US2617950A

US2617950A - Electromagnetic pulsing device

Info

Publication number: US2617950A
Authority: US
Inventors: Donald A Lace
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-07-29
Filing date: 1950-07-29
Publication date: 1952-11-11
Anticipated expiration: 1969-11-11

Description

Nov. 11, 1952 D. A. LACE ELECTROMAGNETIC PULSING DEVICE Filed July 29, 1950 Patented Nov. 11, 1,952

UNITED STATES PATENT OFFICE 2,617,950 ELECTROMAGNETIC PU L SING DEVICE Donald-A. Lace, Highland Park, Ill.

Application July 29, 1950, Serial No: 1763615 S'Claims.

If This invention relates-to electrical pulsing devices, more particularlyto electromagnetic devices which produce electrical pulses at more or less regular intervals, and it is an object-of'the invention to provide novel and usefulapparatus of this character.

Electrical pulsing devices of the character indi-- determining the time interval of exciting the Winding, and thereby determining-the time inter-- val of the pulses. Such devices are useful-in many fields such, for-example,- aslig-ht signalling,

sonic signalling, protective-fence charging, andpulsing devicesgenerally. Moreover, it is fre--- quently necessary to leave the-pulsing devicesun attended for long periods'oftimeand under all weather conditions, and the character ofserviceis often such that failure cannot be tolerated.

Prior devices of the character and for the purposes indicated have been relatively complicated andhave had numerousmov-ing-parts.

It is a further-object of the inventionto provide novel'and useful apparatusof-thecharacter indicated having relatively few mo-vingeparts, and

which is simple in character and efiicient in operation.

It is a furtherobject of the invention'to provide, in apparatus of the character indicated, means whereby deterioration of the contacts in the coil circuit is substantially reduced and long lifeand satisfactory operation of the device are assured.

his a further object of: the invention to' provide novel and useful apparatus of the characterindicated wherein the drain of energy, from the source of supply is reduced to a minimum whereby the device may be used overlong-intervals of time ithout attention.

It is a further object of'the inventionto provide novel anduseful apparatusef the character indicated; which ymay-be p1aced-in'-'any:position- 1 without having EhBFz-tillle "interval of the pulses -produced ;varied-,=- and whose time interval remains constant-atthelvaluechosen;

It is a further object of the invention to providenovel and useful apparatus of the character in-- dicated which is reliable and: small *in size. f

In carryingout the invention .in one form", an

electromagnetic; pulsingdevice is provided which comprises; a -magnetic:oore-sincluding a: nonmagnetic' gap: substantially transversely :of :the core for creating a magnetic flux in the core and across 2. the gap when the-winding is energized. a balanced armaturedisposed so as to overlie the gap and beingattractable by the flux the gap whenthe winding is energized, shaft means for pivotally mounting the armature, biased open contact means associated with the core and in circuit with the winding; atleast one; of the contact means being insulatedfrqm the core, means on said-armatureengaging the contact meansin the normal position of the armaturewhen the winding is unenergizedfor holding the contact means closed, meansfor storingup energy during the movement of the armature toward the gap when the winding- -is energized and-for impartingsuch energy to the armature when the contact means open tode-energize the winding to move thearmature in P the opposite direction, the holding means being disposed whereby the contact means are 7 held closed; until the armature has reached substanti'allyits-final position whereupon the contact'means are'jpermitted to open, and further means for storing up energy as the armature moves in the opposite direction for returning the Y armature to its normal position, and output means associated with thewinding t n r V I For a more complete understanding of the invention,'referenceshouldbe had to the accompanying drawings in which: I a p i n r t Figure l is a perspective view of a pulsing device embodying the invention; I H n Fig. 2 is afragmentary view taken substantially in the direction of the arrows 2-2; p i V Fig. '3 is a view taken substantially in the same direction as Fig; 2,; but with certain components of the apparatus in a different operative position; Fig. 4 is a further view similar to Figs. 2 and 3 with the operating components in a still further ti Fig. 5 is a fragmentary view on a larger scale of the apparatus shown in Fig. 1; V Fig.- 6 is a sectional view taken substantially in the direction of the arrows 66 of Fig. 7 V Fig-7 is a fragmentary top view of the apparatus'shown'in'Fig. 1; V v I Y t Fig. 8 is a. circuit diagram illustrating circuitsembodying the apparatus, and a 7 v Figs. 9, 10 and '11 are functionally related views in end elevation and on a larger scale of certain, components of the'apparatus shown in the figures. Referring. to the drawings; the apparatus is shown as comprising a pulsing" device [0, includ' ing a magnetic "core ll,'.upon"which'a primary may be composed of laminaticns of any desired shape which include a central leg which, when assembled, provides the member not shown which the windings surround. The laminations when assembled, however, provide a gap l5 which may be left as an air gap or may be filled with any desired nonmagnetic material. In the assembled condition, the laminations are held together to form the core by suitable bolts or other similar elements at the four corners of the core. Brackets it and i9 may be disposed at the base of the core for mounting the device in any position desired.

