US2910559A - Electromagnetic relay - Google Patents

Description

Oct. 27, 1959 A .WHARTQN ELECTROMAGNETIC RELAY Filed June 5, 1957 INVENTOR. ARMISTEAD WHARTON AGENT UnitedStates Patent G ELECTROMAGNETIC RELAY Armistead Wharton, Rochester, N.Y., assignor to General Dynamics Corporation, Rochester, N.Yt, a corporation of Delaware Application June 5, 1957, Serial No. 663,846

Claims. (Cl. 200-93) My invention relates to improvements in electromagnetic relays in general and more particularly to low power, polarized relays.

It has been the practice to provide multicontact relays in which armature actuated contacts and their fixed contact counterparts are approximately tensioned and aligned by permanent mechanical adjustment. Such relays are dependent upon armature overtravel and the resulting contact follow? to insure minimum operated tension between each pair of armature and fixed contact springs after the armature has become fully operated. In miniature and subminiature relays, where power available for operation is necessarily small owing to design or application limitations, it has been found that the use of contact follow to insure minimum pressure is not necessarily satisfactory because the energy required to obtain such follow may approach or even exceed the total power available for relay operation. Similarly, the dependence of conventional relays upon springs for the restoration of the armature to its normal position, where the force to be overcome during operation is at best proportional to the displacement of the armature from itsnormal posi tion, adds substantially to the power requirements of the relay. I

Another problem encountered in relays which are magnetically polarized (i.e., having a magnetically biased armature with a neutral position and movable to first and second operated positions upon forward and reverse energization, respectively, of the relay'winding or windings) is insuring restoration of the armature to neutral upon thedenergization of the windings. The armatures of the previously designed relays have shown a tendency to re-" main in the last assumed operated position because the armature is suspended in the permanent magnetic field in an unstable equilibrium. Such relays require the use of power consuming restoring springs which tend to defeat the objectives of low power relay design.

Accordingly, it is an object ofmy invention to provide a new and improved relay. 7

Another object of my invention is to provide a new and improved relay having low power requirements.

Another object of my invention is to provide a new and improved relay restored to its normal position by a magimproved relay capable of use in the presence of vibration, shock, or acceleration.

Z,Ql,559 Patented Oct. 27, 1959 "ice specification, and in which:

Fig. 1 shows a perspective view of an assembled relay;

Fig. 2 shows an end view of a contact bead for the relay oi the invention;

Figs. 3a, 3b and 30 show in skeletonized form the action of the apparatus within the relay shown in Fig. 1 during the contact equalizing operation;

Fig. 4 shows a skeletonized view of a relay similar to the one shown in Fig, 1,-.but having a different contact arrangement; and,

Fig. 5 shows a skeletonized view of a relay having a difierent magnetic circuit configuration from the relay shown in Fig. 1.

Referring to Fig. 1', the relay forming the preferred embodiment of my invention'has a permanent magnetic circuit comprising a bar magnet 1'(having north and south poles labelled N-and S, respectively) and leg portions 2a and 2b. The elements of the permanent magnetic circuit are arranged so that magnet 1 and legs 2a and 2b lie in a C-sha'p'ed configuration, with both leg portions extending from the ends and on the same side of magnet 1. Opposite magnetic poles are therefore induced in the free ends 'of legs 2:: and 2b. A soft'iron high permeability barshcped armature 3 is suspended by pin 4 in the air gap formed between the jaws of the'C-shape'd magnetic circuit so that its ends are "adjacentthe free ends of legs 2a and 2b. The free ends oflegs 2a and 2b have projecting portions extending in the direction of the ends of armature 3 so that flux is'encouraged to enter the ends of armaturefi in a direction generally parallel to the longitudinalaxis of the armature. The magnetic field existing betweenthe'free ends of legs 2a and 2b induce opposite poles inthe opposing ends of armature 3. A

Pivot pin 4extends vertically through the longitudinal axis andsubstantially at the midpoint of armature 3. The pin is also located at substantially the midpoint of the above referred to air gap'a'nd lies on the mean magnetic flux path. Pin 4 is fixedrelative to the permanent magnetic circuitby upper and lower support members 5a and 5b, respectively, which-*inturn are fixed to permanent magnet 1.-' In thismanner,"armature 3, which is symmetrical about its"longitudinal axis, is Jorie'nted'within the air gap so that it is in stableequilibrium "when the longitndinal axis of armature 3 lies substantially'parallel with a net magnetic flux path 'inthe air gap. This stable equilibriurn position is also the neutral position of armature 3.

