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Publication numberUS20050280199 A1
Publication typeApplication
Application numberUS 11/115,650
Publication dateDec 22, 2005
Filing dateApr 27, 2005
Priority dateMay 3, 2004
Publication number11115650, 115650, US 2005/0280199 A1, US 2005/280199 A1, US 20050280199 A1, US 20050280199A1, US 2005280199 A1, US 2005280199A1, US-A1-20050280199, US-A1-2005280199, US2005/0280199A1, US2005/280199A1, US20050280199 A1, US20050280199A1, US2005280199 A1, US2005280199A1
InventorsHelmut Steinhilber, Karl-Heinz Niggemann, Ludwig Bantle
Original AssigneeHelmut Steinhilber, Karl-Heinz Niggemann, Ludwig Bantle
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method and device for separation of sheets of a recording carrier from a stack
US 20050280199 A1
Abstract
For separation of sheets of a recording carrier from a stack for feeding to an office machine, printer or the like, a pick-up device is placed on the rear end of the stack. The pick-up device pushes the sheets against the belt in overlapping fashion, which raises the front edge of the first sheet arriving first from the stack. The holding element is then pivoted into the gap between the first sheet and the second sheet. The holding element holds the second sheet on the stack and forces the first sheet against a given transport roller with a pressure roller. Separation elements are pushed between the first sheet and the second sheet in order to separate the first sheet from the second sheet. The pick-up device is raised so that the first sheet can be withdrawn by the transport rollers from the stack and fed to the ejection rollers.
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Claims(20)
1. Method for separation of sheets of a recording carrier from a stack for feeding to an office machine, a printer or the like with the following steps:
exerting a pick-up effect on the uppermost first sheet of the stack on its rear end region in the feed direction, through which the upper sheets are pushed forward in overlapping fashion against a stop in the feed direction, wherein the first sheet is first to reach the stop with its front edge facing in the feed direction because of overlapping;
raising the front edge of the first sheet by the stop from the stack so that a gap is formed between the front edge of the first sheet and the front edge of the corresponding next second sheet;
moving at least one holding element into the gap between the front edge of the first sheet and the second sheet;
grasping the front edge of the first sheet by the transport rollers and holding the second sheet by the holding element on the stack;
releasing the first sheet from the pick-up effect and pushing at least one separation element between the first sheet and the second sheet and separating the first sheet flatly from the second sheet;
pulling the first sheet from the stack by the transport rollers and transporting it to ejection rollers by which it is grasped;
moving the at least one holding element out from the stack and releasing the second sheet and retracting the at least one separation element from the stack;
feeding the first sheet by the ejection rollers to the office machine or the like; and
exerting the pick-up effect on the rear end region of the second sheet that is exposed by pulling off of the first sheet so that the corresponding separation and feed cycle for the second sheet begins.
2. The method according to claim 1, wherein the first sheet is moved with a greatest advance and the subsequent sheets with a smaller advance.
3. The method according to claim 1, wherein a pick-up device is positioned on the uppermost sheet in order to exert the pick-up effect and raised from the uppermost sheet in order to release it from the pick-up effect.
4. The method according to claim 1, wherein the at least one holding element forces the front edge of the uppermost sheet against the transport roller.
5. The method according to claim 1, wherein the at least one separation element is retracted essentially simultaneously with withdrawal of the uppermost sheet from the stack.
6. The method according to claim 3, wherein the pick-up device is initially placed on the rear end region of the uppermost sheet without a pick-up effect and the pick-up effect is only started after contact.
7. The method according to claim 1, wherein the stop is moved upward at a steep angle with reference to sheet plane of the stack and the front edge of the corresponding uppermost sheet is carried along with friction or shape mating.
8. A device for separation of sheets of a recording carrier from a stack for feeding to an office machine, printer or the like for execution of the method according to claim 1, wherein a pick-up device can be positioned on the rear end region of the stack with reference to the feed direction of sheets, wherein the upper sheets of the stack are pushed against the stop in overlapping fashion by the pick-up device, wherein the stop raises the front edge of the uppermost sheet from the subsequent retracted second sheet, wherein at least one holding element can be moved between the front edge of the raised first sheet and the second sheet, wherein the at least one holding element secures the second sheet of the stack on the stack in the position moved into the stack, wherein the front edge of the corresponding first sheet raised by the stop is grasped by the transport rollers and pulled off, wherein at least one separation element can be pushed between the first sheet raised on its front edge and the second sheet and wherein the transport roller transports the corresponding first sheet to the ejection rollers.
9. The device according to claim 8, wherein the at least one holding element can be pivoted around an axis parallel to the front edge of the stack and engages with a finger between the raised front edge of the first sheet and the second sheet sits with this finger on the second sheet and holds it on the stack and with its top brings the first sheet into engagement with the transport rollers.
