Lithographic plate processor

Method and apparatus for processing lithographic plate which includes two sprayer/scrubber stations separated by a water rinse. The fluids to be sprayed are continuously circulated through fluid feed tubes provided with externally actuable metering orifices. The valve operators for the orifices are pneumatically operated in a periodic manner to provide even dispersion of the fluid.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to lithographic plate processing 
techniques and more particularly to a metered, periodically actuated fluid 
spray for use in such a processor. 
2. Description of the Prior Art 
In conventional lithographic plate processing techniques, fluids are 
generally brushed or rubbed into the plate to insure an even distribution 
and effectiveness of the fluids. The excess fluid is then typically 
removed from the plate by passing it through a series of squeeze rollers 
and the plate is eventually dried with hot air. 
Typical fluid dispensing and brushing apparatus are illustrated in U.S. 
Pat. No. 3,608,464 to Harrell et al. and U.S. Pat. No. 3,682,078 to Parker 
et al. In these patents, the fluid to be dispensed is pumped from a 
reservoir in through a solenoid valve directly onto the brushing area. 
Since the fluid is dispersed through the brushes themselves, a straight 
through fluid flow is utilized. However, due to the character of the 
fluids which must be used in lithographic plate processing, the direct 
application of the fluid to the brushes is not always satisfactory. Fluid 
suspension may be disrupted due to the filtering action of the brushes. 
Therefore, for some types of fluid, it is more advantageous to apply the 
fluid directly to the plate prior to brushing or rubbing it into the 
surface of the plate. Thus, there has been a need for a technique for 
maintaining the fluid in the proper suspension and properly dispensing it 
onto a lithographic plate prior to rubbing or brushing it into the 
surface. The present invention satisfies that need. 
SUMMARY OF THE INVENTION 
The lithographic plate processing technique of the present invention 
provides a fluid dispensing station in which the fluid to be dispensed is 
continuously maintained in proper suspension and selectively dispensed in 
a manner which maintains that suspension and provides an even coating of 
the lithographic plate prior to the scrubbing operation. Thus, 
lithographic plates processed with the technique provided by the invention 
have more uniform characteristics resulting in higher quality lithographic 
printing. 
The fluid dispensing apparatus of the invention includes a fluid feed tube 
in which a fluid is maintained in continuous flow by means of a reservoir 
and pump. The feed tube is provided with a plurality of metering orifices 
normally closed by valve members externally connected to pistons slidably 
mounted within piston chambers. The pistons are normally spring biased in 
a direction to close said orifices and are movable to open said orifices 
under pneumatic pressure within the piston chambers. The pneumatic 
operation of the metering orifices is preferably done in a periodic manner 
to maintain the agitation in the suspension fluid and to evenly disperse 
thw fluid over the lithographic plate. The piston is limited in its 
pneumatic movement within the piston chamber by means of a metering screw 
mounted concentric with the biasing spring and against which the piston 
abuts when it is at the end of its desired limited movement. 
In an illustrated use two spraying and scrubbing stations are provided 
which are separated by a water rinsing station. In this way, two different 
types of fluid, such as an asphaltum-gum-etch solution, may be applied at 
one station and a gum arabic solution may be applied to the plate at 
another station in a developing process prior to passing the plate through 
the hot air drying station. The scrubbers provided are elongated brush 
members, the ends of which are eccentrically mounted for movement in a 
substantially rotary manner for even scrubbing action. 
These and other features of the present invention will become apparent when 
considered with the detailed description of the presently preferred 
embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning now to the drawings, and particularly FIG. 1 thereof, there is 
illustrated in diagrammatic form a lithographic plate processor 
incorporating the features of the invention. In the illustration, a 
lithographic plate 10 which is ready for processing, moves from a carrier 
12 through a pair of squeeze rollers 14 and 16, past a fluid dispensing 
tube 18, while still being supported by the carrier 12. 
In the presently preferred embodiment of the invention, the fluid 
dispensing tube 18 has a continuous flow of fluid therethrough provided by 
a fluid reservoir 20 which supplies fluid to a pump 22 which pumps the 
fluid through a conduit 24 to the dispensing tube with the fluid returning 
through a conduit 26 to the reservoir 20. The constant circulation of the 
fluid through the dispensing tube 18 insures that the fluid maintains the 
proper suspension of particles. The circulation of the fluid in the 
dispensing tube 18 and rotation of the squeeze rollers is activated by the 
plate 10 engaging one of a pair of microswitches 19 embedded in the 
carrier 12 in front of the rollers 14 and 16 which activates the pumps 22 
and 64 and the system drive motors (not shown) through a control line 21. 
