DE102019130670A1 - Heating element, device and method for hot gas welding of plastic parts - Google Patents

Abstract

The invention relates to a heating element, a device and a method for hot gas welding of plastic parts. The object of the present invention is to provide the simplest and most cost-effective, yet reliable, means for hot gas welding of plastic parts. To achieve the object, the invention provides a heating element (2) for hot gas welding of plastic parts (20), with a heating element surface (3) for heating a joining surface (21) of a plastic part (20) along a welding line with a predetermined contour, the contour the heating element surface (3) is adapted to the contour of the welding line, characterized in that the heating element surface (3) comprises an outer surface (5) with pores (4) of a pore body (6) through which a hot gas can flow.

Description

The invention relates to a heating element, a device and a method for hot gas welding of plastic parts.

It is basically known to weld plastic parts together by melting the plastic in the area of surfaces to be connected by means of a gas heated to a suitable temperature, and then pressing the plastic parts together with the melted surfaces. After cooling, the plastic parts are firmly bonded to one another.

From the DE 100 19 163 A1 For example, a device is known which comprises an outflow frame with outflow openings for hot gas on its top and bottom, which direct the hot gas jet onto the joining surfaces of plastic parts to be connected to one another. The plastic parts, for example half-shells of vehicle tanks, are joined by placing the outflow frame between the joining surfaces of the plastic parts and directing a jet of hot gas onto the joining surfaces of the plastic parts through the outflow openings until the plastic has melted in this area. The outflow frame is then pivoted out of the area of the joining surfaces and the plastic parts are brought into contact and held at the joining surfaces at least until the plastic has largely solidified again.

From the EP 1 415 789 81 B1 a method and a device for connecting plastic parts along a welding line are known, the plastic parts to be connected each being heated along the welding line by thermal radiation and simultaneously exposed to a hot gas from a row of nozzle bores following the welding line, and the plastic parts are then pressed together along the welding line become. The device according to EP 1 415 789 81 B1 provides a welding body with a central, rectangular or square plate, on the upper and lower side of which there are attachments in which radiation bodies are embedded, in which the rows of nozzle bores are provided.

The known hot gas welding devices are comparatively complex and therefore expensive. In addition, the energy requirement is relatively high and the welding times that can be achieved are comparatively long, which also leads to increased costs.

The object of the present invention is to provide a means for hot gas welding of plastic parts that is as simple and inexpensive as possible, but also reliable. In particular, it is the object of the invention to provide a heating element which has a comparatively low energy requirement and enables short welding times.

To solve the problem, the invention provides a heating element for hot gas welding of plastic parts,
with a heating element surface for heating a joining surface of a plastic part along a welding line with a predetermined contour, wherein the contour of the heating element surface is adapted to the contour of the welding line, and wherein the heating element surface comprises an outer surface with pores of a pore body through which a hot gas can flow, through whose pores the Hot gas can flow in the direction of the joining surface.

In the heating element according to the invention for hot gas welding of plastic parts, the heating element surface comprises an outer surface of a pore body through which hot gas can flow. Through the open pores of the porous body, which can for example be a porous metal or ceramic body, hot gas can flow in the direction of the joining surface of a plastic part. The hot gas flows through the porous body in a turbulent manner, which improves the heat transfer and increases energy efficiency. Linked to this is a more uniform temperature saturation of the gas flowing out of the heating element surface, which enables the formation of a high quality and very reliable weld seam. In addition, the invention enables a joining speed that is higher than the prior art and thus a reduction in the welding time.

The heating element according to the invention can be adapted to different requirements and weld line contours. The heating element according to the invention can be individually adapted to the respective requirements, for example through the design of the heating element surface.

The term "hot gas welding" is used here in relation to the material connection of plastic parts with the aid of a gas heated to a suitable temperature, i.e. a temperature corresponding to or above the melting temperature of the plastic.

“Hot gas” is understood here to mean a gas heated to a suitable temperature. The temperature of the hot gas depends on the plastic to be melted and possibly other parameters such as the desired welding time and the materials that come into contact with the hot gas. The term also includes compounds that are not yet gaseous at room temperature, but are gaseous at or below the melting temperature of the plastic to be melted are. The term “gas” also includes mixtures of gases.

A “porous body through which a hot gas can flow” is understood to mean a body which has cavities (pores) which are connected to one another in such a way that a hot gas can flow through the body in at least one direction. The porous body is preferably made of a thermally stable material, i.e. a material which is essentially stable at temperatures as required for plastic welding, i.e. essentially does not decompose or deform. For example, it can be a metallic or ceramic porous body, e.g. an open-pored metal foam body (metal sponge), which is produced, for example, by sintering metal particles, e.g. in the 3D printing process using selective laser sintering (SLS) or selective laser melting (welding, SLM) of metal particles can be. The term also includes bodies, for example metal or ceramic bodies, with a honeycomb or lattice structure (lattice structure). A “pore body through which a hot gas can flow” is understood here in particular to mean a pore body whose pores are connected to one another in such a way that a hot gas can or flows through the body in a turbulent manner at least in one direction.

