IMPROVEMENTS IN RAILWAY SIGNALS
Year: 1877

page_text: LETTERS PATENT to Harry Robert Kempe, of St. James's Rectory, Piccadilly, in
the County of Middlesex, for the Invention of "IMPROVEMENTS IN RAILWAY
SIGNALS."
Sealed the 20th October 1877, and dated the 4th May 1877.
PROVISIONAL SPECIFICATION left by the said Harry Robert Kempe at the
Office of the Commissioners of Patents on the 4th May 1877.
HARRY ROBERT KEMPE, of St. James's Rectory, Piccadilly, in the County of
Middlesex. "IMPROVEMENTS IN RAILWAY SIGNALS."
"
The semaphore signals of railways are usually counterweighted, so that they are
caused to rise to and stand in the "danger" attitude unless when the signal pull, by
raising the counterweight, permits them to descend to the "safety" attitude.
Sometimes it has happened that in consequence of the loading of the semaphore arm
with snow or other causes a signal has assumed the "safety" attitude when it
ought to have been at "danger," and serious accidents have been thus occasioned.
My Invention relates to means of preventing accidents of this nature by such an
arrangement and construction of the signal pull, counterweight, signal rod, and
parts connected therewith that the semaphore is securely retained at the "danger"
attitude except when the signal pull is drawn to its full extent, or nearly so, for the
purpose of lowering the signal to "safety." For this purpose, instead of connecting
the signal rod directly to the weighted lever, so that it must move equably there-
with, I connect it by a pin working in a slotted hole, or by a flexible connection,
such as a piece of chain or jointed links, and I provide a loaded detent which, by
catching in a notch or on a projection on the signal rod, holds the semaphore arm at
danger. When by drawing the signal pull the counterweight is raised, the semaphore
remains at "danger" until the counterweighted lever approaches the extreme of its
stroke, when it releases the detent, and so permits the semaphore arm to descend.
When again the signal pull is slacked, the counterweight being so permitted to
descend raises the signal to " danger," and the detent again becoming engaged
maintains it in that attitude.
. According to a modified form of the apparatus I joint the signal rod to one arm

page_text: of a lever, another arm of which is connected by a slotted rod, jointed link, or
portion of chain to the counterweight lever. When the semaphore is at "danger,"
its rod and the arm to which it is jointed are vertical, or nearly so, and as its weight
thus acts on a dead centre it has no tendency to move the lever, but when by
drawing the signal pull the counterweight is raised as it approaches the end of its
stroke it causes the lever to rock on its fulcrum, and the signal rod and the arm to
which is jointed being thus moved off the dead centre, the semaphore descends.
When again by slacking the signal pull the counterweight is allowed to descend, it
brings the signal rod and arm of the lever back to the vertical position, whereby
the semaphore is retained in the danger attitude.
The lever to which the signal rod jointed may be mounted on the same fulcrum
with the weighted lever, and be provided with stops, between which the latter has
room to play, until it approaches either end of its stroke.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Harry Robert Kempe in the Great Seal Patent Office on the 30th
October 1877.
HARRY ROBERT KEMPE, of St. James's Rectory, Piccadilly, in the County of
Middlesex. "IMPROVEMENTS IN RAILWAY SIGNALS."
The semaphore signals of railways are usually counterweighted, so that they are
caused to rise to and stand in the "danger" attitude, unless when the signal pull,
by raising the counterweight, permits them to descend to the "safety" attitude.
Sometimes it has happened that in consequence of the loading of the semaphore arm
with snow or other causes a signal has assumed the "safety" attitude when it
ought to have been at "danger," and serious accidents have been thus occasioned.
My Invention relates to means of preventing accidents of this nature by such an
arrangement and construction of the signal pull, counterweight, signal rod, and
parts connected therewith, that the semaphore is securely retained at the "danger"
attitude except when the signal pull is drawn to its full extent, or nearly so, for the
purpose of lowering the signal to "safety." For this purpose, instead of connecting
the signal rod directly to the weighted lever, so that it must move equably therewith,
I connect it by a pin working in a slotted hole, or by a flexible connection, such as
a piece of chain or jointed links, and I provide a loaded detent which, by catching
in a notch or on a projection on the signal rod, holds the semaphore arm at " danger."
When by drawing the signal pull the counterweight is raised the semaphore remains
at "danger" until the counterweighted lever approaches the extreme of its stroke,
when it releases the detent, and so permits the semaphore arm to descend. When
again the signal pull is slacked, the counterweight being so permitted to descend,
raises the signal to "danger," and the detent again becoming engaged maintains it
in that attitude.
The accompanying Drawings shew front elevations of two forms of safety signal
apparatus according to my Invention.
In Fig. 1, A is the semaphore arm, which is in this case supposed to be more than
counterbalanced by a weight B or otherwise. C is the signal rod, extending down
the post, and jointed at c to the projecting segment d of a disc D; this disc D is
furnished in part of its periphery with ratchet teeth, with which a weighted pawl E
engages, and on the disc D there is a stud or stop F, against which bears the loaded
lever G. The signal pull H is attached to a bar K, on which is mounted a pulley L.
Round this pulley is passed a piece of chain h, attached at one end g to the end of
the loaded lever G, and at the other end to the disc D at f. In the upper part of
the bar K is a slotted hole k, taking a stud e on the pawl lever E. M, M, are stops
limiting the movement of the disc D. When the pull H is drawn down by action
of the signal lever at a distance, the bar K is also drawn down with its pulley L,

