DE202021101884U1 - Device for welding plastic parts - Google Patents

Abstract

Device for welding plastic parts (10, 12; 10a, 12a; 10b, 12b) along joining surfaces (14, 16) to be welded together, with a heating block (22), from which hot gas to the joining surface (14, 16) at least one the plastic parts (10, 12; 10a, 12a; 10b, 12b) can be supplied, with a gas guide block (26) extending along the joining surface (14, 16) which has a channel-shaped recess (38) in the form of a channel-shaped recess (38) extending along the joining surface ( 14, 16), wherein in the gas guide block (26) a plurality of supply channels (39; 42, 44) are provided for the supply of hot gas, which open at an angle into the channel-shaped recess (38), the gas guide block (26) at least is formed in segments in one piece with the channel-shaped recess (38).

Description

The invention relates to a device for welding plastic parts, with which two plastic parts to be welded together are welded together by means of two mutually facing joining surfaces, at least one, preferably both, of the joining surfaces being heated and the two plastic parts then being welded together by pressing the joining surfaces together, whereby the joining surfaces are flown against and heated by means of a hot gas stream.

From the DE 100 19 300 A1 a device for welding plastic parts is known. A tool consisting of a heating plate with welding blocks attached to the top and bottom is used, the tool being inserted between the plastic parts to be joined, the plastic parts being heated with the help of the tool without contact by radiant heat, while at the same time a stream of hot inert gas is generated the workpiece area to be welded is guided. The plastic parts are heated to a temperature above the softening temperature so that they become doughy and can be pressed together and thus welded after the tool has been removed.

In this way, plastic parts can basically be welded to one another without contact. Since the welding is non-contact, the radiators will not stick. The use of radiant heat and an additional hot inert gas flow to heat the plastic parts should result in accelerated heating and good heat distribution.

In practice, however, it has been shown that welding plastic parts along the joining surfaces requires a considerable heating time for each of the plastic parts.

Since such plastic parts are often used in large series, for example in automobile construction, particularly short cycle times are of considerable importance.

Furthermore, it is known through use in the prior art to heat the joining surfaces of the plastic parts to be welded together by means of a hot gas stream that flows from a distributor via a large number of tubes arranged essentially parallel to one another, the outlet openings of which end at an approximately uniform distance in front of the joining surfaces , is aimed at the joining surfaces.

Although this enables relatively uniform heating of the joining surfaces, there are still considerable heating times for the plastic parts to be welded.

From the WO 2020/164978 A1 it is known to arrange mutually parallel angles on a surface facing the joining surface, between which hot gas is introduced via channels. This should result in a shortened heating time for the plastic parts to be welded.

However, this arrangement is also in need of improvement. In particular, the assembly of such angles is complex and only straight, at most uniformly curved joining surfaces can be realized.

Against this background, the invention is based on the object of specifying a device for welding plastic parts with which contactless welding is possible, by means of which two plastic parts to be welded together are welded together by means of two mutually facing joining surfaces and the joining surfaces are heated to the desired target temperature takes place in the shortest possible time.

The object of the invention is achieved by a device for welding plastic parts along joining surfaces to be welded together with a heating block from which hot gas can be supplied to the joining surface at least one of the plastic parts, with a gas guide block extending along the joining surface, which has a channel-shaped recess Has the shape of a channel extending along the joining surface, with a plurality of supply channels for supplying hot gas being provided in the gas guide block, which open at an angle into the channel-shaped recess, the gas guide block being at least segmentally formed in one piece with the channel-shaped recess.

The object of the invention is completely achieved in this way.

According to the invention, the joining surface is heated by means of a hot gas stream which is directed onto the at least one joining surface through a recess in a gas guide block extending along the joining surface. As a result, the hot gas flow is concentrated on the joining surface, which leads to a considerable reduction in the heating time.

