Abstract:
The invention provides an apparatus and a method for recovering good solder for re-use from dross. Dross is introduced into a chamber ( 108 ) which is heated, whilst agitation is provided by means e.g. of an impeller ( 116 ). Recovered solder is drained through a drain valve ( 118 ) which is suitably thermally activated. Waste can be collected by inversion of the vessel via a motorised pivot.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to industrial soldering methods and devices, and in particularly relates to a method and a device for solder recovery from dross. 
       BACKGROUND 
       [0002]    During industrial soldering, a heated solder bath is maintained and it is necessary to scrape off dross from the top of the solder bath at frequent intervals, the dross primarily being formed of oxides of tin and good solder. The generation of dross is higher in a Sn—Ag—Cu alloy (Pb-free solder) than in a Sn—Pb solder (leaded solder). 
         [0003]    Dross collected from industrial soldering contains a good amount of usable solder and an oxidized residue, which should be disposed. However, with conventional methods of solder recovery, the oxidized residue cannot be completely removed, and the oxidized residue still contains substantial amount of solder. 
         [0004]    A conventional method of recovering solder from dross is through heating the dross and agitating the heated dross. The solder is collected subsequently after the operator has removed the upper oxidized residue with a ladle. However, this solder recovering method, in addition to removing the oxidized residue, also collects the usable solder. Further, as the process is more or less manual, it demands high level of user skill. Still, the efficiency is not what is expected. Further there are safety concerns, as the environment in which the process is carried out is generally dusty and temperatures are significantly high to work. The operation is generally very labour-intensive. Finally, there is a significant risk of operator exposure to flux fumes, which can be toxic. 
         [0005]    Accordingly, there is need for a method and/or a device that is not only safe to use, but also efficient in terms of the amount of solder it helps recover from the dross. 
       BRIEF DESCRIPTION OF THE PRIOR ART 
       [0006]    US2010187732 discloses a solder recovery device including a melter which melts solder dross stored in a melting crucible, an agitation unit which agitates the melted solder dross, so as to separate the melted solder dross up and down into an oxidized residue and a recycled solder in the melting crucible, and a suction unit which sucks the oxidized residue generated by the agitation, the suction unit sucking the oxidized residue in an upper portion of the melting crucible to be removed. 
         [0007]    WO9525823 discloses an apparatus and a method for recovering solder from dross. Dross is poured into a heated chamber ( 1 ). The heated dross is then compressed by a piston ( 21 ) to force good solder out of the dross into a collecting tray ( 17 ), also referred to as a drain tray. 
       OBJECTS 
       [0008]    Some of the objects of the system of the present disclosure, which satisfies at least one embodiment of the present disclosure are as follows: 
         [0009]    It is an object of the system of the present disclosure to ameliorate one or more problems of the state of the art or to at least provide a useful alternative. 
         [0010]    It is an object of the present disclosure to facilitate recovery of higher amounts of usable (good) solder from the dross than what is achievable using the conventional methods and/or devices. 
         [0011]    Another object of the present disclosure is to provide an automated device for solder recovery from dross, which involves minimal human intervention and skill. Yet another object of the present disclosure is to provide a method and/or a device for solder recovery that is safe and easy to use. 
       SUMMARY OF THE INVENTION  
       [0012]    According to a first embodiment, the invention provides an apparatus for solder recover, comprising:
       i) a chamber for receiving dross, the chamber being provided with an inlet for dross and an outlet through which recovered solder can pass;   ii) a heater for heating dross in the chamber;   iii) an agitator inside the chamber for agitating heated dross, to separate good solder from the residue.       
 
         [0016]    According to a second embodiment, the invention provides a method of recovering solder from dross, the method comprising the steps of
       i) introducing dross into a chamber being provided with an inlet for dross and an outlet through which recovered solder can pass;   ii) heating the dross;   iii) stirring the dross;   iv) allowing molten solder to flow out of the outlet after a period of time.       
