GB2142188A

GB2142188A - Electrical relays

Info

Publication number: GB2142188A
Application number: GB08317331A
Authority: GB
Inventors: P D Eldridge
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1983-06-25
Filing date: 1983-06-25
Publication date: 1985-01-09
Also published as: GB8317331D0; GB2142188B

Abstract

The movable armature (2) of a relay extends through a coil (1) and is arranged to operate contact sets (3) via insulating stirrups (5) connected to movable contacts (6). The contact force of the contact sets (3) is enhanced by means of a permanent magnet (10) and two pole pieces (8,9) coupled thereby. In a monostable version (as illustrated) the areas of the pole pieces (8,9) via which coupling to the armature (2) occur are different in size, so that when the coil (1) is de-energised the armature (2) will always restore to the same position (as illustrated). In a bistable version the pole piece coupling areas are the same so that the armature is held in its last set position upon coil de-energisation. <IMAGE>

Description

SPECIFICATION Electrical relays This invention relates to electrical relays and in particular, but not exclusively, to polarised relays.

According to the present invention there is provided an electrical relay comprising a coil, an armature extending through the coil and movable with respect thereto upon passage of current through the coil, at least one contact set arranged to be operated by movement of the armature, and a permanent magnet serving to enhance the contact force of the at least one contact set.

Embodiments of the invention will now be described with reference to the accompanying drawing which shows somewhat schematically a monostable version of polarised relay in the unenergised state.

The relay illustrated in the drawing comprises a coil, an armature 2 which passes through the coil 1, four changeover contact sets 3 (only two of which are visible in the drawing) and a pole-piece assembly 4. The armature 2 is moveable within the coil 1; and the coil 1, the contact sets 3 and the pole-piece assembly 4 are mounted in fixed positions with respect to one another and an enclosure (encapsulation package) for the relay (not shown). The armature 2 is supported in the enclosure by means of insulating stirrups 5, for example of a plastics material, which also flexibly couple it to the movable blades 6 of the four changeover contact sets 3. The armature 2 is shaped like a straight-sided invented "U", the downwardly inclined vertical limbs 7 being external to the coil 1 and movable between respective contact faces of pole pieces of the pole-piece assembly 4.The pole-piece assembly 4 comprises two nested "U" shaped pole pieces 8 and 9 which are coupled by a permanent magnet 10. The contact faces of the pole pieces 8 and 9 are polarised by the permanent magnet 10. The opposite ends of the armature 2 are coupled via the pole pieces 8 and 9 to respective opposite ends of the permanent magnet 10. Since the areas of the contact faces of the pole pieces 8 and 9 couplable to each end of the armature 2 are different, the force acting on the armature 2 due to the permanent magnet 10 is greater in one direction of movement of the armature than the other. Thus, when the coil 1 is de-energised, the armature 2 will always return to the same position, the larger area contact faces, and hence the device is monostable.

When the coil 1 is energised, whereby to operate the relay, the direction of current flow is such as to cause magnetic polarities to be induced at either end of the armature 2 which are the same as and thus oppose the polarities, existing at the contacted contact faces of the pole pieces 8 and 9, due to the permanent magnet, and thus the armature 2 is caused to move due to repulsion. At a point in the travel of the armature its induced poles will be attracted to the opposite poles, due to the permanent magnet, existing on the other contact faces of the pole pieces. Thus during the armature travel both repulsion and attaction forces act on the armature to provide high acceleration. The armature 2 and the pole pieces 8 and 9 are manufactured from soft magnetic materials having high permeability and low remanence.However, when the gap between them is very small even a low value of remanence is sufficient to delay the release of the armature when the coil is de-energised. For this reason remanence slugs of copper or brass 11 may be used to maintain a small non-magnetic gap between the parts to overcome the effects of remanence. In the monostable version illustrated the remanence slugs 11 are mounted to the contact faces of the pole pieces which are contacted when the relay is operated upon energisation of the coil, that is the smaller area contact faces.