A “hot gas” is understood to mean a gas or gas mixture that is heated to a temperature suitable for plastic welding. The temperature depends, for example, on the intended use and the plastic to be welded. For polypropylene, for example, the temperature can be between 230 ° C and 280 ° C, for polystyrene between 270 ° C and 310 ° C.

The expression “joining surface of a plastic part” denotes the surface of a plastic part that is intended to be at least partially melted and joined to a surface of another plastic part.

A “weld line” is understood to be a preferably continuous linear stretch on the joining surface of a plastic part, along which the plastic is to be melted or has melted.

The expression "the heating element surface conforms to the contour of the weld line" means that the heating element surface is shaped to follow the contour of the weld line. As a rule, the welding line corresponds to the contour of the respective joining surface of a plastic part. The welding line and thus also the heating element surface do not necessarily have to lie in one plane. Rather, different courses of the heating element surface in the room are possible. In this way, irregular joining surfaces and / or joining surfaces that protrude and recede in relation to a plane can also be welded.

The expression “in fluid communication with the pores of the pore body” in relation to a hot gas channel means that hot gas exiting the hot gas channel can enter the pores of the pore body directly or indirectly. “Entering indirectly” can mean, for example, that a hot gas first passes from the hot gas duct into a chamber which is in fluid communication with the pores of the pore body, and from there enters the pores. “Indirectly” can also mean that a hot gas first arrives from the hot gas duct into a further porous body through which hot gas can flow and via this porous body into a chamber which in turn is in fluid communication with the pores of the porous body. The expression, according to which “the at least one hot gas channel is in fluid communication with a chamber which is in fluid communication with the pores of the pore body” means that the hot gas channel opens into a chamber with which the pores of the pore body are in communication. A hot gas can flow from the at least one hot gas channel into the chamber and from there into and through the porous body.

The term “meandering” in relation to a hot gas duct means a curved or meandering course of the duct which does not correspond to the shortest course leading to the opening.

“Plastic parts” are parts that are made of or contain plastic. It can be parts of air springs, for example. Suitable plastics are thermoplastics. It can be, for example, half-shells of plastic housings or the like. Of course, it is also possible to weld several plastic parts together.

“Half-shells” are understood here to mean two parts of a hollow body which, when joined together, produce the hollow body. For example, it can be essentially hemispherical parts which, when placed together with the open sides, form an essentially spherical hollow body. However, the term also encompasses other geometries. The parts can have the same dimensions, for example be rotationally symmetrical or mirror-symmetrical. The hollow body formed by the half-shells can be essentially circular, oval or angular in cross section, e.g. triangular, square, rectangular or otherwise polygonal. Irregular shapes of the hollow body are of course also possible.

In a preferred embodiment, the heating element according to the invention comprises a heating element body with at least one hot gas duct, which is in fluid communication with the pores of the porous body. The at least one hot gas channel can be in fluid communication directly or indirectly with the pores of the pore body. The at least one hot gas duct can, for example, end with its opening directly at or in front of the porous body, without an intermediate space being present. The at least one hot gas channel can, for example, also end in a chamber to which the porous body then adjoins. The heating element body is preferably used to heat the hot gas on its way through the at least one hot gas duct to the heating element surface.

In a preferred embodiment of the heating element according to the invention, the at least one hot gas duct, in the case of a plurality of hot gas ducts, preferably each hot gas duct, runs at least in sections in a meandering manner within the heating element body. The meandering course of the hot gas duct or the hot gas ducts within the heating element body enables a compact construction of the heating element. The distance covered by the gas in the heating element body is comparatively long, which for a given flow rate of the gas leads to an increased dwell time in the heating element, as a result of which less energy is required to heat the gas. A ratio selected as large as possible between the length and the diameter of the at least one hot gas duct or, in the case of a plurality of hot gas ducts, the respective hot gas ducts enables the hot gas to be heated up quickly. Due to the compact design and the comparatively low mass of the heating element, it can also be heated more quickly and with less energy consumption. The heating element is preferably heated electrically or inductively.

