US1904847A - Electromagnetic device - Google Patents

Description

April 18, 1933. B.` .1, BABBITT ELECTRMAGNETIC DEVICE Filed NOV. l0, 1928 Patented Apr. 18, 1933 UNITED STATES PATENT OFFICE BETHEL JAY BABBITT, OF RIVERSIDE, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK y ELECTROMAGNETIC DEVICE Application tiled November 10, 1928. Serial No. 318,323.

' This invention relates to electromagnetic devices, and more particularly to electromagnetic relays for use in signaling systems. The primary object of the invention is to '5 provide an electromagnetic device of simple and durable construction having improved operating characteristics.

One embodiment of the invention contemplates the provision of an electromagnetic structure in which a frame having a core extending into a magnetizing coil supports an armature with a core secured thereto eX- tending into the coil directly opposite the core of the frame. VThese cores are constructed and mounted to provide an air gap between them at the center of the magnetizing coil so that upon energization of the coil the magnetic flux which is of maximum density at the center of the coil will produce powerful tractive forces across the air gap to actuate the armature,

It is believed that a clear understanding of the invention may be had by reference to the following description, taken in con- 125 junction with the accompanying drawing,

in which Fig. 1 is a plan View of an electromagnetic relay embodying the invention;

Fig. 2 lis a side elevation thereof, and

Fig. 3 is a longitudinal sectional view taken on line 3 3 of Fig. 1.

Referring to the drawing wherein like numerals designate similar parts throughout the various views, the4 numeral 10 designates a plate made of magnetic material, such as a suitable grade of soft iron, having an `upturned lug 11 for supporting one end of an armature 12 and provided with threadi ed apertures 13-13vfor purposes of mount-` ing. As shown in Figs. 1 and 2, the armature is hinged to the lug 11 by means of a reed spring 14 of thin sheet steel secured to both the lug and the armature. The plate 1.0` and armature 12 are provided with right r angled portions 17 and: 18 for limiting the downward movement of the armature and with substantially perpendicular tongues 15 and 16 separated by a small air gap and formed from partially severed parts of the 5 plate and armature, respectively.

Rigidly secured to the upper side of the plate 10 and the underside of the armature 1 2 and medially of the tongues 15-16 and right angled portions 17-1'8 are cores 22 and 21 made of magnetic material. To afford sufficient clearance between a magnetizing coil to be hereinafter described and the movable core 21, the core 21 is made smaller than the core 22. These cores are mounted directly opposite each other and are separated by a minute air gap when the right angled portions 17-18 are in engagement with each other. The right angled portion 17 has secured thereto a threaded pin 23 extending through and beyond an aperture in the right angled portion 18 and an adjustable stop nut 24 threaded on the pin 23 limits the upward movement of the armature 12.

A hollow spool 30 having a plurality of turns of insulated wire 31 is so ina-de that a forced fit is obtained on the lower stationary core 22 secured onthe frame 10. This spool is usually made of phenol libre but it may be made of metalV such as the spools often made of copper which are used for relays when the space available makes it impracticable for mechanical strength reasons to employ phenol fibre. When metal spools are used a slot 32 is provided for preventing eddy currents. By mounting the magnetizing coil on the lower core 22, the assembly is simplified so that form wound coils can be used to reduce the cost of the relay. As has been previously explained, the core 21 of the armature 12 is made slightly smaller than core 22 so that there will be suiiicient clearance between the spool 30 and the movable core 21 to permit the required movement thereof in actuating the armature.' The ends of the wire 31 forming the magnetizing Winding on the spool 30 are connected to terminals 33-34 which are insulatively mounted on the plate 10 by means of screws 36-36 threaded therein, whereby the terminals can be readily connected to a source of electric-al energy to energize the winding.

In -addition to the terminals 33-34, contact springs 37-38 and 39-40 separated by a' plurality of small insulators 42 are also mounted on the plate 1() byscrews 36-36. 100

, flux is of greatest density, creates a powerful These contact springs are provided at one end with a terminal porti-on 45 and at the other end with a contact 46. Springs E37- 3S are disposed so as to be normally out of engagement and maintain their contacts 46 separated, whereas the springs 39-40 are arranged toy normally press together and make contact.

The armature l2 has laterally extending arms 48-48 at its forward end which carry insulating pins 49 and 50. The insulating pin 49 engages the contacting spring 37 and the insulating pin 50 protrudes through an opening in the spring 39 and engages the spring 40. The armature 12 is thus normally heldin engagement with a stop nut 24 by the resilience of the contacting springs 37 and 40 acting against the insulating pins 49-50 carried by the armature 12.

1n operation, the terminals 33 and 34 are connected to a source of electrical energy (not shown) to energize the coil of wire 31 encircling the cores 21-22. An electric current traversing the turns of wire 31 sets up a magnetic flux, which is of greatest density at the center of the magnetizing coil. The soft iron cores 21 and 22 in conjunction with the parts 10, l2 and 15-18 afford a path of very low reluctance for the flux With the result that the cores become magnetized and the adjacent core faces assume opposite polarity which result-s in mutual attraction between the stationary core 22 and the movable core 21. Since the cores are encircled by the magnctizing coil all of the flux passes through the cores to produce traction. The action of this flux in the air gap between the adjacent faces of the cores positioned midway between the ends of the magnetizing coil where` the tractive effort in accordance with Maxwells formula P=B2AK, in which B is the flux density, A is the area of the core faces, and K is a proportionality constant, whence it is Seen the pull P is proportional to the square of the flux density in the armature air gap.