The armature i4 is disposed relative to the gap 25 in order that it may be attracted by the magnetic flux produced at the gap when current is flowing in the winding i2. The armature id is mounted by shaft means which may include stub members 2i and 22 extending outwardly from the body of the armature. While so shown, it will be understood that a shaft extending all the way across the armature and attached thereto in any desired manner may be utilized. The ends of the stub members 2! and 22. are pointed and may be received in correspondingly formed openings in

screws

23 and 26, thereby forming substantially frictionless bearings for the armature. The

screws

23 and 24 may be received in suitably disposed ears which may form part of strip H held to the core by the same bolts which hold the laminations assembled. The armature M is balanced about the axis of shaft members 2! and 22 in order that the device may be placed into any position without having gravitational forces exerted on the armature which tend to rotate it about its axis.

A pair of

conact springs

25 and 26 are mounted on the member ll by means of a lip 28 and disposed so as to be actuated by a trigger 21 attached to armature Hi. Lip 28 extends upwardly from member I? and may be integral therewith, the

contact springs

25 and 25 being attached thereto by means of a rivet it, for example as shown. A block of insulating material 223 separates contact spring 25 from lip 28, and a block of insulating material 29 separates

contact springs

25 and 2 6. As may be seen best in Fig. 6, the hole in contact spring 25, through which the rivet it extends, is larger than the rivet so that contact spring 25 is insulated from the lip 28 and the core generally. Contact spring 2% is, however, grounded to the core by means of rivet 55. Contacts 3i and 32, which may be of arc resisting material, are attached to the ends of

contact springs

25 and 2%, respectively, for making and breaking a circuit to be described subsequently in this specification.

A spring 33 is disposed so as to return the armature M to a normal position Whenever it has been rotated counterclockwise from the position shown in Fig. 1. This operation may be understood best by referring to Figs. 2, 3 and 4 in connection with Fig. l. The spring 33 may, for example, be attached to and extend outwardly from the member H as shown in Fig. l, the spring including a portion lying underneath and biased 'against the underside of the armature id rearwardly of shaft means 2!, 22. As the armature rotates counterclockwise, the spring 33 is defiected downwardly thereby storing energy in the spring and causing it to exert a sufficient force to return the armature to the position shown in Fig. 1 with a time delay. Friction in the bearings formed between the stub shafts and the cooperating bearing screws may be ignored sub- 4 stantially since the bearings are largely frictionless.

The armature it has a normal position, as may be seen in Figs. 1, 2 and 7, wherein the end of the trigger 27? engages the outside surface of the contact spring 25 at the tip 36 thereof (see also Fig. 10). The tip 35 of contact spring 25 (seen best in Figs. 9, 10 and 11) is bent so as to lie at an angle relative to the main body of the contact spring. The trigger 2?, in the normal position of the armature, engages tip 39 adjacent the top thereof. By virtue of this angulari-ty, clockwise movement of the armature beyond the position of Fig. 2 is resisted slightly since the are which trigger 21 swings in lies inside of the lower part of tip 3%. In the normal position of the armature, the force exerted by spring 33 causes sufficient torque to be exerted by the armature so that the trigger 2? moves the contact spring 25 toward the contact spring 25 by virtue of the U angularity of tip 3%, thereby bringing contacts SI and 32 into engagement with each other (compare Figs. 9 and 10). When trigger 27 does not engage tip 3%, the

contacts

31 and 32 are separated due to their natural bias. The consequent resistance to further movement of the armature i l causes it to remain in the position shown in Figs. 1 and 2 unless the coil i2 is energized. While the spring 33, which returns the armature Hi to its normal position, has been shown as a cantilever type spring, it will be understood that other forms of springs may be used if desired.

