Sheet feeding or delivering – Feeding – By means to convey sheet
Reexamination Certificate
2001-03-26
2003-06-17
Walsh, Donald P. (Department: 3653)
Sheet feeding or delivering
Feeding
By means to convey sheet
C271S275000, C271S276000, C271S069000, C271S314000
Reexamination Certificate
active
06578846
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a device for transporting a sheet for a sheet-processing machine, particularly a rotary printing machine, in a processing direction, the transporting device having first grippers for gripping the sheet at a leading gripper edge, as viewed in the direction of processing, the first grippers revolving in a first direction during operation; a cylinder bearing the first grippers, the cylinder having a support surface formed at the circumference thereof for supporting the sheet gripped by the first grippers; second grippers for taking over the leading gripper edge of the respective sheet from the first grippers, the second grippers revolving in a second direction opposite to the first direction; and at least one pair of sheet supports rotating about a rotational axis and formed with a pitch surface disposed concentric with the rotational axis, the pitch surface having an extent along the rotational axis less than the width of a respective nonprinted lateral margin of the respective sheet, and serving to press the sheet against the support surface within a respective lateral margin in regions of common normals of the support surface and the pitch surfaces. The invention also relates to a sheet-fed printing machine, particularly a rotary printing machine, that is equipped with the sheet-transporting device.
A device of the aforedescribed type has been disclosed heretofore by the published Japanese Patent Document JP SHO 55-18194 Y2, in accordance with which it is used to transfer a printed sheet from a printing unit to a delivery, including a continuous conveyor with grippers disposed at revolving gripper bars, by which a leading gripper edge of the sheet is grippable, the sheet, after leaving the impression cylinder, being further conveyable by the trailing edge thereof at its own resources. However, all that is achieved by this method is that the sheet is positively guided at the nonprinted side margins thereof until the trailing edge thereof passes the regions of the common normals of the cylinder surfaces and the support surface of the impression cylinder.
In order to guide the sheet farther along the path thereof to a stacking or pile station without causing smearing, it has become known heretofore, particularly, to provide sheet guide surfaces and to create flow relations between those sheet guide surfaces, on the one hand, and the respective sheet, on the other hand, which has been withdrawn therefrom, that keep the sheet at a given floating height above the sheet guide surfaces.
Alternatively, it has also been proposed heretofore in the prior art that the sheets, after exiting from a printing unit, be guided on a path to a stacking or pile station by leading edge grippers and trailing edge grippers revolving out of phase relative to one another (note the published German Patent Document DE 42 18 421 A1). To realize this, however, it is necessary that a trailing gripper margin of the sheet be gripped securely by the trailing edge grippers. But the published German Patent Document DE 42 18 421 A1 does not disclose any way of satisfying this requirement.
German Patent 627 851 offers a proposal for realizing the grasping or gripping of the trailing gripper margin by trailing edge grippers. According to this proposal, the sheet is transferred from an impression cylinder by leading edge grippers and is drawn by a first chain drive including the leading edge grippers over guide rails extending along the bottom strands of the first chain drive, namely the strands which pull the sheet, beneath these strands. Beneath these strands a second chain drive is disposed having upper strands which move in the same direction as the lower strands of the first chain drive. The second chain drive bears trailing edge grippers, which grasp the trailing gripper margin when this margin of the sheet which is supported on the guide rails reaches a location at which the upper strands of the second chain drive leave a diverting wheel or guide roller that is situated upline relative to the direction of motion of these upper strands. The trailing gripper margin of the sheet is blocked from dropping below a prescribed level by the guide rails; there is no assurance, however, that the gripper margin will not make a flapping or whipping movement after running onto the guide rails. Besides the foregoing, this construction is suitable only for first-form or single-side printing, and then only if any marks which may occur on the nonprinted side of the sheet due to a rubbing thereof across the guide rails be taken into consideration, which is highly doubtful, particularly when the obverse or reverse side of the sheet is subsequently printed in a later pass or run.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a device for transporting a printed sheet for a rotary printing machine without smearing, the transporting device being produced without having to resort to the use of stationary guiding devices.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a device for transporting a sheet for a sheet-processing machine in a processing direction, comprising first grippers for gripping the sheet at a leading gripper edge, as viewed in the direction of processing, the first grippers revolving in a first direction during operation; a cylinder bearing the first grippers, the cylinder having a support surface formed at the circumference thereof for supporting the sheet gripped by the first grippers; second grippers for taking over the leading gripper edge of the respective sheet from the first grippers, the second grippers revolving in a second direction opposite to the first direction; and at least one pair of sheet supports rotating about a rotational axis and formed with a pitch surface disposed concentric with the rotational axis, the pitch surface having an extent along the rotational axis less than the width of a respective nonprinted lateral margin of the respective sheet, and serving to press the sheet against the support surface within a respective lateral margin in regions of common normals of the support surface and the pitch surfaces; and suction grippers revolvable in the second direction and for taking over from the cylinder a trailing gripper margin of the sheet which has been placed on the support surface of the cylinder by the sheet supports.
In accordance with another feature of the invention, the transport device includes a sheet guiding drum comprising the second grippers, the sheet supports and the suction grippers.
In accordance with a further feature of the invention, the transport device includes a transfer drum connected in series with the sheet guiding drum and operationally rotating in the first direction, the transfer drum having third grippers for taking over the leading gripper margin from the second grippers, and having suckers following the third grippers for taking over the trailing gripper margin from the suction grippers; and an operationally revolving continuous conveyor including pregrippers and post-grippers, whereof the pregrippers are for taking over the leading gripper margin from the third grippers, and the post-grippers are for taking over the trailing gripper margin from the suckers.
In accordance with an added feature of the invention, the transport device includes an operationally revolving continuous conveyor comprising the second grippers, for taking over the leading gripper margin of the respective sheet from the first grippers, and trailing edge grippers for taking over the trailing gripper margin of the respective sheet from the suction grippers.
In accordance with an additional feature of the invention, the trailing edge grippers grasp the trailing gripper margin in an outlet wedge of a nip formed between the support surface and the pitch surfaces.
In accordance with yet another feature of the invention, the sheet supports have an adjustable mutual spacing.
In accordance with yet a further feature of th
Maul Albert
Rautert Jürgen
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Locher Ralph E.
Miller Jonathan R
Stemer Werner H.
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