Inasmuch as all of the flux traverses the cores, the flux density B is a maximum and a very effective pull is exerted whereby the core 21 and the armature 12 are actuated to control any circuits connected to the contacting springs 3?-38 and 39-40 through the movement of the insulating blocks 4Q- 50 associated with the armature. Also, the right angled portions 17 and 18 serve as a return path for the flux and provide an auxiliary source of tract-ion in producing a tractive force across the air gap therebetween before the armature is actuated. The tongues 15 and 1G are positioned close together before actuation of the armature and provide a path of low reluctance to thus assist in producing a greater tractive force by increasing the amount of effective flux. Upon actuation of the armature the tongue 16 moves at an angle relative to the other tongue 1 5 and increases the distance therebetween to expedite the release of the armature when the energizing circuit is opened.

lVhen it is desired to restore the relay to its original condition, the energizing circuit to theterminals 33-34 is opened. The current then ceases to flow in the magnetizing winding, the cores are demagnetized, and the armature is returned to its normal pos'p tion against the stop nut 24 by the resilience of the contacting springs 37 and 40.

The construction shown permits the use of a large number of contacting springs for controlling a great number of clrcuits from one relay; form wound magnetizing coils can be used to facilitate manufacture and assembly and reduce the cost; and the positioning of the air gap medially of the ends of the magnetizing coil reduces the leakage of the flux to a minimum and thus produces a very quick acting, heav duty relay, since all the magnetic flux is e ective in exerting tractive effort across the air gap within the magnetizing coil. Moreover, the placing of the air gap at the center of the magnetizing coil reduces the possibility of dirt and foreign material becoming lodged in the air gap and thus reducing the efliciency of the relay by obstructing the free movement of the armature.

The above described type of structure is also particularly well adapted to produce a relay having slightly retarded release characteristics by having the spool on which the coil is wound made of copper and eliminating the slot therein. For this type of relay,thetimeofreleaseoftliecontactingsprings throughout a wide range of tensions imposed thereon can be very accurately determined by specifying the size of the cores, the number of exciting ampere turns, and the saturation value of the magnetic material of which the cores are made.

It will be understood that the invention herein described and illustrated is capable of many other modifications Without departing from the spirit and scope'of the invention.

What is claimed is:

1. In an electromagnetic device, a. coil arranged to be traversed by an electric current for establishing an electromagnetic field, a magnetic member having a portion extending into the coil, a tongue fixed to the magnetic member, an armature hinged to the magnetic member and having a portion thereof extending into the magnetic field at the point of its maximum flux density, and a tongue fixed to the armature and cooperating with the tongues fixed to the magnetic member to provide between the armature and the magnetic member an air gap and path of low reluctance which will be increased upon actuation of the armature.

2. In an electromagnetic device, a coil a1'- ranged to be traversed by an electric current for establishing an electromagnetic field, a magnetic member having a portion extending into the coil, a tongue formed on the magnetic member, an armature hinged to the magnetic member and having a portion thereof extending into the magnetic iield at the point of its maximum flux density, a tongue formed on the armature and cooperating with the tongue formed on the magnetic member to provide between the armature and the magnetic member an air gap and path of low reluctance which will be increased upon actuation of the armature, and means for limiting the amount of movement of the armature outwardly and for providing another air gap between the armature and the magnetic member.

3. A relay having a plurality of iiat spring contact members extending substantially parallel to each other, an operating coil having its axis transversely arranged with respect to said contact members, and a magentic circuit including an armature moving in the axis of said coil for operating said contact members, said magnetic circuit comprising an elongated extension for supporting said sprmgs.

4. A relay having a plurality of flat spring contact members extending substantially parallel to each other, an operating coil having its axis transversely arranged with respect to said contact members, and a magnetic circuit including an armature moving in the axis of said coil for operating said contact members, the axis of said coil being short as compared with its average diameter, and the overall length of the relay being several times as great as the axis ofthe coil.

5. A relay having a plurality of flat spring contact members extending substantially parallel to each other, an operating coil having its axis transversely arranged with respect to said contact members, and a magnetic circuit including an armature moving in the axis of said coil for operating said contact members, said armature extending within the coil to form a short air gap therein between itself and the adjacent portion of the magnetic circuit, and said springs being mounted on the structure of said magnetic circuit at a point remote from said coil.

6. A relay comprising an elongated frame of magnetic material, an operating coil within said frame near one end thereof and have ing its axis arranged transversely of said frame, a transverse support mounted on said frame near the opposite end thereof, a plurality of spring contact members mounted on the extremities of said support and extending parallel with said frame on opposite sides of said coil, one side of said frame being movable and carrying an armature in line with the axis of .said coil, and means carried by said movable side of the frame for actuating said springs.

In witness whereof, I hereunto subscribe my name this 29thday of October, A. D., 1928.

BETHEL JAY BABBITT.

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