US2540294A - Rotary magnetic switch - Google Patents

Description

Feb, 6, 1951 H. E. SCHLEICHER 2,540,294

ROTARY MAGNETIC SWITCH Filed Nov. 26, 1943 7 Sheets-Sheet 1 Feb. 6, 1951 H. E. SCHLEICHER ROTARY MAGNETIC SWITCH 7 Sheets-Sheet 2 Filed Nov. 26, 1943 Feb. 6, 1951 H. E. SCHLEICHER 2,540,294

ROTARY MAGNETIC SWITCH Filed Nov. 26, 1943 7 Sheets-Sheet 5 Feb. 6, 1951 H. E. SCHLEICHER 2,540,294

ROTARY MAGNETIC swITcH Filed Nov. 26, 1945 7 Sheets-Sheet 4 Feb. 6, 1951 H. E. SCHLEICHER 2,540,294

ROTARY MAGNETIC SWITCH Filed Noll. 26, 1945 7 Sheets-Sheet 5 al a 5x4445140 Feb. 6, 1951 H. E. SCHLEICHER 2,540,294

RDTARY MAGNETIC SWITCH Filed Nov. 26, 1943 7 Sheets-Sheet 6 i a; a vliliiefiiilm A L52 V 50 Feb. 6, 1951 H. E. SCHLEICHER 4 2,540,294

ROTARY MAGNETIC SWITCH Filed Nov. 26, 1943 7 Sheets-Sheet 7 Patented Feb. 6, 1951 aoranr menarrc swrrcn Harold E. Schleicher, West Hartford, Conn., as-

signor to The Arrow-Hart & Hegeman Electric Company, Hartford, Conn., a corporation of Connecticut Application November 26, 1943, Serial No. 511,855

25 Claims. 1

This invention relates to electromagneticallyoperated circuit makers and breakers capable of operation locally, or b remote control if desired, and having provision for automatic overload operation incorporated into the switch.

Modern battle conditions require electrical control apparatus to withstand high impact shocks, the shock test requirements having recently been increased more than tenfold. Attempts heretofore to meet the test requirements involved the addition of counterweights, inertia. hammers, special brush-type contacts, etc., to existing conventional commercial structures. These have proved unsatisfactory under the new require-- ments. A new approach to the problem was needed to produce a scientifically designed device in which the movable parts would be dynamically and statically balanced.

It is an object of the present invent on to provide an electromagnetically-operated circuit maker and breaker designed to withstand high impact tests by providing for dynamic and static balance of its movable parts. A related object is to provide an improved design of electromagnetic circuit maker and breaker requiring a mini mum amount of energy to produce initial and succeeding movement and to maintain the mechanism in closed position.

Another object is to provide an improved electromagnetic switch structure which can be mounted in any position without entailing increased energy consumption in its operation to overcome gravity, heavy biasing springs, or the like, and which requires less energy under any conditions than prior devices for similar usage.

Another object is to provide an electromagnetic switch of the above type which will have a more Other objects of the invention will become apparent as the invention is described in connection with the drawings.

Although useful in military fields because of its peculiar advantages, the invention is nevertheless useful in a wide variety of domestic situations.

In the drawings Fig. 1 is a perspective view of a device embodying the invention;

Fig. 2 is a side elevation view of the device of Fig. 1;

Fig. 3 is an exploded perspective view of certain parts employed in the device of Figs. 1 and 2;

Fig. 4 is an elevational section view taken alon line 4-4 of Fig. 2;

Fig. 5 is a plan view of the electromagnetic structure which is located within the forward uniform pull on its armature, a higher sealing pull, with quieter operation and less wattage loss in alternating current use.

Another object is to provide an electromagnetic switch of the above type for the use of dual magnet coils to enable, optionally, the use of the device on difl'erent voltages.

Another object is to provide for remote or local manual control of the device.

Another object is to provide overload protection for a device of the above type, in which the shock-proof features are embodied and in which the principles of dynamic balance are observed and incorporated, not only to preserve the effectiveness of the incorporation of the same principle in the other parts of the device, but also to insure operation accurately and only at the time and under certain predetermined conditions.

end of the device in Fig. l, the housing being removed;

Fig. 6 is a vertical section view taken along line 66 of Fig. 4;

Fig. '7 is an exploded perspective view of'certain parts of the electromagnetic structure;

Fig. 8 is an elevational section view taken along line 8-8 of Fig. 2, showing the details of'auxiliary switch for the holding-circuit and its manual operating means;

Fig. 9 is an exploded perspective view of the bridging contact of the holding circuit auxiliary switch;

Fig. 10 is a horizontal section view of the mechanism of Fig. 8, taken along line Ill-l0 of Fig.

Fig. 11 is an elevational detail view of the spring-biasing structure associated with the main shaft;

Fig. 12 is a section view of the spring-biasing structure, taken along line l2-l2 of Fig. 11;

Fig. 13 is an elevational section view taken along line l3--l3 of Fig. 2 and illustrating one set of the line contacts;

Fig. 13a is a fragmentary detail of the line contact mounting structure;

Fig. 13b is a section view taken along line l3b-i3b of Fig. 13a;

Fig. 14 is an exploded perspective view of the main-line bridging contact assembly; v

Fig. 15 is an elevational section view, taken along line l5l5 of Fig. 2, of the section of the device containing the overload protective devices;

Fig. 16 is a view similar to Fig. 15 but with the heater coils and fixed control contacts removed;

Fig. 17 is a section view taken transversely along line |'|-l 1 of Fig. 15, of the portion of the invention illustrated in Fig.

Fig. 18 is a section view taken along line |8-.|8 of Fig. 15;

Fig. 19 is a section view taken along line Ill-I9 of Fig. 15;

Fig. 20 is an elevational section view taken along line 2|J-2|J of Fig. 2 and shows the opposite side of the section of the device illustrated in Fig. 15;

Fig. 21 is a view similar to Fig. 20, with some of the tripping -mechanism and its resetting means removed;

Fig. 22 is a detail view showing in elevation tripping mechanism that was removed from Fig. 20;

Fig. 23 is an exploded perspective view of the tripping mechanism of Fig. 22; and

Fig, 24 is a wiring diagram illustrating connections for a two-coil form of electromagnet and a common three wire form of contact arrangement, such as that illustrated in the preceding figures.

Referring to the drawings, the main switch contacts, certain control circuit contacts and electromagnetic operating mechanism therefor are housed within a cylindrical sectional casing, built up from molded insulating discs 60, I02, I08, H2, I22, |3O and a metal shell 34, all of which are ultimately supported from a base plate 30 by means of the mounting plates 3| and 32 bolted on said base plate and extending at right angles to the face thereof. The immediate support for the casing sections is four spaced parallel rods 36, 31, 38, 39 (Figs. 2, 3 and others), running between and supported by mounting plates 3|, 32. Holes are formed in each of the parts that make up the casing so they may he slid on the rods.

