IMPROVEMENTS IN SIGNALS AND IN SIGNALLING, AND IN APPARATUS USED IN SIGNALLING
Year: 1871

page_text: LETTERS PATENT to John Hickman, of Desborough, near Market
Harborough, in the County of Leicester, Clerk, for the Invention
of "IMPROVEMENTS IN SIGNALS AND IN SIGNALLING, AND IN APPARATUS USED
IN SIGNALLING."
Sealed the 10th November 1871, and dated the 30th May 1871.
PROVISIONAL SPECIFICATION left by the said John Hickman at
the Office of the Commissioners of Patents, with his Petition, on
the 30th May 1871.
.
I, JOHN HICKMAN, of Desborough, near Market Harborough, in the
County of Leicester, Clerk, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN SIGNALS AND IN SIGNALLING, AND IN APPARATUS
USED IN SIGNALLING," to be as follows:-
My Invention relates principally to signals used on railways and to
signalling on railways, but my Invention is also applicable to other
purposes, such, for example, as signalling in mines, and for signalling
generally.

page_text: My improvements in signals are as follows:-I construct a transparent
chamber having by preference flat parallel sides. The said chamber
when in use is fixed vertically, its parallel sides being turned in the
direction in which the person whose duty it is to observe it will most
readily see through it. The said flat parallel sides of the chamber are
made of glass or other transparent material, and in order that it may
be the more readily observed the marginal portions of the sides may be
blackened or encased, leaving only central transparent portions. This
chamber communicates at bottom with a reservoir containing a colored
or black liquid, the said reservoir being closed excepting with respect of
the opening by which the chamber communicates with it, and one other
opening. The opening last referred to is in communication with a pipe
or tube communicating with a condensing pump, by working which
pressure may be put on the surface of the liquid in the reservoir and the
said liquid made to rise in the transparent chamber. By the rising of
the liquid to a greater or less height in the chamber the whole or a
greater or less part of the transparent portion of the chamber may
colored or rendered opaque.
be
A code of signals is arranged by which the positions which may be
given to the liquid in the transparent chamber will convey the required
message. Instead of producing the elevation and depression of the
signalling liquid in the transparent chamber by pressure on the liquid in
the reservoir, the same effect may be produced by a greater or less
exhaustion of the air in the upper part of the transparent chamber.
The colored or black liquid I employ may be alcohol containing the
required black or coloring matter in solution, or other liquid which will
not freeze.
To prevent evaporation of the liquid a flexible diaphragm may extend
across the reservoir between the liquid and the pipe, transmitting the
pressure, and the top of the transparent chamber may be closed by a
flexible diaphragm. Although I prefer to communicate the required
pressure or exhaustion by means of a column of compressed or rarified
air, yet the required effect may be produced by a liquid column, or by a
rod, wire, or chain extending from the signal to a point where the
working of the signal is to be effected.
I work the signal by means of levers or other mechanical appliances
operated upon by a passing train or by hand. I call the appliances for
raising and depressing the liquid in the signal an operator.

page_text: My improvements in signalling and in apparatus used in signalling
are as follows:-In carrying this part of my Invention into effect I
prefer to employ signals of the kind constituting the first part of my
Invention, but I do not limit myself thereto, as other signals may be
employed.
I will describe this part of my Invention as carried into effect by
means of signals of the kind herein-before described.
This part of my Invention has for its object to block portions of the
line of railway so that by the driver of a train observing the signals
the blocked portions of the line will not be entered upon by the train
until it is free from any other train. I arrange the signals in pairs, the
second of each pair being at or near the entrance the portion of the
line to be blocked, and the first behind it, the two signals of each pair
being at such a distance apart that a train can be readily brought to rest
between them. The exact distance depends upon the gradient of the
line at the place where they are situated.
The operators which are put into operation by the passing of a train
are of two kinds. One kind, which I will call a positive operator, effects
the signalling, and the other, which I will call a negative operator,
reverses or neutralizes the signal, or reverses the action of the positive
operator. When a train passes along the line it acts on a positive
operator situated a short distance past the first pair of signals. This
positive operator is connected with both the signals of the first pair, and
the action of the train upon it raises the colored or black liquid in the
signals, thus showing that there is a train on the portion of the line to
be blocked in advance of the first pair of signals. If a second train
arrives at the first signal the driver sees that the line is blocked and has
time to stop the train before it reaches the second signal of the first pair.
As the first train passes off the blocked portion of the line it first acts
upon a positive operator connected with the second pair of signals, and
thus puts the second portion of the line of railway in block, and imme-
diately afterwards acts on a negative operater, by which the first pair of
signals are brought to their normal state, and the first portion of the
line is unblocked and the second train may safely advance, the said
second train operating on the signals in the manner described with
respect to the first train. By this method of signalling a train in
passing a pair of signals causes them to show that the line in advance is
blocked, this being done in such a manner that a second train has time
0

