Heating element for heating plastic profiles and method for removing material outside the welding zone

Description

[0001] The invention relates to a heating element for heating plastic profiles before their connection by welding, comprising at least one contact plate with a contact surface facing at least one plastic profile, at least one heating element which is in operative connection with the contact plate, wherein the contact plate has at least one recess which is arranged in the contact surface and which interrupts the contact surface, wherein the recess completely penetrates the contact plate or the recess has a bottom surface.

[0002] The invention further relates to a device for welding plastic profiles with a heating element and to a method for welding plastic profiles, in particular using a device according to the invention.

[0003] The device is suitable for removing material outside the welding zone of one or more plastic profiles.

[0004] The production of frames, particularly for windows or doors, from plastic profiles is a well-known process. Differently shaped plastic profiles are first sawn to size and mitered and then welded to form frames. A reliable and cost-effective method for this type of welding is what is known as mirror welding. The end faces of the plastic profiles are first pressed against a heating element, the welding mirror, whereby the material of the plastic profiles is softened and melted or plasticized by the heat transferred from the welding process. Once this process is achieved, the welding mirror is removed, and the plasticized plastic profiles, which are plasticized on their end faces, are pressed together and thus welded. The plasticized material of one plastic profile bonds with the plasticized material of another plastic profile.This creates a continuous, long-term stable, material-locking connection between two plastic profiles.

[0005] A disadvantage of this joining technique is that when the plasticized end faces of the plastic profiles are pressed together, a weld bead forms on the outer surfaces of the joint. This weld bead is formed by material displaced during compression. The weld bead results in an irregular surface at the joint and is visually unsightly on visible surfaces. Several approaches already exist in the state of the art to prevent this weld bead or, if this is not possible, to remove it after welding.

[0006] One way to prevent a weld bead is to remove material adjacent to the future visible surfaces of the plastic profiles before welding. This can be done, for example, by milling off part of the circumference of the plastic profiles. By removing material in this way, there is no longer any material plasticized during welding adjacent to the visible area, which is then pushed outwards when the plastic profiles are pressed together. This can prevent a weld bead. Despite this removal of material adjacent to the visible area of ​​the plastic profiles, it can still happen that at least partial plasticization occurs in the area of ​​the removed material and that unwanted deformations still occur in the visible area when the plastic profiles are pressed together or welded. For example, the abutting outer surfaces of the plastic profiles are pressed inwards or outwards.

[0007] US 7,328,734 B2 discloses a machine and method for welding thermoplastic gutters or other workpieces together. A stationary and a movable platen are each attached to a frame assembly. Workpiece holders and corresponding clamps, specifically configured for clamping gutters or other workpieces, are arranged on the stationary and movable platens, along with a spacer plate for positioning and holding the ends of two workpieces in a position for welding the ends together. A heater is provided to heat the ends of the workpieces to a desired welding temperature, and a press is provided to press and hold the deformed ends of the workpieces together for welding.

[0008] WO 2013 132 406 A1 describes a method for welding profile elements made of plastic, in particular PVC. Two profile elements are produced, arranged so that the respective areas to be welded face each other. A groove is then formed in correspondence with at least one area of ​​the profile elements to be welded. After heating the areas to be welded, they are joined together, with the profile elements being pressed against each other to keep the zones to be welded in mutual contact. A pressure pad prevents the formation of a weld bead on the surface of the profile elements.

[0009] EP 0 139 350 A1 discloses a resistance heating element for the sterile welding of thermoplastic pipes, wherein a fusible signaling means is provided that enables the first use of the heating element to be indicated. The signaling means provides an electrical signal, which is eliminated before the first use by melting the signaling means, thereby initiating the first use. If the electrical signal is not generated upon reuse of the heating element, the sterile joining apparatus in which the heating element is used is programmed to reject the heating element.

[0010] An object of the present invention is to propose solutions with which the surface quality, in particular a smooth and continuous appearance when welding plastic profiles, can be further improved.

[0011] A heating element according to the invention is defined in claim 1.

[0012] According to the invention, a heating element is proposed that is improved over the prior art. This heating element is intended as a welding mirror for use in mirror welding. The invention is described in connection with the mirror welding of plastic profiles. Of course, a heating element according to the invention can also be used for heating or welding other plastic parts, such as plates or rods. A heating element according to the invention is also suitable for welding plastic profiles intended for applications other than window or door construction.

[0013] A heating element according to the invention comprises at least one contact plate which is intended to be brought into contact with a plastic profile to be welded. This contact plate has a contact surface which faces the plastic profile during welding. During welding, the contact surface at least partially touches the plastic profile, in particular its end face or end surface. The contact plate with the contact surface is intended to heat and plasticize material on the end face of a plastic profile. Typically, a heating element for producing frames from plastic profiles comprises two contact plates, each having a contact surface. In this case with two contact surfaces, one of these contact surfaces faces a first plastic profile and the other of the contact surfaces faces a second plastic profile to be welded to the first.Furthermore, a heating element according to the invention comprises at least one heating element. The heating element is intended to heat the heating element. The heating element can, for example, comprise an electric heating coil. However, the heating element can also be heated using other technologies. The heating element is operatively connected to the contact plate. "Operative connection" here means that heat is transferred between the heating element and the contact plate. Good heat transfer is achieved, for example, by the contact plate and the heating element resting flatly and touching.

[0014] According to the invention, the contact plate has at least one recess which is arranged in the contact surface and interrupts the contact surface. When one end face of a plastic profile is heated, there is no contact between the contact plate and the plastic profile in the region of the recess. As a result, no heat is transferred from the heating element to the plastic profile in the region of the recess. The areas of the plastic profile which are arranged opposite the recess during heating are therefore not heated or are heated only to a very small extent. The recess in the contact surface thus ensures that the plastic profile to be welded is not heated in certain areas. As a result, the material of the plastic profile remains significantly stronger in this area than in the area where the contact surface rests on the plastic profile and plasticizes it.Advantageously, the recess in the contact surface is arranged such that when the heating element is brought together with the plastic profile, it faces an outward-facing visible surface of the plastic profile. This means that the outer peripheral area of ​​the plastic profile is not heated, or only heated to a very small extent, while the areas away from the visible surface that are in contact with the contact surface are heated and plasticized. During subsequent compression and / or welding of the plastic profile, the areas opposite the recess remain in a solid state. This significantly reduces deformation in these areas during compression. Because the material has greater strength in these areas, it is less easily deformed during compression and thus remains more dimensionally stable.The surface quality at the connection point between the plastic profile and another plastic profile is thus significantly improved. According to the invention, the recess can penetrate the contact plate completely. The recess can, for example, be milled out of the contact plate. In this case, a through opening is provided in the contact plate in the area of ​​the recess. Alternatively, the recess can be pocket-shaped. Such a pocket-shaped recess then has a bottom surface that delimits the recess on the side facing away from the contact surface. In this embodiment, the bottom surface is set back from the contact surface so that the bottom surface is arranged at a distance from the plastic profile when it is joined to the plastic profile and therefore does not touch the plastic profile.

[0015] A heating element according to the invention with at least one recess heats a plastic profile during or before welding only in certain areas. In other areas, the plastic profile is not heated and remains in a solid state. During welding of the plastic profile, this area, which is in a more solid state, remains dimensionally stable, thus resulting in a significantly improved surface quality of the joint.

[0016] A heating element according to the invention can be used as part of a device for removing material from one or more plastic profiles, leaving a gap of material outside the weld area of ​​the plastic profile(s). Removing material outside the weld area is particularly beneficial for achieving good surface quality in this area. This procedure is also referred to as "cut out of welding zone," or COW for short.

[0017] When a plastic profile is heated by the heating element, the contact surface rests on the end face of the plastic profile. The area where contact occurs between the heating element and the plastic profile is the support surface. At least one recess in the contact surface is designed to define the support surface. This limitation ensures that the plastic profile is only strongly heated and plasticized in specific areas. In the area of ​​the recess, the contact plate does not rest on the plastic profile, so no heating occurs there and the plastic profile remains in a solid state.

