Ink jet printer

• US 4,412,232 A
• Filed: 04/15/1982
• Issued: 10/25/1983
• Est. Priority Date: 04/15/1982
• Status: Expired due to Fees

• Current Assignee: NCR Corporation (NCR Voyix Corporation)
• Original Assignee: NCR Corporation (NCR Voyix Corporation)
• Inventors: Reitberger, Peter H., Weber, Helmut, Konig, Walter, Bader, Leonhard
• Primary Examiner(s): Griffin, Donald A.
• Application Number:
  US06/368,611
• Time in Patent Office: 558 Days
• Field of Search: 346/1.1, 346/75, 346/140
• US Class Current: 347/68
• CPC Class Codes: B41J 2/175 Ink supply systems ; Circuit parts therefor

Abstract

An ink jet printer includes a print head having a plurality of piezoelectric driving elements selectively energizable to cause ejection of droplets of ink through nozzles in a nozzle plate. Ink is supplied to the print head from an ink reservoir which is connected to a bellows device. The ink reservoir and the bellows device together form an air-tight container. The bellows device has a resilient form of construction so as to tend to increase the volume of the container. As a result, an appropriate underpressure is maintained in respect of the ink in the nozzles, such underpressure being necessary to prevent ink escaping from the nozzles under quiescent conditions. In operation, the bellows device progressively collapses so as to reduce the rate at which the underpressure increases as ink is ejected, thereby prolonging the period for which the underpressure is maintained within a desired operating range. In two other embodiments, the reservoir is enclosed by a piston or a membrane, both biased against collapse by a compression spring. In yet another embodiment, underpressure within the reservoir is maintained by a capillary tube that at one end is immersed in ink and at the other end is open to the exterior of the printer.

Claims

1. A hand-held ink jet printer, comprising:

a housing;

at least one wheel rotatably mounted on said housing to support said housing for manual movement over a medium onto which characters are to be printed by the printer;

a movement sensing device for sensing the rotation of said wheel;

a print head within said housing and having a plurality of nozzles and a piezoelectric element associated with each of said nozzles for being selectively energizable to cause ejection of a droplet of ink from its associated nozzle, said piezoelectric element driven in response to the movement of said housing;

a container having an ink reservoir and connected for supplying ink to be ejected through said nozzles, the ink in said ink reservoir maintained at a predetermined underpressure relative to atmospheric pressure outside said container so that the ejection of ink can be controlled by the energization of each said piezoelectric element; and

a collapsible bellows device connected by a tube to said ink reservoir, said bellows device having resilient side walls so that, as ink is ejected through said nozzles, said bellows device collapses to reduce the interior volume of said container, with said resilient side walls biased against the collapsing of said bellows device in order to maintain the predetermined underpressure of the ink in said ink reservoir.

2. An ink jet printer including a print head having at least one piezoelectric driving element selectively energizable to cause ejection of a droplet of ink through a nozzle associated therewith, an ink reservoir for supplying ink to said print head, and capillary means connecting the interior of the ink reservoir with the ambient atmosphere with one end of said capillary means being so arranged as to be immersed in operation in ink contained in the reservoir, the reservoir being air-tight in operation apart from the provision of said capillary means whereby a predetermined underpressure is maintained in respect of the ink in said nozzle, any increase in underpressure as ink droplets are ejected being inhibited by virtue of the intake of air into the reservoir via said capillary means.

3. The ink jet printer of claim 2, wherein said capillary means comprises a tube having a sufficiently small inner diameter such that air from the atmosphere will pass from said tube and into the reservoir only when the predetermined underpressure is exceeded.

4. The ink jet printer of claim 3, wherein the diameter of said nozzle is approximately 0.07 millimeters, said tube is glass, and the inner diameter of said tube is in a range of approximately 0.3 to 1.2 millimeters.

5. The ink jet printer of claim 2, wherein the diameter of said nozzle is approximately 0.07 millimeters, said tube is nickel, and the inner diameter of said tube is in a range of approximately 0.15 to 0.9 millimeters.

6. An ink jet printer, comprising:

a print head having at least one piezoelectric driving element selectively energizable to cause ejection of a droplet of ink through a nozzle associated therewith;

an ink reservoir for supplying ink to said print head;

said ink reservoir at least partially constituting a container which is air-tight in operation of the printer; and

a bellows device for tending to increase the volume of said container so as to create an underpressure in respect of the ink in said nozzle and for permitting a decrease in the volume of said container as ink droplets are ejected so as to reduce the rate of any increase in the underpressure brought about by ink ejection;

said bellows device being linked to said ink reservoir by a tube so arranged that in operation ink from said ink reservoir is prevented from entering said bellows device.

7. The printer according to claim 6, wherein the inside surface of said tube is coated, at least in part, with a material which is not wetted by the ink in said ink reservoir.

8. The printer according to claim 7, wherein the ink in said ink reservoir is a water-based ink, and said coating material is silicon oil.

9. An ink jet printer, comprising:

a print head having at least one piezoelectric driving element selectively energizable to cause ejection of a droplet of ink through a nozzle associated therewith; and

an ink reservoir for supplying ink to said print head;

said ink reservoir comprising an open-ended cylinder, a piston member slidably mounted for axial movement in said ink reservoir and providing an air-tight seal therefor, and resilient means being arranged within said ink reservoir for exerting pressure on said piston member, thereby tending to cause expansion of the volume of said ink reservoir so as to create an underpressure in respect of the ink in said nozzle.

10. An ink jet printer, comprising:

a print head having at least one piezoelectric driving element selectively energizable to cause ejection of a droplet of ink through a nozzle associated therewith;

an ink reservoir for supplying ink to said print head;

a flexible membrane providing an air-tight seal at one end of said ink reservoir; and

resilient means being arranged within said ink reservoir to be compressed as ink droplets are ejected through said nozzle and for exerting pressure on said membrane to increase the volume of said ink reservoir so as to create an underpressure in respect of the ink in said nozzle, said membrane having a fold that provides slack so that said membrane does not tear as it follows the compression of said resilient means.