Method and system for covering inner walls of a cavity with a protective layer made of anti-corrosion wax or anti-corrosion agent

Abstract

A method for covering inner walls of a cavity with a protective layer made of anti-corrosion wax, in particular for use on vehicle bodies and add-on parts for vehicle bodies. Anti-corrosion wax is brought into an atomized form (protective agent mist) by a mist generator and supplied through an outlet opening to the cavity to be preserved. The protective agent mist is deposited on inner walls of the cavity and forms an anti-corrosion agent layer.

Claims

1. A method for covering inner walls of a cavity of a vehicle body or an add-on part for a vehicle body with a protective layer made of an anti-corrosion wax or a wax-based anti-corrosion agent, including the following steps: an anti-corrosion wax or a wax-based anti-corrosion agent is brought by a mist generator into an atomized form as a protective agent mist and the protective agent mist is supplied through an outlet opening to the cavity of the vehicle body or the add-on part for the vehicle body to be preserved, wherein the protective agent mist consists of air and droplets of the anti-corrosion wax or the wax-based anti-corrosion agent, and the average diameter of the droplets of the protective agent mist is <60 m, and the protective agent mist is deposited on inner walls of the cavity of the vehicle body or the add-on part for the vehicle body and forms an anti-corrosion agent layer on the inner walls.

2. The method as claimed in claim 1, wherein the average diameter of the droplets of the protective agent mist is <30 m.

3. The method as claimed in claim 2, wherein the average diameter of the droplets of the protective agent mist is <10 m.

4. The method as claimed in claim 1, wherein the droplets of the protective agent mist emerge from the outlet opening at a speed of <10 m/s.

5. The method as claimed in claim 1, wherein the supplying of the protective agent mist into the cavity occurs at a first introduction point, and during the supplying of the protective agent mist into the cavity at the first introduction point, a gas is supplied to the cavity at a second introduction point different from the first introduction point in order to influence a flow direction of the protective agent mist in the cavity and/or in order to reduce the speed of the protective agent mist in the cavity.

6. The method as claimed in claim 1, wherein a volumetric flow of the protective agent mist which is supplied to the cavity is less than 200 g/minute.

7. The method as claimed in claim 1, wherein the protective agent mist is supplied at a plurality of points or at alternating points within the cavity to be preserved, and/or the protective agent mist is supplied by a plurality of mist generators and/or through a plurality of outlet openings which are arranged at different points within the cavity to be preserved and/or are arranged in different directions relative to the cavity to be preserved.

8. The method as claimed in claim 1, wherein the protective agent mist is moved within the cavity by generation of a pressure difference between two spaced-apart partial regions of the cavity.

9. The method as claimed in claim 1, wherein a periodically repeated movement of the protective agent mist is generated in the cavity by alternating generation of a positive pressure and a negative pressure in at least one partial region of the cavity.

10. The method as claimed in claim 1, wherein the mist generator is operated at least in phases in a pulsed mode in which parameters of the mist generation change in an alternating manner, or in which the mist generation is interrupted in phases.

11. The method as claimed in claim 10, wherein in the pulsed mode, the alternating parameters change or the interruptions in the mist generation take place at an average frequency of between 0.1 Hertz and 5 Hertz.

12. The method as claimed in claim 1, wherein the mist is generated by at least two mist generators which are operated such that a first of the two mist generators and a second of the two mist generators alternately discharge relatively greater volumetric flow of protective agent mist.

13. The method as claimed in claim 1, where the mist generator generates the protective agent mist by mixing pressurized anti-corrosion wax or wax-based anti-corrosion agent and pressurized air.

14. The method as claimed in claim 13, wherein for the purpose of atomizing the anti-corrosion wax or the wax-based anti-corrosion agent, the air is accelerated within a two-substance nozzle to at least 100 m/s.