[0018] In a preferred embodiment of the proposal, it is provided that the contact surface is designed to be homogeneous in itself, wherein the contact surface is flat or has a regular contour, for example a ribbed surface. The contact surface is designed to be homogeneous in itself. This means that the surface is regular over the entire area of ​​the contact surface. In the simplest case, the contact surface is flat and smooth. To increase the contact surface, however, the contact surface can also be contoured. Such a contoured design can be created, for example, by ribs arranged regularly on the contact surface. These ribs can have a prism-like or semicircular cross-section.

[0019] Furthermore, it is provided that the recess has a bottom surface, and that the bottom surface is flat or has a regular contour. In the embodiment in which the recess has a bottom surface, this can be flat or also contoured. Typically, such a bottom surface is flat. Such a flat design of the bottom surface can be easily created by machining the recess with a milling cutter.

[0020] In an advantageous embodiment, the recess has a bottom surface, and the bottom surface runs parallel to the contact surface. This embodiment is also particularly easy to produce by milling.

[0021] Cleverly, it is provided that the contact plate and the heating element are designed as different components, with the contact plate resting at least partially flat on the heating element to ensure good heat transfer between the two components. In this embodiment, the contact plate and heating element are formed by different components. This has the advantage that a single heating element can be alternately connected to several differently designed contact plates. The contact plate and heating element are designed so that there is the greatest possible surface contact between the two components. This contact ensures good heat transfer from the heating element to the contact plate. Advantageously, the heating element is plate-shaped and the contact plate is shaped to fit the heating element on the side facing away from the contact surface.

[0022] Furthermore, it is advantageously provided that the shape of the recess in a plan view of the contact surface corresponds at least partially to the shape of the outer contour of the end face of a plastic profile to be welded. The shape of the recess is selected in this embodiment such that in a plan view of the contact surface it corresponds at least partially to the outer contour of the plastic profile to be welded. In the area of ​​the recess, there is no or only very slight heating of the plastic profile. This slight heating is advantageous particularly at the outer contour, where the visible surface is located after the plastic profile has been welded, since the material remains solid at this point due to the slight heating and retains its shape during welding. In the case of a window frame, however, there is not a visible surface over the entire peripheral area of ​​a plastic profile.To achieve a good surface quality on the visible surface, it is often sufficient to arrange one or more recesses on the welding plate so that, when joined to the plastic profile, they are positioned at the points where the visible surfaces will later be located. A recess is not absolutely necessary at points on the outer contour of the plastic profile where no visible surfaces will later be present.

[0023] Advantageously, the inner contour of the recess corresponds to the shape of the outer circumference of a plastic profile to be welded, and the outer contour of the recess encloses a larger area than the inner contour of the recess. In this embodiment, the recess is delimited by an inner contour and an outer contour. The outer contour of the recess faces the outer edge of the contact plate or contact surface, while the inner contour is the boundary of the recess that faces away from the outer edge of the contact surface. Advantageously, the shape of the inner contour of the recess is the same as the shape of the outer circumference of the plastic profile to be welded. During welding, the heating element is positioned relative to the plastic profile so that the outer circumference of the plastic profile is congruent with the inner contour of the recess.The outer circumference of the plastic profile is understood to be the outer circumference that encloses the end face or front surface of the plastic profile. The recess extends from its inner contour, the shape of which corresponds to the outer circumference of the plastic profile, outwards to the outer contour of the recess. During welding, the recess is thus positioned opposite the area that adjoins the outer circumference of the front surface of the plastic profile. This means that the area outside the outer circumference of the plastic profile is not touched by the heating element and is therefore not heated directly. In this embodiment, too, it is usually sufficient if the recess defined by the inner and outer contours only encloses part of the outer circumference of the plastic profile, namely where visible surfaces will later be present and a particularly good surface quality is required after welding.

[0024] Furthermore, the proposal advantageously provides that the recess, in a plan view of the contact surface, has a plurality of linearly extending regions which are positioned at those points on the contact surface which are intended to lie opposite the outer contour of the profile provided with a visible surface when the heating element is brought together with a profile to be welded. In this embodiment, the recess is designed such that it is only arranged in regions where, during heating, areas of the plastic profile rest against which will later form a visible surface. These areas of the visible surfaces are usually linear, which means that the corresponding areas of the recess are also linear. Of course, these areas of the recess can also have a different shape if the plastic profile has a different, non-linear shape at this point.

[0025] According to the invention, the heating element has at least one connecting element that releasably and firmly connects the contact plate to the heating element. According to the invention, the contact plate and heating element are formed by different components that can be easily and reliably connected and separated via a connecting element. Such a design enables easy replacement of the contact plate and thus a simple adaptation of the heating element to different plastic profiles. The connecting element can be designed as a simple screw or plug connection. Furthermore, it is possible for guides to be provided on the heating element into which the contact plate is inserted.Furthermore, various designs of clamping devices are suitable as connecting elements, which press the contact plate force- and / or form-fittingly against the heating element and thus ensure good heat transfer between both parts.

[0026] Furthermore, it is provided that the connecting element comprises at least one actuating lever and at least one pressure piece, wherein the pressure piece is designed to be movable towards and away from the heating element by the actuating lever, and the pressure piece is designed to be at least partially complementary in shape to an edge of the contact plate. In this embodiment, the connecting element is designed as a multi-part mechanism. The connecting element comprises a pressure piece which encompasses at least a region of the contact plate and a region of the heating element. The pressure piece can be moved towards and away from the heating element by an actuating lever. When removed from the removal element, the contact plate can be removed or a contact plate can be moved towards the heating element.The actuating lever is then activated, which moves the pressure piece toward the heating element and then positively connects the contact plate to the heating element. Such a mechanism is easy to operate and provides a stable connection between the contact plate and the heating element.

[0027] In an advantageous embodiment, the contact plate is made of an aluminum-based material with a coating containing Teflon. Generally, any material with good thermal conductivity is suitable for the contact plate. Good thermal conductivity ensures that the heat from the heating element is quickly transferred to the plastic profile to be welded, which is adjacent to the contact surface. In practice, aluminum or an aluminum-based material has proven particularly suitable for the contact plate. Of course, other materials with good thermal conductivity, both metals and non-metals, can also be used for a contact plate.To prevent plastic material from the plastic profile from remaining on the contact plate during welding or heating, it is advantageous to provide it with a coating that reduces or prevents the plastic from sticking. In practice, Teflon coatings have proven particularly suitable because they reliably prevent adhesion and are also temperature-stable. Such Teflon coatings can be applied to the contact surface in the form of a film, for example. However, it is also possible to apply a Teflon coating to the contact surface using a spray or by applying it with a brush or roller. Other non-stick coatings based on other materials are also suitable for the contact plate.In some cases, no coating is required at all; it is sufficient to polish the surface of the contact plate sufficiently smooth to prevent plastic material from sticking during heating.

[0028] Cleverly, two contact plates are provided, which in the operating state are each arranged on one side of the heating element and which are symmetrical to one another with respect to the center plane of the heating element. In this embodiment, the heating element comprises two contact plates. These contact plates are connected to the heating element on opposite sides of the latter. This embodiment is intended to heat or plasticize two plastic profiles simultaneously. This application is typical in the manufacture of frames from plastic profiles. The operating state here means that the heating element is ready for use to heat plastic profiles. In this operating state, the two contact plates are connected to the heating element.To connect two plastic profiles with identical cross-sections, the contact plates are designed symmetrically to the center plane of the heating element. Both contact plates have recesses positioned to prevent contact with certain areas of the plastic profile being purchased.

[0029] Furthermore, it is advantageously provided that the contact plate is designed in several parts and has at least one insert that can be separated from the rest of the contact plate, thereby enabling adaptation of the contact plate to a differently shaped plastic profile by removing or replacing this insert. In this embodiment, adaptability of the heating element to different geometries of plastic profiles is enabled not by completely replacing the contact plate, but by replacing an insert of the contact plate.

[0030] Such an insert is designed to be detachable from the rest of the contact plate. The connection between the insert and the rest of the contact plate can be achieved, for example, by a plug-in connection. The advantage of this design is that the spare parts required to adjust the heating element are small and inexpensive.

