IMPROVEMENTS IN THE MEANS AND APPARATUS FOR INTERLOCKING THE TELEGRAPHIC BLOCK INSTRUMENTS WITH THE POINTS AND SIGNALS OF RAILWAYS.
Year: 1879

page_text: LETTERS PATENT to Charles Hodgson, of Canterbury Road, Kilburn, in the
County of Middlesex, for the Invention of "IMPROVEMENTS IN THE MEANS
AND APPARATUS FOR INTERLOCKING THE TELEGRAPHIC BLOCK INSTRUMENTS
WITH THE POINTS AND SIGNALS OF RAILWAYS.**
Sealed the 27th December 1879, and dated the 15th October 1879.
PROVISIONAL SPECIFICATION left by the said Charles Hodgson at the
Office of the Commissioners of Patents on the 15th October 1879.
CHARLES HODGSON, of Canterbury Road, Kilburn. in the County of Middlesex.
"IMPROVEMENTS IN THE MEANS AND APPARATUS FOR INTERLOCKING THE TELE-
GRAPHIC BLOCK INSTRUMENTS WITH THE POINTS AND SIGNALS OF RAILWAYS."
My Invention relates to means and apparatus for effecting the interlocking of the
telegraphic block instruments employed on railways with the points and signals
thereof in such a manner as to give greater security to the traffic. In the apparatus
which I employ for this purpose there are three principal organs, namely, first, a
locking handle which can he moved by hand into either of two positions so as to
lock and unlock the point and signal levers: secondly, a commutator with its
plunger for making electrical connections and transmitting telegraphie signals to
another station; and, thirdly, a detent which is connected to and worked either by
one of the ordinary semaphore signals, or by a treadle or trigger acted on by a
passing train, the connections for this purpose being either mechanical or electrical.
The locking handle works a rocking shaft or slide bar which, according to any
known arrangement of interlocking gear. locks or releases according to its position
certain of the point and signal levers. It is itself locked in one of its positions by
the commutator and the detent. The commutator is arranged to move into either
of two positions.so as to bring electrical connections for transmittingsignals opposite
to one another, and the contacts can thereupon be made by pushing in a plunger of
the commutator in the usual way. The commutator in its one position locks the
locking handle, in its other position leaves it free, and in this position it is itself
locked by the movement of the locking handle, which can only be effected while
the plunger of the commutator is pushed in. The detent locks the commutator
and the locking handle in one position of each. unless it is released either by the

page_text: raising of the danger signal to which it is connected, or by the passage of a train
over the trigger or treadle to which it is connected. When it is so released, the
commutator can be moved if the position of the locking handle permits it, or the
locking handle may be moved on pushing in the commutator plunger. In order to
explain the operation of this apparatus. I will assume that it is situated at a station
A in electrical connection with a station B at the other end of one section of the
line. I will also assume that the block instrument shews "line blocked," that the
commutator at A is in position for sending to B the signal of line blocked," and
that the locking handle is in the position locking such of the points and signals as
should be locked to prevent any obstruction of the section by shunting or otherwise.
The semaphore signal having been raised to "danger," or the trigger or treadle having
been acted on by a train. the detent is in position to leave the commutator and the
locking handle free. A train being about to enter the section at B to proceed to A,
the signalman at B informs A thereof, whereupon the signalman at A moves the
commutator, and by then pressing in the plunger, transmits to B the signal of
"line clear." By this movement of the commutator he has locked the locking
handle, renlering it impossible to shift any of the points or signals controlled by it.
By the same movement of the commutator, the detent is set in a position ready to
lock the commutator when the latter is moved back. The train having entered the
section, 13 informs A thereof, whereupon the signalman at A moves back the com-
mutator, and by pressing the plunger, signals to B "line blocked." When the
commutator has been thus moved back, the detent becomes engaged, locking both
the commutator and the locking handle. This condition remains until the train is
about to enter the succeeding section, having to pass the trigger or treadle. By its
passage over this it releases the detent, or when the detent, instead of being con-
nected to a trigger or treadle, is connected to the semaphore signal which protects
the succeeding section, the raising of this semaphore to " danger" releases it. The
apparatus is now in the condition in which it was when the operation began, and
is ready for being worked in like manner for a succeeding train.
