METHOD OF DEPOSITING WET PRINTED SHEETS AND FORMING A SHEET STACK

Abstract

A method for depositing wet printed sheets and forming a sheet stack in a delivery of a printing machine. An auxiliary stack which is separate from the sheet stack has sheet-shaped intermediate layers that are usable as moisture barriers in the sheet stack. A plurality of sheets are stacked on top of one another to form a first section of the sheet stack. Then an intermediate layer is moved from the auxiliary stack onto the section of the sheet stack. A plurality of sheets are stacked on top of one another and on the intermediate layer to form a further section. The intermediate layer is thus arranged in the sheet stack between the first section and the further section. The placement of the intermediate layers provides a way of reducing or even eliminating quality losses in sheets and/or sheet stacks caused by moisture and moisture exchange.

Claims

1. A method of depositing wet printed sheets and forming a sheet stack in a delivery of a printing machine, the method comprising: a) providing sheet-shaped intermediate layers on an auxiliary stack that is different from the sheet stack, the intermediate layers being configured to be used as moisture barriers in a sheet stack; b) depositing a plurality of sheets on top of one another and forming a first section of the sheet stack; c) moving an intermediate layer from the auxiliary stack onto the first section of the sheet stack; and d) depositing a plurality of sheets on the intermediate layer and on top of one another to form a further section of the sheet stack, with the intermediate layer arranged between the first section and the further section of the sheet stack.

2. The method according to claim 1, wherein the moving step comprises moving the intermediate layer from the auxiliary stack to the sheet stack at a specified point in time.

3. The method according to claim 1, wherein the moving step comprises moving the intermediate layer from the auxiliary stack to the sheet stack after a predefined number of sheets has been deposited on top of one another.

4. The method according to claim 1, which comprises repeating steps c) and d) multiple times to arrange multiple intermediate layers in the sheet stack.

5. The method according to claim 1, which comprises placing a first intermediate layer on a lower side below the sheet stack.

6. The method according to claim 1, which comprises placing a last intermediate layer on a top of the sheet stack.

7. The method according to claim 1, wherein the moving step comprises moving the intermediate layer from the auxiliary stack to the sheet stack during a flying phase of a sheet being deposited.

8. The method according to claim 1, wherein the intermediate layer is a plastic film or a plastic sheet having a thickness of less than 1 mm.

9. The method according to claim 1, which comprises removing the intermediate layer from the sheet stack during further processing of the sheet stack.

10. The method according to claim 4, which comprises removing the intermediate layers from the sheet stack during further processing of the sheet stack.

11. The method according to claim 1, wherein the intermediate layer has a lower side and an upper side each in contact with a respective sheet of the sheet stack.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0037] FIG. 1 illustrates a side view of a printing machine carrying out a preferred embodiment of the method of the invention; and

[0038] FIG. 2 is a flow chart of a preferred embodiment of the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0039] Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a printing machine 1 such as an inkjet printing machine or a lithographic offset printing machine. The printing machine comprises a delivery 2 including a chain conveyor 3 with grippers 4 for holding the printed sheets 5. Reference symbol 5a indicates a sheet that is being transported (and held in gripper engagement); reference symbol 5b illustrates a falling sheet (in its flying phase) that is being deposited on a sheet stack 6. The sheet stack has a lower side 6a and an upper side 6b. The sheet stack is located on a stack pallet 9 and is preferably vertically adjustable. In the vicinity of the stack pallet, there is an auxiliary stack pallet 10 supporting an auxiliary stack 8 of intermediate layers 11. The auxiliary stack pallet is preferably likewise vertically adjustable.

[0040] In accordance with the method of the invention, intermediate layers 11 (at least one, preferably multiple intermediate layers) are introduced into the sheet stack 6. In this way, sections 7 (here, 7a and 7b) of the sheet stack 6 are created. As shown, the intermediate layers 11 are located inside the sheet stack 6 and both the lower sides 11a and the upper sides 11b contact adjacent sheets 5. It is further shown that a first intermediate layer 12 may be disposed on the lower side 6a of the sheet stack 6 and a last intermediate layer 13 may be disposed on the upper side 6b of the sheet stack. In a case in which a last intermediate layer 13 is provided, no further sheet 5 is deposited on the sheet stack.

[0041] The intermediate layers 11 are fed/moved by means of a feed device 14, which may, for instance, comprise at least two rollers 15. The feed device 14 may be controlled by a computer 16 of the printing machine 1.

[0042] FIG. 2 is a flow chart of a preferred embodiment of the method of the invention. Optional and preferred steps of the method are illustrated within dashed-line boxes. Step 20 comprises providing the intermediate layers 11 on the auxiliary stack 8. In an optional step 21, a first intermediate layer 12 is arranged on the lower side 6a of the sheet stack 6. In a step 22, a plurality of sheets 5 is disposed on top of one another and a section 7/7a of the sheet stack is formed. In a step 23, an intermediate layer 11 is moved from the auxiliary stack 8 onto the section of the sheet stack 6. In a step 24, a plurality of sheets 5 is deposited on top of one another and on the intermediate layer 11 and a further section 7/7b of the sheet stack 6 is formed with the intermediate layer 11 arranged between the section and the further section of sheet stack. Steps 23 and 24 may be carried out multiple times to allow multiple intermediate layers to be introduced into the sheet stack. In an optional step 25, a last intermediate layer 13 is arranged on the upper side 6b of the sheet stack 6. In an optional step 26, the intermediate layer that has been introduced or the multiple intermediate layers may be removed from the sheet stack 6.

[0043] While the layers 11 are described as intermediate layers, it will be understood that they are also used as a stack base layer, or a lowermost layer under a sheet stack, and as a top layer, i.e., the uppermost layer on a sheet stack.

[0044] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: [0045] 1 printing machine [0046] 2 delivery [0047] 3 chain conveyor [0048] 4 gripper [0049] 5 sheet [0050] 5a transported sheet [0051] 5b falling sheet (flying phase) [0052] 6 sheet stack [0053] 6a lower side of the sheet stack [0054] 6b upper side of the sheet stack [0055] 7 section/sections of the sheet stack [0056] 7a section/sections of the sheet stack [0057] 7b section/sections of the sheet stack [0058] 8 auxiliary stack [0059] 9 stack pallet [0060] 10 auxiliary stack pallet [0061] 11 intermediate layer [0062] 11a lower side of the intermediate layer [0063] 11b upper side of the intermediate layer [0064] 12 first intermediate layer [0065] 13 last intermediate layer [0066] 14 feed device [0067] 15 rollers [0068] 16 computer, controller [0069] 20 step of providing [0070] 21 optional step of providing a first intermediate layer [0071] 22 step of depositing a plurality of sheets [0072] 23 step of moving an intermediate layer [0073] 24 step of depositing a plurality of sheets [0074] 25 optional step of providing a last intermediate layer [0075] 26 optional step of removing the intermediate layer