GB1583712A - Electromagnetic relay - Google Patents

Abstract

The relay has two changeover switches inside the cavity of the coil (2). Each changeover switch has a normally-open contact yoke (3) and a contact spring yoke (4) with a contact spring (8) attached to the contact spring yoke and an armature (9) disposed on the contact spring and a normally-closed contact piece (5). The yokes (3, 4) and the normally-closed contact piece of each changeover switch are inserted into grooves (1a, 1b or 1c, 1b) of the coil body (1). The magnetic return takes place through a metal cover plate (10) which, when the relay is embedded in the potting resin, prevents the resin from penetrating the contact area which is hermetically sealed. The relay is intended, for example, for installation in printed circuit boards for which relays with contacts closely packed in glass tubes are less suitable due to the tensions occurring due to the bending of the circuit board. <IMAGE>

Description

(54) ELECTROMAGNETIC RELAY (71) We, INTERNATIONAL STAN DARD ELECTRIC CORPORATION, a Corporation organised and existing under the Laws of the State of Delaware, United States of America, of 320 Park Avenue, New York 22, State of New York, United States of America. do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an electromagnetic relay whose contacts are inside its coil.

Relays are known whose contacts are inside the core of the coil, e.g. relays with sealed reed contact units. These relays have good sensitivity, and very good consistency of contact resistance as the contacts are sealed, and due to the absence of any mechanical parts subjected to abrasion.

Unfortunately the need to seal the contact blades causes manufacturing problems, i.e.

the exact alignment of the contact blades while sealing at relatively high temperatures is rather expensive. Further, the glass-tometal seal introduces some dangers since care must be taken that the seals are not subjected to mechanical stresses.

Further it is difficult to provide changeover contacts with sealed reed relays since the contact blades are subjected to at least partly contradictory requirements with respect to their mechanical and magnetic properties. Hence it is an object of this invention to provide an electro-magnetic relay having the mentioned advantages of the known reed contact relays, but avoiding their drawbacks.

According to the invention there is provided an electromagnetic relay which includes a coil former with a space extending along the axis of the coil within which the relay contacts are arranged, at least one change-over contact set including a fixed contact and a contact spring support with a contact spring fixed thereto, an armature fixed to said contact spring within said space, a ferromagnetic member lined with an insulating foil and arranged to close the magnetic circuit outside the coil, and an envelope of synthetic resin which is prevented by the ferromagnetic member from penetrating into said space and which hermetically seals the space containing the contacts.

An embodiment of the invention will now be described in conjunction with the accompanying drawing in which Figure 1 is a perspective view of the relay in a partly assembled condition and Figure 2 is a section view of the relay in a plane through the axis of the coil.

Figure 1 and 2 show a relay with two change-over contact sets, designed for insertion into printed circuit boards.

In Figure 2, the sectional plane of the relay is parallel to the printed circuit board (not shown). In Figure 1 the parts belonging to one of the two change-over contact sets are assembled into the coil former whereas the parts belonging to the other change-over contact set are shown outside the coil former.

A coil former 1 has flanges at its ends, and it carries a coil 2. The coil former 1 has a core opening of rectangular cross-section including on each of the two larger side-wall three longitudinal grooves extending over the whole length of the core. Two of these grooves are directly adjacent to the smaller side of the rectangle whereas the third pair of grooves is in the middle between the two other pairs. Each outer groove is intended to receive a fixed contact 3 and a fixed contact 4 and a contact 3 and a contact 4 are inserted from the same side into two different grooves. Into the middle groove a fixed contact piece 5 is inserted from each of the two sides. The dimension of the grooves and of the pieces to be received therefrom are so designed that the inserted pieces are maintained in a predetermined position without further operations, owing to their own elastic deformation (contact piece 5) or due to elastic deformation of the coil former.

The flanges of the coil former 1 have on their outer side recesses into which bent portions 3a and 4a of the contacts 3 and 4 fit so that with inserted contacts a plane surface is provided at the coil flanges. Each coil flange has at its ends two H-section members 6 for the reception of a coil terminal spring 7 which is bifurcated and can be inserted into the groove of each member 6 and which is maintained in the correct position by an enlargement of one leg of the spring.

