US2322574A - Electromagnet - Google Patents

Description

0 t) d U A \J blu June 22, 1943. L. J. GOLDBERG 2,322,574

ELECTROMAGNET Original Filed July 17, 1940 2 Sheets-Sheet 1 Page. 80

Inventor:

Leon J.Goldb PQ,

His ttofrwey.

June 22, 1943. 1 GOLDBERG I 2,322,574

ELECTROMAGNET Original Filed July 17. 1940 2 Sheets-Sheet 2 IM; l *L .L

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Inventor: Le on J. Gol cibercg,

)Dy/gw 6' y His Attorney.

atented June 22, 1943 UNITED Vul vll STATES PATENT OFFICE ELECTROMAGNET Leon J. Goldberg, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Original application July 17, 1940, Serial No. 345,969, now Patent No. 2,291,465, dated July 28, 1942. Divided and this application May 15, 1941. Serial No. 393.551

4 Claims.

My invention relates to electromagnets, more particularly to electromagnets for operating electric switches or circuit breakers and has for its object a simple, reliable and compact electromagnet structure.

This application is a division of my copending application, Serial No. 345,969, filed July 17, 1940, now Patent No. 2,291,465, granted July 28, 1942, for Circuit breaker, in which application I have claimed the circuit breaker contact structure disclosed in this application.

In my copending divisional application, Serial No. 393,552, led May l5, 1941, now Patent No 2,291,466, granted July 28, 1942, for Circuit breaker, I have claimed the blow-out coil and arc chute structure described in this application.

More particularly, among the objects of my present invention is to `p11g,\l,cle a siinplewapilrugged self-aligning mountingfourmthe armature of tiijirijt, a rle' shader having'neipsd portion in which e eat is generated, and simple and compact means for securing the coil in place and for forming a. st QpiQrthe armature.

For a more complete understanding of my invention, reference should be had to the accompanying drawings in which Fig. l is a fragmentary plan view of a contactor embodying my invention; Fig. 2 is a side elevation View of the device shown in Fig. l looking toward the right hand; Fig. 3 is a fragmentary view in section taken along the line 3 3 of Fig. l looking in the direction of the arrows; Fig. 4 is a view mainly in section taken along the line 4--4 of Fig. l looking in the direction of the arrows; Fig. 5 is a fragmentary view of the arc chute and insulating base; Fig. 6 is an exploded view of the stationary contact and blow-out coil assembly; Fig. 'l is a view in perspective of the stationary magnet core, and shading coils disassembled therefrom; Fig. 8 is a fragmentary side elevation View showing the movable contacts turned to permit removal of the stationary contact; while Fig. 9 is an elevation view of an arc chute provided with a modified form of my invention; and Fig. l0 is a perspective view of the core of the blowout coil.

Referring to the drawings, in one form of my invention, the switch parts are mounted on a steel base plate I0 which can be secured upright to a suitable panel or other support. A stationary magnet frame (Fig. 7) is secured by brackets I2 and I3 to the su-pport l0 by means of suitable screws (not shown) a layer of electrically insulating material (not shown) being provided between the brackets I2 and I3 and the support and the screws being electrically insulated from the support. As shown, the magnet frame or core member is U-shaped and provided with two pole faces lying in a common plane. It is mounted on the base plate I0 with one pole above the other and with the plane of the pole faces substantially upright, as shown in the drawings. Also secured directly to the support I0 is a base member I4 (Fig. 5), made of a suitable electrically insulating material such as a molded phenolic condensation product, having its righthand side, as seen in Fig. 1, secured to the plate I0 over the bracket I2 by means of a bolt I5 passing through the two parts. A spring clamp I6 (Fig. 3) is provided underneath the head of the bolt to take up irregularities in I0 or I4 instead of allowing either I0 or I4 to bend to compensate for these irregularities. One other bolt, not shown, near the left hand side of I4 is also provided to secure the supports I0 and |4 rigidly together, a layer of insulating material Il being provided between them. On its side adjacent the support I0, the support I4 is provided with a large recess I9 in which lie the heads of screws or bolts hereinafter referred to in detail for securing various switch parts to the other side or front of the insulating base I4, the layer of insulation II further insulating these heads from the metal support I0.

