The present invention relates to a soldering machine, comprising a vessel for molten solder and at least one rise tower placed in the vessel, which tower is provided at its top with at least one outflow slot for forming a solder wave. Such soldering machines are generally known.

These soldering machines are mostly used for soldering chip components. These are components which are generally of small dimensions and which are fixed on the solder side of the printed circuit board. For this purpose they are initially positioned on the printed circuit board, for instance by means of glueing, wherein the solder surfaces of the chip components are fixed against the corresponding solder surfaces of the conductor paths on the printed circuit board. The printed circuit boards thus provided with components are then carried through a soldering machine of the type described in the preamble, wherein the soldering process takes place.

To obtain good quality soldered connections it is impor¬ tant that the rise tower of the soldering machine is provided with a narrow outflow slot. Thus obtained is a narrow, power- ful solder wave which can also penetrate into the space bet¬ ween the surfaces of the components for soldering and the printed circuit board.

In practice it has been found that such a narrow outflow slot quickly becomes dirty as a consequence of solder oxides and the flux used during the soldering process. This contami¬ nation and the oxidization products are deposited in the outflow slot, whereby this becomes blocked and the resulting solder wave is irregular and a reliably soldered connection is no longer obtained. The object of the present invention is to provide a soldering machine wherein the above stated problems are avoid¬ ed.

This object is achieved by a scraping member arranged in the slot movably in the lengthwise direction of the slot.

Because the scraping member is caused to move regularly through the slot, the slot is kept clean so that the outflow- ing solder wave remains regular and reliable soldered connec¬ tions are obtained.

The present invention will be further elucidated herein¬ after with reference to the annexed drawings, in which: fig. 1 shows a perspective view of a soldering machine in which the present invention is applied; fig. 2 shows a perspective, partially broken away view of a solder vessel provided with a solder tower with an out¬ flow slot, in which the present invention is applied; fig. 3 shows a view corresponding with fig. 2 of another embodiment of the present invention; fig. 4 is a sectional view of the device according to the present invention; fig. 5 shows a detail view of the device according to the present invention; fig. 6 is a perspective detail view of a scraping member applicable in the device according to the present invention; and fig. 7 and 8 show two alternative embodiments of the scraping member. The soldering machine 1 depicted in fig. 1 is substan¬ tially formed by a housing 2 through which extends a conveyor belt 3. A solder vessel 4, which is further shown in fig. 2, is arranged in the soldering machine under the conveyor belt 3. The solder vessel 4 is provided with a heating device (not shown in the drawing) in order to keep the solder situ¬ ated in the vessel 4 in the liquid state. Further arranged in the solder vessel 4 is a first outlet tower 5 which is provi¬ ded with an outflow slot 6 for molten solder. A second outlet tower 7 is further arranged.

The conveyor belt 3 is arranged such that the printed circuit boards 8 for soldering are carried along above both

outlet towers 5 and 7 such that the solder waves 9, 10 genera¬ ted by these towers solder the components arranged on the underside of the printed circuit board 8 onto the board. The conveyor belt further forms no part of the present invention, so it will not be discussed further. Each of the outlet towers 5, 7 is further provided with a pump (not shown) to raise the molten solder. The first outlet tower is provided with a narrow outflow slot 6 for forming of a first narrow, powerful solder wave 9. As a result of the small thickness and the force of the solder wave it will penetrate well into the space between the surfaces for soldering so that a good sol¬ dered connection is obtained. The wave generated by the second outlet tower 7 has a gently flowing surface, since it is then no longer necessary to penetrate into the space between the solder surfaces; the soldered connection has already been brought about using the first solder wave.

This outflow slot becomes blocked as a result of oxides from the outflowing molten solder and as a result of the flux present in the solder bath which is deposited in the fairly narrow outflow slot 6.

According to the present invention this contamination can be regularly removed by causing a scraping member 11 to move regularly back and forth in the outflow slot 6, which member removes deposits of dirt during the reciprocating movement. This scraping member 11 is fixed to a block 13 by means of a holder 12. This block 13 is movable in the length¬ wise direction of the slot 6 since this block 13 is guided on a guide rod 14. For this purpose the block 13 is provided with an opening 15, through which the guide rod 14 extends. In order to drive the block 13, and therefore the scraping member 11, in lengthwise direction, a screw spindle 16 is arranged which extends parallel to the guide rod 14. The screw spindle 16 extends through an opening 17 provided with screw thread and arranged in the block 13. The screw spindle 16 is drivable by means of an electromotor 18. Just as the guide rod 14 and the screw spindle 16 the electromotor 18 is fitted onto a bracket 19 which is fixed against the vessel 4.

Once a certain number of soldering operations have been carried out, and therefore after the passage of a certain number of printed circuit boards 8, energy is supplied to the electromotor 18 so that the screw spindle 16 is driven, the block 13 moves along the guide rod 14 and the scraping member 11 performs a linear reciprocating movement through the out¬ flow slot 6. The soldering process is subsequently resumed. After a number of soldering operations have once again been carried out this scraping action is repeated. Fig. 3 shows another embodiment of the scraping member which otherwise wholly corresponds with the embodiment shown in fig. 2, with the understanding that, instead of the screw spindle 16, a second guide rod 20 is arranged. For this pur¬ pose a second guide opening 21 is arranged in the block 13. Arranged for driving of the scraping member 11 is a linear drive member 22 which for instance can be formed by a pneuma¬ tically or hydraulically driven cylinder or by a linear elec¬ tromotor.

It is however also possible to place the drive member of the scraping member at some distance from the solder bath 4, which may be attractive in respect of the temperatures pre¬ vailing in the vicinity of this solder bath and the danger of dirtying by solder. A bowden cable for instance can then be used for the coupling between the linear drive member and the block 13.

Fig. 4 shows a sectional view of the first solder tower 5 on which the scraping member 11 according to the present invention is used. This shows a number of construction de¬ tails. Shown in fig. 5 is a perspective detail view which shows the construction of the scraping member in more detail. Also shown here is that the slot 6 is provided on both sides with a broadening 23 in which the scraped off dirt can collect. The solder oxides and flux collected in the broadening are removed by the solder wave flowing out of the slot. If neces¬ sary, this broadening could also be cleaned by hand at regular intervals, for instance daily.

Although in the drawing the broadening is shown as being rectangular, it is possible to embody the broadening with another shape, for instance a round shape.

Finally, fig. 6 and 7 show two alternative embodiments of the scraping member. In the embodiment shown in fig. 6 two parallel extending blades 24 are used which are both fixed on the holder 12 by means of a rivet or pop rivet 25. In the embodiment shown in fig. 7, there is one blade 26 which ex¬ tends slopingly in the slot 6.

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