Due to the concentration of the hot gas flow on the joint surface that is actually to be heated, unintentional heating of surrounding parts is significantly reduced, so that the Risk of damage is reduced. Since the gas guide block is at least segment-wise, together with the channel-shaped recess, of one piece and can be machined in a suitable manner by milling and drilling, the feed channels through which the hot gas is passed into the recess can be precisely arranged.

Overall, this results in a significantly simplified and more reliable construction and a significantly reduced heating time.

In a preferred development of the invention, the recess has a shape curved concavely towards the outside at its bottom.

As a result, the supply of the hot gas is further concentrated in the direction of the joining surface to be heated.

In a preferred development of the invention, the recess has an essentially U-shaped cross section.

This results in a particularly good adaptation to the part to be heated and thus a particularly rapid heating.

According to a further embodiment of the invention, the recess is three-dimensionally curved.

In this way, heating of three-dimensionally curved joining surfaces can be achieved.

For this purpose, first bore sections can be provided in the gas guide block, which essentially extend in an extension of the axial direction of the opening tubes and which are connected to the recess of the gas guide block via second bore sections extending at an angle thereto.

In this way, the supply of hot gas into a three-dimensionally curved recess of the gas guide block is made possible in a simple manner.

In a further embodiment of the invention, the guide block consists of aluminum or an aluminum alloy and the heating block consists of an iron alloy, preferably steel.

Since the temperature in the recess of the gas guide block is about half as high (e.g. in the range of about 200 ° C) as in the area of the heating block from which the hot gas is supplied (e.g. about 400 ° C), an adjustment can be made in this way the thermal expansion of the different materials (aluminum or steel) can be achieved, as the expansion coefficient of aluminum is about twice as high as that of steel. In addition, aluminum is a particularly good conductor of heat and thus supports uniform heating of the joining surface to be heated.

In a further embodiment of the invention, the heating block is connected to the supply channels in the gas guide block via a plurality of tubes, the tubes preferably extending essentially parallel to one another.

This enables a simplified structure.

If the tubes used for the gas supply are not precisely aligned with the associated bores in the gas routing block, this can be tolerated to a certain extent.

It also avoids having to adjust the direct supply of hot gas via tubes to the joining surfaces by hand in the prior art by bending the tubes in order to compensate for errors, as was previously necessary in the prior art. In the prior art, manual bending of the tubes led to imprecise and, in some cases, wave-like bent tubes in the area of their mouths.

According to a further embodiment of the invention, the tubes are attached to the heating block and preferably engage with play in the supply channels of the gas guide block.

This ensures, on the one hand, that the hot gas is reliably guided into the gas guide block into the channel-shaped recess. On the other hand, the addition of a play (for example a diameter that is approximately 0.2 mm larger) ensures sufficient tolerance to enable simple assembly without manual bending of the tubes.

According to a further embodiment of the invention, the recess has a shape that is concavely curved in relation to the joining surface at its bottom.

According to a further embodiment of the invention, the recess has an essentially U-shaped cross section.

These measures result in a particularly good adaptation for a concentration of the hot gas for rapid heating of the joining surface.

In an additional development of this design, individual segments extend over a Length of up to about 150 mm, preferably of up to about 100 mm in the direction of the at least one joining surface.

In this way, thermal stresses can be compensated for over slight gaps between adjacent segments, provided that they are compensated for as a result of still remaining differences between the thermal expansion coefficients of the materials and not completely precise adjustment in the different expansion coefficients.

According to a further embodiment of the invention, the recess is three-dimensionally curved, with first bore sections preferably being provided in the gas guide block, which essentially extend in an extension of the axial direction of the small opening tubes and which are connected to the recess of the gas guide block via second bore sections extending at an angle thereto .

In this way, three-dimensionally curved joining surfaces can also be heated in a simple manner via three-dimensionally correspondingly adapted recesses in the gas guide block.

