Polarized power relay

A relay has a polarized magnetic system (2) with a three-pole magnet (17) arranged above a coil (14) and rocking armature (18) which actuates a contact spring (30) arranged beneath the coil by means of a frontally arranged slide (23). The contact spring (30) is inserted from one side into the base body, by means of an elongated spring carrier (29), whereas a counter contact element (33) is inserted therein from the opposite side. This relay allows with a compact design long insulating sections between the magnetic system and the set of contacts, as well as a short circuit-resistant design of the set of contacts.

BACKGROUND OF THE INVENTION 
The invention relates to a polarized electromagnetic relay having a coil, 
an elongated permanent magnet which is arranged above the coil and 
parallel to the coil axis and which has like end poles at each of its two 
ends and a center pole opposite thereto in its center, having a core which 
is arranged inside the coil and which is coupled at both ends to the two 
ends of the permanent magnet by means of yoke legs and also having an 
elongated rocking armature which is mounted above the center pole of the 
permanent magnet and forms a working air gap with each of the two yoke 
legs. 
Such a relay having a three-pole magnet and a rocking armature mounted 
above the magnet is disclosed, for example, in European reference EP-A-O 
197 391. In the latter, however, the contact system is also arranged above 
the coil in the region of the armature, the contact springs arranged on 
both sides of the armature being directly linked to it and performing 
their switching movements directly with the armature. 
The same magnet system having a three-pole permanent magnet and a rocking 
armature is also already used in German reference DE-A-21 48 377. However, 
in that case permanent magnet and armature are arranged to the side of the 
coil and actuating pins attached to the armature ends act on contact 
springs which are underneath the coil and can be moved in a plane parallel 
to the base plane of the relay. 
Common to these known relays is the fact that the contact elements are 
situated with small spacings in the region of the armature and of the 
magnet system. These systems are consequently suitable only for switching 
low currents. 
European reference EP-A-186 160 (corresponding to U.S. Pat. No. 4,688,010) 
furthermore discloses a relay for switching higher powers in which a 
housing is subdivided into a coil enclosure for receiving an electromagnet 
system and a switching enclosure for receiving a contact arrangement. An 
armature which carries a permanent magnet is arranged in front of the end 
face of the coil and fits into the contact enclosure by means of a firmly 
molded-on actuating arm. 
SUMMARY OF THE INVENTION 
The object of the present invention is to exploit the advantages of the 
polarized system described at the outset, namely the high sensitivity 
accompanied by optionally adjustable monostable or bistable switching 
characteristics and the low sensitivity of the centrally mounted armature 
to vibrations, for switching higher currents and voltages. 
According to the invention, this object is achieved in a relay of the type 
mentioned at the outset in that the armature is mounted by means of a 
bearing spring which is attached directly to its center section and can be 
latched to the permanent magnet on both sides, in that a contact assembly 
having at least one contact spring arranged approximately parallel to the 
coil axis and at least one fixed contact element is arranged underneath 
the coil and in that there is arranged in front of one end face of the 
coil a slide which can be moved perpendicular to the coil axis and is made 
of insulating material and which is coupled, on the one hand, to a movable 
end of the armature and, on the other hand, to a movable end of the 
contact spring. 
In the case of the invention, therefore, the contact elements are arranged 
at the underside of the relay right next to the connection side, so that 
short connecting elements do not generate unduly high heat losses even 
when carrying high currents. Since the armature with the iron parts of the 
magnet system is situated opposite the contact elements on the upper side 
of the coil, a large insulating clearance between contact system and 
magnet system is already produced as a result of the spatial distance. In 
addition, the coil and the entire magnet system can be screened by 
suitable structural design of a main body to create long insulating 
clearances with respect to the contact system. Such a main body, in which, 
for example, the contact assembly having connecting elements brought out 
to the underside is arranged, preferably forms a partition between contact 
assembly and coil, at which partition side walls formed on at the bottom 
surround the contact assembly and/or side walls formed on at the top 
surround the magnet system in a U-shaped or trough-shaped manner. The 
partition may additionally have a laterally open slot into which an 
insulating-material plate is inserted. In this way, three 
insulating-material walls situated one above the other are obtained 
between contact assembly and coil and this ensures the voltage-sustaining 
capability required for certain applications. The insulating-material 
slide which is arranged at one end face of the coil and which produces a 
link between armature and contact system may create labyrinth-like 
insulating clearances as a result of suitable overlaps with the main body. 
