Fuser Assembly Bellcrank Nip Force Reduction
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Solution Overview
Problem
Fuser assemblies in imaging devices often exert excessive force on smaller media like envelopes, causing wrinkling, and attempts to reduce this force can result in insufficient pressure for proper media advancement through the fusing nip.
Innovation Solution
A bellcrank mechanism is introduced to bias the nip loading spring, reducing the force between the heated and backup members when an access door opens, while maintaining contact and uniform force distribution using a flexible lever or wire that compresses the spring with a predetermined force during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spring force is increased to ensure sufficient pressure for media advancement, then media transport reliability is improved, but wrinkling of smaller media increases
Solution Approach 1:
The bellcrank mechanism transforms the static spring force into a dynamic, adjustable force. When the access door is closed, the bellcrank geometry reduces the effective spring force on the nip, preventing wrinkling. When the access door opens, the bellcrank returns to its neutral position, allowing full spring force to ensure reliable media transport. This dynamic adjustment resolves the contradiction between maintaining sufficient pressure and preventing wrinkling.
Solution Approach 2:
The invention changes the force parameter of the spring dynamically based on the access door position. The bellcrank mechanism modifies the spring constant effectively by changing the mechanical advantage ratio. In the closed door position, the bellcrank creates a mechanical disadvantage that reduces the output force to prevent wrinkling. In the open door position, the bellcrank returns to a neutral state, restoring full spring force for reliable media advancement.
2Object-affected harmful factors
If devices are introduced to remove spring force to prevent wrinkling, then wrinkling of smaller media is reduced, but insufficient force remains to advance media through the nip
Solution Approach 1:
Instead of completely removing the spring force, the bellcrank mechanism dynamically modulates it. The mechanism provides partial force reduction when needed (access door closed) while maintaining full force capability when appropriate (access door open). This dynamic approach ensures that sufficient force is always available to advance media through the nip, while preventing wrinkling during specific operational states.
Solution Approach 2:
The bellcrank acts as an intermediary mechanism between the spring and the nip loading point. It transmits the spring force while modifying its magnitude based on the access door position. This intermediary function allows the system to maintain the spring's force-generating capability while controlling the actual force applied to the media, resolving the contradiction between preventing wrinkling and ensuring sufficient advancement force.
3Object-affected harmful factors
If the spring force is reduced to prevent wrinkling, then wrinkling of smaller media is minimized, but contact between heated and backup members may be insufficient
Solution Approach 1:
The bellcrank mechanism dynamically adjusts the force transmission to the nip, ensuring that sufficient contact force is maintained between the heated and backup members. When the access door is closed, the bellcrank reduces the force to prevent wrinkling while still maintaining adequate contact. When the access door opens, the bellcrank returns to its neutral position, restoring full contact force. This dynamic adjustment resolves the contradiction between preventing wrinkling and maintaining reliable member contact.
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
This solution effectively reduces wrinkling on smaller media while ensuring sufficient pressure for proper media advancement through the fusing nip, maintaining contact between the heated and backup members with a reduced but consistent force.
Implementation Method 1
A bellcrank contacts the nip loading spring such that upon opening of an access door of the imaging device, the bellcrank acts on the nip loading spring to reduce a force between the backup member and the heated member
Implementation Method 2
A cam pivots as an access door to the imaging device opens and engages the wire to compress the nip loading spring with a predetermined force during use
Implementation Method 3
A nip loading spring biases into contact the two members
Data Source
AI summary
A fuser assembly includes a heated member and backup member forming a fusing nip. A nip loading spring biases into contact the backup member and the heated member. A bellcrank contacts the nip loading spring such that upon opening of an access door of the imaging device, the bellcrank acts on the nip loading spring to reduce a force between the backup member and the heated member but keeping in contact the backup member and the heated member. The bellcrank typifies a wire or other flexible lever. A cam pivots as the access door opens and engages the wire to compress the nip loading spring during use.