Improvements in Apparatus for Ensuring Safety on Single Lines of Railway.
Year: 1896

page_text: Date of Application, 27th Mar., 1996
Complete Specification Left, 21st Jan., 1897-Accepted, 27th Feb., 1897
Complete Specification Left, 21st Jan., 1897-Accepted, 27th Feb., 1897
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Ensuring Safety on Single Lines of
Railway.
We, SAMUEL TELFORD DUTTON, Civil Engineer, Marl Bank, in the City of
Worcester, and RALPH HENRY CHRISTOPHER NEVILE, of Crown Lea, Malvern, in
the County of Worcester, Civil Engineer, do hereby declare the nature of this
invention to be as follows:-
In our Specification No. 17195 of 1895 we bave described apparatus for ensuring
safety on single lines of railway. Our present invention relates to improvements in
the apparatus and method of operating therein set forth.
At the terminal stations we provide a new or modified tablet instrument from which
a square or a round tablet can be issued according to whether the intermediate
stations are closed or open.
The issue of square or round tablets may be controlled by a key like that of the
exchanging box described in our previous specification or by a lever or other suitable
instrument.
An electric current sent by the extra wire may serve to determine whether the
tablet released is square or round it being provided that the current allowing issue of
a square tablet can only be sent when all the intermediate stations are closed.
The intermediate stations may be closed as described in our previous specification
and may be reopened by currents sent by the extra wire or by their receiving a round
tablet issued by a terminal station.
Suitable existing tablet instruments may be used in this way but we prefer an
instrument which may be used also for general tablet working.
In this instrument one slide or its equivalent is used for removing a tablet and
another for returning a tablet.
The withdrawing slide should be normally in, and capable of being drawn out only
by permission from the other station.
The other slide should be normally out and capable of being pushed in only when
a tablet is put in it, the tablet being thus transferred to the body of the instrument.
In order to simplify explanation we may term the withdrawing slide I, and the
introducing slide O. These slides are electrically controlled so as to operate as
follows.
Slide I after being withdrawn can only be pushed in by a current from another
station transmittable only when a tablet is placed in the O slide and pushed in or
when a tablet is placed in the O slide at the same station and pushed in. Slide O
having been closed cannot be withdrawn until a current, indicating that the other
station is clear and the I side in, comes therefrom. In the event of a tablet being
returned at the same station where it was withdrawn the other station being clear
could give permission for its immediate withdrawal.
The intermediate stations may be closed by means of tablets in the following
manner.
Assuming that there are 3 stations A.-B. C, B on obtaining tablets from A and C
can by placing these tablets in a receptacle release his day key close his station
and then by currents sent by the extra wire can release the exchanging keys at
A and C.

page_text: Any number of stations may be closed in the manner described in our previous
specification and may be reopened by the issue to them of round tablets. In this
case it is advisable to open one station electrically and the others by means of
tablets.
Thus supposing there are 5 stations A, B B, CC, D D, E, the intermediate stations
having duplex instruments as described in our previous specification.
Then if D, for instance, be opened electrically by perinission of A and E, C may
be opened by D issuing a tablet belonging to C, D section B by a tablet belonging to
the B, C section and so on.
Either B or D may be electrically opened according to the direction of the train
conveying the opening tablet.
For operating according to our present improvements the relays required may be
reduced in number by utilising moving parts of the tablet or train staff instruments
to make and break many of the contacts.
In order to provide for moving a wagon into or out of a siding which is temporarily
closed when its station is switched out we provide a special set of points for this
siding which can be moved by a lever controlled by the through tablet, or by using
the through tablet for returning the interlocking lever in the signal cabin to its
middle position the points being thereby freed as long as the through tablet remains
in the cabin.
We may also use a special ground frame whereby the necessary points and point
locks can be moved through sway bars one end of each of which is connected to the
lever in the ground frame and the other to the lever in the cabin, the middle point of
the sway bar being connected to the points or lock to be operated this frame being
released by a lever controlled by the through tablet.
We may also provide, substantially as described in the Specification No. 11850
of 1894 means whereby the points required to be moved can be temporarily
disconnected by the use of the through tablet from the rods leading to the cabin and
worked by levers on the ground.
In all these cases provision would be made that before the through tablet could be
removed to continue the journey the points would have to be returned to and secured
in their normal position for through working.
Also instead of the exchanging boxes at the terminal stations described in our
previous specifications, there may be, besides the one tablet instrument used for
ordinary traffic, a second instrument for through traffic, these instruments being
interlocked so that only one can be used at a time.
Obviously in operating as we have described, a staff may in many cases be
substituted for a tablet, or both may be used, suitable exchanging boxes being
provided.