A fru'ther spring 35 also shown as being or" the cantilever type is arranged to have its front end engage the undersurface of the armature and to be deflected thereby if the armature moves in the clockwise direction from the position shown in Fig. 2. The rear end of the spring may be attached by welding, for example, to a projection 36 forming part of the member ii. in the normal position of the armature, as shown in Fig. 2, the forward end of spring 35 just barely touches the underside of the armature so that the spring is not stressed and does not prevent the armature from holding the contacts 3| and 32 closed, as already described, but pivoting of the armature in the clockwise direction from the normal position immediately stresses the spring 35 and thus stores energy therein.

It has been found advantageous to make spring 35 of magnetic material so that it will be attracted by flux in gap 35. 'Spring 35 may then be made stifier and thus store more energy on deflection. The time delay produced by the device may be altered in this manner.

The armature H3 is the only essentially moving par-t whereby the likelihood of the device failing due to wear of parts is reduced to a minimum. All of the operative parts lie essentially in the top plane of the core whereby the minimum of space is occupied.

The remaining structure and the operation of the device may best be understood by referring to Fig. 8 in connection with the other figures. In Fig. 8 a battery 31 is shown which may be connected to the primary winding 12 by means of a switch 38 through a circuit including conductor 39, winding [2, conductor 4|, contact spring 25 contacts 3| and 32, contact spring 26, and conductor 42. Since in the normal position of armature It contacts 3| and 32 are closed, current flows in the circuit described (switch 38 is closed), the magnetic core ll becomes energized and the flux at the gap l5 attracts the armature [4. Under this attraction the armature [4 moves clockwise from the position of Fig, 2 to thatof Fig. 3 during which thetrigger 21 wipes along the outer surface-oftip 30;as -already described. The top surface of the tip 30' is so disposed that the trigger 27, in coming to its normal position 5 in the clockwise direction, moves just to the right of the tip, as shown in Fig. 9; The'tip'30 maybe narrower than the body of spring 26-, as seen best in Figs. 9, 10 and 11 to assure that trigger?! will move thereover. Because of the angularity-of tip 10 30, the contact springs 25 and 26"are'caused'to move slightly toward theleft, as maybe visualizedby referring toFigs. 2, 3,4, 9, 10 and 1'l,-as'the trigger moves downward1y;- The movement toward the left of contactsprings-25 and 26 causes 15 hancedbyproviding a slightly'curvedlip 40 at the lower end of tip 30.

As soon as the armature begins to move clockwise, it begins to deflect spring 35 thereby storing up energy in this spring. When the armaturehas moved downwardly toaposition shown'in 5 Fig. 3, the trigger 2l will have movedbelow the tip 33 (Fig. 11) thereby releasing the contact spring 23 whereupon it deflects toward the right as shown (dotted position in Fig. 8) This movement'effects opening of the contacts 3|and-32 thereby interrupting the circuit previously described ior coil l2. The'magnetic core consequently becomes de-energizedand the fluxin gap l5 collapses rapidly. Thearmature |4- is released andflipped upwardly or counterclockwise by the spring 35,215 may be seen'in Fig.- 4 (dotted position in Fig. 8) v r The stored-up energy in spring35- is transmitted substantially to the armature M as a result of which it pivots-upwardly to the position shown dotted in Fig. 4. The lower edge of tip 30 lies toward the right of trigger 21 when thearmature is in its final attractedpositionin which it is substantially horizontal. Consequently, during the counterclockwise movement 4 of the armature, trigger 21 moves behindthe-contact spring 26 thereby maintaining'thecontacts 3| and 32 separated and insuring that thecircuit to the winding l2 remains open. The final position of armature l4 (shown dotted) is determined by the spring. constant of spring 33- since all of the energy imparted to the armatureby spring 35 is transferredto spring 33 by the time the armature comes to rest; The time delay produced is a function not only of the moment of inertia of the armature and the constant of spring 33, but also of the constant of spring 35 which determinesby its deflection the energy imparted-to the armature. By causing the armature to move through a cycle after each actuation, desired time delays between pulses may be obtained. If the moment of inertia of the armature and the spring constant 33 are chosen so that small deflections occur when the armature is deflected upwardly by spring 35, then relatively short time delays are obtained, and when these members are so chosen that-the armature defleets further, a relatively longer time interval is obtained.

