Method and apparatus for sensing and maintaining a gap between an ink jet printhead and a print medium

1. A method of operating an ink jet printer, comprising the steps of

positioning a printhead to jet ink onto a print medium;

attaching a conduit to said printhead, said conduit having a first opening opposing the print medium, and said conduit having a second opening;

causing air to flow through said conduit by blowing air through said opening;

measuring a pressure within said conduit;

providing a fluid resistor in said conduit, said fluid resistor interconnecting a first section of said conduit including said first opening and a second section of said conduit including said second opening, said first section containing a backpressure, said second section containing a static pressure; and

adjusting a printhead gap between said printhead and the print medium dependent upon said measuring step.

2. The method of claim 1 , comprising the further step of scanning said printhead across the print medium, said causing measuring and adjusting steps being performed substantially continuously during said scanning.

3. The method of claim 2 , wherein said adjusting step comprises maintaining a height of the printhead gap constant substantially throughout said scanning step.

4. The method of claim 1 , wherein said measuring step comprises measuring said backpressure within said first section of said conduit.

5. The method of claim 1 , wherein said first opening of said conduit has a width, said method comprising the further step of positioning said conduit such that a gap between said first opening and the print medium is less than 25% of said width of said first opening.

6. An apparatus for positioning an ink jet printhead relative to a print medium onto which said printhead jets ink, said apparatus comprising:

a first conduit configured to be attached to the printhead, said first conduit having a first opening configured to be disposed in opposition to the print medium, said first conduit having a second opening and a third opening;

a second conduit fluidly connected to said third opening;

an air-moving device configured to move air through said first conduit, said air-moving, device being in direct communication with said second opening;

a pressure-sensing device attached to said second conduit, said pressure sensing device being configured to sense pressure within said first conduit;

a gap-adjusting assembly configured to move at least one of the printhead and the print medium dependent upon the pressure sensed by said pressure-sensing device; and

a fluid resistor disposed between said second opening and said third opening, wherein said fluid resistor interconnects a first section of said first conduit including said first opening and a second section of said first conduit including said second opening, said first section containing a backpressure, said second section containing a static pressure.

7. The apparatus of claim 6 , wherein said first opening of said conduit is configured to be disposed within 2 millimeters of the print medium.

8. The apparatus of claim 6 , wherein said first opening of said first conduit has a width, a gap between said first opening and the print medium being configured to be less than 25% of said width of said first opening.

9. The apparatus of claim 6 , wherein said second opening of said first conduit is configured to receive air from said air moving device.

10. The apparatus of claim 6 , wherein said pressure-sensing device includes a housing fluidly connected to said second conduit, said housing having a side comprising a flexible diaphragm.

11. The apparatus of claim 10 , wherein a deflection of said diaphragm is dependent upon a gap between said first opening of said first conduit and the print medium.

12. The apparatus of claim 6 , wherein said first conduit comprises a first flexible tube, said second conduit comprising a second flexible tube.

13. The apparatus of claim 6 , wherein said first conduit includes a nozzle tapering to said first opening.

14. The apparatus of claim 6 , wherein said first opening of said first conduit is configured for being oriented substantially parallel to the print medium.

15. The apparatus of claim 6 , wherein said first opening of said first conduit is adjacent to the printhead.

16. An ink jet printer for printing on a print medium, comprising:

an ink jet printhead;

a first conduit configured to be attached to said printhead, said first conduit having a first opening configured to be disposed in opposition to the print medium, said first conduit-having a second opening and a third opening;

a second conduit fluidly connected to said third opening;

an air-moving device configured to move air through said first conduit, said second opening being in direct communication with said air-moving device;

a pressure-sensing device configured to sense pressure within said first conduit, said pressure-sensing device being attached to said second conduit; and

a gap-adjusting assembly configured to move at least one of said printhead and the print medium dependent upon the pressure sensed by said pressure-sensing device; and

a fluid resistor disposed between said second opening and said third opening, wherein said fluid resistor interconnects a first section of said first conduit including said first opening and a second section of said first conduit including said second opening, said first section containing a backpressure, said second section containing a static pressure.

17. The printer of claim 16 , wherein said first opening of said first conduit is configured to be disposed within 2 millimeters of the print medium.

18. The printer of claim 16 , wherein said first opening of said first conduit has a width a gap between said first opening and the print medium being configured to be less than 25% of said width of said first opening.

19. The printer of claim 16 , wherein said second opening of said first conduit is configured to receive air from said air-moving device.

20. The printer of claim 16 , wherein said pressure-sensing device includes a housing fluidly connected to said second conduit, said housing having a side comprising a flexible diaphragm.

21. The printer of claim 20 , wherein a deflection of said diaphragm is dependent upon a gap between said first opening of said first conduit of said first conduit and the print medium.

22. The printer of claim 16 , wherein said first conduit comprises a first flexible tube, said second conduit comprising a second flexible tube.

23. The printer of claim 16 , wherein said first conduit includes a nozzle tapering to said first opening.

24. The printer of claim 16 , wherein said first opening of said first conduit is configured for being oriented substantially parallel to the print medium.

25. The printer of claim 16 , wherein said first opening of said first conduit is adjacent to said printhead.