 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0021]    The present disclosure will now be explained in relation to non-limiting accompanying drawings, in which: 
           [0022]      FIG. 1  illustrates a schematic representation of a solder recovery device (solder recovery device), in accordance with an embodiment of the present disclosure; 
           [0023]      FIG. 2  illustrates a top view of the solder recovery device of  FIG. 1  showing an impeller, in accordance with an embodiment of the present disclosure; 
           [0024]      FIG. 3  illustrate another schematic representation of the solder recovery device  100  in operation, in accordance with an embodiment of the present disclosure; 
           [0025]      FIG. 4  illustrates another schematic representation of the solder recovery device of  FIG. 1  with a filter device, in accordance with an embodiment of the present disclosure; 
           [0026]      FIG. 5  illustrates removal of residue from the solder recovery device of  FIG. 1  following solder recovery, in accordance with an embodiment of the present disclosure; 
           [0027]      FIG. 6  illustrates an actual representation of a solder recovery device showing a tilting arrangement, in accordance with an embodiment of the present disclosure; 
           [0028]      FIG. 7  illustrates an actual representation of the impeller of the solder recovery device of  FIG. 6 , in accordance with an embodiment of the present disclosure; 
           [0029]      FIG. 8  illustrates an actual representation of the solder recovery device of  FIG. 6  showing the coupling of a motor with a rotor shaft of the solder recovery device, in accordance with an embodiment of the present disclosure; 
           [0030]      FIG. 9  illustrates another actual representation of the solder recovery device of  FIG. 6  showing an output section of the solder recovery device, in accordance with an embodiment of the present disclosure; 
           [0031]      FIG. 10  illustrates various representations of the filter device of the solder recovery device of  FIG. 6 , in accordance with an embodiment of the present disclosure; 
           [0032]      FIG. 11  is a photograph of a complete unit according to the invention; 
           [0033]      FIG. 12  is a photograph of dross being loaded into the inlet hopper of the device; 
           [0034]      FIG. 13  is a photograph of recovered solder pouring from the outlet of the device into a solder collection tray; 
           [0035]      FIG. 14  is a photograph of the filter unit of the apparatus; 
           [0036]      FIG. 15  is a photograph of the filter unit, showing the filtration medium inside; 
           [0037]      FIG. 16  shows ingots of solder recovered from dross (left hand), together with waste oxide by-product (right hand). 
       
    
    
     DETAILED DESCRIPTION 
       [0038]    During soldering on an industrial scale, a heated solder bath is maintained and it is necessary to scrape off dross from the top of the solder bath at frequent intervals, the dross primarily being formed of oxides of tin and lead. However, up to 90% of the solder can be lost with the dross. Good solder can be reclaimed from the dross and conventionally this is done by simply heating the dross. However, this is a relatively inefficient method and barely economic. 
         [0039]    It is understood that dross consists of pockets of good solder which are surrounded by a crust-like envelope of tin and lead oxides (in the case of lead solder) or other metal oxides (in the case of lead-free solder). In the existing technology, when the dross is heated and compressed, the oxide crust bursts and liquid solder can escape. In addition, any free solder in the dross removed from the solder bath will also be recovered. 
         [0040]    In an improved method known in the art, the dross is heated and compressed with a piston. This leads to greater recovery of good solder compared with simply heating. Using this procedure, recovery of between 50 to 75% of the available solder is possible. 
         [0041]    Surprisingly, it has now been found that if instead of compressing the solder, the dross is heated and appropriately agitated, e.g. with an impeller or stirring paddle, not only is greater recovery of solder realised, but also the recovered solder is of higher purity, including up to the manufacturer&#39;s specification. Using the method of the invention, between 65 and 85% solder recovery is possible. 
         [0042]    An exemplary solder recovery device and a method of recovering solder from dross will now be described in accordance with the present disclosure and with reference to the accompanying drawings, which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration. 
         [0043]    The embodiments herein and the various features and advantageous details thereof are explained with reference to one or more non-limiting embodiment in the following description. Description of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein. 
         [0044]    Briefly the apparatus of the invention comprises a chamber for receiving dross, the chamber being provided with an inlet for dross and an outlet through which recovered solder can pass; a heater for heating dross in the chamber and an agitator inside the chamber for agitating heated dross, to separate good solder from the residue. 
         [0045]    The chamber (also referred to as the “solder pot”) may be of any suitable shape, but is typically generally cylindrical with a frustoconical lower end. This arrangement facilitates drainage of the solder from the chamber after agitation. The chamber may be formed of any suitable material, but necessarily must be capable of withstanding the temperatures employed during the process. Accordingly, metal is preferred, and stainless steel is more preferred. 
