Ultrasonic cleaning apparatus

Abstract: A workpiece is immersed in a cleaning solution (4) in a cleaning tank (2). The cleaning tank (2) has an ultrasonic vibrator (3) disposed on its bottom for radiating ultrasonic energy into the cleaning solution (4) to remove foreign matter or burrs off the workpiece. A deaerating device (5) is connected to said cleaning tank (2) for supplying a deaerated cleaning solution (4) to said cleaning tank (2). The deaerating device (5) comprises a sealed tank (6a,6b) for being supplied with the cleaning solution (4) from said cleaning tank (2). A vacuum pump or ejector (7a) is connected to the sealed tank (6a,6b) to evacuate said sealed tank (6a,6b) to release dissolved gas from the cleaning solution which is supplied to said sealed tank (6a,6b) and exposed to an evacuated space (18a,18b) in said sealed tank (6a,6b).

Description: The present invention relates to an apparatus for ultrasonically cleaning a workpiece, and more particularly to an ultrasonically cleaning apparatus having an ultrasonic vibrator mounted on the bottom of a cleaning tank for radiating an ultrasonic energy into a cleaning solution supplied to the cleaning tank to remove foreign matter or burrs off a workpiece immersed in the cleaning solution. More specifically, the present invention is concerned with an ultrasonically cleaning apparatus having a deaerating device for deaerating a cleaning solution to supply a deaerated cleaning solution to a cleaning tank. Heretofore, there are known ultrasonically cleaning apparatus having a cleaning tank with an ultrasonic vibrator mounted on its bottom. After the cleaning tank has been supplied with a cleaning solution, ultrasonic energy is radiated from the ultrasonic vibrator into the ultrasonic solution to clean a workpiece immersed in the cleaning solution. When ultrasonic energy is radiated from the ultrasonic vibrator into the cleaning solution, the cleaning solution is cavitated, and the workpiece is exposed to shock waves or microjets that are produced when the cavitation is collapsed. Foreign matter or burrs can be removed from the workpiece by those shock waves or microjets. For efficiently cleaning workpieces, it is necessary to provide conditions which facilitate the generation of the cavitation in the cleaning solution. It is known that the cleaning solution can be cavitated more easily if the concentration of a gas dissolved in the cleaning solution is lower. If the concentration of a gas dissolved in the cleaning solution in too high, then the dissolved gas is converted into bubbles by the ultrasonic energy radiated by the ultrasonic vibrator, and the cleaning solution is lens cavitated as the ultrasonic energy is absorbed by the bubbles. It is important, therefore, to control the amount of a gas dissolved in the cleaning solution. There have been proposed various deaerating devices for supplying a deaerated cleaning solution to the cleaning tank. One known deaerating device has a boiling tank for boiling the cleaning solution to release any dissolved gas from the cleaning solution. In another conventional deaerating device, a high-temperature layer is produced in a deaerated cleaning solution in the vicinity of its surface in the cleaning tank, thus generating a low-temperature layer below the high-temperature layer. Because air is dissolved into the cleaning solution at different rates at different solution temperatures, the high-temperature layer is effective to prevent air from being dissolved into the cleaning solution, thereby keeping the cleaning solution deaerated in the low-temperature layer. Still another prior deaerating device has a hollow fibrous gas separating membrane module. While a cleaning solution is flowing through the hollow fibrous membranes, the pressure outside the hollow fibrous membranes is lowered to draw any dissolved gas from the cleaning solution out of the hollow fibrous membranes, thus deaerating the cleaning solution. However, the known deaerating devices suffer various problems. Specifically, the deaerating device with the boiling tank is relatively large in size and taken a long period of time to deaerate the cleaning solution. This type of deaerating device is not practical as the deaerating accuracy is not high. The deaerating device which forms high- and low-temperature layers in the cleaning solution is not suitable for use with cleaning solutions that contain a solvent of low boiling point because of the high-temperature layer that must be generated. The deaerating device with the gas separating membrane module is disadvantageous in that the hollow fibrous membranes are expensive and open to attack by certain solvents such as higher alcohols. Therefore, the deaerating device of this type can use only