Inking System for Printing Machines

It has been known in the past that temperature has a major effect upon the printing process, the temperature depending upon ambient conditions and also upon heat build-up during long press runs. U.S. Pat. No. 2,260,364 describes an inking system in which the fountain and inking rollers are intentionally heated in order to be able to use inks that are capable of flowing only at a high temperature. German Pat. No. 1,179,225 teaches the heating of an ink film on a roller at a thermostatically maintained temperature. It is proposed in German Auslegeschrift No. 1,611,233 that heat build-up during a long printing run may be counteracted by cooling the rollers in the vicinity of the plate cylinder.

However, our studies show that prior heating and cooling schemes are not capable of maintaining constant printing conditions, particularly in the face of long press runs. We have found that it is desirable to separately maintain a constant regulated temperature both at the ink fountain and at the vibrated roller, or rollers. A regulated temperature at the fountain roller tends to maintain constant the amount of ink which is fed per unit time past the fountain blade, and hence the ink density in the full tone areas of the printing plate. Maintaining the vibrator rollers at regulated temperature is found to have a different but supplemental effect, namely, the maintenance of a predetermined printing contrast in the screened or half tone areas of the printing plate, to prevent dot gain or dot loss.

It is, accordingly, an object of the present invention to provide an inking system in which the temperature at the fountain roller and the temperature at the vibrated roller, or rollers, are both regulated so as to produce consistent and optimum printing in the full tone areas and half tone areas of a printing plate in spite of long press runs and over a wide range of conditions, including conditions in the press itself as well as ambient temperature conditions.

It is a more specific object of the present invention to provide an inking system for a printing press in which the temperature of the fountain roller and vibrated roller roller is maintained constant by circulating through the rollers a fluid such as water derived from a fluid reservoir which is maintained at a desired temperature using both heat and refrigeration, alternatively, and with the heat and refrigeration being switched on correctively in accordance with a thermostat responsive to the temperature of the fluid which is discharged from the rollers.

It is a more specific object to provide an inking system for a printing press which not only includes means for constantly and automatically regulating the temperature of the fountain roller and vibrated rollers but which includes provision for manually applying a "shot" of heat or a "shot" of cold in the form of hot or cold fluid, with constant monitoring of temperature, for bringing the rollers quickly to the desired operating temperature, following which the system may be turned over to automatic regulation.

It is an object of the invention in one of its aspects to provide a temperature control system including a pump for pumping liquid at controlled temperature through the rollers and in which automatic means are provided for turning off the pump when the press slows down to a predetermined speed and for turning on the pump when the press is restored to operating speed.

It is a still further object to provide a temperature control system for the rollers in a printing press which is especially desirable for presses of the lithographic type permitting maintenance of temperature at a level which is sufficiently low as to inhibit the evaporation of water from the plate due to heat build-up in extended operation, which in turn produces a paper deposit on the blanket cylinders. As a result washing intervals may be greatly extended.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

FIG. 1 is a diagram showing a typical ink feed system employed in a printing press and to which the invention has been applied;

FIG. 2 shows an automatic temperature regulating system for the fountain roller and vibrated rollers in FIG. 1, with provision for accelerated application of heat and cold, the system being shown in simplified diagrammatic form;

FIG. 3 is a diagram showing a modified form of the invention in which two separately regulated systems are employed to control the temperatures of the fountain and vibrated rollers.

While the invention has been described in connection with certain preferred embodiments, it will be understood that we do not intend to limit the invention to the particular embodiments shown but intend, on the contrary, to cover the various alternative and equivalent forms of the invention included within the spirit and scope of the appended claims.

Turning now to FIG. 1 there is shown an inking system 10 for inking a printing plate (not shown) upon a plate cylinder 11. The plate cylinder is rotated by a press drive 12, and it will be understood that such cylinder is used with the usual blanket and impression cylinders which, for the sake of simplicity, have not been shown. The inking system 10 includes a fountain 15 having a fountain roller 16 rotating in contact with a body of ink 17. As the ink fountain roller 16 slowly rotates in the direction shown, being driven from the press drive through a speed reducer 18, a film of ink is formed on the surface of the roller by means of a fountain blade 19. The fountain blade has the usual provision for point-to-point adjustment of the film thickness along the length of the blade.