As shown, the circuit breaker is a three-circuit device such as for a three-phase circuit, the details for one circuit only, i. e., one stationary and one movable contact, being shown in detail.

Each stationary contact 20 (Fig. 8) is mounted on an electrically conducting, non-magnetic supporting member 2|, preferably made of copper, and secured thereto by means of a screw 22 passing through a slot 23 in the end of the contact adjacent the insulating base I4. Preferably a boss (not shown) is provided on the member 2| around the screw 22 for engaging a corresponding recess on the contact 20 so as to further position the contact.

As shown in Fig. 4, the stationary contact supporting member 2| is secured by screws 25 to the insulating base I4. It is provided with a length 26 (Fig, 6) extending outward at right angles to the base I4 and with a portion extending upward as seen in Fig. 4 and slightly curved back toward the base in conformity with the curvature of a blow-out coi1 21 but spaced from the blow-out coil. This blow-out coil, mounted inside or behind the member 2| is formed from a strap of electrically conducting material, such as copper, which is wound edgewise into a coil.

o nulli One end 21a (Fig. 6) of the coil is Welded directly to the contact supporting member 2| while its other end is welded to a terminal strap 23 which is secured to the support |4 by a screw 29. A magnet iron core 30 extends axially of the blow-out coilv and pole piece plates 3| and 32 made of magnet iron are welded to the ends of this core. In the assembly of the plates 3| and 32, they are bent or shaped to rest tightly against the edges or sides of the supporting member 2| and are secured and pressed suitably in place while they are welded to the core member 30.

Thus the blow-out coil 21, the core 30, the pole pieces 3| and 32, and the support 2| are securely assembled together by welding into a unitary construction. The ends 3|a and 32a (Fig. 6) of the pole pieces project slightly beyond the member 2| at the lower end of the upright portion of the member 2| so as to bring the flux passing between these ends of the pole pieces in the region of the contact surface on the stationary contact 20 which lies between these projecting ends, as seen in Fig. 4. It will be noted, however, that the pole pieces extend upward, as seen in Fig. 4, beyond the upper end of the stationary contact 20 but substantially flush with the outer surface of the member 2| so as to form a magnetic eld between the poles along the upper region of the member 2|. This magnetic field moves the end of the arc upward along the member 2| so as to increase the length of the arc and tend to extinguish it.

A distinguishing feature of this assembly of the stationary contact, blow-out coil and other parts is its compactness, i. e. it is only slightly wider in a direction parallel with the axis of the core 30 than the width of the contact 2|).

The movable contact 33 (Fig. 4) which is a substantially straight strap of conducting material, such as copper, is mounted on an irregularly shaped rotatable member or shaft 34 having its ends pivotally mounted on metal supporting brackets 35 and 36 secured to the supporting plate I0. This rotatable shaft or member 34 is made of a suitable electrically insulating material, such as a molded phenolic resin. At each end, it is preferably provided with a tubular portion 36a (Fig. 8) fitting over a cylindrical bearing member 361) carried by the brackets 35 and 3B so as to support the member 34 for rotation about a predetermined axis parallel with the support I0.

As shown in Fig. 4, the support 34 is provided with an arm or bracket 31 against which the movable contact 33 is pressed by a helical spring 38, the opposite end of the spring being secured to a cross bar 39 forming a part of the support 34. Also the bracket 31 is provided with a wedgeshaped bearing projection 40 which engages a notch in the adjacent side of the contact 33 and forms a pivot bearing for the contact. The spring 38 bears on the contact on an area between the bearing 40 and the end 31a of the bracket 31 so as to hold ,the contact on the bearing which is adjacent the lower end of the contact, as seen in Fig. 4, and to press the contact against the end of the bracket 31, shown as a cross bar 31'a forming a part of the supporting member 34. Preferably the upper end of the contact 33 is provided with a slightly curved contact making portion 4| which prevents making current on a sharp edge when 33 engages with 20.

