IMPROVE- MENTS IN SELF-ACTING RAILWAY SIGNALS
Year: 1861

page_text: PROVISIONAL SPECIFICATION left by Robert Crammond at the Office
of the Commissioners of Patents, with his Petition, on the 23rd
October 1861.
I, ROBERT CRAMMOND, of Newtown, in the County of Roxburgh, Timber
Merchant, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN SELF-ACTING RAILWAY SIGNALS," to be as follows, that is to say:-
This Invention relates to the arrangement and construction of railway
signals of that class in which the mere passage of the train causes the signals
to be put on and off quite independent of any manual attention."
Under one modification of these improvements a lever is arranged at the
side of the rail, and nearly upon a level with it, so that the lever may be
depressed when the engine passes over the spot. This lever is fast to one
extremity of a horizontal rod which extends outwards in a lateral direction, and
has fitted near to its other extremity a vertical lever, which is connected to a
wire cord or chain and counterweight or belical or other spring. The counter:
weight is attached to one end of the cord or chain and the other end is carried
up the signal post and is made fast to a spring catch. This catch is imme-
diately contiguous to the inner end of the signal arm, and when the weight is
free it draws back the spring catch out of the way of the signal arm. The
object of arranging the lever by the side of the rail, and which lever is actuated
by the wheel of the engine is, to take the weight off the spring catch; this is
done by inserting a link having a laterally projecting catch in the length of the

page_text: wire cord. When the lever is depressed by the wheel the operative motion of
the vertical lever draws this projecting part of the link piece under a catch
formed at the free extremity of a blade spring arranged over the link piece,
and so liberates the catch spring by the signal arm. The wheel of the engine
now depresses a second lever similar to the first, and having a corresponding
vertical lever which is connected to the signal arm. The motion of the lever
actuates a segmental wheel or other similar contrivance, which moves the
inner end of the signal arm so as to raise it to the horizontal position indi-
cating that a train has just passed. The inner end of the signal arm in its
descent comes under the catch of the blade spring connected to the counter-
weight before referred to, and so long as this catch is not interfered with the
signal will remain up. When the train has travelled a safe distance beyond
the signal it is caused to descend by means of a lever or rod actuated from the
van of the train. This lever or rod is caused to depress a lever arranged by
the side of the rail, and similar to those herein-before referred to. The vertical
lever of this arrangement is attached by a wire cord or chain to the spring
catch which retains the counterweight. The motion of the lever raises the
spring and liberates the weight. The effect of this is to withdraw the spring
catch from the signal arm which then descends and indicates that the line is
clear. The lever or rod in the guard's van is set so as to depress the rail lever
with the same certainty as the wheel of the carriage, but as a precautionary
measure it is preferred to have the means of lifting the actuating rod or lever,
and so prevent the signal being put down when required, which could not be
done if the signal was actuated by the wheel of the van. The same general
arrangement is also applicable for actuating the lamps used for night signals, so
as to indicate the proximity of a train by self-acting means.