U.S. patent application number 10/012268 was filed with the patent office on 2002-04-11 for sliding valve vacuum holddown method and apparatus.
Invention is credited to Downing, Steven P., Madsen, Jeffrey C..
Application Number | 20020041068 10/012268 |
Document ID | / |
Family ID | 23488835 |
Filed Date | 2002-04-11 |
United States Patent
Application |
20020041068 |
Kind Code |
A1 |
Madsen, Jeffrey C. ; et
al. |
April 11, 2002 |
Sliding valve vacuum holddown method and apparatus
Abstract
A vacuum holddown has a holddown member with an outer surface
for temporarily capturing a flexible sheet material via a vacuum
force distributed across the outer surface through discrete vacuum
channels. A vacuum force valving mechanism abuts an inner surface
of the holddown member in a selectable sliding engagement. The
valving mechanism has a pattern of apertures therethrough in
predetermined pattern such that discrete valve mechanism positions
produce discrete vacuum force patterns at the outer surface of the
holddown member.
Inventors: |
Madsen, Jeffrey C.;
(Vancouver, WA) ; Downing, Steven P.; (Camas,
WA) |
Correspondence
Address: |
HEWLETT-PACKARD COMPANY
Intellectual Property Administration
P. O. Box 272400
Fort Collins
CO
80527-2400
US
|
Family ID: |
23488835 |
Appl. No.: |
10/012268 |
Filed: |
November 6, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10012268 |
Nov 6, 2001 |
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09693262 |
Oct 20, 2000 |
|
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10012268 |
Nov 6, 2001 |
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09377368 |
Aug 18, 1999 |
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Current U.S.
Class: |
271/183 |
Current CPC
Class: |
B65H 2406/3614 20130101;
B65H 2406/332 20130101; B65H 2220/04 20130101; B65H 2220/01
20130101; Y10S 209/905 20130101; B65H 5/226 20130101; B41J 13/226
20130101; B41J 11/0025 20130101; B65H 2511/10 20130101; B41J
11/0085 20130101; B65H 2511/10 20130101 |
Class at
Publication: |
271/183 |
International
Class: |
B65H 029/68 |
Claims
What is claimed is:
23. A vacuum drum printer vacuum drum device comprising: 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 having a sleeve outer surface in sliding
face-to-face contact with the drum inner surface and having
apertures therethrough in a second predetermined array such that
discrete sleeve positions produce discrete vacuum patterns at the
outer surface of the drum.
24. A vacuum holddown apparatus, having a vacuum source,
comprising: at least two sheets of material, said sheets separating
a substrate held by vacuum from the vacuum source, wherein each of
the sheets is provided with a plurality of vacuum ports and each
sheet has a different pattern of the vacuum ports; and said sheets
are mounted in sliding contact engagement such that shifting said
engagement varies the pattern of vacuum application through the
pair.
25. The apparatus as set forth in claim 24, comprising: one of said
sheets having a surface for exerting a vacuum force on said
substrate through the respective vacuum ports thereof, wherein
sliding said at least two sheets relative to each other causes
re-distribution of the vacuum force at said surface in accordance
with the immediate alignment of the at least two sheets.
26. The apparatus as set forth in claim 25, comprising:
re-alignment of the sheets provides vacuum distribution width
adjustment across the surface.
27. The apparatus as set forth in claim 25, comprising:
re-alignment of the sheets provides vacuum distribution length
adjustment across the surface.
28. The apparatus as set forth in claim 25, comprising: re-aligning
the sheets provides vacuum distribution dynamic length adjustment
across the surface.
29. The apparatus as set forth in claim 25, comprising:
re-alignment of the sheets provides predetermined vacuum
distribution depletion zones across the surface.
30. The apparatus as set forth in claim 25, comprising:
re-alignment of the sheets provides substantially simultaneous,
dynamic, vacuum distribution width adjustment and vacuum
distribution length adjustment across the surface.
31. The apparatus as set forth in claim 24, comprising: said sheets
include a plurality of concentric, sliding sleeves having
controllable relative positioning.
32. A method for distributing a vacuum holddown vacuum force to a
substrate holding surface having a plurality of vacuum transmitting
first apertures therethrough in a first predetermined pattern, the
method comprising: adjacently to said surface, mounting a valve for
redistributing the vacuum force between predetermined sets of
channels wherein said valve has a complementary shape and size with
respect to said surface, said valve means having vacuum
transmitting second apertures therethrough arrayed in a second
predetermined pattern; and selectively moving the valve to align
selected ones of said second apertures to selected ones of said
first apertures in accordance with producing a predetermined vacuum
force distribution at said first surface.
