Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/06—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by exposure to radiation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/0288—Controlling heating or curing of polymers during moulding, e.g. by measuring temperatures or properties of the polymer and regulating the process
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B3/00—Drying solid materials or objects by processes involving the application of heat
  • F26B3/28—Drying solid materials or objects by processes involving the application of heat by radiation, e.g. from the sun
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
  • B29C2035/0827—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using UV radiation

Definitions

• This invention relates to the curing of materials applied to substrates, such as printed or other manufactured articles, by means of ultraviolet light.
• Inks and coatings that can be "cured” or hardened through exposure to ultraviolet light have gained wide application in recent years in part because they are less injurious to the environment than traditional solvent-based inks and coatings, and due to related work place safety considerations. They also afford efficient operation by providing more rapid curing than solvent-based inks and coatings.
• ultraviolet light curable materials are applied by a printer or other application means to substrates and, as part of the same process, are thereafter cured by ultraviolet light projected from a lamp within an enclosed ultraviolet processor.
• the substrates are transported through the ultraviolet processor on a movable conveyor.
• substrates in the form of a continuous web can be passed through the processor by a system of application, tension and directional rolls.
• the speed at which the substrate passes through the ultraviolet processor can vary for different reasons. For example, the operator may need to vary the substrate speed to accommodate a variable printing or application rate or variations in thickness, coverage or material composition.
• the amount of ultraviolet light and attendant heat to which the substrates and substrate conveyor are exposed varies with the speed at which they move through the ultraviolet processor.
• a curing process parameter such as substrate speed
• a curing process parameter is monitored automatically to develop a signal which indicates such a curing process parameter.
• a characteristic of the ultraviolet light projected by a light source such as its intensity, is adjusted based on the signal to automatically maintain the characteristic within desirable limits to optimize the curing of the material on the substrate.
• improved circuitry for detecting ultraviolet lamp operating conditions is provided utilizing semiconductor solid state signal processing means. Costly and environmentally sensitive solenoid operated relays are thus replaced by reliable, inexpensive and environmentally stable circuit elements.
• Figure 1 is a schematic view of an apparatus for applying a material and curing the material through exposure to ultraviolet light;
• FIG. 2 is a block diagram of an ultraviolet light processor for use in the apparatus of Figure 1;
• Figure 3 is a schematic diagram of an automatic power control circuit of the processor of Figure 2;
• Figure 4 is a schematic diagram of a portion of a typical lamp control circuit of the processor of Figure 2;
• Figure 5 is a schematic diagram of a lamp power circuit of the processor of Figure 2;
• Figure 6 is a schematic diagram of a further portion of the lamp control circuit of Figure 4 including lamp operation monitoring circuitry;
• Figure 7 is a schematic diagram illustrating an alternative embodiment of an ultraviolet light processor providing continuously variable lamp power control
• Figure 8 is a schematic diagram of a further alternative embodiment of an ultraviolet light processor providing continuously variable lamp power control
• FIG. 9 is a schematic illustration of an ultraviolet light processor employing two lamps
• Figure- 10 is a schematic diagram of lamp shutter control circuitry for the processor of Figure 9 providing independently operable " shutter actuation; and Figure 11 is a schematic illustration of a further embodiment of the present invention providing an ultraviolet light processor having adjustable lamp distance control.
• FIG. 1 illustrates a system 20 for applying an ultraviolet light (UV) curable material, such as UV curable ink, coatings, or adhesives to a substrate and subsequently curing the applied material by exposure to ultraviolet light.
• the system includes a belt conveyor 22 having an endless belt 24 driven by rollers 26 and 28 powered by an electric motor (not shown for purposes of simplicity and clarity) .
• a substrate 30, such as a printed substrate or manufactured article, is shown as it is transported on an upper surface of the conveyor from left to right in the drawing.
• the system 20 further includes a printer or other application means 34 for applying UV curable ink or other material to an upper surface of the substrate 30.
• a printer or other application means 34 for applying UV curable ink or other material to an upper surface of the substrate 30.
