WO2003002274A1

WO2003002274A1 - Ultrasonic cleaning apparatus

Info

Publication number: WO2003002274A1
Application number: PCT/AU2002/000826
Authority: WO
Inventors: Lee Wah-Tong
Original assignee: Soniclean Pty Ltd
Priority date: 2001-06-27
Filing date: 2002-06-27
Publication date: 2003-01-09
Also published as: AUPR597501A0; AU2005239661B2; AU2005239661A1

Abstract

The present invention is for an ultrasonic cleaning apparatus for cleaning items including an access chamber located above and in sealed communication with an ultrasonic cleaning tank, doors sealing between the access chamber and the tank. A moveable platform extends between the chamber and the cleaning tank and allows the parts to be raised and lowered from said access chamber into said tank. The access chamber includes a cooling means to condense any moisture when the access chamber has been sealed and to cool the parts. The apparatus may further include a chiller chamber and a vapour chamber located between the access chamber and the tank, the chiller chamber further cooling the parts and preventing any solvent vapours from entering the access chamber. The access chamber may further include a heating means. Parts to be cleaned are placed on the platform the access chamber and sealed in the apparatus. The cooling means then condenses any moisture and cools the parts that are then lowered through the chiller chamber for further cooling and into the vapour chamber where the cold parts rapidly condense solvent providing a rinsing effect. The parts are then lowered into the tank for ultrasonic cleaning the parts are raised through the vapour and chiller cambers into the access chamber where they can be heated for removal, the heating ensuring that the parts do not condense any moisture as they are taken out of the apparatus. The chiller chamber includes two separate zones cooling of different temperatures to cool the parts and prevent any vapours from rising into the access chamber.

Description

Ultrasonic cleaning apparatus

The present invention relates to an ultrasonic cleaning apparatus and in particular to an ultrasonic vapour degreaser having multiple chambers to assist in cleaning.

BACKGROUND OF THE INVENTION

Ultrasonic energy is created within a liquid by transducers that convert electrical energy into acoustic energy. The transducers consist of vibrating elements tuned to the specific frequency required and are generally bonded to the side or underside of a cleaning tank containing the cleaning liquid or are encased in stainless steel for immersion within a liquid. An electronic generator transforms electrical energy from a power source into a suitable form for efficiently energizing the transducers at the desired frequencies.

The mechanism of ultrasonic cleaning depends on the formation and instantaneous collapse of millions of tiny cavities. Cavitation is produced by the alternating patterns of compression and rarefaction generated by the rapidly expanding and contracting transducers during sound wave transmission. As the liquid is stretched beyond its tensile strength during rareification these bubbles grow from microscopic nuclei and then upon compression they implode violently. This phenomenon occurs at a rate proportional to the ultrasonic frequency generated. Although individually these minute cavities release only an extremely small amount of energy, their cumulative effect is intense.

The overall effectiveness of the cleaning is dependent upon the cleaning liquid. The size of the tank is dependent upon the size of the parts to be cleaned and the number of transducers and generators is determined by the tank size. The choice of the cleaning solution depends on the parts being cleaned and the contaminates to be removed. Generally the cleaning solutions may be of the aqueous type, acidic type, or solvent type.

Solvent cleaners generally have a lower surface tension than water and are much denser and work on the basis of dissolving the contaminant. Solvents generally have low surface tension permitting it to penetrate fine cracks or blind holes and dissolve organic oils and other contaminants. The solvents penetrating action also remove inorganic contaminants. The use of solvents in Ultrasonic Cleaning Machines or Vapour Degreasers used to be prevalent up until the 1980' s when the use of Freon and other ozone damaging solvents was phased out. These can now only be used under exceptional circumstances.

Recently, new solvents have been developed that do not interact with the ozone and can thus be freely used. However, these solvents are quite expensive and having a low boiling point makes them prohibitive for general use due to evaporation of the solvent. Further, there is not data yet available whether these solvents have any impact upon health.

Another difficulty with present systems is that the cleaning process requires several steps and separate chambers. These are generally located adjacent each other and require separate mechanisms for the insertion and removal of the parts to be cleaned. Accordingly these types of cleaners can be quite labour intensive and require complicated mechanical arrangements.

It is an object of the present invention to provide an ultrasonic vapour degreaser that overcomes at least some of the abovementioned problems or provides for a useful alternative.

It is a further object of the present invention to provide an ultrasonic cleaner that minimises the loss of solvent and reduce the complexity of using multiple chambers.

SUMMARY OF THE INVENTION

Therefore in one form of the invention there is proposed an ultrasonic cleaning apparatus for cleaning items including: an ultrasonic cleaning tank housing solvent and an access chamber, said access chamber located above and in sealed communication with said cleaning tank, said access chamber having a sealable door enabling access into said chamber; a platform adapted for supporting said items and movable between said access chamber and into said tank; wherein said access chamber includes a cooling means adapted to cool the access chamber and the items supported in said platform.

Preferably said apparatus further includes a chamber door separating and isolating the access chamber from said tank, wherein when said platform is in the access chamber said door is closed isolating the access chamber from said tank. Preferably the access chamber further includes a heating means. This assists in heating the parts, which is important when they are about to be removed from the apparatus so that no ambient moisture condenses on them.