page_text: to come to rest before it comes on to any part of the blocked portion
of the line. The blocked portion of the line is not unblocked until the
first train has blocked a second portion of the line. By this overlapping
of the ends of the blocked portions of the line the extreme of safety is
secured.
Although I have only described the operators as being acted upon by
passing trains, yet the said operators may also be operated upon by
hand, and in addition to the operators fixed on the line of the railway
other like operators may be fixed at stations or other convenient or
desirable places for the purpose of acting on the signals and blocking
or unblocking portions of the line.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Hickman in the Great Seal Patent Office
on the 24th November 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HICKMAN, of Desborough, near Market Harborough, in the County of
Leicester, Clerk, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirtieth day of May, in the year of
our Lord One thousand eight hundred and seventy-one, in the thirty-
fourth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said John Hickman, Her special licence that
I, the said John Hickman, my executors, administrators, and assigns,
or such others as I, the said John Hickman, my executors, adminis-
trators, and assigns, should at any time agree with, and no others,
from time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exercise, and vend,
within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN SIGNALS
AND IN SIGNALLING, AND IN APPARATUS USED IN SIGNALLING," upon the condition
(amongst others) that I, the said John Hickman, my executors or
administrators, by an instrument in writing under my, or their, or one
of their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent

page_text: Office within six calendar months next and immediately after the date
of the said Letters Patent.
NOW KNOW YE, that I, the said John Hickman, do hereby declare
the nature of the said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and
by the following statement thereof, that is to say :—
My Invention relates principally to signals used on railways and to
signalling on railways, but my Invention is also applicable to other
purposes, such, for example, as signalling in mines, and for signalling
generally.
My improvements in signals are as follows:-I construct a transparent
chamber having by preference flat parallel sides. The said chamber
when in use is fixed vertically, its parallel sides being turned in the
direction in which the person whose duty it is to observe it will most
readily see through it. The said flat parallel sides of the chamber are
made of glass or other transparent material, and in order that it may be
the more readily observed the marginal portions of the sides may be
blackened or encased, leaving only central transparent portions. This
chamber communicates at bottom with a reservoir situated below it
containing a coloured or black liquid, the said reservoir being closed
excepting with respect to the opening by which the chamber communi-
cates with it, and one other opening. The opening last referred to is in
the upper part of the reservoir and above the liquid, and is in com-
munication with a pipe or tube communicating with a condensing
pump, by working which pressure may be put on the surface of the
liquid in the reservoir and the said liquid made to rise in the transparent
chamber. By the rising of the liquid to a greater or less height in the
chamber the whole or a greater or less part of the transparent portion
of the chamber may be colored or rendered opaque.
A code of signals is arranged by which the positions which may be
given to the liquid in the transparent chamber will convey the required
message. Instead of producing the elevation and depression of the
signalling liquid in the transparent chamber by pressure on the liquid
in the reservoir, the same effect may be produced by a greater or less.
exhaustion of the air in the upper part of the transparent chamber. The
colored or black liquid I employ may be alcohol containing the required
black or coloring matter in solution, or other suitable liquid which will
not freeze.

page_text: To prevent evaporation of the liquid a flexible diaphragm may
extend across the reservoir between the liquid and the pipe transmitting
the pressure, and the top of the transparent chamber may be closed
by a flexible diaphragm. Although I prefer to communicate the
required pressure or exhaustion by means of a column of compressed
or rarefied air, yet the required effect may be produced by a liquid
column, or by a rod, wire, or chain extending from the signal to a point
where the working of the signal is to be effected.
I work the signal by means of levers or other mechanical appliances
operated upon by a passing train or hand. I call the appliances for
raising and depressing the liquid in the signal an operator.
My improvements in signalling and in apparatus used in signalling
are as follows:-In carrying this part of my Invention into effect I
prefer to employ signals of the kind constituting the first part of my
Invention, but I do not limit myself thereto, as other signals may be
employed.
I will describe this part of my Invention as carried into effect by
means of signals of the kind herein-before described.
This part of my Invention has for its object to block portions of the
line of railway, so that by the driver of a train observing the signals the
blocked portions of the line will not be entered upon by the train until it
is free from any other train. I arrange the signals in pairs, the second
of each pair being at or near the entrance of the portion of the line to
be blocked, and the first behind it, the two signals of each pair being
at such a distance apart that a train can be readily brought to rest 2
between them. The exact distance depends upon the gradient of the
line at the place where they are situated.
The operators which are put into operation by the passing of a train
are of two kinds. One kind, which I will call a positive operator, effects
the signalling, and the other, which I call a negative operator, reverses 3
or neutralizes the signal or reverses the action of the positive operator.
When a train passes along the line it acts on a positive operator situated
a short distance past the first pair of signals, or I make one operator
answer both purposes. This positive operator is connected with both the
signals of the first pair, and the action of the train upon it raises the 3
colored or black liquid in the signals, thus showing that there is a train
on the portion of the line to be blocked in advance of the first pair of

