| 摘要 |
A power-driven tool comprises a drive motor and gearbox. At least one chamber is provided in the wall of the gearbox to permit pressure-balancing between the interior and the external atmosphere. In the preferred embodiment, the pressure -balancing chamber contains a diaphragm, esp. of an elastic, heat-resistant material impermeable to air and lubricant. The outer opening of the pressure-balancing chamber is pref. closed by an air-permeable filter, more specifically of a sintered material.
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