US2827527A - Non-bouncing magnetic contactor - Google Patents

Description

March 18, 1958 -T. H. LEE

NON-BOUNCING MAGNETIC CONTACTOR 3 Sheets-Sheet 1 Filed Dec. 29, 1954 BY Harris/flake March 18, 1958 1'. H. LEE 2,827,527

NON-BOUNCING MAGNETIC CONTACTOR Filed Dec. 29. 1954 3 Sheets-Sheet 2 C" 1 KISS POS/T/ON 5 m V DROP our pos/r/o/v K/SS POS/T/ON DROP our POS/T/QN "W K/SS POSITION A v V OPEN POSITION KISS v POS/T/ON OPEN POS/ T/ON IN V EN TOR.

Xtwrny T. H. LEE

NON-:BOUNCING MAGNETIC .CONTACTOR March 18, 1958 3 Sheets-Sheet 3 Filed Dec. 29, 1954 INVENTOR. BY 7%0765 1G6 United States Patent NON-BOUNCING MAGNETIC CONTACTOR Thomas Henry Lee, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application December 29, 1954, Serial No. 478,251

13 Claims. (Cl. 200-87) My invention relates to magnetically actuated apparatus for opening and closing electrical contacts in response to electrical currents.

More particularly, my invention relates to magnetic contactors having fairly heavy magnetic armatures which upon deenergization of the electromagnet drop away from the magnetic core and open a pair of electrical contacts by this drop-out movement.

In such magnetic contactors, backstops are normally provided for limiting the drop-out movement of the armature to an air-gap distance between the armature and pole faces of the electromagnet determined primarily by the magnetic force characteristic desired as well as by the contact separation desired. One of the long standing problems in the design of such contactors has been the tendency of heavy armatures to rebound after striking the backstop thereby causing the movable electrical contact connected thereto sometimes lightly to restrike the stationary contact. The electrical current passing through these momentarily lightly engaging surfaces of the electrical contacts may be sufiicient to weld the contacts together or cause arcing which burns or otherwise damages the electrical contacts. Accordingly, an important object of the invention is to provide a contactor construction which inherently clamps out and reduces the amplitude of rebound of the magnetic armature after striking the backstop.

Another object of the invention is to provide an armature rebound reducing mechanism which can be easily incorporated in existing magnetic contactors without major change in the design of the contactors.

In general, in accord with the invention, a magnetic contactor is constructed and arranged so that either the armature or its backstop has an additional degree of freedom of movement upon impact and the force of their impact is transmitted to and absorbed by an inertia member or mass during movement of the armature or backstop along this additional path or degree of freedom. The additional degree of freedom of movement may be linear movement or rotational movement but should be along a differently directed path from that taken by the magnetic armature during its drop-out movement toward the backstop. It has been found that the provision of this additional degree of differently directed freedom of movement in the armature or in the backstop in itself tends to reduce rebound of the armature and that the presence of an inertia mass or friction restricted member within this second degree of freedom functions to reduce to an unusual extent the initial rebound of the armature by immediate and almost total absorption of the energy of impact between the armature and its backstop.

The invention may be easily embodied in contactors having armatures which move along arcuate as well as linear paths. The inertia mass or friction restricted member may be constrained to move along a path corresponding to the second degree of freedom by respective connection to. either the armature or the backstop and this movement may either be linear or areuate.

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The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, together with further objects and advantages thereof can be easily understood by referring to the following description taken in connection with the accompanying drawings in which:

Figure 1 is a side view partly in section of the magnet and armature portion of a contactor embodying the invention;

Figure 2 is a front view in outline of the contactor of Figure 1;

Figure 3 is a pair of comparative charts of tests illustrating the difference in magnitude of rebound in a contactor such as illustrated in Figure 1 before and after the incorporation of the rebound reducing mechanism of the invention; 7

Figure 4 is a side view partly in section of another magnetic contactor embodying the invention;

Figure 5 is a perspective view of a friction restricted resilient mounting means for the armature of the contactor of rigure 4; and

Figure 6 is a pair of charts similar to Figure 2 of tests taken in connection with a contactor such as illustrated by Figure 4.