[0031] Advantageously, the contact plate comprises at least one movable element, wherein this movable element is movable via an adjustment mechanism and the contact plate can be adapted to the shape of a profile piece by the movement of the movable element. In this embodiment, the contact plate can be adapted to different plastic profiles by means of a movable element, without the need to replace all or part of the contact plate. The position of the movable element can be changed via an adjustment mechanism. By changing the position of the movable element, the shape and position of the recess in the contact plate can be varied. A threaded spindle, which is operated using a socket wrench, can be provided as the adjustment mechanism, for example.Of course, several movable elements can also be provided to allow even more flexible adjustment of the recess or recesses.

[0032] The object of the invention is also achieved by a device for welding plastic profiles according to claim 4.

[0033] A device according to the invention is based on a welding device or a welding unit according to the prior art. The device according to the invention is constructed on a base plate to which the other components of the device are fixedly or movably attached. The device is intended for welding plastic profiles to form frames, in particular frames for windows or doors. The plastic profiles are clamped in holding elements which hold them during welding and during the other processing steps. A device according to the invention has at least two such holding elements. A device according to the invention can, however, also have several holding elements. It is also possible to combine two or more devices according to the invention to form one automatic welding machine. The holding elements are designed to be movable relative to the base plate.This mobility is required to advance and align the plastic profiles for the processing steps with the processing tool and the heating element. Furthermore, the mobility is required to ultimately press the plastic profiles together during welding. A device according to the invention further comprises a processing tool which is intended to remove material from the plastic profile or profiles. For example, the processing tool can be designed as a milling tool which removes partial areas of the end face of the plastic profiles by machining. The processing tool is intended to remove partial areas of the end face before the plastic profiles are welded and thus counteract the formation of welding beads. Such removal of material is advantageously carried out where visible surfaces of the plastic profiles or the frame will later be present after welding.

[0034] A device according to the invention further comprises at least one heating element according to one of the previously described embodiments. A particularly advantageous feature of a device according to the invention is the interaction between the processing tool and the heating element according to the invention. A significant improvement in the surface quality and the appearance of a connection point between two welded plastic profiles can be achieved by first using a processing tool to remove part of the surface to be welded on the end face of the plastic profiles and then heating this processed end face selectively, i.e. only in certain areas, using a heating element according to the invention. During the final welding process, no unwanted weld bead is then created because there is no longer any material in the visible area that can swell outwards.At the same time, the visible surfaces remain in a solid state due to the much lower heating by the heating element according to the invention and are therefore not deformed when pressed together.

[0035] Furthermore, the proposal advantageously provides for the machining tool to be designed as a milling tool, wherein the machining tool is designed to be movable between a parking position and a working position. A milling tool is particularly suitable as a machining tool because milling allows material to be removed from the plastic profiles quickly and precisely. However, the machining tool can also be designed differently. In general, all technologies that enable the selective removal of material from the end face or adjacent to the end face of plastic profiles are suitable. For example, a laser can be used to remove material. A laser also has the advantage that when material is removed, heat is already introduced into the plastic profile. This heat can then be used in the next step to heat or plasticize the plastic profile.In addition, the machining tool can also be a simple knife, a grinding tool, a piercing tool, or a pair of pliers. The parking position is the position in which the machining tool is placed when not being used to remove material from the plastic profile. The parking position is selected so that the machining tool, in this position, does not hinder the mobility of the other components of the device. The working position is the area in which the machining tool is located when removing material from the plastic profile. The working position is therefore not a single position, but a work area.

[0036] In a preferred embodiment of the proposal, the machining tool comprises at least one face milling cutter, and the machining tool is movable along at least two spatial axes in the working position, such that the machining tool is suitable for removing material along the entire circumference of at least one plastic profile. In this embodiment, the machining tool comprises at least one face milling cutter, which removes material from the plastic profile. A face milling cutter enables simultaneous smoothing and planing of the entire end face of the plastic profile and, in addition, the selective removal of material in the edge region of the end face. For this selective removal in the edge region, the machining tool is moved around the end circumference of the plastic profile.This is made possible by the fact that the machining tool is designed to be movable in its working position along at least two mutually perpendicular spatial axes. In this embodiment, the machining tool also includes the guides and drives required for this mobility.

[0037] Furthermore, the heating element is arranged at a distance from other components of the device in its rest position and is easily accessible for an operator, which makes it possible to replace or clean the contact plate in the rest position. During operation of the device, it can happen that plastic residue remains on the heating element due to the heating of the plastic profiles, which contaminates the heating element. In this case, the heating element must be cleaned from time to time. In addition, the contact plate of the heating element usually has to be replaced in order to adapt the device to processing a different plastic profile. The heating element must be easily accessible and reachable for a processor or machine operator, at least in its rest position, for both cleaning and replacing the contact plate.This can be achieved by positioning the heating element's resting position at a distance from other components of the device. A suitable distance is within a few centimeters, for example, in the range of 2-15 cm. This distance is suitable for reaching the heating element's contact plate with the hand. The greater the distance, the more ergonomic the device can be operated.

[0038] In an advantageous embodiment, a temperature warning device is provided which measures the temperature of the contact plate at least when the heating element is in the rest position and issues a warning signal at a temperature that could cause injury if the contact plate was touched by an operator. In this embodiment, a warning device is provided to protect the operator from burns. The heating element typically has a temperature of more than 100°C when the device is in operation. Thus, there is a significant risk of burns if the heating element is touched with bare hands. The temperature warning device continuously measures the temperature of the heating element and thus of the contact plate. If this measured temperature is within a range where injuries could occur, a warning signal is issued. This warning signal can be visual or acoustic.Furthermore, a barrier may be provided on the device which physically protects the warm or hot parts of the heating element from access as long as their temperature is in a range where injuries may occur.

[0039] The object of the invention is also achieved by a method for welding plastic profiles according to claim 7.

[0040] The method according to the invention is preferably carried out using a device according to the invention. However, the method can also be carried out using other aids or tools. First, the plastic profiles to be welded are sawn, whereby the dimensions of the set plastic profiles are somewhat larger than the required final dimensions for the frame to be produced. Subsequently, in method step A, the plastic profiles are clamped, i.e. fixed to the device used for the method. Clamping is advantageously carried out in the movable holding elements of a device according to the invention. Subsequently, in method step B, part of the end faces of the plastic profiles are removed using a machining tool.In this case, material can first be removed from the entire end face, whereby the rough-sawn surface of the plastic profiles is smoothed and brought into the angle required for welding. The machining tool then removes additional material from the peripheral area of ​​the plastic profiles, particularly where visible surfaces are arranged after welding. By removing material in these areas, the formation of a weld bead after welding is prevented. After the removal of material in step B, the subsequent process step C melts or plasticizes at least some of the end faces or end surfaces of the plastic profiles. In this process, only those areas of the end face of the plastic profiles that remain after parts of the end face have been removed B by the machining tool are melted.For melting C, a heating element according to the invention is used which has at least one recess in each contact surface. For melting C, two contact plates are arranged on the heating element, one of which is each brought into contact with an end face of a plastic profile to be welded. This bringing into contact is achieved by the plastic profiles being pressed into a specific position against the heating element and the contact plates using the movably mounted holding elements. This position is selected such that the recesses in the contact surfaces are at least partially opposite the areas of the plastic profiles machined during removal B. This ensures that the machined areas in which material was removed remain spaced apart from the heating element and are therefore heated less or not at all.This has the previously described effect that the material in the areas where material has been removed remains solid and dimensionally stable, while the material adjacent to the contact surface of the heating element is plasticized for welding. During melting C, melting occurs only locally and selectively; some areas of the end face of the plastic profiles are not melted.

[0041] Finally, in process step D, the selectively melted end faces of the plastic profiles are pressed together, thereby actually welding the two profiles. The pressing together or pressing together is preferably achieved by moving the holding elements in which the plastic profiles are clamped. After pressing together and cooling, a process according to the invention produces a welded joint between two plastic profiles that does not have a weld bead. At the same time, the surface quality, in particular flatness and a visually appealing appearance at the joints, between the two profiles is significantly better than with the prior art.

[0042] Preferably, the process according to the invention is carried out exactly in the described order of process steps, alphabetically ordered from A to D.

