Abstract:
In one aspect the invention provides a method of cleaning molten solder from the hot tip of a soldering iron that does not require a water-laden sponge. The hot tip of the iron is wiped against a block of dry open-celled melamine foam. The block is formed with an inclined through-hole that leads to the bottom of a receptacle holding the block. The hot tip is wiped against the foam surrounding an upper end of the through-hole, and the molten solder removed from the tip accumulates in the receptacle below.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. patent application Ser. No. 11/117,285 filed Apr. 29, 2005, now U.S. Pat. No. 7,870,990, the contents of which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to methods and apparatus for cleaning the hot tip of a soldering iron that do not involve use of water. 
     DESCRIPTION OF THE PRIOR ART 
     A soldering iron used to make an electrical or electronic circuit must be cleaned frequently during use. The object is to remove excess molten solder from the tip of the iron and also solder that has become contaminated with burnt residual flux and other materials that impair soldering. Current practice is to wipe the hot tip of the iron against a cellulose sponge soaked with water to avoid burning of the sponge. 
     Various devices have been proposed in the prior art to implement such a wet cleaning method. A wide-spread practise is to incorporate the sponge into a soldering iron stand. The stand includes a base, a soldering iron holder mounted to the base, and a receptacle in the base for receiving a sponge and water. Other implementations may be found in U.S. Pat. No. 3,990,623 to Fortune; U.S. Pat. No. 4,118,821 to Kuhn; and U.S. Pat. No. 4,803,748 to Quasney. 
     Other arrangements have been proposed that involve holding the tip of an iron held against dry rotating wiping elements. Examples are to be found in U.S. Pat. No. 3,765,047 to Tashjian; U.S. Pat. No. 4,394,785 to Vogler; and U.S. Pat. No. 4,625,355 to Miyashita. Similar methods and apparatus have also been proposed in Japanese patent JP8192264 to Mizuta et al published on Jul. 30, 1996; German patent DE 4429873 to Kroes published on Mar. 16, 1995; and German patent DE19727181 published on Jul. 2, 1998. 
     There are significant shortcomings to using a wet sponge to wipe the hot tip of a soldering iron. The principal problem is that the tip cools quickly upon contact with the water-laden sponge. This tends to solidify the molten solder remaining on the tip, and requires the user to wait while the tip to reheats before wiping again. This process may be repeated several times before all solder is removed. Once the tip is clean, the user must wait until the tip is restored to an operating temperature before continuing soldering. 
     The prior art cleaning method also tends to damage the tip of the soldering iron, impairing application of solder. More specifically, acid residues from solder tend to corrode the tip. As well, use of water in wiping sponges is conducive to build up of salts, especially in areas where local water has a high mineral content. In short order the tip must be replaced. 
     Despite such shortcomings, the practice of placing a pad of water-laden sponge into a receptacle and wiping the hot tip of a soldering iron against the pad continues. 
     SUMMARY OF THE INVENTION 
     In one aspect, the invention provides a method of cleaning molten solder from the hot tip of a soldering iron without use of water. The method involves wiping the hot tip against a dry block of open-celled melamine foam. Such sponge material has been used for household cleaning as it is durable and mildly abrasive. The tip of a soldering iron may typically achieve a temperature of about 450 degrees centigrade, and melamine foam, which has a melting point of about 350 degrees centigrade, can adequately withstand the higher temperature during the brief contact required in normal wiping. Significantly, melamine foam also has the characteristic of becoming more rigid upon application of heat. This is ideal for soldering applications since repeated exposure to a hot iron tends to impart structural rigidity to the surface of the foam, keeping it from falling apart. 
     Therefore, it is contemplated that various embodiments of the apparatus of the invention may include melamine foam in which at least a first portion of the melamine foam is at least partially more rigid than a second portion of the melamine foam. This rigidity of first portion of the foam may be accomplished through the application of heat or heat and compression to the melamine foam, either during or after manufacture of the foam, for example during the active use of the foam such as by the use of a hot soldering iron on the foam. The second portion of the melamine foam would typically be that which was not exposed to the heat or heat and compression. Examples of such manufacturing processes are described in U.S. Pat. No. 6,608,118 to Kosaka et al. and international application number PCT/US2004/022162 by Goldstein et al., both of which are hereby incorporated by reference. Thus, various embodiments of the invention may also include the method rendering the first portion of the melamine foam more rigid through the application of heat or heat and compression, in combination with other limitations. 
     A major advantage of using melamine foam is that cleaning time is significantly reduced. Since the tip is not exposed to water, which has a high thermal capacity, the user is not obliged to wait repeatedly for the tip to reheat in order to complete wiping. As well, the user does not have to wait a significant period of time for the tip to restore to an operating temperature before resuming soldering operations. 
