US2291968A

US2291968A - Magnet design

Info

Publication number: US2291968A
Application number: US369567A
Authority: US
Inventors: Lincoln M Keefe
Original assignee: Individual
Current assignee: Individual
Priority date: 1940-12-11
Filing date: 1940-12-11
Publication date: 1942-08-04
Anticipated expiration: 1959-08-04

Description

L.. M. KEEFE MAGNET DESIGN Aug. 4, 1942.

Filed Dec. l1, 1940 Irisa/a fiar;

INVENTOR 12217200311, Mjf

41AM #glw ATTORNEYS Patented Aug. 4, 1942 UNITED STATES PATENT OFFICE MAGNET DESIGN Lincoln M. Keefe, Springfield, Mass.

Application December 11, 194.0, Serial No. 369,567

(Cl. 17E-336) 6 Claims.

This invention relates to improvements in magnet design and has for an object the provision of electro-magnets in which the average air gap between the movable armature and the stationary head when the armature is positioned to be attracted when the electro-magnetic winding is energized, is a minimum as compared to conventional types.

Another obj ect ofthe invention is the provision, in an electro-magnet, of magnetizable heads which together with a magnetizable tube and the armature completely enclose the electro-magnetic winding and define a path for the lines of force set up in the core of the electromagnet when its winding is energized.

A further object is to form an opening in one of said magnetizable heads and pivotally mount in this opening an armature of substantially the same thickness as that of the head. The air gap between the outer edges of the armature and the inner edges of the opening is substantially uniform and Varies Very slightly from the open to the closed (or attracted) positions.

Yet another object of the invention is the provision of serrations on the inner face of the armature, and in other instances of serrations on the core head adjacent to the armature. These serrationsv maybe circumferential or of any other desired form, and serve as ilux intensiilers. When the winding is energized an intense fringe or brush of ilux extends from each serration, producing a magnetic field comprised of a series of zones in which the magnetic ux is intensified with zones in which the flux is of less intensity therebetween.

Another object of the invention is the provision of an electro-magnet for actuating switching means or for instituting mechanical movement, formed of parts which fit together in accurate relation and may be permanently secured together without the necessity for fastening members, thereby producing a, device of the maximum accuracy at a minimum of cost. Devices of this form may be grouped in close order, due to the symmetry thereof, and therefore space is saved in the mechanisms in which these devices are employed.

Other objects will be apparent to those familiar with the art in which electro-magnets, relays and the like fall.

Referring to the drawing:

Figure 1 is an elevation of my new and improved electro-magnet device;

Figure 2 is a sectional elevation of the electromagnet taken along the line 2-2 of Figure 1;

Figure 3 is a plan view showing details of the armature and the method of mounting it;

Figure 4 is a view of the magnet in Figure 1, as seen from the bottom looking upwardly; and

Figure 5 is a sectional view taken along the line 5-5 of Figure 2, and showing serrations formed in the surface of the armature.

Referring to the drawing, the magnet, generally designated by the numeral I0 includes a core II having reduced portions at each end thereof, one of which is designated by the numeral I2, forming shoulders. Heads I3 and I4 formed of insulation material rest upon the shoulders. A disk I5 formed of magnetizable material has a hole formed therein fitting the portion I2 of the core II. After the head I3 and the disk i5 are placed on the core the end of the core is riveted down to permanently secure the head and the disk thereon.

A similar disk i5 is mounted on the opposite end of the core and said end is riveted down to secure this disk and the head I4 thereon.

The lower end, as viewed in Figure 2 of the core, has a tapped hole Il formed therein. This hole may be engaged by a threaded stud on the winding machine for applying the windings I8 to the core. suitable leadout wiresV I9 and 2l);`-

Secured to the core by means of a screw 2| engaging the threaded hole Il is a comparatively thick head 22 of iron or other ferrous material. The hole formed in the head 22 for the passage of the screwr2| is countersunk so that the head of the screw is flush with the outer surface of the head. The head 22 also has formed therein

holes carrying bushings

23 and 23a through which the leadout Wires I9 and 20 pass. The head 22 also has beveled

flat portions

24, 25 and 26.

