IMPROVEMENTS IN SAFETY SIGNAL APPARATUS FOR RAILWAYS."
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by John Edwards at the Office of the
Commissioners of Patents on the 3rd March 1876.
JOHN EDWARDS, of No. 6, Cassland Crescent, South Hackney, in the County of
Middlesex. "IMPROVEMENTS IN SAFETY SIGNAL APPARATUS FOR RAILWAYS."
Mechanism has been provided upon locomotives connected to a steam whistle or
other alarum thereon, such mechanism consisting of a lever or arm which is moved
by coming in contact with a trigger or stop arranged by the line of rails, so as to
call the driver's attention to the condition of signals or to act as a signal for him,
and the said trigger or stop has been mechanically connected to the signals or
their pulls in such a manner that it acted on the whistle or alarum when the signal
stood at danger, but did not so act when the signal stood at safety. My Invention
relates to a method and apparatus for working such trigger or stop by means of
electricity or fluid pressure, so that its action is rendered independent of mechanical
connections with the signals or their pulls. For this purpose I arrange the said
trigger or stop to slide or oscillate in such a manner that it can easily be moved
within range or out of range of the alarum mechanisin on the locomotive, and I so
counterweight it or press it by a weight or spring that ordinarily in what may be
called its normal condition, corresponding to the danger attitude of the ordinary
signal, the trigger or stop remains within range of the alarum mechanism on the
locomotive, and will when the locomotive passes it cause tho whistle or alarum
thercon to sound.
When I employ electricity for working the alarum I apply to the trigger or stop
an electro-magnet, which when it is rendered active by the passage of a current of
electricity through its coils withdraws the trigger or stop out of range of the
locomotive alarum mechanism, so as to correspond with the condition of the ordinary
signal when it is lowered to safety, and in that case the locomotive passes without
the alarum being given. I connect the coil of the electro-magnet by a wire to a
battery or other source of electricity, such wire having a contact making and
breaking key, preferably in the signal box near the lever that works the ordinary
semaphore signal, and connected with the said lever in such a way that when the
lever is in its normal position, corresponding to the signal at danger, the contact
remains broken, and the trigger or stop, as above explained, remains ready to act on
the locomotive alarum; but when the signal lever is pulled over so as to lower the
semaphore to safety electric contact is made, whereby the electro-magnet is rendered

page_text: active and causes the trigger or stop to be withdrawn, allowing the locomotive to
pass without alarum.
In order to ensure that the trigger or stop shall not be withdrawn until the signal
lever is pulled fully over I prefer to work the contact key by the spring catch rod of
the lever, so that contact is not made till the said catch is dropped into the back
notch of the quadrant.
When I employ fluid pressure for working the alarum I connect a piston, bellows,
or flexible diaphragm at the trigger or stop by a pipe with a corresponding piston,
bellows, or diaphragm at the ordinary signal lever, and the said pipe being charged
with air or other fluid when the signal lever is pulled over it moves the one piston,
bellows, or diaphragm, causing a change of pressure in the communicating pipe, and
this change of pressure operating the other piston, bellows, or diaphragm causes
the trigger or stop to be withdrawn.
The arrangements for alarum, which I have described as working along with the
ordinary semaphore signals, may obviously be employed without such signals, and
may serve in lieu of fog signals.