page_text: signals. If a second train arrives at the first signal the driver sees that
the line is blocked, and has time to stop the train before it reaches the
second signal of the first pair. As or soon after the first train passes off
the blocked portion of the line it first acts upon a positive operator con-
nected with the second pair of signals, and thus puts the second portion
of the line of railway in block, and immediately afterwards acts on a
negative operator, by which the first pair of signals are brought to their
normal state and the first portion of the line is unblocked, and the
second train may safely advance, the said second train operating on the
signals in the manner described with respect to the first train. By this
method of signalling a train in passing a pair of signals causes them to
show that the line in advance is blocked, this being done in such a
manner that a second train has time to come to rest before it comes
on to any part of the blocked portion of the line. The blocked portion
of the line is not unblocked until the first train has blocked a second
portion of the line. By this overlapping of the ends of the blocked
portions of the line the extreme of safety is secured.
Although I have only described the operators as being acted upon
by passing trains, yet the said operators may also be operated upon
by hand, and in addition to the operators fixed on the line of railway
other like operators may be fixed at stations or other convenient or
desirable places for the purpose of acting on the signals and blocking
or unblocking portions of the line.
Having explained the nature of my Invention, I will proceed to
describe with reference to the accompanying Drawings the manner
in which the same is to be performed.
My signal consists of a signal chamber with appendages constructed
in the following manner, and represented in Figure 1. I take two
circular disks of glass a, a, by preference made by being cut from strong
plate glass. Between these disks I place a ring or washer of vulcanized
india-rubber 6 of a thickness about equal to th of an inch. The
external diameter of this ring is equal to the external diameter of the
glass disks. Portions of the ring 6 are cut away at the extremities of
the same diameter, so that when the nearly half rings are placed
between the glass disks a, a, concentric therewith there is formed a
flat circular chamber or vessel having two openings in it, the one
opposite the other. In order to fix the glass disks a, a, and the divided
india-rubber half rings 6 between them I surround the said disks with a

page_text: trough-shaped india-rubber ring c through holes in which the tubes d, e
pass in such manner that the india-rubber shall overlap and cover the
edges of the disks and rings. I make the trough-shaped india-rubber
ring c much smaller in diameter than the glass disks a, so that it has
to be stretched with great force when being put on, and being on it fits
the circumference of the disks air-tight. The structure thus built up
when the tubes d, e, are closed forms an air-tight bottle with two
necks which are the tubes d, e, and this structure I call my signal
chamber.
I sometimes surround the signal chamber with an opaque frame of
metal or wood. In such cases when the frame is of wood I cut out
a circular aperture in the centre thereof, and I cut a recess around the
said aperture concentric with it of a depth nearly equal to the thickness
of my signal chamber and of the same diameter as the signal chamber,
in which recess I fix the signal chamber by means of a ring which may
be of wood or metal having an internal diameter equal to that of the
said aperture, which ring being placed concentric with the signal
chamber I screw it firmly to the frame of wood. The said aperture
is made of such diameter that the wood of the frame and the ring may
slightly overlap the edge of the trough-shaped india-rubber ring c. To
enable the signal chamber to lie snug in its recess I cut grooves in the
wood of the frame and the ring, or in one of them, to receive the
tubes d, e. When the frame is of metal I fix the signal chamber
therein in the same manner, except that the recess for it and the grooves
for the tubes d, e, though similar in character are not made by cutting
away the metal, but by shaping it in any of the ways in which such
recesses and grooves are commonly made by workers of metal. Or I
make the frame of a plain sheet of metal, and make a ring of metal or
wood with the recess for the edges of the signal chamber therein, and
also grooves for the tubes d, e.
In order the more effectually to make the signal chamber air-tight
all the surfaces of the india-rubber divided ring and the trough-shaped
ring which come in contact with the glass disks may be coated previous
to the putting together of the parts with a thin coating of india-rubber
cement, that is, a solution of india-rubber in bisulphide of carbon,
benzine, or any of its other well-known solvents, or any other varnish
or cement not dissolved or attacked by alcohol may be used for making
the several junctions air-tight.

page_text: Figure 2 represents a signal chamber C in a frame F, fixed thereto
by a ring R with its appendages a, b, and which I proceed to describe.
The said signal chamber may be fixed on a post about 10 feet above the
level of the rails. a, b, are metal hollow spheres of which 6 should not
be greater than a made up of flanged hemispheres. Between the flanges
in each sphere is bolted the flange of a thin india-rubber hemisphere of
such dimensions as to fit the interior of one of the hemispheres of its
sphere. The tube c¹ leads to the lower hemisphere of 6 and the tube c
to the lower hemisphere of a, and from the top of a there proceeds a
tube which forms part of a tube, herein-after described, as the main
tube. At the top of 6 there are drilled sundry small holes. The tube c
does not communicate with the interior of the sphere a directly, but is
screwed into the metal of what externally has the appearance of a boss
at the bottom of a, but which is a small antechamber, communicating
with the spherical interior of a by numerous small holes drilled through
the portion of the wall of the sphere between it and the antechamber
(see Figure 3), in which the tube c is seen screwed into the ante-
chamber d. In like manner the main tube t communicates with the
upper hemisphere of a through a similar antechamber and perfora-
tions c¹ also communicates with the lower hemisphere of 6 in a similar
manner. The size of the part 6 is adjusted so that its interior volume
or capacity is about equal to but not greater than the capacity of the
signal chamber, and it is so fixed that the bottom of its interior is about
on a level with or a little higher than the top of the visible part of this
glasses of the signal chamber C.
I fix the structure represented in Figure 2 vertically in such place
as may be desired for signals to be exhibited in such manner as may
be most convenient. Before I bolt or screw the india-rubber diaphragm
between the flanges of 6 I fill the signal chamber C and the tube
leading from 6 to it with colored alcohol, which I do while the main
tube t is open to the atmosphere if it be short, but if it be long that
is not necessary.
It is obvious that the introduction of the liquid into the signal
chamber C will drive the air from into a, by which the diaphragm
in a will be driven upwards. The flanges of 6 are then bolted together,
its diaphragm being in contact with the lower hemisphere throughout.
It is obvious that if air be driven with sufficient force through t
into a, and that in a be thereby driven into C, the liquid in C will be

