Typewriting machines – Sheet or web – For feeding web record-medium
Reexamination Certificate
1998-12-31
2001-02-06
Eickholt, Eugene (Department: 2854)
Typewriting machines
Sheet or web
For feeding web record-medium
C400S629000, C101S222000, C101S232000
Reexamination Certificate
active
06183152
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a printer and, in particular, to a printer having a paper handling mechanism that reduces paper curling and improves print quality.
Generally, a serial printer operates by moving a recording head in the main scanning direction and feeding paper along a line in a direction perpendicular to the main scanning direction. A paper sheet is fed towards the recording head by a pair of paper feed rollers and is discharged into a stacker by a pair of paper discharge rollers located downstream from the recording head. As the trailing edge (bottom) of a paper is released from the pair of paper feed rollers, the trailing edge is raised towards the recording head as it approaches the nip portion of the pair of paper discharge rollers as a result of the force caused by the weight of the paper being discharged to the stacker. The result is that the size of a gap formed between the recording head and the paper is altered causing the print quality at the bottom of the paper to be adversely affected.
To overcome this problem, Japanese Unexamined Patent Publication No. Hei 7-132658 discloses a technique whereby the paper discharge rollers are inclined toward the recording head so that the trailing edge of the paper is prevented from rising as it is released from the paper feeding rollers.
Typically, in a paper feeding mechanism the rotational speed of the discharge rollers is slightly higher than that of the paper feed rollers so that tension is applied to the portion of the paper that extends between the paper discharge and paper feed rollers. As a result, if the discharge rollers are inclined toward the recording head, as described above, curling of the trailing edge of paper will occur when the tension applied to the paper is released as the trailing edge disengages from the paper feed rollers. Accordingly, it is desirable to provide a printer having a paper handling mechanism that reduces the curling of the paper while maintaining a constant gap size between the recording head and the paper.
SUMMARY OF THE INVENTION
The present invention is directed to overcoming the shortcomings of the prior art. The present invention is directed to a printer having a paper handling mechanism that includes a pair of paper feed rollers located upstream in the paper feeding direction with respect to the recording head. A pair of paper discharge rollers is located downstream of the recording head, which each pair of rollers being inclined toward a recording head. A platen is positioned between the paper feed rollers and the paper discharge rollers, wherein the platen, when viewed from upstream to downstream, includes a first flat face that is slightly lower than a nip portion of the paper feed rollers, a gradually upwardly rising sloped portion, a second flat face for forming a paper gap, a downward sloped portion and a third flat face that is lower than a nip portion of the paper discharge rollers.
Using a paper handling mechanism and platen formed in this manner, paper that is fed to the first flat face of the platen is fed in a direction away from the recording head by the paper feed rollers. Then, as the leading edge of the paper is advanced from the first flat face, it travels across the gradually upwardly rising sloped portion to the second flat face, where a paper gap is formed with the recording head, and then proceeds down across the downward sloped portion to the third flat face. In this way, curling of the leading edge of the paper is prevented. Also, because the trailing edge of the paper is fed in the direction away from the recording head by the paper discharge rollers, the curling of the trailing edge is also prevented. As a result, the print quality at the top and bottom of the paper is maintained.
Accordingly, it is an object of the present invention to provide a printer having a paper handling mechanism that can prevent the curling of the trailing and leading edges of a paper.
It is another object of the present invention to provide a printer having a paper handling mechanism that maintains a constant gap size between the recording head and the paper so that the print area at the top and bottom of the paper can be increased without diminishing the print quality.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.
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Kanamitsu Masatomo
Kumai Eiji
Tomii Tsuyoshi
Eickholt Eugene
Seiko Epson Corporation
Stroock & Stroock & Lavan LLP
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