Feeder of a machine for processing single sheets and method for operating a feeder of a machine for processing single sheets

Abstract

The invention relates to a paper feeder (01) of a machine for processing sheets, having a stack table (06) designed to accommodate a stack (07) of sheets, at least one separating mechanism (14) by means of which the uppermost sheet (03) of the stack (07) of sheets can be gripped in a separating plane (15) and can be displaced into a sheet guide plane (20) which is vertically spaced from the separating plane (15), at least one conveying mechanism (16) by means of which the respective sheet (03) can be conveyed in a conveying direction (T) away from the stack (07) of sheets into a conveying path which is connected downstream, and a blowing device (18), wherein the blowing device (18) has a plurality of outlet openings (29) which are arranged spaced apart from one another transversely to the conveying direction (T) and is designed to generate, for the respective sheet (03) in a sequence of sheets, a succession of a plurality of blowing air jets which start at a time offset from one another and which are directed below the respective sheet (03). The invention also relates to a method for operating a paper feeder (01).

Description

Technical Field

[0001] This invention relates to a paper feeder for a machine that processes single sheets of paper and a method for operating the paper feeder of the machine that processes single sheets of paper. Background Technology

[0002] In sheet-fed machines, a common practice is to place the sheets to be processed as a stack on a liftable stacking platform, and then separate the sheets from the top of the stack, exiting as an overlapping flow below. For this purpose, a sheet separator is installed on the top of the stack. The separator's mechanism, such as a separation suction device, a conveying suction device, or a probe, grasps the topmost sheet of the stack during the machine's cycle time, separating it from subsequent sheets and feeding it along the conveying direction. Control of the air jets used for grasping, separating, and feeding the sheets is achieved using valve units, which are also followed during the machine's cycle time.

[0003] When separating individual sheets from the stack, the sheets are first loosened from all directions at the feeder by a continuous stream of air from a fan. After being sucked in by a separator suction device and separated by a separator, a separation air jet is needed to freely separate the sheets from the stack. Among numerous other components and parameters, the separation air jet is crucial to the quality of sheet handling, especially for substrates with a basis weight below 135 g / m². The direction, quality, flow rate, and control of the separation air significantly affect sheet handling and continuous printing performance.

[0004] In solutions known from existing technologies, the control of the provided separation air is primarily achieved through a cam-controlled piston valve or rotary slide valve. The required amount of separation air must be large enough to form an air cushion under the entire sheet of paper to be separated.

[0005] The amount of air delivered below the corresponding sheet of paper by the corresponding separate air jet will be affected by the blowing pressure and the blowing duration.

[0006] To generate a sufficiently large volume of separating air, solutions known in the prior art operate at a nominal pressure in the range of 1.2 to 1.4 bar, and this separating air jet continues even when the conveyor suction begins its cycle of motion to deliver the corresponding sheet. Higher pressures are avoided due to concerns about sheet deformation.

[0007] DE19815104A1 discloses a sheet separator in a paper pusher for separating and conveying the topmost sheet in a stack of sheets. The sheet separator has: a separation suction device that grips the topmost sheet in a rear region along the feeding direction of the topmost sheet and lifts it approximately perpendicular to the stack of sheets; a conveying suction device that receives the sheet sucked up by the separator suction device and conveys it along the conveying direction; and a probe foot that is placed in the rear region of the stack of sheets after the topmost sheet is separated.

[0008] DE102005054138A1 discloses a printing press for printing single sheets of paper, the printing press including a paper feeder and a printing unit. The paper feeder includes a separation fan and / or a paper loosening fan.

[0009] DE102020107836B4 discloses a sheet-fed paper feeder, comprising a feeder, a take-up unit, and one or more offset printing units and / or coating units arranged between the feeder and the take-up unit. The feeder includes a stacking space with a stacking carrier. In the stacking space, the separation of the topmost sheet from the sheet stack is assisted by compressed air supplied by a separation fan or by compressed air supplied by a probe foot.