page_text: driven back into b, and that the capacity of 6 being equal to that of C
whatever the tension of the air in C may be no air can pass from it
into b.
The alcohol I employ may be tinged red by cochineal or blue by
ammonia, sulphate of copper, or by the aniline dyes, or by other
coloring matter soluble in alcohol. I do not use absolute alcohol but
proof spirit or a mixture of alcohol and water, which will not freeze at
any temperature to which the signal is likely to be exposed. The
main tube is a continuation of the tubet from a to an apparatus
herein-after described which I call an operator. The said main tube
is made of white metal tube known in commerce as compo tube; a tube
of one quarter of an inch internal diameter answers the purpose. The
main tube is laid in the ground or is otherwise protected, and is in all
respects treated as if it were for the conveyance of illuminating gas, for
which purpose such tubing is generally used.
In lieu of the signal before described I sometimes so adjust the size
of the signal chamber and the capacity of the receptacle for receiving
the alcohol when it is expelled from the signal chamber that the alcohol
may never fill more than a portion of the latter, in which case I
place the sphere or receptacle for the alcohol at such a level that the
alcohol cannot rise in the signal chamber above the level intended.
Thus if I intend to fill only the lower half of the signal chamber with
alcohol I place the receptacle c, Figure 4, which has a capacity equal
to half the capacity of the signal chamber C, with its lowest part in the
same horizontal plane as the middle horizontal section of the signal
chamber. The receptacle in the said Figure 4 is a hemisphere flanged
with a plate or disc fixed thereon, a suitable diaphragm being held
between the flanges of the hemisphere and the plate, and the plate
having small holes drilled through it. This is an example of the way
which I vary the form of the receptacle for alcohol while the principle is
retained. I prefer receptacles for alcohol constructed on this principle
to such as may be made of india-rubber bags or bags of other flexible
material.
in
Figure 5 represents an operator or such parts of it as require a
diagram to explain them; S is a hollow sphere of cast-iron built up
with a diaphragm in the same way as the hollow sphere a in Figure 2.
The main tube enters S at a. From the lower antechamber a pipe b, c,
leads to a chamber d, upon the top of which and communicating with

page_text: it a force pump P
stands and also a pipe e, f.
A tap or sluice valve h is
From e, f, a pipe e, g,
placed in e, f. At the
There is
leads back to b, c.
top of e, f, there is a diaphragmed hollow sphere which I call the
reservoir, similar to S except that it has no antechamber. The pipe e, f,
enters it direct, and a simple aperture is left at the top of it. Where
b, c, enters d there is a valve which opens upwards into d.
also a valve opening upwards where the pipe e, f, enters d. I do not
describe the construction of the pump, nor the mode of connecting the
pump, the pipes, the tap, or sluice valve, or the two valves connected
with the chamber d, for they may be any such as every plumber is
familiar with. I fix this operator on a stand or floor or to an upright
post, according as convenience requires at the place at which the
signalman has to work the signal. It is so fixed that the pipe e, f,
shall be vertical.
The dimensions of the various parts of my operators depend upon the
length of the main tube, that is, on the distance of the signal which the
operator is intended to work. For a main tube of 2,000 yards I prefer
to make S with an interior diameter of 12 inches, and I make its shell
of an inch thick, I make the pipes 1½ inches internal diameter, and
the pump of an internal diameter of 3 inches with a 7-inch stroke.
To use the operator I first open the tap or valve at h and fill the
sphere S, all the pipes, and the chamber d with glycerine or other liquid
which will not freeze, in doing which I keep the pump piston down; I
pour the liquid into the lower hemisphere of the reservoir S' after which
I close this sphere, taking care to leave as little air as possible below its
diaphragm, which lies in contact with the lower part of S³. By pouring
in the liquid I raise the diaphragm of S and drive the air above the
diaphragm into the main tube a. If at the beginning of this operation
the main tube is connected as before described with the sphere a above
the signal chamber C, Figure 2, and the signal chamber be charged
with colored alcohol, as the tension of the air in the main tube is in-
creased the alcohol will pass from the signal chamber into the sphere b
connected therewith, where it will remain. When I wish to cause it
to return into the signal chamber I close the tap or sluice valve at h and
by working the pump P I force the glycerine from the sphere 8 into
the reservoir S³, which operation tends to create a vacuum in S and
causes the air to rush into it from the main tube, and that which remains
in the main tube has its tension reduced and the alcohol flows back