Preferably the access chamber further includes an airflow means. Typically this is an electric fan that circulates the air in the access chamber and creates turbulence, the air passing through cooling or heating means as is required.

Preferably the access chamber includes a rear wall defining a cavity at the rear of said access chamber, and aperture in said rear wall enabling fluid communication between said access chamber and said cavity, said cooling means positioned within said cavity, said access chamber including a ceiling space within which is mounted said airflow means, said ceiling space and said cavity being in fluid communication, said airflow means including an outlet into said access chamber wherein operation of the airflow means causes air to be drawn through the aperture in the rear wall into said cavity, through the cooling means where it is cooled and through the air flow outlet back into the access chamber.

Preferably the access chamber includes a ceiling space within which is mounted said airflow means, said access chamber further including a rear wall having a first inlet aperture and a second inlet aperture, said first inlet aperture being in fluid communication with a cavity housing said cooling means, said cavity being in fluid communication with said ceiling space, said second inlet aperture being in fluid communication with said ceiling space, wherein operable sealing means control the fluid flow communication through said first and second inlet apertures, said access chamber including operable closure means operated so that fluid flow enters said ceiling space either through said first inlet aperture or said second inlet aperture.

Preferably disposed below said cooling means is a condensation collection means, said collection means re-directing the flow of condensed fluid out of said access chamber.

Advantageously a heating 'means is further located within said ceiling space.

Preferably the apparatus further includes a chiller chamber located in-between said access chamber and said tank, said chiller chamber adapted to cool the chamber.

Preferably the chiller chamber includes an upper a primary chiller zone and a lower secondary chiller zone, said primary zone maintained at a temperature lower than the secondary zone. An ultrasonic cleaning apparatus as in claim 10 wherein said primary zone is cooled to a temperature of approximately -20° C.

Advantageously the secondary zone is cooled to a temperature of approximately between 0° C and 4° C.

Advantageously each zone includes a collection means to collect said condensed solvent.

Preferably the apparatus further includes boil tanks adapted to vaporise ultrasonic cleaning solvent, said vaporised solvent permeating through a vapour chamber located in between said chiller chamber and tank.

Preferably the apparatus includes a solvent holding tank fluidly connected to said ultrasonic tank.

Preferably the overflow from said tank is fed into at least one water and scum separation assembly that separates the solvent from water and other debris collected during the cleaning process and feeds the solvent into a solvent collection tank and the water and scum into a scum collection tank.

Preferably the water and scum separation assembly includes a first tank and second tank housed in said first tank said second tank of a size and shape to fit within said first tank leaving a small gap between them, said second tank including a plurality of slits on its bottom, wherein water and scum being heavier than solvent seeps through the slits and occupies the gap between the tanks, a first pipe in fluid connection with said gap feeding said water and scum into the scum collection tank, a second pipe extending through said first and second tanks, the top of said pipe being slightly below the top of said second tank wherein solvent that is lighter than water and scum feeds into said second pipe and into the solvent collecting tank.

Preferably the solvent collecting tank is fluidly connected to said ultrasonic tank.

Preferably the solvent collecting tank is fluidly connected to said solvent holding tank.

Advantageously the apparatus further includes a cooling system for cooling any condensed solvent.

Advantageously the platform includes a cage, said cage having a plurality of slits to allow for the passage of ultrasonic power therethrough. Advantageously the platform is mounted on a shaft, wherein rotation of the shaft in one direction causes the platform to be raised and in the other direction causes it to be lowered.

In a further from of the invention there is proposed a method of cleaning parts using solvent in a cleaning apparatus said method including the steps of:

(a) placing said parts in a closed in a first chamber;

(b) cooling said first chamber to condense ambient moisture and cool said parts;

(c) moving said parts to a second chamber within which extends vaporised solvent, wherein said now cooled parts cause said solvent to condense on and rinse said parts;

(d) moving said rinsed parts into an ultrasonic cleaning tank where they are ultrasonically cleaned;

(e) moving said ultrasonically cleaned parts to said first chamber;

(f) removing said parts from said first chamber.

Preferably said method further includes the step of heating said parts after step (e) above before they are remove from said first chamber.

Further advantages of the apparatus are described herein under in detail.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several implementations of the invention and, together with the description, serve to explain the advantages and principles of the invention. In the drawings,

Figure 1 is a schematic perspective view of an ultrasonic vapour degreaser embodying the present invention;

Figure 2 is a schematic cross-sectional left hand side view of the degreaser of Figure 1 ;

Figure 3 is a schematic cross-sectional front view of the degreaser of Figure 1;

Figure 4 is a schematic cross-sectional right hand side view of the degreaser of Figure 1;

Figure 5 is a partial interior sectional view of the degreaser of Figure 1 illustrating the various coils of the refrigeration system; Figure 6 is a perspective illustrative view of the tank and overflow tank systems used in the degreaser;

Figure 7 is an exploded perspective view of the solvent separation system used in the degreaser;

