Coating apparatus for coating moving sheet

Coating apparatus is provided for use in coating a sheet of goods which is carried on a counter-roller. The coating apparatus includes a coating zone which is formed along the sheet to be coated. At least one deflector is provided in the coating zone for deflecting the return flow of coating material deflected at the coating blade to a divergence angle of less than 90 degrees relative to the emerging flow of fresh coating material from the outlet port of the chamber containing the coating material. In general, angle of divergence between the two opposing flows of coating material is less than 60 degrees. In this manner, the amount of agitation and turbulence in the flow of material is minimized.

BACKGROUND OF THE INVENTION 
The present invention relates generally to coating apparatus and, more 
particularly, to coating apparatus adapted to evenly and uniformly apply a 
coating material to a moving sheet of goods with little or no streaking. 
In order to achieve an even and uniform application of a coating material 
on a moving sheet of goods, the amount of air which is introduced at the 
point of coating, i.e., the coating zone, must be minimized. An example of 
coating apparatus which is intended to eliminate or minimize the 
introduction of air into the coating zone is the apparatus described in 
U.S. Pat. No. 4,250,211. In the apparatus of this patent, the coating 
material emerges from a chamber or reservoir and is introduced into a 
coating zone through a slotted outlet port. The coating material is 
maintained under pressure in this coating zone. 
The coating zone of the apparatus described in U.S Pat. No. 4,250,211 is 
bound or defined by the sheet of goods to be coated which is carried 
around a guide cylinder; an anterior throttle plate; the opening of the 
outlet port of the chamber; and a coating blade. The coating material 
emerges from the coating zone through a throttle slit which is created 
between the anterior throttle plate and the moving sheet of goods in a 
direction opposite the direction of the movement of the sheet. Such a 
configuration serves to reduce the amount of air which is introduced into 
the coating zone and, as such, is able to effect the coating operation 
relatively unimpeded by air pockets. 
One of the inherent problems with such apparatus, however, is that the 
coating material tends to streak as it is applied to the sheet. This 
streaking is due to ripples which develop in the coating material within 
the coating zone. As can be readily appreciated, streaking of the coating 
material on the sheet of goods can prove commercially unacceptable. 
Against the foregoing background, it is primary object of the present 
invention to provide coating apparatus which can uniformly and evenly 
apply a coating to a sheet of goods. 
It is another object of the present invention to provide such coating 
apparatus where the amount of air which is introduced into the coating 
zone of the apparatus is minimized. 
It is still another object of the present invention to provide such coating 
apparatus which will not streak the coating material on the sheet of goods 
to be coated. 
SUMMARY OF THE INVENTION 
To the accomplishments of the foregoing objects and advantages, the present 
invention, in brief summary, comprises apparatus for applying a coating 
material to a moving sheet of goods which is carried on a rotatable 
cylinder or counter-roller. The apparatus includes a chamber for 
delivering the coating material into a coating zone through the mouth of 
an outlet port and a coating blade for deflecting the coating material and 
returning excess material back into the chamber. The coating zone is 
defined by an anterior throttle plate, the mouth of the outlet port and 
the coating blade. Deflector means are provided in the coating zone to 
further deflect the returning flow of coating material deflected by the 
coating blade relative to the emerging flow of fresh coating material from 
the outlet port. The angle of divergence between the returning flow of 
coating material and the emerging flow of fresh coating material from 
outlet port is less than 90 degrees. 
Deflectors may be provided at either end of the diverter means so that the 
angle of divergence is less than 60 degrees. 
In an alternative embodiment of the apparatus of the present invention, a 
baffle may be provided which extends into the coating zone from the 
chamber. In such embodiment, the outlet port is defined by the baffle and 
an anterior wall of the chamber and a return port is defined by the baffle 
and a posterior lateral wall of the chamber for the return of coating 
material from the coating zone. The baffle may form a throttle-type slot 
for directing the coating material against the sheet to be coated. 
In such alternative embodiment, the end of the baffle which is contained in 
the chamber may be curved or rounded and a curved deflector is provided 
within the chamber opposite the rounded end of the baffle. The combination 
of the two serves to divert the returning flow of coating material and the 
angle of divergence between the returning flow of coating material and the 
emerging flow of coating material is less than 90 degrees.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The coating apparatus of the present invention, which is illustrated 
generally in FIG. 1 thereof, includes a reservoir or chamber 1 adapted to 
store the coating material which is to be applied to a moving sheet of 
goods which is carried on a counter-roller C. The chamber 1 is defined by 
lateral walls 4 and 5. Anterior lateral wall 4 supports an anterior 
throttle plate 7 by means of a shim 6 and terminates against 
counter-roller C. The coating material is delivered from the chamber 1 
into a coating zone 16 through an outlet port 3. The coating blade 2 is 
provided for evenly applying the coating material on the sheet against the 
sheet being coated and for deflecting excess coating material and 
initiating a return flow of such excess material back into the chamber 1. 
The emerging flow of the coating material from chamber 1 through outlet 
port 3 and into coating zone 16 for application against the sheet on the 
counter-roller C is represented by the arrows. A pre-determined amount of 
coating material contained in the coating zone 16 is applied against the 
sheet of goods as it is carried on counter-roller C in the direction of 
the arrow. 