Referring to Figures 1 and 2 the invention is shown in connection with a magnetic contactor 9 of the type having an armature assembly 10 pivotally mounted at one end to provide an arcuate drop-out path, designated by arrow A, between the other end 12 of armature 11 and a pole face 13 of a U-shaped magnetic core 14 of the eiectrornagnet 15. Contactor 9 has a supporting backplate 16 upon which magnetic core 14 is mounted by suitable supporting brackets 17. Armature 11 is U- shaped and has flat end faces 18 and 19 confronting and constructed to engage pole faces 13 and 20,-respectively, of magnetic core 14 when in magnetically attracted position. Resilient pole-shading clips 21 and 22 fit within suitable recesses 23 and 24, respectively, in the pole faces 13 and 20 of magnetic core 14.

A bifurcated bracket 25 of armature assembly 16 carries armature 11 and is fastened to a pivotally mounted shaft 26. Spaced brackets 27 secured to supporting backplate 16 serve pivotally to support shaft 26 within suitable bearings 23. As best seen in Figure 2, shaft 26 carries a movable contact 29 which engages stationary contacts 30 when the shaft 26 is rotated by the attraction of armature assembly 11 toward magnetic core 14.

In accord with the invention, a backstop member 31 is arranged to arrest the movement of armature assembly 11 by engagement during drop out with a stop pin 32 carried by the armature mounting bracket 25. Stop pin 32 preferably comprises an inner cylindrical metal rod 33 surrounded by a cylinder 34 of tough non-metallic shock absorbent material.

The backstop assembly including backstop member 31 is resiliently mounted on supporting backplate 16 by virtue of interconnected metal strips 35 and 36 and spring washer fastening means 37 and 38. More specifically, backstop member 31 has a downwardly extending portion 39 which receives the impact of stop pin 32 and a laterally extending portion 40 which is fastened by bolt 41 to the metal strip 35. Strip 35, in turn, is spot welded at its other end to mounting strip or bracket 36 which is resiliently mounted on backplate 16 by screws 37 and 38 under the resilient tension of spring washers 42 and 43.

A coil 44 for energizing electromagnet 15 is mounted on metal strip 35 between a downwardly extending flange 45 of backstop member 31 and an upwardly extending flange 46 of supporting bracket 36 which flanges bear against opposite sides of coil frame 47.

In accord with the invention the flat under-surface of coil carrying metal strip 35 bears against and slides upon the upper flat surface of magnet core 14 in frictional engagement therewith. The entire resiliently mounted backstop assembly com-prising backstop member 31 and connecting strips 35 and 36 has a degree of freedom of movement along a path or direction B generally corresponding to the plane of the upper surface 48 of core 14. The movement of this backstop assembly within this degree of freedom is impeded, however, by the inertia of the system including the mass of coil 44 carried thereon as well as by the friction generated between the undersurface of strip 35 and the upper surface 48 of core 14. It will be appreciated that relative movement between these surfaces is possible since the core structure is securely supported on panel 16 whereas bracket 36 is resiliently mounted on panel 16 and capable of having some displacement therefrom. As shown in Figure l, a nonmagnetic shim 49 may be inserted between these relatively moving surfaces to take up any play and to increase the friction, if necessary. When armature assembly drops out of contact with magnetic core 14 as a result of the deenergization of coil 44, stop pin 32 strikes backstop portion 39 and the force of impact produces a slight linear movement of the backstop assembly as determined by the inertia, friction and resilient mounting of the backstop assembly. Substantially the entire kinetic energy in the moving armature assembly 10 is transmitted to and immediately absorbed by the differently directed and friction restricted movement of the backstop assembly such that the armature assembly comes to rest with relatively little rebound as compared to similar magnetic contactors where the backstop is rigidly supported or has a freedom of movement only in the same direction or along the same path as the armature assembly was traveling when striking the backstop.