Figure 8 is a cross-sectional view of the solvent separation system of Figure 7;

Figure 9 is a typically flow chart diagram illustrating the operation of the degreaser embodying the present invention;

Figure 10 is a flow chart diagram of a second embodiment of a vapour degreaser embodying the present invention where any overflow solvent is not recycled;

Figure 11 is a flow chart diagram of a third embodiment of the present invention illustrating the details of operation where solvent is recycled through two water separation units;

Figure 12 is a flow chart diagram of a fourth embodiment of the present invention illustrating the details of operation where there is provided a further scumming distillation holding tank;

Figure 13 is a perspective partial sectional view of an alternate embodiment of the access chamber;

Figure 14 is a partial perspective sectional view of a further embodiment of the access chamber including individual cooling and heating facilities for the access chamber;

Figure 15 is a cross-sectional view of the operation of the access chamber of Figure 14

Figure 16 is a diagram illustrating the typical temperatures within different zones in the apparatus through a test mode; and

Figure 17 is a diagram illustrating the typical temperatures within different zones in the apparatus through a cleaning mode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description of the invention refers to the accompanying drawings. Although the description includes exemplary embodiments, other embodiments are possible, and changes may be made to the embodiments described without departing from the spirit and scope of the invention. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts.

Turning now to the drawings in detail and specifically to Figures 1-5 there is illustrated an ultrasonic cleaning apparatus 10 including an ultrasonic cleaning tank 12 having an ultrasonic vibrator (not shown), a vapour chamber 14, a chiller chamber 16, and an access chamber 18. The chambers are arranged in a vertical stack arrangement in ascending order so that the access chamber is on top of the others. The chiller chamber includes two separate zones, a primary, and a secondary cooling zone. These will be discussed in more detail shortly.

Access to the apparatus 10 is via a swing-type door 20 allowing entry into the access chamber 18. The door 20 includes a see-through glass panel 22 enabling one to see into the chamber 18 when the door 20 is closed.

The apparatus 10 is generally sealed to the outside, with a sealing means, typically a rubber seal (not shown) extending around the door 20, so that with the door 20 closed a seal of the access chamber 18 is then achieved. The door 20 is openable via handle 24 and may be lockable using different standard locking mechanisms that would be appreciated by the person skilled in the art.

Extending through the apparatus from the access chamber 18, through the chiller chamber 16, the vapour chamber 14, to the tank 12, is a lifting means including at least one but typically two geared shafts 26. The geared shafts 26 support a platform 28 in such an arrangement that rotation of the shafts in one direction causes the platform to be lowered and in the other to be raised.

The shafts 26 include ends 30 that protrude out of the access chamber 18, the ends sealed by known techniques to ensure that the seal of the access chamber is maintained. Pulley wheels 32 mounted on the ends 30 of the shafts 26 are rotatably driven by a belt 34 that engages the pulley wheels 32, the belt itself driven through pulley 36 by a power device, such as an electric motor (not shown).

It will be appreciated by a person skilled in the art that the shafts 26, platform 28, and the pulley arrangements allow the platform 28 to be raised and lowered through apparatus 10. In addition, the speed of ascent and descent can be accurately controlled. Further, the platform can be raised and lowered to fixed positions within the apparatus for desirable and pre-determined periods. The skilled addressee will be aware of various techniques including microprocessor controls that enable accurate control of the power means to control the position of the platform. The various chambers are supported within the apparatus 10 by use of frame 38. The apparatus may further include front, side and rear panels (not shown) to enclose the various chambers and associated equipment. This equipment is located behind the chambers to the rear of the apparatus 10 and includes various individual units and controls that affect each chamber including its environment. These will be discussed in further detail shortly.

Briefly the operation and purpose of each chamber is as follows:

(a) The access chamber 18 provides an access point for the insertion and removal of parts to be cleaned onto platform 28. The access chamber 18 includes a cooling or refrigeration system that cools the parts to be cleaned, typically to a pre-selected temperature around 0° C. This cooling also acts to condense any moisture in the access chamber whereupon it is removed from the access chamber. Typically the cooling coils that provide the cooling of the access chamber 18 will lower the temperature to some -20° C to ensure that residual solvent vapours are condensed onto the cooling coils and the condensed solvent collected into the ultrasonic rinse tank below via a gutter into the solvent water scum separation units. Residual solvent is likely to be present during the drag-out of parts from the ultrasonic rinse tank or the vapour condensate from the vapour zone below.

(b) The chiller chamber 16 includes two separate zones. The first or upper zone 56 supercools the environment and thus the parts when they are in that zone to a temperature of some -20° C. This layer of cool air also acts as a barrier to prevent any vapours and in particular solvent vapour from rising into the access chamber 18. The supercooling also acts as a barrier to reduce the likelihood of moisture entering the fluid system, preventing the latent heat of the boiling process being altered when the solvents are no longer pure. Further, if the parts are supercooled this will assist in the vapour cleaning process described below. The second or lower zone 64 of the chiller chamber 16 is cooled to a temperature of approximately between 0° C and 4° C and acts as the primary solvent vapour condenser.

