EP1885510A1

EP1885510A1 - Method and device for applying beads of a pasty mass

Info

Publication number: EP1885510A1
Application number: EP06742870A
Authority: EP
Inventors: Josef Schucker
Original assignee: SCA Schucker GmbH
Current assignee: Atlas Copco IAS GmbH
Priority date: 2005-06-03
Filing date: 2006-05-11
Publication date: 2008-02-13
Also published as: WO2006128560A1; DE102005026050A1

Abstract

The invention relates to a method of applying beads (12) of a pasty mass (14), having an at least two-component hardenable adhesive or sealant, to workpieces (16), a first component (B) and a second component (H) being fed to a mixing chamber and being mixed in the latter, and the pasty mass (14), for forming the beads (12), being applied to the workpieces (16) under the application of pressure via an application nozzle (20). According to the invention, provision is made for the mixing ratio of the first and the second component (B,H) to be varied during the application of the beads (12) by means of a control unit (30) by time-dependent control of the volumetric feed of the two components (B,H) into the mixing chamber.

Description

METHOD AND DEVICE FOR APPLYING RAILS OF A PASTOSIS MASS

description

The invention relates to a method and a device for applying beads of a two-component curable adhesive or sealant having pasty mass on workpieces according to the preamble of claim 1 and according to the preamble of claim 18th

_* 0 In industrial manufacturing, for example in the automotive industry, two-component adhesives are increasingly used for joining workpieces, which are applied in the form of a pasty mass as a bead on the workpieces. For application, a gun is used, which has a mixing chamber into which the two components of the

15 adhesive introduced and mixed by means of a stirrer. The pasty mass, which consists of the components mixed with the adhesive and, if appropriate, of further admixed additives, is applied to the workpieces via an application nozzle, optionally with turbulence by means of a pressurized gas. For this purpose, the 0 components are supplied to the application head under pressure, so that when the application nozzle is opened, the pressurized pasty mass is pressed out of the mixing chamber.

When the job of a bead is finished, the glue supply into the

25 mixing chamber interrupted until the workpiece or another workpiece is positioned to the gun so that the next bead can be applied. This positioning may take some time, but begins to cure the adhesive mixture contained in the mixing chamber. As the degree of reaction increases, the curing of the adhesive mixture increases

30 whose viscosity. If the viscosity rises above a critical level, the adhesive mixture can no longer be processed and there is a risk that it will no longer be removed from the mixer can, so that it becomes unusable. The adhesive mixture can therefore be left in the mixing chamber only during a so-called open time. The end of the open time is defined by the so-called pot life. If between the application of two beads of pasty mass passes a time that is greater than the pot life, therefore, the mixing chamber must be rinsed out. This is done by the present in the mixing chamber pasty mass is emptied with the already partially reacted adhesive mixture by tracking the two components from reservoirs into the mixing chamber. In particular, for longer interruptions of the bead application thereby larger amounts of the pasty mass are lost.

It is therefore an object of the invention to provide a method and a device of the type mentioned in such a way that even at longer interruptions of the track application can be worked more economically.

The object is achieved by a method having the features of claim 1 and a device having the features of claim 18. Advantageous developments of the invention are the subject of the dependent claims.

The invention is based on the idea that by varying the mixing ratio of the first and the second component, the reaction rate during curing and thus also the pot life can be varied. If at the end of the order of a bead, the two components are supplied in a mixing ratio in the mixing chamber, which ensures a slow curing and thus a long pot life, the mixing chamber is filled after the end of the application process with a slow-curing adhesive mixture and it is possible the up - To interrupt process for a long time without the mixing chamber must be rinsed out. The slow-setting adhesive mixture can be removed from the mixing chamber when the next bead is applied and form the beginning of the caterpillar. The curing time of this bead start may be too long to ensure a reliable connection between workpieces. However, if the two components are supplied to the mixing chamber in a quantitative ratio for the purpose of displacing the slow-setting adhesive mixture from the mixing chamber, which ensures a short curing time, and thus a large part of the bead has an adhesive mixture with a short curing time, this is generally not critical ,

