Sheet feeding or delivering – Feeding – Separator and conveyor
Reexamination Certificate
1999-06-08
2002-12-31
Skaggs, H. Grant (Department: 3653)
Sheet feeding or delivering
Feeding
Separator and conveyor
C271S010110, C271S111000, C271S114000, C271S265020, C271S266000, C271S270000
Reexamination Certificate
active
06499733
ABSTRACT:
The present invention is directed to a method for inputting sheet material into a printer or copier.
BACKGROUND OF THE INVENTION
In known methods for inputting sheet material, a cover sheet respectively lying at the outside is pulled from a stack of sheets in response to a start signal and is transported with a draw-in speed in the direction of a sub-section of the conveying path wherein it is conveyed with an approximately constant, rated conveying speed that corresponds to the draw-in speed.
What is disadvantageous in the known method for inputting sheet material is that the spacing between successive sheets varies. This is to be attributed thereto that the frictional connection between draw-in rollers or, respectively, draw-in belts and the sheets is not 100% assured, so that what is referred to as a micro-slip occurs. The occurring micro-slip is dependent on the paper properties such as, for example, paper thickness and surface roughness. An adjustment of the draw-in force, particularly when pulling the sheets from the stack, leads to a variation of the spacing between successive sheets. When pulling the sheets from the stack, a minimum shift of the sheets neighboring the cover sheet cannot be prevented, so that the exact position of the leading sheet edge in conveying direction is also not known upon draw-in. The result is again that a variation of the spacing between successive sheets occurs.
Over one hundred sheets per minute are printed in high-performance printers. Fluctuations of the sheet spacing between a lower and an upper limit value necessarily lead to a loss of speed when printing compared to a printing with the lower limit value. One must proceed on the basis of the poorest value when specifying the printable number of sheets per time unit. However, the user wants an unchanging printing speed that can be calculated.
European Patent Application EP 0 428 922 A2 discloses an apparatus for document processing. The conveying density is increased in that the spacing between the documents is set with the assistance of a plurality of light barriers for acquiring the position of the documents.
European Patent Application EP 0 167 091 Al discloses a separating mechanism for letter mailings. The spacing between the letter mailings can be set more exactly by taking a prescribed value for the acceleration path upon draw-in into consideration.
German Laid-Open Publication DE 27 58 007 A explains a method for controlling the haul-off event in a means for the output of separated mailings of different length. In order to increase the conveying density given letter mailings of different length, the reference edge for setting the spacing between successive letter mailings is automatically selected.
Therefore, there is a need for a simple method for inputting sheet material that enables an approximately constant sheet spacing between the successively input sheets.
SUMMARY OF THE INVENTION
The aforenoted need is satisfied by the present invention wherein, in a first aspect of the invention is based on the perception that the sheet spacing can be most simply set when drawing the sheets in, since a later correction of a spacing would result in a variation of the topical position of all following sheets. An adjustment of the spacing should be possible both when a rated spacing is downwardly transgressed as well as upwardly transgressed. Given the first aspect of the invention, the transport of the sheet is therefore delayed such that a predetermined, identical spacing between sheets transported immediately following one another derives before the sub-section is reached. The setting of the spacing between the sheets thus ensues upon draw-in of the sheets into the printer. When the draw-in speed is relatively low, then there is hardly any or no delay at all. When the draw-in speed, however, is relatively high, then the delay is longer in order to set the rated spacing. Even when the draw-in speed is lower or equal to the conveying speed, a spacing can be set by delaying the cover sheet upon draw-in when the sheets are pulled from the stack with a spacing relative to one another that is smaller then the predetermined, identical rated spacing.
The delay of the transport is a simple technical measure that, for example, can be implemented by arresting a draw-in means or by decelerating said means.
Given the method according to the first aspect of the invention, the draw-in speed is greater then the conveying speed of the sheets within the sub-section. Delay time for controlling the spacing is gained on the basis of this measure. The spacing when pulling the sheets can thus be increased and the rated spacing can also be exceeded, the pulling thus becoming more reliable since having the sheets run up onto one another is avoided. The range of control of the spacing ultimately increases when increasing the draw-in speed. run up onto one another is avoided. The range of control of the spacing ultimately increases when increasing the draw-in speed.
The number of printed sheets per time unit is not diminished due to the first exemplary embodiment of the invention.
In an exemplary embodiment of the first aspect of the invention, a pre-draw-in position at which the position of the sheet is identified is located between sheet stack and sub-section. What this measure achieves is that the position of the sheet can be employed for further control events. The varying positions of the sheets in the sheet compartment no longer has any influence on a possible variation of the sheet spacing due to the recognition of the exact position of the sheet and measures based thereon.
In a further exemplary embodiment of the first aspect of the invention, the sheet is arrested between sheet stack and sub-section and, after the expiration of a holding time, it is preferably further-conveyed with the draw-in speed. Expediently, the sheet is arrested exactly at the pre-draw-in position. The holding time is dimensioned such that the predetermined, identical spacing between the cover sheet and a previously pulled sheet of the sheet stack—as viewed in conveying direction—is established during transport of the cover sheet up to the sub-section. The holding time can be calculated by simple path/time calculations. The distance between holding position and conveyor means and the draw-in speed are thereby known. The arresting can be realized, for example, via stepping motors and/or couplings.
A second aspect of the invention is directed to a means for drawing in sheet material into a printer or copier, particularly for the implementation of a method described above. The aforementioned technical effects are thus also transferred onto the means for drawing sheet material in according to the second aspect of the invention.
In an exemplary embodiment of the second aspect of the invention, the haul-off roller acting on the cover sheet is employed, the respectively to assure a dependable draw-in, the conveyor means seizes the built sheet before the trailing edge thereof is conveyed past the haul-off roller. What this measure assures is that the haul-off roller that is usually not arranged immediately at the leading edge of the sheet stack can be enabled by the conveyor means when seizing the sheet until the sheet has been completely pulled from the sheet stack. What this prevents is that further sheets are pulled from the sheet stack by the haul-off roller before the cover sheet has been completely pulled from the sheet stack.
In an exemplary embodiment of the second aspect of the invention, the sheet position is acquired with a first light barrier immediately following the draw-in means. Dependent on a signal of the first light barrier that, for example, is generated by the interruption of a light beam by the leading edge of the sheet, the draw-in means is disconnected, so that the sheet rests in the pre-draw-in position. A second light barrier is preferably arranged approximately in the predetermined spacing in conveying direction following the first light barrier. Dependent on a signal of the second light barrier that, for exampl
Oberhoffner Gerhard
Pilsl Stephan
Oce Printing Systems GmbH
Schiff & Hardin & Waite
Skaggs H. Grant
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