Apparatus for curtain coating objects

Curtain coater apparatus is disclosed for coating objects wherein the coater head is maintained substantially full of coating material, the material is discharged through an elongated adjustable orifice at a rate to form a stable or unbroken curtain, and an object is conveyed through the curtain at a velocity to deposit a layer of the material of pre-determined thickness onto the object. The heat is provided with a longitudinally split, resilient, metallic, tubular member, with orifice knives carried thereby along the split, one knife being movable by hydraulic actuators with respect to the other knife to define the elongated adjustable orifice. A crank and rack arrangement, carried by the head, is used to adjust the stroke of the hydraulic actuators, and thereby to regulate the orifice width. The tubular member is provided with an elongated filler tube that has a trough in its upper quadrant to distribute the material evenly throughout the entire length of the tubular member, thus reducing turbulence near the entry. The filler tube and the tubular member form passages therebetween, which provide for an increased speed of the material as it approaches the orifice, thereby reducing precipitation of solids. The ends of the tubular member are sealed by end assemblies that accommodate to the changing shape of the tubular member. Windscreens surround the head to protect the curtain. Hydraulic cylinder apparatus is provided which can raise, lower, and level the head longitudinally, and laterally. A narrow receptacle, which minimizes the amount of material used in the coater, and aids in the conveying of small objects, is provided on the conveyor. An hydraulic drive system is utilized to control the curtain coater.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to curtain coater apparatus and more particularly, to 
apparatus for coating objects with fluid material by passing the objects 
through a curtain of the material. 
2. Description of the Prior Art 
A problem associated with conventional curtain coater application heads, 
whether their curtain is formed by forcing coating material through an 
orifice, or over a weir, is that they contain pools that permit solids to 
precipitate from many coating materials used in coating objects. The 
relatively large volume of coating material that is required to fill a 
conventional curtain coater reservoir, pumping unit, and coating head, 
must be re-circulated many times as it is slowly used. Multiple 
re-circulation of a large volume of coating material causes degradation of 
the material. The two exposed surfaces of the curtain, and force 
circulation of air that safety precautions require for solvent vapor 
removal, necessitates on-line mixing to maintain proper solid content for 
process control. However, accurate monitoring of viscosity is complicated 
by evaporation cooling. Furthermore, it becomes unreliable as an indicator 
of solid content if viscosity changes as a result of the mechanical 
agitation and heat generated by re-circulation of coating material through 
a pump, filter, and a curtain-forming orifice. Significant, too, are 
evaporation rates of the constituents of a blended solvent. As evaporated 
solvent is replaced in response to an increase in viscosity, the system 
becomes progressively richer in that constituent which evaporates more 
slowly. Because a given volume of one constituent has a different effect 
on viscosity than another, viscosity again becomes a poor indicator of 
solid content. Moreover, as the system becomes richer in the slower 
evaporating solvent constituent, its drying characteristics change. 
Conventional curtain coaters generally are indifferent to such 
time-associated deterioration of coating materials. 
Prior curtain coaters also failed to provide for safety of operation. The 
conveyors of such apparatus characteristically travel at relatively high 
speed and have considerable inertia, but are not provided with means for 
emergency stops. In this regard, the positive pumping units utilized in 
such prior curtain coaters were not provided with relief valves. Relief 
valves were omitted because of the clean-up problem involved in their use, 
and where hot-melt coating materials were used, the valves ceased to 
function when most needed, for example, when the coating materials became 
cold and solidified. 
Another major problem associated with prior art curtain coaters is that of 
turbulence created at the point of entry of the coating material into the 
curtain coater heads, which adversely affects the uniformity of the 
curtain produced. 
A large percentage of the operator's time is spent in cleaning a 
conventional coater. Rather than simplifying the clean-up process, 
conventional coaters have been provided with multiple coater heads, 
pivoting over single, or multiple troughs, or with exchangeable center 
sections, so that the time consuming clean-up process can take place 
off-line. 