10. The device according to claim 9, wherein the at least one holding element has a freely rotatable pressure roller on its finger pivotable into the stack, which forces the first sheet against the drivable transport roller.
11. The device according to claim 8, wherein the at least one separation element is a strip, especially an electrically conducting strip and especially a steel strip, which can be pushed against the feed direction of sheets by the front side of the stack between the first sheet and the second sheet.
12. The device according to claim 8, wherein the stop consists of at least one endlessly revolving drivable belt, whose run facing the stack runs up at a steep angle and entrains the front edge of the first sheet lying against it by friction.
13. A device for separation of sheets of a recording carrier from a stack for feeding to an office machine, printer or the like comprising
means for exerting a pick-up effect on the uppermost first sheet of the stack on its rear end region in the feed direction and for moving the first sheet,
a stop for stopping a movement of a picked up sheet and for raising the front edge of the first sheet;
means for moving at least one holding element by the front side of the stack into a gap between the front edge of the first sheet and a second sheet;
transport rollers for grasping the front edge of the first sheet;
a holding element for holding the second sheet on the stack;
means for releasing the first sheet from the pick-up effect and pushing at least one separation element between the first sheet and the second sheet and separating the first sheet flatly from the second sheet,
ejection rollers for grasping the first sheet pulled from the stack by the transport rollers;
means for moving the at least one holding element out from the stack and releasing the second sheet and retracting the at least one separation element from the stack, wherein the ejection rollers feed the first sheet to the office machine or the like, and wherein means exert the pick-up effect on the rear end region of the second sheet that is exposed by pulling off of the first sheet so that the corresponding separation and feed cycle for the second sheet begins.
14. The device according to claim 13, wherein the means for exerting a pick-up effect are a pick-up device which can be positioned on the rear end region of the stack with reference to the feed direction of sheets, wherein the upper sheets of the stack are pushed against the stop in overlapping fashion by the pick-up device, wherein the stop raises the front edge of the uppermost sheet from the subsequent retracted second sheet, wherein at least one holding element can be moved by the front side of the stack between the front edge of the raised first sheet and the second sheet, wherein the at least one holding element secures the second sheet of the stack on the stack in the position moved into the stack, wherein the front edge of the corresponding first sheet raised by the stop is grasped by the transport rollers and pulled off, wherein at least one separation element can be pushed between the first sheet raised on its front edge and the second sheet and wherein the transport roller transport the corresponding first sheet to the ejection rollers.
15. The device according to claim 14, wherein the at least one holding element can be pivoted around an axis parallel to the front edge of the stack and engages with a finger between the raised front edge of the first sheet and the second sheet, sits with this finger on the second sheet and holds it on the stack and with its top brings the first sheet into engagement with the transport rollers.
16. A device for separation of sheets of a recording carrier from a stack for feeding to an office machine, printer or the like comprising:
a pick-up device which can be positioned on a rear end region of the stack with reference to the feed direction of sheets,
a stop against which upper sheets of the stack are pushed in overlapping fashion by the pick-up device, wherein the stop raises the front edge of the uppermost sheet from the subsequent retracted second sheet,
at least one holding element which can be moved by a front side of the stack between a front edge of a raised first sheet and the second sheet, wherein the at least one holding element secures the second sheet of the stack on the stack in the position moved into the stack, wherein the front edge of the corresponding first sheet raised by the stop is grasped by transport rollers and pulled off,
at least one separation element which can be pushed between the first sheet raised on its front edge and the second sheet and wherein the transport roller transport the corresponding first sheet to ejection rollers.
17. The device according to claim 16, wherein the at least one holding element can be pivoted around an axis parallel to the front edge of the stack and engages with a finger between the raised front edge of the first sheet and the second sheet, sits with this finger on the second sheet and holds it on the stack and with its top brings the first sheet into engagement with the transport rollers.
18. The device according to claim 17, wherein the at least one holding element has a freely rotatable pressure roller on its finger pivotable into the stack, which forces the first sheet against the drivable transport roller.
19. The device according to claim 16, wherein the at least one separation element is a strip, especially an electrically conducting strip and especially a steel strip, which can be pushed against the feed direction of sheets by the front side of the stack between the first sheet and the second sheet.
20. The device according to claim 16, wherein the stop consists of at least one endlessly revolving drivable belt, whose run facing the stack runs up at a steep angle and entrains the front edge of the first sheet lying against it by friction.
Description

