IMPROVEMENTS IN THE CONSTRUCTION OF RAILWAY SIGNALS."
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by Mark Walls at the Office of the
Commissioners of Patents on the 14th May 1877.
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MARK WALLS, of Bolton, in the County of Lancaster. IMPROVEMENTS IN THE
CONSTRUCTION OF RAILWAY SIGNALS."
These improvements relate to the ordinary semaphore signals used upon railways,
and the objects of the Invention are,-
Firstly. To compensate in a simple and effectual manner for the expansion and
contraction of the wire which connects the lever in the pointsman's cabin with the
lever on the signal post which works the semaphore, and thus to prevent the
possibility of a doubtful signal.
Secondly. To indicate with certainty in the pointsman's cabin whether or not
the signal acts when the lever is moved.
Thirdly. To allow the signal to be put to "caution.”
And, Fourthly. To cause the semaphore arm or signal to indicate "danger" in
the event of the coming out of the pin which connects the upright rod with the
semaphore arm.
The lower end of the upright rod is connected to a weighted lever mounted on
the signal post, and so arranged that its tendency is to keep the signal always at
danger; and the semaphore arm itself is also counterbalanced, so that in the absence
of the pin the arm will rise to "danger "at all times. To the end of the lever
furthest from the weight is attached a chain passing under a guide pulley and made
fast to the connecting wire. The other end of the connecting wire is also provided
with a piece of chain which passes under a guide pulley, and thence upwards and
over a larger pulley with teeth or projections which catch or hold the links of the
chain, and the end of the latter hangs down on the other side of this pulley, and
has a weight attached to it. This weight is sufficiently heavy to keep the con-
necting wire always tight and allow for any expansion or contraction, but not
heavy enough to counterbalance the weight on the signal post lever which holds
the semaphore in the "danger" position. The toothed chain pulley is mounted so
as to turn loosely on a horizontal axle mounted in a suitable framing in the points-
man's cabin, and fixed to this pulley (or cast with it) is a spur wheel. The signal
:

page_text: lever is also mounted so as to rock loosely upon the horizontal axle and is provided
with a spring bolt having a handle close to the handle of the lever, so that by
grasping the bolt handle the bolt may be made to unlock from the teeth of the
wheel, and on releasing the bolt handle the spring locks it into the teeth.
"
When the pointsman desires to lower the signal to "all clear" he pushes the lever
handle over away from him, grasping the bolt handle, and then by releasing the
latter he locks the lever and wheel together; he then pulls the lever towards him,
causing the wheel to turn and pull the signal down to "all clear," or to "caution
if he pulls the lever only half way, a catch hung to the lever falling into a notch
upon a quadrant and locking it in either position till released. The signal can be
released and allowed to rise to the "danger" position at any time by withdrawing
the spring bolt without moving the lever.
In order to indicate to the pointsman in his cabin, if the signal should stick fast
or fail to rise to "danger" when released, I attach a rod to the hanging weight, and
this rod rises up through a box in the cabin, the top of the rod being of any suitable
form, and painted red, or otherwise, so as to be conspicuous. This rod is so arranged
that when the signal. is at "danger" the top of the rod projects from the box, but
when the signal is all "all clear" it does not project, and as this rod is attached
direct to the chain which works the signal it is evident that it will at once indicate
whether the signal is working or not. This rod is capable of adjustment, so that it
can be set higher or lower to compensate for the expansion or contraction of the
connecting wire.
If the chain or wire should break the weighted lever on the signal post will raise
the arm to "
danger," where it will remain till pulled down; and in the event of
the pin at the top of the signal rod coming out the arm is counterbalanced so as to
rise to "danger" of its own accord.
It will be evident that the lever can at the same time be connected with any
ordinary interlocking or other arrangement for working the points without inter-
fering in any way with its action on the signal.