DEVICE AND METHOD FOR APPLYING A VISCOUS MATERIAL CONTAINING AT LEAST TWO COMPONENTS TO WORKPIECES

Description

[0001] The invention relates to a device for applying a viscous material comprising at least two components to workpieces according to the preamble of claim 1.

[0002] Such devices (cf. US 2015 / 174541 A1) are used particularly in vehicle construction and serve to produce a viscous material by mixing at least two components and applying it to a workpiece. In particular, such devices are used for applying two-component adhesives. Another area of ​​application that has recently gained importance is the application of fire-protection compounds to battery casings of electric vehicles. Such fire-protection compounds are currently only available as at least two-component materials. Known devices of this type have a dosing unit through which a number of material feed channels extend, corresponding to the number of components of the viscous material. Each of the material feed channels can be closed and opened by a dosing valve to enable precise dosing of each component.Through each of the material feed channels, one of the components is metered into a static mixer, where the components are mixed to form the viscous material. The static mixer has a mixing tube, usually containing a mixing helix, which has a material inlet at its first end and a material outlet at its second end. The mixing tube is housed in a sturdy outer tube that supports the mixing tube when high material pressures are applied. A nozzle for dispensing the viscous material is connected to the material outlet. This nozzle has an application opening from which the material is dispensed. The use of seals in the form of rings is known from US 2005 / 103889 A1.

[0003] Such devices have been used successfully for years to apply two- or multi-component materials to workpieces. However, it is occasionally criticized that in some applications, viscous material penetrates between the mixing tube and the outer tube, making it difficult to replace the mixing tube. Furthermore, it is occasionally criticized that the beginning and / or end of an application path of the viscous material cannot be defined with sufficient precision in terms of shape and / or size.

[0004] It is therefore an object of the invention to further develop a device of the type mentioned at the outset in such a way that the sealing at the material inlet and at the material outlet is improved.

[0005] 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.

[0006] The invention is based on the basic idea that the mixing tubes used in such a device can only be used for a few hours before they become clogged with hardening material. The mixing tube must then be replaced, and the mixing tube clogged with hardened material must be disposed of. Such a disposable article is therefore usually made of plastic and cannot withstand high pressures. For this reason, the mixing tube is housed in a stable outer tube, which is preferably made of metal. The outer tube, against whose inner surface the mixing tube rests with its outer surface preferably over its entire length, particularly when the components are introduced under pressure, supports the mixing tube when high material pressures are applied. The mixing tube is preferably held loosely or detachably in the outer tube so that it can be removed and disposed of, while the outer tube can be reused.The mixing tube is advantageously inserted into the outer tube with some play to ensure it can be easily inserted and removed again. Typically, its outer diameter is a few tenths of a millimeter smaller than the inner diameter of the outer tube. Its outer surface then presses against the inner surface of the outer tube through elastic expansion when the pressure inside it rises to a few bar, for example around 5 bar. According to the invention, the sealing by means of circumferential cutting edges addresses the problem that, if the sealing is inadequate, viscous material or its components can escape into the environment at the material inlet or outlet and penetrate between the mixing tube and the outer tube, so that the two tubes can no longer be separated from one another.The invention is based on the idea that the cutting edges each cut into a front surface of the mixing tube, which is usually made of soft plastic, thus providing an excellent seal. Since the mixing tube is disposable, damage caused by the cutting edges is irrelevant.

[0007] Advantageously, a first of the two cutting edges is connected to the dosing unit, while the second of the two cutting edges is connected to an end piece containing the material outlet channel. The end piece can contain the application nozzle, the outlet valve, and optionally other components. Furthermore, it is preferred that the dosing unit and the end piece are each detachably connected to the outer tube by means of a quick-release clamp. A quick-release clamp allows the application of a large force, allowing the cutting edges to cut into the end faces. It also enables the connection to be quickly released when the mixing tube needs to be replaced.

[0008] According to an advantageous development, the dosing unit and the end piece are detachably connected to one another by means of a connecting device. The connecting device expediently has a first connecting part connected to the dosing unit and a second connecting part connected to the end piece, wherein the first and second connecting parts are longitudinally displaceable relative to one another by means of a guide device. This enables better positioning of the components relative to one another, so that a pre-centering of the components relative to one another occurs when the mixer is changed. The guide device expediently has an end stop that defines an end position of the end piece relative to the dosing unit, in which end position the cutting edges cut into the end faces of the mixing tube. The end position is expediently reached or almost reached when the quick-release clamps are tightened.This measure facilitates assembly because it ensures that sufficient sealing is achieved by the cutting edges cutting into the end faces of the mixing tube when the end piece is in or approaching its end position with respect to the dosing unit. Advantageously, the guide device has a further end stop which defines a further end position of the end piece with respect to the dosing unit, in which the cutting edges are arranged at a distance from one another that is greater than the mutual distance between the end faces on the mixing tube. Releasing the connection between the dosing unit and the outer tube and between the end piece and the outer tube then allows the end piece to move into the further end position with respect to the dosing unit, but still remains connected to it and does not have to be put aside, which in turn facilitates assembly.

