IMPROVEMENTS IN APPARATUS FOR CONTROLLING RAILWAY POINTS AND SIGNALS
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by Henry Oakden Fisher at the Office
of the Commissioners of Patents on the 2nd November 1877.
"
HENRY OAKDEN FISHER, of Cardiff. IMPROVEMENTS IN APPARATUS FOR
CONTROLLING RAILWAY POINTS AND SIGNALS."
This Invention has for its object improvements in apparatus for controlling
railway points and signals.
At the present time it is common in connection with facing points to employ a
locking bolt worked from a lever in the signal cabin; this bolt holds the switch rails
in position by shooting into one or other of two holes formed in a strut bar by
which the switch rails are connected; the interlocking apparatus in the cabin
prevents the signal levers being moved to lower the signals until the locking bolt
lever has first been so placed as to shoot the bolt and secure the switch rails.
There is also a treddle bar by the side of one of the rails in the immediate
vicinity of the switches, and this is connected with the bolt in such manner as to
prevent it being moved when a train is in the act of passing. These arrangements
fail however to give absolute security, for in case of anything going wrong with the
connection between the switch rails and the switch lever in the cabin the switch
rails may fail to move when the lever is put over; the bolting apparatus will then
lock them in this false position, leaving the signals free to be worked in accordance
with the position of the switch lever, or in other words, at variance with the
position of the switch rails. To remove this source of danger, I employ two
locking bolts in place of one, and I arrange these bolts in such manner that for the
purpose of locking the switch rails they are worked by the signal levers in the
cabin; one bolt is shot when the main line signal is lowered, the other when the
branch signal is lowered; the signal in either case can only be lowered if the switches
have first been accurately placed, for otherwise the bolt when it advances does not
find the hole in the strut bar in place to receive it; with this arrangement if the
bolting takes place it must be with the switches in correspondence with the signal,
for there is but one hole in the strut bar to receive the bolt, the connection between
the signal levers and the bolt is such, that raising the signal does not cause the bolt to
be withdrawn. The withdrawal is effected by the movement of a lever in the
cabin, corresponding with the existing locking bolt lever which operates in all
ED.

page_text: respects as at present, except that it no longer has the function of shooting the bolt,
this function as already stated being conferred on the signal levers, leaving the
locking bolt lever simply a permissive control
It sometimes happens that the switch rails get out of gauge, and accidents may
happen from this cause. To avoid this source of danger I sometimes substitute for
the strut bar mentioned above a double or divided bar, the parts of which are
attached respectively to the two switch rails; the parts meet and overlap at the
part where they receive the locking bolt, and each part is perforated for the bolt;
the holes in the two parts of the bar ought to coincide (and will do so if the switch
rails are in gauge); if they do not, the bolt cannot be shot and the signal cannot
be lowered.