WO2006040525A2

WO2006040525A2 - Cleaning apparatus and method

Info

Publication number: WO2006040525A2
Application number: PCT/GB2005/003876
Authority: WO
Inventors: David Jones
Original assignee: Alphasonics Limited
Priority date: 2004-10-11
Filing date: 2005-10-10
Publication date: 2006-04-20
Also published as: WO2006040525A3; GB0422658D0

Abstract

A cleaning apparatus comprising an ultrasonic working tank (10) containing solvent (12) through which contaminated items are passed (14). Contaminated solvent (12) is removed for cleaning using a flocculation tank (30) and filter (44). Additives may be added to the solvent (12) to modify its properties. The cleaned solvent (12) is then re-used to clean further contaminated items. The invention aims to reduce the amount of solvent (12) used in a cleaning process in addition to reducing the volume harmful contaminants released into the environment.

Description

Title: Cleaning apparatus and method

Description:

The present invention relates to a cleaning apparatus and method, and in particular to a cleaning apparatus and method suitable for use in the cleaning of printing or painting equipment.

Printing equipment, such as flexographic print rollers, ink trays, wiper blades etc. tend to become contaminated with ink or pigment during use. When one print run is stopped, and before starting the next, it is generally advisable to clean the equipment to prevent permanent contamination and clogging etc, in addition to preventing colour transfer (e.g. magenta ink from one print run being transferred to the cyan roller of another run).

Normally, the equipment is cleaned by rinsing it with a suitable solvent, e.g. water for water-based inks. The solvent, of course, becomes contaminated with ink and quickly becomes discoloured. This can lead to ineffective cleaning and/or ink transfer between components. It is therefore necessary to have a continuous supply of relatively clean solvent if an effective cleaning regime is to be maintained. However, continuous purchase of clean supply of solvent can be expensive. More importantly however, the disposal of contaminated solvent is costly and environmentally harmful.

It is therefore an object of the invention to attempt to overcome one or more of the above problems. Specifically, the invention aims to provide an improved cleaning system and/or method and/or to provide an apparatus/method for reclaiming, recycling and/or reusing contaminated solvent with a view to minimising wastage and environment harm.

Accordingly, a first aspect of the invention provides a cleaning apparatus comprising; a working tank having one or more ultrasonic transducers arranged to impart ultrasonic vibration energy, either directly or indirectly to contaminated items as they pass at least partially through working tank, the working tank containing a solvent, in use, through which the contaminated items are at least partially passed; wherein the cleaning apparatus further comprises a solvent cleaning means for substantially removing contaminant from the solvent. The working tank of the invention is capable of retaining a quantity (e.g. 100 litres) of solvent. The working tank may be enclosed or open topped, but will be provided with at least one aperture such that the contaminated parts can be introduced into and removed therefrom as desired. Additionally, the working tank preferably has means (e.g. inlet and outlet apertures) through which clean solvent can be introduced and contaminated solvent removed. The inlet and outlet apertures may be the same aperture.

The solvent can be either organic or inorganic depending on the application, e.g. for use in the removal of water-based ink from printing press parts, water may be a preferred solvent. A surfactant may be added to the solvent to improve the cleaning properties thereof. Because ultrasonics are used in the cleaning process, a low or anti- foaming surfactant may be preferred. Additionally or alternatively, anti-foaming agents, viscosity and acidity modifiers may be added to the solvent.

The ultrasonic transducers may be fitted to the interior of the working tank to impart ultrasonic energy to the solvent. Preferably, however, the one or more ultrasonic transducer is fitted to the exterior of the tank to indirectly apply ultrasonic energy to the contaminated items via the tank wall and solvent.

The one or more ultrasonic transducer can be of any suitable type. Preferably, the one or more ultrasonic transducer comprises a piezoelectric stack (e.g. lead- zirconate-titanate or barium-titanate) sandwiched between a pair of conducting electrodes. The one or more piezoelectric transducer is preferably actuated by the application of an alternating voltage to the electrodes. The one or more ultrasonic transducer may be secured in-situ by any suitable means, e.g. rivets, welds, screws, clips or adhesive, although it/they are preferably removable for servicing, repair and/or replacement purposes.