In a particularly preferred embodiment of the heating element according to the invention, the at least one hot gas channel opens into a chamber which is in fluid communication with the pores of the pore body. In the case of a plurality of hot gas ducts, all of the hot gas ducts preferably open into the chamber. The chamber provides a buffer volume which is used to ensure that the volume and pressure distribution in the outlet area of the hot gas is as uniform as possible, i. H. the outer surface of the pore body, and to achieve an even more uniform temperature distribution. The chamber is arranged in the flow direction of the hot gas between the end of the at least one hot gas channel and the porous body. In this preferred embodiment of the device according to the invention, the gas thus flows through the at least one, preferably at least partially meandering hot gas duct, preferably through a plurality of preferably at least partially meandering hot gas ducts, into the chamber, and from there through the porous body and its exterior Area in the direction of the joining area of a plastic part. In a variant of this embodiment, a further pore body through which hot gas can flow can also be arranged between the at least one hot gas duct and the chamber, so that the hot gas initially flows through the at least one hot gas duct into the further porous body and through the further porous body into the chamber, from where it flows into and through the porous body in the direction of the joining surface of a plastic part.

The heating element preferably comprises at least one, preferably two, three or more rows of hot gas channels, each of which, directly or indirectly, is in fluid communication with the pores of the pore body. The rows preferably follow the contour of the heating element surface and thus the contour of the weld line. The hot gas ducts in different rows can be arranged, for example, parallel and without offset to one another. The hot gas channels can, however, also be arranged offset to one another. The at least one, preferably two, three or more rows of hot gas channels preferably open into a chamber which is in fluid communication with the pores of the pore body.

In a preferred embodiment of the heating element according to the invention, the heating element surface forms the end face of a heating rib which protrudes from the heating element body. In this embodiment, the heating element body, which preferably contains meandering sections of the hot gas ducts, comprises a heating rib which protrudes from the rest of the heating element body and has an end face within which the outer surface of the pore body lies or which is formed by the outer surface of the pore body. In this embodiment, the heating element has, for example, a generally conical cross section, i.e. a cross section which tapers towards the heating element surface. The heating rib with the heating element surface is preferably adapted to the contour of the weld line. In addition, the heating rib is preferably dimensioned so that the end face, and in particular the outer surface of the pore body through which the hot gas flows in the direction of the joining surface, essentially corresponds to the surface of the joining surface to be melted, i.e. the same size as this or only slightly larger or smaller is. The front surface or the outer surface of the pore body can, however, also be dimensioned larger than the joining surface to be melted and, by means of suitable measures, for example by means of hot gas guiding elements, can be essentially limited to an area that corresponds to the joining surface to be melted.

In this embodiment it is further preferred if sections of the hot gas ducts lying within the heating rib run linearly and parallel to one another. In such an embodiment, the chamber is also preferably arranged within the heating rib. In this embodiment, meander-shaped hot gas ducts running at least in sections are therefore preferably located in a part of the heating element body with a larger cross section, while within the heating rib preferably linear sections of the hot gas ducts lead to the chamber and open there. In the flow direction of the hot gas, after the chamber inside the heating rib, the porous body follows, the upper surface of which forms at least part of the heating element surface.

The heating rib can be designed in one piece with the heating element body or at least in sections it can be designed to be detachable from the heating element body. For example, a separate attachment can be provided which encompasses the porous body and is designed in such a way that it forms the chamber when it is placed on the heating element body. For this purpose, the heating element body can, for example, comprise a section of the heating rib, which is also referred to below as a “heating rib stump”, at the end of which the at least one hot gas channel opens, and the attachment can be designed as a sleeve that encompasses the porous body at one end and at the the other end has legs with which the attachment can be placed on the section of the heating rib.

The porous body can be a porous metal or ceramic body. It is preferably a porous metal body, for example a metal foam body, for example a sintered metal body. A metal foam body can be produced, for example, by means of a 3D printing process using, for example, laser radiation. A porous ceramic body can also be produced by means of sintering.

In a further preferred embodiment of the heating element according to the invention, the heating element surface is flanked and / or limited by hot gas guide elements projecting over the heating element surface in the direction of flow of the hot gas, i.e. in the direction of the joining surface. The hot gas guide elements can, for example, serve to channel, direct and limit the hot gas flow flowing out of the porous body. The hot gas guide elements can form a flow slot following the welding line, through which the hot gas flows in the direction of the joining surface. For example, the hot gas guide elements can also be used to compensate for an offset of the joining surface compared to the target position or to limit the dimension, i.e. the expansion, of the hot gas flow so that the flow is optimally adapted to the dimension of the joining surface. For this purpose, the hot gas guide elements can cover, for example, part of the heating element surface, in particular part of the outer surface of the pore body, so that hot gas flows only from an area of the outer surface of the pore body that is kept free and opposite the joining surface. The hot gas guide elements can be metal or ceramic guide plates, guide sleeves and the like. The hot gas guide elements can be formed in one piece with or separately from the heating element. In the case of hot gas guide elements formed in one piece with the heating element, these can for example be formed by the wall of the heating rib or parts thereof, which extend in the direction of flow of the hot gas.

