Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
1999-09-14
2002-07-30
Ellis, Christopher P. (Department: 3651)
Sheet feeding or delivering
Feeding
Separators
C271S038000, C271S110000, C271S118000, C271S120000, C271S121000, C271S124000
Reexamination Certificate
active
06425578
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method and apparatus for recording an image on a recording plate.
DESCRIPTION OF THE PRIOR ART
Lithographic printing plates for which this invention is particularly well suited typically comprise a rectangular aluminum substrate onto which is deposited a thin layer of photographic polymer. In addition a further thin protective coating of a polymer such as PVA is often added.
Recording of the image information onto such a plate is typically achieved in an image scanner using a scanned laser beam which hardens the photographic polymer in a selective manner. Following recordal of the image in the image scanner, the lithographic plate is later used within lithographic printing apparatus. A similar system for the recording of an image may also be used in connection with photographic plates and for the purposes of this invention both lithographic and photographic plates are described as a recording plate or plates.
In order to achieve high productivity it is desirable to use an image scanner in conjunction with automatic feeding apparatus to sequentially feed recording plates from a store and deliver them to the image scanner via a transport system. Typically the store contains a stack of such recording plates separated by interleaved sheets which protect the sensitive surface of the plates on which the image will be recorded. The delivery of individual plates to the transport system is achieved by removing the top plate from the stack using a feed system. The stack of plates has a typical mass of up to 60 kg, all plates within the cassette being of equal size. It is desirable that the apparatus can supply these plates to the image scanner without manual intervention. Manual intervention is undesirable as it slows the overall process considerably and further increases the risk of exposure of the image recording surfaces to radiation. For similar reasons it is therefore desirable that the interleaved sheets are automatically removed from the plate feeding path and are placed in a receptacle for later disposal. These interleaved sheets are often made from paper which is considerably different in mechanical properties when compared with the recording plates.
The established practice in existing image processing systems is to withdraw the recording plates sequentially from the stack using vacuum-activated suckers. The suckers are mounted upon a movable gantry and engage the topmost recording plate, then lifting it clear of the stack. The gantry then moves the recording plate to a receiving position for feeding into the image scanner. Separating means are often provided for the removal of an interleaved sheet when this is the topmost constituent in the stack. For example such means may include a roller which is moved to engage with the topmost sheet and withdraw it from the stack towards a bin. However, due to adhesion between the topmost recording plate and one or more plates or interleaved sheets beneath, a multiple feed operation can occur which is required to be remedied by separation of the plates and sheets. Known methods of performing this separation include the blowing of air between the interfaces of the plates and sheets, or simply holding the topmost plate in an elevated position above the stack such that the action of gravity eventually causes separation of the mis-fed items beneath.
Typical problems with such a system are that oxygen depletion under the suckers causes degradation of the emulsion, and secondary vacuum effects lead to multiple plate feeding.
One major problem with the use of vacuum suckers is that they engage in a localized manner with the fragile coated surface of the recording plate. As the vacuum is supplied, the plate deforms locally in the areas under the suckers producing characteristic circular marks on the processed plate. A second problem that occurs in such vacuum systems, is that the vacuum pressure required to lift a plate vertically is different from that to lift a sheet. If the pressure is not adjusted between the feeds then, since the paper is porous, the suckers will lift an interleaved sheet as well as the plate below. The vacuum system must therefore be capable of distinguishing between plates and sheets and, having set the correct vacuum level and lifted the topmost item, must confirm that the separation has been achieved before the selected plate or sheet is moved away from the stack. The time required to perform these steps is relatively large and in many cases rate limiting to the productivity of the complete system. This method is also unable to be optimized for a full range of plate sizes and thicknesses. In addition the apparatus is costly and often unreliable.
Downstream of the plate store and feeding apparatus conventional systems load the recording plate into the drum image scanner and in such equipment the plate may be supported on an internal or external surface of a drum for the recording of an image. Typically the loading of the plate into the image recording position is achieved using rollers or drive belts. As the exact positioning of the plate is particularly important, such systems include the use of guides and stops to ensure correct alignment with the image recording device. De-skewing of the plate is conventionally achieved when the plate is in the imaging position, by applying of a trail edge force via a sprung system which applies a variable force at different points depending on the skewing of the plate. However, this relies upon low frictional forces between the plate and the drum, particularly in the case of drums having a small radius of curvature.
It is also important to ensure that the surface of the plate conforms with that of the drum, i.e. each part of the plate surface is in contact with the surface of the drum. Prior art systems typically achieve this by either using mechanical means to apply a force to the plate causing it to bow and therefore conform with the drum, or by applying a vacuum to the drum surface causing the plate to be held in the conforming position. An example of the former method involves the loading of the plate into the apparatus such that the leading edge abuts some end stops. Subsequently, fingers are driven against the rear edge of the plate causing it to bow outwards and conform with the drum. As the apparatus may be used with different sizes of plates, the fingers in this case may be controlled with stepper motors or a sprung system to ensure the correct degree of movement based upon plate size information given to the apparatus controller by an operator.
In the second case where a vacuum system is used to conform the plate to the drum surface, it is conventional to provide a plurality of grooves within the surface of the drum. The grooves are connected to apertures and a vacuum is applied to the grooves using suitable means. The grooves are respectively attached to separate vacuum circuits which are either switched on or off using a plurality of electronically controlled valves in order to apply a vacuum to an area corresponding to the size of the recording plate.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention we provide image recording apparatus for recording an image on a recording plate, the apparatus comprising;
a plate store for storing a stack of recording plates separated by interleaved sheets;
a drum image scanner on which recording plates are located for recordal of an image; and
a frictional feed apparatus for withdrawing recording plates from the store and feeding them singly to the drum image scanner.
In accordance with the second aspect of the present invention we provide a method of feeding recording plates from a plate store containing a stack of plates with interleaved sheets, to a drum image scanner, the method comprising withdrawing plates from the store and feeding them singly to the drum image scanner all under frictional control.
It has been found that frictional feeding apparatus can be used to successfully withdraw plates from a stack of interleaved plates and sheets in order t
Fox Stephen Edward
Marshall Colin
Wood James Buckingham
Deuble Mark A.
Ellis Christopher P.
Fujifilm Electronic Imaging Limited
Sughrue & Mion, PLLC
LandOfFree
Image recording apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image recording apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image recording apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2869443