Patent Publication Number: US-2023144913-A1

Title: Transport system for transporting material to be soldered through a soldering apparatus, and soldering apparatus with laterally movable middle support

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application relates and claims priority to German Patent Application No. 20 2021 106 103.0, filed Nov. 9, 2021, the entirety of which is hereby incorporated by reference. 
     BACKGROUND 
     The invention relates to a transport system for transporting material to be soldered, in particular of populated printed circuit boards, by means of a soldering apparatus, having at least one transport track extending in the transport direction, in which the material to be soldered can be transported in the transport direction in a transport plane, wherein the transport track comprises two transport bars extending in the transport direction and at least one middle support with a middle bar extending in the transport direction, wherein the middle bar has a circulating conveying means with folding elements, wherein the conveying means provides a feed in the transport direction and a return counter to the transport direction, and wherein the folding elements are displaceable between a support position, in which they are folded up towards the transport plane, for supporting the material to be soldered, and with an adjusting device for transverse adjustment of the at least one middle support in a transverse direction running perpendicular to the transport direction. 
     Such transport systems convey the particular material to be soldered in the transport direction by contacting the edges running parallel to the transport direction. For this purpose, conveying means are provided in the transport bars, for example, in the form of chains or belts. The transport bars can have a length of several meters and be composed of several rail sections. Furthermore, it is known, in addition to the two outer transport bars which support the material to be soldered at the edges, to provide middle support with a middle bar which supports the material to be soldered in the middle region. Middle supports are advantageous in particular when comparatively large printed circuit boards or goods carriers are soldered or dried. They prevent the material to be soldered from bending or sagging in the middle region, which can occur, in particular, due to the heating of the material to be soldered, and therefore ensure functionally reliable transport. 
     The invention also relates to a soldering apparatus, in particular a reflow soldering apparatus for continuous soldering of material to be soldered, or a drying system for drying populated printed circuit boards, in which material to be soldered can be transported along a transport direction. 
     Reflow soldering apparatus are used to solder so-called SMD components (surface mounted devices) onto the surface of printed circuit boards by means of soldering paste. The soldering paste, which is in particular a mixture of metal solder granules, flux and pasty components, is applied or printed onto the surface of the printed circuit boards for reflow soldering. Subsequently, the components to be soldered are placed into the soldering paste. In the reflow soldering process, the material to be soldered, i.e., the assembly consisting of a printed circuit board, soldering 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 soldering paste. As a result, the soldering paste melts, and the soldering joints are formed. In a cooling zone, if one is present, the material to be soldered is cooled until the melted solder solidifies before it is removed from the reflow soldering apparatus. 
     With reflow soldering apparatus, the process channel is generally formed by two channel halves, an upper and a 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 hood. Further components such as, for example, nozzle plates, fan units, air ducts conducting 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 hood. Overall, a desired temperature profile is thereby provided along the transport direction in the process channel, wherein the process gas is blown into the process channel, sucked out therefrom, in particular cooled in the cooling zone, cleaned, and fed back to the process channel. 
     A soldering apparatus with transport units for transporting material to be soldered is 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 material to be soldered through a soldering apparatus with 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 bars running parallel to one another and extending in the transport direction. In order to be able to accommodate different sizes and, in particular, different widths of material to be soldered, it is also known that the transport tracks are designed to be adjustable transversely to the transport direction. 
     It has been shown that middle supports, in particular when they are not needed, can have a disadvantageous effect on the soldering process. In particular, it cannot be ruled out that the middle supports shield a heat transfer towards the material to be soldered so that the warm air flow striking the material to be soldered is inhomogeneous, and therefore adversely affect the soldering process. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide a transport system for transporting material to be soldered through a soldering apparatus, and a soldering apparatus with a transport system in which a middle support can be used, but should not negatively affect the soldering process — in particular when said middle support is not needed. 
     This object is achieved by a transport system. Consequently, it is provided in particular that the distance A between an underside of at least one transport bar facing away from the transport plane and the transport plane is smaller than the distance B between an upper side of the at least one middle support facing the transport plane and the transport plane, and that the adjustment device is designed such that the middle support with folding elements in the folded position is can be moved in the transverse direction underneath the at least one transport bar into a parked position provided laterally next to the transport bar. 
