Coating processes – Spraying
Reexamination Certificate
2002-02-14
2004-01-27
Meeks, Timothy (Department: 1762)
Coating processes
Spraying
C427S230000, C427S236000, C427S424000
Reexamination Certificate
active
06682781
ABSTRACT:
This invention relates to a device for wetting a flexible mat-shaped carrier material comprising guiding elements for the transport and guiding of the carrier material configured in such a way that at least one hollow space limited by the carrier material is constituted into which a spray device can be introduced for wetting the upper surface of the carrier material which is turned to the inner side of the hollow space. Furthermore, the invention relates to a method for wetting a flexible mat-shaped carrier material in which the carrier material is guided by constituting at least one hollow space and the upper surface of the carrier material which is turned to the inner side of the hollow space is wetted.
A device and a method of the above mentioned type are known, among others, from DE 196 33 656 C1. For the carrier materials, they can be, for example, nonwovens and fiber mats made of plastics, glass fibers and natural fibers, whereby these materials can exist as primary raw materials as well as as recycled materials or as a mixture thereof. Such carrier materials must often be provided with a stiffening matrix material by spraying on liquid existing components. For the liquid existing components, they are generally two-component resins, for example polyurethane resins, epoxy resins and the like. Due to the adhesive effect and the curing process, there result moulded parts with an inherent stability which can be used, for example, in the automotive industry, in the furniture industry and for consumer goods.
For the device for wetting such mat-shaped carrier materials according to DE 196 33 656 C1, a continuous carrier material web is guided over deflection rollers as well as a chain conveyor guide through a wetting device in which it can be wetted on both faces. For this purpose, the carrier material web is guided over two parallel tunnel chain wheels so that it constitutes the surface area of a cylindrical hollow space (tunnel, drum) between these wheels. The inner side of this surface area is then sprayed with the wetting agent and thus wetted on one face. The losses and emissions of the wetting agents to the outside are limited by the fact that the wetting takes place in the inner part of a hollow space. For the double faced coating of the carrier material web, a second pair of tunnel chain wheels is placed in the wetting device by means of which a second cylindrical (tunnel-shaped) hollow space is constituted. Hereby, the inner side of the surface area of the hollow space is however constituted by the other face of the carrier material, i.e. the face which is not yet wetted. Thus, the second side of the carrier material can also be wetted in this second hollow space.
Moreover, methods are known for which two carrier material mats are simultaneously worked, since they constitute together a hollow space for wetting because of corresponding guides. Here, a double-faced coating can also be achieved by turning the two mats.
The so-called high-pressure spray technique constitutes a further state of the art. Wetting agent spray mist is produced here with high pressure and with a relatively high flow rate of additional air. High-pressure spray heads work with an admission pressure up to 80 bar and also use this high pressure for a hydrodynamic mixing effect in the spray head.
The spray heads are most of the time guided by a robot. The output of such systems reaches 2 to 3 m
2
/min (one-faced) depending on the precision requirements. Since this method is very flexible to use because of the free programmability and is variable with respect to the quantities to be sprayed, it requires high investment costs and a high regular expenditure of cleaning which reduces the daily availability of the system. Furthermore, the system requires much space for the equipment for a relatively low output per area unit. The high overspray quantities, i.e. the quantities of wetting agent which do not reach the aimed place and are sprayed lost in the environment, are also disadvantageous. Finally, there also result high waste quantities of production auxiliary materials, such as for example covering foils.
For the roller-laminating methods, wetted spreader rolls apply the wetting agent onto the carrier materials. Herbey, there does not result or there only results little overspray and only a slight pollution of the ambient air. Moreover, these methods achieve a high output per area unit but cause considerable pollution problems in the installation.
Furthermore, linearly guided spray heads in spray tunnels are known. These spray heads require slightly less investment costs and less installation surfaces than the high-pressure spray technique for the same output per area unit. They can also be compared to those with respect to their daily availability and the secondary waste quantities. The spray systems can work with or without air (“airless”).
Concerning the airless methods, spray heads with a mechanical compulsory mixer have been developed which can be operated with relatively low media admission pressure up to 15 bar and only very low quantities of additional air (Tartler company, Lützelbach, Germany). In a certain embodiment, a spray head with a centrifugal wheel is provided with a continuous rotary axle which is preferably screw-shaped for the transport of the wetting agent to its front end. At the front end of the axle, there is a centrifugal disk with a diameter of a few centimeters. The screw and the centrifugal disk rotate at work with numbers of revolutions up to 4000 revs./min. Due to the impact of the wetting agent onto the centrifugal disk, the wetting agent is centrifuged because of the centrifugal forces radially outwards where it reaches the object to be wetted. For wetting carrier materials in the mat cut-out piece with such a device, the mat can be fixed on the inner wall of a rotary drum. The mat upper surface turned to the inner side of the drum can then be wetted by the above described centrifugal wheel spray head. With this method, only one-faced wetting of the carrier materials is possible, since the inner side of the drum would be contaminated by the already wetted upper surface of the carrier material if the mat would be used turned in the drum. Since the wetting agents often are resin components and thus substances which can also be used as adhesives, the contamination of wetting installations with the wetting agent constitutes a particular problem.
It is a disadvantage of the above mentioned “drum wetting methods”, among others, that, when the installation is being switched off, they leave either only partially wetted raw mats (i.e. wetted on one face), or they require a relatively high expenditure of technique in order to avoid this. For example devices for the “self threading” of the mat ends must be provided for. If two mat webs have to be worked simultaneously, due to the double layout of machine parts (unwinding, drying, material storing, discharging device, assembling device), this causes relatively high investment costs which can only be defended for an utilization of the very high possible output.
Furthermore, a non-homogeneity of the wetting result appears with the known drum wetting methods, when a horizontally guided centrifugal spray device is introduced into the hollow space (drum, tunnel).
Finally, with the methods with a chain or toothed disk guiding, the fault is found that they have practically no flexibility with respect to the variation of the cut-out dimension of the raw mat, which is however often desired for an optimization of the production.
The aim of this invention was to improve a device of the type mentioned above in such a way that its construction is simpler and that it can thus be produced with less costs, that the coating result is homogeneous and that cut-out dimensions as different as possible can be flexibly worked.
Accordingly, it is the question of a device for which, similarly to the “drum wetting methods”, a flexible mat-shaped carrier material is formed over guiding elements in such a way that a hollow space is created which is limited b
Hoogen Norbert
Lencer Dieter
Pekal Christoph
Fuller Eric B
Heidel GmbH & Co. KG
Kueffner Friedrich
Meeks Timothy
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