Apparatus for applying a foam-forming flowable reaction mixture to a substrate

The present invention is directed to an apparatus for applying a foam-forming flowable reaction mixture onto a substrate comprising an applicator tube connected to a mixer, said tube being provided with outlet openings and extending transversely over the substrate, further characterized in that the applicator tube is connected to a vibrating means.

BACKGROUND OF THE INVENTION 
The present invention relates to an apparatus for applying a foam-forming 
flowable reaction mixture to a substrate. The apparatus comprises an 
applicator tube which is connected to a mixer. The tube is provided with 
outlet openings and extends transversely over the substrate. 
Apparatus of this type are used during the continuous production of 
laminated foam products and during the continuous production of 
polyurethane block foam on installations of this type. A continuous 
surface (e.g., a conveyor) with a surface layer placed on it, usually a 
sheet of paper, is passed beneath the applicator tube. The apparatus is 
also used during the discontinuous production of foam panels in a box and 
during the discontinuous production of block foam in a chest. The 
substrate rests in the form of an oblong box or an oblong chest while the 
applicator tube is passed over it. It goes without saying that the box or 
the chest can also be lined with a sheet. 
The use of such an applicator tube is limited to small working widths 
because such an undesirable flow profile is formed with longer tubes that 
the substantially non-flow interface region on the internal wall increases 
in thickness towards the ends of the applicator tube. Due to the increased 
residence time in this region, the reaction mixture reacts fully before 
leaving the applicator tube, and cakes on and clogs up the applicator tube 
in the course of time. This leads to a rise in pressure in the applicator 
tube and the formation of larger cells which have a negative effect on the 
thermal conductivity of the finished polyurethane foam. During production 
of foam webs, i.e. polyurethane foam webs, it has proven advantageous, for 
this reason, and due to the requirement for a film of reaction mixture 
which as far as possible, is uniformly thick over the working width, to 
apply the foam mixture via a mixer head which oscillates over the working 
width. The applicator tube is oriented in the delivery direction of the 
product to be produced. The zig-zag application must be distributed and 
spread equally on the substrate. The outlay for the oscillation of the 
mixer head and optionally the spreading out of the layer applied is 
considerable. For working widths exceeding one meter it becomes more 
difficult to produce uniformly thick film with rapidly reacting chemical 
systems and/or high production rates. 
With block foam installations in which the applied layer of reaction 
mixture is a few centimeters, the distribution of the reaction mixture is 
not quite so problematic. An applicator tube which branches into several 
outlets has been used for larger working widths. Nevertheless, there is a 
risk that the various streams will create transition zones in the 
cross-section of the foam block produced in those central regions in which 
they converge. The transition zones have a pore size or density which 
differs from that in other regions. 
The object of the present invention is therefore to improve the apparatus 
of the type mentioned in such a way that it cannot clog as the result of 
reacting reaction mixture during operation and so that a uniform 
application is ensured for achieving a perfect end product, even with 
greater working widths.

An applicator tube 3 which is connected via a branching outlet tube 4 to a 
mix head 5 is arranged transversely above the inlet region over the 
surface of the lower belt 2 of a laminator for the production of foam webs 
laminated with paper surface layers. On its lowest convex surface line, 
the tube has outlet openings 6. The tube is arranged so as to oscillate by 
connecting one end to a vibrator 7 and the other end to an abutment 8. A 
frequency controller 9 is connected to the vibrator 7. The vibrator 7 and 
abutment 8 are fixed on the frame 11 by means of an oscillation-insulating 
bearing 10. A paper web 12 is carried on the surface 1 and is folded up 
and supported at the sides by side strips 13. The reaction mixture issuing 
from the outlet openings 6 is charged onto this paper web. The guidance 
frequency is adapted to the distance between the outlet openings 6 such 
that the issuing reaction mixture forms fans 14 which overlap one another 
so that a closed curtain 15 is formed immediately before it strikes the 
paper web 12. 
Although the invention has been described in detail in the foregoing for 
the purpose of illustration, it is to be understood that such detail is 
solely for that purpose and that variations can be made therein by those 
skilled in the art without departing from the spirit and scope of the 
invention except as it may be limited by the claims.