Moreover, when one considers that a conventional coater is cleaned by 
filling it with solvent and re-circulating, then draining, refilling, and 
re-circulating until it is washed clean, the magnitude of the fire hazard, 
the air pollution, and the health hazard to the operator can be readily 
appreciated. 
Example of prior art devices are revealed in U.S. Pat. Nos. 2,935,424; 
2,963,002; 2,976,837; 3,067,060; 3,088,633; 3,132,968; 3,205,089; 
3,299,195 and 3,468,099. 
SUMMARY OF THE INVENTION 
Apparatus for coating objects with material which involves maintaining the 
head of a curtain coater full of the material, discharging the material 
through an elongated adjustable orifice at a rate to form an unbroken 
curtain, and conveying the objects through the curtain at a velocity to 
deposit a layer of the material of predetermined thickness. 
Accordingly, one object of the invention is the provision of curtain coater 
apparatus which is safe to operate, has on-off capability of one portion 
relative to another, and can be quickly stopped. 
One other object is to provide curtain coater apparatus wherein the coating 
head can be hydraulically supported, and its height readily adjusted. 
Another object is the provision of curtain coater apparatus which 
eliminates movable knives retained by spring loaded cap screws, wherein a 
balance must be found between sufficiently heavy loading to prevent leaks, 
and sufficiently light loading to permit sliding of the movable knife over 
a gasket on the surface to which it attaches. 
Another object is the provision of a curtain coater apparatus utilizing 
orifice-forming, relatively movable knives, which readily permits 
alignment of the movable knife relative to the fixed knife so that the 
curtain-forming orifice defined by the knives is of uniform width. 
Another object is the provision of a curtain coater apparatus that readily 
permits exact duplication of orifice adjustment, and that readily permits 
opening of the orifice for cleaning and returning to its prior setting. 
Another object is the provision of a curtain coater apparatus with pressure 
relief apparatus in the coating material circulation system to prevent 
damage to a pressure head, pump, or connecting lines. 
Another object is the provision of a curtain coater apparatus having 
pressure relief apparatus in the coating material circulation system which 
is so located that it is not exposed directly to the coating material, and 
therefore does not require clean-up. 
One other object is the provision of a coating head which is readily 
accessible for cleaning, and wherein turbulence at the point of entry of 
coating material is reduced to provide a uniform curtain of the material. 
Still another object of the present invention is the provision of curtain 
coater apparatus with a head capable of producing a curtain of material 
which minimizes the entrapment of air. 
Another object is the provision of curtain coater apparatus which 
eliminates the need for material viscosity monitoring, and solvent make-up 
equipment. 
One other object is the provision of curtain coater apparatus which can be 
intermittently operated. 
Still other objects, advantages, and features of the present invention will 
become more fully apparent as the description proceeds.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1-3, curtain coater apparatus 10 of the present 
invention generally comprises a conveyor 12 having a pair of side frames 
22 and 24. A belt 23 is positioned around a plurality of rollers 25-32, 
mounted for rotation between conveyor frames 22 and 24. A fluid motor 34 
is secured to frame 22, and drives roller 25, to move belt 23 for 
conveying an object 36 thereon, under a head 38, for coating with material 
flowing from the head. A power unit 39, for supplying fluid under 
pressure, is positioned in the vicinity of conveyor 12. A control console 
41 for controlling operation of the curtain coater apparatus 10 is 
provided on frame 24. 
Head 38, best shown in FIGS. 4-6, 7A and 7B, comprises a longitudinally 
split, resilient, metallic tube 42, positioned within head supporting 
brackets 43-49, and to which orifice knife carrying members 52 and 53 are 
attached. 
