Electric Pencil Sharpener Autostop Control via Sensor and Delay
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Solution Overview
Problem
Existing pencil sharpeners, both manual and electric, often cause excessive wear and waste by oversharpening, particularly in children due to lack of experience or coordination, and existing solutions like pencil tip stops or fly-away cutters can be confusing or unreliable, leading to unwanted noise and mechanical complexity.
Innovation Solution
An electric pencil sharpener with a conical housing, rotary blade, and a switch assembly that includes a shutoff mechanism and an electronic control unit providing a time delay between switch actuation and motor deactivation, along with a fly-away mechanism to prevent over-sharpening and ensure a consistent sharpening process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fly-away cutter mechanism is used to prevent over-sharpening, then the sharpening control is improved, but the device complexity increases and the motor continues to run causing unwanted noise
Solution Approach 1:
The patent replaces the mechanical fly-away cutter disengagement system with an electronic control system. A sensor detects when the pencil reaches the contact plate, sends a signal to a control circuit, which then deactivates the motor. This substitution eliminates the mechanical complexity of fly-away cutters while maintaining reliable sharpening control and stopping the motor to prevent noise.
Solution Approach 2:
The electronic control system automatically detects when sharpening is complete through the sensor-contact plate interaction and autonomously deactivates the motor without requiring mechanical disengagement. The system serves itself by using the pencil's own contact with the plate as the trigger signal, eliminating the need for complex mechanical self-disengagement mechanisms.
2Reliability
If a mechanical pencil-tip contact plate switch is used to stop the motor, then the sharpening control is improved, but the device complexity increases due to precise mechanical tolerances required
Solution Approach 1:
The patent replaces the mechanical switch system requiring precise tolerances with an electronic sensor system. The sensor detects the pencil's contact with the plate and triggers an electronic control circuit to stop the motor. This eliminates the need for precision-machined mechanical switches and their associated tolerance requirements, simplifying the overall device while maintaining reliable motor shutdown control.
3Reliability
If pencil tip stops providing resistance feedback are used, then the sharpening control is improved, but the ease of operation deteriorates because children cannot sense the feedback
Solution Approach 1:
The patent replaces the tactile resistance feedback system with an electronic sensor-based detection system. The sensor automatically detects when the pencil reaches the contact plate and triggers motor shutdown, eliminating the need for users to sense resistance changes. This makes the system equally effective for children who cannot detect subtle resistance or pitch changes, significantly improving ease of operation while maintaining sharpening control.
Solution Approach 2:
The system implements automatic electronic feedback through the sensor that detects pencil contact with the plate and triggers motor shutdown. This electronic feedback loop replaces the mechanical resistance feedback, providing reliable sharpening control that does not depend on user sensory detection capabilities, making it accessible to children and inexperienced users.
Data Source
AI summary
An electric pencil sharpener comprising a motor; a cutter assembly operatively connected to the motor, wherein the cutter assembly further includes: a conical housing defining a conical cavity therein for receiving a pencil; and at least one rotary blade mounted in close proximity to the conical cavity, wherein the at least one rotary blade further includes spiral cutting edges for sharpening the pencil; a switch assembly positioned at the narrow end of the conical housing, wherein the switch assembly further includes: a shutoff switch operative to deactivate the motor; mechanical means for actuating the shutoff switch when a desired degree of sharpening has been achieved by the cutter assembly; and an electronic control unit in electrical communication with the switch assembly and the motor, wherein the electronic control unit is operative to provide a delay of a predetermined period of time between when the shutoff switch is activated and when the motor is deactivated.