In this condition, the apparatus may be employed for shunting in the following
manner: The signalman at A pushing the plunger of the commutator signals to B
"line blocked," and while he keeps the plunger pressed in, he releases the locking
handle. He then moves this handle so as to release the point and signal levers
that were locked by it, and moves these levers so as to pass trains for shunting.
By the movement of the locking handle he has locked the commutator, so that it
cannot be moved for the purpose of indicating line clear until the locking handle
is moved back to its previous position, and this cannot be done till the point and
signal levers are in the first place restored to their previous condition consistent
with safety of traffic on the section.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Charles Hodgson in the Great Seal Patent Office on the 29th
January 18S0.
CHARLES HODGSON, of Canterbury Road, Kilburn, in the County of Middlesex.
"IMPROVEMENTS IN THE MEANS AND APPARATUS FOR INTERLOCKING THE TELE-
GRAPHIC BLOCK INSTRUMENTS WITH THE POINTS AND SIGNALS OF RAILWAYS."
My Invention relates to means and apparatus for effecting the interlocking of the
telegraphic block instruments employed on railways with the points and signals
thereof in such a manner as to give greater security to the traffic. In the apparatus
which I employ for this purpose there are three principal organs, namely, first, a
locking handle which can be moved by hand into either of two positions so as to
lock and unlock the point and signal levers; secondly, a commutator with its
plunger for making electrical connections, and transmitting telegraphic signals to
another station; and, thirdly, a detent which is connected to and worked either by
one of the ordinary semaphore signals, or by a treadle or trigger acted on by a
passing train, the connections for this purpose being either mechanical or electrical.
The locking handle works a rocking-shaft or slide-bar, which, according to any
known arrangement of interlocking gear, locks or releases according to its position
certain of the point and signal levers. It is itself locked in one of its positions by
the commutator and the detent. The commutator is arranged to move into either
of two positions, so as to bring electrical connections for transmitting signals
opposite to one another. and the contacts can thereupn be made by pushing in a
plunger of the commutator in the usual way. The commutator in its one position
locks the locking-handle; in its other position leaves it free, and in this position it
is itself locked by the movement of the locking handle, which can only be effected
The detent locks the commu-
while the plunger of the commutator is pushed in.
tator and the locking handle in one position of each, unless it is released either by
the raising of the danger signal to which it is connected, or by the passage of a
train over the trigger or treadle to which it is connected. When it is so released.
the commutator can be moved if the position of the locking handle permits it, or
the locking handle may be moved on pushing in the commutator plunger. In order
to explain the operation of this apparatus. I will assume that it is situated at a
station A in electrical connection with a station B at the other end of one section
of the line. I will also assume that the block instrument shews "line blocked,"
that the commutator at A is in position for sendingto B the signal of" line blocked."
and that the locking handle is in the position locking such of the points and signals
as should be locked to prevent any obstruction of the section by shunting or other-
wise. The semaphore signal having been raised to "danger," or the trigger or
treadle having been acted on by a train, the detent is in position to leave the com-
mutator and the locking handle free. A train being about to enter the section at
B to proceed to A. the signalman at B informs A thereof, whereupon the signalman
at A moves the commutator. and by then pressing in the plunger, transmits to B
the signal of line clear." By this movement of the commutator he has locked the
locking handle, rendering it impossible to shift any of the points or signals con-
trolled by it. By the same movement of the commutator the detent is set in a
position ready to lock the commutator when the latter is moved back. The train
having entered the section, B informs A thereof. whereupon the signalman at A
moves back the commutator, and by pressing the plunger signals toB"line blocked."
