US2938978A - Relay - Google Patents

Description

L. J. KAMM May 31, 1960 RELAY Filed May 1.9, 1954 .MGE kj/ ANN,

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LAWRENCE Hy/Etn BY W (vwv United States Patent O RELAY vFiled May 19, 1954, Ser. No. 430,819

1'3 Claims. (Cl. 200-87) This invention relates to electro-magnetic relays, and more particularly to relays which may be made small in size, but robust in construction, and capable of operation under conditions of severe acceleration and deceleration.

`Relays are important components in many electrical control system-s and they have wide military and civilian application. Their design becomes increasingly more diflcult with their application to uses such as high speed projectiles, guided missiles, aircraft and the like. The high lacceleration forces in guided missiles, for example, often vcause relays to operate when they are not supposed to and, alternatively, to prevent intended operation.

It isutherefore one object of this invention to provide a relay which will -operate under adverse conditions such as vibration, acceleration and deceleration.

- It is another object of the invention to provide a relay which is small in size, sensitive in operation and capable of controlling relatively large amounts of electrical power.

It is another object vof the invention to provide a relay which may be readily mounted on terminal boards, printed circuits and any Aother environment in which relays are used.

Yet another object is to provide a relay which is hermetically sealed, yet capable of ecient assembly with precisely controlled contact gaps.

l In accordance -with the invention an electromagnetic relay can be assembled with an elongated core piece mounted coaxia'lly within a longer tubular casing, the two being electrically isolated and the toroidal space therebetween filled bythe coil. One end of the core is formed with a radially extending portion presenting -a large surface area-to the inside of the casing to afford a fixed magnetic ux lgap of relatively low reluctance. The other end of the core carries an enlarged forwardly tapering head the apex of which constitutes 4a first fixed electrical contact of the relay. Mounted in a freely suspended fashion next to this contact, and itself carrying a contact to engage it, is a cupshaped armature.

Facing the enlarged head, the armature establishes therewith an air gap of low and variable reluctance which closes, along with the contacts, when the coil is energized. The periphery or flanged edge of the armature is close to the inside wall of the casing to form still another magnetic gap by means of which the tlux loop of the relay returns, via the casing, to the coil. The armature is free to engage the casing at a single tangent point by edgewise movement in any direction.

l The armature is resiliently urged, as by a spring reacting near its periphery, away from the first xed contact against `a second fixed contact which is electrically isolatedv from the rst and from the casing. The relay can be connected in an electrical circuit by means of terminals connected, respectively, to the core, which carries the first zfxedcontact, the casing, which is linked electrically through a -exible coupling to the armature contact, and tothe secondviixed contact. Thus the electrical and magnetic circuitsanalge use, of common conducting portions. The relay is virtually insensitive to acceleration or der' t ICC celeration radial with respect to its core and casing axis, the result being minimum edgewise displacement of the armature into engagement with the casing to which it is already electrically connected. In engagement with the casing at a tangent point, the armature can become a pivotal member, the swinging action ofk which can control the contact action with complete effectiveness. Axial displacement of the amature is opposed either by a relatively strong resilient means or by the electro-magnetic force of the coil, both of these forces being relatively high with respect to the mass of the armature so that only the highest acceleration or deceleration forces axially of he casing can adversely affect contact operation.

The invention as well as other features and objects thereof maybe better understood-by reference to the following specification of a preferred embodiment thereof taken in conjunction with the accompanying drawings in which:

Figure 1 is a view in longitudinal section of Ia relay formed in accordance with the invention;

Figure 2 is an end view of the relay of Figure 1;

Figure 3 is a schematic diagram showing the electrical and magnetic circuits of the relay of Figure l; and

`Figure 4 is a view in transverse section taken on the line 4 4 of Figure 1, looking in the direction of the arrows, and showing part of the armature mounting.

Referring to Figure l, the invention is shown as embodied in a relay assembly housed in a tubular casing 10 formed of magnetically and electrically conducting material of low magnetic retentivity, the casing being open-ended. Mounted coaxially within the casing and more or less centered between the ends, is a fixed core piece 11, formed of a magnetic material of low retentivity such as Perrnalloy or Armco ingot iron. Fitted in the toroidal space between the core and the casing is a coil or winding 12.

`I oosely fitted in the casing 10 near the right-hand end of the core 11, as viewed in Figure 1, is van armature 13 of material of low magnetic retentivity centrally apertured to receive a double ended electrical contact element 14. Embracing the contact on opposite sides of the armature are spaced-apart stationary contacts 15 and 16, with the movement of the armature between' these contacts comprising the relay action.