a limited range of cleaning solutions. Furthermore, the effectiveness of the hollow fibrous membranes is lowered quickly when oily substances are attached to the hollow fibrous membranes or biological membranes are deposited thereon due to the growth of microorganisms. It is known from JP-A-2 233 190 to provide apparatus for ultrasonically cleaning a workpiece, comprising: a cleaning tank for storing a cleaning solution therein, said cleaning tank having an ultrasonic vibrator disposed therein for radiating ultrasonic energy into the cleaning solution to remove foreign matter, burrs or the like off a workpiece immersed in the cleaning solution; and deaerating means connected to said cleaning tank for supplying a deaerated cleaning solution to said cleaning tank, said deaerating means comprising a sealed tank for being supplied with the cleaning solution from said cleaning tank, and evacuating means including means disposed outside of said sealed tank for discharging air therefrom, for evacuating said sealed tank to release dissolved gas from the cleaning solution supplied to said sealed tank and exposed to an evacuated space in said sealed tank. US-A-4 193 818 discloses apparatus for cleaning surgical instruments including a cleaning tank for containing cleaning liquid, with a void space above the surface of the liquid which is evacuated. The liquid is subjected to ultrasonic energy. GB-A-2 192 348 discloses degassing apparatus for removing extraneous gas from water used as an ingredient in beverage production. The apparatus has a plurality of vertically spaced foraminous sheets through which liquid trickles whilst being subjected to a vacuum. The vacuum is created by the removal of air via an outlet at the top of the degassing chamber. It is an object of the invention to provide an ultrasonic cleaning apparatus with a deaerating device of the kind disclosed in JP-A-2 233 190 that may be relatively small in size, inexpensive, may be used with various different cleaning solutions, and may deaerate a cleaning solution accurately within a short period of time. The present invention is characterised in that said deaerating means comprises means for introducing the cleaning solution downwardly into said sealed tank from an upper portion thereof, whereby the cleaning solution is exposed to the evacuated space in said sealed tank while flowing downwardly therethrough, and in that said evacuating means comprises a discharge pipe extending vertically in said sealed tank and having a plurality of holes defined in a wall thereof, the discharge pipe being connected to the air discharging means disposed outside of said sealed tank. Preferably the vibrator is arranged on or adjacent the bottom of the cleaning tank. When the cleaning solution introduced into the sealed tank is brought into contact with the evacuated space in the sealed tank, the dissolved gas is released from the cleaning solution, i.e., the cleaning solution is deaerated. Accordingly, the cleaning solution can be deaerated highly accurately in a short period of time without using an expensive gas separating membrane module, and the ultrasonic cleaning apparatus may be relatively small in size. The ultrasonic cleaning apparatus may use any cleaning solution as it has no gas separating membrane module and it does not generate a high-temperature layer in the cleaning solution. While the cleaning solution is flowing from the upper portion of the sealed tank downwardly through the sealed tank, the cleaning solution is exposed to the evacuated space in the sealed tank through an increased area of contact. Therefore, any dissolved gas can easily be discharged from the cleaning solution. The means for discharging air from the sealed tank to evacuate the sealed tank may comprise a vacuum pump or an ejector with a valve vented to atmosphere, for example. The discharge pipe may have means for preventing the cleaning solution from being drawn into the discharge pipe through the holes. The evacuating means can uniformly evacuate the sealed tank by discharging air from the sealed tank, and the cleaning solution flows downwardly through the sealed tank without being drawn by the evacuating means. The means for preventing the cleaning solution from being drawn into the discharge pipe may comprise covers attached to the discharge pipe in overhanging relationship to the holes, respectively. Since the cleaning solution flows along the covers, it is effectively prevented from being drawn into the evacuating means. Air in the sealed pipe is drawn into the holes through gaps defined between the discharge pipe and distal ends of the covers. Therefore, the covers do not obstruct the discharge of air from the sealed tank. The evacuating means may include additional