Patent EP0208484A2 successfully refreshed from Google Patents.
EP0208484A2
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Control circuit for an ink jet head
Assignee: Olivetti SpA
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Filing: 1986-06-27
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Granted: —
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Expires: 2006-06-27
Abstract
Abstract Two consecutive volotage pulses of equal duration (T 1 , T 2 ) and opposite polarities are applied to the control circuit. The two pulses which are combined together and amplified give rise to a signal of a particular wave form, which is applied to the piezoelectric transducer (104) for the expulsion of a drop of ink, free from disturbances caused by vibration of the meniscus at the time of separation of the drop, and to provide for cancellation of the reflected waves in the conduit. The transducer (104) forms in the ink conduit (102) a pressure wave of complex form, a first portion thereof contributing to the expulsion of a drop of ink and a second portion which is suitably out-of-phase with respect to the first portion neutralising the reflection phenomena caused by the first portion. An amplifier transistor (118, 120) is biased by means of a resistive network (114) supplied with a constant reference voltage (Vr) and is connected at its output to an RC filter (122) for modifying the slope of the signal which is amplified by the transistor (118). FIG.1
Inventors
- 👤 Alessandro Scardovi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 17:15
CPC Classifications
B; B41; B41J; B41J2/00; B41J2/005; B41J2/01; B41J2/015; B41J2/04; B41J2/045; B41J2/055
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
78 words
A control circuit (10) for an ink jet head in which the drops of ink are expelled from a nozzle (103) of a conduit (102) filled with ink, in response to a control signal, the ink forming in the nozzle a meniscus (M) having a natural resonance frequency, characterised in that the circuit is operable to generate a control signal (Vc) which neutralises the resonance, whereby expulsion of the drop (G) leaves the meniscus in a rest condition.
Claim 2
Dependent Claim
78 words
A control circuit (10) for an ink jet head in which the drops of ink are expelled from a nozzle (103) of a conduit (102) filled with ink, in response to a control signal, the ink forming in the nozzle a meniscus (M) having a natural resonance frequency, characterised in that the circuit is operable to generate a control signal (Vc) which neutralises the resonance, whereby expulsion of the drop (G) leaves the meniscus in a rest condition.
Claim 3
Dependent Claim
62 words
A control circuit (10) according to claim 1, wherein the meniscus (M) is excited to oscillate at the resonance frequency, on each expulsion of a drop (G), characterised in that the circuit comprises regulating means (114) for controlling the harmonic content of the signal in such a way that the harmonic content is opposite in phase to movement of the meniscus (M).
Claim 4
Dependent Claim
66 words
A circuit according to claim 2, characterised in that the control signal (Vc) comprises a negative half-wave followed by a positive half-wave, and by comprising means (118, 120) for amplifying the signal, the regulating means (114) comprising an electrical system (115,116) connected to the amplifying means for controlling the value of the positive and negative peaks of the half-waves with respect to a mean value (Vm).
Claim 5
Dependent Claim
53 words
A circuit according to claim 3, characterised in that the electrical system (115,116) comprises first and second resistors in series, the amplifying means (118, 120) being connected to an intermediate point (110) between the resistors whereby the ratio of the values of the resistors determines the relationship between the peaks of the half-waves.
Claim 6
Dependent Claim
27 words
A circuit according to claim 2 or claim 4, characterised in that the peak-to-peak value of the control signal (Vc) is determined independently of the regulating means.
Claim 7
Dependent Claim
54 words
A circuit according to claim 3, 4 or 5, characterised in that the amplifying means (118, 120) comprises a transistor (118) having a base connected to the intermediate point (110) and a third resistor (120) connected to the emitter of the transistor (118), the third resistor controlling the peak-to-peak value of the signal (Vc).
Claim 8
Dependent Claim
35 words
A circuit according to claim 6, characterised in that the third resistor (120) is a variable resistor, and in that the setting of the variable resistor control the speed of expulsion of drops of ink.
Claim 9
Dependent Claim
50 words
A circuit according to claim 6 or claim 7, characterised in that the amplifying means (118, 120) comprises an electrical filter (122) connected in series between a dc feed voltage source (Va) and the collector of the first transistor (118) for suppressing the higher harmonics of the control signal (Vc).
Claim 10
Dependent Claim
26 words
A pilot control circuit according to claim 8, characterised in that the electrical filter (122) comprises a resistor (124) connected in parallel with a capacitor (123).
Claim 11
Dependent Claim
30 words
A pilot control circuit according to claim 8, characterised in that the filter (122) comprises an active electrical circuit for generating portions of constant slope in the control signal (Vc).
Claim 12
Dependent Claim
123 words
A circuit according to any of claims 3 to 10, comprising a generator (Q) for generating control pulses for the circuit (10) and in which the regulating means vary the form of the half-waves in such a way as to cancel acoustic reflections in the conduit (102), characterised in that the generator (Q) generates two consecutive and symmetrical pulses for enabling the amplifying means (118, 120) to generate the control signal (Vc), such as to form in the conduit (102) a main pressure wave followed by a secondary pressure wave for cancelling any reflection of the main wave, whereby emission of the drops (G) of ink from the nozzle (103) is free from disturbances produced by oscillations in the pressure in the conduit.
Claim 13
Dependent Claim
66 words
A circuit according to claim 11, characterised in that it comprises an electrical system (115,116) operable to control the amplitude of the half-waves, the first of the pulses causing the amplifying means (118, 120) to generate a first half-wave such as to form in said conduit the main pressure wave, and the second of the pulses causing the amplifying means to generate the secondary pressure wave.
Claim 14
Dependent Claim
25 words
A circuit according to any of claims 3 to 12, characterised in that the electrical system (115,116) is fed by a reference voltage source (Vr).
Claim 15
Dependent Claim
66 words
An ink jet print head including a control circuit according to any of the preceding claims, characterised in that the conduit (102) for the ink comprises a rigid tube and that the transducer (104) comprises a sleeve of piezoelectric material which is rigidly fixed to the outside surface of the tube to generate a pressure wave within said tube in response to the control signal (Vc).
Claim 16
Dependent Claim
80 words
An ink jet print head including a circuit according to any of claims 1 to 13, characterised in that the conduit (102) comprises a chamber for the ink, the chamber having parallel epipedic shape and having a wall provided with a nozzle, and in that the transducer comprises a plate portion forming another wall of the chamber, opposite to the nozzle, the transducer being operable to generate a pressure wave within the chamber in response to the control signal (Vc).
Claim 17
Dependent Claim
39 words
A print head according to claim 14 or claim 15, characterised in that the conduit (102) is connected to a container (S) for the ink by means of a connection of elastic material and a filter for said ink.
References Cited (Backward Citations)
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