The device may be conveniently considered as 3 comprising a number of sections or units. Referring to Fig. 2, in the section A at the left end is the electromagnetic operating means, the electric tenninal connections for which extend through the left end cover or cap plate 33, which may conveniently be made of molded insulating material and secured against the face of the mounting plate 3| by screw bolts.

In the section B are a switch and its manual operating means for local control of operation of the device.

In the sections C, D and E are the main circuit making and breaking contacts for the three lines of a three-wire power system. However, the invention is applicable equally to the making and breaking of any number of lines, the three line form having been chosen for illustration as a preferred embodiment because of its common usage. Each section includes a pair of fixed contacts and a movable bridging contact structure, hereinafter more fully described.

In section F are located the overload protective devices which, in the form illustrated, are for a three-wire line.

The movable bridging contact structure and the movable portion of the electromagnetic operating mechanism are mounted upon a main shaft 40 (Figs. 3, 4, 6 and others) whose axis is the main axis of the device. The main shaft 40 has its end journalled in and supported by the mounting plates 3| and 32.

The electromagnetic operating means The parts of the electromagnetic operating means are protected by and located within a twopart magnetic sheet metal housing (Figs. 1, 2, 6). One part 34 has a cylindrical wall and an integral end wall. The other part '35 is a sheet metal disc completely covering the open end of the part 34. The end wall of part 34 lies against the mounting plate 3| and both end wall and cover plate 35 are apertured centrally for passage of the main shaft. Louvers 3421 for ventilation may be formed in the cylindrical wall of part 3. As will presently appear, the housing 34, 35 completely surrounds the electromagnetic parts and is in close proximity thereto, providing a flux path around the coil sides.

Referring particularly to Figs. 3, 4 and 7, it will be observed that the laminated armature 50 of the electromagnet is substantially of Z-shape, with the oppositely directed ends of its arms 50a, 5% made arcuate. A square passageway is formed through the central portion of the armature to enable it to be slid upon and to turn with the main shaft 40, which, also, is square in section. The nature of the armature structure is such that the armature is dynamically balanced upon the main shaft, so that it possesses dynamic and static equilibrium at all times, eliminating, for all practical considerations, tendency for the armature and shaft to turn, unless acted on by an outside force.

The curved end portions 50a, 50b of the armature are adapted to move in and out of hollow toroidal solenoid coils 52, 53 positioned diametrically opposite each other about the main shaft 40. These coils may be connected electrically either in series or in parallel. In case of use, for example, on a 220-volt 3-wire line, if the coils are each -volt coils they may be connected in series across the 220-volt lines; or they may be connected in parallel between the neutral and one outside line, supplying 110 volts. Alternatively, the coils may have dual windings, each winding comprising a 110-volt coil which may be connected in series or in parallel with its neighbor, in a manner similar to that just described, and in series or parallel with the opposite dual coil. In any case, the electromagnetic effect of the coils will be cumulative, creating a greater force and a more uniform pull on the armature than a single coil.

Cooperating with the coils 52 and 53 are pole pieces (designated as a whole by 54 and 56) made up of laminated magnetic material. These pole pieces are identical and are generally arcuate in form, being enlarged near one end as at 54a and having an arcuate extension such as c concentric with, but of less radius than, the main portion of the pole piece. The extensions 54c and 560 extend into one end of each of the coils 52 and 53, while the main portions of the pole pieces bridge the air gap between the ends of the coils 52 and 53, said portions lying just beyond but closely adjacent the paths of movement of the arcuate portions 50a and 50b of the armature. Lying against the inner face of the pole pieces are non-magnetic shield or liner members 55 and 51. These shield members are channelled in shape and arcuate in form to fit around the inner and side faces of the pole piece which they shield. They may be aflixed to the pole pieces by riveting. A tongue, such as 55a, is bent inwardly toward the axis of the armature adjacent one end of each shield member, so as to lie along the inclined surface of the enlargement 54a of the pole piece. When the armature is returned to inactive position by a spring, as hereinafter described, upon deenergization of the coil of the magnet the back side of its radial arms will abut the tongue 55a, preventing the armture from sticking to the pole piece. The liners also provide a momentary time delay, while the flux field is building up to strength needed for moving the armature. This and the non-sticking feature insure that the initial pull on the armature will be unopposed by the armature itself.

To fix the pole pieces and the coil in position resiliently, circular apertures, such as 54p, are provided in the arcuate portions of the pole pieces to enable the pole pieces to be mounted on the mounting rods 36-39, inclusive. As illustrated, the pole piece 56 is mounted upon the rods 36 and Il. To position or space the pole pieces, small coiled compression springs 58 are mounted on the rods, between the pole pieces and the inner surface of that portion of the housing which lies against the plate 3|; and on the opposite side of the pole piece, similar small compression springs 58 (also mounted upon the mounting rods) lie between the pole pieces and the next adjacent section B.

' To allow limited, but to prevent excessive, side thrust of the pole pieces, stud pins such as 548, are attached to the opposite side faces thereof and are engageable with the side walls of the enclosure in which the magnet is housed.

From the foregoing, it may be observed that as the coils are energized, a magnetic field will be set up and will be concentrated at the ends of the coils in the pole pieces and concentrated in the oscillatory path of the armature, reducing losses to a minimum. The force of the magnetic field will draw the arcuate portion of the armature into the coil and against the faces 54d, 56d of the extensions 54c, 580. (These faces may conveniently be provided with shading coils in the conventional manner.) Upon deenergization of the coils, the armature will be retracted to its original po:ition by spring means hereinaiterto be described. The oscillatory movement of the armature is communicated to the main shaft of the device because the shaft is of the square section. An insulating sleeve M is provided to insulate the shaft from all the parts it carries.

To return the shaft 40 to the position normally occupied when the electromagnet is deenergized, a fiat coil spring 42 (Fig. 3) is placed around the end of the shaft near mounting plate 32, between v a spring-tension and stop member 44- and an anchor member 45. The stop and spring tensioning member is a small sheet metal stamping of irregular shape (see Fig. 3) with a square aperture for the square main shaft 40 and spaced, laterally-bent, radially-extending stop lugs a which are adapted to butt against a circular stud or pin 46 extending from the mounting plate 32 as the shaft 40 oscillates. On the opposite side of the member at its periphery is a spring tensioning lug 44c bcnt normal to the member and embraced by the ends of the coil spring 42. Also embraced by these coil spring ends is a similar lug 450 on the stationary anchor member 45. The anchor member 45 is a small sheet metal disc-shaped stamping with a keyhole aperture which interengages with a circumferential groove 409 in the end of the shaft 40 to hold the shaft against axial movement but permit its rotation when the anchor member is fixedly secured within a countersunk recess 32r in the mounting plate 32.

