Patent Publication Number: US-2023143981-A1

Title: Transport system for transporting soldering material through a soldering apparatus, and a soldering apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application relates and claims priority to German Patent Application No. 10 2021 129 127.5, filed Nov. 9, 2021, the entirety of which is hereby incorporated by reference. 
     BACKGROUND 
     The invention relates to a transport system for transporting soldering material through a soldering apparatus, having two transport tracks running parallel to one another and extending in the transport direction, wherein each of the transport tracks comprises two transport rails, and wherein for the width adjustment of the respective transport track at least one of the two transport rails of the respective transport track is adjustable in the transverse direction running transversely to the transport direction. The soldering material can take the form of a printed circuit board populated with electronic components or as a goods carrier for goods, and in particular for printed circuit boards populated with electronic components. The soldering apparatus can in particular be a reflow soldering apparatus for the continuous soldering of printed circuit boards populated with electronic components or be a drying system for drying populated printed circuit boards. 
     Such transport systems generally grip the respective soldering material at the edges running parallel to the transport direction and convey said soldering material in the transport direction by means of transport rails, in which, for example, chain conveyors run. The transport rails can have a length of several meters and be composed of a plurality of rail sections. Such transport rails are also referred to as transport bars. Furthermore, it is known to provide, in addition to the two outer transport rails supporting the soldering material at the edges, a further transport rail for a central support supporting the soldering material in the central region. Central supports are advantageous in particular when comparatively large printed circuit boards or goods carriers are being soldered or dried. Said central supports prevent sagging of the soldering material in the central region, which can occur in particular due to the heating of the soldering material, and thus ensure functionally reliable transport. 
     The invention also relates to a soldering apparatus, in particular a reflow soldering apparatus for the continuous soldering of populated printed circuit boards or a drying system for drying populated printed circuit boards in which soldering material can be transported along a transport direction. 
     Reflow soldering apparatuses can be used to solder what are known to as SMD components (surface-mounted devices) onto the surface of printed circuit boards by means of solder paste. The solder paste, which is in particular a mixture of metal soldering granules, flux and paste-like components, is applied to or printed onto the surface of the printed circuit boards for reflow soldering. The components to be soldered are then set into the solder paste. In the reflow soldering process, the soldering material, i.e., the assembly consisting of a printed circuit board, solder paste and components to be soldered, is preheated along the process channel in a preheating zone and heated in a soldering zone to a temperature above the melting point of the solder paste. As a result, the solder paste melts and the solder joints form. In a cooling zone, if one is present, the soldering material is cooled until the melted solder solidifies before being removed from the reflow soldering apparatus. 
     In reflow soldering apparatuses, the process channel is generally formed by two channel halves, one upper and one lower channel half. The lower channel half is provided in or on a base body, and the upper channel half is provided in or on a cover hood. Further components, such as, for example, nozzle plates, fan units, air ducts guiding the process gas, filter elements and/or cooling elements, are generally provided in or on the process channel or in or on the base body and in or on the cover hood. Overall, a desired temperature profile is thus provided along the transport direction in the process channel, wherein the process gas is blown into the process channel, extracted therefrom, in particular cooled in the cooling zone, cleaned and fed back to the process channel. 
     Soldering apparatuses having transport units for transporting soldering material are known from DE 10 2019 128 780 A1 and DE 10 2005 055 283 A1. Furthermore, it is known from DE 10 2019 125 981 A1 to provide a transport system for transporting soldering material through a soldering apparatus having two transport tracks running parallel to one another and extending in the transport direction, wherein each of the transport tracks comprises at least two transport rails running parallel to one another and extending in the transport direction. In order to be able to accommodate soldering material of different sizes and, in particular, of different widths, it is also known for the transport tracks to be designed to be width-adjustable transversely to the transport direction. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide a transport system for transporting soldering material through a soldering apparatus and a soldering apparatus having a transport system, in which a width adjustment of the transport tracks is possible in a functionally reliable and flexible manner in such a way that maximally wide or maximally narrow soldering material can be transported through the soldering apparatus. 
