Heat Roller Coupling Structure Preventing Cap Slip
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Solution Overview
Problem
The existing heat rollers in image forming devices experience cap slippage during high-speed operations, leading to short circuits due to inadequate coupling between the gear cap and the heat roller pipe, which can result in twisting of connection terminals and damage.
Innovation Solution
A heat roller design featuring a gear cap divided into a cap and a gear, with a coupling unit that includes elastic members and projections to securely couple the cap, internal expanding pipe, and roller pipe, preventing slippage and enhancing the coupling force between components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If screw coupling is used between gear cap and heat roller pipe, then assembly is simple, but cap slips off during counter rotation causing short circuit
Solution Approach 1:
The gear cap is divided into two separate components: a cap portion and a gear portion. The cap portion couples with the heat roller pipe through press-fit engagement, while the gear portion couples with the cap portion through protrusion-recess engagement. This segmentation allows each component to be optimized for its specific function, preventing slippage during counter rotation.
Solution Approach 2:
The gear portion is nested within the cap portion, forming an integrated gear cap assembly. The gear portion fits into the cap portion through precisely matched protrusions and recesses, creating a nested structure that prevents relative movement between the gear and cap during operation.
2Strength
If male-female screw threads are used, then coupling force is sufficient, but screw threads are demolished under high torque causing rotation
Solution Approach 1:
The screw thread structure is completely removed from the design. Instead of using male-female screw threads between the gear cap and heat roller pipe, the patent employs a press-fit coupling mechanism with interference fit, eliminating the vulnerable threaded connection that could be demolished under high torque.
Solution Approach 2:
The cap portion is designed with a press-fit structure that creates preliminary engagement with the heat roller pipe before operation begins. The interference fit between the cap portion's outer surface and the pipe's inner surface establishes a strong initial coupling that prevents slippage under operational loads.
3Device complexity
If cap and gear are integrated, then structure is simple, but coupling force between cap and internal expanding pipe is insufficient
Solution Approach 1:
The gear cap is segmented into a cap portion and a gear portion that are coupled together. This segmentation allows the cap portion to be specifically designed for strong press-fit engagement with the heat roller pipe, while the gear portion is designed for meshing engagement, achieving both strong coupling and proper gear function.
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
The solution effectively prevents cap slippage and short circuits by providing a robust coupling mechanism that maintains contact between the cap, internal expanding pipe, and roller pipe, even under high-speed and temperature variations, ensuring reliable operation of the heat roller.
Implementation Method 1
a coupling unit which presses an inner surface of the internal expanding pipe towards the roller pipe
Implementation Method 2
current flows through the resistive heat element 12 via the electrodes 13a and 14a and the connection terminals 15 and 15 when alternative current (AC) from an AC power source is applied to carbon brushes 17a and 17b
Implementation Method 3
an internal expanding pipe 16 which strongly pushes the resistive heat element 12 toward the roller pipe 11
Data Source
AI summary
A heat roller for a laser printer has a roller pipe, a resistive heat element accommodated in the roller pipe, an internal expanding pipe installed in the roller pipe which restricts the resistive heat element by pushing the resistive heat element toward the roller pipe, caps coupled to both end portions of the internal expanding pipe and provided with electrodes which supply a current to the resistive heat element, a gear coupled to any one of the caps, and a coupling unit which restricts at least one of the caps from slipping along the internal expanding pipe. The heat roller has the enhanced secure coupling between the internal expanding pipe, the roller pipe, the coil and the insulation layer. Accordingly, it is possible to prevent slip off and coil short circuit.