This application claims priority from German Patent Application No. 102004022010.7, which was filed on May 3, 2004; German Patent Application No. 20 2004 009 234.4, which was filed on May 3, 2004; and, German Patent Application No. 10 2004 028 578.0, which was filed on Jun. 15, 2004, and are incorporated herein by reference in their entirety.

TECHNICAL FIELD OF THE INVENTION

The present invention generally relates to the method and device for separation of sheets of a recording carrier from a stack for feed to an office machine, printer or the like.

Sheets of a recording carrier, generally paper sheets, are ordinarily supplied in office machines, printers and similar machines in a stack. The sheets are pulled off separately from this stack and fed to the office machine or the like. In modern machines high requirements are imposed on separation in numerous respects. In particular, separation must operate at high speed so that the working speed of the subsequently connected machine that processes the sheets is not adversely affected by the frequency of sheet feeding. In addition, separation must operate with high reliability and rule out double sheet pull-in even at different ambient temperature and humidity. Separation is also supposed to be suitable for a wide range of sheet qualities, for example for sheets of different weight, different stiffness, different surface condition, etc.

SUMMARY OF THE INVENTION

The underlying object of the invention is to provide a method and device for separation of sheets of a recording carrier from the stack for feeding to an office machine, printer or the like that satisfies these requirements in the best possible manner.

This object can be achieved according to the invention by a method for separation of sheets of a recording carrier from a stack for feeding to an office machine, a printer or the like with the following steps of exerting a pick-up effect on the uppermost first sheet of the stack on its rear end region in the feed direction, through which the upper sheets are pushed forward in overlapping fashion against a stop in the feed direction, wherein the first sheet is first to reach the stop with its front edge facing in the feed direction because of overlapping; raising the front edge of the first sheet by the stop from the stack so that a gap is formed between the front edge of the first sheet and the front edge of the corresponding next second sheet; moving at least one holding element by the front side of the stack into the gap between the front edge of the first sheet and the second sheet; grasping the front edge of the first sheet by the transport rollers and holding the second sheet by the holding element on the stack; releasing the first sheet from the pick-up effect and pushing at least one separation element between the first sheet and the second sheet and separating the first sheet flatly from the second sheet; pulling the first sheet from the stack by the transport rollers and transporting it to ejection rollers by which it is grasped; moving the at least one holding element out from the stack and releasing the second sheet and retracting the at least one separation element from the stack; feeding the first sheet by the ejection rollers to the office machine or the like; and exerting the pick-up effect on the rear end region of the second sheet that is exposed by pulling off of the first sheet so that the corresponding separation and feed cycle for the second sheet begins.

The first sheet can be moved with a greatest advance and the subsequent sheets with a smaller advance. A pick-up device can be positioned on the uppermost sheet in order to exert the pick-up effect and raised from the uppermost sheet in order to release it from the pick-up effect. The at least one holding element may force the front edge of the uppermost sheet against the transport roller. The at least one separation element can be retracted essentially simultaneously with withdrawal of the uppermost sheet from the stack. The pick-up device can initially be placed on the rear end region of the uppermost sheet without a pick-up effect and the pick-up effect is only started after contact. The stop can be moved upward at a steep angle with reference to sheet plane of the stack and the front edge of the corresponding uppermost sheet can be carried along with friction or shape mating.