page_text: into the signal chamber. The rapidity with which the signal chamber
is cleared of alcohol depends chiefly on the height of S³, and the rapidity
of the return of the alcohol on the length of the main tube t and the
capacity of S. The air which transmits the force of the operator to the
signal is wholly confined, so that if it is required to keep the signal
chamber free from alcohol the time required to reduce the tension to its
original state when the signal chamber was charged is lengthened. To
avoid this and to enable me to work the signal both ways with greater
rapidity I introduce a valve which I call the equilibrium valve, which
I proceed to describe.
Figure 6 represents a section through centre of the valve, which is
made wholly of cast iron. a, b, a, is a circular table cast with a conical
projection 6 in its centre; c, c, is a dome-shaped casting with a truncated
cone d, d, e, e, cast with it. c, c, has a flange which rests on a, b, a.
The lower part of d, d, e, e, is turned accurately, and at e, e, it is bevilled
to a sharp edge. The face of the flange which rest on a, b, a, is turned
truly; a, b, a, is also turned smooth on the part of its face on which
the flange of c, c, rests, as well as on the upper face of its conical pro-
jection b. The two castings are bolted together so as to be concentric,
and with a thin rubber washer between them. The dimensions of the
valve and its several parts are made to depend on the tension of the air
in the main tube (with which it is connected), which is required to keep
the signal chamber clear of alcohol. If for this purpose a tension of
8 ozs. above the atmosphere be wanted I make the largest interior
diameter about 5 inches, as near as may be; the edge e, e, is brought to
within of an inch of the base of a, a, and the diameter of the edge
and of 6 in the same plane are respectively 2 inches and 1½ inches, the
latter being the exterior diameter of 6 in the said plane. The pro-
jection 6 rises 1 inch above this plane to the height where it ceases to
be conical, at which place its exterior diameter is % of an inch, and the
interior diameter of d, d, e, e, in the same plane is 1 inches. The
valve is fixed with its base horizontal near to the signal, and it is
connected with the main tube by a short branch tube which joins the
main tube very near its entrance to the upper sphere and enters c, c,
near to d, d, e, e, the top of which communicates with the atmosphere.
I put mercury into the valve, so that when it stands level its surface
is of an inch above the edge e, e. From the proportions given it
follows that if air be driven from the main tube into the valve equal to

page_text: a tension of 1 inch of mercury the surface of the mercury outside e, e,
will be reduced to the level e, e, and the surface between d, e, e, d,
and 6 will stand 1 inch above e, e, in which position there will be a
state of equilibrium and no air will escape from the valve; but if the
tension of the enclosed air exceeds 1 inch of mercury the air will escape
from the valve. On the other hand, if the tension of the air in the valve
be reduced below that of the atmosphere by 100 of an inch of mercury
air will enter the valve from the external atmosphere and pass into the
main tube. By the use of this valve I am able to inject the air from a
hollow sphere of any size into the main tube in order to expel the alcohol
from the signal chamber, and therefore by using adequate power to
expel it rapidly, and all the air not required to keep the signal chamber
clear escapes through the valve into the atmosphere. On the other hand
I am able by the use of the same large sphere to reduce the tension
in the main tube and fill the signal chamber rapidly, and the air which
is required to restore the tension to that of the atmosphere, or nearly
so, will enter by the valve. Whatever operator I employ to increase
and reduce the tension of air in the main tube will, it is obvious, work
all the signals which are in connection with the main tube, that is to
say, a system of signals; but the operator which I have described is one
which I use to operate upon a multiplicity of systems of signals, to
effect which I have but to place a tap just below the point g as at k in
the pipe b, c, Figure 5, and to lead the pipe which has the tap h in it
into a main proceeding from e in e, f, and that which has a tap at k into
a main proceeding from d. It is obvious that I may thus connect any
number of spheres similar to S with the said mains, and operate upon
the air or glycerine of any one of them without affecting the contents
of the others. In such cases I prefer to enlarge the reservoir S³.
The operator already described is intended chiefly to work signals
which are at a long distance from it, and which are worked by hand.
I generally prefer to work the signals at short distances by means of
simple elastic air-tight chambers, which may be of any convenient
form and structure, but I prefer india-rubber cylinders, such as that
represented in Figure 7, which is a section of a hollow cylinder of india-
rubber embraced at the top by a couple of discs of wood or iron with
rounded edges, which are screwed tightly together with the rubber
between them by a bolt in which there is an eye at the top. The bottom
of the rubber cylinder is similarly held by two other such disks, except

page_text: that the lower disk of this pair is larger than the other, and also larger
than the diameter of the cylinder, the object of which enlargement is
to supply the means of introducing screws, whereby the cylinder may be
held down to the floor of the signal box, or to some other convenient
base where there is no hut. The object of the eyc in the upper bolt is
explained hereafter. The interior of the cylinder communicates with
the main tube by the end of the latter being introduced through the two
disks and rubber which form the bottom of the cylinder.
In order that the signalman may reverse his signal when the operator
is worked by a simple lever by a quick operation I use the arrangement
of parts represented in Figure 8. i is a lever jointed after the manner
of a carpenter's two-foot rule, one arm of which is longer than the other,
and at the end of the longer arm I attach a weight k; and in order to
keep the cylinder vertical I attach a guide rod 7 to the eye m in the top
bolt of the cylinder, which rod I connect by means of eyes and pins
with another rod, which again I connect with the lever exactly after
the manner frequently used in common force pumps. The guide rod
is also placed in guides after this manner. I thus work the top of the
cylinder up and down in all respects, as the plunger of a common force
pump is worked, and with the same appliances, except that in lieu of
the pump handle I have a lever jointed as described, to which the
connecting rod is attached near or at the joint and on the short arm of
the lever. The end of this arm is fixed by a pin to a support. To
compress the cylinder with this apparatus the lever is straightened out,
and to elevate the cylinder the weighted arm of the lever is thrown
back on the shorter arm. With an operator of this kind the equilibrium
valve Figure 6 may or may not be used at pleasure.
When it is expedient I connect the lever which works the operator
just described with the wires or rods or ropes by which points or
switches are worked, that is, I adapt it to the locking system so called.
I adapt the operator first described to the locking system by using a
sluice valve with a large wheel, in which case I prolong the metal of
the screw which works the valve, so that it passes out on the opposite
side of the wheel, and the part thus passing out carries a drum or
bobbin on to or off which a chain is wound by turning the wheel to
open or close the sluice valve, and as the character of the signal which
is on depends on the valve being open or closed I make the signal
and the state of the points accord.

