Abstract:
There is provided a method of ultrasonically cleaning a workpiece, the method having the steps of providing a cleaning vessel being at least partially filled with a cleaning fluid and having a series of transducers mounted to couple sonic energy into the cleaning fluid, placing the workpiece within the cleaning vessel such that at least a portion of the workpiece is submerged in the cleaning fluid, supporting the workpiece on a set of rollers by one or more rounded surfaces of the workpiece, operating the transducers to transmit sonic energy to the workpiece through the cleaning fluid, the sonic energy being sufficient to clean debris attached to the workpiece, and rotating the workpiece on the set of rollers within the cleaning vessel.

Description:
FIELD 
       [0001]    This relates to cleaning a workpiece using ultrasonics. 
       BACKGROUND 
       [0002]    It is known to clean workpieces submerged in a cleaning fluid with the use of ultrasonics. PCT publication no. WO 2011/075831 (Phillips et al.) entitled “Apparatus for Cleaning industrial Components” and PCT publication no. WO 2013/056378 (Tevely et al.) entitled “Method and Apparatus for Cleaning Diesel Particulate Filters” relate to different principles that may be applied to cleaning workpieces using transducers. 
       SUMMARY 
       [0003]    There is provided a method of ultrasonically cleaning a workpiece, comprising the steps of: providing a cleaning vessel being at least partially filled with a cleaning fluid and having a series of transducers mounted to couple sonic energy into the cleaning fluid; placing the workpiece within the cleaning vessel such that at least a portion of the workpiece is submerged in the cleaning fluid; supporting the workpiece on a set of rollers by one or more rounded surfaces of the workpiece; operating the transducers to transmit sonic energy to the workpiece through the cleaning fluid, the sonic energy being sufficient to clean debris attached to the workpiece; and rotating the workpiece on the set of rollers within the cleaning vessel. 
         [0004]    According to an aspect, the workpiece may be a heat exchanger comprising a housing enclosing a set of exchanger tubes. 
         [0005]    According to an aspect, the set of rollers may be carried by a skid. The skid may be removed from the cleaning vessel. The skid may comprise a superstructure having lifting attachments. The superstructure may be removed from the skid. 
         [0006]    According to an aspect, the workpiece may be oriented horizontally in the cleaning vessel. 
         [0007]    According to an aspect, the method may further comprise the step of providing the workpiece with the one or more rounded surfaces prior to supporting the workpiece on the set of rollers. 
         [0008]    According to an aspect, the series of transducers may be submerged within the cleaning fluid. 
         [0009]    According to another aspect, there is provided an apparatus for cleaning a workpiece. The apparatus comprises a cleaning vessel that is at least partially filled with a cleaning fluid. A plurality of transducers are mounted to the cleaning vessel for coupling sonic energy into the cleaning fluid. A set of rollers is within the cleaning vessel. The set of rollers support a workpiece to be cleaned. A drive source rotates the workpiece on the set of rollers. 
         [0010]    According to an aspect, the set of rollers may be arranged to conform to one or more rounded surfaces of the workpiece. 
         [0011]    According to an aspect, the set of rollers may he mounted to a skid. The skid may he removable from the cleaning vessel. The skid may comprise a superstructure having lifting attachments. The superstructure may be removable from the skid. 
         [0012]    According to an aspect, the set of rollers may comprise at least one roller that is driven by a power source, the set of rollers causing, the workpiece to rotate. 
         [0013]    According to an aspect, the transducers may be mounted diagonally within the cleaning vessel. 
         [0014]    These and other aspects that will be apparent from the description and claims below may be combined in any reasonable combination. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to he in any way limiting, wherein: 
           [0016]      FIG. 1  is a partially transparent perspective view of an apparatus for cleaning a workpiece. 
           [0017]      FIG. 2  is a perspective view in section of the apparatus. 
           [0018]      FIG. 3  is a perspective view of a set of rollers. 
           [0019]      FIG. 4  is a perspective view of a set of rollers with a drive mechanism. 
           [0020]      FIG. 5  is a perspective view of a skid with rollers. 
           [0021]      FIG. 6  is a perspective view of a workpiece on the skid. 
           [0022]      FIG. 7  is a perspective view of a skid with a superstructure. 
           [0023]      FIG. 8  is an exploded perspective view of the skid and superstructure. 
           [0024]      FIG. 9  is a perspective view of an alternative skid and superstructure. 
           [0025]      FIG. 10  is an exploded side elevation view of a workpiece. 
           [0026]      FIG. 11  is a side elevation view of a workpiece. 
           [0027]      FIG. 12  is an end elevation view of a workpiece. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Referring to  FIG. 1 , there is shown an apparatus, generally indicated by reference numeral  10 , for cleaning a workpiece  16 . Apparatus  10  includes a cleaning vessel  12  that is at least partially tilled with a cleaning fluid  14 . Workpiece  16  to be cleaned is shown partially submerged within cleaning fluid  14 . Referring to  FIG. 2 , a plurality of transducers  18  are mounted to cleaning vessel  12  for coupling sonic energy into cleaning fluid  14 . Transducers  18  are preferably attached to the inside of cleaning vessel  12  at a level to be submerged within cleaning fluid  14 . Transducers  18  are driven with sufficient power and at a desired frequency to clean workpiece  16 . The actual power and frequency, or combination of powers and frequencies that may be used in order to clean workpiece  16  will depend on, for example, the type of workpiece, the type of debris or contaminants to be cleaned, and the client and may be determined by those skilled in the an based principles known in the art. 
