Combustion Tool Lockout Device Prevents Premature Valve Sleeve Unsealing
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Solution Overview
Problem
Conventional combustion-powered-fastener-driving tools malfunction when the valve sleeve unseals before the piston returns to the pre-firing position, leading to loss of vacuum pressure and subsequent tool malfunction.
Innovation Solution
A lockout device is introduced to ensure the valve sleeve remains sealed until the piston returns to the pre-firing position, utilizing a retainer pin and retainer pin receiver mechanism operably connected to the trigger, preventing premature unsealing of the combustion chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the workpiece-contact element is removed from the workpiece before the piston returns to the pre-firing position, then the operator can prepare for the next operation, but the valve sleeve moves to the unsealed position causing loss of vacuum pressure and tool malfunction
Solution Approach 1:
The lockout device is activated in advance when the trigger is pulled, securing the valve sleeve in the sealed position before the piston completes its return stroke. This preliminary locking action ensures that even if the workpiece-contact element is removed early, the combustion chamber remains sealed and vacuum pressure is maintained until the piston returns to the pre-firing position.
2Ease of operation
If the valve sleeve is allowed to move freely between sealed and unsealed positions, then the operator has flexibility in operation timing, but the combustion chamber may unseal prematurely causing vacuum pressure loss
Solution Approach 1:
The lockout device provides dynamic control of the valve sleeve position based on trigger actuation. When the trigger is pulled, the lockout device engages to lock the valve sleeve in the sealed position. When the trigger is released, the workpiece-contact element returns to the extended position, causing the lockout device to disengage and allowing the valve sleeve to move to the unsealed position. This dynamic control maintains reliability while preserving operational flexibility.
3Reliability
If a lockout device is added to prevent premature unsealing, then vacuum pressure is maintained reliably, but the device complexity increases
Solution Approach 1:
The lockout device utilizes the existing trigger mechanism and workpiece-contact element movement to control the valve sleeve positioning. The same mechanical movements that control firing also control the lockout engagement and disengagement, allowing one set of mechanical components to serve multiple functions: triggering the spark, locking the valve sleeve during firing, and releasing the lock after firing. This multi-functionality reduces the need for additional dedicated components.
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 ensures consistent operation by maintaining the combustion chamber sealed until the piston is fully retracted, preventing premature loss of vacuum pressure and ensuring reliable fastener driving cycles.
Implementation Method 1
a spark plug to spark and ignite the fuel/air mixture in the combustion chamber. This generates high-pressure combustion gases that expand and force the piston to move through the cylinder
Implementation Method 2
some of the combustion gases that propel the cylinder exhaust through the check valves to atmosphere. This combined with heat exchange to the atmosphere and the fact that the combustion chamber remains sealed during firing generates a vacuum pressure above the piston and causes the piston to retract
Data Source
AI summary
The present disclosure provides various embodiments of a combustion-powered-fastener-driving tool that include a lockout device to ensure the tool's valve sleeve doesn't move to an unsealed position and the tool's combustion chamber remains sealed until the piston returns to the pre-firing position. The lockout device is engageable with a lockout device engaging member operably connected to the tool's trigger, which gives the operator direct control over locking the valve sleeve in the unsealed position.