Outboard member 52 carries a fixed orifice knife 56, secured thereto by a 
clamp 57, fastened as by cap screws (not shown). Inboard member 53 carries 
a movable orifice knife 58, also suitably secured by a clamp 59. Fixed and 
movable orifice knives 56 and 58 define an orifice, or slot 60, positioned 
over, and across belt 23, grooves are machined into the knives to prevent 
coating material from accumulating on their orifice edges. Flat gaskets 62 
and 64 of Teflon or the like, having enlarged edges 66 and 68, 
respectively, are positioned in grooves 70 and 72, to provide sealing 
between members 52 and 53, and respective knives 56 and 58. Restraint of 
seal edges 74 and 76 is also provided, so that flow of coating material 
above the curtain coating orifice 60 is not obstructed. 
The position of movable knife 58, which is controlled by a plurality of 
similar, adjustable stroke, hydraulic actuators 80-84, mounted on head 38, 
determines the width of orifice opening 60. Positioning of knife 58 is 
accomplished by turning hand crank 86, and gear 87 thereon, to cause 
control shaft 88 with upper rack 89 to translate. Translation of a lower 
mounted rack 94 through a distance equal to its pitch, or tooth spacing, 
for example, causes gears 90, which are threadedly secured on rear piston 
rods 92 of actuators 80-84, to move along the axes of those rods, and 
thereby change the length of each of their strokes by an exemplary 
distance of 0.001 inches. Because inner rods 95 are threaded into member 
53, which carries movable knife 58, the width of orifice 60 is similarly 
changed. 
After a desired setting is made, orifice 60 may be fully opened, and then 
returned to that setting by actuating hydraulic control valve 96, which is 
adapted to be connected to a source of fluid pressure, to be hereinafter 
more fully described, to apply fluid pressure simultaneously to one face 
of actuator pistons 97, and then to the other, by means of fluid conduit 
lines 98 and 99. In this manner, orifice 60 can be fully opened to clear 
obstructions, when desired. 
The strokes of actuators 80-84 are accommodated by the transverse sliding 
of the teeth of gears 90 across the teeth of lower rack 94. 
Normally, once positioned, knives 56 and 58 need not be disturbed. However, 
if it becomes necessary to remove knives 56 and 58, they can be exactly 
repositioned by first aligning their ends, and those of clamps 57 and 59, 
with the ends of members 52 and 53. The securing cap screws (not shown) of 
clamps 57 and 59 are finger-tightened. Gears 90 are then turned so that 
they will not abut the frame of head 38 when knives 56 and 58 are closed. 
Control valve 96 is now actuated to close knives 56 and 58, and while thus 
held firmly together by actuators 80-84, the clamp cap screws (not shown) 
are tightened. Gear 87 on hand crank 86 is then disengaged, and gears 90 
are turned until they abut the frame of head 38. Shaft 88 is positioned 
with its end abutting stop-screw 91, and gears 90 are simultaneously 
engaged by bottom rack 94. With gear 87 still disengaged, hand crank 86 is 
rotated until the "0" mils mark 93 on a scale (not shown), on the hub of 
gear 87, aligns with index mark 95 on head 38. Gear 87 is then engaged, 
and secured with thumb screw 101. 
Knives 56 and 58 are now held at zero orifice width by actuators 80-84. 
Gears 90 on actuators 80-84 are set at zero clearance from head 38. 
Control shaft 88 has zero clearance with stop-screw 91, and zero indexing 
is obtained. Thus, as hand crank 86 is turned, movement equal to one tooth 
causes gears 90 on actuators 80-84 to reduce their strokes by an exemplary 
one mil. The reading on the scale (not shown), on the hub of gear 87, at 
index mark 95, indicates the total reduction in length of stroke, which 
equals the width, in mils, of orifice 60. Thus, actuators 80-84 hold 
moveable knife 58 in precise alignment with, and at a precise distance 
from, fixed knife 56. 
