Information
-
Patent Grant
-
6240260
-
Patent Number
6,240,260
-
Date Filed
Friday, January 29, 199925 years ago
-
Date Issued
Tuesday, May 29, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 396 570
- 396 612
- 396 613
- 396 622
- 396 624
- 355 27
- 355 28
- 355 47
- 347 262
- 347 264
- 347 215
- 271 303
- 271 304
- 271 186
- 242 5332
- 242 5334
- 242 5335
- 242 5336
-
International Classifications
-
Abstract
A system and method for transferring and buffering sheets of media between first and second components of an imagesetting system operates by: rotating a transfer buffer having at least two storage devices, to align a first storage device with the first component while concurrently aligning a second storage device with the second component; transferring a first sheet of said media from the first component to the first storage device; rotating the transfer buffer to align the first storage device with the second component while concurrently aligning the second storage device with the first component; and transferring the first sheet of said media from the first storage device to the second component while simultaneously transferring a second sheet of said media from the first component to the second storage device. The transfer system includes: a transfer buffer; at least two storage devices mounted onto the transfer buffer, each storage device moveable within the transfer buffer and capable of storing one sheet of imaged media; and a controller for automatically controlling operation of the transfer system.
Description
FIELD OF THE INVENTION
The invention relates generally to buffering and transferring sheets of cut media between functional components having different processing speeds within an imagesetting system, and more specifically to a method and system for compensating for a speed differential between an imagesetter and an on-line development/finishing processor in an electronic pre-press system.
BACKGROUND OF THE INVENTION
In existing electronic pre-press systems, images to be printed by offset printing are scanned from photographic sources and digitized. The digitized images are then transmitted to a raster image processor (RIP) for half-tone screening and image rasterization. The rasterized image is then transmitted to an imagesetter for recording of the image onto a medium. Such recording is referred to as imaging or imagesetting, and may for example be performed by photographic recording of an image onto a photosensitive medium such as paper, film, or printing plates. A medium which has had an image recorded onto it by an imagesetter is referred to as imaged medium.
Existing pre-press systems typically include independent functional units for recording images and for subsequent processing. A typical photographic imagesetter operates to record a predefined image onto a medium, for example by first mounting the medium onto the internal surface of a drum (i.e. in an internal drum imagesetter), then exposing the medium with a laser beam via a rotatable, optically reflective element mounted on the interior of the drum. The medium typically may be supplied as a web or as a cut sheet.
Subsequent to imaging, the imaged medium is passed to a development/finishing processor, where the medium will undergo chemical processing for photographically developing, fixing and washing. Alternatively, if the image was burned into the media by a laser, then mechanical finishing would occur in the processor. If the media was supplied by a continuous web, each sheet of exposed media is cut prior to entry into the processor.
Early pre-press systems used off-line development processors. In such early systems, imaged media was collected onto a take up cassette connected to an output of the imagesetter, and then manually transported to the off-line processor. More recent systems have coupled the imagesetter to an on-line processor, which inputs the imaged media directly, automatically from the imagesetter.
A significant drawback of existing systems using on-line processors results from the different processing speeds of the imagesetter and the processor. This and other problems were addressed in U.S. Pat. No. 5,769,301 issued Jun. 23, 1998 to Hebert et al. herein incorporated by reference in its entirety for supplemental background information which is not essential but is helpful in appreciating the applications of the present invention. Hebert et al. discloses a media transport bridge for use in transporting and buffering imaged media between an imagesetter and a processor. When a medium is output from the imagesetter, it is transferred to a bridge mechanism between the imagesetter and the processor. The bridge mechanism holds the medium for a predetermined period of time while waiting for the processor to become available. When the processor's availability is detected, the medium is transferred from the bridge to the processor, and the bridge thereafter becomes available to store a second sheet of media from the imagesetter. However, during the time while the bridge is waiting for the processor to accept the second sheet of media, the imagesetter may have to be stalled, waiting for the bridge to become available. Such stalling of the imagesetter potentially causes an unacceptable reduction in overall media throughput. Moreover, existing bridge mechanisms often have high profiles, resulting in undesirably large form factors for products in which they are included.
