GB2450889A

GB2450889A - A method of cleaning a filter element

Info

Publication number: GB2450889A
Application number: GB0713368A
Authority: GB
Inventors: Nikolay Pavlovich Belenkiy; Sergei Botov
Original assignee: FG TECHNOLOGIES Ltd
Current assignee: FG TECHNOLOGIES Ltd
Priority date: 2007-07-10
Filing date: 2007-07-10
Publication date: 2009-01-14
Also published as: GB0713368D0

Abstract

A method of cleaning a filter element, each filter element comprising a portion which may be used to remove contaminants from a fluid, the method comprising: providing a filter element; providing an ultrasound-transmissive fluid which is transmissive to ultrasonic waves, at least part of the article being in contact with the ultrasound-transmissive fluid; and passing ultrasonic waves through the ultrasound-transmissive fluid such that at least part of the filter element is cleaned. The ultrasonic waves may comprise a first set having a characteristic frequency and a second set having a different characteristic frequency from the first set. Preferably there are two different ultrasound-transmissive fluids and more than one filter element wherein the filter elements are grouped together for cleaning. Preferably a container is provided for the ultrasound-transmissive fluid and the filter element is passed through an inlet in the container prior to the ultrasound-transmissive fluid. Further inventions to a method of cleaning articles and to an apparatus for cleaning articles are disclosed.

Description

Method and apparatus for cleaning articles The present invention

relates to a method and apparatus suitable for cleaning articles such as filter elements, particularly (but not exclusively) those filter elements used to remove particulates from fluids, such as fuel or air.

Articles such as filter elements may be used to remove contaminants from fluids, such as fuel or air. The contaminants may comprise particulates. Such filter elements, once used, may be thrown away and disposed of in landfill sites (optionally after the majority of any contaminating liquids have been removed) . Some filters may be cleaned and re-used. Reuse may apply to filter elements made from plastics materials. Dirty filter elements are typically contaminated with particulate and the fluid which they have been used to filter, such as fuel (for example, petrol or diesel) or hydraulic fluid. One method of cleaning such filter elements involves the use of cleaning agents which, after use, have to be disposed of. Disposal of such cleaning agents often presents a problem because of the environmentally-unfriendly nature of such cleaning agents.

Furthermore, the cleaning process used, on occasion, does not produce the desired cleaning effect, even if environmentally-unfriendly cleaning agents are used. A further method of treating filter elements contaminated with oil or the like is to compress the filter elements to expel excess liquid and then burn the compressed filter element material. Burning obviously provides its own environmental problems.

The present invention seeks to mitigate one or more of the

problems of the prior art.

In accordance with a first aspect of the present invention, there is provided an apparatus for cleaning articles, the apparatus comprising: (i) a container for holding a fluid transmissive to ultrasonic waves, the container being provided with an inlet for the introduction into the container of articles to be cleaned and an outlet for the removal from the container of articles which have been cleaned, the outlet being spaced from the inlet and (ii) means for generating ultrasonic waves in a fluid provided in the container.

Those skilled in the art will realise that the ultrasound-transmissive fluid is not an essential part of the apparatus in accordance with the present invention.

The present invention provides an effective apparatus for the cleaning of articles. In use, ultrasonic waves are generated and transmitted through a fluid (typically a liquid), the ultrasound waves causing cavitation in the fluid. Without wishing to be bound by the theory, it is thought that the collapse of the cavities produces implosions which assist in the cleaning process.

It is preferred that the inlet and outlet are remote from one another. In particular, it is preferred that the container is elongate, and the inlet is provided at (or near) one end of the container and the outlet is provided at (or near) the other end of the container.

It is preferred that the inlet is provided by an inlet aperture, the inlet aperture being associated with an inlet aperture closure means, the inlet aperture closure means being movable between a first position in which the introduction of articles through the inlet aperture into the container is inhibited and a second position in which the introduction of articles through the inlet aperture into the container is permitted. It is preferred that when the inlet aperture closure means is in the first position, a seal is provided for inhibiting egress of liquid from the container through the inlet.

It is preferred that the outlet is provided by an outlet aperture, the outlet aperture being associated with an outlet aperture closure means, movable between a first position in which the removal of articles through the outlet aperture out of the container is inhibited and a second position in which the removal of articles through the outlet aperture out of the container is permitted. It is preferred that when the outlet aperture closure means is in the first position, a seal is provided for inhibiting egress of liquid from the container through the outlet.

It is preferred that the container is defined by a base-forming surface and at least one wall-defining surface extending from the base-forming surface. It is preferred that one or both of the inlet and outlet are defined in a wall-defining surface. It is preferred that the container is defined by a base-forming surface and a plurality of wall-defining surfaces extending from the base-forming surface.

It is preferred that the inlet is defined in one wall-defining surface and the outlet is provided in a different wall-defining surface.

The at least one wall-defining surface may have a lower portion associated with the base-forming surface and an upper portion remote from the base-forming surface, wherein one or both of the inlet and outlet are located in the lower portion of a wall-defining surface. It is preferred that the inlet and outlet are provided in different wall-defining surfaces.

The apparatus may be further provided with a means for moving the articles into the container through the inlet, such as an endless loop conveyor which may be in the form of a pinion or belt.

The apparatus may be further provided with a means for moving the articles out of the container through the outlet, such as a conveyor (such as an endless loop conveyor) or a pinion.

The apparatus may be further provided with one or more carriers for carrying article into and out of the container.

The carrier may be in the form of a basket. The carrier may be provided with one or more apertures for the passage of fluid (preferably liquid) therethrough.

The apparatus may be provided with one or more carrier supports for supporting one or more carriers. The carrier support may be arranged for movement by the means for moving the articles into the container through the inlet. It is preferred that the carrier support is provided with a mounting portion for mounting the carrier support on the means for moving the article into the container through the inlet. It is further preferred that the mounting portion is for engaging with a portion of an endless loop (such as the teeth or apertures of a rack) so that movement of the endless loop causes movement of carrier support. In this case, the carrier support may engage with a portion of an endless loop, such as may be formed ay a rack of a rack-and-pinion.

Alternatively, the mounting portion is for engaging with the teeth of a pinion. In this case, the carrier support may itself form the rack of a rack-and-pinion.

It is preferred that the mounting portion comprises a plurality of mutually-spaced engagement members for engaging with the apertures or teeth of a rack or the teeth of a pinion so that movement of the rack or pinion causes movement of carrier support. The engagement members may comprise teeth or bars, for example.

It is preferred that each carrier support is capable of supporting a plurality of carriers. It is preferred that a carrier support is provided with at least one carrier-receiving aperture, each carrier-receiving aperture being for the receipt of a carrier.

It is preferred that the carrier support is flexible. It is preferred that the carrier support comprises a mesh.

