Pressure wave damper apparatus for continuous liquid printing

1. A nozzle assembly for a printing apparatus having a movable printing head, the nozzle assembly being adapted to deposit a liquid ink onto a surface as the printing head is displaced with respect to the surface, motion of the printing head acting to impose pressure variations within a liquid ink being supplied to the nozzle assembly, the nozzle assembly comprising:

a nozzle body;

a nozzle disc supported by the nozzle body at a predetermined position therein, the nozzle disc having a nozzle opening,

a throttle plate mounted in the nozzle body at a location spaced from the nozzle disc, the throttle plate having a passage therein, the passage in the throttle plate being in fluid communication with the nozzle body, the throttle plate being operative to impart a throttling action on a flow of liquid ink passing into the nozzle body;

the nozzle body having a flexible portion, the flexible portion being positioned between the nozzle disc and the throttle plate, the flexible portion being able to define an accumulation space within the nozzle body in response to a pressure variation in the ink,

whereby, the throttling action by the throttle plate coupled with the definition of the accumulation space being operable to mitigate pressure variations in a liquid ink.

2. The nozzle assembly of claim 1 wherein the flexible portion forms part of the nozzle body between the nozzle disc and the throttle plate.

3. The nozzle assembly of claim 2 wherein the flexible portion is integral with and defined by a thinner region of the material of the nozzle body.

4. The nozzle assembly of claim 3 wherein the flexible portion is an annular member.

5. The nozzle assembly of claim 1 wherein the flexible portion is separate from but connected to the nozzle body.

6. The nozzle assembly of claim 1 wherein the flexible portion comprises a membrane attached to the interior surface of the nozzle body, the membrane and the surface of the nozzle body cooperating to define a closed volume having a compressible gas therein.

7. The nozzle assembly of claim 1 wherein the flexible portion comprises a separate member mounted within the nozzle body, the separate member enclosing a volume, the volume having a compressible gas therein.

8. The nozzle assembly of claim 7 wherein the compressible gas is an inert gas.

9. The nozzle assembly of claim 7 wherein the separate member is annular.

10. The nozzle assembly of claim 1 wherein the dimension of the passage in the throttle plate is adjustably selectable.