The movable contact 33 is so mounted on the bracket 31 that the three points, its point of initial engagement with the stationary contact,

` lie in a common plane. With this arrangement,

the two contacts engage without sliding action, but when the movable armature 43 secured to the member 34 seats or seals on the stationary magnet core a slight sliding action is produced between the contacts. This minimum sliding action reduces the wear on the contacts and prolongs their life. Also the small amount of sliding action that takes place occurs on the current carrying engaging surfaces of the contacts whereby these surfaces are maintained clean.

Moreover, the stationary contact 20, as seen in Fig. 4, has its upper contacting portion, which is straight, in substantially parallel relation with the movable contact but converging toward its end slightly toward the movable contact. By reason of this arrangement, the line of engagement between the two contacts starts near the upper ends of the two as they first touch and then moves downward as the movable contact rolls slightly on the stationary contact. This action minimizes bouncing of the contacts and thereby minimizes any tendency for the contacts to weld together during their engaging action, Also the lowering movement of the line of contact tends to break any incipient welds between the contacts. Moreover, by reason of the plane contacting surface of the stationary contact and the similar plane surface of the movable contact, except for the bend at the upper end of the movable contact, and the bend at the lower part of the stationary contact, the line of engagement between the two is given a maximum movement downward, as seen in Fig. 4.

Another feature of the movable contact 33 is the extension 44 (Fig. 4) on its lower end below the pivot which extension provides sufficient mass to prevent vibration or bouncing of the movable contact during the opening movement. It will be understood that when the supporting member 34 is moved in a clockwise direction, as seen in Fig. 4. from the closed to the open position, the upper end 31a of the bracket 31 strikes the movable contact a sharp blow, and because a considerable portion of the mass of the movable contact lies above the end of the bracket, there is a tendency for the contact to turn in a counterclockwise direction about the upper end of the bracket as a pivot, the lower end leaving the bearing 40. Such action would result in wear on the bearing 40 and, moreover, produce irregular opening movement of the contact. It might even cause the movable contact to reengage the stationary contact after it has moved away slightly from the stationary contact. The extra mass 44 of material on the lower end of the movable contact eliminates this irregular action by balancing the mass of the movable contact on each side of the upper end of the bracket 31 which engages the movable contact with a blow. In fact, this mass 44 tends to cause the movable contact to pivot about its bearing 40 when the blow is given it. The contact, therefore, does not leave its bearing and, moreover, the opening movement of its upper end is accelerated. This is a distinct advantage when the gap between the contacts is small for it overcomes the tendency for the arc to remain stationary and burn the contacts.

As seen in Figs. 1 and 3, the U-shaped magnet armature 43 is mounted between the sides of a channel-shaped metal arm 45, the lower end of which is secured to the insulating shaft or support 34 by screws 45h. Thus the supporting arm 45 is secured to the support 34 in offset relation with respect to the axis 42 so that when the arm 45 is moved to a substantially parallel position with respect to the plane of the pole faces of the magnet core, the arm 45 is spaced from the pole faces to provide room for the coil 54. The lower end 46 of the amature 43 extends through an aperture 41 in the bot* im or cross portion of the arm 45 and is provided with a slot 4B loosely embracing the lower `dge of the aperture at a point adjacent the lower pole face of the core II. The upper end 49 of the armature extends through a slot or opening between the sides of the arm 45. A second bearing for the armature in addition to that provided by the slot 48 is provided by a protruding rounded projection 45a on the arm 45 which engages the armature at a point equidistant from the armature pole faces. Movement of the armature on the arm 45 is, furthermore, limited in a clockwise direction, as seen in Fig. 3, about the bearing 45a by a bolt 50 extending between the sides of the arm 45,

this bolt being surrounded by an insulating fiber cylinder I (Fig. l) which is engaged by the upper end of the armature. The bolt 50 is also insulated from at one end, thereby preventing 45 and 50 from forming a closed electric circuit around the armature. Aperture 41 extends to-the end of 45 as shown by 41a, thereby preventing the lower part of 45 from forming a closed electric circuit around the armature. Moreover, the bolt forms a stop to limit the clockwise movement of the support 34, the bolt coming to rest against an arm 52 secured to a strap 53, made of a non-magnetic material such as brass, extending through the operating coil 54 and secured by a screw 55 to the stationary magnet core I I.