[0010] DE102011120475A1 discloses a paper feeder with two suction rollers. For separation, the topmost sheet of paper in the stack is lifted, and separation air is blown between the lifted sheet and the stack of sheets in a specific manner. Thus, the top sheet is separated from the stack of sheets and lifted onto the suction rollers positioned above by the separation air.

[0011] DE3907037A1 discloses an apparatus for measuring sheet length in a sheet-fed printing press. The apparatus includes suction air measuring nozzles aligned with the trailing edge of the sheet. These suction air measuring nozzles have switching elements in a machine drive circuit when connected to a suction air source. The feeder aligns the sheets to be processed at stops at the leading edge of the sheets and lifts the sheets from the sheet stack by means of blown air jets that start at staggered times and are directed below the respective sheets.

[0012] DE102020124433A1 discloses a paper feeder for a machine that processes or handles single sheets of paper, and a method for assisting in the separation of single sheets of paper in the paper feeder of a machine that processes or handles single sheets of paper.

[0013] EP0453835A2 describes a sheet feeder for single sheets in a sheet-processing machine with a paper-loosening blower and other air nozzles, which blows air onto the topmost sheet by means of a separate, independently adjustable blown air source.

[0014] The blowing time achieved in known solutions typically covers a range of 150 to 210 degrees within a corresponding 360-degree machine cycle. This blowing time causes the sheet to vibrate, producing ripples, vibrations, and instability. Consequently, the sheet becomes flat, inevitably shortening unevenly due to ripples, and forming irregular stacks of sheets on the conveyor belt. As machine speed increases, the accuracy of the sheet stacking deteriorates, and sheets protrude from the stack. This leads to paper pushing problems and ultimately, machine downtime. Summary of the Invention

[0015] The object of this invention is to provide a paper feeder for a machine that processes single sheets of paper and a method for operating the paper feeder of the machine that processes single sheets of paper.

[0016] In particular, the object of the present invention is to provide a feeder for a machine for processing sheet paper and a method for operating the feeder for a machine for processing sheet paper, which achieves smoother and more uniform sheet paper operation and reduces ripple formation.

[0017] According to the present invention, this objective is achieved by the features of claims 1 and 16, respectively.

[0018] The advantages that can be achieved by utilizing this invention are particularly evident in that it improves the operational reliability of the paper feeder in separating individual sheets from a stack of sheets.

[0019] In particular, it can improve the quality and uniformity of the lower overlap and paper cutting.

[0020] According to one embodiment, the flow rate of the blown air discharged from the output opening can be adjusted more precisely.

[0021] Another advantage of this implementation is that the supply of separate air no longer depends on the speed of production operation. Attached Figure Description

[0022] An embodiment of the invention is shown in the accompanying drawings, and will be described in more detail below.

[0023] in:

[0024] Figure 1 A schematic diagram of a paper feeder, which schematically shows the transport path leading to one or more downstream processing assemblies;

[0025] Figure 2A detailed illustration shows a single-sheet paper separator with a paper feeder and a blowing device. Detailed Implementation

[0026] This invention is described using the paper feeder 01 of a machine for processing single sheets of paper as an example. The machine for processing single sheets of paper is also called a machine for processing single sheets of paper substrate 03 or a single sheet processing machine. It can be designed as a printing press, especially a single sheet offset printing press.

[0027] A printing press, particularly a sheet-fed offset printing press, includes, in addition to a feeder 01 for providing, for example, a sheet-like substrate, particularly a sheet 03 or simply sheet 03, multiple printing units, particularly offset printing units, arranged sequentially along the substrate path for printing, particularly on the same substrate surface, and a product delivery device, such as a stacking delivery device. The printing press may additionally include one or more coating units in the substrate path. Instead of multiple printing units, exactly one printing unit may also be provided. A component of the printing press may be a flipping device for achieving double-sided printing, wherein all printing units arranged in the substrate path before the flipping device print on one substrate surface, and all printing units arranged in the substrate path after the flipping device print on the other substrate surface.