     Such an arrangement has the advantage that the at least one middle support, when not needed, can be completely moved laterally out of the region below the soldering plane under the transport bars or transport bars. Due to the fact that the respective middle support is thus not located below the material to be soldered and, in particular, also not below the transport bars, but laterally next to the transport bars on the side of the transport bars facing away from the material to be soldered in the parked position, the particular middle support does not have any negative effects on the heat transfer towards the printed circuit board, and therefore also has no effect on the soldering result. 
     With the adjusting device, the middle supports can consequently be moved out of the particular process region transversely to the transport direction until it is ensured that they do not negatively influence the soldering result. 
     According to the invention, the folding elements, which can in particular be designed as folding spring tabs, are such that they support the material to be soldered in the support position from below. In the folded position, the folding elements are preferably oriented running in the horizontal direction so that the middle support together with the folding elements can be moved in the transverse direction underneath the respective transport bar. 
     The parked position is selected, in particular, such that the middle support is arranged in the parked position, in particular, in the horizontal direction and in the vertical direction at a distance from the transport bar under which it is moved into the parked position. 
     It is further advantageous if two or more transport tracks are provided and if an independent separate middle support is provided for each of the transport tracks, wherein each of the middle supports is adjustable in the transverse direction with an adjusting device independently of the other middle support such that each middle support can be moved into a parked position. The parked positions can each be provided laterally next to the particular transport bar on which the side of the transport bar facing away from the particular material to be soldered. It is also conceivable that the middle supports can be moved in different directions into the particular parked position, or in the same directions into the particular parked position. In particular, when two transport tracks and two middle supports are provided, it is advantageous to move one middle support in the one transverse direction, and the other middle support in the opposite transverse direction, into the particular parked position laterally next to the particular outer transport bar. 
     Furthermore, it is advantageous if the individual middle supports are each present in an independent transport track, or together in one of the two transport tracks, for supporting the particular material to be soldered. In the transport tracks, the folding elements in the feed are in particular in the support position in order to support the particular material to be soldered. For example, it can be provided that both middle supports support the same transported good, in particular when the transported good is comparatively wide. On the other hand, it is conceivable that each of the middle supports supports material to be soldered in an independent transport track independently of the other middle support. 
     Furthermore, it can be provided that two middle supports are provided, and that the folding elements of the particular middle supports laterally contact the particular conveying means, the folding elements of which are provided on sides of the two middle supports facing away from one another or on sides facing one another. In particular when two middle supports are provided, it is advantageous if the folding elements are provided on the particular middle support on sides facing away from one another. 
     Furthermore, it is advantageous if, in the parked position, the folding elements are in the folded position in the feed and/or return. This saves installation space upward, so that the vertical distance between the transport bars and the particular middle support can be comparatively small. 
     Furthermore, it is advantageous if at least one folding device is provided which is provided for displacing the folding elements between the support position and the folded position. Such a folding device can, in particular, be actuated externally to displace the folding elements. 
     Advantageously, at least one folding device is configured in such a way that, before or during the movement of the at least one middle support into the parked position, the folding elements are in the folded position in the feed, and preferably also in the return. This ensures that, when the middle support is moved underneath the particular transport bar into the parked position, the folding elements are not in their vertical position but rather in their, in particular, horizontal folded position. 
     Furthermore, it is advantageous if the at least one folding device is configured such that the folding elements are always in the folded position in the return. This ensures that installation space can be saved vertically downward, since the folding elements are, in particular, in the horizontal folding position. 
     The aforementioned object is also achieved by a soldering apparatus in which material to be soldered can be transported along a transport direction, wherein such a soldering apparatus comprises a transport system according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details and advantageous embodiments of the invention can be found in the following description with which exemplary embodiments of the invention are described and explained in more detail. 
       In the drawings: 
         FIG.  1    shows a side view of a reflow soldering apparatus; 
         FIG.  2    shows a cross section of a first transport system; and 
         FIG.  3    shows a cross section of a second transport system. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a reflow soldering apparatus  10  for continuously soldering material to be soldered. The reflow soldering apparatus  10  has an entrance  12  and an exit  14 , wherein the material to be soldered reaches the reflow soldering apparatus  10  via the entrance  12  and is discharged from the reflow soldering apparatus  10  via the exit  14 . The material to be soldered 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 . 