This suspension for the armature 43 .provides freedom for the armature to align itself on the pole faces of the stationary core regardless of slight manufacturing inaccuracies in the support for the armature and the mounting of the stationary core. The armature is loosely supported at each end but with small clearances, which provides for a small amount of universal pivotal movement on the bearing projection 45a, and the armature is thus supported with its pole faces lying in a common plane passing through the axis 42. Moreover, the pole faces of the stationary core are located in a plane passing through the axis of rotation 42 of the support 34 by reason of which sliding of the armature on the stationary core and resulting abrasive action is "minimized This sliding action is also minimized by the support for the armature at its lower end with slight clearances whereby the lower end is free to move but slightly toward the stationary core during the opening or closing movement. The weight of the armature is supported on the lower wall of the aperture 41.

As shown in Fig. 3, the pole shader 56 on the upper leg of the magnet extends through the operating coil 54 and has a portion exterior of the coil substantially as large as the other portion. Also, as shown in Fig. 7, this exterior portion 51 has a reduced cross section so that the preponderant amount of heat is generated in this portion outside of the coil. It will be understood that the remaining portion of the shader inside the coil has a cross section too large to VVMI VII shader is kept from resting on the bottom of the slot. This arrangement prevents the shock of the armature striking the stationary core from being transmitted to the shader and breakage of the shader by metal fatigue. To further minimize the effect of these shocks, the shader is made of very light material such as aluminum or an aluminum alloy. The pole shader is furthermore secured by projections 5I provided in it which projections lie in a notch 62 in the stationary core and are held therein by the strap 53 extending over the notch.

The pole shader 53 on the lower leg, which is not subjected to the severe shocks of the upper leg, extends toward the outside of the stationary core and lies in a notch 54. It is secured in this notch by a U-shaped spring 55 (Fig. 3) having its ends secured in holes 65 (only one of which is shown) in the supporting brackets I2 and I3.

A single piece molded arc chute 61 covers all three pairs of switch contacts including the blow-out coils and blow-out pole pieces. This chute is molded from a suitable electrically insulating material such as an asbestos compound. As shown in Fig. 5, the arc chute is provided with chambers or recesses 68 which receive the pairs of switch contacts. Moreover, the insulating base I4 is provided with walls 59 between the pairs of stationary contacts. These walls dovetail in tightly fltting relation with the walls on the arc chute 51, dovetail joints 10 and 10a being :provided. Also each recess 68 in the arc chute leads outward through a restricted arc extinguishing opening 1I in which the arc is extinguished quickly.

It will be noted that the shaft or support 34 for the movable contact has no metal parts adjacent the switch contacts and since the blowout coil and pole pieces 3| and 32 are conned substantially within the width of the stationary contact supporting members 2l, the pole pieces and the members 2I are the electrically conducting parts nearest each other. Consequently the maximum insulating requirements are presented by these parts, which are completely electrically insulated by the walls 68 of the arc chute. Moreover, barriers 12, Figs. 1 and 4, are provided on the rotatable support 34 on each side of each movable contact 33. These barriers have edges 13 which are arcuate with the axis of support 34 as a center and are in closely spaced relation with similar complementary concave arcuate edges 14 on the chute 51.

Also this rotatable member is provided with barriers 15 between the flexible conducting shunts 15 leading to the movable contacts.

As shown, in Fig. 4, the arc chute 61 is hung on an upper cross bar or ledge 11 forming 'an integral part of the insulating base I4, and hooks over the upper end of the contact support 2|. The arc chute is provided with projections 18 which extend downward behind or on the righthand side of the cross bar 11 as seen in Fig. 4 between this cross bar 11 and the upper projecting end of the stationary contact supporting member 2l. Therefore, the arc chute can be slipped in place or removed very readily.