A bistable version of the relay may be achieved by arranging for the contact faces of the pole pieces to be of the same area, so that the permanent magnet force will retain the armature in the last position to which it was set, as dictated by the direction of the coil flux. If the relay is to be used with current reversing electronics, a single coil may be employed which will switch the armature position with reversal of the current in the coil. Once reversed it is not necessary to maintain the coil current as the permanent magnet force will be sufficient to hold the armature in position. If only unidirectional currents are available from the electronics with which the relay is to be used, then flux reversal can be achieved either by the use of reversing contacts, or by the use of two coils wound in different directions.

The monostable and bistable relays described above are particularly suitable for manufacture in a miniature form in a DIL (dual-in-line) outline package (16 pin type, using 3 pins for each of the four contact sets plus 2 pins for the coil) and are TTL compatible.

Such a DIL package is 10 mm high, 20 mm long and 10 mm wide. The design of the monostable and bistable versions of the relay is the same except for two piece parts, the pole pieces, thus facilitating manufacture.

The relays have high sensitivity, large contact clearances and high contact forces and are highly efficient. The high efficiency of the relay is achieved by placing the moving armature within the coil and using a permanent magnet to enhance the contact force. Typically for such a miniature TTL compatible polarised DIL relay the contact force is greater than 3 grams (for four changeover contact sets), the contact clearance is 0.75 mm, the operate time is less than 10 msec and the release time (TTL connected) is less than 10 msec. Whereas the relays described above employ four contact sets, two at each end of the armature, versions for the operation of a single contact set, or two contact sets can be similarly constructed.

1. An electrical relay comprising a coil, an armature extending through the coil and movable with respect thereto upon passage of current through the coil, at least one contact set arranged to be operated by movement of the armature, and a permanent magnet serving to enhance the contact force of the at least one contact set.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Electrical relays This invention relates to electrical relays and in particular, but not exclusively, to polarised relays. According to the present invention there is provided an electrical relay comprising a coil, an armature extending through the coil and movable with respect thereto upon passage of current through the coil, at least one contact set arranged to be operated by movement of the armature, and a permanent magnet serving to enhance the contact force of the at least one contact set. Embodiments of the invention will now be described with reference to the accompanying drawing which shows somewhat schematically a monostable version of polarised relay in the unenergised state. The relay illustrated in the drawing comprises a coil, an armature 2 which passes through the coil 1, four changeover contact sets 3 (only two of which are visible in the drawing) and a pole-piece assembly 4. The armature 2 is moveable within the coil 1; and the coil 1, the contact sets 3 and the pole-piece assembly 4 are mounted in fixed positions with respect to one another and an enclosure (encapsulation package) for the relay (not shown). The armature 2 is supported in the enclosure by means of insulating stirrups 5, for example of a plastics material, which also flexibly couple it to the movable blades 6 of the four changeover contact sets 3. The armature 2 is shaped like a straight-sided invented "U", the downwardly inclined vertical limbs 7 being external to the coil 1 and movable between respective contact faces of pole pieces of the pole-piece assembly 4.The pole-piece assembly 4 comprises two nested "U" shaped pole pieces 8 and 9 which are coupled by a permanent magnet 10. The contact faces of the pole pieces 8 and 9 are polarised by the permanent magnet 10. The opposite ends of the armature 2 are coupled via the pole pieces 8 and 9 to respective opposite ends of the permanent magnet 10. Since the areas of the contact faces of the pole pieces 8 and 9 couplable to each end of the armature 2 are different, the force acting on the armature 2 due to the permanent magnet 10 is greater in one direction of movement of the armature than the other. Thus, when the coil 1 is de-energised, the armature 2 will always return to the same position, the larger area contact faces, and hence the device is monostable. When the coil 1 is energised, whereby to operate the relay, the direction of current flow is such as to cause magnetic polarities to be induced at either end of the armature 2 which are the same as and thus oppose the polarities, existing at the contacted contact faces of the pole pieces 8 and 9, due to the permanent magnet, and thus the armature 2 is caused to move due to repulsion. At a point in the travel of the armature its induced poles will be attracted to the opposite poles, due to the permanent magnet, existing on the other contact faces of the pole pieces. Thus during the armature travel both repulsion and attaction forces act on the armature to provide high acceleration. The armature 2 and the pole pieces 8 and 9 are manufactured from soft magnetic materials having high permeability and low remanence.However, when the gap between them is very small even a low value of remanence is sufficient to delay the release of the armature when the coil is de-energised. For this reason remanence slugs of copper or brass 11 may be used to maintain a small non-magnetic gap between the parts to overcome the effects of remanence. In the monostable version illustrated the remanence slugs 11 are mounted to the contact faces of the pole pieces which are contacted when the relay is operated upon energisation of the coil, that is the smaller area contact faces. A bistable version of the relay may be achieved by arranging for the contact faces of the pole pieces to be of the same area, so that the permanent magnet force will retain the armature in the last position to which it was set, as dictated by the direction of the coil flux. If the relay is to be used with current reversing electronics, a single coil may be employed which will switch the armature position with reversal of the current in the coil. Once reversed it is not necessary to maintain the coil current as the permanent magnet force will be sufficient to hold the armature in position. If only unidirectional currents are available from the electronics with which the relay is to be used, then flux reversal can be achieved either by the use of reversing contacts, or by the use of two coils wound in different directions. The monostable and bistable relays described above are particularly suitable for manufacture in a miniature form in a DIL (dual-in-line) outline package (16 pin type, using 3 pins for each of the four contact sets plus 2 pins for the coil) and are TTL compatible. Such a DIL package is 10 mm high, 20 mm long and 10 mm wide. The design of the monostable and bistable versions of the relay is the same except for two piece parts, the pole pieces, thus facilitating manufacture. The relays have high sensitivity, large contact clearances and high contact forces and are highly efficient. The high efficiency of the relay is achieved by placing the moving armature within the coil and using a permanent magnet to enhance the contact force. Typically for such a miniature TTL compatible polarised DIL relay the contact force is greater than 3 grams (for four changeover contact sets), the contact clearance is 0.75 mm, the operate time is less than 10 msec and the release time (TTL connected) is less than 10 msec. Whereas the relays described above employ four contact sets, two at each end of the armature, versions for the operation of a single contact set, or two contact sets can be similarly constructed. CLAIMS