     A communication unit  36  is provided with a screen and an input device, by means of which communication can occur with a machine controller of the reflow soldering apparatus  10 . 
     The material to be soldered, that is to say the printed circuit board provided with the soldering paste and populated with electronic components, is first heated in the preheating zone  20  to a temperature which is below the melting temperature of the soldering paste. In the soldering zone  22 , the printed circuit board is heated for a certain duration to a process temperature which is above the melting point of the soldering paste so that it melts in the soldering zone in order to solder the electronic components to the printed circuit board. In the cooling zone  24 , the material to be soldered is cooled so that the liquid solder solidifies before the material to be soldered is removed at the exit  14  of the reflow soldering apparatus  10 . 
     A transport system  34  is provided within the reflow soldering apparatus  10  for transporting the circuit boards along the transport direction  18 . 
     In a cross section of the transport system  34  according to  FIG.  2   , a transport track  35  with two transport bars  38 ,  40  is shown, in each of which a conveying means, in particular in the form of a revolving chain or a revolving region, has. On the conveying means, support sections  42  are provided on which the material to be soldered, i.e. the printed circuit board  44 , rests in the feed  43 . Since the support sections  42  move in the direction of transport  18  in the feed  43 , the material to be soldered  44  is ultimately transported in the transport direction  18 . The return  46  can be seen in the lower region of the transport bars  40  where the support sections  42  are moved counter to the transport direction  18 . In the embodiment shown in  FIG.  2   , the transport bar  40  is arranged rigidly within the soldering apparatus, and the transport bar  38  is contrastingly adjustable in the transverse direction  48  and adaptable to the width of the material to be soldered  44 . 
     In  FIG.  2   , a middle support  50  is shown in the middle region between the two transport bars  38  and  40 , which middle support  50  comprises a middle bar  52  in which a circulating conveying means  54 , in particular a chain or a belt, is provided, the feed  56  of which middle support is moved in the transport direction  18  synchronously with the feed  43  of the support sections  42  of the transport bars  38 ,  40 . In the middle bar  52 , the return  58  of the conveying means  54  directed counter to the transport direction  18  is shown below the feed  56 . 
     As is clear from  FIG.  2   , folding elements  60  are provided on the conveying means  54 , which folding elements each laterally contact the conveying means  54 . The folding elements  60  can be moved between a support position  62  shown in  FIG.  2    at the feed  56 , in which the folding elements  60  are arranged running in the vertical direction for supporting the material to be soldered  44 , and a folded position  64 , in which the folding elements  60  are folded in the horizontal direction. In the middle region of  FIG.  2   , the folded position  64  of a folding element  60  is indicated by dashed lines. 
     In the case in which a middle support  50  for supporting a circuit board  44  is not needed, the middle support  50 , as also shown in  FIG.  2   , can be moved horizontally in the transverse direction  48 . To this end, the folding elements  60  are first displaced into the folded position  64 . The middle support  50  can then be moved in the horizontal direction so far in the transverse direction  48  by means of an adjusting device, which is not shown in  FIGS.  2  and  3   , that the middle support  50  can be moved underneath the transport bar  40  into a parked position  45  which is provided laterally next to the transport bars  40 . In order to enable this, the design is such that the distance A between a transport plane  66  within which the printed circuit board  44  lies and the underside  68  of the transport bars  38 ,  40  facing away from the transport plane  66  is smaller than the distance B between the transport plane  66  and an upper side  70  of the middle support  50  facing the transport plane  66 . 
     In the parked position  45 , the middle support  50  has a distance C from the transport bar  68  in the horizontal direction and a distance D from the transport bar  68  in the vertical direction. This ensures that, in a soldering process in which the middle support  50  is in the parked position  45 , no negative impairment of the heat conduction towards the printed circuit board takes place. 
     Suitable adjusting devices for adjusting the transport bar  38  and/or the middle support  50  in the transverse direction  48  are, for example, threaded spindles or toothed racks extending in the transverse direction which are known from the prior art. 