The device according to the invention can be used for a method for welding plastic parts, in which two plastic parts to be welded together are welded to one another by means of two mutually facing joining surfaces, which are preferably designed to be complementary to one another, with at least one of the two joining surfaces being heated and the two plastic parts are then welded to one another by pressing the joining surfaces together, the at least one joining surface being heated by means of a hot gas flow which is directed onto the at least one joining surface through a channel-shaped recess of a gas guide block extending along the joining surface, the hot gas flow being angled through a plurality of feed channels opening into the recess in the gas guide block, the feed channels preferably each being supplied with hot gas via tubes which open into the feed channels, and wherein the gas guide block is also supplied with hot gas ndest is formed in one piece with the channel-shaped recess in segments, for example made from a block by milling and / or drilling.

It goes without saying that the features of the invention mentioned above and those yet to be explained below can be used not only in the respectively specified combination, but also in other combinations or on their own, without departing from the scope of the invention.

• 1 einen Teil-Querschnitt durch ein Kunststoffteil, das aus zwei Einzelteilen besteht, die jeweils in Umfangsrichtung verlaufende Fügeflächen aufweisen, wobei die beiden Einzelteile mit ihren zueinander komplementär ausgebildeten Fügeflächen, entlang derer eine Verschweißung erfolgen soll, aufeinander gelegt sind;
• 2 einen Teil-Querschnitt durch ein Kunststoffteil gemäß 1, bei dem die Fügeflächen sägezahnartig zwecks einer Oberflächenvergrößerung ausgebildet sind;
• 3 einen Teil-Querschnitt durch ein Kunststoffteil gemäß 1, bei dem die Fügeflächen zwecks einer Oberflächenvergrößerung gewellt ausgebildet sind;
• 4 eine längs geschnittene perspektivische Ansicht durch eine Vorrichtung zur Erhitzung eines Kunststoffteils, das hier mit Abstand zu der Vorrichtung angeordnet ist;
• 5 einen Teil-Querschnitt durch den Gasführungsblock mit zugeordnetem Heizblock und einem zugeordneten, zu erhitzenden Kunststoffteil und
• 6 einen Teil-Querschnitt durch eine abgewandelte Ausführung der erfindungsgemäßen Vorrichtung, wobei der Gasführungsblock dreidimensional gekrümmt ist, um ein Kunststoffteil mit einer dreidimensional gekrümmten Fügungsfläche erhitzen zu können.

Further features and advantages of the invention emerge from the following description of preferred exemplary embodiments with reference to the drawing. Show it:

• 1 a partial cross-section through a plastic part, which consists of two individual parts, each having joining surfaces running in the circumferential direction, the two individual parts with their mutually complementary joining surfaces, along which a welding is to take place, are placed on top of one another;
• 2 a partial cross-section through a plastic part according to 1 , in which the joining surfaces are designed like a sawtooth for the purpose of increasing the surface area;
• 3rd a partial cross-section through a plastic part according to 1 , in which the joining surfaces are designed to be corrugated in order to increase the surface area;
• 4th a longitudinally sectioned perspective view through a device for heating a plastic part, which is arranged here at a distance from the device;
• 5 a partial cross-section through the gas guide block with an associated heating block and an associated plastic part to be heated and
• 6th a partial cross-section through a modified embodiment of the device according to the invention, wherein the gas guide block is curved three-dimensionally in order to be able to heat a plastic part with a three-dimensionally curved joining surface.

1 shows a partial cross-section through a plastic part that consists of two individual parts 10 , 12th consists, each with a circumferential joining surface 14th , 16 have, on which welding can take place. The two joining surfaces 14th , 16 are designed to be complementary to one another. For welding, both joining surfaces are heated on a heating device until they become doughy and can then be welded to one another by pressing them together.

The 2 and 3rd show alternative designs of the joining surfaces with a sawtooth-shaped structure for the plastic parts 10a , 12a according to 2 and with wavy joining surfaces 14th , 16 with the plastic parts 10b , 12b according to 3rd .

In comparison to a flat joining surface according to FIG 2 the outer surface in this area is increased by a factor of approximately 2. In some cases, such designs of joining surfaces are used in order to shorten the heating time.

