Method and device for welding two hollow plastic profile bars

Abstract

Method for welding two hollow profile bars (4) made of plastic to form a window frame, in which the profile bars (4) to be joined together are heated to a predetermined temperature by inserting a welding mirror (3) between their connecting surfaces and pressing them against the welding mirror (3) to form outer and inner beads (8a, 8b) and, after removal of the welding mirror (3), are joined together under pressure while simultaneously enlarging the welding bead, characterized in that after removal of the welding mirror (3), only the outer beads (8a) formed on the visible surfaces of the future window frame in the region of the connecting points of the two profile bars (4) are pressed slightly inwards to form an oblique edge and then removed together with the inner beads (8b), and that the connecting surfaces of the two profile bars (4) are subsequently joined together.

Description

[0001] The invention relates to a method for welding two hollow profile bars made of plastic to form a window frame, in which the profile bars to be joined together are heated to a predetermined temperature by inserting a welding mirror between their connecting surfaces and pressing them against the welding mirror to form a partially external welding bead and, after removal of the welding mirror, are joined together under pressure while simultaneously enlarging the welding bead, as well as to a device for carrying out the method.

[0002] For the production of window frames from plastic profile bars with continuous chambers, welding devices are known with which – depending on the design of the production device – one corner, two corners, or all four corners of a window frame can be welded together simultaneously. Each welding device has a welding head with a heated welding mirror for each corner, as well as a clamping unit for each profile bar. Each clamping unit has an upper and a lower limit ramp, between which a profile bar is held.

[0003] For the actual welding or joining process, the two profile bars, which are approximately 3 mm longer at each end than the dimensions of the finished window frame, are first aligned and secured in a position in which the two connecting surfaces are held far enough apart that the welding iron, heated to a predetermined temperature, can be inserted between them. The connecting surfaces of the two profile bars are then pressed against the welding iron and melted until the length of the profile bars is reduced by approximately 2 mm. This pressing process creates the first part of a so-called welding bead in all areas of the profile bars. The profile bars are then briefly withdrawn from the welding iron so that it can return to its original position.The heated joining surfaces of the two profile bars are then pressed against each other again, whereby the aforementioned welding bead increases and at the same time the length of the profile bars is further shortened by about 1 mm, so that they have already reached the final dimension specified for the window frame at the welded or joined ends.

[0004] The welding beads created by joining the profile bars in the area of ​​the connecting surfaces are present not only all the way around the outside, but also on all the webs inside the profile bars. These welding beads can sometimes have sharp edges and do not create an attractive appearance on the visible surfaces of the subsequent window frame. For this reason, these welding beads are removed, at least from the visible surfaces of the welded or joined window frame. This is done using special knives and / or milling cutters on the top or front side and on the bottom or back side of the welded window frame in at least one subsequent, additional work step, usually creating a so-called shadow groove. These additional work steps not only inevitably increase the time required to manufacture a window frame, but also require additional equipment.In addition, a shadow groove has a slightly rougher surface than the rest of the window frame, which promotes the deposition of dirt particles.

[0005] In order to avoid at least some of the effort required to remove the visible and therefore disturbing weld beads and thus reduce the time required to manufacture a window frame, a method has become known from German Offenlegungsschrift DE 10 2015 013 439 A1, in which, after the welding mirror has been removed, the outer parts of the welding beads created on the visible surfaces of the future window frame in the area of ​​the connection points between the two profile bars are pressed inwards, that the welding mirror is then moved again between the connection surfaces of the profile bars and the connection surfaces are reheated while simultaneously deforming the inwardly pressed welding beads and that finally, after the welding mirror has been removed, the connection surfaces of the two profile bars are joined together.

[0006] However, this known method does not achieve the desired results for all profile bar cross-sections and plastics used in the manufacture of window frames. Furthermore, it is considered disadvantageous that the joints of the finished window frame are usually completely flat on the top (front) and bottom (back) sides.

[0007] WO 2016 / 177715 A1 discloses a method and device in which, at the time of compressing the profile ends, a formed part is placed on the outer surface of the profiles in such a way that it protrudes beyond the free end edge of the respective profile part. This prevents a weld bead from escaping and creates a flat surface.

