IMPROVEMENTS IN RAILWAY SIGNALLING APPARATUS, WHICH IMPROVEMENTS COMPENSATE FOR THE EXPANSION AND CONTRACTION OF THE WIRE FROM THE SIGNAL CABIN TO THE SIGNAL POST
Year: 1876

page_text: LETTERS PATENT to William Thompson and Robert Thompson, both of New-
sham, near Blyth, in the County of Northumberland, for the Invention of
"IMPROVEMENTS IN RAILWAY SIGNALLING APPARATUS, WHICH IMPROVEMENTS
COMPENSATE FOR THE EXPANSION AND CONTRACTION OF THE WIRE FROM THE
SIGNAL CABIN TO THE SIGNAL POST."
Sealed the 14th October 1876, and dated the 18th April 1870.
PROVISIONAL SPECIFICATION left by the said William Thompson and Robert
Thompson at the Office of the Commissioners of Patents on the 18th April
1876.
WILLIAM THOMPSON and ROBERT THOMPSON, both of Newsham, near Blyth, in
the County of Northumberland. "IMPROVEMENTS IN RAILWAY SIGNALLING
APPARATUS, WHICH IMPROVEMENTS COMPENSATE FOR THE EXPANSION AND CON-
TRACTION OF THE WIRE FROM THE SIGNAL CABIN TO THE SIGNAL POST."
The object of our Invention is to remedy the defects in railway signalling caused
by the wire that actuates the signal arm varying in length according to the state
and temperature of the atmosphere. This variation in the length of the wire often
occasions the signal arın to assume an abnormal position, and in some instances to
such an extent as to deceive the locomotive driver. To obviate this fault we would
substitute a balanced wheel in lieu of the balanced lever now used. This wheel
would turn on the same pivot or pin as the lever formerly did, and is attached in
the ordinary manner to the vertical rod that moves the signal arm.
The wire rope,
however, is not fastened as in the lever to the wheel, but passes in a groove over
the wheel and has at the free end a weight hanging down so that when the wire
either expands or contracts the said weight falls or rises accordingly.
The mode of action is similar in every respect to the ordinary balanced lever,
the friction of the wire rope over the balanced wheel being sufficient to turn the
signal to "all right." The signal being put for "danger" the momentum of the
falling weight tightens up any slackness there may be in the wire.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Thompson and Robert Thompson in the Great Seal Patent
Office on the 17th October 1876.
WILLIAM THOMPSON and ROBERT THOMPSON, both of Newsham, near Blyth, in
the County of Northumberland. "IMPROVEMENTS IN RAILWAY SIGNALLING
APPARATUS, WHICH IMPROVEMENTS COMPENSATE FOR THE EXPANSION AND CON-
TRACTION OF THE WIRE FROM THE SIGNAL CABIN TO THE SIGNAL POST."
The object of our Invention is to remedy the defects in railway signalling caused
by the wire that actuates the signal arm varying in length according to the state
and temperature of the atmosphere. This variation in the length of the wire often
'occasions the signal arm to assume an abnormal position, and in some instances
to such an extent as to deceive the locomotive driver. To obviate these faults
we would substitute a balanced or weighted wheel in lieu of the balanced lever
as now generally used. This wheel might turn on the same pivot or pin as the
lever formerly did, and be attached by any ordinary means to the vertical rod that
works the signal arm. The wire rope, however, is not fastened (as in the lever)
to the wheel, but passes in a groove over the said wheel, and has at its free end
a weight hanging down so that when the wire either expands or contracts the said
weight falls or rises accordingly.
In Figure 1 of the accompanying Drawing is shewn a signal post fitted with our
improvements.
A is the signal post, and B a plate provided with a pivot pin or axle c and a stop
piece d, the former for the loose wheel E to turn on and the latter to control the
extent of motion of such wheel. The said plate is suitably secured to the signal
post, and the vertical rod F descending from the signal arm is attached by any
ordinary means to the weighted portion g of the aforesaid wheel. The length of
the rod and position of the wheel is so arranged that when the latter comes to rest
of its own accord, due to the gravity of the weighted portion, the signal arm shall
appear at "danger," or should the wire break in the course of time a similar result
would follow.
The signal arm is put down or to "all right" by the signal man pulling, over the
hand lever shewn in Figure 2, which is connected to the signalling apparatus by
a wire rope h passing in the usual way over or under guide pulleys to the signal
post where it is made fast to a chain i, Figure 1.
This chain is conducted over
the wheel E and kept taught or tight by a weight k as shewn. The act of pulling
over the said hand lever draws up the weight k, and the friction of the chain
running over the grooved wheel E puts in motion the said wheel, which motion
continues until the arm of the wheel rests on the stop piece d; the arm of the
signal is now within the post to the "all right" position. Should, however, the
wire rope be over tight, caused by contraction due to the weather, the chain i slips
or surges over the wheel while. the signal arm remains at rest in the "all right
position. On returning the hand lever to its former position the weight / drops,
and the friction of the chain in the grove of the wheel E puts in motion the said
wheel, which motion continues until the weighted portion of the wheel rest on
the stop piece d; the arm of the signal is now at "danger." Should the wire rope
prove too slack, caused by expansion due to the state of the weather, the chain i
slips or surges over the wheel without influencing the signal arm.
Figure 3 shews an cularged view of the wheel (E, Figure 1), 7, 1x, are the two
arms that control the travel of the said wheel; g is the weighted portion thereof
to which the vertical rod (F, Figure 1) is connected by a pin; m is the groove in
which the chain (i, Figure 1) is placed, and n a stub or stud rising from the bottom
of the groove for the chain to take a firm hold of the wheel when the hand lever
is pulled over by the signal man, the stud has, however, no action upon the chain
when the hand lever is returned. This stub may not always be necessary, and
should be placed, when employed, in such relation to the tangent the chain makes

page_text: on leaving the wheel that it shall be free from such chain when the wheel has
completed its journey to "all right," and allow the chain to slip or surge.
The addition of the stud or stub is particularly useful in exposed situations
where the action of the apparatus may suffer from the accumulation of snow
and ice or the rashness of the signalman in pulling the hand lever too quickly
over.
Having now described our said Invention, and in what manner the same is to
be or may be carried into effect, we claim the method and means above described and
illustrated upon the accompanying Drawing for compensating for the expansion and
contraction of the wire from the signal cabin to work the signal arm of a signal
post.
In witness whereof, I, the said William Thompson, have hereunto set my hand
and seal, the Fourteenth day of October, in the year of our Lord One
thousand eight hundred and seventy-six.
WILLIAM THOMPSON. (L.S.)