Thermal printer

Claim 2

A thermal printer as claimed in claim 1, characterized in that said control means comprises: decoding means (422) responsive to the energy code for each heating element for generating a pulse width code representing one of at least two pulse widths for said heating element; and energizing means (16 1 , 16 2 , 16 3 , ..., 16 n , 22, 424) connected between said decoding means and said heating elements for energizing each heating element for a length of time corresponding to its pulse width code.

Claim 3

A thermal printer as claimed in claim 2, characterized in that said energizing means first energizes selected ones of said heating elements corresponding to a first pulse width code, and then energizes selected ones of said heating elements corresponding to a second pulse width code. -

Claim 4

A themal printer as claimed in claim 2, characterized in that said energizing means energizes selected ones of said heating elements for overlapping time periods according to at least two different pulse width codes to minimize the total printing time-

Claim 5

A thermal printer as claimed in claim 3 or 4, characterized in that said energizing means comprises: a drive circuit (161, 162, 163, ..., 16 n ) connected to each heating element and said power supply means to drive said heating element; a shift register (22) connected to said drive circuits to selectively actuate said drive circuits in accordance with gating signals (Y); and a multiplexer (424) connected to said decoding means and said shift register and responsive to the pulse width codes to generate at least two sets of gating signals, one set of gating signals corresponding to each pulse width.

Claim 6

A thermal printer as claimed in claim 5, characterized in that said energizing means further comprises a timing circuit (426) connected to said multiplexer and said shift register to selectively couple the sets of gating signals to said shift register and to latch the sets of gating signals stored in said shift register to said drive circuits to drive said heating elements for a predetermined period of time.

Claim 7

A thermal printer as claimed in claim 1, characterized in that said memory means comprises RAM (38) and said energy code means comprises: logic memory means (36) connected to said control means and said RAM for storing energy codes at fixed addresses; and . an address decoder (34) connected to said RAM and said logic memory means to convert the incoming information signal and the previous energy code for each heating element to an address for said heating element, said energy code means supplying the address to said logic memory means to look up the energy code stored in said logic memory means.

Claim 8

A thermal printer as claimed in claim 7, characterized in that said thermal printer further comprises a second control means (46) connected to said R AM, said logic memory means and said address decoder for controlling the transfer of energy codes between said energy code means and said control means.

Claim 9

A thermal printer for printing information on heat-sensitive paper during a plurality of printing cycles, said thermal printer characterized by comprising: a plurality of heating elements (121, 12 2 , 12 3 , ... , 12n); power supply means (18) for supplying said heating elements with electrical power; control means (161, 16 2 , 163, ..., 16 n , 22, 42) connected between said heating elements and said power supply means for controlling the amount of electrial power supplied to each one of said heating elements in accordance with an energy code (Nl, N 2 ) for each heating element; energy code means (34', 36', 62) connected to said control means for generating an energy code for each heating element in response to (a) the incoming information signal (G) for said heating element, (b) the previous energy code (M l , M 2 ) for said heating element generated by said energy code means during the previous printing cycle, and (c) the previous adjacent energy codes (M l , M 2 ) for heating elements adjacent to said heating element generated by said energy code means during the previous printing cycle; and - memory means (38) connected to said energy code means for storing the energy codes generated by said energy code means, said memory means supplying the energy codes to said energy code means during the next printing cycle as the previous codes.

Claim 10

A thermal printer as claimed in claim 9, characterized in that said memory means comprises a RAM (38) and said energy code means comprises: logic memory means (36') connected to said control means and said RAM for storing energy codes at fixed addresses; and an address decoder (34') connected to said RAM and said logic memory means to convert the incoming information signal, the previous energy code for each heating element, and the previous adjacent energy codes to an address for said heating element, said energy code means supplying the address to said logic memory means to look up the energy code stored in said logic memory means.

Claim 11

A thermal printer as claimed in claim 10, characterized in that said address decoder comprises: at least three pairs of flip-flop circuits (821 to 82 6 ) connected to said second memory means and arranged as a shift register to shift the contents of each pair of flip-flop circuits from one to another; and a pair of input gates (84 1 , 84 2 ) connected between said first memory means and the first of said pair of flip-flop circuits to input to said first pair of flip-flop circuits energy codes from said first memory means.

Claim 12

A thermal printer as claimed in claim 10, characterized in that said energy code means further comprises a demultiplexer (62) connected between said RAM and said address decoder to receive the previous energy codes and the previous adjacent energy codes for said heating elements and supply the previous energy codes and the previous adjacent energy codes to said address decoder.