page_text: One of the advantages of my signal and method of working the same
is, that I can work two or more signals which I call a system of signals
almost contemporaneously situated on or in connection with one main
tube. With this view I lay a long main tube from the operator
extending say a mile from the said operator along the line of railway,
with which I connect two signals, one at the end and the other inter-
mediate, say half way, by means of a short branch tube, annexing an
equilibrium valve to the far one only. When therefore the operator
causes the alcohol to flow into or from the signal chamber of the one,
it will also cause it to flow into or from that of the other. I color the
alcohol in the far signal green, that of the near signal red, or with such
colors as may be agreed upon to indicate caution and danger respectively.
By such a system the necessity of the signals being visible at a distance
is removed, for if the caution signal be on it is sufficient for the driver
of an approaching train to see it when he reaches it inasmuch as he
can pull up his train before he reaches the second or danger signal.
In order to render my signals visible at night and in fogs I illuminate
them at such times by placing a light behind them, that is, on the side
opposite to that from which they are viewed.
I do not limit myself to any special mode of illumination. I prefer
to make the signal itself with its frame constitute one side of a lamp,
that is, of a chamber to hold a lamp, and this arrangement has the
advantage of warming the the alcohol, for in such case the sphere b,
Figure 2, is within the chamber and receives heat from the lamp, which
is transmitted to the glass disks of the signal chamber, by which means
they in turn are warmed, so that snow or hoar frost cannot remain
thereon. When the illumination is not required, but the appearance
of the weather indicates the probability of snow or frost I place a small
lamp within the illuminating chamber below and near to the sphere b,
Figure 2, for the purpose of warming the same, for which purpose what
is commonly known as a night light is sufficient.
I use a reflector either removeable with the illuminating lamp or not.
When gas is not to be had conveniently I prefer to use petroleum,
or some of the common and cheap hydrocarbon oils for illumination,
for inasmuch as I do not generally place my signals much above the
level of the driver's eye my signal supports are not liable to be shaken
as those of the common highly raised signals are, so that the chimneys

page_text: necessarily used in burning such oil can be used with safety. This is
advantageous both in respect to economy and intensity of illumination.
Another advantage which my signal supplies is to be found in the
simple and certain means which it renders available for informing the
signalman or others than the drivers whom it is desirable to inform of
the nature of the signal on, for a glass pressure guage attached at any
point by a small branch tube to the main tube must always tell by its
motion or its position when at rest what is going on or done at the
signal.
So far as I have described the method by which I expel the alcohol
from the signal chamber by increasing the tension of the air in the main
tube, but I also sometimes effect the same by the method of exhaustion,
that is, by reducing its tension sufficiently below that of the atmosphere,
to effect which, so far as concerns the signal itself, I have but to place
the sphere b, Figure 2, below the level of the signal chamber, for when
so placed if the tension in the main tube be reduced below that of the
atmosphere the pressure of the atmosphere will drive the liquid into the
signal chamber. This method may be employed with the operators
described without modification. The quantity of air which I inject or
withdraw in working my signals depends upon the rapidity with which
I wish to work them, but the quantity which has to be injected or with-
drawn simply for the purpose of reversing the signal apart from time
depends on the capacity of the system to which the signal belongs and
the vertical range of the alcohol in the signal chamber. By the capacity
of the system I mean the capacity of the main tube and the signal
chambers, and of such branch tubes as may be connected therewith (for
the purpose of attaching pressure gauges or otherwise), provided the
communication between them and the main tube be always open.
Thus if the range of the alcohol in the signal chamber be 12 inches and
the capacity of the system be a cubic foot, the air to be injected or
withdrawn, simply to reverse the signal without regard to time, is in
round figures about 3 of a cubic foot, and for every cubic foot of
capacity in the system 3 of a cubic foot has to be injected or withdrawn.
The operator represented in Figure 5 has a sphere of 12 inches in
diameter, and therefore of a capacity of nearly 900 cubic inches. If the
operator is employed to work a system of a pair of signals each having a
vertical range of 12 inches, one of which is 1,000 yards and the other
2,000 yards from it, and the whole of the air from the sphere, that is,