• the ink or other material has been applied to the substrate 30 and it is being transported by the conveyor 22 towards an ultraviolet light processor 36 which will project ultraviolet light onto the upper surface or edges of substrate 30 as it passes beneath the processor 36 through a light exposure position.
• the UV light incident on the substrate 30 cures or hardens the material applied thereto by the application means 34 through a photochemical reaction.
• the speed of the conveyor 22, and therefore of substrate 30 is detected by the combination of an idle roller 38 of the conveyor 22 coupled with a tachometer and tachometer signal circuit 40.
• the tachometer and circuit 40 provide a plurality of control signals at an output 42 thereof representing the speed at which the substrate moves with the conveyor 22 through the light exposure position beneath UV light processor 36.
• the tachometer and tachometer signal circuit 40 are described below in greater detail.
• UV light processor 36 includes one or more UV light sources, such as mercury vapor lamps.
• Practical UV light sources generate substantial amounts of infrared emissions as well as high levels of UV light, and thus tend to rapidly heat the substrate and conveyor.
• Many substrates and conveyor materials are susceptible to damage caused by excessive heat and UV light exposure. Accordingly, it is necessary to limit the heat and UV light absorption of these materials.
• the intensity of the UV light projected onto the substrate by the processor 36 is selected from at least two non-zero intensity values as a function of the rate at which the substrate passes through the UV light exposure position, so that the UV exposure of the substrate is maintained between acceptable maximum and minimum values.
• This is achieved in the embodiment of Figure 1 by providing such a processor 36 capable of projecting at least two different UV light intensities under the control of a signal received at a control input terminal 44 thereof.
• the output signal at terminal 42 of tachometer 40 is provided to the input 44 of processor 36. In this manner, a characteristic of the UV light, i.e.
• the speed of the substrate is directly proportional to the duration of substrate exposure, and thus is representative thereof, as well as of the total amount of UV light received by the substrate so long as other process variables (such as UV light intensity profile and lamp input power) are held constant. Since the total intensity of UV light emitted by the lamp(s) varies with the input power applied thereto, it will be appreciated that, by selecting the lamp input power as a function of substrate speed, in accordance with the embodiment of Figure 1, the total UV light exposure of the substrate can be regulated.
• FIG. 2 illustrates the UV light processor 36 in block diagram format. Alternating current electrical power is supplied to processor 36 through power legs 48 and 50. Power is supplied to ventilation control circuits 52 through stepdown transformer 54, and to the remaining control circuits of processor 36 under the control of circuits 52 via its output terminal 56. Since the processor circuits handle relatively high electrical power levels and, thus generate substantial amounts of heat, the processor 36 is provided with heat ventilation subsystems for exhausting heated air from the lamp housing, as well as from its power and control circuits. It is essential that these ventilation units be operating satisfactorily as a condition of supplying power to the lamps and circuitry. Accordingly, the ventilation control circuits control the provision of electrical power to the remaining circuitry of processor 36 to ensure their proper ventilation before power is applied thereto. Circuits 52 also include well known means for automatically locking the high voltage lamp ballast or power supply circuit housings so long as power is applied and for affording an emergency power cutoff under manual control.
• circuits 58 include variable power control relays energized by respective solenoids 1CR, 2CR and 3CR under control of normally open relay contacts 60, 61 and 62, respectively.
• Relay contacts 60-62 are controlled by means of the control signals output by the tachometer and tachometer signal circuits 40. More specifically, the control signals
• Power from output terminal 56 is also applied to system condition monitors and interlock controls 64.
• the monitors and controls 64 in known fashion monitor system variables to determine whether they are within acceptable levels and control the provision of power to the lamp power (or ballast) and control circuits accordingly.
• the system of Figure 2 includes two mercury vapor ultraviolet lamps supplied with power through respective lamp power circuits or ballasts 66 having identical circuit configurations. Circuits 66 are described in greater detail below. It will be appreciated that the number of lamps employed in accordance with the invention need not always be two and will vary depending on the particular UV processing application.
