US1920764A

US1920764A - nickle

Info

Publication number: US1920764A
Authority: US
Publication date: 1933-08-01
Anticipated expiration: 1950-08-01

Description

Aug. 1, 1933. c. A. NICKLE 1,920,754

ELECTRICAL INSTRUMENT Filed Oct. 19. 1951 Inventor-- CliffordANickls,

His Attorney Patented Aug. 3, i933 ELECTRECAL rus'rapiuanr I Clifford A. Nickle, Schenectady, N. it, assiglnor to General Electric Company, a Corporation of New York Application October 19, 1931. Serial No. 569,616

8 Claims.

My invention relates to electrical instruments and dynamo-electric devices and in particular to devices employing a magnetic field produced by a permanentmagnet.

An object of my invention is the production of electrical devices of decreased size and weight for a given capacity. A more specific object of my invention is the production of electrical instruments of decreased size and weight and increased stability without loss of sensitivity. A further object of my invention is the production of inherently shielded compact instruments. Another object of my invention is the provision of an electrical instrument which may be quickly and conveniently magnetized.

In accordance with my invention I provide a current conducting coil and a core therefor which is permanently magnetized in a direction transverse to its axis. Means are provided for the relative rotation of the permanent magnet with respect to the current conducting coil or vice versa. In place of the external permanent magnet usually used in devices of this kind I surround the coil and its magnetized core with a soft iron ring which provides a return path for the lines of magneticinduction and inherently shields the device from external magnetic fields. The magnetized core is preferably composed of a high grade permanent magnet material such as cobalt steel which may be magnetized to a high intensity and retains its magnetism with great stability. The features of my invention which I believe to be novel and patentable are pointed out in the appended claims.

In order to obtain a better understanding of my invention reference maybe had to the accompanying drawing in which Fig. 1 represents an elevation partly in section of an embodiment of my invention taking the form of an indicating electrical instrument, Fig. 2 is a cross-section of the instrument shown in Fig. 1, taken on line 2-2; Fig. 3 is a schematic diagram illustrating the relation between the magnetic paths and the coil, and Fig. 4 represents a modification arranged as a contact-making instrument.

Referring now more in detail to the drawing in which like reference characters refer to like parts throughout, 1 provide a movable coil 11 surrounding a permanently magnetized core 12, both of which are surrounded by the magnetic shield 13 which is preferably of soft iron. To

further shield the instrument and to protect the moving element against air currents and mechanical injury I may also provide soft iron plates 23. The magnetized core 12 may be composed of cobalt steel or other highly retentive material and is magnetized in a direction transverse to the axis of rotation of the coil 11.

The coil 11 is carried by a shaft 14 supported by the bearings 15 and 16 mounted upon the (Cl. ill-$5) Although I have shown the core 12 with a vertical hole coaxial therewith in order to permit the passage of the shaft 14 through the core it will be understood that the permanent magnet might also be solid and the coil 11 might be provided with stub shafts instead of a single shaft extending from bearing 15 to hearing 16.

In order to obtain the maximum lightness of v the ,moving parts, and consequently the maximum sensitivity, I prefer to mount the coil 11 as the rotatable element and the permanent magnet 12 as a stationary element but it will be understood that any method of mounting may be employed in which relative rotation is permitted between the current conducting coil 11 and the permanent magnet 12.

From Fig. 3 it will be seen that this method of construction provides the maximum efiiciency of the permanent magnet since the magnetic flux is confined to the air gap of the instrument. It will be understood that the air gap between the permanent magnet 12 and shield 13 may be made as small as is consistent with the mechanical limitations imposed by the requirement that coil 11 shall be freely rotatable in the space between permanent magnet 12 and magnetic shield 13. Since this air gap may be made as small as thatin the dArsonval instruments employing an external permanent magnet and since the area of the air gap is increased to that of the entire cylindrical surface of permanent magnet 12 it will be understood that a very great field inten sity may be obtained in the air gap for a given strength of the magnet. The parts 12' and 13 are shown concentric and the air gap uniform. but the invention is not limited to this exact arrangement.

