US5864351A — Heater power compensation for thermal lag in ther…

Claim 1

Independent Claim 163 words

A printing apparatus comprising: a thermal print head which comprises: (a) a plurality of drop-emitter nozzles; (b) a body of ink associated with said nozzles; (c) a pressurizing device adapted to subject ink in said body of ink to a pressure of at least 2% above ambient pressure, at least during drop selection and separation to form a meniscus with an air/ink interface; selection apparatus operable upon the air/ink interface to select predetermined nozzles and to generate a difference in meniscus position between ink in selected and non-selected nozzles, the drop selection apparatus including a heater operated in response to energizing power; and (e) drop separation apparatus adapted to cause ink from selected nozzles to separate as drops from the body of ink, while allowing ink to be retained in non-selected nozzles; a programmable power supply for energizing said heater; and control means for predeterminedly controlling said power supply to predeterminedly vary the power applied to said heater during energization pulse periods thereof.

Claim 2

Dependent Claim 163 words

A printing apparatus comprising: a thermal print head which comprises: (a) a plurality of drop-emitter nozzles; (b) a body of ink associated with said nozzles; (c) a pressurizing device adapted to subject ink in said body of ink to a pressure of at least 2% above ambient pressure, at least during drop selection and separation to form a meniscus with an air/ink interface; selection apparatus operable upon the air/ink interface to select predetermined nozzles and to generate a difference in meniscus position between ink in selected and non-selected nozzles, the drop selection apparatus including a heater operated in response to energizing power; and (e) drop separation apparatus adapted to cause ink from selected nozzles to separate as drops from the body of ink, while allowing ink to be retained in non-selected nozzles; a programmable power supply for energizing said heater; and control means for predeterminedly controlling said power supply to predeterminedly vary the power applied to said heater during energization pulse periods thereof.

Claim 3

Dependent Claim 30 words

The invention defined in claim 1 wherein said control means includes counter means for producing a signal(s), during such pulse periods, indicative of the then elapsed time of such period.

Claim 4

Dependent Claim 32 words

The invention defined in claim 2 wherein said counter means provides a signal indicating the amount of then elapsed time during an energizing pulse as a proportion of the entire pulse duration.

Claim 5

Dependent Claim 30 words

The invention defined in claim 2 wherein said control means includes look-up means for outputting signals indicative of required power levels in response to input signals from said counter means.

Claim 6

Dependent Claim 21 words

An apparatus as claimed in claim 2 where the counter function includes circuitry which produces a non-linear representation of elapsed time.

Claim 7

Dependent Claim 53 words

An apparatus as claimed in claim 1 where the heater power supply voltage is determined according to the equation: k(t)≅P(t), where P(t) is an optimum power function with respect to time required for the heater and k t! is a sampled approximation of the power function suitable for storing in an electronic memory.

Claim 8

Dependent Claim 19 words

An apparatus as claimed in claim 1 further comprising means for compensating the power supply voltage for print density.

Claim 9

Dependent Claim 19 words

An apparatus as claimed in claim 1 further comprising means for compensating the power supply voltage for ambient temperature.

Claim 10

Dependent Claim 23 words

An apparatus as claimed in claim 1 further comprising means for compensating the power supply voltage for both print density and ambient temperature.

Claim 11

Dependent Claim 154 words

An apparatus as claimed in claim 1 where the heater power supply voltage is determined according to the equation: ##EQU4## where: V PS is a voltage specified to the programmable power supply 320, R OUT is an output resistance of the programmable power supply 320 including connections to the print head; R H is the resistance of a single heater; p is a number representing the number of heaters that are turned on in a current enable period; n is a constant equal to the number of heaters represented by one least significant bit of p; t is time, divided into number of steps over the period of a single enable pulse; P(t) is a function defining a power input to a single heater required to achieve improved drop ejection; T E is the temperature required for drop ejection in °C.; and T A is the `ambient` temperature of the print head in °C.

