| 摘要 |
An improved driving mechanism for a motor driven retractable down draft vent system of the type having a vent inlet member slidably mounted for vertical movement between a lowered position and a raised position. A first drive member is fixedly connected to a drive motor which drives the first drive member between a first position and a second position corresponding to the lowered and raised positions of the vent member, respectively. A second drive member supported from the movable vent inlet member is disposed in the path of the first drive member. The first drive member abuttingly drivingly engages the second drive member in moving from its first to its second position to positively drive the vent inlet member from its lowered to its raised position. The second drive member is simply driven by the weight of the vent inlet member to follow the first drive member when it returns from its second to its first position to releasably carry the vent inlet member to its lowered position. Since there is no positive connection between the first and second drive members, the only force applied to an obstruction blocking the return of the vent inlet member will be the weight of the vent inlet member itself. Consequently, neither the obstruction, the vent inlet member nor the motor is likely to be damaged.
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