When the-contacts 3| and 32 are separated,

ducing the necessary rapid rate of current change. I

As may be seen in Fig. 8; a secondary winding I3 may be wound upon the core'so as to be coupled-with winding 2 When the primary circuit isin'terrupt'ed'by-theopening of contacts 3| and 32, the storedenergy due to the current flow in winding |2isdissipated'very rapidly and a high voltageappears across the winding l3. This high voltage maybe utilized in any well known manner, suchfor example as to flash a neon light 45- connected to winding l3 by

conductors

46 and 41. Suitable warnings or signals may be produced in this fashion;

Itis not essential that a-secondary winding l3 be provided since, for many purposes, the voltage appearing across winding l2, upon interruption-of the primary circuit contacts, is sufficient. Accordingly, there are shown connected to the ends of winding |2 a pair of conductors 48 and 49 (dotted) which may be connected to any suitable control or energy-receiving element. If, for example, the energy-receiving element is a device requiring relatively heavy current, such as an'incandescent lamp, it may be connected directly to conductors 48 and 49. Consequently, when contacts 3| and 32 are closed, the energy-receiving element is connected in parallel with winding I2 and receives a surge of current which is interrupted when the contacts 3| and 32 are opened. In these instances the condenser 50 may be of a different value of capacity, as is well understood, than in the case'of utilizing the winding 3 to produce a high voltage.

Because the armature I4 is balanced, it does not tend to rotate about its shaft when the device I0 is placed in any position. Rather, it always assumes the position shown in the figures under the influence of spring 33. Consequently, the same periodicity'of pulses is obtained in any position of the device.

The trigger member 21 may be made of insulating material, if desired, whereupon the voltages appearing throughout the various portions of the circuit need never appear in the armature mechanism.

The current drain'on the battery 31 should be as smallas possible in order to have long life and to reduce the amount of servicing needed. Hence, the contacts 3|, 32 should be closed as short a time as possible as is necessary to build up the maximum current neededto produce the effect desired. After that, the contacts should be interrupted and should stay open until a new cycle is ready. In the device as shown, the contacts 3! and 32 are open until the armature reaches'the normal position of Fig. 2. Then, during the attraction of the armature, the contacts stay closed until the armature reachessubstam tially the position of Fig. 3that is so say, until trigger member 21 passes lip 49 of tip 33'. Thereafter the contacts remain open until the armature returns to normal position. The length of time needed for the armature to move from the position of Fig. 2 to that of Fig. 3 is short. Hence, the current flow is short and the drain on the battery is small; The time for this movement of the armature is reduced while still having sufiicient movement to deflect spring 35 to obtain the necessary energy storage by mounting the armature at an angle in its initial position. In this manner thearmature, at its shaft, is close to the air gapl5 whereby a large attractive force is developed which continues as the armature thecontacts, This-condenseralso-assists in p1'O-75J l er-t0 these/p, and at the same time the end of the armature is spaced upwardly from the core sufficiently so that the spring 35 may be deflected a substantial distance.

By making the spring 35 of magnetic material, the spring also is attracted by the gap. Hence, the spring may be made stifier without delaying the time of armature movement from the position in Fig. 2 to that in Fig. 3. Greater energy is thus stored upon deflection of the spring with resultant greater time delays and more positive armature action without increasing the drain on the battery.

The energy needed to cause trigger 27 to effect wiping of contacts 3i and 32 during the first stage of operation is supplied by the magnet. After contacts 3i and 32 open, there is no substantial energy absorbed from the armature l6 and spring 33 system. Consequently, the time delays produced are constant with each succeeding operation.

The operation of the device is cyclical, since, if switch 38 remains closed, the armature is attracted until contacts El, 32 open. Thereafter the armature flips back under the impulse from spring 35 until motion is stopped by spring 33. Spring 33 returns the armature to normal position whereupon contacts 3! and 32 reclose and the cycle repeats.

While particular embodiments of the invention have been shown, it will be understood, of course, that the invention is not limited thereto since many modifications may be made, and it is, therefore, contemplated by the appended claims to cover any such modifications as fall within the true spirit and scope of the invention.

She invention having thus been described, what is claimed and desired to be secured by Letters Patent is:

1. An electromagnetic pulsing device comprising, a magnetic core, a winding thereon, a balanced magnetically responsive armature pivotally mounted with respect to said core whereby energization of said winding will attract said armature and effect pivoting thereof in one direction from a normal position of balance, biased open contact means in circuit with said winding, means for connecting a source of energy in circuit with said winding, means on said armature engageable with said contact means for effecting closing thereof when said armature is in said normal position of balance and disengageable with said contact means and effecting opening thereof when said armature has substantially reached a terminal of pivotal movement in said one direction, and resilient means engageable with said armature for effecting return thereof from said terminal position to said normal position of balance.

