Method of multi-tone printing

Claim 3

The method as claimed in Claim 1, characterised by said electrically actuable means effecting droplet ejection from said channels by displacement of respective side wall portions thereof.

Claim 4

The method as claimed in Claim 1, characterised by said electrically actuable means effecting droplet ejection from said channels by displacement of respective, piezo-electric side wall portions of said channels.

Claim 5

The method as claimed in Claim 1, characterised by said electrically actuable means effecting droplet ejection from said channels by causing thermal stress in the ink therein.

Claim 6

The method as claimed in Claim 4, characterised by said electrically actuable means effecting droplet ejection from said channels by causing bubble nucleation and collapse therein.

Claim 8

The method claimed in Claim 6, characterised by effecting droplet deposition on said substrate from each channel in approximately two thirds of the pitch of said printing element areas.

Claim 9

The method claimed in Claim 6 or Claim 7, characterised by enabling deposition on each printing element area from the corresponding channel of any number, up to sixty-four, of droplets.

Claim 10

The method claimed in Claim 6, Claim 7 or Claim 8, characterised by effecting droplet deposition on said substrate symmetrically with respect to the printing element area printed by said channel.

Claim 13

The method claimed in Claim 11, and in which the channels are arranged in two groups, characterised by enabling for droplet ejection selected channels of one of said groups at an interval following enabling of selected channels of the other of said groups of a half cycle of the frequency of pulses applied by said electrically operated means to the channels selected for droplet ejection.

Claim 16

The method claimed in Claim 14, characterised in that the frequency of pulses applied by said electrically operated means to the channels is above 25KHz.

Claim 17

The method claimed in Claim 15, characterised in that said frequency is in the range 50 KHz to 250 KHz.

Claim 19

The method claimed in Claim 1, in which the channels are arranged in a plurality of rows extending transversely to the direction of relative motion of the substrate and the apparatus and the nozzle pitch in each row is a multiple equal to the number of said rows of the pitch of said printing element areas in the direction transverse to said direction of relative motion, characterised by disposing the rows of channel and their nozzles so that the nozzles of one row serve to print picture element areas of a row of such areas on the substrate which are being printed which extends normal to said direction of relative motion which are interleaved with those which the nozzles of the other rows serve to print.

Claim 21

The method claimed in Claim 19, characterised by printing by depositing droplets from the channel nozzles in the centre of each printing element area printed.

Claim 25

The method claimed in Claim 22, characterised by holding the substrate stationary relatively to the ink channel during printing.

Claim 29

The method claimed in Claim 25, characterised by providing for each printing element area of the substrate a group of four channels having respective ink supplies of black ink and ink of the three primary colours thereby to enable printing of each printing element area in black or one of the said primary colours,

Claim 30

A multi-channel array, electrically pulsed droplet deposition apparatus, comprising a multiplicity of parallel channels, mutually spaced in an array direction normal to the length of the channels, said channels having respective side walls which extend in the lengthwise direction of the channels, and in a direction which is both normal to said lengthwise direction and normal to the array direction, respective nozzles communicating with said channels for ejection of droplets of liquid, connection means for connecting said channels to a source of droplet deposition liquid and electrically actuable means located in relation to said channels to effect, upon actuation of any selected channel, application of pulses of energy to droplet liquid in said selected channel to effect droplet ejection from the nozzle communicating therewith, characterised in that said channels have length dimensions and nozzle dimensions and locations to afford channels of high longitudinal acoustic resonant frequency and said electrically actuable means are adapted to apply in successive periods to droplet liquid in respective numbers of channels selected for actuation in each of said periods respective sequences of pulses of energy of amplitude and frequency to cause droplet ejection from the selected channels at or near the resonant frequency of the channels, each sequence of pulses containing a number of pulses to eject a corresponding number of discrete droplets, said number being determined by the tone of printing required to be effected from the channel.