[0008] JP 2013-151816 A discloses a connection of profile ends in which an escaped welding bead is separated by means of knives that can be moved parallel to the profile surface.

[0009] DE 3614673 A1 proposes placing shaped parts on the joining area of ​​the profile ends during heating and subsequent welding, which are intended to retain a welding bead.

[0010] The present invention is based on the object of specifying a method and a device which can be used therefor for welding two profile bars made of plastic which serve to form a window frame, which can be used for all cross-sections of the profile bars and the plastics used for the production of window frames and by means of which a type of shadow groove is created in the area of ​​the connection points of the finished window frame on its top or front side and on its bottom or rear side.

[0011] To achieve this object, according to the invention, in a method of the type described at the outset, it is proposed that after the welding mirror has been removed, only the outer beads formed on the visible surfaces of the future window frame in the area of ​​the connection points of the two profile bars are pressed slightly inwards to form an oblique edge and then removed together with the inner beads, and that the connection surfaces of the two profile bars are then joined together.

[0012] This process is applicable to all cross-sections of profile bars and plastics used in the manufacture of window frames, and it creates a kind of shadow groove that improves the visual appearance of the window frame. There are also no longer any bulges on the visible surfaces of the window frame.

[0013] The invention is explained in more detail below with reference to an embodiment shown in a drawing in a highly simplified manner and not to scale. The Fig. 1 to 5 only partially show the essential parts of a device for carrying out the invention in successive process steps.

[0014] In the Fig. In Figures 1 to 4 of the drawing, only a so-called limiting ramp 1, a slider 2, and a welding mirror 3 of an inventive device for welding profile bars to form a known window frame can be seen. These are components of a known welding head, which is therefore not shown. The limiting ramp 1 shown rests on the upper side of a hollow plastic profile bar 4, which is only partially visible. Both end faces of the bar are mitered and the interior of which is normally divided into several continuous chambers of different sizes by appropriately arranged webs.On the underside of the profile bar 4 (not visible in the drawing) there is a second limiting ramp 1, which is advantageously identical and arranged as a mirror image of the first limiting ramp 1, the profile bar 4 being clamped between the two limiting ramps 1 and protruding with its end face by a predetermined amount, usually about 3 mm, beyond the inclined end face 5 of the limiting ramp 1. This end face 5 runs at an acute angle of approximately 45 to 70°, advantageously less than 60°. The slider 2, which has a wedge-shaped cross-section and an end face 7 running perpendicular to the profile bar 4, is slidably guided on this end face 5, so that here a right or approximately right angle exists between the end face 7 and the base surface of each limiting ramp 1.

[0015] The aforementioned welding head now takes, as only the Fig. 5, a second profile bar 4, which is also clamped between two limiting ramps 1 in the manner already explained above and in which the limiting ramp 1 is also assigned a slide 2. This arrangement is, as is known, mirrored on the other side of the welding mirror 3. Depending on the design of the welding system, it can be equipped with two, four, or six welding heads.

[0016] To initiate the welding or joining process, the heated welding mirror 3, which is normally located outside the area of ​​the profile bars 1, is inserted between the end or connecting surfaces of the two profile bars 4, with each limiting ramp 1 initially having a distance of approximately 3 mm from the welding mirror 3 ( Fig. 1). Now, the profile bars 4 are pressed against the welding plate 3 with a predetermined force. This heats and melts the end faces or connecting surfaces of the two profile bars 4. Since the magnitude of the contact force of the profile bars 4 against the welding plate 3 is maintained, the distance between each limiting ramp 1 and the welding plate 3 decreases, and a bead 8a, 8b ( Fig. 2), the shape of which may vary and deviates from the simplified drawing. As soon as the distance between the limit ramp 1 and the welding plate 3 has decreased by approximately 2 / 3 – that is, approximately 2 mm – the contact pressure is reduced and the profile bars 4 are retracted from the welding plate 3. The welding plate 3 is then removed from the area of ​​the profile bars 4.