[0043] Furthermore, it is provided that in process step C (melting) the remaining end face of the plastic profiles has a width and the contact surfaces of the heating element have at least two recesses which are arranged at a distance from one another, wherein the width corresponds to the distance and during melting C the width is positioned congruent with the distance. In this embodiment, the end face of the plastic profiles remaining after the removal of material in step B has a width. This width is of course not limited to just one spatial direction; several widths can also remain in different spatial directions. Width is understood to be the dimension that defines the distance between the edges of the remaining end face. Different widths can therefore remain in different directions after the removal of material.The contact surfaces of the heating element have at least two recesses that interrupt the contact surface and are arranged at a distance from one another. This distance between the recesses is selected so that it corresponds to the respective width of the end face of the plastic profiles. When the plastic profiles are pressed against the contact surfaces, the remaining end face comes into contact with the surface of the holding element between two recesses, defined by the distance. For this purpose, the distance is aligned congruently with the width in process step C. For this alignment or positioning, either the heating element can be moved towards the plastic profiles or, conversely, the plastic profiles, preferably clamped in the holding elements, can be moved towards the heating element.This positioning between width and distance can be carried out when using a device according to the invention, for example, by fine adjustment of the welding position of the holding element.

[0044] In an advantageous embodiment, it is provided that in method step C (melting) the remaining end face of the plastic profiles has a width and the contact surfaces of the heating element have at least two recesses which are arranged at a distance from one another, wherein the width is smaller than the distance and during melting C the distance is positioned such that it completely covers the width. In this embodiment too, the remaining end face of the plastic profiles has a width. The description for the previous embodiment applies to this width. Here too, the contact surfaces have at least two recesses between which there is a distance. The explanation for the previously described embodiment also applies to this distance. In this alternative embodiment of the method, however, the distance between the recesses is selected to be greater than the width of the remaining base.This minimizes the risk that the width and distance do not exactly overlap during melting C, and that the entire area of ​​the remaining base is not melted across its entire width. For a larger distance, the distance is positioned relative to the width so that it extends beyond the width on both sides, thus covering it. This choice of dimensions allows for tolerances during profile machining and slight misalignments when aligning the plastic profiles to the heating element and vice versa.

[0045] Cleverly, it is provided that in method step C (melting) the remaining end face of the plastic profiles has a width and the contact surfaces of the heating element have at least two recesses which are arranged at a distance from one another, wherein the width is greater than the distance and during melting C the distance is positioned such that it rests on the plastic profile within the width. In this alternative embodiment of the method too, the remaining width of the plastic profiles after the removal of material and the distance between at least two recesses on the heating element are defined as in the two previously described embodiments. Alternatively, however, the distance between two recesses is now selected to be smaller than the remaining width of the end face of the plastic profiles. As a result, the contact surface of the holding element no longer rests on the entire remaining end face with the defined width.In process step C, edge regions of the remaining end face are no longer touched by the contact surface and are therefore not directly melted. In these edge regions, a not fully plasticized region of material remains. This remaining region does not cause any problems during subsequent welding or pressing, as this region is at least softened and can be deformed accordingly when pressed together. Alternatively, the remaining region can also be removed again in an additional process step carried out before pressing together, as described below. The advantage of this embodiment, in which the distance is selected to be smaller than the width, is that the distance between the melted region and the visible area arranged on the outside edge of the plastic profiles is even greater than in the previously described embodiments.This means that the visible area around the outer perimeter of the plastic profiles is heated to an even lower degree, thus remaining even more dimensionally stable. This further improves the surface quality in the visible area of ​​the welded joint.

[0046] In a further preferred embodiment, the following additional steps are carried out after melting C and before compression D: B2. Removing part of an end face of the plastic profiles again and / or at least partially removing material displaced by melting C from the plastic profiles by means of a processing tool, C2. Remelting the end faces of the plastic profiles remaining after removal B2 by bringing them into contact with a heating element according to one of the previously described embodiments, wherein the recesses of the contact surfaces of the heating element are positioned relative to the end face such that the recesses are opposite the areas of the plastic profiles processed by removal B2.

[0047] In this embodiment, two further process steps B2 and C2 are carried out after melting C and before compression D. During melting C, the end faces of the plastic profiles are pressed against the heating element, whereby the material in contact with them is plasticized at the contact surface. Any material that has already melted is displaced outwards. This increases the contact surface of the plastic profiles compared to a non-melted state, which is beneficial for a later, stable welded joint. A disadvantage, however, is that material is also displaced into the areas where visible surfaces will later be present. For this reason, in the described alternative embodiment of the process, the material is first melted once, in process step C, and then part of the end face of the plastic profiles is removed again using the machining tool.Preferably, the material displaced towards the visible area during the first melting step C is removed again. However, the material used in other areas is not removed, so that the surface area of ​​the end face of the plastic profiles is larger after the second removal step than after the first removal step B. After the renewed removal B2, melting takes place a second time, analogous to the first removal B, namely in process step C2. The renewed melting C2 is carried out analogously to melting C and the heating element is positioned accordingly to the end faces of the plastic profiles. By inserting the two optional process steps B2 and C2, the welded area between the two plastic profiles is enlarged and thus the strength of the welded joint is improved. At the same time, however, the advantages of the process according to the invention in terms of significantly improved surface quality are retained.Of course, additional, similarly designed intermediate melting and removal steps can also be added. For example, it is possible to perform a total of three melting and three removal steps in succession before the plastic profiles are pressed together and welded.

[0048] Furthermore, it is provided that after melting C and before compression D, the following additional step is carried out: B2. Re-removal of part of an end face of the plastic profiles and / or at least partial removal of material displaced by melting C from the plastic profiles by means of a processing tool.

[0049] In this embodiment of the method, only an intermediate step B2 is carried out between melting C and compression D. After melting C, the areas of the plastic profiles in which contact occurred between the end face and the contact surface have softened or plasticized. Material has also already been displaced in the process, usually also into the areas in which a visible surface is later to be created after compression D. In this embodiment of the method, material in the area of ​​the end faces of the plastic profiles is again removed by a processing tool after melting C while the material is still in a heated state. Preferably, only the material that was displaced into the area of ​​the visible surface is removed. This renewed removal of material B2 is carried out while the material is still in a softened or plasticized state.Such removal of softened material is possible, for example, with a machining tool designed as a milling tool. This renewed removal of material B2 is carried out quickly so that the material does not cool down significantly during removal and remains in its softened state. After the renewed removal of material B2, the end faces of the plastic profiles are then pressed together and welded without remelting. At this point, the material in the area of ​​the end faces is still in a softened, plasticized state. In this way, the surface quality in the visible areas can be improved by the renewed removal of material, and at the same time, the process time for welding the plastic profiles is only insignificantly extended, namely by the second removal step B2.A second melting step after the second removal step B2 is not required in this embodiment of the method.

[0050] In this context, it is particularly noted that all features and properties described with reference to the device, as well as procedures, are also transferable mutatis mutandis to the formulation of the method according to the invention and can be used within the meaning of the invention and are considered to be co-disclosed. The same applies in reverse, meaning that structural features mentioned only with reference to the method, i.e., features related to the device, can also be considered and claimed within the scope of the device claims and are also considered part of the disclosure.

[0051] The invention is illustrated schematically in exemplary embodiments in the drawings. They show: Fig. 1 is a perspective view of a heating element according to the invention with a plastic profile in contact with the contact plate, Fig. 2 is a perspective view of a heating element according to the invention without a plastic profile, Fig. 3 is a perspective view of a device according to the invention, Fig. 4 is a schematic representation of a plastic profile positioned relative to a heating element according to the invention, Fig. 5 is a schematic representation of the melting results at different distances between recesses in the heating element in views 5a and 5b, Fig. 6 is a schematic representation of process steps when welding plastic profiles, Fig. 7 is a perspective view of a device according to the invention with further components of a welding machine, Fig. 8 is a perspective view of a device according to the invention with a heating element in the welding position and in the rest position.

[0052] In the figures, identical or corresponding elements are designated by the same reference numerals and are therefore not described again unless expedient. The disclosures contained in the entire description are analogously applicable to identical parts with the same reference numerals or the same component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., refers to the directly described and illustrated figure and, in the event of a change in position, is to be analogously applied to the new position. Furthermore, individual features or combinations of features from the various embodiments shown and described can represent independent, inventive or inventive solutions in themselves.