The stop plate or member 44 has its travel limited in both open and closed contact positions. The stoppage in the closed position enables the 6 armature and magnets to align themselves freely: otherwise the magnets would be forced against the mounting rods and prevented from assuming natural adjustment.

The foregoing electromagnet structure is also described and is claimed in my divisional application Serial No. 185,422 filed September 18, 1950.

The local control contacts and their operating mechanism In customary practice, the control of the electromagnet is usually accomplished by a push button station that often is remote from the magnet itself. However, in some fields of use, it is desirable that the device be manually operable locally. To meet such a demand, a local control is provided for in the present invention in the section B of the device.

My invention, without preventing the use of conventional remote control buttons, provides for local control manually by utilizing, as control contacts and in a reconstructed and novelly-improved and manually operable arrangement, the contacts in the conventional sealing-in circuit. In normal manual local operation, these control contacts not only seal-in the main contacts, but these control contacts form the primary circuitclosing means for bringing about energization of the electromagnet coil.

If, however, it is desired to use the invention in a remote control circuit arrangement, the dual functioning sealing-in and control contacts can be utilized for their sealing-in function after the energization of the solenoid; and the provision of the supplementary remote control can be made without affecting the operability of the local control arrangements.

The current carrying parts, except the terminals, are housed wholly within insulating discs 60, which are recessed for the stationary and movable contacts and for the mechanism by which the contacts are or may be manually manipulated. The discs 60 and. the similar purpose discs for the remaining sections hereinafter described are all mounted on the rods 3639 by sliding the rods through suitable apertures Bilr in the discs.

Two identical stationary contacts, designated generally by the numerals 62, 64, are irregular, stamped, sheet metal parts. From a circular, central portion having a screw-threaded aperture, there extends an arcuate arm, such as 622), whose end turns at right angles inwardly toward the axis of the device, as 620, to form a contact blade. From the circular central portion of the contact member, in a position substantially degrees from the position of extension of the arm 62b, there extends another arm 62d Wl'ZOSe end portion 62a is bent at right angles to arm 62d to form a wire terminal. The portions 622) and d, lying in one plane, are countersunk within a re cess molded within the base of the insulating mounting disc 60. A contact and terminal member 64, identical to contact 62, lies in a diametrically opposite position on the disc 60.

The contacts 62 and 64 are adapted to be engaged and disengaged by movable bridging contact structure made up of the parts clearly shown in the exploded view of Fig. 9. This movable contact structure comprises a pair of identical stamped sheet metal, highly-conductive members 66 of a form illustrated in Fig. 9, namely having a large central circular section with a large circular central aperture and with a pair of diametrically oppositely-extending resilient arms forming contact blades 66c. Within the circular apertures of the members 66 lies a cylindrical collar 61 having four lugs 61a extending from the edges thereof on each side of the collar and adapted to be received within apertures provided in a pair of disc-shaped spring-tensioning drivin; members 68, 69, which lie against the opposite outslde faces of the conductive members 66.

The ends of the lugs 61a are peensd over to permanently hold the spring tensioning members and the conductive members 66 together as a unit. Coiled around the collar 67 and located between the conductive members 66 is a coil spring 10, whose ends are radially outturned to engage the end portions of arms 68a, 69a radially extending from the spring tensioning members 68 and 69. The arms are so located on the spring tensioning members 68 and 69 that when these members are secured together by the peening over of the end of the collar 61, the radially-extending arms will lie side by side, covering an arc equivalent to the sum of the widths of the ends of the arms. For the dual purpose of spacing the conductive members 66 apart and for establishing a resilient or lost-motion connection between the conductive member 66 and the spring tensioning members 68, 69, an arcuate member I2 is placed between the inner face of the conductive member adjacent the edges of said members. This arcuate member 12 is riveted fixedly in position by means of rivets passing through the conductive members and the arcuate member. In a diametrically opposite position, a member 74 is placed between the conductive members 66. In thickness, this operating member 74 is the same as member 12 and in shape it is somewhat similar to the member 12 with the exception that a radial extension protrudes outwardly from beyond the edges of the conductive member 66 in position to be engaged by portions of manual actuating members, hereinafter to be described.

' When the movable contact structure is assembled, it will comprise a unit capable of mounting upon the square section of the main operating shaft 40 of the device, so that the spring tension members 68 and 69 will turn as a unit with the shaft. Since the outturned ends of the spring 18 embrace the arms 68a, 69a of th spring tensioning members and the spacing member 12, and since the latter is Permanently connected with the conductive members 66, the whole movable contact structure will normally turn as a unit with the shaft. As the shaft turns counterclockwise from the position shown in Fig. 8 under the influence of the electromagnetic cperating means, the contacts 62 and 64 will be bridged; in like manner, when the electromagnetic means is deenergized and the shaft rotates clockwise, the contacts 62 and 64 will be disengaged by the bridging contacts.

In order to cause engagement or disengagement of the bridging contact with the fixcd- contacts 62 and 64 by manual operation when conditions so require, regardless of the condition of the electromagnetic operating means, there are provided circuit making and circuit breaking thumb members 80 and 82 plvotally mounted upon the mounting rods 36 and 31. These thumboperated members 80 and 82 may conveniently be molded from insulating material in the form illustrated in Figs. 3 and 8. Preferably they will be formed with a generally curved or circular formation, such as 800, at one end, through which is bored a circular hole for the reception of the mounting rods 36 and 31. From this portion extends a winged or thumb-engaging portion 6flt which protrudes through and beyond the edge of the insulating disc 60, so that at the exterior of the device it will be engageable for manipulation by one's thumb or forefinger. For engaging and moving the movable contact structure, extensions 86a, 82a, from portions 800, 820, are directed inwardly of the device into the path of movement of the radial extensions 14a of the contact structure and are so placed as to be engageable with opposite sides of that radial extension. To permit depression of the thumb pieces and 82, the mounting disc 60 is provided with recesses, such as 60a.

Referring to Fig. 8, with the parts in the position there shown, if the thumb piece 80 be depressed, the extension 8lla will engage the radial extension "a to rotate it counterclockwise, thereby causing the movable contact member 66, which is fixed to part 14, to rotate counterclockwise and to engage the fixed contact. During such movement, the main shaft of the device, and thus the spring tensioning members 68 and 69 affixed thereto, would normally remain stationary. Thus, one end of the coil spring 10 will be held stationary by reason of its engagement with the arm of the spring tensioning members 68 and 69. The other end of the spring, however, would be moved by reason of the engagement therewith of the arcuate member 12 moving with the conductive member 66. Because the spring is relatively weak as compared with the friction and inertia of the shaft 40 and the parts it carries, the tension of the spring does not cause the shaft to move.

