US3048749A - Electric relay - Google Patents

Description

1952 G. N. KOEHLER 3,048,749

ELECTRIC RELAY Filed March 2, 1959 2 Sheets-Sheet l 1962 G. N. KOEHLER 3,048,749

ELECTRIC RELAY Filed March 2, 1959 2 Sheets-Sheet 2 States trite The present invention concerns improvements in the construction of low-power relays.

Relays comprise, basically, an electric circuit which includes a coil, a magnetic circuit comprising a core, an armature and a spring device which returns the armature to the inoperative position, as also a system of contacts, some of which are closed when the coil is energized (offnormal contacts), while the others are closed when the coil is not energized (normal contacts). All these elements should be so arranged as to ensure great safety even after prolonged operation, while being of simple construction. A large number of known constructions do not meet these requirements. It has been proposed in particular to employ coil springs as the return spring for the armature. This type of spring tends to oscillate for some time after the triggering of its action and can consequently produce variations in the time of operation and faulty contact-making. Flat springs supporting the armature have also been proposed, but in this case the armature was separated by an air gap from the fixed member supporting the said spring, which increased the reluctance of the magnetic circuit. Pre-bent leaf springs (bending by exceeding the elastic limit) have also been proposed. This arrangement does not afford the same length of service as a plane spring leaf operating below its elastic limit. In addition, the adjustment of the pressure of the armature on its contacts has sometimes been effected by modifying the bend of such a spring, which could not give constant results. In some constructions, the magnetic circuit comprises defective joints between the armature and one or more fixed members of the said circuit when the armature is in the inoperative position, whereby the reluctance of the circuit is increased. With the use of a pin joint or knife-edge joint, it is necessary to allow the armature some freedom in the direction perpendicular to the movement in order to avoid jamming. This results in an ill-defined initial position of the armature, which causes dispersion in the operating times and increases the danger of jamming of the armature at the levels of the contacts as a result of transfer of metal due to the electric arcs.

Finally, the armature is sometimes connected to a lead-out pin by a braid soldered over the said armature. This arrangement is not very practical.

An object of the present invention is to devise a relay of improved construction with a view to obviating the foregoing disadvantages.

Accordingly, the return spring of the armature is a flat leaf-spring, the attachment of which involves flexure well below its elastic limit. It is secured to the armature, on the one hand, and to a fixed member fast with a fixed yoke of the magnetic circuit on the other hand. The pressure of the armature on its normal contacts is adjusted by bending the said fixed member to a variable extent. The armature is maintained in contact with the said fixed yoke of the magnetic circuit by the said flat leaf spring, whereby the reluctance of the corresponding joint is reduced. The electric circuit extends through the armature, the fiat spring, the fixed member to which the spring is secured and the yoke of the magnetic circuit, so that a direct soldered connection between the armature and the lead-out pin is unnecessary, at least as long as the atom strength of the current supplied does not exceed a certain limit.

The invention therefore concerns an electromagnetic relay comprising normal and off-normal contacts, a fixed magnetic yoke constituting with the magnetic core of the electromagnet and a rigid armature resting on the said yoke the magnetic circuit, in which the armature is maintained against a bearing surface of the yoke by an initially plane leaf spring and fixed on one side to the said arma-= ture and on the other side to a supporting member fast with the yoke in such manner that the said spring leaf receives a certain flexure well below its elastic limit when the armature is in contact with its normal contact or contacts.

For a better understanding of the invention and to show how it may be carried into effect, the same will now be described, by way of example, with reference to the accompanying drawings, in which:

FIGURE 1 is an elevational view of a relay according to the invention,

FIGURE 2 is a plan view of the relay,

FIGURE 3 is an elevational view of a part of the relay,

FIGURE 4 is a plan view corresponding to FIGURE 3,

FIGURES 5 and 6 are fragmentary perspective views illustrating two modifications of the relay, and

FIGURE 7 is a perspective view of the relay.

In FIGURES l and 2 the illustrated relay comprises an external casing l, a movable armature 3, a return spring 2, an energizing coil 4 wound around a magnetic core 12, the latter being fixed to a member '7 which forms a yoke for the magnetic circuit and which is being extended towards the left and secured to a pin shown at 13 in FIGURE 1 and at 24? in FIGURE 2. The lead-in wires of the electric circuit are shown at 9, the lead-out pins being the pins l8, 1% and it 2.1 (one pin being designated by like references in FIGURES i and 2). The relay comprises two fixed double contacts 3a and 8b connected to the pins 17, 21 and 17, 19 respectively, the first through the member 16, and the second through the member 14, which comprises a portion 14a. The lower cheek of the frame 6 of insulating material of the coil is extended to a point below the end of the member 4 anchored in the said frame so as to support the latter with respect to the yoke 7, which serves as a level reference. The spring 2 is fixed at the points 11 and 18, on the one hand to the armature 3 and on the other hand to a member 5 screwed on the yoke 7 of the magnetic circuit.