The object can also be achieved by a device for separation of sheets of a recording carrier from a stack for feeding to an office machine, printer or the like for execution of the above method, wherein a pick-up device can be positioned on the rear end region of the stack with reference to the feed direction of sheets, wherein the upper sheets of the stack are pushed against the stop in overlapping fashion by the pick-up device, wherein the stop raises the front edge of the uppermost sheet from the subsequent retracted second sheet, wherein at least one holding element can be moved by the front side of the stack between the front edge of raised first sheet and the second sheet, wherein the at least one holding element secures the second sheet of the stack on the stack in the position moved into the stack, wherein the front edge of the corresponding first sheet raised by the stop is grasped by the transport rollers and pulled off, wherein at least one separation element can be pushed between the first sheet raised on its front edge and the second sheet and wherein the transport roller transport the corresponding first sheet to the ejection rollers.

The at least one holding element can be pivoted around an axis parallel to the front edge of the stack and engages with a finger between the raised front edge of the first sheet and the second sheet, sits with this finger on the second sheet and holds it on the stack and with its top brings the first sheet into engagement with the transport rollers. The at least one holding element may have a freely rotatable pressure roller on its finger pivotable into the stack, which forces the first sheet against the drivable transport roller. The at least one separation element can be a strip, especially an electrically conducting strip and especially a steel strip, which can be pushed against the feed direction of sheets by the front side of the stack between the first sheet and the second sheet. The stop may consist of at least one endlessly revolving drivable belt, whose run facing the stack runs up at a steep angle and entrains the front edge of the first sheet lying against it by friction.

The object can furthermore be achieved by a device for separation of sheets of a recording carrier from a stack for feeding to an office machine, printer or the like comprising means for exerting a pick-up effect on the uppermost first sheet of the stack on its rear end region in the feed direction and for moving the first sheet, a stop for stopping a movement of a picked up sheet and for raising the front edge of the first sheet; means for moving at least one holding element by the front side of the stack into a gap between the front edge of the first sheet and a second sheet; transport rollers for grasping the front edge of the first sheet; a holding element for holding the second sheet on the stack; means for releasing the first sheet from the pick-up effect and pushing at least one separation element between the first sheet and the second sheet and separating the first sheet flatly from the second sheet, ejection rollers for grasping the first sheet pulled from the stack by the transport rollers; and means for moving the at least one holding element out from the stack and releasing the second sheet and retracting the at least one separation element from the stack, wherein the ejection rollers feed the first sheet to the office machine or the like, and wherein means exert the pick-up effect on the rear end region of the second sheet that is exposed by pulling off of the first sheet so that the corresponding separation and feed cycle for the second sheet begins.

The means for exerting a pick-up effect can be a pick-up device which can be positioned on the rear end region of the stack with reference to the feed direction of sheets, wherein the upper sheets of the stack are pushed against the stop in overlapping fashion by the pick-up device, wherein the stop raises the front edge of the uppermost sheet from the subsequent retracted second sheet, wherein at least one holding element can be moved by the front side of the stack between the front edge of the raised first sheet and the second sheet, wherein the at least one holding element secures the second sheet of the stack on the stack in the position moved into the stack, wherein the front edge of the corresponding first sheet raised by the stop is grasped by the transport rollers and pulled off, wherein at least one separation element can be pushed between the first sheet raised on its front edge and the second sheet and wherein the transport roller transports the corresponding first sheet to the ejection rollers. The at least one holding element can be pivoted around an axis parallel to the front edge of the stack and engages with a finger between the raised front edge of the first sheet and the second sheet, sits with this finger on the second sheet and holds it on the stack and with its top brings the first sheet into engagement with the transport rollers.

The object can furthermore be achieved by a device for separation of sheets of a recording carrier from a stack for feeding to an office machine, printer or the like comprising a pick-up device which can be positioned on a rear end region of the stack with reference to the feed direction of sheets, a stop against which upper sheets of the stack are pushed in overlapping fashion by the pick-up device, wherein the stop raises the front edge of the uppermost sheet from the subsequent retracted second sheet, at least one holding element which can be moved by a front side of the stack between a front edge of a raised first sheet and the second sheet, wherein the at least one holding element secures the second sheet of the stack on the stack in the position moved into the stack, wherein the front edge of the corresponding first sheet raised by the stop is grasped by transport rollers and pulled off, at least one separation element which can be pushed between the first sheet raised on its front edge and the second sheet and wherein the transport roller transports the corresponding first sheet to ejection rollers.

