Image recording apparatus

Electrophotography – Document handling – Copy

Reexamination Certificate

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Details

C399S068000, C399S400000

Reexamination Certificate

active

06285854

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an image recording apparatus, and more particularly to an image recording apparatus for recording an image on a continuous recording medium such as paper, a sheet type plastic film and the like.
Various kinds of image recording apparatus for recording an image on a continuous paper have been developed. For example, the image recording apparatus is provided with an image recording portion for actually performing printing on the continuos paper. As a printing mode in this image recording portion, an impact mode using a wire or a hammer and a non-impact mode represented by an electrophotographic mode are known.
As a method for feeding the continuous paper, there are two methods, i.e., a method using feed perforations and a frictional feed method using a roller. In the feed method using the feed perforations, a plurality of pins are fitted in the feed perforations formed on the continuous paper. These pins are provided on the belt surface of a tractor having a rotary driving portion. When the belt of the tractor is rotationally driven, the continuous paper is given a feeding force.
When the image recording portion performs image printing (development and transfer printing in practice) on the continuous paper to which the feed perforations are formed by the electrophotographic mode, the continuous paper is fed to a fixing part by the tractor. In the fixing part, the image on the continuous paper is stabilized by carrying out a fixing process.
In general, the fixing part is provided with a heating roller and a pressure roller at an inside thereof. The continuous paper is sandwiched between these rollers and drawn from an image recording portion to the inside of the fixing part. Thus, when the continuous paper is fed from the image recording portion to the fixing part by the tractor, disadvantages such as slack or cutoff of the continuous paper is resulted if a large difference in speed between the tractor and the both rollers in the fixing part occurs.
For example, JP-A-8-50382 discloses that tension is applied to the continuous paper to absorb the abovementioned difference in speed in order to prevent these problems from occurring. This publication discloses a plate which pivotally comes into contact with the entire area of the back surface of the continuous paper in order to apply the tension to the continuous paper. A pivot position of the plate is adjusted. Since only printing on one surface of the continuous paper is described in this prior art, an unfixed image is not distorted even if the plate is brought into contact with the entire area of the back surface opposed to the printed surface.
However, in this prior art, when trying to print on the both surfaces of the continuous paper, since the plate is brought into contact with the entire area of the back surface of the continuous paper, the unfixed image is distorted and a normal result cannot be obtained. Since the need for printing a multi-color image or a full-color image on both surfaces has been increased in recent years, the technique disclosed in this prior art is not sufficient. Further, in this prior art, the plate is simply brought into contact with the continuous paper, and therefore, there is also a problem that the continuous paper tends to be displaced in the width direction thereof.
Further, as another prior art, there is JP-A-5-310351. In this prior art, disclosed is a technique that a continuous paper is printed by a laser printer and then in an after processing device, the printed continuous paper is cut into sheets of a predetermined size to be stacked. In this case, a roller which floats on the continuous paper stretching between two fixed rollers is provide in order to absorb a difference between a feeding speed in the laser printer and a fetching speed in the after processing device, and the continuous paper is given a slack, thereby absorbing the difference in speed. Since the continuous paper has been already fed out from the laser printer, fixation of an image formed on the continuous paper is already completed. Typically, a tractor and a fixing part are provided in the inside of the laser printer. This prior art does not clearly disclose means for solving problems which may occur when there is a difference in speed between the tractor and the fixing part.
SUMMARY OF THE INVENTION
Therefore, a subject matter of the present invention is to provide an image recording apparatus capable of obtaining an excellent printing result on both surfaces of a continuous recording medium such as paper, a sheet type plastic film and the like.
To achieve the subject matter, an image recording apparatus of the present invention comprises: image recording means, having a toner carrier, for transferring a toner image formed on a surface of the toner carrier onto a continuous recording medium; feeding means for feeding the recording medium having the toner image transferred thereon; and fixing means for fixing the toner image on the recording medium fed by the feeding means, wherein there is provided speed difference absorbing means for giving predetermined slack to the recording medium by coming into contact with non-printing portions on both side ends of the recording medium to apply tension to the recording medium and for absorbing a speed difference generated between the feeding means and the fixing means.
According to this structure, the speed difference absorbing means applies tension in a direction substantially vertical to a feeding direction for the recording medium to impart predetermined slack to the recording medium. In this case, the speed difference absorbing means comes into contact with the non-printing portions of the recording medium on the both side ends to apply tension. Consequently, even if unfixed toner images exist on both surfaces of the recording medium, the toner images cannot be distorted, thereby obtaining excellent recorded images after fixation.
The speed difference absorbing means is provided with a guide roller which comes into contact with the nonprinting portion of the recording medium on the both side ends and rotates as the recording medium is fed, and the guide roller is characterized by being capable of moving in the vertical direction. According to this structure, a slack quantity of the recording medium is adjusted by that the guide roller in contact with the recording medium moves in the vertical direction, and a speed difference generated between the feeding means and the fixing means can be thereby absorbed.
Further, in an image recording medium having the same structure as described above, the present invention is characterized by comprising: a guide roller which is provided between the feeding means and the fixing means and gives predetermined slack to the recording medium by coming into contact with a non-printing portion of the recording medium on both side ends to apply tension to the recording medium; detecting means for detecting a position of said guide roller; and controlling means for controlling a feeding speed for the recording medium in such a manner that the detected position of the guide roller is in a predetermined range.
According to this structure, the guide roller moves in a direction substantially vertical to the feeding direction for the recording medium to apply tension to the recording medium, and at this time a position of the guide roller is detected by the detecting means. A slack quantity of the recording medium can be obtained by detecting the position of the guide roller in this way. As a result, it is possible to indirectly grasp a speed difference generated between the feeding means and the fixing means. Additionally, the controlling means controls a feeding speed for the recording medium in such a manner that the position of the guide roller is in a predetermined range, namely, the speed difference is eliminated.
The guide roller is provided with restricting means for restricting the position of the recording medium in the width direction. The restricting means may be a flange portion p

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