The contaminated items may be introduced into and removed from the working tank by any suitable means, e.g. by hand. Preferably, however, the introduction of contaminated items and the removal of cleaned items is automated. In a preferred embodiment of the invention, a conveyor system is used to transport items into and out of the working tank. In a most preferred embodiment of the invention, the conveyor comprises a slung-basket system whereby the baskets are dipped into, transported through and then removed from the solvent in a continuous manner. Where a conveyor is used, it is preferably user-overridable to facilitate loading and unloading of the baskets. The working tank may be provided with a sensor for sensing the contamination level of the solvent in use. The sensor may be of any suitable type, e.g. a conductivity sensor. Alternative sensors may be optical (e.g. opacity), chemical (e.g. pH) or mechanical (e.g. viscosity) sensors. The solvent cleaning means can be of any type capable of removing at least some of the contaminant from the used solvent. Preferably, the working tank and solvent cleaning means are provided in a loop such that contaminated solvent is circulated through the cleaning means, back into the working tank for re-use. The solvent cleaning means may comprise; a flocculation tank; a filter; and a holding tank, wherein the flocculation tank comprises a stirrer for agitating the solvent and flocculant dispensing means for dispensing flocculant into the solvent and sensor for measuring a property of the solvent.

The flocculating tank comprises a stirrer, which may take any suitable form, for example a motorised paddle or a magnetic bar actuated remotely by another rotating magnet. The walls of the flocculating tank may be provided with vanes and/or stators to improve the agitation of the solvent. Additionally or alternatively, the walls of the tank may be adapted to move, either rotationally or axially to stir or assist the stirring of the solvent. The flocculant dispensing means is preferably adapted dispense flocculant into the solvent until the sensor senses a change or predetermined value of a property of the solvent, whereupon the flocculant dispensing means stops dispensing flocculant into the solvent. The flocculant dispensing means may comprise a hopper-fed tube with a shut of valve, where the flocculant is a powder material. The flocculant dispensing means may further comprise a sieving means to either remove large clumps of flocculant (e.g. where it has got wet during storage) or to more finely disperse the flocculant.

The solvent property sensed by the sensor can be its conductivity. Where the sensor is a conductivity sensor, the flocculant dispensing means is preferably adapted to stop dispensing flocculant into the solvent when the conductivity of the solvent rises to a predetermined value.

Alternative sensors may be optical (e.g. opacity), chemical (e.g. pH) or mechanical (e.g. viscosity) sensors. The flocculation tank is preferably provided with an outlet aperture for draining it as and when desired. The outlet aperture, where provided, is preferably fitted with a shut-off valve.

The filter can be of any suitable type. In a possible embodiment of the invention, the filter is a cloth-lined basket into which flocculated solvent can be dropped. Any other suitable filter could be used, e.g. a gauze or semi-permeable membrane. The filter is preferably chosen to separate the liquid solvent from the flocculated contaminants. The decontaminated liquid solvent is collected in the holding tank. When the filter becomes clogged or the filter basket, where provided becomes full, it can be removed/cleaned/replaced. The holding tank may have a heating means associated therewith, e.g. an electric heating element to maintain the cleaned solvent at a desired temperature.

Where a heating means is provided, it is preferably thermostatically controlled. A sensor may also be provided within the holding tank for sensing a property of the solvent, e.g. its temperature, acidity, opacity, viscosity etc. Provision is preferably made in the holding tank for the addition of additives, e.g. bleaches, surfactants, acidity modifiers etc. In a particular example, chlorine bleach tablets can be added to the holding tank to break up micelles of magenta ink that can cause a slight discolouration of the cleaned water. The operation of the invention is preferably automated and/or computer controlled, although manual overrides may be provided to enable manual intervention with some or all aspects of the operation of the invention.

A second aspect of the invention provides a solvent cleaning means for substantially removing contaminant from a solvent comprising; a flocculation tank; a filter; and a holding tank, wherein the flocculation tank comprises a stirrer for agitating the solvent and flocculant dispensing means for dispensing flocculant into the solvent and sensor for measuring a property of the solvent.