It is particularly preferred if the heating element according to the invention is designed in such a way that a joining surface of a plastic part is heated essentially only or at least predominantly by the heat of the hot gas and not by radiant heat that is radiated from the material of the heating element surface or the heating element body. It is therefore preferred if the ratio of the sum of the areas of the pores in the outer area of the pore body, which forms part of the heating element area or the entire heating element area from which the hot gas flows, to the total area of the heating element area, ie including the areas of the pores in the outer surface of the pore body, is as large as possible. For example, the ratio of the sum of the areas of the pores in the outer area of the pore body to the total area of the heating element area can be at least 0.25: 1, preferably at least 0.3: 1, 0.4: 1, 0.5: 1; 0.6: 1, 0.7: 1; 0.8: 1, 0.9: 1 or 1: 1. In addition, it is preferred if the at least one heating element, with the exception of the heating element surface or the area of the heating element with the heating element surface, is thermally insulated so that little or no radiant heat is given off.

The heating element according to the invention, which can be produced, for example, by a 3D printing process, including the pore body, can be produced from a single piece, for example a suitable metal. However, the heating element can also consist of individual heating element modules which, when put together, form the heating element. The heating element modules each have heating element module heating surfaces which, when the heating element modules are placed next to one another, join together to form the heating element in such a way that the heating element module heating surfaces form the heating element surface. The heating element modules are designed in such a way that the desired heating element area results after they are placed together as intended, ie a heating element area that is the desired one Weld line contour follows. The heating element modules can be designed identically or differently depending on the shape of the desired weld line. In the case of a circular welding line, the heating element modules can be designed, for example, in such a way that the individual heating element module heating surfaces cover a ring segment. For example, five heating element modules that cover a ring segment of 72 ° each can be joined together to form a heating element that can produce a complete circular weld seam. However, the heating element can also be composed of any other number of heating element modules, which can also be different from one another.

The circular arrangement is only given here as an example. Different sections of an irregular welding line can also be mapped, for example, by means of differently designed heating element modules. Different geometries, for example polygonal as well as irregular contours, can be realized by appropriate design of the heating element modules. The heating element module heating surfaces do not have to lie in the two dimensions of a plane, but can also have a three-dimensional profile with a corresponding shape. What was said here for a multi-piece heating element composed of several heating element modules applies equally to the case of a one-piece heating element. Even in the case of an irregular welding line, it is not necessary to assemble the heating element from several heating element modules. Rather, the heating element can also be in one piece in this case.

Individual heating element modules, in embodiments with a chamber between the at least one hot runner and the porous body, can each have their own chamber, which is separate and closed off from the chambers of other heating element modules, or can be designed in such a way that, in the installation situation, a common chamber from the individual chambers of the heating element modules composite continuous chamber is formed.

Individual heating element modules can also be exposed to different temperatures. For this purpose, the heating element modules can have separate gas connections and separate heating devices, for example. If necessary, the heating element modules can also be thermally insulated from one another. In one embodiment, each heating element module therefore has its own gas connection, via which gas can, for example, be directed into a hot gas distributor duct within the heating element body and from there distributed to individual hot gas ducts that lead to the heating element module heating surface.

The heating element surface preferably forms a closed heating frame. This is particularly preferred for the production of plastic hollow bodies from half-shells or other parts in which the joining surfaces of the half-shells are designed like a frame. The joining surfaces of the half-shells and the heating frame adapted to them can have different regular or irregular geometries, for example circular, elliptical, square, rectangular or polygonal.

In a further aspect, the invention also relates to a device comprising at least one heating element according to the invention.

In a particularly preferred embodiment, the device according to the invention comprises at least two vertically opposite heating elements, the heating element surfaces of which are oriented in opposite directions. In “opposite direction” means that the heating element surfaces are oriented in directions pointing away from one another. Such an embodiment is particularly suitable for the simultaneous heating of two plastic parts with complementary joining surfaces. The contours of the heating element surfaces of the heating elements, which are oriented in the opposite direction, for example upwards or downwards, are designed to be complementary to the respective joining surfaces which they are to heat.

The present invention also relates to a method for hot gas welding of plastic parts. In the method according to the invention, the joining surface of a plastic part is melted using hot gas from the pores of the heating element surface of a heating element according to the invention along the contour of the heating element surface with the aid of a heating element according to the invention described in more detail above or a device comprising a heating element according to the invention.