I have found that an instrument constructed as here shown may very conveniently be magnetized by placing the instrument completely assembled with its magnetic shield 13 between the poles of an electromagnet furnishing a strong magnetic. field. Preferably I employ about 40.000 ampere turns in the electromagnet when magnetizing the instrument" in this manner. Such a high field strength completely saturates the shield 13 permitting lines of force to pass through and magnetize the core 12. By using cobalt steel, for example, an alloy which is about 46% cob'alt'I find that the permanent magnet may be magnetized in a single operation to the desired strength and that the permanent magnet will retain this strength with great stability. I

have not found it necessary to resort to aging of the permanent magnet or to over-magnetization initially, followed by a demagnetizing process in order to obtain stability of the permanent magnet. I have also foundthat my instrument is not injured magnetically by allowing it to be subjected to a field of excessive strength or to an alternating-current field after it has been calibrated.

It will be obvious that electrical instruments constructed in the manner here shown have the advantage of very materially reduced size and weight over instruments employing the usual form of exterior horseshoe permanent magnet, and I have found that the sensitivity of the instrument is not impaired as compared to the constructions employing exterior permanent magnets. Since the instrument is inherently shielded against external fields it has a further advantage over instruments employing external permanent magnets when it is desired to produce a fully shielded instrument.

Although I have explained the principle of my invention in connection with a measuring instrument, it will be understood that my invention is not limited thereto but includes any device in which\ a permanent magnet and a current conducting coil are arranged in inductive relation or are relatively movable. For example, Fig. 4 illustrates one form of a relay in which the pointer 21 carries a contact 25 cooperating with a pair of contacts 26. Obviously my invention also includes recording instruments and currentresponsive instruments of many types including not only voltmeters and ammeters but also instruments utilizing compound coils, ratio instruments and other devices utilizing crossed coils and any other instruments in which permanent magnetic fields are used.

Obviously my invention is not limited to devices in which the relative rotation between the coil and the permanent magnet is restricted to a fraction of a revolution, but may also be utilized in magnetos and other devices in which a continuous rotation takes place between a permanent magnet and a current conducting coil.

While I have described my invention in concrete form and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto since various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A current-responsive instrument comprising in combination, a current conducting coil, a shaft rotatably supporting said coil, and a permanent magnet of substantially circular cross section magnetized in a direction transverse to its axis, and having a coaxial opening therein to permit said shaft to be mounted substantially in the axis of said magnet, said coil surrounding said magnet so as to be in inductive relation therewith.

2. A current-responsive instrument comprising in combination, a rotatable current conducting coil and a permanent magnet composed of cobalt steel, said'magnet having a substantially circular cross section, being laterally supported at only one side within said coil and being magprising relatively high coercive force material, 3i

a shield comprising relatively permeable material, surrounding and spaced from said magnet and presenting a return path for the lines of magnetic induction passing through said magnet, non-magnetic means attaching one side of 9 said magnet to and spacing it from the corresponding side of said shield, and a current conducting coil occupy g a portion of the space between said magnetand said shield, said magnet and said coil being mounted to permit relative 9 motion between said coil and magnet.

4. A torque producing element comprising a permanent magnet composed of a material retaining a relatively high intensity of magnetization, and a rotatably defiectable rotatable current conducting coil surrounding said permanent magnet in inductive relation therewith, said permanent magnet being magnetized in a direction transverse to the axis of rotation of said coil and having a surface conforming in shape to the surface generated by the deflection of said coil.

5. A current-responsive instrument comprising a permanent magnet comprising relatively high coercive force material substantially symmetrical with respect to a given axis and magnetized transversely thereto, a current conducting coil mounted to permit relative motion with respect to the magnet, and a magnetic shield spaced from and surrounding said parmanent magnet, said coil occupying the space between said shield and said magnet.

6. A current-responsive instrument comprising a substantially cylindrical-transversely magnetized permanent magnet comprising a material of relatively high coercive force, a substantially annular magnetic shield spaced therefrom and coaxial therewith, and a current conducting coil occupying the space between said shield and u said magnet, and rotatable about their common axis. I

7. An electrical relay comprising a rotatable current -conducting coil, a contact-making element controlled thereby, a stationary core within said coil comprising a material of relatively high coercive force permanently magnetized transversely 41o the axis of rotation of said coil, and conforming substantially in shape to the space circumscribed by the rotation of said coil, and a substantially annular stationary shield surrounding said core and coil.

8. An electrical measuring instrument comprising a transversely magnetized stationary cylindrical permanent magnet comprising a material of relatively high coercive force, a stationary annular magnetic shield spaced therefrom and coaxial therewith, and a current-conducting coil mounted to rotate within the space between said magnet and shield about their common axis.

CLIFFORD A. NICKLE.