Where a heating means is provided, it is preferably thermostatically controlled. A sensor may also be provided within the holding tank for sensing a property of the solvent, e.g. its temperature, acidity, opacity, viscosity etc. Provision is preferably made in the holding tank for the addition of additives, e.g. bleaches, surfactants, acidity modifiers etc. In a particular example, chlorine bleach tablets can be added to the holding tank to break up micelles of magenta ink that can cause a slight discolouration of the cleaned water. The invention is preferably adapted for use in conjunction with a cleaning apparatus, e.g. for printing equipment, such that clean solvent can be used to clean contaminated items, and once contaminated, re-used after having been cleaned.

In a preferred embodiment of the invention, the solvent cleaning means is used in conjunction with cleaning apparatus comprising; a working tank having one or more ultrasonic transducers arranged to impart ultrasonic vibration energy, either directly or indirectly to contaminated items as they pass at least partially through working tank, the working tank containing a solvent, in use, through which the contaminated items are at least partially passed. The working tank of the invention is capable of retaining a quantity (e.g. 100 litres) of solvent. The working tank may be enclosed or open topped, but will be provided with at least one aperture such that the contaminated parts can be introduced into and removed therefrom as desired. Additionally, the working tank preferably has means (e.g. inlet and outlet apertures) through which clean solvent can be introduced and contaminated solvent removed. The inlet and outlet apertures may be the same aperture.

The contaminated items may be introduced into and removed from the working tank by any suitable means, e.g. by hand. Preferably, however, the introduction of contaminated items and the removal of cleaned items is automated. In a preferred embodiment of the invention, a conveyor system is used to transport items into and out of the working tank. In a most preferred embodiment of the invention, the conveyor comprises a slung-basket system whereby the baskets are dipped into, transported through and then removed from the solvent in a continuous manner. Where a conveyor is used, it is preferably user-overridable to facilitate loading and unloading of the baskets. The working tank may be provided with a sensor for sensing the contamination level of the solvent in use. The sensor may be of any suitable type, e.g. a conductivity sensor. Alternative sensors may be optical (e.g. opacity), chemical (e.g. pH) or mechanical (e.g. viscosity) sensors. The solvent cleaning means can be of any type capable of removing at least some of the contaminant from the used solvent. Preferably, the working tank and solvent cleaning means are provided in a loop such that contaminated solvent is circulated through the cleaning means, back into the working tank for re-use. The operation of the invention is preferably automated and/or computer controlled, although manual overrides may be provided to enable manual intervention with some or all aspects of the operation of the invention.

A third aspect of the invention provides a cleaning apparatus comprising; a working tank having one or more ultrasonic transducers arranged to impart ultrasonic vibration energy, either directly or indirectly to contaminated items as they pass at least partially through working tank, the working tank containing a solvent, in use, through which the contaminated items are at least partially passed; wherein the cleaning apparatus further comprises a solvent cleaning means for substantially removing contaminant from the solvent, the solvent cleaning means comprising; a flocculation tank; a filter; and a holding tank, wherein the flocculation tank comprises a stirrer for agitating the solvent and flocculant dispensing means for dispensing flocculant into the solvent and sensor for measuring a property of the solvent.

A fourth aspect of the invention provides a method of cleaning comprising the steps, in any order, of; at least partially passing contaminated items through a working tank containing solvent; using one or more ultrasonic transducers, imparting ultrasonic vibration energy, either directly or indirectly to the contaminated items as they pass at least partially through the working tank; and cleaning the solvent using a solvent cleaning means to substantially remove contaminant from the solvent.

A fifth aspect of the invention provides a method of substantially removing contaminant from a solvent comprising the steps of; at least partially filing a flocculation tank with contaminated solvent; agitating the contaminated solvent using a stirrer; dispensing a quantity of flocculant into the contaminated solvent; sensing a property of the contaminated solvent using a sensor; stopping dispensing of the flocculant when the sensor senses a predetermined condition; and then emptying the flocculation tank into a holding tank through a filter.