33. The method as set forth in claim 32, the method further
comprising: varying the predetermined pattern of second apertures
to accommodate a variety widths, lengths and thicknesses of the
substrate to be held.
34. The method as set forth in claim 32, the method further
comprising: establishing predetermined, variable, vacuum
distributions associated with predetermined flexible sheet material
parameters for a given holding surface configuration by realigning
the first predetermined pattern and the second predetermined
pattern in combination.
35. The method as set forth in claim 34, the method further
comprising: capturing the flexible sheet material on the outer
surface by aligning the first predetermined pattern and the second
predetermined pattern to a first position wherein the vacuum force
is distributed only to channels substantially adjacent a leading
edge of the flexible sheet material, and dynamically realigning the
first predetermined pattern and the second predetermined pattern by
sliding the valve means correspondingly in synchronization with the
receipt of downstream regions of the leading edge of the flexible
sheet material.
36. A hard copy apparatus, having a vacuum source producing a
predetermined vacuum force, the apparatus comprising: a platen
having a holddown surface and a plurality of vacuum transmitting
first apertures therethrough channels in a first predetermined
array, each of the first apertures fluidically coupling the vacuum
force to the surface; and mounted in sliding abutment and
separating the platen from the vacuum source, at least one vacuum
distribution altering device having vacuum transmitting second
apertures therethrough in a second predetermined array such that
discrete positions of the vacuum distribution altering device with
respect to the platen produce discrete vacuum force patterns at the
surface.
37. The apparatus set forth in claim 36, the vacuum distribution
altering device comprising: a valving device for redistributing the
vacuum force between predetermined sets of vacuum transmitting
apertures wherein said valving device has a complementary shape and
size with respect to said surface, and the valving device is
mounted in the sliding abutment for moving the valving device to
align selected ones of said second apertures to selected ones of
said first apertures in accordance with producing a predetermined
vacuum force distribution at said surface.
38. The apparatus as set forth in claim 37, second predetermined
pattern further comprising: varied patterns of the second apertures
for accommodating a variety widths, lengths and thicknesses of
print media held.
39. The apparatus set forth in claim 36, further comprising: said
sliding abutment establishes predetermined, variable, vacuum
distributions associated with predetermined print media parameters
for a given said surface configuration by realigning the first
predetermined pattern and the second predetermined pattern in
combination.
40. The apparatus as set forth in claim 36, the apparatus further
comprising: capturing sheet media on the surface by aligning the
first predetermined pattern and the second predetermined pattern to
a first position wherein the vacuum force is distributed only to
channels substantially adjacent a leading edge of the sheet media,
and dynamically realigning the first predetermined pattern and the
second predetermined pattern by sliding the valving device
correspondingly in synchronization with the receipt of downstream
regions of the leading edge of the sheet media.
Description
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 09/377,386, filed on Aug. 18, 1999.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] 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.
[0004] 2. Description of Related Art
[0005] 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.]
[0006] 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.]
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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 of the medium.
[0011] 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
[0012] In its basic aspects, the present invention provides a
vacuum holddown apparatus, having a vacuum source, including: at
least two sheets of material, said sheets separating a substrate
held by vacuum from the vacuum source, wherein each of the sheets
is provided with a plurality of vacuum ports and each sheet has a
different pattern of the vacuum ports; and said sheets are mounted
in sliding contact engagement such that shifting said engagement
varies the pattern of vacuum application through the pair.
[0013] In another aspect, the present invention provides a method
for distributing a vacuum holddown vacuum force to a substrate
holding surface having a plurality of vacuum transmitting first
apertures therethrough in a first predetermined pattern, the method
including: adjacently to said surface, mounting a valve for
redistributing the vacuum force between predetermined sets of
channels wherein said valve has a complementary shape and size with
respect to said surface, said valve means having vacuum
transmitting second apertures therethrough arrayed in a second
predetermined pattern; and selectively moving the valve to align
selected ones of said second apertures to selected ones of said
first apertures in accordance with producing a predetermined vacuum
force distribution at said first surface.