     Another significant advantage of the invention is very effective cleaning. The microcell construction of melamine results in a mildly abrasive cleaning action that removes flux residues very effectively. With prior art methods, fumes potentially hazardous to the user may be seen rising from the tip of the iron, which suggests that contaminants have not be entirely removed. The cleaning method of the invention is sufficiently effective that virtually no noticeable fumes are produced. Since melamine foam is largely free of halides, fibre and CFC&#39;s, the foam is also less likely to release toxic substances in response to heat from a soldering iron, particularly since wiping action involves only short contact between iron and foam. 
     Another advantage of the invention is that the life of the soldering iron tip is extended. One factor is that the method provides very effective removal of acid residues. Another is that the hot tip is not exposed to water so there is no consequent build-up of salts. Since corrosion is reduced, the tip need not be replaced as frequently. 
     Another advantage of the invention relates to disposal of spent solder that accumulates after repeated cleaning of a soldering iron tip. In the prior art, there has been a tendency to dispose of spent solder beads in a conventional drain, which introduces lead and other toxic materials into local water. Since the method of the invention does not involve a water-laden sponge, there is no need to separate spent solder from water, and users can very conveniently deposit the solder in dry disposal containers. 
     Other aspects of the invention, including apparatus for implementing the methods of the invention, will be apparent from a description below of a preferred embodiment, and will be more specifically defined in the appended claims. This specification refers to a “through-hole” formed, for example, in a block of melamine foam. For certainty of interpretation, a “through-hole” should be understood as an open-ended passage extending fully between two spaced-apart surfaces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood with reference to drawings illustrating a preferred embodiment, in which: 
         FIG. 1  is a perspective view of a block of melamine adapted for cleaning of a soldering iron tip; 
         FIG. 2  is a vertical cross-section of the block of foam of  FIG. 1  and a receptacle that retains the block of the foam; 
         FIG. 3  is a perspective view of another block of melamine foam and a receptacle adapted for cleaning of a soldering iron tip; 
         FIG. 4  is a perspective view of yet another block of melamine foam adapted for cleaning of a soldering iron tip; 
         FIG. 5  is a vertical cross-section of the block of melamine foam of  FIG. 4  and a receptacle that retains the block of the foam; and, 
         FIG. 6  is a vertical cross-section of the block of melamine foam and a receptacle which are a variant of the apparatus of  FIG. 5 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Reference is made to  FIGS. 1 and 2  which show a generally rectangular block  10  of dry open-celled melamine foam and a receptacle  12  shaped to retain a lower portion of the block  10 . The block  10  of foam has a funnel-shaped recess  14  in its top surface  16 . The recess  14  has a conical upper portion  18  and a cylindrical lower portion  20  that extends fully to the bottom surface  22  of the block  10 . As apparent in  FIG. 2 , a soldering iron  24  is cleaned by wiping the hot tip  26  of the iron  24  against the inclined surfaces of the conical portion  18  of the recess  14 . Molten beads  28  of solder travel along the inclined surfaces of the conical portion  18  into the cylindrical portion  20  of the recess  14 , accumulating at the bottom of the receptacle  12 . When soldering is done, the user can simply invert the block  10  and the receptacle  12  over a dry waste container (not shown) to remove accumulated solder  28 . 
       FIG. 3  shows alternative apparatus for cleaning the soldering iron tip  26 . Once again, the apparatus includes a generally rectangular block  30  of dry open-celled melamine foam, and a generally rectangular receptacle  32  shaped to receive a lower portion of the block  30 . A cylindrical through-hole  34  with an oval, circular, or other shaped cross-section extends vertically through the block  30  of foam. The user has the option of wiping the tip  26  of the soldering iron  24  along the top surface  36  of the block  30  of foam. Alternatively, the user can insert the tip  26  partially into the through-hole  34 , and then wipe the tip  26  against the upper edge of the through-hole  34  or against the foam surrounding the upper end of the through-hole  34 . 
       FIGS. 4 and 5  illustrate yet another apparatus for cleaning the tip  26  of the soldering iron  24 . Once again, the apparatus includes a block  38  of dry open-celled melamine foam, and a generally rectangular receptacle  40  for receiving a lower portion of the block  38 . 
