Sheet Conveyance Path Double-Feed Detection Timing Control
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Solution Overview
Problem
In image forming apparatuses, the issue of double-feed sheets being mixed into printed products due to shortened conveyance paths, where the time to detect and divert double-fed sheets is reduced, leading to incomplete discharge onto an escape conveyance path.
Innovation Solution
A sheet conveying apparatus with a double-feed detector and a controller that switches between two modes: discharging detected double-fed sheets via an escape conveyance path or stopping them on the normal path, based on the timing and number of detections, ensuring effective diversion without mixing with printed products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the conveyance path is shortened to downsize the sheet conveying apparatus, then the apparatus size is reduced, but the time period from detection of double-fed sheets to switching of the conveyance path is reduced, causing double-fed sheets to cannot be conveyed to the escape conveyance path
Solution Approach 1:
The double-feed detector is positioned upstream of the branch-off portion to detect double-fed sheets before they reach the branching point. This preliminary detection allows the system to prepare for path switching in advance, ensuring that even with a shortened conveyance path, there is sufficient time to divert double-fed sheets to the escape conveyance path before normal printing occurs.
2Productivity
If the conveyance path is shortened to increase productivity, then the printing speed is improved, but the response time for detecting and diverting double-fed sheets is reduced
Solution Approach 1:
By placing the detector upstream, the system performs detection earlier in the conveyance process, creating a time buffer that allows for rapid path switching without compromising printing speed or productivity.
Solution Approach 2:
The escape conveyance path acts as an intermediary pathway that branches off from the main conveyance path. This intermediate structure allows double-fed sheets to be diverted without interfering with the main printing workflow, enabling rapid separation of defective sheets while maintaining overall productivity.
3Reliability
If the detector is positioned upstream to provide sufficient detection time, then the diversion reliability is improved, but the conveyance path length is increased
Solution Approach 1:
The conveyance system is segmented into two separate paths: the main conveyance path for normal sheets and the escape conveyance path for double-fed sheets. This segmentation allows the detector to be positioned upstream on the main path without necessarily increasing the overall apparatus size, as the escape path is a separate, dedicated route for handling detected defects.
Data Source
AI summary
A sheet conveying apparatus includes a sheet stacking portion, a sheet feeding portion, a sheet conveyance path, an escape conveyance path branching off from the sheet conveyance path at a branch-off portion, a sheet discharge portion, a double-feed detector configured to detect double-feed of the sheet at a detection position, and a controller. A path length in the sheet conveyance path from the detection position to the branch-off portion is shorter than a length of a conveyable sheet. The controller switches a mode between a first mode of discharging the sheet for which the double-feed has been detected onto the sheet discharge portion via the escape conveyance path and a second mode of stopping the sheet for which the double-feed has been detected on the sheet conveyance path without discharging the sheet onto the sheet discharge portion in accordance with timing at which the double-feed detector detects the double-feed.