     In the embodiment according to  FIG.  3   , two transport tracks  35 . 1  and  35 . 2  are provided, wherein printed circuit boards  44 . 1  and  44 . 2  can be transported through the soldering apparatus  10  in each of the transport tracks  35 . 1  and  35 . 2 . Since the printed circuit boards  44  to be soldered are of different widths, the two transport tracks  35 . 1  and  35 . 2  have a different width. Each of the transport tracks  35 . 1  and  35 . 2  has two transport bars  38 . 1  and  40 . 1  as well as  38 . 2  and  40 . 2 . As can be seen in  FIG.  3   , a total of two middle supports  50 . 1  and  50 . 2  are provided, which are used in  FIG.  3    for supporting the printed circuit board  44 . 1  and  44 . 2 . The design of the middle supports  50 . 1  and  50 . 2  corresponds to the design of the middle support  50  according to  FIG.  2   . 
     The two middle supports  50 . 1  and  50 . 2  are adjustable independently of one another in the transverse direction  48  via adjusting devices (not shown). The transport bars  38 . 1 ,  40 . 1  and  38 . 2  are also adjustable in the transverse direction. Only the transport bar  40 . 2  is rigidly arranged in the soldering apparatus  10 . 
     The arrangement of the two middle supports  50 . 1  and  50 . 2  and the design of the adjusting devices is such that both middle supports  50 . 1  and  50 . 2 , as shown in  FIG.  3   , can support the printed circuit board  44 . 1  or  44 . 2 . However, it is also conceivable that the middle support  50 . 2  or  50 . 1  is adjustable in the transverse direction so far that it supports only the printed circuit board  44 . 2  or  44 . 1 . Due to the fact that the middle supports  50 . 1  and  50 . 2  are arranged at a distance from the transport bars  38 . 1 ,  40 . 1  and  38 . 2 ,  40 . 2  in the horizontal direction, they can be moved freely below the transport bars  38 . 1 ,  40 . 1  and  38 . 2 ,  40 . 2 . 
     In this respect, the two middle supports  50 . 1  or  50 . 2  – when they are not needed – can be displaced into a right or left parked position  45 , as shown on the right and left in  FIG.  3   , in which they are at a distance from the particular transport bar  38 . 1  or  40 . 2  in the horizontal direction. The two middle supports  50 . 1  and  50 . 2  are then each located outside the region of the particular printed circuit board  44 . 1 , or  44 . 2  below the two transport tracks  35 . 1  and  35 . 2 . The printed circuit boards  44 . 1  and  44 . 2  can then be heated by means of heating elements (not shown) without such heating being adversely affected by the middle supports  50 . 1  and  50 . 2 , for example by shielding or a shadow effect. Before displacing the middle supports  50 . 1  and  50 . 2  into the parked position  45 , at least the folding elements  60  of the feed  56  are displaced from their support position into the folded position, as shown in  FIG.  3    on the right and left. 
     In order to displace the folding elements  60  into the particular support position or folded position, it is conceivable that one or more folding devices (not shown in the figures) are provided. The particular folding device is in particular such that, shortly before or during the movement of the middle support  50  into the parked position  45 , the folding elements  60  are moved into the folded position at least in the feed  56 . It is also advantageously provided that the folding elements  60  are always in the folded position in the return. 
       FIG.  4    shows a detail of the conveying means  54 , which is designed as a chain, in side view, in plan view, and in cross section, as it may be used in the middle support  50 . Folding elements  60  in the form of folding spring tabs are provided that laterally contact the conveying means  54 . The folding spring tabs are formed from bent wire sections and can be displaced between the support position  62 , in which the folding elements  60  extend in the vertical direction, and the folded position  62 , in which they are located essentially in a horizontal position, by means of a folding device (not shown). The height H of the folding elements  60  is greater than the distance B and, in the shown embodiment, also greater than the distance B, and is dimensioned such that the free end of the folding elements  60  serves to support the printed circuit board  44  in the support position. 
     According to the invention, further arrangements (not shown in the figures) are conceivable. In particular, it is conceivable to provide a third transport track and a third middle support for the third transport track. The three middle supports are then preferably arranged in such a way that all middle supports can be moved independently of one another in the transverse direction, so that, for example, two or all three middle supports are assigned to a transport track, or all three middle supports can be moved laterally next to the particular transport bar into a parked position.