If the auxiliary switch (comprised of contacts 62, 64, 66) be connected in the holding circuit of the electromagnetic operating means in shunt with the usual start switch (not shown), it will be obvious that as soon as the contacts 62, 64 are bridged, the electromagnet will be energized, thus causing the main shaft of the device to rotate counterclockwise following the partially-completed counterclockwise rotation of the bridging member 66 and completing that counterclockwise motion to hold the bridging contact in engagement with the stationary contact and thereby maintaining the device in closed circuit position.

An opposite result may be obtained by pressing the thumb piece 82 when the device is in closed circuit position. In that position, the radial extension 14a will lie adjacent the upward extension 82a of the thumb piece; and depressing the thumb piece 82 will rotate the movable contact 66 in clockwise direction, disengaging it from the stationary contacts. This rotation of the movable contact member will take place without the necessity of any movement of the main shaft. As soon as the holding circuit is broken, the device will be free to resume open circuit position under the force of the return spring 10, as hereinbefore described. Thus, the auxiliary switch 62, 64, 66 performs the functions of the usual holding or sealing in contacts but in addition it can function as a local control switch for both opening and closing electromagnetically-operated main contacts.

The line contactors and their operation There are three sets of power line contactors, each set including a pair of fixed contacts and a bridging contact member for engaging the fixed contacts. When used in a three-line power system, one set of contacts will be employed for each of the power lines. Each contactor is housed in a separate section (C, D or E), the housing for each section comprising a s acing disc I and a mounting disc I02, H2 or I22. On the latter are mounted the fixed current carrying parts. The discs may be of molded insulation suitably recessed and apertured for the fixed contacts, the movable contact structure and the mounting and terminal rods.

In the section C is the ccntactor for the neutral line. This section is made up of molded insulation discs I08, I02. The fixed contact members for this set are identical in structure and comprise stamped sheet metal pieces I00 of irregular shape, as indicated in Fig. 3. mounted upon the mounting disc I02 by means of screw bolts. The members I00 have a flat central portion lying in a radial recess adjacent the periphery of the disc I02. A portion I00a of the members I00 extends radially inward into a circular recess molded into the face of the disc, within which recess the movable contact member I04' may oscillate. Welded transversely onto the edge of the inwardly-extending portions of the members I00 are rectangular contact blocks I000 of good contact material, such as silver, positioned so as to be engaged and disengaged by similar contact blocks I04c on the end of the arms I04b of the movable contact. The fixed contact members I00 may have an outwardly-extending terminal portion I00b which may be twisted at right angles to the central portion of the members I00.

The rotatable contact member I04 comprises a stamped sheet metal member I04a having a large central portion with a pair of counterbalancing arms I041) extending in diametrically opposite directions. To the ends of the arms I04b the contact tips I040 are permanently afiixed.

For the purpose of maintaining the circuit in case of momentary disengagement of contact blocks I000 and I000, dual supplementary contact members IOS stamped from sheet metal and lying against opposite faces of the central member may be provided. Arcuate fingers I06a conforming substantially to the curvaure of a radius about the axis of the movable contact may he provided on opposite sides of the main central portion in diametrically opposite positions so as to engage and disengage the inwardly-extending end I00a of the fixed contact members I00.

In order that these circuit maintaining sup plomentary contacts I05 shall engage their stationary counterparts after the butt-contact tips I04c engage the stationary contact blocks I000 and disengage before the contacts I040 separate from the contacts I000, the center I04a of the contact member I04 is provided with four equally-spaced, concentrically-placed, arcuate key hole slots I04s, through each of which passes one of four pins I061) that join the pair of supplementar contacts I06 by means of peened-over ends of said pins. The enlargement of the ends of the slots I04s around the pins I06p provides limited relative motion between the pins and the contact I04 to take care of manufacturing inaccuracies and to insure proper contact engagement. Lyin in said slots I04s and pressin at one end against one end of the slot and at the otherend against the pins I061) are small coiled compression springs I01, the springs being held in said slots by the adjacently-lying surfaces of.

the mid-portion of the contact members I06.

The supplementary contacts I06 and the main contacts I04 are so dimensioned that, in the disengaged or open-circuit condition, the angular distance between supplementary contacts IBM 10 and I06 is greater than the angular distance tween the butt contacts I 000 and I04c. Thus the butt contacts will engage first.

Since the supplementary contacts I06 turn with the shaft 40 by reason of the non-circular connection with the shaft 40, the supplementary contacts will be positively moved to disengage the fixed contact members and will do so while the butt contacts I040 are still maintained in engagement with contacts I000 by the action of the springs I01. S nce the butt contact I040 will engage first and disengage last, the supplementary contacts will normally only be called on to maintain the circuit in case of any tendency of the butt contacts to separate. The described structure, thus, maintains continuously the closed-circuit relation of the fixed and movable contact structures, considered as a whole, by reason of the engagement of contacts I06a and I00c. so long as the shaft 40 remains unmoved, even though vibration or other causes might tend momentarily to separate the butt contacts I04c, I00c.

Against the outside surfaces of the supplementary contact members I06 metal driving discs I09 are placed; and all of these parts are then secured together to form a permanent dynamically and statically balanced unit. A square aperture is formed in each of the parts, except the member I04a which has a large circular aperture, for the reception of the main shaft of the device, so that the movable contact unit will move with the main shaft as it oscillates.

When the spacing disc I08 and the mounting disc I02 are placed face to face with their recesses adjacent, the movable current carrying parts are enclosed and are insulated from the parts within the sections B and D.

The movable contacts within the sections D and E are or may be identical with that within the section C.

The stationary contacts in sections D and E may be identical with those in section B. However, when it is desired to use overload protection in connection with these devices, one of the contacts IOI in each of these sections D and E need not have an outside terminal portion. Such contacts may be connected to the overload heater coil in the section F by bolts I I6, I I8 which perform the functions of a securing means and a connector. These bolts may pass through registerin apertures, such as II 2a, I 22a, near the periphery of the mounting discs H2, I22 and the spacing discs I08. For connection with the bolt ends, an arcuate extension or arm IOIe may be formed upon the contact members IM to lie within recesses of similar shape (such as N21, for example) molded in the discs II2, I22 adjacent their peripheries. The end of such arcuate extension I0 Ie is enlarged and apertured with the aperture inregister with the apertures II7a, I22a in the discs II2, I22. By having the extension IOIe embedded within and flush with the surface of the discs II2, I 22, it is possible to have the spacing discs lie flat against the surface of the discs II2, I22, and at the same time to substantially enclose the current carrying parts.