[0053] Fig. 1 shows a perspective view of a heating element 1 according to the invention with a plastic profile 2 in contact with the contact plate. In the illustration, a plastic profile 2 is positioned relative to the heating element 1 such that a portion of the end face of the plastic profile 2 comes into contact with the heating element 1. In the position shown, the plastic profile 2 is heated or plasticized by the heating element 1 according to the method according to the invention. Fig. 4, 5 and 6 The areas shown, where material has been removed from the front side of the plastic profile 2, such as in the removals 25, 26, are shown in Fig. 1 not shown for the sake of clarity. Of course, plastic profiles 2 with material removed from the front side, as shown by the removals in Fig. 4, 5 and 6 shown, as shown in Fig. 1 to the heating element 1 and brought into contact with it. Further components or assemblies, which are required for the practical positioning of the plastic profile 2 to the heating element 1, are not shown in this view for the sake of clarity. The heating element 1 has a centrally or centrally arranged heating element 13. A contact plate 11 is arranged on each side of the plate-shaped heating element 13. The contact plates 11 are also plate-shaped. The contact plates 11 lie with their rear side flat against the heating element 13, thereby ensuring good heat transfer from the heating element 13 to the contact plates 11. Two recesses 14 are milled into the contact plate 11, which is oriented towards the front in the illustration. These recesses 14 are used in connection with Figur 2 in more detail. The heating element 13 has two connections 131 oriented to the rear left, which serve to supply the heating element 13 with energy. The heating element 13 can be heated directly with electrical energy, for example. Alternatively, it is also possible to supply a liquid heating medium, such as hot water or oil, to the heating element 13 via the connections 131 and thus heat it. In the illustration, the connecting element 15 can be seen arranged at the upper edge of the heating element 13. This connecting element 15 serves to detachably and firmly connect the contact plates 11 to the heating element 13. The pressure piece 152 is connected to the actuating lever 151. In the state shown, the pressure piece 152 is in a moved position relative to the heating element 13.In the illustrated state, the pressure piece 152 encloses a portion of the upper edge of the contact plates 11 in a complementary shape and thereby presses them against the heating element 13. A portion of the upper edge of the contact plates 11 is beveled or provided with a chamfer. The pressure piece 152 has corresponding chamfered areas on its downward-facing side. The pressure piece 152 rests with its chamfered areas on the chamfered areas of the contact plates 11. Due to the chamfers, which are aligned at an angle of approximately 45° to the side surface of the heating element 13, a force is generated when the pressure piece 152 is pressed vertically onto the contact plates 11 due to the wedge effect, which presses the contact plates 11 firmly against the surfaces of the heating element 13. To separate the contact plates 11 from the heating element 13, the actuating lever 151 is moved upward.This also moves the pressure piece 152 away from the heating element 13 and the contact plates 11. The positive connection between the parts is thereby released, so that the contact plates 11 can then be removed from the heating element 13. The connecting element 15 further comprises a holding piece 153 arranged at the lower edge of the heating element 13. When the contact plates 11 are connected to the heating element 13 by the connecting element 15, the lower edge of the contact plates is first inserted into the holding piece 153. Subsequently, the actuating lever 151 and the pressure piece 152 are positioned downward, creating a positive connection and a frictional connection between the contact plates 11 and the heating element 13. The holding piece 153 also has areas with a chamfer, whereby the chamfer is oriented upwards here and serves as an insertion aid for the contact plates 11. The holding piece 153 is permanently and firmly connected to the heating element 13.

[0054] Fig. 2 shows a perspective view of a heating element 1 according to the invention without plastic profile 2. In Fig. 2 the heating element 1 is off Fig. 1 without a plastic profile 2. The heating element 1 in Fig. 2 corresponds to heating element 1 in Fig. 1 , so that the description of heating element 1 from Fig. 1 also for Fig. 2 applies. In Fig. 2 the forward-facing contact plate 11 is not covered by a plastic profile 2 and can therefore be seen in every detail. The contact surface 12 of the front contact plate 11 faces forward. The contact surface 12 here has a homogeneous, smooth surface. In an alternative embodiment, however, the contact surface 12 can also have a regular contour, for example regularly arranged ribs. Such ribs can be used to enlarge the contact surface 12. The contact surface 12 is intended to come into contact with a plastic profile, in particular with the end face of a plastic profile. The outer contour 21 of the end face of a plastic profile 2 is drawn on the contact surface 12. This outer contour 21 is an auxiliary line drawn only in the illustration to facilitate understanding of the following description.The contact surface 12 is homogeneous and smooth; the outer contour 21 is not actually present or visible. Two recesses 14 are arranged in the contact surface 12, one in the upper region of the contact surface 12 and one near the lower edge. In the case shown, the two recesses 14 are pocket-shaped and are each delimited on the side facing away from the contact surface 12 by a base surface 141. The base surface 141 is set back from the contact surface 12 and is also flat here. Alternatively, the recesses 14 can also be designed such that they penetrate the contact plate 11 completely and then have no base surface 141. In the case shown, the recesses 14 are milled out of the contact plate 11. In . Fig. 1 The rearward-facing second contact plate 11 is not visible. This second contact plate 11 is designed symmetrically to the forward-facing first contact plate 11 with respect to the center plane of the heating element 13. Thus, the second, rearward-facing contact plate 11 also has two recesses 14, which are arranged symmetrically to the two recesses 14 in the forward-facing contact plate.

[0055] The two recesses 14 are arranged so that their shape and position partially or partially border on the outer contour 21 of the plastic profile. Fig. 1 The plastic profile 2 shown has a flat visible surface at the top and bottom. Furthermore, there is another visible surface curved towards the front and right. The recesses 14 are shaped such that their inner contour, facing the outer contour 21, corresponds to the outer contour 21 of the plastic profile in these areas of the visible surfaces. By arranging the recesses 14 in this way, it is achieved that the plastic profile 2 is not heated by the contact plate 11 in the area of ​​its visible surfaces. The remainder of the end face of the plastic profile 2, which is enclosed by the outer contour 21, is, however, contacted and heated by the contact plate 11.Because the edge regions of the plastic profile 2, where the visible surfaces are located, are not touched by the heating element 1 according to the invention, these visible areas remain in a solid state, resulting in a significantly improved surface quality of the subsequent welded joint. Of course, recesses 14 can also be arranged in other areas in the contact plate 11. The width of the recesses 14, starting from their inner contour facing the outer contour 21 of the profile, is selected such that the area where the visible surfaces of the plastic profile 2 are located is definitely not touched by the contact plate 11. Furthermore, the distance also prevents the material in the area of ​​the visible surfaces from heating up without contact, for example through thermal radiation emanating from the contact plate 11.

[0056] Fig. 3 shows a perspective view of a device 100 according to the invention. A device 100 according to the invention is used to weld plastic profiles for producing frames, for example for doors or windows. The device 100 shown comprises a base plate 101 on which the other elements or assemblies of the device 100 are arranged. In the case shown, the base plate 101 is formed by a metal plate. The base plate 101 can also comprise further elements, such as a fastening element with which the device 100 is anchored at the production site or to a machine frame. One of the two holding elements 102 can be seen at the bottom left. This holding element 102 is used to clamp plastic profiles 2 for processing. Plastic profiles 2 are not shown in this view for the sake of clarity.The holding element 102 is designed to be movable and can be fed to the work steps with a plastic profile 2 clamped therein. In the embodiment shown, the holding element 102 comprises two plates arranged vertically one above the other, between which a plastic profile 2 can be clamped. In the embodiment shown, the holding element 102 is designed to be movable from front to back, into the plane of the drawing. This movable design allows the holding element 102 with the plastic profile to be fed, for example, to the heating element 1 shown in the background. On the right-hand side of the illustration, the processing tool 103 can be seen, which here is formed by an assembly. The processing tool 103 is connected to the base plate 101 by the holder 1031 and fastened to the latter. The tool arm 1032 is arranged to be movable relative to the holder 1031.The tool arm 1032 can be moved vertically and horizontally in a direction parallel to the holder 1031 via actuators. This mobility allows the tool arm 1032 to be advanced toward a plastic profile 2 clamped in the holding element 102. Appropriate drives and guides are provided to realize this mobility. Of course, the tool arm 1032 can also be designed to be movable in other spatial axes. At the rear left end of the tool arm 1032, a face milling cutter 1033 is arranged, which is intended to remove material from the front side of a plastic profile. The face milling cutter 1033 is thus the active element of the machining tool 103 for removing material.