         [0046]    The inlet (or “input section”) is generally provided at or near the top of the chamber, so that dross may be fed into the chamber by gravity. 
         [0047]    The outlet (or “output section”) is generally provided at or near the base of the chamber. This enables good solder to be drained out of the chamber under the influence of gravity. In a preferred embodiment, the outlet is provided at the base of a frustoconical lower section of the chamber, to facilitate complete drainage of good solder from the chamber. 
         [0048]    The heater can be any conventional heater known in the art, and can be, for example, an electrical heating element disposed either inside the chamber or around the outside of the chamber (the latter being preferred). The chamber can be, and preferably is, jacketed with insulating material to provide greater thermal stability and reduce power consumption. Heating by means of gas jets etc. is also a possibility. 
         [0049]    The agitator preferably provides mechanical agitation to the dross contained within the chamber. This may be in the form of a vertical mashing motion, or a side-to-side motion, but preferably is provided by an agitator adapted to rotate within the chamber, such as a paddle or impeller. 
         [0050]    The description hereinafter, of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. 
         [0051]      FIG. 1  illustrates a schematic representation of a solder recovery device (solder recovery device)  100 , in accordance with an embodiment of the present disclosure. In the present embodiment, the solder recovery device includes an input section  102 , a processing section  104  flow connected to the input section  102 , and an output section  106  flow connected to the processing section  104 . During operation, dross is poured into the solder recovery device  100  through the input section  102 , which may be a hopper. 
         [0052]    From the input section  102 , the dross reaches the processing section  104 . In an embodiment, the processing section  104  includes a solder pot  108 , which is enclosed in an enclosure  110 . The dross reaches the solder pot  108  where it is heated at high temperatures so as to melt the dross. The temperature inside the solder pot  108  depends on the melting point of the dross poured into the solder recovery device  100 . In an implementation, the dross poured into the solder recovery device  100  is heated up to a temperature ranging from about 250° C. to 400° C. However, in other implementation, where, for example, hard solder is to be processed, the temperature may further be increased. 
         [0053]    Once melted, the dross is agitated inside the solder pot  108 . For this purpose, the solder recovery device  100  preferably includes at least one motor  112 , whose drive shaft (shown in  FIG. 8 ) is coupled to a rotor shaft  114 , which passes through the solder pot  108  where the dross is to be heated. At a far end of the rotor shaft  114  inside the solder pot  108 , an impeller  116  having one or more agitator blades is coupled to the rotor shaft  114 . The motor  112 , via the rotor shaft  114 , rotates the impeller  116  in a clockwise/anticlockwise direction repeatedly so as to separate the dross from the good solder. In an embodiment, a geared motor powered by alternating current (AC) or direct current (DC) can be used. However, the present disclosure is not limited to any extent by the choice of the motor that is implemented for the purpose. 
         [0054]    The good solder separated from the dross is drained out of the output section  106  via a drain valve  118 . In an embodiment, the output section  106  is cooled by a cooling unit, such as a fan (shown in  FIG. 3 ). Further, the output section  106  includes a filter device (shown in  FIG. 4 ), which filters the solder before the solder leaves the output section  106  via the drain valve  118  into an ingot tray  120  (or drain tray). 
         [0055]    In this way, the solder is separated from the dross and is recovered. The dross that is left inside the solder pot  108  after the solder recovery is residue. This residue is removed from the solder pot  108  using steps discussed in the later part of the description. 
         [0056]    In a preferred embodiment, the sequence of heating, stirring and draining is operated under computer or microprocessor control. After the operator has introduced dross into the chamber, they initiate the microprocessor or computer, which controls the heating and stirring at the appropriate rates to obtain optimum good solder recovery, and then also controls the draining of the solder into the ingot tray. 