A preferred embodiment of the invention shall now be described, by way of example only, with reference to the accompanying drawings, in which;

Figure 1 shows a schematic of the first and fourth aspects of the invention; Figure 2 shows a schematic of the second and fifth aspects of the invention;

Figure 3 shows a schematic of the third aspect the invention;

Figure 4 shows a schematic of the loading and transport system of the invention; and

Figure 5 is a perspective view of a preferred embodiment of the invention. Referring now to Figure 1, an apparatus 5 is shown having a working tank 10 containing 100 litres of water 12. A loading and transport system 14 is disposed above the working tank 10 such that contaminated items (not shown) can be passed through the water 12 in baskets 16. Ultrasonic transducers 18 are fitted to the underside of the working tank 10, which assist the cleaning of the contaminated items by indirectly imparting ultrasonic vibrations to the water 12.

The working tank has a conductivity sensor 20 therein that senses the conductivity of the water 12. As the water 12 becomes more contaminated, its conductivity rises. The sensor 20 detects this rise and triggers an alarm signal when the water becomes too contaminated to clean effectively. When the alarm signal is raised, a valve 22 is opened thereby draining the working tank 10 through a pipe 24. A pump 24 is fitted in-line with the pipe 24 to assist in removing the water 12 from the working tank 10. A solvent cleaning means 35 is also provided for removing contaminants from the water 12. A second pump 28 then pumps the cleaned water back into the working tank 10.

The cleaning cycle, i.e. draining the water 12, cleaning the water 12 and reintroducing it into the working tank 10 can be initiated manually (i.e. without recourse to the sensor 20). In that respect, the sensor 20 can serve as an additional automation device thereby preventing the apparatus operation outside of predetermined process parameters (i.e. when the water 12 is too contaminated).

Figure 2 shows a solvent cleaning means 35 comprising a flocculation tank 30 containing a quantity of water 12. The water 12 is stirred using a motor 32 driven paddle 34. A conductivity sensor 36 is also is also disposed within the flocculation tank 30 in contact with the water 12.

A flocculant dispensing means 38 is also provided, as is a flocculation tank empting valve 40. A basket 42 is located below the flocculation tank-emptying valve 40. The basket 42 is lined with cloth 44, which serves to separate solid matter from the water 12 as the water 12 passes therethrough.

A holding tank 46 is also provided for collecting the filtered water 12. The holding tank 46 can hold 300 litres of water 12 and is fitted with a thermostatically regulated heating element 48 for maintaining the water 12 at a relatively constant 45⁰C. An acidity sensor 50 is also provided for sensing the acidity of the water 12.

The operation of the solvent cleaning means 35 is as follows:

Contaminated water 12 is introduced into the flocculation tank 30 via an inlet pipe 24. The water 12 is stirred using the stirrer 34 and a quantity of flocculant is added to the water 12 using the flocculant dispensing means 38. The conductivity of the water 12 is monitored throughout using the sensor 36. As the contaminants flocculate, then conductivity of the water 12 changes, which change is detected by the sensor 36. When a pre-determined conductivity level is reached (indicative of complete flocculation), no more flocculant is added. The water 12 is then stirred for a further 60 seconds or so to ensure complete flocculation. The motor 32 is then switched off, and the valve 40 opened. The water 12 falls through the filter basket 42 into the holding tank 46. Flocculated solid material is caught by the filter cloth 44, leaving de-contaminated water in the holding tank 46. In certain cases, a small amount of discolouration can occur to the water 12 in the holding tank 46. This problem is overcome by adding a bleach tablet to the water 12, which serves to break-up any micelles that may be present. The concentration of bleach can me monitored using the acidity sensor 50. Clean water 12 can be extracted from the holding tank 46 using an outlet pipe 52.

Figure 3 shows the cleaning apparatus and solvent cleaning means 35 used in conjunction with one another to form a complete cleaning apparatus. Because the contaminated water 12 can be circulated (i.e. cleaned and re-used), the apparatus can be used for extended periods of time. Also, because the holding tank 46 can hold up 300 litres of water 12, there is normally more than an adequate supply of clean water 12 to use the apparatus continuously.

The apparatus simply needs periodic topping up with water 12 (as some is inevitably spilt or evaporates), replenishment with flocculant and the filter cloth 44 changing. The volume of solids collected by the filter cloth 44 is significantly less than the volume of contaminated water produced by cleaning, thereby reducing operation and waste disposal costs.