The apparatus may be provided with a degasser for decreasing the amount of gas dissolved in a liquid. The container may be in fluid communication with the degasser so that fluid from the container may be delivered to the degasser for treatment. The container may be further in fluid communication with the degasser such that degassed liquid may be delivered to the container.

The container may be in fluid communication with a filter for removing contaminants from a liquid. It is preferred that the filter is suitable for removing particulate contaminants from a liquid. The container may be in fluid communication with the filter such that fluid may be delivered from the container to the filter for treatment.

The container may further be in fluid communication with the filter so that filtered fluid may be delivered to the container.

The apparatus may comprise a storage vessel for storing liquid. The storage vessel may be in fluid communication with the container so that fluid (such as ultransound-transmissive fluid) may be transferred between the storage vessel and the container. The storage vessel may, in use, be located below the container so that liquid is transferable from the container to the storage vessel by gravity.

The storage vessel may be in fluid communication with the degasser so that fluid is transferable to the degasser for treatment, preferably without the fluid passing through or into the container. It is further preferred that the storage vessel is in fluid communication with the degasser so that fluid is transferable from the degasser to the storage vessel after treatment, preferably without the fluid passing through or into the container.

The storage vessel may be in fluid communication with the filter so that fluid is transferable to the filter for treatment, preferably without the fluid passing through or into the container. It is further preferred that the storage vessel is in fluid communication with the filter so that fluid is transferable from the filter to the storage vessel after treatment, preferably without the fluid passing through or into the container.

The apparatus may be provided with a means for decreasing pressure in the container, such as a vacuum pump. The apparatus may be operable so that operation of the means for decreasing pressure causes flow of liquid from the storage vessel into the container.

In accordance with a second aspect of the present invention, there is provided an apparatus for cleaning an article, the apparatus comprising (i) a first container for holding a fluid transmissive to ultrasound waves; (ii) means for generating ultrasonic waves in a fluid provided in the first container; (iii)a second container for holding a fluid; and (iv) a means for moving the article between the first container and the second container, the apparatus being operable to lower the article towards the first container and/or raise the first container towards the article from a first, non-cleaning position to a second, cleaning position in which the article is at least partially located in the first container. l0

This provides an apparatus which is especially suitable for cleaning bulky articles and large groups of articles which are not readily passed through inlets and outlets provided in containers, such as in US5333628. Furthermore, the use of lowering and raising means that inlets and outlets do not have to be provided below the line of the ultrasound-transmissive liquid, such inlets possibly being prone to leakage or which inlets and outlets necessitate the removal of at least some liquid from a container prior to the articles being passed through the inlet and outlet.

It is further preferred that the apparatus is further operable to raise the article away from the first container and/or lower the first container away from the article, from the second position to the first position.

The apparatus may be provided with a means for moving the article between the first and second positions relative to the first container. The means for moving the article between the first and second positions relative to the first container may comprise a bias means for urging the article into the second position. The bias means may, for example, comprise a spring, such as a compression spring. The means for moving the article between the first and second positions relative to the first container may comprise an actuator, such as a piston. The actuator may work in combination with the bias means to control the movement of the article. For example, in a first actuator state the actuator may not resist the biasing operation of the spring, and the article is urged into the second position. This may be achieved, for example, if no power is supplied to the actuator. In a second actuator state, the actuator may act to raise the article against the biasing operation of the spring so that the article may be moved to the first position.

The apparatus may be provided with a means for moving the first container between the first and second positions.

It is preferred that the apparatus is operable to lower the article towards the second container and/or raise the second container towards the article from a first position in which the articles are not located in the second container to a second position in which the article is at least partially located in the second container.

It is further preferred that the apparatus is further operable to raise the article away from the second container and/or lower the second container away from the article, from the second position to the first position.

S

The apparatus may be provided with a means for moving the article between the first and second positions relative to the second container. The means for moving the article between the first and second positions relative to the second container may be the means for moving the article between the first arid second positions relative to the first container. Alternatively, the apparatus may comprise means for moving the article between the first and second positions relative to the second container in addition to the means for moving the article between the first and second positions relative to the first container. The means for moving the article between the first and second positions relative to the second container may comprise those features described above with respect to the means for moving the article between the first and second positions relative to the first container.

The second container may be used as a rinsing container (in which case the second container will be downstream of the first container) . In this case, the second container is typically provided with water or other suitable rinsing agent.

The second container may be used to remove gross contamination from the article prior to cleaning the article with ultrasound. In this case, the second container will be upstream of the first container.

The apparatus may be provided with a means for moving the second container between the first and second positions. The means for moving the second container between the first and

I

second positions may be the means for moving the first container between the first and second positions.

Alternatively, the means for moving the second container between the first and second positions may be in addition to the means for moving the first container between the first and second positions.

The apparatus may further comprise a third container for receipt of the article.

The third container may be upstream or downstream of the first container. In the event that the second container is upstream of the first container, it is preferred that the third container is downstream of the first container. In the event that the second container is downstream of the first container, it is preferred that the third container is upstream of the first container. If the third container is upstream of the first container, it is preferred that the third container is for removing gross contamination from the article. If the third container is downstream of the first container, it is preferred that the third container is for rinsing the article.

tt is preferred that the apparatus is operable to lower the article towards the third container and/or raise the third container towards the article from a first position in which the article is not located in the third container to a second position in which the article is at least partially located in the third container.

It is further preferred that the apparatus is further operable to raise the article away from the third container and/or lower the third container away from the article, from the second position to the first position.

The apparatus may be provided with a means for moving the article between the first and second positions relative to the third container. The means for moving the article between the first and second positions relative to the third container may be the means for moving the article between the first and second positions relative to the first container. Alternatively, the apparatus may comprise means for moving the article between the first and second positions relative to the third container in addition to the means for moving the article between the first and second positions relative to the first container. The means for moving the article between the first and second positions relative to the third container may comprise those features described above with respect to the means for moving the article between the first and second positions relative to the first container.

The apparatus may be provided with a means for moving the third container between the first and second positions. The means for moving the third container between the first and second positions may be the means for moving the first container between the first and second positions.

Alternatively, the means for moving the third container between the first and second positions may be in addition to the means for moving the first container between the first and second positions. &

It is preferred that the apparatus comprises a means for moving the article between the first arid third containers.

It is preferred that the means for moving the article between the first and second containers and the means for moving the article between the first and third containers is provided by a conveyor, such as an endless ioop conveyor. A pinion or belt may be arranged as an endless loop conveyor. I0

It is preferred that the conveyor is arranged so that at least a portion of the conveyor is operable to be lowered and raised so as to lower and raise the article between the first and second positions relative to the first container.

This may conveniently be achieved by the conveyor being associated with the means for moving the article between the first and second positions relative to the first container.

