Improvements in the Generation of Rhythmic Electric Currents.
Year: 1888

page_text: Date of Application, 10th Nov., 1888
Complete Specification Left, 30th July, 1889-Accepted, 31st Aug., 1889
PROVISIONAL, SPECIFICATION.
Improvements in the Generation of Rhythmic Electric Currents.
I, CHARLES LANGDON-DAVIES of Mowbray House, Victoria Embankment London
W.C. Electrician, do hereby declare the nature of this invention to be as follows:-
When it is desired to generate secondary electric currents at a fixed rate by means
of regular interruptions in a primary circuit, or when it is desired to interrupt any
electrical circuit or current at a fixed rate, it is customary to employ as part of the
circuit to be interrupted a pendulum, tuning fork or other vibrator whose natural rate
of action or vibration is the same as the rate of interruption desired. This organ
called a break, is placed in front of the core of an electro-magnet, the coil of which
also forms part of the circuit, and the break presses upon the contact point or screw
in the circuit in such a position as that, when the circuit is closed through a battery,
the break is attracted to the core; the circuit being thereby broken, the break returns
by its own natural motion to the contact and remakes the circuit to be broken again
as before.
This action does not produce, either primary or secondary currents at the same rate
as the rate of the break and, therefore, the results expected in many instruments, such
as harmonic telegraphs and others, from the supposed regularity of the currents have
not been obtained.
I find that the following is the cause of this failure:-When the circuit is at rest
the break is pressing upon the contact screw; on closing the circuit through the
battery the following actions take place:
1. The circuit is instantly broken by the break.
2. The circuit remains broken while the break is travelling towards the core and
back again as far as the contact screw, at about its natural rate, say for about half a
vibration.
3. The break is arrested at about the middle point of vibration by the contact screw
which prevents it from completing the vibration already commenced and, by
remagnetising the core, obliges it to commence a new vibration, this instantly breaks
the circuit again.
The results in a secondary circuit are as follows:-Two induced currents, one at
the junction and one at the separation of the break and contact-are generated close
together; there is then an interval while the break travels to and fro for half a vibra-
tion, during which interval there is no current, and then two currents are generated
close together as before.
The result in a primary circuit is, not a current and a break of equal duration in
time, but an exceedingly short current and a long break.
In proof of these facts a telephone in the circuit, instead of roporting a note having
some relation to the note of the break, will report a confused, harsh and discordant
croak.
I overcome this difficulty in the following manner:
The vibrating organ whose note is intended to regulate the currents 1 employ solely
as a governor, and not as a break. It is preferably not connected with the circuit.
I call it the governor.
My break is a spring whose natural speed of vibration is much faster and much
weaker than that of the governor.
This break presses upon a contact screw and is placed in the circuit in the ordinary
It is extended beyond the contact screw so that it may touch that side of the
governor which is nearest to the core of the electro magnet.
way.
The action of my governor is as follows:- When the circuit is closed the governor
being drawn towards the core carries away my break from its contact screw and keeps

