Sheet feeding or delivering – Feeding – By means to convey sheet
Reexamination Certificate
1999-08-18
2001-04-03
Ellis, Christopher P. (Department: 3651)
Sheet feeding or delivering
Feeding
By means to convey sheet
C271S183000, C271S196000
Reexamination Certificate
active
06209867
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to vacuum holddown apparatus and methods of operation and, more specifically, to a cut-sheet print media vacuum holddown particularly useful for a hard copy apparatus, such as an ink-jet printer.
2. Description of Related Art
It is known to use a vacuum induced force to adhere a sheet of flexible material to a surface, for example, for holding a sheet of print media temporarily to a platen. [Hereinafter, “vacuum induced force” is also referred to as “vacuum induced flow,” “vacuum flow,” or more simply as just “vacuum” or “suction”.] Such vacuum holddown systems are a relatively common, economical technology to implement commercially and can improve machine throughput specifications. For example, it is known to provide a rotating drum with holes through the surface so that a vacuum through the drum cylinder provides a suction force at the holes in the drum surface. [The term “drum” as used hereinafter is intended to be synonymous with any curvilinear implementation incorporating the present invention; while the term “platen” can be defined as a flat holding surface, in hard copy technology it is also used for curvilinear surfaces, such as a common typewriter rubber roller; thus, for the purposes of the present application, “platen” is used generically for any shape holddown surface used in a flexible material holddown apparatus.]
Generally in a hard copy apparatus implementation, the platen is used either to transport cut-sheet print media to a printing station of a hard copy apparatus, such as a copier or a computer printer, or to hold the cut sheet print media at the printing station while images are formed (also known as the “print zone”), or both. [In order to simplify discussion, the term “paper” is used hereinafter to refer to all types of print media. No limitation on the scope of the invention is intended nor should any be implied.]
One universal problem, particularly pertinent in the adaptation of a vacuum holddown to use in a hard copy apparatus, is the management of different sizes, shapes, and thicknesses of available paper. Open holes around the edges of a sheet smaller than the dimensions of the vacuum field across the platen surface results in vacuum losses and a lower or ineffective holding force. In other words, too many exposed vacuum ports result in a loss of suction at the platen surface and the paper is not firmly adhered to the surface.
One technique for controlling a vacuum holddown is proposed by Rasmussen et al. in U.S. Patent Application Ser. No. 09/292,767 for a PRINT MEDIA VACUUM HOLDDOWN (assigned to the common assignee of the present invention and incorporated herein by reference). A vacuum holddown for sheet materials has a surface having a field of vacuum ports in which each individual port is gated. When a vacuum is applied to the underside of the holddown, the gates close. When a sheet of material is introduced onto a region of the field, the gates only within vacuum manifold passageway covered by the material are configured to spring open, applying a suction force to the sheet via the now opened ports. The holddown thus automatically adjusts to material size. An implementation for use in an ink-jet printer with cut-sheet print media is demonstrated.
Another technique is demonstrated by Rhodes et al. in U.S. patent application Ser. No. 09/292,125 for a VACUUM CONTROL FOR VACUUM HOLDDOWN (assigned to the common assignee of the present invention and incorporated herein by reference). A mechanism for manifolding a vacuum force to separate surface sectors of a vacuum holddown uses subsurface ducting to apply the vacuum to separate subsurface vacuum plenums wherein each is fluidically coupled to a separate surface sectors. The plenum is segregated by a diaphragm into surface side and vacuum side cavities. Trigger ports and appropriate ducting through the holddown subjacent the surface associated with each sector determine how the vacuum is routed. Only when a trigger port is covered is the vacuum routed to the surface sector associated therewith. The system can be implemented in planar or curvilinear constructs and be provided with features to accommodate a near-continuous range of flexible material sizes. A specific implementation in an ink-jet hard copy apparatus is also described.
Related to the Rasmussen et al. and Rhodes et al. Applications, U.S. patent application Ser. No. 09/292,838 for a VACUUM SURFACE FOR WET DYE HARD COPY APPARATUS by Wotton et al. (assigned to the common assignee of the present invention and incorporated herein by reference) shows a platen surface structure construct, particularly useful in a hard copy apparatus for a vacuum holddown, configured by dimensioning print media platen surface structure channels and ports in order to ensure print media leading edge and trailing edge holddown. The vacuum is distributed across the platen surface in accordance with predetermined dye flow characteristics based upon known dye composition and known print medium composition and such that print artifacts are not created by vacuum pulling wet dye through the capillaries Df the medium.
There is a continuing need to direct vacuum forces to specific locations of a holddown to increase vacuum efficiency and improve holddown force. Moreover, there is a need for a vacuum holddown for sheet material transport that can adjust to hold a variety of sizes of materials.
SUMMARY OF THE INVENTION
In its basic aspects, the present invention provides a vacuum holddown apparatus including: first mechanisms for distributing a vacuum force, having a first mechanism's outer surface and a first mechanism's inner surface, such that the first mechanism's outer surface is configured for receiving and holding flexible sheet materials there against by having a plurality of channels of a first predetermined pattern, each of the channels having a through port for coupling an associated channel with the vacuum force; and second mechanisms for distributing the vacuum force, having a second mechanism's outer surface and a second mechanism's inner surface, the second mechanism's outer surface abutting the first mechanism's inner surface in a substantially fluidically tight sliding engagement, the second mechanisms having a plurality of apertures therethrough, the plurality of apertures having a second predetermined pattern across the second mechanisms, such that sliding the second mechanisms relative to the first mechanisms causes redistribution of the vacuum force to the channels in accordance with the immediate alignment of the first mechanisms and the second mechanisms.
In another basic aspect, the present invention provides a method for distributing a vacuum holddown vacuum force to a first surface having a plurality of vacuum channels in a first predetermined pattern wherein each channel is separately ported to a second surface for drawing a vacuum therefrom, the channels adapted for securing a flexible sheet material to the first surface via influence of the vacuum force. The method includes the steps of: adjacently to the second surface, mounting a valve mechanism for redistributing the vacuum force between predetermined sets of channels wherein the valve mechanism has a substantially identical shape and size of the second surface, the valve mechanism having apertures therethrough arrayed in a second predetermined pattern; and selectively moving the valve mechanism to align selected ones of the apertures to selected ones of the ports in accordance with producing a predetermined vacuum force distribution at the first surface.
In another basic aspect, the present invention provides, a vacuum drum printer vacuum drum device including: a drum having a plurality of vacuum channels in a first predetermined array across a drum outer surface, each of the vacuum channels having a vacuum port fluidically coupling an associated vacuum channel to a drum inner surface; and mounted within the drum, at least one sleeve
Downing Steven P.
Madsen Jeffrey C.
Bower Kenneth W.
Ellis Christopher P.
Hewlett-Packard
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