Dated this 27th day of March 1806
ABEL & IMRAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in Apparatus for Ensuring Safety on Single Lines of
Railway.
We, SAMUEL TELFORD DUTTON, Civil Engineer, Marl Bank, in the City of
Worcester, and RALPH HENRY CHRISTOPHER NEVILE, of Crown Lea, Malvern, in the
County of Worcester, Civil Engineer, 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 :-
In our Specification No. 17195 of 1895 we have described apparatus for ensuring

page_text: safety on single lines of railway. Our present invention relates to improvements in
the apparatus and method of operating therein set forth.
At the terminal stations we provide a new or modified tablet instrument from
which a square or a round tablet can be issued according to whether the intermediate
stations are closed or open.
The issue of square or round tablets may be controlled by a koy like that of the
exchanging box described in our previous specification or by a lever or other suitable
instrument.
An electric current sent by the extra wire may serve to determine whether the
tablet released is square or round it being provided that the current allowing issue
of a square tablet can only be sent when all the intermediate stations are closed.
The intermediate stations may be closed as described in our previous specification
and may be reopened by currents sent by the extra wire or by their receiving a
round tablet issued by a terminal station.
Suitable existing tablet instruments may be used in this way but we prefer an
instrument which may be used also for general tablet working.
Figure A of the accompanying drawings is a perspective view of the instrument
for round tablets showing the upper slide out and the lower slide in.
Figure 1 is a longitudinal section and Figure 2 is a diagram shewing the electrical
connections on which the instrument operates. There are two slides, an upper slide O
which is normally out to receive a fablet, and a lower slide I which is normally in
but on permission being communicated electrically from another station can be drawn
out with a tablet that can be removed from it. The upper slide O is shewn in
Figure 1 with a tablet T in position ready to drop into a receptacle t which contains
a number of tablets, the lowest of which lies in a recess i of the lower slide I. The
tablet T is held by two springside clips S supporting its edges, which clips as the
slide approaches the position shewn, meet inclined stops that spread them apart
allowing the tablet to drop into the receptacle t. As the movement of the slide O affect
a number of electrical connections provision is made to prevent it from being pushed
in unless there is a tablet T in it. For this purpose the tablet is made with certain
hollows and over it a lever L pivotted at 7 has at its one end a roller which bears
on the surface of the tablet, and at its other end a lock plato l' made with ward-slots
shaped to suit the bollows of the tablet. A stud on the slide O projects into these
ward-slots, and consequently unless the roller is moved by the tablet T so as to
bring the lock plate into such positions that it offers no impediment to the stud 13,
the slide O cannot be pushed in. When the instrument has to receive ordinary
tablets without hollows the lock plate is dispensed with, and a lever arm is pivotted
at of such length as to reach the front of the tablet opening when it is only partly
pushed in, this arm stopping its farther movement unless there is a tablet in the
opening.
In this case the side clips S for supporting the edges of the tablet may be
dispensed with, the tablet being free to fall when it is sufficiently far advanced.
When the slide O is pushed in a pawl o engages in a notch of the slide, the pawl
being connected by a link o¹ to a pawl lever m below so that it is disengaged as
will hereafter he described when the lower slide I is disengaged, by the action of an
electro-magnet M raising the pawl lever m. The slide O has projecting studs (one of
which is shewn at o) engaged between springs which, as the slide is moved to and
fro make and break electrical contacts as will be explained with reference to
Figure 2. A contact lever 14 is raised by one of the studs o³ so as to break contact
when the slide is moved from its out or in position.
The lower slide has a notch to receive the pawl of the lever in which carries the
armature m' facing the poles of the electro-magnet M so that the slide can be pulled
out only when the magnet M is excited by a current. On the slide I are projecting
studs of which one is shewn at which as the slide is moved to and fro make and
break electrical contacts as will be explained with reference to Figure 2. In order to-
shorten the stroke of these studs and the studs o' they are fixed, not on the slides O and I
themselves but on upper pieces which slide on O and I and are moved by catches on

page_text: the slides (shewn at for the lower slide) whereby the pieces carrying the studs are
first drawn forward a certain distance as the slides are drawn out, then left while the
slides complete their outstroke by the catch passing on to an incline . This however
is not essential, as the studs o' and might have the full stroke of the slides O and I.
A contact lever 15 is raised by one of the studs 2 when the slide I is moved from
its out or in position. At the sides of the slides are formed V shaped notches in
which engage the upper and lower wedge ends of a vertical sliding rod R constituting
a mechanical interlocking of the two slides O and I so that each can be moved only
when the other is in proper position to permit the movement.