Claim 12

Dependent Claim 192 words

A printing apparatus comprising: a thermal print head; a heater operable in response to energizing power; a programmable power supply for energizing said heater; and control means for predeterminedly controlling said power supply to predeterminedly vary the power applied to said heater during energization pulse periods thereof, where the heater power supply voltage is determined according to the equation: ##EQU5## where: V PS is a voltage specified to the programmable power supply 320, R OUT is an output resistance of the programmable power supply 320 including connections to the print head; R H is the resistance of a single heater; p is a number representing the number of heaters that are turned on in a current enable period; n is a constant equal to the number of heaters represented by one least significant bit of p; t is time, divided into number of steps over the period of a single enable pulse; P(t) is a function defining a power input to a single heater required to achieve improved drop ejection; t is the temperature required for drop ejection in °C.; and P(t) is the `ambient` temperature of the print head in °C.

Claim 13

Dependent Claim 192 words

A printing apparatus comprising: a thermal print head; a heater operable in response to energizing power; a programmable power supply for energizing said heater; and control means for predeterminedly controlling said power supply to predeterminedly vary the power applied to said heater during energization pulse periods thereof, where the heater power supply voltage is determined according to the equation: ##EQU5## where: V PS is a voltage specified to the programmable power supply 320, R OUT is an output resistance of the programmable power supply 320 including connections to the print head; R H is the resistance of a single heater; p is a number representing the number of heaters that are turned on in a current enable period; n is a constant equal to the number of heaters represented by one least significant bit of p; t is time, divided into number of steps over the period of a single enable pulse; P(t) is a function defining a power input to a single heater required to achieve improved drop ejection; t is the temperature required for drop ejection in °C.; and P(t) is the `ambient` temperature of the print head in °C.

Claim 14

Dependent Claim 162 words

A printing apparatus comprising: a thermal print head which comprises: (a) a plurality of drop-emitter nozzles; (b) a body of ink associated with said nozzles, said body of ink forming a meniscus with an air/ink interface at each nozzle; (c) drop selection apparatus operable upon the air/ink interface to select predetermined nozzles and to generate a difference in meniscus position between ink in selected and non-selected nozzles, the drop selection apparatus including a heater operable in response to energizing power; and (d) drop separation apparatus adapted to cause ink from selected, nozzles to separate as drops from the body of ink, while allowing ink to be retained in non-selected nozzles, said drop selection apparatus being capable of producing said difference in meniscus position in the absence of said drop separation apparatus; a programmable power supply for energizing said heater; and control means for predeterminedly controlling said power supply to predeterminedly vary the power applied to said heater during energization pulse periods thereof.

Claim 15

Dependent Claim 162 words

A printing apparatus comprising: a thermal print head which comprises: (a) a plurality of drop-emitter nozzles; (b) a body of ink associated with said nozzles, said body of ink forming a meniscus with an air/ink interface at each nozzle; (c) drop selection apparatus operable upon the air/ink interface to select predetermined nozzles and to generate a difference in meniscus position between ink in selected and non-selected nozzles, the drop selection apparatus including a heater operable in response to energizing power; and (d) drop separation apparatus adapted to cause ink from selected, nozzles to separate as drops from the body of ink, while allowing ink to be retained in non-selected nozzles, said drop selection apparatus being capable of producing said difference in meniscus position in the absence of said drop separation apparatus; a programmable power supply for energizing said heater; and control means for predeterminedly controlling said power supply to predeterminedly vary the power applied to said heater during energization pulse periods thereof.

Claim 16

Dependent Claim 30 words

The invention defined in claim 12 wherein said control means includes counter means for producing a signal(s), during such pulse periods, indicative of the then elapsed time of such period.

Claim 17

Dependent Claim 32 words

The invention defined in claim 13 wherein said counter means provides a signal indicating the amount of then elapsed time during an energizing pulse as a proportion of the entire pulse duration.

Claim 18

Dependent Claim 30 words

The invention defined in claim 13 wherein said control means includes look-up means for outputting signals indicative of required power levels in response to input signals from said counter means.

Claim 19

Dependent Claim 21 words

An apparatus as claimed in claim 13 where the counter function includes circuitry which produces a non-linear representation of elapsed time.