     This object is achieved by a transport. In this case, in particular two transport tracks running parallel to one another and extending in the transport direction are provided, wherein each of the transport tracks comprises at least two transport rails, and wherein for the width adjustment of the respective transport track at least one of the two transport rails of the respective transport track is adjustable in the transverse direction running transversely to the transport direction. Furthermore, it is provided in particular that a plurality of guide elements are in each case provided at least on the adjustable transport rails, which guide elements interact with transverse rods extending in the transverse direction, wherein guide elements adjacent in the transverse direction of transport rails adjustable in the transverse direction are each guided displaceably on the same transverse rod toward one another and away from one another. In addition, it is provided in particular that the guide elements each have at least one recess and/or at least one projection extending in the transverse direction in such a way that a projection of the respective one guide element engages in a recess of the respective other guide element when adjacent guide rails are displaced toward one another. 
     Such an arrangement has the advantage that adjacent guide rails of different, in particular adjacent transport tracks can be moved to a maximum extent close to one another in order to thus allow a maximum or minimum width of the one or other transport track. Due to the provision of the recesses and projections that engage with each other, the guide elements do not prevent the adjacent transport rails from moving toward one another. It is advantageously conceivable that the design is such that adjacent guide rails of adjacent transport tracks can be moved toward one another to such an extent that they come into abutting contact with one another. 
     Because the guide elements nevertheless extend sufficiently in the transverse direction to be able to be supported securely on the transverse rods, the transport rails can overall be adjusted in a functionally reliable manner in the transverse direction. 
     Due to the fact that guide elements adjacent in the transverse direction of different transport tracks are each guided displaceably in the transverse direction on the same transverse rods for width adjustment, the number of transverse rods can overall be kept comparatively small. This results in a relatively simple structure overall. 
     According to one embodiment of the invention, it is provided that, in particular between the transport rails and the transverse rods, rotatably drivable rotary rods running parallel to the transport rails are provided, and that the transverse rods have a toothing on their side facing the respective transport rail, which toothing meshes with gear wheels provided on the respective rotary rods. By rotating the individual rotary rods, the associated transport rails can consequently be displaced in the transverse direction. In order to achieve a uniform displacement over the entire length of the transport rails, the transverse rails have a toothing that meshes with gear wheels provided on the rotary rods. In other words, if the respective rotary rod is rotated, it is ensured that the associated transport rod is uniformly adjusted over its entire length parallel to the transport direction. The respective transport rail is guided in a functionally reliable manner by the respective associated coupling elements or the associated guide elements on the respective transverse rods. 
     A further advantageous embodiment results when at least one guide element has a recess and when the guide element adjacent thereto in the transverse direction of the other guide track has a projection complementary to the recess. Consequently, the recesses and projections are in particular designed to be complementary in such a way that they can securely engage with one another and that secure guiding of the guide elements on the transverse rods is made possible without a width adjustment of the respective tracks being hindered. 
     It has been found to be advantageous if at least one guide element is formed wider in the transport direction than the transverse rod with which it interacts, and if the projection or the recess of the at least one guide element is formed narrower in the transport direction than the transverse rod. Overall, secure guiding of the respective guide element on the associated transverse rod is thereby made possible despite the provision of a projection or a recess. 
     Furthermore, it is advantageous if a plurality of coupling elements are fastened to at least one of the transport rails if the coupling elements each have a rotary receptacle for the rotary rod and if the coupling elements each provide a guide element. The respective coupling element consequently forms the connecting element, which ultimately connects the transport rail to the rotary rod and the associated guide element. 
     Furthermore, it is advantageous if drivable transport chains are provided on which preferably the edges of the soldering material and of the transport along the transport direction come to rest, wherein the transport chains run at least in portions inside the transport rails. For this purpose, the transport rails can be designed, for example, as profile elements. 