For the purpose of picking off a portion of the film for transfer to the remainder of the inking system, a well-known type of ductor roller 20 is used mounted upon a pair of oscillating arms 21 which are rocked by an oscillating mechanism, generally indicated at 22, driven by the press drive 12. The usual means (not shown) may be provided for determining the duration of "dwell" of the ductor 20 against the surface of the fountain roller 16.

The film of ink is transferred via rollers 29, 30 into a smoothing arrangement which includes vibrated rollers in the form of hollow reciprocating drums 31, 32, 33, rubber rollers 34, 35 being interposed as shown. From the oscillated rollers ink is conveyed to the plate of the plate cylinder by a set of four form rollers 36-39, inclusive. The vibrated rollers, or drums, 31-33 have separate driving connections to the press drive, which have been indicated diagrammatically, for the purpose of reciprocating the rollers endwise while driving them at press surface speed.

In carrying out the present invention the fountain roller 16 and the vibrated rollers 31-33 are of hollow metallic construction having fluid connections 41, 42 and 43, 44 at the respective ends, the fluid connections being conventional and of the "slip" type. The connections 41, 43 receive fluid via a supply line 45 whereas the connections 42, 44 discharge into a common return line 46. Flow into, and out of, the lines 45, 46 is under control of a first selector valve 50 having inlet connections 51, 52, 53 from which fluid is selectively fed to a common outlet connection 54 by means of a slidable valve plunger 55. Associated with the return line 46 is a similar selector valve 60 having outlet connections 61, 62, 63 to which fluid is selectively fed from a common inlet connection 64 under the control of a valve plunger 65. The valve plungers are bridged together for movement in unison via a connection 66. It will be understood that means (not shown) are provided for biasing the plungers into their illustrated central or "normal" positions. The operation will be discussed with the valve plungers in such normal positions, following which means will be described for moving the plungers, under manual control, to respective shifted positions.

For the purpose of furnishing fluid to the supply line 45, a fluid reservoir 70 is provided having selectable sources of heat and cold. The source of heat is preferably a heating element 71 having a supply connection 72 used for control purposes. The source of cold is a cooling coil 73 which is connected to a refrigeration unit indicated generally at 74 which is capable of circulating refrigerant through the coil 73 under the control of a control device 75 which receives its instructions from an electrical control line 76. For the purpose of pumping fluid from the reservoir 70 into the bodies of the rollers, a fluid pump 80 is used driven by a motor 81 to which current is supplied via a line 82 and selector switch 83 from a suitable current source 84. Under normal conditions the switch 83 is closed.

For the selective energization of the heating coil 71 and cooling coil 73, a thermostatic regulator is provided having a double-throw switch. While the present invention is not limited to any particular form of thermostatic regulator, we have illustrated a regulator 90 of the bulb and bellows type. The regulator includes a bulb 91 which is thermally coupled to the return line 46 and which is connected by a capillary 92 to a bellows 93. The bellows 93 is mechanically coupled to a movable switch contact 94 which is selectively engageable with a "heat" contact 95 and a "cold" contact 96. The "heat" contact 95, as shown, supplies the heating element 71 through line 72, while the "cold" contact 96 is connected to the refrigeration controller 75 through line 76. For the purpose of manually setting the equilibrium temperature of the regulator, the bellows 93 may be mounted upon a movable base 97 which is positioned by a cam 98 under the control of a manual setting knob 99.

In accordance with one of the aspects of the invention the flow of fluid into the two branches of the system may be differentially adjusted by means of throttle valves 101, 103. Such valves may take many different forms and may, in the simplest aspect, be a pivoted manually settable vane for partially throttling the flow so that the fluid arriving in the supply line 45 is divided in predetermined ratio. Separate means are provided for monitoring the outlet temperatures in lines 42, 44. In the simplest form, such monitors may be in the form of thermometers 102, 104 thermally coupled to the respective lines. Since the throttle valves 101, 103 by controlling the flow differentially affect the regulated values of temperature in the fountain and vibrated rollers, respectively, such valves form an effective part of the regulator 90.