Provision is made for preventing the complete removal of the screws 22 (Fig. 8) from the member 2|. To provide access to the screw 22 for the removal or adjustment of the stationary contact, the member 34 is turned in a clockwise direction to the position shown in Fig. 8, the arc chute 51 having been removed and also the stop 52 for the armature. In this position of the member 34,

a projection 19 on the member lies just behind the screw 22 so that the screw can be turned out only until its head engages the stop 19, as indicated in Fig. 8. This completely releases the stationary contact 2D but the screw remains in engagement and supported by the member 2|. This stop 'I9 prevents complete removal of the screw from the member 2| and thereby avoids loss of the screw and the tedious process of rethreading it in the member 2|.

The iiexible shunts 16 are made of braided copper wire but for compactness instead of having terminals at each end, the ends are dipped in hot tin or solder to form solid terminals a and 1Gb. Also the terminal 1Gb (Fig. 4) is extended and turned back away from the movable contact 4| to form an arcing horn. When the switch is opened the arc is stretched between the upper end of the supporting member 2| and this arcing horn provided by the extension of the terminal 1Gb.

The operating coil 54 (Fig. 3) is seated upon a sponge rubber ring 80 which in turn rests at one side against a bracket 8| secured to the stationary magnet core by the screw 55 and on the opposite side against the stationary magnet core. The stop 52 is forked and extended back and downward against the outer end of the coil 54 to form a holding projection 82 on each side of the strap 53 engaging the front or outer end of the coil and holding the coil against the rubber ring 89. It will be observed that the removal of the part 52 by removal of the screw 83 makes accessible for removal the coil 54, and the stationary and movable contacts.

Moreover, the coil 54 is mounted by positioning of the bracket 8| in a tilted position downwards, as seen in Fig. 3, with respect to the leg of the stationary core that it encircles. This positioning of the coil with its outer end tilted toward the lower leg and also the projection of the coil toward the right-hand beyond the end of the stationary core pole face into the air gap makes the magnetic flux more effective in applying a pulling force to the armature. The legs of the armature 43 are slightly longer than the projecting end portion of the coil 54 which extends out beyond the end of the upper magnet core leg so that the upper leg of the armature can extend into the outer end of the coil and into abutting engagement with the end of the magnet core leg surrounded by the coil.

As shown in Fig. 3, the rotatable operating member 34 is provided with a projection 84 which, when the switch is closed engages and moves downward an operating rod 85 for a bridging interlock contact 86 which is biased to the open position by a compression spring 81. This bridging contact 86 is mounted, as shown, so that its contact faces are at an angle with the faces of the stationary contacts and, as a result, make contact with a rolling wiping action.

Also other operating projections similar to the projection 84 are provided on the member 34 for the operation if required of additional interlock switches or time delay interlock switches and also to p-rovide for the mechanical interlocking by a pivoted member engaging these projections at its ends of two switches placed side by side.

It will be also observed from Fig. 4 that the terminal connecting member 28 has its end bent toward the left so as to pass under the transverse bar 11 on the insulating base member.

It will be understood that the openings 1| in the arc chute 61 extend through the arc chute member from the exterior into communication with the recesses 68 When the circuit breaker has two or more poles, as in the device disclosed,

the possibility exists of the arcs playing through the openings 1| for such a distance on the exterior of the arc chute that they will come together and short circuit the poles of the circuit breaker. For the purpose of preventing this, I have in Fig. 9 shown a modified form of my invention in which each of the openings in the arc chute is subdivided by projections or barriers forming relatively short openings which are in staggered relation with each other. As shown, the two outside openings are each subdivided by two arc splitting barriers 89 and 89 to form three relatively short openings 90, 9| and 92. The central opening is provided with only one arc splitting barrier 93 which subdivides it into two openings 94 and 95 of substantially equal length. It will be observed that the openings 94 and 95 are in staggered relation with the openings 90, 9|' and 92.

The use of the barriers not only reduces the extent to which the arcs play externally of the arc chute, but also by reason of the staggered relation prevents the high points of two adjacent arcs from being adjacent each other. Or, in other words, the arrangement increases the distance between the high points of the arcs and thereby increases their electrically insulating relation with respect to each other.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto, since many modifications may be made and I, therefore, contemplate by the appended claims to cover any such modications as fall within the true spirit and scope of my invention.