Expediently, the slide has in each case recesses into which deformable 
ends of the contact spring, on the one hand, and of the armature, on the 
other hand, fit.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The relay shown in FIGS. 1 to 4 has a main body 1 having a central 
partition 3 which is arranged parallel to the base side and on which side 
walls 4 and 5 and also 6 and 7 formed on at the top form a trough-like 
recess for a magnet system 2 which can be inserted from above. At the 
bottom the partition 3, together with a parallel base wall 8 and an 
extension of the side wall 4, surrounds in an approximate U-shape a 
contact enclosure 9 which is open on the right in FIG. 1. Together with a 
cap 10 which can be mounted from above, the main body 1 forms a housing 
which is closed all round. 
The magnet system 2 has a tubular coil former 11 having end flanges 12 and 
13 between which a winding 14 is arranged. Inserted from both sides into 
the tubular opening of the coil former 11 is one core yoke 15 or 16 having 
a core leg 15a or 16a, respectively, in each case so that the two yoke 
legs 15b and 16b, which are bent at right angles, project upwards in 
parallel. Arranged between the two yoke legs above the coil and parallel 
to the coil axis is a rod-like three-pole magnetized permanent magnet 17 
which has like poles, for example S, in each case in the region of the two 
yoke legs and a pole opposite thereto, for example N, in the center 
region. The permanent magnet comprises, for example, an AlNiCo alloy and 
may in this case simply be cut out of a strip. The magnet can be attached 
to the coil former by thermoplastically deforming the coil flanges. The 
core yokes 15 and 16 are also fixed to the coil former in a suitable 
manner. 
From FIG. 4 it is evident that the core legs 15a and 16a are designed in a 
step-like manner so that, when situated next to one another, they form a 
large overlap region. In this way, the two core yokes can be of identical 
design and, nevertheless, make possible a good flux transmission between 
the two parts. 
The number of parts and manufacturing steps is consequently reduced. 
An armature 18 designed as a rocker is mounted on the center pole N of the 
permanent magnet 17. In its center region, the armature is bent slightly 
in a V-shaped manner towards the permanent magnet so that the ends 18a and 
18b each form an air gap with the corresponding yoke leg 15b or 16b, 
respectively. A bearing spring 19 which preferably comprises ferromagnetic 
material serves to mount the armature, which bearing spring 19 is attached 
to the lower side of the armature by riveted joints 20 to the latter and 
is attached by latching with laterally bent latching tabs 21 in 
corresponding recesses of the permanent magnet 17. The bearing spring 19 
forms a torsion strip bearing for the armature. This arrangement and shape 
of the bearing spring ensures that the armature is frictionlessly mounted 
and that, at the same time, a good flux transmission takes place from the 
permanent magnet 17 to the armature 18. Furthermore, the armature is held 
or secured in the bearing from above by a rib 22 formed on the cap 10. 
Since the armature is mounted at its center of gravity, its switching 
state is largely insensitive to vibrations. 
The armature movement is transmitted via a slide 23 to a contact spring 
assembly which has still to be described, the slide being arranged between 
the side wall 5 of the main body and a side wall of the cap 10 and being 
capable of moving perpendicular to the connecting plane or to the coil 
axis. This arrangement of the insulating slide between insulating walls 
produces long labyrinth-like creepage clearances and air clearances 
between the metal parts of the magnet system and the contact spring 
assembly. The coupling between anchor 18 and slide 23 takes place through 
(two) extensions 24 of the armature end 18b which fit into corresponding 
recesses 25 of the slide. In addition, for securing purposes, a separating 
plate 26 having one retaining tab 26a in each case is provided which, 
according to FIG. 1 may be bent upwards or, according to the detailed 
drawing in FIG. 5, may be bent downwards. Another coupling possibility is 
shown in the detailed diagram of FIG. 6. In this case, a hook-like 
extension 27 which is hooked into a suitably designed recess 28 of the 
slide 23 is formed on in each case to the armature end 18b. Other 
embodiments of this coupling are also conceivable. 