The at least one holding element can be pivoted around an axis parallel to the front edge of the stack and engages with a finger between the raised front edge of the first sheet and the second sheet, sits with this finger on the second sheet and holds it on the stack and with its top brings the first sheet into engagement with the transport rollers. The at least one holding element may have a freely rotatable pressure roller on its finger pivotable into the stack, which forces the first sheet against the drivable transport roller. The at least one separation element can be a strip, especially an electrically conducting strip and especially a steel strip, which can be pushed against the feed direction of sheets by the front side of the stack between the first sheet and the second sheet. The stop may consist of at least one endlessly revolving drivable belt, whose run facing the stack runs up at a steep angle and entrains the front edge of the first sheet lying against it by friction.

Separation of sheets from the stack is achieved according to the invention with high speed and high reliability, during which separation is largely independent of environmental effects and in which a very broad range of sheet qualities can be used in the same manner. This is achieved by a combination of several steps as follows.

The upper sheets of the stack are initially pushed forward in overlapping fashion by pick-up and during this overlapping the upper sheet of the stack is pushed forward the most, whereas the subsequent sheets are pushed forward with a smaller advance. This overlapping fanning of the upper sheets of the stack by pick-up is independent of the sheet quality, that is, the sheet thickness, sheet stiffness and surface condition. Different sheet qualities can only influence the speed of advance and therefore the rapidity of overlapping, but not the reliability of overlapping fanning of the sheets. Because of this a situation is achieved in which the method according to the invention can be used for a very wide range of sheet qualities in the same way with the same reliability.

The sheets are pushed forward in overlapping fashion against a stop, in which case because of overlapping the uppermost sheet of the stack is first to reach the stop with its leading edge facing in the feed direction. The front edge of the uppermost sheet is raised by the stop from the stack and therefore especially from the subsequent second sheet. A very limited protrusion of the front edge of the uppermost sheet relative to the front edge of the next sheet in the overlapping sequence is sufficient in order to reliably separate the front edge of the uppermost sheet from the second sheet that has still not reached the stop. Double sheet pull-in is reliably prevented on this account.

As soon as the front edge of the uppermost sheet has been raised from the next second sheet, a holding element is moved into the gap so formed between the front edge of the uppermost sheet and the front edge of the second sheet, which holds the second sheet on the stack while the front edge of the uppermost sheet is grasped by the transport rollers. At least one separation element is then moved between the uppermost sheet and the next second sheet with high speed. The separation element separates the uppermost sheet from the next second sheet so that air can penetrate between the uppermost first and the subsequent second sheet in order to prevent adhesion of the sheets by partial vacuum. The at least one separation element can also be designed electrically conducting in order to prevent electrostatic charging and therefore electrostatic attraction between the first and second sheets. The uppermost sheet can now be pulled by the transport rollers from the second sheet, in which case the pick-up device releases the uppermost sheet. The holding element then holds the following second sheet, while the separation element causes an air cushion to be formed between the uppermost sheet and the held second sheet, on which the sheet being pulled off slides and in which no electrostatic charge can form from friction of the uppermost sheet on the second sheet.

The transport rollers convey the uppermost sheet to the ejection rollers, which grasp the uppermost sheet on its front edge and withdraw it at high speed and feed it to the office machine or the like. During removal of the uppermost first sheet, the at least one holding element is retracted from the stack and the at least one separation element is retracted from the stack together with pulling off of the uppermost sheet.

As soon as the front edge of the uppermost sheet is grasped by the ejection rollers, the pick-up device can already engage on the now rear end region of the following second sheet now being released and push it forward with a pick-up action against the stop, since the front edge of the second sheet has been released in the meantime by the holding element. Since the second sheet has already covered most of the path to the stop because of the overlapping fanning of the upper sheets of the stack, the front edge of the second sheet during the pick-up effect very quickly reaches the stop and is separated from the next third sheet there. This can occur in overlapping fashion with removal of the first sheet by the ejection rollers so that overall high speed of separation can be achieved. The overlapping separation and removal of the sheets has an advantageous effect on the speed in the case of long sheets in the feed direction. However, the invention can also be used advantageously in short sheet in the feed direction in which only a limited or no overlapping occurs.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further explained below by means of a practical example depicted in the drawing. In the drawing