We prefer however to employ, instead of the simple interlocking bar R shewn in
Figure 1, a bar as shewn in Figure 3 having an arm r pivotted at its lower end,
and on its side a sliding spring catch at its upper end. The upper slide O has on
its under side a rib which is cut away at ² and still more deeply at 3 and in front of
that rib it has a ratchet stop. The lower slide I has a V notch, some distance
beyond that, a ratchet stop and behind that a sloping step to a lower level
When both slides are in, the lower end of the bar R is engaged in the notch * and
the upper end of the bar is free, but immediately; under . In this condition as R
can rise only as far as permitted by the lower slide can be a little withdrawn until
it is stopped by the arm meeting. The upper slide O is thus prevented from
being moved. On restoring the lower slide L, the upper slide O can be drawn out,
the top of the bar R being then under the part of the rib and free to rise till it
meets the rib. The lower slide can now be withdrawn the arm r riding over and
finally the lower end of the bar R lodging on 7. The upper slide can be pushed
in, the stop depressing and passing which is then in position to stop
that the upper slido O cannot be drawn out again until the lower slide is pushed in
and the bar R again engaged in
so
Referring now to Figure 2 which shews the state of the electrical contacts when
the lower slide is in and the upper slide O is out, 1, 2, 3, 4, 5, 6, and 22 are pairs
of springs which are electrically connected by studs such as on the lower slide
when these studs are between the springs, and are disconnected when the studs are
withdrawn ;-the springs 15 indicate the contact lever 15 shewn in Figure 1. Some
of the springs 1, 4, and 22 are of greater length than the others so that these
contacts are made sooner and broken later than the others by the movement of the
slide I.
Pairs of contact springs 7, 8, 9, and 10 serve for making and breaking contacts
according as the studs such as o2 on the upper slide are between the springs or not
between them; 14 indicates the contact lever 14 shewn in Figure 1. 12 and 13 are
contacts made by the lever L when its roller is down, but broken while that roller
is held up by the slide O or a tablet in it, M is the electro-magnet which acts on the
pawl levers m and o; 26 is the polarised relay, 27 is a plunger which normally
connects 17 and 18 but when pushed breaks contact 17 and connects 18 to 16 and
28 to 29. 30 is the ordinary line wire, 31 and 32 lines respectively to the negative
and positive terminals of the battery; G is a galvanometer.
The upper and lower slides may be electrically interlocked in the following
manner. The springs of contact 4 are shortened so that on beginning to draw out
the slide I the contact 4 is broken, an additional contact X operated by the slide I
and another contact Y operated by the slide O are connected as shown by the
dotted lines.
When both slides are in, immediately on beginning to draw out slide I, the contact
at 4 leading to the magnet is broken and consequently the pawl m falls before the
slide becomes unlocked. When the upper slide O is out, although contact at 4 is
broken, the current can pass by X and Y to the magnet until the slide I is
sufficiently advanced to be free from the locking pawl m, the long springs of X main-
taining the contact for some time.
Such being the construction of the tablet instruments at each of two stations and
the electrical connections affected by it, it is operated as follows.
When it is desired to withdraw a tablet, say at station A, the signalman at

page_text: station B being apprised by his bell signal operated from A, holds in his plunger 27
whereupon a + current from 32 flows by 6, 8, 16, 18, G to line 30, and a
current from 31 flows by 7, 5, 29, and 28 to earth E. When the + current sent
by line 30 arrives at station A it flows by 30, G, 18, 17, 15, 14, to relay 26 and
earth. The relay tongue being thus deflected to + connects 31 to 20; the + current
from the local battery then from 32 by 2, 6, 10 to coil of magnet M, then by 4 and
20 to 31. The magnet M attracting its armature releases the lower slide I which
can be withdrawn delivering a tablet. As the slide is withdrawn contact 4 is broken,
and the magnet ceases to attract its armature, so that the pawl m drops and locks
slide 1 in its out position. The signalman at station A having taken a tablet from
his instrument acknowledges it by pressing his plunger. As both slides are now
out O being normally out and I just drawn out, the movement of the plunger
connects 32 by 2, 29 and 28 to earth, and connects 31 by 3, 8, 16, 18 and Ġ to 30
thus sending a negative current to station B. As the magnet M at B is not excited,
the slides at that station remain locked. The tablet from A is carried by train to B
where the signalman places it in his upper slide O and pushes the slide in, so that
the tablet falls into the receptacle t the roller dropping and making the contacts 12
and 13, while the slide breaks the contacts 7 and 8 and makės 9. and 10. The
signalman at B presses his plunger 27 and thus the terminal of his battery is
connected by 31, 12, 16 and 18 to line 30, while the + terminal is connected by
32, 2, 29, and 28 to earth. Thus a current is transmitted to station A deflecting
the relay tongue there to the side, and thus connecting the terminal through
19, 1, and the coil of M back to the + termiual. The action of M releases the lower
slide I at A which is then pushed in by the signalman there, who then, by pressing
his plunger 27 transmits a + current to B, which through contacts 20 and 4
excites the magnet M releasing both slides at B, but until the upper slide is drawn
out the interlocking bar R prevents the lower slide from being drawn out. When
the upper slide at B is drawn out, the apparatus is again in operative condition.