[0057] On the side of the tool arm 1032 facing rearward in the drawing, a further face milling cutter 1033 is arranged parallel to the illustrated face milling cutter 1033. This makes it possible to simultaneously machine two plastic profiles 2 to be welded together using the tool arm 1032, with one face milling cutter 1033 coming into contact with an end face of each plastic profile. For clamping and guiding, the device 100 naturally also has a second holding element 102, which is, however, concealed by other device parts in the illustration. In the illustration, the machining tool 103, in particular the tool arm 1032, is shown in a parked position. To remove material, the tool arm 1032 is moved into a working position so that the face milling cutters 1033 come into contact with the end faces of the plastic profiles clamped in the holding elements 102.

[0058] In the illustration at the back left, the heating element 1 can be seen. The heating element 1 is also arranged so that it can move relative to the base plate 101. In the illustration in Fig. 3 The heating element 1 is in the welding position. In this welding position, plastic profiles 2 clamped in the holding element 102 can be fed to the heating element 1 in a simple linear movement. The welding position of the heating element 1 is adjusted so that the end faces of the plastic profiles 2 are correctly positioned relative to the recesses 14 in the contact surface 12 of the heating element 1. For this correct positioning of the heating element 1 relative to the end faces of the plastic profiles, Fig. 1 and 2and the associated description. The heating element 1 can be moved from the illustrated welding position into a rest position away from the plastic profiles. When the heating element 1 is moved into the rest position, it is moved parallel to the large surface of the holder 1031 facing forwards to the left, with the heating element 1 moving upwards to the right. In the rest position, the heating element 1 is spaced apart from other components of the device 100, so that it is easily accessible for cleaning or for replacing contact plates 11. When the device 100 is in operation, either only the processing tool 103 or the heating element 1 is in the working position or welding position. After the profiles have been clamped in the holding elements 102, the processing tool 103 is first moved into the working position and then partially removes material from the end faces of the plastic profiles.The processing tool 103 is then moved to the illustrated parking position. The heating element 1 is then moved to the illustrated welding position, and the plastic profiles are pressed against the contact surfaces 12 of the heating element 1 using the holding elements 102, thereby plasticizing the contact surfaces. The heating element 1 is then also moved to its rest position, as a result of which no fixture parts are left between the plasticized end faces of the plastic profiles 2. In this state, the clamped plastic profiles 2 are then pressed together using the holding elements 102 and welded.

[0059] Fig. 4 shows a schematic representation of a plastic profile 2 positioned relative to a heating element 1 according to the invention. Fig. 4 is a highly simplified representation and serves to illustrate the relationship between the dimensions of a plastic profile 2 and the position of two recesses 14 in a contact plate 11 of a heating element 1 according to the invention. The heating element 1 is presented here only as a section of a contact plate 11. Of course, the heating element 1, as for example Fig. 1 and Fig. 2 described, further elements. In the contact plate 11, two recesses 14 are arranged here, which break through the contact surface 12. The recesses 14 are pocket-shaped and are each delimited on their side facing away from the contact surface 12 by a bottom surface 141. The contact surface 12 and bottom surfaces 141 are each flat here. The recesses 14 have a depth v, starting from the contact surface 12 down to the bottom surface 141. In the illustrated embodiment, the depth v is the same for the recesses 14. The two recesses 14 are arranged in the contact plate 11 at a distance s from one another. This distance s corresponds to the shortest distance between the side walls of the two recesses 14.

[0060] On the left side of Fig. 4 The right end of a plastic profile 2 is shown. The right-facing end of the plastic profile 2 is aligned at a right angle to the length of the plastic profile 2. This embodiment allows for the simplest representation. In most cases, however, particularly in the manufacture of frames, the end of the plastic profile 2 is arranged at a different angle to the length of the profile. In most cases, the plastic profile 2 is mitered, so that the end is usually arranged at a 45° angle to the length of the profile. Fig. 4 In the state shown, material has already been removed from the end face or front surface of the plastic profile 2. In the illustration, facing upwards and downwards, the plastic profile 2 has surfaces on its long side which are visible after welding to the frame and thus form visible surfaces. Adjacent to the upward-facing and downward-facing visible surfaces of the long sides of the plastic profile 2 there is a removal 25, 26. These removals 25, 26 were created by the prior removal of material by a machining tool. Material is therefore missing in the area of ​​the removals 25, 26. In the case shown, the two removals 25, 26 have two boundary surfaces oriented at right angles to one another to the plastic profile 2. The two inner boundary surfaces 251, 261 are those boundary surfaces of the removals 25, 26 which run parallel to the longitudinal direction of the plastic profile 2.The two inner boundary surfaces 251, 261 form the width h of the end face of the plastic profile 2 remaining after the removal of material. The remaining end face is the end face facing to the far right on the plastic profile 2 and is delimited by the two recesses 25, 26. This remaining end face with the width h is relevant for the interaction with the recesses arranged at a distance s in the contact plate 11 of the holding element shown opposite. The two recesses 25, 26 each have a depth t in the longitudinal direction of the plastic profile 2, which in the case shown is the same for both recesses 25, 26. In the case shown, the distance s between the two recesses 14 is exactly the same as the width h of the remaining end face of the plastic profile 2.To heat or melt the remaining end face of the plastic profile 2, the latter is moved, starting from the illustrated state, in the longitudinal direction of the plastic profile 2 towards the contact plate. The remaining end face of the plastic profile 2 then lies congruently on the contact surface 12 between the two recesses 14, the dimensions of which correspond to the distance s. The depth v of the two recesses 14 is greater than the depth t of the two ablated portions 25, 26. The distance between the two side surfaces of the two opposite recesses 14 facing upwards and downwards in the illustration is greater than the total width of the plastic profile 2, which results from the sum of the width h and the width of the boundary surfaces 251, 261.This dimensioning ensures that contact between the plastic profile 2 and the contact plate 11 only occurs in the area intended for such contact between the width h and the distance s, and that the areas of the front side of the plastic profile located outside the width h never come into contact with the contact plate 11. Furthermore, the areas adjacent to the width h and the distance s are so far apart that only very little radiant heat is transferred from the contact plate 11 to the plastic profile 2. This ensures that the material adjacent to the visible surfaces of the plastic profile 2 is not softened by radiant heat emanating from the heating element 1.

[0061] The plastic profile 2 has surfaces facing upwards and downwards, which later form visible surfaces. In the embodiment shown, these visible surfaces are aligned centrally to the width of the two recesses 14. The width of the recesses 14 is understood to be the dimension that runs from top to bottom in the plane of the drawing and forms an interruption in the contact surface 12. A central positioning of the visible surfaces relative to the width of the recesses 14 is particularly advantageous, since the end of the visible surfaces facing to the right is thereby minimally heated by radiant heat from the contact plate 11. For such a central positioning, the position and width of the recesses 14 are adapted to the plastic profile 2 to be processed. Of course, the positioning of the visible surfaces of the plastic profile 2 can also be off-center to the width of the recesses 14.

[0062] In Fig. 4 The thickness of the contact plate 11 is relatively thick in relation to its height, in the direction of the dimension arrow to the width s, in particular more than three times as thick as the depth v of the recesses 14. However, the contact plate 11 can also be made significantly thinner in relation to its height. For example, a thickness of the contact plate 11 that corresponds to the depth v is also suitable for the contact plate 11. With such dimensions, the recesses 14 are then continuous and penetrate the entire contact plate 11. Furthermore, thinner contact plates 11 with pocket-shaped recesses 14, for example with a thickness 1.5 times as large as the depth v, are also suitable for a heating element 1.

[0063] In the following described Fig. 5a und 5b melting results are shown, which are based on alternative constellations of width h and distance s.

[0064] Fig. 5 shows in views 5a and 5b the different results of melting at different distances s from recesses 14 in the heating element 1. In Fig. 5a und Fig. 5b is only the one in Fig. 4 The corresponding plastic profiles 2 are shown in a highly simplified manner. The illustrations show the appearance of the plastic profiles 2 after they have been brought into contact with the contact plate 11 of a heating element 1. This shows the state in which the end face of the plastic profiles 2 has already been melted. For the definition of the dimensions of the contact plate 11 and the plastic profile 2, Fig. 4 and the corresponding description.