Turbulence at the point of entry of coating material into a conventional 
curtain coater head adversely affects the uniformity of the curtain 
formed. In head 38 of the present invention there is provided a filler 
tube 100 having an upper quadrant outer surface 102 forming a trough for 
evenly distributing coating material thoughout the length of head 38. One 
end of tube 100 is provided with an inwardly tapered surface portion 103, 
terminating in a flat portion 105, and forming with upper quadrant inner 
surface 107, an end cavity 109. Surfaces 102 and 107 form a lip 111, at 
the one end of tube 100. The other end of tube 100 is similar, but has no 
lip corresponding to lip 111. 
Passageways 106 and 108, provided within head 38, between filler tube 100 
and tube 42, conduct the coating material at a relatively high velocity, 
from trough 102, into chamber 110, above the orifice forming knives 56 and 
58. By the time the coating material is forced through orifice 60, 
irregularities in its flow will have dissipated, and curtain 112 will be 
uniform across the width of orifice 60. Guide members 113 are positioned 
and movably attached adjacent the opposite ends of orifice 60 (see FIG. 
8A) and function to provide guide members along which the lateral edges of 
curtain 112 can travel and to move free of part 36 on contact. The upper 
ends of guide members 113 pass through apertures 159 (see FIG. 8A) with 
their heads 114 being biased outwardly by springs 115. The guide members 
113 may be readily removed for cleaning by manually compressing the 
springs 115. The relatively high velocity of the small volume of coating 
material that is within head 38 at a given time minimizes the opportunity 
for solids to precipitate. Passageways 106 and 108 are so shaped that 
there are no ledges, or crevices to promote accumulation of solids. The 
flattest surfaces within resilient tube 42 have approximately 45.degree. 
slopes which are constantly washed by the coating material. 
The ends of tube 42 are closed by removable assemblies 116 and 117, best 
shown in FIGS. 5 and 5A, which provide sealing that accommodates to the 
varying shape of tube 42, as the settings of orifice 60 change. Assembly 
116 consists of an end flange 118 having a cylindrical portion 120 
carrying a piston 122. A tapered member 124 is positioned on one face 123 
of piston 122, and secured thereto, as by screws 126. A flat Teflon, or 
like material, gasket 127 is positioned intermediate face 123, and tapered 
member 124. Piston 122 is spring biased toward resilient tube 42, as by an 
arrangement of a spring 130 and bolt 132, threadedly engaged in flange 
118. A flat Teflon washer 137 is retained between bolt head 134 and end 
flange 118 to seal the threads. Flange 118 is connected to bracket 43 by a 
plurality of nut and stud arrangements 136. Gasket 127, on face 123 of 
piston 122, abuts the end of tube 42 to effect sealing therebetween due in 
part to the urging of spring 130. As tapered member 124 is received in 
cavity 109, in the one end of filler tube 100, the tapered member and the 
tube become substantially concentric, thus defining passgeways 106 and 
108. A passageway for the flow of coating material to trough 102 is formed 
by substantially coaxial openings 138, 140, and 142, through tapered 
member 124, piston 122, and flange 118, respectively. The lip 111, formed 
by surface 102 and 107, at the one end of filler tube 100, enters a cavity 
143 in tapered member 124 to restrain the filler tube from rotating about 
its axis and thereby to maintain trough 102 alignment with openings 138 
and 140. Pipe 144 supplying coating material is fastened, as by welding 
around opening 142, in flange 118. Pipe 144 enters the enlarged portion 
145 of opening 140 in piston 122 so as to prevent the rotation of the 
piston relative to cylinder 120. Consequently, trough 102 is maintained in 
substantial coaxial alignment with openings 138, 140, and 142. 
Although the hydraulic pressure of the coating material is substantially 
equal on both faces 123 and 125 of piston 122, the effective area of face 
125 is greater, which results in a differential force urging piston 122 
toward flexible tube 42, further to effect sealing. Spring 130 need urge 
piston 122 and its associated parts against the end of tube 42 with no 
greater force than that required to establish sealing. As the pressure to 
be contained in tube 42 increases, the force resulting from the hydraulic 
imbalance increases to provide the necessary sealing. 