The contact spring assembly arranged in the contact enclosure 9 underneath 
the coil has a contact spring 30 which is attached to a spring support 29 
and is split up at its free end in a fork-like manner into two spring legs 
31 and 32. A fixed, normally open contact element 33 is arranged above the 
contact spring 30. At the same time, a movable main contact piece 34 
mounted on the spring leg 31 forms, with an oppositely situated fixed main 
contact piece 35 of the contact element 33, a main contact whose contact 
pieces comprise noble metal. In addition, an early contact whose contact 
pieces comprise tungsten or a comparable metal in a known manner is formed 
with a movable early contact piece 36 on the spring leg 32 and an 
oppositely situated, fixed early contact piece 37 on the contact element 
33. 
During the assembly, the contact spring support 29 and the fixed, normally 
open contact element 33 are inserted into the main body 1 which is 
U-shaped in the lower section from different sides, and in particular, the 
spring support 29 is inserted from one side, in FIG. 2 from the left, and 
the normally open contact element 33 is inserted from the right in FIG. 2. 
The mounting takes place in each case by pressing into corresponding 
insertion grooves. 
Complete support of the spring support 29 on the base wall 8 is achieved by 
additionally twisting the connecting pin 29a. This measure produces for 
the contact spacing a narrow tolerance zone which provides the condition 
for obtaining low variations in the characteristic relay values. 
Furthermore, during the assembly, the lower end of the slide 23, which has 
a recess 38, is pushed over the hook-shaped ends 31 a and 32a of the 
contact spring and latched. This is shown in FIG. 7. 
Incidentally, during the assembly, the magnet system 2 is pressed from 
above as an exact fit between the side walls 4, 5, 6 and 7 and 
additionally fixed by gluing. This eliminates a subsequent alignment. For 
the purpose of additionally improving the insulation between magnet system 
and contact enclosure, at the point where the spacing between magnet 
system and contact region is less than 2 mm an insulating film 39 is 
inserted into a main-body slot 40 on the long side. As a result of this 
measure, the three insulating walls required by VDE regulations are 
produced. 
In the present case, the spring support 29 is produced from a nonmagnetic 
material with good electrical conduction, for example a copper alloy. 
Since the connecting pin 29a of the spring support is located in the 
vicinity of the right-hand edge of the main body in FIG. 1, while the 
attachment point of the contact spring is near the left-hand edge, the 
spring support extends almost over the entire length of the relay. The 
current path of the spring support is deliberately designed in this way 
long enough between connecting pin and spring attachment for opposite 
current directions in the spring support, on the one hand, and in the 
contact spring, on the other hand, to be able to generate electrodynamic 
forces which increase the normally open contact force. Very high contact 
forces are consequently intended to be generated during a short circuit, 
which reduce the contact resistance and consequently reduce the risk of 
welding. 
However, the contact force increase due to the above-mentioned opposite 
current directions between spring support and spring might not under some 
circumstances be sufficient in the event of prolonged service life of the 
relay because the spacing between the spring support 29 and the contact 
spring 30 becomes increasingly larger in the course of time because of the 
contact erosion at the contact pieces. This increasing erosion also 
reduces the contact forces which are exerted by the magnet system on the 
contact spring via the slide. Consequently, in the event of a short 
circuit there might nevertheless be the risk of a functional failure if 
the relay had performed a fairly large number of switching cycles. 
In order to counteract this danger, the normally open contact element 
comprises in the present case ferromagnetic material; in addition, it is 
crimped in its center section 33a (which switching current does not flow 
through) so that, in this region, it is situated as near the contact 
spring 30 as possible. This has the following effect: a short-circuit 
current flowing in the center spring generates a magnetic field which 
would tend to attract the ferromagnetic, normally open contact element. 
Since the latter is firmly anchored, however, in the main body, the 
contact spring together with its contact piece 34 is, on the contrary, 
attracted to the fixed, normally open contact element 33. The force of 
attraction becomes all the greater the smaller the spacing between the 
contact spring 30 and the normally open contact element 33. In the 
short-circuit case, this additional type of contact force reinforcement 
has the very particular advantage that the force of attraction and, 
consequently, also the contact force becomes larger with increasing 
contact erosion. 