Figure 4 shows the transport and loading system 14 comprising a conveyor 52 wrapped around a pair of rollers 54. Support frame elements 56 are attached to the conveyor 52. Pivotally mounted on the support frame elements 56 are baskets that can be manually or automatically loaded with contaminated equipment (not shown) to be cleaned.

Finally, Figure 5 shows a perspective view of the invention, with component parts labelled as per Figure 1 to 3. Also shown in Figure 4 is a control circuit 58 for controlling the operation of the system, i.e. the valves, sensors, motors, pumps, heater etc.

Claims

Claims:

1. A cleaning apparatus comprising; a working tank having one or more ultrasonic transducers arranged to impart ultrasonic vibration energy, either directly or indirectly to contaminated items as they pass at least partially through working tank, the working tank containing a solvent, in use, through which the contaminated items are at least partially passed; wherein the cleaning apparatus further comprises a solvent cleaning means for substantially removing contaminant from the solvent.

2. A cleaning apparatus as claimed in claim 1, wherein the working tank has means through which clean solvent can be introduced and contaminated solvent removed.

3. A cleaning apparatus as claimed in claim 1 or claim 2, wherein the one or more ultrasonic transducers are fitted to the interior of the working tank to impart ultrasonic energy to the solvent.

4. A cleaning apparatus as claimed in claim 1 or claim 2, wherein the one or more ultrasonic transducer is fitted to the exterior of the tank to indirectly apply ultrasonic energy to the contaminated items via the tank wall and solvent.

5. A cleaning apparatus as claimed in any of claims 1 to 4, wherein the one or more ultrasonic transducer comprises a piezoelectric stack sandwiched between a pair of conducting electrodes.

6. A cleaning apparatus as claimed in any of claims 1 to 5, wherein contaminated items are introduced into and removed from the working tank by a conveyor system.

7. A cleaning apparatus as claimed in claim 6, wherein the conveyor system comprises a slung-basket system whereby the baskets are dipped into, transported through and then removed from the solvent in a continuous manner.

8. A cleaning apparatus as claimed in any of claims 1 to 7, wherein the working tank is provided with a sensor for sensing the contamination level of the solvent.

9. A cleaning apparatus as claimed in claim 8, wherein the sensor is any one of the group comprising; a conductivity sensor, an optical sensor, a chemical sensor and a mechanical sensor.

10. A cleaning apparatus as claimed in any of claims 1 to 9, wherein the working tank and solvent cleaning means are provided in a loop such that contaminated solvent is circulated through the cleaning means and back into the working tank for re¬ use.

11. A cleaning apparatus as claimed in nay of claims 1 to 10, wherein the solvent cleaning means comprises; a flocculation tank; a filter; and a holding tank, wherein the flocculation tank comprises a stirrer for agitating the solvent and flocculant dispensing means for dispensing flocculant into the solvent and sensor for measuring a property of the solvent.

12. A solvent cleaning means for substantially removing contaminant from a solvent comprising; a flocculation tank; a filter; and a holding tank, wherein the flocculation tank comprises a stirrer for agitating the solvent and flocculant dispensing means for dispensing flocculant into the solvent and sensor for measuring a property of the solvent.

13. A solvent cleaning means as claimed in claim 12, wherein the stirrer is a motorised paddle or a magnetic bar actuated remotely by a rotating magnet.

14. A solvent cleaning means as claimed in claim 12 or claim 13, wherein the walls of the flocculating tank are provided with vanes and/or stators to improve the agitation of the solvent.

15. A solvent cleaning means as claimed in any of claims 12 to 14, wherein the flocculant dispensing means is adapted dispense flocculant into the solvent until the sensor senses a change or predetermined value of a property of the solvent, whereupon the flocculant dispensing means stops dispensing flocculant into the solvent.

16. A solvent cleaning means as claimed in nay of claims 12 to 15, the flocculant dispensing means comprises a hopper-fed tube with a shut of valve.