An O-ring gasket 135 is carried in a groove in cylinder 120 to effect 
sealing between piston 122 and the cylinder, so as to prevent leakage of 
coating material from the cylinder. Screw 132 is provided with a 
hexagon-shaped socket 139 in its exposed end to receive an Allen wrench, 
for rotation, by means of which it is moved inward, to push piston 122 out 
of cylinder 120, so that all surfaces exposed to coating material are 
readily accessible for thorough cleaning. 
Removal of end seal assemblies 116 and 117 makes accessible the interior of 
tubular member 42 for cleaning. 
Assembly 117 is similar to assembly 116, and like numerals designate like 
parts, as illustrated in FIG. 5A. Since the other end of tube 100 does not 
have a lip corresponding to the lip 111, tapered member 124 of assembly 
117 is not provided with a cavity similar to the cavity 143 of tapered 
member 124 in assembly 116. 
Windscreens are provided to surround the curtain 112, below the 
curtain-forming orifice 60. A portion 150 of a drip pan 152 serves as an 
infeed screen. Drip pan 152 is positioned beneath hydraulic knife 
actuating cylinders 80-84. 
In the event of a leak in cylinders 80-84, oil is caught and drained to the 
side of the curtain coater apparatus 10. Outfeed screen 153 is a 
replaceable, transparent, plastic window, carried in a suitable holder 
154, attached to member 52, as by nut and stud arrangements 156, and the 
bar 158. End screens 160 are secured to flange 118 by nut and stud 
arrangement 136. 
Referring to FIG. 8, the height and lateral levelness of coating head 38 is 
readily adjustable by a pair of similar, supporting, equalized hydraulic 
actuators 164, mounted on frames 22 and 24, and vibration-absorbing mounts 
168, and 170. Each actuator 164 has a piston rod 172, with a tapped hole, 
to receive a cap screw 174, passing through an orifice 177 in a plate 176, 
resilient mounting member 168, and a plate 175. Plate 176 is mounted on 
head 38, as by recessed cap screws 178. Vibration-absorbing mounting 
member 168 is fashioned from Neoprene, or the like, and is fastened to 
plate 176 by screws 180. Member 170 is attached to the top surface of 
plate 175 by bolt and nut arrangements 186, and is fashioned from material 
similar to member 168. A stud 188 is locked by means by jam nut 190 into 
plate 176. stud 188 projects downward from plate 176 through a clearance 
bushing in member 170. A wing nut 192, threadedly engaged with stud 188, 
bears against the top surface of the bushing, and can be rotated in one 
direction, against member 170, to urge stud 188 and the end of plate 176 
in an upward direction. 
Rotation of nut 192 in the opposite direction, away from mount 170, serves 
to urge the bolt away from plate 176, resulting in a lowering of the plate 
end. Manipulation of nuts 192, as hereinbefore set forth, can be utilized 
to provide lateral leveling of head 38, as desired. 
A receptacle 196, best shown in FIG. 9, receives that portion of the 
curtain 112 not intercepted by object 36. A baffle plate 198, which 
prevents splashing of coating material, covers the upper portion of a 
trough 200 of receptacle 196. A cavity with a sloped bottom, below plate 
198, serves as a reservoir 202. Flow of coating material through trough 
200, which is flat sided, and relatively narrow, into reservoir 202, 
provides sufficient agitation of the material to prevent the settling of 
solids. The relatively small surface area of the coating material reduces 
evaporation of the material solvent. Plate 198 is perforated at 204, in 
the area where the curtain 112 impinges, to permit the coating material to 
flow into reservoir 202, and to prevent objects from falling into the 
reservoir. A wire grid 206, positioned over trough 200, and reservoir 202, 
facilitates the passage of small objects to be coated over the coating 
area. Flanges 208, having holes 210, which accommodate studs 212 on the 
frames 22 and 24, serve to position receptacle 196 on conveyor 12, between 
pulleys 27 and 30. Bolts 214 are threaded through flanges 208, and bear 
against frames 22, and 24, and serve to level receptacle 196. Receptacle 
196 is additionally provided with coating material inlet 218 and outlet 
216. 
