Air-Spring Power Tool Flapper Valve for Unintended-Firing Control
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Solution Overview
Problem
Pneumatic nailers using air springs are susceptible to failures or malfunctions that can result in unintended and dangerous firing of fasteners due to the release of the piston with significant force, and existing electronic safety systems are prone to failure.
Innovation Solution
A power tool incorporating an air spring cylinder with a flapper valve that seals the air spring cylinder from the air accumulator in the non-firing position, using a pivot pin and plunger mechanism to control the release of compressed air, reducing the force applied to the piston in case of inadvertent release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single tooth of a pinion gear is used to prevent piston release, then the device complexity is reduced, but the reliability deteriorates because failure or slight rotation of the motor can cause unintended firing
Solution Approach 1:
The safety mechanism is segmented into two independent components: a mechanical safety device (lifter gear and rack) and an electronic safety system (sensor and controller). This segmentation ensures that failure of one component does not compromise overall safety, as the other component remains functional to prevent unintended firing.
Solution Approach 2:
The mechanical safety device is designed to engage beforehand to prevent piston release. The lifter gear normally engages with the rack to hold the piston in place, and only releases when both mechanical and electronic safety conditions are satisfied. This beforehand engagement provides a safety buffer against motor failure or unintended rotation.
2Extent of automation
If electronic safety systems are used to detect workpiece contact, then the manufacturing precision and automation are improved, but the reliability deteriorates due to susceptibility to failure and disablement
Solution Approach 1:
The mechanical safety device acts as an intermediary between the electronic safety system and the piston release mechanism. Even when the electronic system fails, the mechanical lifter gear and rack provide a physical barrier that prevents piston release unless properly engaged, serving as a reliable intermediary safety layer.
Solution Approach 2:
The patent replaces purely mechanical safety mechanisms with a combined electronic-mechanical system. The electronic sensor and controller monitor workpiece contact and control the motor, while the mechanical lifter gear and rack provide fail-safe physical prevention of unintended firing, substituting electronic control with reliable mechanical backup.
3Productivity
If compressed air is used to power the nailer, then the productivity and driving force are improved, but the object-generated harmful factors worsen due to unintended firing creating dangerous projectiles
Solution Approach 1:
The electronic safety system provides feedback by using a sensor to detect whether the workpiece is properly positioned before allowing the motor to rotate and release the piston. This feedback loop ensures that compressed air is only released when safe, preventing unintended firing while maintaining high productivity during proper operation.
Solution Approach 2:
The mechanical safety device performs preliminary action by engaging the lifter gear with the rack to prevent piston release before the firing sequence is initiated. Only after both mechanical and electronic safety conditions are satisfied does the system allow the compressed air to drive the piston, eliminating the harmful effect of unintended firing while preserving driving efficiency.
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 system effectively reduces the force applied to the piston during unintended releases, enhancing safety by minimizing the impact of accidental firings and maintaining operational efficiency without increasing the tool's weight or altering its operation.
Implementation Method 1
An air spring uses the compressibility of gas, which may be air, nitrogen, etc., (herein referred to simply as 'air') to store energy which is released to forcefully move a driver which in turn forces the fastener into a workpiece.
Implementation Method 2
When the piston is released the compressed gas forces the piston to move rapidly along a working axis of the nailer.
Implementation Method 3
A WCE is typically a springloaded mechanism which protrudes forwardly of the nose portion of the nail gun from which a nail is driven. In operation, the WCE is pressed against a work piece into which a nail is to be driven. As the WCE is pressed against the work piece, the WCE compresses the spring and generates an axial movement
Data Source
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Figure 3
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AI summary
A power tool includes an air spring cylinder. A piston is movably positioned within the cylinder. A head valve assembly of the power tool includes a flapper valve configured to seal the air spring cylinder from an air accumulator when the flapper valve is in a non-firing position.