[0009] According to an advantageous development of the invention, each dosing valve is assigned a material supply channel that can be closed and opened by the respective dosing valve. The material supply channels open into the material inlet, and the device has an application nozzle connected to the material outlet, an application opening for dispensing the viscous material, and an outlet valve for blocking and opening a material outlet channel extending from the material outlet to the application opening. This development is based on the idea of ​​being able to use the outlet valve to block the material outlet channel until a sufficient pre-pressure of the viscous material has built up in it, thus enabling more precise material application.Furthermore, the material application can be specifically terminated by blocking the material outlet channel using the outlet valve, without material residue escaping from the application opening in an undefined quantity or form. For this purpose, a control device is advantageously provided that controls the outlet valve to block and release the material outlet channel. A pressure sensor is expediently provided to measure the pressure of the viscous material in the material outlet channel. By measuring the pressure in the material outlet channel, a pre-pressure of the viscous material upstream of the outlet valve can be specifically built up. The control device can then control the outlet valve depending on the pressure measured by the pressure sensor. However, it is also possible for the control device to control the outlet valve depending on the control of the dosing valves.In particular, it can be provided that the outlet valve is only opened to release the material outlet channel when the pressure measured by the pressure sensor reaches or exceeds a setpoint. Alternatively or additionally, it can be provided that the control device activates the outlet valve to release the material outlet channel with a predetermined time delay after the material supply channels have been opened by the metering valves. A method is particularly preferred in which the outlet valve is opened at the earliest a predefined time period after the metering valves have opened, but generally only when a predetermined pre-pressure is measured in the material outlet channel.In order to keep the pressure of the viscous material constant until the end of the material application, it is preferred that the control device, at the end of a material application, first controls the outlet valve to block the material outlet channel and then the metering valves to block the material supply channels or controls the outlet valve and the metering valves simultaneously.

[0010] The invention will be explained in more detail below with reference to an embodiment shown schematically in the drawing. Fig. 1 shows a device for applying a two-component viscous material to workpieces in perspective view; Fig. 2a to c the device according to Fig. 1 in a longitudinal section and detailed views W and X and Fig. 3 a detailed view of the device according to Fig. 1

[0011] The device 10 shown in the drawing is used for applying a two-component viscous material to workpieces, in this case, in particular, for applying a two-component fire-protection compound to battery housings of electric vehicles. It comprises a dosing unit 12 and a static mixer 14, into which the two components are metered and pressurized. Connected to this mixer is an end piece 16, which has an application nozzle 18 with an application opening 20, from which the viscous material emerges and is applied to the workpieces.

[0012] Material feed channels (not shown in detail in the drawing) extend through the dosing unit 12, with one material feed channel being provided for each of the two components. The dosing unit 12 also has two dosing valves 22 designed as needle valves, each of which is assigned to one of the material feed channels and serves to block it or open it for the passage of the respective component. The static mixer 14 has an outer tube 24 made of metal and a mixing tube 26 made of plastic received in the outer tube 24, which has a material inlet 28 at its first end facing the dosing unit 12, into which the material feed channels open. These can open directly into the material inlet 28 or can be merged before opening into a central feed channel, which in turn opens into the material inlet 28.At a second end facing away from the first end and toward the end piece 16, the mixing tube 26 has a material outlet 30 which opens into a material outlet channel 32 running through the end piece 26 to the application opening 20. In order to better mix the components to form the viscous material, a mixing coil 34 is arranged inside the mixing tube 26. The mixing tube 26 is accommodated in the outer tube 24 with a slight clearance and, as soon as the pressure inside it reaches several bar, its outer surface 36 elastically expands over its entire length to bear against an inner surface 38 of the outer tube 24, so that it is supported on the outer tube 24 in order to be able to withstand even higher pressures of the material contained therein.

[0013] The end piece 16 has an outlet valve 40 designed as a needle valve, which serves to open or close the material outlet channel 32. It also has a base body 42 connected to the static mixer 14, which carries the application nozzle 18 and to which the outlet valve 40 is mounted. The end piece 16 further has a pressure sensor 44, which measures the pressure of the viscous material in the material outlet channel 32. The pressure measurements determined by the pressure sensor 44 are transmitted to a control device not shown in detail in the drawing.