Reference is again made to FIG. 1. Provided on frame 24 are fluid pump 220, 
and fluid motor actuator 222, for rotating the pump through belt 224, and 
pulleys 226, and 228. One end of pump 220 is connected, by means of a 
threeway valve 230, through a conduit 232, to a source of coating material 
234, and through a conduit 236 to head 38. The other end of pump 220 is 
connected, through conduit 238, to fitting 216 of receptacle 196, FIG. 9. 
Pump 220 is preferably of the helical screw type, which can pump coating 
material equally well in either direction, depending on the direction of 
rotation of motor 222. 
Reference is now made to FIG. 10 wherein the hydraulic fluid system 240 of 
the present invention is shown in detail. Power unit 39 consists of a pair 
of fluid pumps 242, and 244, driven by an electric motor 246, a source of 
fluid 248, such as oil, an emergency stop valve 250, and a fluid filter 
252. 
A fluid circuit is provided wherein pump 242 is suitably connected, through 
orifice control valve 96, to knife actuators 80-84. Also, fluid circuit 
connection is made through a spring-centered head control valve 256, to 
head support actuators 164, to provide fluid for raising, holding, 
lowering, and leveling of head 38. A flow divider 258 is provided in the 
circuit, which directs essentially one-half of the total fluid flow to 
each of the two actuators 164. A pilot-operated check valve 260 is 
included, which serves to maintain head 38 at an intermediate level, while 
two relief valves 262 and 264 provide for the longitudinal leveling of 
head 38. 
Another circuit is suitable connected to utilize fluid from pump 242 to 
drive motor 222, which actuates pump 220. A pump control valve 268 and 
speed control 270 are provided for controlling motor 222. A gauge 272 for 
measuring fluid line pressure is included in the fluid circuit. 
Pump 244, suitably connected, supplies fluid pressure to belt drive motor 
34, through belt control valve 274. Provided in the belt drive fluid 
circuit is a belt speed controller 276, a relief valve 278, a check valve 
280, and an emergency stop valve 250. A gauge 282 measures the line 
pressure in the belt drive circuit. Relief valve 278 cushions the circuit 
when emergency stop valve 250 is operated. 
Both controllers 270 and 276 are throttle valves, which provide a 
predetermined fluid flow rate regardless of changes in pressure or 
temperature. 
Pumps 242 and 244 are pressure-compensated and deliver that volume of oil 
that valves 270 and 276, respectively, are adjusted to pass while 
maintaining predetermined pressures. If either of the valves 270 or 276 is 
closed, its respective pump will relieve internally. 
Referring again to FIGS. 7A and 7B, there is shown a three-way valve 288 
carried by head 38, which, when operated by valve controller 286, serves 
to apply air pressure from a source (not shown) to a valve actuator 289 
through lines 290, 291, and 292. A gauge 294 is utilized for measuring 
line pressure in the actuator circuit. Normally, valve control 286 is 
outwardly spring biased, and rides in a groove (not shown), provided on 
control shaft 88. As long as shaft 88 occupies a position, as shown, which 
corresponds to an opened orifice 60, valve 288 remains open, and air 
pressure is applied to actuator 289 to close the valve 295, which 
interconnects inlet 144 of assembly 117, and conduit 293. However, when 
shaft 88 is positioned with its end abutting screw 91, providing zero 
width to orifice 60, controller 286 is urged out of the groove (not 
shown), and opens valve 288 to exhaust air pressure from actuator 289. 
Actuator 289 now opens valve 295, which remains open as long as shaft 88 
abuts screw 91. 