15. The method as claimed in claim 13, wherein for the purpose of atomizing the anti-corrosion wax or the wax-based anti-corrosion agent, the anti-corrosion wax or the wax-based anti-corrosion agent is supplied to the mist generator at a speed of 2 m/s (+/0.5 m/s).

16. The method as claimed in claim 13, wherein the air is supplied to the mist generator at a positive pressure of between 1 bar and 3 bar for mixing with the anti-corrosion wax or the wax-based anti-corrosion agent.

17. The method as claimed in claim 13, wherein the anti-corrosion wax or the wax-based anti-corrosion agent is supplied to the mist generator at a positive pressure of between 1 bar and 3 bar for mixing with the air.

18. The method as claimed in claim 1, wherein the mist generator generates the protective agent mist by pressurized forcing of the anti-corrosion wax or the wax-based anti-corrosion agent through a nozzle opening, or the mist generator generates the protective agent mist by means of an actuator vibrating at high frequency.

19. The method as claimed in claim 1, wherein the mist generation takes place through at least one nozzle opening with a diameter of less than 0.5 mm, and the anti-corrosion wax or the wax-based anti-corrosive agent is supplied to the nozzle opening at a pressure of at least 20 bar.

20. The method as claimed in claim 1, wherein the protective agent mist emerges from the outlet opening in a direction which is angled in relation to a main direction of extent of the cavity, and/or after emerging from the outlet opening, the protective agent mist is influenced in a targeted manner in respect of its movement direction.

21. The method as claimed in claim 1, wherein a mist generation chamber is connected upstream of the outlet opening, and the mist generator is configured for generating the protective agent mist in the mist generation chamber.

22. The method as claimed in claim 1, wherein the method is used for supplying the protective agent mist into the cavity, the cavity being located between walls of a double-walled hollow body of the vehicle body or the add-on part for the vehicle body, or the method is used for supplying the protective agent mist into the cavity, the cavity having inner walls which are concealed, starting from the positioning of the outlet opening within the cavity, at least in sections by other wall sections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and aspects of the invention emerge from the claims and from the description below of preferred exemplary embodiments of the invention, which are explained below with reference to the figures.

(2) FIGS. 1 and 2 show an exemplary workpiece with a cavity, the surfaces of which are to be provided with anti-corrosion agent.

(3) FIG. 3 shows the introduction of atomized anti-corrosion agent into the cavity through an outlet opening on an end side of the workpiece.

(4) FIG. 4 shows the cavity after the anti-corrosion agent has been deposited on the walls.

(5) FIG. 5 shows a possible design of a mist generator in the form of a mist nozzle through which the anti-corrosion agent can be introduced and is atomized to form mist.

(6) FIG. 6 shows a variant in which the mist discharge is improved by movement of the outlet opening.

(7) FIGS. 7a and 7b show a variant in which a movement of the protective agent mist is achieved by targeted generation of positive pressure and/or negative pressure in the hollow body.

(8) FIGS. 8 and 9 show variants in which a swirl is generated in the protective agent mist by the supply of air or by a particular alignment of mist outlet openings.

(9) FIG. 10 shows a variant in which the mist generation takes place in a mist generation chamber not belonging to the workpiece, and the generated mist is only subsequently supplied to the cavity of the workpiece.

(10) FIGS. 11, 12 and 13 show a variant in which mist generators are provided at the respective ends of the cavity.

(11) FIGS. 14-16 show a variant in which the protective agent is introduced into the cavity iteratively.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

(12) FIGS. 1 and 2 show an exemplary workpiece 10 which can be, for example, a subsection of a sill of a motor vehicle. FIG. 1 illustrates a sectioned view and FIG. 2 a perspective sectioned view. As can be seen, a cavity 12 of said sill is bounded not only by a cylindrical outer wall 20, but also by bulkhead plates 22.

(13) It is the aim of the method described here to cover the surfaces within the cavity with anti-corrosion wax or a wax-based anti-corrosion agent. However, the bulkhead plates 22 mentioned make it impossible to reach all of the surfaces, starting from an end side region 14 of the cavity 12, by spraying anti-corrosion agent.