When the commutator has been thus moved back the detent becomes engaged.
locking both the commutator and the locking-handle. This condition remains until
the train is about to enter the succeeding section, having to pass the trigger or
treadle. By its passage over this it releases the detent, or when the detent, instead

page_text: ii
"
of being connected to a trigger or treadle, is connected to the semaphore signal
which protects the succeeding section, the raising of this semaphore to danger
releases it. The apparatus is now in the condition in which it was when the
operation began, and is ready for being worked in like manner for a succeeding
train. In this condition the apparatus may be employed for shunting in the
following manner-The signalman at A pushing the plunger of the commutator
signals to Bline blocked," and while he keeps the plunger pressed in. he releases
the locking handle. He then moves this handle so as to release the point and
signal levers that were locked by it, and moves these levers so as to pass trains for
shunting. By the movement of the locking handle he has locked the commutator
so that it cannot be moved for the purpose of indicating "line clear" until the
locking handle is moved back to its previous position, and this cannot be done till
the point and signal levers are in the first place restored to their previous condition
consistent with safety of traffic on the section.
The Figures on Sheet I. of the accompanying Drawings shew one construction of
apparatus according to my Invention. Fig. 1 is a front view of the apparatus
applied to an ordinary block signalling instrument, the outline of the ensing of
which is indicated by the dotted lines; Fig. 2 is a vertical section on the line X, X,
of Fig. 1: Fig. 3 is a plan on Y, Y, and Fig. 4 is a plan of the commutator plunger
and its slide on the line %, 4. A is the handle and spindle which acts in the
usual way for locking and unlocking the point and signal levers according as it is
turned parily round in the one direction or the other. On its spindle is fixed a
segment A, having its upper edge straight, and behind it a segmental hoss A°
notched at A³, its upper angle. There is also fixed on the locking spindle A an arm
A. Bis the spring plunger of the commutator by which electrical signals are
transmitted in the usual way. This plunger is fitted in a slide 13 which can be
moved horizontally to the dotted position B. Through the front of the casing
there is a rectangular aperture which, when the plunger slide B¹ is in the position
shewn in Fig. 1, is closed by a screen 13 attached to the plunger slide. On the
screen 13 may be marked "line blocked." On the end of the plunger B is fixed a
tappet B, which, when the plunger is pushed in to give a signal, moves one arm of
a bell crank lever C, the other arm C of which is thus released from the notch A³
of the segmental boss A. I) is a detent carrying an armature facing the poles of an
electromagnet M. This detent rests upon an arm E projecting from a rocking
shaft E which carries a plate E. having at its upper angle a stud E. Upon the
plate E may be marked "line closed." F. F₁, is a lever, the one arm F of which
bears against a stop projecting from the casing, and the other arm F¹ butts against
the angle of the commutator slide 13. On the axis of the lever F, F, is another
arm F, which butts against the arm A of the locking spindle A. In the position
of the parts as shewn in Fig. 1, the locking handle A cannot be turned in the
direction of the arrow, because the arm A is stopped by the lever arm F. Nor
can the plunger slide 131 be moved to the left, because it is stopped by the lever
arm F. In this condition the signalman, by pushing in the plunger B, can transmit
the signal line blocked." When a train has passed a certain point of the line,
either by the action of the train on a trigger or treadle, or by the action of the
signalman in putting his signal to "danger," an electric impulse is transmitted
which, exciting the electromagnet M, causes it to attract its armature, raising the
detent D. The arm E being thus released, the plate E falls, its stud F3 strikes the
lever arm F. thereby raising the arms F and F, and so releasing the slide B' and
the arm A of the locking spindle A. The signalman can now operate in either of
two ways. First, he can move the slide 131 to the position B, and pushing in the
plunger B. can signal "line clear." By thus moving the slide over the straight

page_text: edge of the segment A', he locks the locking handle A,and so prevents any alteration
of the point or signal levers. By the movement of the slide B' he also raises the
plate E, so that the arm E becomes again engaged with the detent D. The operator
can now move the slide B¹ back to the right, where it becomes locked by the
dropping of the arm F. Or, secondly, the signalman, instead of moving the slide
B', can turn the locking handle A in the direction of the arrow, so as to enable him
to alter the point and signal levers. But before doing so, he has to push in the
plunger B so as to signal line blocked," and to hold it pushed in, so as by the
action of its tappet 13 on the lever C, to maintain the arm C clear of the notch
A³ in the segmental boss A². When he turns the handle A, part of the circular
edge of A enters a hollow in the slide B', and prevents the slide from being moved
to the left, until the handle A is turned back to the position shewn in Fig. 1. in
which position it becomes again locked by the arm C¹.
