DE2353792A1 - DEVICE FOR PRODUCING A PRINTING PLATE - Google Patents

Description

Dr. Ing.Walter Abitz

Dr. Dieter F. Morf '■' October 26, 1973

Dr. Hans-A. Browns 2256

B Munich 88, Pleraenauartfr. 2t

ITEK CORPORATION Maguire Road, Lexington, Mass., V.St.A.

Device for making a printing plate

The present invention relates to an apparatus for Manufacture of a printing plate with the following parts:

a) an exposure station and

b) a device for conveying a printing plate to this exposure station and to the holder the same for the purpose of exposure, the conveyor and. Holding device comprises the following parts:

i) a conveyor belt which is movable between a first and a second station and which has a first and a second surface opposite the first, a perforated area with .a number

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of openings which extend from the first surface to the second surface, as well as an essentially imperforate area which is arranged in front of the perforated area when the conveyor belt moves from the first to the second station,

ii) a conveyor for conveying the printing plate in abutment with the first surface of the conveyor belt, the conveyor having an adjustment device for adjusting the leading edge of the printing plate in alignment with it. the front edge of the perforated area of the conveyor belt,

iii) means for reducing the pressure on the second surface of the conveyor belt, around the pressure plate against the first surface of the conveyor belt by means of the to attract openings in the perforated area of the conveyor belt and to hold, and

iv) a drive device for moving the conveyor belt from the first station to second station for the purpose of moving the plate held on the conveyor belt to the exposure station for exposure of the same.

The present invention relates to apparatus for making a printing plate, and more particularly a device for conveying a printing plate to an exposure film and back and to the holder

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the printing plate at the exposure station during the exposure of the same.

It is already known in an electrostatic Apparatus for making a printing plate to use an endless conveyor belt to move the electrostatic charged, photosensitive printing plates to an exposure station and there to hold during exposure. In such systems it is also known to use a vacuum plate or the like. To use the printing plate in the focal plane of an optical exposure system during the exposure by means of a through openings in the Keep the conveyor belt closed to the suction force exerted.

However, it has been shown in practice that the known arrangement has various shortcomings. A A particular problem is, for example, the guidance of the conveyor belt. Because the conveyor belt is endless and is always moved in the same direction, errors in the guidance of the conveyor belt have the Aiming to be cumulative and to cause a noticeable sliding movement of the conveyor belt around its guide rollers, with the conveyor belt against the edges of the guide rollers or other surfaces of the machine are frictional. This frictional effect leads to rapid wear of the Conveyor belt and its frequent replacement, furthermore, it often leads to a breakage of the conveyor belt comes during operation.

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To the mentioned errors in the guidance of the conveyor belt To reduce, one has used crowned rollers to support the belt. With such an arrangement however, the maintenance and renewal of the conveyor belt becomes a complicated process, which requires a lot of time and considerable skill. Furthermore, when using crowned guide rollers, the conveyor belt be somewhat elastic and it is therefore more difficult to keep the conveyor belt completely flat and free of waves to keep what is required during operation is to achieve proper alignment of the printing plate in the focal plane of the exposure system.

Another difficulty arose with the known devices in that the conveyor belts essentially were perforated along their entire length. It stayed when a printing plate was only partially on the conveyor belt a significant number of the perforations were uncovered. During this period of time, a fan or other suction source sucks air through the uncovered Perforations, which make the pressure plate itself effective suction is reduced. To therefore during A relatively large fan must be used to keep the pressure plate precisely on the conveyor belt during these periods of time or a relatively large pump that maintains a strong suction effect can be used. This requires a greater power requirement for the device, and generally makes them more expensive.

According to the invention, some of the above are described Defects eliminated by using a conveyor belt

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is used, which is between a dispensing roller and a take-up reel is wound and unwound to a to bring charged printing plate to the exposure station for "exposure" and for the subsequent development to withdraw. In particular, the conveyor belt used is not an endless conveyor belt, that is constantly moving in the same direction, but rather is arranged on rollers to be moved forward from a first loading station to a second exposure station to be guided back to the first station with each exposure process to become.

Several advantages are obtained by this arrangement. At one point there are leadership errors when moving forward of the conveyor belt essentially during the backward movement of the conveyor belt corrected by itself. Leadership errors are therefore not cumulative like this is the case when using an endless conveyor belt which only moves in one direction. This extends the life of the conveyor belt and it also becomes unnecessary to have crowned leadership roles to use which In the maintenance and in the exchange the conveyor belts are not problem-free.

