ADF Interlock Switch Segmentation for Jam Recovery Detection
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Solution Overview
Problem
Conventional automatic document feeders (ADFs) with interlock switches that combine power supply switching and open/close detection functions experience false detection issues during jam recovery, as the motor rotation induced by user motion generates voltage, leading to incorrect detection of the sheet feed cover state.
Innovation Solution
An ADF design incorporating a switch unit with a first terminal for driving motor voltage and a second terminal connected to the motor, along with an open/close-detection circuit using a zener diode and transistor to differentiate between the driving motor's voltage and a threshold voltage, ensuring accurate detection of the sheet-feed cover's open or closed state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an interlock switch combines power supply switching and open/close detection functions, then device complexity is reduced, but measurement precision deteriorates due to false detection during jam recovery
Solution Approach 1:
The patent segments the interlock switch into two independent components: a power supply switch unit that controls motor power, and an open/close detection unit that detects cover state. This segmentation prevents the voltage generated during jam recovery from affecting the detection circuit, thereby maintaining detection accuracy while reducing overall device complexity through functional separation.
Solution Approach 2:
The patent introduces an intermediary element (the separate detection circuit with its own voltage source) between the cover and the detection system. This intermediary detection circuit independently verifies the cover state without being influenced by the motor voltage, thus preventing false detection while maintaining a relatively simple overall structure.
2Reliability
If power supply is interrupted when cover is open to ensure safety, then reliability is improved, but ease of operation deteriorates during jam recovery
Solution Approach 1:
The patent implements dynamic control where the power supply switch responds differently based on the cover state: when the cover is open, power is interrupted to ensure safety; when the cover is closed, power is supplied for normal operation. This dynamic response ensures safety during jam recovery while maintaining ease of operation during normal document feeding.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents false detection of the sheet-feed cover's state during jam recovery, maintaining accurate power supply control and detection, thereby enhancing the reliability of the interlock switch functionality.
Implementation Method 1
an open/close-detection circuit using a zener diode and transistor to differentiate between the driving motor's voltage and a threshold voltage
Implementation Method 2
the motor rotation induced by user motion generates voltage
Data Source
AI summary
According to an embodiment, an ADF includes: a sheet-feed cover unit; a switch unit to be switched on or off depending on whether the sheet-feed cover unit is open or closed and including a first terminal, to which a first voltage, by which a driving motor is driven, is input, and a second terminal connected to the driving motor; and an open/close-detection circuit unit that includes a first switch circuit and a second switch circuit. The first switch circuit is switched on or off based on a threshold voltage that is larger than a second voltage to be generated in the driving motor by a jammed-document removing motion and smaller than the first voltage. The open/close-detection circuit unit detects that the sheet-feed cover unit is closed when the second switch circuit is energized, but detects that the sheet-feed cover unit is open when the second switch circuit is de-energized.