Hand-held Pneumatic Hammer Drill Air Spring Stiffness Control
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Solution Overview
Problem
High-powered hand-held pneumatic hammer drills face difficulties in controlling the guidance of the tool when pressed against a substrate, leading to excessive loading and reduced precision during chiseling operations.
Innovation Solution
A hand-held percussion power tool with a pneumatic chamber, an electric motor, and a percussion mechanism that includes an exciter, a pneumatic chamber, an intermediate chamber, and a rivet header, utilizing a check valve and shut-off valve to control air flow and pressure, allowing for increased stiffness and percussive power adjustment, enabling precise positioning and robust operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the pneumatic chamber allows free air flow between chambers, then the air spring remains soft and easy to compress, but the tool positioning precision and stiffness are reduced
Solution Approach 1:
The patent implements dynamic control of air flow between chambers using valves that respond to operational conditions. The first valve allows air flow during initial positioning, while the second valve restricts flow during chiseling operations, enabling the air spring to transition between soft and stiff states based on operational phase
Solution Approach 2:
The patent changes the air flow parameters between chambers by introducing controllable valves. The first valve opens during positioning to maintain softness, while the second valve closes during chiseling to increase stiffness, thereby adjusting the physical parameters of the air spring to match operational requirements
2Ease of operation
If the pneumatic chamber volume is increased to reduce percussive power, then tool control improves, but the percussive power becomes insufficient for effective chiseling
Solution Approach 1:
The patent dynamically adjusts the effective pneumatic chamber volume during operation. The second valve restricts air flow between chambers during chiseling, effectively reducing the compliant volume and increasing percussive power when needed, while maintaining better tool control through the controlled air spring stiffness
Solution Approach 2:
The patent applies preliminary anti-action by using the air spring to counterbalance the weight of the tool and compensate for friction forces before chiseling operations begin. This preliminary compensation reduces the required percussive power and improves tool control during subsequent chiseling operations
3Productivity
If the percussion mechanism remains active during non-contact periods, then readiness for operation is maintained, but excessive loading and wear occur
Solution Approach 1:
The patent uses feedback from user contact pressure to control the percussion mechanism activation. The operating condition detection unit detects when the user applies contact pressure to the tool, and the control unit activates or deactivates the percussion mechanism accordingly, preventing operation during non-contact periods when it would cause excessive loading
Solution Approach 2:
The system automatically activates or deactivates the percussion mechanism based on detected operational conditions without requiring manual intervention. The control unit monitors contact pressure and self-regulates the percussion mechanism state, ensuring it operates only when needed and remains ready for immediate operation when activated
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 solution enhances the tool's ability to position itself on a substrate with increased stiffness and adjustable percussive power, improving control and reducing the risk of excessive loading, thereby facilitating more precise and robust chiseling operations.
Implementation Method 1
A pneumatic chamber forms an air spring, which couples a percussion means to an exciter that is moved by the motor
Implementation Method 2
A check valve, which blocks air flowing from the first channel opening to the second channel opening and opens to allow air to flow from the second channel opening to the first channel opening is arranged in the channel
Implementation Method 3
A shut-off valve is arranged at the second channel opening and is forced into a position in which it seals the second channel opening when the rivet header is in the working position
Data Source
AI summary
The invention relates to a striking hand-held machine tool having a tool holder for holding a striking tool on a working shaft, an electric motor, and a striking mechanism. In the striking direction, the striking mechanism has an exciter piston, a pneumatic chamber, a striker, an intermediate chamber and a rivet snap following one another. A closed channel connects a first channel opening in the pneumatic chamber and a second channel opening in the intermediate chamber. A non-return valve, which shuts off during an air flow from the first channel opening to the second channel opening and opens during an air flow from the second channel opening to the first channel opening, is arranged in the channel. Arranged on the second channel opening is a shut-off valve, which is forced into a position closing the second channel opening when the rivet snap is in the working position.