The remarkable improvement in reduction of rebound in a contactor embodying the invention is illustrated by the curves of Figure 3. Curve C is a copy of an actual plot taken by a position recorder of the movement of the armature of a magnetic contactor such as is illustrated in Figure l but with the backstop assembly rigidly mounted by omitting spring washers 42 and 43 and securely tightening bolts 37 and 38. Curve D is a similar plot with the backstop assembly resiliently mounted in accord with the invention described above. With the rigidly mounted backstop arrangement plotted by curve C the armature typically rebounded to a small distance S corresponding to a small distance between the contacts 29 and 30 carried by shaft 26. Any additional shock or vibration of the contactor might increase the amplitude of armature rebound such thatthe contacts would lightly retouch or kiss causing welding or other damage to the contacts. With the differently directed freedom of movement of the resiliently mounted backstop assembly of the invention, the armature assembly 10, as shown by curve D, upon striking the backstop 32 almost immediately returns with practically no rebound to its drop-out position such that the distance S between the contacts 29 and 30 always remains great enough that simultaneous vibration cannot cause the contacts to retouch.

Referring now to Figure 4, the invention is shown in connection with a magnetically actuated contactor 50 in which the armature assembly 51 is constructed and arranged to move along a linear drop-out path rather than along an arcuate path as in contactor 9 of Figure 1. Contactor 50 comprises a supporting backplate 52 having a pair of spaced horizontally extending arms 53 (only one shown) which carry the general magnetic core assembly including a coil frame and armature guide assembly 54. A metal mounting bracket 55 inserted through a central aperture in coil 56 of electromagnet 57 is fastened to backplate 52. by bolts 53 and functions to carry the laminations of magnetic core'59 as wellas to provide mounting means for one end of L-shaped backstop strip member 60 secured thereto by bolts 61. The other end of backstop member 60 is supported on backplate 52 within a suitable slot 62 therein.

Armature assembly 51 comprises an armature 63 of U-shaped section carrying pole shading clips 64, 65 and mounted on a plunger or guide member 66. Plunger 66 is also of U-shaped section having a pair of vertically extending arms 67 and 68 connected by horizontal cross piece 69 inserted within channels 70, 71 formed in the upraised legs of the armature laminations 63. Guide arms 67 and 68 of plunger 66' are slidable within suitable recesses or channels 72 vertically extending along the sides of coil frame 54.. The upper ends of guide arms 67 and 68 are connected by bolts 73 to an insulating cross bar 74. Cross bar 74 carries the contact assembly 75 including a pair of interconnected contacts '76, 77 which bridge a pair of stationary contacts 78 and 79, respectively, when brought into engagement therewith by the vertical motion of armature assembly 51.

In accord with the invention, armature assembly 51 is constructed to strike its backstop member 60 along an axis 80 offset fromthe region of support of armature 63, and the armature 63 is provided with an additional freedom of movement, namely a freedom to move slightly in a rotational or arcuate path relative to the line or axis of contact 80 between the armature and its backstop 60. More specifically, backstop member 60 is bent upward slightly along its horizontal leg 81 in order that the vertically descending armature 63 will strike the apex of the bent portion 81 of backstop 60 along the apex line 80. This is in contrast with prior constructions where leg 81 was formed and supported parallel to the bottom surface of armature 63 in order that both fiat surfaces might make plane-to-plane large area contact previously thought desirable. As a result of the-upwardly bent condition of backstop leg 81, armature 63 tends to rock about its initial impact axis 80. This rocking motion of armature 63 is permitted by virtue of a predetermined looseness of fit or play between the armature 63 and the cross piece 69 of guide member 66 on which it is mounted. The mechanism for mounting armature 63 on plunger 66 preferably also includes means'for resiliently returning the armature to the position wherein its pole faces are parallel to those of magnetic core 59 and also for frictionally impeding the rocking motion of armature 63 after impact with backstop 60.