The first component of the adhesive is suitably a base component and the second component is a hardener component. In order to obtain a good and already after a short time solid connection between the workpieces, the mixing ratio of base component and hardener component is advantageously varied over time so that each bead over a majority of their length a faster curing first adhesive mixture and over the rest of their length having slower curing second adhesive mixture. The majority of the caterpillar is then cured after a short time and ensures a stable connection, which is no longer significant that a small part of the length of the bead hardens more slowly. To achieve this, it is expedient to admix a larger proportion of hardener component to form the first adhesive mixture than to form the second adhesive mixture.

Advantageously, the mixing chamber is supplied with a temporally constant total amount of base component and hardener component. The total amount can either be based on mass or volume, so that either a constant total mass or a constant total volume of the mixing chamber is supplied. As a result, the bead is either always uniformly thick or formed with a constant mass per unit length. The total amount is expediently specified by a control robot. Preferably, before the end of the application of a first bead of the mixing chamber, the base component and the hardener component are supplied in a quantity ratio corresponding to the second adhesive mixture. The supply of this quantitative ratio is expediently carried out at such a time that the mixing chamber is completely filled with the second adhesive mixture before or at the end of the application of the first bead. It is important that after the end of the application process in the mixing chamber only the second, slow-curing adhesive mixture with a long pot life is included. Although it is possible for the second adhesive mixture located after application of the first bead in the mixing chamber to be removed from the mixing chamber before application of a second bead following the first bead. However, it is preferred that the second bead following the first bead is formed over part of its length from the second adhesive mixture located after application of the first bead in the mixing chamber. For this purpose, it is expedient to remove the second adhesive mixture from the mixing chamber by supplying the base component and the hardener component in a quantitative ratio corresponding to the first adhesive mixture. This ensures that only the beginning of the second bead has a slow-curing adhesive mixture.

If it is already foreseeable which time interval will pass between the application of two successive beads, it is advantageous that the mixing ratio of the base component and the hardener component in the second adhesive mixture is varied as a function of this time interval. If this period of time is relatively short, it is possible to mix in a larger amount of hardener component of the second adhesive mixture.

An advantageous further development of the invention provides that measured variables influencing the curing time of the adhesive are measured by means of a sensor unit and transmitted to the control unit and that the control unit determines the mixing ratio of the first and / or the second component in the mixing chamber as a function of the transmitted measured variables varied. The curing times of the adhesive influencing variables are, for example, the humidity and the ambient temperature or the temperature in the mixing chamber or the speed of a mixing rotor located in the mixing chamber. The humidity and the ambient temperature influence the curing time of the adhesive in the applied bead. Accordingly, it is advantageous if the humidity is measured by means of a humidity sensor and the mixing ratio of base and hardener component of the first adhesive mixture is regulated as a function of the humidity. Likewise, the ambient temperature is expediently measured by means of an ambient temperature sensor and the mixing ratio of base component and hardener component of the first adhesive mixture is regulated as a function of the ambient temperature. Although it is also possible to regulate the mixing ratio of base component and hardener component of the second adhesive mixture as a function of ambient temperature and air humidity. However, this does not play a major role, since the stability of the adhesive bond is mainly dependent on the first adhesive mixture. However, it is advantageous that the temperature in the mixing chamber is measured by means of a further temperature sensor and the mixing ratio of the two components contained in the mixing chamber is regulated as a function of the temperature in the mixing chamber. This is particularly important for the second adhesive mixture, as it depends on their pot life, at which intervals the mixing chamber must be rinsed.

In order to obtain a uniform bead from the beginning, the paste-like mass to be applied must be pre-pressurized at the beginning of the application process. This is dependent on its viscosity. For this reason, it is advantageous if the admission pressure is regulated by the control unit as a function of the mixing ratio of the two components contained in the mixing chamber. Furthermore, the pasty mass emerging from the application nozzle can be swirled with pressurized gas. In this case, the gas pressure and / or the volume flow of the compressed gas is appropriate regulated by the control unit as a function of the mixing ratio of the two components contained in the mixing chamber. The turbulence of the pasty mass is used to set a given bead width. Alternatively, the application nozzle can be rotated by means of an electric motor about a bezüg- the workpieces linearly moving, pointing to the workpieces axis, wherein the rotational movement is controlled depending on the mixing ratio of the two components contained in the mixing chamber.

