IMPROVEMENTS IN APPARATUS FOR TRANSMITTING AND RECEIVING SIGNALS AND ORDERS OR MESSAGES
Year: 1878

page_text: LETTERS PATENT to James Rettie, of Hatton Garden, in the County of
Middlesex, Engineer, for the Invention of "IMPROVEMENTS IN APPARATUS
FOR TRANSMITTING AND RECEIVING SIGNALS AND ORDERS OR MESSAGES."
Sealed the 6th December 1878, and dated the 8th June 1878.
PROVISIONAL SPECIFICATION left by the said James Rettic at the Office of
the Commissioners of Patents on the 8th June 1878.
JAMES RETTIE, of Hatton Garden, in the County of Middlesex, Engineer. "IM-
PROVEMENTS IN APPARATUS FOR TRANSMITTING AND RECEIVING SIGNALS AND
ORDERS OR MESSAGES."
This Invention relates to improvements in apparatus for transmitting and
receiving signals and orders or messages, and particularly to that class of presont
known apparatus, in which the transmitting and receiving instruments are con-
nected by a single flexible connection for transmission of the message, and by a
second single flexible connector for the reply. Hitherto in such instruments,
balanced weights or springs (one at each end of the flexible connector) have been
employed to maintain the flexible connector taut, and thereby maintain the indi-
cator of the receiving instrument in the various positions into which it is inoved by
the operator. In practice, it has been found when weights have been employed,
that to obtain sufficient weight, the apparatus has to be made very cumbersome.
It has also been found when springs have been employed difficult, if not impossible,.
to maintain the two springs in equilibrium, and the mechanism has therefore to be
held in position by other means.
According to my Invention, at some point in the length of the flexible connector,
by preference at one end, and again by preference in the transmitter, the flexible
connector passes over a cam or excentric pulley so adjusted in reference to the two
springs, that the spring most extended, and therefore the strongest, shall pull on the

page_text: short leverage of such cam or excentric pulley, and the spring the least extended,
and therefore the weakest, shall pull on the longer leverage. Thus, by a proper
adjustment, the pull of the two springs may be balanced at any and every portion
of the part revolution of the said cam or excentric pulley.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said James Rettie in the Great Seal Patent Office on the 7th December
1878.
JAMES RETTIE, of Hatton Garden, in the County of Middlesex, Engineer.
" IM-
PROVEMENTS IN APPARATUS FOR TRANSMITTING AND RECEIVING SIGNALS AND
ORDERS OR MESSAGES."
This Invention relates to improvements in apparatus for transmitting and re-
ceiving signals and orders or messages, and particularly to that class of such present
known apparatus in which the two instruments called the transmitter and the
receiver respectively are connected by a single flexible connector for transmitting
the message, and a second single flexible connector for repeating the message
received back on the transmitter or for reply. Hitherto in such instruments
balanced weights or springs in tension (one at each end of each of said flexible con-
nectors), have been employed to maintain the flexible connectors taut, and thereby
hold the indicators on the two instruments in the positions into which they have
been moved by the operators. In practice, it has been found when weights have
been employed, that (amongst other disadvantages) to obtain sufficient strain on
the flexible connectors, the weights have to be comparatively heavy, and the
apparatus consequently cumbersome. It has also been found when springs have
been employed difficult, if not impossible, to maintain the two springs (pulling one
at each end of the flexible connector) in equilibrium, and the mechanism of the two
instruments has therefore had to be controlled or held in the position desired by
other means.
According to my Invention (with which are used the springs as above described),
at some point in the length of each flexible connector, it (the connector) passes over
a cam or excentric pulley so adjusted (in reference to its different radii) in relation to
the two springs that that are most tensed, and therefore exerting the greatest pull
on the connector, shall pull over the smaller radius or leverage of the said cam or
excentric pulley and the spring the least tensed, and therefore the weakest, shall
pull over the larger radius or leverage of such excentric cam or pulley. Thus, by a
proper adjustment, the pull of the two springs may be balanced at any and every
portion of the part revolution of the said cam or excentric pulley. When desired,
more than one such excentric cam or pulley may be employed in the length of each
of said flexible connectors.