A sleeve member 21 also formed of iron or other ferrous material has struck-out

portions forming ears

28 and 29 having holes 30, 3| respectively formed therein to accommodate mounting screws. The shell has a counterbored portion 32 at one end thereof forming a press lit with the head 22 and a counterbored portion 33 forming `\a press t with a head 34.

The head 34 is similar to the head 22 in so far as thickness is concerned. However, it has an opening formed therein to accommodate an armature. 'I'he opening has a portion 35 which is circular and concentric with the outer diameter of the head 34. The opening has ilat portions 36 and 31 and a slotted portion 38. A hole 39 extends through the head at right angles to The windings are provided withVV and passing through the slot 33 (see Figure 3).

Referring now to Figure 2, an amature 4I has a tongue portion 4I which nts the slot 38, and a pivot pin 42 is mounted in the hole 39 and passes through the corresponding hole in alignment therewith in the tongue 4I. 'I'he head 34 is also provided with beveled

flat portions

43, 44 and 45.

In assembling the electro-magnetic device, the head 22 is secured to the core II by means of the screw 2I and this assembly is pushed into the tubular shell 21 until the head 22 is flush with the lower end of the tube. In so doing, the head 22 comes to rest against the shoulder 32a. I'hen the head 34, the armature 40 having been previously pivotally mounted therein, is pressed into the upper end of the tube until the head 34 comes to rest against the shoulder 33a.

The

heads

22 and 34 are then retained in positlon against the shoulders 32a. and 33a respectively by deforming the tubular shell and causing portions thereof to overlie the beveled

flat portions

24, 25, 26 and 43, 44, 45 respectively.

The armature 40 may be provided with any suitable type of extension in accordance with the instrumentalities it is desired to control with the device herein shown and described. In one use of the device, for example. a positionable member is to be controlled; an arm 46 is preferably formed integral with the armature 40. This arm may have a portion milled away forming a shoulder 41, and a face 48 on the web 49. The web 49 may have a tapped hole 50 formed therein. Suitable means connecting the arm 46 to the positionable device (not shown) may be provided and may be secured to the web 49 by means of a screw engaging the threads 50 and located by means of the shoulder 41. Suitable spring means may be associated with the positionable member or with the means connecting the same to the arms 46, for urging the armature 40 away from the core II and the disk I5. A suitable notch formed in the arm 46 comes to rest against the head 34 and serves as a stop for limiting the upward swing of the armature 40.

In other uses of the device, spring means for urging the armature away from the core may be carried on the head 34 or on the tubular shell 21; for example, a cotter pin 52 may be secured to the arm 46 in the manner shown, and the shell 21 may have an ear 53 extended outwardly in a manner similar to the

ears

28 and 23, and the spring 54 may have one end connected to the ear 53 and the other end connected to the cotter pin 52.

The armature 40 may be provided with a nonferrous rivet 51 to prevent the armature from coming in metallic contact with the disk I5 and the end of the core II and sticking The surface of the armature 40 facing the core II may be provided with serrations 55 which may be disposed in the surface in any desired form. For example, the serrations 55 may be comprised of a plurality of concentric grooves.

In the embodiment herein shown and described, the surfaces of the grooves or serrations are at an angle of 60 with the horizontal. There are eighty serrations per inch and the depth of each groove is .008".

The disk I5 may also have its surface facing the armature 40 provided with serrations 50. In the embodiment illustrated this disk may have 60 serrations, eighty to the inch and .008" deep.

By providing the magnet with a serrated area I4 and the amature with the serrated area 55. the action of the device when the winding Is energized is facilitated due to the fact that the magnetic flux forms concentrated fringes on the peaks of these serrations and thereby provides a series of concentrated annuli with areas less concentrated therebetween.