In 4th a device according to the invention for heating the joining surface of a plastic part by means of hot gas is shown and as a whole with the number 20th designated.

An associated plastic part 10 , its joining surface 14th with this device 20th can be heated is shown at a distance from it. This is an oval plastic part, with only the first plastic part here 10 is shown with the complementary second plastic part 12th to be welded together.

It goes without saying that the joining surfaces of the plastic parts to be welded together 10 , 12th or. 10a , 12a or. 10b , 12b can have any shape, in particular can be three-dimensionally curved.

The elevations and depressions of the joining surfaces then preferably extend along the longitudinal direction of the joining surfaces, so that mutually complementary structures result, facing elevations or depressions, which interlock when the heated plastic parts are later joined.

According to the invention, the joining surface on each of the plastic parts is heated by means of a hot gas stream which is directed specifically at the joining surface from the associated device. According to the invention, a gas guide block is used for this purpose in which a recess is provided which extends along the joining surface and through which the hot gas stream is directed in a concentrated manner onto the joining surface, as will be explained below with reference to FIG 5 is explained in more detail.

The device 20th has a heating tool 34 on that by means of electrical heating elements 30th is heatable. On the heating tool 34 is a record 36 arranged in the cavities 28 are provided. Through the cavities 28 lines run 32 , which are provided with radial outlet openings, from which compressed air is fed into the cavities 28 can emerge. In the cavities 28 there is also a quartz sand filling, through which the heat transfer surface for heating the compressed air is further enlarged.

The plastic part to be heated 10 is on the device by means of a handling device 20th and can then be heated to the target temperature in a short time using hot air.

From the cavities 28 heated compressed air reaches a circumferential annular distribution channel 29 in an attached heating block 22nd is trained. From the distribution channel 29 the hot gas arrives directly in the tube 24 and flows from there into a gas guide block 26th with a U-shaped recess 38 as follows using 5 is explained in more detail.

The gas guide block 26th is according to 5 Manufactured in one piece from a block and preferably consists of an aluminum alloy. In the gas guide block 26th is a channel-shaped recess 38 of preferably U-shaped cross-section, which extends along the joining surface to be heated 14th extends. The gas guide block 26th becomes together with the channel-shaped recess 38 produced together from a block by milling and / or drilling. In the case of larger gas guide brackets, this can be done in segments.

The plastic part to be heated can preferably 10 with its joining surface 14th into the recess 38 protrude during the heating process.

The gas guide block 26th is about spacers 41 with the heating block 22nd screwed (in 4th not shown). The associated tubes 24 that are in the heating block 22nd are held and from the manifold 29 are supplied with hot gas, end directly at the gas guide block 26th . In the gas guide block 26th are assigned holes 39 provided, through which the hot gas from the tube 24 into the recess 38 flows. The bores end at an angle, preferably essentially at right angles, in the recess 38 .

The contour of the gas guide block 26th and the recess provided therein 38 is the course of the joining surface to be heated 14th of the plastic part 10 adapted so that the hot air supplied directly to the joining surface to be heated 14th is concentrated.

By the shape of the recess 38 and the relatively small gap between the recess 38 and the joining surface 14th the heating time can be significantly reduced compared to conventional heating by means of hot air exiting from tubes, for example from 25 seconds when using tubes to less than 15 seconds when using the gas guide block according to the invention.

The heating block 22nd is typically made of steel, while the gas guide block 26th typically consists of an aluminum alloy. The temperature of the distribution duct 29 is significantly higher than the temperature in the area of the recess 38 of the gas guide block 26th . While the temperature in the manifold 29 is for example about 400 ° C, the temperature of the gas guide block is 26th in the area of the recess 38 for example about 200 ° C. To compensate for these temperature differences, the different materials - Aluminum for the gas guide block 26th and steel for the heating block 22nd - used. Since the coefficient of expansion of aluminum is about twice as high as that of steel, there is approximately the same thermal expansion of the heating block on the one hand and the gas routing block at twice as high a temperature in the area of the heating block 26th on the other hand. Displacements of the tubes 24 that are in the heating block 22nd are fixed and in the assigned holes 39 in the gas guide block 26th intervene with a play of 0.2 mm, for example, are minimal in this way and can be tolerated.