17. A solvent cleaning means as claimed in any of claims 12 to 16, the flocculant dispensing means further comprises a sieving means to either remove large clumps of flocculant or to more finely disperse the flocculant.

18. A solvent cleaning means as claimed in any of claims 12 to 17, wherein the sensor is any one of the group comprising; an electrical sensor, an optical sensor, a chemical sensor and a mechanical sensor.

19. A solvent cleaning means as claimed in claim 18, wherein the sensor is a conductivity sensor.

20. A solvent cleaning means as claimed in claim 19, wherein the flocculant dispensing means is adapted to stop dispensing flocculant into the solvent when the conductivity of the solvent rises to a predetermined value.

21. A solvent cleaning means as claimed in any of claims 12 to 20, wherein the flocculation tank is provided with an outlet aperture and a shut-off valve for draining it as and when desired.

22. A solvent cleaning means as claimed in any of claims 12 to 21, wherein the filter comprises a cloth-lined basket.

23. A solvent cleaning means as claimed in any of claims 12 to 22, wherein the holding tank has a heating means associated therewith.

24. A solvent cleaning means as claimed in claim 23, wherein the heating means is thermostatically controlled.

25. A solvent cleaning means as claimed in any of claims 12 to 24, wherein the holding tank comprises a sensor for sensing a property of the solvent.

26. A solvent cleaning means as claimed in any of claims 12 to 25, wherein the flocculant dispensing means is adapted dispense flocculant into the solvent until the sensor senses a change or predetermined value of a property of the solvent, whereupon the flocculant dispensing means stops dispensing flocculant into the solvent.

27. A cleaning apparatus comprising; a working tank having one or more ultrasonic transducers arranged to impart ultrasonic vibration energy, either directly or indirectly to contaminated items as they pass at least partially through working tank, the working tank containing a solvent, in use, through which the contaminated items are at least partially passed; wherein the cleaning apparatus further comprises a solvent cleaning means for substantially removing contaminant from the solvent, the solvent cleaning means comprising; a flocculation tank; a filter; and a holding tank, wherein the flocculation tank comprises a stirrer for agitating the solvent and flocculant dispensing means for dispensing flocculant into the solvent and sensor for measuring a property of the solvent.

28. A method of cleaning comprising the steps, in any order, of; at least partially passing contaminated items through a working tank containing solvent; using one or more ultrasonic transducers, imparting ultrasonic vibration energy, either directly or indirectly to the contaminated items as they pass at least partially through the working tank; and cleaning the solvent using a solvent cleaning means to substantially remove contaminant from the solvent.

29. A method as claimed in claim 28, further comprising the step of adding a an additive to the solvent.

30. A method as claimed in claim 29, wherein the additive is any one or more of the group comprising; a surfactant, a low or anti-foaming surfactant, an anti-foaming agent, a viscosity modifier and an acidity modifier.

31. A method of substantially removing contaminant from a solvent comprising the steps of; at least partially filing a flocculation tank with contaminated solvent; agitating the contaminated solvent using a stirrer; dispensing a quantity of flocculant into the contaminated solvent; sensing a property of the contaminated solvent using a sensor; stopping dispensing of the flocculant when the sensor senses a predetermined condition; and then emptying the flocculation tank into a holding tank through a filter.

32. A method as claimed in claim 31, further comprising the sep of adding an additive to the holding tank.

33. A method as claimed in claim 32, wherein the additive is any one or more of the group comprising; a bleaching agent, a surfactant, an acidity modifier.

34. A method as claimed in claim 31, comprising the steps of; introducing contaminated water into the flocculation tank via an inlet pipe;. Stirring the solvent using a stirrer; adding a quantity of flocculant to the solvent using a flocculant dispensing means; sensing the conductivity of the water using a conductivity sensor; when a pre-determined conductivity level is reached, adding no more flocculant; stirring the water for a interval switching off the stirrer; and allowing the solvent to exit the flocculation tank through the filter basket into the holding tank.

35. A method as claimed in claim 34, further comprising the step of periodically adding a bleach tablet to the solvent in the holding tank.

36. A cleaning apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

37. A solvent cleaning means substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

38. A method of cleaning substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

39. A method of substantially removing contaminant from a solvent substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.