[0014] In yet another aspect, the present invention provides a hard
copy apparatus, having a vacuum source producing a predetermined
vacuum force, the apparatus including: a platen having a holddown
surface and a plurality of vacuum transmitting first apertures
therethrough channels in a first predetermined array, each of the
first apertures fluidically coupling the vacuum force to the
surface; and mounted in sliding abutment and separating the platen
from the vacuum source, at least one vacuum distribution altering
device having vacuum transmitting second apertures therethrough in
a second predetermined array such that discrete positions of the
vacuum distribution altering device with respect to the platen
produce discrete vacuum force patterns at the surface.
[0015] In another 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
having a sleeve outer surface in sliding face-to-face contact with
the drum inner surface and having apertures therethrough in a
second predetermined array such that discrete sleeve positions
produce discrete vacuum patterns at the outer surface of the
drum.
[0016] Some of the advantage of the present invention are:
[0017] it provides a means for directing vacuum forces to specific
areas for maximum media hold down;
[0018] it provides improved vacuum efficiency by making an
adjustment as a variable sized sheet is delivered to the holddown,
focusing the highest vacuum forces at the leading edge and a region
where the rest of the sheet progressively comes into contact with
the holddown;
[0019] it supplies the highest relative vacuum forces on the
leading and trailing edges of the sheet;
[0020] it is useful to adjust for different widths of sheets by
sealing off the vacuum ports with are outside a chosen sheet
width;
[0021] it provides a low cost manufacturing solution to the problem
of distributing vacuum forces across a holddown where adjustment
for held sheet widths is required; and
[0022] in a vacuum drum hard copy apparatus implementation, a paper
transport system implementation is operable while being moved at a
relatively high speed of rotation.
[0023] The foregoing summary and list of advantages is not intended
by the inventor to be an inclusive list of all the aspects,
objects, advantages and features of the present invention nor
should any limitation on the scope of the invention be implied
therefrom. This Summary is provided in accordance with the mandate
of 37 C.F.R. 1.73 and M.P.E.P. 608.01(d) merely to apprize the
public, and more especially those interested in the particular art
to which the invention relates, of the nature of the invention in
order to be of assistance in aiding ready understanding of the
patent in future searches. Other objects, features and advantages
of the present invention will become apparent upon consideration of
the following explanation and the accompanying drawings, in which
like reference designations represent like features throughout the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIGS. 1A through 1D demonstrate a first embodiment of the
present invention in a planar illustration, showing vacuum
distribution for different positions of a vacuum valve sleeve.
[0025] FIGS. 2A through 2B demonstrate a second embodiment of the
present invention as shown in FIGS. 1A through 1D.
[0026] FIGS. 3A and 3B demonstrate a third embodiment of the
present invention as shown in FIGS. 1A through 2B.
[0027] FIG. 4 is a vacuum drum platen in accordance with the
present invention as demonstrated in FIGS. 1A through 3B.
[0028] The drawings referred to in this specification should be
understood as not being drawn to scale except if specifically
annotated.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0029] Reference is made now in detail to a specific embodiment of
the present invention, which illustrates the best mode presently
contemplated by the inventors for practicing the invention.
Alternative embodiments are also briefly described as
applicable.
[0030] FIG. 1A shows a vacuum holddown 401 in accordance with the
present invention. It is intended that the present invention be
implemented in any form of holddown that is constructed to fit the
particular use. For example, FIG. 4 shows a cylindrical holddown
platen 402 embodiment of the present as would be useful in a vacuum
drum printer. FIG. 4 shows that the drum platen 402 has an outer
surface 403 having a substantially symmetric pattern 405 of vacuum
channels 407. Each vacuum channel 407 has at least one vacuum port
409 located at a predetermined position, such as at the midpoint,
of the channel and extending through to the inner surface 411 of
the platen. A sliding valve mechanism 413, such as a plate or a
sleeve depending on the holddown surface configuration needed, is
contained within the cylindrical vacuum drum platen 402. The
sliding valve mechanism 413 has an inner surface 415 and a
plurality of apertures 417 arrayed in a predetermined pattern as
described in more detail hereinafter.
[0031] Note that other curvilinear shapes may be implemented. For
convenience of explanation, the present invention will be described
with respect to the planar embodiments of FIGS. 1A-3B; no
limitation on the scope of the invention is intended by the
inventors in using this exemplary embodiment nor should any such
limitation be implied therefrom.