In the method according to the invention, the joining surfaces of at least two plastic parts to be fused are preferably melted and pressed together until the molten joining surfaces solidify. The plastic parts are held with the aid of the device according to the invention and the heating elements are arranged between the plastic parts. The mutually complementary joining surfaces of the plastic parts are preferably brought into close proximity to the heating element surface of an associated heating element, apart from an air gap, and melted along the intended welding line by means of hot gas flowing out of the pores of the pore body. After the joining surfaces are sufficiently melted, the heating elements are placed between the plastic parts removed and the plastic parts are pressed in a suitable manner with their joining surfaces until the melted areas of the joining surfaces solidify again and the plastic parts are positively connected to one another. The plastic parts are preferably half-shells of a plastic hollow body, which are welded to one another at their joining surfaces.

In the method, the joining surfaces of the plastic parts are preferably heated only or essentially by means of the hot gas and not by radiant heat from the heating elements.

In the context of the present invention, it is preferred if air, carbon dioxide or nitrous oxide (N ₂ O), preferably air, is used as the hot gas. However, a protective gas such as nitrogen (N ₂ ), argon, helium or a mixture thereof can also be used.

• 1. Räumliche Ansicht einer beispielhaften Ausführungsform einer erfindungsgemäßen Vorrichtung zum Heißgasschweißen von Kunststoffteilen.
• 2. Frontalansicht zu der in 1 dargestellten Ausführungsform einer erfindungsgemäßen Vorrichtung.
• 3. Räumliche Detailansicht der Heizelementeanordnung der in 1 dargestellten Ausführungsform einer erfindungsgemäßen Vorrichtung.
• 4. Schnitt durch die in 3 dargestellte Heizelementeanordnung.
• 5. Räumliche Ansicht einer Ausführungsform eines erfindungsgemäßen Heizelements.
• 6. Schnittansicht des Heizelements aus 5.
• 7. Schnittansicht einer weiteren Ausführungsform eines erfindungsgemäßen Heizelements.
• 8. Schnittansicht eines Teils verschiedener Ausführungsformen eines erfindungsgemäßen Heizelements.
• 9 und 10. Schnittansichten von Teilen weiterer Ausführungsformen eines erfindungsgemäßen Heizelements.

The invention is explained in more detail below by way of example for purposes of illustration with the aid of the attached figures.

• 1 . Three-dimensional view of an exemplary embodiment of a device according to the invention for hot gas welding of plastic parts.
• 2 . Front view of the in 1 illustrated embodiment of a device according to the invention.
• 3 . Spatial detailed view of the heating element arrangement of the in 1 illustrated embodiment of a device according to the invention.
• 4th . Section through the in 3 illustrated heating element arrangement.
• 5 . Three-dimensional view of an embodiment of a heating element according to the invention.
• 6th . Sectional view of the heating element 5 .
• 7th . Sectional view of a further embodiment of a heating element according to the invention.
• 8th . Sectional view of part of various embodiments of a heating element according to the invention.
• 9 and 10 . Sectional views of parts of further embodiments of a heating element according to the invention.

1 shows, purely by way of example, a simplified spatial representation of an embodiment of a device according to the invention 1 for hot gas welding of plastic parts 20th . The device comprises a heating element arrangement 25th , the oppositely arranged heating elements 2 includes, where in 1 just one of the heating elements 2 , here the upper heating element 2 , is visible. The heating elements 2 are with brackets 33 on a profile frame 35 attached, in turn on a sled 36 is attached, which is on guide rails 37 , as indicated by the double arrow in the figure, is arranged to be linearly movable in the horizontal direction. The sled 36 can here by means of an electric drive 40 on the rails 37 be moved back and forth. On the profile frame 35 are handles in this embodiment 34 arranged. The heating elements 2 are through a heat-resistant coating 32 , for example fireclay panels, surrounded by insulating material. A pressing device 38 with a scaffolding 39 has not shown here superimposed holding devices for plastic parts to be welded 20th on. To take into account different plastic parts and / or to compensate for any inclination of a plastic part, the holding devices for the plastic parts 20th also be hinged.

Two plastic parts 20th can in the pressing device 38 above and below the heating elements 2 fixed with the help of the holding devices and in the vertical direction with their joining surfaces 21 be brought together and welded together. The heating element assembly 25th is first used for this purpose with the help of the slide 36 between the plastic parts fixed on top of each other 20th arranged. The plastic parts 20th are then by means of the pressing device 38 with their joining surfaces 21 except for an air gap close to the respective heated heating element surfaces 3 the heating elements 2 guided. After the joint surfaces 21 through that out of the pores 4th of the pore body 6th the heating elements 2 exiting hot gas are melted, the heating element assembly 25th by means of the slide 36 from the area of the pressing device 38 between the plastic parts 20th led out, so that this by means of the pressing device 38 with their mutually facing joining surfaces 21 can be moved together and pressed together. After the joint surfaces have cooled down sufficiently 21 are the plastic parts 20th firmly connected to one another.

