Transparent Sheet Protection in Image Reading Apparatus
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Solution Overview
Problem
In image reading apparatuses, the leading edge of a document being conveyed collides with the document discharge guide, causing scratches on the transparent sheet member and interference fringes in the read image, especially when using a single contact glass setup.
Innovation Solution
An image reading apparatus with a transparent sheet member and a guide member, where a conveyance guide sheet presses the transparent sheet toward the contact glass, and projections bias the sheet to maintain close contact, preventing collisions and scratches, and reducing air clearance for stable image focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a transparent sheet member is provided between the contact glass and the document being conveyed, then the collision between the document leading edge and the discharge guide is prevented, but the document conveying surface of the transparent sheet member is scratched
Solution Approach 1:
The patent introduces a guide member as an intermediary component between the document and the transparent sheet member. This guide member has a leading end that enters the conveyance path upstream of the reading position, allowing it to guide the document and prevent direct contact between the document and the transparent sheet member, thereby preventing scratches while maintaining protection
Solution Approach 2:
The patent segments the protective function into two separate components: the transparent sheet member that prevents document-discharge guide collision, and the guide member that prevents document-transparent sheet contact. This segmentation allows each component to perform its specific function without causing harmful effects to the other
2Object-affected harmful factors
If the transparent sheet member is arranged to cover the reading position, then protection is provided, but air clearance forms between the sheet and contact glass causing interference fringes
Solution Approach 1:
The guide member acts as an intermediary that controls the positioning of the transparent sheet member. By having its leading end enter the conveyance path upstream of the reading position, it ensures the transparent sheet member is properly positioned and maintained in contact with the contact glass, preventing air clearance and interference fringes while preserving the protective function
3Ease of operation
If the document passes through the reading position while rubbing the transparent sheet member, then the document is guided, but the transparent sheet member is scratched
Solution Approach 1:
The guide member serves as an intermediary guidance mechanism that replaces direct contact between the document and transparent sheet member. The guide member's leading end enters the conveyance path upstream of the reading position, providing the necessary guidance function while eliminating the rubbing action that would scratch the transparent sheet member
Data Source
AI summary
An image reading apparatus includes a first housing, a second housing, a document conveyance path, a transparent member, a guide member, a transparent sheet member and a first pressing member. The second housing is openable and closable with respect to the first housing. The document conveyance path is arranged in the second housing and conveys a document passing through a first position. The guide member is arranged on the transparent member at a side downstream of the first position. The transparent sheet member is arranged on the transparent member to cover the first position. The first pressing member is arranged to cover a part of the transparent sheet member upstream of the first position from above and presses the transparent sheet member. An end portion of the first pressing member is arranged inwardly of an end portion of the transparent sheet member in the main scanning direction.