IMPROVEMENTS IN APPARATUS FOR COMPEN- SATING THE EXPANSION AND CONTRACTION BY ALTERATION IN TEMPERATURE OF WIRES USED FOR ACTUATING SIGNALS
Year: 1876

page_text: LETTERS PATENT to William Braithwaite, of Stratford, in the County of
Essex, for the Invention of "IMPROVEMENTS IN APPARATUS FOR COMPEN-
SATING THE EXPANSION AND CONTRACTION BY ALTERATION IN TEMPERATURE
OF WIRES USED FOR ACTUATING SIGNALS."
Sealed the 28th March 1877, and dated the 22nd November 1876.|
PROVISIONAL SPECIFICATION left by the said William Braithwaite at the
Office of the Commissioners of Patents on the 22nd November 1876.
WILLIAM BRAITHWAITE, of Stratford, in the County of Essex. "IMPROVEMENTS
IN APPARATUS FOR COMPENSATING THE EXPANSION AND CONTRACTION BY ALTERA-
TION IN TEMPERATURE OF WIRES USED FOR ACTUATING SIGNALS."
This Invention relates to wires used for actuating signals on railways, in mines.
or other positions where the signal itself is placed at a distance from the handle or
other device used for actuating it, and it has for its object improvements in apparatus
by which the variation in the length of such wires caused by alternations of heat and
cold is compensated.
In signalling apparatus as ordinarily used upon railways a signal arm is used
suspended upon a joint at its upper end, and contained in a sheath or recess in a
vertical signal post. This arm is actuated by means of a lever, often placed at a
great distance from the signal post, which is connected by means of levers and
pullies to one end of a wire, the other end of which is connected in a similar way
to the signal arm, which can thus be placed in any desired angular position varying
from vertical to horizontal. Where the connecting wire is of great length, and is
subjected to a great alteration in temperature, it sometimes happens that the
alteration in length of the wire is so great that the signal arm does not stand in
its proper position relative to that of the lever, and may thus mislead the engine
driver or other person by whom it is intended that it should be observed, and the
method usually adopted to obviate this uncertainty is to continually slacken or
tighten the connecting wire as may be required by means of one or more adjusting
screws.
My Invention consists in arranging a lever turning upon a centro at or near the
middle of its length, which centre is fixed firmly to a foundation of wood or other

page_text: suitable material. At or near each end of the lever is arranged a pulley, and th
apparatus is fixed in such a position that the connecting wire between the lever and
the signal arm, as above described, passes at any convenient part of its length over
one of the pullies, and under the other pulley. By this arrangement if one end of
the lever is depressed the wire is tightened, and if it is raised the wire is slackened.
At the centre of the lover is formed or attached a short arm or lever at right angles
or other convenient angle to the one first described, and to this short lever is fixed
or connected one end of a bar of copper or other inaterial capable of considerable
expansion and contraction by heat or cold. The other end of this bar is firmly
fixed or connected to an abutment, preferably fixed to or forming part of the foun-
dation which carries the centre upon which the lever turns.
The action of the apparatus is as follows:-When by an increase of temperature
the connecting wire is lengthened, and so becomes too slack, the copper bar is
lengthened in the same way, and thus turns the lever upon its centre, raising one
of its ends and depressing the other end, and thus tightening the wire. When the
wire is tightened by a decrease of temperature the contrary effect to that described
takes place upon the lever, and the wire is slackened to a corresponding extent.
Where the wire is of any great length two or more levers and bars, arranged as
described, may be used at different parts of its length. The length of the arms of
the lever and of the copper bars are proportioned to the length of the connecting
wire to be compensated. A guide pulley for the connecting wire should be fixed
to a post or foundation near each end of the lever.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Braithwaite in the Great Seal Patent Office on the 22nd May
1877.
"IMPROVEMENTS
WILLIAM BRAITHWAITE, of Stratford, in the County of Essex..
IN APPARATUS FOR COMPENSATING THE EXPANSION AND CONTRACTION BY ALTERA-
TION IN TEMPERATURE OF WIRES USED FOR ACTUATING SIGNALS."
My Invention relates to wires used for actuating signals on railways, in mines, or
other positions where the signal itself has to be placed at a distance from the handle
or other device used for actuating it, and it has for its object improvements in
apparatus by which the variation in the length of such wires caused by alternations
of heat and cold is compensated.
The signalling apparatus as ordinarily used upon railways consists of a signal
arm suspended upon a joint at its upper end, and contained in a sheath or recess in
a vertical signal post. This signal arm is actuated by means of a lever (often placed
at a great distance from the signal post) connected by means of levers and pullies
to one end of a wire, the other end of which is connected in a similar way to the
signal arm, so that the latter can thus be placed in any desired angular position
varying from vertical to horizontal. Where the connecting wire is of great length,
and is subjected to much alterations of temperature, it sometimes happens that the
alteration in length of the wire is so great that the signal arm does not stand in its
proper position relative to that of the lever, and may thus mislead the engine driver
or other person by whom is is intended that it should be observed. The method
usually adopted to obviate this uncertainty is to continually slacken or tighten
the connecting wire as may be required by means of one or more adjusting
screws.
•
My present Invention consists in arranging a lever turning upon a centre at or
near the middle of its length, which centre is fixed firmly to a foundation of wood
or other suitable material. At or near each end of the lever is arranged a pulley,
and the apparatus is fixed in such a position that the connecting wire between the
lever and the signal arm, as above described, passes at any convenient part of its