On the contact 4 there is fixed a changeover contact spring 8 which carries an armature 9. As can be seen from Figure 2 the two contacts 3 and 4 inserted into the same groove have a gap between them which is bridged by the armature 9. The distance between the two contacts 3 and 4 is such that while the leakage flux between the two contacts 3 and 4 is as small as possible, the armature 9 overlaps the two contacts by a sufficient amount to achieve a high sensitivity for the relay. The magnetic circuit is closed by a U-shaped ferromagnetic return member 10 which has on its inner side a thin plastics foil 11. When contacts 3 and 4 and the contact member 5 are in position the member 10 with its foil 11 is so mounted on the relay that the legs of the U abut against the bent portions 3a and 4a of the contacts 3 and 4 which form with the remainder of the coil flanges a continuous surface. The foil 11 serves as insulation since the members 3 and 4 are in contact portions, i.e. they are at a certain voltage. In addition the thin foil provides a small but defined air gap having the same effect as the usual residual plate, i.e. it prevents the armature from sticking due to remanence after the operating current is cut-off. A further effect of the foil is that it seals the contact space against the penetration of synthetic resin during moulding as it will be described later-on.

The contact-end of the change-over spring 8 is bifurcated to provide the double contact arrangement often required. As can be seen from Figure 2 the spring 8 abuts against a contact 5a on the contact 5 when its coil is non-energized and abuts against a contact 3b arranged on the contact 3 when the coil is energized. The bent portions of the contacts 3 and 4 have with pin-like extensions 3c and 4b extending perpendicularly to the axis of the coil and serving as soldering tabs to connect the contacts with a printed circuit. The contact piece 5 is provided with a similar extension Sb. The contacts 3b and Sa have precious metal plating whose composition is so chosen that gases emerging from the synthetic resin of the envelope have no adverse effect on the contact properties. Further the contacts are so profiled that the welding operation of the contacts on their carriers can be done without the precious metal coating coming into contact with the welding electrode.

The relay with all its contact members and with the member 10 is placed in a mould filled with a predetermined amount of a curable synthetic resin with the contact pins on the top, and it sinks down therein. It is obvious that the member 10 with its insulating foil seals the contact space, but since the abutting face of the coil flange consists of some different parts small gaps exist into which the synthetic resin can penetrate. The above mentioned manner of moulding causes the synthetic resin to penetrate simultaneously into all gaps by capillary action, so that the air in the contact space cannot escape and a state of equilibrium is achieved between the capillary force and the air pressure in the contact space. When the synthetic resin is cured there results a hermetically sealed contact space. If by appropriate processing and cleaning methods during assembly it is ensured that the contact space is clean at the time of the moulding operation one obtains a relay with good properties with respect to the consistency of contact resistance as known reed relays. Since each contact spring carries has its own armature no transmission elements made from plastic material are needed to convey the armature motion, which elements would produce abrasion products which would be deposited between the open contacts due to the electrostatic field.

As the present contact arrangement is symmetrical about its vertical axis, i.e.

about the axis normal to the coil axis and to the printed circuit board, the arrangement of the contact-pins is symmetrical with respect to that vertical axis so that no special coding-pins are needed since the insertion of the relay into a printed circuit board can be performed both in a first position and also in a second position, after a rotation by 1800 about the vertical axis.

WHAT WE CLAIM IS: 1. An electromagnetic relay which includes a coil former with a space extending along the axis of the coil within which the relay contacts are arranged, at least one change-over contact set including a fixed contact and a contact support with a contact spring fixed thereto, an armature fixed to said contact spring within said space, a ferromagnetic member lined with an insulating foil and arranged to close the magnetic circuit outside the coil, and an envelope of a synthetic resin which is prevented by the ferromagnetic member from penetrating