[0028] Each printing unit includes a plate cylinder, which is driven either by a gear train of a main drive unit (not shown) that drives multiple printing units, or by a drive motor that is mechanically independent of the main drive unit. During production operations corresponding to printing runs, the plate cylinder cooperates with one or more inking rollers of the inking unit and, preferably, at least one damping roller of the damping unit.

[0029] This invention is not limited to machines designed for processing sheet paper as printing presses, but can be used on all types of sheet paper processing machines, or as a component of sheet paper processing machines.

[0030] In a preferred embodiment, the machine for processing single sheets of paper can be designed as a machine for mechanically processing single sheets of paper 03, such as embossing, cutting, or particularly stamping, having one or more assemblies for mechanically processing single sheets of paper 03, such as having at least one stamping or embossing unit or breaking unit.

[0031] In a preferred embodiment of the machine, it can also be designed as a hybrid machine for processing single sheets of paper, having at least one stamping or embossing unit and at least one printing unit arranged in the substrate or conveying path before the stamping or embossing unit. A product receiving device, such as a stacking receiving device for this type of machine, can also be configured for receiving assemblies formed from single sheets of paper 03.

[0032] Other assemblies, such as drying units, painting units, calendering units, or other assemblies that act on individual sheets of paper 03, can also be set in the conveying path.

[0033] On the output side of the paper feeder 01, a feeding device 02 is connected along the conveying direction T. This device is preferably in the form of a belt table 02, particularly a suction belt table 02. The feeding device or belt table receives single sheets of paper 03 to be fed from the paper feeder 01 and, if necessary, conveys them through other feeding devices downstream of the machine's sole or first unit or assembly. The belt table 02 is designed, for example, as a suction belt table 02, and preferably includes at least two rollers 19, of which only one is shown downstream as the first roller. One of the rollers is designed as a drive roller 19, and one or more of the other rollers are designed as guide rollers. One or more platform plates 21 extend between the rollers 19, forming, for example, the upper side of the multiple perforations of the suction box 22. Two rollers 19 are wound with sheets of paper 03 by at least one conveyor belt 23. The conveyor belt, like the platform 21 extending above it, is multi-perforated, so the conveyor belt is not fixedly attached to the platform 21, but rather the sheets of paper 03 are attached to the conveyor belt 23. In the area where the sheets of paper 03 to be fed meet, a roller 24, such as a beat roller 24, is provided above the rollers 19 on the input side of the belt table 02 after the paper feeder 01. This roller presses the sheet of paper 03 against the belt table 02 within the beat of the incoming sheet of paper 03.

[0034] In the paper feeder 01, stacks 07, particularly sheet stacks 07, are placed on a stacking platform 06 located in the stacking space 04. The stacking platform 06 is height-adjustable, particularly by means of a controllable first drive device 05, so that the corresponding uppermost sheet 03 in the sheet stack 07 is maintained at a fixed or only slightly variable height suitable for transferring the sheet 03 to the subsequent feed device 02, regardless of the number of sheets 03 in the sheet stack 07. In the figure, the sheet 03 in the sheet stack 07 is placed directly on the stacking platform 06; however, a pallet may also be placed between the sheet stack 07 and the stacking platform 06, on which the sheet stack 07 is transported to the stacking platform 06 and placed.

[0035] On the side of the stacking space 04 pointing in the conveying direction T, there is a stop device 08, such as a single-piece or multi-piece front stop device 08. The stop surface of this front stop pointing in the opposite direction T defines a vertical plane that serves as a stop for the front edge of the sheet 03 in the sheet stack 07, that is, the edge that is moving forward during the conveying process. This stop device 08 does not extend vertically to the upper stack edge, but extends as needed within its vertical alignment through the stop face of the active feed device 11, which is also called the sheet baffle 11. For this purpose, the feed device 11 can move between an active position, such as a pivoted raised position, and a non-active position, such as a pivoted lowered position. In particular, it is pivotable. The active position is the pivoted position in which its stop surface is located on the conveying path of the sheet 03 to be conveyed from the feeder 01; the non-active position is the pivoted position in which its conveying path is open.

