Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-12-06
2004-09-28
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S049000
Reexamination Certificate
active
06796630
ABSTRACT:
The present invention relates to a droplet deposition apparatus such as, for example, a drop-on-demand inkjet printer.
A typical drop-on-demand ink jet printer includes one or more printheads mounted on the carriage or printer body of a printer, with ink being ejected from one or more ink reservoirs located in the printer through nozzles formed in the or each printhead.
In view of the demand for higher resolution drop-on-demand inkjet printing, it is desirable to control accurately the precise locations at which ink ejected from the nozzles lands on a print surface. Accordingly, each printhead is individually aligned on the carriage or printer body. If one of the printheads were to become defective in any way, it is necessary to remove the defective printhead and re-align accurately the replacement printhead on the carriage or printer body. This can be a difficult, and therefore time-consuming, operation.
In its preferred embodiments, the present invention seeks to solve these and other problems.
In a first aspect, the present invention provides droplet deposition apparatus comprising a base and a printhead adjustably mounted on the base and positionable relative to a datum on the base such that a swath of print produced by the printhead is in a predetermined position relative to the datum, the base being locatable on a printer using the datum.
As the swath of print produced by a printhead is aligned with a datum formed on the base and used to mount the base to the printer, the printhead can be easily replaced without any loss of alignment of the produced print swath relative to the carriage or body of the printer. The alignment of the swath with a single datum formed on the base also improves the ease of alignment of the swath relative to the carriage or printer body; as the print may be ejected at an angle to the axes of the nozzles of the printhead, the position of the printhead is adjusted in relation to the produced print swath.
In a preferred arrangement, the apparatus comprises a plurality of printheads, each printhead being adjustably mounted on the base and positionable relative to the datum on the base such that swathes of print produced by the printheads are in respective predetermined positions relative to the datum.
Thus, the above advantages in respect of a single printhead are also provided with a multi-printhead arrangement, so that, for example, if the printer were to become defective, the base can be removed from the defective printer and accurately mounted on the replacement printer using the datum, that is, without having to re-align each individual printhead, so that the swaths of print to be produced by the printheads are still in the correct alignment.
Furthermore, when using a plurality of printheads in order to increase print width, it is important that the first nozzle of a second printhead is positioned as close as possible to one pitch after the last nozzle of the first printhead in order to maintain a high print quality between the printheads. By means of the present invention, this positioning can be conducted quickly and easily.
The printheads may be arranged in pairs on the base, for example, side-by-side pairs. This can increase the density of the mounting of the printheads on the base, thus providing for a compact droplet deposition apparatus.
In a preferred embodiment, the apparatus comprises means for adjusting the position of the or each printhead on the base relative to the datum. This can enable individual printheads to be positioned on the base so that the swaths of print produced by the printheads are in the predetermined positions relative to the datum.
The adjusting means may comprise means for adjusting the location of the or each printhead relative to the datum and means for adjusting the orientation of the or each printhead relative to the datum. Thus, the location and orientation of the printhead on the base can be individually adjusted.
The adjusting means may comprise a plurality of adjustment members engaging the or each printhead, each adjustment member being movable relative to the base so as to adjust the position of the printhead on the base. For example, each adjustment member may comprise a tapered surface, the printhead being urged against the tapered surface so that movement of a tapered surface relative to the base adjusts the position of the printhead on the base. One suitable adjustment member is a tapered screw having a screw thread engaging a conformingly-profiled threaded bore formed in the base, with axial movement of the screw within the bore causing the printhead, urged against the tapered surface, to move relative to the base. As the motion of the screw within the bore may be accurately controlled, the alignment of the swath of print from the printhead with the datum on the base is thus also accurately controlled.
The printhead may have a conformingly tapered surface engaging the tapered surface of the adjustment member. The engagement of the conformingly tapered surfaces can enable the printhead to be held against the base by the adjustment members.
The apparatus preferably comprises means, resiliently mounted on the base, for urging a printhead against the adjustment means. This can ensure that any adjustment of the adjustment means is transferred substantially completely to the printhead.
The apparatus preferably comprises means, mountable on the base, for shielding the adjustment means in order to prevent accidental adjustment of the position of the or each printhead on the base.
The apparatus may further comprise a slotted member, mountable on the base, having at least one slot formed therein so that fluid ejected from the or each printhead passes through a respective slot.
Each printhead may comprise a plurality of nozzles formed in a nozzle plate, the nozzle plate and the walls of the slot through which ink ejected from the nozzles passes defining at least part of a recess into which ink removal means is movable to remove any ink collected in the recess following ejection from one of the nozzles.
The present invention also provides apparatus for positioning an object relative to a datum, said apparatus comprising a base bearing said datum and comprising means for receiving an object, a plurality of tapered adjustment members each being movable relative to the base, and means for urging a received object against the adjustment members so that movement of an adjustment member relative to the base adjusts the position of a received object relative to said datum.
Preferably, said adjustment members comprise a first adjustment member for adjusting the location of a received object relative to the datum and a second adjustment member for adjusting the orientation of a received object relative to the datum.
Preferably each adjustment member comprises a tapered screw engaging a conformingly tapered bore formed in the base.
Preferably, the urging means is resiliently mounted on the base.
The receiving means may comprise a frame for receiving an object, the position of the frame relative to the datum being adjustable by moving said adjustment members.
The present invention further provides apparatus for positioning a plurality of objects relative to a datum, said apparatus comprising a base bearing said datum and comprising a plurality of receiving means each for receiving a respective object, and, for each receiving means, a plurality of tapered adjustment members each being movable relative to the base and means for urging a received object against the adjustment members so that movement of an adjustment member relative to the base adjusts the position of a received object relative to said datum.
The apparatus is preferably for positioning one or a plurality of printheads such that a swath of print produced by the or each printhead is in a predetermined position relative to the datum, the base being locatable on a printer using the datum.
The present invention yet further provides a method of positioning an object relative to a datum borne by a base comprising means for receiving an object, a plurality of tape
Ison Robert M.
Zaba Jerzy M.
Zapka Werner
Dudding Alfred
Marshall & Gerstein & Borun LLP
Meier Stephen D.
Xaar Technology Limited
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