| 摘要 |
PURPOSE:To ensure cleaning or exchange of the filter by a method wherein the operating time of a fan is integrated and when the integrated operating time has arrived at a predetermined value, it is informed. CONSTITUTION:A circuit, consisting of a movable contact piece 36, movable contacts 37, 38, a motor 33 and an indication lamp 48, is connected in series to the contacts (a), (b) of a timer 43 and to a fan motor 20 in parallel. The motor 33 is connected to the contact 38 and the indication lamp 48 is connected to the contact 37 respectively while the movable contact piece 36 contacts with the contact 38 during the normal operating condition of the instrument, therefore, a cam 34 is rotated in a low speed by the motor 33 during the conduction of the fan. When the conduction of the fan is cut once and the fan is conducted again, the cam continues it's rotation from the position where the conduction is cut last time. That means the cam 34 integrates the conducting time. When the integrated time has arrived at a predetermined value, the movable contact piece 36 is switched from the contact 37 to the contact 37 to stop the cam 34 and inform by lightening the indicating lamp 48. In this case, the pawl 34a of the cam 34 has been arrived at a position opposing to the movable pawl 39a, therefore, the rear lid 13 of the instrument may be opened easily and the belt of filter 30 may be cleaned or exchanged easily. |
