IMPROVEMENTS IN SIGNALLING ON RAILWAYS, AND IN THE MEANS AND APPARATUS EMPLOYED THEREFOR."
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by John Sheddens Campbell at the
Office of the Commissioners of Patents on the 26th November 1877.
JOHN SHEDDENS CAMPBELL, of Glasgow, in the County of Lanark, North Britain,
Die Sinker. "IMPROVEMENTS IN SIGNALLING ON RAILWAYS, AND IN THE MEANS
AND APPARATUS EMPLOYED THEREFOR."
This Invention has reference to a new or improved mode and means of
alarming or signalling to the engine-driver and guards of railway trains while
running at any speed by the use of a special electro-magnetic arrangement of
mechanism and signal bell, placed on the engine or in the van beside them, or in
both, so that they may pull up and stop the train as soon as possible after passing
the station where the signal is given by the signal-man, who effects this by a
special mechanical arrangement fitted at every signal station along the line, or at
some considerable distance on either side of passenger or other stations where
trains have to stop, or where such signal stations and men are required, and which it is
considered will prevent all the collisions and accidents which happen from careless-
ness in not observing or from inability to see the signals and lights which so often
become invisible in dark or foggy weather.
And the nature and novelty of the Invention consist first in the construction and
arrangement of the said special signalling apparatus to be fittted on the engine,
tender, or van, or other part of the train, where the driver, fireman, guard, or
conductor of the train is sure to hear it; and this improvement consists of a sinall
simple ordinary arrangement of electro-magnetic signal or alarm bell, with the
opposite poles or ends of its wires closely connected or soldered to end plates
properly insulated and laid nearly close together and in front of an improved
arrangement of engaging and disengaging horizontally sliding bar or commutator,
with hinged or it might be spring switch or switches for bearing on these plates
and forming the the metallic contact to complete the circuit and ring the bell when
the bar is shifted towards the plates, and vice versa stop the signal bell when shifted
backwards from the plates; one switch answering when the one plate is directly
connected to the frame of the sliding bar.
This improved sliding and engaging and disengaging bar is actuated and held in

page_text: position by a wheel and lateral side catches respectively mounted and fixed at the
back end or that opposite the switches through a vertical reciprocating bar,
working in suitable slide or roller guides down through the carriage, with a corres-
ponding pulley mounted on its upper end, acting as it rises on the pulley of the
horizontal bar, and with notched grippers or holders on each side which take on to
the said lateral catches of the sliding bar, and hold it securely in either its engaged
or disengaged position when the vertical bar is in its lower or raised position
respectively, thus disengaging the sliding bar or commutator, as the vertical bar
rises to shift it forward as described, and fixing it in its outward or insulated
position as the vertical bar falls.
The raising of the vertical bar in its slides or guide rollers (for so shifting the
horizontal sliding switch circuit producing bar to sound the alarm or signal bell and
give the signal to the engine-driver or guard) is effected by a roller mounted on its
lower end, so as to take on to the upper inclined or curved surface of a lever or spring
fitted and raised under it between the rails by a lever or other equivalent actuated
by the signal-man at the side of the line, through rods or chains and levers and
pulleys, as used for the shifting of ordinary signals and points; the curved or
inclined surface being of considerable length in either direction of the travel of the
carriage parallel to the line of rails, so as to give a gentle rising and falling action
to the vertical bar in passing it at the signal station; the raising lever acting either
transversely or longitudinally as found best.
The vertical bar after having shifted the signal switch or circuit contact bar into
its acting position falls as soon as it passes the angled or curved switch, and
immediately locks the commutator in this position, so that the bell continues to ring
until the attendant's attention is drawn to it, when he can stop the train, and then
raise the vertical bar and shift the switch or commutator out of contact or action,
where it is locked all ready for giving a fresh alarm at the next signal station.
Instead of rollers at the back end of the horizontal sliding bar and the top of the
vertical bar for shifting the former into contact or action, inclined surfaces on one
.or both may be used; and instead of using a sliding horizontal bar, a metallic ball
might be used, set on an insulated hollow inclined rest close over the top of the
lifting bar, which could have an inverted sharp pointed prong, which when it was
lowered would enter a tapered hole in the ball and hold it in its seat; but the
moment it was raised by passing over the raised curved or inclined signal switch at
the station on the railway, the prong would rise out of the ball and free it and then
also push it off its seat on to the groove between the two insulated plates of the
wires of the battery and bell, so as to complete the circuit and ring the bell in the
same manner as the sliding commutator and its switch; a guard being provided
over the top of the ball and at the sides of the plate to insure its proper action and
prevent the ball being thrown out. And the vertical bar might be made short and
have its lower end rounded or fitted with a small antifriction pulley over and in
the cleft of a heart or double outward curved cam on the upper short end or arm of
a pendent lever fulcrumed close up below the frame of the engine, tender, or van,
so that the longer arm hangs down in the vertical plane of the angled or curved
signalling switches on the line between the rails, and which when raised to give the
signal, would shift the said longer arm of the pendent lever to either side, according
to the direction the train was running, and by one or other of the curved cam arms
above raise the upper lifting bar, and so shift the make and break contact bar or
ball to ring the signal bell, all otherwise, as described, by the long vertical lifting
bar.
When the alarm bells in the engine and the van were connected by circuit wires
throughout the train, they could also be used by the driver and guard for signalling
to each other by a concerted arrangement as to the duration and number of strokes
of the bell given for certain words or orders; and the bell could be placed where it
could be seen striking as well as heard ringing, as, for instance, between the
windows in the engine-driver's weather screen.

page_text: The battery and electric mechanism entire would preferably be enclosed in a
case, or covered in by a strong wood or sheet metal lid, as well as the wires all
covered in to secure them against accident or their being tampered with, except the
lower end of the vertical lifting bar or long oscillating lever mounted over the
station signal switches, which must be free to act on the upper angled or curved
surfaces of these.