Another 'important feature of the present er- • ^; invention relates to the construction of the conveyor belt itself. In particular, only a portion of the conveyor belt is perforated and not the entire conveyor belt, and the movement of the conveyor belt is with the feeding of the pressure plate; on the tape. Synchronized in such a way that the perforated section of the conveyor belt in the

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essentially at the same time with the printing plate for Vacuum plate arrives. This means that there is not a large number of uncovered perforations, through which air is sucked in, reducing the suction acting on the printing plate, and accordingly, less power is required to achieve the to achieve the required suction to hold the pressure plate on the conveyor belt. This improved holding effect also eliminates the need to use wire guides or other retention arrangements to ensure that the pressure plate is firmly in contact with the conveyor belt at all times.

Furthermore, in the embodiment according to the invention the conveyor belt may not be particularly elastic and a flat, wave-free conveyor belt can be achieved more easily and generally requires less tension application to keep it smooth.

The present invention provides an efficient system for conveying electrostatically charged printing plates in a device for producing a printing plate available and eliminates some of the shortcomings known Devices, the use of the invention resulting in a compact and efficient system. Further Advantages of the invention emerge from the following description of a preferred exemplary embodiment in conjunction with the drawings j it show:

Fig. 1 in a schematic representation of an exposure station of an apparatus for producing a Pressure plate, which the plate conveyor and holding device used according to a preferred embodiment of the invention,

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Pig. 2 an execution form of the conveyor belt according to a preferred embodiment of the invention.

Fig. 1 shows schematically an exposure station 10 for use in a device for production an electrostatic printing plate * A photoconductive one Printing plate "11, which has been provided with an electrostatic charge in a known manner the exposure station 10 and in alignment in the focal plane 15 of an optical exposure system arranged, which is shown schematically by a lens 12 is indicated, wherein the printing plate is exposed to the desired image.

To hold the pressure plate and to move it to exposure station 10 and back is a Conveyor belt 13 is provided. This conveyor belt, which preferably made of "Mylar" plastic, but also could consist of a fabric * a film or some other material is at its ends a delivery roller 14 and a take-up roller 16 attached. The rollers 14 and 16 are driven by a reversible drive motor l8 via a mechanical Connection 17 driven to the conveyor belt 15 over the focal plane 15 of the optical exposure / systems 12 with the pressure plate 11 back and forth- ' to lead. In particular, the conveyor belt Ij is for movement guided over the focal plane 15 around guide rollers 19 and 21. One or more idlers 22, or an equivalent arrangement, may also be provided to keep the conveyor belt maintain proper tension and to ensure that the conveyor belt is held flat and free of waves en will. ', -.-

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With the optical exposure system 12 is aligned a vacuum plate is provided, which in the illustrated embodiment consists of a vacuum chamber 23 with a perforated base 24 and a device such as a fan 26 or a pump for reducing the air pressure in the chamber 23. The base plate 24 is essentially " perforated over its entire surface, so that the fan 26 when the air pressure is reduced in the chamber 23 air up through the perforations pulls and creates a suction effect, as will be explained in more detail later. The conveyor belt 13 is over the base plate 24 out and also has perforations, as will be explained.

A charged printing plate is exposed in in the manner described below. First, a loaded printing plate 11a comes from a non-illustrated one Loading station to exposure station 10. The printing plate is in an inclined position, for example with an angle of inclination of 30 ° compared to the Focal plane 15 supplied. If so desired, a guide 27 can be used to achieve a correct Alignment can be used. The plate is between the guide roller 19 and a cooperating therewith Guide roller 28 supplied, which is in contact with the lower surface of the conveyor belt 13, which is guided around the guide roller 19. The web speed the supplied pressure plate and the conveyor belt are ·. essentially synchronized to ensure proper operation of the device.

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As soon as the pressure plate arrives in the area of the vacuum chamber-23 and preferably immediately ■ next dl.e ^: pressure plate passes between the guide _{rollers 19 and 28 4} is due to the suction through the ^i! Perforations: in the base plate 24 and the perforations in the conveyor belt 13, the conveyor belt and the pressure plate carried on it are attracted to the base plate 24 and held in the focal plane 15 of the optical exposure system 12. The conveyor belt Γ5 continues its movement from the delivery roller 14 to the take-up roller ^l6;., and performs the printing plate so far as is, is arranged to them precisely aligned with the BelichtuhgssyStem 12 at this time, operates the front edge of the printing plate 11.einen switch 29, which is connected via an electrical connection J51 with the 'drive motor · l8 is to the drive motor;. unwind and vernindera another movement- of the conveyor belt, Ih this position, the pressure plate 11 exactly in Fluchtuhg; with the ^ι focal plane 15 of the optical "see system 12 and is further through die'Saugwirkung which engages via the perforations in the base plate 24 and in the conveyor belt 11, halfcen securely in their position. The printing plate can then be exposed in a known manner by the attachment system 12 with the '^^' desired A ""'image,' ■ '. "■"'^{.; I} '-

After the exposure, the pressure plate is toip Rüefe ':: ^;> guidance to the exposure station and i ^ ^Λ guidance "to * smß. r- B ready »Dies ebf ^ Qigt- iii & 0.ν following termination- d / ep Belieiitung w | -PA dep Dr.bsmotQr. Iß.

