Conveying Shingled Mail Groups Using Time Lag Control
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Solution Overview
Problem
Merging two groups of shingled mail items often results in uneven thickness, sagging, or swelling, leading to inefficiencies and errors in mail processing, particularly when one group travels along a curved path or changes direction, causing inaccuracies in the merged group's length and sequence.
Innovation Solution
A system utilizing conveyor belt systems with sensors to detect the position and length of mail groups, and a control unit that adjusts the start-off times of each group to ensure precise overlap and merging, compensating for stretching or contraction effects along curved paths by modifying the motion equations to maintain consistent spacing and prevent sagging or swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If two groups of shingled mail items are merged along converging paths, then the throughput of the conveying system is improved, but the merged group may become uneven in thickness, causing sagging or swelling
Solution Approach 1:
The control unit calculates and sets predetermined time lags for each group before merging, so that groups arrive at the intersection zone at precisely controlled intervals. This preliminary timing adjustment prevents uneven thickness distribution at the merge point, eliminating sagging and swelling while maintaining high throughput
Solution Approach 2:
The system uses sensors to detect the actual positions and lengths of mail groups, feeds this information to the control unit, which then adjusts the time lags to compensate for variations in group dimensions. This closed-loop feedback ensures consistent merge quality even when group characteristics vary
2Adaptability or versatility
If a group travels along a curved path or changes direction, then the conveying system can handle complex routing, but the group length changes due to stretching or contraction
Solution Approach 1:
The control unit calculates the expected stretching or contraction of groups based on the known geometry of curved paths beforehand, and compensates by adjusting the time lags accordingly. This preliminary compensation ensures that groups maintain accurate lengths despite path curvature
Solution Approach 2:
The system modifies the time lag parameters based on the specific geometry of each conveying path segment. For curved paths, larger time lags are applied to compensate for stretching, while for straight paths, smaller lags are used, optimizing group length accuracy for each path configuration
3Productivity
If the merged group has uneven thickness, then the conveying speed may increase to maintain throughput, but the retaining surfaces move apart causing items to collapse
Solution Approach 1:
By predetermined time lags, groups are spaced to maintain uniform thickness at merge points, preventing retaining surface separation and item collapse even at high conveying speeds
Solution Approach 2:
The system proactively prevents uneven thickness distribution by adjusting time lags before merging occurs, thereby preemptively avoiding the condition that would cause retaining surfaces to move apart and items to collapse
Data Source
Figure 1A~1B
Figure 1C~4
Figure 2~3
AI summary
A method of conveying and merging, at a relative intersection zone (CZi), at least one (i-1)th group (2) of shingled mail items with an ith group (2') of shingled mail items, the method including the step of : a) conveying the (i-1)th and ith groups (2, 2'), as of a start time (tSTART), along respective paths to the intersection zone (CZi); the method also including the steps of : b) determining, for each group (2, 2') of shingled mail items to be conveyed and merged, at least the position (P(i-1)0, Pi0) of its head (2H, 2H') at the start time (TSTART) ; and c) controlling start-off of each group (2, 2') to the intersection zone (CZi) on the basis of at least the position (P(i-1)0, Pi0) of its head (2H, 2H') at the start time (tSTART). There is also described a conveying and merging system designed to implement the above method.