means in the sealed tank for exposing the cleaning solution which is introduced downwardly into the sealed tank to the evacuated space therein through an increased area of contact. Since the cleaning solution is exposed to the evacuated space through an increased area of contact, the cleaning solution can be deaerated highly efficiently. The means in the sealed tank for exposing the cleaning solution to the evacuated space may comprise a plurality of vertically spaced partitions dividing the space in the sealed tank into a plurality of chambers, each of the partitions having a plurality of small holes. Upon downward flow of the cleaning solution in the sealed tank, the cleaning solution is dispersed each time it reaches one of the partitions, and hence is exposed to the space in the sealed tank through an increased area of contact. The means in the sealed tank for exposing the cleaning solution to the evacuated space may also comprise a filler for allowing the cleaning solution to flow on a surface thereof. While the cleaning solution is flowing downwardly along the surface of the filler in the sealed tank, the cleaning solution is exposed to the space in the sealed tank through an increased area of contact. With the filler used, the cleaning solution remains exposed to the space in the sealed tank for a period of time longer than if it were dispersed only by the small holes in the partitions. Thus, the cleaning solution can be deaerated highly efficiently. The filler may preferably be in the form of a spirally wound net of SUS or plastic as it is inexpensive and any oily or biological deposits can easily be washed away for reusing the filler. The means in the sealed tank for exposing the cleaning solution to the evacuated space may comprise both a plurality of vertically spaced partitions dividing the space in the sealed tank into a plurality of chambers, each of the partitions having a plurality of small holes, and a filler disposed in the chambers for allowing the cleaning solution to flow on a surface thereof. Both the partitions and the filler jointly operate to expose the cleaning solution to the evacuated space in the sealed tank through an increased area of contact. The spaced partitions in the sealed tank also serve to stiffen the sealed tank. Accordingly, even when the sealed tank is evacuated, the sealed tank is protected from deformation. The cleaning tank has an outlet port for discharging the cleaning solution from the cleaning tank and an inlet port for supplying the cleaning solution into the cleaning tank, further including circulating means for circulating the cleaning solution from the outlet port to the inlet port, the deaerating means being connected in the circulating means. Since the cleaning solution in circulated for deaeration, the cleaning solution can be reused and hence may be consumed in a relatively small amount. The deaerating means may include debubbling means for eliminating bubbles produced in the sealed tank when the dissolved gas is released from the cleaning solution, the debubbling means being positioned in a portion of the sealed tank where the bubbles are produced. Since the bubbles are eliminated in the sealed tank, they are prevented from being drawn into the evacuating means. The debubbling means may comprise an ultrasonic vibrator disposed in an upper portion of the sealed tank for applying an ultrasonic energy to the bubbles produced from the cleaning solution. The debubbling means may be connected between the sealed tank and the means for discharging air. With such an arrangement, inasmuch as the bubbles are eliminated before they reach the evacuating means, they are prevented from being drawn into the evacuating means. The debubbling means may comprise solid debubblizer which can eliminate the bubbles upon contact therewith, the solid debubblizer being shaped not to obstruct the passage of a gas therethrough. The solid debubblizer may be a silicone-base solid debubblizer. Embodiment of the invention will now be described by way of example and with reference to the accompanying drawings in which:- FIG. 1 is a schematic view of an ultrasonic cleaning apparatus according to an embodiment of the present invention; FIG. 2 is a cross-sectional view of a deaerating device of the ultrasonic cleaning apparatus shown in FIG. 1; FIG. 3 is a cross-sectional view taken along line III - III of FIG. 2; FIG. 4 is an enlarged fragmentary elevational view of a structure for preventing a cleaning solution from being drawn; and FIG. 5 is a cross-sectional view of a modification of the deaerating device of the ultrasonic cleaning apparatus shown in FIG. 1. FIG. 1 schematically shows an ultrasonic cleaning apparatus according to another embodiment of the present invention. As