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automatically by a switch (not shown) switched on and drives the conveyor belt Γ3 in the reverse direction back to its starting position. -This is the conveyor belt 13 from the take-up reel unwound and wound onto the dispensing roller 14, the pressure plate with the conveyor belt moved back through the gap of the guide rollers 19 and 28 will. When exiting between the guide rollers the pressure plate falls through, as shown at 11b The effect of gravity counter to a holding frame 52, the at an angle of about 30 to the Focal plane is inclined downwards and becomes the next, not-shown stage of the device continued. After the printing plate has completely left the exposure station, the conveyor belt fully wound on the delivery roller 14 and located is again in its starting position, around the next printing plate arriving from the loading station to record. The drive motor is also switched off, to be ready for the next printing plate.

The present invention obviates many of the shortcomings of known devices by providing a. Conveyor belt is provided which is moved from a first position to a second position and back to the first position in order to bring a printing plate to the loading station. for the exposure to be taken away after the exposure. There, that? _v : conveyor belt for each exposure process in two. .,? - Moved in different directions ·, will, r become path-r _; ; . errors reduced to a minimum .; whereby 4

Lifetime of the conveyor belt increased and an economical working system is obtained. Furthermore, it is not necessary in the present invention, to use crowned guide rollers to reduce web guiding errors. This will make the maintenance of the system is considerably easier than with known ones Devices and it is also not necessary to use elastic conveyor belts, which is required when crowned guide rollers are used. If elastic conveyor belts are used, the tendency for wave formation increases noticeably, and so does it there must be considerable tension on the conveyor belt, Exercise to keep it smooth and flat. In the device according to the invention, the conveyor belt needs not to be elastic and therefore the required tension is less. This also contributes to an increase contributes to the service life of the conveyor belt.

Finally, through the feeding of the printing plates to the exposure station and its removal from the exposure station on the same side created a compact arrangement. In the same way the fact that no endless conveyor belt is used is effective.

.Fig. Figure 2 shows another important feature of the present invention. In FIG. 2, in particular, a section of a conveyor belt 13 is shown. which is used in the system of FIG. This conveyor belt is equipped with a perforated area 6 and a non-perforated area 37. The non-perforated area 37 is located during the movement of the conveyor belt from the. Dispensing roll. 14 for recording _L r,

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roll 1-6 in the direction of the arrow in front of the perforated area 3> β. If the conveyor belt is in its starting position and waiting to receive a printing plate 11 , then essentially the entire area underneath a vacuum chamber 23 consists of the imperforate area 37 The feeding of the printing plate 11 is synchronized in such a way that the leading edge of the printing plate reaches the base plate 24 of the vacuum chamber 23 substantially at the same time as the first rows of perforations 38 of the perforated section 36. This has several important advantages.

The printing plate 11 and the first rows 38 arrive the perforations 39 to the vacuum chamber 23 so is the remaining part of the conveyor belt under the vacuum chamber is imperforate. Thus essentially act all suction forces generated by the vacuum chamber on the pressure plate. There are no exposed ones There are perforations in the conveyor belt through which air can flow while weakening the suction effect. This means that less suction is sufficient to hold the pressure plate firmly on the conveyor belt keep. The more the pressure plate is under the vacuum chamber moved forward, the more increases-, the-per-, formed area "of the same in order to hold the printing plate in place over its entire length. In other words, in accordance with the present invention this is Conveyor belt essentially only perforated where

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the printing plate is held and therefore there is no significant loss of energy like this the case is "if air is also sucked through perforations that are not covered. This is permitted a reduction in the size of the fan, which is required to generate the suction effect, resulting in savings in acquisition and energy costs result. In known devices that. use an endless conveyor belt that goes over his entire length is perforated, air is not only through the perforations in the area of the pressure plate sucked in, but also through uncovered perforations, so that larger fans are required, to generate the considerably greater suction that is necessary to hold the pressure plate on the conveyor belt. To ensure the correct alignment of the supplied printing plate to achieve with the first cleans of the perforations J58, can be any sensing or timing relay device be used. ■

The perforations 39 in the conveyor belt are preferably elongated according to FIG. 2 and cooperate with the essentially circular perforations 41 in the base plate 24 of the vacuum chamber. This ensures that suction is maintained at all times during the movement of the conveyor belt. that no time is available 'during which the perforations in the conveyor belt with the perforations of the plate not ausgerichtet'sind lh. Obviously the -form of the perforations could '^ varied' being or else angeordfiefc'-seiri.-

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Preferably the perforations are on the conveyor belt arranged offset from one another, preferably in a plurality of rows, with alternating rows Ranks straight pig. 2 are offset from one another. this helps to ensure that the printing plate is held securely and evenly at all times. Through the The present invention thus provides an apparatus for making a printing plate which is inexpensive in its construction and which still needs no maintenance or repair for a long time. If maintenance is required, this can be done quickly and carried out with a minimum of technical skill. The invention also provides a very Compact arrangement available that without difficulty could be built into different devices for making a printing plate.

