Sub-harmonic phase control for an ink jet recording system

Claim 3

The method of claim 1 wherein said accumulating step comprises: rectifying said amplifying signals; and integrating said rectified signals for a predetermined period.

Claim 4

The method of claim 1 additionally comprising the step of: disabling said electrostatic deflection field during said sync test cycle.

Claim 5

In an ink jet recording system which comprises a source of conductive fluid, nozzle means for projecting said conductive fluid in a continuous stream, perturbation means operating at a predetermined rate to cause said continuous stream to break into a stream of substantially uniform droplets, charging means for selectively creating charging fields of predetermined duration to selectively impart charges to said droplets, deflection means for deflecting said charged droplets, gutter means for receiving substantially undeflected ones of said droplets, and synchronizing means for controlling the relative phase of said perturbation means and said charging means, the improvement comprising: sync testing means for applying a series of test charge signals substantially narrower than said predetermined duration to said charging means at a repetition rate which is a sub-harmonic of said predetermined rate; induction sensing means for sensing droplets charged by said test charge signals; detection means for detecting in a narrow frequency band centered at said repetition rate and accumulating signals from said induction sensing means and phase detection means for comparing said accumulated signals to a predetermined level for supplying a phase indicating signal to said synchronizing means in response to said comparison.

Claim 6

In an ink jet recording system which comprises a source of conductive fluid, nozzle means for projecting said conductive fluid in a continuous stream, perturbation means operating at a predetermined rate to cause said continuous stream to break into a stream of substantially uniform droplets, charging means for selectively creating charging fields of predetermined duration to selectively impart charges to said droplets, deflection means for deflecting said charged droplets, gutter means for receiving substantially undeflected ones of said droplets, and synchronizing means for controlling the relative phase of said perturbation means and said charging means, the improvement comprising: sync testing means for applying a series of test charge signals substantially narrower than said predetermined duration to said charging means at a repetition rate which is a sub-harmonic of said predetermined rate; induction sensing means for sensing droplets charged by said test charge signals; detection means for detecting in a narrow frequency band centered at said repetition rate and accumulating signals from said induction sensing means and phase detection means for comparing said accumulated signals to a predetermined level for supplying a phase indicating signal to said synchronizing means in response to said comparison.

Claim 7

The apparatus of claim 4 wherein said detection means comprises: narrow band amplification means for filtering and amplifying said signals from said induction sensing means in said narrow frequency band centered at said repetition rate; and accumulation means for accumulating said amplified signals.

Claim 8

The apparatus of claim 5 wherein: said induction sensing means is mounted at said gutter means.

Claim 9

The apparatus of claim 6 wherein said accumulation means comprises: a rectifier for rectifying said amplified signals; an integrator for integrating said rectified signals; and gate means for operating said integrator during the expected arrival time period at said induction sensing means of said test droplets.

Claim 10

The apparatus of claim 6 wherein: said gutter is arranged to be an electrical shield; said induction sensing means comprises an insulated wire mounted along and projecting from said gutter so that droplets entering said gutter move from an unshielded condition near said wire to a shielded condition with respect to said wire.

Claim 11

The apparatus of claim 8 additionally comprising: means for disabling said deflection means during said application of test charge signals and continuing through operation of said detection means.

Claim 12

In an ink jet recording system which comprises a source of conductive fluid, nozzle means for projecting said conductive fluid in a continuous stream, perturbation means operating at a predetermined rate to cause said continuous stream to break into a stream of substantially uniform droplets, charging means for selectively creating charging fields of predetermined duration to selectively impart charges to said droplets, deflection means for deflecting said charged droplets, gutter means for receiving substantially undeflected ones of said droplets, and synchronizing means for controlling the relative phase of said perturbation means and said charging means, the improvement comprising: a sync test circuit for applying a series of test charge pulses substantially narrower than and centered with respect to said predetermined duration to said charging means at a repetition rate which is a sub-harmonic of said predetermined rate; an induction sensor for sensing droplets charged by said test charge signals; a narrow band amplifier for filtering and amplifying said signals from said induction sensor in a narrow frequency band centered at said repetition rate; an accumulation circuit for accumulating said amplified signals; and a phase indicating circuit for comparing said accumulated signals to a predetermined level and supplying a phase indicating signal to said synchronizing means in response to said comparison.

Claim 13

In an ink jet recording system which comprises a source of conductive fluid, nozzle means for projecting said conductive fluid in a continuous stream, perturbation means operating at a predetermined rate to cause said continuous stream to break into a stream of substantially uniform droplets, charging means for selectively creating charging fields of predetermined duration to selectively impart charges to said droplets, deflection means for deflecting said charged droplets, gutter means for receiving substantially undeflected ones of said droplets, and synchronizing means for controlling the relative phase of said perturbation means and said charging means, the improvement comprising: a sync test circuit for applying a series of test charge pulses substantially narrower than and centered with respect to said predetermined duration to said charging means at a repetition rate which is a sub-harmonic of said predetermined rate; an induction sensor for sensing droplets charged by said test charge signals; a narrow band amplifier for filtering and amplifying said signals from said induction sensor in a narrow frequency band centered at said repetition rate; an accumulation circuit for accumulating said amplified signals; and a phase indicating circuit for comparing said accumulated signals to a predetermined level and supplying a phase indicating signal to said synchronizing means in response to said comparison.