[0017] Now the slide 2 comes into action. It is moved by a drive of known design (not shown) along the front face 5 of the limiting ramp 1 from its position according to the Fig. 1 and Fig. 2 in the position of Fig. 3. In this position, the advantageously slightly rounded tip of the slider 2 is located approximately in the middle of the thickness of the outer wall of the profile bar 4. During this movement of the slider 2, in particular the outer bead 8a, which is still plastic due to the previous heating, is inevitably pressed inwards or downwards, whereby the two welding beads 8a and 8b combine to form a larger welding bead 8c, the shape of which also does not exactly match the drawn shape ( Fig. 3).

[0018] In a subsequent work step, a knife 9, for example held on a carriage (not shown), is moved perpendicular to the plane of the drawing along the end face 7 of the slide 2, whereby at least the largest part of the bead 8c of a profile bar 4 is severed ( Fig. 4). It is advantageous if the carriage (not shown) accommodates another knife 9, so that the largest part of the beads 8c is simultaneously severed on both end faces of the profile bars 4 to be joined. The severed parts of the beads 8c can now be removed from the area of ​​the profile bars 4 to be joined, for example, by means of an air stream. Subsequently, the two sliders 2 are first moved back from the profile bars so far that they are outside the wall, as is clearly shown by the Fig. 5. The end faces of the two profile bars 4, which are still in the heated and thus plastic state and are mitred, are then pressed against each other and welded ( Fig. 5). This figure also shows that a small, V-shaped groove 10 remains on the surface in the area of ​​the connection point between the two profile bars 4. Depending on the design of the tip of the slides 2, this groove 10 can also have a slightly different shape.

[0019] After removing the separated beads 8c, it is possible to move the welding mirror 3 again into the area of ​​the two profile bars 4 and to press the profile bars 4 again against the welding mirror 3. However, this pressing process is only carried out for a short time and with extremely low contact force, so that the length of the profile bars 4 is only insignificantly shortened, but the end faces of the profile bars 4 are reheated.

[0020] As is known, the plastic profile bars 4 used to form a window frame are rarely completely flat on the upper or front surface. Usually, a bevel or rounded section is present on the inner and / or outer edge. To ensure that no external bulge is formed in these areas, the slider 2, for example, can be profiled. It is possible to provide at least two separate sliders 2, of which the second slider 2 extends at an angle to the first slider 2.

Claims

[1] A method for welding two hollow profile bars (4) made of plastic to form a window frame, in which the profile bars (4) to be joined together are heated to a predetermined temperature by inserting a welding mirror (3) between their connecting surfaces and pressing them against the welding mirror (3) to form outer and inner beads (8a, 8b) and, after removing the welding mirror (3), are joined together under pressure while simultaneously enlarging the welding bead, characterized by that after removing the welding mirror (3), only the outer beads (8a) created on the visible surfaces of the future window frame in the area of ​​the connection points of the two profile bars (4) are pressed slightly inwards to form a sloping edge and then removed together with the inner beads (8b) and that the connection surfaces of the two profile bars (4) are then joined together. [2] Method according to claim 1, characterized by that after the removal of the inner and outer beads (8a, 8b) the welding mirror (3) is briefly moved again between the connecting surfaces of the profile bars (4) and the connecting surfaces are reheated. [3] Device for carrying out the method according to claim 1 or 2, consisting of a welding head with a welding mirror (3) and two clamping units each having an upper and a lower limiting ramp (1) and receiving the two profile bars (4) and pressing their connecting surfaces against a welding mirror (3), characterized bythat in the region of the mutually facing end faces (5) of each limiting ramp (1) at least one slider (2) movable perpendicular to the visible surface of the later window frame is assigned to deform the beads (8a, 8b) and that each limiting ramp (1) is assigned a separating device preferably designed as a knife (9) and movable parallel to the surface of the later window frame. [4] Device according to claim 3, characterized by that the effective end face (5) of each limiting ramp (1) extends at an angle of approximately 45 to 70 ° to the base surface thereof. [5] Device according to one of claims 3 and 4, characterized by that the slide (2) has a wedge-shaped cross-section and its free end face (7) together with the base surface of each limiting ramp (1) forms a right or approximately right angle. [6] Device according to one of claims 3 to 5, characterized bythat both separating devices of a window corner are guided on a common slide. [7] Device according to claim 6, characterized by that both separating devices are held on the carriage in a height-adjustable manner.

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