If larger plastic parts are to be heated, the gas guide block is used 26th composed of several segments. Individual segments are preferably up to about 100 mm in size and are then joined to the next segment via a small gap. The gaps enable further compensation for different thermal expansions.

If three-dimensionally curved plastic parts with three-dimensionally curved joining surfaces are to be heated, this is also possible using the device according to the invention. The gas guide block 26th is here accordingly with a three-dimensionally curved recess 38 provided, which is adapted to the three-dimensionally curved joining surface of the plastic part to be heated.

As in 6th shown, the tubes provided for supplying the hot gas run 24 at an even distance from the hot gas block. The holes in question from which the over the tubes 24 supplied hot air into the recess 38 arrives, are advantageously composed of two bore sections. A first bore section runs in each case 42 in the axial direction of an associated tube 24 , while a second bore section arranged at an angle thereto 44 into the recess 38 opens out at the desired point. This is preferably done approximately at right angles.

In this way, three-dimensionally curved joining surfaces can also be made using a suitable gas guide block 26th be heated.

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 10019300 A1 [0002]
• WO 2020/164978 A1 [0008]

Claims (13)

Device for welding plastic parts (10, 12; 10a, 12a; 10b, 12b) along joining surfaces (14, 16) to be welded together, with a heating block (22), at least one of which is hot gas to the joining surface (14, 16) the plastic parts (10, 12; 10a, 12a; 10b, 12b) can be supplied, a gas guide block (26) extending along the joining surface (14, 16) which has a channel-shaped recess (38) in the form of a channel-shaped recess (38) extending along the joining surface ( 14, 16), wherein in the gas guide block (26) a plurality of supply channels (39; 42, 44) are provided for the supply of hot gas, which open at an angle into the channel-shaped recess (38), the gas guide block (26) at least is formed in segments in one piece with the channel-shaped recess (38). Device according to Claim 1 , in which the heating block (22) is connected to the supply channels (39; 42, 44) in the gas guide block (26) via a plurality of tubes (22). Device according to Claim 1 or 2 , in which the gas guide block (26) together with the channel-shaped recess (38) is manufactured at least in segments from one block. Device according to Claim 3 , in which the gas guide block (26) together with the channel-shaped recess (38) is manufactured at least in segments from a block by milling and / or drilling. Device according to one of the preceding claims, in which the gas guide block (26) consists of aluminum or an aluminum alloy and that the heating block (22) consists of an iron alloy, preferably steel. Device according to one of the preceding claims, in which the heating block (22) is connected to the supply channels (39; 42, 44) in the gas guide block (26) via a plurality of small tubes (22), the small tubes (22) preferably being substantially extend parallel to each other. Device according to Claim 6 , in which the tubes (22) are attached to the heating block (22) and preferably engage with play in the feed channels (39; 42, 44) of the gas guide block (26). Device according to one of the preceding claims, in which the recess (38) has a shape curved concavely towards the outside at its bottom (40). Device according to Claim 8 , in which the extension has a substantially U-shaped cross-section. Device according to one of the preceding claims, in which the gas guide block (26) is constructed in one piece at least in segments. Device according to Claim 10 , in which the individual segments extend over a length of up to approximately 150 mm, preferably of up to approximately 100 mm. Device according to one of the preceding claims, in which the recess (38) is three-dimensionally curved. Device according to Claim 12 , in which first bore sections (42) are provided in the gas guide block (26), which essentially extend in an extension of the axial direction of the small opening tubes (42) and which have second bore sections (44) with the recess (38) extending at an angle thereto of the gas guide block (26) are connected.

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