Device for applying a multi-component viscous material to workpieces

Abstract

The invention relates to a device (10) for applying a multi-component viscous material to workpieces, comprising a metering unit (12) having a number of metering valves corresponding to the number of components of the viscous material and a coupling device (16), and a mixing unit 20 having a material inlet (28) and a coupling part (26) detachably connected to the coupling device (16) at a first end (24) and an outlet opening (34) for the viscous material at a second end (32), as well as a mixing structure (36) arranged in the mixing tube (22) for mixing the components during passage through the mixing tube (22) from the material inlet (28) to the outlet opening (34).According to the invention, a needle valve (40) is provided for releasing and closing the outlet opening (34), which has a valve needle (42) extending in a longitudinal direction (38) from the material inlet (28) to the outlet opening (34), which releases the outlet opening (34) in a release position and closes it in a closing position by resting against a valve seat (46).

Description

[0001] The invention relates to a device for applying a multi-component viscous material to workpieces according to the preamble of claim 1.

[0002] Such a device is known, for example, from DE 10 2018 119 838 A1. It is used to apply a viscous material with at least two components to workpieces, in particular to vehicle parts during production. The previously known device comprises a dosing unit having a number of dosing valves corresponding to the number of components of the viscous material and a coupling device by means of which the dosing unit is detachably connected to a mixing unit. The dosing unit doses the individual components of the viscous material and feeds them into a material inlet at the first end of the mixing unit. The mixing unit comprises a mixing tube and a mixing structure arranged in the mixing tube, which ensures thorough mixing of the components as they pass through the mixing unit from the material inlet to an outlet opening at the second end.In particular, the viscous material, which has been mixed from the multiple components in the mixing unit, is applied to the workpieces in bead form. However, it is difficult to precisely define the end of a material bead. When the metering valves are closed to end the material application, there is still material in the mixing unit that can escape from the outlet opening. To prevent the applied material bead from being undesirably lengthened, the application device is often moved back a little at the end of the material bead in order to position any dripping material in the area of ​​the already applied material bead by means of such a path reversal. However, this measure increases the cycle time at which the application device is operated.

[0003] It is therefore an object of the present invention to further develop a device of the type mentioned at the outset in such a way that the material tear at the outlet opening can be better defined.

[0004] This object is achieved according to the invention by a device having the features of claim 1. Advantageous developments of the invention are the subject of the dependent claims.

[0005] The invention is based on the idea of ​​using a needle valve to precisely cut off the material application from the outlet opening by closing it with the valve needle against the valve seat. Once the outlet opening is closed by the valve needle, no material can drip from the mixing unit, allowing the end of the material application to be defined much more accurately. A path reversal is then no longer necessary, enabling shorter cycle times.

[0006] The mixing unit can be a so-called X-grid mixing unit, whose mixing structure comprises two groups of diagonal struts that intersect along a crossing line running transversely to the longitudinal direction. The valve needle then runs centrally through the diagonal struts. It is also possible for the mixing unit to be a so-called quadro mixing unit. However, it is preferred that the mixing structure has an inner tube that is arranged in the mixing tube and extends in the longitudinal direction. The valve needle then extends through the inner tube, and a mixing helix protrudes radially from the inner tube, along which the components flow from the material inlet to the outlet opening and mix with one another as they flow. It is preferred that the valve needle protrudes from the inner tube at a front end facing the valve seat and is guided in a sealed manner at the front end of the inner tube by means of a sealing element.The valve needle is then separated from the viscous material and only comes into contact with it in the area of ​​the valve seat. The seal at the front end of the inner tube prevents internal leaks, especially the penetration of material into the inner tube, thereby improving the mixing quality and enabling higher material pressures in the mixing unit. In all cases, the material inlet of the mixing unit communicates with the feed channels of the dosing unit, through which the components of the viscous material are metered into the mixing unit. These channels can be blocked and released using one of the dosing valves.