Thus in the case of the combination present here the two different types of 
contact force reinforcement, namely, on the one hand, the repulsion of the 
contact spring by its spring support 29 with current flowing through it 
and, on the other hand, the attraction to the ferromagnetic, normally open 
contact element 33 add in the combination present here. If, in the event 
of contact erosion, the one effect becomes smaller, the other effect 
becomes larger at the same time so that the relay remains fully 
serviceable during its entire service life even in the event of a short 
circuit. The high short-circuit contact forces which occur prevent a 
welding of the contacts because of the low contact resistance produced. 
The ferromagnetic, normally closed contact element 33 has, in addition, the 
further advantage that it attracts the arc which is produced in the case 
of the tungsten early contact 36, 37 during switching on and off. As a 
result, the main contact 34, 35, which comprises, for example, silver, is 
less heavily contaminated by the tungsten evaporation. The electrical 
conductivity of tungsten is, after all, lower than that of silver for the 
same contact force by a factor of 3.5. The lower conductivity of the 
normally open contact element 33 is, however, taken into account by two 
parallel connecting pins 33b. 
A particular advantage of the combination, according to the invention, of 
polarized rocking armature/magnet system with the contact assembly 
described above is also that the contact is closed at the top by means of 
a movement of the armature arm 18b. Consequently, the shorter normally 
open contact element can be arranged above the longer spring support 29, 
between the contact spring 30 and the coil 14. This results in a 
particularly beneficial space utilization underneath the coil former, as a 
result of which a particularly compact structure of the relay is made 
possible. 
However, a modification of the relay would also be conceivable in which a 
further counter contact element would additionally be arranged beneath the 
contact spring in order to form a double-throw contact in this way. The 
spring support 29 would then have to be shaped differently in a suitable 
manner. 
FIGS. 8 to 10 show yet a further embodiment of a relay designed in 
accordance with the invention. If individual parts of this exemplary 
embodiment are not described in detail, they are identical or similar to 
the previous exemplary embodiment. 
The relay shown in FIGS. 8 to 10 has a main body 41 which is essentially of 
trough-shaped design in the upward direction and of U-shaped design in the 
lower section, like the main body 1. Inserted into the upper part of the 
main body is a magnet system 42 which has a coil former 43 having a 
winding 44 and two L-shaped core yokes 45 and 46. In this case, the core 
yokes are stepped in such a way that they lie one on top of the other in 
the center region and, in this way, have larger contact areas in the 
overlap region. However, in this case, they cannot be of identical design. 
A three-pole magnet 47 situated on the coil is of thicker design in the 
region of its center pole and tapered towards the two end poles so that 
the armature 48 mounted above the center pole and designed as a flat plate 
can perform a rocker movement, in all cases alternatively, towards one of 
the two core yokes. 
The armature 48 is enclosed by injection molding in its center region by a 
plastic ring 49 which forms a pivot pin 50 on both sides of the armature. 
The armature is rotatably mounted on both sides in bearing holes 51 of the 
main body by means of said pivot pins 50. 
Formed onto the right-hand end of the armature is an actuating finger 52 
which is coupled to a slide 53 and, as in the preceding case, moves the 
latter in front of the end face of the coil and perpendicularly to its 
axis. The slide 53 actuates a contact spring 54 which is mounted in the 
main body by means of a spring support 55. A contact piece 56 of the 
contact spring interacts with a contact piece of a normally open contact 
element 58 which is also anchored in insertion grooves of the main body. A 
baseplate 59 forms, together with a cap 60, a housing which encloses the 
relay on all sides. 
Of course, various combinations of individual elements from the two 
exemplary embodiments described are also possible, in particular as 
regards the design of the contact elements and the configuration as 
normally closed, normally open or double-throw contact. 
The invention is not limited to the particular details of the apparatus 
depicted and other modifications and applications are contemplated. 
Certain other changes may be made in the above described apparatus without 
departing from the true spirit and scope of the invention herein involved. 
It is intended, therefore, that the subject matter in the above depiction 
shall be interpreted as illustrative and not in a limiting sense.