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Device for feeding a high frequency oscillating tool

  • US 5,294,896 A
  • Filed: 07/13/1992
  • Issued: 03/15/1994
  • Est. Priority Date: 11/13/1989
  • Status: Expired due to Fees
First Claim
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1. A system for driving a high-frequency oscillating tool arrangement (1), which includes;

  • inter alia, a device (1a), such as a piezoelectric crystal, whose form will change when subjected to changes in voltage;

    an electric drive circuit (2), adapted to generate an alternating voltage, which can be applied to said device (1a), the frequency of which is given, through a first control circuit (7), a value which momentarily corresponds to the resonance frequency of a first oscillating circuit (C1,L1 and R), representing said device (1a) in an equivalent, simplified electrical circuit diagram, in which the reactive elements (L1,C1) vary during a working operation;

    a second oscillating circuit (C2,L2), wherein the capacitive component (C2) thereof is representing said device (1a) in an equivalent, simplified electrical circuit diagram, in which said capacitive component (C2) does not vary appreciable with prevailing tool operating conditions (can be considered to have a constant capacitance value of the crystal structure), and the inductive component thereof is, via a second control circuit (4), given different inductance (L2) values, wherein said first oscillating circuit (CI,LL and R) and said second oscillating circuit (C2,L2) consitute two parallel-connected circuits, said first and said second oscillating circuits are operating in a common resonance frequency mode, characterized in that the inductive component (L2) of said second oscillating circuit (C2,L2) is parallel-connected to its capacitive component (C2), that a required frequency adjustment of the generated alternating voltage towards resonance frequency for the first oscillating circuit (C1,L1) is effectivated by utilizing the positive value of the derivative at an intersection point (150), applicable at said resonance of an argument curve as a function of the frequency, where minimum impedance frequencies and real impedance frequencies coincide, and that the difference (time distance at zero-crossing) between momentary phase values of the voltage and the current constitutes required frequency change control magnitude, for changing the frequency of the generated alternating voltage towards resonance for said first oscillating circuit.

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