Photocopying – Contact printing – Light boxes
Patent
1994-09-08
1996-09-03
Braun, Fred L.
Photocopying
Contact printing
Light boxes
271 303, 271184, 271301, 355315, G03G 2100
Patent
active
055528759
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates generally to liquid toner electrographic imaging systems and more particularly to duplex printing apparatus for liquid toner electrographic imaging systems.
BACKGROUND OF THE INVENTION
Apparatus for duplex copying of documents and for duplex printing by means of laser printers are known in the art. U.S. Pat. No. 4,949,949 to Holmes et al. describes a "Hybrid Sequencing Duplex Automatic Document Handling System" which includes apparatus for handling document sheets both sides of which are to be copied and for making duplex (i.e. double-sided) copies of such document sheets. The apparatus involve the use of one or more pairs of reversible rollers, lengthy inversion paths, and buffer trays for the handling of the documents and the copy paper prior to and in the course of making duplex copies. U.S. Pat. No. 4,884,794 to Dinatale et al. describes a document handler for duplex photocopying having first and second inverting path segments, which are utilized to re-orient the copy paper prior to duplex copying. U.S. Pat. No. 5,003,355 to Tanzawa describes a sheet transport control apparatus for use in a duplex unit of a laser printer, the apparatus including a transport system and a switchback system, and a series of driving motors and sensors. All the systems described in the prior art share the common feature of being mechanically complex, and they all involve transporting the paper through relatively lengthy and convoluted paths after printing on the first side so as to be able to print on the second side.
SUMMARY OF THE INVENTION
The present invention provides apparatus and a method for duplex printing that is significantly simpler than those described in the prior art. More specifically, the present invention provides apparatus and a method for duplex printing involving a short and straight transport path, without need for inverting segments and/or complex control mechanisms. As a consequence, the present invention affords duplex printing that is remarkably fast and efficient, and enables printing on both sides of a sheet of paper without any significant waiting time. There is therefore provided in accordance with the invention imaging apparatus for duplex printing on a substrate having first and second sides and a leading edge and a trailing edge, the apparatus including: support first and second images thereon; substrate engages the image support surface, leading edge first, at a transfer region; the first side of the substrate at the transfer region while at least partially fusing and fixing the image thereon; after transfer of the first image thereto and prior to the transfer of the second image thereto; transfer thereto; substrate directly from the second member and selectably deflect the substrate towards the waiting station or the output station for delivery thereto; and the trailing edge of the substrate after the substrate has been delivered to the waiting station and for delivering the substrate back to the second member, the second member being operative to deliver the substrate to the transfer region, whereat the second image is transferred to the second side of the substrate.
In accordance with a preferred embodiment of the invention, the second member includes gripping means for gripping the edge of the substrate which enters the transfer region first and is adapted for repeatedly engaging the same side of the substrate with the image support surface, such that at each engagement a different color image is transferred thereto.
In accordance with another preferred embodiment of the invention, the deflector means includes a roller and a set of wheels engaging the roller and forming a nip through which the substrate is transported, the set of wheels being adapted to engage the roller at first and second positions, at the first position the angle of release of the substrate from the nip is such that it is deflected to the waiting station, and at the second position the angle of release of the substrate from the nip is such that the it is def
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Blum Yoram
Landa Benzion
Sagiv Oded
Braun Fred L.
Indigo N.V.
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