IMPROVEMENTS IN LEVELLING INSTRUMENTS
Year: 1884

page_text: I BENJAMIN JOSEPH BARNARD MILLS of the firm of Harris and Mills of
23 Southampton Buildings in the County of Middlesex, Patent Agent do
hereby declare the nature of the said Invention for IMPROVEMENTS IN
LEVELLING INSTRUMENTS a communication to me from abroad by James
Macdonald of the City, County and State of New York in the United States
of America to be as follows:-
The present invention has for its object improvements upon an invention for
which Letters Patent were granted to me dated June 19. 1883 N° 3034.
According to the present invention the conical plugs and inner brass tube con-
necting them together as described in the specification of the Patent above referred
to are dispensed with.
The graduations are put on the outside of what is now the only brass tube,
instead of as formerly on the glass tube and an indicator is employed which when
in use indicates the position which the surface of the fluid takes and this position
is noted on the graduated scale.
This indicator may consist of a ring or cylindrical spring sliding up and down
the brass tube either inside or outside thereof in which case such ring or cylindrical
spring is preferably made with guide pieces entering and fitting the vertical slots.
Or the indicator may consist of a float resting on the surface of the liquid.
In the cap is a float valve which is made of any suitable light material and is in
shape cylindrical with one end closed and formed in the shape of a cone.
This conical end fits a corresponding seat in the upper part of the cap and this
seat communicates with the vent hole. This valve is prevented from falling below
a given point by a pin or stop and it is provided with, or works within, suitable
guides which conduct it correctly to its seat.

page_text: The object of the float valve is to provide a valve which will rise with the fluid
and by closing the vent hole prevent the escape of the fluid. The float valve is also
formed open at its lower end so that when floating on the liquid the air is confined
in it on the principle of the diving bell, if the instrument should be turned upside
down the air would escape and the valve fill with the liquid thereby causing such
valve to sink and close the vent.
When the level is vertical the valve drops and allows air to enter.
If desired the float valve may be made spherical and the valve seat of suitable
form for the same.

page_text: down the brass tube a either outside as shown at Figures 1 and 2 or inside between
the brass tube a and the glass tube b as shown at Figures 5 and 6. This indicator c is
preferably made with guide pieces c¹ entering and filling the vertical slots a² in the
brass tube a.
Or the indicator may consist of a float resting on the surface of the fluid
contained within the glass tube b.
The cap d is screwed into the brass tube a and a packing ring d' insures a
watertight joint. An air vent hole d² being formed in the top of the cap as usual
and the lower part of such vent is flared out or undercut to form a seat for a valve
as hereinafter described.
Within the cap d is a float valve e which is made of any suitable light material
but preferably of hard rubber.
It is preferably cylindrical in shape and has one end closed and formed in the
shape of a cone e¹ to fit a corresponding seat d³ on the underside of the vent hole d
at the upper part of the cap d.
This valve e is prevented from falling below a certain point by a stop d in the
form of a ring screwing into the cap d; or a pin might be employed for this
purpose.
1.
Guide wings e² are formed upon the valve e, or they might be upon the interior
of the cap d, to conduct the valve correctly to its seat and the valve e is formed
open at its lower end e³ for the purpose hereinafter' mentioned.
The object of this' float valve is to provide a valve which will, when the
instrument is in use and one standard is raised above the level of the other, rise
with the fluid in the lower one and by closing the vent hole d² therein prevent the
escape of the fluid therefrom.
When the valve e is floating on the fluid the air is confined therein 'on' the
principle of the diving bell and if the instrument should be turned upside down
the air would escape from the valve e and the valve would fill with the fluid
thereby causing it to sink and close the vent hole d². When the instrument is
vertical the valve drops until arrested by the stop d'.
If desired the float valve e may be spherical or partly spherical and the valve
seat ds of suitable form for the same.
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
ค
1. In a levelling instrument of the character herein described the employment
of an indicator acting in conjunction with a graduated scale in manner substantially
as herein shown and described and for the purpose stated.
!
2. In a levelling instrument of the character herein described, the employment
of a valve acting in conjunction with a valve seat. in manner substantially as
herein shown and described and for the
purpose stated.
Dated this 20th def
1007