Sheet feeding or delivering – Delivering – By pneumatic conveyor
Reexamination Certificate
2000-09-11
2002-07-09
Skaggs, H. Grant (Department: 3651)
Sheet feeding or delivering
Delivering
By pneumatic conveyor
C271S264000, C406S086000, C219S121630, C219S121640, C029S890039
Reexamination Certificate
active
06416051
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a sheet guiding device, in particular for contact-free guidance of printed paper sheets in or in connection with printing machines, for example, in a dryer connected to a printing machine, and a method of producing the sheet guiding device.
In sheet-fed offset printing, particularly multi-color printing, printing inks and dispersion coatings are frequently used, which require a given length of time and amount of light radiation, i.e., infrared (IR) and ultraviolet (UV) as well as heat possibly for the drying thereof. Correspondingly, not yet smudge-proof printed sheets or dispersion varnishes must be handled without damaging the fresh print. The sheets must run without smearing. The drying of the printing inks is frequently accelerated by heat. Serving for this purpose are dryers, which are provided with infrared radiators or UV-radiators of relatively high output, for example, up to 30 kW. Modern sheet-fed offset printing machines are capable of printing up to 21,000 sheets per hour, each sheet being able to have a maximum length of 1 m. This results in a very high production speed and running speed of the sheets and a very short dwell time in the dryer, which, in turn, results in the high required dryer outputs. The high thermal outputs cannot, however, be completely absorbed by the sheets. Part of the heat virtually unavoidably affects guide plates which are arranged opposite the infrared or UV-radiator for guiding the sheets in the dryer. Heat effects must, however, be kept away from the printing machine in order to avoid any impairment of the proper function thereof. An attempt has therefore been made to provide the guide plates with water cooling for carrying excess heat away.
In this regard, the published German Patent Document DE 196 02 514 C1 discloses a guiding device with a cooled guide plate which is connected to coolant channels at the rear side opposite from the guide face. For this purpose, a cooling trough plate is fastened onto the rear side of the guide plate by spot welding or pulse welding and is sealed off from the guide plate by a sealing element, such as a flexible or soft rubber ring.
Overheating resulting from applied radiation can cause the sealing rings to shrink, and the connections between the guide plate and the cooling trough plate to leak.
From the published German Utility Patent Document G 9418358 U1, it has also become known heretofore to use, as a guiding device, a guide plate having a further guide plate welded onto a rear side thereof by a laser welding method. In this regard, the plates are selected with different thicknesses. If the enclosed intermediate space is filled with compressed air, the thinner guiding plate is to be plastically (permanently) deformed, the thinner plate being provided with a curvature, and consequently a hollow body being formed, which then serves as a guiding device.
A method for producing hollow bodies with pre-shaped plate parts is disclosed, for example, in the published German Patent Document DE 34 07 770 C2. This method serves for producing fuel tanks from plate half-shells having like plate thickness. Both plate half-shells are provided with a peripheral flange-like border. The borders are welded by the laser welding method. It is essential that this weld seam be gastight, in order to prevent fuel from escaping. To achieve this, it is necessary, in the course of the laser welding operation, to build up a high contact pressure between the plate parts which are involved. For this purpose, in the region of the weld seam that is to be formed, the flange of one half shell is provided with a bead, which appears as a projection with respect to the half shell lying opposite thereto. In this regard, the bead has a depth corresponding approximately to the plate thickness and the width of the weld seam later to be formed. A pressing force between the half-shells is transferred completely by the bead, so that, during welding, a concentration of force and, consequently, an intimate material bonding occurs here, i.e., in the region of the weld seam to be formed. To make the surface pressure in the region of the bead as great as possible, the bead must be formed as narrow as possible, i.e., not wider than the laser beam. Consequently, the desired virtually linear contact between the parts to be welded is achieved.
In the case of guiding devices for printed sheets, however, it is not a matter of obtaining a gastight connection which, if need be, can withstand a crash, as in the case of a fuel tank, but rather, as good a surface as possible, which is provided for guiding printed sheets. In particular, in the case of printing machines which print sheets on both sides thereof, for example, on one side by first-form or recto printing, and on the other side, facing the guide plate, by perfector or verso printing, or on both sides by first-form or recto printing, what matters is guiding the sheet as far as possible without any contact. Therefore, as heretofore known in practice, the corresponding sheet guiding devices can be guided by sheet guiding members, so-called sheet guiding plates having air nozzles. The latter produce an air cushion on and along which the printed sheet is guided.
The published German Patent Document DE 44 27 448 A1 discloses a sheet guiding plate of this type, the guiding face of which has openings into which air blowing nozzles are inserted flush with the surface of the guiding face and adhesively secured or cemented therein. The air blowing nozzles are arranged so that the air flow formed over the surface is determined by a first velocity component in the direction of movement of the sheet and two further velocity components in the direction of the two side edges of the path of movement. Consequently, contact-free guidance of the sheet is assured.
In the guidance of the sheet, what matters is that the sheet slides so securely or reliably on the air cushion, even at high transporting speeds, as to avoid damage to a print on the side of the sheet facing the guide plate. In addition, the sheets are to be guided through the dryer at a speed corresponding to the output of the printing machine, which requires correspondingly high dryer outputs and, as a consequence, correspondingly high cooling capacities at the sheet guiding device.
SUMMARY OF THE INVENTION
Starting from the foregoing state of the art, it is accordingly an object of the invention to provide a sheet guiding device for guiding sheets which have been printed on both sides thereof, without causing any damaging thereto.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a sheet guiding device having a top plate formed with a smooth side facing towards sheets to be guided past the device, comprising at least one depression defining at least one connecting region, the at least one depression being formed in the top plate from the smooth side thereof, and at least one rear element fastened to a rear side of the top plate and having at least one connecting portion assigned to the at least one connecting region, the at least one rear element bearing against the top plate and being connected thereto by laser weld seams forming a connection to the top plate at the at least one connecting region defined by the at least one depression, the at least one depression formed in the top plate being deeper than any deformation induced by the laser weld seams.
In accordance with another feature of the invention, the at least one rear element is a further plate whereon the at least one connecting portion assigned to the at least one connecting region is formed, and a fluid chamber formed between the top plate and the further plate is included, and is accessible via at least another connection.
In accordance with a further feature of the invention, the fluid chamber is a coolant chamber having an inlet connection and an outlet connection and, therefrom, the top plate being, from the rear side thereof, in direct heat exchange
Heidelberger Druckmaschinen
Mayback Gregory L.
Skaggs H. Grant
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