[0065] In Fig. 5a The result of the melting is shown for the case in which the distance s between two recesses 14 is greater than the width h of the remaining end face of the plastic profile 2. During the melting process carried out previously, the distance s on both sides exceeded the width h. When the plastic profile 2 was pressed against the contact plate 1, the material in this area was plasticized and partially displaced outwards into the recesses 25, 26. The displaced material is thus absorbed by the recesses 25, 26. If the recesses 25, 26 are sufficiently large, the displaced material can remain there. When two plastic profiles 2 are subsequently pressed together in the Fig. 5a In the state shown, no material then bulges beyond the visible surfaces, the material located in the ablations connects the plastic profiles 2 within the visible surface. In this case, no weld bead is formed on the visible surfaces or at the joint. If a longer infeed movement is carried out between the plastic profiles and the contact plate 11 during melting, during which more material is displaced into the ablations 25, 26, it can happen that too much material is present in the ablations 25, 26 during the subsequent compression and is displaced outwards beyond the visible surface. In this case, either the dimensions of the ablations 25, 26 can be increased or the displaced material is removed after melting in a further removal step using a machining tool.

[0066] In Fig. 5b The result of the melting is shown for the case in which the distance s between two recesses 14 is smaller than the width h of the remaining end face of the plastic profile 2. In contrast to Fig. 5a was that in Fig. 5b The previously melted plastic profile 2 is brought into contact with a contact plate, in which the distance s between the two recesses 14 is smaller than the width h of the remaining end face of the plastic profile 2. As a result, the contact surface 12 between the two recesses 14 no longer contacts the plastic profile 2 over the entire width h. Thus, the entire width h was not heated and the material located there was not plasticized everywhere. After melting, the protruding edge regions 27, 28 remain in the areas where the contact surface 12 was not in contact with the end face. These edge regions 27, 28 are not plasticized but are nevertheless softened by the heating of adjacent areas. When two plastic profiles 2 are pressed together in the manner shown in Fig. 5b In the state shown, the edge regions 27, 28 are pushed away and surrounded by plasticized material. Thus, in this embodiment, a sufficiently strong connection is created during welding. Alternatively, the edge regions 27, 28 can also be removed by a machining tool in a further removal step following the melting process.

[0067] Fig. 6 shows schematic representations of process steps in the welding of plastic profiles 2 in views 6a to 6f. These views are highly simplified. As in Fig. 4 und 5 the front face of the plastic profile 2 shown is also in Fig. 6 perpendicular to the longitudinal direction of the plastic profile 2. Of course, the end face can also be aligned at a different angle, for example at a 45° angle to the longitudinal direction of the plastic profile 2.

[0068] Fig. 6a shows the state of a plastic profile 2 as it is being fed into the welding process. The right-facing end of the plastic profile 2 has been sawn off and is in a rough-sawn condition. The rough-sawn surface is uneven. During the sawing process, an excess was left on the plastic profile 2, so the final dimension for welding must be adjusted in the following steps.

[0069] Fig. 6b shows the plastic profile 2 after the partial removal of material from the end face / front surface by a machining tool. In the illustration above and below, adjacent to the visible surfaces of the plastic profile 2, the removal areas 25, 26 on the circumference were removed by the machining tool. These removal areas 25, 26 are intended to absorb material that swells outwards during welding. Furthermore, the machining tool removed material from the remaining front face facing to the right, which is represented by volume 29. By removing volume 29, the previously rough-sawn surface was leveled and the angle of the front face to the long side of the profile was adjusted. To remove volume 29, a machining tool design as a positional milling cutter is particularly advantageous, since such a tool can machine large surfaces quickly and precisely with very good surface quality.

[0070] Fig. 6c shows the plastic profile 2 during melting in contact with the contact plate 11 of the heating element 1. The state shown in this view corresponds to a state that starts from Fig. 4 after the plastic profile 2 and contact plate 11 come into contact. In the state shown, the plastic profile 2 is pressed against the hot contact plate 11. In the process, material on the remaining end face of the plastic profile 2 is melted and plasticized. This plasticized material swells outwards. If the plastic profile 2 is pressed against the contact plate 11 for a longer period of time, more and more material is displaced. As a result of the melting, the plastic profile 2 moves towards the contact plate 11 under contact pressure. In the process, material is continuously burned off the end face, and the length of the plastic profile 2 is reduced. This burn-off, which can be adjusted by contact pressure and contact time, can be used to influence the final dimension of the plastic profile 2.

[0071] Fig. 6d shows the state of the plastic profile 2 after an optional, second material removal step. In this second removal step, the material produced during melting in Fig. 6c Material displaced in the removals 25, 26 is removed again. The machining tool was also used for this optional removal step. In contrast to the removal in Fig. 6b no material was removed from the remaining end face.

[0072] Fig. 6e shows the plastic profile 2 during a second melting process. After the second removal step, the plastic profile 2 is melted according to Fig. 6d analogous to Fig. 6c melted again. The Fig. 6d und 6e The steps shown are optional. However, these steps can be repeated multiple times to individually adjust the quality and strength of the weld.

[0073] Fig. 6f shows the condition of the plastic profile 2 after being pressed together and welded to another plastic profile 2 shown on the right. The material in the middle of the two plastic profiles 2 has fused together, creating a strong and continuous welded joint. However, due to the previously applied removals 25, 26 and the use of a contact plate 11 according to the invention with recesses 14, the material in the boundary regions 211, 212 to the visible surfaces has not fused together. In this region, the material remained solid and unplasticized before being pressed together. For this reason, the surface quality in these boundary regions 211, 212 is particularly good, since in particular no bulging or indentation occurred when the two plastic profiles 2 were brought together.

[0074] When pressed together, the plastic profiles 2 are moved toward each other parallel to their longitudinal direction. Particularly favorable welding results are achieved when the outer visible surfaces abut one another in the boundary areas 211, 212, without pressure developing between the visible surfaces in the boundary areas 211, 212 when pressed together. This ensures that no undesired deformations occur. However, the process also tolerates slight contact pressures between the visible surfaces in the boundary areas 211, 212, since the material here is in a non-plasticized, solid state, which is suitable for absorbing and compensating for slight contact pressures.

[0075] Fig. 7 shows a perspective view of a device 100 according to the invention with other components of a welding machine. In Fig. 7 the device 100 is made of Fig. 3 arranged on a welding machine, which includes further components. The welding machine is based on a machine frame 200. This machine frame 200 is intended to support one or more devices 100. One device 100 is shown top left as an example. A device 100 is required for each connection point between two plastic profiles 2. To produce a frame, four devices 100 are usually used, each of which creates a corner of the frame. Another term for device 100 is welding head; a welding machine with four devices 100 is often also referred to as a four-head welding machine. The machine frame 200 includes a first guide 201, which runs from left to right in the illustration. The device 100 can be moved linearly along this first guide 201.For this purpose, elements for moving the device 100, such as motors and gears, are provided on the device 100 or on the first guide 201. Opposite the device 100 shown, a further device 100 is arranged on the first guide 201, which is not shown here for the sake of clarity. The second device 100 is also movable along the first guide 201, so that the two devices 100 can be moved towards and away from each other along the first guide 201. This mobility allows the plastic profiles 2 clamped in the devices 100 to be advanced to the heating element 1, to the processing tool 103, and when pressed together after melting. In the drawing view, a further, second guide is usually arranged in front of the first guide 201 shown, which is designed similarly or identically to the first guide 201.Two devices 100 are also arranged on the second guide so as to be linearly movable relative to one another. A drive assembly 203 is arranged between the first guide 201 and the second guide. This drive assembly 203 is intended to move the two guides with the devices 100 mounted thereon towards one another. The drive assembly 203 is connected to the first guide 201 and the second guide (not shown). The movement of the two guides towards one another, enabled by the drive assembly 203, enables the production of rectangular frames. The drive assembly 203 enables the plastic profiles 2 to be fed perpendicularly to the first guide 201 towards the heating element 1, to the processing tool 103, and during compression after melting. The drive assembly 203 comprises the necessary guides, gear elements, and motors to move two guides 201 towards one another and away from one another.During the production of a rectangular frame from plastic profiles 2, the two devices arranged on a guide 201 are each moved towards each other, while at the same time the two guides 201 arranged parallel to each other are also moved towards each other with the help of the drive assembly 203.