From tests made with this new and improved magnetic device, it has been found that the device will operate unfailingly on electrical impulses of very short duration passing through the windings, therefore it is fast acting. Furthermore, it will operate under the influence of longer lived impulses of greatly reduced current value and is therefore believed to be very efficient.

Although a single embodiment of the new and improved electro-magnetic device is herein shown and described, it is obvious that many changes may be made in the device without departing from the spirit of the invention as set forth in the annexed claims.

What is claimed is:

1. In an electro-magnetic device, a permeable magnetic core, a winding on said core, permeable magnetic heads at each end of said core, one of said heads having an opening formed therein, an armature mounted in said opening, a pin passing through said last head and pivotally engaging said armature, a permeable magnetic sleeve joining said heads embracing said winding and forming a return path for the magnetic flux generated in said core, said sleeve covering the ends of said pin and confining the same in said last head, and means on said armature and movable therewith for controlling a positionable device.

2. In an electro-magnetic device, a core, a winding carried on said core, permeable magnetic members carried on each end of said core, said members being larger in diameter than the diameter of the core, permeable magnetic heads at each end of said core, said heads being adjacent to said members and one of said heads having an opening formed therein, an armature mounted in said opening and adapted to be attracted by flux distributed over the surface of one of said members, a pin positioned in said head and forming a pivotal support for said armature, a permeable magnetic sleeve forming with said heads a housing for said core and said winding and forming a return path for the magnetic flux in said core, said sleeve also serving to retain said pin in said last head, and means carried on said armature and movable therewith.

3. In an electro-magnetic device, a core having insulating heads at each end thereof, a winding on said core between said insulating heads, permeable magnetic members carried on each end of said core and adjacent to said insulating heads, said members being larger in diameter than the diameter of said core, a permeable magnetic head in contact with one of said members at one end of said core, a second permeable magnetic head adjacent to the other of said members and having an opening formed therein of an area larger than the area of said last mentioned member, an armature positioned in said opening in said last mentioned head, said armature being adapted to be attracted by flux distributed over the surface of said last mentioned member, a pivot pin in said last head forming a pivotal support for said armature, a permeable magnetic tube forming with said heads a housing for said core and said winding, forming a return path for the magnetic flux generated in said core and serving as a retainer for retaining said pin in said head, and means carried on said armature for connection to movable means outside said device.

4. An electro-magnetic device according to claim 3 in which said sleeve has integral portions of its wall remote from the ends of said sleeve extending outwardly and forming lugs for mounting said device.

5. In an electro-magnetic device, a permeable magnetic core, a winding on said core, permeable magnetic heads at each end of said core, one of said heads having an opening formed therein, an armature mounted in said opening, a pin passing through said last head and-pivotally engaging said armature, a permeable magnetic sleeve joining said heads together and embracing said winding, said sleeve being adapted to form a return path for the magnetic ux generated in said core and also covering the ends of said pin and confining the same in said last head, said core having a free end spaced apart from said armature and the surface of said free end of said core being serrated to present a. plurality of magnetic fringes toward said armature, and means on said armature and movable therewith for controlling a positionable device.

6. In an electro-magnetic device, a core, insulating heads on each end thereof, a winding on said core, permeable magnetic members carried on each end of said core, said members being larger in diameter than the diameter of said core and backing up said insulating heads, permeable magnetic heads at each end of said core, one of said heads being in contact with one end of said core, and the other of said heads having an opening formed therein, said Opening being generally circular in form and terminating in an inwardly directed slot formed therein, an armature mounted in said opening similar in shape to the shape of said opening and having a tongue portion lying in said slot, a pin in said head extending through said tongue portion and said slot for pivotally suD- porting said armature in said last head, a permeable magnetic tube forming with said heads a housing for the core and its winding and forming a return path for the magnetic flux, said tube also serving to retain said pin in said last head, the other end of said core being slightly spaced apart from said armature and forming a free pole, a plurality of serrations formed in the surface of said pole, a plurality of other serrations formed in the surface of said armature facing said pole, and means on said armature and movable therewith controlling a positionable member external to said device.

LINCOLN M. KEEFE.