page_text: And in order that my Invention may be clearly understood and readily carried
into effect, I will proceed to describe the same with the aid of the accompanying
Drawings, reference being had to the letters and figures marked thereon, and in
which Figure 1 is a front elevation partly in section of the transmitter instrument
with my improvements attached; Figure 2, a like view of the receiver with my
improvements attached; and Figure 3 a side sectional view taken at the line a-b,
Figure 1.
The same letter or figure denotes the same part or parts in each of the several
Figures.
In the application of my Invention illustrated, there are two of said excentric or
cam pulleys to each flexible connector, placed one at each end, and the two springs
are enclosed, one in each of such excentric or cam pulleys in the form of a coil
A is
spring, the said cams or excentrics thus taking the form of the spring boxes.
the flexible connector, by means of which the message is communicated from the
transmitter (Figure 1), to the receiver, Figure 2; it is attached at one end to cam
or excentric B (Figure 1), whence it passes upwards through the standard C of the
transmitter over pulley D, and downwards again through the standard C, round
pulley E, and away around suitable other pulleys to the receiving instrument F,
whence it is led round pulley G, and over and round cam or excentric pulley H to
which its other end is attached. The message has been given by drawing the
handle I (Figure 1) over into the position shewn. The bandle I being attached (as
shewn by dotted lines, Figure 3) to the pulley D, has carried the latter with it, and
this has in its turn caused the flexible connector A which is attached to it to move
with it in the directions shewn by the arrows. The portion of connector attached
to cam or excentric B has been drawn upwards, and has unwound itself from
the cam, giving motion to same, and winding up the spring contained therein. The
other end of connector A has been let out, and following up the slack thus given,
cam H (at its other end and in the receiver) has taken it up by its spring uncoiling.
The spring in B is thus most tightly tensed, and therefore the stronger, but is
pulling on cam or excentric H over the latter's shorter radius or leverage, and
therefore balances with spring in H, which being the weakest, pulls on B over tho
latter's longer radius or leverage. Thus, the difference in the leverage resulting from
the shape of the cams, must always correspond with and equalise the difference of
the powers of the two springs. Any next message must be given by moving handle
I in a direction contrary to its last motion, viz., in the direction indicated by the
arrow. For example, suppose it to be moved into the position indicated by the
dotted lines at the word stop (Figure 1); this will be half its full traverse,
pulley D will be carried round a corresponding portion of a circle in the direction
indicated by the arrow, and the end of connector A attached to cam or excentric B
will be let out; spring in B will uncoil and revolve B in the direction also of the
arrow thereon, picking up the slack of A, and weakening spring in B. Meanwhile,
the other end of A is drawn in and uncoiled from cam or excentric H, coiling up
the spring therein to the same extent as that in B was uncoiled. B at the same
time obtaining a large leverage on H, and the latter a smaller leverage on B, and
thus the two are maintained in equilibrium. The pulley D in the transmitter turns
loosely on its spindle, the message being indicated in that instrument on the outside
rim by the point i attached to handle I. Pulley G in the receiver turns with the
spindle, to which is attached pointer J which indicates on the face the same word
as pointer on the communicator. It will be observed that cams or excentrics B
and H do not make a complete revolution. Care must therefore be taken that the
pull travel of the circumference of pulley D will equal the full travel of the circum-
ferences of cams or excentrics B and H. For the return message, a similar device
is employed, and a similar process is gone through from the receiving instrument,
the reply being given by handle K and this and pulley L acting in an exactly
similar manner on flexible connector M, and cams or excentrics N and O.
i
Spiral or other springs pulling over the cams or excentrics, may be used when
desired instead of the coiled spring as shewn.

page_text: Having thus particularly described and ascertained the nature of this my said
Invention, and the manner in which the same is to be or may be performed, I
claim as my Invention to be secured by the berein-before in part recited Letters
Patent, in apparatus for transmitting and receiving signals and orders or messages,
passing the flexible connector at one or more points of its length, round or partially
'round excentric or cam pulleys or pulley, substantially as herein-before set forth
and described, and illustrated in the accompanying Drawings.
In witness whereof, I, the said James Rettie, have hereunto set my hand and
seal, this Seventh day of December, in the year of our Lord One thousand
eight hundred and seventy-eight.