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Control of Skew Correction Mechanism for Thin Paper

IP.com Disclosure Number: IPCOM000013414D
Original Publication Date: 2001-Jun-26
Included in the Prior Art Database: 2003-Jun-18

Publishing Venue



Disclosed is a control method for a paper skew correction mechanism with a shutter plate for the paper top edge alignment. The method is effective to prevent skew correction failure due to a thin paper easily being buckled at the shutter plate. FIG-1 shows all elements of the skew correction mechanism for which the method is applicable. They are Upper Feed Roller (1), Lower Feed Roller (2), Paper-In Detection Sensor (3), Alignment Detection Sensor-Left (4), Alignment Detection Sensor-Right (5), Shutter (6), Lower Guide Plate (7), and Upper Guide Plate (8). As shown in FIG-2, Upper Feed Roller (1) consists of Drive Shaft (a), Roll (b) being fixed on the shaft, and Roll (c) being flexibly mounted on Roll (b). Roll (c) has bigger outer diameter than Roll (b), and can be eccentric and free-rotated against Roll (b) due to its construction shown in FIG-3. When the mechanism is ready for paper insertion, Upper Feed Roller (1) is lifted up a little so that a gap exists between Roll (b) and Lower Feed Roller (2), but no gap between Roll (c) and Lower Feed Roller (2). At this timing, Shutter (6) is lowered to close the paper path. On this condition, the skew correction proceeds by the following steps in sequence. (i) Paper-In Detection Sensor (3) detects a inserted paper, then Upper Feed Roller (1) and Lower Feed Roller (2) start rotation. (ii) Roll (c) and Lower Feed Roller (2) transport the paper toward Shutter (6). (iii) After advanced corner (left-upper or right-upper) of the paper reaches to Shutter (6), Roll (c) which locates at the advanced corner side starts slipping, and Roll (c) which locates at the delayed corner side rotates the paper until the paper top edge aligns to Shutter (6). (iv) After both of Alignment Detection Sensor-Left/Right (4) (5) detect the paper, the rollers stop rotation. (v) Shutter (6) retracts upper side, and Upper Feed Roller (1) is lowered so that Roll (b) has enough pressure against Lower Feed Roller (2). (vi) The rollers restart rotation to transport the paper beyond Shutter (6). In the case of a thin paper being inserted, the advanced corner likely has buckling at (iii) of the above steps, then it results incorrect skew correction. Though very low feeding speed (such as 1 ips) does not cause the buckling, to introduce such feeding speed degrades the process speed and operator's usability at the insertion. Accordingly, the disclosed method introduces the following additional steps (iv-a, iv-b) after step (iv). (iv-a) Backward feed for about 5 mm to release the buckling using stiffness of the paper. (iv-b) Forward feed using very low feed speed until the both of Alignment Detection Sensor-Left/Right (4) (5) detect the paper. By these additional steps, the incorrect skew correction due to the buckling generated by normal feed speed can be prevented. 1