Method of operating an on demand-type ink jet head and system therefor

Claim 1

A method of operating an on-demand type ink jet head, which comprises a pressure chamber (2) with an inlet (4) which communicates with a supply of ink (6) and an outlet .(3) which communicates with the atmosphere, and an electro-mechanical transducer (9) which is arranged to alter the volume of the pressure chamber (2), comprising the steps of: applying an electrical signal to the electro-mechanical transducer (9) so that the volume of the pressure chamber (2) is increased whereby ink is drawn into the pressure chamber (2); and changing the said signal so that the volume of the pressure chamber (2) is reduced whereby ink (6) is propelled out of the said outlet (3) , characterised in that the said signal is changed at a time when the amplitude of oscillation of a mechanical system formed by the electro-mechanical transducer (9), at least part of the pressure chamber (5), and ink (6) within the pressure chamber (2) is substantially at a maximum.

Claim 2

A method of operating an on-demand type ink jet head, which comprises a pressure chamber (2) with an inlet (4) which communicates with a supply of ink (6) and an outlet .(3) which communicates with the atmosphere, and an electro-mechanical transducer (9) which is arranged to alter the volume of the pressure chamber (2), comprising the steps of: applying an electrical signal to the electro-mechanical transducer (9) so that the volume of the pressure chamber (2) is increased whereby ink is drawn into the pressure chamber (2); and changing the said signal so that the volume of the pressure chamber (2) is reduced whereby ink (6) is propelled out of the said outlet (3) , characterised in that the said signal is changed at a time when the amplitude of oscillation of a mechanical system formed by the electro-mechanical transducer (9), at least part of the pressure chamber (5), and ink (6) within the pressure chamber (2) is substantially at a maximum.

Claim 8

A method as claimed in any preceding claim characterised in that the said signal is applied to the electro-mechanical transducer (9) by signal supply means which comprises a transistor drive circuit, the electro-mechanical transducer (9) being connected in parallel with a resistor (13), the parallel arrangement (9,13) being connected to the collector of an output transistor (31) of the said circuit.

Claim 14

A system as claimed in any of claims 8 to 11 characterised in that the electro-mechanical transducer (9) is a piezo-electric transducer (9) and that the polarity of the said signal when it causes the volume of the pressure chamber (2) to be decreased is the same as that of the polarization voltage of the piezoelectric transducer (9).

Claim 15

A method for operating a demand type ink jet head, said ink jet head having a pressure chamber of a predetermined volume, a nozzle one end of which communicates with the atmosphere and the other end with said pressure chamber, means for supplying ink to said pressure chamber, and electro-mechanical conversion means operatively coupled for deforming a wall of said pressure chamber, comprising the steps of connecting the power source of the driving circuit of said electro-mechanical conversion means to establish said wall of said pressure chamber in the standby position, an application of an electrical signal to said electro-mechanical conversion means to displace said wall Ωf said pressure chamber to increase the volume of said pressure chamber thereby to draw ink from said ink supplyiag means into said pressure chamberi and suspending application of said electrical signal to said electro-mechanical conversion means in synchronisation with damped oscillation of a mechanical system formed by said wall of said pressure chamber, said electro-mechanical conversion means and said ink at such a time that said wall of said pressure chamber is abruptly restored in said standby position to thereby jet ink droplet from said nozzle.

Claim 16

A method for operating a demand type ink jet head, said ink jet head having a pressure chamber of a predetermined volume, a nozzle one end of which communicates with the atmosphere and the other end with said pressure chamber, means for supplying ink to said pressure chamber, and electro-mechanical conversion means operatively coupled for deforming a wall of said pressure chamber, comprising the steps of connecting the power source of the driving circuit of said electro-mechanical conversion means to establish said wall of said pressure chamber in the standby position, an application of an electrical signal to said electro-mechanical conversion means to displace said wall Ωf said pressure chamber to increase the volume of said pressure chamber thereby to draw ink from said ink supplyiag means into said pressure chamberi and suspending application of said electrical signal to said electro-mechanical conversion means in synchronisation with damped oscillation of a mechanical system formed by said wall of said pressure chamber, said electro-mechanical conversion means and said ink at such a time that said wall of said pressure chamber is abruptly restored in said standby position to thereby jet ink droplet from said nozzle.