A roller 56 carries on one of its ends a cam 74 which activates a suitable 
cam following device such as a microswitch 76, which periodically 
activates a solenoid valve 80 in a line 81 from an air supply source 83 by 
means of a control line 78. 
The solenoid valve 80 controls the supply of air through the air conduit 82 
to the actuating section 34 of a metering valve to be described below. 
Thus, conduit 82 is also connected to the actuating sections 84 of another 
fluid dispensing tube 60 to be described below. Thus, as the plate 10 
passes beneath the dispensing tube 18, a periodic spray of processing 
fluid is sprayed onto the plate. To prevent loss of fluid, a collecting 
funnel 36 is provided with a drain conduit 38 back to the reservoir 20. 
As the plate 10 moves past the dispensing tube 18, it passes to a scrubbing 
station 40 which includes an upper scrubbing element 42 which is 
eccentrically mounted at its ends, as shown in FIG. 2, and which provides 
a rotary scrubbing motion to scrub the emulsion fluid into the top surface 
of the plate 10. The plate 10 is supported during scrubbing by a backing 
plate 43 suitably ribbed (not shown) to prevent movement of the plate. 
As the plate moves past the scrubbing station 40, it passes between a 
second pair of squeeze rollers 44 and 46 to remove the excess fluid. 
The plate then passes under a water rinse station which includes a water 
sprayer 48 which is connected through a conduit 50 and valve 52 to a water 
supply tank 54. A trough 55 and drain 57 are provided to catch the rinse 
water. The plate 10 is rinsed and then passes through a third pair of 
squeeze rollers 56 and 58 into a second spraying and scrubbing station 
which includes the second fluid dispensing tube 60 typically supplied with 
gum arabic solution through a conduit 62 from a pump 64 connected to 
reservoir 66. Again, a return conduit 68 is provided between the 
dispersion tube 60 and the reservoir 66. Again, a collecting funnel 70 
catches excess solution as the plate 10 moves past the spraying station 
and which is connected through a conduit 72 to the reservoir 66. As for 
the first station, the dispersion of fluid from the tube 60 is controlled 
by the cam 74 on the squeeze roller 56 as described above. Again, the air 
pump 80 supplies pneumatic pulses through a conduit 82 to the actuating 
mechanism 84 of the metering orifice valves, as discussed in detail below. 
From the second spraying station, the plate 10 passes again through a 
scrubbing station 86 including an eccentrically mounted scrubbing element 
88 and a backing plate 89. Following the scrubbing, the plate 10 passes 
through a fourth set of squeeze rollers 90 and 92 to remove the excess 
solution. The plate 10 then passes through a hot air drying station 94 
which includes a blower 96 connected through a duct 98 to an air baffle 
100 to circulate the air around the plate. From the air drying station 94, 
the plate passes through a fifth set of squeeze rollers 102 and 104 to an 
exit tray 106 where the plates are successively stacked. 
FIG. 3 is a diagrammatic perspective view of the eccentric mounting and 
operation of the scrubbing elements 42 and 88 shown in FIGS. 1 and 2 and 
FIG. 4 is a phantom view showing the rotary action of the scrubbing 
element. As can be seen, the ends 108 and 110 of the scrubbing element are 
rotatably pinned through pins 112 and 114 on the peripheries of crank 
disks 116 and 118 which have drive shafts 120 and 122 which are commonly 
rotated by means of pulley wheels 124 and 126 and drive belt 128, the 
whole being rotated by a drive motor 130 through a drive shaft 132 
co-axial with the shaft 122. The shafts 132, 122 and 120 rotate together 
to cause the rotary positional changes illustrated in FIG. 4. 
