PURPOSE: To restrict the vibration of a piezoelectric tuning fork when a load exceeding a specified value is applied on a moving detecting part, by isolating an object to be detected and the piezoelectric tuning fork by an isolating member, and providing the moving detecting part on the isolating member, in a load detecting device using the piezoelectric tuning fork.
CONSTITUTION: When an electric power source is turned on, a signal is applied to an energizing piezoelectric element 4a, vibrating pieces 3a, 3b vibrate, its vibration is detected by a detecting piezoelectric element 4b, and is fed back positively to an amplifier 10, and as a result, the oscillation is continued. If a load such as powder is applied on an elastic sheet 2 of the detecting part, vibration of the detecting vibrating piece 3b coupled by a support 7 is restricted, a positive feedback loop is cut off and the oscillation is stopped. In accordance with stop of this oscillation, a detecting signal appears in a detecting terminal 10a. This detecting signal is supplied to a controlling circuit 20, and a circuit of the following stage is controlled. In this way, there is no possibility at all that powder adheres onto the vibrating pieces 3a, 3b and a malfunction occurs, and it is possible to detect the excess of a load by exactly stopping the oscillation.
KUMADA AKIRA
JPS5437782A | 1979-03-20 | |||
JPS50108961A | 1975-08-27 | |||
JPS576025B2 | 1982-02-02 | |||
JP56061421B |
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