[0032] Referring also to FIG. 1B, the illustrated holddown 401 can
be visualized as a planar holddown or as an unrolled print media
cylindrical vacuum platen holddown 401 of FIG. 4--also referred to
in the art as a "vacuum drum"--where the height of the rectangle is
the circumference of the cylinder, the width of the rectangle the
axial width of the cylinder. For convenience of explanation, the
latter will be used as an exemplary embodiment; this visualization
thus represents the view of the concentric cylinders of FIG. 4 from
the inside of the holddown 401. The outer surface 403 of the drum
platen 402 would be oriented in the plane of the page, so the
surface channels 407 are shown in phantom line. The holddown 401
includes a sliding valve mechanism 413, also referred to
hereinafter for convenience as the "sliding sleeve 413."
[0033] The sliding sleeve 413 is in an internal, sliding,
face-to-face, substantially fluid tight, contact with the platen
402. A specific pattern of apertures 417 is provided through the
sliding sleeve 413. The pattern is designed such that when the
sleeve is moved axially (see labeled arrow 101) relative to the
drum platen 402, regions of the sleeve outer surface 419 or
apertures 417 respectively close or expose vacuum ports 409 in
predetermined, design-specific patterns. Therefore, as vacuum force
is drawn across the inner surface of the sliding valve plate sleeve
413 in a known manner, e.g., with an exhaust fan (not shown),
exposed vacuum ports 409 transmit the vacuum force into their
associated channels 407.
[0034] With the patterns of apertures 417 and the ported channels
407 and the sliding valve plate sleeve 413 positioned with respect
to the drum platen 402 as shown in FIG. 1A, a vacuum distribution
represented by the shaded channels 421 is created as shown in FIG.
1B (sliding valve plate/sleeve 413 positioned as in FIG. 1A removed
for purpose of demonstration).
[0035] To continue the drum printer platen analogy, if the
dimensions of the outer surface are designed to generally handle
A-size media (up to 8.5.times.14 inch, legal), the position of
FIGS. 1A and 1B would be appropriate to distributing the vacuum to
an outer surface 403 region for a post card or an index card size
sheet of paper, e.g., 3.times.5-inches or perhaps a 4.times.6-inch
photograph.
[0036] FIG. 1C illustrates the repositioned sleeve 413, shifted
axially 101 to the right from FIG. 1A. In this relative position of
the sleeve 413 with respect to the drum platen 402, additional
vacuum ports 409 have been fluidically coupled to the vacuum across
the inner surface 415 of the sleeve, creating a different vacuum
distribution shown in FIGURE ID. This distribution would be
appropriate to distributing the vacuum to an outer surface 403
region to capturing and temporarily securing the print media
leading edge at surface region 423 and trailing edge at surface
region 424 for or a letter size (8.5.times.11 inch) sheet of paper.
Further shifting of the sleeve as shown in FIGS. 1A and 1C axially
101 to the right would similarly shift the vacuum trailing edge
distribution surface region 424 to a legal size sheet of paper.
[0037] Any suitable mechanism for shifting the sliding sleeve 413
from a simple, low cost, end-user controlled manual switch to a
fully automated system capable of recognizing the next size of
media to be captured based upon the print data set can be employed
with the present invention. Such an automated system can be
employed to dynamically change the vacuum distribution in real-time
holddown operational conditions when needed.
[0038] An alternative embodiment, suited for producing vacuum
patterns for any length sheet up to the length of the outer surface
403 having vacuum channels 407 therein by controlling the axial
position of the sleeve 413 is illustrated in FIGS. 2A and 2B. This
embodiment's sliding valve sleeve 413 apertures 417 configuration
is also shown in FIG. 4. The sliding valve sleeve 413 axial
displacement is shown in FIG. 2A as being part way through its full
range of motion and the distribution pattern created is illustrated
in FIG. 2B. Note that some vacuum ports 409 are partially covered
which may result in a lower vacuum force, or vacuum depletion
zones, for associated platen surface channels 407; this is depicted
by a lighter shading of those channels. As the sliding valve sleeve
413 has trailing edge apertures 417 connected into a diagonal band
across the outer surface 403, when the sleeve 413 slides within the
drum platen 402 axially from left to right the vacuum influenced
region 425 of the platen for a leading edge of the sheet remains
fully under the vacuum influence while the vacuum influenced region
426 of the platen for a trailing edge of a sheet moves from top to
bottom (or around the circumference toward downstream regions of a
sheet).