The Figures on Sheet II. shew a modified construction of the apparatus, Fig. 5
being a front view, and Fig. 6 a side view thereof. In these Figures, the reference
letters indicate parts corresponding with those marked by similar letters in the
Figures of Sheet I. The principal modification consists in mounting the commutator
plunger B on an arm which can turn on the axis E¹ of the plate E, so that it moves
in a circular are from 3 to 12, instead of sliding in straight guides. The locking of
B in the position shewn in Fig. 5 is effected by the catch Fi being engaged with a
segment. The locking of the handle A is effected by the arm F engaging in a
recess A' in the segment A. and also by the arm C₁ engaging in a notch A³. The
plunger B and the handle A interlock each other by their respective segments A¹
and 1, either of these segments, when it is turned partly round, entering a hollow
of the other segment, and so preventing it from turning. When, by the release of
the detent D. the plate E falls, its stud Estriking the projection F on 13. releases
from B, and F from A When B is moved over to B2, the stud 135 on the
segment B raises the plate E, so that the arm E becomes engaged with the detent
D; also when the commutator is moved back to B. the counterweight F³ causes Fl
and F to re-engage with B and A' respectively.
!
Although I have shewn in the Drawings the detent D as being worked by an
electromagnet M, it is obvious that it might he moved mechanically by wires or
rods connected to a trigger or treadle or to a signal. The slide or arm B₁ carrying
the signalling plunger and the segment A¹ on the spindle of the locking handle A
will obviously interlock with each other independently of the detent D, plate E³,
and lever F. which portions of the apparatus may therefore in some cases he dis-
pensed with. In such a case the signalman can only move the locking handle
when the plunger is in position to signal "line blocked," and by then moving the
handle, he locks the plunger in that position. If, on the other hand, he should
move the plunger so as to signal "line clear," he thereby locks the locking handle,
and consequently cannot alter the points or signals.
Having thus described the nature of my said Invention, and in what manner the
same is to be performed, I claim,-
First. The combination of the handle used for locking and unlocking point and
signal levers with the signalling plunger mounted on a slide or arm. so as to he
moveable into two positions for transmitting different signals, and with a detent
acted on by the passage of a train, or by the movement of a signal, so as to effect
mutual interlocking, substantially as and for the purposes herein set forth.
Second. The combination of the handle used for locking and unlocking point and
signal levers with the signalling plunger mounted on a slide or arm, so as to be
moveable into two positions for transmitting different signals, so that the said
handle and the plunger slide or arm mutually interlock, substantially as herein
described.
Third. The construction of apparatus for interlocking telegraphic block instru-
ments with points and signals as herein described with reference to Figs. 1, 2. 3,
and 4, on Sheet I. of the accompanying Drawings.

page_text: Fourth. The modified construction herein described with reference to Figs. 5 and
6 on Sheet 11. of the accompanying Drawings.
In witness whereof, 1, the said Charles Hodgson, have hereunto set my hand
and seal, this Twenty fourth day of January, in the year of our Lord One
thousand eight hundred and eighty.
דוידז"
IA
CHARLES HODGSON. (S.)