shown in FIG. 1, the ultrasonic cleaning apparatus, generally designated by the reference numeral 21, has an ultrasonic cleaning tank 22a with an ultrasonic vibrator 23 mounted on its bottom. A workpiece to be cleaned is immersed in a cleaning solution 24 supplied to the cleaning tank 22a, and ultrasonic energy is radiated from the ultrasonic vibrator 23 into the cleaning solution 24 to remove foreign matter or burrs off the workpiece. The ultrasonic cleaning apparatus 21 employs tap water containing 10 % of a nonionic surface active agent detergent as the cleaning solution 4 The cleaning tank 22a has an outlet port 25a in its side wall for discharging the cleaning solution 24 from the cleaning tank 22a, and an inlet port 25b in its side wall for supplying the cleaning solution 24 into the cleaning tank 22a, the outlet and inlet ports 25a, 25b being positioned in diametrically confronting relationship to each other. Flow rectifying units (not shown) are disposed in the respective outlet and inlet ports 25a, 25b for preventing air from being trapped in the cleaning solution 24. An deaerating device 28 for deaerating the cleaning solution 24 before it is supplied to the cleaning tank 22a is disposed outside of the cleaning tank 22a. The deaerating device 28 is connected to the outlet port 25a through a supply conduit 27a and also to the inlet port 25b through a supply conduit 27b. The supply conduits 27a, 27b jointly serve as a circulation system which includes the deaerating device 28. The deaerating device 28 will be described in detail below with reference to FIG. 2. FIG. 2 shows the deaerating device 28 in cross section. As shown in FIG. 2, the deaerating device 28 has a sealed tank 31 in the form of a pipe of SUS whose opposite ends are hermetically closed. The supply conduit 27a is connected to an upper side wall of the sealed tank 31 for supplying the cleaning solution 24, which is to be deaerated, into the sealed tank 31. A supply pump 32 is connected in the supply conduit 27a. The supply pump 32 and the supply conduit 27a jointly serve to introduce the cleaning solution 24, to be deaerated, through the supply conduit 27a into the sealed tank 31. The sealed tank 31 houses a plurality of axially spaced partitions 34 which divide the interior space of the sealed tank 31 into a vertical array of chambers, each of the partitions 34 having a number of small holes 33 defined therein. The partitions 34 serve to increase the area of contact between the cleaning solution 24 and the space in the sealed tank 31. When the cleaning solution 24 is introduced into the sealed tank 31 through the supply conduit 27a by the supply pump 32, the cleaning solution 24 flows through the small holes 33 in the partitions 34 downwardly in the sealed tank 31. The sealed tank 31 can be evacuated by a discharge pipe 35 extending axially through an upper end cap 31m of the sealed tank 31 and the partitions 34 and hence vertically in the sealed tank 31, and an ejector 36 disposed outside of the sealed tank 31 and connected to the discharge pipe 35. The ejector 36 serves to discharge air from the discharge pipe 35, and has a valve (not shown) vented to atmosphere. The discharge pipe 35 has a plurality of holes 37 defined in its pipe wall at axially spaced intervals. The discharge pipe 35 also has a plurality of covers 38 attached its outer surface in covering relationship to the respective holes 37 for preventing the downwardly flowing cleaning solution 24 from being drawn into the holes 37. A filler 39 is filled in the sealed tank 31 around the discharge pipe 35 in spaces between the partitions 34. The filler 39 is also effective to increase the area of contact between the cleaning solution 24 and the space in the sealed tank 31. The filler 39 may be of any material and structure insofar as the cleaning solution 24 can flow along the surface of the filler 39. For example, a spirally wound net of SUS or plastics id preferable as it is inexpensive and any oily or biological deposits can easily be washed away for reusing the filler 39. The supply conduit 27b is connected to a lower side wall of the sealed tank 31 near the bottom thereof. A supply pump 40 is connected in the supply conduit 27b. The supply pump 40 and the supply conduit 27b jointly serve to deliver the deaerated claiming solution 24 through the supply conduit 27b to the cleaning tank 222a. A communication pipe 41 interconnecting upper and lower spaces in the sealed tank 31 is disposed outside of and extends along the sealed tank 31. The supply conduits 27a, 27b open respectively into the upper and lower spaces that are interconnected by the communication pipe 41. The communication pipe 41 has two spaced level switches 42a, 42b of the electrostatic capacitance