(c) The vapour chamber 14 is where the parts to be cleaned are exposed to the solvent vapour. The solvent vapour temperature is of the order of the boiling temperature of the solvent used. The solvents mentioned above have a boiling temperature of around 39° C. A temperature sensor is located adjacent the top of the vapour zone in the vapour chamber to ensure adequate hot solvent vapour density is reached. Since the parts have been cooled to a temperature approaching -20° by passing through the chiller chamber 16, or by being supercooled by use of the re-circulating fan blowing onto the parts within the access chamber 18, the temperature differential between the parts and the ambient temperature is in the first instance quite large, of the order of 50° C. This results in heavy condensation forming on the super cooled parts and therefore assists in rinsing or cleaning the parts.

(d) The ultrasonic tank 12 contains solvent at a temperature of some 15° C to 18° C and cleans the parts using conventional ultrasonic techniques when they are inserted into the tank 12. Due to the solvents used having a low boiling point, the high vapour pressure created in the ultrasonic tank form ultrasonic activity, intermittent pulses of various energy bursts of ultrasonic power assisting in improving mechanical scrubbing by this degassing technique.

Referring again to Figures 1 to 5 there is then shown the general configuration of the apparatus 10. The access chamber 18 includes flap doors 40 located at the bottom that can be closed to seal the access chamber 18 from the chiller chamber 16. The doors 40 open downwardly and outwardly to allow for the passage of the platform 28 theretlirough. When the platform has passed through the doors 40, they are closed to isolate the access chamber 18 from the rest of the apparatus.

A heat exchanger includes a refrigeration unit 42 that provides heat exchange to the access chamber 18 through condenser coils 44 located within the rear wall 46 of the access chamber 18. Apertures 48 and 50 in the rear wall enable air to flow through the coils 44, said airflow controlled by use of a fan 52 (see also Figure 13). The fan 52 also creates turbulence within the access chamber 18 that assists with drying the parts as they are raised from the rinse and vapour chambers. Although not shown, when the coils condense any vapours, the condensed liquid flows along in-built channels into water separator 54. The water separator will be discussed fully later. The heat exchanger provides two functions. It heats the access chamber 18 to evaporate any solvent/water within the chamber 18. It also acts to cool the access chamber 18 to then condense any vapours. Alternate embodiments of the access chamber 18 are described further in the specification.

As discussed above the chiller chamber 16 has two individual cooling zones. The first zone 56 is cooled using a refrigeration unit 58 that provides heat exchange to coils 60 extending generally around the upper perimeter of the chiller chamber 16 and which are cooled to a temperature of some -20° C. Located under the coils and extending around the edge of the chiller chamber 16 is a channel or gutter 62 designed to collect any condensed vapours and feed the liquid to the water separator 54.

The second zone 64 of the chiller chamber 16 is the primary vapour condensation system where coils 66 are cooled by a further refrigeration unit. Since in this zone, there is significant concentration of vapour, the refrigeration unit must be capable of keeping the temperature in the range of 0° C to 4° C. For this reason, the refrigeration unit includes a thermal storage unit 68, also known as an "Ice Bank" thermal storage unit, which is cooled by a condenser system 70. The thermal storage unit 68 is able to store significant thermal energy thereby ensuring that the temperature in the coils 66 is always within the desired range. The condensed vapours in the second zone 64 are re-directed to the water separator 54 by channel or gutter 72.

The third chamber is the vapour or rinse chamber 14. Through the vapour chamber solvent vapours are dominant. When the parts to be cleaned are lowered into the rinse chamber 14 on the platform 28 they have been pre-cooled to a very low temperature. The person skilled in the art will then readily appreciate that the temperature of the parts will cause the vapour to be condensed at a significant rate, leading to a cleaning and rinsing effect of the parts. The vapour that has been condensed is then fed through appropriate plumbing to the water separator 54. As explained above, the rising vapours are kept within the vapour chamber due to the presence of the two chilling zones 56 and 64 in the chiller chamber 16 that condense any vapours that may rise.

The ultrasonic tank 12 is filled with the necessary solvent. When the platform 28 is lowered into the tank 12 the supercooled parts are subjected to normal ultrasonic cleaning action. However, the cooled parts also lower the temperature of the solvent. The effect of lower solvent temperature is to increase the cavitation activity, which assists the mechanical cleaning activity.

Located at the side and underneath the tank 12, and in fluid communication with it, are boiling tanks 74. These tanks have a number of heating coils that raise the temperature of the solvent to its boiling point, typically around 50° C. The heating coils are arranged so that each heats the solvent by an incremental temperature. The boil tanks 74 are relatively small and have a small cross-sectional configuration. This results in the amount of solvent within the boil tanks kept to a minimum. One skilled in the art will appreciate that this minimises the residual heat when the heaters are switched off. A level- sensing tank 76 ensures that the level of the solvent within the tank 12 is kept at a desirable level.