page_text: length over one of the pullies and under the other pulley. By this arrangement if
one end of the lever is depressed or moved round the centre the wire is tightened,
and if it is raised or moved in the other direction the wire is slackened. At the
centre of the lever is formed or attached a short arm or lever at right angles or
other convenient angle to the one first described; and to this short lever is fixed or
connected one end of a bar of copper or other material capable of considerable
expansion and contraction by heat or cold. The other end of this bar is firmly fixed
or connected to an abutment, preferably fixed to or forming part of the foundation
which carries the centre upon which the lever turns.
The
copper bar may be connected to the principal lever instead of to a short arm
or lever formed upon or attached to it as described.
The principal lever may be arranged so as to be ordinarily vertical or horizontal
or at other suitable angle, and the action of the apparatus is as follows:- -When
by an increase of temperature the connecting wire is, lengthened, and so becomes
too slack the copper bar is lengthened in the same way, and thus turns the lever
upon its centre, moving its ends in opposite directions, and thus tightening the wire.
When the wire is tightened by a docrease of temperature the contrary effect to that
last described takes place upon the lever, and the wire is slackened to a corre-
sponding extent. Where the wire is of very great length two or more levers and
bars, arranged as described, may be used at different parts of its length. The
length of the arins of the lever and of the copper bar are made proportioned to
the length of the connecting wire to be compensated. A guide pulley for the
connecting wire should be fixed to a post or foundation near each end of the
lever.
I prefer to substitute chain for wire at the part where the latter passes over the
pulleys upon the lever.
The accompanying Drawing is in illustration of my Invention.
Figure 1 is an elevation, and Figure 2 a plan of the apparatus.
a is a lever turning upon the fixed centre b, and having pulleys c and d at its
extremities, under one of which and over the other the signal wire e passes, ns
shewn; is a joint upon the lever a, and connected to one end of a copper bar g,
the other end of which is fixed to the abutinent h. When the copper bar g expands
by heat it shortens the wire e by turning the lever in the direction shown by the
arrows. When it contracts it turns the lever in the other direction, and allows the
wire e to contract.
Having now described my Invention and the manner in which it is to be per-
formed I claim, the method of compensating the contraction and expansion of a
signal wire by cold or heat by passing such signal wire or chain connected to the
same round pulleys upon a lever turning upon a centre, and operated by the
contraction and expansion of a fixed bar, substantially as described and shewn in
the Drawing.
In witness whereof, I, the said William Braithwaite, have hereunto set my
hand and seal, this Twelfth day of May, in the year of our Lord One
thousand eight hundred and seventy-seven
WILLIAM BRAITHWAITE. (L.S.)