FIG. 1 shows a top view of a device according to the invention,

FIG. 2 shows a side view of the device in the first phase of separation,

FIG. 3 shows a view corresponding to FIG. 1 in a second phase,

FIG. 4 shows a view corresponding to FIG. 2 in a third phase, and

FIG. 5 shows the process of the method according to the invention in a time diagram.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order to supply paper sheets of a recording carrier, for example paper sheets to an office machine, printer or similar machine, these sheets are generally kept in a stack 10. The uppermost sheet 11 of stack 10 is separated and pulled off separately from the following second sheet 12 of stack 10 and fed to the office machine or the like not shown in the drawing to the right in FIGS. 1 to 4.

A pick-up device 16 can be mounted in controlled fashion on the rear end region of stack 10 (to the left in the drawing) with reference to the feed direction and can be lifted from this end region. The pick-up device is designed, for example, in the form described in DE 100 16 793 C2. The pick-up device 16 has freely rotatable pick-up rollers 18 mounted on endless belts, which are moved (from left to right in the drawing) with adjustable pressure over the uppermost sheet 11 of stack 10. The pick-up rollers 18 then have a pick-up effect on the uppermost sheet 11 and an increasingly weaker effect on the subsequent sheets 12, 13, etc. Because of this pick-up effect the upper sheets 11, 12, 13, etc. are pushed forward in overlapping fashion, which means the first sheet 11 is pushed forward the most and the following sheets 12, 13, etc. are moved with a smaller advance.

A sheet stop is arranged in front of the end of stack 10 in the feed direction of sheets 11, 12, 13 (the right end of the drawing), against which sheets 11, 12, 13 are moved by means of pick-up device 16. In the depicted practical example the sheet stop consists of a revolving endless belt 20 which can be driven (clockwise in the drawing). The run of belt 20 facing stack 10 then runs in front of the upper front edge of stack 10 with reference to the plane of the sheets of stack 10 steeply upward.

On both sides of belt 20 and in the direction of the front edge of stack 10 a holding element 22 is arranged at a spacing from this belt 20. The holding elements 22 have the shape of a hook that can be mounted to pivot around an axis 24 parallel to the front edge of stack 10. The free end of the holding element 22 is designed as a finger 26 that faces stack 10 and is designed roughly in the form of a circular arc with reference to axis 24 as center point. The holding elements 22 are driven in controlled fashion to pivot around axis 24 between a rest position in which their finger 26 is situated outside of and in front of stack 10 and an engagement position in which the finger 24 is pivoted over stack 10 and sits with its free tip on stack 10. A pressure roller 28 is mounted to rotate freely on the top of finger 26 of holding element 22. In the pivoted engagement position the pressure rollers 28 lie against the drivable transport rollers 30.

One or more separation elements 32 are also arranged in front of the front edge of stack 10 facing in the feed direction. One separation element each 32 is arranged to the side outside of holding elements 22. The separation elements 32 are designed as elongated strips, preferably steel strips with limited material thickness. The cross-sectional profile of the strips is slightly arched in order to give these strips the necessary longitudinal rigidity. On the end of the separation elements 32 directed against stack 10 a sliding tip 34, for example, made of plastic, felt or the like can be positioned in order to prevent damage to the sheets by the separation elements 32. The separation elements 32 can be driven in controlled fashion (to the left in the drawing), can be introduced to stack 10 parallel to its surface and can be pulled out again from the stack in the feed direction of the sheets. The drive of the separation elements 32 is shown in the drawing by dry rollers 36 which engage on the separation elements 32 by friction.

Ejection rollers 38 that grasp the sheet pushed forward by the transport rollers on its front edge and feed it at higher speed to the office machine or the like (not shown) are arranged behind the transport rollers 30 in the sheet feed direction.

It is apparent without difficulty that the holding elements can also have a different shape and movement if they only engage between the first and second sheet and hold the second sheet on the stack. Separation elements can also have a different shape and movement and, for example, also be introduced from the side between the raised first sheet and the second sheet.

