Power Tool Battery Pack Venting for Water- and Dust-Resistant Sealing
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Solution Overview
Problem
Existing battery packs for electric power tools lack effective water and dust resistance, particularly in handling gas generated from rechargeable battery cells, leading to potential damage and malfunction.
Innovation Solution
A battery pack design featuring a sealed rechargeable battery unit with a relief valve that releases gas when pressure builds up, a double-walled structure with a non-airproof outer shell, and a circuit board protected by waterproof sheets, ensuring gas is released externally while maintaining water and dust resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery case is sealed to improve water and dust resistance, then water and dust resistance is improved, but gas generated from battery cells cannot escape causing pressure buildup
Solution Approach 1:
The patent employs a relief valve mechanism with a flexible membrane that can deform under pressure. The membrane acts as a thin film that remains sealed under normal conditions but opens when gas pressure exceeds a predetermined threshold, allowing controlled gas release while maintaining water and dust resistance during normal operation.
Solution Approach 2:
The relief valve is designed to change its operational state based on pressure parameters. Under normal conditions, the valve maintains a sealed state for water and dust resistance. When gas generation causes pressure to reach a predetermined value, the pressure parameter change triggers the valve to open, releasing gas while maintaining the sealed structure's integrity.
2Object-affected harmful factors
If the battery case is made airtight to prevent water and dust ingress, then protection is improved, but internal gas pressure damages the battery case
Solution Approach 1:
The relief valve is pre-configured with a predetermined opening pressure threshold. This preliminary setup ensures that before gas pressure can damage the battery case, the relief valve automatically activates at the safe pressure threshold, releasing gas in advance and preventing strength degradation of the battery case structure.
Solution Approach 2:
The relief valve mechanism serves as a protective cushioning system that anticipates potential pressure buildup. By providing a predetermined pressure release path, it cushions the battery case structure from the harmful effects of excessive internal pressure, preventing damage before it occurs.
3Object-generated harmful factors
If pressure relief is enabled to release generated gas, then gas management is improved, but water and dust resistance is compromised
Solution Approach 1:
The relief valve utilizes a flexible membrane that maintains the sealed structure's integrity under normal conditions, preserving water and dust resistance. When gas pressure activates the valve, the membrane flexes to open the release path, and the valve design ensures that the opening mechanism itself maintains protection against water and dust ingress.
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 design prevents damage to the battery case and reduces failures by releasing gas externally, enhancing water and dust resistance and maintaining operational integrity.
Implementation Method 1
The relief valve is configured to open when the at least one rechargeable battery cell generates gas and builds up pressure in the battery case to a predetermined value or greater
Data Source
Figure 1~2
Figure 3
AI summary
A battery pack (12) for an electric power tool (10) is adapted for attachment in a removable manner to a tool body (11) of the electric power tool (10). The battery pack (12) includes an outer shell (21) and a rechargeable battery unit (22) accommodated in the outer shell (21). The rechargeable battery unit (22) includes at least one rechargeable battery cell (26), a battery case (25) that is sealed accommodating the at least one rechargeable battery cell (26), and a relief valve (29) arranged on the battery case (25). The relief valve (29) is configured to open when the at least one rechargeable battery cell (26) generates gas and builds up pressure in the battery case (25) to a predetermined value or greater.