[0036] Although other mechanisms can be pre-adjusted to move the sheet stop 11 between the two positions mentioned above, it is preferable to pivotally support the sheet stop 11 in the paper feeder 01 about a pivot axis. For this purpose, a support element 12, for example, acting as or designed as a shaft 12, such as a baffle shaft 12, can be provided to support the sheet stop 11.

[0037] The paper feeder 01 includes various conveying tools 14, 16 for removing individual sheets 03 from the sheet stack 07 and conveying the sheets 03 to or within a feeding device 02 arranged after the paper feeder 01. The conveying tools 14, 16 are preferably housed in or surrounded by a so-called sheet separator 13.

[0038] The conveying tools 14 and 16 are preferably driven by independently controllable drive devices. In particular, the separating mechanism 14 serves as the conveying tool 14 for grasping the corresponding sheet of paper 03 in the sheet separation plane 15 and moving the corresponding sheet of paper 03 to the sheet guide plane 20, which is vertically spaced from the sheet separation plane 15. The separating mechanism 14 is particularly designed as a separating suction device 14, and more preferably as a spring suction device 14.

[0039] Preferably, the sheet separator 13 further includes a conveying tool 16 designed as a conveying mechanism 16, particularly a drag-type suction device 16. The conveying tool 16 removes the corresponding sheet 03 from the separator 14 and conveys it along the feeding device 02 in the sheet guide plane 20. The separator 14 and / or the conveying mechanism 16 are particularly formed by a single or preferably multiple suction devices 14, 16.

[0040] For example, multiple separation suction units 14 on the sheet separator 13 can be arranged as separation mechanisms 14 above the sheet stack 07 in the region of the rear edge along the conveying direction T of the sheet 03, and can move substantially vertically. The rear edge of the sheet stack 07 or the rear edge of the sheet 03 indicates the starting point of the conveying path.

[0041] In addition, multiple traction suction devices 16 are provided as conveying mechanisms 16. These traction suction devices 16 are arranged near the front stop device 08 on the sheet separator 13 along the conveying direction T and can move horizontally along and against the conveying direction T. As another tool, so-called probe feet 17 can also be provided, particularly as a component of the sheet separator 13. The probe feet 17 can be guided into the contour of the sheet stack 07. Preferably, the probe feet 17 are driven by a probe foot drive device that moves the probe feet 17 between upper and lower end positions, wherein, in the lower end position, the probe feet 17 are supported on the upper side of the sheet stack during production operation. Between the two end positions, the movement of the probe feet 17 may include a horizontal movement component in addition to vertical movement, and the probe feet 17 may pivot. The probe feet 17 may also be designed as or include a nozzle for generating a bearing air cushion.

[0042] The sheet separator 13 is arranged in the paper feeder 01 in a height-adjustable manner. A controllable second drive unit 10 is used to realize the adjustment movement of the sheet separator 13.

[0043] Specifically, at least one separation mechanism 14 and / or at least one conveying mechanism 16 and / or blowing device 18 are components of the sheet separator 13, wherein the sheet separator 13 is equipped with a controllable drive device 10 for raising and lowering the sheet separator 13.

[0044] To facilitate the separation of the received sheet 03 from the remaining sheet stack 07, a loosening fan 26 can be arranged in the upper area of ​​the sheet stack 07. The loosening fan 26 can be arranged on the rear side of the sheet stack, i.e., on the side opposite to the conveying direction T, particularly at the rear edge of the sheet stack 07. Alternatively or as an alternative to the arrangement of the loosening fan 26 on the rear edge of the stack 07 at the beginning of the conveying path, the loosening fan 26 can also be arranged on both sides of the sheet stack 07, and used to generate blowing air jets directed towards the center of the sheet stack. The loosening fan 26 specifically constitutes a continuous blowing air jet during the operation of the feeder 01.