The method according to the invention for separation and feed of sheets is explained below with reference to the time diagram of FIG. 5.

The time periods in which the different functional elements are active are shaded dark in the lines of this diagram. In the horizontal time scale of the diagram one division line corresponds, for example, to about 10 ms.

The entire device is initially started from the rest state. The sheets 11, 12, 13, etc. are situated congruent on each other in stack 10. The pick-up device 16 is raised from the stack 10. The holding elements 22 are pivoted out from stack 10 (clockwise to the right in the drawing). The separation elements 32 are pulled out from stack 10 (to the right in the drawing).

On a start signal at time a1 the pick-up device 16 is lowered and positioned on the rear end region of stack 10. The pick-up device 16 therefore sits on the rear end region of the uppermost first sheet 11. The duration of contact of the pick-up device 16 on stack 10 is shown in line 1.

As soon as the pick-up device 16 is positioned on the first sheet 11, the drive of the pick-up device 16 is started at time b1 so that the pick-up effect begins. The duration of the pick-up effect is shown in line 2.

The upper sheets 11, 12, 13, etc. of stack 10 are pushed forward by the pick-up effect toward the stop formed by belt 20. A first sensor, whose response time is shown in line 3, determines at time c1 that the leading front edge of the first sheet 11 has come to a stop on belt 20. The drive on belt 20 is started by the signal with this first sensor, that is at time c1. The time during which belt 20 is driven is shown in line 4.

The belt 20 during its upward movement entrains the front edge of the first sheet 11 lying against it and raises it from the second sheet 12 that is slightly retracted by overlapping. Because of this a vertical gap is formed between the front edge of first sheet 11 and the front edge of the second sheet 12, which still lies on stack 10. This situation is shown in FIG. 2. A second sensor, whose response time is shown in line 4 a, reports that the front edge of the first sheet 11 has been raised at time d1.

The drive of the holding elements 22 is started at time e1 by the signal of the second sensor. The holding elements 22 are pivoted (counterclockwise in the drawing) into the stack 10 for the period shown in column 5. During this pivot movement the fingers 26 of the holding elements 22 engage in the gap between the front edges of the first sheet 11 and the second sheet 12. The fingers 26 during this pivot movement force the front edge of the first sheet 11 upward with their upper backs and raise this front edge above the upper reversal point of belt 20. The pressure roller 28 then engages on the bottom of the front edge of the first sheet 11 and forces it against the corresponding pressure roller 28. This situation is shown in FIG. 3.

As soon as the front edge of the first sheet has been raised sufficiently from the second sheet 12 in order to form the required gap, the drive of the pick-up device 16 can be disengaged at time d1.

If the first sensor determines at time f1 that the front edge of the first sheet 11 is moved away upward by the holding element 22 from the stop formed by the belt 20 and is grasped by the transport roller 30, the pick-up device 16 is raised upward from the first sheet 11 at time g1. The first sheet 11 is held on its raised front edge between the transport roller 30 and the pressure roller 28 of holding element 22. The second sheet 12 is forced against stack 10 by the finger 26 of holding element 22 and held against stack 10. The pick-up device 16 is raised from stack 10 and therefore from the first sheet 11. The strip-like separation elements 32 are now started at time h1 and are pushed from the front edge between the first sheet 11 and the second sheet 12, as shown in FIG. 4. The duration of travel of the separation elements 32 is shown in column 6. As soon as the strip-like separation elements 32 have covered the entire length of the first sheet 11 at time k1, as shown in FIG. 4, the first sheet 11 is separated from the second sheet 12 so that air can penetrate between the first sheet and the second sheet. Insertion of the separation elements 32 is possible owing to the fact that the front edge of the first sheet 11 is held between the transport roller 30 and the pressure roller 28 so that the front edge of the second sheet 12 is secured by finger 26 of the holding element 22 against stack 10 and the pick-up device 16 is raised from the rear edge of the first sheet 11.

As soon as the separation elements 32 are pushed sufficiently far into the stack, the drive of the transport roller 30 is started at time i1. The duration of driving of transport roller 30 is shown in column 7. The transport rollers 30 pull the first sheet 11 from stack 10 in cooperation with the pressure rollers 28 and feed the first sheet 11 with its front edge to the ejection rollers 38, which grasp the first sheet and feed it to the office machine or the like. As soon as the ejection rollers 38 have grasped sheet 11, the holding elements 22 are pivoted out from stack 10 at time j1.