The overload protective devices 7 tent in the protective end of the device is the need to prevent actuation, when shocks occur, for unless the overload or protective devices be shockproof, they may operate under shock conditions to trip the breaker open in spite of all precautions taken in making the breaker itself shockproof.

The overload protective devices themselves are mounted upon a molded insulation mounting disc I30 which is suitably and symmetrically recessed at various points and places on each side of a vertical axis of symmetry for the individual elements which make up the dual protective devices.

On one side of the mounting disc I30 are mounted the heater coils and bimetallic strips (see Figs. 15 and 16); on the other side (see Figs. 20 and 21) is mounted the balanced tripping mechanism which controls a rotary switch connectible in the electromagnetic circuit so as to accomplish deenergization of the magnet and resultant circuit opening movement of the whole device on overload. The tripping mechanism is a removable unit (see Fig. 22 wherein it is removed) which can be tripped by the action of bimetallic strips I44 and I45 responsive to heat developed on overload in resistance wire coils I32, I34 carrying main line current and placed next to the bimetallic strips.

Outside connections to the heater coils are made through identical stamped sheet metal terminal members I35, I38 mounted in diametrically opposite radially directed recesses at the periphery of the mounting disc I30 having their terminal portions, such as I38a, extending beyond. To accommodate the heater coils and bimetal members. oblique channels I33, I35 convergent from the inner ends of the terminal members I38, I38 are formed in the mounting disc. At the inner ends of these channels. L-shaped stamped sheet metal connectors I40, I42 form a. mounting to which one end of the heater coils is secured, their opposite ends being screwed to the terminals I38, I38, whereby the coils are positioned in the upper part of the channels.

Electric connection of the heaters I32, I34 to the main contact extensions IOIe of the sections D and E respectively is by the connectin bolts I I8, "-8 respectively, insulating sleeves II8s and Has being placed around the shanks of the bolts to insure insulation of the bolts from other parts of sections through which they may pass. Boltreceiving apertures I30b are formed in the disc I30 in register with apertures II2a. I 22a in sections D and E for the bolts H8 and H8.

Located beneath. and substantially parallel to the axis of the heaters I32, I34 are bimetal strips I44, I46 mounted at one end of small brackets I43, I45. The brackets are each secured at one end to the mounting disc I30 by through bolts I41.

To adjust the bimetal strips one end of the bimetal supporting brackets I43 receives a screw bolt I50, which is bored through and internally threaded to receive a calibration-compensating screw I52 that engages one end of a lever I 54 pivotally mounted near one end in the disc I30. The other end of the lever engages the under surface of the bimetal so that on turning the adjustment bolt and screw the lever is rocked to vary the position of the bimetal with resultant variation in the amount of flexure thereof that will cause the latch I88 to trip free of the latch disc 200. Suitable locking means, as shown, are

12 provided to maintain the position of adjustment of the screw I52 and bolt I50.

In order that the bimetal strips may act on the tripping mechanism on the opposite side of the mounting disc I30, the disc is pierced with openings I30a (Figs. 21 and 16) beneath the free ends of the bimetal strips at the end of the channels I33, I35, where the connectors I40, I42 are. As the bimetal strips flex on overload, their ends (one or both) enter the openings I30a to engage buttons I98 on the trigger member of the tripping mechanism now to be described.

The tripping mechanism is carried by a frame that may be stamped from sheet metal in the form best indicated in Fig. 23. The central portion of this frame I is in the form of a parallelogram, from the opposite corners of which there are extensions I82, I84. The extension I82 has lateral arms or lugs I86 bent up at right angles thereto, between which is located the dynamically and statically balanced pivoted trigger member I88 which is preferably formed from molded insulating material into hexagonal prismatic form. In order to resiliently maintain the trigger member in a neutral position, obliquelyangled leaf spring members I92, I94 each have one arm lying upon and screwed to the face of the frame I80, while the other arm extends obliquely upward to engage converging adjacent faces of the trigger member I88. On the opposite side of the trigger member from said converging faces semispherical buttons or nubs I98 are located near the ends of the trigger in position to be engaged by the ends of the one or the other of the bimetallic members. Thus, when either of the bimetallic members bend and press against either of the nubs or heads I98, the trigger member I88 will be caused to pivot. In the central portion of the trigger member is molded a balanced tripping member which is balanced by having similar fingers such as I98 extending in opposite directions. The finger I98 extends radially of the pivotal axis beyond the surface of the tripping member in position to be engaged by the radial shoulder on a dynamically balanced rotary latch disc 200 which is driven onto, keyed to. or otherwise secured to, a stud shaft 202. To afford support for bearings for the stud shaft 202, the frame I80 has its extension I84 turned up at right angles to the central section of the frame I80 and its end again turned at right angles so as to lie parallel to the central section I80. Conical hearing holes are formed in the end of the stud shaft 202 to receive the conical bearing member 204 located in the central portion of the frame I80 and to receive the conical end of a journal pin 206 which is screw-threaded into an aperture in the arm I co-axial with the conical bearing member 204. The pin 308 may be adjusted to remove all excess play and prevent movement under impact.

In order to bias the latch disc 200 in one direction normally, a coil spring 208 is placed around the end of the stud shaft 202 with one end of the spring 208 anchored in the frame I80, and the other anchored in the latch disc. In order to limit the rotation of the latch disc, an arcuate recess 200a is formed adjacent the periphery thereof and extending through an angle of approximately 60 degrees. A pin I80a aflixed in the central portion of the frame I 80 extends up into the aperture 200a and acts as a stop to limit the rotation of the latch disc 200.

Carried by the stud shaft 202 at its end, is a movable self-aligning contact member made up of a pair of insulating discs 2"), between which and to which are riveted a pair of bridging contact members 2I2 having the form illustrated in Fig. 23, namely a ring-shaped portion with diametrically opposite apertures for the rivets and with contact blades diametrically opposite each other but spaced 90 degrees from the rivet holes. An insulating spacer disc 2 is placed between the two bridging contact members, so that the blades of the members may engage opposite sides of fixed contact fingers 2I6a (see Figs. 8 and 19). These fingers 2I8a extend radially inward as extensions from contact and terminal members 2IG that may conveniently be stamped from highly conductive sheet metal into the oblique form shown in Fig. 15. The members 2I6 are bolted to the mounting disc I30 in symmetrical positions of the axis of symmetry on opposite sides. Recesses having the same form and shape as the members 2I8 are provided for embedd ng said members in the base of the mounting disc I28. The outer ends of the members 2 l6 are bent to provide terminal lugs, which are provided with terminal screws in conventional fashion.

