Arrangement for and method of determining the amount of dampening agent on a printing-image carrier

Claim 2

An arrangement for determining the amount of dampening agent on a printing-image carrier, said arrangement comprising: (a) a radiation source for directing radiation at the carrier; (b) first means for generating first signals in response to radiation which returns from the carrier add has a predetermined wavelength at least approximating an absorption wavelength of the dampening agent; and (c) second means for generating second signals representative of the amount of dampening agent on the carrier, said second means being arranged to receive said first signals and to relate a preselected first signal generated while the carrier is substantially dry to another first signal generated while the carrier is damp, and said second means being designed such that the second signals are derived from the relationship between said preselected and other first signals, said second means being further arranged to receive and process a glancing signal so as to compensate for errors due to radiation which is directed towards the carrier from said source and glances off the dampening agent applied to the carrier.

Claim 3

An arrangement as defined in claim 1, wherein said second means comprises memory means for storing said preselected first signal.

Claim 4

An arrangement as defined in claim 2, wherein said memory means comprises a working memory.

Claim 5

An arrangement as defined in claim 1, wherein said source is arranged to irradiate a predetermined region of the carrier.

Claim 6

An arrangement as defined in claim 1, wherein the carrier is rotatably mounted in an offset printing press.

Claim 7

An arrangement as defined in claim 1, wherein said source is arranged to emit radiation in pulses.

Claim 8

An arrangement as defined in claim 1, wherein said source is arranged to irradiate the carrier during printing, said first and second means being arranged to generate said signals during printing.

Claim 9

An arrangement as defined in claim 1, wherein said first means comprises a photoelectric transducer.

Claim 10

An arrangement as defined in claim 1, wherein said first means is arranged to detect radiation returned outside of the angle of reflection of the radiation which impinges on the carrier from said source.

Claim 11

An arrangement as defined in claim 1, wherein said second means is arranged to receive and process a cross-talk signal so as to compensate for errors due to cross-talk.

Claim 12

An arrangement as defined in claim 10, wherein said second means comprises memory means for storing said preselected and cross-talk signals.

Claim 13

An arrangement as defined in claim 1, wherein said second means comprises memory means for storing said preselected and glancing signals.

Claim 14

An arrangement as defined in claim 1, comprising additional means for generating reference signals in response to radiation of said predetermined wavelength which impinges upon said additional means directly from said source, said second means being arranged to receive said reference signals and to form ratios of said preselected and other signals with respective ones of said reference signals.

Claim 15

An arrangement as defined in claim 13, wherein said additional means comprises a photoelectric transducer.

Claim 16

An arrangement as defined in claim 13, wherein said second means comprises memory means for storing said reference signals.

Claim 17

An arrangement as defined in claim 13, wherein said source is arranged to emit radiation in pulses and said preselected signal and its respective reference signal are derived from the same pulse, said other signal and its respective reference signal also being derived from the same pulse.

Claim 18

An arrangement as defined in claim 13, wherein said second means is arranged to receive and process at least one cross-talk signal so as to compensate for errors due to cross-talk, said additional means being arranged to generate a reference cross-talk signal, and said second means being designed to receive said reference cross-talk signal and to form a ratio between said one and reference cross-talk signals.

Claim 19

An arrangement as defined in claim 17, wherein said source is arranged to emit radiation in pulses and said one and reference cross-talk signals are derived from the same pulse.

Claim 20

An arrangement as defined in claim 1, comprising a reflector for directing radiation returned from the carrier towards said first means, said reflector having a pair of focal points including one which coincides with the carrier and another which coincides with said first means.

Claim 21

An arrangement as defined in claim 19, wherein said reflector is substantially elliptical.

Claim 22

An arrangement as defined in claim 1, wherein said source and said first means are incorporated in a unit and shielding means is provided to shield said unit against contamination, said shielding means being transparent to and substantially non-reflective for radiation of said predetermined wavelength.

Claim 23

An arrangement as defined in claim 21, wherein said shielding means comprises a disc.

Claim 24

An arrangement as defined in claim 21, wherein said unit comprises a reflector for directing radiation returned from the carrier to said first means.

Claim 25

An arrangement for determining the amount of dampening agent on a printing-image carrier, said arrangement comprising: (a) A radiator source for directing radiation at the carrier; (b) first means for generating first signals in response to radiation which returns from the carrier and has a predetermined wavelength at least approximating an absorption wavelength of the dampening agent; (c) second means for generating second signals representative of the amount of dampening agent on the carrier, said second means being arranged to receive said first signals and to relate a preselected first signal generated while the carrier is substantially dry to another first signal generated while the carrier is damp, and said second means being designed such that the second signals are derived from the relationship between said preselected and other first signals, said second means being further arranged to receive and process at least one glancing signal so as to compensate for errors due to radiation which is directed towards the carrier from said source and glances off the dampening agent applies to the carrier; and (d) additional means for generating reference signals in response to radiation of said predetermined wavelength which impinges upon said additional means directly from said source, said second means being arranged to receive said reference signals and to form ratios of said preselected and other signals with respective ones of said reference signals, and said additional means being designed to generate a reference glancing signal, said second means being arranged to receive said reference glancing signal and to form a ratio between said one and reference glancing signals.

Claim 26

An arrangement for determining the amount of dampening agent on a printing-image carrier, said arrangement comprising: (a) A radiator source for directing radiation at the carrier; (b) first means for generating first signals in response to radiation which returns from the carrier and has a predetermined wavelength at least approximating an absorption wavelength of the dampening agent; (c) second means for generating second signals representative of the amount of dampening agent on the carrier, said second means being arranged to receive said first signals and to relate a preselected first signal generated while the carrier is substantially dry to another first signal generated while the carrier is damp, and said second means being designed such that the second signals are derived from the relationship between said preselected and other first signals, said second means being further arranged to receive and process at least one glancing signal so as to compensate for errors due to radiation which is directed towards the carrier from said source and glances off the dampening agent applies to the carrier; and (d) additional means for generating reference signals in response to radiation of said predetermined wavelength which impinges upon said additional means directly from said source, said second means being arranged to receive said reference signals and to form ratios of said preselected and other signals with respective ones of said reference signals, and said additional means being designed to generate a reference glancing signal, said second means being arranged to receive said reference glancing signal and to form a ratio between said one and reference glancing signals.

Claim 27

An arrangement as defined in claim 24, wherein said source is arranged to emit radiation in pulses and said one and reference glancing signals are derived from the same pulse.

Claim 30

A method as defined in claim 26, comprising the steps of measuring a dry reference value and a damp reference value of said characteristic; and establishing ratios between said dry reference value and said one dry value and between said damp reference value and said one damp value, the step of establishing said relationship being performed with said ratios.

Claim 31

A method as defined in claim 26, comprising the step of correcting for cross-talk.

Claim 32

A method as defined in claim 28, wherein the step of correcting for cross-talk comprises the operations of obtaining an actual and a reference crosstalk value; and establishing a ratio between said actual and reference cross-talk values.

Claim 33

A method as defined in claim 26, wherein the step of correcting for glancing radiation comprises the operations of obtaining an actual and a reference glancing value; and establishing a ratio between said actual and reference glancing values.

Claim 34

A method as defined in claim 26, wherein the measuring steps are performed for radiation returned from said carrier outside of the angle of reflection of the radiation directed at said carrier during the irradiating step.

Claim 35

A method as defined in claim 26, wherein the correcting step comprises generating a glancing signal by applying an excess of said dampening agent to said carrier, and irradiating the latter while said excess is on said carrier.