A substantially linear relationship exists between the speed of pump 220 
pumping coating material, the speed of belt 23 conveying the article 36 to 
be coated, and the thickness of the coating of material applied to the 
article. Generally, doubling pump speed requires the doubling of belt 
speed to maintain a pre-determined coating thickness. 
From a curtain coater, constructed in accordance with the present 
invention, wherein the curtain 112 width was 53.8 inches, drive pulley 25 
for belt 23 had a 6 inch diameter, and pump 220 was capable of pumping 
2.02 gallons of coating material for every 100 revolutions, the graph of 
FIG. 11 was derived, relating coating thickness T, in mils, to the belt 
speed (RPM.sub.B), in revolutions per minute, and the pump speed 
(RPM.sub.p), in revolutions per minute. 
Operation of curtain coater 10 can best be understood by having reference 
mainly to FIG. 10. Initially, to prepare the coater 10 for coating an 
object, orifice adjust control handle 86 is rotated to position mark 93 
opposite index 95, which corresponds to a zero opening of orifice 60. 
Orifice control valve 96 is set to the "CLOSE" position. Belt control 
valve 274 is set to "OFF." Pump control valve 268 is set to "ALIGN," the 
position which provides no fluid flow to pump actuator motor 222, and 
accordingly, no rotation of pump 220 in either direction. Pump speed valve 
270 is set to an arbitrary position, for example, one that would provide 
approximately 250 RPM to pump 220, when motor 222 is actuated. 
Next, the control lever of coating valve 230 is set to open conduit 232 to 
pump 220, and the start switch (not shown) is operated to start motor 246, 
which actuates pumps 242 and 244 of power unit 39. 
At this point, to avoid spilling coating material onto belt 23, and 
automatically to level head 38, head control valve 256 is held in the 
"Down" position, which supplies fluid under pressure from pump 242 to 
cylinders 164, in such a direction to effect lowering of head 38. After 
head 38 has bottomed, valve 256 is held in the "DOWN" position for a few 
seconds, to allow relief valves 262 and 264 to effect the automatic 
leveling. 
Pump 220 is now primed by pouring approximately one quart, for example, of 
the coating material into reservoir 202. Pump control valve 268 is then 
moved to the "FILL" position, which supplies fluid under pressure, from 
pump 242, in such a direction, as to rotate fluid motor 222 to actuate 
pump 220 to draw coating material from source 234, through conduit 232, 
valve 230, pump 220, conduit 238, and into reservoir 202. When the coating 
material in reservoir 202 reaches a level which covers slots 204 of baffle 
plate 198, pump control valve 268 is then moved to the "ALIGN" position, 
which stops supply of fluid pressure to motor 222, and consequently stops 
pump 220. 
Three-way coating valve 230 is now positioned to open conduit 236 to head 
38, and pump control valve 268 is moved to the "COAT" position. Motor 222 
rotates in the opposite direction, and pump 220 drives the coating 
material from reservoir 202, through conduit 236, to head 38. As head 38 
fills with material, air is discharged through valve 295, conduit 293, and 
into reservoir 202. 
When head 38 has completely filled with coating material, pump control 
valve 268 is moved to the "ALIGN" position, three-way valve 230 is 
positioned to open conduit 232, and pump control valve 268 is moved to 
"FILL." Coater material again flows from container 234, through conduit 
232, valve 230, pump 220, and into reservoir 202. When the material again 
rises to cover slots 204, coater 10 is fully filled. 
Pump control valve 268 is next moved to "ALIGN," three-way valve 230 is 
moved to connect pump 220, through conduit 236, to head 38, and valve 268 
is then moved to the "COAT" position. Material now circulates from pump 
220, through head 38, by-pass valve 295, line 293, into reservoir 202, and 
returns through line 238 to pump 220. 
