US1610744A - Electromagnet - Google Patents

Description

Dec. 14 1926. 1,610,744

E. R. CARICHOFF ELECTROMAGNET Filed Feb. 18 1922 -nnllmmmllfl f Cgi/4 j la l vl/T\I\/el*ltor'-Z Eugene FQ. carichoff, WM 24. g H15 Attorney.

Patented Dec. 14,v 1926. A

UNITED STATES' l 1,610,744 PATENT OFFICE.

EUGENE R. AQARICHOFF, OF SCHENECTADY, NEW YORK, 'ASSIGNOR T0 GENERAL ELEC- TRIC COMPANY, A CORPORATION F N 132Wl YORK.

Application filed February .18,41922. Serial No. 537,607.

The present invention is directed to im` the invention has a particular application in electromagnetic switches of the series lockout type. In a prior patent issued to Benjamin W. Jones and myself, No. 1,445,994, datedFeb. Q0, 1923, and assigned to the same assignee as this application, there is described an improved form of series lockout vtype velectromagnetic switch to'which the improvements ofthe present invention apply Y'to great advantage, and the principles of this invention will therefore be explained in connection with a switch of the type disclosed in the said Carichof and Jones application. In the said Carichoi' and Jones application there is disclosed and broadly claimed an electromagnetic switch having a series coil and a movable magnetic memE ber or 4plunger disposed within the series coil so as to form a part of the magnetic circuit of the switch. The plunger is connected to a switch member and is disposed with respect to the magnetic circuit of the switch so as to provide two air gaps, one of which is a holding open7 air gap and the other is a closing air gap. The arrangement is such that the plunger will be magnetically held in its biased or open position by the magnetic pull across the holding open air gap when the current in the series vcoil is above a predetermined value and the lungerY will be operated to and magnetically eld in the closed position oi the switch by the magnetic pull across the closing gap when the current in the series coil drops to the predetermined value. A shunt coil is disposed on the magnetic circuit of the switch for insuring that the switch will positively close when the currentin the series coil is lbelow the predetermined value, and for insuring that the switch will not automatically reclose after opening when the current through the seriesl coil is reversed..

(Dine ci the objects of my invention `is to prevent the series exciting coil of the switch electroniagnet from interfering with the movements of the movable magnetic member' or plunger.

Another cbiect of my invention is to prevent interiierenec by the series exciting coil of the electromagnet with the adjustment of the Calibrating device for adjusting the holding open air gap of the electromagnet.

Another object is to provide an improved arrangement in which the movable magnetic member of the electromagnet is perfectly free to move within the series coil without any wedging action.

A further object is. to provide an im-` proved arrangement lfor supporting the movable magnetic member of the electromagnet when the said member is in its biased position.

Another object is to provide an improved arrangement involving the use of a magnetic tube on whichthe series coil is disposed and on which the movable magnetic member is supported in such a manner that dirt and dust is prevented from entering the tube.

A still further object of the invention is .to provide an arrangement whereby the movable magnetic member or plunger is prevented from operating at the calibrated value when the current in increasing quickly passes through that value. Thus, in case the electromagnet is used in a switch for controlling -the acceleration of a motor in response to the current taken by the motor, when the motor is first connected to the supply circuit, there is a rush of current and it is desired that the switchY shall close when the motor current drops to theipredetermined or calibrated value and not when the current passes through that value while the value of the current is increasing.

Further objects and purposes of the invention will appear in the course of. the :tol-

lowing specilication in which I shall disclose' the invention embodied in concrete form for purposes of illustration.

Referring to the drawings, Fig. l is a side vie-wwf an electromagnetic switchl of the series contactor type, disclosed and broadly claimed in the said patent of BenjaminW'. Jones and myself, with the improvements of the present application incorporated therein; F ig. 2 is a front view of the switch shown in Fig. l; Fig. 3 is 'a cross-section detail of the series' electromagnet of the switch of Figs. l and 2, with the improvements of the present invention shown in detail; Fig. 4 is a detail showing a modification of Fig. 3 in the manner of supporting the plunger associated with the series electromagnet; and Fig. 5 is a very simple diagram ofY connections showing the'series contactor employed in the control of an electric motor.