SUMMARY
It is an object of the present invention to provide in an imagesetting system an apparatus and method for transferring and buffering imaged media sheets between two components so as to compensate for any transfer speed differential between the components. It is another object to provide such an apparatus and method for transferring and buffering imaged media sheets between an imagesetter and an image processor in an imagesetting system, so that the apparatus is compact with a low profile which significantly decreases the overall weight and dimensions of the imagesetting system. These and other objects of the present invention will become apparent in view of the following description, drawings and claims.
A system and method for transferring and buffering sheets of media between first and second components of an imagesetting system operates by: moving a transfer buffer having at least two storage devices, to align a first storage device with the first component while concurrently aligning a second storage device with the second component; transferring a first sheet of said media from the first component to the first storage device; moving the transfer buffer to align the first storage device with the second component while concurrently aligning the second storage device with the first component; and transferring the first sheet of the media from the first storage device to the second component while simultaneously transferring a second sheet of the media from the first component to the second storage device. The transfer system includes: a transfer buffer having at least two storage devices mounted thereon, each said storage devices moveable within the transfer buffer and capable of storing one sheet of imaged media; and a controller for automatically controlling operation of the transfer system.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood by reference to the following detailed description of the preferred embodiments in conjunction with the drawings (not necessarily drawn to scale), where like components are labeled with the same reference numerals and where:
FIG. 1
is a schematic view of an imagesetting system built in accordance with the principles of the invention and including an internal drum imagesetter, a first preferred embodiment of a transfer buffer therein, and an on-line processor.
FIGS. 2
,
3
and
4
are schematic views of various orientations of components of a second preferred embodiment of a transfer buffer during normal operations;
FIG. 5A
is a perspective view of a media storage device used with the transfer buffer of
FIG. 1
;
FIG. 5B
is an end view of the media storage device of
FIG. 5A
just prior to acceptance of a medium for storage;
FIG. 5C
is an end view of the media storage device of
FIG. 5A
having a medium partially wrapped thereon;
FIG. 6
is a perspective view of selected components of the transfer buffer of
FIG. 1
;
FIG. 7A
illustrates an inside surface of an end plate of the transfer buffer of
FIG. 1
;
FIG. 7B
illustrates an outside surface of an end plate of the transfer buffer of
FIG. 1
;
FIG. 7C
is a cross-sectional view along line A-A′ of the end plate of
FIG. 7A
; and
FIG. 7D
illustrates the outside surface of the end plate as shown in
FIG. 7B
, including additional hardware for driving various system components.
FIG. 8
is a flow chart outlining the operation of the imagesetting system of FIG.
1
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1
is a schematic view of selected portions of an electronic pre-press system
1
including an internal drum imagesetter
10
and an on-line development/finishing processor
12
. The imagesetter
10
includes: a media supply cassette
11
which supplies a photosensitive media
8
as a web; drum input rollers
6
; an imaging drum
14
; drum output rollers
15
, web cutters
16
; a first sensor
17
; a transfer buffer
18
; a second sensor
22
; and a controller
3
. The controller
3
automatically controls and runs a predetermined sequence of operations of the imagesetting system
1
. The processor
12
includes a pair of input rollers
20
.
During operation of the system
1
of
FIG. 1
, a portion of the media
8
resident in the media supply cassette
11
is drawn onto the internal drum surface
9
of the drum
14
via drive rollers
6
until the leading edge of the media
8
is detected by the sensor
17
. A laser imaging system (not shown) transfers and records an image onto the media resident within the drum. The laser imaging system typically includes a laser diode located at or near the main central axis of rotation of the drum on a carriage that allows translation along the drum axis. The output beam from the laser diode is scanned by a rotating mirror across the media on surface
9
in successive circumferentially extending bands or paths referred to as scan lines. The laser diode output beam exposes specific pixel locations of the media along those scan lines to form the desired image. Because the imaged media is associated with a single color component of the image, the laser diode is turned-on or off for those pixel locations that contain that color component and depending on whether a positive or negative image is being generated.
