GB1574947A

GB1574947A - Electromagnetic relay

Info

Publication number: GB1574947A
Application number: GB1767277A
Authority: GB
Original assignee: CP Clare International NV
Current assignee: CP Clare International NV
Priority date: 1976-05-03
Filing date: 1977-04-27
Publication date: 1980-09-10
Also published as: FR2350678B1; DE2719230A1; FR2350678A1; IT1077746B; DE2719230C3; NL7704489A; DE2719230B2; SE7704730L

Description

(54) ELECTROMAGNETIC RELAY (71) We, C. P. CLARE INTER NATIONAL N.V., a joint stock company organized under Belgian law, of Overhaamlaan, B-3700 Tongeren, Belgium, 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, for example to the kind known as a reed relay.

Reed relays comprise a reed contact unit in the form of a sealed capsule containing switch contact means, which reed contact unit is located lengthwise within an energizing coil.

According to this invention there is provided an electromagnetic relay comprising: a coil; switch contact means provided with co-operating ends arranged longitudinally in a substantially axial opening provided in the coil; an outer tube comprising magnetic material, arranged substantially coaxially around the coil; first and second inner tubes, arranged at different regions along, and substantially coaxially around, the switch contact means, between the switch contact means and the coil, such that the adjacent ends of the first and second inner tubes are spaced apart to form a gap in the region of said co-operating ends; and first and second substantially disc-shaped members comprising magnetic material, arranged at respective ends of the coil and each provided with a substantially central opening for receiving a respective one of the first and second inner tubes, each discshaped member being located against the inner surface of the outer tube.

At least one of the first and second substantially disc-shaped members could be a magnet. Alternarively, at least one of these substantially disc-shaped members could comprise a plurality of substantially rectangular magnets embedded in a non-magnetic material, for producing a radial magnetic field.

Preferably, the switch contact means are provided by a reed contact unit.

The invention will now be described by way of example with reference to the accom panying drawings, in which: Figure 1 shows an exploded view of an assembly of a reed relay according to the invention, Figure 2 shows a lengthwise, sectional view of the reed relay shown in Figure 1, in assembled form, Figure 3 shows a schematic representation showing the flux lines of the magnetic field produced when a coil of the assembly shown in Figure 2 is energized, and Figure 4 shows an end view of another embodiment of part of the assembly shown in Figure 2.

Referring to Figures 1 and 2, a reed switch capsule 1 containing switch contact means is surrounded by a coil 2. Two inner tubes 5 comprising magnetic material extend lengthwise over the capsule 1, within the coil 2, and are spaced apart such that a gap 6 is formed therebetween. The gap 6 has a predetermined axial length and is located axially in the region of co-operating ends of the switch contact means in the capsule 1. Two disc-shaped flange members 7 comprising mag netic material are located against the end flanges of the coil 2. Furthermore, an outer tube 8 comprising magnetic material extends lengthwise over, and envelopes, the coil 2.

A housing for the assembly comprises a base plate 3 and a cover 4. Pins 9 are received by holes provided in the base plate 3, and serve to connect the relay with external cir cuitry. Each flange member 7 is provided with a central opening which receives a res pective one of the two inner tubes 5 such that it is urged against the inner surface of the outer tube 8 (see Figure 2).

An important feature of this assembly is the length of the gap 6 between the inner tubes 5. When considering the relay sensitivity as a function of the length of this gap 6, is is found that the sensitivity is a maximum for a particular gap length. The reason is believed to be that, when the length of the gap 6 is too small, the magnetic flux bridges the two inner tubes 5 and, when the length of the gap 6 is too large, the reluctance in creases strongly such that the sensitivity is caused to decrease.

Referring to Figure 3, magnetic flux lines F appear to concentrate in the region C od the co-operating ends of the switch contact means. In this way there is obtained a combination of the advantages of a long coil with a great number of turns and a relatively low resistance, and of a short coil with a concentrated magnetic field and a relatively high resistance. Thus, a relatively high mag netic field can be produced at a well defined location, i.e. the region C, with a reduced number of turns for the coil 2. This results from the fact that magnetic flux lines having the same direction attract one another.

The assembly described above can be used to realize a "make contact" (sometimes known as a "1 Form A") relay. The length of the gap 6 can be selected to give a relay which requires a power of 3.5 mW at a nominal operating voltage.

Also, a "break-contact" relay (sometimes known as a "1 Form B" relay can be realized, in which a magnetic field keeps the switch contact means closed during the time that the coil 2 is not energized. To achieve this, at least one of the flange members 7 is re placed by a magnet. In one arrangement, use is made of an annular magnet having an axial opening suitable for housing a respective one of the inner tubes 5, which magnet produces a radial magnetic field. In another arrange ment, shown in Figure 4, rectangular magnets 11 are embedded in a non-magnetic material 12, for example a plastics material, such that a radial magnetic field is produced. The arrows in Figure 4 indicate the direction od the magnetic field for each magnet.

A holding relay is also realizable, using an . arrangement similar to. that used for the "break contact" relay described above, but in which the magnets have a well-defined strength.

Claims

WHAT WE CLAIM IS:-

1. An electromagnetic relay comprising: a coil; switch contact means provided with co-operating ends arranged longitudinally in a substantially axial opening provided in the coil; an outer tube comprising magnetic material, arranged substantially coaxially around the coil; first and second inner tubes, arranged at different regions along, and substantially coaxially around, the switch contact means, between the switch contact means and the coil, such that the adjacent ends of the first and second inner tubes are spaced apart to form a gap in the region of said cowoperating ends; and first and second substantially discshaped members comprising magnetic material, arranged at respective ends of the coil and each provided with a substantially central opening for receiving a respective one of the first and second inner tubes, each disc-shaped member being located against the inner surface of the outer tube.

2. An electromagnetic relay according to claim 1, wherein at least one of the first and second substantially disc-shaped members is a magnet.

3. An electromagnetic relay according to claim 1, wherein at least one of the first and second substantially disc-shaped members comprises a plurality of substantially rectangular magnets embedded in a non-magnetic material, for producing a radial magnetic field.

4. An electromagnetic relay according to any preceding claim, wherein the switch contact means are provided by a reed contact unit.

5. An electromagnetic relay substantially as herein described with reference to Figures 1, 2 and 4 of the accompanying drawings.