The means for moving the article between the first and second positions relative to the first container may comprise an arrangement for passage therethrough of a portion of belt or endless loop, the belt or endless loop forming part of a conveyor. The arrangement for passage therethrough of the portion of belt or endless ioop may comprise a set of a plurality of rollers, with a gap between at least two of the rollers for the passage therethrough of the portion of belt or endless loop. The set of a plurality of rollers may be lowered and raised on operation of the means for moving the article between the first and second positions relative to the first container. (

Likewise, it is preferred that the conveyor is arranged so that at least a portion of the conveyor is operable to be lowered and raised so as to lower and raise the article between the first and second positions relative to the second container. This may conveniently be achieved by the conveyor being associated with the means for moving the article between the first and second positions relative to the second container. The means for moving the articles between the first and second positions relative to the second container may comprise an arrangement for passage therethrough of a portion of a belt or endless loop, the belt or endless loop forming part of a conveyor. The arrangement for passage therethrough of a portion of belt or endless loop may comprise a set of a plurality of rollers, with a gap between at least two of the rollers for the passage therethrough of a portion of belt or endless loop.

The set of a plurality of rollers may be lowered and raised on operation of the means for moving the article between the first and second positions relative to the second container.

Likewise, it is preferred that the conveyor is arranged so that at least a portion of the conveyor is operable to be lowered and raised so as to lower and raise the article between the first and second positions relative to the third container. This may conveniently be achieved by the conveyor being associated with the means for moving the article between the first and second positions relative to the third container. The means for moving the articles between the first and second positions relative to the third container may comprise an arrangement for passage therethrough of a portion of belt or endless loop, the belt or endless loop t forming part of a conveyor. The arrangement for passage therethrough of a portion of belt or endless loop may comprise a set of a plurality of rollers, with a gap between at least two of the rollers for the passage therethrough of a portion of belt or endless loop. The set of a plurality of rollers may be lowered and raised on operation of the means for moving the articles between the first and second positions relative to the third container.

The apparatus may be further provided with one or more carriers for carrying an article into and out of the first container. The carrier may be in the form of a basket. The carrier may be provided with one or more apertures for the passage of fluid (preferably liquid) therethrough.

The apparatus may be provided with one or more carrier supports for supporting one or more carriers. The carrier support may be arranged for movement by the means for moving the article between the first and second containers. It is preferred that the carrier support is provided with a mounting portion for mounting the carrier support on the means for moving the article between the first and second containers. It is further preferred that the mounting portion is for engaging with a portion of an endless loop (such as the teeth or apertures of a rack) so that movement of the endless loop causes movement of the carrier support.

In this case, the carrier support is mountable on the rack or other endless ioop.

Alternatively, the mounting portion may be for engaging with the teeth of a pinion so that so that movement of the pinion t causes movement of the carrier support. In this case, the carrier support itself acts as the rack of a rack-and-pinion.

It is preferred that the mounting portion comprises a plurality of mutually-spaced engagement members for engaging with the teeth of a pinion so that movement of the teeth causes movement of carrier support. The engagement members may comprise teeth or bars, for example.

It is preferred that each carrier support is capable o supporting a plurality of carriers. It is preferred that a carrier support is provided with at least one carrier-receiving aperture, each carrier-receiving aperture being for the receipt of a carrier.

The apparatus may be provided with a degasser for decreasing the amount of gas dissolved in a liquid. The first container may be in fluid communication with the degasser so that fluid from the container may be delivered to the degasser for treatment. The first container may be further in fluid communication with the degasser such that degassed liquid may be delivered to the first container.

At least one of the first container, the second container and the third container (if present) may be in fluid communication with a filter for removing contaminants from a liquid. It is preferred that the filter is suitable for removing particulate contaminants from a liquid. The at least one of the first container, the second container and the third container may be in fluid communication with the filter such that fluid may be delivered from the respective container to the filter for treatment. The respective container may further be in fluid communication with the filter so that filtered fluid may be delivered to the respective container.

The apparatus may comprise a storage vessel for storing liquid. The storage vessel may be in fluid communication with one or more of the first container, second container and third container so that fluid (such as ultransound-transmissive fluid) may be transferred between the storage vessel and the respective container. The storage vessel may, in use, be located below the respective container so that liquid is transferable from the respective container to the storage vessel by gravity.

The storage vessel may be in fluid communication with the degasser so that fluid is transferable to the degasser for treatment, preferably without the fluid passing through or into any one of the first, second or third containers. It is further preferred that the storage vessel is in fluid communication with the degasser so that fluid is transferable from the degasser to the storage vessel after treatment, preferably without the fluid passing through or into the first, second or third containers.

The storage vessel may be in fluid communication with the filter so that fluid is transferable to the filter for treatment, preferably without the fluid passing through or into the first, second or third containers. It is further preferred that the storage vessel is in fluid communication with the filter so that fluid is transferable from the filter to the storage vessel after treatment, preferably without the fluid passing through or into the first, second or third containers.

The apparatus may be provided with a means for decreasing pressure in at least one of the first, second or third containers, such as a vacuum pump. The apparatus may be operable so that operation of the means for decreasing pressure causes flow of liquid from the storage vessel into the first, second or third containers.

In accordance with a third aspect of the present invention, there is provided a method of cleaning article, the method comprising: (i) providing an article (ii) providing a fluid which is transmissive to ultrasonic waves, at least part of the article being in intimate contact with the ultrasound-transmissive fluid (iii) passing ultrasonic waves through the ultrasound-transmissive fluid such that at least part of the article is cleaned The ultrasound-transmissive fluid is typically a liquid and may be a liquid provided with a cleaning agent. It is preferred that the article comprises a filter element. It is preferred that the filter element comprises plastics material. The filter element may comprise a portion which may be used to remove contaminants from a fluid, and it is preferred that this portion comprises plastics material.

It is preferred that step (iii) comprises passing a first set of ultrasonic waves through the ultrasound-transmissive fluid, the first set of waves having a characteristic frequency or characteristic range of frequencies and then passing a second set of ultrasonic waves through the ultrasound-transmissive fluid, the second set of waves having a different characteristic frequency or different characteristic range of frequencies from the first set of waves.

It is preferred that the method comprises at least part of the article being in intimate contact with two different ultrasound-transmissive fluids, and passing ultrasonic waves through those ultrasound-transmissive fluids. For example, the article may be in intimate contact with a neutral medium (such as water) and subjected to ultrasonic treatment, and then immersed in an alkali medium through which ultrasonic waves are passed.

It is preferred that the method comprising degassing the ultrasound-transmissive fluid. This has been found to be beneficial to the cleaning process.

The method may comprise removing gross contamination from the article prior to step (iii) This may take place in a contamination container. The article may be moved from the contamination container into a container in which step (iii) is performed.