In order to reset the thermal-overload opened contacts 2I2 into position to bridge the contacts 2I5a, there is provided a resetting button in the form of a depressible insulating bar I60 sliding in a rectilinear tangential passage I62 in the d'sc I30. A spring I84 in the bottom of passage I62 urges the button outwardly of the passage; and a laterally extending arm I 56 near the inner end of the button is positioned to engage a pin I68 extending up from the surface of the latch disc 288. When the button is depressed, the engagement of arm and pin cause rotation of the latch disc 280 against the urge of spring 288 until the tongue I98 falls back of the shoulder on the latch disc to hold said disc latched. In that position the contacts 2 I2 and 2 I6 are engaged.

From the foregoing description of the parts, it may be observed that when either one or the other of the heater coils becomes overheated by excess current, it will cause one or the other of the bimetallic members to bend, so that its end engages and turns the trigger member I88, causing its tongue Or extension I98 to disengage the shoulder on the latch disc 280 (the positioning springs I92 and I94 for maintaining the latch ng member I88 in neutral position ar not of sufficient strength to interfere with the overload operation of the bimetallic member). As soon as the latch disc 208 is free, the spring 208 will cau e it to rotate. Since the stud shaft 202 turns with the latch disc, the movable contact structure will also turn with it and the bridging contact member 2 I 2 thereof will thereupon disengage the fixed contact members to break the control circuit. In conventional practice, the contacts controlled by this tripping mechanism will be in the holding circuit of the electromagnet and their disengagement will cause the energization of the electromagnet coil, whereupon under the influence of the biasing spring the electromagnet conta ts and the shaft on which they are mounted wll rotate into open circuit position, causing the switch to open.

The dynamic balance of movable parts is carried out in the overload devices by the-structure of the trigger i88 with its oppositely-extending mutually balancing fingers I98 and the springs I92, I94 which balance it in latching position, and in the balanced rotary contact structure 2I0, 2I2 2 in which, also,'the stationary contacts are engaged on both sides so as to prevent momentary disengagement due to shock occurring in an axial direction.

In Fig. 24 there is shown diagrammatically one possible method of connecting the form of invention illustrated in the preceding figures. In this diagram like reference characters indicate equivalent physical parts of the device illustrated in the preceding figures. illustrates one form of connections, the invention in no sense is limited thereto.

In considering the functions, advantages and novel features, the following should be noted:

Long angular rotation of the armature is one of the factors desirable for securing a high interrupting gap of th contacts for direct current ratings, without resorting to condensers or blow out coils. In the present invention, the air gap of the armature can be regulated to any intermediate position, to suit various interrupting characteristics, by governing the location of the stop-plate lugs 44a. On maximum stroke, the armature moves within that portion of the solenoid that produces the maximum constant magnetic force value, with a minimum of inrush current.

Due to the high starting torque resulting from the novel magnet construction, the armature return spring may be of sufficient strength to arrange the same contacts in normally closed position if required, such as by reversing the fixed and bridging contacts and plac ng the bridging contact degrees from its present position on the main shaft. The contacts will then face oppositely from the present showin and will be normallv engaged. This reversal will not interfere with the d namic and static balance or condit on of eouilibrium of the device, since all the movable parts are individually balanced.

Being totally enclosed, the movable parts are protected aga n t tampering, atmospheric conditions, and the like.

From the foregoing it will be observed that all mo able part are in balanced condition, in both open and clo ed po itions. Since the return spring 2 which normally would move the parts to open position, is overcome by the electromagnet while the latter is energized there is no tendency by weight, bias, or location of the movable parts to move when the whole device is suddenly subjected to shock or violent motion. The balance of the parts and condition of equilihrium avoids such tendency. At the same time it prov de a more ea ily operable device. requiring le s power with better holding qualifications.

Many modifications within the scope of the invention will occur to tho e skilled in the art. Therefore I do not limit the invention to the embodiment disclosed.

I cla m:

1. In an electromagnetic switch, a rotary arma ure ha ing counterbalancing oppo itely extending arms, a shaft actuated by said armature, oppo ite electromagnet coils acting on said armature solid inflexible movable contact means mounted on said shaft, rigid fixed contact means engageable by said movable contact means, said movable contact means having counterbalancing ort ons to maintain static and dynamic equilibrium and to avoid tendency to move from a given po ition when the switch is subjected to shock or motion, and a plurality of coiled springs between said shaft and said movable contact means to permit limited motion of said shaft Although the diagram after engagement of said fixed and movable contact means.

2. In an electromagnetic switch, a rotary armature having counterbalancing oppositely extending arms, a shaft actuated by said armature, opposite electromagnet coils acting on said armature, a solid inflexible movable contact member mounted on said shaft, solid inflexible fixed contact means engageable by said movable contact means, said movable contact member having counterbalancing portions to maintain static and dynamic equilibrium and to avoid tendency to move from a given position when the switch is subjected to shock or motion, and means including a plurality of independent spring members to resiliently mount said solid inflexible movable contact means on said shaft permitting limited motion of said shaft after engagement of said contact means.

3. In an electromagnetic switch, a rotary armature having counterbalancing oppositely extending arms, a shaft actuated by said armature, opposite electromagnet coils acting on said armature, rigid movable contact means mounted on said shaft, rigid fixed contact means engageable by said movable contact means, said movable contact means having counterbalancing portions to maintain static and dynamic equilibrium and to avoid tendency to move from a given position when the switch is subjected to shock or motion, said fixed contact means halting said rigid movable contact means on engagement thereof, and means to resiliently mount said movable contact means on said shaft permitting limited motion of said shaft after engagement of said contact means.

4. In an electromagnetic switch, a rotary armature, a shaft actuated by said armature, electromagnet coils to actuate said armature, contact means moved by said shaft, fixed contact means 'engageable by said movable contact means, a non-rigid connection between said shaft and movable contact means permitting movement of said contact means relative to said shaft, manually operable means to move said movable contact means into or out of engagement with said fixed contact means regardless of the condition of energization or deenergization of the electromagnet.

5. In an electromagnetic switch, a rotary armature, a shaft actuated by said armature, electromagnet coils to actuate said armature, fixed contact means, movable contact means on said shaft engageable with said fixed contact means, means resiliently connecting said shaft and movable contact means and permitting movement of said movable contact means independently of said shaft. manually actuated means for moving said movable contact means independently of said shaft.

6. In an' electromagnetic switch, a rotary armature, electromagnet coils to actuate said armature, a shaft actuated by said armature, control contact means moved by said shaft and nonrigidly mounted thereon, fixed contact means engageable by said movable contact means, main contact means movable by said shaft, main fixed contact means engageable by said main movable contacts, manually actuated means for moving said movable control contact means without moving said shaft.