2. An electromagnetic pulsing device comprising, a magnetic core, a winding thereon, a balanced magnetically responsive armature pivotally mounted with respect to said core whereby energization of said winding will attract said armature toward said core from a normal position of balance, biased open contact means in circuit with said winding, means for connecting a source of energy in circuit with said winding, means on said armature and engageable with said contact means for eifecting closing thereof when said armature is in said normal position of balance and being disengageable with said contact means and effecting opening thereof upon said armature having substantially reached a fully attracted position with respect to said core, first resilient means engageable by said armature when the 1 terisattractedtoward saidcore for efiecting movement of said armature away from said core subsequent to said armature having reached said fully attracted position, and said second resilient means'engageable by said armature subsequent to movement thereof by said first resilient means for effecting return of said armature to said normal position of balance.

3. In an electromagnetic pulsing device, the combination comprising, a magnetic core including a nonmagnetic gap substantially transversely thereof, a winding disposed on said core, a balanced armature pivotally mounted on said core and disposed in overlying relation with respect to said gap whereby energization of said winding will effect movement of said armature toward said gap from a normal position of balance, biased open contact means mounted on said core and in circuit with said winding, at least one of said contact means being insulated from said core, means for connecting a source of energy in circuit with said winding, means on said armature engageable with said contact means when said armature is in said normal position of balance for holding said contact means closed and disengageable with said contact means and efiecting opening thereof upon said armature having substantially reached a fully attracted position with respect to said gap, first resilient means operable by said armature when attracted to said gap for effecting movement of said armature away from said gap to a position beyond said normal position of balance subsequent to said armature having reached a fully attracted position with respect to said gap, and a second resilient means operable by said armature subsequent to the latter being moved by said first resilient means for effecting return of said armature to said normal position of balance; the moment of inertia of said armature about the pivot axis thereof being chosen relative to the spring constants of said first and second resilient means thereby to produce a predetermined periodicity of armature operation.

4. In an electromagnetic pulsing device, the combination comprising, a magnetic core including a nonmagnetic gap substantially transversely thereof, a windin disposed on said core, a balance-magnetically responsive armature pivotally mounted on said core and in overlying relation with respect to said gap whereby energization of said Winding will effect movement of said armature toward said gap from a normal position of balance, biased open contact means mounted on said core and in circuit with said winding, means for connecting a source of energy in circuit with said winding, means on said armature engageable with said contact means when said armature is in a normal position of balance for holding said contact means closed and effect energization of said winding, resilient means engageable with said armature for effecting return thereof from said fully attracted position to said normal position of balance; said contact means being sufficiently wide whereby said holding 9 ing afnonmagnetic gapsubstantiallytransversely thereof, a winding disposed on said' core," an

armature disposed so as tooverliev said gap, shaft means disposed at aright angle with respect to said gap -for pivotally mounting said armature on said core to movesubstantially in a plane transversely of said core, said armature being attracted toward said gap wfrom a-normal position of balance upon energization of said windingfbiased opencontact means mounted on said core and in circuit with said'winding, at least one of said contact means being insulated from said core, means for connecting'a source of energy in circuit withsaid winding; means on said armature engageable with said contact means when said armature is in said normal position of balance for holding said contact means closed, first resilient means operable by said armature when the latter is attracted toward said gap on energizationof said winding for eiiecting movement of said armature away from said gap to a position beyond said normal position of balance after 'de energization of said winding, second resilient means operable'by said armature subsement to movement thereof by said first resilient means for effecting return of said armature to said normal position of balance; said contact means being sufficiently wide whereby said holding means moves therealong during movement of said armature toward said gap and holds said contact means closed until said armature substantially reaches said gap whereupon said holding means moves away from said contact means thereby permitting said contact means to open and effecting de-energiaztion of said winding.