page_text: the disc D being kept stationary by the pawl E, and the point f being therefore
stationary, the pull on the chain h raises the loaded end of the lever G. When the
bar K descends so far that the end of its slot k comes to bear on the stud e, then by
the farther movement the pawl E is raised out of gear with the teeth of the disc D,
which is thus left free. The pull on the point thereupon causes the disc D to turn
partly round, pulling down the rod C, and lowering the semaphore arm A. On
Blacking out the pull H the loaded arm of G descends, and bearing against the stud F
causes the disc D to turn so as to raise the signal rod C and the semaphore arm, and
the stud e being at the same time left free in the slot the pawl E drops into gear
with the teeth of D, and prevents it fron turning back, the semaphore being
thus held at "danger," notwithstanding that it may become loaded with ice or
snow. If the pull H should break, even while the semaphore is in its "safety
attitude, then the weighted lever G, being left free, raises the signal to "danger," and
the pawl E holds it in that attitude.
"
According to the modified arrangement shewn in Fig. 2 the semaphore arm N is
not counterweighted, its rod O is provided with a collar o, on which engages a
loaded pawl R, and the lower end of the rod O is made with a slot S that takes a
stud g on the loaded lever Q, to which is attached the pull P. On drawing the
pull Ŕ the loaded end of the lever Q is raised, the signal rod O being held stationary
by the pawl R until the lever Q comes to bear against 7, whereupon the pawl R being
disengaged from o the rod O is left free, and the signal descends to "safety." On
slacking the pull P the loaded end of the lever Q descends, pulling down the rod O,
and raising the signal to "danger," in which attitude it is retained by the pawl R
engaging on the collar o, and the same action will result if the pull P should be
broken.
Having thus described the nature of my Invention, and in what manner the same
is to be performed, I claim, the use for working railway signals of apparatus wherein
the signal, having a slotted connection with a loaded lever moved by the signal pull,
is held by a detent in the "danger" attitude until the said lever in approaching
the end of its stroke releases the detent, and causes or permits the descent of the
signal to its "safety" attitude, substantially as and for the purposes herein set
forth.
In witness whereof, I, the said Harry Robert Kempe, have hereunto set my
hand and seal, this Twenty-ninth day of October, in the year of our Lord
One thousand eight hundred and seventy-seven.
HARRY ROBERT KEMPE. (L.S.)