In 1 are, for the sake of clarity, the gas lines for supplying gas, e.g. air, to the heating elements 2 not shown. Only the connections are visible 31 for the gas supply. The gas is supplied through the connections 31 into the heating elements 2 directed where it is heated. The heating devices for heating up the heating elements 2 are not shown. In 1 is only part of a plastic part for the sake of clarity 20th visible, here part of an air spring.

The heating element surfaces 3 are annular here, around the annular welding lines on the annular joining surfaces with the embodiment shown 21 the plastic parts to be connected 20th to create. The heating element surfaces 3 but can of course by designing the heating elements accordingly 2 to the contour of the weld line to be generated or the contour of the joint surfaces to be welded 21 the plastic parts 20th be adjusted. It is of course also possible to use interchangeable heating elements 2 or entire replaceable heating element assemblies 25th to keep in mind the respective shape of the joint surfaces 21 the plastic parts 20th are adjusted accordingly.

2 FIG. 11 shows a front view of that in FIG 1 illustrated exemplary embodiment of a device according to the invention 1 . Like here better than in 1 can be seen, there is the heating element arrangement 25th of two heating elements opposite one another in the vertical direction 2 with heating element surfaces facing away from each other 3 . The heating element surface 3 of the upper heating element 2 faces up, the heating element surface 3 of the lower heating element 2 downward. The heating elements 2 are by means of a sheath 32 isolated from fireclay panels. The two heating elements 2 are adjustable separately. Here is a plastic part 20th shown, the one with its joining surface 21 in the immediate vicinity of the heating element surface 3 of the lower heating element 2 is brought. Holding devices that hold the plastic part 20th fix are not shown. For the sake of clarity, an upper plastic part is also shown 20th has been omitted, its joining surface 21 by means of the upper heating element 2 melted. Also in 2 are only the gas connections 31 shown, but not the supplying gas lines. Heating devices for heating the heating elements 2 are also not shown here.

In 3 is the heating element arrangement in greater detail 25th the device 1 from the 1 and 2 shown in a spatial view. The two opposite each of a heat-resistant coating 32 surrounding heating elements 2 are each about brackets 33 with the profile frame 35 connected. With the help of hand movements 34 on opposite sides of the profile frame 35 (see 2 ) the profile frame 35 be moved manually if necessary. Here, too, are the gas connections 31 good to see. The supplying gas lines are again not shown here. As can be seen in this figure, the heating elements exist 2 in this embodiment, each from individual heating element modules 10 . In the case of the circular arrangement here, there are five such heating element modules 10 , which each form a ring segment of 72 °, to a heating element 2 put together. The five heating element module heating surfaces 11 the heating element modules 10 together result in the circular ring-shaped heating element surfaces 3 , whereby a ring-shaped closed heating frame is formed.

4th shows a sectional view of the in 3 shown heating element arrangement 25th . As can be seen here, the heating element modules comprise 10 one heating element body each 7th , the one protruding heating fin 9 includes, the end face of which is the heating element module surface 11 forms or includes (see also 5 to 10 ). As in the right part of the 4th can be seen are in the heating element body 7th Hot gas channels 8th provided by a hot gas manifold 14th starting at least in sections in a meandering shape through the heating element body 7th and in a straight line through a section of the heating fin 9 run away. The hot gas channels 8th open into a chamber in the embodiment shown here 13th with a porous body through which hot gas can flow 6th is in fluid communication.

How out 5 It can be better seen that a simplified three-dimensional view of a single heating element module 10 represents, the openings end 17th the hot gas ducts 8th , as indicated schematically here, in a chamber 13th . The openings 17th and the area 12th of the heating element module 10 in which the openings 17th are arranged and parallel to the heating element module surface 11 runs, are here within the heating element module 10 indicated with broken lines. As can be seen here, there are three rows of hot gas ducts 16 present, an outer, middle and inner row 16 that are parallel to each other below and along the heating element module surface 11 are arranged and with corresponding openings 17th into the chamber 13th flow out. The associated hot gas channels 8th in the heating element module 10 are not shown. Every opening 17th belongs to a separate hot gas duct 8th . Three openings each 17th of the ranks 16 lie here on one to the surface 12th transverse straight line. The porous body 6th , for example a porous metal or ceramic body, is inside the heating fin 9 above the chamber 13th arranged. Hot gas can come out of the hot gas ducts 8th into the chamber 13th and from there through the porous body 6th and from pores 4th in the outer surface 5 of the pore body 6th stream.