In order to rotate armature 3 about pin 4, electromagnetic means comprising coils 7a and 7b wound'on cores 6a and 6b,'respectively, are fixed by means (not shown) relative to armature 3 andthe permanent magnetic circuit and are oriented in'the manner next described. Pole pieces 9a and 9b are'fixed to the ends of core 6a and extend upwardlyfto' the top of the left-hand end of armature 3. The inward facing sides'of pole pieces 9a and 9b are substantially parallel to and equally spaced apart from the adjacent ones of the sides of armature 3 when the latter is in neutral position. Pole pieces and 9d attached to core 6b "areisirnilarly oriented with respect to the rightfhan'd end of armature 3.

windings 7a and 7b are connected by wire 8b in such a manner that'when a source of direct current, such as a battery, is connectedbe'tw'een wires 8a and 80, which are connected to the otherft'erminal's of coils 7a and 7b, respectively; currenf'fiowi'ng through windings 7a and 7b creates magnetic'filds between pole pieces 9a9b and 9c+9d which are substantially at right angles to the longitudinal axes and at opposite ends of armature 3. The flow of current through each coil is such that like poles are induced in pieces 9a and 9c and in 9b and 9d, the polarity being determined by the direction of current flow between wires 8a and 8c.

Rotation of armature 3 about pin 4 is achieved in the next described manner. The permanent magnetic circuit is effective for inducing south and north poles in the leftand right-hand ends, respectively, of armature 3. When the electromagnetic circuit is energized in a direction hereinafter referred to as forward, north poles are induced in pole pieces 9a and 9c and south poles are induced in pole pieces 9b and 9d. The left-hand end of armature 3 is therefore attracted to pole piece 9a and repelled from pole piece 9b. Similarly, the right-hand end of armature 3 is attracted to pole piece 9d and repelled from pole piece 90. Therefore, armature 3, viewed from the top, rotates in a counterclockwise direction. By a similar line of reasoning, it can be seen that when the flow of current through coils 7a and 7b is reversed, the ends of armature 3 are attracted to pole nieces 9b and 9c and repelled from pole pieces 9a and 9d, so that armature 3 is rotated in a clockwise direction. 7

The rotation of armature 3, in the above described manner, is used in the manner set forth in the following paragra hs for controlling first and second contact sets com rising pairs of vertical rods 10a10b and 11a11b, respectively. The rods in each pair are insulated from and fixed substantially parallel to each other by insulating board 12 which in turn is fixed bv sup orts 13 a prescribed distance from the permanent magnetic circuit and armature 3. Thus the rod'pairs constitute first and second devices ma n ined in fixed s aced relati nshi to each other and to the rest of the relav structure including armature 3. u the preferred embodiment of mv invention, the rel tionshi is such that the axis of pin 4 passes between the rod airs and lies at substantially equal distances from e ch rod pair.

A relay actuator comprising armature 3 carries a pivotallv mounted bail assembly including side members 14b and 14c and lon itudinal member 14a and beads 15a and 15b. The bail is C-shaped, straight member 14a lying substantially parallel to the axis of armature 3 and from which side members 14b and 140 extend at substantially right angles. Member 14a is positioned transverse to the lengths of rod pairs 10a10b and 11a11b. The free ends of members 14b and 14c are pivotally connectedby means including bearings (not shown) to the ends of armature 3 so that in the absence of other influences,

member 14a rotates about pin 4 with the rotation of armature 3 and around the longitudinal axis of armature 3. The axis of rotation of the bail assembly is different from the axis of rotation of armature 3, the two being at substantially right angles in the preferred embodiment of my invention. Metallic beads 15a and 15b are threaded onto stralght portion 14a. An insulating bushing 19 within the opening of each bead indicated in Fig. 2 is effective to electrically separate bead 15a from member 14a and the relay frame and from'bead 15b in the event that member 14a is formed from electrically conducting material. Beads 15a and 15b, used in a manner to be described for establishing electrical connections between the rods in each of pairs 10a-10b and 11a11b, respectively, are free to move along the length of member 14a. The motion is limited by the presence on member 1441 of tight ly fitting sleeves 16, one of which is placed on either side of each bead.

The bail assembly is provided with auxiliary members 22a and 22b which are extensions of side members 14b and 140, respectively. The auxiliary members extend below the points at which the bail assembly is pivoted, and terminate in mass members 23a and 23b. The pur- P se of the auxiliary and mass members is to balance the ball member and the attached structure such. as beads 15a and 15b inorder to prevent disturbance of the contact members when the relay is subjected to shock, vibrafiq l or acceleration. Therefore, the moment of inertia of the combination of the auxiliary members 22a and 22b and mass members 23a and 23b is chosen so that it is equal to the moment of inertia of the bail assembly and the structure carried on bail 14.

Spaced apart retainers 17 and 18 fixed to the underside of board 12 are separated from each other by a distance substantially greater than the diameter of member 14a. Member 14a is received between members 17 and 18, the retainers being effective for preventing bail 14 from turning about its pivotal mounting on armature 3 to the point where the beads engage the corresponding ones of the rod pairs; however, the separation is suflicient so that retainers 17 and 18 do not interfere with the rotation of bail member 140 about its own pivotal axis to the point of preventing the next described contact equalization action.

