US1338548A - Electromagnet - Google Patents

Description

C. E. AVERY.

ELECTROMAGNET.

APPLICATION FILED MAR.27,19I7.

2 SHEETSSHEET 1.

C. E. AVERY.

ELECTROMAGNET. AFPLICATION FILED MAR. 27, 1917.

1,338,548. Patented Apr. 27,1920.

2 SHEETS-SHEET 2.

UNITED STATES PATENT crease;

CHARLES E. AVERY, OF TRENTON, NEW JERSEY, ASSIG-NOR T0 MANHATTAN ELECTRICAL SUPPLY COMPANY, INC, 013 JERSEY CITY, NEW JERSEY, A COR- PORATION OF MASSACHUSETTS.

ELECTROMAGNET- Specification of Letters Patent.

Patented Apr. 27, 1920.

Application filed March 27, 1917. Serial No. 157,738.

To all whom it may concern:

Be itknown that I, GHARLEs E. AVERY, a citizen of the United States of America, and residing in Trenton, in the county .of Mercer and State of New Jersey, have invented a certain new and useful Improvement in Electromagnets, of which the following is,- a specification.

My invention rel tes to electromagnets and particularly to alternating current magnets, the object of'my invention being to so construct a magnet of thistype as to eliminate the chatter of the armature and associated parts which is commonly incident to the operation of the magnet due to the vibrations icaused by the alternating current, and to secure an increased range of movement for the armature whether operated by direct or alternating current.

In the following drawings,

Figure 1 is a plan, with cover removed, of an electromagnet for operating a fire gong and in which my invention is embodied in one form;

Fig. '2 is a section through the magnet coils showing the armature and supporting that brackets;

Figs. 3, 4 and 5 are sections on the lines 3-3, 4-4:, and 5-5, Fig. 1 respectively;

Fig. 6 is a diagrammatic elevation of a modified construction;

Fig. 7 is a broken elevation at right angles to Fig. 6; and

Fig. 8 is an elevation and Fig. 9 a broken plan of one of the coil spools.

One of the difliculties incident to the useof alternating current to energize electromagnets is the rapid oscillation constantly imparted to the armature during the maintenance of the field. When the armature operates a switch, this oscillation results in \a'poor contact at the point ofengagement between the switch members. When the armature operates a gong hammer, it causes the hammer head to tremble against the gong and produces a. muflied instead of a clear sound. Various ways have been here- 'tofore devised which meet this difliculty with'more or less success, but none in so simple and eflicient a manner, I believe, a's

for which I now ask the grant of suitable patent protection.

Briefly stated my invention consists -1n so arranging the armature with relation to the magnetic field that .upon energization of the magnet, the armature passes through the area of greatest magnetic attraction to a point at which said attraction is practically counter-balanced by the effort (gravity, counterweight or spring) of -the armature to return to normal position.

In the construction here shown the magnet comprises a pair of coils 10 and 11 supported within the casing 12 by brackets 13 and 14: of non-magnetic material, such as brass. These coils are here shown wound in multiple, the lead wires 15 and 16 being connected to terminal plates 17 and 18' mounted on a block 19 of insulating material carried by the side wall of the casing 12-and to which the wire mains entering through the conduit 20 are connected.

The armature 21 is rigid'with the spindle 22 pivoted on the bracket 23, and the gong hammer-24 is fast on the spindle 22 gong 25 when the armature is drawn down so that it is swunginto contact with the as a result of the energization of the magnet are substantially equal at both points. The

armature-is pierced so that when operated the pole 26 passes into the armature and the pole 27 passes internally through it, the holes being somewhat larger than the poles which cannot come in contact with the armature. Aspring 28 may be attached at one end to the armature at 29 and at its other end 30 to the casing to counter-balance to a large extent the weight of the gong lever 24 and thus render the action of the armature more delicate. Less current is thus required to actuate the gong lever.