[0014] The dosing unit 12 and the end piece 16 are each connected to the static mixer 14 by means of a quick-release fastener 46, allowing for rapid replacement of the static mixer 14. As soon as the mixing tube 26 becomes clogged with hardening or hardened material to an unacceptable extent, the two quick-release fasteners 46 are released, and the static mixer 14 is replaced with a new static mixer. The mixing tube 26 clogged with the material is then removed from the outer tube 24 and disposed of, while the outer tube 24 is fitted with a new mixing tube, creating a new static mixer. To prevent the viscous material or its components from escaping into the environment at the transitions from the dosing unit 12 to the static mixer 14 and from the static mixer 14 to the end piece 16, seals 48 are provided at each of the transitions.These each have a circumferential and, in plan view, circular cutting edge 50, with one cutting edge 50 being fastened to the dosing unit 12 and one to the end piece 16. The static mixer 14 is clamped between the dosing unit 12 and the end piece 16 by means of the quick-release clamps 46 in such a way that the cutting edges 50 each forcefully cut into an end face 52 of the mixing tube 26 and ensure a good seal at the material inlet 28 and the material outlet 30 against the environment.

[0015] The device 10 also has a connecting device 54 that connects the dosing unit 12 and the end piece 16 to one another. The connecting device 54 has a first connecting part 56 mounted on the dosing unit 12 and a second connecting part 58 mounted on the end piece 16. A connector 60 connected to the first connecting part 56 serves to mount the device 10 on a robot arm. The connecting device 54 also has a guide device 62 that allows limited displacement of the connecting parts 56, 58. The guide device 62 has an elongated hole 64 in the second connecting part 58 and an elongated elevation 66 on the first connecting part 56 that engages in the elongated hole 64.The engagement of a first end 68 of the elevation facing the dosing unit 12 with a first end 70 of the elongated hole 64 facing it defines an end stop, which is characterized in that the cutting edges 50 are arranged at a distance from one another that is smaller than the mutual distance between the end faces 52, so that they cut into the end faces 52. A further end stop is defined by the second end 72 of the elevation 66 facing away from the dosing unit 12 and the second end 74 of the elongated hole 64 facing this end. If the connecting parts 56, 58 are in the position defined by the further end stop, the cutting edges 50 are arranged at a mutual distance from one another that is greater than the mutual distance between the end faces 52, so that the sealing effect is canceled and the static mixer 14 between the dosing unit 12 and the end piece 16 can be removed.The static mixer 14 can then be replaced without disconnecting the dosing unit 12 and the end piece 16. These remain connected to each other by means of the connecting device 54.

[0016] To apply the viscous material to workpieces, the metering valves 22 are first opened so that the components are metered and fed into the static mixer 14 under pressure. Typically, a pre-pressure is built up in front of the metering valves 22 before they open. The outlet valve 40 opens when a sufficient pre-pressure has been built up in the material outlet channel 32 in front of the outlet valve 40. This is typically the case shortly after the metering valves 22 open, so that the control device can trigger the outlet valve 40 to open with a time delay after the metering valves 22. The pressure in the material outlet channel 32 can also be measured using the pressure sensor 44. The measured pressure is then transmitted to the control device, which checks whether the measured pressure at least reaches a predetermined target value.If this is the case, the outlet valve 40 is opened at the specified time after the metering valves 22 open. If this is not the case, the outlet valve 40 remains closed until the pressure measured by the pressure sensor 44 reaches the setpoint. However, it is also possible to omit the pressure sensor 44 and open the outlet valve 40 exclusively after the metering valves 22 via the specified time delay. After the end of the application process, the outlet valve 40 is closed, thus blocking the material outlet channel 32. Simultaneously or with a short delay, the metering valves 22 are then closed and the material supply channels blocked.

[0017] In summary, the following can be stated: The invention relates to a device 10 for applying a viscous material having at least two components to workpieces, comprising a dosing unit 12 which has a number of dosing valves 22 corresponding to the number of components of the viscous material, comprising a static mixer 14 which has a mixing tube 26 for mixing the components as they pass from a material inlet 28 at its first end to a material outlet 30 at its second end, wherein each dosing valve 22 is assigned a material feed channel which can be blocked and released by the respective dosing valve 22, and wherein the material feed channels open into the material inlet 28, and comprising an application nozzle 18 which is connected to the material outlet 30 and has an application opening 20 for dispensing the viscous material.According to the invention, an outlet valve 40 is provided for blocking and releasing a material outlet channel 32 extending from the material outlet 30 to the application opening 20.