[0039] Another alternative embodiment is illustrated by FIGS. 3A
and 3B. Since it is important to maintain flatness of the sheet
during printing to provide uniform clearance to the writing
instrument, more apertures 417 can be added to the sliding valve
sleeve 413 to produce whatever level of vacuum force is desired
again at a sheet leading edge region 427, a sheet trailing edge
region 429, and a vacuum depletion region 428 therebetween.
[0040] It should be noted that in a drum printer embodiment the
sleeves 413 may be interchangeable, giving the end-user flexibility
of operation. For example, the sliding valve embodiment of FIG. 1A,
having specifically targeted vacuum zones related to predetermined,
commercially available, media sizes, might be swapped out for the
embodiment of FIG. 2A or 3A when using special media.
[0041] Another feature of the present invention such as shown in
the embodiments of FIGS. 2A-3B, particularly advantageous for a
drum printer using hard-to-hold media, is the opportunity to begin
loading media with all of the vacuum concentrated in a single band
when the paper leading edge meets the platen. By dynamically
coordinating the rotation of the drum platen with the paper feed,
sleeve movement at a rate which would allow the second band of
vacuum 426, to appear and effectively remain at the sheet loading
point until the trailing edge of the media is captured. At that
time the sleeve stops translating and the second band stays with
the trailing edge during printing operations. This has a positive
effect on vacuum efficiency, since waste flow through exposed holes
is kept to a minimum. Higher concentrations of vacuum stay with the
leading and trailing edges of the sheet where higher holddown force
is needed.
[0042] Thus, the combination of platen 402 with the sliding valve
plate sleeve 413 provides discrete sleeve positions to produce
discrete vacuum patterns at the outer surface 403 of the holddown
401. It will be recognized by a person skilled in the art that the
vacuum distribution features of a holddown in accordance with the
present invention--width adjust, length, dynamic length adjust,
depletion zone creation, and the like as might be useful in a
particular implementation--can be combined as desired through
creative shapes and orientation of valve apertures 417 for any
given platen surface 403 structure. Thus, ideal flexible sheet
material handling ability can be tailored to the need at hand.
[0043] As can now be recognized, the sliding sleeve 413 need not be
a unitary part. Two or more sleeves residing side-by-side in the
axial direction would allow keeping some channels, or columns of
channels, closed for use of a narrow print medium. This avoids
larger vacuum losses through exposed holes.
[0044] Moreover, a plurality of layered or concentric sliding
sleeves 413 having controllable relative positioning allows a
greater number of open/closed aperture combinations. This, again,
is particularly useful for narrow media which would leave
relatively extensive exposure of open vacuum ports and lead to a
large vacuum loss.
[0045] Still further, the relative motion between the sleeve and
platen could alternatively or combinatorially be in the rotational
direction. A benefit of this approach is that it can mobilize the
zone intended for the leading/trailing edge vacuum capture. In
other words, the leading edge vacuum zone can be moved to a
position on the drum where the next sheet will be presented, saving
time which might be consumed if the sheet has to wait for a fixed
leading edge vacuum capture zone to arrive.
[0046] The foregoing description of the preferred embodiment of the
present invention has been presented for purposes of illustration
and description. It is not intended to be exhaustive or to limit
the invention to the precise form or to exemplary embodiments
disclosed. Obviously, many modifications and variations will be
apparent to practitioners skilled in this art. Particularly, it
will be recognized by those skilled in the art that a wide variety
of combinations of outer surface channels 407 with associated
vacuum ports 409 can be designed to fit the needs of a specific
design goal for the hold down 401 specific use; thus, no limitation
on the scope of the invention is intended by the inventors in using
these exemplary embodiments nor should any such limitation be
implied therefrom. Similarly, any process steps described might be
interchangeable with other steps in order to achieve the same
result. The embodiments were chosen and described in order to best
explain the principles of the invention and its best mode practical
application, thereby to enable others skilled in the art to
understand the invention for various embodiments and with various
modifications as are suited to the particular use or implementation
contemplated. It is intended that the scope of the invention be
defined by the claims appended hereto and their equivalents.
Reference to an element in the singular is not intended to mean
"one and only one" unless explicitly so stated, but rather means
"one or more." Moreover, no element, component, nor method step in
the present disclosure is intended to be dedicated to the public
regardless of whether the element, component, or method step is
explicitly recited in the following claims. No claim element herein
is to be construed under the provisions of 35 U.S.C. Sec. 112,
sixth paragraph, unless the element is expressly recited using the
phrase: "means for . . . "
* * * * *