type for detecting the solution level in the sealed tank 31 with floats that vertically move in unison with the solution level in the sealed tank 31. These level switches 42a, 42b are electrically connected to a deaeration controller 43. The deaeration controller 43 is electrically connected to the supply pumps 32, 40. When a predetermined upper limit position for the solution level in the sealed tank 31 is detected by the level switch 42a, the deaeration controller 43 deactivates the supply pump 32 and activates the supply pump 40 to discharge the deaerated cleaning solution 24 from the sealed tank 31 and supply it through the supply conduit 27b to the cleaning stank 22a. When a predetermined low limit position for the solution level in the sealed tank 31 is detected by the level switch 42b, the deaeration controller 13 deactivates the supply pump 40 and activates the supply pump 32 to introduce the cleaning solution 24, to be deaerated, into the sealed tank 31. An ultrasonic vibrator 44 is attached to an upper wall surface of the sealed tank 31 for eliminating bubbles which may be produced when a dissolved gas is discharged particularly if the cleaning solution 24 contains a detergent such as a surface active agent. As shown in FIG. 1, a reserve tank 22b is positioned adjacent to the cleaning tank 22a for receiving an overflow of cleaning solution from the cleaning tank 22a when a workpiece to immersed in the cleaning solution 24 in the cleaning tank 22a. Discharge conduits 29a, 29b are connected to the bottoms, respectively, of the cleaning tank 22a and the reserve tank 22b. The discharge conduits 29a, 29b are connected to the supply conduit 27a upstream of the supply pump 32. The conduits 27a, 27b, 29a, 29b have flow regulating valves for regulating the rates of the cleaning solution 24 flowing therethrough. Operation of the ultrasonic cleaning apparatus 21 will be described below. The deaerated cleaning solution 24 is filled in the cleaning tank 22a, and the ultrasonic vibrator 23 to actuated to remove foreign matter or burrs from a workpiece which is immersed in the cleaning solution 24 in the cleaning tank 22a. Since repetition of the cleaning process results in an increase in the amount of dissolved gas in the cleaning solution 24, the cleaning solution 24 is supplied through the supply conduit 27a to the sealed tank 31 by the supply pump 32. After the cleaning solution 24 has been deaerated in the sealed tank 32, it is discharged from the sealed tank 32 by the supply pump 40, and returned through the supply conduit 27b to the cleaning tank 22a. The deaerating device 28 deaerates the cleaning solution 24 as follows: The cleaning solution 24 drawn from the cleaning tank 22a is introduced into the sealed tank 31 through the supply conduit 27a by the supply pump 32. At this time, the sealed tank 31 has been evacuated through the discharge pipe 35 by the ejector 36. Inasmuch as the discharge pipe 35 extends vertically and the holes 33 are defined in its wall, the sealed tank 31 may be evacuated uniformly to a pressure level of about - 650 mmHg. The cleaning solution 24 supplied to the sealed tank 31 flows downwardly while being exposed to the evacuated space in the sealed tank 31. Therefore, any dissolved gas to released from the cleaning solution 24 while it is flowing downwardly through the discharge pipe 35. The partitions 34 in the sealed tank 31 will be described below with reference to FIG. 4. As shown in FIG. 3, the small hole, 33 are defined in each of the partitions 34 around the discharge pipe 35. Therefore, the cleaning solution 24 introduced into the sealed tank 31 is dispersed by the small holes 33 while flowing down the sealed tank 31. The cleaning solution 24 is thus exposed to the space in the sealed tank 31 through a large area of contact, and the dissolved gas can efficiently be released from the cleaning solution 24. Inasmuch us the cleaning solution 24 also flows along the surface of the filler 39 filled between the partitions 34, the cleaning solution 24 is further exposed to the space in the sealed tank 31 through an increased area of contact. The cleaning solution 24 is exposed to the space in the sealed tank for a longer period of time than would be if it were not for the filler 39. Consequently, the dissolved gas is discharged from the cleaning solution 24 at an accelerated rate with a high deaeration efficiency. The cleaning solution 24 flowing down the filler 39 is dispersed by the small holes 33 each time it reaches one of the partitions 34. The cleaning solution 24 is thus prevented from being localized in the sealed tank 31 so that the dissolved gas can be released from the cleaning solution 24 highly efficiently. The axially spaced partitions 34 in the sealed