IMPROVE- MENTS IN ELECTRIC TELEGRAPH APPARATUS
Year: 1864

page_text: PROVISIONAL SPECIFICATION left by John McElroy at the Office of
the Commissioners of Patents, with his Petition, on the 14th April
1864.
I, JOHN MCELROY, of Stretford, in the County of Lancaster, Book-
keeper, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN ELECTRIC TELEGRAPH APPARATUS," to be as follows:-
My Invention refers to that description of electric telegraph apparatus
which is called the printing telegraph, and the main feature thereof consists
in the use of a certain arrangement by which I am enabled with less useless
motions of the type wheel or carrier than are necessary under the present
systems to effect the required signals. In doing this I avail myself of the
known principle of permutation, whereby any one of a number of letters may
be brought to a certain point by moving so many steps in the one or the
other direction. Motive power derived from a spring, weight, or other such
source is applied to a shaft, which is connected by wheelwork to another shaft
capable of sliding to and fro. Upon this is a drum or other surface provided
with one or more grooves constituting cams, and within which is placed a pin
connected to the magnetic needle. These grooves are of different lengths
corresponding to the different spaces above alluded to, through which the type
carrier is to pass, and one of them answers, for instance, to motion thereof to
the right or positive side, and the other to the left or negative side. At the

page_text: In trans-
end of each of these intervals of grooves is a stop, and when the pin of the
magnetic needle is against such stop, then the motive power cannot cause
the drum to revolve, and the type carrier will remain stationary; but when
the said pin is moved to the right or the left, then the drum or other surface
will act as an escapement wheel, and will be free to rotate; but as the pin
is fixed for that time, an inclined side of the groove will cause the shaft on
which the drum is mounted to slide in the one direction or the other. This
sliding motion brings a clutch box into 'gear, which by means of toothed
wheels causes the type carrier to rotate in the one direction or the other.
The cam grooves in the drum are of various lengths corresponding to the
spaces the type wheel is to pass through, and the duration of motion imparted
through the clutch boxes will therefore determine the extent of motion in the
type carrier. Upon the aforesaid drum are other cam grooves, within which is
a fixed pin acting as a governor for insuring the correct motion.
mitting signals the type carrier will, as before mentioned, have to move
through various spaces before the letter required to be printed is in the right
position for receiving the impression, and the paper' on which such impression
is to be effected must therefore be kept back until the proper moment. To
effect this I employ an escapement weight, which being liberated when the
type carrier is put in motion falls downward; if, however, a preparatory
movement of the type carrier is being effected, then the weight has time to
fall a certain distance only, and is then arrested; but if a final signal is given,
then the said weight can fall a further distance, and allow an escapement
cam to act, which cam advances the paper and presents it to the type to be
printed, and the said cam also at alternate times advances the inking roller.
The apparatus by which the weight is arrested is a revolving surface, pro-
vided with elevations and depressions corresponding to the permutation
Connected to the escapement cam
grooves of the cam formerly described.
which effects the printing are rods or levers, which force the type carrier
back to its original position. The apparatus through which the operator acts I
construct after the manner of pianoforte keys. When one of these is depressed
a zig-zag groove or pins are caused to act against a rod, pushing it backward
and forward so as to make a positive or negative contact and effect a right-
hand or left-hand motion of the type wheel, and the said grooves or pins are
differently arranged for each letter or other signal to be printed, and so that
they correspond to the permutation intervals before mentioned, which prin-
ciple, it will now be seen, pervades the whole of my system.
According to another method of transmitting I employ a set of moveable
pieces in number equal to the signals required. Each of these pieces is of a

page_text: different form, having parts thereon which make or break contact corre-
sponding to so many intervals to the right or so many intervals to the left,
and each one may therefore be considered as a Diagram representing a
signal. These pieces are set up like type on a cylinder, but in a spiral form,
and when the said cylinder is caused to revolve, it is caused also to slide
upon its shaft by means of a screw or other ordinary apparatus, whereby the
whole length of the spiral may be caused to transmit a message. Upon the
type carrier above described are one or more positions, which may be reserved
for bells or other such signals.