Claim 31

A multi-channel array, electrically pulsed droplet deposition apparatus, comprising a multiplicity of parallel channels, mutually spaced in an array direction normal to the length of the channels, said channels having respective side walls which extend in the lengthwise direction of the channels, and in a direction which is both normal to said lengthwise direction and normal to the array direction, respective nozzles communicating with said channels for ejection of droplets of liquid, connection means for connecting said channels to a source of droplet deposition liquid and electrically actuable means located in relation to said channels to effect, upon actuation of any selected channel, application of pulses of energy to droplet liquid in said selected channel to effect droplet ejection from the nozzle communicating therewith, characterised in that said channels have length dimensions and nozzle dimensions and locations to afford channels of high longitudinal acoustic resonant frequency and said electrically actuable means are adapted to apply in successive periods to droplet liquid in respective numbers of channels selected for actuation in each of said periods respective sequences of pulses of energy of amplitude and frequency to cause droplet ejection from the selected channels at or near the resonant frequency of the channels, each sequence of pulses containing a number of pulses to eject a corresponding number of discrete droplets, said number being determined by the tone of printing required to be effected from the channel.

Claim 32

Apparatus as claimed in Claim 27, characterised in that said channels include respective displaceable side wall portions and said electrically actuable means are adapted to effect displacement of said side wall portions to impart said energy pulses to droplet liquid in the channels.

Claim 33

Apparatus as claimed in Claim 27 or Claim 28, characterised in that said channels are formed in a body of piezo-electric material and have side wall portions poled so as to be displaceable by operation of said electrically actuable means.

Claim 34

Apparatus as claimed in Claim 29, characterised in that said side wall portions are poled so as to be displaced in shear mode by said electrically actuable means.

Claim 35

Apparatus as claimed in Claim 30, characterised in that said channels are arranged in a plurality of groups of interleaved channels, the channels of the respective groups being disposed in repeated sequences and said electrically actuable means are adapted to cause selected channels of each group to be enabled for actuation simultaneously and to effect enabling of the groups of channels in successive intervals of duration to allow ejection of several drops from the enabled channels.

Claim 36

Apparatus as claimed in Claim 31, in which all channel dividing side walls are actuable and facing channel side walls are displaced by said electrically actuable means to effect droplet ejection from a channel therebetween, characterised in that the channels are arranged in at least three groups of interleaved channels.

Claim 37

Apparatus as claimed in Claim 32, characterised in that said electrically actuable means are adapted to provide that the period that selected channels are enabled by said electrically actuable means is sufficient for ejection therefrom of up to sixty-four droplets.

Claim 38

Apparatus as claimed in Claim 28, in which all channel dividing side walls are displaceable and facing channel side walls are displaced by said electrically actuable means to effect droplet ejection from a channel therebetween, characterised in that the channels are arranged in two groups of interleaved channels and said electrically actuable means are adapted to enable simultaneously selected channels of the respective groups and to enable the groups of channels in sequence, the period that channels of the groups are enabled being adequate to allow ejection of several droplets therefrom.

Claim 39

Apparatus as claimed in Claim 34, characterised in that said electrically actuable means are adapted to enable droplet ejection from adjacent channels at successive half cycles of the frequency of actuation pulses applied to the channels.

Claim 40

Apparatus as claimed in Claim 34 or Claim 35, characterised in that said electrically actuable means are adapted to enable each channel for a period sufficient for ejection therefrom of up to sixty-four droplets.

Claim 41

Apparatus as claimed in any one of Claims 28 to 36, characterised in that the channel length, channel nozzle diameter and channel density respectivly lie in the range 10 to 1mm, 20 to 10µm and 2 to 12 per mm.

Claim 42

Apparatus as claimed in Claim 27, characterised in that said electrically actuable means are adapted to cause droplet ejection from said channels by causing thermal stress in the droplet liquid therein.

Claim 43

Apparatus as claimed in Claim 38, characterised in that said electrically actuable means are adapted to cause droplet ejection from said channels by causing bubble nucleation and collapse in the droplet liquid therein.