7. In an electromagnetic switch, a rotary armature, electroma-gnet coils to actuate said armature, a shaft actuated by said armature, control contact means moved by said shaft and nonrigidly mounted thereon, fixed contact means engageable by said movable contact means, connecting means between said fixed and movable contact means and said coils for controlling the energization of said coils, main contact means movable by said shaft, main fixed contact means engageable by said main movable contacts, manually actuated means for moving said movable control contact means without moving said shaft to cause energization or deenergization of said coils.

8. In an electromagnetic switch, a rotary armature, electromagnet coils to actuate said armature, a shaft actuated by said armature, control contact means moved by said shaft and nonrigidly mounted thereon, fixed contact means engageable by said movable contact means, connecting means between said fixed and movable contact means and said coils for controlling said coils, main contact means movable by said shaft, main fixed contact means engageable by said main movable contacts, manually actuated means for causing engagement or disengagement of said control contact means to cause deenergization or energization of said coils and to actuate said main contact means.

9. In an electromagnetic switch, a rotary armature, electromagnet coils to actuate said armature, a shaft actuated by said armature, control contact means moved by said shaft and nonrigidly mounted thereon, fixed contact means engageable by said movable contact means, main contact means movable by said shaft, main fixed contact means engageable by said main movable contacts, manually actuated means for moving said movable control contact means without moving said shaft, each of said movable contact means and said armature being constructed, arranged and mounted on said shaft in dynamically and statically balanced conditon to avoid tendency to move from a given position when the switch is subjected to shock or motion.

10. In an electromagnetic switch, a rotary armature, electromagnet coils to actuate said armature, a shaft actuated by said armature, control contact means moved by said shaft and non-rigidy mounted thereon, fixed contact means engageable by said movable contact means, main contact means movable by said shaft, main fixed contact means engageable by said main movable contacts, manually actuated means for moving said movable control contact means without moving said shaft, each of said movable contact means and said armature being separately mounted on said shaft and being removable therefrom and being constructed and arranged in dynamically and statically balanced condition, said condition of ba'ance being undisturbed by removal of any of said contact means.

11. An electromagnetic switch comprising plural separate sections, cooperating insulating discs forming certain of said sections and housing separate sets of contact means, a shaft passing through said sections, rotary contact means within said contact housing sections connected and moved by said shaft, and fixed contact means engaged by said rotary contact means, rotary electromagnetic operating mechanism in one of said plural sections for moving said shaft comprising an armature on said shaft, and plural toroidal coils for actuating said armature.

12. An electromagnetic switch comprising plural separate sections, cooperating insulating discs forming certain of said sections and housi7 ing separate sets of contact means, a shaft passing through said sections, rotary contact means within said contact housing sections connected and moved by said shaft, and fixed contact means engaged by said rotary contact means, rotary electromagnetic operating mechanism in one of said plural sections for moving said shaft comprising an armature on said shaft, and plural toroidal coils for actuating said armature, said movable contact means and said armature being constructed and mounted on said shaft in individual and combined dynamic and static balance to avoid tendency to move from a given position when said switch is subjected to shock or motion.

13. In an electromagnetic switch, a rotary armature, electromagnet coils to actuate said armature, a shaft actuated by said armature, control contact means moved by said shaft and non-rigidly mounted thereon, fixed contact means engageable by said movable contact means, main contact means movable by said shaft, main fixed contact means engageable by said main movable contacts, means normally urging said shaft into a certain position, said urging means being overcome by energization of said coils and manually actuated means for moving said movable control contact means without moving said shaft to cause energization of said coils for moving said shaft electromagnetically, or deenergization of said coils for permitting said urging means to return said shaft to normal position.

14. A rotary electromagnetically operate switch comprising a shaft, an armature mounted to turn said shaft, electromagnet coils to actuate said armature, movable control contact means operable by said shaft, fixed contact means engageable by said movable control contact means, movable main contact means operable by said shaft, fixed main contact means engageable by said movable main contact means, means normally urging said shaft into one position when said coils are deenergized, means connecting said movable control contact means to said shaft permitting relative motion by the control contact means while the shaft remains stationary, manual actuating means for moving said movable control contact means to deenergize the coils to permit return of said shaft to normal position by said urging means, or to energize the coils to overcome the urging means and move said shaft to energized position, said connecting means and shaft and electromagnet cooperating to cause said control contact means to remain in engaged or disengaged position after manual movement thereto, until subsequent opposite movement of said shaft or actuation of said manual means.

15. In an electromagnetic switch, electromagnetic operating means comprising coils, a rotary shaft and a balanced armature on said shaft, in combination with local operating means for controlling said magnet, and main contact means operated by said shaft, said local control means comprising movable contact means operated by said shaft and fixed contact means engaged thereby, manual actuating means for said local movable contact means for causing energization or deenergization of said magnet, means mounting said movable local control contact means on said shaft and causing movement of said local movable contact means with said shaft but permitting independent movement thereof by said manual actuating means.

18. In an electromagnetic switch, electromagnetic operating means comprising coils, a rotary shaft and a balanced armature on said shaft, in combination with local operating means for controlling said magnet, and main contact means operated by said shaft, said local control means comprising movable contact means operated by said shaft and fixed contact means engaged thereby, manual actuating means for said local movable contact means for causing energization or deenergization of said magnet, means mounting said movable local control contact means on said shaft and causing movement of said local movable contact means with said shaft but permitting independent movement thereof by said manual actuating means, said main contact means and said movable local contact means having balanced moving parts for the purpose of avoiding tendency of said shaft to move from a given position when the switch is subjected to shock or movement.

17. An electromagnetic switch comprising a rotary armature, oppositely located arcuate arms on said armature, arcuate magnetic pole pieces lying outside the arc of movement of said arms but adjacent thereto, arcuate electromagnet coils oppositely located, said pole pieces lying between the ends of opposite coils to form a flux path, each pole piece having an extension entering the end of a coil, a shaft actuated by said armature, a solid inflexible movable contact means mounted on said shaft, rigid fixed contact means engageable by said movable contact means, said movable contact means having counterbalancing portions to maintain static and dynamic equilibrium and to avoid tendency to move from a given position when the switch is subjected to shock or motion, and a plurality of coiled springs between said shaft and said movable contact means to permit limited motion of said shaft after engagement of said fixed and movable contact means.

18. An electromagnetic switch comprising a rotary armature, oppositely located arcuate arms on said armature, arcuate magnetic pole pieces lying outside the arc of movement of said arms but adjacent thereto, arcuate electromagnet coils oppositely located, said pole pieces lying between the ends of opposite coils to form a flux path, each pole piece having an extension entering the end of a coil, a shaft actuated by said armature, contact means moved by said shaft, fixed contact moans engageable by said movable contact means, a non-rigid connection between said shaft and movable contact means permitting movement of said contact means relative to said shaft, manually operable means to move said movable contact means into or out of engagement with said fixed contact means regardless of the condition of energization or deenergization of the electromagnet.