Referring to Fig. 3a, in the case chosen for illustration, armature 3 is assumed to be rotated in a clockwise direction, and that, owing to manufacturing tolerances, the distance between bead 15b and rod pair 11a11b is smaller than the distance between bead 15a and rod pair 1ila--10b when the armature is in the above described neutral position. Upon the rotation of armature 3 in a clockwise direction, bail member 14a also rotates in the above described manner so that the assembly including bead 15b is moved in the direction of rod pair 11a11b. Bead 15b is positioned on member 14a by stops 16 so that it contacts the first of rod pair 11a11b at a point lying between the axes of the rods, as shown in Fig. 3b.

, Thereafter, further rotation of member 14a about pivot.

pin 4 causes bead 15b to slide along the length of member 14a until the bead also contacts the other rod of pair 11a11b. Thereupon, rotation of bail member 14 about pivot pin 4 is stopped, and further rotation of armature 3' causes bail member 14a to be rotated about its pivotal mounting points on armature 3 until bead 15a engages. rod pair 10a10b, as shown in Fig. 3c. Bead 15a is: moved into contact with both conductors 10a and 10b in: the same manner that bead 15b was aligned with both conductors 11a and 11b.

After bead 15b has been moved into engagement with both rods 11a and 11b and during the period that bail member 14a is being rotated about its own pivotal mounting on armature 3, the bead, 15b, is free to slide in adirection taken along the lengths of rods 11:: and 11b. The rotation of armature 3 and bail member 14a about their respective pivotal mountings causes movement of member 14a along its own length with respect to rod pair 11a-11b. Therefore, bead 15b, having a rounded surface and being free to slide within limits along the length of portion 14a, is retained in contact with both rods of pair 11a11b, so that the further rotational movement of armature 3 does not interfere with the electrical connection established between conductors 11a and 11b by bead 15b.

Upon the establishment of contact between each bead and its corresponding rod pair, torque thereafter exerted on armature 3 is transmitted through bail member 14a to force each head into engagement with its corresponding rodpair. The ratio of the forces applied at beads 15a and 15b is inversely proportional to the length of the effective lever arm of the beads, i.e., the distance between each head and the axis of rotation of armature 3. In the preferred embodiment of my invention, as indicated in Figs. 3a, 3b and 3c, the eifective lever arms are substantially equal, so that the forces exerted at the above referred to first and second points (i. e., at rod pairs 10a-- 10b and 11a11b) by the beads are also substantially equal.

Upon deenergization of the electromagnetic means, the above described torque exerting magnetic fields are removed from the ends of armature 3, so that armature 3 restores ,to the above described neutral position under the influence of the permanent magnetic circuit field only.

By constructing the relay so that ball member 14acomes into contact with the conductor rod pairs in the above described manner without allowing armature 3 to come into contact with any of pole pieces 9a through 9d, it is not necessary to provide non-magnetic members to stop the motion of the armature 3, and makes easier the design of the relay with respect to the problem of insuring the restoration of armature 3 to normal position under the influence of the permanent magnetic circuit.

While I have described in the above paragraphs a relay having only two sets of make contacts operable when the armature is rotated in a clockwise direction, it is to be understood that other possible contact configurations, such as the one shown in Fig. 4, may be provided. The arrangement in Fig. 4 shows first pairs of contact rods a--10b and 11a-11b disposed in the above described manner to be actuated when armature 3 is rotated in a clockwise direction; additional third and fourth contact rod pairs 20a20b and 21a21b, positioned by member 12, are oppositely disposed to rod pairs 10a-10b and Ila-11b with respect to the armature 3. With this arrangement, contact between each of the rod pairs 2tlzz20b and 21a--21b is effected by beads a and 15b when armature 3 is rotated in a counterclockwise direc tion, the action of bail member 14 and beadslSa and 1515 being substantially the same as that described above in connection with the relay shown in Fig. 1.

Similarly, while I have shown and described as the preferred embodiment of my invention a relay having a C-shaped magnetic circuit of the type shown in Fig. 1, Fig. 5 shows a circuit suitable for use in a relay of the type described in which the permanent magnetic circuit elements are arranged in an E configuration. With this arrangement, a permanent magnet 1a is provided as the middle member of the three projections from stem member 24. Side members and 2d project from the same side of member 24 as magnet 1a. Armature 3a is pivotally connected to the member 1a in a manner similar to the one in which armature 3 is connected to permanent magnet 1 shown in Fig. 1. Assuming that the free end of magnet 1a is the north pole in this arrangement, permanent magnet 1a induces north poles at the ends of armature 3a, and south poles in the free ends of each of members 2c and 2d. Thus, armature 3a assumes a neutral position in which its longitudinal axis most nearly coincides with the net permanent flux path through armature 3a.