While the ejection rollers 38 pull the first sheet 11 from the stack, the separation elements 32 are also retracted, beginning at time j1. The separation elements 32 are therefore pulled out parallel and simultaneously with pulling of the first sheet 11 back into their initial position from stack 10. The air cushion introduced by the separation elements 32 between the first sheet 11 and the second sheet 12 favors pulling off of the first sheet 11 from the secured second sheet 12. The electrically conducting strips that form the separation elements 32 simultaneously prevent electrostatic charging from any friction remaining between the first sheet 11 and the second sheet 12, which might lead to adhesion of the first sheet 11 and the second sheet 12. Withdrawal of the separation elements 32 is shown in column 8.

The third sensor, whose response time is shown in line 9, is directly arranged on the ejection rollers 38. This third sensor determines at time k1 that the first sheet is grasped by the ejection rollers 38 and reports at time l1 that the trailing rear edge of the first sheet 11 has left the ejection rollers 38, which means that the first sheet 11 is fully taken up by the ejection rollers 38. On this signal of the third sensor the drive of the transport rollers 30 is switched off at time m1. The separation and feed cycle of the first sheet 11 is therefore completed.

The separation cycle of the second sheet 12 can begin in time overlap with removal of the first sheet 11.

After the transport rollers 30 have pulled the first sheet 11 sufficiently from the stack beginning at time i1, the trailing rear edge of the first sheet 11 is pulled out under the pick-up device 16. The holding elements 22 are pivoted out from the stack at time j1 and therefore release the front edge of the second sheet 12. In addition, the separation elements 32 are retracted at time j1. The pick-up device 16 can therefore now be lowered at time a2 onto the now exposed rear end region of the second sheet 12. The pick-up device 16 is started at time b2 in order to exert the pick-up effect on the second sheet 12, which is then pushed against belt 20 at time c2. When the second sheet 12 has reached the belt at time b2 and is raised by it, the rear edge of the first sheet 11 has just left the transport roller 30 at time l1 and their drive is switched off. The separation and feed cycle for the second sheet 12 can now be continued in the manner described above.

The separation and feed cycle for the third sheet 13 and the subsequent sheets of stack 10 follows accordingly.

As is apparent from the time diagram in FIG. 5, the duration for lowering of pick-up device 16 in line 1 and for driving of pick-up device 16, i.e., the pick-up effect in line 2 in the first sheet is longer than in the second sheet and subsequent sheets. This is due to the fact that at the beginning the pick-up device 16 must be lowered from is rest position onto stack 10, whereas in the subsequent sheets it is only slightly raised from the stack and the duration of the lowering movement is correspondingly shorter. The shorter pick-up time also results from the fact that the first sheet 11 must initially be advanced by the pick-up effect from its position lying congruent on stack 10 against belt 20, whereas the subsequent sheets 12, 13, etc. have already been pushed forward by overlapping and need only cover a limited path until they come in contact with belt 20.

The diagram in FIG. 5 shows that a very high speed can be achieved by controlling separation and overlapping of the individual cycles. In the depicted practical example a time of about 350 ms is obtained for the duration of a separation and feed cycle, which corresponds to a separation feed of about 170 sheets per minute.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7387297 *Jun 24, 2005Jun 17, 2008Xerox CorporationPrinting system sheet feeder using rear and front nudger rolls
US7621522 *Jan 24, 2008Nov 24, 2009Pfu LimitedSheet feeding device
US8382107Mar 22, 2010Feb 26, 2013Grg Banking Equipment Co., Ltd.Sheet separating mechanism
Classifications
U.S. Classification271/121
International ClassificationB65H3/52, B65H3/56, B65H3/50
Cooperative ClassificationB65H3/56
European ClassificationB65H3/56
Legal Events
DateCodeEventDescription
Sep 28, 2005ASAssignment
Owner name: BDT AG, GERMANY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BANTLE, LUDWIG;STEINHILBER, HELMUT;REEL/FRAME:016594/0634;SIGNING DATES FROM 20050722 TO 20050818