Figure 6 illustrates the typical configuration of the tank 12. The tank includes a weir or scumming gutter lip 78 over which drains any solvent and/or scum mixture 80 floating in the tank 12 into the water separation unit (not shown). Generally the scum 80 will consist of water, oil, and debris whose specific densities will be lighter than water and will hence float on top of the solvent. The gutter lip 78 is typically of a V-type configuration to increase its surface area. In case there is too much solvent or other liquid within the system, an overflow tank 82 is connected to the tank 12 through connecting pipe 84 and can be discharged through a tap (not shown). In addition, the overflow tank 84 collects any overflow in cases where the water separation unit, discussed earlier, may be blocked. Illustrated in Figures 7 and 8 is the water separation unit 54 that performs the scumming or the separation of the solvent and water 80. The water separation unit 54 includes an outer tank 86 and an inner tank 88, the inner tank 88 of a size and shape to fit within the outer tank 86 leaving a physical gap 90 between the two tanks. A lid 92 encloses the tanks. At the bottom of the inner tank 88 is a plurality of thin slits 94. During scumming water and scum is fed into the separation unit through pipe 96 and into the gap 90. Since the solvent is much heavier than the water it sinks to the bottom of the gap and then seeps through the slits 94 into the inner tank 88. A conduit or pipe 98 extends generally upright within the inner tank 88 and when the solvent has reached the top of the pipe 98 it is drained through the pipe 98 into solvent tank 100. The water and the scum remain within the gap 90 and a pipe 102 located towards the top of the outer tank 86 drains the water and scum into the scum collection tank 104.

The solvent tank 100 includes a further pipe 106 that allows the solvent to be fed further into the system. Similarly the scum tank also includes a pipe or plumbing 108 that is generally simply used to drain and dispose of the scum.

The solvent tank includes two floating sensors typically being float sensors. The first float 110 provides information to the operator that the solvent tank 100 is full. The second float 112 provides information that the solvent tank 100 is empty. The person skilled in the art will appreciate that the floats may be used with simple electro-mechanical switches to achieve this result. The scum tank also includes a float switch 114 to alert the operator when the tank is full.

Figures 9 to 12 illustrate different plumbing or flow chart arrangements for degreasers embodying the present invention. A typical plumbing operation of the apparatus 10 is illustrated as a schematic diagram in Figure 9.

As discussed above, the vapour chamber 14 and the chiller chamber 16 include gutters 72 and 62 respectively that feed any condensed liquid into the water separation unit 54. The solvent and the water/scum is separated and then fed separately into the solvent tank 100 and the water/scum tank 104. A tap 116 is used to drain the water and scum through outlet 118.

The solvent that is held in the solvent tank is pumped by the use of pump 120. A preferred feature is to include a turbidity sensor 122 to provide information about the solvent. The solvent may also be sampled through sample pipe and tap 124. Pressure sensor 126 provides and indication of the fluid pressure within the system. When the apparatus is in the cleaning mode, the condensed solvent is generally warm and needs to be cooled. It is therefore fed through a cooling tank 128, access into and out of the cooling tank controlled by taps 130 and 132 and by solenoid 134.

Alternatively, the solvent may be fed into holding tank 136 to be stored. From here the solvent may be accessed through outlet 138 by using tap 140. It can also be fed back into the rinse tank 12 by using tap 142 the solvent first passing through debris strainer 144 and back into the rinse tank 12. This part of the pipe can also be controlled by the use of solenoid 146.

Although not shown, the fluid flow may be rearranged so that the solvent always passes through the cooling tank and into the holding tank in a series arrangement rather than in a parallel arrangement as described above.

The rinse tank 12 is in fluid communication with the boil tanks 74. Fluid and debris collected at the bottom of the tank is drained and passed through another strainer 148 and fed back to the pump 120. The mixture may also be sampled through outlet 150 controlled by taps 152 and 154. A solenoid 156 may also be used to control the fluid flow.

The rinse tank is also connected to a level tank 76. If the level of the solvent exceeds a predetermined height the extra liquid is fed into the overflow tank 82. From here, the solvent may be drained through outlet 158 controlled by tap 160 or it may alternatively be fed back into the main fluid line through tap 162.

A sight glass 164 allows visual observation of the fluid flow through the main plumbing line. Valve 166 also allows the line to be isolated. It will be appreciated by the person skilled in the art that the sight glass can also be resident within the turbidity sensor (not shown).

The condensed solvent from the vapour zone is collected by a gutter 168 and fed directly into the solvent tank 100 or into the rinse tank 12. The condensate does not require cleaning since it is composed essentially of pure solvent. It may also be sampled through outlet 170 and tap 172 its flow direction controlled by the use of solenoids 174 and 176.

The flow of solvent from the solvent tank may also be controlled by the use of solenoid 178. Similarly solenoid 180 controls the fluid flow from the solvent pump 120 to the holding tank 136. Solvent can be introduced into the system through fill inlet 182 and taps 184. At times it may be desirous to have a system where there is no re-cycling of the overflow from the rinse tank and all overflow is fed into the boil tanks (heaters) and to the boil tank where it remains until cleaned water/scum mixture from the boil tanks, and the collected material or the rubbish is simply solvent. This may be advantageous where the parts to be cleaned need to be cleaned to the highest possible quality. In that case, the plumbing or the fluid flow schematic is illustrated in Figure 10 where any overflow from the rinse tank 12 is fed into the boil tanks 74 and boil level tank 186 and unlike the flow in Figure 9 does not go into an overflow tank to be recycled. A sight glass 188 enables one to observe the fluid flowing from the water and scum separation unit 54 and into the water and scum collection tank 104.