The method may comprise rinsing the article subsequent to step (iii) . This may take place in a rinsing container. The article may be moved from the container in which step (iii) is performed to the rinsingcontainer.

It is preferred that the method comprises providing a container in which the ultrasound-transmissive fluid may be contained during the passage therethrough of ultrasonic waves. The container may comprise an inlet for the introduction into the container of article to be cleaned and an outlet for the removal from the container of article which have been cleaned. The outlet may be spaced from the inlet. The inlet and outlet may be remote from one another.

It is preferred that the method comprises passing the article through the inlet into the container. It is preferred that the article is passed through the inlet into the container prior to introducing ultrasound-transmissive fluid into the container. The method further preferably comprises passing the article through the outlet out of the container. It is preferred that ultrasound-transmissive fluid is removed from the container before the article is passed through the outlet out of the container.

It is preferred that the container is elongate and that the inlet is provided at (or near) one end of the container and the outlet is provided at (or near) the other end of the container.

It is preferred that the inlet is provided by an inlet aperture, the inlet aperture being associated with an inlet aperture closure means, the inlet aperture closure means being movable between a first position in which the introduction of the article through the inlet aperture into the container is inhibited and a second position in which the introduction of the article through the inlet aperture into the container is permitted. It is preferred that when the inlet aperture closure means is in the first position, a seal is provided for inhibiting egress of liquid from the container through the inlet.

It is preferred that the outlet is provided by an outlet aperture, the outlet aperture being associated with an outlet aperture closure means, the outlet aperture closure means being movable between a first position in which the removal of the article through the outlet aperture out of the container is inhibited and a second position in which the removal of the article through the outlet aperture out of the container is permitted. It is preferred that when the outlet aperture closure means is in the first position, a seal is provided for inhibiting egress of liquid from the container through the outlet.

It is preferred that the inlet is defined in one wall-defining surface and the outlet is provided in a different wall-defining surface. It is preferred that the inlet and outlet are provided in different wall-defining surfaces.

The at least one wall-defining surface may have a lower portion associated with the base-forming surface and an upper portion remote from the base-forming surface. It is preferred that one or both of the inlet and outlet are located in the lower portion of a wall-defining surface. It is preferred that the inlet and outlet are provided in different wall-defining surfaces.

It is preferred that the method comprises introducing the ultrasound-transmissive fluid into the container. The method may further comprise introducing the article into the container prior to passing ultrasonic waves through the ultrasound-transmissive fluid. The article may be removed from the container, preferably after ultrasonic waves are passed through the ultrasound-transmissive fluid. It is preferred that at least some of the ultrasound-transmissive fluid is removed from the container prior to the article being removed from the container. It is preferred that the majority of the ultrasound-transmissive fluid is removed from the container prior to the article being removed from the container. The ultrasound-transmissive fluid removed from the container may be transferred to a storage vessel.

It is preferred that the ultrasound-transmissive fluid may be transferred to the storage vessel by the action of gravity.

V

The method may further comprise transferring ultrasound-transmissive fluid from the storage vessel to the container, preferably by reducing pressure in the container.

The method may further comprise providing a means for moving the article into the container. The means for moving the article into the container may comprise a conveyor or a pinion, and may move the article through the inlet. I0

The method may further comprise providing a means for moving the article out of the container through the outlet. The means for moving the article out of the container through the outlet may comprise a conveyor or a pinion.

It is preferred in one embodiment of the method of the present invention that the article is lowered towards the first container and/or the container containing the ultrasound-transmissive fluid is raised towards the article from a first, non-cleaning position to a second, cleaning position in which the article is at least partially located in said container.

The method may comprise providing a second container for holding a fluid.

The method may comprise providing a means for moving the article between the container containing the ultrasound-transmissive fluid and the second container.

The method may further comprise raising the article away from the container containing the ultrasound-transmissive fluid and/or lowering the container containing the ultrasound-transmissive fluid away from the article, from the second position to the first position.

The method may further comprise providing a means for moving the article between the first and second positions relative to the container containing the ultrasound-transmissive fluid. The means for moving the article between the first and second positions relative to the container containing the ultrasound-transmissive fluid may comprise a bias means for urging the article into the second position. The bias means may, for example, comprise a spring, such as a compression spring. The means for moving the article between the first and second positions relative to the container containing the ultrasound-transmissive fluid may comprise an actuator, such as a piston. The actuator may work in combination with the bias means to control the movement of the article. For example, in a first actuator state the actuator may not resist the biasing operation of the spring, and the article are urged into the second position. This may be achieved, for example, if no power is supplied to the actuator. In a second actuator state, the actuator may act to raise the article against the biasing operation of the spring so that the article may be moved to the first position.

The method may further comprise providing a means for moving the container containing the ultrasound-transmissive fluid between the first and second positions.

The method may further comprise lowering the article towards the second container and/or raising the second container towards the article, from a first position in which the article is not located in the second container to a second position in which the article is at least partially located in the second container.

The method may further comprise raising the article away from the second container and/or lowering the second container away from the article, from the second position to the first position.

The method may comprise providing a means for moving the article between the first and second positions relative to the second container. The means for moving the article between the first and second positions relative to the second container may be the means for moving the article between the first and second positions relative to the container containing the ultrasound-transmissive fluid.

Alternatively, the apparatus may comprise means for moving the article between the first and second positions relative to the second container in addition to the means for moving the article between the first and second positions relative to the container containing the ultrasound-transmissive fluid. The means for moving the article between the first and second positions relative to the second container may comprise those features described above with respect to the means for moving the article between the first and second positions relative to the container containing the ultrasound-transmissive fluid.

The second container may be used to remove gross contamination from the articles prior to cleaning the article with ultrasound. In this case, the second container will be upstream of the first container.

The method may comprise providing a means for moving the second container between the first and second positions. The means for moving the second container between the first and second positions may be the means for moving the container containing the ultrasound-transmissive fluid between the first and second positions. Alternatively, the means for moving the second container between the first and second positions may be in addition to the means for moving the container containing the ultrasound-transmissive fluid between the first and second positions.

The method may further comprise providing a third container for receipt of the article.

The third container may be upstream or downstream of the container containing the ultrasound-transmissive fluid. In the event that the second container is upstream of the container containing the ultrasound-transmissive fluid, it is preferred that the third container is downstream of the ( container containing the ultrasound-transmissive fluid. In the event that the second container is downstream of the container containing the ultrasound-transmissive fluid, it is preferred that the third container is upstream of the container containing the ultrasound-transmissive fluid. If the third container is upstream of the container containing the ultrasound-transmissive fluid, it is preferred that the third container is for removing gross contamination from the article. If the third container is downstream of the container containing the ultrasound-transmissive fluid, it is preferred that the third container is for rinsing the article.

