Electrophotography – Document handling – Copy
Reexamination Certificate
1999-04-21
2001-07-31
Grainger, Quana (Department: 2852)
Electrophotography
Document handling
Copy
C399S006000
Reexamination Certificate
active
06269237
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is directed to an apparatus, particularly a printer or copier, having a first electrographic printing unit that prints an image pattern onto a sheet-shaped material, having an input section via which the sheet-shaped material can be individually supplied in succession, and having an output section via which the printed, sheet-shaped material is individually successively output.
In a known high-performance printer having only a single printing unit, the individual printer components are exactly matched to one another, so that an extremely dependable operating condition with high printing performance is achieved. In order to increase the printing performance even farther, design changes must be undertaken at these components, this leading to a high development expense and increasing the probability of failure due to the redesign of the individual components.
U.S. Pat. No. 5,208,640 discloses a printer that comprises two identical printing units to which sheets to be printed can be supplied individually in succession via a common input section.
Given a printer disclosed by DE 38 18 982 C2, pairs of transport rollers are arranged in the transport path of the paper. Various pairs of transport rollers are thereby driven in common via synchronous belts by a single drive or a few central drives.
When the transport of the sheet-shaped material makes it necessary that pairs of transport rollers have different speeds or must change their rotational sense, then the rollers of the pairs of transport rollers in the previous solutions have been driven via switchable couplings. Further, gearings were arranged preceeding the transport rollers in order to set the speed and the rotational sense according to the required operating mode. Switchable couplings must also be arranged preceding these gearings. It has now been shown that such switchable couplings have great tolerances in the switching times and that high accelerations result when these couplings are switched. A further disadvantage is that the drive belts for the synchronous drive of the transport rollers are extremely long in part. The known solution is therefore very involved and has low operating dependability.
SUMMARY OF THE INVENTION
An object of the invention is to specify an apparatus of the type initially cited whose transport system for sheet-shaped material enables a plurality of operating modes of the apparatus and that can be realized with little expense.
In the method and apparatus of the present invention, a first electrographic printing unit is provided that prints an image pattern on a sheet-shaped material. An input section via which the sheet-shaped material is supplied individually in succession is provided. An output section is provided over which the printed sheet-shaped material is output individually in succession. A turning device is provided for the sheet-shaped material. A substantially identical second printing unit is provided with sheet-shaped material being supplied thereto via the input section. The sheet-shaped material printed by the second printing unit is output via the output section. Transport roller pairs driven by drives are arranged in transport paths for the sheet-shaped material from the input section to the output section, the transport roller pairs having a spacing from one another slightly smaller than a dimension of the material in a conveying direction of the material. The transport roller pairs have different rotational speeds and conveying directions dependent on an operating mode of the apparatus. Stepping motors with reversible rotational sense or clock-controlled motors are provided as the drives. Predetermined, driven transport roller pairs are combined to form groups directly coupled to one another and respectively driven by a single drive. A first transfer printing transport path along the first printing unit, and a separate, second transfer printing transport path along the second printing unit, are provided. The input section contains a shunt that supplies the sheet-shaped material either to the first transfer printing transport path or to the second transfer printing transport path. The first transfer printing transport path and the second transfer printing transport path are connected by a connecting channel through which sheet-shaped material is conveyed in one or in both conveying directions. The sensor is arranged at a plurality of the transport roller pairs, the sensor signaling passage of an edge of the sheet-shaped material. A predetermined transport roller pair is accelerated or retarded dependent on signals of the sensor.
Two substantially identically constructed printing units are utilized in the apparatus of the invention. The components for these printing units, for example the electronic control, the developer units, the toner delivery and discharge devices, etc. can be retained nearly unmodified. In and of itself, thus, each printing unit has very high operating dependability. Both printing units use a common input section via which the sheet-shaped material is supplied. Both printing units likewise use an output section in common for delivering the printed, sheet-shaped material. As a result thereof, the new apparatus is very compactly constructed and can be manufactured with little expense. The printing performance is clearly enhanced due to the two printing units.
Stepping motors reversible in rotational sense are provided as drives in the invention. These stepping motors can be set to the desired speed on the basis of a predetermined clock frequency, whereby high synchronism with other, identical drives is assured during acceleration and when decelerating the drive. Various driven transport rollers are combined to form groups that are driven by a single stepping motor. The group formation leads to the fact that the structural expense is reduced, whereby the flexibility for setting specific speed profiles continues to be established. As a result of the employment and arrangement of these drives, switching couplings and gearings are not required, as a result whereof the operating dependability is enhanced and the hardware outlay remains small. The division into groups, on the one hand, and into individual drives within the apparatus, on the other hand, leads to the fact that a plurality of paper paths can be realized in order to still be able to implement printing jobs with the remaining, other printing units given potential outage of one printing unit.
In the invention, single sheets on different transport sections in the printer can have different speeds, which partially amount to a multiple of the transfer printing speed. As a result thereof, it is possible to convey the respective single sheet following and preceding the transfer printing with a higher speed then the transfer printing speed. In this way, the overall throughput in the printer can be enhanced and longer dwell times on a path section due, for example, to passage through a shunt or a turn-over unit, can be in turn compensated by high conveying speeds. Due to the high speed outside the printing units, it can also be assured that the prescribed spacings between single sheets that are output are adhered to and the proper output sequence is observed despite potentially different paths of the individual sheets in the printer.
It is provided according to one exemplary embodiment that a sensor unit is arranged at a plurality of transport roller pairs, preferably at each transport roller pair, said sensor unit signaling the passage of a leading edge or of a trailing edge of the sheet-shaped material. This sensor unit preferably contains two light barriers, the one being arranged preceeding the transport roller pair and the other being arranged following the transport roller pair. Due to the signals of the sensor unit, where a single sheet is located can be determined at any time. Further, jam situations in the apparatus can be recognized. Dependent on the recognition of a leading edge or of a trailing edge of the single sheet, the respective transport roller pair
Olbrich Otto
Thiemann Peter
Grainger Quana
Hill & Simpson
Oce Printing Systems GmbH
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