US2144546A

US2144546A - Permanent magnet construction

Info

Publication number: US2144546A
Application number: US194870A
Authority: US
Inventors: Reese Rudolf; Huttig Hans
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1937-05-05
Filing date: 1938-03-09
Publication date: 1939-01-17
Anticipated expiration: 1956-01-17

Description

Jan. 17, 1939. R. REEsE ET AL 2,144,546

PERMANENT MAGNET CONSTRUCTION Filed March 9, 1938 Inventors: Rudolf Reese. Hans Hutti W .J

cnw n P O t t A .m e h T H IIF A 4 m b M AJUSTABLE TEMPERATURE COMPENSATION SHUNT NON MA GNET/C D CAST TER/AL Patented Jan. 17, 1939 2,144,546

UNITED STATES PATENT OFFICE PERMANENT MAGNET CONSTRUCTION Rudolf Reese, Berlin, and Hans Hiittig, Berlin- Pankow, Germany, auignors to General Elec:

tric Company, a corporation of New York Application March 9, 1938, Serial No. 194,870 In Germany May 5, 1937 4 Claims. (Cl. 175-21) Our invention relates to improvements in per- H are provided and fitted through an opening manent magnets, particularly those used for or openings in the yoke part III and enter well damping magnets in meters and the like, and it into the die-cast material as shown in Fig. 5. has for its object an improved construction Such holding screw is preferably inserted in which minimizes grinding operations, facilitates place prior to the die-casting operation. Howadjustment of magnetic strength and provides for ever, the screw hole in the yoke may also be used temperature; \compensation where that is desirto insert the die-casting material and the screw able. hole is then subsequently bored out and tapped The features of our invention which are beand the screw inserted. The bar magnet II is lieved to be novel and patentable will be pointed thus secured to the inner surface of one limb of 10 out in the claims appended hereto. For a better the yoke l0 and extends towards the other limb understanding of our invention reference is made to form the air gap at H. in the following description to the accompanying The screw 15, Figs. 1 and 6, may comprise a drawing. Fig. 1 represents a plan view of a screw for adjusting the strength of the magnet.

1 permanent magnet structure embodying our in- For example, if the die-cast material l6 be of vention; Fig. 2 may represent a sectional view non-magnetic material as is preferable and the taken on. line 2-2, Fig. 1, prior to the final unitscrew ii of magnetic material, the depth to ing of the iron yoke part It and bar permanent which the screw [5 is adjusted along the magmagnet part II; Fig. 3 represents a section of netic axis will vary the strength of the flux bar magnet part II taken on line 3--3, Fig. 2; crossing the air gap at H, Fig. 2. If the screw 3 Fig. 4 is a plan view of the bar magnet part ll; 15 be fully inserted, it will shunt more or less and Figs. 5 and 6 are fragmentary sections taken of the flux between the opposite poles of the on line 5-5 and 6-6 respectively of Fig. 1 and permanent magnet and decrease the flux which representing holding and compensating features passes about the yoke portion l0 and crosses the to be described. air gap. Then, by raising the screw l5, it will The main parts of the magnet here illustrated have less and less shunting eifect and the flux comprise a horse shoe shaped magnetic yoke part across air gap i! will be increased. Such ad- Ill and a permanent magnet bar part II. The justable screw may be of a magnetic material yoke part I0 is made of a relatively inexpensive having constant permeability with temperature suitable magnetic iron or soft steel that can be change in which case it will. merely serve to readily formed into the shape desired, and maadjust the magnetic strength independently of chimed. Part H is a cast bar magnet of high temperature changes. If temperature compensacoercive force material which is permanently tion is desired another screw vertically adjustable magnetized along one axis as indicated by the in opening I! may be made of a magnetic mate- 5 poles designated N and S, Fig. 2. It is provided rial having a positive or negative temperature cowith a central axial cavity or opening I! which efllcient of permeability. For example, a screw is preferably oblong in shape as indicated in Fig. made of an iron-copper-nickel alloy will have a 4. This opening may extend through the magnet negative temperature coefilcient oi permeability. but we generally prefer to close the lower end When fully inserted in its opening, such screw as indicated, in Figs. 2 and 3. This cavity is will shunt flux between the ends of the per- 40 formed during the casting operation and its inmanent magnet. This shunting efiect will deterior surface is generally rough and is prefercrease with rise in temperature and hence, comably larger in one dimension at the bottom end pensate the entire magnet structure for the to secure a. dove-tail efiect as best illustrated in tendency of such a magnet to decrease in Fig. 3. It is only necessary to grind the end polar strength with temperature rise. Then, by raising 45 surfaces of this bar magnet casting. After the the screw, this compensation may be decreased parts iii and II have been formed to the proper until just the desired temperature compensation shape and dimensions, these parts are united by is obtained. At the same time the proper filling the cavity II by suitable material by a strength of magnetic field at a given temperature high pressure die-casting operation. The diemay be obtained by adjustment of screw I5.

cast material is preferably non-magnetic and The temperature compensation desired may can be readily machined. The yoke i0 is pro- 'be predetermined by experiment and a nonvided with o e or re o e s l3 opposite adjustable temperature compensating member of cavity I! through which the die-casting material the required characteristic may be inserted in is forced. One or more holding bolts or lag screws the cavity of the permanent magnet prior to the an otherwise relatively inexpensive magnet construction. They are suitable for use with bar permanent magnets generally, independent of the use of a yoke part such as part Ill. The yoke l may be provided with one or more bolt holes I! for securing the same to the meter or other device on which it is used.

In accordance with the provision of the patent statutes, we have described the principle of operation of our invention together with the apparatus which we now consider to represent the best embodiment thereof but we desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

2. A permanent magnet comprising a barshaped permanent magnet comprising a casting of high coercive force magnetic material polarized along one axis, said casting containing a cavity extending along its polarized axis containing non-magnetic die-cast material, and a shunt for said magnet supported in said diecast material said shunt being made of a magnetic material the permeability of which varies with temperature changes.

3. A permanent magnet comprising a casting of high coercive force magnetic material, polarized along one axis, a cavity extending from one end nearly through said casting along said axis, a non-magnetic die-cast material filling said cavity, and a shunt for said magnet in the form of a screw threaded into said die-cast material along said axis, said shunt being made of a magnetic material the permeability of which varies with changes in temperature.

4. A permanent magnet comprising a barshaped casting of high coercive force magnetic material polarized along one axis, a cavity extending throughout the greater length of the magnetic axis of said magnet, said cavity being filled with a machinable non-magnetic material containing a pair of parallel,'threaded screw holes extending in the direction of said axis, an adjustable screw made of a constant permeabilitymagnetic material threaded in one hole and an adjustable screw made of a magnetic material having a temperature coeflicient of permeability which varies with temperature threaded in the HANS Humor.