Apical position detection apparatus

United States Patent [w]

Otsuka

[54] APICAL POSITION DETECTION APPARATUS

[75] Inventor: Masahiro Otsuka, Kawasaki, Japan

[73] Assignee: Toei Electric Co., Ltd., Kanagawa,

Japan

[21] Appl. No.: 09/190,829

[22] Filed: Nov. 12, 1998

[30] Foreign Application Priority Data

Aug. 24, 1998 [JP] Japan 10-237262

[51] Int. C I. A61C 19 04

[52] U.S. CI 433/72; 128/776

[58] Field of Search 433/72, 75, 27;

128/776

[56] References Cited

U.S. PATENT DOCUMENTS

5,017,134 5/1991 Saito et al 433/72

5,096,419 3/1992 Kobayashi et al. .
5,211,556 5/1993 Kobayashi et al. .

FOREIGN PATENT DOCUMENTS 4126753C2 ol 0000 Germany .

4139424C2 ol 0000 Germany . 19854223 5/1999 Germany .

Primary Examiner—Nicholas D. Lucchesi

Attorney, Agent, or Firm—Laff, Whitesel & Saret, Ltd.; J.

Warren Whitesel

[57] ABSTRACT

The present invention provides an apical position detection apparatus for accurately detecting the lact that a measuring electrode arrives at the apical position. The apparatus has a first current value measuring means for measuring a first frequency value by supplying a first frequency signal between the measuring electrode and the oral electrode, a second current value measuring means for measuring a second frequency value by supplying a second frequency signal between the measuring electrode and the oral electrode, arithmetic means for obtaining logarithmically converted calculation value by using a first measurement signal and a second measurement signal, and position signal formation means for obtaining an apical position detecting signal by addition or subtraction of the first measurement signal and the arithmetic value.

8 Claims, 8 Drawing Sheets