Polymer Exciter Piston Copper Rings Friction
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Solution Overview
Problem
Existing hand-held power tools with pneumatic percussion mechanisms face challenges in thermal efficiency and stress due to differing thermal expansion coefficients between materials, leading to increased friction and potential mechanical failures.
Innovation Solution
The use of a polymer-made exciter piston with copper rings and a polymer guide tube, where the copper rings reduce friction and compensate for thermal expansion differences, ensuring efficient thermal management and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the exciter piston and guide tube are made of the same polymer material to match thermal expansion coefficients, then thermal efficiency improves and gap dimensions can be minimized, but friction increases due to direct polymer-to-polymer contact
Solution Approach 1:
The exciter piston is designed with different materials for different functional zones: the main body is polymer for thermal efficiency, while copper rings are embedded at the sliding contact surfaces to reduce friction. This local differentiation allows each area to optimize for its specific function.
Solution Approach 2:
The exciter piston combines polymer and copper materials in a composite structure. The polymer base provides thermal expansion matching with the guide tube, while copper inserts provide low-friction sliding surfaces at the contact points with the guide tube.
2Force
If copper rings are added to the exciter piston to reduce friction, then friction and thermal loss decrease, but device complexity increases due to additional components
Solution Approach 1:
The copper friction-reducing rings are integrated directly into the polymer exciter piston body, merging the friction-reduction function with the piston structure itself rather than using separate movable components. This reduces device complexity while maintaining the friction-reduction benefit.
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 enhances thermal efficiency and reduces stress, allowing for a smaller gap dimension in the exciter piston and improved performance by minimizing thermal losses and mechanical stress, thus enhancing the reliability of the hammer drill mechanism.
Implementation Method 1
The rings containing copper can reduce the coefficient of friction to such an extent that an increased thermal loss and stress caused by different coefficients of thermal expansion are overcompensated.
Implementation Method 2
The exciter piston is preferably guided in a guide tube made of a polymer, which thermally insulates the pneumatic chamber in the radial direction.
Implementation Method 3
The use of the same material for the guide tube and the exciter piston ensures that they have the same thermal expansion coefficient, which in turn allows the exciter piston to be manufactured with a small gap dimension.
Data Source
AI summary
The hand-held power tool of the invention comprises a tool holder (2) for accommodating a tool along an operating axis (11). A pneumatic percussion mechanism (6) includes an exciter piston (13) which is periodically urged along the operating axis (11) by a motor (5), and a percussion member (14) which is coupled to the exciter piston (13) via a pneumatic chamber (18). The exciter piston (13) has a cylindrical main body (21) made of a polymer. One or more copper-containing rings (24) embrace the main body (21). The rings (24) protrude radially from the main body (21).