The vapours collected from the vapour zone gutter 168, vapour chamber gutter 72 and the chiller chamber gutter 62 are cooled and condensed in a solvent condenser and cooler unit 190 before being fed into the water separation unit 54. Since the overflow from the rinse tank is no linger recycled the solvent collected from the water separation unit 54 can be fed directly into the rinse tank 12 through pipe 98, rather than into a solvent tank, sight glass 192 allowing for visual inspection of that flow. Tap 194 controls the flow path between the holding tank 136 and the water separation unit 54.

Solenoid 196 controls the flow between the rinse tank 12 and the boil tanks 74. A further filter 198 is disposed between the fill inlet 182 and the system to minimise contamination of the solvent, as is filter 200 disposed between the solvent pump and the holding tank.

To be able to remove solvent from the holding tank, there is proved tap 202 and outlet 204. Finally tap 206 and outlet 208 provide for a water/scum drain on the water separation unit.

The skilled addressee will now appreciate that the apparatus as defined in Figure 10 ensures that any overflow of the rinse tank, where the debris is expected to collect and float, is not re-cycled back into the system but is rather collected separately to be disposed of later.

In cases where a considerable amount of water/scum separation is required, there may be provided a two-stage water separation cleaning system including two water separation units connected in series. As illustrated in Figure 11, there are two water separation units, 54a, and 54b. The solvent output pipe 98 of the first water separation unit 54a is fed into the second water separation unit 54b instead of directly to a solvent tank as in Figure 9 or the rinse tank as shown in Figure 10. Both scum and water outputs 102a and 102b of the two units 54a and 54b are fed into the water and scum collection tank 104. Both units can also be drained through tap and outlet 206 and 208 as in Figure 10. Solenoid 210 assists in the direction of the solvent through the system between the water separation unit 54b and the rinse tank 12. A tap 212 and outlet 214 enable one to drain the boil tanks 74. A sight glass 216 allows for inspection of the fluid between the water separation units 54a, and 54b and the boil tanks 74. Solenoid 218 controls the flow between the rinse tank and the input of the water separation unit 54a. The skilled addressee will now appreciate that the flow illustrated in Figure 11 results in the boil tanks being filled through two water scum separation units connected in series.

To fully separate the cleaning operations and to further cool the solvent, since solvent is easier to clean when cool, an alternate embodiment of the apparatus is illustrated in Figure 12. Although the general schematics are the same as the previous Figures 9 to 11, this embodiment includes a scumming/distillation holding tank 220 that is used in the operation of the apparatus for recycling. The holding tank 136 is used to hold only fresh new solvent, that is, one that has not been used at all in the system. The scumming/distillation holding tank 220 supplies solvent to the rinse tank and the water separation units 54a and 54 b trough tap 2222 strainer or filter 224 and solenoid 226, the alternate operation of the solenoids 14 and 226 controlling from where the solvent is sourced. Similarly solenoids 180 and 228 control the input to the holding tanks from the solvent flow path through the system. Solenoid 180 is typically closed during use of the apparatus and is opened when the system is not operating normally for in use the typical solvent temperature is some 50° C to 60° C.

A further feature of the apparatus in Figure 12 is the addition of a separate flow line 230 between the output of the water separation unit 54b that joins the output from the boil tanks controlled by tap 212 and solenoid 232. This is then fed through filter 234 and solenoid 236 into the main output from the rinse tank as illustrated above. A further solenoid 238 controls the flow from the rinse tank directly into the system into the scumming/distillation holding tank 220 or the ice bath cooling tank 130 and is primarily a feature to assist in cooling the solvent in the boil tanks. The systems in Figure 12 provides for the development of an external vapour generating chamber(s) to direct (with or without assistance) vapour clouds onto the parts to be cleaned.

Illustrated in Figure 13 is an alternate embodiment of the platform to house the parts to be cleaned. One can appreciate that instead of a platform, the parts are placed into a basket 240, the basket including multiple apertures 242 so sized to allow for the propagation of the ultrasonic wavelength through the basket. The size and placement of these apertures will be known by those skilled in the art. Further, the fan is enclosed within a manifold 244 to draw air from within the access chamber and feed it directly into aperture 50. This ensures that the air within the access chamber passes through the condenser coils in a relatively short time to remove any moisture, the turbulence assisting in this process. The flap doors 40 ensure that the access chamber 18 is isolated from the rest of the apparatus so that the stratification within the rest of the apparatus remains relatively undisturbed. Illustrated in Figure 14 is an alternate embodiment of the access chamber 18. The access chamber has been re-designed to enable one to heat and cool the air. The space behind the rear wall 46 of the access chamber 18 is partitioned into two separate chambers 246 and 248, chamber 248 including refrigeration coils 250 and a solvent gutter 252. A heater 254 is located within the enclosure 256 enclosing fan 52. The first chamber is partitioned into two further cavities 258 and 260 by a wall 262, apertures 264 and 266 allowing for air flow from the access chamber into the respective cavities, and aperture 268 allowing for air flow between the two cavities 258 and 260.