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

l. An electromagnet comprising a U-shaped magnet core having two legs of substantially equal length with transverse pole faces on their ends lying in a common plane, a coil surrounding one of said legs having an axial length substantially greater than the length of said one leg so that the pole face on said one leg is in the interior of said coil and one end of said coil projects beyond said one leg, said coil being substantially larger than said one leg, means supporting said coil on said one leg in position with the outer end of said coil tilted toward the other one of said legs, a pivoted armature supporting member, and a U-shaped armature loosely mounted on said supporting member with its two legs extending toward said pole faces so as to be movable with said supporting member into abutting engagement with said pole faces, the leg on said armature engaging said one leg being long enough to extend through said projecting end of said coil.

2. An electromagnet comprising a U-sliaped magnet core having two legs of substantially equal length with transverse pole faces on their ends lying in a common plane, a coil surrounding one of said legs having an axial length substantially greater than the length of said one leg so that the pole face on said one leg is in the interior of said coil, said coil being substantially larger than said one leg, means supporting said coil on said one leg in position with the center line of said coil at an angle with said one leg so that the outer end of said coil is tilted toward `the other one of said legs, apivot support having its axis lying substantially in the plane of said pole faces, an armature supporting member, means securing one end of said supporting member to said pivot support -in oset relation with the pivot of said support so that said supporting member when movable into substantially parallel relation with the plane of said pole faces is in spaced relation with said pole faces thereby to provide space for said coil, and a U-shaped armature loosely mounted on said supporting member with its two legs extending toward said pole faces.

3. An electromagnet comprising a U-shaped magnet core having two legs of substantially equal length with transverse pole faces on their ends lying in a common plane, a coil surrounding one of said legs having an axial length substantially greater than the length of said one leg so that the pole face on said one leg is in the interior of said coil, said coil being substantially larger than said one leg, means supporting said coil on said one leg in position with the center line of said coil at an angle with said one leg so that the outer end of said coil is tilted toward the other one of said legs, a pivot support below said core having its axis lying in the plane of said pole faces, a channel-shaped armature supporting member, means securing one end of said channel member to said pivot support in offset relation with the pivot of said support so that said channel member extends upward and when moved into substantially parallel relation with the plane of said pole faces is in spaced relation with said pole faces thereby to provide space for said coil, the bottom of said channel member being adjacent said pole faces and the sides of said channel member extending away from said pole faces and said bottom being provided with an opening opposite each of said pole faces thereby to provide a transverse supporting member between said pole faces, a U-shaped armature between the sides of said channel support with its two legs projecting through said openings toward said pole faces and its central portion pivotally engagin said transverse member.

4. An electromagnet comprising a U-shaped magnet core having two legs of substantially equal length with transverse pole faces on their ends lying in a common plane, a coil surrounding one of saidlegs having an axial length substantially greater than the length of said leg so that the pole face on said leg is in the interior of said coil, said coil being substantially larger than said leg, means supporting said coil on said one leg in position with the center line of said coil at an angle with said one leg so that the outer end of said coil is tilted toward the other one of said legs, a pivot support below said core having its axis lying in the plane of said pole faces, a channel-shaped armature supporting member, means securing one end of said channel member to said pivot support in offset relation with said pivot support so that said channel member extends upward and when moved into substantially parallel relation with the plane of said pole faces is in spaced relation with said pole faces thereby to provide space for said coil, the bottom of said channel member being adjacent said pole faces and the sides of said channel member extending away from said pole faces and said bottom being provided with an opening opposite each of said pole faces thereby to provide a transverse supporting member between said pole faces, a U-shaped armature bey tween said sides of said channel member with its two legs projecting through said openings toward said pole faces and its central portion engaging said transverse member, a projection on said transverse member forming a pivot bearing for the central portion of said armature, the lower end of said armature being provided with a transverse slot substantially parallel with the plane of said pole faces with the sides of said slot embracing the lower edge of the lower one of said openings thereby to support pivotally the lower end of said armature on said channel member, a transversely extending pin on the upper end of said channel member providing a stop for the upper end of said armature thereby to limit the movement of said armature with respect to said channel member, and a stop arm secured to said magnet core engaged by said stop pin when said armature is in its unattracted position.

LEON J. GOLDBERG.

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