page_text: it away with the governor for one half of a vibration of the governor. The break is
so much weaker than the governor as not to interfere with the action of the governor.
The break being faster than the governor returns with it to the middle point of vibra-
tion when the circuit is again completed by the break and screw; but the governing
vibrator is free to leave the break and continue its vibration, which it does, and while
it is doing so contact is maintained in the circuit for that half of its vibration until it
reaches the middle point of vibration again. Thus, during the first half of each
vibration of the governor the break interrupts the circuit, and for the second half of the
vibration the break maintains the circuit.
The change being always made at the middle point, secondary currents, generated
by this action in a primary, are equi-distant from each other in time, while the duration
of a primary or direct current is always half a vibration and the duration of the
interruption is the same.
When a telephone is put into a circuit governed by this instrument it gives forth
the musical note of the governor.
It is necessary in employing this governor to duly proportion the parts. The
magnetism of the core must not be permitted to overcome the tendency of the governor
to vibrate at its natural rate, and the natural action of the break must be much faster
and much weaker than the natural action of the governor.
The same governor can be employed to regulate more than one break and thereby
alternate the currents and make various commutations in one or more circuits.
Dated this 9th day of November 1888.
C. LANGDON-DAVIES.
COMPLETE SPECIFICATION.
Improvements in the Generation of Rhythmic Electric Currents.
I, CHARLES LANGDON-DAVIES, of Mowbray House, Victoria Embankment, London,
W.C., Electrician, 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 :-
When it is desired to generate secondary electric currents at a fixed rate by means
of regular interruptions in a primary circuit, or when it is desired to interrupt any
electric current at a fixed rate, it is customary to employ as part of the circuit to be
interrupted, a pendulum, tuning fork, reed or other vibrator whose natural rate of
action or vibration is the same as the rate of interruption desired. This organ is
usually called a break.
Fig. 1 is a diagram of such a circuit comprising a key K a coil B B a battery P
a contact screw S and a break A. The coil BB is wound round an iron core C¹
(and it may be the primary of an induction coil). The break A is placed in
front of the core C₁ and, when the circuit is open, the break touches the contact
screw S.
On closing the circuit, say by means of K, the core C attracts the
break A away from the screw S thereby immediately opening the circuit again
at S¹. The elasticity of the break causes it to return at once to S closing the
circuit which is instantly opened again as before; this continues as long as the
key K is pressed.
The Diagrams in fig. 3 explain the action of the break under these conditions.
Fig. 3 shews the break at rest and the dotted lines indicate the amplitude of
vibration of which it would be capable if it were free. Fig. 3b shows the position
of the break when attracted towards the core on the closing of the circuit. Fig. 3°
shows its position when it has been brought back by its own elasticity to the
screw S.
This screw being fixed, the break cannot complete its vibration but
having made contact it is at once drawn away again by the core. When, as to
Fig. 3, the elasticity of the break is such as to permit it to bend, it will remain
somewhat longer upon the screw S.
It is thus obvious that the length of the currents permitted to flow in this

page_text: circuit depends upon the duration of the contact at S. not upon the natural rate
of the break; and, further that the length of such a current bears no necessary
relation to the length of the interval by which it is separated from the succeeding
current. Even when the period of interruption bears a relation to the period of
the vibration, which is not always the case, the rate of interruption bears no
relation to the natural rate of the vibration, because the vibrator, before com-
pleting one vibration, is forced to commence another vibration.
Fig. 6. shows at Fig. 6ª the resulting short currents in the primary, separated
by long intervals; and at Fig. 6b the resulting impulses in the secondary, namely
two impulses exceedingly close together separated by a long interval.
Instead therefore of generating secondary impulses separated by regular intervals,
these impulses are separated by intervals of varying lengths as between 1 and 2
and between 2 and 3.
A telephone inserted in a secondary circuit subject to these impulses, instead of
reporting the clear note due to the vibration of the break, produces a harsh
and discordant croak.
This irregularity has hitherto been a serious disadvantage to harmonic telegraph
and other instruments, whose perfect action depends upon the rhythmic generation
of the currents.
It has been sought to overcome the difficulty by placing a light spring upon
the break as is shewn diagrammatically in Fig. 4. Fig. 4 shews the position of
rest Fig. 4b the second position when the break is drawn towards the core Fig. 4°
the third position when the break is returning by its own elastic force.
If the period and amplitude of each vibration of the spring could be made to
correspond exactly with those of the break, so that the spring would naturally
move through the same space as the break in the same time, it might be possible
to obtain rhythmic action by these means, but, such exactitude of construction
being practically impossible, rhythmic action is not so obtained.
When the spring is too slow, it leaves the screw S too soon (Fig. 4) the current is
thus too short and the interval is too long.
When the spring is too quick, it remains too long upon the screw S (Fig. 4º) and
then the current is too long and the interval is too short.
My Invention relates to means of overcoming these difficulties in the following
manner.
I arrange the vibrating organ A so that it shall be as free as possible to vibrate at
its natural rate.
I prefer to employ it thus solely as a Governor without using it as a break.
I provide a separate organ to perform the office of break, but the action of this
break is governed by that of the vibrator A which I therefore call the rate governor.
I arrange the break so that it remains upon its contact stop for one half of the
period required for a complete vibration of the Governor and is kept away from the
contact stop for the other half period.
Fig. 2 shews a circuit similar to that indicated in Fig. 1 but with the alterations
therein required to carry out my invention. A is the vibratory organ as before, but I
prefer that it should not form part of the circuit.
The work done by the break A in Fig. 1, that is to say, the making and breaking of
contact is done by the break V in Fig. 2, which is arranged to touch the screw S.
The break V extends beyond the point S and touches that side of the Governor A
which is nearest to the core C¹.
It is necessary that the break V should bear two proportions as regards the
Governor A.
1. The break V must have a period of vibration somewhat less than that of the
Governor A and must tend to move faster.
2. The break V must be mechanically weaker than the rate governor A.
The action of the apparatus is as follows:-
When the circuit is closed by the key K Fig. 2 the Governor A being drawn
towards the core carries away the break V from its contact screw S and keeps it away