. Forpurposes of description the relay may be regarded as constituted of four sub-assemblies, including, workingl from right to left as viewed in Figure 1, the terminal and end sealing assembly including the contact 15, the armature assembly, the coil and core assembly, and the terminal and end assembly sealing the other end of the relay. The structural details of each of these sub-assemblies are described below in order.

Fitted in the open right-hand end of the tubular casing 10 is an end assembly including a header 17, which can be formed of ceramic material skirted by a metal soldering ring 17a air-tightly soldered to the casing 10. Attached, as bycementing for example, to the inside surface of the header 17 is an electrically insulating disc 18 having a central recess 19 in which is mounted the contact 15. Within the recess the disc is formed with a countersunk central bore 20 in which the contact 15 and its shank 15a are seated, this bore being in axial alignment with a through bore 21 in the header 17.

An electrically conducting lead 22 from the contact 15 is brought through and soldered to the bores 20 and 21 in a sealing bushing or eyelet 23, which is bonded to the header. l The lead 22 may take the form of a pigtail lead as shown or alternatively of a short soldering terminal, 4

binding post or the like. The insulating disc 18 can be formed with a peripheral notch 24 within which is received'a sealing ring 25 of soft resilient material such asA silicon rubber to prevent solder and tlux from entering the 3 armature chamber of the relay and to supplement the hermetic seal of the solder joint between the header 17 and the casing 10.

The armature assembly is disposed within a cavity 26 disposed to the left of the end assembly just described, and includes the magnetic amature 13, a llexible, electrically conducting bridging member '28, and a helical spring 29. The armature 13 is preferably cup-shaped, having a cylindrical ilange 13a which 4 provides a large surface area opposing the inner surface of the casing 10. The armature is loosely lltted in the casing with a radial clearance small enough to provide, in conjunction with the large peripheral surface area, a low reluctance air gap, but is sufficiently large to permit the armature to tilt slightly out of its illustrated plane normal to the axis of the relay. The face of the contact 15 is preferably conical to allow for the tilting action, which is limited in its magnitude by the adjacent annular Ainsulating surface 18a of the disc 18.

The amature is urged to the right, closing contacts 14-15, by the helical spring 29 which reacts between the peripheral regions of the armature and an abutment ring 30 seated in a groove 31 in the casing. The spring surrounds but does not touch the contact 16, which is part of the core 11 and which is normally out of engagement with the armature contact 14. The contact 16 is formed with a conical surface facing the armature to facilitate tilting action of the armature, discussed more fully below, and tl e conical surface is extended by means of a llange 16a to increase the surface area opposing the armature so as to reduce the reluctance of the air gap between these two parts.

The ilexible bridging member 28, which joins the armature and casing electrically, can (as best seen in Figure 4) take the form of a ilat ring attached as by a soldered or brazed joint 28a at its lower end to the lower end of the armature 13, and attached at its upper end to the casing by means of a laterally extending arm 28b. The arm 28h can be brought out of the casing to form one terminal of the relay, viz. the terminal connected to the moving pole or contact. Alternatively, the arm 28b can be terminated Within the casing, and a supplementary terminal 28C, attached to the outside of the casing, can be used. The member 28 should be so constituted as to permit the armature to move freely between the contacts 14 and 16, to tilt in all directions, and to shift slightly edgewise or radially. As an alternative mounting, the member 28 can be attached to the armature at the contact 14 by providing a radial nger extending from the contact `downwardly .to the ring portion, omitting the joint 28a.

The sub-assembly including the core 11 and coil 12 can be built up as a unit around the core. To this end the core can be formed with a shoulder 32 near the contact 16, a turned cylindrical shank 33, and a radially extending llange 34 carrying a ilared or cylindrical portion 35 at its edge. The cylindrical portion 3S is disposed close to but is electrically insulated from the casing 10 to form a low reluctance flux gap. Thus there is provided a linking means which defines a flux path between the core and the casing. The coil 12 is wound on the cylindrical shank 33 and is separated from the shoulder 32 by washers 36 and from the llange 34 by a washer 37. The outside surface of the coil is insulated from the casing by an insulating liner 38 and the inside from the shank 33 by an insulating liner 39.

An insulating disc 40 is fitting within the cylindrical core portion 35 and is joined thereto and to the left-hand face of the llange 34 as by cementing. The llange 34 and washer 37 are notched at 41 to receive an inwardly extending, channelled portion 40a formed integrally with the disc 40 and through which pass electrical leads 42 and 43 of the coil 12. The leads may be kept separate within the channel by means of an insulating bushing 44.