In the following the invention will be explained in more detail with reference to an embodiment schematically illustrated in the drawing. Show it

1 shows a block diagram of a device for applying a two-component adhesive; and

Fig. 2 is a schematic representation of a workpiece with applied adhesive bead.

An apparatus 10 for applying a bead 12 (FIG. 2) of a pasty mass 14 to a workpiece 16 according to FIG. 1 has an application head 18 which contains a mixing chamber. In the mixing chamber, the components of the pasty mass 14 are mixed together and then applied pressurized via an application nozzle 20 to the workpiece 16. In the present exemplary embodiment, the pasty mass 14 consists of a two-component adhesive mixture which is formed from a base component and a hardener component by mixing the two components in the mixing chamber of the application head 18. The base and hardener components are conveyed from separate storage tanks 22B.22H by means of feed pumps 24B.24H. By means of dosing 26B.26H they are supplied in a predetermined amount ratio of the mixing chamber and mixed there to the adhesive mixture 14. B stands for base component, H for hardener component. At this point is still mentions that instead of feed pumps in some application examples also constant pressure generator and instead of metering gear pumps are used.

The device 10 includes a control robot 28, which determines the application amount of adhesive mixture per unit time measured in volumes per second and the feed rate of the applicator head 18 relative to the workpiece 16. These values are transmitted to a control unit 30, which controls the metering devices 26B.26H. By controlling the metering devices 26B, 26H by the control unit 30, the quantitative ratio of base component and hardener component, which is supplied to the mixing chamber, regulated.

Background of the regulation of the quantity ratio of base and hardener component in the adhesive mixture 14 is the property of the adhesive to cure faster with a higher proportion of admixed hardener component than with a smaller proportion. In this case, on the one hand a rapid curing of the adhesive mixture 14 is desirable when this is applied as a bead 12 on a workpiece 16 (in Fig. 2, a body part of a motor vehicle). However, if after the completion of the bead 12, the application process is interrupted, it is desirable that the remaining material in the mixing chamber cures only slowly, so that it can remain in the mixing chamber during longer processing breaks between the application of two beads. The pot life of the material contained in the mixing chamber, which defines the end of its processability, should therefore be as long as possible. For this reason, the quantity ratio of the basic and hardener component supplied to the mixing chamber is varied in time by the control unit 30, as outlined in FIG. 2. At a starting point S, the application of the bead 12 to the body part 16 begins, wherein the application head 18 is moved in the application direction R at a predetermined speed. First, in the mixing chamber, a slow-curing adhesive mixture with a small proportion of hardener compo- nente, which is applied to the body part 16 to form a hatched in Fig. 2 illustrated beginning portion 32 of the bead 12. To apply the adhesive mixture 14, base and hardener components are introduced under pressure into the mixing chamber in an altered quantity ratio controlled by the metering devices 26B.26H with a larger proportion of hardener component. After complete application of the slow-setting adhesive mixture, the faster-curing adhesive mixture with an increased proportion of the hardener component is applied to the body part. Shortly before the end of the bead application, the mixing ratio of base component and hardener component is changed again by the control unit 30, so that the two components are supplied to the mixing chamber in a proportion corresponding to the mixing ratio of the slow-curing adhesive mixture. Accordingly, the bead 12 at one end section 34 again consists of the slow-setting adhesive mixture (shown hatched in FIG. 2). After completion of the bead application, the slow-curing adhesive mixture is thus again contained in the mixing chamber. The total amount of introduced per unit time in the mixing chamber components is always kept constant.