[0045] Attached to the paper-loosening blower 26 or as a stand-alone unit, a blowing device 18 is provided at the beginning of the conveying path, preferably in the area at the rear edge of the sheet stack 07. The blowing device 18 is preferably fixed relative to the frame, but it can also be supported in a height-adjustable manner, or designed to be height-adjustable together with the sheet separator 13.

[0046] The blowing device 18 has a plurality of output openings 29, which are arranged transversely to the conveying direction T at intervals from each other.

[0047] The output opening 29 is a component of each separate air nozzle.

[0048] The output opening 29 may be configured with multiple mechanisms for selectively interrupting the air supply to the output opening 29, or may cooperate with mechanisms for selectively interrupting the air supply to the output opening 29.

[0049] Preferably, all output openings 29 are connected via individual inlet pipes to a central device for supplying blowing air, and each inlet pipe is equipped with a mechanism for selectively interrupting the blowing air supply. With the aid of the corresponding mechanism for selectively interrupting the blowing air supply, a jet of blowing air can be generated at the respective output opening 29 by temporarily releasing the interruption of the blowing air supply in the respective inlet pipe. In particular, the mechanism for interrupting the blowing air supply to each output opening 29 can be controlled independently of the other output openings 29, preferably by a central machine controller. In addition to individual output openings 29, multiple groups of output openings 29 can also be provided with mechanisms for interrupting the air supply or in conjunction with such mechanisms.

[0050] The output openings 29 can all have the same geometry or different geometries. In particular, the output openings 29 can be designed as elliptical or circular.

[0051] For the circular output opening 29, the diameter of the output opening is preferably less than 6 mm. In particular, the cross-sectional area of ​​the output opening 29 can be 30 square millimeters or less.

[0052] The blowing device 18 may include a pulse-controlled high-pressure valve. Specifically, a mechanism for selectively interrupting the supply of blowing air is formed by the pulse-controlled high-pressure valve. The pulse-controlled high-pressure valve is preferably arranged between the compressed air generator and the output opening 29. Here, each of these pulse-controlled high-pressure valves may be equipped with exactly one output opening 29. Preferably, multiple output openings 29 are assigned to these pulse-controlled high-pressure valves.

[0053] To control the air supply, the blowing device 18 may also include multiple cam-controlled valves or one or more rotary slide valves. In particular, one or more cam-controlled valves or rotary slide valves may be arranged between the compressed air generator and one or more output openings 29.

[0054] The blowing device 18 is designed to generate a series of multiple blowing air jets that start at different times and are directed below the corresponding sheet 03 in the sheet sequence.

[0055] According to the design and arrangement of the blowing device 18, the blowing air jet is directed at least approximately in the conveying direction T.

[0056] In order to separate individual sheets 03 from the sheet stack 07, the corresponding uppermost sheet 03 in the sheet stack 07 is gripped by the separation device 14, particularly by means of low pressure in the separation plane 15, and then the sheet is conveyed, particularly lifted, into the sheet guide plane 20, which is vertically spaced from the separation plane 15. It is sufficient that the corresponding uppermost sheet 03 on the side of the sheet stack 07 opposite to the downstream conveying path of the sheet stack 07 is lifted.

[0057] The blowing device 18 outputs multiple blowing air jets for the corresponding sheet of paper 03 delivered from the separation plane 15, and these blowing air jets are directed downwards from the sheet of paper 03. In other words, the process of the blowing device 18 outputting a series of blowing air jets is timed in such a way that the blowing device 18 is controlled to output multiple blowing air jets when the corresponding sheet of paper 03 passes through the blowing device 18 vertically during its journey into the sheet of paper guide plane 20.

[0058] The corresponding blowing air jet in a series of blowing air jets pointing below the corresponding sheet of paper 03 begins, specifically before the corresponding sheet of paper 03 is about to reach the sheet of paper guide plane 20, or when the corresponding sheet of paper 03 reaches the sheet of paper guide plane 20, or slightly after the corresponding sheet of paper 03 reaches the sheet of paper guide plane 20.

[0059] The last of a series of blowing air jets pointing below the corresponding sheet of paper 03 ends either during the time interval before the conveyor 16 begins to move the corresponding sheet of paper 03 or at the start of the conveyor 16 moving the corresponding sheet of paper 03.