[0007] The mixing unit can be manufactured conventionally, in particular as a single piece or multiple pieces by drilling, turning, milling, or injection molding, or a combination of such processes. However, it is advantageous to manufacture the mixing unit as a single piece using 3D printing. Different materials can be used for this purpose. In particular, the mixing tube and the mixing structure can be made of a first material, with materials consisting of or at least comprising polylactide (PLA) or an acrylonitrile-butadiene-styrene copolymer (ABS) being preferred, while the valve seat and the sealing element can each be made of a different second material. ABS, in particular, can be designed to provide protection against electrostatic discharge (ESD protection). It is possible to manufacture the valve seat and the sealing element from the same second material or to use two different materials here too.

[0008] The needle valve expediently has a drive unit for moving the valve needle, in particular a pneumatic drive unit. A motor-driven spindle drive, a hydraulic drive, or a lifting magnet can also be used for this purpose. The drive unit can advantageously be detachably connected to the dosing unit in order to enable the needle valve to be easily replaced. In this case, it is possible for the valve needle to be movable by means of the drive unit in the longitudinal direction into the closed position and counter-longitudinal direction into the release position. However, the needle valve can also be designed as a so-called snuffback valve, in which the valve needle can be moved by means of the drive unit in the longitudinal direction into the release position and counter-longitudinal direction into the closed position.A snuffback valve has the advantage that material located in the area of ​​the valve seat is not pushed out of the outlet opening when the valve is closed, but is at least partially retracted into the outlet opening, so that the end of the material application can be defined even better.

[0009] To achieve better mixing of the components, the mixing structure can be mounted in the mixing tube so that it can rotate about a longitudinal axis of rotation. A motorized drive for the mixing structure is preferred, for example, via a hollow shaft through which the valve needle also extends, at least in part.

[0010] The valve needle is advantageously made of metal or hard metal. Hard metal is a metal matrix composite material in which hard materials in particle form are held together by a metal matrix. Hard materials used include, in particular, metal carbides or metal nitrides, such as tungsten carbide, titanium carbide, titanium nitride, niobium carbide, tantalum carbide, or vanadium carbide. Metal, and especially hard metal, are wear-resistant materials. Furthermore, the valve needle can be manufactured together with the mixing unit using 3D printing. This is particularly advantageous when the needle valve is designed as a snuffback valve, as the valve needle then does not have to be laboriously inserted from the outlet opening into the mixing unit. When the needle valve is designed as a snuffback valve, it is also advantageous to design the valve needle in two parts.The two parts of the valve needle are inserted into the mixing unit from opposite directions and then firmly connected to each other.

[0011] A device for generating a vacuum in the mixing tube is advantageously provided. Keeping the mixing tube under vacuum further minimizes the risk of material dripping from the outlet opening.

[0012] The invention is explained in more detail below with reference to exemplary embodiments schematically illustrated in the drawings. They show: Fig. 1 a device for applying a viscous material in a schematic representation in section; Fig. 2a,b a mixing unit for a device according to Fig. 1 according to a first embodiment in section and an enlargement of the section B and Fig. 3a,b a mixing unit for a device according to Fig. 1 according to a second embodiment in section and an enlargement of the section F.

[0013] The application device 10 shown in the drawing is used to apply a multi-component viscous material to workpieces, according to the present embodiment, a two-component viscous material, for example, an adhesive mixed from two components, namely a base component and a hardener. It has a dosing unit 12, which has a feed channel 14 for each of the components, through which the respective component is fed. Each of the feed channels 14 can be blocked and opened by means of a dosing valve (not shown in the drawing), so that each component can be fed in a dosed manner. The dosing unit 12 also has a coupling device 16, to which a mixing unit 20 is detachably attached. The mixing unit 20 has a mixing tube 22, at the first end 24 of which a coupling section 26 is arranged, which serves for the detachable connection to the coupling device 16.Also arranged at the first end 24 of the mixing tube 22 is a material inlet 28, into which the feed channels 14 open. In the exemplary embodiment shown here, the material inlet 28 has two material inlet channels 30, with one of the feed channels 14 opening into each of the material inlet channels 30. Of course, this principle is also applicable to the application of a viscous material consisting of more than two components, whereby a number of feed channels and metering valves corresponding to the number of components is always provided in the metering unit 12, which feed channels and metering valves open into the material inlet 28, which can then also have a number of material inlet channels corresponding to the number of components.