After imaging, the media is thereafter transferred from the drum
14
to the transfer buffer
18
via drive rollers
15
. The media is transferred through a media path from the drum which in this example is defined as the media path traversing from the rollers
15
to the opening
23
between the platens
21
. After a predetermined length of the media
8
passes by the sensor
17
, the cutters
16
cut the media. The sheet of cut, imaged media entering the transfer buffer
18
continues being drawn into the system
18
by drive rollers
34
until the trailing edge (not shown) of the sheet is in the vicinity of the opening
23
. Another strip of media is drawn into the drum
14
by rollers
6
until the leading edge is again detected by the sensor
17
. The operations of the imagesetting system
1
are controlled by a pre-installed software program in the controller
3
. Moreover, the web supply roll
11
of
FIG. 1
may be replaced by a source of precut sheets of media.
As described above, sheets of cut, imaged media are moved into the transfer buffer
18
after imaging in the drum
14
. There they are stored in one of the storage devices
28
or
30
, before being transferred to the processor
12
. A preferred configuration for the transfer buffer
18
includes two storage devices
28
and
30
, although more than two storage devices could be used if desired.
FIG. 2
is a schematic view of a second preferred embodiment of a transfer buffer
18
in a first, i.e. initial, orientation. The nip between the rollers
34
is aligned with the opening
23
of the platens
21
so that the cut, imaged media
8
will pass between the rollers
34
and enter into the first storage device
28
. Similarly, the nip between the rollers
36
is concurrently aligned with the platens
25
which in turn is aligned with the opening
37
of the processor
12
. In this embodiment, the first storage device
28
includes a pair of driven rollers
34
which operate to draw the media sheet
8
into the first storage device
28
until the trailing edge of the sheet is in the vicinity of the opening
23
. A second storage device
30
includes the drive rollers
36
. The storage devices
28
and
30
are preferably rollers which will be described in more detail hereafter. However, any kind of storage devices which can be used for storing media can be used, such as rollers, nip rollers, cassettes, containers of any shape, etc. Moreover, the storage device
28
and
30
(or the whole transfer buffer
18
) could optionally be designed to be easily removable by an operator so that they could be stored for future use, or transferred to another system, if desired.
After the cut sheet of imaged media
8
is completely wound into the first storage device
28
, the transfer buffer
18
is rotated about its transfer buffer axis
19
as shown in
FIG. 3
to a subsequent orientation shown in
FIG. 4
where the nip between the rollers
34
is aligned with the opening
37
of the processor
12
and the nip between the rollers
36
is aligned with the opening
23
of the platens
21
. Note that during rotation of the storage devices
28
and
30
about their respective axes,
29
and
31
, within the transfer buffer
18
a portion of the medium sheet
8
remains in contact with the drive rollers
34
so that the sheet can be subsequently easily removed from the first storage device via the drive rollers
34
.
In
FIG. 4
, the drive rollers
34
transfer the medium sheet
8
from the first storage device
28
to the processor
12
. Another sheet of imaged media
8
is simultaneously transported through the opening
23
of the platens
21
, to the nip between the drive rollers
36
, and into the second storage device
30
as shown. While the exemplary embodiment of
FIGS. 1-4
shows a transfer buffer having two media storage devices mounted thereon, three or more media storage devices may be used if desired.
As the sheet of exposed media
8
exits the transfer buffer
18
and moves towards the processor
12
, it is detected by a second sensor
22
(see FIG.
1
), which operates to generate a media present signal. The media present signal may be used to initiate driving of the input rollers
20
in the processor
12
.
The first preferred embodiment of the transfer buffer
18
and associated hardware is further illustrated by a rotatable transfer buffer
18
in
FIGS. 5A
,
5
B,
5
C,
6
and
7
A-
7
D. Each storage device
28
or
30
is constructed as illustrated in FIG.
