Digital display measuring apparatus

• US 4,578,868 A
• Filed: 03/30/1984
• Issued: 04/01/1986
• Est. Priority Date: 04/01/1983
• Status: Expired due to Term

• Current Assignee: Mitutoyo Mfg. Co., Ltd.
• Original Assignee: Mitutoyo Mfg. Co., Ltd.
• Inventors: Arai, Yoshihiro, Yamaguchi, Yasuyuki, Matsumoto, Toshiyuki, Sasaki, Kohji
• Primary Examiner(s): Stearns, Richard R.
• Application Number:
  US06/595,248
• Time in Patent Office: 732 Days
• Field of Search: 33/1 PT, 33/143 L, 33/147 N, 33/166, 33/170, 33/172 E
• US Class Current: 33/819
• CPC Class Codes: G01B 3/18 Micrometers
• CPC Class Codes: G01D 5/2403 by moving plates, not forming part of the capacitor itself, e.g. shields
• CPC Class Codes: G01D 5/2415 adapted for encoders

Abstract

A digital display measuring system includes a movable and stationary members between which an object to be measured is located, these members respectively supporting transmitter and receiver electrodes which define a variable capacitor having its electrostatic capacity which is adapted to change as the movable member is displaced relative to the stationary member. The change of electrostatic capacity is detected and converted into an electrical signal which is digitally indicated on a display to show the mechanical displacement of the movable member.

Claims

1. A digital display measuring apparatus comprising a display, a movable measurement element adapted to engage an object to be measured and an encoder for detecting the displacement of the measuring element and converting it into an electrical output signal which is digitally indicated on said display, the measuring apparatus being characterized in that said encoder comprises a stationary plate on a base of said apparatus, a rotary plate positioned opposed to the stationary plate and adapted to rotate depending on the displacement of the measuring element, a plurality of transmitter electrodes disposed circumferentially on the stationary plate at regular intervals, a ring-shaped receiver electrode located on the stationary plate concentrically with the circular train of the transmitter electrodes, coupling electrodes located on said rotary plate in such a manner that the coupling electrodes straddle and are spaced away from said transmitter and receiver electrodes, said coupling electrodes electrostatically connecting the transmitter and receiver electrodes with each other, and earthing electrodes disposed on the rotary plate in such a manner that the earthing electrodes straddle and are spaced away from the transmitter and receiver electrodes, the coupling and earthing electrodes being alternately disposed circumferentially on the rotary plate, whereby the displacement of said measuring element can be detected in accordance with an output signal of the receiver electrode varied by the rotation of said rotary plate when AC voltages having different phases are applied to the respective transmitter electrodes.

2. A digital display measuring apparatus as defined in claim 1, wherein said stationary plate supports two sets of eight transmitter electrodes and wherein said rotary plate supports two coupling electrodes each of which covers four of said transmitter electrodes on said stationary plate.

3. A digital display micrometer comprising a display, a spindle movable on the micrometer body and adapted to engage an object to be measured, and an encoder for detecting the displacement of the spindle and converting it into an electrical output signal which is digitally indicated on said display, said micrometer being characterized in that said encoder comprises a stationary cylinder on a base of the micrometer, a rotating member fitted to the stationary cylinder and spaced away from the internal or external wall of said stationary cylinder, said rotating member being adapted to rotate in response to the movement of the spindle, a plurality of tramsmitter electrodes located on one of the opposing walls of said stationary cylinder and rotating member and spaced away from one another at regular intervals, a belt-like receiver electrode disposed on said one wall arranged parallel to said transmitter electrodes, coupling electrodes located on the other wall in such a manner that said coupling electrodes straddle and are spaced away from the transmitter and receiver electrode, said coupling electrodes electrostatically connecting said transmitter electrodes with the receiver electrode, and earthing electrodes on the other wall in such a manner that said earthing electrodes straddle and are spaced away from the transmitter and receiver electrodes, said coupling and earthing electrodes being alternately arranged circumferentially on the other wall, whereby the displacement of said spindle can be detected in accordance with the output signal of said receiver electrode varying in response to the rotation of the rotating member when AC voltages having different phases are applied to the respective transmitter electrodes.

4. A digital display micrometer as defined in claim 3, wherein said trasmitter electrodes include two or more units of n transmitter electrodes and wherein said AC voltages applied to said respective transmitter electrodes are respectively out of phase by 360°

/n .