The fourth and last sub-assembly which seals the left-` hand end of the relay includes an electrical conductor 45 soldered or otherwise connected electrically to the core flange 35, and electrical conductors 46 and 47 seated in the disc 40 and joined in suitable electrical connections to the coil leads 42 and 43, respectively. The assembly is completed by means of an insulating spacer sleeve y48 and a ceramic header 49 having a flanged metal soldering ring 49a, corresponding to the ring 17a of the header 17, and which may be soldered to the inside of the casing 10. Suitable bushings or eyelets 50, 51 and 52 (as best seen in Figure 2) can be provided for the conductors 45, 46 and 47 respectively to complete the airtight seal. Outside of the relay, the conductors 45, 46 and 47 become terminals which may take the form of pigtail leads, as shown, or alternatively binding posts, soldering lugs or the like.

The relay may be assembled in a simple and effective manner by lrst seating the abutment ring 30 in groove 31 inside the casing lll, then inserting the core assembly, including the core 11, washers 36 and 37, coil 12, and insulating disc 40, followed on the left by the terminal leads 45, 46 and 47 (suitably connected), the spacer 48 and header 49. The header is pressed in to remove all end play and soldered in place, and the leads are soldered in the bushings 50, 51 and 52 to complete the end seal. The spring 31 and armature 13, with its flexible strip 28, are inserted in the right-hand end of the casing, fol# lowed by the disc 1S, contact 15 and header 17. The header is then pressed inwardly to seat the spring 29 on the abutment ring 30 and to close the contacts 14-16, then retracted a. measured distance to establish the contact gap 14-16, and the header 17 soldered in place. In this fashion the relay becomes completely hermetically sealed and the small, invisible contact gap within the relay is accurately set and measured despite manufacturing tolerances.

To complete the electrical insulation the outside of the casing 1t) can be covered by an insulating Sleeve 53 and the inside lined with an insulating sleeve 54.

Referring now to Figure 3, it will be seen that a magnetic circuit is set up in which flux, induced by the coil 12 when energized through the terminals 46 and 47, passes from the core shank 33 to the cylindrical portion 35, across a fixed low reluctance gap to the casing 10, across a low reluctance gap to the flange 13a of the armatureV 13, across the variable reluctance gap between the arma-A ture and the stationary contact 16, and backto the core shank 33. The electrical circuit includes the terminal 45 connected .to contact 16 via the core 11, the terminal- 28o connected to the movable contact of the armature 13 via the casing and the flexible member 28, and the terminal 22 connected to the contact 15. The core, armature and casing therefore accommodate both magnetic tlux and electrical current.

The operation of the relay depends upon movement of the contact 14 or armature from right to left as viewed in Figure l under the influence of the ux concentrated in `the variable reluctance gap between the stationary contact 16 and the armature. The contacts 14 and 16 will remain closed as long as the coil 12 is energized. When the coil is deenergized the tlux eld will decay, permitting the spring 29 to cause the armature contact 14 to engage the stationary contact 15. With respect to the armature acion, the flux which crosses the gap between the cas-v ing 10 and the flange 13a of the armature 13 would be expected to have no vmechanical effect if the gap were prefectly symmetrical. In practice however ux .concentrations will exist to pull the armature radially to one side, asvpermitted by its mounting, until Vit rests against the easing in a point contact. This effectively lowers they reluctance of that gap and also sets up a pivot point about which the armature 'may swing in a tilting or rolling action to operate the contacts.

It should be understood that radial or edgewise displacement of the armature may occur as a 'result of outsidelf'orces suchas vibration, acceleration or deceleration, as a result of internal magnetic forces, or both. In any case the armature remains free to move to either contact under the net magnetic and spring forces. The abutment surface 18a of the insulating disc 18 together with the conical surfaces of the iixed contacts and 16 prevent closing of more than one pair of contacts at a time when the armature is caused to tilt. Also, the main pressure of the spring 29 .produces useful contact pressure while any small eccentric component due to manufacturing tolerances is resisted by the insulating disc 18.

It -will be understood therefore, that the relay operates wholly independently `of radial accelerations and decelerations. Furthermore, since the center of gravity of the armature lies substantially on a radius through the point of pivoting rolling contact, accelerating forces in any direction perpendicular to the axis of the relay will produce negligible turning moments affecting armature roll or pivot.