     Furthermore, it is conceivable that a motor for rotatably driving the respective rotary rod is in each case provided on a free end of the respective rotary rods. During the width adjustment of the individual transport rails, the motors then move together with the respective transport rail. Overall, a compact design can thereby be achieved. 
     The aforementioned object is also achieved by a soldering apparatus, in particular a reflow soldering apparatus or a drying system, in which soldering material can be transported along a transport direction, wherein such a soldering apparatus provides a transport system according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details of the invention can be found in the following description, on the basis of which an embodiment of the invention is described and explained in more detail. 
       In the drawings: 
         FIG.  1    is a side view of a reflow soldering apparatus; 
         FIG.  2    is a front view of the reflow soldering apparatus according to  FIG.  1   ; 
         FIG.  3    shows a detail of a transport system of the soldering apparatus according to  FIG.  1    and  FIG.  2   ; 
         FIG.  4    shows an enlarged detail IV from  FIG.  3   ; 
         FIG.  5    shows an enlarged detail V from  FIG.  3   ; 
         FIG.  6    is another perspective view according to  FIG.  5   ; 
         FIG.  7    shows an enlarged detail VII from  FIG.  3   ; 
         FIG.  8    is another perspective view according to  FIG.  7   ; 
         FIG.  9    is a perspective view of the coupling element shown in  FIGS.  7  and  8   ; 
         FIG.  10    is another perspective view of the coupling element according to  FIG.  9   ; 
         FIG.  11    is the plan view of the coupling element according to  FIGS.  9  and  10   ; 
         FIG.  12    is a view of an embodiment corresponding to the detail according to  FIGS.  7  and  8    with a different coupling element; and 
         FIG.  13    shows the detail shown in  FIG.  12    in another perspective view. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a reflow soldering apparatus  10  for the continuous soldering of soldering material. The reflow soldering apparatus  10  has an entry  12  and an exit  14 , wherein the soldering material that is to be soldered reaches the reflow soldering apparatus  10  via the entry  12  and is discharged from the reflow soldering apparatus  10  via the exit  14 . The soldering material is transported along a transport direction  18  through a process channel  16  indicated in  FIG.  1   . A preheating zone  20 , a soldering zone  22  and a cooling zone  24  are provided in the process channel  16 . 
     As is clear from  FIGS.  1  and  2   , a communications unit  36  is provided with a display screen and an input device by means of which it is possible to communicate with a machine controller of the reflow soldering apparatus  10 . 
     The soldering material, i.e., the printed circuit board provided with the solder paste and populated with electronic components, is first heated in the preheating zone  20  to a temperature below the melting temperature of the solder paste. In the soldering zone  22 , for soldering the electronic components to the printed circuit board the printed circuit board is heated for a certain duration to a process temperature above the melting point of the solder paste such that it melts in the soldering zone. In the cooling zone  24 , the soldering material is cooled such that the liquid solder solidifies before the soldering material is removed at the exit  14  of the reflow soldering apparatus  10 . 
     A transport system  34  is provided inside the reflow soldering apparatus  10  for transporting the printed circuit boards along the transport direction  18 . 
     As is also clear from  FIG.  2   , the reflow soldering apparatus  10  has a base body  11  and a cover hood  25 . The cover hood  25  can be pivoted open about a hood axis  32  extending parallel to the transport direction  18 . By the cover hood  25  pivoting open, the interior of the process channel  16  and the transport system  34  becomes accessible in order to check visually, maintain, clean, set up, replace, and optionally repair them. 
       FIG.  3    is a plan view of a detail of the transport system  34 . The transport system  34  comprises two transport tracks  38  and  40  running parallel to one another in the transport direction  18 . The two transport tracks  38  and  40  are each delimited by two transport rails  42 ,  44  and  46 ,  48 . It would be conceivable for a central support having a further transport rail for supporting the soldering material in the central region to be provided between the transport rails  42 ,  44  and  46 ,  48 . 