Claim 13

A thermal printer for printing information on heat-sensitive paper during a plurality of printing cycles, said thermal printer characterized by comprising: a plurality of heating elements (121, 122, 123, .. ., 12n); power supply means (18) for supplying said heating elements with electrical power; control means (161, 16 2 , 16 3 , ..., 16 n , 22, 42) connected between said heating elements and said power supply means for controlling the amount of electrical power supplied to each one of said heating elements in accordance with an energy code (N l , N 2 ) for each heating element; energy code means (34, 36) connected to said control means for generating an energy code for each heating element in response to (a) the incoming information signal (G) for said heating element, (b) the previous energy code (Ml, M 2 ) for said heating element generated by said energy code means during the previous printing cycle, and (c) the transmission time (T a ) of the information in the previous printing cycle; and memory means (38) connected to said energy code means for storing the energy codes generated by said energy code means, said memory means supplying the energy codes to said energy code means during the next printing cycle as the previous energy codes.

Claim 14

A thermal printer as claimed in claim 13, characterized by further comprising a transmission time detection circuit (52) responsive to synchronization information (PRD) in the incoming information signal and connected to said energy code means to detect the transmission time of the information in the previous printing cycle and to supply the transmission time to said energy code means.

Claim 15

A thermal printer as claimed in claim 14, characterized in that said thermal printer further comprises a sync separator (54) connected to said transmission time detection circuit to extract synchronization information from the incoming information signal and supply the synchronization information to said transmission time detection circuit.

Claim 16

A thermal printer for printing information on heat-sensitive paper during a plurality of printing cycles, said thermal printer characterized by comprising: a plurality of heating elements (121, 12 2 , 12 3 , .. ., 12n); power supply means (18) for supplying said heating elements with electrical power; control means (16 1 , 16 2 , 16 3 , ..., 16 n , 22, 42) connected between said heating elements and said power supply means for controlling the amount of electrical power supplied to each one of said heating elements in accordance with a energy code (Nl, N 2 ) for each heating element; energy code means (34", 36") connected to said control means for generating an energy code for each heating element in response to (a) the incoming information signal (G) for said heating element, (b) the previous energy code (Ml, M 2 ) for said heating element generated by said energy code means during the previous printing cycle, (c) the previous adjacent energy codes (Ml, M2) for heating elements adjacent to said heating element, and (d) the transmission time (Ta) of the information in the previous printing cycle; and memory means (38) connected to said energy code means for storing the energy codes generated by said energy code means, said memory means supplying the energy codes to said energy code means during the next printing cycle as the previous energy codes.

Claim 17

A thermal printer for printing information on heat-sensitive paper during a plurality of printing cycles, said thermal printer characterized by comprising: a plurality of heating elements (121, 12 2 , 12 3 , ..., 12n); power supply means (18) for supplying said heating elements with electrical power; a drive circuit (161, 16 2 , 163, ..., 16n) connected to each heating element and said power supply means to drive said heating element; a shift register (22) connected to- said drive circuits to selectively actuate said drive circuits; a first control circuit (42) connected to said shift register to control said shift register in accordance with an energy code (N 1 , N 2 ) for each heating element; memory means (38) for storing the energy codes; energy code means (34, 36) connected to said memory means and said first control circuit for generating an energy code for each heating element during each printing cycle in response to an input signal, said input signal including an incoming information signal (G) for said heating element and an energy code (Ml, M 2 ) generated by said energy code means for said heating element during the preceding printing cycle and stored in said memory means; and a second control circuit (46) connected to said energy code means and said memory means to control the transmission of energy codes between said memory means and said energy code means and to control the transmission of energy codes from said energy code means to said first control circuit.

Claim 18

A thermal printer as claimed in claim 17, characterized in that the input signal to said energy code means further includes energy codes generated by said energy code means during the preceding printing cycle for heating elements adjacent to said heating element.

Claim 19

A thermal printer as claimed in claim 17, characterized in that the input signal to said energy code means further comprises a signal (P) representing the transmission time (T a ) of the information in the preceding printing cycle.

Claim 20

A thermal printer as claimed in claim 17, 18 or 19, characterized in that said control means comprises: conversion means (422) responsive to the energy codes for generating at least two sets of gating signals; and timing means (424, 426) connected to said conversion means for enabling said conversion means to successively couple the sets of gating signals to said shift register, said timing means further latching the set of gating signals stored in said shift register to said drive circuits to drive said heating elements for a predetermined period of time.

Claim 21

A thermal printer as claimed in claim 20, characterized in that said timing means generates a first latch pulse to latch a first set of gating signals from said shift register to said drive circuits for a first time period and a second latch pulse to latch a second set of gating signals from said shift register to said drive circuits for a second time period.

Claim 22

In a thermal printer for printing information on heat sensitive paper during a plurality of printing cycles, said thermal printer comprising a plurality of heating elements (121, 12 2 , 123, ..., 12 n ) and a memory (38), a method for supplying different amounts of energy to drive said heating elements, said method characterized by comprising the steps of: generating an energy code (N 1 , N 2 ) for each of said heating elements in response to at least the previous energy code (Ml, M 2 ) for said heating element and the incoming information (G) to be printed by said heating element; storing the energy codes in said memory for use during the next printing cycle as the previous energy codes; using the energy codes generated during each printing cycle to generate at least two sets of pulse width codes for driving said heating elements; driving said heating elements first in accordance with the first set of pulse width codes; and driving said heating elements second in accordance with the second set of pulse width codes.