• circuits 66 The power supplied to the lamps by circuits 66 is controlled by respective lamp control circuits
• Control circuits 68 have identical circuit configurations and are illustrated schematically in Figure 4 as follows. Power is supplied to the circuits from the system monitors and interlock controls 64 over power legs 74 and 76. System startup is controlled manually by switch LSS. As indicated in Figure 4, switch LSS is a three position, two pole switch having a first pole 78 which is closed only in the second or “on” position and in the third or “start” position. The “start” position is a momentary "on” position and is the only position at which second pole 80 is closed.
• a circuit breaker CB described below in greater detail with reference to Figure 5, is shown in a "fault” or power cutoff position, so that in normal operation, the poles 78 and 80 are coupled through circuit breaker CB.
• relay solenoids are indicated by circular circuit element symbols enclosing the identifying symbols therefor and the corresponding relay contacts are indicated by the same identifying symbols.
• Normally closed contacts i.e., those forming a short circuit when the relay solenoid is not energized
• normally open contacts are indicated by the absence of such a diagonal line.
• Capacitor bank 90 includes the parallel combination of (a) a capacitor 92, (b) a capacitor 94 in series with a normally open contact of relay NDK, and (c) a capacitor 96 in series with a normally open contact of relay HDK. It will be appreciated that, by closing the contacts of relays NDK and HDK, the total capacitance of bank 90 is increased, thus decreasing the impedance to the flow of current therethrough, increasing the current supplied to lamp 88 and, concomitantly, increasing its UV power output.
• Power circuit 66 includes a circuit breaker CB connected to the center tap of transformer 86 which serves to detect a fault in the secondary thereof to disable power to circuit 66 by deenergizing relay solenoid LC of the corresponding lamp control circuit 68.
• the lamp 88 is provided with a pair of shutters (not shown for purposes of simplicity and clarity) which block the transmission of UV light to the conveyor 22 so long as an associated shutter solenoid (98 in Figure 4) is not energized, and which open upon energization of the solenoid 98 to permit such transmission.
• a typical shuttered UV lamp apparatus is disclosed in U.S. Patent No. 4,025,795 issued May 24, 1977 entitled ULTRAVIOLET LIGHT PROCESSOR HAVING ROTATING SHUTTERS which is incorporated herein by reference.
• Mercury vapor lamps, such as lamps 88, will not emit UV light when initially energized. Rather, upon the application of a .
• the ready state is detected in the embodiment of Figure 2 by sensing the voltage across the lamp and determining by means of a solid state threshold detector that it has risen sufficiently to exceed a predetermined "ready" or threshold level.
• the circuit of Figure 5 includes a step down transformer 100 whose primary is connected across lamp 88 to sense the voltage thereacross. The transformer
• a voltmeter 102 (which may be switched between the various lamp power circuits 66 by the provision of suitable switching circuitry) provides a direct indication of lamp voltage to the operator.
• a lamp voltage monitoring circuit 103 having an input terminal 104 coupled to the secondary of transformer 100.
• Input terminal 104 provides the voltage from the secondary winding of transformer 100 to the input of a signal conditioning circuit 105 having a diode 106 and electrolytic capacitor 108 connected in series which serve to provide a peak detected version of the voltage from the secondary winding at their common node.
• the peak detected voltage is applied across a pair of series connected resistors 110 and 112 of signal conditioning circuit 105 which, in turn, provide a scaled down version of the peak detected signal at their common node to the inverting inputs of two semiconductor solid state operational amplifiers 114 and 116.
• the scaled down peak detected voltage is further smoothed by electrolytic capacitor 118 connected in parallel across resistor 112.
• Signal conditioning circuit 105 also includes a series connected zener diode 120 and resistor 122.
• the cathode of diode 120 is connected to the common node of diode 106 and capacitor 108 and its anode is coupled in series through resistor 122 to ground.