The advantage of the permanent magnetic configuration shown in Fig. 5 is that the relay can be energized by a single electromagnet. The electromagnet shown includes core 60 bearing a winding 70 to which wires 8d and 8e are attached. Core 6c is disposed so that the pole faces at its ends are adjacent to the ends of armature 3a. When potential is placed across conductors 8d and 8e, current flowing in winding 7c induces north and south poles in opposite ends of core 60, the polarity being determined by the direction of current flow in winding 7c. Because like poles are induced in the ends of armature 3a by permanent magnet 1a, one of the ends of armature 3a is repelled from and the other end attracted to the corresponding faces of core 60 when winding 70 is energized. In this manner, armature 3a may be caused to rotate in a clockwise or counterclockwise direction, depending upon the direction of current flow through the coil 70.

While I have shown and described specific embodiments of my invention, other modifications will readily occur to those skilled in the art. I do not, therefore, desire my invention to be limited to the specific arrangements shown and described, and I intend in the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim is:

1. In a relay, first and second contact sets maintained in spaced relationship to each other, a bar shaped armawas ymmetiie'ai aboufi'ts lbngitudinal aids and pivoted to rotate about a point taken through the center of its dinal a s; le troma ne ic m an ,fst t said armature, an assembly pivotally attached to said armature to rotate about an different from the rotational axis of said armature for engaging said first and second contact sets in order to transmit torque applied to said armature to said contacts and means including a permanent magnetic circuit disposed to urge said armature into its normal position whereby said armature and said assembly are restored to normal position when said electromagnetic means is deenergized.

2. The relay set forth in claim 1 in which the axes of rotation of said armature and said assembly are at substantially right angles to each other.

3. The relay set forth in claim 2 wherein the axis of rotation of said armature passes between said contact sets and the distance between each of said contact sets and the axis of rotation of said armature are substantially equal.

4. The relay set forth in claim 3 wherein said assembly comprises a bail pivoted to rotate about the longitudinal axis of said armature.

5. The relay set forth in claim 4 wherein said first and said second contact sets comprise first and second pairs of parallel spaced apart rods, respectively, and said bail has first and second beads threaded thereon for engaging said first and said second rod pairs, respectively, said beads being slidable along the length of said bail, whereby the first of said beads to engage one of the correspond ing one of said rod pairs is retained between the rods as said armature and said bail are rotated about their respective axes to the point Where the other of said beads engages its corresponding rod pair.

6. In a relay, first and second contact sets maintained in spaced relationship with each other, an armature pivoted to rotate about an axis intermediate said contact ets, torque applying means for rotating said armature and a contact assembly pivotally attached to said armature to rotate about an axis substantially perpendicular to the rotational axis of said armature for contacting said first and second contact sets whereby torque applied to said armature is transmitted through said assembly to said contacts.

7. The relay set forth in claim 6 wherein said armature comprises a bar pivoted to rotate about a point on its longitudinal axis and said assembly comprises a bail pivoted to rotate about the longitudinal axis of said armature.

8. The relay set forth in claim 7 wherein said first and said second contact sets comprise first and second pairs of parallel spaced apart rods, respectively, and said bail has first and second beads threaded thereon for engaging each of said rods in said first and said second rod pairs, respectively, said beads being slidable along the length of said bail, whereby the first one of said beads to engage one of the corresponding one of said rod pairs is retained between the rods as said bar and said bail are further rotated about their respective axes to the point where the other of said beads engages its corresponding rod pair.

9. An electrical contact comprising a pair of conductive rods fixed substantially parallel to and insulated from each other, a wire transverse to the length of said rods, a metallic bead slidably threaded on said wire for making electrical connection between said rods, and means for moving said wire along its own axis with respect to said rods and toward said rods, whereby said bead is retained in engagement with both said rods after contact between said head and said rods has been established and as said wire is moved along its own length with respect to said rods.

10. The device set forth in claim 9 and having in addition motion limiting means carried by said wire for positioning said head to initially contact either of said rods at a point lying between the axes of said rods in order to 7 8 insure the movement of said bead along the length of said 754,689 Pearne et a1 Mar. 15, 1904 wire to the point where said bead is in contact with both 1,889,515 Hammerly Nov. 29, 1932 said rods. 1,995,449 Edwards Mar. 26, 1935 2,092,478 Summermeyer Sept. 7, 1937 References Cited in the file of this patent 5 2,706,756 Brewer Apr. 19, 1955 UNITED TA PATENTS 2,747,045 Parmer May 22, 1956 Re. 24,209 Bernstien Sept. 4, 1956 2,767,357 Naybor Oct. 16, .1956

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