Sheet feeding or delivering – Feeding and delivering
Reexamination Certificate
2000-03-27
2001-10-30
Bollinger, David H. (Department: 3651)
Sheet feeding or delivering
Feeding and delivering
C271S003150, C271S003170, C271S004020, C271S004030, C271S157000
Reexamination Certificate
active
06308946
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sensor used to detect a printing sheet in a image forming machine, especially to technology for preventing malfunction of the sensor covered by foreign material such as paper powder or dust.
2. Description of the Related Art
Generally, in an image forming machine such as a stencil printing machine, printing sheets are stacked on a predetermined position, and the sheets are picked up one by one and fed into an image forming section. Then, the sheet is discharged therefrom after an image is formed on the sheet. In such image forming machine, a sensor may be situated for obtaining a detection signal of the printing sheet to control timing of printing operation or to detect jamming of the printing sheet during printing operation.
For example, the printing sheet picked up from the predetermined position is conveyed by rollers through a conveying path composed of guiding plates, and then the sheet is detected by a light sensor of non contact type at a leading end thereof, so that it is judged whether conveying timing of the printing sheet is appropriate.
During the conveyance of the printing sheet by the rollers through the conveying path made of the guiding plates, the printing sheet produces much foreign material while being rubbed against edges of holes where the rollers are situated. Accordingly, as shown in FIG.
6
(
a
), paper powder I accumulates on the light sensor of the non-contact type, thereby deteriorating detecting function of the sensor. To prevent this, a transparent cover may be attached onto the light sensor of the non-contact type; however, this is not actually adopted due to troublesome assembly operation needed by the complicated structure.
Further, as shown in FIG.
6
(
b
), a light sensor of reflective type may be arranged downward above the conveying path to reduce accumulation of the foreign material. This structure requires periodic cleaning of a bottom surface of the sensor since the paper powder inevitably adheres thereto in a long term. Further, the problem arises from not only the paper powder, but also dust accumulated in a long term.
An object of the present invention is to simply and periodically clean a sensor that tends to be covered by paper powder or dust in an image forming machine having the sensor to detect a printing sheet.
SUMMARY OF THE INVENTION
An image forming machine with a foreign material removal apparatus as defined in a first aspect of the present invention comprises: a sheet feeding table which is vertically movable and supports printing sheets thereon; sheet feeding means situated adjacent to the sheet
25
feeding table and feeding the printing sheets stacked on the sheet feeding table one by one; image forming means situated near the sheet feeding means and forming an image on the printing sheet fed by the sheet feeding means; detecting means situated adjacent to the sheet feeding means and detecting the printing sheets fed by the sheet feeding means; and foreign material removal means situated adjacent to the detecting means and removing foreign material covering the detecting means by allowing air to flow thereto, the foreign material removal means being driven by vertical movement of the sheet feeding table.
An image forming machine with a foreign material removal apparatus as defined in a second aspect of the present invention comprises: a sheet feeding table which is vertically movable and supports printing sheets thereon; sheet feeding means situated adjacent to the sheet feeding table and feeding the printing sheets stacked on the sheet feeding table one by one as the sheet feeding table moves upward; detecting means situated adjacent to the sheet feeding means and detecting the printing sheets fed by the sheet feeding means; conveying means situated adjacent to the sheet feeding means and conveying the printing sheets fed by the sheet feeding means; image forming means situated near the conveying means for forming an image on the printing sheets fed by the sheet feeding means; foreign material removal means situated near the detecting means and removing foreign material covering the detecting means by allowing air to flow thereto, the foreign material removal means being driven by vertical movement of the sheet feeding table; and control means connected to the sheet feeding table to control downward movement of the sheet feeding table.
In an image forming machine with a foreign material removal apparatus according to a third aspect of the present invention, the image forming machine is formed according to the second aspect, wherein the detecting means is a first sensor for detecting the printing sheets conveyed just before the image forming means, and the control means drives the image forming means and the conveying means in synchronization with each other on the basis of a signal from the first sensor.
In an image forming machine with a foreign material removal apparatus according to a fourth aspect of the present invention, the image forming machine is formed according to the third aspect, wherein the image forming machine further comprises a sheet sensor for detecting whether the printing sheets are stacked on the sheet feeding table, the control means moving the sheet feeding table downward when the control means judges on the basis of a signal from the sheet sensor that the printing sheets are not stacked on the sheet feeding table.
In an image forming machine with a foreign material removal apparatus according to a fifth aspect of the present invention, the image forming machine is formed according to the third aspect, the image forming machine further comprises a discharge sensor for detecting a printing sheet discharged from the image forming means, on which an image is formed by the image forming means, the control means moving the sheet feeding table downward when the control means judges on the basis of a signal from the discharge sensor that a predetermined number of the printing sheets is printed.
In an image forming machine with a foreign material removal apparatus according to a sixth aspect of the present invention, the image forming machine is formed according to the fifth aspect, wherein the control means moves the sheet feeding table downward when the control means judges on the basis of difference of timing in detecting the printing sheet between the first sensor and the discharge sensor that jamming occurs in conveying the printing sheet.
REFERENCES:
patent: 4801135 (1989-01-01), Povio
patent: 5335901 (1994-08-01), Nonomura et al.
Bollinger David H.
Kanesaka & Takeuchi
Riso Kagaku Corporation
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