Claim 17

A method for operating a demand type ink jet head, said ink jet head having a pressure chamber of a predetermined volume, a nozzle one end of which communicates with the atmosphere and the other end with said pressure chamber, means for supplying ink to said pressure chamber, and electro-mechanical conversion means operatively coupled for deforming a wall of said pressure chamber, comprising the steps of applying an electrical signal to said electro-mechanical conversion means to preliminarily displace said wall of said pressure chamber inwardly to increase the volume of said pressure chamber thereby, removing said electrical signal from said electro-mechanical conversion means to allow the latter to restore its original state with elastic energy stored in the said wall of said pressure chamber and said electro-mechanical conversion means allowing to draw ink into said pressure chamber from said ink supplying means; and then applying said electrical signal to said electro-mechanical conversion means in synchronization with damped oscillation of a mechanical system formed by said wall of said pressure chamber, said electro-mechanical conversion means and said ink at such a time that said wall of said pressure chamber is abruptly restored to thereby jet ink jet droplet from said nozzle.

Claim 18

A method for operating a demand type ink jet head, said ink jet head having a pressure chamber of a predetermined volume, a nozzle one end of which communicates with the atmosphere and the other end with said pressure chamber, means for supplying ink to said pressure chamber, and electro-mechanical conversion means operatively coupled for deforming a wall of said pressure chamber, comprising the steps of applying an electrical signal to said electro-mechanical conversion means to preliminarily displace said wall of said pressure chamber inwardly to increase the volume of said pressure chamber thereby, removing said electrical signal from said electro-mechanical conversion means to allow the latter to restore its original state with elastic energy stored in the said wall of said pressure chamber and said electro-mechanical conversion means allowing to draw ink into said pressure chamber from said ink supplying means; and then applying said electrical signal to said electro-mechanical conversion means in synchronization with damped oscillation of a mechanical system formed by said wall of said pressure chamber, said electro-mechanical conversion means and said ink at such a time that said wall of said pressure chamber is abruptly restored to thereby jet ink jet droplet from said nozzle.

Claim 19

A method for operating a demand type ink. jet head, said ink jet head having a pressure chamber of a predetermined volume, a nozzle one end of which communicates with the atmosphere and the other end with said pressure chamber,means for supplying ink to said pressure chamber, and electro-mechanical conversion means operatively coupled for deforming a wall of said pressure chamber, comprising the steps of applying an electrical signal of the first polarity to said electro-mechanical conversion means to displace said wall of said pressure chamber inwardly to decrease the volume of said pressure chamber, applying an electrical signal of the second ' polarity which is opposite of said first polarity to said electro-mechanical conversion means to displace said wall of said pressure chamber upwardly to increase the volume of said pressure chamber and thereby draw ink into said pressure chamber from ink supplying means; and the changing of said second polarity to said first polarity of said electrical signal applied to said electro-mechanical conversion means in synchronisation with damped oscillation of a mechanical system formed by said wall of said pressure chamber, said electro-mechanical conversion means and said ink at such a time that said wall of said pressure chamber is abruptly restored inwardly to thereby ink droplets from said nozzle.

Claim 20

A method for operating a demand type ink. jet head, said ink jet head having a pressure chamber of a predetermined volume, a nozzle one end of which communicates with the atmosphere and the other end with said pressure chamber,means for supplying ink to said pressure chamber, and electro-mechanical conversion means operatively coupled for deforming a wall of said pressure chamber, comprising the steps of applying an electrical signal of the first polarity to said electro-mechanical conversion means to displace said wall of said pressure chamber inwardly to decrease the volume of said pressure chamber, applying an electrical signal of the second ' polarity which is opposite of said first polarity to said electro-mechanical conversion means to displace said wall of said pressure chamber upwardly to increase the volume of said pressure chamber and thereby draw ink into said pressure chamber from ink supplying means; and the changing of said second polarity to said first polarity of said electrical signal applied to said electro-mechanical conversion means in synchronisation with damped oscillation of a mechanical system formed by said wall of said pressure chamber, said electro-mechanical conversion means and said ink at such a time that said wall of said pressure chamber is abruptly restored inwardly to thereby ink droplets from said nozzle.