Sheet Material Dispenser Roller Design to Reduce Tearing and Jamming
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Solution Overview
Problem
Existing sheet material dispensers often cause tearing and jamming issues due to mechanical arms contacting sheets in small areas, especially with thin materials like toilet seat covers, which lack tensile strength and fail to disengage properly.
Innovation Solution
A sheet material dispensing apparatus featuring a shaft connected to a supply roller and a retracting roller with radiused and truncated portions, a motor, an activating cam with a microswitch, and a flexible mounting plate that deflects during dispensing, allowing the supply roller to translate and disengage from the stack without tearing the sheets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a mechanical arm contacts the outermost sheet in a small area to tear it away from the stack, then the sheet can be separated from the remainder of the stack, but the sheet is prone to tearing during dispensing due to concentrated force on thin material with low tensile strength
Solution Approach 1:
The dispensing mechanism is divided into multiple rollers (supply roller, retracting roller, and intermediate rollers) that work together to distribute the dispensing force. Each roller contacts the sheet at different locations, segmenting the force application process to prevent concentrated stress on any single point of the thin sheet material.
Solution Approach 2:
The rollers are designed with specific surface properties and contact areas optimized for different functions: the supply roller has a larger contact area for gentle sheet extraction, while the retracting roller has specific radiused and truncated portions to prevent snagging. This local differentiation of contact qualities ensures force distribution appropriate for each stage of dispensing.
2Ease of operation
If a mechanical arm is used to dispense sheets, then the sheet can be torn away from the stack, but the mechanical arm may not disengage the outermost sheet after tearing, causing difficulty in ultimate removal of the sheet material from the dispenser
Solution Approach 1:
Instead of using a mechanical arm that grasps and pulls the sheet forward, the system uses a retracting roller that actively pulls the dispensed sheet backward away from the dispenser. This inverted approach ensures positive disengagement by creating a clear separation force that prevents the sheet from remaining snagged on the dispensing mechanism.
Solution Approach 2:
The retracting roller acts as an intermediary element between the dispensed sheet and the user. It provides a controlled interface that ensures the sheet is fully extracted and separated from the dispenser before being handed off to the user, eliminating the need for users to manually fish sheets out of the mechanism.
3Productivity
If the supply roller remains in contact with the stack during dispensing, then continuous sheet feeding is possible, but the roller may cause tearing or jamming of thin sheet materials
Solution Approach 1:
The supply roller operates with periodic engagement and disengagement cycles rather than continuous contact. During each dispensing cycle, the roller contacts the sheet stack to feed a sheet, then disengages to allow the retracting roller to pull the sheet away. This periodic action prevents excessive friction and heat buildup that could damage thin materials while maintaining adequate dispensing speed.
Solution Approach 2:
The system employs dynamic control of roller positions and contact forces. The supply roller's contact pressure and position are adjusted based on the dispensing phase, and the retracting roller dynamically engages to pull sheets away. This dynamic adjustment ensures optimal force application that maintains productivity while preventing sheet damage.
Data Source
AI summary
A sheet material dispensing apparatus, including a shaft operatively connected to a supply roller and a retracting roller, wherein the retracting roller has a radiused portion and at least one truncated portion; a motor configured to cause the shaft to rotate; an activating cam operatively connected to the supply roller; a microswitch operatively associated with the activating cam, the microswitch being configured to limit operation of the motor; a supporting plate engaged and disengaged by the retracting roller during operation, wherein the disengagement of the radiused portion from the supporting plate causes the supply roller to translate toward a wall of the apparatus; and at least one article of sheet material housed within the apparatus.