5
A. They each include: a body
100
substantially shaped as a roller and having a surface
104
; an axle
110
of the roller
100
; two or more leaf springs
90
fastened to the surface
104
via fasteners
106
; a retaining rod
102
fastened to the leaf springs
90
via fasteners
108
; and wheel bearings
92
at either end of the rod
102
. The bearings
92
and axles
110
each extend beyond the end surfaces
114
of the rollers
100
.
The end plates
112
of the transfer buffer
18
are illustrated in
FIGS. 7A-7D
.
FIG. 7A
illustrates an inside surface
120
of an end plate
112
;
FIG. 7B
illustrates an outside surface
122
:
FIG. 7C
is a cross-sectional view along line A-A′ with slots
124
drawn in shadow; and
FIG. 7D
is a view of the outside surface
122
of
FIG. 7B
, including additional hardware for driving various system components. The storage devices
28
and
30
are mounted onto the end plates
112
, via axles
110
and with bearings
92
engaged into slots
124
. Each slot
124
includes an indent
150
which accepts the bearings
92
when initializing the positions of the storage devices
28
and
30
prior to transferring media thereto.
FIG. 7A
illustrates an inside surface
120
of an end plate
112
including: a rotating axle
130
around which the whole transfer buffer
18
rotates; axles
110
around which the storage devices
28
and
30
rotate; axles
126
of the drive rollers
34
of the storage device
28
; axles
132
of the drive rollers
36
of the storage device
30
; and slots
124
which engage the wheel bearings
92
of the storage devices
28
and
30
.
FIG. 7C
clearly shows that the slots
124
are engageable with the bearings
92
from the inside surfaces
120
of the end plates
112
.
In the preferred embodiments of the buffer
18
illustrated herein, the buffer is rotatable about an axis
130
as shown in FIG.
7
A. However, the buffer
18
is not limited to being rotatable. For instance, the transfer of storage devices and the media stored within could occur by moving the storage devices within the buffer first along a linear path, and then turning the storage device 180 degrees to return along an adjacent linear path.
FIG. 6
is a perspective view of a partially constructed transfer buffer
18
which includes two storage devices
28
and
30
. A motor (not shown) is connected, external to the transfer buffer
18
, to a pulley
140
which rotates about an axis
128
. A belt
142
connects pulley
140
to pulley
138
which, in turn, is connected to and drives one axle
126
of the rollers
34
. The two rollers
34
form a tight nip therebetween so that when one roller
34
is driven, the other roller
34
follows. Similarly, rollers
36
are driven via a system containing a motor (not shown), a pulley
144
rotating about an axle
132
and a pulley rotating about an axis
146
. The storage devices
28
and
30
are driven via an external motor (not shown) which engages the gears
136
to rotate the axles
110
. The motors and associated hardware can be mounted external to, or within the transfer buffer
18
, as desired. Moreover, the dimensions of the storage devices
28
and
30
are variable to accommodate different size media sheets.
The operation of the imagesetting system
1
including the transfer buffer
18
is detailed by the flow chart of FIG.
8
. The operating sequence is controlled by the controller
3
which, in turn is dependent upon software executed therein. At step
60
, media
8
is provided to the imagesetter
10
, for example by a supply cassette
11
also referred to as a web supply roll. Media may alternatively be supplied by a number of pre-cut sheets, for example stored in a stack. At step
62
, the supply rollers
6
move the media
8
onto the recording support surface
9
of the drum
14
. At step
64
, the imagesetter
10
records a predetermined image onto the media
8
while it is located over the recording support surface
9
. After or during the recording of the image onto the medium
8
and prior to removal of the medium
8
from the recording support surface
9
, the transfer buffer
18
is initialized at step
66
. The steps of initialization include (i) aligning the nip between the rollers
34
with the opening
23
of the platens
21
, (ii) aligning the nip between the rollers
36
with the opening
37
of the platens
25
, and (iii) indexing each of the bearings
92
into indents
150
of slots
124
of the end plates
112
(see FIGS.