In reviewing the operation of the system as thus far described, it will be understood that the switch 83 is manually closed, thereby energizing the motor 81 which drives the pump 80 and energizing the contact 94 in the regulator 90. The fluid impelled by the pump thus flows through valve 50, through line 45 and valves 101, 103 into the two branches of the system. The outlets discharge into a common return line 46 which returns the fluid through selector valve 60 back to the reservoir 70. It will be assumed that at the outset the temperature is below the desired equilibrium temperature set by the knob 99 so that contact is made between contacts 94 and 95, thereby energizing the heating coil 71. This heats the fluid in the reservoir until the fluid in the return line reaches the desired equilibrium temperature, at which time the heating element is turned off. In the event that the temperature of the returned fluid should exceed the equilibrium value, the bellows expands causing a circuit to be made through contacts 94, 96 with the result that the control unit 75 turns on the refrigerator 74 to circulate refrigerant through the cooling coil 73 to bring the temperature back down to the equilibrium level. The "dead band" between the contacts 95, 96 is sufficiently wide to avoid overtravel or hunting. In this way, any departure of the temperature in the return line from the desired temperature produces immediate corrective action.

The effect of the above is to keep the ink on fountain roller 16 at such a constant temperature that, with the fountain blade left at a constant setting, the same thickness of ink is deposited on the fountain roller in spite of changes in ambient temperature and in spite of the frictional working of ink in the ink fountain during long press runs, both changes tending to affect ink viscosity. Consequently, the same amount of ink per unit time will be transported by the ductor and the same amount of ink per unit time will reach the printing plate, so that the density of the ink in the full tone, or solidly printing, areas of the plate will remain constant. The effect of the above is also to keep the ink on the vibrated rollers 31-33 at such a constant temperature that the same viscosity ink is deposited at all times on the "dots" which make up the screened half tone areas of the plate, regardless of changes in ambient temperature and regardless of the frictional working of the ink on the ink rollers, with consequent heat build-up, during long press runs. Thus printing quality is optimized and made uniform in both full tone and half tone areas. Since the optimum temperature at the fountain is close to the optimum temperature at the vibrated rollers, the temperature may be maintained constant by using a single regulated reservoir 70, with localized adjustment being obtainable by use of differentially adjustable throttle valves 101, 103 adjusted in accordance with the readings of monitoring thermometers 102, 104.

In accordance with one of the aspects of the present invention means are provided for bringing the system to the equilibrium temperature at an accelerated rate as required, for example, in starting up the press. In short, means are provided for manually applying a "shot" of heat or a "shot" of cold. Turning first to the auxiliary heating system indicated at 110, it includes a reservoir 111 having a source of heat 112 connected to a current source 113. For pumping fluid from the reservoir 111 a pump 114 is used mechanically connected to a motor 115 which is energized by a manual switch 116. Connected to the switch via a line 117 is a "heat" solenoid 118 having an armature or plunger 119.

Similarly an auxiliary source of cold 120 is used having a cold reservoir 121 including a cooling coil 122 supplied from a refrigeration unit 123. Cold fluid is pumped by a pump 124 driven by a motor 125 under the control of a switch 126. The switch, in addition, serves to energize a control line 127 leading to a "cold" solenoid 128 having an armature or plunger 129.

Thus when a "shot of heat" is desired, switch 116 is temporarily closed (switch 83 being opened). Closure of the switch 116 applies voltage to line 117 which energizes solenoid 118 so that the valve plungers 55, 65 are drawn to the right, thereby establishing a fluid connection to supply line 45 through valve port 52 and a fluid connection to return line 46 via port 62 in valve 60. At the same time closure of switch 116 turns on the motor 115 to drive pump 114 so that fluid at relatively high temperature is furnished to the fountain roller 16 and vibrated rollers 31-33. Switch 116 is maintained closed until the monitoring thermometers 102, 104 indicate that the temperature is approaching the desired equilibrium level. At such time switch 116 is opened and switch 83 is closed so that the automatic temperature regulator 90, previously described, takes over control.

In the event that the temperature of the rollers is initially too high so that rapid refrigeration is necessary, switch 126 is closed, applying voltage to line 127 thereby energizing solenoid 128 so that the valve plungers are drawn to the left, thereby connecting the cold reservoir 121 to the rollers via valve ports 53, 63. Closure of switch 126, energizing motor 125, drives pump 124 so that fluid from the cold reservoir 121 is directly circulated into the rollers of the ink system. Again, when the temperature indicated by the monitoring thermometers 102, 104 indicates that the desired equilibrium temperature is approached, switch 126 may be opened and switch 83 closed so that fluid is thereafter supplied to the rollers from the regulated reservoir 70. The use of separate pumps 80, 114, and 124 enables delivery to be tailored to the need and to the reservoir capacity.