• the series connection of diode 120 and resistor 122 serves to protect the circuit 103 from excessive DC voltage levels.
• Operational amplifier 114 together with its output circuitry serves to energize the solenoid of a "ready” relay once the voltage across lamp 88 has achieved a “ready” or operational level.
• the noninverting input terminal of amplifier 114 is coupled to receive a reference voltage V Read which is set by an adjustable resistive voltage divider (not shown for purposes of simplicity and clarity) .
• V Read is selected such that it is equal to the voltage at the inverting input terminal of amplifier 114 when the voltage across the lamp 88 has reached an operating level.
• the cathode of a light emitting diode (LED) 124 is connected to the output terminal of amplifier 114 and its anode is coupled through a normally closed contact of a "fail" relay FL to the first terminal of a ready relay solenoid RY and to the anode of a diode 126 connected in parallel across relay solenoid RY.
• the second terminal of relay solenoid RY is coupled to the positive voltage supply level V cc of the circuit's low voltage DC power supply (not shown for the sake of simplicity and clarity) . Accordingly, once the voltage across lamp 88 has reached the operating value, the output of amplifier 114 will go low, thus energizing the ready relay solenoid and light emitting diode 124.
• Operational amplifier 116 and its output circuitry serve to detect the failure of lamp 188 and to energize the fail relay solenoid FL which in turn serves to remove power from the corresponding lamp power circuit 66.
• the noninverting input terminal of amplifier 116 is connected to a source of reference voltage V Fail which is set by an adjustable resistive voltage divider (not shown for purposes of simplicity and clarity) .
• the output of amplifier 116 is connected to a first terminal of the fail relay solenoid and to the anode of a diode 128.
• the opposing terminal of fail relay solenoid FL and the cathode of diode 128 are connected to V cc .
• Lamp 88 can fail in several ways. For example, failure can occur upon an attempt to initially energize lamp 88 if this fails to strike an arc through the lamp. Failure can also occur during operation if, for some reason, an excessive amount of cooling air should cause lamp 88 to overcool. Upon lamp failure, it will open-circuit and the voltage thereacross will rise to the open circuit voltage across the secondary of transformer 86. This voltage level is typically several hundred volts above the operational voltage level of the lamp. Accordingly, one set of fail relay contacts is connected in series with the ready relay solenoid in order to deenergize it upon lamp failure, since it will otherwise continue to indicate (erroneously) that the lamp is "ready". Prior art circuits employed for detecting the
• a digital signal processor is coupled to receive the voltage provided at the common node of resistors 110 and 112. This voltage is converted to a digital signal by an analog-to-digital signal converter by reference to a signal such as the predetermined voltage level that will appear at the common node of resistors 110 and 112 when the lamp fails and open-circuits. This digital signal is then processed to detect lamp “ready” and “fail” conditions by comparison thereof with known digital representations of the "ready" and “fail” voltage levels. It will be readily appreciated that such digital signal processing can be performed by any known digital processing means such as hard-wired logic circuits or microprocessor based signal processing means.
• solenoid of relay 1CR of Figure 3 is energized.
• the shutter solenoid 98 is connected in series with a fuse 136 and a normally open contact of solenoid 1CR. Accordingly, since the solenoid of the ready relay RY has now been energized, it will be seen that once the minimal operating speed has been achieved solenoid 1CR operates to open the shutters by energizing the shutter solenoid 98.
• relay 1CR will deenergize in order to close the shutters of the lamp 88 in order to prevent overexposure and overheating of the conveyor and any substrate that may be in proximity to the lamp 88.
• the solenoid of relay 2CR is once again energized through a series connected pair of normally open contacts of relays 2CR and RY. With reference to Figure 5, it will be appreciated that this will once again connect capacitor 94 into the circuit feeding power to the lamp 88, thus increasing the current supplied thereto, thereby increasing its power output.
• the solenoid of relay 3CR is energized which in turn energizes the solenoid of relay HDK to couple capacitor 96 of Figure 5 in parallel with capacitors 92 and 94 to maximize the current through lamp 88 and thereby maximize its power output.