FIGS. 5, 6 and 7 illustrate the actuating mechanisms (34, 84) and fluid 
metering orifices utilized in the present invention. In particular, an 
actuating mechanism 132 is mounted perpendicular to a fluid dispensing 
tube 134. A pneumatic conduit 136 is connected to each actuating mechanism 
132 with pneumatic communication therewith. The actuating mechanism 132 
includes a mounting section adapted to be mounted on the dispensing tube 
134 by providing a transverse cylindrical surface 140 on one end thereof 
which mates with the cylindrical surface 142 of the tube. The upper end of 
the cylindrical mounting section 138 is externally threaded with the lower 
end of the threaded portion terminating in a rectangular annular groove 
146 for receiving a sealing O-ring 148. The upper end 144 of the mounting 
section 138 also includes an axial bore 150 terminating at its lower end 
with a smaller diameter valve bore 152 which communicates between the bore 
150 and the inside 154 of the tube 134. Diametrically opposite the bore 
152 is a metering or fluid dispensing orifice 156 through the wall of the 
tube 134. The orifice 156 is substantially conically shaped with the apex 
being external of the wall of the tube 134. The orifice 156 is located in 
tube 134 diametrically opposite the valve bore 152 in mounting section 
138, which also extends through the tube 134. 
A cylindrical valve seal fitting 158 is received in the bore 150 and is 
provided at a lower end 160 which abuts a bottom 162 of the bore 150 with 
a shallow counterbore 164 which defines with the bottom 162 an annular 
rectangular recess which is provided with an O ring 166. The fitting 158 
has a diametrically reduced bore 168 adjacent the O-ring seal 166 which is 
the same size as the bore 152 through the wall of the tube 134. The 
fitting 158 further has a bore 170 open to the top of the fitting. The 
fitting 158 also has an external annular groove 172 including a radial 
bore 174 through to the bore 170. Threadably mounted in an axial bore 176 
through the mounting section 138 to the annular groove 172 is a pneumatic 
fitting which can be connected to a source of air pressure. 
Axially mounted through the bore 170 in the fitting through the O-ring seal 
166 and thence through the tubing 134 is a metering pin 178 terminating at 
its lower end in a conically shaped metering point 180 which when in 
contact with the metering orifice 156 closes that orifice. The metering 
pin 178 by means of O-ring 166 effectively seals the inside 154 of the 
tubing 134 from the inside of the fitting 158. 
Mounted atop the metering pin 178 and fixed to it is a piston 182 which 
includes on its external periphery an annular rectangular groove 184 
containing an O-ring 186. A cap 188 including a bore 190 terminating at 
its open end in an internally threaded counterbore 192 is adapted to be 
threadably mounted on the mounting section 138 so that a shoulder 194 
defined by the counterbore 192 engages a flange 196 on the upper end of 
the fitting 158 to lock it in place atop the mounting section 138. The 
lower open end 200 of the cap 188 engages the O-ring 148 to seal the 
inside of the piston chamber 202. 
A valve closing force for the metering orifice 156 is provided by means of 
a compression spring 204 fixed in the piston chamber bore 190 between a 
top surface 206 of the piston 182 and the closed upper end 206 of the bore 
190. In the closed valve position, the spring 204 is under compression, 
which provides the valve closing force. This is the situation illustrated 
in FIG. 6. 
When the valve is opened, air pressure is applied through the pneumatic 
fitting 176 through the bore 174 into the piston chamber defined by the 
bore 190 and bore 170. The pneumatic pressure forces the piston 182 up and 
compresses the spring 204 raising the metering pin 178 to open the metered 
orifice 156. 
Metering is accomplished by means of a metering screw 208 threadably 
mounted in an internally threaded bore 210 concentric with the piston 
chamber 190. With the metering screw 208 in position, the piston can rise 
in the piston chamber 190 only until the end 212 of the screw abuts the 
top surface 205 of the piston. The metering position of the screw is 
maintained in place by means of a lock nut 214 on the metering screw 208 
on a top surface 216 of the cap 188. 
Thus, the metering orifice valve system with its actuating system provides 
positive metered fluid dispensation while maintaining the fluid in proper 
suspension and agitation to provide uniform spraying and application of 
the fluids to the surfaces of a lithographic plate. When combined with he 
scrubbing apparatus of the invention, a uniform coating is applied to a 
succession of lithographic plates, resulting in uniform light sensitivity 
from plate to plate and finally resulting in an overall improved printed 
product. 
While a particular preferred embodiment of the invention has been described 
in detail, it should be appreciated that many structural variations are 
possible so that the scope of the invention is not to be limited, except 
by the following claims.