The device 10 furthermore has a sensor device which has an air humidity sensor 36, an ambient temperature sensor 38 and a further temperature sensor 40. The ambient temperature sensor 36 measures the ambient temperature to which the bead 12 applied to the body panel 16 is exposed. The humidity sensor 38 measures the humidity. Both the ambient temperature and the humidity affect the curing time of the adhesive bead 12. The dependence of the curing time on the proportion of the hardener component in the adhesive bead 12 and on the ambient temperature and the humidity is known and stored in the control unit 30. Depending on the ambient temperature and humidity, the control unit 30 controls the mixing ratio of the base component and the hardener component in the bulk the caterpillar 12 forming fast-curing adhesive mixture so that this part of the bead 12 hardens in a desired, predetermined time. In the mixing chamber is another temperature sensor 40, which measures the temperature prevailing there. The determined temperature value is forwarded to the control unit 30, which adjusts the mixing ratio of base and hardener components of the slow-setting adhesive mixture as a function of the temperature in the mixing chamber so that the adhesive mixture has a desired, predetermined pot life.

The adhesive mixture 14 emerging from the application nozzle 20 is swirled by means of a compressed gas stored in a compressed gas container 42, in the present case with compressed air, for adjusting the width of the bead 12. With regard to the technical realization of the swirling process, reference is made to EP 0 576 498 B2, the disclosure content of which is hereby incorporated into the present application The volume flow of compressed air required for setting a predetermined bead width depends on the viscosity of the adhesive mixture With the variation of the mixing ratio of the base and hardener components, the control unit 30 also varies the air pressure by controlling a valve 44 to obtain a bead of constant width the control unit 30 regulates a pre-pressure generated by the metering devices 26B, 26H depending on the mixing ratio of base component and hardener component before the start of a bead application.

In summary, the following should be noted: The invention relates to a method for applying beads 12 of a at least two-component curable adhesive or sealant having pasty mass 14 on workpieces 16, wherein a first component B and a second component H fed to a mixing chamber and in this be mixed, and wherein the pasty mass 14 to form the beads 12 under pressure aufschlagung an application nozzle 20 is applied to the workpieces 16. According to the invention, it is provided that the mixing ratio of the first and second components B ₁ H during the application of the beads 12 by means of a control unit 30 by time-dependent control of the quantity supply of the two components B ₁ H is varied in the mixing chamber.

Claims

claims

1. A method for applying beads (12) of a at least two-component curable adhesive or sealant having pasty mass (14) on workpieces (16), wherein a first component (B) and a second component (H) fed to a mixing chamber and in these are mixed, and wherein the pasty mass (14) for forming the beads (12) is applied to the workpieces (16) under application of pressure via an application nozzle (20), characterized in that the mixing ratio of the first and the second component (B ₁ H) during the order of the beads (12) by means of a control unit (30) by time-dependent control of the amount of supply of the two components (B ₁ H) is varied in the mixing chamber.

2. The method according to claim 1, characterized in that as a first component (B) a base component and as a second component (H) a hardener component are fed into the mixing chamber.

3. The method according to claim 2, characterized in that the mixing ratio of the base component (B) and hardener component

(H) is varied in time such that each bead (12) has a faster-curing first adhesive mixture over much of its length and a slower-setting second adhesive mixture over the remainder of its length.

4. The method according to claim 3, characterized in that for the formation of the first adhesive mixture, a larger proportion of hardener component (H) is mixed than for the formation of the second adhesive mixture.

5. The method according to any one of claims 2 to 4, characterized in that the mixing chamber is a temporally constant total amount of base component (B) and hardener component (H) is supplied.

6. The method according to any one of claims 3 to 5, characterized in that before the end of the order, a first bead of the mixing chamber, the base and the hardener component (B ₁ H) are supplied in a quantity corresponding to the second adhesive mixture.

7. The method according to claim 6, characterized in that the mixing chamber is completely filled with the second adhesive mixture before or at the end of the order of the first bead.

8. The method according to claim 7, characterized in that a second bead (12) following the first bead is formed over a part of its length (32) from the second adhesive mixture located after application of the first bead in the mixing chamber.