The details of this friction restricted mounting between the contact operating mechanism and the armature assembly are shown in Figure 5. Cross piece 69 of plunger 66 has a slight central spherical depression 82. A flat, slightly resilient thin metal plate 83 rests on cross piece 69 with its opposite ends beneath inturned projections 84, 85 of armature 63. Flexible plate 83 also has a central spherical depression 86 resting within depression. 82 of cross piece 69 but of slightly greater depth such that the bottom of depression 86 applies a downward pressure resiliently biasing the'remaining laterally ex tending portions 69" of cross piece 69 in spaced relation both to the coextending portions of plate 83 as well as in spaced relation to the channels 70 and 71 in armature 63. An insulating shim 87 may be inserted beneath cross piece 69 on the upper fiat surface of armature 63 inorder to take up any extra play between the surfaces, although this shim may not be necessary. If used, shim 87 is slightly spaced from the side portions 69 of cross piece 69 in order to permit a slight rocking motion of armature 63 before either shimj87 or plate 83 comes into contact with the side portions of cross piece 69. During such rocking motion the depressed portion 82 of cross piece 69 acts as a bearingsurface upon which the depressed portion 86 of plate 83 is journalled. The sliding or rocking motionof the bottomsurface of spherical depression 86of plate83 on the upper spherical surface of depres- R2 of cross piece 69 and the upper contacting area of shim 87 immediately beneath this surface introduces additional friction impeding the rocking motion of armature 63. It will be appreciated that the rocking motion of armature 63 on the bearing surface formed by the depression 82 in plunger cross piece 69 results from the transmittal of the rocking motion of the armature 63 about the line of contact 80 between the armatur 63 and the bent backstop 60. After the shock of impact and consequent rocking and rebound of armature 63 has passed, the armature returns to an at rest position shown in Figure 4 as a result of the resilient nature of plate 83 and the symmetry of the spherical depression 86 and 82.

The typical reduction in rebound resulting from the use of the invention in a contactor such as shown in Figure 4 is illustrated by the curves of Figure 6. In Figure 6 curve E is a plot taken by a position recorder of the position of movable contact 76, 77 relative to stationary contact 78, 79 during drop out of a contactor identical with that shown in Figure 4 with the exception that horizontal backstop leg 81 was perfectly flat and parallel to the undersurface of armature 63-such that there is no rocking motion of armature 63 induced. Curve F of Figure 6 is a similar plot of the same contactor during drop out with the horizontal backstop leg 81 bent upward to provide the off-center initial striking axis 80 in accord with the invention. The improvement in reduction of rebound is apparent from a comparison of these curves.

Although I have disclosed specific embodiments of the invention, many modifications can be made and I intend by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

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

l. A magnetically actuated device comprising supporting means, a backstop assembly on said supporting means, a magnetic armature assembly on said supporting means arranged to strike said backstop assembly during dropout movement along a first general path, one of said assemblies being supported for movement after impact between said assemblies along a dilferently directed path from said armature assembly drop-out path, a substantially rigid member supported on said supporting means remote from the region of backstop engagement between said assemblies, and a friction restricted member frictionally engaging said rigid member and connected for movement after said impact by and with the assembly movable along said differently directed path thereby to reduce rebound of said armature assembly after striking said backstop assembly.

2. The magnetically actuated device of claim 1 wherein the armature assembly is supported for movement along a difierently directed path from its drop-out path after striking the backstop assembly and the friction restricted member is connected for movement after impact between said assemblies by and with the armature assembly.

3. The magnetically actuated device of claim 1 wherein the backstop assembly is supported for movement along a difierently directed path from said armature assembly drop-out path after being struck by said armature assembly, and the friction restricted member is connected for movement after said impact by and with the backstop assembly.

4. The magnetically actuated device of claim 1 wherein the armature assembly strikes said backstop assembly by drop-out movement along an arcuate path, and one of said assemblies is supported for movement along a linearly directed path after impact between said assemblies.

5. The magnetically actuated device of claim 1 wherein the armature assembly strikes the backstop assembly by drop-out movement along a linear path, and one of said assemblies is supported for movement along an arcuate path after impact between said assemblies.