It should also be noted that the term "printing plate" as used in the present context should include all photosensitive media, such as "electrofax" paper and the like and not on lithographic printing plates according to the described preferred embodiment is limited. Further modifications of the invention are possible within the scope of the appended claims are included in these

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Claims (9)

,. ir Pat entansprüche [Iy device for making a printing plate, marked by; a) a credit station and b) a device for conveying a printing plate for Belichtungsstation and for holding the printing plate on the same, the conveyor and Holding device comprises the following parts: i) a conveyor belt * which goes back and forth between a first station and a second station is floating and which is a first surface and has a second opposing surface and a perforated area with a number of openings, which ■ extend from the first surface to the second surface extend, and one substantially imperforate Area which during the movement of the conveyor belt from the first to the second Station is located in front of the perforated area, ii) a device for feeding the. Pressure plate to the first surface of the conveyor belt, wherein the "feeding device a Means to be substantially aligned around the leading edge of the printing plate to be arranged with the front edge of the perforated area of the conveyor belt, 4098 19 ¹ ^ I 050 ORIGINAL INSPECTED iii) a device for reducing the pressure in the region of the second surface of the conveyor belt to the printing plate through a perforated through the openings The area of the conveyor belt to maintain effective suction against the first surface and iv) a drive means for moving the conveyor belt from the first station to the second station and thereby to guide the conveyor belt carried by the pressure plate for exposure to ^J exposure station. 2. Device according to claim 1, characterized in that the number of openings in the conveyor belt from one Number of perforations. 3. Device according to claim 2, characterized in that that the conveyor belt has a perforated area and a substantially non-perforated area has, and that the device for arranging the Pressure plate includes means for substantially aligning the pressure plate on the conveyor belt align with the perforated area of the conveyor belt. 4. Apparatus according to claim 3 * characterized in that that the essentially non-perforated area of the conveyor belt is in front of the perforated area, when the conveyor belt is moving in the forward direction, • and that the device for arranging the pressure plate means for arranging the leading edge of the printing plate substantially in alignment with the - 16 A 0 9 8 19/10 ^ Q ν ...... .,.-__. ORlGiNAtINSPECTED front edge of the perforated area when, see the conveyor belt "moving" in the forward direction 5. Device according to one of claims 1 to 4, characterized characterized in that the device for reducing the pressure, from a vacuum chamber with reduced There is pressure, which extends across the exposure station, and that the vacuum chamber a Has base plate with a number of openings, ■ and also a device for "holding the conveyor. tape in one movement past the base plate is provided, and the reduced pressure in the vacuum chamber pushes the pressure plate against the first upper * - keeps the conveyor belt flat when the drive device moves the * conveyor belt over the base plate ' moves, as a result of the suction, which through the openings in the base plate and in the conveyor belt, becomes effective *. "* ^,. ·,, .6. Apparatus according to claim T, characterized by a device to move the conveyor belt backwards from the second position to the steady position in order to remove the printing plate from the exposure station after the exposure has been tracked ^. · ■ · ■■; - 7. The device according to claim 6, characterized in that the feeding arrangement has a device to bring the pressure plate to the first surface of the conveyor belt synchronously with the movement of the conveyor belt from the first station to the second Bt ai £ ön '! In such a way that'- be ± the Ähkunfif of the ^ "'""conveyor belt 'to"the' second station iiti essential '" - 17 -. ORIOINAL INSPECTED A 23R3792 the entire printing plate next to the perforated area of the conveyor belt and is held against it by suction. 8 * Device according to one of claims 1 to 7, characterized characterized in that the feeding device for the Pressure plate includes the following parts: a) a first and second guide roller between which the conveyor belt is passed and b) a guide device around the printing plate between the first and second guide rollers in abutment with the first surface of the conveyor belt bring to. 9. The device according to claim 8, characterized in that the guide device has a device around the pressure plate between the first and second guide rollers at a first angle of inclination feed opposite the conveyor belt. 10 * Device according to claim 9 * characterized by a device for removing the printing plate from Conveyor belt after exposure, which has a device to the plate between the lead away said guide rollers at a second angle of inclination with respect to the conveyor belt, the differs from said first angle of inclination. - 18 4.09 8 1 9/1050 ORIGINAL INSPECTED