6th shows a section through a heating element module 10 of a heating element according to the invention 2 as it is in 5 is shown. The hot gas channels 8th arise from a common hot gas distribution channel 14th in the base of the heating element module 10 , into the gas via the gas connections 31 can be introduced, and open with their openings 17th in a chamber 13th . The hot gas channels 8th run in the area of the heating rib 9 linear, while they are in the area of the rest of the heating element body 7th meander at least in sections. Every single one of the openings 17th is with one separate hot gas duct 8th connected. Above the chamber 13th is a porous body through which hot gas can flow 6th with an outer face 5 and one opposite to the chamber 13th directed, inner surface 22nd arranged. The outer surface 5 of the pore body 6th here essentially corresponds to the heating element module area 11 . From pores 4th in the outer surface 5 can hot gas, which through the hot gas ducts 8th into the chamber 13th from the heating element module surface 11 in the direction of the joint surface 21 flow of the plastic part to be welded.

7th shows a sectional view of a further embodiment of a heating element according to the invention 2 or heating element module 10 . In this embodiment there is part of the heating fin 9 as a sleeve-like attachment that is open on both sides 18th formed, which with one end on a heating rib stump 19th on the heating element body 7th is put on. The essay 18th can also be used with the heating rib stump if necessary 19th be firmly connected, for example by welding. In the other end of the sleeve-like attachment 18th is the porous body 6th arranged. The chamber 13th is here between the heating rib stump 19th and the porous body 6th through the essay 18th educated. The walls of the essay 18th extend over the porous body 6th out in the direction of the heating element body 7th . In this embodiment there are also hot gas guide elements 15th shown. The hot gas guide elements 15th jump over the heating element surface 3 in front of and flank or limit this. In 7th is schematically part of a plastic part 20th shown, which deviates with its actual position (continuous lines) from a target position (dashed lines). To the hot gas on the area of the joint surface 21 The hot gas guide elements are to be concentrated according to its actual position 15th arranged so that they are part of the outer surface 5 of the pore body 6th cover so that hot gas just comes out of pores 4th the outer surface 5 in that of the hot gas guide elements 15th left free area in the direction of the joining surface 21 flows.

8th shows by way of example that the porous body 6th can have different geometric shapes. Here is only part of the heating fin 9 of a heating element according to the invention 2 reproduced. In 8A is for example the outer surface 5 convex in cross section, in 8B concave. However, various other forms are also conceivable, which can be selected depending on the application. In addition, there are flanking hot gas guide elements 15th shown here a flow slot 23 form. In 8A are the hot gas guide elements 15th designed as separate elements on the heating rib 9 can be put on. In 8B the hot gas guide elements are formed in one piece with the heating rib. Either 8A as well as 8B show embodiments of the heating element according to the invention 2 with a chamber below 13th .

The 9 and 10 show sectional views of further embodiments of the heating element according to the invention 2 . For the sake of clarity, only part of the heating element is shown here 2 with the heating rib 9 shown. 9 shows an embodiment in which the porous body 6th so in the integral with the heating element body 7th connected heating rib 9 is arranged that it is with its the outer surface 5 opposite inner surface 22nd directly on the surface 12th with the openings 17th the hot gas ducts 8th lies. There is no chamber here 13th intended.

At the in 10 The embodiment shown is the heating rib 9 with the porous body arranged therein 6th not integral with the heater body 7th formed, but as a separate element that, for example, simply on the heating rib stump 19th can be put on. In this embodiment it is inside the heating fin 9 between the at the end of the heating rib stump 19th in the area 12th lying openings 17th the hot gas ducts 8th and that of the outer surface 5 opposite to the heating element body 7th oriented inner surface 22nd of the pore body 6th another porous body through which hot gas can flow 6 ' with an outer face 5 ' and an opposite inner surface 22 ' arranged. The further porous body 6 ' is also referred to below as the proximal porous body 6 ' , the porous body 6th as a distal porous body 6th designated. Between the inner surface 22nd of the distal pore body and the outer surface 5 ' of the proximal pore body 6 ' is a chamber 13th arranged. The pores of the proximal pore body 6 ' in its outer surface 5 ' open to the chamber 13th . In this embodiment, the hot gas comes out of the hot gas ducts 8th first in the proximal porous body 6 ' , flows through it and enters the chamber 13th from which it enters the distal porous body 6th got. It flows through this and leaves the pores 4th in the area 5 of the distal pore body 6th in the direction of a joining surface 21 a plastic part 20th . In the 10 The embodiment shown combines features of the in 9 shown heating element 2 with features of the 6th and 7th shown heating elements 2 . Here is one like in 9 illustrated embodiment of a heating element 2 where the porous body 6th directly in the flow direction of the hot gas, ie without an intermediate chamber 13th , to the hot gas ducts 8th connects to a separate sleeve-like attachment 18th supplemented, which has a porous body at the end in the flow direction of the hot gas 6th has and extends over the inner surface 22nd of the pore body 6th towards the heater body 7th extends beyond so that a chamber 13th is formed. The heating element surface 3 in the embodiment with the essay 18th is essentially of the area 5 of the (distal) pore body 5 educated. If the essay 18th is removed, the embodiment corresponds essentially to that in FIG 9 illustrated embodiment with a comparatively shorter heating rib 9 , where the heating element area 3 then essentially from the area 5 ' of the proximal pore body is formed. This embodiment, too, can optionally contain hot gas guide elements 15th have that extend over the heating element surface 3 extend out in the flow direction of the hot gas. This embodiment can be implemented in a comparatively simple manner by a heating element 2 with chamber 13th into a heating element 2 without chamber 13th be transformed, or vice versa.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 10019163 A1 [0003]
• EP 141578981 B1 [0004]