page_text: 900 cubic inches, be driven into the main tube, since such a system will
have a capacity of but little more than 2 cubic feet, and only about
108 cubic inches of the injected air will be wanted to keep the signal
chambers clear of alcohol, nearly 800 cubic inches will be used for the
purpose of expediting the action on the alcohol, and after serving this
purpose it will escape into the atmosphere through the equilibrium
valve. I prefer to make such operators intended to work remote signals
with a large excess of capacity over that which is required for the
purpose of maintaining equilibrium when the signal is on or off. I do
not, however, limit myself to the use of the kind of operator represented
in Figure 5 for remote signals, nor do I always use all the power of my
operator.
The other operator, Figures 7 and 8, is such as I generally prefer to
use for signals not very remote from it, and may be taken as designated
to work a signal or a pair of signals, the more distant of which is
600 yards from it, in which case the quantity of air which must be
injected into or withdrawn from the system is but about 66 inches.
Whatever is injected in excess goes out at the valve. In such cases
I prefer to make the interior disks of the operator 4 inches in diameter,
and give the other parts such dimensions that the range of the operator
may be 8 inches, whereby in this case also I have some excess of power.
My block system, which I prefer to work automatically, but which
may be worked by hand, is as follows:-A, B, Figure 9, represents a
line of railway on which the trains run in the direction from A to B.
At certain distances, which need not be always the same, I place
signals 8, S, s, S¹, which may be taken as being 1, a mile apart; 8 and S
The distance between the
belong to one system, 8¹, S¹, to another.
signals of each pair depends upon the gradients, and is such that a train
passing a signal 8 may always be able to pull up with certainty before
reaching the signal S. When a train is going from A to B I cause it
by means herein-after described to put on the signals 8, S, as it passes
some point between 8 and S, or at a point just beyond S, and when the
train reaches a point R near to (by preference just past) S¹ I cause it by
similar means to put on the pair of signals 8', and S¹, and by means
hereafter described at the same time or immediately after I cause it to
take off the first pairs and S. I color the signals & and 8³, that is, the
first of each pair, for caution, and S and S₁ for danger or block, so that a
following train coming up to 8 while the signal caution is on knows that
13

page_text: danger or block is on S, and can reduce speed, and if it find block on
S pull up before it passes it, or at least before it reaches the operator by
which this signal is worked. The system to which 8 and S belong has
one extremity at 8 and the other extremity at R; that to which s¹ and
S¹ belong begins at &¹ and ends at R³, and so on.
By placing pairs of signals along the line so that the system of each
pair overlaps or is overlapped by the neighbouring systems I cause every
train to block effectually a sufficient length of line behind itself, and to
take off the block from this portion when it has blocked another length
sufficient to protect itself. At intervening stations or sidings I affix in
suitable places pressure gauges by means of branch tubes, which enter
the main tube or tubes for the purpose already explained. I also connect
by means of branch tubes suitable operators to be worked by hand, so
that if, for example, k be a station or siding at which a train has
shunted, the line when desired behind k may be opened, and if open may
again be blocked when the shunted train is about to resume its place on
the line. The same operator it is obvious supplies the means of blocking
the line behind k if k be the starting place of a train. If a train be
started from k and the signals be put on s' and S¹ to protect it by the
operator at k and the signals so put on are taken off by the train itself
at R', it is obvious that the operator at k is not left in a position to
put on &¹ and S¹ again. In order that the operator may be placed in
position to put on 8¹ and S¹ again under such circumstances I attach a
tap opening to the atmosphere to it at a suitable place, generally its
top, and I insert another tap in the main tube not far from where it
emerges from the operator. By closing the latter tap and opening
the former I can expand the operator and fill it with air from the
atmosphere without, the operation affecting the air in the main tube,
when it is in a position to put on 8¹ and S¹ again.
My operations for working my signals on the automatic system differ
from those which are worked by hand, inasmuch as the same operator
though it may in some cases be used both to put on the signals of one
system and take off those of another is not used to put on and take off
the same signals. I act on these operators either by means of the wheels
of the passing trains or by preference by means of an appendage attached
to the last break van of the train. In the latter case if a train become
in some part uncoupled and the latter parts be left behind the line
behind this part will remain blocked. When the wheels act on the

page_text: operator I prefer to joint a symmetrical double curved lever in a slotted
rail by a pin passed through the centre of the lever and the limbs of the
rail on either side the slot in such manner that when one of the arms of
the lever is flush with the surface of the slot the other may rise above
this surface. This arrangement is illustrated by Figure 10. A lever thus
fixed oscillates by the passage of the wheels of a train just as the beam of
an ordinary beam steam engine is made to oscillate by the movement of
the piston. Rods connect the ends of such lever with a pair of air pumps
placed in a suitable receptacle below the rail, by which air pumps the
signals are worked. The length of the slot and its double lever is such
that a second wheel of a carriage cannot be on it until the preceding
wheel has passed off it, and must be less than what is called the wheel
base of the vehicle which has the smallest wheel base on the line.
To cause the apparatus last described to put on a pair of signals I fix
at the most convenient place at the side of the line and adjacent to the
apparatus a flanged and diaphragmed sphere (see Figure 11) similar to S,
Figure 5, and connect its upper hemisphere with the air pumps by a
forked tube which enters the sphere at p, each pump receiving an
extremity of the fork from the bottom of the lower hemisphere. I lead
a tube as represented with its reservoir similar to that in Figure 5 at
the top. The action of the air pump drives the air through p into
the sphere. The effect of this is that the glycerine which I place below
the diaphragm of the sphere and in the tube leading to the reservoir is
driven in whole or in part into the reservoir, as the passage of the air
into the main tube which is small is generally, and especially when the
passing train is at high speed, much slower than the supply from the
air pumps. After such train has passed more or less air is still in the
sphere, and being subject to the pressure due to the column of glycerine
it is gradually driven into the main tube, and any excess above what is
required to keep the signal on escapes at the equilibrium valve.
.
In constructing the air pumps for the last described apparatus I
carefully avoid such a construction as would allow the pistons to be
driven home to the ends of the cylinders.
In order to use the said apparatus to take off signals I reverse the
positions of the reservoir and sphere, that is, I place the sphere which is
connected with the main tube and air pumps at the top of the pipe and
the reservoir at the bottom.