Claim 20

Dependent Claim 154 words

An apparatus as claimed in claim 12 where the heater power supply voltage is determined according to the equation: ##EQU6## where: V PS is a voltage specified to the programmable power supply 320, R OUT is an output resistance of the programmable power supply 320 including connections to the print head; R H is the resistance of a single heater; p is a number representing the number of heaters that are turned on in a current enable period; n is a constant equal to the number of heaters represented by one least significant bit of p; t is time, divided into number of steps over the period of a single enable pulse; P(t) is a function defining a power input to a single heater required to achieve improved drop ejection; T E is the temperature required for drop ejection in °C.; and T A is the `ambient` temperature of the print head in °C.

Claim 21

Dependent Claim 160 words

A printing apparatus comprising: a thermal print head which comprises: (a) a plurality of drop-emitter nozzles; (b) a body of ink associated with said nozzles, said body of ink forming a meniscus with an air/ink interface at each nozzle and said ink exhibiting a surface tension decrease of at least 10 mN/m over a 30° C. temperature range; (c) drop selection apparatus operable upon the air/ink interface to select predetermined nozzles and to generate a difference in meniscus position between ink in selected and non-selected nozzles, the drop selection apparatus including a heater operable in response to energizing power; and (d) drop separation apparatus adapted to cause ink from selected nozzles to separate as drops from the body of ink, while allowing ink to be retained in non-selected nozzles; a programmable power supply for energizing said heater; and control means for predeterminedly controlling said power supply to predeterminedly vary the power applied to said heater during energization pulse periods thereof.

Claim 22

Dependent Claim 160 words

A printing apparatus comprising: a thermal print head which comprises: (a) a plurality of drop-emitter nozzles; (b) a body of ink associated with said nozzles, said body of ink forming a meniscus with an air/ink interface at each nozzle and said ink exhibiting a surface tension decrease of at least 10 mN/m over a 30° C. temperature range; (c) drop selection apparatus operable upon the air/ink interface to select predetermined nozzles and to generate a difference in meniscus position between ink in selected and non-selected nozzles, the drop selection apparatus including a heater operable in response to energizing power; and (d) drop separation apparatus adapted to cause ink from selected nozzles to separate as drops from the body of ink, while allowing ink to be retained in non-selected nozzles; a programmable power supply for energizing said heater; and control means for predeterminedly controlling said power supply to predeterminedly vary the power applied to said heater during energization pulse periods thereof.

Claim 23

Dependent Claim 30 words

The invention defined in claim 18 wherein said control means includes counter means for producing a signal(s), during such pulse periods, indicative of the then elapsed time of such period.

Claim 24

Dependent Claim 32 words

The invention defined in claim 19 wherein said counter means provides a signal indicating the amount of then elapsed time during an energizing pulse as a proportion of the entire pulse duration.

Claim 25

Dependent Claim 30 words

The invention defined in claim 19 wherein said control means includes look-up means for outputting signals indicative of required power levels in response to input signals from said counter means.

Claim 26

Dependent Claim 21 words

An apparatus as claimed in claim 19 where the counter function includes circuitry which produces a non-linear representation of elapsed time.

Claim 27

Dependent Claim 154 words

An apparatus as claimed in claim 18 where the heater power supply voltage is determined according to the equation: ##EQU7## where: V PS is a voltage specified to the programmable power supply 320, R OUT is an output resistance of the programmable power supply 320 including connections to the print head; R H is the resistance of a single heater; p is a number representing the number of heaters that are turned on in a current enable period; n is a constant equal to the number of heaters represented by one least significant bit of p; t is time, divided into number of steps over the period of a single enable pulse; P(t) is a function defining a power input to a single heater required to achieve improved drop ejection; T E is the temperature required for drop ejection in °C.; and T A is the `ambient` temperature of the print head in °C.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2002-01-25	2002-07-27	2003-01-26	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2006-01-25	2006-07-27	2007-01-26	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2010-01-25	2010-07-27	2011-01-26	$7700.00	Window Closed / Lapsed

Heater power compensation for thermal lag in thermal printing systems

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