tank 31 also serve to stiffen the sealed tank 31. Accordingly, even when the sealed tank 31 is evacuated, the sealed tank 31 is protected from deformation. The holes 37 in the discharge pipe 35 confront the filler 39, and might draw in the cleaning solution 24 which flows down the filler 39. However, the cleaning solution 24 is prevented from being drawn into the discharge pipe 35 by the covers 38 which cover the holes 37. The covers 38 will be described in more detail with reference to FIG. 4. As illustrated in FIG. 4, the covers 38 are attached at upper ends thereof to the discharge pipe 35 and extend downwardly in overhanging relationship to the holes 37, leaving gaps 37a between the discharge pipe 35 and the lower ends of the covers 38. The gas in the sealed tank 31 is drawn into the discharge pipe 35 through the gaps 37a, whereas the cleaning solution 24 which flows downwardly is prevented by the covers 38 from being drawn into the discharge pipe 35. The cleaning solution 24 thus deaerated is accumulated in the sealed tank 31, and its level gradually increases as more cleaning solution 24 is deaerated. When the level of the cleaning solution 24 increases in the sealed tank 31, it enters the discharge pipe 35, but is not drawn by the ejector 36. Since the cleaning solution 24 contains a surface active agent, it is bubbled violently as the dissolved gas is discharged, and bubbles fill up the sealed tank 31. Since these bubbles will not easily be eliminated automatically, they will move upwardly as the level of the cleaning solution 24 goes upwardly, and might eventually be drawn into the ejector 36. However, the bubbles can be eliminated by the ultrasonic energy radiated from the ultrasonic vibrator 44 mounted on the upper inner wall surface of the sealed tank 31. When the level of the accumulated cleaning solution 24 in the sealed tank 31 reaches a predetermined upper limit position, the level switch 42a in the communication pipe 41 sends a detected signal to the deaeration controller 43. In response to the detected signal from the level switch 42a, the deaeration controller 43 deactivates the supply pipe 32 and actuates the supply pump 40. As a result, the deaerated cleaning solution 24 that is accumulated in the sealed tank 31 is supplied through the supply conduit 27b to the cleaning tank 22a by the supply pump 40. When the deaerated cleaning solution 24 is thus supplied to the cleaning tank 22a, the level of the cleaning solution 24 in the sealed tank 31 descends and reaches a predetermined lower limit position. Then, the level switch 42b sends a detected signal to the deaeration controller 43, which stops the supply pump 40 and activates the supply pump 32. The cleaning solution 24, to be deaerated, is now introduced into the sealed tank 31 through the supply conduit 27a, and the deaerated cleaning solution 24 starts being accumulated in the sealed tank 31. Consequently, each time a certain amount of deaerated cleaning solution 24 is accumulated in the sealed tank 31, it is automatically supplied to the cleaning tank 22a. When the supply of the deaerated cleaning solution 24 to the cleaning tank 22a is finished, the deaerated cleaning solution 24 automatically starts to be accumulated in the sealed tank 31. The level of the cleaning solution 24 in the sealed tank 31 is thus prevented from rising excessively into the ejector 36. The deaerated cleaning solution 24 can also be supplied efficiently to the cleaning tank 22a. In this embodiment, only one deaerating device 28 is connected to the cleaning tank 22a. However, a plurality of deaerating devices 28 may be connected parallel to each other, and may be actuated one after another to supply the deaerated cleaning solution 24 uninterruptedly to the cleaning tank 22a. FIG. 5 shows a modification of the deaerating device 28. In FIG. 5, a debubbling tank 45 is connected between the discharge pipe 35 in the sealed tank 31 and the ejector 36. The debubbling tank 45 houses a silicone-base solid debubblizer (UNFALL MT-9, manufactured by Daiichi Seiysku Co., Ltd.) which is shaped not to obstruct the passage of a gas through the debubbling tank 45. Even if bubbles produced when the dissolved gas is released from the cleaning solution 24 are drawn from the discharge pipe 35 toward the ejector 36, they are eliminated by contact with the solid debubblizer in the debubbling tank 45, and hence prevented from being drawn into the ejector 36. The ultrasonic vibrator 44 shown in FIG. 2 is dispensed with, but may be disposed in the upper space in the sealed tank 31. The other structural details of the modified deaerating device shown in FIG. 5 are the same as the deaerating device 28 shown in FIG. 4. Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.

