Coating processes – Spraying
Patent
1993-09-22
1995-05-30
Beck, Shrive
Coating processes
Spraying
427424, 427426, 427 8, 118679, 118680, 118683, 118684, 118688, 118692, 239300, 239407, B05D 102
Patent
active
054199301
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method and a device for applying a paste or paste-like mass, in particular a hardenable glue or sealer, onto a workpiece, in which the paste is fed by feed pressure to a spray device, in particular to the application nozzle of a spray head, is separated or mixed by, the action of a compressed gas preferably consisting of compressed air or inert gas and is sprayed onto the workpiece, with the workpiece and the spray device being moved relative to one another.
BACKGROUND OF THE INVENTION
In a known method of this type, which is utilised in the industrial processing of car-body parts, namely during the gluing of car-body sheet metal panels, a hardenable glue is sprayed with the help of a spray head onto the edge of the inner surface of an outer car-body sheet metal panel, which is supposed to be glued to an inner sheet metal panel. This is done by the glue being mixed with compressed air in the spray head and being then sprayed onto the edge of the car-body outer sheet metal panel. The width of the sprayed-on strip of glue depends decisively on the relationship between the amount of glue and the amount of compressed air. The inner sheet metal panel is subsequently placed onto the car-body outer sheet metal panel and the edge of the outer sheet metal panel, which edge is sprayed with the glue, is folded around the inner sheet metal panel. The hardening process can then be activated, for example, by heating this arrangement.
By spraying on the glue no undesired air pockets occur in the fold during the hardening operation, which air pockets would bring about a danger of corrosion. However, variations in the consistency of the strand of glue exiting from the spray head, or in the amount conveyed can occur during the spray application, which can result in changes in the width of the strip of glue sprayed onto the workpiece even with a constant compressed-gas supply. These variations can, for example, be due to a change in the viscosity of the glue, which in turn can be due to variations in the temperature or changes in the composition of the glue. This can result either in an incomplete filling of the areas to be glued or in protruding glue. Both cases have disadvantages. When the strip of glue is too narrow, the gluing of outer sheet metal panel to the inner sheet metal panel is insufficient, whereas when the strip of glue is too wide glue can protrude over the edge of the fold, which can lead to difficulties during the hardening operation and during the later cleaning operation.
Starting out from this, an object of the invention is to develop a method and a device of the above-mentioned type, with which an even application of glue onto the workpiece surface is guaranteed.
To attain this purpose the invention suggests that the amount of compressed gas supplied per unit of time and/or its flow speed is controlled in such a manner that a strip of paste of an essentially constant width is sprayed on along the workpiece.
In order to achieve this, it is possible according to an advantageous development of the invention to measure the feed pressure of the paste prior to its entry into the spray device and to control the amount of compressed gas supplied per unit of time in functional dependency of the measured feed pressure.
A further advantageous or alternative development of this method is to measure the temperature of the paste prior to its entry into the spray device and to control the amount of compressed air or inert gas in functional dependency of the measured temperature.
A further advantageous development of the invention provides that the volume or mass stream of the paste is adjusted to a desired value by varying the feed pressure at a constant flow cross section of the spray device. This is done, for example, in such a way that the feed or mass stream is adjusted to a predetermined value by varying the driving pressure or the electrical driving performance of a preferably electrically driven metering device. The compressed gas supplied per unit of time c
REFERENCES:
patent: 4709858 (1987-12-01), Stern et al.
patent: 4987854 (1991-01-01), Hall
Beck Shrive
Maiorana David M.
SCA Schucker GmbH
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