[0076] In Fig. 7 A holding element 102 is shown in the open state on the device 100. The holding element 102 comprises a lower clamping plate 1021, which is triangular in this case, and an upper clamping plate 1022, which is also triangular. The plastic profile 2 is clamped between the two clamping plates 1021 and 1022. In the state shown, the upper clamping plate 1022 is moved upwards for the sake of clarity, so that the plastic profile 2 is not clamped or held in the state shown. For clamping, the upper clamping plate 1022 is moved vertically downwards until it rests on the plastic profile 2. In the illustration, the plastic profile 2 rests against a heating element 1 which is currently in the welding position. On the side of the heating element 1 opposite the plastic profile 2 shown, there is a further holding element 102 with another plastic profile 2 clamped therein.The second plastic profile 2 with the further holding element 102 is also not shown for the sake of clarity. A cleaning bar 1023 is arranged on the upper clamping plate 1022. This cleaning bar 1023 serves to remove dirt from the plastic profile, which can arise, for example, during processing by the processing tool 103. The cleaning bar 1023 has channels inside it that open into nozzles. Compressed air is connected to the cleaning bar 1023 so that, if desired, compressed air emerges from the nozzles and cleans the plastic profile 2 by blowing it off. This escaping compressed air is symbolized by lines 1024. Of course, a device 100 or a holding element 102 can also be designed without a cleaning bar 1023. In . Fig. 7 the machining tool 103 is in its parking position and is largely concealed by other elements of the device 100.

[0077] Fig. 8 shows a perspective view of a device 100 according to the invention with a heating element 1 in welding position and in rest position. Fig. 8 shows a device 100 from a different perspective than in Fig. 3 and Fig. 7 . In the illustration in Fig. 8 The heating element 1 is shown in the welding position S at the bottom right and in the rest position R at the top left. In reality, the heating element 1 is only present once and is located either in the welding position S or in the rest position R. In the welding position S shown at the bottom right, the heating element 1 is positioned so that the plastic profile 2, as for example Fig. 4 described in detail, can be moved towards the heating element 1 for melting. For this approach or feed movement, the Fig. 7 described elements, for example guide 201 and drive assembly 203, are used. In the rest position R shown top left, the heating element 1 is spaced apart from other elements or assemblies of the device 100. The heating element 1 is thus easily accessible by the machine operator in the rest position R, so that cleaning or maintenance work on the heating element 1 can be carried out ergonomically in the rest position R. In the rest position R, changing the contact plates 11 on the heating element 1 is also possible in a simple manner. Fig. 8 For the sake of clarity, only one holding element 102 is shown. As in Fig. 7 the upper clamping plate 1022 is moved away from the plastic profile 2. To fix or clamp the plastic profile 2, the upper clamping plate 1022 is moved vertically downwards towards the lower clamping plate 1021. The holding element 102 has a corresponding drive for this feed movement of the two clamping plates 1021, 1022. The device in Fig. 8 also has a Fig. 3 shown machining tool 103, which in Fig. 8 but is hidden by other elements of the device and is therefore not visible.

Claims

1. Heating element (1) for heating plastic profiles before they are joined by welding: a) at least one contact plate (11) with a contact surface (12) facing at least one plastic profile, b) at least one heating element (13), which is in operative connection with the contact plate (11), c) wherein the contact plate (11) has at least one recess (14), which is arranged in the contact surface (12) and which interrupts the contact surface (12), d) wherein the recess (14) completely penetrates the contact plate (11) or the recess (14) has a bottom surface (141), wherein the bottom surface (141) delimits the recess (14) on the side of the recess (14) facing away from the contact surface (12) and the bottom surface (141) is set back relative to the contact surface (12), e) wherein the contact plate (11) and the heating element (13) are designed as different components, and f) wherein the contact plate (11) rests at least partially flat on the heating element (13) in order to ensure good heat transfer between the two components, characterised g) in that the heating element (1) has at least one connecting element (15) which firmly connects the contact plate (11) to the heating element (13) in a detachable manner, and h) in that two contact plates (11) are provided, which in the operating state are arranged on one side of the heating element (13) in each case and which are designed symmetrically to one another in relation to the centre plane of the heating element (13).

2. Heating element (1) according to one of the preceding claims, characterised in that the shape of the recess (14) in a plan view of the contact surface (12) corresponds at least partially to the shape of the outer contour of the end face of a plastic profile to be welded.

3. Heating element (1) according to claim 1, characterised in that the connecting element (15) comprises at least one actuating lever (151) and at least one pressure piece (152), the pressure piece (152) being actuated by the actuating lever (151). (151) is designed to be movable towards and away from the heating element (13) and the pressure piece (152) is at least partially complementary in shape to an edge of the contact plates (11).

4. Device (100) for welding plastic profiles, comprising a) a base plate (101), b) at least two retaining elements (102), which are intended to hold a plastic profile (2) in each case, the retaining elements (102) being arranged in such a way that, relative to the base plate (101) are designed to be movable, c) at least one machining tool (103), which is intended to remove material from at least one part, at least one plastic profile (2) at its end face or adjacent to its end face, d) at least one heating element (1) according to one of claims 1 to 3, e) wherein the heating element (1) is designed to be movable relative to the base plate (101) between a welding position and a rest position, f) wherein the heating element (1) is positioned in the welding position relative to the plastic profiles (2) to be welded in such a way that the recess (14) of each contact plate (11) is arranged at least partially opposite the outer contour (21) of the plastic profile (2) to be welded.

5. Device (100) according to claim 4, characterised in that the machining tool (103) is designed as a milling tool, wherein the machining tool (103) is designed to be movable between a parking position and a working position.

6. Device (100) according to claim 4 or 5, characterised in that the machining tool (103) comprises at least one face milling cutter and the machining tool (103) is movable in the working position along at least two spatial axes, so that the machining tool (103) is suitable for this purpose, to remove material along the entire circumference of at least one plastic profile (2) and / or the heating element (1) is arranged in its rest position at a distance from other components of the device (100) and easily accessible to an operator, whereby replacement or cleaning of the contact plate (11) is possible in the rest position.

7. Method for welding plastic profiles, in particular using a device (100) according to one of claims 4 to 6, comprising the steps, A. Clamping the plastic profiles, B. Removal of at least part of an end face of the plastic profiles using a machining tool, C. Melting of the end faces of the plastic profiles remaining after removal B by bringing them into contact with a heating element (1) according to one of claims 1 to 3, wherein the heating element (1) has two contact plates (11) each with at least one contact surface (12), and wherein in each case one contact surface (12) is brought into contact with an end face of a plastic profile, and the recesses (14) of the contact surfaces (12) of the heating element (1) are positioned relative to the end faces in such a way that the recesses (14) are opposite the regions of the plastic profiles processed by the removal B, D. Pressing together and welding the ends of the plastic profiles that have been melted by melting C.

8. Method according to claim 7, characterised in that in method step melting C the remaining end face of the plastic profiles has a width (h) and the contact surfaces (12) of the heating element (1) have at least two recesses (14) which are arranged at a distance (s) from one another, wherein the width (h) corresponds to the distance (s) and during melting C the width (h) corresponds to the distance (s). (h) is positioned congruently to the distance (s).

9. Process according to claim 7 or 8, characterised in that the following additional steps are carried out after melting C and before compression D: B2. removing again a part of an end face of the plastic profiles and / or at least partially removing material displaced by the melting C from the plastic profiles by means of a processing tool, C2. re-melting of the end faces of the plastic profiles remaining after removal B2 by bringing them into contact with a heating element (1) according to one of the preceding claims, wherein the recesses (14) of the contact faces (12) of the heating element (1) are positioned relative to the end face in such a way that the recesses (14) lie opposite the regions of the plastic profiles which have been processed by removal B2.

10. Process according to one of claims 7 to 9, characterised in that the following additional step is carried out after melting C and before compression D: B2. removing again a part of an end face of the plastic profiles and / or at least partially removing material displaced by the melting C from the plastic profiles by means of a processing tool.