The method may further comprise lowering article towards the third container and/or raising the third container towards the article, from a first position in which the article is not located in the third container and a second position in which the article is located in the third container.

The method may further comprise raising the article away from the third container and/or lowering the third container away from the article, from the second position in which the articles are located in the third container to the first position in which articles are not located in the third container.

The method may further comprise means for moving the article between the first and second positions relative to the third container. The means for moving the article between the first and second positions relative to the third container may be the means for moving the article between the first ( and second positions relative to the container containing the ultrasound-transmissive fluid. Alternatively, the apparatus may comprise means for moving the article between the first and second positions relative to the third container in addition to the means for moving the article between the first and second positions relative to the container containing the ultrasound-transmissive fluid. The means for moving the article between the first and second positions relative to the third container may comprise those features described above with respect to the means for moving the article between the first and second positions relative to the container containing the ultrasound-transmissive fluid.

The method may further comprise providing a means for moving the third container between the first and second positions.

The means for moving the third container between the first and second positions may be the means for moving the container containing the ultrasound-transmissive fluid between the first and second positions. Alternatively, the means for moving the third container between the first and second positions may be in addition to the means for moving the container containing the ultrasound-transmissive fluid between the first and second positions.

The method may further comprise providing a means for moving the article between the container containing the ultrasound-transmissive fluid and third containers.

It is preferred that the means for moving the article between the container containing the ultrasound-transmissive fluid and second containers, and the means for moving the article between the container containing the ultrasound-transmissive fluid and third containers is provided by a conveyor, such as an endless loop conveyor. A pinion or belt may be arranged as an endless loop conveyor. A belt may be arranged in a configuration other than an endless loop.

It is preferred that the conveyor is arranged so that at least a portion of the conveyor is operable to be lowered and raised so as to lower and raise the article between the first and second positions relative to the container containing the ultrasound-transmissive fluid. This may conveniently be achieved by the conveyor being associated with the means for moving the article between the first and second positions relative to the container containing the ultrasound-transmissive fluid. The means for moving the article between the first and second positions relative to the container containing the ultrasound-transmissive fluid may comprise an arrangement for passage therethrough of a portion of a belt or endless loop, the belt or endless ioop forming part of a conveyor. The arrangement for passage therethrough of the portion of the belt or endless loop may comprise a set of a plurality of rollers, with a gap between at least two of the rollers for the passage therethrough of the portion of belt or endless loop. The set of a plurality of rollers may be lowered and raised on operation of the means for moving the article between the first and second positions relative to the container containing the ultrasound-transmissive fluid. r

Likewise, it is preferred that the conveyor is arranged so that at least a portion of the conveyor is operable to be lowered and raised so as to lower and raise the article between the first and second positions relative to the second container. This may conveniently be achieved by the conveyor being associated with the means for moving the article between the first and second positions relative to the second container. The means for moving the article between the first and second positions relative to the second container may comprise an arrangement for passage therethrough of a portion of belt or endless loop, the belt or endless loop forming part of a conveyor. The arrangement for passage therethrough of the portion of belt or endless loop may comprise a set of a plurality of rollers, with a gap between at least two of the rollers for the passage therethrough of the portion of belt or endless loop. The set of a plurality of rollers may be lowered and raised on operation of the means for moving the article between the first and second positions relative to the second container.

Likewise, it is preferred that the conveyor is arranged so that at least a portion of the conveyor is operable to be lowered and raised so as to lower and raise the article between the first and second positions relative to the third container. This may conveniently be achieved by the conveyor being associated with the means for moving the article between the first and second positions relative to the third container. The means for moving the article between the first and second positions relative to the third container may comprise an arrangement for passage therethrough of a portion of belt or endless loop, the belt or endless loop

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forming part of the conveyor. The arrangement for passage therethrough of the portion of belt or endless loop may comprise a set of a plurality of rollers, with a gap between at least two of the rollers for the passage therethrough of the portion of belt or endless loop. The set of a plurality of rollers may be lowered and raised on operation of the means for moving the article between the first and second positions relative to the third container.

The method may further comprise providing one or more carriers for carrying the article into and out of the container containing the ultrasound-transmissive fluid. The carrier may be in the form of a basket. The carrier may be provided with one or more apertures for the passage of fluid (preferably liquid) therethrough.

The method may further comprise providing one or more carrier supports for supporting one or more carriers. The carrier support may be arranged for movement by the means for moving the article into the container containing the ultrasound-transmissive fluid through the inlet or the means for moving the article between the container containing the ultrasound-transmissive fluid and the second container. It is preferred that the carrier support is provided with a mounting portion for mounting the carrier support on the means for moving the article into the container containing the ultrasound-transmissive fluid through the inlet or the means for moving the articles between the container containing the ultrasound-transmissive fluid and the second container. It is further preferred that the mounting portion is for engaging with a portion of a endless loop (such as the teeth or aperture of a rack) so that movement of the endless loop causes movement of the carrier support. In this case, the carrier support may be mounted on the rack of a rack-and-pinion.

Alternatively, the mounting portion may be for engaging with the teeth of a pinion so that movement of the pinion causes movement of the carrier support. In this case, the carrier support acts as the rack of a rack-and-pinion.

The method may further comprise providing a degasser for decreasing the amount of gas dissolved in a liquid. The container containing the ultrasound-transmissive fluid may be in fluid communication with the degasser so that fluid from the container containing the ultrasound-transmissive fluid may be delivered to the degasser for treatment. The ( container containing the ultrasound-transmissive fluid may be further in fluid communication with the degasser such that degassed liquid may be delivered to the container containing the ultrasound-transmissive fluid.

At least one of the container containing the ultrasound-transmissive fluid, the second container and the third container (if present) may be in fluid communication with a filter for removing contaminants from a liquid. It is preferred that the filter is suitable for removing particulate contaminants from a liquid. The at least one of the container containing the ultrasound-transmissive fluid, the second container and the third container may be in fluid communication with the filter such that fluid may be delivered from the respective container to the filter for treatment. The respective container may further be in fluid communication with the filter so that filtered fluid may be delivered to the respective container.

The method may further comprise providing a storage vessel for storing liquid. The storage vessel may be in fluid communication with one or more of the container containing the ultrasound-transmissive fluid, second container and third container so that fluid (such as ultransound-transmissive fluid) may be transferred between the storage vessel and the respective container. The storage vessel may, in use, be located below the respective container so that liquid is transferable from the respective container to the storage vessel by gravity. (

The storage vessel may be in fluid communication with the degasser so that fluid is transferable to the degasser for treatment, preferably without the fluid passing through or into any one of the container containing the ultrasound-transmissive fluid, or the second or third containers. It is further preferred that the storage vessel is in fluid communication with the degasser so that fluid is transferable from the degasser to the storage vessel after treatment, preferably without the fluid passing through or into the container containing the ultrasound-transmissive fluid, or the second or third containers.