Claim 44

Apparatus as claimed in Claim 27, characterised in that the channels are arranged in a plurality of rows extending in operation when said apparatus is printing on printing element areas of a substrate transversely to the direction of relative motion between the apparatus and the substrate and the nozzle pitch in each row is a multiple equal to the number of said rows of the pitch said printing element areas in the direction transverse to said direction of relative motion and said channels and their nozzles are disposed so that the nozzles of each row serve to print picture element areas of a row of such areas on the substrate which are being printed which extends normal to said direction of relative motion and which are interleaved with those which the nozzles of the other rows serve to print.

Claim 45

Apparatus as claimed in any one of Claims 27 to 40, characterised in that the array of channels is arranged in a set or sets of four rows of channels, the rows of each set being adapted for the supply thereto respectively of black ink and ink of one of the three primary colours, and the nozzles of the rows of each set are disposed to enable printing of printing element areas by any channel of said set in black ink or ink of any one of the three primary colours.

Claim 46

An electrically pulsed droplet deposition apparatus, comprising a liquid channel having an ink ejection nozzle, droplet liquid supply means connected with said channel and electrically actuable means for supplying pulses of energy to liquid in said channel to effect droplet ejection therefrom, characterised in that the dimensions of the channel and the dimensions and location of the nozzle are adapted to provide the channel with a high longitudinal acoustic resonant frequency so that application to ink in the channel of one or a sequence of pulses of energy of amplitude and frequency at or near the resonant frequency of the channel causes ejection of droplets corresponding in number to said applied pulses whereby the number of droplets deposited from the nozzle can be selected to correspond with a desired tone of printing.

Claim 47

An electrically pulsed droplet deposition apparatus, comprising a liquid channel having an ink ejection nozzle, droplet liquid supply means connected with said channel and electrically actuable means for supplying pulses of energy to liquid in said channel to effect droplet ejection therefrom, characterised in that the dimensions of the channel and the dimensions and location of the nozzle are adapted to provide the channel with a high longitudinal acoustic resonant frequency so that application to ink in the channel of one or a sequence of pulses of energy of amplitude and frequency at or near the resonant frequency of the channel causes ejection of droplets corresponding in number to said applied pulses whereby the number of droplets deposited from the nozzle can be selected to correspond with a desired tone of printing.

Claim 48

Apparatus as claimed in Claim 42, characterised in that there is provided a group of four such channels respectively supplied with black ink and ink of the three primary colours, the nozzles of the channels being arranged so that any printing element area of a substrate can be printed with any of said inks.

Claim 49

Apparatus as claimed in Claim 42 or Claim 43, characterised in that translating means are provided for moving the channel or group of channels relatively to a substrate to be printed.

Claim 50

A drop-on-demand printing apparatus for depositing ink droplets on a substrate comprising an array of printing channels provided with respective nozzles for depositing ink droplets on respective printing element areas of said substrate, ink supply means connected with said channels and electrically actuable means for applying pulses of energy to ink in said channels to effect droplet ejection therefrom, characterised in that the length of the channels and the location and dimensions of the nozzles provide the channels with high longitudinal resonant frequency so that application to ink in the channels of a pulse or sequence of pulses of energy of amplitude and frequency to cause droplet ejection from the channels at or near the resonant frequency of the channels causes ejection of droplets from the channels corresponding in number to the number of energy pulses applied to the ink therein whereby the number of droplets deposited from each nozzle can be selected to correspond with a desired tone of printing and effect printing with the substrate stationary relatively to the apparatus.

Claim 51

A drop-on-demand printing apparatus for depositing ink droplets on a substrate comprising an array of printing channels provided with respective nozzles for depositing ink droplets on respective printing element areas of said substrate, ink supply means connected with said channels and electrically actuable means for applying pulses of energy to ink in said channels to effect droplet ejection therefrom, characterised in that the length of the channels and the location and dimensions of the nozzles provide the channels with high longitudinal resonant frequency so that application to ink in the channels of a pulse or sequence of pulses of energy of amplitude and frequency to cause droplet ejection from the channels at or near the resonant frequency of the channels causes ejection of droplets from the channels corresponding in number to the number of energy pulses applied to the ink therein whereby the number of droplets deposited from each nozzle can be selected to correspond with a desired tone of printing and effect printing with the substrate stationary relatively to the apparatus.