Referring to the drawings, and particularly to Fig. 3, the series operating electromagnet of the switch is provided with a series winding which is mounted upon a spool 11 of insulating material. This spool and the winding are mounted upon the tube 12 of magnetic material which is of a substantial rigid construction, so that the winding spool and winding are securely held with respect to this tube. The plunger 13 has its major portion disposed within the tube 12, and this plunger has an enlarged 1- head 14 which projects from and is supported by the upper end of the tube 12, so that when the plunger is in its biased position (that shown in the drawing), the plunger will be separated from the upper end ofAthe adjustable plugl of magnetic material so as to provide an air gap which is commonly termed the holding open air gap. The enlarged head 14 of the plunger rests upon a washer or spacer 16 of non-magnetic mate- J rial which magnetically separates the plunger from the tube to prevent the p unger i from sticking tothe tube and provides what amounts to an air gap whereby the* plunger will not operate when the current increasing through the series coil-passes quickly through the operating value. The cylinder 17 of non-magentic material such as brass or the like, is disposed within the tube 12 so as to prevent the plunger 13 from sticking to the side walls of the tube 12, and also to serve as a shading coil for the flux passing from the tube into the plunger. I have Vfound that it is desirable that the crosssection of the Iplunger within the tube shall be about fifty percent greater than the crosssection of the tube 12, although my invention is not necessarily limited to thisparticular relation between the cross-section of the two parts. The spool 11 is securely held with respect to thetube 12 by means of the spring washer 18 which is suitably interlocked with the upperendof the tube 12 as shown. With the adjustable plug 15 mounted in the lower end of the tube 12, this tube is closed at its lower end, and this lower end of the tube is secured in a frame 19 of magnetic material which extends upward and over the projecting head of the plunger so as to form an air gap between the upper surface of the enlarged head of the plunger and the magnet frame. This air gap which is designated by the numeral 2O is termed the closing air gap.

Instead of supporting the plunger within the tube 12 as shown in Fig. 3, this plunger may be supported in other ways, as for example, by a small cylinder of insulating material 21 as shown in Fig. 4.

Referring now to Figs.l 1 and 2, the enlarged or upper end of the plunger 13 is piv- -motor armature to the source otally connected to one arm of the bell crank of current below the calibrated'valuemthat .i

value at which the switch is no longer magnetically held in the open position--,` and also for insuring that the switch will not reclose after opening in response to a reversal of current through the series coil 10.

The magnetic blowout which is disposed adjacent the switch contacts 22 and 23 comprises plates of magnetic material 25 and 26 between which the are chute 27 of refractory material is supported. The plates 25 and 26 are respectively connected by means of the strips 28 and 29 of magnetic material so as to be across the closing gap 20. A. very simple magnetic blowout -is thereby provided, and this magnetic blowout is dis closed and claimed in a .prior patent of mine No. 1,503,091, dated July 29, 1924, and assigned to the same assignee as this invention. The various parts of the switch aremounted upon a suitable base 30 of insulating material. t

As thus constructed Aand arranged, and with the parts in their respective positions as shown in the drawings, the operation of the switch may be described in connection with Fig. In order to connect the motor having an armature 31 and a shunt field 32 to the supply circuit 33, the disconnecting switch 34 is first closed, thereby energizing the shunt field 32 of the motor directly across the supply circuit. In order to connect the pilot lswitch 35 will be closed, thereby energizing the line contacter 36 to close and 'thus connecting the motor armature to the source of supply with the accelerating resistor 3T included in circuit therewith. The series coil 10 of the switch described in connection with Figs. 1, 2, 3 and 4 is included in series with the arn'iature of the motor and the shunt coil 24 is connected across the source of supply bythe closing of the lauxiliary switch 38 associated with the line contactor 36. The plunger 13 will be magnetically held by the pull across the holding open gap between the lower end of the plunger and the upper lend of the adjustable plug 15 as long as the current through the motor armature is in excess of the predetermined value.

It will be lobserved that when the'motor armature circuit is established, the current through the series coil 10 quickly rises from the zero value through the predetermined lllfi lll) lil]

operating or calibrated value to a value at (which the switch is magnetically locked open. The arrangement in accordance with` my invention will prevent the plunger from operating when the current passes quickly through the calibrating value as the current increases, and While I do not limit myself to any particular theory of operation, I believe the explanation of this desirablefeature of ,the invention to be as follows: As previously pointed out, the spacci" 16 provides What amounts to an air gap between the upper edge of the tube 12 and the lower surface of the enlarged head 14 of the-plunger. The path for the magnetic flux from the tube 12 to the plunger/is damped by the cylinder 17 so that an appreciable flux passes across this air gap from the upper edge of the tube to the head of the plunger, thus producing a magnetic holding down effect which prevents the plunger temporarily from rising,` As soon as the rate of change of the current bccomes substantially constant, the damping effeetof the cylinder 17 ceases and the mayor portion of the flux passes directly into the lower portion of the plunger. When the current drops to the predetermined value, the pull across the closing gap 20 will predominate and the plunger 13 Willbe mag-. netically raised into operative engagement With the magnet frame 19, thereby closing the air gap 20. This will cause the switch contact 22 to make engagement withthe stationary contact 23 and thereby short circuit the accelerating resistor 37. After the switch is thus closed, it will be magnetically held closed by reason of the magnetic yeffect upon the plunger 13.

