Exciter Piston Sealing for Pneumatic Handheld Tools
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Solution Overview
Problem
Existing hand-held power tools with pneumatic percussion mechanisms face challenges in sealing efficiency due to the need for elastic sealing rings that must be stretched during assembly, which can lead to assembly difficulties and potential leaks.
Innovation Solution
The design features a pot-shaped base body with a tubular jacket body and a sealing ring placed in an annular groove, allowing the sealing ring to be slid over the side wall without stretching, and then the jacket body is pushed onto the side wall to close the groove, ensuring a secure and airtight seal. The sealing ring can be made of materials like plastic with a hardness of at least 85 Shore or brass alloy, and the base and jacket bodies can be made of different thermoplastics for optimal temperature resistance and friction coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an elastic sealing ring is used that must be stretched during assembly, then sealing capability is achieved, but assembly difficulty increases and potential leaks occur
Solution Approach 1:
The exciter piston is divided into a base body and a jacket body that are separate during assembly. The sealing ring is placed in a groove on the base body before the jacket is assembled, allowing the sealing ring to be installed without stretching while maintaining its sealing function when the jacket is in place.
Solution Approach 2:
The sealing ring is pre-installed in the groove on the base body before the jacket body is assembled. This preliminary placement allows the sealing ring to be positioned correctly without being stretched, and the jacket body is then closed over it to complete the sealing arrangement.
2Ease of operation
If the sealing ring is made softer for easier assembly, then assembly becomes easier, but sealing efficiency and temperature resistance decrease
Solution Approach 1:
By separating the installation process into two stages (placing the sealing ring in the groove, then closing the jacket), the sealing ring can be made from harder material (85-90 Shore) that provides better sealing efficiency and temperature resistance, while still allowing easy assembly in the open groove configuration.
3Ease of manufacture
If the sealing ring is stretched during assembly to fit over the side wall, then the sealing ring can be installed, but the sealing ring may be damaged or lose its sealing properties
Solution Approach 1:
The sealing ring is pre-positioned in the groove on the base body before the jacket body is closed. This allows the sealing ring to be installed in its natural, unstretched state, preserving its material properties and sealing durability while still achieving proper installation.
4Productivity
If dead volumes are not minimized in the pneumatic chamber, then assembly is simpler, but pneumatic efficiency and performance decrease
Solution Approach 1:
The sealing ring is pre-installed in the groove before the jacket body is closed, allowing the jacket to be positioned precisely to minimize dead volumes in the pneumatic chamber while maintaining assembly simplicity. The base body with the pre-installed sealing ring serves as a template for optimal jacket positioning.
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 configuration simplifies assembly, enhances sealing efficiency, and reduces dead volumes, providing a reliable and durable pneumatic seal that maintains performance across a range of temperatures.
Implementation Method 1
A sealing ring with a hardness from 85 Shore, in particular in the range between 85 Shore and 90 Shore, has lower coefficients of friction in the metal guide tube of the hammer mechanism.
Implementation Method 2
The base body can be selected with regard to temperature resistance and the jacket body with regard to a favorable coefficient of friction with the guide tube. The base body is formed in particular from a plastic which has a high degree of rigidity at elevated temperatures in the range between 100° C. (Celsius) and 150° C.
Data Source
Figure 1~3
Figure 4~5
AI summary
A hand-held power tool (1) has a tool holder (2) for receiving and locking a tool (3), a pneumatic impact mechanism (8), and a motor (12). The pneumatic impact mechanism (8) has, on a working shaft (4), an exciter piston (13), a striker (9), and a pneumatic chamber (23) enclosed between the exciter piston (13) and the striker (9). The motor (12) drives the exciter piston (13). The exciter piston (13) has a cup-shaped base (16), a sealing ring (18), and a tubular outer body (17). The cup-shaped base (16) has a side wall (21) enclosing the working shaft (4) and a collar (19) projecting radially from the side wall (21). The hollow cylindrical shell body (17) is arranged on the base body (16) surrounding the side wall (21) and spaced apart from the collar (19) by a groove (27) along the working axis (4). The sealing ring (18) is arranged in the groove (27).The side wall (21) encloses a cylindrical cavity in which a bearing (34, 35) for a connecting rod (33) is arranged.