6. Magnetically actuated apparatus for operating electrical contacts comprising, supporting means, a backstop assembly on said supporting means, a magnetic armature assembly on said supporting means connected to move one of said contacts and constructed to strike said backstop assembly during drop-out movement along a first general path, one of said assemblies being supported for movement after impact between said assemblies along a differently directed path from said armature assembly drop-out path, a substantially rigid member supported on said supporting means remote from the area of impact between said assemblies, a movable member frictionally engaging said rigid member and connected for movement after impact between said assemblies by and with the assembly movable along said differently directed path, and resilient means connected to said latter assembly for returning said magnetic armature assembly to substantially its initial striking position.

7. Magnetically actuated apparatus for operating electrical contacts, comprising a backstop assembly and a magnetic armature assembly connected to move one of said contacts and arranged to strike said backstop assembly during drop-out movement along a first general path, resilient mounting means for said backstop assembly and friction inducing means contacting said backstop assembly in an area remote from the area of impact between said assemblies for frictionally reducing movement of said backstop assembly on its resilient mounting after being struck by said armature assembly.

8. The magnetically actuated apparatus of claim 7 wherein said friction inducing means supports and guides said backstop for movement along a differently directed path from said armature assembly drop-out path.

9. Magnetically actuated apparatus for operating electrical contacts, comprising an electromagnet having a magnetic core and a magnetic armature assembly connected to move one of said contacts, a resiliently mounted backstop assembly located in the drop-out path of said magnetic armature assembly, said backstop assembly being resiliently movable on its mounting in frictional engagement with a surface of the magnetic core of said electromagnet in an area removed from the area of impact between said assemblies.

10. The magnetically actuated apparatus of claim 9 wherein a coil for said electromagnet is carried by said backstop assembly.

ll. A magnetically actuated apparatus for operating electrical contacts comprising, a supporting plate, an electromagnet having a stationary portion rigidly mounted on said plate and having a movable magnetic armature assembly connected to operate said electrical contacts, a backstop assembly having one end resiliently mounted on said supporting plate and having a portion remote from said one end in the path of drop-out movement of said armature assembly, and means carried by said backstop assembly for frictionally engaging said electromagnet stationary portion during movement of said backstop assembly on its resilient mounting after impact with said magnetic armature assembly.

12. Magnetically actuated apparatus for operating electrical contacts comprising, a supporting plate, an electromagnet having a magnetic core assembly rigidly mounted on said supporting plate and having a movable armature assembly for operating said contacts, means supported by said core assembly for guiding said armature assembly to move in a linear drop-out direction relative to said core assembly, means resiliently mounting said armature assembly for limited rotational movement about a small area bearing surface of said guiding means, and a backstop member located to be struck by said armature assembly during its drop-out movement in an area remote from and eccentric to said bearing surface area thereafter to translate the linear motion of said armature assembly into a rotational motion, thereby to reduce rebound of said armature assembly.

a seam-e27 13. Magnetically. actuated apparatus for operating electrical contacts comprising a supporting plate, anelectromagnet having amagnetic core assembly rigidly mounted on said supporting plate and a movable armature, a contact operating mechanism connected between one of said electrical contacts and said armature, said operating mechanism being supported on said core assembly for sliding movement along a generally linear drop-out path, means resiliently mounting. said armature for frictionally restricted rotation on a spherical bearing surface of said operating mechanism and a backstop member connected between said supporting plate and said core assembly, said backstop member having atconfiguration and location to be struck by said armature in an area remote and eccentric from saidspherical bearing surface of said resilient mounting means. thereby to translate linear dropout motionof saidjarmature into a frictionally restricted rotational motion.. J

7 References Cited'in the file of this patent UNITED STATES PATENTS;

990,512 I Barnum n- Apr. 25, 1911 1,331,290 Stratton Feb. 17, 1920 1,334,144 Eaton Mar. 16, 1920 1,764,819 Anderson June 17, 1930 1,948,688 Ad-am 5; Feb. 20, 1934 2,235,391 Williams et al.- -'Mar; 18, 1941 2,240,589 Wagar' May 6, 1941 2,361,808 Ayers -a Oct. 31, 1944 2,412,304 Staley Dec. 10, 1946- 2,584,707 Jarvis et al, -a Feb. 5, 1952'

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