Upon the energization of the coils a magnetic fieldis created which is approximately illustrated in Fig. 2. As indicated in the drawing, the armature normally lies bev the area X of greatest magnetic eflort. The I throw of the armature, however, under the influence of the magnetic field, carries it not only into this area but through it to a point of rest against the non-magnetic bracket 14, at which point the magnetic attraction is substantially counterbalanced by the tendency ofthe lever 24 to return to its position of rest by gravity. The armature consequently lies quietly in this position without the usual tremble resulting from the oscillation of the alternating current in the magnet coils. It is emphasized that the bracket 14 is of brass, or other non-magnetic material, and has no influence upon the armature 21,.as would be the case were the bracket of iron or like material.

In fire alarm systems a weak supervising current is constantly maintained on the signal circuit to insure the maintenance of the latter in operative condition. The position of the armature 21 must therefore be such with relation to the magnetic field that it is not materially affected by the slight pull of the field under the influence of the supervising current. On the other hand, it must be sufliciently close to the maximum effort df the 'field to respond at once and with certainty when the operating current is impressed upon the circuit. Moreover, its tendency to return to position of rest must be sufliciently strong to overcome the weak vmagnetic field caused by the supervising current so that upon the break of the operating circuit the lever returns to position, its

inertia being sufiicient to carry it through gongs, since the magnet may with equal value be utilized to operate a contact lever or other member. It is applicable to all A. Cfima end of its stroke is desired.

"It will be noted that the armature ahd the magnet core are both laminated, the advantages of which construction are wellknown. It will also be noted that as an incident to'the accomplishment of the result stated, the branch 27 of the magnet core extends beyond the outer face of the armature when the latter is operated by the magnet. Th1s has a determining effect inlocating the magnetic field in the desired area. i The nonmagnetic brackets 13 and 14 are s lit or slotted to avoid theformation of eddy currents which if present would require greater power to energize the magnet, as is well understood by those skilled in the art.

One detail of value in the construction of the-magnet is illustrated in Fig. 8 and reets in which the elimination-of the vibration of the actuated memberitt he coils a sufiicient lates to the spool upon which the magnet coil is wound. The hollow body 31of the latter head 34. Both heads areretaine in theirv extreme positions against the flanges 32 and 35 by the coil'when the latter is wound on the spool. The projecting portion 36 of the spool body is engaged by the bracket 14 on Which one end of the magnet is supported. In order to prevent the edges of the laminations of the core from coming into contact with. the walls of th -spindle 31 insulating strips 37 may be intgrp'osed. One of ,these strips is preferablyjlocated on he same side of the spindle as't'he spaced edges a and b of the sheet, thus serving to maintain these edges spaced apart and prevent the formation ofeddy currents in, the spindle.

In Figs. 6 'and 7 I have illustrated diagrammatically. a modified construction in which the armature 38 is mounted on an axis 39 Cparallel to the plane of thebranches '26 an 27 of the core instead of at right angles,

thereto as in Figs. 1 to, 5. The magnetic field is the same in this arrangement as in the one above described, and the location of the armature with reference thereto may be similarly predetermined. The advantage of the construction in Figs. 1 to 5 is merely one of greater leverage for the armature within a iven space.

arious modifications in details of construction will readily occur to those skilled in the art which do not depart from what I claim as my invention.

1 claim 1. An alternating current magnet comprising magnet coils, pole pieces therefor projecting be 0nd the ends of the istance to establish an area of maximum magnetic attraction be yond the ends of the coils, a rigid armature spaced from said poles but pivoted at a point such that, on excitation of the magnet, the armature is free to pass through said area of maximum attraction, together with igid stop means halting said armature in sta e position at a magnetic attraction is su stantially counterbalancedby the effort of the armature to return to normal position.

2. In a construction such as specified in claim 1, a lever associated with said armapoint at which the ture and moved to ope ative position by the latter on the excitation of the magnet.

3. In a construction such as specified in claim 2, a spring arm carried by said lever and temporarily flexed into action by the .being moved into operative position by the impingement of the armature against its movement of the "armature on the excitation stop. 4 o of the magnet.

4:- In a construction such as specified in In testimony whereof I have signed my 5 claim 1, a lever rigid with said armature name to this specification.

and extending on the opposite side of the pivotal mounting of the armature, said lever CHARLES E. AVERY.

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