[0060] The total duration of the series of blowing air jets is significantly shorter than the time interval between the arrival of the corresponding sheet of paper 03 at the sheet guide plane 20 and the start of the conveying motion of the conveying mechanism 16 for conveying the corresponding sheet of paper 03.

[0061] Preferably, the blowing device 18 is designed to generate blowing air jets that are staggered in time through different output openings 29.

[0062] Specifically, the blowing device 18 is designed to generate a series of blowing air jets from different output openings 29 for each individual sheet of paper 03. First, the output openings 29 located in the central region of the sheet stack 07 output air jets, followed by output openings 29 spaced apart from the center of the sheet stack 07. In this control scheme, an air wedge is advantageously formed, which reliably separates and laterally unfolds the sheet of paper 03.

[0063] The blowing device 18 is preferably designed to generate a series of blowing air jets in the cycle of a single sheet sequence. The cycle is defined as a 360-degree angle, and a new cycle begins after every 360-degree interval, during which the elements of the feeder 01 that move in accordance with the cycle repeat their movement.

[0064] The duration of each blowing air jet in the series can be as long as 45 degrees, thus each lasting for one-eighth of a beat.

[0065] The duration of the blowing air jet can also be in the range of 20 to 70 degrees or 30 to 60 degrees.

[0066] The blowing device 18 can also be designed to generate a blowing air jet for each sheet 03 in the sheet sequence, and the duration of the blowing air jet is the same for all sheets 03 in the sheet sequence, so that the duration of the blowing air jet is independent of the speed of the feeder 01 or the machine that processes the sheets.

[0067] Preferably, in this case, the duration of the blowing air jet is 25 milliseconds or in the range of 10 to 40 milliseconds.

[0068] The blowing device 18 can be specifically designed such that in the region of at least one or all of the output openings 29, the pressure of the corresponding blowing air jet is equal to or greater than 1.5 bar, or equal to or greater than 2 bar.

[0069] Therefore, the central unit used for blowing air supply generates a pressure equal to or greater than 1.5 bar, or equal to or greater than 2 bar.

[0070] In an advantageous manner, the blowing device 18 is designed to cause the respective blowing air jets to start at staggered intervals within a time range of 1 to 5 milliseconds in a series of blowing air jets for the respective sheet of paper 03.

[0071] Air blown into the sheet layer from the blowing device 18 separates the sheet 03 from the sheet stack 07 and forms an air cushion under the sheet 03. Driven by the horizontal movement of the conveying mechanism 16, the sheet 03 is pushed onto the belt table 02 on the air cushion, passing over the sheet baffle 11 which subsequently moves to a stationary position.

[0072] Specifically, the blowing device 18 generates a jet of blowing air for each sheet 03 in the sheet sequence, the duration and / or flow rate of which are the same for all sheets 03 in the sheet sequence.

[0073] List of reference numerals

[0074] 01 Paper feeder

[0075] 02 Feeding device, belt conveyor, suction belt conveyor

[0076] 03 Substrate single sheet paper, single sheet paper

[0077] 04 Stacking Space

[0078] 05 First Drive Unit

[0079] 06 Stacking Platform

[0080] 07 Stacking, Single Sheet Stacking

[0081] 08 Stop device, front stop device

[0082] 09-

[0083] 10 Second drive unit

[0084] 11. Paper pushing device, single sheet paper baffle

[0085] 12 load-bearing elements, shafts, baffle shafts

[0086] 13 Sheet Separators

[0087] 14. Conveying tools, separation mechanisms, separation suction devices, spring suction devices, suction devices

[0088] 15 Separation plane

[0089] 16. Conveying tools, conveying mechanisms, traction suction devices, suction devices