     For adjusting the width  50  of the transport track  38  or the width  52  of the transport track  40 , the adjacent transport rails  44  and  46  of the two transport tracks  38  and  40  are adjustable in the transverse direction  54 . Furthermore, the transport rail  42  is adjustable in the transverse direction. In the embodiment shown, the transport rail  48  is rigid in the transverse direction and therefore not adjustable. In the setting of the transport system  34  shown in  FIG.  3   , the track  40  is set with its width  52  comparatively wide and the track  38  is set with its width  50  comparatively narrow. 
     As is clear from  FIG.  3   , transverse rods  56  extending in the transverse direction  54  are provided, which transverse rods are provided in particular for guiding and holding the transport rails  42 ,  44 ,  46  that are adjustable in the transverse direction. 
     In order to adjust the central transport rails  44  and  46 , a plurality of coupling elements  72  are provided on each of the transport rails  44  and  46 , each of which comprises guide elements  58  and  60 . The transport rail  42  also provides coupling elements  72  having guide elements  61 . For guiding the transport rails  42 ,  44 ,  46 , the guide elements  58 ,  60 ,  61  rest with their underside on the upper side of the respective transverse rods  56 . As is clear from  FIG.  3   , the guide elements  58 ,  60  and  61  of different transport rails  44 ,  46 , which guide elements are adjacent in the transverse direction  54 , are each displaceable in the transverse direction on the same transverse rod  56 . The free ends of the transverse rods  56  are each fastened with supports  64  in a stationary manner inside the soldering apparatus  10 . 
     As is clear from  FIGS.  4 ,  5  and  6   , the transverse rods  56  each have a toothing  66  on their lower side facing the transport rails  42 ,  44 ,  46 . The upper side of the transverse rods  56  is flat such that the guide elements  58 ,  60  and  61  can be guided slidingly thereon. 
     In this case, rotatably drivable rotary rods  68  running parallel to the transport rails  42 ,  44 ,  46  are provided between the transport rails  42 ,  44 ,  46  and the transverse rods  56 . A plurality of identical gear wheels  70  that mesh with the toothings  66  of the transverse rods  56  are each provided on the rotary rods  68 . 
     The coupling elements  72  are fastened to the transport rails  42 ,  44 ,  46  and each comprise the guide element  58 ,  60  and  61  as well as a rotary receptacle  74  for rotatably receiving the respective rotary rod  68 . 
     As is clear from  FIG.  3   , motors  62  with which the rotary rods  68  can be rotatably driven are provided at the free ends of the rotary rods  68  in the region of the entry  12 . The arrangement is such that by rotating the rotary rods  68  or the gear wheels  70 , the guide rails  42 ,  44 ,  46  can be adjusted toward or away from one another in the transverse direction  54  on the transverse rods  56 . In contrast, the transport rail  48  is fastened to the transverse rod  56  in a clamping manner by means of a plurality of clamping elements  63 . 
     In order to ensure that the two central transport rails  44 ,  46  can be moved toward one another as far as possible without the transport rails  44 ,  46  being hindered by the guide elements  58 , the guide elements  58 ,  60  of the two central transport rails  44  and  46  have a special design. 
     As is clear from  FIGS.  4 ,  5  and  6   , the guide element  58  has a recess  76  that extends in the transverse direction and is designed in such a way that a projection  78  that runs on the respective associated guide element  60 , likewise in the transverse direction, can engage in the respective recess  76 . 
       FIG.  4    shows how the projection  78  engages in the recess  76 . The projection  78  is formed complementarily to the recess  76 . Due to the provision of the recess  76  or of the projection  78 , the two adjacent guide rails  44 ,  46  can be moved toward one another as far as possible, wherein secure guidance of the guide rails  44 ,  46  by the guide elements  58 ,  60  on the respective transverse rod  56  is nevertheless ensured. 
     Both the recess  76  and the projection  78  are designed in such a way that they have a width  80 ,  82  in the transport direction that is in each case smaller than the width  86  of the transverse rods  56  extending in the transport direction  18 . 
