An Improvement in Railway Point or Signal and Tablet Interlocking Gear.
Year: 1891

page_text: ate of Application, 29th Jan., 1891-Accepted, 7th Mar., 1891
COMPLETE SPECIFICATION.
An Improvement in Railway Point or Signal and Tablet
Interlocking Gear.
We, EDWARD TYER, Electrical Engineer, of Ashwin Street, Dalston Junction,
in the County of Middlesex, and ROBERT TWEEDY, Mechanical Engineer, of
Metcalf Street, Carlisle, in the County of Cumberland, do hereby declare the
nature of this invention, and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement :-
On many lines of railway, particularly single lines it is a rule that each train
shall carry a staff or its equivalent a tablet, which, having to be taken by the train
from one station to a farther station, ensures that no other train shall be on that
section of the line at the same time. Our invention relates to means whereby a
tablet employed in this way shall automatically control point or signal levers at a
station or at intermediate sidings between stations, and such levers shall control the
issue of a tablet, as we shall describe referring to the accompanying drawings which
illustrate our invention applied to a pair of interlocked levers.
Fig. 1 is a transverse section through the lever frame.
Fig. 2 is a plan, with part of the cover removed, to show the interlocking gear
below.
A and A2 are a pair of levers of the usual kind, with interlocking gear of the
kind known as tappet and plunger gear, that is to say each lever has connected to
it a sliding bar or plunger B₁ and 13, each of which has an oblique notch cut on its
edge as at C of the plunger B and at C2 of the plunger B2. A bar or tappet T
is fitted to slide transversely to the plungers B1 B³, this tappet having its opposite
ends inclined to fit the notches C'C' respectively. When the levers A' A² are in
their back position as shewn in Figs. and 2, the one end of the tappet T is
engaged in the notch of B2 and consequently the lever A² cannot be moved
forwards, but the lever A' can be moved until the notch C' comes in line with
the tappet T.
The lever A can then be moved, the inclined side of the notch C₁ thrusting the
end of T out of C2 and pushing its other end into the notch C' of the plunger Bl
which is thus bolted, so that now A¹ cannot be moved back.
This, so far, is the arrangement and operation of well known tappet and plunger
interlocking gear as applied to two levers, and to this we make no claim except as
part of the combination which we shall now describe for applying a tablet as means
of locking the levers and of being locked up by them. We provide a slide D which
can be pulled out or pushed in between the plungers B1 B2 by hand applied to its
outwardly projecting end d. On this slide D there are two studs d³ corre-
sponding to the holes and notches which are usually cut in the tablet E, which is
conveniently made as shewn, in form of a circular disc of metal with a hole through
its middle. On one side of the slide D is a sloping notch Fin such a position that,
when the slide D is pushed in, a sloping projection g² from a second tappet or cross
slide G can enter this notch.
On the same tappet G is a second higher sloping projection and beyond it a
rectangular projection which enters a notch in the edge of the plunger B'.
While the slide D is drawn out, and while it remains out the plunger B2 is held
by the projection urged by a spring into its notch, consequently the lever A²
cannot be moved, and A which is held by the tappet T as above explained, cannot
be moved. If the slide D be pushed in, the conditions are the same, both levers A'A²
remaining locked. These are the conditions when there is no tablet employed at
the apparatus, that is to say, while a train somewhere on the section is in possession
of the tablet, in which case there should be no power to move a lever such as A¹

page_text: or A that could shift a point or lower a signal so as to admit or invite another
train upon the same section. But when the train arrives and delivers its tablet E,
this is placed on the slide D in the position determined by the studs d2 3 and the
slide and tablet being pushed in, the round edge of the tablet E acts on the sloping
side of g and pushes the tappet Gaside so that its projection g³ is moved out of
the notch g of the plunger B which is thus unlocked leaving the lever A2, and
after it A, free to be moved. But the disc D in causing release of B2 brings the
projection g into the notch F of the slide D and if the plunger B³ is moved so as
no longer to present the notch of for admitting ³, the projection g² cannot move out
of the notch and consequently the slide D is locked and cannot be drawn so as to
give out the tablet until both the levers A A² are moved from the position shewn,
in which position they become locked afresh by the pulling out of the slide D to
give the tablet out for the use of a train.
Although we have described our invention applied in connection with a pair of
interlocked levers, in many cases a single lever is used, the tappet G being then
alone necessary for its interlocking with the tablet and its slide.
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is
In combination with a point or signal lever or with the tappet and plunger inter-
locking gear of a pair of point or signal levers, a slide and tappet so arranged that
when no tablet is present on the slide no lever can be moved, unlocking being
effected when a tablet is pushed in on the slide, which itself becomes locked by the
movement of a lever, substantially as herein described.
Dated this 20th day of January 1891
ABEL & IMRAY,
Agents for the Applicants.