Actuator

• US 4,623,840 A
• Filed: 07/05/1984
• Issued: 11/18/1986
• Est. Priority Date: 07/05/1983
• Status: Expired due to Fees

• Current Assignee: Institute of Science and Engineering Service Incorporated, Kabushiki Kaisha Tokyo KOKI Seizosho, K.K. Tokyo Koki Seizosho
• Original Assignee: Institute of Science and Engineering Service Incorporated, K.K. Tokyo Koki Seizosho
• Inventors: Fujii, Tsutomu, Fujimura, Tadato
• Primary Examiner(s): Kreitman, Stephen A.
• Assistant Examiner(s): WILLIAMS, HEZRON
• Application Number:
  US06/627,905
• Time in Patent Office: 866 Days
• Field of Search: 336/136, 336/30, 324/207, 324/208, 324/59, 73/168, 340/870.31
• US Class Current: 324/207.16
• CPC Class Codes: F15B 15/28 Means for indicating the position, e.g. end of stroke
• CPC Class Codes: F15B 15/2861 using magnetic means
• CPC Class Codes: G01B 7/02 for measuring length, width or thickness G01B7/004, G01B7/12 take precedence
• CPC Class Codes: G01D 5/2013 by a movable ferromagnetic element, e.g. a core G01D5/2033 takes precedence
• CPC Class Codes: G01D 5/2046 by a movable ferromagnetic element, e.g. a core

Abstract

An actuator has a cylindrical body, on the outer peripheral surface of which an induction coil is formed directly and a piston accommodated in the body and functioning as a core. The displacement of the piston can be detected by a detecting circuit for the change of the coil inductance in response to the displacement of the piston.

Claims

1. A pressure fluid operated actuator comprising:

(a) a cylindrical body made of non-magnetic substance taken from the group consisting of carbon-fiber reinforced non-magnetic material, silicon-carbide, phenol-formaldehyde and boron-carbide and having pressure fluid inlet-outlet means at each end thereof;

(b) a piston with a piston rod thereon, said piston being slidable in the cylindrical body in substantially fluid tight relationship therewith so as to be movable under the pressure of pressure fluid fed thereinto through one of said inlet-outlet means and for pumping pressure fluid out of said cylindrical body through the other of said outlet means, said piston being of a material for functioning as a core;

(c) an induction coil directly on the outer peripheral surface of the cylindrical body; and

(d) circuit means connected to said coil for detecting the change of the inductance of the coil in response to the displacement of the piston.

2. An actuator according to claim 1, wherein the coil is wound in two double-layer windings near the opposite end of the cylindrical body, respectively.

3. An actuator according to claim 1 wherein said piston is made of a permalloy.

4. An actuator as claimed in claim 1 wherein said carbon-fiber reinforced non-magnetic material is carbon-fiber reinforced plastic.