5
B and
7
A). In the state of initialization, the leaf springs
90
are each in an open or extended position so that the retaining rod
102
is spaced apart from the body
100
of the storage device
28
. Once the initialization is complete, the imaged medium
8
is removed from the drum via output rollers
15
and new media is brought into the drum from the supply cassette
11
via input rollers
6
at step
68
. At step
70
, the image sensor
17
detects the traversal of the leading edge of the media and initiates power to the drive rollers
34
at the same transfer speed as the rollers
6
and
15
. The transfer speed of the various drive rollers indicates to the controller
3
the exact position of the leading edge of the imaged medium
8
. Thus, the imaged medium
8
is driven through rollers
34
until it is positioned between the surface
104
and the bearing
92
as shown in FIG.
5
B. At this point, the roller
100
of the storage device
28
is activated to rotate about its axis
110
at the same transfer speed as the other rollers, causing the rods
102
to move out of the indents
150
and to clamp down on the medium
8
as shown in FIG.
5
C. The imaged medium
8
is thereafter wrapped onto the external surface of the roller
100
as shown in FIG.
5
C. Note that once the roller
100
begins to turn, the spring
90
is contracted so that the bearing
92
is removed from its initial position in the indent
150
(FIG.
7
A). The bearing
92
thus pinches the medium
8
onto the surface
104
, holding the medium
8
in place as it wraps around the roller
100
as illustrated in FIG.
7
C.
When the appropriate length of media
8
has passed by the sensor
17
, the cutters
16
cut the medium sheet and the rollers
6
and
15
stop (step
72
). The drive rollers
34
and the roller
100
in the storage device
28
continue to operate until the trailing edge of the cut medium is in the vicinity of the opening
23
. At this point, the drive rollers
34
and
100
stop and the first cut sheet of media is fully stored in the storage device
28
. A next image is transferred onto the media in the drum as previously described. Meanwhile, at step
74
the transfer buffer
18
moves the storage devices therein. For instance, for the cylindrically shaped transfer buffer
18
shown in
FIGS. 2-4
, the buffer is moved so that the nip between the rollers
34
is now aligned with the opening
37
of the platens
25
and the nip between the rollers
36
is aligned with the opening
23
of the platens
21
. In this way, the cut medium
8
which is stored on the storage device
28
is ready for transfer into the processor
12
, while an empty storage device
30
is available to receive the next sheet of imaged medium
8
from the drum
14
. At step
76
, the drive rollers
34
and
100
are activated and the medium
8
stored in the storage device
28
is transferred through the platen
25
into the processor
12
. When the sensor
22
detects the leading edge of the medium
8
, it transmits an electronic signal to the controller
3
which, in turn, activates the processor input rollers
20
at the same transfer rate as the rollers
34
and
100
. When the trailing edge of the medium
8
being transferred into the processor
12
is detected by the sensor
22
, the rollers
34
and
100
are deactivated.
The above described process repeats itself for each imaged sheet of media
8
. Thus, media sheets are either being input into the drum or imaged, while simultaneously being transferred from the drum into the transfer buffer
18
, and transferred from the transfer buffer
18
to the processor
12
. In this manner, the imagesetting system
1
operates at a high level of efficiency.
Although the first and second preferred embodiments of the present invention, as described herebefore with reference to the drawings, include a generally cylindrically shaped transfer buffer
18
, the particular shape of the buffer
18
is not critical to the principles of the invention. Hence, the transfer buffer
18
is not limited to a cylindrical shape. In fact, the movement of the storage devices
28
and
30
from one point to another within the buffer
18
can be implemented by any known transfer means, such as via a belt driven or chain driven transfer system. The particular cylindrical shape of the embodiments of the transfer buffer
18
illustrated in the drawings allows an easy manner to transfer the storage devices from one point to another within the buffer
18
. In fact rather than rotating, the buffer
18
could cause the devices to move in a linear path or along a combination of linear and angular paths. Any path for transferring the media (via multiple storage devices) from one component to another within the imagesetting system
1
is a viable alternative for implementing the inventive concepts.
