Improvements in Relays.
Year: 1899

page_text: Date of Application, 10th July, 1899-Accepted, 12th Aug., 1899
COMPLETE SPECIFICATION.
Improvements in Relays.
We, Dr. LUIGI CEREBOTANI, of Sendlingerstrasse, No. 63, in the City of
Munich, in the Kingdom of Bavaria, and German Empire, Professor, and ALBERT
SILBERMANN, of Blumenstrasse, No. 74, in the City of Berlin, in the Kingdom of
Prussia, and German Empire, Manufacturer, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement;-
The essential features which must characterize a relay which shall be really
effective in its operation, are as follows:
Sensibility, .e., that it responds at once to even the weakest current.
Obedience, .e., that all the impulses of current, even the most rapid, are re-
produced through the relay..
Uniformity of the stroke of the armature, i.e., that the energy of the armature
stroke remains the 'same, even though there should be many variations in the
line current.
.
Reliability and permanency of the polarisation, .e., that if the relay is a
polarised one, its polarisation will not undergo any change through alteration in
the current.
Limitation, ie, that the rolay may respond only to currents the strength of
which is within certain limits.
These features are all united in the relay forming the subject of the present
invention.
Fig. 1 is a plan view of the relay, showing also the course of the currents.
Fig. 2 is an underside view of a part of the apparatus, and
Fig. 3 is a vertical section seen in the direction of the arrow, Fig. 1.
The relay consists of 2 pairs of electro-magnets a a¹, 56'.
The arrangement of each of the magnetic pairs is such that one part lies on
the right and the other on the left of the armature. The connection of the iron
cores is shown in Fig. 2. The lever h, turning about the point o forms the
common armature (cp., Fig. 3). It is so constructed that if no force is exerted
upon it, it remains in any position in perfectly stable equilibrium.
o is a set screw for adjusting the point of suspension.
If the one pair of magnets, for instance, a a¹, is excited by the current, the
lever turns, moving towards the left at a and towards the right at a'. If on
the other hand the magnetic force acts at 6 6, the action will be the reverse.
The magnets are arranged in a particular manner. The line L first passes
through the coilib and then through a¹ 31 and a, finally going to carth. But whilst
The magnet pair bb is only wound with the line wire, the magnet pair a a¹ is
wound also with a second wire, indicated on the drawing by a thicker line. This
second winding is included in the circuit of a local battery B, and consists of only
comparatively fow turns, but of relatively thick wire.
To regulate the local current a resistance 10 is inserted in the circuit. The
coils of the line. L are very numerous and the wire very fine. A second local
battery circuit M is arranged for the purpose of operating the receiving
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page_text: apparatus E. This local battery circuit, however, is only made when the arma-
ture is attracted by the electromagnets 661, i.e., when the nose f of the said
armature strikes the contact s. The latter is adjustable, as also is the counter
block v.
As mentioned, the armature h only leaves its position of rest if one or other
magnet pair exerts a force.
If, however, the battery B is constantly in action, and there is no line current,
the contact naturally bears against the stop and can only be drawn in the
contrary direction by the greater force exerted by the magnet pair 6. Such
force is only exerted
(1.) When the line current runs in an opposite direction to the local current.
(2.) When its strength is greater than half the strength of the local current.
For if the line current is in the same direction as the local current, the magnetic
influence exerted by the coils of the magnet a a¹ is obviously greater, since here
the two currents (the line and the local current) supplement each other.
If the direction of the line current is a contrary one, however, the resultant
effect of the magnet pair a a' is equal to the difference between the effect of the
local current and that of the line current. If, then, this difference is smaller
than the effect of the line current alone, the armature will turn.
Supposing now that the magnetic effect caused by the current from the local
battery B is a very small one (and any( even an exceedingly small force suffices
to attract the lever h; which turns with extreme readiness), the line current will
still, with the greatest certainty, exert its force, no matter how considerable the
decrease in the line inay be; for as already stated, the smallest force-such us
that of the local current is-is sufficient to cause the magnet pair bb to pre-
dominate that over of the pair a a¹.
As is clear, the effect of the line current with this arrangement is two-fold, viz.
firstly, the resistance is overcome; secondly, the whole of the magnetic force
resulting from the current is exerted.
It need scarcely be remarked that the resistance of the coils is very small com-
pared with the great resistance of the line.
From what has been said it is clear that the relay possesses the first of the
features mentioned at the cominencement of this specification, i.e. sensibility.
The second feature follows from the first.
The reason why the relays ordinarily in use do not always respond to the fre-
quency of the current impulses, is that the current has to overcome a resist-
ance viz., the contact spring, which cannot be a strong one on account, firstly, of
the diminution in the line, and secondly on account of the current strength only
being very slightly expressed when the impulses of current are very short. If,
however, the spring is a very weak one, it does not promptly enough react when
the impulse is of extremely short duration.
With the above described relay, on the contrary, the spring is replaced by the
local current, which exercises a constant effect. The latter, as already explained,
does not have to be overcome, but remains quite out of action, so that the line
current operates with its full strength, without experiencing resistance.
A second reason why the ordinary relays do not respond to short impulses is
the so callled residual magnetism. With the present arrangements, however,
there is no residual magnetism, or it exercises no effect.
The uniformity of the stroke of the armature depends upon the magnetic effect
which expresses itself, as also the energy of attraction, always remaining the same.
This feature also is possessed by the improved relay, when the line current exer-
cises a like or somewhat greater effect than the local current.
If, for instance, the magnetic effect of the local current is 5 and that of the
line current 12, the resulting effect of aal is 7; the effect of 361, on the other
hand is 12; consequently 5 more than of a a'.
If, however, the magnetic effect of the line current becomes weaker or stronger,
for instance 36, the resulting effect of the magnetic pair a u̟'
= 31, and on the

page_text: contrary of bb¹ = 36; consequently the latter is again 5 times greater than the
former.
From this the lemma follows:. The attractive effect both at the electro-mag-
net a a and b is always equal (that is, that resulting from the local current B),
notwithstanding the variations and changes which may take place in the intensity
of the line current.
That the polarisation of the present relay (the fourth of the requirements
referred to, and one not fulfilled, as is well known, by steel magnet relays) is
very reliable and constant, need not here be pointed out, being nothing but a
result of tho above.
Most remarkable is the fifth requirement referred to, i.c., the limitation of the
exercising of the magnetic effect. There are many strong current relays in use,
but polarised relays which either only operate with a weak current, or which only
operate in response to currents within certain definite intensities, do not, so far
as the present applicant is aware, up till now exist.
This requirement is fulfilled by the present invention, inasmuch as there can
be fewer coils wound round the magnet pair 66 than round the pair aal.
In this case (where the effect resulting from the line current is smaller than
at a a) there is a limit to the increase of the line current intensity, the magnetic
effect of the pair a a¹ being also predominant in consequence of the subtraction.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
wo claim is:-
-
A polarised relay consisting of two magnet pairs (aal bb1), the cores of
which cross each other, having a common armature (h) oscillating on a fulcrum
between suitable contact pieces, said magnet pairs being contained in the line
circuit and one pair also in a local battery circuit in the manner substantially as
described.