Acceleration forces in the axial direction affect the armature directly. The minimum acceleration which will shift the armature axially, however, is proportional to the armature mass and yinversely proportionaito 4the net spring and magnetic force. This arrangement is such that the ratio o-f armature mass to-net spring and magnetic force is inherently small and therefore the relay is also capable of resisting high axial acceleration. `A relay formed in accordance with the present invention, for example, was found to be able to withstand axial accelerations of 25g without Contact interruption.

While :the invention has been described with specific reference to the accompanying drawings it is not to be Vlimited save as defined in the appended claims.

I claim: l. In an electro-magnetic relay, a magnetic casing, a magnetic core in the casing, linking means defining a ux path between the casing and the core, said casing including wall means defining an armature chamber adjacent the core and spaced from the linking means, a radially a'nd axially movable magnetic armature accommodated in the chamber, said armature being slightly smaller in size than the chamber to aiford a slight radial clearance in all directions between the Wall means defining lthe chamber and the periphery of the armature, whereby the armature is free to move radially in all directions to engage the wall means to =form a low reluctance magnetic coupling between th`e' armaturearid the Wall means and to afford a pivot about which the armature can be tilted, resilient means to urge the armature awayfrom the core, means to oppose said resilient meansY to position the armature a preestablished distance from the core,'coil means in the casing to set up a ux loop including :the core, the linking means, the casing, the armature and back to the core, to displace the armature with both a radial component to engage the wall means and an axial component toward the core electrical contact means operated by the armature, and means for tilting the armature relative to `the coreto cause the armature to engage the casing when the armature engages the core.

2. In an electro-magnetic relay, a magnetic casing, a magnetic core in the casing, linking means defining a flux path between the casing and the core, said casing including wall means defining an armatrue chamber adjacent the core and spaced 'from the linking means, a radially and axially movable magnetic armature accommodated in the chamber, said armature being slightly smaller in size than the chamber to afford a slight radial clearance in all directions between the wall means defining the chamber and the periphery of the armature, whereby the armature is free to move radially in all directions to engage the wall means to form a low reluctance magnetic coupling between the armature and the wall means and to aord a pivot about which the armature can be tilted, resilient means to urge the armature away from the core, means to oppose said resilient means to position the d armature a preestablished distance from the core, coil means in the casing to set up a flux loop including the core, the linking means, the casing, the armature and back to the core, to displace the armature with both a radial component to engage the wall means and an axial component toward the core, electrical contact means operated by the armature, a liexible electrical conductor connected to the armature to aord limited radial and axial motions thereof, said electrical contact means comprising first contact means carried by the armature adjacent its center, and second contact means adapted tobe engaged and disengaged by the first contact means upon axial movement of the armature.

't 3. A relay according to claim 2, said second contact means being disposed on the core at a point proximate to the center of the armature and said iirst contact means carried thereby, said means to position the armature being disposed proximate to the center of the armature and comprising third contact means and abutment means adjacent the periphery of the armature for limiting the pivotal movement of the armature.

-4. A relay according'to claim 2, said second contact means including an enlarged tip on said core having walls tapering toward a contact point proximate to the center of the armature and the lirst contact means carried thereby to afford a relatively large surface area facing thek armature to decrease the reluctance of the ux gap therebetween and to permit tilting of the armature in the chamber without engaging the enlarged tip of the core.

,5. A relay according to claim 4, said means to urge the armature away from the core including a helicalspring surrounding said enlarged tip and engaging the armature near its periphery.

6. A relay according to claim 3, including first, second and third terminal means electrically connected respectively to said core, casing, and third contact means, means connecting said exible electrical conductor to the casing at a point diametrically opposed to the place of attachment to the armature, and low reluctance means to electrically insulate the casing from the core, whereby the core and the casing are both adapted to carry both electrical currents as controlled by the contact means and magnet ilux as generated by the coil means.

7. In an electro-magnetic relay, a magnetic casing, aV

magnetic core in the casing, linking means defining a flux path between the casing and the core, said casing includ-l means, said armature being slightly smaller in size than the chamber to aord a slight radial clearance in all directions between the wall means dening the chamberand the periphery of the armature, whereby the armature is free to move radially in all directions to engage the wall means to form a low reluctance magnetic coupling between the armature and the wall means and to afford a pivot about which the armature can be tilted, resilient means to urge the armature away from the core, means to oppose said resilient means to position the armature a pre-established distance from the core, coil means in the casing to set up a tlux loop including the core, the linking means, the casing, the armature and back to the core, to displace the armature with both a radial component to engage the wall means and an axial component toward the core, and electrical contact means operated by the armature.