• the power output of the lamp 88 varies directly with the speed of the conveyor. Since the total intensity of the lamps 88 also varies directly with the power applied thereto, it will be seen that the system of Figures 2 through 6 provides a means for adjusting the intensity of the light projected onto the substrates carried by the conveyor based upon a signal representing the speed at which the conveyor, and therefore the substrates, are moving through the light exposure position.
• the solenoid of relay CRF will, in turn, be energized upon lamp failure through the closing of normally open contacts 138, upon the occurrence of a secondary fault which trips the circuit break CB to energize the solenoid of relay CRS to close normally open contacts 140, as well as the occurrence of excessive reflector temperature resulting in the deenergization of the solenoid of relay CRT thus reclosing normally closed contacts 142.
• Figures 7 and 8 illustrate alternative embodiments of the invention providing continuous lamp power level control as a function of conveyor and substrate speed.
• elements corresponding to elements illustrated in Figures 1 through 6 bear corresponding labels.
• the embodiments of Figures 7 and 8 include lamp control circuits 68' which perform the same functions as lamp control circuit 68 of the embodiment of Figures 2-6 with the exception of the lamp power control function performed thereby.
• a saturable core reactor 148 is connected in series with a capacitor 150 and the lamp 88.
• the saturable core reactor 148 is a current controlled variable inductance which serves to vary the current supplied to the lamp 88 continuously under the control of a DC current supplied to a control input thereof from the output terminal 146 of lamp control circuits 68'.
• Circuits 68' are coupled to an output terminal 152 of a tachometer signal circuit 151 providing a continuously variable signal representing conveyor and substrate speed to receive the signal therefrom.
• Circuits 68* condition this signal in order to output an appropriate control current to the saturable core reactor 148 in order to adjust the applied power level to the lamp continuously throughout a predetermined range of power levels such that the applied power level varies directly with the substrate speed on the conveyor on a continuous basis.
• the circuit of Figure 8 is identical to that of Figure 7 except that the saturable core reactor 148 has been connected instead in parallel with the capacitor 150 (rather than in series) , and circuits 68' have been altered as necessary to provide an appropriately scaled control current to the saturable core reactor 148 in order to scale the power input to the lamp 88 based upon the signal provided at the output of the tachometer signal circuit 151. It will be appreciated that in place of the saturable core reactors 148 of Figures 7 and 8, a mechanically variable inductance could be utilized together with appropriate control devices.
• Figures 9 and 10 illustrate a further embodiment of the present invention utilizing a pair of lamps and corresponding reflectors illustrated schematically as 160 and 162, each having a first focus Fl and a second focus F2 located at or near the surface of the substrate 30.
• the total intensity of the UV light incident at the surface of the substrate is varied under control of the substrate speed signal by means of the circuit shown in Figure 10.
• the circuit of Figure 10 includes a first shutter solenoid 166 for opening and closing a shutter of lamp and reflector combination 160, and a second shutter solenoid 168 for controlling the opening and closing of a shutter of the lamp and reflector combination 162 of Figure 9.
• Each of the solenoids 166 and 168 is connected in series with a respective normally open relay contact 170 and 172 to receive power therethrough from the ventilation control circuit power output terminals 56, as shown in Figure 1.
• Normally open contact 170 is made to close once the tachometer speed signal from the tachometer signal circuit 40 attains a first signal level indicating a minimum operating speed. Accordingly, shutter solenoid 166 is thereby energized to open the shutters of the lamp and reflector combination 160 so that ultraviolet light is projected toward its second focus F 2 on the surface of the substrate 30.
• shutter solenoid 168 remains deenergized thus maintaining the shutter of the lamp and reflector combination 162 closed. Accordingly, at this lower speed, the substrate 30 is exposed to a relatively low ultraviolet light intensity.