     As is clear in particular from  FIG.  4   , it is also conceivable for at least one of the guide elements  60  to have not only a projection  78  but also a recess  88  for a projection  90  provided on the other guide element  56 . It is important that the design is such that the adjacent guide rails  44 ,  46  of different transport tracks  38 ,  40  can be moved toward one another as far as possible without being hindered by the guide elements  58 ,  60 , specifically in such a way that the guiding of the transport rods  44 ,  46  by the guide elements  58 ,  60  is not adversely affected thereby. 
     As is clear in particular from  FIGS.  5  and  6   , the guide elements  61  of the one outer transport rail  42  are cuboid. 
     It can be seen from  FIGS.  5  and  6    that the guide rails  42 ,  44 ,  46  and  48  are designed as half-profiles  92  in which drivable transport chains are provided onto which the free edges of the soldering material can be placed for transport through the soldering apparatus  10 . 
     In particular before the transport system  34  is put into operation, it is necessary to align the individual transport rails  42 ,  46 ,  44 ,  48  precisely in the transport direction or parallel to one another. The outer transport rail  48 , which is not adjustable via the rotary rods  68 , can be aligned over its length by means of the clamping elements  63 . The clamping elements  63  can be adjusted on the transverse rods  56  in the transverse direction and ultimately fixed. 
     Such an adjustment of the rails  42 ,  44 ,  46 , which can be adjusted in the transverse direction, is not readily possible due to the provision of the rotary rods  68  and the gear wheels  72  that mesh with the transverse rods  66 . In order nevertheless to be able to align these transport rails  42 ,  44 ,  46  precisely parallel in the transport direction, it is provided that the coupling elements  72  each have a guide part  100  on which the respective guide element  58 ,  60 ,  61  is fastened, and a fastening part  102  that is fastened to the respective transport rail  42 ,  44 ,  46  in such a way that the respective fastening part  102  is designed to be adjustable and fixable relative to the associated guide part  100  in the transverse direction  54 . By adjusting the fastening part  102  relative to the guide part  100  in the transverse direction, the respective transport rail  42 ,  44 ,  46  can consequently be aligned in the transport direction  54 . 
     In  FIG.  7    and  FIG.  8   , which each show the transport rail  42  in isolation with the associated coupling element  72 , it becomes clear that the coupling elements  72  are formed from the fastening part  102  fastened to the guide rail  42  and the guide part  100 , wherein the associated guide element  61  is arranged on the respective guide part  100 . 
     The coupling elements  72 , which are provided on the guide rails  44  and  46 , have a corresponding, at least two-part design, in each case having a fastening part  102  and a guide part  100 , such as the coupling elements  72  shown in  FIGS.  7  and  8   . 
     As is clear in particular from  FIG.  7   , the fastening parts  102  are axially adjustable on the respective transport rail  42 ,  44 ,  46  in the transport direction  18 . For fastening, fastening screws  104  are provided that correspond to slot nuts that are displaceably guided in an axial groove  106  on the respective transport rail  42 ,  44 ,  46 . By releasing the screws  104 , the respective fastening part  102  is consequently displaceable in the axial direction. By tightening the screws  104 , the respective fastening part  102  is fastened in place on the respective transport rail  42 ,  44 ,  46 . 
     As is clear in particular from  FIGS.  9  to  11   , the respective fastening part  102  has an actuation section  112  and the respective guide part  100  has a counter-section  110  interacting with the actuation section  112 . The respective actuating section  112  and the associated counter-section  110  are formed lying flat against one another and enclose an acute angle α with the transport direction  18 , as becomes clear from  FIG.  11   . It is thereby achieved that the adjustment of the fastening part  102  in the axial direction is accompanied by a deflection of the respective transport rail  42 ,  44 ,  46  in the region of the respective coupling element  72  in the transverse direction. The transport rail  42 ,  44 ,  46  is consequently pushed away in the transverse direction  54  by the wedge-like actuation section  112  or counter-section  110  during the axial adjustment of the fastening part  102 . Because a plurality of coupling elements  72  are provided in the transport direction  18 , as becomes clear from  FIG.  3   , the respective transport rail  42 ,  44 ,  46  can be aligned in parallel with the transport direction  18  over its longitudinal extension. 