8. In an electro-magnetic relay, a magnetic casing, a magnetic core in the casing, said core having a tapered end, said magnetic casing extending beyond one end of the magnetic core, a radially and axially movable magnetic armature accommodated within the casing extension adjacent the magnetic core, said armature being of a assente size slightly smaller than the surface dening the inner periphery of the casing to afford a slight radial clearance in all directions between the casing and the armature when the armature is centered and untilted Within the casing, the width of the outer periphery of the armature and the radial clearance between the outer periphery of the armature and the inner periphery of the casing being such that the armature makes contact with the casing when it is in a tilted position, a stop spaced apart from the tapered end of the core, means normally urging the armature away from the tapered end of the core and into engagement with the stop, coil means to set up a ux loop through the core, the casing and the armature, said ux displacing the armature with both a radial component to engage the casing and an axial component toward the tapered end of the core, the engagement between the armature and the casing forming a low reluctance coupling therebetween, said tapered end of the core insuring tilting of the armature relative to the core to cause the armature to engage the casing when the armature is in engagement with the core, as well as preventing contact between the armature and the core when the armature is in contact with said stop in tilted position, and electrical contact means operated by the axial displacement of the armature.

9. An electro-magnetic relay as set forth in claim 8 including abutment means surrounding said fixed stop to limit the tilt of the armature when the armature is in contact therewith.

l0. In an electro-magnetic relay, a magnetic casing, a magnetic core in the casing, said magnetic casing extending beyond one end of the magnetic core, a radially and axially movable magnetic armature accommodated in said casing extension, said armature being of a size slightly smaller than the surface defining the inner periphery of the casing to afford a slight radial clearance in all directions between the casing and the armature when the armature is centered within the casing, whereby the armature is free to move radially in all directions to engage the casing, said engagement therebetween forming a low reluctance magnetic coupling between the armature and the casing, a stop spaced apart from the end of the core, resilient means to urge the armature away from the core and into engagement with said stop, and coil means magnetically coupled with the casing to set up a flux loop including the core, the casing and the armature, said ux displacing the armature toward the core, bringing surfaces of each into contact, at least one of the surfaces being tapered to tilt the armature and thereby insure that it engages the casing as well as the core.

11. An electromagnetic relay comprising a casing of magnetizable material, a core of magnetizable material within the casing, said casing and core cooperating to form magnetically linked components of a magnetic flux path, electrical windingV means magnetically coupled to one of the components of the magnetic flux path to magnetize the core, an armature supported within said casing adjacent one end of the core, the armature being slightly smaller. in size than the inner wall of the casing to afford a clearance in all directions before the core is magnetized, means supporting the armature in an inoperative position out of contact with both the core and the casing, .the end of the core adjacent said armature being sloped so as to insure tilting of the armature when the armature is drawn into contact with the end of the core upon magnetization of the core, the outer peripheral surface of the armature being of suicient length in the longitudinal direciton of the core to insure contact with the casing when the armature is tilted by engagement with the tapered end of the core, and electrical contact means actuated by the displacement of the armature into contact with both the core and the casing.

12. An electromagnetic relay comprising a magnetic casing, a magnetic core within the casing, said core being tapered at at least one end thereof, an electrical winding, the ow of current therethrough producing a ux path between the casing and the core which magnetizcs the core, said casing dening an armature chamber adjacent the tapered end of the core, a cup-shaped armature accommodated in the chamber, means supporting the armature out of contact with both the casing and the core when there is no flow of current through the electrical winding, said armature being slightly smaller in size than the chamber to afford a slight clearance in all directions between the inner wall of the casing and the outer perpihery of the armature, the arrangement being such that upon magnetization of the core the armature is drawn into engagement with the tapered end thereof, tilting the armature to insure contact between the outer periphery of the armature and the casing to form a low reluctance magnetic coupling between the core and the casing, and electrical contact means actuated by the displacement of said armature into contact with both the core and the casing.

13. An electromagnetic relay as set forth in claim 12, including a spring accommodated within the armature chamber and acting on the armature to urge it out of contact with the core.

References Cited in the le of this patent UNITED STATES PATENTS 511,731 Doolittle Dec. 26, 1893 705,092 Kaisling July 22, 1902 1,219,949 Kaisling Mar. 20, 1917 1,700,314 Hartwig Jan. 29, 1929 1,932,164 Petit Oct. 24, 1933 2,009,892 Lecce July 30, 1935 2,127,887 Rayburn Aug. 23, 1938

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