AN IMPROVED APPARATUS FOR INDICATING THE REVOLUTIONS OF SCREW OR PADDLE SHAFTS OF STEAM VESSELS, ALSO APPLICABLE FOR INDICATING THE REVOLUTIONS OF OTHER MACHINERY
Year: 1874

page_text: PROVISIONAL SPECIFICATION left by Alexander Walker at the Office
of the Commissioners of Patents, with his Petition, on the 9th
June 1874.
I, ALEXANDER WALKER, of Bow, in the County of Middlesex,
Engineer, do hereby declare the nature of the said Invention for "AN
IMPROVED APPARATUS FOR INDICATING THE REVOLUTIONS OF SCREW OR PADDLE
SHAFTS OF STEAM VESSELS, ALSO APPLICABLE FOR INDICATING THE REVOLUTIONS OF
OTHER MACHINERY," to be as follows:-
This Invention consists in constructing and arranging an improved
apparatus or instrument, which is specially applicable for indicating the
revolutions of the screw propeller or paddle shafts of steam vessels in
such a manner that the desired indications may be seen and ascertained
any and all times by the captain or chief officer upon the bridge on
deck, and also by the engineer in the engine room. This indicator is
also applicable for indicating the revolutions of various parts of
machinery in general.
at
By means of bevil gearing I transmit the motion of the propeller
shaft (or of that part of the machinery the number of whose revolutions
I require to obtain) at a corresponding rate (having regard only to the

page_text: number of revolutions) to a vertical shaft (suitably supported by a
bracket or otherwise) passing upwards from the propeller shaft through
the lower, middle, and upper decks, and the bridge thereon. The said
vertical shaft is made in divisions or parts, which are suitably united
immediately below the said decks, and each of which parts is provided
with a shoulder, which rests upon a journal made in halves, and bolted
in position to the deck at the part through which the said shaft presses.
I utilize the motion of this shaft so as to obtain the number of its (and
consequently of the propeller's shafts) revolutions at the places required
by keying small projecting teeth thereupon, one in the engine room,
and one above the bridge on deck, and by causing these teeth at each
revolution of the shafts each to engage with one of a suitable and
convenient number (say 200) of teeth in a wheel centred by a pivot
carried by the above-mentioned bracket and passing through the centre
of a dial plato (also supported by the said bracket) marked with a series
of numbered divisions, equal in number to that of the teeth upon the
said wheel, and upon the end of which said pivot I make fast and secure
a suitable index finger or pointer. I thus at each of the revolutions of
the propeller shaft and of the said vertical shaft cause the said toothed
wheel to be moved one tooth (and the possibility of its moving more at
a time is prevented by a sufficiently strong spring engaging with its
teeth) and the pointer to be moved from one division of the dial plate to
that next it.
The said dial plate carries a case containing a train of watch or clock
alarm mechanism, which gives motion to a second hand, and imparts
thereto one revolution each minute of time, and which also at the
commencement of each of the revolutions of the second's hand strikes an
alarum, gong, or bell, so that the engineer by noticing the number of
divisions of the dial plate passed over by the said pointer between two
sounds of the gong or bell can immediately ascertain the required
indication.
To render the apparatus as applicable for use, at night as in the day I
apply lamps or lanterns at night-time so as to reflect light down upon
the numbered dial plates.