     In the embodiment shown in  FIGS.  7  to  11   , the respective actuating section  112  has an elongated hole  114  extending in the axial direction, in which elongated hole fastening elements  116  in the form of fastening screws are provided, by means of which, after the respective fastening part  102  has been adjusted in the axial direction, the fastening part  102  can be fastened in place on the guide part  100 . Threaded holes  118  are provided on the respective guide part  100 , by means of which threaded holes the fastening elements  116  can be screwed into the respective guide part  100 . 
     To align the respective transport rail  42 ,  44 ,  46  in the region of the respective coupling element  72 , the fastening part  102  is therefore first displaced in the axial direction in order to adjust the respective transport rail  42 ,  44 ,  46  in the transverse direction. In this case, the screws  104  and the fastening elements  116  are released. After the respective transport rail  42 ,  44 ,  46  has been aligned in the transverse direction in the region of the respective coupling element  72 , the screws  104  and the fastening elements  116  are tightened for fastening. 
       FIGS.  12  and  13    show a further embodiment in which a coupling element  120  is shown that has a different structure from the coupling element  72  shown in  FIGS.  7  to  11   . In  FIGS.  12  to  14   , components corresponding to  FIGS.  7  to  11    are denoted by corresponding reference signs. 
     In order to better illustrate the functioning of the coupling member  120  in  FIGS.  12  and  13   , these figures show a bottom view, which is why the toothing  66  of the respective transverse rod  56  is shown from above. Furthermore, the arrangement according to  FIGS.  12  and  13    is such that the respective rotary rod  68  is not arranged between the respective transverse rod  58  and the respective transport rail  42 ,  44 ,  46 , but laterally next to the respective transport rail  42 ,  44 ,  46 . Furthermore, the respective guide element  61  is formed integrally with the respective guide part  100 . 
     Corresponding to the coupling elements  72 , the coupling elements  120  have, in addition to the guide part  100 , a fastening part  102  that can be adjusted on the respective transport rail  42 ,  44 ,  46  and can be fastened with fastening screws  104 . The fastening part  102  provides an actuation section  112  and the guide part  100  provides a counter-section  110  interacting therewith. Unlike the coupling element  72  shown in  FIGS.  7  to  11   , the slot  114  is, in the case of the coupling element  120 , not provided on the fastening part  102 , but on the guide part  100  and there on the counter-section  110 . It can also be clearly seen from  FIGS.  12  and  13    that the actuation section  112  is designed as a groove-like guide recess in which the counter-section  110  is displaceably arranged. According to the embodiment shown in  FIGS.  7  to  11   , a fastening element  116  in the form of a fixing screw is also provided in the case of the coupling element  112 , by means of which fastening element the counter-section  110  can be fixed on the actuation section  112 . 
     According to the embodiment of  FIGS.  7  to  11   , the actuation section  112  or the counter-section  110  according to the embodiment according to  FIGS.  12  and  13    also encloses an acute angle α with the transport direction. 
     In order to axially align the respective transport rail  42 ,  44 ,  46 , according to the embodiment according to  FIGS.  7  to  11   , the fastening part  102  is first adjusted in the axial direction or transport direction  18  with the screws or fastening means  104  and  116  open to such an extent that the distance in the transverse direction  54  between the respective transport rail  42 ,  44 ,  46  and the respective guide part  100  changes during axial adjustment of the associated fastening part  102 , specifically until the respective transport rail  42 ,  44 ,  46  is aligned in the axial direction in the region of the respective coupling element  120 . The fastening screws or fastening means  104  and  116  are then tightened.