This invention relates to ink jet printers and, more particularly, to a new and useful shield assembly for optimally preparing the print surface or surface contour of the print media during print operations.
Conventional inkjet printers employ a print head assembly having an array of individual nozzles for deposition of ink onto a substrate media or material e.g., plain white paper or a mailpiece envelope. The print head assembly is adapted to accommodate one of two types of print/feed mechanisms, namely, shuttle and in-line printing. Shuttle motion printers employ a moveable print head assembly capable of shuttling back and forth in a direction orthogonal to the direction of paper feed. Consequently, shuttle print head assemblies are capable of fully covering the printable area of a page in bands of coverage. In-line printing, in contrast, employs a stationary print head assembly having a fixed width. Generally, in-line print head assemblies comprise a plurality of adjacent print heads to cover a predetermined print area or region as paper is fed beneath the print heads.
In
To ensure that the print head 112 prints on a substantially planar surface, it is common to employ a movable shield 120 proximal to the print head 112 to press the media 116 against an underlying support structure 122, i.e., typically a resilient elastomer roller or feed cylinder. Furthermore, the shield 120 may be adjusted vertically along bi-directional arrows AV to accommodate thickness variations in print media 116 such as mailpiece envelopes. Due to the bi-directional motion SP of the print head assembly 100 and the direction FP of the feed path, the shield 120 must necessarily be disposed behind the print head 112 and parallel its shuttle motion SP. While the shield 120 is as close as practicable to the print head 112, it will be appreciated that the ability to control the surface contour of the print media diminishes as the distance from the shield increases. Consequently, as best seen in
In
The shield 220 may be configured and mounted in the manner described above principally due to the unidirectional motion of the underlying print media 216. That is, inasmuch as the ink requires a fixed amount of time, albeit small, to dry, the shield 220 may be located along the leading edge LE or upstream of the print head 212, to avoid contact with the drying ink. Additionally, the shield 220 may optimally positioned along side the print head 212 to further improve the efficacy of printing, i.e., controlling the surface contour in region A with greater precision.
While the mounting arrangement of the shield 220 is optimally suited for in-line printing assemblies 200, i.e., wherein the print media 216 moves in a single direction relative to the print head 212, it will be appreciated that a similar mounting arrangement is not possible for shuttle motion printers. That is, should a pair of shields be disposed on each side of a shuttling print head, one of the shields, i.e., the shield disposed downstream of ink deposition will interfere with the drying ink.
A need, therefore, exists for a shield assembly which optimally controls the surface contour of underlying print media while enabling both in-line and shuttle ink-jet printing.
The accompanying drawings illustrate presently preferred embodiments of the invention and, together with the general description given above and the detailed description given below serve to explain the principles of the invention. As shown throughout the drawings, like reference numerals designate like or corresponding parts.
a is a perspective view of a prior art shuttle ink jet printing assembly including a moveable shield disposed behind and parallel to the side-to-side or shuttle motion of the print head SP.
b is a sectional view taken substantially along line 1b-1b of
c is a front view of a prior art in-line ink jet printing assembly including a fixed shield disposed laterally along the leading edge and up stream of the print head to avoid the drying ink.
A shield assembly is provided for use in combination an ink jet printer and is operative to provide a smooth planar surface for printing on a print media. The assembly includes a shield having first and second contact surfaces which define an opening therebetween. The opening of the shield assembly is aligned with the print head of the ink jet printer for permitting the deposition of ink through the opening. The assembly further includes a pivot mount operative to pivot the shield about a rotational axis which is substantially parallel to the feed path of the print media and orthogonal to the motion of the print head. Moreover, the assembly includes a means for pivoting the shield about the rotational axis in a first and second direction thereby causing one of the contact surfaces to engage the print media upstream of the print head when depositing ink on the print media.
The present invention is described in the context of a conventional ink-jet printer having a carriage assembly for bi-directionally shuttling a print head during print operations. While the configuration described includes a conventional carriage assembly guided and displaced along a rail, it should be appreciated that the printing method and shield assembly employed can be adapted for use with any print head assembly which is bi-directionally guided or controlled to print on a print media. Further, while the shield assembly is described in the context of printing on a mailpiece envelope, the invention is applicable to printing on any sheet material, particularly those which may be subject to thickness variations or fluctuations of its surface contour.
In the broadest sense of the invention, and referring to
In the described embodiment, the shield assembly 10 includes a shield 28 forming a unitary structural plate which is pivot mounted to the print carriage 12 about a rotational axis 10A. The structural shield plate 28 may be stamped from sheets of stainless steel and include an opening or aperture 30 disposed between the contact surfaces 20a, 20b. Furthermore, mounting lugs 32a, 32b may be formed during plate manufacture so that pins 34 pivotally mount the plate 28 to the print head carriage 12. In the described embodiment, pins 34 mount the shield 28 to cross members 36 (best seen in
In
In
In the described embodiment, the contact surfaces 20a, 20b are configured to facilitate sliding contact with the print media 14. Consequently, the contact surfaces may define an arcuate region or bend which causes the surfaces 20a, 20b to define a shallow or acute angle E (see
In summary, the shield assembly provides a reliable, low cost method for optimally preparing the surface contour of underlying print media for in-line and bi-directional inkjet printing. Furthermore, the shield assembly may be incorporated with minimal structural changes to existing ink-jet printer hardware and software. Moreover, the proximity of the shield relative to the print head nozzle provides optimum surface contour control, i.e., control of the print media surface.
Although the invention has been described with respect to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention.
While the invention has been described in the context of a motor driven shield assembly, it will be appreciated that other means for actuating or positioning the shield assembly could be employed. For example, a simple trigger or trip mechanism at the end of a carriage assembly run, i.e., when the carriage assembly approaches the end of its travel along the guide bar, may be employed to reposition the shield assembly. That is, the trip mechanism may cause the shield to traverse a spring-biased cam to pivot and maintain its position for the subsequent print head pass. Furthermore, the shield itself may be configured to have a single contact surface disposed laterally of the print head nozzle. As such, the mount may then be configured to reposition the shield from one of two positions. That is, the shield may be pivoted or rotated from one side to the other such that the contact surface engages the print media upstream of the print head nozzle, i.e., the direction/motion of the nozzle.
Number | Name | Date | Kind |
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2166131 | Duncan | Jul 1939 | A |
4859099 | Kanemoto et al. | Aug 1989 | A |
4872026 | Rasmussen et al. | Oct 1989 | A |
Number | Date | Country | |
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20080079770 A1 | Apr 2008 | US |