Next, orifice adjust handle 86 is moved to open orifice 60 and to close 
bypass valve 295, and pump speed controller 270 is adjusted to provide 
pump 220 the minimum speed sufficient to form a stable curtain of the 
material passing through orifice 60. Because coating material pump 220 is 
of the positive displacement type, and all the material that is pumped to 
head 38 must come out through orifice 60, adjustment of the width of 
orifice 60 has virtually no effect upon the quantity of coating material 
applied to object 36. With a given speed of pump 220, adjustment of the 
width of orifice 60 primarily controls the initial downward velocity 
imparted to curtain 112 to accommodate a particular coating material and 
object. The relationship between the speed of pump 220, and the width of 
orifice 60, determines the stability of the curtain. The relationship 
between the speed of pump 220, and the speed of belt 23, determines the 
coating thickness. 
The height of head 38 should now be adjusted by operating valve 256 so that 
object 36, for example, will clear windscreens 150 and 153 by a minimum of 
1/2 inch. Generally, highly contoured objects 36 require greater 
clearance. 
The value of the setting of pump speed regulator 270 is now determined, and 
read on coating thickness graph, FIG. 11, from which the corresponding 
setting of belt speed regulator 276 for a thickness T can be obtained. 
Regulator 276 is now adjusted to this setting, and belt control valve 274 
is moved to the "ON" position. 
At this point in operation, an object 36 is allowed to pass through curtain 
112, and if the curtain breaks, the width of orifice 60 is narrowed to 
impart greater initial downward velocity to curtain 112 or the height of 
head 38 above belt 23 is increased to provide "stretch" in the curtain, to 
accommodate for a difference in the velocity of curtain 112, and the 
velocity of object 36. 
The downward velocity of curtain 112, and the horizontal velocity of object 
36, need not be precisely synchronized, to lay a curtain smoothly onto 
object 36, at a precisely controlled thickness. The magnitude of the 
difference that can be tolerated depends upon the elasticity of the 
coating material, and the shape of object 36. 
If neither a narrower width of orifice 60, nor an increase in the height of 
head 38, eliminates breaks in curtain 112, the speed of pump 220 should be 
increased, with a corresponding increase in the speed of belt 23, as 
provided for in FIG. 11. 
For optimum operation, a combination of a narrower orifice 60, an increase 
in the height of head 38, and increased speeds of pump 220 and belt 23 may 
be required in certain instances. For example, when coating viscous, 
stringy material, such as Neoprene adhesive, head 38 is generally raised 
well above belt 23, the relationship of the speed of pump 220, and the 
width of orifice 60, is such that a considerable initial downward velocity 
is imparted to curtain 112 to avoid entrapping large bubbles of air 
between curtain 112 and object 36. 
Finally, after an unknown curtain 112 has been formed, objects 36 can be 
passed through the curtain on a mass production basis, with ocassional 
spot checks to determine the film thickness T being applied to the 
objects. 
If a particle of foreign matter causes a break in curtain 112, the orifice 
control valve 96 is moved from "CLOSE" to "OPEN" to dislodge the particle. 
Upon returning the valve 96 to "CLOSE" position the movable knife 58 will 
return to its preset position to reestablish orifice 60. 
The curtain coater 10 of the present invention can be placed into a 
stand-by mode for a limited time, which varies with different coating 
materials, and quantity of coating material contained in the coater, when 
placed on stand-by. To place the coater 10 into a stand-by mode, belt 
control valve 274 is moved to the "OFF" position, pump control valve 268 
to "COAT," pump speed control 270 is set so that pump 220 delivers 
approximately three gallons of material per minute, orifice control handle 
86 is set to "0" mils, and orifice control valve 96 is positioned to 
"CLOSE". By-pass valve 295 opens automatically, and the coating material 
slowly circulates through head 38, conduit 293, reservoir 202, conduit 
238, pump 220, valve 230, and conduit 236, to hold particles in 
suspension. 
While there has been illustrated a preferred embodiment of the invention, 
it will be readily understood that various modifications and changes may 
be made therein without departing from the spirit of the invention or the 
scope of the following claims.