The rear of the cavity 260 includes an aperture 270 allowing for airflow into the second chamber 248. A damper seal 272 is pivotable from a first position, where it seals the aperture 270 and allows air to flow from the first cavity 260 into the second cavity 258, to a second position where it allows airflow through the aperture 270 at the rear of the cavity 260 and through the refrigeration coils 250 and seals aperture 268. It is to be understood though that it is not critical that the aperture 268 be sealed but rather that the airflow can be re-directed through the refrigeration coils.

A further damper seal 274 enables air flow from the second cavity 258 to the fan 52 to be closed by sealing aperture 276 at the top of the cavity. Thus in operation, the damper seals 272 and 274 are controlled so that the entire airflow either passes through the refrigeration coils or not. A heater 254 can then be used to heat air that has been either refrigerated or not.

In operating the apparatus when parts to be cleaned are first placed into the access chamber 18 one uses the cool facility to condense any moisture vapours and to cool the parts. When the parts have been cleaned through the apparatus they need to be warmed up to room temperature to vaporise any solvents and to further ensure that when the parts are taken into the ambient air they do not condense any moisture.

Throughout the apparatus various sensors are positioned that measure various physical properties of the apparatus. These are mainly the temperatures for the correct temperatures within each chamber are¹ fundamental to the operation of the apparatus. Illustrated in Figures 16 and 17 are temporal plots of the temperature measurement by various sensors during a start-up mode and cleaning mode and which illustrate the temperatures within the various chambers, in the rinse tank, the boil tanks and ambient over time in seconds.

The apparatus also uses a microprocessor that controls the various refrigeration units is generally required to ensure that the temperatures are maintained within acceptable levels. The use of a microprocessor also enables the system to be programmed for different cleaning programs, that is, the length of time the platform or the basket is in any one chamber and whether the parts to be cleaned go through several stages of cleaning.

One skilled in the art can now therefore appreciate the advantages of the present invention. The sealed system reduces the running costs whilst enabling sophisticated control of the cleaning process. This is achieved by the following:

• Vertically packaged chambers with well controlled and defined temperature profiles.

• Addition of an "active/dynamic chamber" which performs several functions:

o Acts as a barrier to ambient moisture when mixed with the solvent that affects its latent heat.

o Reclaims solvent drag-out by parts (taken out from the ultrasonic tank or the rinsing chamber) by heating the parts and condensing the solvent vapours on the evaporative. This is accomplished with the recirculating fan and the heat exchanger.

o The heat exchanger facilities of this chamber are used to chill the parts to produce a better rinsing when lowered into the vapour chamber.

• Use of much smaller boil tanks to create smaller heating inertia and small thermal storage. This enables better control of vapour generation and reduces unnecessary heat when switched off. Smaller volume of boil tanks also produces more efficient distillation.

• The system incorporates "scrumming" maintenance routines. The purpose is to remove water, oil, and other debris that floats on the surface of the solvent (its specific gravity being approximately 1.5 of water). The system does this by a series of intricate plumbing controls, pumping up clean solvents and discharging into the ultrasonic tank to create overflow through a specially made weir. The discharge is again put through the water separation unit (WSU). Clean solvent flows into the solvent tank that is again used to discharge to create further scumming process. The water scum flows into a separate container to be emptied out.

• The WSU has a built-in strainer, which also collects debris larger than 0.5 mm. This sieve-like construction also enables pure solvent to bleed through faster than water scum, further making the scumming process more efficient. • Distillation is done either internally as part of routine maintenance or externally when the pure solvent is collected into tanks outside the machine via a short tube connection, bypassing the pump and filter.

The two cooling coils in the chiller zone are there to introduce progressive stratification so that the temperature layer is more uniform. The temperature range is chosen for optimal cleaning. Coils are located on the inside perimeter of the chambers so that there is not a sudden drop in temperature that may induce vertical circulation.

The heater in the access chamber is used when the parts are raised from the rest of the apparatus to the access chamber to heat the parts so that when they are removed the solvent will evaporate. The access chamber is then cooled quickly to condense any of the solvent.

Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus.

Claims

1. An ultrasonic cleaning apparatus for cleaning items including: an ultrasonic cleaning tank housing solvent and an access chamber, said access chamber located above and in sealed communication with said cleaning tank, said access chamber having a sealable door enabling access into said chamber; a platform adapted for supporting said items and movable between said access chamber and into said tank; wherein said access chamber includes a cooling means adapted to cool the access chamber and the items supported in said platform.

2. An ultrasonic cleaning apparatus as in claim 1 further including a chamber door separating and isolating the access chamber from said tank, wherein when said platform is in the access chamber said door is closed isolating the access chamber from said tank.

3. An ultrasonic cleaning apparatus as in any one of the above claims, wherein said access chamber further includes a heating means.