• the substrate speed signal activates a solenoid to close normally closed contacts 172, so that shutter solenoid 168 is energized to open the shutters of the lamp and reflector combination 162. Accordingly, at and above this relatively higher conveyor speed, the substrate 30 is exposed to relatively higher intensity ultraviolet light provided by the combination of both lamps.
• FIG 11 schematically illustrates a further embodiment of the present invention wherein the intensity of ultraviolet light to which the substrate and conveyor are exposed is varied directly with their speed by varying the distance of the ultraviolet light source from the substrate and conveyor.
• the apparatus is supported from a floor on a base 180.
• An endless belt conveyor 182 includes idle rollers 184 and 186 mounted for rotation on the base 180 and whose speed of rotation varies directly with the speed of the conveyor.
• a housing 190 mounts an ultraviolet lamp, such as lamp 88 of Figure 5, which is operative to project ultraviolet light downwardly towards a substrate 192 moving with the conveyor 182.
• Light housing 190 is mounted on a plurality of air cylinders 194 operative to raise and lower the housing in response to the application of a differential air pressure applied to opposite sides of air pistons slideably mounted therein. Compressed air is applied to opposite sides of the pistons of the air cylinders 194 through a solenoid operated air valve 196 which supplies compressed air to the cylinders 194 through a pair of air lines represented schematically by the dashed line 198 in Figure 11.
• a tachometer 200 is coupled with idle roller 186 to generate a signal representative of the speed at which the conveyor 182 and substrate 192 are moving instantaneously. Tachometer 200 provides this substrate speed signal to an output terminal 202 thereof.
• the relative height of the housing 190 over the conveyor 182 and substrate 192 is converted to an electrical signal by means of a potentiometer shown schematically at 206.
• a wiper arm of the potentiometer moves with the housing 190 to produce a voltage varying directly with the height of the housing with respect to the conveyor and substrate.
• a differential amplifier 210 has a first differential input terminal coupled to the output 202 of the tachometer 200 to receive the substrate speed signal.
• a second differential input terminal of amplifier 210 is coupled to the wiper arm of the potentiometer 206 to receive the housing height signal therefrom.
• Differential amplifier 210 serves to produce an error voltage at its output, indicated as 212, representing the difference between the substrate speed signal and the housing height signal.
• the output 212 of the amplifier 210 is coupled to the solenoid operated air valve 196 to control the application of air pressure through the lines 198 to the cylinders 194 for raising and lowering the lamp housing 190.
• the values of the potentiometer 206 and the DC voltage applied thereacross, together with the substrate speed signal from the tachometer 200 are scaled appropriately so that, as the speed of the conveyor 182 and substrate 192 varies, the height of the lamp housing 190 likewise will vary such that a desired level of ultraviolet light intensity is received by the substrate 192 and the conveyor 182 at any given operational speed of the conveyor and substrate.
• a system for applying and curing UV curable materials on a substrate wherein a curing process parameter, namely a property of the material applied to the substrate, is used to control a characteristic of the UV light to which the substrate is exposed.
• a curing process parameter namely a property of the material applied to the substrate
• a property of a UV curable printing ink is measured to produce a density signal which serves to adjust the intensity of the UV light applied to the ink on a substrate to optimize the curing.
• the tachometer and tachometer signal circuit 40 are replaced by a reflective densitometer.
• the densitometer is disposed between the printer 34 and the UV light processor 36 to measure the density of the ink printed on the substrate before it passes through the UV light processor.
• the densitometer produces an output signal representative of the ink's density.
• the output signal is appropriately conditioned and, as such, is applied to the processor control input terminal 44. Under the control of the densitometer signal, the intensity of the light projected by the processor 36 is varied according to the measured ink density to effect an optimum cure thereof.

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• Coating Apparatus (AREA)
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• 1991
  • 1991-02-18 CA CA 2036544 patent/CA2036544A1/en not_active Abandoned
  • 1991-02-28 EP EP91905749A patent/EP0517814A1/en not_active Withdrawn
  • 1991-02-28 WO PCT/US1991/001281 patent/WO1991012897A1/en not_active Ceased

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