Sheet feeding or delivering – Delivering – By pneumatic conveyor
Reexamination Certificate
2001-04-17
2003-03-04
Skaggs, H. Grant (Department: 3653)
Sheet feeding or delivering
Delivering
By pneumatic conveyor
C271S204000
Reexamination Certificate
active
06527268
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for contact-free guidance of sheets wherein, in a sheet processing machine, the sheets are fed in a feeding direction along a guide face of a sheet guiding device providing an air cushion between the guide face and the respective sheet. The invention is also directed to a device for feeding sheets along a guide face of a sheet guiding device of a sheet processing machine having air flow openings provided in the guide face for creating an air cushion between the guide face and the respective sheet. Furthermore, the invention relates to a sheet processing machine, in particular, a printing machine, equipped with the device according to the invention.
Methods and devices of the foregoing types are used especially in transporting sheets between successive stations of sheet processing machines. This may involve two successive printing units of a multi-color printing machine, or one printing unit and a following delivery system of a single-color or multi-color printing machine. Devices of the foregoing general type are associated in particular with conveyor systems, usually embodied as chain conveyors, for transporting the sheets to a stacking or pile station. Those devices, in general, have devices for creating an air cushion between the guide face and the sheets.
In a device heretofore known from the published German Patent Document DE 34 11 029 C2, the guide face has air flow openings with a minimum diameter of 15 mm, in an arrangement such that the total cross-sectional area of the air flow openings makes up a proportion of 15 to 30% of the total area of the guide face. At an air pressure of approximately 80 pascals, the air flow openings generate a high volumetric flow of about 1200 m
3
/h. For guiding sheets printed on one side, provision is made for connecting some of the air flow openings to a negative-pressure generator. A disadvantage of this device is that the sheets being fed, depending upon the mode of operation, make more or less major fluttering motions, which, for freshly printed sheets, on the one hand, can impair the quality of the printed image and, on the other hand, is associated with unwanted noise. Furthermore, relatively powerful blowers are required, which take up space and at the same time contribute to producing noise.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to overcome the foregoing disadvantages of the aforedescribed prior art by providing, in particular, largely flutter-free sheet guidance.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method for feeding sheets in a feeding direction along a guide face of a sheet guiding device in a sheet processing machine, which comprises forming an air cushion between the guide face and a respective sheet by providing an air pressure distribution resulting in air flows beneath the respective sheet, the air pressure distribution being based virtually only on the effect of viscosity of the flowing air and being then capable of carrying the sheet.
In accordance with another mode, the method of the invention includes producing the air flows by pressure sources and pressure sinks having flow course lengths therebetween which are short compared to the dimension of the respective sheet in the direction of a respective one of the air flows.
In accordance with a further mode, the method of the invention includes providing an alternating sequence of pressure sources and pressure sinks in at least one direction parallel to the guide face.
In accordance with an added mode, the method of the invention includes providing the alternating sequence of pressure sources and sinks in the feeding direction.
In accordance with an additional mode, the method of the invention includes providing, in the region of at least some of the pressure sinks, at least one of a prevailing atmospheric pressure and a prevailing pressure other than atmospheric pressure.
In accordance with yet another mode, the method of the invention includes, in the region of at least some of the pressure sinks, actively removing air from the air cushion by suction.
In accordance with yet a further mode, the method of the invention includes subjecting the pressure sources to compressed air so that, at a respective one of the pressure sources, a volumetric flow in m
3
/h is adjusted to less than 1% of the weight per unit of surface area, in g/m
2
of the sheet.
In accordance with yet an added mode, the method of the invention includes producing an air pressure adapted to the weight per unit of surface area of the sheet in the region of the pressure sources.
In accordance with yet an additional mode, the method of the invention includes setting the air pressure in the region of the pressure sources to from 1.5 to 4 times the weight per unit of surface area.
In accordance with still another mode, the method of the invention includes setting the air pressure in the region of the pressure sources to approximately twice the weight per unit of surface area.
In accordance with still a further mode, the method of the invention includes producing, in the region of the pressure sources, an air pressure of less than approximately 50 pascals.
In accordance with still an added mode, the method of the invention includes producing, in the region of the pressure sources, an air pressure between 0.5 and approximately 5 pascals.
In accordance with another aspect of the invention, there is provided a device for feeding sheets in a sheet-feeding direction along a guide face of a sheet guiding device of a sheet processing machine, the guide face comprising air flow openings formed therein for producing an air cushion between the guide face and a respective sheet, the air flow openings being distributed over the guide face and being formed, in part, as blast openings for feeding air into the air cushion and, in part, as outflow openings for releasing air from the air cushion, and being disposed alternatingly in at least one direction parallel to the guide face.
In accordance with another feature of the invention, the blast openings and the outflow openings are disposed alternatingly in a direction parallel to the sheet-feeding direction.
In accordance with a further feature of the invention, the air flow openings have a total cross-sectional area equal to less than 15% of the surface area portion of the guide face formed with the air flow openings.
In accordance with an added feature of the invention, the total cross-sectional area of the air flow openings equals between approximately 1% and approximately 10% of the portion of surface area of the guide face formed with the air flow openings.
In accordance with an additional feature of the invention, the total cross-sectional area of the air flow openings equals between approximately 2% and approximately 3% of the portion of surface area of the guide face formed with the air flow openings.
In accordance with yet another feature of the invention, the air flow openings are formed of at least one of holes and slits.
In accordance with yet a further feature of the invention, the air flow openings are formed as holes having a diameter of less than 15 mm.
In accordance with yet an added feature of the invention, the diameter is between approximately 1 mm and approximately 10 mm.
In accordance with yet an additional feature of the invention, the air flow openings formed as slits extend transversely to the sheet-feeding direction.
In accordance with still another feature of the invention, mutually adjacent air flow openings have a mean spacing therebetween of less than 25 mm.
In accordance with still a further feature of the invention, the mean spacing between the mutually adjacent air flow openings is between approximately 5 mm and approximately 20 mm.
In accordance with still an added feature of the invention, more than 30% of the air flow openings serve as blast openings, and less than 70% of the air flow openings serve as outflow openings.
In accordance with still an
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Mayback Gregory L.
Skaggs H. Grant
Stemer Werner H.
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