Claims (19)

Heating element (2) for hot gas welding of plastic parts, with a heating element surface (3) for heating a joining surface (21) of a plastic part (20) along a welding line with a predetermined contour, the contour of the heating element surface (3) being adapted to the contour of the welding line, characterized in that the heating element surface (3) comprises an outer surface (5) with pores (4) of a pore body (6) through which a hot gas can flow. Heating element (2) Claim 1 comprising a heating element body (7) with at least one hot gas channel (8) which is in fluid communication with the pores (4) of the pore body (6). Heating element (2) Claim 2 , characterized in that the at least one hot gas duct (8) runs at least in sections in a meandering manner within the heating element body (7). Heating element (2) Claim 2 or 3 , characterized in that the at least one hot gas channel (8) is in fluid communication with a chamber (13) which is in fluid communication with the pores (4) of the pore body (6). Heating element (2) after one of the Claims 2 to 4th , characterized in that at least one, preferably two, three or more rows (16) of hot gas ducts (8) are present. Heating element (2) after one of the Claims 2 to 5 , characterized in that the heating element surface (3) forms the end face of a heating rib (9) which protrudes from the heating element body (7). Heating element (2) Claim 6 , characterized in that the heating rib (9) is formed in one piece with the heating element body (7). Heating element (2) according to one of the preceding claims, characterized in that the heating element surface (3) is flanked and / or limited by hot gas guide elements (15) protruding over the heating element surface (3) in the direction of the joining surface (21). Heating element (2) according to one of the preceding claims, characterized in that the hot gas guide elements (15) form a flow slot (23) flanking and / or delimiting the heating element surface (3). Heating element (2) according to one of the preceding claims, characterized in that the porous body (6) is a porous metal or ceramic body, preferably a porous metal body. Heating element (2) according to one of the preceding claims, characterized in that the ratio of the sum of the areas of the pores (4) in the outer area (5) of the pore body (6) to the total area of the heating element area (3) is at least 0.25: 1, preferably at least 0.3: 1, 0.4: 1, 0.5: 1; 0.6: 1, 0.7: 1; Is 0.8: 1, 0.9: 1 or 1: 1. Heating element (2) according to one of the preceding claims, characterized in that the heating element (2) consists of individual heating element modules (10) with heating element module heating surfaces (11) which are joined together in such a way that the heating element module heating surfaces (11) meet the heating element surface ( 2) form. Heating element (2) according to one of the preceding claims, characterized in that the heating element surface (2) forms a closed heating frame. Device (1) for hot gas welding of plastic parts, comprising at least one heating element (2) according to one of the preceding claims. Device (1) according to Claim 14 , characterized in that the device (1) has two heating elements (2) opposite one another in the vertical direction, the heating element surfaces (3) of which are oriented in opposite directions. Method for hot gas welding of plastic parts (20), characterized in that the joining surface (21) of a plastic part (20) by means of hot gas from the pores (4) of the heating element surface (3) of a heating element (2) according to one of the Claims 1 to 13th is melted along the contour of the heating element surface (3). Procedure according to Claim 16 , characterized in that the joining surfaces (21) of two plastic parts (20) are melted and then pressed together until the molten joining surfaces (21) solidify. Procedure according to Claim 17 , characterized in that half-shells of a plastic hollow body are welded to one another at their joining surfaces (21). Method according to one of the Claims 16 to 18th , characterized in that the hot gas is air, carbon dioxide, nitrogen gas, nitrous oxide, argon, helium or a mixture thereof, preferably air.

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