Ultrasonic wave generating apparatus with voltage-controlled filter

{
  "publication_number": "US4277758A",
  "country": "US",
  "kind": "A",
  "title": "Ultrasonic wave generating apparatus with voltage-controlled filter",
  "abstract": "The present invention deals with an ultrasonic wave generating apparatus with voltage controlled filter, comprising a phase comparator which detects a shifted value from a predetermined phase difference between a driving voltage or a driving current of an ultrasonic transducer and a vibratory velocity signal, and a voltage-controlled band-pass filter which is controlled by the output of the phase comparator and which is provided in a feedback loop from the vibratory velocity signal to an input of a driving amplifier of the ultrasonic transducer, wherein the oscillating frequency is changed while following the resonant frequency of the ultrasonic transducer, so that stable operation is materialized without developing abnormal oscillation in subresonant frequencies and permitting very small following error.",
  "claims": [
    "1. An ultrasonic wave generating apparatus comprising: ultrasonic transducer means for producing ultrasonic waves and a vibratory velocity signal; driving amplifier means for driving said ultrasonic transducer means; phase comparator means for comparing the output of said driving amplifier means with the said vibratory velocity signal for detecting a shifted value from a predetermined phase difference and producing a phase difference signal in response thereto; a voltage controlled band-pass filter means, said phase difference signal controlling said voltage controlled band-pass filter means; said voltage controlled band-pass filter means being directly connected to said vibratory velocity signal in a feedback loop.",
    "2. An ultrasonic wave generating apparatus according to claim 1, wherein said voltage controlled band-pass filter means is a bridged T filter.",
    "3. An ultrasonic wave generating apparatus comprising: ultrasonic transducer means for producing ultrasonic waves and a vibratory velocity signal; driving amplifier means for driving said ultrasonic transducer means; a voltage to current converter inserted between said ultrasonic transducer means and said driving amplifier means; phase comparator means for comparing the output of said driving amplifier means with the said vibratory velocity signal for detecting a shifted value from a predetermined phase difference and producing a phase difference signal in response thereto; a voltage controlled band-pass filter means, said phase difference signal controlling said voltage controlled band-pass filter means; said voltage controlled band-pass filter means being directly connected to said vibratory velocity signal in a feedback loop.",
    "4. An ultrasonic wave generating apparatus according to claim 3, wherein said voltage-controlled band-pass filter means is a bridged T filter.",
    "5. An ultrasonic wave generating apparatus according to claim 3 or 4, wherein said ultrasonic transducer is an electro-strictive transducer."
  ],
  "description_excerpt": "The present invention relates to an ultrasonic wave generating apparatus with voltage-controlled filter which will be operated in a state of maximum efficiency by permitting the oscillating frequency of an oscillating device which drives an ultrasonic transducer to follow a resonant frequency of the ultrasonic transducer.\n\nIn general, ultrasonic transducers employed for the ultrasonic appliances have their own mechanical resonant frequencies, and should desirably be operated at their resonant frequencies so that their electro-mechanical conversion efficiencies can be enhanced. The resonant characteristics, however, have high Q values. The Q values become great particularly when the amplitude of vibration is amplified using a horn, establishing sharp resonant characteristics. Moreover, in practice, the resonant frequencies are changed by the external conditions such as temperature at which the ultrasonic transducer is used, driving level and loading level, and by the horn or attached tool or chip employed for the ultrasonic machining apparatus. Therefore, the oscillating frequency of the driving oscillator must desirably follow the resonant frequency of the ultrasonic transducer.\n\nFor this purpose, a motional feedback oscillator has so far been widely employed by picking up vibratory velocity signals from the ultrasonic transducer by means of a vibration detector such as electro-strictive element, and by feeding back the thus picked up signals as input signals to the driving amplifier so that the resonant frequency of the ultrasonic transducer can be followed.",
  "cpc": [
    "H03L 7/02",
    "B06B 1/0253",
    "B06B 2201/57",
    "H03B 5/323"
  ],
  "ipc": [
    "B06B 1/02",
    "H03B 5/32",
    "H03L 7/02"
  ],
  "assignees": [
    "Taga Electric Co Ltd"
  ],
  "inventors": [
    "Shoji Mishiro"
  ],
  "filing_date": "1979-08-09",
  "publication_date": "1981-07-07",
  "grant_date": "1981-07-07",
  "priority_date": "1979-08-09",
  "application_number": "US-6516179-A",
  "family_id": "22060734",
  "cited_by_count": 79,
  "citations": [
    "US2752512A",
    "US2917691A",
    "US3889166A",
    "US3931533A",
    "US3967143A",
    "US3975650A"
  ]
}