Combustion Fastener Tool Lockout for Piston Return
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Solution Overview
Problem
Combustion-powered fastener-driving tools are limited to sequential operation due to the slow vacuum return of the piston, which restricts their ability to operate in a repetitive cycle mode and is prone to manufacturing deviations and shock-induced damage, leading to incomplete piston return and chamber opening issues.
Innovation Solution
An electromechanical lockout device is integrated to manage the combustion chamber in a sealed position for a specific duration, using an electromagnetic latch to prevent the valve sleeve from opening the chamber until the piston returns to its pre-firing position, accommodating manufacturing tolerances and reducing shock-induced damage by allowing valve sleeve overtravel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If self-generative vacuum is used for piston return, then the tool can operate with simpler structure, but the piston return time is significantly longer limiting repetitive cycle operation
Solution Approach 1:
The lockout device is activated in advance to seal the combustion chamber before piston return begins, preparing the system for rapid vacuum generation. This preliminary sealing action ensures that the vacuum can be generated effectively without chamber opening interruptions.
Solution Approach 2:
The lockout device maintains continuous chamber sealing throughout the piston return cycle, preventing any interruption in the vacuum generation process. This continuous sealing enables the piston to complete its return stroke without delay, supporting higher firing rates.
2Reliability
If the valve sleeve is prevented from overtravel, then the combustion chamber sealing is maintained, but the lockout device is subjected to shock-induced damage
Solution Approach 1:
The dampening element is positioned to engage before the valve sleeve can overtravel and cause shock damage. This cushioning element absorbs the excess kinetic energy of the valve sleeve, protecting the lockout device from shock-induced damage while maintaining chamber sealing.
Solution Approach 2:
The dampening element acts as an intermediary between the valve sleeve and the lockout device. It mediates the interaction by absorbing shock energy, preventing direct transmission of harmful forces to the lockout device while still allowing the valve sleeve to perform its sealing function.
3Reliability
If the lockout device is positioned to engage the valve sleeve, then the chamber sealing is controlled, but manufacturing tolerances cause inconsistent engagement
Solution Approach 1:
The lockout device is designed with adjustable engagement parameters, allowing the engagement force and position to be optimized. This adjustability compensates for manufacturing tolerances in the valve sleeve, ensuring consistent chamber sealing across different production units.
Solution Approach 2:
The lockout device incorporates dynamic engagement characteristics, allowing it to adapt its engagement force based on the actual position and condition of the valve sleeve. This dynamic adjustment ensures reliable chamber sealing despite variations in manufacturing precision.
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
Enables reliable vacuum return of the piston and maintains the combustion chamber closed during repetitive cycles, ensuring complete piston return and reducing the risk of premature chamber opening, thus enhancing the tool's operational efficiency and durability.
Implementation Method 1
an electromagnet configured for engaging the valve sleeve in a sealed position
Implementation Method 2
the combustion in the chamber causes the acceleration of the piston/driver blade assembly
Implementation Method 3
the surrounding lower temperature aluminum components cool and collapse the gases, thereby creating a vacuum
Data Source
Figure 1
Figure 2
Figure 3~3A
AI summary
A combustion-powered fastener-driving tool (10) includes a combustion-powered power source (14) including a cylinder head (42) and a combustion chamber (18) defined by the cylinder head, a valve sleeve (36) and an upper surface of a reciprocating piston (22), the valve sleeve reciprocable relative to the cylinder head between a rest position and a pre-firing position The valve sleeve has a range of positions between a first sealing position in which the combustion chamber is closed, and said per-firing position in which the valve sleeve is prevented from further movement A lockout device is associated with the power source and has an actuated position configured for preventing the reciprocation of the valve sleeve beyond the first sealed position to open the combustion chamber, but permitting movement of the valve sleeve from the first sealed position to the per-firing position until the piston returns to a piston pre-firing position post combustion