         [0057]      FIG. 2  illustrates a top view of the solder recovery device  100  of  FIG. 1  showing the impeller  116 , in accordance with an embodiment of the present disclosure. As shown, the impeller  116  is capable of rotating in clockwise/anti-clockwise directions via the motor  112  (shown in  FIG. 1 ), thereby producing an agitating flow and centrifugal forces inside the solder pot  108 . These forces and flows separate the solder from the dross. In an embodiment, the impeller  116  is coupled to the rotor shaft  114  of the motor  112 . In the present embodiment, the impeller  116  has three blades. However, it will be appreciated by a person skilled in the art that the number of blades may be less than or more than the number of blades as disclosed in the present embodiment, depending on the requirement in particular setting. In an embodiment, the blades of the impeller  116  are attached offset to a central axis of the rotor shaft  114  so as to provide a slanted configuration of the blades with respect to the rotor shaft  114 . Slanting or tapering provides efficient dross removal. In an embodiment, the impeller  116  is rotated in a direction opposite to the direction of the slant of the blades so as to provide a screw conveyor type action. For example, if the blades are offset towards left of the rotor shaft  114  so as to give a clockwise configuration when seen in line with the axis of the rotor shaft  114  from a side where the impeller is attached to the rotor shaft  114 . With such a configuration of the blades, the motor  112  is configured to rotate in the opposite direction, i.e., in the anti-clockwise direction. 
         [0058]      FIG. 3  illustrate another schematic representation of the solder recovery device  100  in operation, in accordance with an embodiment of the present disclosure. 
         [0059]    Here, the cooling unit is shown as a fan  302 , which is placed near the output section  106  of the solder recovery device  100  from where the good solder  304  drains out. The fan  302  could be an external fan or a fan inbuilt in the solder recovery device  100  itself. In an implementation, the drain valve  118  lets the good solder  305  flow out of the drain valve  118  automatically when the fan  302  is stopped. The stop/flow of the good solder through the drain valve  118  is governed by the conduction of heat inside the solder pot  108 . When the fan  302  is ON and in running condition, the heat is taken away from the drain valve  118  and because of that, a temperature around the drain valve  118  falls below the melting point of the dross inside the solder pot  108 . Because of this, the good solder  304  stops flowing. When the fan  302  is OFF, and the temperature around the drain valve  118  is equivalent to the melting temperature of the dross, the good solder  304  starts flowing out of the drain valve  118 . In a preferred embodiment, heater ( 119 ) is added on the drain valve ( 118 ). It will start heating if the molten solder does not come out in a stipulated time. 
         [0060]      FIG. 4  illustrates a schematic representation of the solder recovery device  100  of  FIG. 1  with a filter device  402 , in accordance with an embodiment of the present disclosure. As shown, the output section  106  of the solder recovery device  100  includes the filter device  402 , which filters the solder that is drained out of the solder recovery device  100  through the output section  106 . The filter device  402  is positioned in the output section  106  just above the drain valve  118 . In an embodiment, the filter device  402  is a removable gauze filter having at least a perforated steel disc and stainless steel wool trapped inside the filter device  402  by the perforated steel disc (shown in  FIG. 10 ). The filter device  402  can be removed and cleaned after a few cycles of solder removal and may also be replaced after completing its cycle. For the purpose, a handle  404  is provided which is attached to the filter device  402  and allows attachment/detachment of the filter device  402  to/from the solder recovery device  100 . 
         [0061]      FIG. 5  illustrates removal of the residue from the solder recovery device  100  of  FIG. 1  following solder recovery, in accordance with an embodiment of the present disclosure. Following draining out the good solder from the solder recovery device  100 , the residue that remains inside the solder pot  108  is removed into a separate dross container  502 . For the purpose, the solder recovery device  100  is tilted using a tilting mechanism (shown in  FIG. 6 ), which can be a motor, separate from the motor  112 , coupled to an appropriate transmission mechanism. In an embodiment, the motor for tilting the solder recovery device  100  is coupled to the solder recovery device  100  via a chain and sprocket arrangement (shown in  FIG. 6 ). When activated, the motor for tilting, through the chain and sprocket arrangement, makes the solder recovery device  100  tilt at a predetermined angle, so as to let the residue removed from the solder recovery device  100 , for example, through the same input section  102  (i.e., via the hopper) from which the dross to be processed was initially poured into the solder recovery device  100 . In addition to the tilting, the impeller  116  is also rotated simultaneously using the motor  112 , so as to remove almost the entire residue deposited inside the solder pot  108  following recovery of the solder. 
