P1 and P3 respectively. The pressure caused by the force of the valve spring remains constant with respect to time. When the valve spring's component of pressure is combined with that from the fluid, curve F + V is produced, where V is the pressure created by the valve spring. This combined pressure oscillates between the minimum and maximum values of P and P respectively.

Curve A represents the variation in pressure of the air with respect to time. As shown, the pressure steadily increases until it reaches a value of greater than P2. When this occurs at a time corresponding to a pulse trough in the fluid pressure, the valve 33 can open to release bubbles of air into the fluid stream.

The valve 33 will then close to allow the pressure in the air circuit 31 to increase until it can release another volume of air.

Of course, this is only a preferred method of introducing bubbles of air into the supply of cleaning fluid and other methods are envisaged. For example the air could simply be released at regular periods of time governed by a timing circuit. In addition the orifice of the valve 33 or perhaps a valve outlet nozzle plate can be constructed so that it produces a greater dispersion of bubbles, for example by having a plurality of fine holes. Furthermore a pulsing pump similar to that used in the fluid circuit 21 could be used to provide pulses of air.

In order to disperse the bubbles of air in the cleaning fluid, an impeller may be provided as shown in Figs. 4 and 5. The impeller 35 is connected to the circuit in series between valve 33 and output manifold 23. The impeller 35 has its axis aligned with the direction of flow of the fluid and gas and includes a plurality of helical or screw-type vanes 37. The impeller rotates under the force of the fluid incident on it which causes the gas to be dispersed in the fluid.

The impeller 35 is also provided with a section 39 on the upstream side for directing the fluid and gas flow onto the impeller and section 41 provided on the downstream side for stabilising the fluid flow. The two sections 39 and 41 preferably include a plurality of vanes aligned longitudinally along the direction of flow such that the flow is divided into more than one stream, for example into four.

If the apparatus 1 is to be used to clean endoscopes, then ordinary tap water rather sterile water can be used in the fluid circuit 21, because the endoscope is used in areas of the body where the germs normally present in tap water can be dealt with by the body's immune system. Similarly, a separate pump for the disinfection stage is not necessary if the apparatus 1 is only intended to clean endoscopes. Instead a supply of disinfectant can be connected to the filter 13 of Fig. 2 and pumped through the fluid circuit 21 into the endoscope in a similar manner as to that of the previously mentioned operation with the cleaning fluid.

Air would not be released from circuit 31 at this stage.

Once all the air bubbles in the endoscope have been removed, the disinfectant can be allowed to stand by simply turning off the fluid pump 15. When rinsing is required, a supply of rinsing fluid, for example water, can be connected to the filter 13 and pumped flushing disinfectant from the apparatus 1 and through the endoscope. Then to dry the endoscope, the fluid pump 15 can be switched off and the air compressor 25 switched on so that a stream of air is blown through output nozzle 3 and through the endoscope. Thus the remaining rinsing fluid is blown out of the passageways, drying the instrument.

The present invention is not intended to be restricted to simply cleaning endoscopes and other cannulated medical instruments, but instead other applications are envisaged. For example applications in tubular elements used in mechanical fields such as fluid hoses used on machinery or in engines. Here the pulsing action of the cleaning fluid might remove oil and grease or perhaps hard water deposits. These of course would require different pressures and frequencies of the sonic pulses, with ideally the frequency being tailored to a resonant frequency of the debris.

Claims

Claims:

1. A method of cleaning a tubular element by passing a cleaning fluid through the element wherein the fluid is pulsed at a frequency in or below the audible range.

2. The method of claim 1 wherein the frequency of the pulses is below about 17 kHz.

3. The method of claim 1 wherein the frequency of the pulses is between 20-500 Hz.

4. The method of claim 1 wherein the frequency of the pulses is between 50-250 Hz.

5. The method of any of claims 1 to 4 wherein bubbles of gas are introduced into the pulsed fluid.

6. The method of claim 5 wherein the bubbles are introduced intermittently.

7. The method of claim 5 or 6 wherein the gas is introduced into low pressure regions of the cleaning fluid.

8. A method of cleaning a cannulated medical instrument by passing a cleaning fluid through the instrument wherein the fluid is pulsed at a frequency in or below the audible range.

9. Apparatus for cleaning a tubular element including means for providing a pulsed flow of cleaning fluid through the element wherein the frequency of the pulses is in or below the audible range.

10. The apparatus of claim 9 wherein the cleaning fluid is pulsed by a linear pump.

11. The apparatus of claim 9 or 10 wherein the frequency of the pulses is below about 17 kHz.

12. The apparatus of claim 9 or 10 wherein the frequency of the pulses is between 20-500 Hz.

13. The apparatus of claim 9 or 10 wherein the frequency of the pulses is between 50-250 Hz.

14. The apparatus of any of claims 9 to 13 further including means for introducing bubbles of gas into the cleaning fluid.

15. The apparatus of claim 14 wherein the means for introducing the bubbles of gas introduces the bubbles intermittently.

16. The apparatus of claim 14 or 15 wherein the means for introducing the bubbles of gas introduces the gas into low pressure regions of the cleaning fluid.

17. The apparatus of claim 14, 15 or 16 wherein the means for introducing the bubbles of gas is a compressor.

18. The apparatus of any of claims 14 to 17 wherein the apparatus further comprises an inlet valve through which the gas is introduced into the cleaning fluid, the valve being urged into a closed position by the pressure of the cleaning fluid and urged into an open position by the pressure of the gas, the valve opening under the gas pressure when subjected to low pressure regions of the cleaning fluid.

19. The apparatus of claim 18 wherein the pressure of the gas is increased continuously or in steps until the pressure opens the valve.

20. The apparatus of any of claims 9 to 19 further comprising means for dispersing the gas bubbles in the cleaning fluid.

21. The apparatus of claim 20 wherein the means for dispersing comprises an impeller.

22. The apparatus of claim 21 wherein the impeller includes a plurality of helical or screw-type vanes.

23. The apparatus of claim 20 or 21 wherein the means for dispersing the gas further comprises means for directing the fluid and gas flow onto the impeller.

24. The apparatus of claim 23 wherein the means for directing the flow includes a plurality of vanes aligned longitudinally along the direction of flow such that the flow is divided into more than one stream.

25. The apparatus of claim 24 wherein the means for dispersing the gas comprises further means for directing the flow provided on the downstream side of the impeller.

26. Apparatus for cleaning a cannulated medical instrument including means for providing a pulsed flow of cleaning fluid through the instrument wherein the frequency of the pulses is in or below the audible range.

27. A method for cleaning tubular elements comprising the steps of: passing a cleaning fluid through the element; flushing disinfectant through the element; rinsing the element to remove the disinfectant; and drying the element by passing gas through the element.

28. The method of claim 27 wherein the cleaning fluid is pulsed at a frequency in or below the audible range.

29. Apparatus for cleaning tubular elements, comprising: means for providing a flow of cleaning fluid through the element; means for flushing disinfectant through the element; means for rinsing the element to remove the disinfectant; and means for drying the element by passing gas through the element.

30. The apparatus of claim 29 wherein the cleaning fluid is pulsed at a frequency in or below the audible range.

31. A method of cleaning a tubular element substantially as hereinbefore described with reference to any of the accompanying drawings.

32. Apparatus for cleaning a tubular element substantially as hereinbefore described with reference to any of the accompanying drawings.