Claims: Apparatus (21) for ultrasonically cleaning a workpiece, comprising: a cleaning tank (22a) for storing a cleaning solution (24) therein, said cleaning tank having an ultrasonic vibrator (23) disposed therein for radiating ultrasonic energy into the cleaning solution to remove foreign matter, burrs or the like off a workpiece immersed in the cleaning solution; and deaerating means (28) connected to said cleaning tank for supplying a deaerated cleaning solution to said cleaning tank, said deaerating means comprising a sealed tank (31) for being supplied with the cleaning solution from said cleaning tank, and evacuating means (36) including means disposed outside of said sealed tank for discharging air therefrom, for evacuating said sealed tank to release dissolved gas from the cleaning solution supplied to said sealed tank and exposed to an evacuated space in said sealed tank; characterised in that said deaerating means (28) comprises means for introducing the cleaning solution downwardly into said sealed tank (31) from an upper portion thereof, whereby the cleaning solution is exposed to the evacuated space in said sealed tank while flowing downwardly therethrough, and in that said evacuating means (36) comprises a discharge pipe (35) extending vertically in said sealed tank and having a plurality of holes (37) defined in a wall thereof, the discharge pipe being connected to the air discharging means disposed outside of said sealed tank. Apparatus as claimed in claim 1, wherein said discharge pipe (35) has means (38) for preventing the cleaning solution from being drawn into said discharge pipe through said holes. Apparatus as claimed in claim 2, wherein said means for preventing the cleaning solution from being drawn in comprises covers (38) attached to said discharge pipe in overhanging relationship to said holes, respectively. Apparatus as claimed in any of claims 1, 2 or 3, wherein said evacuating means includes means (33, 34, 39) in said sealed tank (31) for exposing the cleaning solution which is introduced downwardly into said sealed tank to the evacuated space therein through an increased area of contact. Apparatus as claimed in claim 4, wherein said means in said sealed tank (31) for exposing the cleaning solution to an increased contact area comprises a plurality of vertically spaced partitions (34) dividing the space in the sealed tank into a plurality of chambers, each of said partitions having a plurality of small holes (33). Apparatus as claimed in claim 4 or 5, wherein said means in said sealed tank (31) for exposing the cleaning solution to an increased contact area comprises a filler (39) for allowing the cleaning solution to flow on a surface thereof. Apparatus as claimed in claim 4, wherein said means in said sealed tank (31) for exposing the cleaning solution comprises a plurality of vertically spaced partitions (34) dividing the space in the sealed tank into a plurality of chambers, each of said partitions having a plurality of small holes (33), and a filler (39) disposed in said chambers for allowing the cleaning solution to flow on a surface thereof. Apparatus as claimed in any preceding claim, wherein said cleaning tank (22a) has an outlet port (25a) for discharging the cleaning solution from the cleaning tank and an inlet port (25b) for supplying the cleaning solution into the cleaning tank, further comprising circulating means (27a, 27b) for circulating the cleaning solution from said outlet port to said inlet port, said deaerating means (31) being connected in said circulating means. Apparatus as claimed in any preceding claim, wherein said deaerating means (31) includes debubbling means (44) for eliminating bubbles produced in said sealed tank (31) when the dissolved gas is released from said cleaning solution, said debubbling means (44) being positioned in a portion of said sealed tank where said bubbles are produced. Apparatus as claimed in any of claims 1 to 8, wherein said deaerating means comprises debubbling means (45) for eliminating bubbles produced in said sealed tank (31) when the dissolved gas is released from said cleaning solution, said debubbling means (45) being connected between said sealed tank and said air discharging means.

Inventors: SHIBANO YOSHIHIDE, SHIBANO, YOSHIHIDE
Applicants: SHIBANO YOSHIHIDE, SHIBANO, YOSHIHIDE
Application year: 1992
Main classification: B08B3
IPC codes: B01D19, B08B3