2. A relay as claimed in claim 1, wherein the armature includes an elongate central portion and end portions disposed externally of the coil and extending in a direction substantially perpendicular to the elongate portion.

3. A relay as claimed in claim 2, including a first and second substantially U-shaped pole piece, the first pole piece being smaller than the second pole piece, the pole pieces being nested together with the permanent magnet disposed in a coupling and spacing relation therebetween whereby to induce poles of opposite type in the two pole pieces.

4. A relay as claimed in claim 3, wherein the ends of the first pole piece are disposed between the end portions of the armature and the ends of the second pole piece are disposed externally of the end portions of the armature, wherein in one end position of the armature travel one end portion of the armature is in contact with the adjacent end of the second pole piece and the other end portion of the armature is in contact with the adjacent end of the first pole piece, and wherein in the other end position of the armature travel the one end portion of the armature is in contact with the adjacent end of the first pole piece and the other end portion of the armature is in contact with the adjacent end of the second pole piece.

5. A relay as claimed in claim 4 and adapted for monostable operation, wherein the ends of the pole pieces in contact with the armature for one of said end positions of the armature travel, a rest position, are of larger contact area than the other ends of the pole pieces, and wherein the direction of current flow through the coil in use of the relay serves to induce poles in the armature end portions of the same type as the induced poles of the contacted pole pieces.

6. A relay as claimed in claim 5 including remanence slugs mounted to ends of the pole pieces which are not contacted in the rest position of the armature.

7. A relay as claimed in claim 4 and adapted for bistable operation, wherein the ends of the pole pieces in contact with the armature for either of said end positions are of equal contact area.

8. A relay as claimed in claim 7 and including a second coil through which the armature also extends, the armature being moved in one direction by the passage of current through the said coil and in the other direction by the passage of current through the second coil.

9. A relay as claimed in any one of the preceding claims, wherein the armature operates the at least one contact set by means of a respective insulating stirrup coupled between the armature and a movable contact of the at least one contact set.

10. A relay as claimed in any one of the preceding claims including two contact sets, one arranged at each end of the armature.

11. An electrical relay substantially as herein described with reference to and as illustrated in the accompanying drawing.