(14) FIG. 3 shows how, in the case of the method according to the invention, an applicator 30 with a mist nozzle (not illustrated in the figure) having an outlet opening 32 on the end side is inserted into the cavity 12. The protective agent mist 40 is then introduced into the cavity 12 through the outlet opening 32 of the applicator. The protective agent mist 40 consists of fine droplets having an average diameter of below 60 m. The protective agent mist 40 is distributed within the cavity 12 and is deposited on the surfaces of the outer wall 20 and the bulkhead plates 22.

(15) The introduced mist should be differentiated from spraying, which is already known in the sphere of cavity preservation. The mist generation within the context of the invention and the known spraying agree in the provision of the liquid cavity preservative in the form of small droplets which are introduced into the cavity. However, in the case of the mist generation, it is provided that the average droplet diameter is smaller, preferably less than 30 m, particularly preferably less than 10 m, and that the droplets at least mostly do not strike directly against a wall of the hollow body and remain there, but rather form a mist atmosphere within the hollow body, said mist atmosphere moving only very slowly within the hollow body. The predominant quantity of the cavity preservative which is introduced into the cavity also does not enter into wall contact for 5 seconds after the introduction.

(16) FIG. 4 shows the cavity with a protective agent layer 50 which has been deposited on the walls. In particular, there is also a protective agent layer 50 in regions 52 which would not have been reachable directly from the outlet opening 32 by spraying, but only by means of the inclination of the protective agent mist 40 can be distributed homogeneously in the cavity 12 and can be deposited on the surfaces.

(17) FIG. 5 shows by way of example a single-substance nozzle forming the mist generator 31. Said single-substance nozzle can be provided on the end side in the applicator 30. It has a thin nozzle channel 34, the opening of which defines the outlet opening 32, wherein, for the purpose of breaking up the anti-corrosion agent into fine drops, a sharp-edged configuration is provided at edges 36 of said outlet opening 32. The anti-corrosion agent is supplied under high pressure by a supply channel 38. The higher the pressure, the finer are the resulting droplets of the anti-corrosion agent. It is of particular advantage if the anti-corrosion agent in the channel 38 has a pressure of between 80 and 120 bar.

(18) FIG. 6 once again shows, similarly to FIG. 3, the introduction of the anti-corrosion agent into the cavity. The particular characteristic resides here in the fact that the outlet opening 32 is shifted within the cavity in the manner indicated by the arrow 2. By this means, an even more homogeneous distribution of the mist can be brought about. Depending on the penetration depth of the applicator 30 into the cavity, the required time needed until the mist has been homogeneously distributed can also be shortened. This serves for achieving short cycle times.

(19) In the configuration according to FIGS. 7a and 7b, it is provided that pressure channels 70, 72 are in each case connected to the two opposite end regions 14, 16 of the cavity 12. Said pressure channels make it possible to allow a positive pressure or a negative pressure to arise in a targeted manner in the regions 14, 16. By this means, in turn, the mist cloud 40 can be moved to and fro in a targeted manner within the cavity 12, as indicated by the arrows 4a, 4b. In particular, the complete covering of the bulkhead plates 22 with anti-corrosion agent is thereby promoted.

(20) The pressure channel 72 on the side opposite the nozzle can already be of advantage during the introduction of the mist cloud since it makes it possible, by introduction of air at the pressure channel 72 at the same time as mist droplets are introduced by the applicator 30, to generate an air cushion which prevents too high a portion of the droplets from being deposited directly on a wall of the cavity 12 because of their outlet speed.

(21) FIG. 8 shows a configuration in which, in addition to the applicator 30, two air nozzles 60 are inserted in the end region of the cavity, wherein said air nozzles in each case define an outlet direction of the air, said outlet direction not running solely in the main direction of extent 1 of the cavity 12, but rather, in each case by contrast, the two outlet directions being angled in the clockwise direction or the two outlet directions being angled counterclockwise. By this means, a helical swirl can be generated in the mist 40 which is brought about as if it were a type of screwing of the mist into the cavity and thereby in turn promotes the even covering of surfaces to which access is difficult.