It is one of the features of the present invention that the pump 80 in the regulated system is automatically turned off when the speed of the press drops to below a predetermined operating level. Such automatic turn off is achieved in the present instance by a tachometer generator 130 (see FIGS. 1 and 2) which is driven from the regular press drive 12 by a belt 131 or the like. The output voltage from the tachometer generator is fed into the coil 132 of a relay having a set of normally open contacts 133 connected in series with the motor 81. As illustrated in FIG. 2, the press is at operating speed so that the contacts 133 are closed, permitting normal operation of the motor. However, in the event that the press drive 12 drops substantially below operating speed, the voltage from the tachometer generator is no longer sufficient to hold the contacts 133 closed so that the motor circuit opens to shut off the pump 80. However should the press speed rise again to near rated level, the relay 132 will be re-energized, reclosing the contacts 133 to again turn on the pump. Such automatic shut-off and re-start enables the controlled rollers to maintain a surface temperature during shutdown and reduced speed running which corresponds more nearly to normal running conditions.

It will be apparent, then, that the system shown in FIG. 2 is capable of maintaining the fountain roller and vibrated rollers at a predetermined equilibrium temperature which is optimum for the ink being used, which temperature is constantly and automatically maintained. That is to say, the temperature maintained at the fountain roller is such as to insure that the amount of ink being fed past the fountain blade will remain constant regardless of changing conditions thereby to maintain a predetermined density in the ink in the full tone areas of the printing plate. At the same time, the vibrated rollers, or drums, 31-33 are maintained at their optimum temperature so that the printing characteristics of the ink are kept constant with the result that the printing contrast remains the same in the half tone areas of the printing plate, notwithstanding a change in the operating or ambient conditions and in spite of long press runs.

In the embodiment discussed above differential adjustment of the throttle valves 101, 103 feeding the two portions of the system is relied upon to establish divided flow, thereby to create separate optimum conditions of temperature in the two branches. However in accordance with one of the aspects of our invention means may be provided for separate regulated control of the fountain roller on the one hand and of the vibrated rollers, or drums 31-33 on the other. Such a dual system is disclosed in FIG. 3, in which corresponding reference numerals are employed to indicate corresponding parts with addition of subscript a or subscript b in the respective halves of the circuit. One difference between the circuit of FIG. 3 and that shown in FIG. 2 is that the circuit of FIG. 3 has a common reservoir for furnishing a "shot" of heat and a common reservoir for furnishing a "shot" of cold for achieving the desired equilibrium temperature at an accelerated rate, the shared elements carrying a subscript c.

The operation in FIG. 3 is otherwise the same as in FIG. 2. Taking the right-hand portion of the circuit which supplies regulated fluid to fountain roller 16, turning on switch 83a starts pump 80a to begin circulation of the fluid. The temperature of the fluid in return line 46a is measured by the bulb of the regulator 90a, causing the controlled contact 94a to either turn on the heating coil 71a or the cooling coil 73a, as appropriate. To apply a "shot", of heat the plungers of valves 50a, 60a are shifted to the left, temporarily connecting the hot reservoir 111c to the fountain roller, with the temperature being monitored by a thermometer 102a. The selector valve plungers are restored to central position when the monitored temperature approaches the equilibrium level to restore automatic control. Conversely, if the fountain roller is initially too warm, requiring refrigeration, the plungers of selector valves 50a, 60a are moved to the right to connect into the circulation circuit the cold reservoir 121c.

The identical mode of control is achieved in the left-hand portion of the circuit which furnishes fluid at a separately regulated temperature to the vibrated rollers 31-33. Here again a "shot" of heat may be obtained by moving the plungers of valves 50b, 60b to the right and a "shot" of cold by moving them to the left.

While a rudimentary on-off form of regulator has been illustrated in FIGS. 2 and 3 to simplify the showing of the invention, it will be understood that more elaborate "proportioning" regulators may be used without departing from the invention.