         [0029]    Referring to  FIG. 2 , apparatus  10  includes a set of rollers  20 , an example of which is shown in  FIGS. 3 and 4 . Rollers  20  may be incorporated into a skid  22 , as shown in  FIGS. 5 and 6 . Preferably, rollers  20  on skid  22  are designed to conform to a rounded surface in order to properly support workpiece  16 . Referring to  FIGS. 1 and 2 , workpiece  16  is positioned in cleaning vessel  12  on rollers  20  and may be partially submerged. In the depicted example, a baffle  24  may be used to effectively shorten vessel  12  and reduce the amount of cleaning fluid  14  required to sufficiently submerge workpiece  16 . 
         [0030]    Apparatus  10  is particularly useful in cleaning workpieces such as heat exchangers, which are made up of a series of exchanger tubes. Exchanger tubes are typically enclosed within a housing, but are preferably removed from the housing for cleaning, as shown in  FIG. 6 . Referring to  FIG. 10 , there is shown a bundle of exchanger tubes  26 . Exchanger tubes in bundle  26  may be straight with an opening at each end of the bundle as shown, or may only have openings at one end in the case of a u-tube exchanger bundle. Bundles  26  may be arranged in a round bundle with one or two end sheets  32  and intermediate baffle plates  34  to support the tubes. While exchanger bundles  26  will often have a round cross section, this may not always be the case, as shown in  FIG. 12 . Other equipment or workpieces that may he cleaned may also not have a round cross-section. Referring to  FIGS. 11 and 12 , round collars  28  may be attached that allow objects that are not round to rotate on rollers  20 . As will be understood, the portion of workpiece that engages the rollers, either as part of the workpiece, or attached to the workpiece, should be rounded to allow the workpiece to turn on the rollers. Workpiece  16  may be temporarily modified for cleaning purposes if necessary, as has been done in  FIG. 12 , where collars  28  have been attached to an exchanger bundle  26 . In the example depicted in  FIG. 4 , set of rollers  20  is driven by a chain  30  to cause rollers  20  to turn in order to rotate workpiece  16  in cleaning vessel  12 . Other designs for rotating the workpiece may also be used, as will be recognized by those skilled in the art. For example, the rollers may have an integral motor, such as an electric or hydraulic motor, that drives one or more rollers. 
         [0031]    By rotating the workpiece in the fluid during cleaning, the ultrasonic waves are swept across the tubes within, more evenly distributing the energy and increasing the cleaning efficiency. The rotation also helps dislodge material from the part because of the motion (changes in attitude) and momentum transfer (moving through the liquid) and liquid exchange rate increase near the surface of the part. The motion should be “slow enough” so as not to significantly agitate the solution internally (disrupt sound waves) or at the surface (gasification). In addition, rod style transducers are preferably mounted diagonally with respect to the tube orientation (which is preferably horizontal) such that the wave nodes sweep across the length of the tubes as they rotate. It has been found that mounting transducers horizontally or vertically will clean the workpiece with less consistency along its length. As the workpiece rotates, this results in “bands” of areas that may be cleaned less or more than others. Other types of transducers or transducer mountings may be used. For example, the mountings may move the transducers relative to the walls of the vessel, such as in a cyclic movement, or in a linear movement with a horizontal and/or vertical component. The position of the transducers may also be adjustable, either automatically or manually within the vessel, such as to adjust for a particular size and shape of a workpiece, or to adjust the cleaning force being applied to the workpiece as the cleaning process progresses. This may be used to distribute the ultrasonic energy more equally along the workpiece. The frequencies and power requirements of the transducers may be optimized by those skilled in the art. The action of the tubes raising and lowering from the fluid also helps to flush the inside of the tubes, where, depending on the exchanger design, the exchanger is preferably mounted on the skid such that it is slightly tilted to one end or the other. The rollers on the skid may be positioned anywhere along the length of the skid to accommodate different length exchangers (and balance the weight) and may be moved vertically to accommodate different end diameters, as well as to allow a slight tilt. 
         [0032]    Referring to  FIG. 1 , the heat exchanger will preferably be submerged at least half way in the tank. In addition, the exchanger tubes within the heat exchanger must be opened to the liquid to allow the cleaning liquid to enter each tube. 
         [0033]    The skid has the added benefit of eliminating slings used typically to raise and lower the exchanger. Referring to  FIG. 7-9 , preferably, skid  22  has some sort of superstructure  36  used as hoist points for a spreader bar or slings from a crane. Superstructure  36  may be tall enough to extend out of the cleaning fluid in the vessel, or at least extends to a known position, such that superstructure  36  can be more accurately and more easily engaged by a crane or other lifting device. Skid  22  may carry more than one set of rollers spaced along its length or, as can be seen in  FIG. 7 , superstructure  36  may have more than one position that can carry rollers  20 . The outer pockets  38  hold rollers in a position used for larger diameter workpieces, while the inner pockets  40  are useful for smaller diameter workpieces. Superstructure  36  may have upper pieces  42  that are removable to provide access to the rollers  20  from above, such that a crane can be used to manipulate the position of a workpiece. Alternatively, referring to  FIGS. 8 and 9 , the entire superstructure  36  may be removable from skid  22  to reduce the amount of material and obstacles in the cleaning tank in order to achieve a higher cleaning efficiency. As seen in  FIG. 8 , superstructure  36  may he a rigid structure, or referring to  FIG. 9 , it may be attached by chains. Referring to  FIG. 7 , the bottom of the superstructure  36  or skid  22  may be shaped to engage the bottom of a tank, such that the superstructure  36  or skid  22  may be used in an existing cleaning tank. It will be understood that superstructure  36  and skid  22  may be integrally formed, or may take other shapes aside from those described herein. In one example, the skid may be 30 feet long with a capacity of up to 50 tons. 
         [0034]    In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. 
         [0035]    The following claims are to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, and what can be obviously substituted. The scope of the claims should not be limited by the preferred embodiments set forth in the examples above.