9. The method according to claim 7, characterized in that the second adhesive mixture located in the mixing chamber after application of the first bead is removed from the mixing chamber prior to application of a second bead following the first bead.

10. The method according to any one of claims 8 or 9, characterized in that for removing the second adhesive mixture from the

Mixing this of the base and the hardener component (B ₁ H) are supplied in a quantity corresponding to the first adhesive mixture.

11. The method according to any one of claims 3 to 10, characterized in that the mixing ratio of the base and the hardener component (B ₁ H) in the second adhesive mixture in dependence is varied by the lapse of time between the order of two consecutive beads.

12. The method according to any one of the preceding claims, character- ized in that by means of a sensor unit (36,38,40) measuring the curing time of the adhesive influencing measured variables and transmitted to the control unit (30) and that the control unit (30) in dependence the transmitted measured variables vary the mixing ratio of the first and the second component (B, H) in the mixing chamber.

13. The method according to claim 12, characterized in that by means of an air humidity sensor (36), the humidity is measured and the mixing ratio of base and hardener component (B ₁ H) of the first adhesive mixture is regulated in dependence on the humidity.

14. The method according to claim 12 or 13, characterized in that by means of an ambient temperature sensor (38) the ambient temperature is measured and the mixing ratio of basic and

Hardener component (B ₁ H) of the first adhesive mixture is regulated as a function of the ambient temperature.

15. The method according to any one of claims 12 to 14, characterized in that by means of a further temperature sensor (40) the

Measured temperature in the mixing chamber and the mixing ratio of the two components contained in the mixing chamber (B ₁ H) is regulated as a function of the temperature in the mixing chamber.

16. The method according to any one of the preceding claims, characterized in that a pre-order of a bead (12) fitting Vorlage pressure is controlled by the control unit (30) as a function of the mixing ratio of the two components contained in the mixing chamber (B ₁ H).

17. The method according to any one of the preceding claims, characterized in that from the application nozzle (20) exiting paste pastöse mass (14) is swirled with compressed gas, wherein the gas pressure and / or the volume flow of the compressed gas by the control unit (30) in Depending on the mixing ratio of the two components contained in the mixing chamber (B ₁ H) is regulated.

18. The method according to any one of claims 1 to 16, characterized in that the application nozzle (20) for varying the width of the bead (12) about a relative to the workpieces (16) linearly moved axis is rotated and that the rotational movement by the control unit

(30) is controlled as a function of the mixing ratio of the two components contained in the mixing chamber (B, H).

19. An apparatus for applying beads (12) of a pasty mass (14) having a at least two-component curable adhesive or sealant to workpieces (16), comprising an application head (18) having a mixing chamber for mixing a first and a second component ( B ₁ H) of the adhesive and an application nozzle (20) for applying the pasty mass (14), characterized by a control unit (30) for time-dependent control of the amount of supply of the two components (B ₁ H) in the mixing chamber and for time-dependent control of Mixing ratio of the two components (B ₁ H) in the mixing chamber.

20. Device according to claim 19, characterized by a sensor unit (36, 38, 40) for measuring the curing time of the adhesive. influencing measured variables and for transmitting the measured variables to the control unit (30).

21. The device according to claim 20, characterized in that the sensor unit comprises a humidity sensor (36).

22. Device according to claim 20 or 21, characterized in that the sensor unit has an ambient temperature sensor (38) for measuring the ambient temperature.

23. Device according to one of claims 20 to 22, characterized in that the sensor unit has a further temperature sensor (40) for measuring the temperature in the mixing chamber.

24. Device according to one of claims 19 to 23, characterized by a compressed gas unit (42,44) for supplying compressed gas into the applicator head (18) for mixing with the from the application nozzle (20) emerging pasty mass (14), wherein the gas pressure and / or the volume flow of the compressed gas by the control unit (30) is controllable.

25. Device according to one of claims 19 to 23, characterized by a controllable by the control unit (30) electric motor for generating a rotational movement of the application nozzle (20) about a relative to the workpieces (16) linearly movable axis.