Improvements in Electric Logs or Apparatus for Measuring the Speed of Ships.
Year: 1890

page_text: Date of Application, 3rd June, 1890-Accepted, 30th May, 1891
COMPLETE SPECIFICATION.
Improvements in Electric Logs or Apparatus for Measuring the
Speed of Ships.
I, WILLIAM PUDDICOMBE GRANVILLE of 36 Oakfield Road, Stroud Green in
the County of Middlesex, Electrician, do hereby declare the nature of this invention
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
This invention has for its object improvements in electric logs.
In the Specification of a former Patent granted to me No. 12242 in the year 1888
I have described an electric log. The instrument which is towed through the water
by a conducting line (which need not be insulated) carries a fly with inclined blades
and the fly revolves independently of the log body. On the log body is a mass of
zine which however is not in metallic connection with the tow line. A water tight
box is also provided on the log body within which there is a soft iron contact maker.
The two ends of the contact maker are alternately attracted by a magnet upon the
fly as the fly rotates.
In one position of the contact maker a circuit is closed from the mass of zinc
immersed in the sea, through the contacts, the tow line, the coils of an electric counter
on board the ship, and the ships hull, and so back to the sea. In the other position
of the contact maker this circuit is open. Currents are thus caused to pass which
actuate the counter.
According to my present invention I much simplify the instrument by dispensing
with the water tight box, the magnet and the magnetic contact maker; I cause the
fly by means of a worm upon it to rotate a worm wheel on which is a pin or
projection. As the wheel revolves the pin or projection rubs at intervals upon a
spring finger connected with the mass of zinc.
All these parts are immersed in the water but this does not interfere with the
efficient action of the log; a current passes through the log line and operates the
counter when contact is made with the spring finger by a part metallically connected
with the log line but ceases when this contact is discontinued notwithstanding that
the water has free access to the contact surfaces.
In order that my said invention may be fully understood and readily carried into
effect I will proceed to describe the drawings hereunto annexed.
DESCRIPTION OF THE DRAWING.
The drawing shows the log ship constructed in accordance with my invention;
a is the tow line, it may consist of a bare wire or small strand of copper, bronze, iron,
or any other suitable metal having when submerged in salt water approximately the
same electro chemical action as the hull of the ship. Although not necessary
I prefer for mechanical convenience and safety to combine the wires with hemp, flax,
or jute, and so as to prevent corrosion, to cover the wires with a thin coating of
gutta percha, india rubber or any durable elastic varnish. The log line may be
constructed as follows. Around a cod line is laid spirally five copper wires thinly
covered with gutta percha also five yarns of hemp etc. a yarn being laid between
each wire so as to fill up the interstices. The whole is then braided with hemp or
flax etc. the outside diameter of the completed log line being about three eights of
an inch. At each end the five wires are connected together so that they form one
multiple conductor of about one ohm resistance or less.
I prefer to employ gun metal for all the metallic parts of the log ship with the
exception of the body which is of zinc. The tow line a is well connected both
mechanically and electrically with the eye b. In connection with the eye there is
a pin 6x and I wind the wires of the tow line around the pin and secure them by

page_text: soldering. I envelop the joint in gutta percha to prevent corrosion. When the
log ship is prepared for use the eye is secured by two bolts 26 to the fork c
which is screwed on to the end of the spindle d. The log line is connected with
bare metal immersed in the water and thus is uninsulated whether the wires of the
line itself be covered with insulating material or otherwise. Upon the spindle are
two vulcanite discs e and fand between these the zinc body bis held so that it is
insulated by the vulcanite from the spindle. Upon the spindle at its rear end the
fly is mounted; it consists of a metal sleeve g upon which is a worm gl. A nut
upon the end of the spindle keeps the sleeve in place. is a cylindrical block of
vulcanite fixed upon the sleeve; it is closed in rear by a screw plug of the same
material. The block carries four or other number of metal blades which are
inclined or of screw like form so that they cause rotation of the fly as the log ship
is drawn through the water. The spindle is prevented from revolving by its
attachment to the log line which resists torsion.
The worm g engages with the teeth of a small wheel which is mounted on a
pin or axis held in a forked arm projecting from the spindle; this wheel has a cam
like projection upon it on one side. is a spring finger which is screwed into the zinc
body it passes through a small vulcanite bush which is firmly fixed in a cavity
prepared for it in the body. This bush is intended to prevent local action where
the two metals come into contact. Once in each revolution of the wheel & the cam
piece rubs strongly upon the spring and then there is metallic connection
between the zinc body of the log ship and the hull of the ship through the
indicator on board the vessel and an electric current passes. Or the second
connection of the indicator coils might be to some other mass of metal immersed in
the sea.
The indicator on board the ship may consist simply of an electro magnet and
armature, a train of counting wheels and an escapement lever or pawl which propels
the wheels or permits them to turn one step each time the magnet attracts the
armature.
There are pointers on the axes of the wheels which indicate upon dials the
distance run.
The armature is held off from the magnet by a spring or weight,
which yields to the attraction of the magnet; this spring or weight may be adjust-
able. Indicators such as described or of this class are well known and any such if
well made and properly graduated in accordance with the object in view is suitable
provided its coils are of low resistance.
The conducting tow line a is placed in good metallic connection with the coils of
the indicator and these coils at their other end are connected with the hull só as to
establish good metallic connection therewith. Or as before stated metallic
connection may be made with some other mass of metal immersed in the sea but
this is not convenient.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is :-
1. An electric log in which by the rotation of a fly two parts immersed in the sea
are alternately brought together and separated and in which an indicating apparatus
on board the ship is actuated by the currents transmitted to it from the said contacts
through a conducting tow line.
2. In an electric log the combination of the conducting two line; the fly and
worm in electrical connection therewith; the worm wheel and cam piece; and the
zinc body with the finger projecting therefrom upon which the cam piece rubs from
time to time as the fly revolves.
3. An electric log substantially as represented by the annexed drawings.
Dated the on11
T
1000
W. P. GRANVILLE