Welding device

Abstract

Device for welding two plastic profiles, in particular for forming a window frame, comprising two clamping units movable relative to each other in the pressing direction for the welding process, each receiving a plastic profile between a lower and an upper limiting plate with a mitered pressing edge, and a welding mirror, characterized in that the pressing edge (8a) is formed on a separate strip (8) located in a step-like recess (7) of each limiting plate (6), that the strip (8) is guided vertically displaceably in the recess (7) of the limiting plate (6) in the direction of the pressing edge (8a), and that the pressing edge (8a) projects beyond the front edge (6a) of the limiting plate (6) in the basic position of the strip (8) and is designed to be displaceable against a force in the pressing direction when the welding process is initiated.

Description

[0001] The invention relates to a device for welding two plastic profiles, in particular for forming a window frame, consisting of two clamping units that are movable relative to each other in the pressing direction for the welding process, each of which receives a plastic profile between a lower and an upper limiting plate with a mitered pressing edge, and of a welding mirror.

[0002] In the production of plastic window frames, two mitered plastic profiles are clamped together, heated at their joint surfaces to a predetermined temperature using a welding mirror, and then, immediately after the welding mirror is removed, pressed against each other with a predetermined force over a predetermined distance. Welding devices are known for this purpose, which—depending on the design of the window frame manufacturing system—can weld one corner, two corners, or all four corners of a window frame together simultaneously. Each welding device consists of a base frame with two clamping units that are relatively movable relative to each other for each corner to be welded.Each clamping unit carries at least one upper and one lower limit plate, each with a mitered, slightly cutting-edge press edge between which the plastic profiles are held during the welding process. The plastic profiles are positioned between the stacked limit plates such that the end faces of the two plastic profiles protrude approximately 3 mm beyond the press edges of the limit plates.

[0003] After the end faces of the two plastic profiles to be welded are heated with a welding mirror and subsequently removed, the two profiles are pressed together under pressure by the clamping units, thus welding them. However, approximately 0.2 to 0.3 mm of material remains between the two pressed edges. This extruded plastic forms a continuous weld bead around the now joined profiles. This bead can be partially sharp-edged and must be removed, at least in the visible areas. In a subsequent, additional step, the weld bead is then removed from the top / front and bottom / back of the window frame using a knife, creating a so-called shadow groove. This additional step inevitably increases the manufacturing time for a window frame considerably.

[0004] Relevant state of the art can be found in DE 22 01 656 A and JP 2013-151 816 A.

[0005] The invention is based on the objective of designing a device for welding two plastic profiles, in particular those used to form a window frame, in such a way that at least part of the effort required to eliminate the disruptive weld seam is avoided and thus the time required to manufacture a window frame is reduced.

[0006] To solve this problem, the invention proposes, in a device of the type described above, that the pressing edge is formed on a separate strip located in a step-like recess of each boundary plate, that the strip is guided vertically displaceable in the recess of the boundary plate in the direction of the pressing edge, and that the pressing edge projects beyond the front edge of the boundary plate in the basic position of the strip and is designed to be displaceable against a force in the pressing direction when the welding process is initiated.

[0007] This design of the device ensures that the pressing edges of the relatively movable strips of the limiting plates can be brought firmly against each other at the start of the welding process, thus eliminating the previously required gap. This prevents the heated and therefore flowable, but excess, plastic from being forced outwards, instead directing it into the inner, free areas of the plastic profiles. Consequently, no weld bead remains on the top / front and bottom / back of the window frame; the equipment and time required to remove it are eliminated, and the manufacturing time for a window frame is reduced.

[0008] The invention is explained in more detail below with reference to a highly simplified embodiment shown in a drawing. Fig. 1. A top view of a device for welding two plastic profile bars together. Fig. 2 an enlarged representation of two boundary plates with their ribs in their basic position and Fig. 3 the boundary plates with their strips in their welding position.

[0009] In the Fig. Figure 1 of the drawing shows only two clamping units 3, each with a stop bar 4, of a device for manufacturing a window frame from plastic profile bars. Each clamping unit holds a profile bar 1, 2 near its free end and is supported by a frame in a manner known per se, but not shown. The clamping units and stop bars are movable relative to each other on this frame by means of a drive mechanism. Furthermore, the device has a welding mirror 5 against which the two mitered end faces of the two profile bars 1, 2 can be brought into contact via the clamping units 3 and heated to a predetermined temperature, for example, approximately 250 to 300°C.As soon as the end faces of the two profile bars 1, 2 have reached the specified temperature through the welding mirror 5, the welding mirror 5 is removed, and the two profile bars are pressed against each other and welded, also by means of the two clamping units 3, with their end faces against each other.