Referring now to FIGURES 3 and 4, which show the assembly consisting of the armature 3, the spring 2 and the member 5 before its introduction into the relay, it will be seen that the spring 2 is an initially undeformed flat spring formed with a rectangular recess for receiving the wider end of the armature, which recess may be formed simply by cutting in a thin sheet of appropriate metal. The armature has two bent-over ends forming a fork, which are intended to come into contact with the double contacts 8a and 8b. The armature is cut from an iron strip plated with silver or other appropriate metal in such manner as to provide a silver-plated zone opposite each contact. The surface of the armature is protected by burnishing so as to leave the silver surfaces intact. When the member 5 is screwed on to the yoke 7, the spring is flexed, whereby the armature 3 is applied to the contacts 8a. The pressure of the armature 3 on the contacts 8a can be adjusted by deforming the portion 5a of the member 5 by means of pliers. Since the member 5 is thick, this deformation is completely stable. When the relay is energized, the armature. 3 is attracted by the core 12 in such manner as to reduce the reluctance of the magnetic circuit, and the armature 3 comes into contact with the contacts 81;. As soon as the energization of the electric circuit is interrupted, the spring 2 returns the armature 3 to its inoperative position. When the relay is to be used for closing a circuit when energized, the ends of the said circuit must be connected to the pins 18, 2t? and 17, 19. If the relay is to open a circuit, the ends of the said circuit must be connected to the pins 13, 2t and 17, 21. The utilization current is set up through the pins 17, i) or 17, 21, as required, the contact 8a or Sb, the armature 3, the spring 2, the member 5 and the member 7, and the pin 18, 2G. In this construction, it is therefore unnecessary to provide a connection extending from the armature 3 to a lead-out pin, the utilization circuit here extending through the spring and a part of the magnetic circuit. In addition, the joint 15 between the armature 3 and the yoke 7 is with certainty established by the pressure exerted by the spring 2 both in the inoperative position and in the operative position of the armature. This assists in reducing the parasitic reluctance of the magnetic circuit. Finally, referring again to FIGURE 1, it will be seen that the flexed surface of the spring 2 extends in immediate proximity to the pivoting edge of the armature 3: on the yoke 7. Therefore, when the armature 3 is attracted by the core 12-, there is no horizontal sliding of the said armature 3 on the yoke 7, and consequently no tendency for the contact 1.5 to become worn, While at the same time there is no longitudinal friction which might impede the useful movement of the said member 3.

FIGURES 5 and 6 illustrate two constructional variants of the spring. In FIGURE 5, the spring is a rectangular plane leaf fixed by rivets on the one hand to the member 5 and on the other hand to the armature 3, which comprises two bearing surfaces situated on either side of the spring. In FIGURE 6, the spring comprises two arms 2a and 25 each fixed to two arms 5a and 5b of the memher 5, the attachment between the members 2 and 3 not being illustrated in the figure.

The spring could consist of non-magnetic material such as bronze and could be situated below the armature in such manner that a residual air gap equal to the thickness of the said spring is automatically maintained the said spring comes into contact with the core of the electromagnet during the contact of the armature with the offnormal contact or contacts. Such an arrangement is illustrated in FIGURE 5.

In addition, the spring may be simply soldered to the armature.

I claim:

1. In an electro-mechanical relay having an energizetion winding, a magnetic yoke, and an armature, an extremity of which lies by a fulcrum line on a part of said yoke extending laterally to said winding, the improvement consisting of a bracket laterally fixed on said part and presenting a surface oblique with respect to said armature, and a single leaf-spring which is initially plane, for mechanically linking said armature and said surface, said armature and spring having reciprocal forms such that the spring is curved without permanent deformation after an extremity thereof is secured to said bracket, in such a manner that the curved profile of said spring substantially lies in the prolongation of said fulcrum line.

2. An electro-mechanical relay as claimed in claim 1, wherein said leaf-spring is made sufficiently conducting so as to assure electrical linkage between said armature and said yoke.

3. An electro-mechanical relay as claimed in claim 2, wherein said bracket has an angle extension constituting said oblique surface and permitting adjustment of the spring curvature.

4. In an electro-mechanical relay having an energization coil, a magnetic yoke and an armature, an extremity of which lies by a fulcrum line on a part of said yoke substantially parallel to the axis of said coil, in combination, a metallic bracket fixed on said part and having a member oblique with respect to said armature, and a single leaf-spring initially uncurved for electrically linking said armature and said yoke, said spring being adapted to be non-permanently curved when an extremity thereof is fastened on said member, in such a manner that the curved profile of said spring substantially lies in the prolongation of said fulcrum line.

5. In an electrical relay comprising: a yoke in form of an angle-member and of a core bearing an energization coil, an armature an end of which lies on a part of said angle-member which make up a fulcrum line and one leaf-spring secured to said armature and to said yoke to maintain said armature in return position, the improvement consisting in that said leaf-spring, which is initially plane in released, free condition, has one end secured on a lug fastened on said angle-member part, said lug being located and obliquely oriented so that, after assembly, said spring is curved while assuring for itself the accurate position of said armature with respect to said yoke.

References (liter! in the file of this patent UNITED STATES PATENTS 2,061,920 Piifath Nov. 24, 1936 2,423,116 Price July 1, 1947 FOREIGN PATENTS 307,138 Great Britain Mar. 7, 1929 OTHER REFERENCES Telefonbau, German application Serial No. T5719, printed 1956.

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