Sometimes when a tablet is withdrawn say at A, it has to be returned to the
same instrument without being sent on to B. In this case the signalman at A
places it in his upper slide O and pushes the slide in, thus making contacts 22, 9, 13
to magnet M which releases both slides, but the lower slide being out the upper
slide is prevented from being drawn out by the interlocking bar R. When the
lower slide is returned the contact 22 is broken and the magnet M being rendered
inactive, the slides are again locked. In order to be able to draw out his upper
slide, the signalman at A has to signal to B, when the signalman at B, by pressing
his plunger transmits a + current to A, thus exciting the magnet there and allowing
the upper slide to be withdrawn.
It is of advantage to connect to the slides some convenient form of indicator
mechanically connected to them, shewing whether the slides are in or out. Also an
indicator at one station A may be electrically connected with the slides at another
station B so as to shew their condition. The receptacle is preferably glazed in
front to shew the tablets in it.
The stations having tablet instruments as herein described and also tablet
instruments and keys as described in our previous Specification No. 17195 of 1895
above referred to, the intermediate stations may be closed by means of tablets in the
following manner.
Assuming that there are 3 stations A, B, C; B on obtaining tablets froin A and C
can by placing these tablets in a receptacle release his day key, close his station,
and then by currents sent by the extra wire can release the exhanging keys at
A and C.
Any number of stations may be closed in the manner described in our previous
specification and may be reopened by the issue to them of round tablets. In this
case it is advisable to open one station electrically and the others by means of
tablets.
Thus supposing there are 5 stations A, B, C, D, E, each of the intermediate

page_text: stations B, C and D having two instruments as described in our previous
specification.
Then if D, for instance, be opened electrically by permission of A and E. C may
be opened by D issuing a tablet belonging to C, Ď section, B by a tablet belonging
to the B, C section and so on.
Either B or D may be electrically opened according to the direction of the train
conveying the opening tablet.
It will be seen that by the use of tablet instruments such as that above described
making and breaking electrical contacts by the movements of their slides, the
relays required are reduced in number and the operations are considerably simplified
when compared with those required for operating as in our previous Specification
No. 17195 of 1895.
Besides the tablet instruments and electrical connections above described there
may in many cases be additional provisions for safety at the stations. These,
however, comprising apparatus of kinds more or less known, we do not here claim
as of our invention but merely indicate them as being of advantage for ensuring
safety. For instance, in order to provide for moving a wagon into or out of a
siding which is temporarily closed when its station is switched out we may provide
a special set of points for this siding which can be moved by a lever controlled by
the through tablet, or by using the through tablet for returning the interlocking
lever in the signal cabin to its middle position the points being thereby freed as
long as the through tablet remains in the cabin.
We may also use a special ground frame whereby the necessary. points and point
locks can be moved through sway bars, one end of each of which is connected to
the lever in the ground frame and the other to the lever in the cabin, the middle
point of the sway bar being connected to the points or lock to be operated, this
frame being released by a lever controlled by the through tablet.
We may also provide, substantially as described in the Specification No. 11850
of 1894 means whereby the points required to be moved can be temporarily
disconnected by the use of the through tablet from the rods leading to the cabin
and worked by levers on the ground,
In all these cases provision would be made that before the through tablet could
be removed to continue the journey, the points would have to be returned to and
secured in their normal position for through working.
Also instead of the exchanging boxes at the terminal stations described in our
previous specifications there may be, besides the one tablet instrument used for
ordinary traffic, a second instrument for through traffic, these instruments being
interlocked so that only one can be used at a time..
Obviously in operating as we have described, a staff may in many cases be
substituted for a tablet, or both may be used, suitable exchanging boxes or secondary
instruments being provided.
Having thus described and ascertained the nature of our said invention and in
what manner the same is to be performed, we declare that what we claim in
respect of apparatus for ensuring safety on single lines of railway is :-
1. The tablet apparatus having an upper tablet receiving slide and a lower tablet
issuing slide, substantially as described with reference to Figure 1 of the drawings.
2. The electrical connections operated by the tablet apparatus above referred to,
substantially as described with reference to Figure 2.
Dated this 21st day of January 1897.
ABEL & IMRAY,
Agents for the Applicants.