The storage vessel may be in fluid communication with the filter so that fluid is transferable to the filter for treatment, preferably without the fluid passing through or into the container containing the ultrasound-transmissive fluid or the second or third containers. it is further preferred that the storage vessel is in fluid communication with the filter so that fluid is transferable from the filter to the storage vessel after treatment, preferably without the fluid passing through or into the container containing the ultrasound-transmissive fluid, or the second or third containers.

The method may further comprise providing a means for decreasing pressure in at least one of the container containing the ultrasound-transmissive fluid or the second or third containers, such as a vacuum pump. The apparatus may be operable so that operation of the means for decreasing pressure causes flow of liquid from the storage

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vessel into the container containing the ultrasound-transmissive fluid, or the second or third containers.

It is preferred that the method comprises providing a plurality of articles to be cleaned in step (i) It is preferred that in step (ii) at least part of each of the plurality of articles is in intimate contact with the ultrasound-transmissive fluid.

It is further preferred that any references above with respect to the apparatus of the first and second aspects of the invention and the method of the third aspect of the invention to "an article" or "the article" be taken to include "a plurality of articles" and "the plurality of articles" respectively.

It is further preferred that step (i) comprises grouping a plurality of articles together to form a group. In step (ii) it is preferred that at least part of each of the articles in the group is in intimate contact with the ultrasound-transmissive fluid.

It is preferred that the method comprises providing more than one group, each group comprising a plurality of articles.

It is further preferred that any references above with respect to the apparatus of the first and second aspects of the invention and the method of the third aspect of the invention to "an article" or "the article" be taken to include "a group of articles" or "the group of articles".

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The method of the third aspect of the present invention may comprise providing an apparatus in accordance with the first or second aspects of the present invention.

The invention will now be described by way of example only with reference to the following figures of which: Figure 1 is a schematic representation of an embodiment of an apparatus in accordance with the first aspect of the present invention; Figure 2 is a plan view of the apparatus of Figure 1; Figure 3 is an end-on view of part of the apparatus of Figures 1 and 2; Figure 4a is a plan view of a carrier support used in the apparatus of Figure 1; Figure 4b is a side view of the carrier support shown in Figure 4a; and Figure 5 is a schematic cross-sectional view through an example of an embodiment of an apparatus in accordance with the second aspect of the present invention.

Figure 1 is a schematic representation of an embodiment of an apparatus in accordance with the first aspect of the present invention. The apparatus is denoted generally by reference numeral 1 and comprises a container 2 for holding a fluid transinissive to ultrasonic waves, the container being provided with an inlet 13 for the introduction into the container of articles to be cleaned and an outlet 14 for the removal from the container of articles which have been cleaned, the outlet being spaced from the inlet. The

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apparatus further comprises a means 15 for generating ultrasonic waves in a fluid provided in the container.

An ultrasound-transmissive fluid (not shown), in this case a solution of detergent in water, is provided in the container 2. The container is provided with a heater (not shown) for heating the fluid in the container. Heating of the container is desired because the cleaning ability of the apparatus depends markedly on temperature as is generally known to those skilled in the art. The optimal operating temperature will depend, inter alia, on the item to be cleaned and on the properties of the ultrasound-transmissive fluid. The means 15 for generating ultrasonic waves is an ultrasonic transducer. Examples of such transducers are supplied by APC International Limited (Duck Run, Mackeyville, PA-17750, USA) . The transducer may operate at a fixed frequency (such as 28KHz) or may be "tunable" to one of a number of different frequencies. The transducer 15 is powered by a generator (not shown), such as that supplied by APC International Limited (model 90-4OXX) A flow pump 12 is disposed in the ultrasound-transmissive fluid. The flow pump 12 causes fluid to flow around the container and also to pass to a decontamination filter 8 located outside the container 2. The decontamination filter 8 removes particulate contaminants from the ultrasound-transmissive fluid. Such particulate contaminants may be found in the ultrasound-transmissive fluid, particularly if the articles to be cleaned are filter elements which have been used to remove particulate and other contaminants from fluids, such as fuel or hydraulic fluid. Fluid which has

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passed through the decontamination filter 8 may be returned directly to the container 2 or may pass through a degasser 9 prior to being returned to the container 2. The degasser 9 is provided with a vacuum pump (not shown) which assists in removing air and other dissolved gases from the ultrasound-transmissive fluid. It has been found that the presence of dissolved gas inhibits the cavitation process which is thought to assist greatly in cleaning.

The apparatus 1 is provided with a storage vessel 3. The container 2 is in communication with the storage vessel 3 so that fluid may be transferred between the container 2 and the storage vessel 3. A valve 7 is provided to control flow between the container 2 and the storage vessel 3. The storage vessel 3 is located below the container 2 so that fluid may flow under the influence of gravity from the container 2 to the storage vessel 3. A vacuum pump 4 and valve 6 are provided which, in use, enable the pressure in the container 2 to be reduced. A reduction in pressure in the container 2 is used to transfer ultrasound-transmissive fluid from the storage vessel 3 into the container 2. The container is provided with an atmospheric pressure inlet 5 and valve 7 operable to allow pressure in the container to be returned to atmospheric pressure onceultrasound-transmissive fluid has been reintroduced into the container 2. A fluid level sensor (not shown) is used to control the amount of ultrasound-transmissive fluid in the container 2.

The storage vessel 3 is provided with a storage vessel outlet (not labelled) and a valve 10 for controlling flow of fluid from the storage vessel 3 to the decontamination

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filter 8. The storage vessel 3 is further provided with an inlet (not labelled) and a valve 11 for controlling flow of filtered fluid into the storage vessel 3.

Certain features of the apparatus 1 have been omitted from Figure 1 for the purpose of clarity. For example, the apparatus 1 further comprises a mechanism for introducing articles into the container 2, this not being shown in Figure 1. The mechanism for introducing articles into the container 2 is now described with reference to Figures 2, 3, 4a and 4b.

The apparatus comprises carriers (five of which are labelled 31, 32, 33, 34, 35) for carrying articles to be cleaned. The carriers are in the form of baskets. Each of the carriers is located, in use, in a carrier receiving aperture (not shown) provided in a carrier support 24. The apparatus 1 further comprises a means 20a for moving the articles to be cleaned through the inlet 13 and into the container 2. The means 20a for moving the articles to be cleaned through the inlet into the container comprises two rotatable toothed wheels 20, 21.

The teeth provided on the wheels engage with laterally extending bars (two of which are shown as 22, 23) provided on the carrier support 24. The bars 22, 23 fit in the space between adjacent teeth of the wheels 20, 21 and are engaged by the teeth so that turning of the wheels 20, 21 causes movement of the carrier support 24. The carrier support 24 is provided with a set of such laterally-extending bars so that the toothed wheels and carrier support act like a rack and pinion, the wheels proving a pinion and the carrier support providing a rack.