[0014] At the second end 32 of the mixing tube 22, it has an outlet opening 34 from which the viscous material produced by mixing the components emerges for application to workpieces. A mixing structure 36 is arranged in the mixing tube 22 and serves to mix the components as homogeneously as possible on their way from the material inlet 28 to the outlet opening 34. A valve needle 42 of a needle valve 40 extends in the longitudinal direction 38 extending from the material inlet 28 to the outlet opening 34. The needle valve 40 also has a pneumatic drive unit 44 which is detachably connected to the dosing unit 12 and by means of which the valve needle 42 can move to a limited extent in and counter to the longitudinal direction 38. A valve seat 46 is arranged at the outlet opening 34, wherein the valve needle 42 closes the outlet opening 34 in a closed position by contact with the valve seat 46 and releases it in a release position in which it is lifted off the valve seat 46.The valve needle 42 is moved in accordance with the method shown in . Fig. 2a,b, the first embodiment is moved counter to the longitudinal direction 38 into the release position and in the longitudinal direction 38 into the closed position. In contrast, in the second embodiment according to Fig. 3a, Fig. 3b the needle valve 40 is designed as a snuffback valve, and the valve needle 42 is moved in the longitudinal direction 38 into the release position and counter to the longitudinal direction 38 into the closed position.

[0015] In both exemplary embodiments, the mixing unit 20 has an inner tube 48 arranged in the mixing tube 22, through which the valve needle 42 extends. A mixing helix 50 projects radially from the inner tube 48, extends to the mixing tube 22, and forms a helical surface inclined towards the outlet opening 34, over which the components flow and mix as they flow out. The valve needle 42 protrudes from a front end 52 of the inner tube 48 facing the outlet opening 34 and arranged at a distance from it. Also arranged in the inner tube 48 at the front end 52 of the inner tube 48 is a circumferential sealing element 54 which bears sealingly against the valve needle 42 and prevents the viscous material from penetrating the inner tube 48.

[0016] In the present embodiments, the mixing unit 20 is manufactured by 3D printing. The mixing tube 22 and the mixing structure 36 are made in one piece from the same material, in the present embodiment, a polylactide (PLA) or an acrylonitrile-butadiene-styrene copolymer (ABS). The valve seat 46 and the sealing element 54 are generally made from a more wear-resistant material, but are also integrally formed onto the mixing tube 22 and the inner tube 48, respectively, using 3D printing. The valve needle 42 can also be manufactured using the 3D printing process during the manufacture of the mixing unit 20, with metal or hard metal being particularly preferred materials. Manufacturing the valve needle 42 using the 3D printing process is particularly advantageous when the needle valve 40 is designed as a snuffback valve, since the valve needle 42 cannot be inserted into the mixing unit 20 in the longitudinal direction 38.However, a two-part design of the valve needle 42 is also conceivable, in which one part is inserted into the mixing unit 20 in the longitudinal direction 38 and one part is inserted via the outlet opening 34 counter to the longitudinal direction 38, and both parts are then firmly connected to one another. Furthermore, it goes without saying that the invention also encompasses application devices 10 that have a mixing unit with a different mixing structure. Furthermore, the mixing structure 36 can also be rotatable relative to the mixing tube 22 about its longitudinal center axis. In summary, the following can be stated:

[0017] The invention relates to a device 10 for applying a multi-component viscous material to workpieces, comprising a dosing unit 12 which has a number of feed channels 14, each of which can be blocked and released by dosing valves, corresponding to the number of components of the viscous material, as well as a coupling device 16, and a mixing unit 20 which has a material inlet 28 at a first end 24, into which the feed channels 14 open, and a coupling part 26 detachably connected to the coupling device 16, and a mixing tube 22 having an outlet opening 34 for the viscous material at a second end 32, as well as a mixing structure 36 arranged in the mixing tube 22 for mixing the components as they pass through the mixing tube 22 from the material inlet 28 to the outlet opening 34.According to the invention, a needle valve 40 is provided for releasing and closing the outlet opening 34, which has a valve needle 42 extending in a longitudinal direction 38 running from the material inlet 28 to the outlet opening 34, which opens the outlet opening 34 in a release position and closes it in a closed position by contacting a valve seat 46. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2018 119 838 A1

[0002]

Claims

[1] A device for applying a multi-component viscous material to workpieces, comprising a dosing unit (12) having a number of dosing valves corresponding to the number of components of the viscous material, as well as a coupling device (16), and a mixing unit (20) having a mixing tube (22) having a material inlet (28) at a first end (24) and a coupling part (26) detachably connected to the coupling device (16), and an outlet opening (34) for the viscous material at a second end (32), as well as a mixing structure (36) arranged in the mixing tube (22) for mixing the components as they pass through the mixing tube (22) from the material inlet (28) to the outlet opening (34), characterized bya needle valve (40) for releasing and closing the outlet opening (34), which has a valve needle (42) extending in a longitudinal direction (38) running from the material inlet (28) to the outlet opening (34), which opens the outlet opening (34) in a release position and closes it in a closed position by resting on a valve seat (46). [2] Device according to claim 1, characterized by that the mixing structure (36) has an inner tube (48) which is arranged in the mixing tube (22), through which the valve needle (42) extends and from which a mixing helix (50) projects radially. [3] Device according to claim 2, characterized by that the valve needle (42) protrudes from the inner tube (48) at a front end (52) facing the valve seat (46) and is guided in a sealed manner at the front end (52) by means of a sealing element (54). [4] Device according to one of the preceding claims, characterized bythat the mixing unit (20) is manufactured in one piece by means of 3D printing. [5] Device according to one of the preceding claims, characterized by that the mixing unit (20) comprises different materials and that in particular the mixing tube (22) and the mixing structure (36) are made of a first material and the valve seat (46) and optionally the sealing element (54) are made of a second material or different second materials. [6] Device according to one of the preceding claims, characterized by that the needle valve (40) has a preferably pneumatic drive unit (44) for moving the valve needle (42). [7] Device according to claim 6, characterized by that the drive unit (44) is detachably connected to the dosing unit (12). [8] Device according to claim 6 or 7, characterized bythat the valve needle (42) is movable by means of the drive unit (44) in the longitudinal direction (38) into the closed position and counter to the longitudinal direction (38) into the release position. [9] Device according to claim 6 or 7, characterized by that the valve needle (42) is movable by means of the drive unit (44) in the longitudinal direction (38) into the release position and counter to the longitudinal direction (38) into the closed position. [10] Device according to one of the preceding claims, characterized by that the mixing structure (36) is accommodated in the mixing tube (22) so as to be rotatable about an axis of rotation running in the longitudinal direction (38), preferably by a motor. [11] Device according to one of the preceding claims, characterized by that the mixing tube (22) and the mixing structure (36) are made of a polylactide (PLA) or an acrylonitrile-butadiene-styrene copolymer (ABS). [12] Device according to one of the preceding claims, characterized bythat the valve needle (42) is made of metal or hard metal. [13] Device according to one of claims 1 to 11, characterized by that the valve needle (42) together with the mixing unit (20) is manufactured by 3D printing. [14] Device according to one of the preceding claims, characterized by a device for generating a vacuum in the mixing tube.

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