4. An ultrasonic cleaning apparatus as in any one of the above claims wherein said access chamber further includes an airflow means.

5. An ultrasonic cleaning apparatus as in claim 4 wherein said access chamber further includes a rear wall defining a cavity at the rear of said access chamber, and aperture in said rear wall enabling fluid communication between said access chamber and said cavity, said cooling means positioned within said cavity, said access chamber including a ceiling space within which is mounted said airflow means, said ceiling space and said cavity being in fluid communication, said airflow means including an outlet into said access chamber wherein operation of the airflow means causes air to be drawn through the aperture in the rear wall into said cavity, through the cooling means where it is cooled and through the air flow outlet back into the access chamber.

6. An ultrasonic cleaning apparatus as in claim 4 wherein said access chamber includes a ceiling space within which is mounted said airflow means, said access chamber further including a rear wall having a first inlet aperture and a second inlet aperture, said first inlet aperture being in fluid communication with a cavity housing said cooling means, said cavity being in fluid communication with said ceiling space, said second inlet aperture being in fluid communication with said ceiling space, wherein operable sealing means control the fluid flow communication through said first and second inlet apertures, said access chamber including operable closure means operated so that fluid flow enters said ceiling space either through said first inlet aperture or said second inlet aperture.

7. An ultrasonic cleaning apparatus as in claim 5 or 6 wherein disposed below said cooling means is a condensation collection means, said collection means re-directing the flow of condensed fluid out of said access chamber.

8. An ultrasonic cleaning apparatus as in any one of claims 5 to 7 wherein a heating means is further located within said ceiling space.

9. An ultrasonic cleaning apparatus as in any one of the above claims wherein said apparatus further includes a chiller chamber located in-between said access chamber and said tank, said chiller chamber adapted to cool the chamber.

10. An ultrasonic cleaning apparatus as in claim 9 wherein said chiller chamber includes an upper a primary chiller zone and a lower secondary chiller zone, said primary zone maintained at a temperature lower than the secondary zone.

11. An ultrasonic cleaning apparatus as in claim 10 wherein said primary zone is cooled to a temperature of approximately -20° C.

12. An ultrasonic apparatus as in claim 10 or claim 11 wherein said secondary zone is cooled to a temperature of approximately between 0° C and 4° C.

13. An ultrasonic apparatus as in any one of claims 10 to 12 wherein each zone includes a collection means to collect said condensed solvent.

14. An ultrasonic cleaning apparatus as in any one of the above claims wherein said apparatus further includes boil tanks adapted to vaporise ultrasonic cleaning solvent, said vaporised solvent permeating through a vapour chamber located in between said chiller chamber and tank.

15. An ultrasonic cleaning apparatus as in any one of the above claims further including a solvent holding tank fluidly connected to said ultrasonic tank.

16. An ultrasonic cleaning apparatus as in any one of the above claims wherein the overflow from said tank is fed into at least one water and scum separation assembly that separates the solvent from water and other debris collected during the cleaning process and feeds the solvent into a solvent collection tank and the water and scum into a scum collection tank.

17. An ultrasonic cleaning apparatus as in claim 16 where said water and scum separation assembly includes a first tank and second tank housed in said first tank said second tank of a size and shape to fit within said first tank leaving a small gap between them, said second tank including a plurality of slits on its bottom, wherein water and scum being heavier than solvent seeps through the slits and occupies the gap between the tanks, a first pipe in fluid connection with said gap feeding said water and scum into the scum collection tank, a second pipe extending through said first and second tanks, the top of said pipe being slightly below the top of said second tank wherein solvent that is lighter than water and scum feeds into said second pipe and into the solvent collecting tank.

18. An ultrasonic cleaning apparatus as in claim 16 or claim 17 wherein said solvent collecting tank is fluidly connected to said ultrasonic tank.

19. An ultrasonic cleaning apparatus as in claim 16 or claim 17 wherein said solvent collecting tank is fluidly connected to said solvent holding tank.

20. An ultrasonic cleaning apparatus as in any one of the above claims said apparatus further including a cooling system for cooling any condensed solvent.

21. An ultrasonic cleaning apparatus as in any one of the above claims wherein said platform includes a cage, said cage having a plurality of slits to allow for the passage of ultrasonic power therethrough.

22. An ultrasonic cleaning apparatus as in any one of the above claims wherein said platform is mounted on a shaft, wherein rotation of the shaft in one direction causes the platform to be raised and in the other direction causes it to be lowered.

23. A method of cleaning parts using solvent in a cleaning apparatus said method including the steps of:

(a) placing said parts in a closed in a first chamber;

(b) cooling said first chamber to condense ambient moisture and cool said parts; (c) moving said parts to a second chamber within which extends vaporised solvent, wherein said now cooled parts cause said solvent to condense on and rinse said parts;

(e) moving said ultrasonically cleaned parts to said first chamber;

(f) removing said parts from said first chamber.

24. A method of cleaning parts as in claim 23 said method further including the step of heating said parts after step (e) of the above claim before they are remove from said first chamber.