Pneumatic Impact Tool Valve Mechanism for Bit Shaft Impact Control
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Solution Overview
Problem
Existing pneumatic ground piercing tools experience unwanted impacts of the bit shaft against a front stop due to sudden deceleration, leading to potential loosening or fracture of threaded joints and wear of sealing components.
Innovation Solution
A valve mechanism is introduced that allows communication between the front and rear chambers when the bit shaft reaches its forwardmost position, negating the gas spring effect and preventing the bit shaft from impacting the stop, using a seal and vent grooves or passages to control the flow of compressed air and maintain the bit shaft in its extended position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gas spring is used to prevent bit shaft impact, then the bit shaft is protected from unwanted impacts, but the gas spring may be activated prematurely causing premature impact prevention
Solution Approach 1:
The system dynamically switches between two operational modes: normal operation mode where the gas spring is active to prevent unwanted impacts, and impact mode where the valve opens to allow compressed air to escape, enabling the bit shaft to impact the stop deliberately. This dynamic switching resolves the contradiction by allowing impact prevention during normal operation while enabling controlled impact during drilling.
Solution Approach 2:
The valve acts as an intermediary mechanism that controls the communication between the front and rear chambers. During normal operation, the valve closes to maintain the gas spring effect. During impact mode, the valve opens to allow compressed air to escape from the front chamber to the rear chamber, mediating the transition between impact prevention and controlled impact states.
2Reliability
If compressed air is trapped in the front chamber to form a gas spring, then unwanted impacts are prevented, but the bit shaft cannot be positioned forwardly for drilling
Solution Approach 1:
The system dynamically adjusts the pressure distribution in the chambers by opening the valve during impact mode, allowing compressed air to move from the front chamber to the rear chamber. This dynamic pressure redistribution enables the bit shaft to be positioned forwardly for drilling while maintaining impact prevention during normal operation.
Solution Approach 2:
The system changes the pressure parameter distribution by controlling valve opening and closing. When the valve is closed, high pressure is maintained in the front chamber to form the gas spring. When the valve opens during impact mode, pressure equalizes between chambers, enabling forward positioning of the bit shaft for drilling operations.
3Reliability
If the bit shaft is forced forward by gas spring pressure, then impact prevention is achieved, but the threaded joint may loosen or fracture due to sudden deceleration
Solution Approach 1:
The system converts the potentially harmful sudden deceleration force into a beneficial controlled impact. By allowing the bit shaft to impact the stop deliberately in a controlled manner (impact mode), the sudden deceleration is transformed from a harmful force that causes joint loosening into a controlled mechanical action that advances the bit shaft for drilling.
Solution Approach 2:
The system prepares for controlled impact by maintaining the bit shaft in a retracted position during normal operation, then deliberately activates the impact mode before the actual drilling operation begins. This preliminary positioning and controlled activation prevents unwanted impacts while enabling deliberate forward movement when needed.
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 prevents unwanted impacts of the bit shaft against the stop, reducing wear on sealing components and maintaining the integrity of the threaded joint, while ensuring consistent operation by controlling the air spring effect.
Implementation Method 1
Compressed fluid is supplied to the front chamber to form a gas spring that prevents the bit shaft from impacting against a front stop
Implementation Method 2
The valve permits compressed air to pass from the front chamber to the rear chamber
Data Source
AI summary
A ground piercing tool as according to the invention has a front head assembly mounted on a bit shaft. A mid-portion of the bit shaft is mounted between front and rear chambers. Compressed fluid is supplied to the front chamber to form a gas spring that prevents the bit shaft from impacting against a front stop when it receives a blow from the striker. A valve is provided that includes a passage that permits communication between the front chamber and the rear chamber when the bit shaft is in a forwardmost position wherein it contacts the front stop. The valve permits compressed air to pass from the front chamber to the rear chamber, negating the gas spring when the bit shaft is in the forwardmost position.