19. An electromagnetic switch comprising a rotary armature, oppositely located arcuate arms on said armature, arcuate magnetic pole pieces lying outside the arc of movement of said arms but adjacent thereto, arcuate electromagnet coils oppositelyv located, said pole pieces lying between the ends of opposite coils to form a flux path, each pole piece having an extension entering the end of a coil, a shaft actuated by said armature, control contact means moved by said shaft and non-rigidly mounted thereon, fixed contact means engageable by' said movable contact means, main contact means movable by said shaft, main fixed contact means engageable by said main movable contacts, manually actuated means for moving said movable control contact means without moving said shaft.

20. An electromagnetic switch comprising plural separate sections, cooperating insulating discs forming certain of said sections and housing separate sets of contact means, a shaft passing through said sections, rotary contact means within said contact housing sections moved by said shaft, and fixed contact means engaged by said rotary .contact means, rotary electromagnetic operating mechanism comprising a rotary armature, oppositely located arcuate arms on said armature, arcuate magnetic pole pieces lying outside the arc of movement of said arms but adjacent thereto, arcuate electromagnet coils oppositely located, said pole pieces lying between the ends of opposite coils to form a flux path,

each pole piece having an extension entering the end of a coil.

21. An electromagnetic switch comprising a rotary armature dynamically and statically balanced for the purpose of avoiding a tendency to move from a given position when the electromagnet is subjected to shock or motion, said armature having oppositely extending counterbalancing arms with circumferentially curved end portions, electromagnet coils having arcuate open-end cores to receive said arms, magnetic pole pieces adjacentthe arcs of travel of said arms and positioned between the ends of opposite coils, a shaft actuated by said armature, a solid inflexible movable contact member mounted on said shaft, fixed contact means engageable by said movable contact means, said movable contact member having counterbalancing portions to maintain static and dynamic equilibrium and to avoid tendency to move from a given position when the switch is subjected to shock or motion, and means including a plurality of independent spring members to resiliently mount said solid inflexible movable contact means on said shaft permitting limited motion of said shaft after engagement of said contact means.

22. An electromagnetic switch comprising a rotary armature dynamically and statically balanced for the purpose of avoiding a tendency to move from a given position when the electromagnet is subjected to shock or motion, said armature having oppositely extending counterbalancing arms with circumferentially curved end portions, electromagnet coils having arcuate open-end cores to receive said arms, magnetic pole pieces adjacent the arcs of travel of said arms and positioned between the ends of opposite coils, a shaft actuated by said armature, rigid movable contact means mounted on said shaft, rigid fixed contact means engageable by said movable contact means, said movable contact means having counterbalancing portions to maintain on static and dynamic equilibrium and to avoid tendency to move from a given position when the switch is subjected to shock or motion, said fixed contact means halting said rigid movable contact means on engagement thereof, and means to resiliently mount said movable contact means on said shaft permitting limited motion of said shaft after engagement of said contact means.

23. An electromagnetic switch comprising a rotary armature dynamically and statically balanced for the purpose of avoiding a tendency to move from a given position when the electromagnet is subjected to shock or motion, said armature having oppositely extending counterbalancing arms with circumferentially curved end portions, electromagnet coils having arcuate openend cores to receive said arms, magnetic pole pieces adjacent the arcs of travel of said arms and positioned between the ends of opposite coils, a shaft actuated by said armature, fixed contact means, movable contact means on said shaft engageable with said fixed contact means, means resiliently connecting said shaft and movable contact means and permitting movement of said movable contact means independently of said shaft, manually actuated means for moving said movable contact means independently of said shaft.

24. An electromagnetic switch comprising a rotary armature dynamically and statically balanced for the purpose of avoiding a tendency to move from a given position when the electromagnet is subjected to shock or motion, said armature having oppositely extending counterbalancing arms with circumferentially curved end portions, electromagnet coils having arcuate open-end cores to receive said arms, magnetic pole pieces adjacent the arcs of travel of said arms and positioned between the ends of opposite coils, a shaft actuated by said armature, control contact means moved by said shaft and nonrigidly mounted thereon, fixed contact means engageable by said movable contact means, main contact means movable by said shaft, main fixed contact means engageable by said main movable contacts, manually actuated means for moving said movable control contact means without moving said shaft.

25. An electromagnetic switch comprising a rotary armature dynamically and statically balanced for the purpose of avoiding a tendency to move from a given position when the electromagnet is subjected to shock or motion, said armature having oppositely extending counterbalancing arms with circumferentially curved end portions, electromagnet coils having arcuate openend cores to receive said arms, magnetic pole pieces adjacent the arcs of travel of said arms and positioned between the ends of opposite coils, a shaft actuated by said armature, control contact means moved by said shaft and non-rigidly mounted thereon, fixed contact means engageable by said movable contact means, main contact means movable by said shaft, main fixed contact means engageable by said main movable contacts, manually actuated means for moving said movable control contact means without moving said shaft, each of said movable contact means and said armature being constructed, arranged and mounted on said shaft in dynamically and statically balanced condition to avoid tendency to move from a given position when the switch is subjected to shock or motion.

HAROLD E. SCHLEICHER.

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

UNITED STATES PATENTS Number Name Date 365,438 Jacobs June 28, 1887 792,860 Sundh et al June 20, 1905 830,209 Conkling et a1 Sept. 4, 1906 913,104 Cedergren Feb. 23, 1909 928,516 Hellmuncl July 20, 1909 1,222,431 McCarthy Apr. 10, 1917 1,356,290 Kellum Oct. 19, 1920 (Other references on following page) UNITED STATES PATENTS Number Name Date Wood Feb. 19, 1924 Tugendhat May 18, 1926 Spencer Jan. 28, 1930 Apple June 2, 1931 Shepard Dec. 8, 1931 Bossart May 17, 1932 Getty Dec. 31, 1935 Bassett May '7, 1940 Latta May 28, 1940 Kimball Dec. 17, 1940 Reynolds July 8, 1941 Walker July 7, 1942 Number Name Date, Whittaker Feb. 2, 1943 May Apr. 6, 1943 Reynolds Oct. 5, 1943 Snavely Nov. 16, 1943 Cramer Dec. 21, 1943 Bucklen et a1 Jan. 18, 1944 Meuer et a1 Feb. 26, 1946 Kaiser Sept. 21, 1948 FOREIGN PATENTS Country Date Great Britain Dec. 16, 1936 France Mar. 12, 1914

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