The present invention is a criss-cross flow hopper which provides even fluid distribution. The flow hopper includes the first and second hopper half each having a planar surface and a cavity which cooperate to form an inner chamber and an exit slot. A first and second insert are securable to each hopper half in the cavity. These non-contacting inserts form within the chamber first and second half flow slots which direct fluid away from the exit slot but then the fluid combines in a damping chamber bounded by the inserts. The fluid is then directed to the exit slot to the substrate to be coated.

FIELD OF THE INVENTION 
The present invention relates to coating hoppers and more particularly to 
an apparatus for achieving uniform flow distribution in coating hoppers. 
BACKGROUND OF THE INVENTION 
In conventional coating hoppers, including those used for supplying 
photographic emulsions, material flow into the hopper is either center fed 
or end fed. In both flow patterns, achieving adequate widthwise flow 
distribution is a problem. To accomplish adequate widthwise flow 
distribution, contouring of the manifold and lips is often provided. The 
contouring is needed to offset the pressure loss which occurs between the 
inlet in the far end of the manifold. Properly done, the method is 
adequate for a specific set of fluids and flow conditions. However, a 
change in flow conditions or fluids will typically alter the pressure 
relationship in the manifold and create unacceptable flow distribution. 
Rather than contouring the manifold, a different flow path or flow circuit 
has been shown to evenly distribute the pressure of the fluid. One such 
flow circuit is a criss-cross circuit. However, the added complexity of 
the passages needed in the hopper body requires special methods of hopper 
construction which include maintaining the mechanical stability of the 
delivery slot. 
Prior art attempts to solve the above problem are disclosed in U.S. Pat. 
Nos. 4,344,907; 4,552,521; 4,619,802 and 4,789,513. Each of the 
aforementioned references disclose the use of inserts for a dye for the 
purpose of combining two or more materials. However, none of these patents 
teach improvements in total flow uniformity. Other patents, for example 
U.S. Pat. Nos. 4,017,240; 4,411,614 and 4,826,422 each use some sort of 
insert to achieve flow uniformity of a single stream. However, the '240 
and '614 references do not show appreciation for the specific problem 
faced by the applicant because they teach branching the flow into various 
channels which all empty into a final damping cavity. The '422 patent 
achieves its results by branching the flow into layers that overlap when 
they recombine in the damping cavity. 
Furthermore, U.S. Ser. No. 08/098,179 filed Jul. 28, 1993 teaches the use 
of inserts to achieve uniform flow in a criss-cross hopper. However, the 
inserts used in this hopper can affect the gauging of the delivery slot. 
Accordingly, the present invention presents an apparatus for achieving 
uniform flow distribution in a criss-cross hopper while providing a final 
slot dimension that is very accurate, even after repeated disassembly and 
reassembly. 
SUMMARY OF THE INVENTION 
The present invention describes a criss-cross flow hopper which includes a 
first hopper half having a first planar surface, the planar surface 
adjoining a first cavity having an exit end and an entrance end, the 
cavity having a first widthwise flow distribution channel positioned 
between the entrance end and the exit end. A second hopper half is 
included which has a second planar surface, the planar surface adjoining a 
second cavity having an exit end and an entrance end, the cavity having a 
second widthwise flow distribution channel positioned between the entrance 
end and the exit end wherein the first and second hopper halves cooperate 
to form an exit slot bounded by the first and second planar surfaces and a 
chamber bounded by the first and second cavities. A first insert is 
provided which is securable to the first cavity at a position between the 
exit end the first widthwise distribution channel. A second insert is 
provided which is securable to the second cavity at a position between the 
exit end and the second widthwise distribution channel wherein the first 
and second hopper halves and the first and second inserts cooperate to 
form a damping chamber bounded by said first and second inserts which do 
not contact each other and in fluid communication with the exit slot 
wherein when liquid flows through said first and second widthwise 
distribution channels, the liquid is directed toward the entrance end 
through the damping chamber and through the exit slot.

For a better understanding of the present invention, together with other 
advantages and capabilities thereof, reference is made to the following 
detailed description and appended claims in connection with the 
above-described drawings. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The complexity of the criss-cross flow circuit for even distribution of 
fluid requires inserts in the hopper or the dye cavity if the hopper is to 
be made of only two halves. The hopper constructed of two halves is very 
desirable from the standpoint of gauging of the final slot; accurate 
gauging of the final slot is a critical component in making uniform 
coatings. The current method for providing inserts requires that inserts 
form part of the gauging land area. As such repeated removal, for example, 
for cleaning the hopper, as this repeated disturbance would eventually 
destroy the very fine precision required for the final slot (25 micro inch 
uniformity). 