The coating zone 16 of the apparatus of the present invention is bounded or 
defined by the counter-roller C which carries the sheet of goods to be 
coated, the upper portion of the anterior throttle plate 7, the mouth of 
outlet port 3 of the chamber 1, the coating blade 2 and, additionally, by 
a guide hull 13 which is positioned at the mouth of chamber 1. Guide hull 
13, which is attached to the end of the posterior wall 5 of the chamber 1, 
includes deflectors 14 and 15 at its opposite ends. Guide hull 13 may be 
fabricated at least partially of rubber or of any other easily molded 
material so that, if necessary, it can easily be bent to the desired 
deformation of the coating blade 2 induced by contact from pressure tubing 
9. 
One end of the coating blade 2 is attached to the posterior wall 5 of 
chamber 1 by pressure tubing 8. The opposite end of the coating blade 2 is 
adapted to contact and ride against the sheet which is carried on 
counter-roller C. Deformation of the coating blade 2 is effected by 
pressure tubing 9. 
Anterior throttle plate 7 is secured between a shim 6 and the anterior 
lateral wall 4 by pressure tubing 10. A baffle 11 is secured to shim 6 by 
a retaining strip 12 and serves to remove any excess coating material from 
the coating zone 16 which may flow over the upper edge of the throttle 
plate 7. 
The actual flow of the coating material within the coating zone 16 is 
represented by the arrows. As the chamber 1 is opened, an emerging flow 
coating material passes through outlet port 3 and is deflected by first 
deflector 15 on guide hull 13 in a direction opposite to the direction of 
rotation of the sheet of goods to be coated on counter-roller C. The 
coating material then contacts the sheet on the counter-roller C and is 
carried along with the flow of the sheet of goods. 
A second deflection of the coating material occurs at coating blade 2 and a 
return flow is initiated. This second deflection of the coating material 
serves to reduce the streaking in the coating process since the coating 
material does not leave the coating zone 16 as a streak. The return flow 
of coating material caused by the reflection of the coating blade 2, and 
which otherwise would have causing streaking, is directed downwardly where 
it contacts and is again deflected by second deflector 14 on the guide 
hull 13. This second deflection results in two, substantially opposed 
flows of coating material in the coating zone, i.e., the emerging flow out 
of the outlet port 3 and in the direction of rotation of the 
counter-roller C and the returning flow after deflection by the coating 
blade 2 and the second deflector 14. The angle .alpha. of divergence, 
i.e., the angle formed between the two velocity vectors described by the 
aforementioned flows of the coating material, is less than 90 degrees and 
preferably no greater than 60 degrees. In a particularly preferred 
embodiment, the angle of divergence is less than 40 degrees. 
An alternative embodmiment of the coating apparatus of the present 
invention is illustrated in FIG. 2. The coating apparatus of this 
embodiment utilizes essentially the same chamber as in FIG. 1, but 
contains a uniquely configured baffle arrangement. 
In the embodiment of FIG. 2, the chamber 1 and the passageway from the 
chamber 1 to the coating zone 16' are divided into two channels, i.e., an 
outlet port 3' and a return port 20, by a baffle 18 which extends from 
chamber 1 into the coating zone 16'. Outlet port 3' is defined by the 
anterior lateral wall 4 and the baffle 18 and return port 20 is defined by 
the posterior lateral wall 5 and the baffle 18. Outlet port 3' is adapted 
to permit introduction of the emerging flow of the coating material into 
the coating zone 16' while the return channel 20 is adapted to permit the 
returning flow of coating material which is deflected by the coating blade 
2 back into the chamber 1. 
Baffle 18, which is secured to the posterior lateral wall 5 of the chamber 
1 by a spacer 22 and a screw 21, divides the chamber 1 into approximately 
equal portions along its axial length. The end 19' of baffle 18 contained 
within the chamber 1 is rounded to facilitate entry of the returning flow 
of the coating material back into the chamber 1. Spacer plates 25 and 26 
are provided to maintain the position of baffle 18 and to maintain the 
required distance of the baffle 18 to the anterior lateral wall 4 and to 
the posterior lateral wall 5, especially in the area of outlet port 3' of 
the chamber 1. 
The dotted lines indicate another curve of baffle 18 at its end located in 
chamber 1 as well as an additional guide hull 24. The returning flow of 
the coating material is deflected around the baffle 18 at the lower end of 
channel 20 by the rounded bottom portion 19' of the baffle 18 and by the 
curved portion of the guide hull 24. The lower end of channel 20 thereby 
deflects the returning flow of the coating material back into the chamber 
1. The angle of divergence, i.e., the angle between the emerging flow of 
coating material from chamber 1 and the returning flow of coating material 
into chamber 1, is less than 90 degrees. In this manner, the least 
possible disruption of the smooth flow within the chamber 1 is achieved 
similar to that in the configuration of FIG. 1. Thus, only the slightest 
drop in pressure occurs. 
In addition, a guide hull 27 consisting preferably of rubber or of a 
slightly elastic, moldable synthetic material which would prevent 
turbulence in the wedge between the chamber opening and the coating blade 
2 is provided. 
As indicated by the arrows, the emerging flow of coating material flows 
outwardly from the chamber 1 into the coating zone 16' through outlet port 
3'. The coating material thereupon contacts the sheet of goods to be 
coated which is carried on counter-roller C and passes through the space 
23 provided between the baffle 18 and the sheet of goods. The coating 
material is then deflected downwardly by coating blade 2 and the returning 
flow of coating material is introduced into the return channel 20. The 
returning flow of coating material then passes between the rounded end 19' 
of baffle 18 and the guide hull 24 and contacts the coating material 
already contained in the chamber 1. 
Having thus described the invention with particular reference to the 
preferred forms thereof, it will be obvious that various changes and 
modifications may be made therein without departing from the spirit and 
scope of the invention as defined by the appended claims.