| 摘要 |
PROBLEM TO BE SOLVED: To reduce an overload operation of a motor to a practical level by providing a monitoring circuit which monitors an operation pressure of a motor for lifting of a suction grill to prevent continued rotation of the motor under an overload. SOLUTION: A drive system to lift or lower a suction grill 119, namely, a drive system comprising main pulleys 100A and 100B, a shaft 110, a clutch containing a rotating force transmission means, a motor 38 for lifting or lowering the suction grill and the like is arranged collectively on a support plate 151 extending into an opening part of a unit body 50a. A motor operation voltage detection circuit monitors a voltage when the motor 38 is in operation to detect whether or not a load current of the motor 38 is within a normal range. The motor 38 is stopped if a load current of the motor 38 exceeds a value (e.g. 600mA) determined for the rating of the motor. Thus, the overload operation of the motor can be reduced to a practical level. |