[0090] 17-probe pin

[0091] 18 blowing device

[0092] 19 rolls, drive roll

[0093] 20 single-sheet guide plane

[0094] 21 plates

[0095] 22 suction box

[0096] 23 Conveyor Belts

[0097] 24-roller, beat roller

[0098] 25-

[0099] 26 paper blower

[0100] 27-

[0101] 28-

[0102] 29 Output Openings

[0103] T transmission direction

Claims

1. A feeder (01) for a machine for processing single sheets of paper, the feeder having: a stacking table (06) designed to accommodate a stack of single sheets of paper (07); at least one separating mechanism (14) wherein the topmost single sheet of paper (03) of the stack of single sheets of paper (07) can be grasped in a separating plane (15) by means of the at least one separating mechanism and can be displaced into a single sheet guide plane (20) vertically spaced apart from the separating plane (15); At least one conveying mechanism (16) is used to convey the corresponding single sheet (03) away from the single sheet stack (07) along the conveying direction (T) to the downstream conveying path; And a blowing device (18), wherein the blowing device (18) has a plurality of output openings (29) arranged transversely to the conveying direction (T) at intervals from each other, and the blowing device (18) is designed to generate a series of a plurality of blowing air jets that start at different times and point below the corresponding sheet (03) for a corresponding sheet (03) in a sheet sequence.

2. The paper feeder according to claim 1, characterized in that, The blowing air jet points below the corresponding sheet of paper (03) along the conveying direction (T).

3. The paper feeder according to claim 1 or 2, characterized in that, The blowing device (18) used to generate blowing air jets that are staggered in time consists of different output openings (29).

4. The paper feeder according to claim 1 or 2, characterized in that, The output opening (29) is constructed on the same component.

5. The paper feeder according to claim 1 or 2, characterized in that, The blowing device (18) is designed to generate a series of blowing air jets from their respective output openings (29) for each individual sheet of paper (03), wherein the first output opening (29) located in the center of the sheet stack (07) outputs the blowing air jets, and the output openings (29) spaced apart from the center of the sheet stack (07) output the blowing air jets respectively.

6. The paper feeder according to claim 1 or 2, characterized in that, A series of blowing air jets begin at staggered intervals between each other in the range of 1-5 milliseconds for the corresponding single sheet of paper (03).

7. The paper feeder according to claim 1 or 2, characterized in that, The final blown air jet in the corresponding series of blown air jets for the corresponding sheet of paper (03) ends during the time interval before the conveying mechanism (16) for conveying the corresponding sheet of paper (03) begins its conveying motion.

8. The paper feeder according to claim 1 or 2, characterized in that, When the conveying mechanism (16) begins the conveying motion for conveying the corresponding sheet of paper (03), the last blown air jet in the corresponding series of blown air jets for the corresponding sheet of paper (03) ends.

9. The paper feeder according to claim 1 or 2, characterized in that, The blowing device (18) is designed to generate a blowing air jet in the beat of a sheet sequence, wherein each beat of the sheet sequence comprises 360 degrees and the duration of the blowing air jet is correspondingly 45 degrees.

10. The paper feeder according to claim 1 or 2, characterized in that, The blowing device (18) is designed to generate a blowing air jet in the beat of a sheet sequence, wherein each beat of the sheet sequence comprises 360 degrees and the duration of the blowing air jet is correspondingly 20 to 70 degrees.

11. The paper feeder according to claim 1 or 2, characterized in that, The blowing device (18) is designed to generate a blowing air jet in the beat of a sheet sequence, wherein each beat of the sheet sequence comprises 360 degrees and the duration of the blowing air jet is correspondingly 30 to 60 degrees.

12. The paper feeder according to claim 1 or 2, characterized in that, The blowing device (18) is designed to generate a blowing air jet in the beat of a single sheet sequence, wherein the duration of the corresponding blowing air jet is in the range of 10 milliseconds to 40 milliseconds.

13. The paper feeder according to claim 1 or 2, characterized in that, The air pressure of the blown air jet in the area of ​​the output opening (29) is equal to or greater than 1.5 bar.

14. The paper feeder according to claim 1 or 2, characterized in that, The air pressure of the blown air jet in the area of ​​the output opening (29) is equal to or greater than 2 bar.