The general principles of the invention are presented in view of the previously described preferred embodiments. However, those principles are applicable in many variants of an imagesetting system. For instance, the transfer buffer could be used with any internal or external drum imagesetting system. In fact the transfer buffer could be more broadly used to transfer and buffer any imaged media between any two stages or components within a system. For instance in a system which digitally images media, the transfer buffer could be used to transfer media between the drum and the mechanical finishing unit (which would be necessary in place of the chemical processor described herebefore).
Having described the preferred embodiments of the invention other embodiments which incorporate the concepts of the invention will now become apparent to one skilled in the art. Therefore, the invention should not be viewed as limited to the disclosed embodiments but rather should be viewed as limited only by the scope of the appended claims.
Claims
- 1. A method for transferring sheets of media between first and second components of an imagesetting system, the method comprising the steps of:rotating a transfer buffer comprising at least two assemblies about a transfer buffer axis, to align a first assembly with the first component while concurrently aligning a second assembly with the second component, each of said assemblies comprising a storage device, having an axis, for storing one of the sheets of media, and a pair of drive rollers having drive roller axes, said transfer buffer axis being parallel to said storage device axes and said drive roller axes; transferring a first sheet of said media from the first component to the first assembly; moving the transfer buffer to align the first assembly with the second component while concurrently aligning the second assembly with the first component; and transferring the first sheet of said media from the first assembly to the second component while simultaneously transferring a second sheet of said media from the first component to the second assembly.
- 2. The method of claim 1 wherein the first component is an internal or external drum for imaging.
- 3. The method of claim 1 wherein the second component is a chemical processor or mechanical finisher.
- 4. The method of claim 1, wherein the storage devices are removable.
- 5. The method of claim 1 wherein the transfer buffer is removable.
- 6. A method for transferring imaged sheets of media between a drum of an imagesetter and a media processor, the method comprising the steps of:rotating a transfer buffer having at least two assemblies about a transfer buffer axis, to align a first assembly with a media path from the drum, said assemblies each comprising a storage device with a storage device axis and a pair of drive rollers with drive roller axes, said transfer buffer axis, said storage device axes and said drive roller axes being parallel to one another; transferring a first sheet of said media from the drum through the media path to the first assembly; rotating the transfer buffer along the transfer buffer axis to align the first assembly with an input to the media processor and to concurrently align a second assembly with the media path from the drum; and transferring the first sheet of said media to the input of the media processor while simultaneously transferring a second sheet of said media from the drum through the media path to the second assembly.
- 7. The method of claim 6 wherein the media processor is a chemical media processor or a mechanical finishing processor.
- 8. The method of claim 6 wherein the drum is an external imaging drum or an internal imaging drum.
- 9. The method of claim 6 wherein the first and second assemblies are removable.
- 10. The method of claim 6 wherein the transfer buffer is removable.
- 11. A system for transferring imaged sheets of media between a drum of an imagesetter and a media processor, the system comprising:means for rotating a transfer buffer having at least two assemblies about a transfer buffer axis, each of said assemblies comprising a storage device, having an axis, for storing one of the sheets of media, and a pair of drive rollers having drive roller axes, to align a first assembly with a media path from the drum while concurrently aligning a second assembly with an input to the media processor, said transfer buffer axis being parallel to said storage device axes and said drive roller axes; means for transferring a first sheet of said media from the drum through the media path to the first storage device in the first assembly; means for rotating the transfer buffer to align the first with the input to the media processor while concurrently aligning the second assembly with the media path from the drum; and means for transferring the first sheet of said media to the input of the media processor while simultaneously transferring a second sheet of said media from the drum through the media path to the second assembly.
US Referenced Citations (10)
Foreign Referenced Citations (1)
Number |
Date |
Country |
2128593 |
May 1984 |
GB |