IMPROVEMENTS IN APPARATUS FOR WORKING RAILWAY SIGNALS, POINTS, AND SWITCHES
Year: 1868

page_text: PROVISIONAL SPECIFICATION left by Henry Adolph Kehde at the
Office of the Commissioners of Patents, with his Petition, on the
17th November 1868.
I, HENRY ADOLPH KEHDE, of Denmark Road, Kilburn, in the County
of Middlesex, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN APPARATUS FOR WORKING RAILWAY SIGNALS, POINTS, AND
SWITCHES," to be as follows:-
My Invention relates to improvements in apparatus for working
distance and auxiliary signals, points, and switches on railways, by
the aid of which the chains or rods for operating the same are free to
expand or contract by the changes of temperature or other cause
without interfering with the correct working of said signals, points, or
switches.
According to my Invention I mount a chain wheel or drum so as to
turn freely in bearings on a suitable framing or standards. A chain
passes over this drum, one end being connected to the chain of rods by
which the signal point or switch is operated, and to the other (which is
pendent from the wheel) is attached a counterbalance weight for keeping

page_text: the links or rods taut, and at same time assist in maintaining the
signal in position. On the axis of the chain wheel on either side I
mount an oscillating bell crank or other lever, said levers being connected
together at their extremities, and provided with pawls at one end
engaging with ratchet wheels formed one on either side of the chain
wheel, said ratchets and pawls being arranged to act in contrary direc
tions, so that on the bell crank lever being oscillated in either direction
the chain wheel will be partially rotated therewith in order to raise or
lower the signal as desired. The other extremities of these oscillating
levers are connected to the ordinary hand lever, by which they are oscil-
lated in either direction for operating the signal or switch. When these
oscillating levers arrive at either extremity of their course projecting
parts formed on the pawls are brought into contact with friction rollers
suitably mounted near the periphery of the chain wheel in such manner
that the pawls are disengaged from their respective ratchet wheels,
leaving the chain wheel free to be moved in either direction by the
expansion or contraction of the chain of rods communicating with the
signal points or switch,
A modification of the foregoing arrangement consists in mounting the
ratchet chain wheel in a moveable carriage instead of in fixed bearings
as before. In this case the chain of rods is attached to one end of said
carriage (which is mounted on suitable rollers) instead of communicating
direct with the wheel as before, a chain from which the counterbalance
weight is suspended being passed over a roller and attached to the other
end of said carriage. The arrangement of levers and ratchets is similar
to that before described, but the wheel is provided with spur teeth
gearing with a rack rod fixed to the ground, so that on the wheel being
rotated in either direction by means of the oscillating levers and pawls
the carriage will be moved in one direction or the other for operating
the signal. This is effected by means of a frame hinged at one side to
the carriage, and sliding at the other in a socket formed on the rod
communicating with the hand lever by which said frame is raised or
lowered. This movement is transmitted to the oscillating levers by
means of a slotted arm formed on said frame with which the extremity
of the levers engages. In this manner the carriage is always free to be
moved in either direction, either by means of the hand lever for operating
the signal or by the expansion or contraction of the chain or rods, as
the connection between the ratchet and spur wheel is interrupted the

page_text: moment the oscillating levers arrive at either end of their course by the
pawls being disengaged from the ratchets, as before described.
A third arrangement consists in dispensing with the wheel ratchets
and pawls and employing only a bell-crank lever mounted in a moveable
carriage, to the end of which lever the chain of rods is attached. Tho
other extremity is acted on by the hand lever by means of a hinged part
on the carriage as before, said carriage being free to move to or fro as
the rods expand or contract. Two racks are fixed to the ground beneath
the carriage having ratchet teeth inclined in contrary directions, into
which vertical bolts or stops on the carriage are dropped so as to prevent
the latter moving in either direction on the bell-crank lever being oscil-
lated for working the signals or points. When said lever arrives at
either end of its course the hinged part on the carriage lifts the bolts
out of the racks, leaving the carriage again free to move for the purpose
before described.