15. The paper feeder according to claim 1 or 2, characterized in that, The output openings (29) each have an opening cross-sectional area equal to or less than 30 square millimeters.

16. The paper feeder according to claim 1 or 2, characterized in that, The blowing device (18) includes multiple pulse-controlled high-pressure valves.

17. The paper feeder according to claim 1 or 2, characterized in that, The blowing device (18) includes multiple cam-controlled valves or rotary slide valves.

18. The paper feeder according to claim 1 or 2, characterized in that, The at least one conveying mechanism (16) is designed to reciprocate along the conveying direction (T) and convey the corresponding single sheet (03) in the single sheet guide plane (20).

19. The paper feeder according to claim 1 or 2, characterized in that, The at least one separation mechanism (14) and / or the at least one conveying mechanism (16) and / or the blowing device (18) are components of the sheet separator (13), wherein the sheet separator (13) is equipped with a controllable drive device (10) for raising and lowering the sheet separator (13).

20. A method for operating a paper feeder (01) for a machine that processes single sheets of paper, the paper feeder (01) according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or 19, wherein, For a sequence of individual sheets placed on a stacking platform (06) as a stack of individual sheets (07), the uppermost individual sheet (03) in the stack of individual sheets (07) is displaced by at least one separating mechanism (14) from the separating plane (15) forming the upper side of the stack of individual sheets (07) to a single sheet guide plane (20) vertically spaced from the separating plane, at least on the side of the conveying path opposite to the stack of individual sheets (07) that is connected to the stack of individual sheets (07) downstream, and a series of blowing air jets pointing downwards from the raised individual sheet (03) are generated.

21. The method according to claim 20, wherein, The series of blowing air jets includes at least two blowing air jets that begin after the respective single sheet (03) is lifted.

22. The method according to claim 20 or 21, wherein, The series of blowing air jets includes at least three blowing air jets.

23. The method according to claim 20 or 21, wherein, The last of a series of blowing air jets below the corresponding sheet of paper (03) ends during the time interval before the conveying mechanism (16) begins its conveying motion to convey the corresponding sheet of paper (03).

24. The method according to claim 20 or 21, wherein, When the conveying mechanism (16) begins to convey the corresponding sheet of paper (03), the last air jet in a series of blowing air jets below the corresponding sheet of paper (03) ends.

25. The method according to claim 20 or 21, characterized in that, The duration of the blowing air jets is in the range of 10 milliseconds to 40 milliseconds.

26. The method according to claim 20 or 21, characterized in that, The duration of the blowing air jet is the same for all sheets (03) in the sheet sequence.

27. The method according to claim 20 or 21, characterized in that, Multiple air jets, starting at staggered times, are directed below the raised single sheet of paper (03).

28. The method according to claim 20 or 21, characterized in that, Multiple blown air jets from different output openings (29) are directed below the raised single sheet of paper (03).

29. The method according to claim 20 or 21, characterized in that, First, in the central region of the sheet stack (07), a first blowing air jet is discharged toward the underside of the raised sheet (03), and in a time-displaced manner from the first blowing air jet, in a region spaced apart from the center of the sheet stack (07), other blowing air jets are discharged toward the underside of the raised sheet (03).

30. The method according to claim 20 or 21, characterized in that, Multiple air jets, starting at different times from the same or different output openings (29), point below the raised sheet of paper (03). The first air jet ends during the time interval before the conveying movement of the conveying mechanism (16) for conveying the corresponding sheet of paper (03) begins, and the second air jet, starting at a time interval opposite to or after the first air jet, ends after the conveying movement of the conveying mechanism (16) begins.

31. The method according to claim 20 or 21, characterized in that, Multiple air jets, starting at different times from the same or different output openings (29), point below the raised sheet of paper (03). The first air jet ends when the conveying mechanism (16) begins its conveying motion to convey the corresponding sheet of paper (03), and the second air jet, starting at a time different from or after the first air jet, ends after the conveying motion of the conveying mechanism (16) begins.

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