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. of the pieces to be received therefrom are so designed that the inserted pieces are maintained in a predetermined position without further operations, owing to their own elastic deformation (contact piece 5) or due to elastic deformation of the coil former. The flanges of the coil former 1 have on their outer side recesses into which bent portions 3a and 4a of the contacts 3 and 4 fit so that with inserted contacts a plane surface is provided at the coil flanges. Each coil flange has at its ends two H-section members 6 for the reception of a coil terminal spring 7 which is bifurcated and can be inserted into the groove of each member 6 and which is maintained in the correct position by an enlargement of one leg of the spring. On the contact 4 there is fixed a changeover contact spring 8 which carries an armature 9. As can be seen from Figure 2 the two contacts 3 and 4 inserted into the same groove have a gap between them which is bridged by the armature 9. The distance between the two contacts 3 and 4 is such that while the leakage flux between the two contacts 3 and 4 is as small as possible, the armature 9 overlaps the two contacts by a sufficient amount to achieve a high sensitivity for the relay. The magnetic circuit is closed by a U-shaped ferromagnetic return member 10 which has on its inner side a thin plastics foil 11. When contacts 3 and 4 and the contact member 5 are in position the member 10 with its foil 11 is so mounted on the relay that the legs of the U abut against the bent portions 3a and 4a of the contacts 3 and 4 which form with the remainder of the coil flanges a continuous surface. The foil 11 serves as insulation since the members 3 and 4 are in contact portions, i.e. they are at a certain voltage. In addition the thin foil provides a small but defined air gap having the same effect as the usual residual plate, i.e. it prevents the armature from sticking due to remanence after the operating current is cut-off. A further effect of the foil is that it seals the contact space against the penetration of synthetic resin during moulding as it will be described later-on. The contact-end of the change-over spring 8 is bifurcated to provide the double contact arrangement often required. As can be seen from Figure 2 the spring 8 abuts against a contact 5a on the contact 5 when its coil is non-energized and abuts against a contact 3b arranged on the contact 3 when the coil is energized. The bent portions of the contacts 3 and 4 have with pin-like extensions 3c and 4b extending perpendicularly to the axis of the coil and serving as soldering tabs to connect the contacts with a printed circuit. The contact piece 5 is provided with a similar extension Sb. The contacts 3b and Sa have precious metal plating whose composition is so chosen that gases emerging from the synthetic resin of the envelope have no adverse effect on the contact properties. Further the contacts are so profiled that the welding operation of the contacts on their carriers can be done without the precious metal coating coming into contact with the welding electrode. The relay with all its contact members and with the member 10 is placed in a mould filled with a predetermined amount of a curable synthetic resin with the contact pins on the top, and it sinks down therein. It is obvious that the member 10 with its insulating foil seals the contact space, but since the abutting face of the coil flange consists of some different parts small gaps exist into which the synthetic resin can penetrate. The above mentioned manner of moulding causes the synthetic resin to penetrate simultaneously into all gaps by capillary action, so that the air in the contact space cannot escape and a state of equilibrium is achieved between the capillary force and the air pressure in the contact space. When the synthetic resin is cured there results a hermetically sealed contact space. If by appropriate processing and cleaning methods during assembly it is ensured that the contact space is clean at the time of the moulding operation one obtains a relay with good properties with respect to the consistency of contact resistance as known reed relays. Since each contact spring carries has its own armature no transmission elements made from plastic material are needed to convey the armature motion, which elements would produce abrasion products which would be deposited between the open contacts due to the electrostatic field. As the present contact arrangement is symmetrical about its vertical axis, i.e. about the axis normal to the coil axis and to the printed circuit board, the arrangement of the contact-pins is symmetrical with respect to that vertical axis so that no special coding-pins are needed since the insertion of the relay into a printed circuit board can be performed both in a first position and also in a second position, after a rotation by 1800 about the vertical axis. WHAT WE CLAIM IS:

1. An electromagnetic relay which includes a coil former with a space extending along the axis of the coil within which the relay contacts are arranged, at least one change-over contact set including a fixed contact and a contact support with a contact spring fixed thereto, an armature fixed to said contact spring within said space, a ferromagnetic member lined with an insulating foil and arranged to close the magnetic circuit outside the coil, and an envelope of a synthetic resin which is prevented by the ferromagnetic member from penetrating

into said space and which hermetically seals the space containing the contacts.

2. A relay according to claim 1, in which the relay has two change-over contact sets, the space within the coil former having a rectangular cross-section, in which each of the larger sides of the rectangle has three longitudinal grooves, in which in each of the two outer pairs of grooves there is secured a fixed contact and a contact spring support of one said change-over contact set, and in which at each end of the space there is fixed the fixed contact of one change-over contact set and a contact spring support of the second change-over contact set, and in which in the groove in the middle a fixed normally disengaged contact is mounted at each of the ends of the space.

3. A relay according to claim 2, and in which the contact members are fixed within the corresponding grooves by an elastic deformation.

4. A relay according to claim 3, and in which the ends of the fixed contact members and the ends of the contact spring supports are bent and fit into recesses of the coil former to provide an overlapping surface for engagement by the ferromagnetic member.

5. A relay according to claim 4, and in which the bent ends of the contact members and the contact supports have pin-like lateral extensions serving as terminal pins for the relays.

6. An electromagnetic relay substantially as described with reference to the accompanying drawings.