[0010] Each clamping unit 3 is equipped with a lower and an upper limit plate 6, of which in the Fig. However, in figures 1 to 3 of the drawing only the lower limit plates 6 are visible. During the so-called welding process, one limit plate 6 rests against the top and bottom surfaces of the profile bars 1, 2 in the area of ​​the weld point. Each limit plate 6 has a step-like recess 7 in its mitered end face, which extends over the entire width of the limit plate 6 ( Fig. 2) A strip 8 with an approximately rectangular cross-section, having a front pressing edge 8a, is inserted into each recess 7. This strip 8 is supported on the base of the recess 7 on one side and guided on the other side by, for example, two pins 9. These pins 9 are fixedly inserted into the respective limiting plate 6. The strips 8 are held in their home position by, for example, two springs 10 that project into both the limiting plate 6 and the strips 8. Fig. 2 held. In this basic position, the strips 8 project beyond the front mitered edge 6a of the boundary plates 6 by a predetermined dimension, which corresponds to the predetermined pressing path during welding ( Fig. 2).

[0011] These pins 9 enable the strips 8 to move from their position against the force of the springs 10 according to the Fig. 2 into the position according to Fig. 3 can be moved. In this position, the pressing edges 8a of the two boundary plates 8 lie against each other and are located exactly above the mitered edge 6a of the two boundary plates 6.

[0012] For welding the two profile bars 1, 2 together, they are now placed on the limiting plates 6 and the strips 8 and clamped so that their mitered surfaces are perpendicular to the press edges 8a of the strips 8 in the position of Fig. 2. The limiting plates 6 with the strips 8 are, however, positioned far enough apart that the welding mirror 5 can be moved between the end faces of the two profile bars 1, 2 and the end faces can be brought into contact with the welding mirror 5. After the end faces of the two profile bars 1, 2 have been heated, they are briefly pulled away from the welding mirror 5 and immediately after the welding mirror 5 is removed, pressed against each other with a predetermined force. At the same time, the strips 8 with their pressing edges 8a are moved from the position of the Fig. 2 into the position according to Fig. 3 pushed back.

[0013] The use and arrangement of the sliding strips 8 with the pressing edges 8a now results in the absence of a gap between the two pressing edges 8a of the strips 8 during the welding process. The heated and therefore flowable, but excess, plastic can no longer escape between the pressing edges 8a of the two strips 8 to the outside and thus cannot reach the top and bottom surfaces of the profile bars 1, 2. Instead, it is drawn under pressure into the inner, free areas of the two plastic profile bars 1, 2. The device according to the invention thus offers the advantage that when welding two plastic profile bars 1, 2 together to form a window frame, no weld bead is formed on its underside and top surface that would have to be removed in a subsequent operation.This previously always necessary step is now completely eliminated, thus reducing the time required to manufacture a window frame from plastic profile bars.

[0014] In modification of the described and drawn embodiment, the arrangement and guidance of the strips 8 with the pressing edges 8a on the boundary plates 6 can also be designed differently, insofar as this is within the scope of the claims.

Claims

[1] Device for welding two plastic profiles, in particular for forming a window frame, consisting of two clamping units movable relative to each other in the pressing direction for the welding process, each receiving a plastic profile between a lower and an upper limiting plate with a mitered pressing edge, and a welding mirror, characterized by , that the pressing edge (8a) is formed on a separate strip (8) located in a step-like recess (7) of each boundary plate (6), that the strip (8) is guided vertically in the recess (7) of the boundary plate (6) in the direction of the pressing edge (8a), and that the pressing edge (8a) in the basic position of the strip (8) projects beyond the front edge (6a) of the boundary plate (6) and is designed to be displaceable against a force in the pressing direction when the welding process is initiated. [2] Device according to claim 1, characterized by , that the strip (8) is guided in the recess (z) of the boundary plate (6) by means of pins (9). [3] Device according to claim 1 or 2, characterized by , that the force acting in the opposite direction to the pressing direction is formed by at least one spring (10).

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