6. In an electromagnetic pulsing device the combination comprising, a magnetic core including a nonmagnetic gap substantially transversely thereof, a winding disposed on said core, a balanced armature disposed so as to overlie said gap, shaft means disposed at a right angle with respect to said gap for pivotally mounting said armature on said core to move in a plane substantially transversely of said core, said armature being attracted toward said gap from a normal position of balance upon energization of said winding, the pivotal axis of said shaft means being substantially in the plane of said armature and adjacent one edge of said core, biased open contact means mounted on said core and in circuit with said winding, at least one of said contact means being insulated from said core, means for connecting a source of energy in circuit with said winding, means on said armature engageable with said contact means when said armature is in said normal position of balance for holding said contact means closed, said normal position of balance of said armature being at an incline upwardly from said armature shaft means, first resilient means operable by said armature when the latter is attracted toward said gap on energization of said winding for effecting movement of said armature away from said gap to a position beyond said normal position of balance after de-energization of said winding, second resilient means operable by said armature subsequent to movement of the latte by said first resilient means for effecting return of the armature to said normal position of balance; said contact means being sufficiently wide whereby said holding means moves therealong during movement of said armature toward said gap and holds said contacting means closed until said armature sub stantially reaches said gap whereupon said holding means moves away from said contact means 10 thereby permitting said contact means to open and effecting de-energization of said winding.

'7. In an electromagnetic pulsing device, the combination comprising, a magnetic core including a nonmagnetic gap substantially transversely thereof, a winding disposedon said core, a balanced armature disposed so as to overlie said gap, shaft means disposed at a right angle with respect to said gap for pivotally mounting said armature on said core to move in a plane substantially transverse of said core, said armature being attracted toward said gap from a normal position of balance upon ,energization of said winding, the axis of said'shaft' means being substantially in the plane of said armature and adjacent one edge of said'core, biased open contact means mounted on said core and in circuit with said winding, at least one of'said contact means being insulated from said core, means for connecting a source of energy in circuit with said winding, means on said armature engageabl'e with said contact means when saidarmature is in said normal position of balance for holding said gcontact means closed, said normal position of balance of said'armature'being at an incline upwardly from said armature shaft means, magnetically responsively resilient means operable by said armature when the latter is attracted toward said gap on energization of said winding for effecting movement of said armature away from said gap to a position beyond said normal position of balance after de-energization of said winding, said magnetically responsive resilient means being arranged in substantially overlying relation with respect to said gap so as to be attracted thereby simultaneously with said armature, second resilient means operable by said armature subsequent to movement thereof by said magnetically responsive resilient means for effecting return of said armature to said normal position of balance; said contact means being suiiiciently wide whereby said holding means is in engagement therewith during movement of said armature toward said gap and holds said contact means closed until said armature substantially reaches said gap whereupon said holding means moves away from said contact means thereby permitting said contact means to open and effecting de-energization of said winding.

8. In an electromagnetic pulsing device, the combination comprising, a magnetic core including a nonmagnetic gap substantially transversely thereof, a winding disposed on said core, a balanced armature disposed so as to overlie said gap, shaft means for pivotally mounting said armature on said core, said armature being attracted toward said gap from a normal posi tion of balance upon energization of said Winding, biased open contact means mounted on said core and in circuit with said winding, at least one of said contacting means being insulater from said core, means for connecting a source of energy in circuit with said winding, means on said armature engageable with said contact means when said armature is in said normal position of balance for holding said contact means closed, resilient means engageable with said armature for effecting return thereof from said fully attracted position with respect to said gap to said normal position of balance after deenergization of said winding; said contact means being sufiiciently wide whereby said holding means is in engagement therewith during movement of said armature toward said gap and holds said contact means closed until said armature reaches substantially a fully attracted position with respect to said gap whereupon said holding means becomes disengaged from said contact means thereby permitting said contact means to open and efiecting de-energization of said winding, said contact means being mounted eccentrically with respect to said holding means whereby movement of said holding means causes said contact means to wipe together when in a closed relation.

9. An electromagnetic pulsing device comprising a magnetic core including a nonmagnetic gap substantially transversely thereof, a winding on said core for creating a magnetic flux in said core and across said gap when said winding is energized, a balanced pivotally mounted armature disposed so as to substantially overlie said gap and being attractable from a normal position of balance by the created flux in said gap when said winding is energized, biased open contact means associated with said core and in circuit with said winding, at least one of said contact means being insulated from said core, means on said armature engageable with said contact means when said armature is in said normal position of balance for holding said contact means closed, means for storing up energy when said armature is attracted toward said gap and for imparting said stored up energy to said armature upon de-energization of said winding to move said armature away from said gap and efiecting return of said armature to said normal position of balance; said holding means engaging said contact means and efiecting closing thereof until said armature has substantially reached a fully attracted position with respect to said gap whereupon said contact means are permitted to open and said winding is de-energized.

DONALD A. LACE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,452,925 Nottage Apr. 24, 1923 2,127,898 Webster Aug. 23, 1938 2,294,344 Nunn Aug. 25, 1942