Pneumatic Percussion Mechanism Sealing Element Design
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Solution Overview
Problem
Existing pneumatic percussion mechanisms in hand-held power tools require high fitting accuracy and mechanical stability to ensure reliable switching on and off, particularly during percussive operations, to prevent increased load on the tool and user due to energy transfer during empty strikes.
Innovation Solution
A pneumatic percussion mechanism with a pot-shaped exciter cylinder and a flying piston featuring a recess and ventilation openings, where the sealing element seals the ventilation openings during impact but allows airflow through the recess to compensate for air losses, maintaining airtightness and preventing parasitic ventilation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If ventilation openings are provided in the exciter cylinder to compensate for air losses, then the pneumatic space can be ventilated, but parasitic ventilation occurs when the sealing element passes through the ventilation openings
Solution Approach 1:
A closing element is introduced as an intermediary component that selectively controls the ventilation openings. This closing element is designed to close the ventilation openings when the sealing element passes through them, preventing parasitic ventilation while allowing air flow at other times to compensate for air losses in the pneumatic space.
2Reliability
If high fitting accuracy is required between moving elements to ensure airtight seal, then reliable switching is achieved, but mechanical stability and manufacturing complexity increase
Solution Approach 1:
The closing element acts as a mediator that manages the ventilation openings without requiring high fitting accuracy between the flying piston and exciter cylinder walls. This intermediary component handles the sealing function for the ventilation openings independently, reducing the mechanical stability requirements for the main moving elements while maintaining reliable switching.
3Reliability
If the sealing element continuously contacts the jacket-shaped wall to maintain seal, then airtightness is maintained, but air flow compensation through the recess is blocked
Solution Approach 1:
The sealing element is designed with dynamic contact characteristics where it contacts the jacket-shaped wall in certain positions to maintain airtightness, but is spaced apart in the region of the recess to allow air flow compensation. This dynamic positioning enables the sealing element to alternately seal and vent the pneumatic space during the operational cycle.
Solution Approach 2:
The sealing element performs periodic sealing and venting actions as it moves through different positions relative to the recess and ventilation openings. During impact phases, it seals against the wall for airtightness; during recovery phases, it spaces apart from the recess to allow air flow compensation, creating a periodic action that balances sealing and venting requirements.
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 design enhances mechanical stability and enables reliable switching of the percussion mechanism, reducing the load on the tool and user by efficiently managing air flow and energy transfer during both striking and empty strikes.
Implementation Method 1
The flying piston has a sealing element that seals the at least one ventilation opening when the sealing element is opposite the at least one ventilation opening, and that is spaced apart from the jacket-shaped wall in the region of the recess when the sealing element is opposite the recess.
Implementation Method 2
The indentation enables ventilation to compensate for the air losses of the pneumatic space, in that air can flow past a free piston in the area of the indentations during the period of time that the sealing element is opposite the indentation.
Data Source
Figure 1
Figure 2~4
AI summary
The machine tool includes a pneumatic impact mechanism comprising a pot-shaped exciter cylinder (21) with an interior space (31) open in the impact direction (26) and a piston (22) movable within the interior space (31). A recess (32) is provided in a shell-shaped wall (39) of the interior space (31), and at least one ventilation opening (35) is spaced apart from the recess (32) in the impact direction (26). The piston (22) includes a sealing element (53) that seals the at least one ventilation opening (35) when the sealing element (53) is opposite the at least one ventilation opening (35), and which is spaced apart from the shell-shaped wall (39) in the region of the recess (53) when the sealing element (53) is opposite the recess.