Sheet Feeding Cassette Positioning for Accurate Size Detection
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Solution Overview
Problem
Existing sheet feeding apparatuses face challenges in accurately detecting sheet sizes due to high operation forces required for contact type switches and inaccuracies in non-contact photo sensors, especially when the sheet feeding cassette is not accurately positioned.
Innovation Solution
A sheet feeding apparatus with non-contact type detection elements and a positioning unit that aligns the pivotal shafts of size detection levers with an imaginary axis, allowing for accurate sheet size detection without large operation forces and minimizing errors from mounting backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a contact type switch is used as the detection element, then the device complexity is reduced and manufacturing cost is lowered, but a large operation force is required and accurate detection cannot be ensured due to mounting backlash
Solution Approach 1:
The patent replaces the contact type switch (mechanical detection system) with a photo sensor (optical detection system). The size detection lever swings to block light from the light emitting portion to the light receiving portion, turning the photo sensor ON/OFF without physical contact. This eliminates the need for mechanical contact, removing mounting backlash issues and reducing operation force while maintaining detection functionality.
2Measurement precision
If a non-contact type photo sensor is used as the detection element, then the operation force is reduced and detection accuracy is improved, but accurate detection cannot be ensured if the storage cassette and size detection levers are not accurately positioned
Solution Approach 1:
The patent incorporates a positioning protrusion on the storage cassette that engages with a positioning recess on the apparatus body before full insertion. This preliminary positioning action ensures that the size detection levers are correctly aligned with the light emitting and receiving portions of the photo sensor, guaranteeing accurate detection even during the insertion process.
Solution Approach 2:
The positioning protrusion and recess act as an intermediary mechanism between the storage cassette and the detection system. This intermediary structure ensures proper spatial relationship and alignment between the moving lever and the stationary photo sensor components, eliminating positioning errors.
3Device complexity
If a contact type switch is used, then the device structure is simplified, but the mounting base and switch must be pressed against biasing force requiring large operation force
Solution Approach 1:
The patent eliminates the mechanical contact switch and its biasing spring system by using a photo sensor. The detection lever swings to block light paths without needing to physically press against any component. This removes the entire mechanical actuation system including the biasing member, significantly reducing operation force while maintaining the on/off detection capability.
4Ease of operation
If the storage cassette is mounted without accurate positioning, then ease of operation is improved, but sheet size detection accuracy deteriorates with contact type switches
Solution Approach 1:
The positioning protrusion engages with the positioning recess during cassette insertion, performing preliminary alignment before the cassette is fully seated. This ensures that even with simple user insertion operations, the detection levers are pre-aligned with the photo sensor's light paths, maintaining detection accuracy without requiring precise manual positioning.
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
Enables reliable and precise sheet size detection with reduced operation force and improved accuracy by using non-contact detection elements and a positioning unit that ensures proper alignment of detection components, enhancing the overall performance of the sheet feeding apparatus.
Implementation Method 1
light emitted from a light-emitting portion is received by a light receiving-portion or is shielded by a light shielding portion, and thereby in such a manner the photo sensor is intended to be turned ON/OFF
Data Source
AI summary
A sheet feeding apparatus includes an apparatus body, a storage cassette having a cassette body and a regulation member regulating a position of a sheet, and a size detection portion detecting a size of the sheet. The size detection portion has a plurality of size detection levers which are swung around pivotal shaft, a plurality of non-contact type detection elements which are radially arranged around an imaginary axis on the apparatus body and are turned ON/OFF by the plurality of size detection levers in a case where the storage cassette is mounted, and a positioning unit. The positioning unit positions the storage cassette such that the pivotal shaft and an imaginary axis are matched in a case where the storage cassette is mounted on the apparatus body.