page_text: filled with
The action
The reservoir communicating with the atmosphere is
glycerine and the sphere with air when the signals are on.
of the pumps tends to create a vacuum in the sphere and causes the
glycerine to rise therein, and the air from the main tube rushes in.
After the train has passed the descent of the glycerine still tends to
create a vacuum till the sphere is again filled with air from the main
tube. By connecting the air pumps with the sphere of Figure 11 and
that last described, and introducing into the pistons of the said pumps
valves so acting that the air pumped into the former must be withdrawn
from the latter, the signals of the one system are put on and the other
taken off by the same action at the same time, that is, the work done
by the train to put the one pair on and the other pair off is done simul-
taneously.
But I prefer to work my signals automatically, not by the wheels of
the train but by an appendage connected with the last break van of the
train, which appendage consists of an arm descending from the side
frame of the van, and carrying at its foot a pulley or roller working on
an axis at right angles to the length of the van, and so hung that it may
project either on the inside or the outside of the rail on its own side of
the van, and be at such a distance from the rail as to bring it in passing
on to the lever described and placed as illustrated in Figure 12. I fix
a curved lever q parallel to and about 6 inches from the rail, by pre-
ference on the outside of the line. I fix the lever to a suitable foundation
by a pin or axis r. The concave sides of the lever are uppermost. At
its centre it is connected with a pair of connecting rods or a forked
connecting rod, which at 8 are or is connected with the piston rod of
Between the axis 8
a cylinder t, which rod works through a guide at u.
and shoulder v I place a spiral spring which tends to raise the piston
and the lever till the lever occupies the position it has in the Figure,
that is, about 6 inches above the rail. The lever is fixed at such a
height above the level of the rail that neither the foot board of the
break van nor those of the carriages in the train can reach it, and the
arm which carries the roller or pulley is made to descend so low that
the latter may clear the upper edge of the lever at a, but reach it just
past a, and as it rolls on may force the lever down to the level of its own
lower surface.
I have described one appendage or lever attached to one side of the
La Ta such annondages and lowers

page_text: in pairs, one on each side of the van, for otherwise it would frequently
happen, in consequence of the turning of the vans on the line, that the
appendage would be on one side of the line and the lever on the other.
I connect the main tube of the system, the signals of which this pair
of operators is to put on, to the upper end of the cylinders and the main
tube of the adjacent system, the signals of which it is to take off, to
the lower end by causing the main tubes each to terminate in a pair
of short branch tubes, one of which is led to each cylinder. The pistons
of the cylinders are valved so that when the rollers in passing over the
levers depress them and the pistons the air in the lower part of the
cylinders passes into the upper part, and by the action of the spring
this air is driven into the main tube of the system connected there-
with, and the air from the other main tube is drawn into the lower
parts of the cylinders, by which the desired reversal of the signals is
effected.
On lines whereon it is common for several break vans to run in the
same train I so attach the descending arms which carry the rollers to
the vans that they may be raised or lowered at will, in order that in the
event of a break van having such rollers attached should be anywhere
in the train except at its tail, such rollers may be elevated and not act
on the levers which work the operator.
Where I work my signals on the automatic system, as above described,
I do not always adjust my equilibrium valve to allow air to escape from
the system at the minimum tension required to keep signals on, but I
sometimes so adjust it that air can only escape when its tension has a
certain excess over this minimum. In speaking of the air in the system
when the system is such as I have described for working signals
automatically I include in the system the taking-off operator, or such
part of it as is below the piston when it is at rest. I do this in cases
where the operator which takes off the signals is much more remote
from that which puts them on than the signals are, for in such cases
the tension at the more distant of the pair of signals is raised to the
said minimum before the air in the more remote part of the system,
and if air were to escape at this it might arise that by the time that
the tension in the whole system is equal that at the signals might be
reduced below the minimum.
Having now described the nature of my Invention, and the manner
in which the same is to be performed, I wish it to be understood that

page_text: I do not limit myself to the precise details herein described and illus-
trated, as the same may be varied without departing from the nature
of my Invention; but I claim as my Invention of improvements in
signals and in signalling, and in apparatus used in signalling,-
First. The signal or signal chamber herein-before described and
illustrated in the accompanying Drawings, consisting of a flat glass or
transparent chamber or vessel into which a colored or black liquid is
forced and withdrawn either by pressure or by exhaustion, the presence
or position in or absence from the signal chamber of the said liquid being
made to indicate according to an agreed code of signals the information
which it is wished to convey, substantially as and for the purpose
described and illustrated.
Secondly. The several constructions and arrangements of apparatus
herein-before described and illustrated in the accompanying Drawings,
and called operators, for working the said signals.
Thirdly. The arranging of pairs of signals in the manner herein-
before described and illustrated in the accompanying Drawings for
blocking portions of a line of railway, whether the said pairs of signals
be worked automatically, that is, by the action of a passing train, or be
worked by hand.
In witness whereof, I, the said John Hickman, have hereunto set
my hand and seal, this Twenty-third day of November, in the
year of our Lord One thousand eight hundred and seventy-
one.
Witness,
GEORGE SHAW.
JOHN HICKMAN. (L.S.)