Method and apparatus for detecting the presence of liquid

Apparatus for detecting the presence of liquid in a container, said apparatus comprising

• a vibratory element mounted so that a part thereof extends into the container and into contact with liquid if a certain amount of liquid is present, and another part is disposed exterior to the container,
• electro-mechanical means mechanically coupled to said another part of the vibratory element for vibrating in response to an electrical signal to thereby cause the element to vibrate,
• means for applying an electrical signal to said electro-mechanical means to cause it to vibrate,
• means for detecting vibrations of the vibratory element and for producing a first signal indicative of the amplitude of the vibrations,
• means responsive to said first signal for producing a second signal when said vibrations are below a certain amplitude, indicating the liquid is present about the vibratory element dampening the vibrations, and
• gasket means disposed between the electro-mechanical means and the vibratory element and having a coefficient of expansion between that of the electro-mechanical means and that of the vibratory element.

Apparatus for detecting the presence of liquid in a container, said apparatus comprising

• a vibratory element mounted so that a part thereof extends into the container and into contact with liquid if a certain amount of liquid is present, and another part is disposed exterior to the container,
• electro-mechanical means mechanically coupled to said another part of the vibratory element for vibrating in response to an electrical signal to thereby cause the element to vibrate,
• means for applying an electrical signal to said electro-mechanical means to cause it to vibrate,
• means for detecting vibrations of the vibratory element and for producing a first signal indicative of the amplitude of the vibrations,
• means responsive to said first signal for producing a second signal when said vibrations are below a certain amplitude, indicating that liquid is present about the vibratory element dampening the vibrations, and
• wherein said electrical signal applying means further includes
• oscillator means for producing an oscillatory signal whose frequency varies in response to variation in the amplitude of an input signal,
• means for supplying the oscillatory signal to the electro-mechanical means to cause it to vibrate, and
• means for producing an input signal for application to the oscillator means and for varying the amplitude of the input signal over some predetermined range.

A method of detecting the presence of liquid in a container comprising

• (a) providing a vibratory element, a portion of which is exposed to the interior of the container and a portion of which is exterior to the container,
• (b) stimulating that portion of the vibratory element which is exterior to the container during intermittent transmit time phases to cause the element to vibrate, said stimulating step including causing the frequency of vibration of the vibratory element to sweep over a range of frequencies which encompasses the resonant frequency of the vibratory element,
• (c) detecting the amplitude of vibration of the element during receive time phases which alternate with the transmit time phases, and
• (d) producing a signal indicative to the presence of liquid about the element when the amplitude of vibration of the element is below some predetermined level.