The apparatus 1 further comprises a means 25 for moving the articles through the outlet 14 and out of the container 2, is shown in Figure 2. The means 25 for moving the articles through the outlet is a very similar arrangement to that which is used for the means for moving articles through the inlet into the container i.e. two toothed wheels which act as a pinion.

The operation of the apparatus 1 is now described with reference to the Figures. Groups of articles are placed in carriers 41, 42, 43, 44, 45 upstream of container 2. The carriers 41, 42, 43, 44, 45 have been placed in carrier-receiving apertures (not shown) in a carrier support 46. A carrier support 24, with carriers 31, 32, 33, 34, 35 are in the container 2. A carrier support 56 is located downstream of the container, the carrier support 56 provided with carriers 51, 52, 53, 54, 55 that have already passed through the container and already been washed. The apparatus is arranged to move one carrier support containing cleaned articles out of the container and one carrier support containing articles yet to be cleaned into the container.

A cleaning cycle will now be described, starting with introduction of the dirty articles into the container 2. We shall assume that articles carried by carrier support 24 have just been cleaned but are currently in the container 2 and that articles carried by carrier support 46 are about to be cleaned, but are currently upstream of the container 2.

Before articles are introduced into the container 2, sufficient ultrasound-transmissive fluid is removed from the

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container 2 by transfer to the storage vessel 3 so that the level of fluid in the container 2 is below the lowest part of the inlet 13 and outlet 14. Transfer from the container 2 to the storage vessel 3 is by gravity. The inlet 13 and outlet 14 are then opened by moving respective doors (not shown) so that carrier support 46 and carrier support 24 may be moved into and out of the container 2 respectively. The teeth of the means 25 for moving the articles out of the container engages with the laterally-extending bars at the downstream end of the carrier support 24 50 that the carrier support 24 may be moved out of the container 2 through the outlet. The teeth of the means 20a for moving the articles into the container engages with the laterally-extending bars at the downstream end of the carrier support 46 so that the carrier support 46 may be moved into the container 2 through the inlet.

Once the carrier support 46 is in the container, the inlet 13 and outlet 14 are closed so as to form liquid-tight seals, inhibiting egress of ultrasound-transmissive fluid from the container. A decrease in pressure is created in the container by vacuum pump 4. Valve 7 is opened so that fluid stored in storage vessel 3 is transferred into the container 2. A fluid level sensor (not shown) is provided to control the depth of fluid in the container. Once sufficient ultrasound-transmissive fluid has been introduced into the container, valve 7 is closed, as is valve 6. Valve 19 is then opened to allow the container 2 to return to atmospheric pressure. (

The ultrasound-transmissive fluid in the container 2 is then heated to the desired temperature. Once the desired temperature is reached, the ultrasound transducer 15 is activated, thereby instigating ultrasonic cleaning. Flow pump 12 is activated during the cleaning process in order to generate flow in the container 2 and to cause fluid to be transmitted to decontaminating filter 8. The filtered fluid may optionally then be degassed prior to being returned to the container 2.

Once cleaning is complete, ultrasound-transmissive fluid is transferred under the action of gravity from container 2 to the storage vessel 3. Sufficient ultrasound-transmissive fluid is transferred from the container 2 so that fluid level in the container 2 is lower than the lowest part of the inlet 13 and outlet 14. Ultrasourid-transmissive fluid stored in the storage vessel may be filtered and degassed as previously described.

Once sufficient ultrasound-transmissive fluid has been removed from the container, the carrier support 46 may be removed through the outlet by the means 25 for removing the articles out of the container through the outlet.

An example of an apparatus in accordance with the second aspect of the present invention is shown in Figure 5. The apparatus (shown generally by reference numeral 101) comprises a first container 102 for holding a fluid 103 transmissive to ultrasound waves and a means (not shown) for generating ultrasonic waves in the fluid provided in the

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first container. The fluid 103 may be, for example, one of the Ultraclean fluids provided by Ultrawave (Cardiff, UK) The apparatus 101 is operable to lower any articles to be cleaned towards the first container 102 and/or raise the first container 102 towards the articles from a first, non-cleaning position to a second, cleaning position in which the articles are at least partially located in the first container. The operation of the apparatus is described in detail below. The apparatus 101 is provided with a second container 104 which holds a cleaning fluid 105. The second container 104 is upstream of the first container 102 and is used to remove gross contaminants from the articles to be cleaned because those articles are transferred to the first container 102. The apparatus is further provided with a third container 106 containing a rinsing liquid 107, the third container 106 being located downstream of the first container 102 so that articles which have been submitted to ultrasound cleaning in the first container 102 may be rinsed in third container 106.

The means for generating ultrasonic waves is substantially the same as that described above in relation to the apparatus of Figures 1 to 4.

Articles are placed in carriers in the form of baskets (five of which are labelled llOa, ilOb, hOc, hOd, hOe) . The carriers are grouped together and supported by carrier supports lila, hllb, hlic, hid, lhle, hhif. The carriers and carrier supports are essentially as described above with reference to the apparatus of Figures 1 to 4. (

Contrary to the apparatus of Figures 1 to 4, in the apparatus of Figure 5 the carrier supports themselves do not form the rack of a rack-and-pinion. In the apparatus of Figure 5, the carrier supports are mounted on a rack 112, the rack 112 forming an endless ioop 115. Formations provided on the carrier supports engage with corresponding formations provided on the rack 112. The rack 112 is part of a rack and pinion system for moving the articles. The pinion is provided by two driven, toothed wheels 113, 114, one provided at each end of the ioop. Rotation of the wheels 113, 114 drives the rack 112 which in turn causes movement of the carrier supports, carriers and articles.

The apparatus is provided with an arrangement (shown generally by reference numeral 116) for moving the carrier supports (and therefore articles) up and down, and therefore into and out of the first, second and third containers. The arrangement 116 comprises four stations 117a, 117b, 117c, 117d which assist in lowering the carrier supports into (and raising them out of) the first, second and third containers.

Each of stations 117a, 117b, 117c, 117d comprises an actuator in the form of a hydraulic piston (not labelled) and a compression spring 118a, 118b, llBc, 118d.

Central stations 117b, 117c are each provided with a set of two rollers. Rollers 119b, 119b' form one set and rollers 119c, 119c' form another set. The two rollers in each set are mutually spaced so as to permit passage therebetween of the rack 112. The spring 118b, 118c urges the respective roller set downwards. Each piston is operable to work against the force of the spring 118b, 118c and move the respective roller set upwards. Figure 5 shows the carrier supports and articles located within the respective containers. If it is desired to move the articles, pistons are actuated to compress the springs llBb, 118c, thus moving the respective roller sets upwards, away from the containers. Because the rack 112 passes between the rollers of a respective roller set, the rack 112 is also moved upwards, away from the containers.

