Moving iron instrument

• US 4,912,398 A
• Filed: 03/10/1989
• Issued: 03/27/1990
• Est. Priority Date: 04/21/1988
• Status: Expired due to Fees

• Current Assignee: Yokogawa Electric Corporation
• Original Assignee: Yokogawa Electric Corporation
• Inventors: Kawai, Yuji
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Regan, Maura K.
• Application Number:
  US07/322,150
• Time in Patent Office: 382 Days
• Field of Search: 324/147, 324/146, 324/154, 324/153
• US Class Current: 324/147
• CPC Class Codes: G01R 1/38 Arrangements for altering the indicating characteristic, e.g. by modifying the air gap
• CPC Class Codes: G01R 5/18 with pivoting soft iron, e.g. needle galvanometer

Abstract

A moving iron instrument comprising a cylinder divided into two parts, a cylinder member to which a fixed iron vane is attached, and a frame member for holding a moving shaft to which a moving iron vane is attached, wherein the two members are made of an insulating material.

Claims

1. A moving iron instrument comprising

a cylinder;

a fixed iron vane;

a moving iron vane;

a moving shaft having said moving iron vane attached thereto and disposed inside said cylinder having said fixed iron vane;

wherein

said cylinder comprises

a cylinder member made of an insulating material and to which said fixed iron vane is attached, and

a frame member made of an insulating material and to which said moving shaft is held, said frame member being movably fitted within said cylinder member, whereby adjustment of the relative position between the moving iron vane and the fixed iron vane is achieved by rotating the cylinder member relative to the frame member.

2. The instrument of claim 1, wherein said insulating material is plastic.

3. The instrument of claim 1, wherein said moving iron vane comprises a pair of attaching arms extending from two edges thereof, the distal ends of said attaching arms having respective curved portions, said moving iron vane also being attached to said moving shaft by inserting said moving shaft in said curved portions.

4. The instrument of claim 1, wherein said moving iron vane and said fixed iron vane differ in size from each other.

5. The instrument of claim 1, further comprising a field coil, and a shield casing for surrounding said field coil, said field coil producing magnetic fields for exciting said moving iron vane and said fixed iron vane, said shield casing being attached to said frame member by snap fitting.

6. The instrument of claim 1, wherein said cylinder member comprises an elongated hollow cylindrical base portion and a disk shaped top portion;

and said frame member comprises a cylindrical bottom part fitted into the hollow of said cylindrical base portion, a top part aligned with said disk shaped portion and an intermediate stem part connecting said cylindrical bottom part and said top part.

7. The instrument of claim 6, wherein said disk shaped top portion has at least one projection portion on a top surface thereof, and wherein said top part of said frame member has at least one hole therein so that when the top portion and the top part are aligned the projection portion is fitted within said hole, so that by manual movement of said projection portion the relative position of the cylinder member and the frame member is adjusted.

8. A moving iron instrument comprising

a moving section comprising a moving shaft having pivots at both ends thereof, a pointer secured to said moving shaft, and a moving iron vane attached to said moving shaft;

a frame member made of plastic, comprising a member having a bridge to which an upper jeweled screw is attached, a member to which a lower jeweled screw is attached, and a stem portion for connecting said two members, wherein said moving section is held to be rotatable between said upper and said lower jeweled screws;

a cylinder member made of plastic and formed as a cylindrical body, wherein a fixed iron vane different in size from said moving iron vane is attached to an outer side of the cylindrical body, said lower jeweled screw being inserted to be rotatable within a cylindrical space of said cylinder member so that said fixed iron vane faces toward said moving iron vane;

a cylindrical field coil covered with a shield, wherein said cylinder member is insulated within a cylindrical space thereof; and

means for guiding which allow said cylinder member to rotate with respect to said frame member such that the relative position of said moving iron vane and said fixed iron vane is changed thereby adjusting the sensitivity of said instrument.

9. The instrument of claim 8, wherein said moving iron vane comprises a pair of attaching arms extending toward an inner central portion from two edges thereof, the distal ends of said attaching arms having respective curved portions, said moving iron vane also being attached to said moving shaft by inserting said moving shaft in said curved portions.

10. The instrument of claim 8, wherein said frame member is formed by molding, and said cylinder member is formed by molding.