         [0062]    The pivotal mounting of the chamber is advantageous, as it permits easy emptying of the unwanted products of the process, typically a powder of oxides of metal. It also minimizes the surface area or “footprint” of the device, meaning it occupies a smaller space than alternative apparatus. 
         [0063]      FIGS. 6 to 10  show actual representation of the solder recovery device  100  as well as various parts/components of the solder recovery device  100  discussed hereinbefore, in accordance with an embodiment. 
         [0064]    For example,  FIG. 6  illustrates an actual representation of the solder recovery device  100  shown from a side where a tilting mechanism  602  is provided. The tilting mechanism is, in the present embodiment, is a chain and sprocket arrangement  602  coupled to a motor  604 . 
         [0065]      FIG. 7  illustrates an actual representation of an impeller  116  of the solder recovery device  100 , in accordance with an embodiment of the present disclosure. The impeller  116  is coupled to the rotor shaft  114  such that an axis of the impeller  116  is in line with an axis of the rotor shaft  114 . 
         [0066]    Preferably, the impeller includes a plurality of blades disposed radially about a central shaft. Preferably, the blades are slanted or tapered to provide a screw action. Preferably, each blade comprises one or more slots to enhance the agitating effect when rotated. 
         [0067]      FIG. 8  illustrates an actual representation of the coupling of the motor  112  with the rotor shaft  114  of the solder recovery device  100 , in accordance with an embodiment of the present disclosure. The rotor shaft  114  is shown to be coupled to the motor  112  via a belt and pulley mechanism  802 . 
         [0068]      FIG. 9  illustrates an actual representation of the output section  106  of the solder recovery device  100  of  FIG. 1 , in accordance with an embodiment of the present disclosure. The output section  106 , among other things, is shown enclosed in a heat protective covering so as to avoid unwanted heat losses. 
         [0069]      FIG. 10  illustrates various representations of the filter device  402  of the solder recovery device  100  of  FIG. 1 , in accordance with an embodiment of the present disclosure. The filter device  402  is in the form of a cylindrical enclosure. Further, the drain valve  118  attached to one end of the filter device  402  as shown. The handle  404  is connected to the filter device  402  via a coupler  1002 . 
         [0070]      FIG. 10   b  shows a top perspective view of the filter device  402 . As shown, a removable perforated disc  1004  is placed inside the filter device  402  for allowing dross to flow out slowly.  FIG. 10   c  shows a perspective view of the filter device  402  illustrating the removable perforated disc  1002  and a steel wool  1006 . The steel wool is placed below the perforated disc  1004  and taps impurities in the solder draining out of the drain valve  118 . 
         [0071]      FIG. 11  is a perspective view of a solder recovery device according to one embodiment of the invention. Ducting for extraction of hazardous fumes is shown at the top of the unit. 
         [0072]      FIG. 12  is a perspective view of the inlet, or input section, showing dross being introduced into the device. 
         [0073]      FIG. 13  shows recovered solder flowing from the outlet, and into the drain tray. 
         [0074]      FIG. 14  shows an alternative embodiment of the filter device, which includes a slotted cover.  FIG. 15  shows the filter device with the cover removed, showing the filtration medium (in this case wire wool) inside. 
         [0075]      FIG. 16  shows ingots of recovered solder, together with the by-product of the process, in the form of metal oxides. 
         [0076]    In this way, maximum amount of good solder is recovered without involving any human skill or any unnecessary labour. Moreover, as the solder pot  108  is placed inside the enclosure  110 , the whole process of solder recovery is also safe for handlers. 
       TECHNICAL ADVANCEMENTS AND ECONOMICAL SIGNIFICANCE 
       [0077]    The technical advancements offered by the system of the present disclosure which add to the economic significance of the disclosure include the realization of: 
         [0078]    a) a device for recovering good solder from dross to the maximum possible extent; 
         [0079]    b) a cost-effective method of solder recovery from dross; 
         [0080]    c) a method and a device that facilitate safe and secure solder recovery from dross with minimum human intervention and labour. 
         [0081]    Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. 
         [0082]    The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment to achieve one or more of the desired objects or results. 
         [0083]    Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application. 
         [0084]    The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.