(22) FIG. 9 shows that the same can also be achieved by the fact that the mist generator itself has two outlet openings 32a, 32b which are angled in an opposed manner in order to be able to generate the desired swirl. In addition, the applicator 30 can rotate as a whole.

(23) The configuration according to FIG. 10 has a significant difference. A mist generation chamber 80 belonging to the system and not to the workpiece is provided here, in which the protective agent mist 40 is generated by a mist nozzle. From here, the mist is supplied through a channel 90 to the actual cavity. This can take place via a pump 92 or, for example, in addition to the protective agent mist 40, via a separate channel by a positive pressure being caused in the mist generation chamber 80, said positive pressure forcing the protective agent mist 40 through the channel 90 into the workpiece.

(24) FIG. 11 shows a further exemplary embodiment in which, in a departure from the preceding exemplary embodiments, mist generators 31A, 31B, each designed as two-substance mist nozzles, are in each case provided at two ends of the cavity with a protective agent layer. By way of example, these can be nozzles of the type Mod. 970/0 S4 from Dusen-Schlick GmbH from Untersiemau/Coburg. In the case of the exemplary embodiment of FIG. 11, these nozzles are inserted through lateral openings in the workpiece.

(25) The mist generators 31A, 31B are supplied with anti-corrosion agent and air via lines 33A, 33B. Only a small volumetric flow of anti-corrosion agent of approximately 50 ml/min is supplied here. The actual atomization at the outlet nozzle of the mist generators 31A, 31B takes place by feeding in the air at a speed of approximately 250 m/s and at positive infeed pressures of 2 bar in the case of the air and 3 bar in the case of the anti-corrosion agent. The result is the generation of a mist with an average droplet size of approximately 10 m. The mist cloud emerges from the mist generator in the form of a cone, wherein the speed in the center of said cone is approximately 16 m/s and decreases rapidly to the outside to below 10 m/s. By the droplets being small, said droplets undergo a severe deceleration directly after the outlet because of the air resistance. This effect is also reinforced by an air cushion which is brought about by the mist generator which is in each case opposite.

(26) The fine droplet size and the action of said air cushions has the effect that the predominant amount of the introduced anti-corrosion agent first of all forms a stationary or only slightly moving mist atmosphere, the droplets of which remain in the suspended state for at least 5 seconds before they are deposited on a wall. FIGS. 12 and 13 show this phase of the mist formation and the deposition.

(27) It has been shown that, by means of iterative introduction of the anti-corrosion agent, a mist atmosphere which is readily suitable for coating purposes is likewise arrived at with only one mist generator. The introduction can take place, for example, in a phase of a length of 2 to 3 seconds, which is then followed by a short phase of 1 to 3 seconds when the mist generator is deactivated.

(28) FIGS. 14 to 16 show this using an example with two mist generators 31A, 31B. First of all, mist is generated by means of the mist generator 31B which is on the left in the figures, as FIG. 14 shows. Subsequently, the mist generation starts here and the mist generator 31A which is on the right in the figures outputs mist made of anti-corrosion agent. By means of the opposed discharge direction, the two mist clouds have a mutually braking effect. The discharge is then continued in turn with a discharge operation at the left mist generator 31B. The desired dense mist cloud 40 consisting of very fine droplets then arises incrementally, and the droplets are then deposited on the walls in the manner already described.

(29) Although, in the case of the exemplary embodiment of FIGS. 14 to 16, two mist generators are illustrated, even when only one mist generator is used, it has been shown that the iterative or pulsing output of protective agent misti.e. the repeated activation and deactivation of the output of the protective agent mistin comparison to an uninterrupted output leads to improved formation of the mist atmosphere from anti-corrosion agent and to a smaller portion of droplets directly impacting against walls.