Outlying stations ll7a, 117d are also each provided with a roller ll9a, ll9d associated with the respective hydraulic piston and the spring. The spring liSa, llBd urges the respective roller 119a, 119d downwards. Each piston is operable to work against the force of the spring 118a, 118d and move the roller 119a, 119d upwards. When it is desired to move the articles between containers, pistons are actuated to compress the springs 118a, 118d thus moving the rollers upwards, away from the containers. This movement of the outlying rollers 119a, 119d facilitates the movement of the articles between adjacent containers.

Once the carrier supports are clear from the containers, the pinion wheels 113, 114 drive the rack 112, thus moving the carrier supports and articles into the next desired position. The direction of movement is shown by the horizontal arrows in Figure 5. Once a carrier support is in the next desired position, the stations 117a, 117b, 117c, 117d are operated to move the carrier supports downwards so that they are moved into the desired container.

Lower rollers 120, 121 are provided to control the path of rack 112.

The apparatus 101 is further provided with a loading station (not shown) located upstream of the second container 104 and downstream of wheel 113. The location of the loading station is indicated schematically by reference numeral 108. At the loading station, operatives place the articles to be cleaned in the carriers.

The apparatus 101 is further provided with an unloading station (not shown) located downstream of the third container 106 and upstream of wheel 114. The location of the unloading station is indicated schematically by reference numeral 109.At the unloading station, operatives remove the cleaned articles from the carriers.

Those skilled in the art will realise that it would be possible to use more than one means for generating ultrasound. For example, it may be desirable to have three or four ultrasound transducers immersed in the ultrasound-transmissive fluid. Furthermore, the source of ultrasound may be located within the container of may be located external to the container, but driving a diaphragm or the like which forms part of the container.

The methods described above are presented in relation to the use of embodiments of an apparatus in accordance with the first and second aspects of the present invention. Those skilled in the art will realise that the method of the third aspect of the present invention is not limited to methods performed using embodiments of the apparatus of the first and second aspects of the present invention.

Claims

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Claims 1. A method of cleaning a filter element, each filter element comprising a portion which may be used to remove contaminants from a fluid, the method comprising: (U providing a filter element (ii) providing a ultrasound-transmissive fluid which is transmissive to ultrasonic waves, at least part of the filter element being in intimate contact with the ultrasound-transmissive fluid (iii) passing ultrasonic waves through the ultrasound-transmissive fluid such that at least part of the filter element is cleaned
2. A method according to claim 2 wherein the portion which may be used to remove contaminants from a fluid comprises plastics material.
3. A method according to claim 1 or claim 2 wherein step (iii) comprises passing a first set of ultrasonic waves through the ultrasound-transmissive fluid, the first set of waves having a characteristic frequency or characteristic range of frequencies and then passing a second set of ultrasonic waves through the ultrasound-transmissive fluid, the second set of waves having a different characteristic frequency or different characteristic range of frequencies from the first set of waves.
4. A method according to any preceding claim, the method comprising at least part of the filter element being in intimate contact with two different ultrasound-transmissive

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fluids, and passing ultrasonic waves through those ultrasound-transmissive fluids.
5. A method according to any preceding claim comprising grouping a plurality of filter elements together to form a group and then cleaning the group of articles.
6. A method according to any preceding claim comprising degassing the ultrasound-transmissive fluid.
7. A method according to any preceding claim comprising providing a container in which the ultrasound-transmissive fluid may be contained during the passage therethrough of ultrasonic waves.
8. A method according to claim 7 wherein the container comprises an inlet for the introduction into the container of the filter element to be cleaned and an outlet for the removal from the container of the filter element which has been cleaned.
9. A method according to claim 8 comprising passing the filter element through the inlet into the container.
10. A method according to claim 9 wherein the filter element is passed through the inlet into the container prior to introducing ultrasound-transmissive fluid into the container.

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11. A method according to any one of claims 8 to 10 comprising passing the filter element through the outlet out of the container.
12. A method according to claim 11 wherein the ultrasound-transrnissive fluid is removed from the container before the filter element is passed through the outlet out of the container.
13. A method according to any one of claims 7 to 12 comprising introducing the ultrasound-transmissive fluid into the container.
14. A method according to any one of claims 7 to 13 comprising removing the ultrasound-transmissive fluid from the container and transferring the ultrasound-transmissive fluid to a storage vessel.
15. A method according to claim 14 wherein the ultrasound-transmissive fluid is transferred to the storage vessel by the action of gravity.
16. A method according to claim 14 or claim 15 comprising transferring the ultrasound-transmissive fluid from the storage vessel to the container.
17. A method according to claim 16 wherein ultrasound-transmissive fluid is transferred from the storage vessel to the container by reducing the pressure in the container.
18. A method according to any one of claims 7 to 17 comprising providing a means for moving the filter element into the container and a means for moving the filter element out of the cleaning container through the outlet.
19. A method according to any one of claims 7 to 18 comprising providing one or more carriers for carrying the filter element into and out of the container, the carrier being provided with one or more apertures for the passage of liquid therethrough.
20. A method according to claim 19 comprising providing one or more carrier supports for supporting one or more carriers.
21. A method according to any preceding claim comprising removing contaminants from the ultrasound-transmissive fluid.
22. An apparatus for cleaning articles, the apparatus comprising: (i) a first container for holding a fluid transmissive to ultrasound waves; (ii) means for generating ultrasonic waves in a fluid provided in the first container; (iii) a second container for holding a fluid; and (iv) a means for moving the articles between the first container and the second container, the apparatus being operable to lower the articles towards the first container and/or raise the first container towards the articles from a first, non-cleaning position to a second, cleaning position in which the articles are at least partially located in the first container
23. An apparatus for cleaning articles, the apparatus comprising: (i) a container for holding a fluid transmissive to ultrasonic waves, the container being provided with an inlet for the introduction into the container of articles to be cleaned and an outlet for the removal from the container of articles which have been cleaned, the outlet being spaced from the inlet and (ii) means for generating ultrasonic waves in a fluid provided in the container.
24. A method of cleaning an article, the method comprising: (i) providing an article and a container for holding an ultrasound-transmissive fluid, the container being provided with an inlet for the introduction into the container of articles to be cleaned and an outlet for the removal from the container of articles which have been cleaned, the outlet being spaced from the inlet (ii) providing a ultrasound-transmissive fluid which is transmissive to ultrasonic waves, at least part of the article being in intimate contact with the ultrasound-transmissive fluid and (iii) passing ultrasonic waves through the ultrasound-transmissive fluid such that at least part of the article is cleaned.