Removable inserts made of rubber or Teflon have been suggested in U.S. Ser. 
No. 08/098,179 filed Jul. 28, 1993 as an alternative which will not affect 
the gauging of the final slot. The soft rubber or Teflon can be clamped in 
the inner cavity at low enough forces to not greatly affect the gauging of 
the final slot. However, the inner slot formed by the inserts will not be 
as accurate and some disruption of the gauging is inevitable. 
An insert design arrangement for a criss-cross hopper is shown in FIGS. 
1-6. The numbering of the elements in each of FIGS. 1-6 is the same. FIG. 
1 shows a face view of the body piece 11 and cover piece 10. FIG. 2 is an 
enlarged view of an end section of the body piece 11. FIG. 3 shows the 
body piece 11 and cover piece 10 connected together, preferably by bolts 
29. The body piece 11 and cover piece 10 form a main cavity 51. The main 
cavity 51 is in fluid communication with delivery slot 13 which is bounded 
by planar surfaces 20 and 21 on the body and cover piece. The delivery slot 
is formed at the exit end of the hopper. 
Fluid is supplied through passageway 90 in body 11 positioned at the 
entrance end 92 of the hopper. Passageway 90 connects to delivery cavity 
19. Delivery cavity 19 splits the flow in half and is formed in the land 
area 18 (FIGS. 1 and 2) of the main body piece 11 and land area 48 (FIGS. 
1 and 4) of the cover piece 10 and not in the distribution cavity as 
described in U.S. patent application Ser. No. 08/098,179 filed Jul. 28, 
1993. 
Inserts 24 and 25 are secured to the body and cover pieces within the main 
cavity 51. The inserts 24 and 25 are mounted to the body and cover piece 
by blind screws 40. The inserts form slots 42 and 43 within the main 
cavity 51. 
A damping chamber 30 is formed within the main cavity which is bounded by 
the outer surfaces of the inserts. Fluid is supplied to the slots 42 and 
43 by the tapered half flow distribution channels 14, 15 which are 
contained in the inserts 24, 25. Passages 22 and 23 connect the delivery 
cavity 19 to the tapered half flow distribution channels 14, 15 at 
opposite sides 31, 32 of the hopper. This is shown clearly in FIGS. 2, 4, 
5 and 6 which show enlarged views of each side 31, 32 of the body piece 
11. At end 31 in FIG. 2, the delivery cavity 19 is connected to the 
widthwise distribution channel 14. FIG. 5 shows that passage 22 is in 
fluid communication with distribution channel 14. FIG. 6 shows that 
distribution channel 14 is bounded by the insert 24 and the wall of the 
body piece. 
Flow of the fluid in the hopper proceeds through passageway 90 where it is 
split in cavity 19 with half the fluid flowing toward one side 31 of the 
hopper and half flowing towards the other side 32 of the hopper. Passages 
22 and 23 connect each half flow in cavity 19 with the widthwise 
distribution channels 14 and 15. The fluid is then directed toward the 
entrance end 92 of the hopper through slots 42 and 43 on each side of the 
hopper. The flows from each slot 42 and 43 merge and are directed toward 
the exit end through damping chamber 30 and delivery slot 13. 
The impinging and reversing of the half flows also provides improved 
distribution in that any uneven momentum will be redistributed when the 
flow is turned at the entrance end of the hopper where the two flows 
impinge. Current art teaches, whether end fed or center fed, a single 
continuous flow path so that flow impingement is not possible. Current art 
does teach the advantage of momentum distribution by adding internal slots 
for impingement of fluid and hopper parts, but not fluid opposed to fluid 
as shown by this invention. 
The inserts can be easily removed and replaced. This facilitates cleaning 
the hopper cavities. The cleaning can be done by scrubbing and can be 
visually inspected. 
The inserts can be made of titanium or some material as the hopper body and 
cover for maximum accuracy. 
Placing the delivery cavity 19 in the land areas of the body 11 and cover 
10 make it accessible to easy cleaning upon removal of the cover 10. The 
delivery cavity is machined in equal halves in the body 11 and the cover 
10. Sealing of the delivery cavity is ensured by locating it in the land 
areas 18, 21 which must be compressed when the cover 10 is bolted to the 
body. 
While there has been shown and described what are at present considered the 
preferred embodiments of the invention, it will be obvious to those skilled 
in the art that various changes, alterations and modifications may be made 
therein without departing from the scope of the invention.