It Will be observed by reference to Fig; 3 particularly, that the series exciting coil pf the switch electromagnet isprevented from interfering with the movements of the movable magnetic member or plunger 13, be-

{cause of the fact that this coil is rigidly f mounted in position and cannot be distorted from its normal position so as to interfere with the movementsof the plunger. Y The series exciting coil of the electromagnet is prevented from being displacedv and thus interfering With the adjustment of the plug 15 to thereby regulate the value of current through the series coil 10 at which the switch will magnetically close and be held closed. Furthermore, the plunger is supported in its r biased position in a very neat, simple and effective manner, and with the parts prop erly fitted, no Wedging action of the plunger is necessary. The series operating electromagnetl is simple in construction and of such a form that rit lends itself readily to large scale manufacture, as will be readily understood by those skilled in the art. It will also be observed that by reason of the cylinder 17 and the air gap between the upper edge of.

the tube l2 and the head 14.- of the plunger,

the plunger is prevented from operating when the value of current'through the coil 1() rises quickly through the predetermined or Calibrating value. I

In accordance with the provisions of the patent statutes, I have described the prin ciple of operation of my invention, together with the apparatus which I now consider to yrepresent the best embodiment thereof, but I desire to have it understood that the ap: paratus shown is only illustrative and that the invention may be carried out by other means.

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

1. An electromagnet comprising atube of magnetic material closed at one end, an eX- citing coil surrounding the tube, `a plunger biased to one position and disposed in the tube for reciprocation therein under the control of said coil, one end of said plunger projecting from the tube and the other end ofthe plunger separated from the closed end of the tube by a holding air gap across which the flux of'said coil passes to hold the plunger in the biased position, means disposed in the closed end of the tube for adjusting the said holding air gap, and a frame of-magnetic material attached to the closed end of the tube and extending over the projecting end of the plunger to provide a closing air ap between the said rojecting end ofthe p unger and the said flf'ame which is normally open and is closed by the operation of said plunger when the magneticV pull across the same is greater than the magnetic pull across the said holding air gap.

2. An electromagnet comprising a tube of magnetic material, an exciting coil surroundin the tube, a plunger having a major ortion isposed within the tube and an enarged head supported by the tube with an air gap interposed between said head and the supporting end of the tubefa plug of magnetic material closing the other end of said tube and providing an adjustable air4 gap between the plug and the end of the plunger within the said tube, and ay frame lof magnetic material secured to the closed end of said tube and extending over the said enlarged head of the plunger and separated from said head by an air gap.

3. An electromagnetcompri-sing a tube of magnetic material, a spool having a coil supported thereonv disposed over the tube, a-

spring Washer interlocked with the tube for holding the spool with respect to the tube,

a plunger having the major portion thereof disposed withinthe tube and an enlarged head rojecting from and supported by one end o the tube, an adjustable plug of magnetic material closing the other end of the tube and extending toward but separated from the end ofqthe plunger within the tube by an air gap, and a frame of Ymagnetic ing the tube,` a plunger having the major material attached to the'closed end' ofthe tube and extending over the projecting end et the plunger.

4;. An electromagnet comprising a tube ot magnetic material, an exciting coil surroundportion thereofJ disposed in the tube and an enlarged headprojecting from the end of the tube, a spacerof non-ma netic' material betWeentlre-said enlarged hea of the plunger and the one end of'said tube providing one air gap in the magnetic circuit ofthe electromagnet,` a non-magnetic cylinder disposed over the said major portion of the plunger,

` and an adjustable member of magnetic maand tube for holding the spool in position on the tube, a lunger having theJ ma or portion thereof disposed in the vtube an an enlarged head projecting from the end ofthe tube, a spacer of non-magnetic material be e l tween the said enlarged head of the plunger and the said end of the tube, a nonmagnetic metallic cylinder disposed over the said major portion of the plunger, an adjustable plug o1c magnetic material closing the other end of the tube and extending toward but separated from the end of the plunger Within the tube to provide a holding air a and a frame of magnetic material attahdtl to the closed end 4of the tube and extending over the projecting end of the plunger 'to provide a closing air gap which is normally yopen and is closed when the magnetic pull across the same is greater than the pull across said holding air gap.

In Witness whereof, I have hereunto set my hand this 17th day of February, 1922. EUGENE R. CARICHOFF.

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