     The block  38  has an overall rectangular shape with a pair of diagonally opposing corners beveled. The block  38  has a parallel pair of opposing side faces  42  (only on side face apparent) that are planar and vertical. The block  38  also has parallel top and bottom surfaces  44 ,  46  that are planar and horizontal. The block  38  also has forward and rear faces  50 ,  52 . The forward face  50  has a lower surface  54  that is planar and vertical, and an upper surface  56  that is planar and inclined at an acute angle (roughly 45 degrees) relative to the top surface  44  of the block  38 . The rear face  52  has a planar lower surface  58  that is inclined at an acute angle (roughly 45 degrees) relative to the bottom surface  46  of the block  38  and a planar upper surface  60  that is vertical. The lower surface  54  of the forward face  50  and the upper lower of the rear face  52  and are parallel, vertical and spaced for receipt between forward and rear walls  62 ,  64  of the receptacle  40 . A cylindrical or other shaped through-hole  66  extends between the upper inclined surface of the forward face  50  and the lower inclined surface of the rear face  52 . The through-hole  66  is inclined at 45 degrees relative to vertical and has open upper end and an open lower end. Other angles for the through-hole are contemplated and are considered within the inventive scope described herein. This symmetry of this arrangement permits the block  38  of foam to be removed from the receptacle  40 , rotated 180 degrees about a central horizontal axis perpendicular to the side faces  42 , and then reinstalled in the receptacle  40 . When rotated, the orientation of the block  38  is identical to its original orientation shown in  FIG. 5 . The inclined lower surface  58  of the rear face  52  cooperates with the receptacle  40  to define a space or cavity  68  where solder  28  can accumulate. 
     In use, the hot tip  26  of the iron  24  is inserted into the upper end of the through-hole  66  and contacted with the foam surrounding the through-hole  66 . As indicated in  FIG. 4 , the user then rotates the tip  26  around the interior surfaces of the through-hole  66  to wipe molten solder from the tip  26 . (In  FIG. 4 , positions of the soldering iron  24  during such rotation have been shown in phantom outline). The molten solder  28  then travels along the inclined through-hole  66 , escapes through the lower end of the through-hole  66 , and deposits in the space between the receptacle  40  and the inclined lower surface  58  of the rear face  52 . Solder does not cling strongly to the melamine foam; however, should solder accumulate near the upper end of the through-hole  66 , the block  38  can be rotated through 180 degrees relative to the receptacle  40 , and the user can continue soldering and wiping the tip  26  as required. To clean the apparatus, the block  38  of foam is simply removed, and the debris accumulated in the cavity  68  can simply be dumped into a dry disposal container. Any solder clinging to the foam surrounding the through-hole  66  can be dislodged with a finger. 
       FIG. 6  shows a variation of the apparatus of  FIGS. 4 and 5 . Common reference numerals have been used to indicate features common to the two apparatus. The principal difference resides in the configuration of the shape of their respective through-holes. The apparatus of  FIG. 6  has a through-hole  70  with an upper frustoconical portion  72  and a lower frustoconical portion  74 . Each frustoconical portion  72  or  74  expands progressively from the center of the block  38  to the inclined surfaces between which the through-hole  70  extends. This arrangement permits the user to keep the conical tip  26  of the soldering iron  24  substantially normal to the entrance opening of the through-hole  70 . More specifically, limited wrist action is required to wipe the conical surface of tip  26  against the conical inner surfaces that define the conical passage portions  72 ,  74 . Beads  28  of solder forming against those surfaces travel along the inclined trough  76  of the upper passage portion  72  and accumulate in the cavity  68 . 
     It will be appreciated that particular embodiments of the invention have been described and that modifications may be made therein without necessarily departing from the scope of the appended claims. 
     PARTS LIST 
     Cleaning Soldering Iron Tip 
     
       FIGS. 1 and 2 
         
         
           
               10  block 
               12  receptacle 
               14  funnel-shaped recess 
               16  top surface (block) 
               18  upper conical portion 
               20  lower cylindrical portion 
               22  bottom surface (block) 
               24  soldering iron 
               26  hot tip 
               28  beads of solder 
           
         
       
    
     
       FIG. 3 
         
         
           
               30  block 
               32  receptacle 
               34  through-hole 
               36  top surface (block) 
           
         
       
    
     
       FIGS. 4 and 5 
         
         
           
               38  block 
               40  receptacle 
               42  side faces 
               44  top surface 
               46  bottom surface 
               48  (not used) 
               50  forward face 
               52  rear face 
               54  lower surface (forward face—vertical) 
               56  upper surface (forward face—inclined) 
               58  lower surface (rear face—inclined) 
               60  upper surface (rear face—vertical:) 
               62  forward wall (receptacle) 
               64  rear wall (receptacle) 
               66  through-hole 
               68  cavity (accumulating solder) 
           
         
       
    
     
       FIG. 6 
         
         
           
               70  through-hole 
               72  upper frustoconical portion (through-hole) 
               74  lower frustoconical portion (through-hole) 
               76  trough (through-hole)