Year: 1886

page_text: Date of Application, 26th Feb., 1886.
Complete Left, 24th Dec., 1886.
Complete Accepted, 25th Jan., 1887.
I, JAMES MURDOCH NAPIER of Vine Street, York Road, Lambeth in the County of
Surrey, Engineer do hereby declare the nature of this invention to be as follows:-
:-
My improvements refer to speed indicators in which mercury is employed rotated in
a vessel and in accordance with the varying speed of the rotations is caused to rise
and fall in an indicating tube and are designed to prevent the escape of the mercury
from the rotating vessel and from the indicating tube through the passages or aper-
tures which may be provided for air to pass into the vessel as the mercury passes out
of it and into the indicating tube; and into the indicating tube and out of the vessel
as the mercury passes out of the tube and back into the vessel and consist of the use of
cotton wool or other suitable fibrous or porous substance packed into a cavity or
aperture formed or provided at the top of the indicating tube and also into a ring
cavity or stuffing box formed round a circular opening in the top of the rotating
vessel.
CARPMAEL & Co.,
Agents for the Applicant.

page_text: I, JAMES MURDOCH NAPIER of Vine Street, York Road, Lambeth in the County of
Surrey Engineer 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 :-
My improvements refer to speed indicators in which mercury is employed rotated in
a vessel and in accordance with the varying speed of the rotations is caused to rise
and fall in an indicating tube and are designed to prevent the escape of the mercury
from the rotating vessel and from the indicating tube through the passages or apertures
which may be provided for air to pass into the vessel as the mercury passes out of it
and into the indicating tube, and into the indicating tube and out of the vessel as the
mercury passes out of the tube and back into the vessel and consist of the use of
cotton wool or other suitable fibrous or porous substance packed into a cavity or
aperture formed or provided at the top of the indicating tube and also into a ring
cavity or stuffing box formed round a circular opening in the top of the rotating
vessel.
In order that my said invention may be most fully understood and readily carried
into effect I will proceed to describe the drawings hereunto annexed.
DESCRIPTION OF THE DRAWINGS.
Figure 1 is a front elevation partly in section of a speed indicator to which my
present improvements are applied.
2
A is a circular vessel containing mercury it is mounted upon an axis A' which is
driven from the motor or machine the speed of which it is desired to ascertain. B is
a fixed support on which is a boss B¹. C is a radial arm fixed in the boss-this arm
is hollow and communicates with the cavity within the boss B and at its outer end it
terminates in an aperture facing in a direction opposite to that in which the vessel A 2
rotates D is a glass tube fixed into the upright D¹ which is planted on and fixed to
the fixed support B-the glass tube D contains a float of ivory or other material E.
When the vessel A revolves it carries the mercury round with it and causes it to enter
the aperture in the extremity of the arm C the mercury then rises in the tube D more
or less according to the speed at which the vessel A is driven the position of the float 3
being read on a suitable scale marked on or affixed on D' alongside of the tube D
which will give the number of revolutions of the.axis...
These arrangements form no part of my present invention which relates solely to
the means by which I provide for the passage of air into and from the apparatus
whilst preventing the escape of mercury and excluding dust. For this purpose I 3
provide in connection with the rotating vessel A a recess A³ which I fill with cotton
wool or other like material to fit closely around the boss B'. It is unnecessary that
the cotton wool should be strongly compressed for the mercury will not readily divide

page_text: in such a way as to pass through the interstices between the fibres whilst on the other
hand air can find its way freely amongst the fibres even when they are packed some-
what closely together. Thus when the mercury leaves the vessel A and passes into
the tube D'air is able freely to enter into the vessel and on the other hand when the
mercury returns the air passes out without offering any impediment to the mercury.
Similarly I provide for the passage of air into and from the upper end of the tube D.
This tube is represented in the drawings as provided at its upper end with a cap E¹
and in this cap there is a hole receiving a screw plug F. The plug F is hollow and
also has a small vent hole through it at F. The hollow or cavity in the screw is
filled with cotton wool represented at F' which gives ready passage to the air but will
prevent the escape of mercury even if in transport the apparatus should be inverted.
Figure 2 is an underside view of the upper part of the vessel A the cavity to
receive cotton wool is indicated by dotted lines. The cotton wool may be first packed
into the cavity and the boss B₁ then inserted through it or it may be packed in after
the boss B is in position.
Figure 3 shows a section of an alternative form of the cap at the upper end of the
tube D. The letters in this figure indicates parts of a similar kind shown in
Figure 1.
The arrangements which I have described are applicable also to other forms of speed
indicators in which mercury is employed and in which mercury is confined in a vessel
into and from which it is essential that air should be free to pass when the apparatus
is in use.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed I declare that what I claim is :-
1. A speed indicator comprising an indicator tube and a vessel containing mercury
in communication therewith and in which cotton wool or other suitable fibrous or
porous substance is packed into a cavity or aperture formed or provided at the top of
the indicating tube and into a ring cavity or stuffing box formed round a circular
opening in the top of the mercury vessel thereby confining the mercury and excluding
dust whilst free passage is given to air.
2. A speed indicator comprising an indicator tube and a vessel containing mercury
and having in connection with either or both of these the appliance herein described
for confining the mercury and excluding dust whilst giving free passage to air.
3. A speed indicator operating by means of mercury and in which the mercury is
retained by cotton wool or other suitable fibrous or porous substance substantially as
described.
CARPMAEL & Co.,
Agents for the Applicant.