page_text: along with the Governor for one half of the period of a vibration of the Governor as
is indicated at Fig. 5b.
The break tending to move faster than the Governor returns with it to the middle
point of vibration S where the circuit is again completed by the break V and screw S;
but the Governor A is free to leave the break there and to continue its vibration as
indicated at Fig. 5° while it is doing so contact is maintained between V and S during
this half of the vibration of the Governor until it reaches the middle point of vibration
again. Thus during the first half of the period of each vibration of the Governor, the
break opens and keeps open the circuit; and during the second half of the period of
each vibration of the Governor the break maintains the circuit closed.
.
The moment when the Governor A receives its magnetic pluck towards the core Cis
the moment when it can best afford to encounter resistance to its vibration, and this is
the only moment when, according to my invention, it receives such resistance. Even
this is compensated, because the energy which is stored in the break V when it is
being moved towards the core, is nearly all given back to the Governor when it is
moving away from the core, so that, although one part of its vibration is retarded,
another part is accelerated, the whole period being thus adjusted to its normal rate.
By making the break V of steel or iron and placing it at a suitable distance from the
core as in Fig. 2 it receives a small magnetic pluck at the same moment as the
Governor A and thus relieves the Governor from its retarding pressure. The magnetic
action of the core upon the Governor must not however be so strong as to overcome
the tendency of the Governor to vibrate at its normal rate.
The closing or opening of the circuit being always at the middle point of a vibration
the duration of a primary or direct current is always that of half a vibration and the
duration of the interval is the same as indicated at Fig. 7*. The secondary impulses
are therefore equidistant in time as indicated at Fig. 7b.
When a telephone is put into a circuit governed by this instrument, it gives forth
the musical note of the Governor.
In order to increase the durability of the parts composing the contact at S it is
sometimes desirable to arrange a rubbing contact. This can be done as shewn in
Fig. 8 by arranging an additional spring G to take the place of the usual platinum
pin in the screw S and connecting the spring by two links to the screw S so that,
when V presses upon it, the spring G yields a little and so rubs the point of contact,
but is prevented by the attachment to S from following V into that part of its vibra-
tion which is required to keep the circuit open.
Another way is to carry the circuit through the Governor A as it was in the
ordinary break shewn in Fig. 1 and then through the spring V instead of through the
screw; in this case it is necessary to provide a stop behind the spring V to prevent it
from following A in the direction of the core, as shown in Fig. 9.
Fig. 10 shews how the opening and closing of the circuit may be effected by means
of a spring rocker subject to the action of the Governor.
R is a rocking piece moving on a pivot P and having its lower side so shaped that,
after passing its middle position, a spring T carries it towards and holds it against the
one or the other of two contact screws S. The Governor A is engaged in a wedge
shaped recess of the rocker so adjusted that the rocker is thrown against one of the
screws at each half vibration where it remains until A returning throws it over to the
other screw; one of the screws may be merely a stop, or both screws may have such
connections that the current through the coil is reversed at each vibration.
Fig. 11 shews a modification by which the action of a light spring such as is shewn
in Fig. 4 may be improved. A headed pin P fixed in the break A passes through the
light spring permitting the spring to move towards A but preventing it from moving
away from A further than the head of the pin permits.
Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed, I declare that what 1
claim is: 11
1. The herein described method of generating rhythmic electric currents by means

page_text: of vibrating parts so arranged in connection with a coiled iron core and a contact for
the current to the coil, that contact is maintained during one half of each vibration
and that contact is interrupted during the other half of each vibration, the periods of
transmission and of cessation of impulses being thus equalised.
2. In combination with a free tongue or rate governor vibrating under the influence
of a coiled iron core, a subsidiary vibrating tongue of less strength and greater speed
so arranged in connection with the Governor and with a contact stop that it is carried by
the Governor away from the contact during half a vibration of the Governor and
that it rests against the contact during half a vibration of the Governor substantially
as described.
DL
001 1
TI
1000
C. LANGDON-DAVIES.