Claims

1. Apparatus for applying an at least two-component viscous material to workpieces, having a metering unit (12) that has a number of metering valves (22) that corresponds to the number of components of the viscous material, and having a static mixer (14) that has a mixing tube (26) for mixing the components, which are introduced, by means of the metering unit (12), into a material inlet (28) at its first end, passing through from the material inlet (28)to a material outlet (30) at its second end, and an outer tube (24), wherein the mixing tube (26) is accommodated in the outer tube (24), and sealed off, relative to the environment, at the material inlet (28) and the material outlet (30), in each instance, by means of a seal (48), characterized in that the seals (48) have a circumferential cutting edge (50), in each instance, and that the cutting edges (50), when subjected to a force toward one another, cut into an end face (52) on the mixing tube (26), in each instance.

2. Apparatus according to claim 1, characterized in that a first one of the two cutting edges (50) is connected to the metering unit (12), and that the second one of the two cutting edges (50) is connected to an end piece (16) that has the material outlet channel (32), wherein the metering unit (12) and the end piece (16) are preferably releasably connected, by means of a quick-release mechanism (46), to the outer tube (24), in each instance.

3. Apparatus according to claim 2, characterized in that the metering unit (12) and the end piece (16) are releasably connected to one another by means of a connection device (54).

4. Apparatus according to claim 3, characterized in that the connection device (54) has a first connection part (56) connected to the metering unit (12) and a second connection part (58) connected to the end piece (16), wherein the first and the second connection part (56, 58) are longitudinally displaceable relative to one another by means of a guide device (62).

5. Apparatus according to claim 4, characterized in that the guide device (62) has an end stop that defines an end position of the end piece (16) relative to the metering device (12), in which position the cutting edges (50) cut into the end faces (52) on the mixing tube (26).

6. Apparatus according to claim 5, characterized in that the guide device (62) has a further end stop that defines a further end position of the end piece (16) relative to the metering unit (12), in which position the cutting edges (50) are arranged at a distance from one another that is greater than the reciprocal distance between the end faces (52) on the mixing tube (26).

7. Apparatus according to one of the preceding claims, characterized in that the mixing tube (26) lies against an inner surface (38) of the outer tube (24) with its mantle surface (36), in particular when the components are introduced into the mixing tube (26) under pressure, and preferably over its entire length and is preferably loosely or releasably accommodated in the outer tube (24).

8. Apparatus according to one of the preceding claims, characterized in that the outer tube (24) is produced from metal.

9. Apparatus according to one of the preceding claims, characterized in that each metering valve (22) has a material feed channel assigned to it, which channel can be blocked and released by means of the metering valve (22) in question, that the material feed channels open into the material inlet (28), and that the apparatus has an application nozzle (18) that is connected to the material outlet (30) and has an application opening (20) for dispensing the viscous material, and an outlet valve (40) for blocking and releasing a material outlet channel (32) that extends from the material outlet (30) to the application opening (20).

10. Apparatus according to claim 9, characterized by a pressure sensor (44) for measuring the pressure of the viscous material in the material outlet channel (32) and / or a control device for controlling the outlet valve (40) as a function of the control of the metering valves (22) and / or as a function of the pressure measured by the pressure sensor (44).

11. Method for applying an at least two-component viscous material to workpieces by means of an apparatus (10) according to one of the preceding claims, wherein each of the components is supplied, under pressure, by way of a material feed channel to the metering unit (12), which has a number of metering valves (22) that corresponds to the number of components of the viscous material, for releasing and blocking one of the material feed channels, in each instance, wherein the components are introduced into a material inlet (28) of a mixing tube (26) of a static mixer (14) by means of the metering unit (12), in a metered manner, wherein the components are mixed in the static mixer (14) to produce the viscous material, which is passed out of a material outlet (30) of the mixing tube (26) into a material outlet channel (32) that extends to an application opening (20) of an application nozzle (18), and wherein an outlet valve (40) for blocking and releasing the material outlet channel (32) is controlled by means of a control device.

12. Method according to claim 11, characterized in that the pressure of the viscous material in the material outlet channel (32), upstream from the outlet valve (40), is measured by means of a pressure sensor (44), that the pressure measurement values are transmitted to the control device, and that the control device turns the outlet valve (40) on as a function of the pressure measurement values.

13. Method according to claim 12, characterized in that the outlet valve (40) for release of the material outlet channel (32) is only opened when the pressure measured by the pressure sensor reaches or exceeds a reference value.

14. Method according to one of claims 11 to 13, characterized in that the control device turns the outlet valve (40) on for release of the material outlet channel (32) with a predetermined time delay after release of the material feed channels by the metering valves (22).

15. Method according to one of claims 11 to 14, characterized in that the control device, at the end of a material application, first turns on the outlet valve (40) to block the material outlet channel, and then turns on the metering valves (22) for blocking the material feed channels, or turns on the outlet valve (40) and the metering valves (22) at the same time.